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June 14

Synthroid versus Armor thyroid

Synthroid synthetic thyroid replacement hormone is dosed in micrograms. Natural thyroid, such as Armour thyroid, produced by Forest Pharmaceuticals, made from porcine thyroid powder, is dosed in grains. Are there published equivalencies of efficacy of Synthroid micrograms versus Armour thyroid grains? How many grains of Armour would be equivalent to 100 micrograms Synthroid? Edison (talk) 04:07, 14 June 2010 (UTC)

Since they are fundamentally different (Thyrolar/Armour containing both T3 and T4) a comparison of efficacy per dose is particularly ineffective. (edit: I found the contents of Thyrolar here and it makes sense that efforts would be made to allow Thyrolar doses to line up with Armour but again it's synthetic vs porcine so IMHO there is still some room for error.) It all depends on how the patient reacts to the artificial sources, some people are better/worse at converting T4 (in levothyroxine) into T3, and the 'effective' amounts of either vary from person to person as well. If you want to take a very casual look at it, compare the available doses of Armour (1/4 grain to 5 grain) to Synthroid (25 mcg to 300 mcg) as those designing the drugs probably have a similar target audience. *This is advice is for research purposes only and not medical in nature, see your doctor for genuine advice on prescriptions* --144.191.148.3 (talk) 13:54, 14 June 2010 (UTC)

e/c The Desiccated thyroid extract article states that "One grain (about 60 mg) of desiccated thyroid contains about 38 mcg of T4 and 9 mcg of T3". But comparison may be difficult because of the T3 component which isn't a part of the Synthroid formulation. hydnjo (talk) 14:12, 14 June 2010 (UTC)

Rifling and slower bullets

If I understand the rifling article correctly, all sides of a rifle bullet continuously scrape against the inside of the barrel, along the entire barrel length; while in a smoothbore weapon, the bullet (or ball) is smaller than the internal diameter of the barrel, and the bullet basically ricochets a few times against the inside of the barrel before it exits. I assume the hugely larger amount of friction in the rifle would slow down the bullet a lot, compared to the smoothbore; though I might see how in a smoothbore weapon, the bullet wouldn't "capture" as much force from the gases expanding from the gunpowder explosion. So, in "equivalent" rifle and smoothbore weapons, how much slower is the rifle bullet immediately upon exiting the barrel? Comet Tuttle (talk) 04:23, 14 June 2010 (UTC)

I'm not sure a rifle would be slower. If the bullet continuously scrapes against the barrel, that means that the pressure wave from the explosion propelling the bullet stays entirely behind it, propelling it more efficiently. — DanielLC 05:59, 14 June 2010 (UTC)

Our article on internal ballistics has a section on energy transfer during the transit inside the barrel. Rifle rounds engage - they actually squish/expand/melt into the bore rifling, forming a metal-to-metal seal that is extremely precise. Virtually all of the pressure-volume work is transferred to the round. (Of course friction does cause some loss to heating the barrel, but this is much smaller in magnitude compared to the energy lost if there is a gas-escape from an improper round/barrel seal. It's hard to compare, because few rifles have an equivalent smoothbore version. Even those few firearm models that could be equipped with either barrel type are not "exactly" the same between rifled and smoothbore versions - the cartridges, calibers, propellant charges, and so on are different. Even the makeup of the bullet is different, because the materials and alloys that allow a rifle round to expand and engage the grooves are useless in a smoothbore. Typically, though, rifle rounds are faster than smoothbore rounds - this may be a design consequence, and not an effect of the rifling. Because rifle rounds can be more accurate and more stable in flight, it is possible to design them to fire faster, imparting more energy and resulting in more effective terminal ballistics (stopping power, penetration, or other desired ballistic property). Nimur (talk) 06:05, 14 June 2010 (UTC)

Interesting, thank you. Comet Tuttle (talk) 20:29, 14 June 2010 (UTC)

It depends what you are talking about.The main purpose of rifling is to spin the bullet so that it will be gyroscopically stabilized.The rifling in a barrel could be compared to a screw.As the bullet travels through the barrel, the rifling causes the bullet to spin thus making it stable(Gyroscopes.Earlier guns did not have rifling on them and thus suffered a lack of gyroscopic stabilization on their projectiles.Thus the projectiles had short ranges and these weapons were extremely inaccurate.Rifling was added to combat this.Even though the friction caused by rifled weapons is greater that those of smooth bore weapons,the gyroscopic stabilization caused the bullets to travel farther due to their increased stability than of those of smooth bore weapons.However nowadays smooth bore weapons are being used again.The issue of stability is combated using stabilizing fins on the projectile.Although the smooth bore concept is being used extensively in big guns its usage in smaller weapons tend to be limited. --Matrix747 (talk) 02:18, 17 June 2010 (UTC)

If you're interested, most of our articles on particular rifles cartridges list muzzle velocities for typical loads. See for example the slow .30-30 and the fast .22-250. Friday (talk) 15:38, 18 June 2010 (UTC)

Why did SI standardize the mole?

The SI unit of amount of substance is the mole. But there existed already an SI unit, the joule per kelvin, J/K, as the Ideal gas law relates amount of substance n to pressure p, volume V and temperature T by pV = nRT where R is a constant conversion factor, the gas constant. If n is measured in mole then nR is measured in J/K. So I wonder why the mole is standardized as an SI unit? Using the J/K as unit for amount of substance would simplify all formulas involving R. Bo Jacoby (talk) 07:20, 14 June 2010 (UTC).

The Ideal Gas Law only relates to gases though, and as most substances manipulated or calculated aren't gases, that wouldn't be all that much use. --John (talk) 07:29, 14 June 2010 (UTC)

Well, the Ideal Gas Law in its derivation actually applies to the simplest distributed system in statistical mechanics, which in the real world turns out to be warm gases where collisions are rare. Thus using that as the basis for deriving a unit is completely justifiable a priori. Note Planck Units in particular set $k_{B}=1$, which is related to what OP suggests, though it still doesn't give a value for the unitless Avogadro's Number (in physics where we need Planck Units, we just count particles individually until the very end when we convert to real-world values using Avogadro). SamuelRiv (talk) 08:29, 14 June 2010 (UTC)

This is nineteenth century physics with no reference to atomic physics. The gas constant is quoted with 6 decimal digits (even if many substances are not gases). Perhaps this accuracy is insufficient? Bo Jacoby (talk) 13:07, 14 June 2010 (UTC).

The mole makes a convenient standard in that it also allows for one to relate atomic mass units (aka Daltons) to grams, in that 1 dalton-mole = 1 gram. (or 1 gram/mole = 1 dalton) The importance of Avogadro's number is that it is basically the number of particles that will allow that conversion to occur. In a very approximate sense, one mole of nucleons (protons or neutrons) weighs one gram, which is why the mole is so useful as a measure of amount. Specifically, to standardize the mole (since protons and neutrons don't have the same mass, and the mass of a nucleus is also not exactly the total mass of the individual nucleons due to mass-energy equivilances) we use the standard that exactly 12 grams of Carbon-12 contains exactly one mole of atoms. Yes, there are other hypothetical numbers which may be somewhat useful in counting particles in other applications, but the usefulness of Avogadro's number makes it a far more ideal number if you have to pick just one for the SI system. --Jayron32 06:07, 15 June 2010 (UTC)

Thank you for the explanation. I do not find it satisfactory however. The idea behind standardization of units is to clean up the mess, such that there is only one standard unit for each kind of quantity. But there are two SI units for amount of substance: the joule per kelvin and the mole, connected by a conversion factor R. One mole equals 8.31447 J/K. An ideal gas at p pascal and T kelvin contains p/T joule per kelvin per cubic meter. There are (1/k=) 7.24296×10²² molecules in a J/K. The dalton is not an SI unit for mass, and I still do not understand why the mole redundantly has been made an SI unit for amount of substance. Each extra unit gives rise to tiresome conversion factors and blocks the understanding of the subject matter. Bo Jacoby (talk) 09:19, 15 June 2010 (UTC).

You know that R=Lk (where k is the boltzmann constant) ..

• L has clear meaning, and is directly measurable, though somwhat abitrary (12g of Carbon?)
• R appears to be an experimental constant

... clearly there's a relationship between R and k

The origins of k are somewhat hairy to say the least, but if you have already got k , then you can derive R

I think the reason is that constants need to be abitrary rather than experimental (though k is experimental as far as I know it's obtained from a broader range of experiments and is not necessarily dependeant on L); if the value of k can be 'explained' then the situation changes.87.102.18.94 (talk) 10:27, 15 June 2010 (UTC)

The whole point of SI unit is to provide for the most accurate standards of measurements using currently available technology. It turns out that in practice we cannot use many of the fundamental physics relations/identities to do accurate measurements. So, we have ended up with quite a few "redundant" units. Defining the mole to be some precise number and thus effectively removing it from the SI sysem would amount to redefining the Kilogram, but this will only be done if this makes measurements of mass more accurate.

Compare this to the redefinition of the meter in terms of the second. Einstein could have suggested getting rid of the stupid factors of c and measure distances and time intervals in the same units in 1905, but it was only in the 1980s that this was also better from an experimental point of view. Count Iblis (talk) 23:32, 15 June 2010 (UTC)

Old medical terms

Partial question copied from WP:VPP by Gwinva (talk) 08:52, 14 June 2010 (UTC)

"I recently watched the old movie "Bell, Book and Candle" with Jimmy Stewart. In that movie there is a sign outside an herb shop listing various conditions that can be treated by the herbs. These names (as used in that time) were obviously common knowledge at the time (why else would they be used on public signage?) but some of them have fallen out of common usage or been replaced by more precise terminology. I wanted to know what diseases they meant so I went to Wikipedia and found very few answers. Here are the names I did not know, of which only two were actually helpful:

• Milk Leg <-- [redirects]
• Blood Disease <-- What medical conditions did this commonly refer to back then?
• Whites <-- I found no medical use of this term.
• Spleen Trouble <-- ?
• Catarrh <-- This is still called by the same name so this was just a word I didn't know.
• Hollow heels <-- ?
• Wobbles <-- I could only find an animal disease for this name. Was there a human one?
• Thrumps <-- ?

66.102.204.25 (talk) 08:02, 14 June 2010 (UTC)

• Whites = Leucorrhea. DuncanHill (talk) 08:53, 14 June 2010 (UTC)

You might do better on the language desk. I'm pretty sure that wobbles will be a folk term for movement disorders such as Parkinson's disease.--Shantavira|^{feed me} 09:17, 14 June 2010 (UTC)

Wobbles might be an abbreviation for collywobbles. Mitch Ames (talk) 12:23, 14 June 2010 (UTC)

It's possible that they are fictional diseases meant to parody outlandish patent medicine-style claims to cure anything. Nimur (talk) 14:44, 14 June 2010 (UTC)

It's also possible they were words used in that particular district and nowhere else. In the UK, many dialects have their own words for medical conditions and parts of the body. This page gives an example from close to my home patch: Staffordshire medical dialect --TammyMoet (talk) 15:20, 14 June 2010 (UTC)

These were in a mainstream film contemporary to circa 1958 New York City. At best the terms might have been "quaint" for that era but certainly would not have been obscure to the film's audience. 66.102.204.25 (talk) 18:49, 14 June 2010 (UTC)

• Hollow heels in humans - see Pes cavus. Could it also means something horse-related? Those old west drugstores would bunch human, horse and cattle ailments together, wouldn't they? East of Borschov (talk) 19:11, 14 June 2010 (UTC)

Very doubful it is a horse issue as this was set in 1958 Greenwich Village NYC, NY. :) 66.102.204.25 (talk) 19:18, 14 June 2010 (UTC)

Doubtful indeed :)) Good catch, I had to check the film article first. East of Borschov (talk) 19:28, 14 June 2010 (UTC)

• A complicating factor for figuring out modern names for historic diseases is a tendency for multiple diseases to be lumped together under their major symptom. For example, pancreatic cancer, appendicitis, kidney stones, and ovarian torsion might all be covered by the local name for "severe abdominal pain". --Carnildo (talk) 00:49, 16 June 2010 (UTC)

Understood. As an encyclopedia however we ought to be able to provide readers with some useful information even if it is to that effect. Perhaps a dab-type article that says "The term blood disease was used in the early half of 20th century America to ambiguously refer to one of the following conditions: ...". I would suspect on these there might be various medical writeups (perhaps from medical schools?) from the era that could support these facts. 66.102.198.18 (talk) 18:41, 16 June 2010 (UTC)

"Blood disease" and "Spleen trouble" are probably holdovers from humorism (which was still active in scientific medicine into the 19th century, and in folk medicine a good bit longer), and might refer to any of an assortment of conditions (from anemia to fevers to stress in the first case, and from dyspepsia to ulcers to insomnia or irritability in the second). --Ludwigs2 19:01, 16 June 2010 (UTC)

why water form fountain as it goes up?

Answer: water follows a parabolic trajectory

Try this(if u had never tried before): while watering tour garden hold pipe in such away that its mouth is towards sky(or just perpendicular to ground). Water coming out of the pipe will make fountain, it gets spread.

Now hold pipe's mouth towards the ground, u will notice that water gets stream lined as it falls. It makes a cone like structure whose base is mouth of pipe.

The Question Is

Why does this happen? Why not water forms fountain while falling and why not it becomes streamlined while going upwards? -IIT question [--Myownid420 (talk) 09:23, 14 June 2010 (UTC)]

When you point the hose up, the water coming down falls onto the water going up and they scatter each other. This doesn't happen when you point down since the water is all going in the same direction. Staecker (talk) 11:52, 14 June 2010 (UTC)

Water should stay in Laminar flow rather than turbulent flow regardless of whether the hose is pointing up or down (unless you tweak the nozzle when it is travelling upwards). The key variable is how long it stays in laminar flow whilst travelling upwards, primarily as a result of gravity overcoming the upwards force exerted when the water leaves the hose.FramingArmageddon (talk) 12:06, 14 June 2010 (UTC)

Yes, and having two streams of water intersect each other is a sure-fire way to create turbulence, meaning water goes every which way. One stream going up and another falling back down into it matches the bill, nicely. StuRat (talk) 16:58, 14 June 2010 (UTC)

If the droplets of water in the stream did not interact with each other, each one would follow a trajectory that traces part of a parabola, as shown in the picture. Just think about what happens to droplets that start upward along slightly different parabolas, as opposed to starting downward on slightly different parabolas. The upward-oriented ones give a lot more divergence. Looie496 (talk) 19:20, 14 June 2010 (UTC)

(Interesting question!!) The previous answers are excellent - I'd just add that for a given nozzle velocity, the water takes longer to reach the ground when it's aimed upwards than downwards - so any divergent effect will be greatly increased just because the droplets have more time to spread apart. But this is just a contributory factor - I think the previous answers are 90% of the reason. SteveBaker (talk) 00:00, 15 June 2010 (UTC)

Assuming a circular cross section of the water jet, the radius $\scriptstyle r$ will increase upwards as the velocity $\scriptstyle v$ decreases. $\scriptstyle \pi r^{2}v$ is the constant rate of flow of water $\scriptstyle =\pi r_{0}^{2}v_{0}$ where $\scriptstyle r_{0}$ is the radius of the pipe and and $\scriptstyle v_{0}$ is the initial velocity of the water. So $\scriptstyle r=r_{0}{\sqrt {\frac {v_{0}}{v}}}.$ The velocity relates to the height above the mouth of the pipe, $\scriptstyle h$ , by the energy conservation law $\scriptstyle gh+{\frac {v^{2}}{2}}={\frac {v_{0}^{2}}{2}}$ where $\scriptstyle g$ is the gravitational acceleration. So $\scriptstyle v={\sqrt {v_{0}^{2}-2gh}}$ , and $\scriptstyle r=r_{0}{\sqrt {\frac {v_{0}}{\sqrt {v_{0}^{2}-2gh}}}}=r_{0}{\sqrt[{4}]{\frac {v_{0}^{2}}{v_{0}^{2}-2gh}}}.$ The denominator becomes zero, and so the radius of the water jet becomes infinite, at $\scriptstyle h_{\max }={\frac {v_{0}^{2}}{2g}}.$ This marks a breakdown of the assumption that the cross section of the water jet is circular. The water splits into drops when accelerated outwards. It has nothing to do with turbulence. See surface tension. Bo Jacoby (talk) 10:10, 15 June 2010 (UTC).

B₂O₃

how do I get [[B₂O₃]] from Borax ?--אנונימי גבר (talk) 11:26, 14 June 2010 (UTC)

React the borax with hydrochloric acid until you have a slightly acidic pH. Boil the solution of boric acid and sodium chloride produced and cool. The boric acid should precipitate. Heat the boric acid crystals strongly with a blowtorch. They will dehydrate, leaving amorphous boron trioxide. --Chemicalinterest (talk) 12:56, 14 June 2010 (UTC)

Sliver nano

How can we produce a Siliver (Ag) nanoscale fibers (fiber diameter of less than 20 times that of a human hair)--אנונימי גבר (talk) 11:36, 14 June 2010 (UTC)

The article Silver nanoparticles refers to nanoscale particles rather than fibres, along with some production methods although I'm not sure if you were specfically after fibres, rather than particles. FramingArmageddon (talk) 12:08, 14 June 2010 (UTC)

http://www.google.co.uk/search?hl=en&q=nanowire+ag&cts=1276644607250&aq=f&aqi=&aql=&oq=&gs_rfai= this search turns up a few methods. 87.102.18.94 (talk) 23:31, 15 June 2010 (UTC)

(Cr - Pt)

• You can separate chromium from chromium alloy - Platinum (Cr - Pt) How?
  

I think you should give this alloy into a powerful disinfectant, then Platium (Pt) acts as a positive, Chromium (Cr) serves as the cathode (dissolves), then separated chromium salt!

• [Currently, I do not know what the appropriate reagents for reaction!]
  

--אנונימי גבר (talk) 11:57, 14 June 2010 (UTC)

I am not wealthy so I do not have platinum. If I wanted to separate that, I would use a nonoxidizing acid such as hydrochloric acid. The chromium would dissolve, leaving the platinum behind.

I'm sorry, but a disinfectant is used to kill bacteria and viruses, not to separate metal alloys. --Chemicalinterest (talk) 13:00, 14 June 2010 (UTC)

I think he was talking about oxidants, which he somehow confused with disinfectants. John Riemann Soong (talk) 22:04, 15 June 2010 (UTC)

A good way to separate is by electrorefining. Make the alloy the positive terminal, use a dilute acid solution, chromium should be deposited at the negative terminal, with Pt separating out as a solid.

Chemical alternatives include dissolving both, and selectively precipitating one or the other from the solution. Both elemental articles give selective methods for precipitating the elemental ions from solutions.87.102.18.94 (talk) 12:49, 15 June 2010 (UTC)

Relativity

Sir, I am a Higher secondary student.i am very interested in highly advanced theories of physics sush as relativity,Black holes,Galaxies,Time,General relativity etc.I have already referred many articles on Wikipedia but the problem is that every article contains many complex terms which are very difficult for me to understand.Please suggest an article or a website that would help me understand the basic concepts. —Preceding unsigned comment added by Vishnuthelegend (talk • contribs) 11:58, 14 June 2010 (UTC) Changed layout of question. Cuddlyable3 (talk) 12:21, 14 June 2010 (UTC)

Articles on advanced physics assume that the reader know about elementary physics. You cannot really understand Einstein before you understand Newton and Maxwell. Bo Jacoby (talk) 12:56, 14 June 2010 (UTC).

Try plain old physics. --Chemicalinterest (talk) 13:02, 14 June 2010 (UTC)

Try here: http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html Ariel. (talk) 00:29, 15 June 2010 (UTC)

C L I

Is there any way one can fool Caller Line Identification on the landline or mobile phone ? —Preceding unsigned comment added by Jon Ascton (talk • contribs)

From the article you linked to: Most service providers however, allow the caller to block caller ID presentation through the vertical service code *67. --Dismas|^(talk) 13:48, 14 June 2010 (UTC)

Yeah, that's what I am asking - if the service provider does not allow such facility. Is there some software or hardware hacking type trick one can do ? —Preceding unsigned comment added by Jon Ascton (talk • contribs)

We have an article all about this: Caller ID spoofing. SteveBaker (talk) 23:54, 14 June 2010 (UTC)

I know about the article, but what I want is some practical straight forward and fool-proof easy way that one can actually do !—Preceding unsigned comment added by Jon Ascton (talk • contribs)

Is it just me or are you being deliberately confusing? In your first post you asked for a method of "fool" caller ID, so I gave you a way to block it. Then you added an additional requirement, which wasn't in your original question, about what happens if the carrier doesn't allow for *67. And you asked for some software or hardware suggestions. Those are spelled out at the article that SteveBaker pointed out to you. Now you tell us that you already read that article and, for whatever reason, those solutions still don't work for you. So, what about the options in the caller ID spoofing is it that you don't care for? Dismas|^(talk) 04:37, 15 June 2010 (UTC)

The web page below needs to be updated with the correct new information regarding the list of SVHC's.

Substance of very high concern

Please update the web page with the most current list of SVHC's. Thanks Rick Morrison —Preceding unsigned comment added by 63.97.59.73 (talk) 13:42, 14 June 2010 (UTC)

I have copied this non-question to the discussion page of said article. Caesar's Daddy (talk) 13:51, 14 June 2010 (UTC)

Noted on behalf on WP:CHEMS, it's on my list of things to do in the morning. Physchim62 (talk) 23:24, 14 June 2010 (UTC)

 Done Physchim62 (talk) 09:44, 15 June 2010 (UTC)

How does pre-birth gender selection work?

I read someplace that nowadays, parents are able to choose the gender of their unborn child. How does that work? More importantly, how much does it cost? Since it's most likely too expensive in the US, in what countries could it be done for the lowest prices? --Let Us Update Wikipedia: Dusty Articles 14:19, 14 June 2010 (UTC)

Another important question is "is it legal?". In many countries, it isn't. Sex selection answers that, and how it works. You can probably find costs by googling. --Tango (talk) 14:50, 14 June 2010 (UTC)

Looks like it is legal, here is a clinic offering such a procedure in the US. Price is stated as around $18K. Link. Regards, --—Cyclonenim | Chat  17:05, 14 June 2010 (UTC)

It is legal in the US. It isn't elsewhere, eg. most of Europe, China, India, etc.. --Tango (talk) 23:19, 14 June 2010 (UTC)

There are two different things to discuss here: There are many (fairly cheap) techniques that can bias the probability of you getting a male or a female child - simple things like subtle pH variations at the moment of conception can change the statistics. But to absolutely guarantee a male or a female child is more likely to require serious medical intervention - which is much more ethically difficult (eg you might test the sex of the fetus and abort when the gender is not what you want - that is practiced (often illegally) in several places in the world) - or perhaps much more costly (eg in-vitro fertilization). SteveBaker (talk) 23:48, 14 June 2010 (UTC)

So what other countries is it legal in, where anyone would perform it for a far lower price than in the US? --Let Us Update Wikipedia: Dusty Articles 11:32, 15 June 2010 (UTC)

Birdsong Study

In one of Roger Penrose's lectures (video here: http://www.youtube.com/watch?v=f477FnTe1M0 , part in question at 1:12), Penrose talks about some studies done on birdsongs. The studies supposedly had humans give an aesthetic rating the songs of male birds that were then followed in order to determine their reproductive success, and whether it had any statistical correlation with the humans' ratings.

Does anyone know this study (or these studies)? I'd appreciate a citation or journal link! Inasilentway (talk) 14:34, 14 June 2010 (UTC)

Some good links (including studies) on this Google search. Not sure if it's helpful, but it's a start. Regards, --—Cyclonenim | Chat  17:02, 14 June 2010 (UTC)

How hot am I ?

I've noticed that I can't accurately judge if I'm hot or not. I certainly can tell if objects are hot, and if the air is hot, and if my forehead is hotter than my hand, but the only method I have to tell if I am overheating is if I'm covered in sweat. (The sweating means that my body is able to tell that it's hot, even if I can't.) This system doesn't work when in a hot tub, and the first sign I have that I'm getting hot is that I become listless and find it hard to breath enough air. So, am I unusual or does everybody lack an ability to judge their own temperature accurately ? StuRat (talk) 17:27, 14 June 2010 (UTC)

You're normal (well, as normal as a Wikipedian can be! ;)). Thermoception is relative. All it can do is tell you if something in contact with your skin is hotter than your skin or colder than it (and how much so). You can compare your symptoms in a hot tub with Hyperthermia#Signs and symptoms. An added complication is that the symptoms of hyperthermia are quite different to the symptoms of fever, despite both involving your body temperature being above normal (the cause is very different). --Tango (talk) 17:46, 14 June 2010 (UTC)

Funnily when I was working in West Africa and contracted Plasmodium falciparum Malaria the first inkling (and immediate self diagnosis) was turning off the aircon and switching on the heating in a car parked in full sun with an outside temp of 37C. I found myself wondering why I had never switched the heating knob in the car before and then it sunk in. With a core temperature steaming upwards the car seemed cold and I was shivering. --BozMo talk 18:09, 14 June 2010 (UTC)

A simple answer is that your sweat is cooling you down so you don't feel hot. If you feel hot that means your cooling mechanism (sweating) is malfunctioning or overpowered. --Chemicalinterest (talk) 18:28, 14 June 2010 (UTC)

Sweat doesn't work in a hot tub. Obviously sweat on those parts of your body that are underwater can't evaporate, and sweat on the rest of your body won't evaporate much because the air around you will be very humid. --Tango (talk) 19:07, 14 June 2010 (UTC)

There are medical issues that inhibit the brain's ability to sense if the body is hot or cold. As this is a medical issue, I will not make any attempt to diagnose this problem. However, I feel that it is important to point out that this (and pretty much any "Am I normal" question) is asking for a diagnosis of normality. -- kainaw™ 19:14, 14 June 2010 (UTC)

Medical issues aside - mostly the reason we can't tell whether we're hot or cold is because body temperature is well regulated. You can feel whether you are gaining or losing heat to the environment (which is how you know whether the air is hot or cold) - but it's likely that your core temperature is close to whatever is normal for you in all but fairly extreme circumstances. When the environment overpowers your thermoregulation system, you're already in some distress - and you feel the symptoms of that. Your hot tub experience is obviously a case like that. SteveBaker (talk) 23:42, 14 June 2010 (UTC)

Reminds me of a Dilbert in which the boss wakes up and, to his surprise, finds that his underwear, coffee mug and desk are all clammy -- finally, Dilbert suggests that maybe his hands are clammy. I forgot the rest. DRosenbach ^{(Talk | Contribs)} 12:00, 15 June 2010 (UTC)

Sweathog

Thanks. To follow up, if I can't tell when I'm getting hot, how does my body know when to sweat ? StuRat (talk) 15:24, 16 June 2010 (UTC)

Explosion

In a powerful explosion, how long is there between when the explosive detonates and you die? --76.77.139.243 (talk) 19:20, 14 June 2010 (UTC)

At the risk of stating the bleedin' obvious, it depends on the relative positions of the explosive and your body. Even a low power explosive could kill you instantly depeif it goes off on your head or chest. --TammyMoet (talk) 19:29, 14 June 2010 (UTC)

It depends on the time the ₎)) shock wave takes to hit you. Once it hits, then you die. --Chemicalinterest (talk) 19:45, 14 June 2010 (UTC)

People have been blown to a red mist and tiny bits by an explosion. Death is in milliseconds. At the other extreme, someone might be fatally injured by an explosion but linger for any long period before succumbing to the effects, which might include, for instance,sever and ultimately fatal burns, being in a persistant vegitative state, or paralysis leading to fatal complications a long time after. Edison (talk) 20:13, 14 June 2010 (UTC)

As Chemicalinterest says, it depends how far away you are. My grandparents all survived the nuclear bombings of Hiroshima and Nagasaki quite easily, because they were in the eastern USA when it happened. Nyttend (talk) 05:51, 15 June 2010 (UTC)

Shock wave in air travels at several hundred meters per second (more than a speed of sound but less than a thermodynamic limit, which for an ideal gas is 4 times the speed of sound). Fragments from the explosion may travel faster than the shock wave and further than the shock wave. Divide the distance (in meters) from you to the explosion by roughly 1000 m/s, and you will get the order-of-magnitude time (in seconds) before you get hit. (Order of magnitude means that the estimate may well be wrong by a factor of 2 or 3 either way). How long you stay alive after getting hit depends on the nature of your injuries, as Edison explained above. Massive brain injury may be considered instant; anything else may take a few seconds or a few years to take effect. --Dr Dima (talk) 20:33, 14 June 2010 (UTC)

My father survived a direct impact of a bomb in World War 2 - it hit his house. Dad himself had taken shelter under the stairs. He died 64 years later. So this is a bit of an unanswerable question.--TammyMoet (talk) 09:42, 15 June 2010 (UTC)

That must have been a spectacularly slow bomb! – ClockworkSoul 02:51, 16 June 2010 (UTC)

soy

are the estrogen's in soy; fat or water soluble ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 23:02, 14 June 2010 (UTC)

Well, [1] says: "Phytoestrogens are estrogens contained in plants. They have a chemical structure similar to the human hormone estrogen. They have a weak estrogen effect when eaten. The most commonly studied are the isoflavones...". Our articles on Phytoestrogens and isoflavones have much additional information...but I couldn't see any direct statement about solubility. I guess we'll have to wait for one of our expert chemists to swing by with an answer. SteveBaker (talk) 23:34, 14 June 2010 (UTC)

Natural estrogens are fat-soluble, as are pretty much all natural steroids. Physchim62 (talk) 00:18, 15 June 2010 (UTC)

so does soybean oil contain estrogen's ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 20:42, 15 June 2010 (UTC)

Yes, see this. 86.7.19.159 (talk) 21:20, 18 June 2010 (UTC)

Definition of Horology???

I was looking at the Horology article and found it to be inconsistent, horology is defined as "the art or science of measuring time.", but then only talk about mechanical clocks and watches. To me this seams rather much like an article on transportation only discussing different kinds of bags, no ships, trains,trucks and so on.

Is horology only the study of historical/mechanical watches and clocks or does it include modern electronic clocks, GPS-clock synchronization, atomic clocks, astronomical observations of for example radio pulsars and so on??? Gr8xoz (talk) 23:10, 14 June 2010 (UTC)

Wiktionary (and several other dictionaries that I looked at) says: Horology: The art, science and technology of timekeeping and timekeepers, such as clocks, watches and sundials. - which certainly includes modern stuff like digital clocks. However, I would bet good money that almost all actual, practicing horologists are really only interested in mechanical clocks and sundials. The people who care about modern electronic/atomic timekeeping are in the fields of electronics and physics. That being the case, I think our article does a reasonable job of covering the practical nature of horology. Remember - the article isn't about clocks themselves. It's about the nature of the study of clocks. I agree though that we could at least mention more modern timepieces - IF we can find some reference to that kind of thing in a horology journal or whatever. At any rate, this discussion should really be held on the Talk:Horology page, not here on the reference desk - but I see you've already added a comment there with no response. I think you should go to Wikipedia_talk:WikiProject_Time. Of course if you feel strongly about this - you can always fix the article yourself...but I strongly encourage you to provide references for any statements you include. SteveBaker (talk) 23:24, 14 June 2010 (UTC)

The modern and precise measurement of time (eg, "atomic clocks") is usually seen as a subbranch of metrology, because it affects and depends on many other areas of physics. The one exception might be the network of observatories which keeps UTC in time with the Earth's (slightly irregular) rotation, but I would bet that they consider themselves astronomers and not horologists: horologists are people who can actually make a working clock or watch, and deserve every respect for that skill! Physchim62 (talk) 00:27, 15 June 2010 (UTC)

Again, I agree that's what practicing horologists actually do - but that's not what the word means. Also, your interpretation would include people who fabricate atomic clocks, digital watches or crystal oscillators for computers - which is not what people who'd describe themselves as horologists actually do - nor is "horology" what people who make such things describe what they are doing. What we have here is a disconnect between what dictionaries say the word means - and it's actual modern day usage. This is not an uncommon problem because dictionaries tend to lag decades behind changes in usage. SteveBaker (talk) 11:43, 15 June 2010 (UTC)

June 15

Help resolve date discrepancy of an event by finding contemporaneous citation(s)

Regarding the article Rüppell's Vulture -

This bird is considered to be the world's highest flying based on examination of feathers found in a jet engine that collided with a bird over Abidjan, Cote d'Ivoire at an altitude of 11,000m on November 29, 1973 -OR- the same date in 1975.

The source cited in article (Flight Migration by Alerstam) states 1973, however a web search finds other reliable sources quote that the event happened in 1975, an example being [[2]]. A google search doesn't particularly favor one year over the other - both dates show up frequently in a search.

To resolve the discrepancy I have tried to find an article published in 1973, 1974, 1975 or 1976 that references this event so I can establish the correct year.

I have searched the online archives at flightglobal.com and newyorktimes.com looking for any articles published from 1973 to 1976 that include the word "vulture" or "cote d'ivoire" and did not find any articles that reference the event.

I have not been able to turn up any references to the particulars of the aircraft involved (military? civilian? private? commercial? airline? flight number?...) but have assumed that the following is probably accurate:

• The aircraft was jet powered
• Event happened on November 29th
• Event happened in 1973 -or- 1975
• Event happened over Abidjan, Cote d'Ivoire
• Event happened at or around 11,000m (36,100 ft) or 37,000 ft altitude

I do not have easy access to printed archives of potentially relevant scientific journals, nor do I even know which journals would be relevant. I am not associated with a university/company that might give me "free" access to online versions of scientific journals via an organizational subscription.

If you can turn up a relevant, authoritative citation that is contemporaneous to the event, please either cite it here so I can update the article or edit the article adding the exact date and citation. Obviously if we find something published in 73 or 74 the 1975 date can't be correct, plus I'm hoping that any article contemporaneous to the event will simply state the date it happened, resolving the discrepancy without question.

I'm also willing to do more work myself, but I need the ornithology and/or aviation and/or reference experts to give me some ideas on where to look next.

Thanks. Ch Th Jo (talk) 00:48, 15 June 2010 (UTC)

(I edited this to provide more information.)

Usually Google Scholar gives better results for things like this than Google Web. I was able pretty quickly to find that the original source everybody cites is Collision between a vulture and an aircraft at an altitude of 37,000 feet, R. C. Laybourne, The Wilson Bulletin, Wilson Ornithological Society, 1974. Looie496 (talk) 03:20, 15 June 2010 (UTC)

Thanks, that's perfect. Before now I wasn't aware of Google Scholar, so thanks for that as well. Ch Th Jo (talk) 18:25, 15 June 2010 (UTC)

laxatives

Hi All. First, let me be clear that this is in no way a medical question! I was reading a trivia book and there was a story about an inmate wo used large amounts of laxatives to get skinny enough to squeeze (barey) through the bars and escape (he was caught later). My question is: what are the health risks of using large dosages of laxatives in order to "slim down?" 99.250.117.26 (talk) 01:42, 15 June 2010 (UTC)

This certianly sounds like a medical question... See the article Laxatives#Problems_with_use. The more pressing question is that how the inmate obtained large amouts of laxatives needed, and how he got through the bars which go both up and down and left to right ;) 01:47, 15 June 2010 (UTC) —Preceding unsigned comment added by 76.229.161.119 (talk)

side effects would be extreme dehydration, electrolyte imbalance, cramping... Fragrantforever —Preceding unsigned comment added by Fragrantforever (talk • contribs) 05:42, 15 June 2010 (UTC)

At the risk of stating the bleedin' obvious, we have a diarrhea article. Vimescarrot (talk) 06:02, 15 June 2010 (UTC)

Anorexia and Bulimia might have some info you'd find relevant. 63.17.59.215 (talk) 11:29, 15 June 2010 (UTC)

I'd be surprised that they'd put the bars far enough apart to allow your head to get through - and no amount of laxatives are going to shrink the size of your skull. The problem with trivia books is that they have a lot of incentive to include amazing "facts" and almost zero incentive to check that they are actually true - they are the biggest purveyors of untruth outside of the Internet! If it actually happened that way - there ought to be more sources backing it up. SteveBaker (talk) 11:53, 15 June 2010 (UTC)

Oddly enough this is reported by what might be classed as reliable sources; Google for /robert cole laxative/ for example and you'll see mentions in The Guardian and New Statesman. Of course, maybe these are just passing on trivia, but this appears to be a reliable secondary source. Tonywalton ^Talk 12:09, 15 June 2010 (UTC)

Digital Camera

If one wants to buy a digital camera, how much mega-pixel is ideal ? —Preceding unsigned comment added by Jon Ascton (talk • contribs)

If you just want to view images on your computer, 2 or 3 megapixels is fine. If you want to generate large images for printing or reproduction in magazines, then you need as high as possible. ~Amatulić (talk) 04:55, 15 June 2010 (UTC)

The chances are that any camera currently on the market will have more pixels than you need. See The Megapixel Myth (compare megahertz myth). There are a lot of other features that differentiate point-and-shoot cameras. For example, some do better in low-light conditions than others; some have better flash illumination; some have optical viewfinders while others don't; some let you control the exposure time and aperture, while others don't; some can take wider angle photos than others; some have tiltable LCD screens; some have better lenses, and some just plain take better looking pictures. Sites like dpreview.com can help you compare picture quality and features of different models. -- BenRG (talk) 05:17, 15 June 2010 (UTC)

Agree with the others, megapixels are largely irrelevant over 8-10MP unless you're wanting to make large scale prints of your photographs (I'm talking exhibition-size prints). Most cameras on the market offer this amount of megapixels because it sounds impressive even if you just want to do some photos at a friend's wedding. There are many other factors that are more important, especially with single lens reflex (SLR) cameras, most importantly of which are the speed of the lenses/apertures, ISO, noise reduction etc. Regards, --—Cyclonenim | Chat  10:01, 15 June 2010 (UTC)

I'll second the above, except I'll suggest that the "largely irrelevant" threshold is even lower. 5-6 MP, on a camera with a good lens, is more than sufficient for general use. I've blown up pictures from my 6 MP camera to 30"x20" with excellent results. If you're not going to print stuff larger than 8"x10", you can go even lower -- 3-4 MP would be fine. And as Cyclonenim noted, at this point, every new camera with a decent lens will be at this point or higher. You might want to check various consumer magazines; I'd expect that Consumer Reports (among others) has done several digital camera evaluations. — Lomn 13:10, 15 June 2010 (UTC)

You want to leave some room for people to crop and use the so called "Digital zoom". APL (talk) 14:21, 15 June 2010 (UTC)

However, CCD chips come in limited sizes. Within a given class of cameras, more pixels usually means smaller pixels, which means more thermal noise. So you may get a higher nominal resolution, but more details will be lost in the noise, and the image will look washed-out. 5 megapixels used to be the sweet spot when I looked a while back. --Stephan Schulz (talk) 14:58, 15 June 2010 (UTC)

Nobody has mentioned battery life! This is one of the the most differentiating parameters left between otherwise "equivalent" performance cameras. If this factor is important, consider the negative impact of a larger sensor, LCD screen, and more powerful processor that often go along with "high-end" cameras. This is a parameter which can vary widely between different vendors. Nimur (talk) 14:58, 15 June 2010 (UTC)

Nanostructure induced flavorings

Reading the taste and taste bud articles didn't really help answer something I've been wondering about for a long time:

Is it possible for a surface to have a microstructure (nanostructure?) at the molecular level that interacts with and stimulates taste receptors? Chemically, I guess it would be like a catalyst, that doesn't actually react with anything but instead aids in a reaction.

Such a surface would have a permanent flavor, wouldn't it? Is it feasible? ~Amatulić (talk) 04:55, 15 June 2010 (UTC)

Not really. As our article on taste buds points out, taste is generated by flavour components which are dissolved in saliva, so your nanostructured surface wouldn't get to the receptors it needs to, even if it were capable of stimulating those receptors (which isn't certain itself). In addition, much of our experience of flavour comes not from the taste buds but from smell receptors in the back of the nose – flavour is a combination of taste and smell, which is why food tastes bland when you have a cold. Obviously your surface would be volatile, and so could stimulate the smell receptors. Physchim62 (talk) 10:01, 15 June 2010 (UTC)

Moreover, taste receptors are not really on the tongue surface as much as they are on the surfaces of the taste buds, and that would even more specifically be on the lateral walls of the very small projections you may be able to see on your tongue. It would be pretty difficult to get a surface to match up with these receptors to produce the taste you'd be looking for. And Physchim62's mention of olfactory involvement is right on -- so little of "taste" is actually taste. But assuming you'd be going for a purely sweet taste (incorporating no odor, let's say), You'd have to get your nanostructure to act as ligands to the taste receptors. That's like asking for an inert nanosurface to be able to excite a muscle by reacting with the acetylcholine receptors of the neuromuscular junction -- highly unlikely. You's be able to do it with a liquid medium, and I actually do this every morning. I call it Snapple :) DRosenbach ^{(Talk | Contribs)} 12:27, 15 June 2010 (UTC)

OK, thanks. I'm not convinced of two things: (1) that the components need to be dissolved in saliva, as I can taste things that don't seem to be soluble (certain oils, nonpolar solvents, etc.) - I guess it's sufficient to be liquid; (2) that a sense of smell is needed, unless I have olfactory receptors in my mouth (my nose really doesn't work for smelling). As DRosenbach pointed out, some sweet substances have no odor.

I think what I'm really curious about is whether there are any solid substances that would have a permanent flavor without actually dissolving. Nanostructure was one possibility I thought of, but there may be a way to stimulate taste receptors chemically without actually modifying the phase of the stimulant. ~Amatulić (talk) 21:29, 15 June 2010 (UTC)

Blackberry Vs I Phone

We are big fans of the I Phone and we have been using the I Phone since its launch with very satisfying results. Initially we had the 2G 16 gb version which still works like a dream and we also have a 3G and the latest 3GS model. The I Phone 4 hasnt launched here and Im sure it would be part of our family soon.

My husband and I were talking to a friend yesterday over coffee and he was raving about his Blackberry and he said the blackberry can do several things the I Phone cant even imagine:)))

I didnt retort but I thought let me ask this question to my friends here on Wikiepedia who have a scientific bend of mind.

This question is not about personal likes and dislikes. I want to scientifically compare these two phones. When I googled it, the search results only speak about the virtues of one or the other. I would like a feature by feature comparison or a point by point comparison.

My Question is : I Phone Vs the Blackberry - what are your thoughts, ease of operation, aesthetic looks, functions, pricing - what are the plus points and negetives of these phones.

Pls feel free to give your feedback. Fragrantforever 05:39, 15 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

For a 'scientific' comparison of the phones, the best thing to do would be to try to find the manual or description of features on the appropriate manufacturers' websites. As for opinions on aesthetic looks, pricing etc, these things are probably better sought on an internet forum (either a couple of neutral ones, or one that seems pro-iPhone and one that seems pro-Blackberry to play them off against each other) rather than a reference desk. Bear in mind that the iPhone 4 was announced only a few days ago so a lot of old comparison articles are out of date. Brammers (talk/c) 08:18, 15 June 2010 (UTC)

In Japan it's apparently very common for people to pick a phone based on features - they compare a checklist and whichever one has more wins - even if they never use those features. It results in phones packed with everything, and yet totally unusable. See this article about it. So it's impossible to compare a phone that way. Compare a phone based on what YOU will use it for. Now obviously there could be features that you would like but are not aware are possible. But just straight comparing features will give you information - but not useful information. Ariel. (talk) 09:04, 15 June 2010 (UTC)

Broadly it depends what you're wanting to do with it, I've not seen any scientific comparisons, but a number in sites like Lifehacker and Really Mobile do user comparisons. As the iPhone is increasingly being seen as an enterprise business phone it's being competed against the Blackberry but the majority of comparisons that I've seen don't include Blackberry as it's a very different device.

It's worth looking at the heritage, the Blackberry grew from a need to have a handheld email device and it's developed from that basis. The iPhone is designed first and foremost as a handheld computer.

I would suggest that you need to do your own comparison from the available information, run Blackberry, iPhone, Android and WebOS against one another.

Of course Ease of Use and aesthetics are both qualitative not quantitative so not particularly scientific measures.

By way of providing a baseline my company has recently made a decision about a new phone deployment for all of our consultants. We compared Blackberry, WebOS, Android and iPhone, opting for the iPhone as the most appropriate for our needs given the cost options that were on the table from our supplier. Blackberry is quite an old fashioned device in comparison to the other three.

ALR (talk) 10:38, 16 June 2010 (UTC)

My wife has an iPhone. She loves it, but doesn't like the fact that she can't use YouTube or most other video sites because they use Flash video, which Steve Jobs is allergic to. According to our article, the Blackberry has had Flash capability since Nov, 2009, so that would seem to be a huge plus for anyone who likes watching streaming videos. Matt Deres (talk) 16:18, 16 June 2010 (UTC)

The YouTube player is part of the standard package.

ALR (talk) 21:38, 16 June 2010 (UTC)

meringue food technology

Unsatisfied with meringue bases bought from a local store (and the squirty cream can) and wishing to emulate the excellent meringue from a village store further down the road (even the big stores don't seem to make them) I stirred two egg whites, a bit of sodium bicarbonate,cornflour and masses of castor and granulated sugar until it became semi-solid, and then put it in my fan oven for two and a half hours at 100 C. The result was like a bland lump of concrete, and I don't know where the sweet flavour of all that sugar went. Do the good meringues use microwave cooking, or is there some other secret? —Preceding unsigned comment added by 80.1.88.16 (talk) 08:52, 15 June 2010 (UTC)

Castor as in Castor oil? Why would you put that in? Also, I wouldn't put in any sodium bicarbonate, add a little cream of tartar and give it some extra whipping time for fluffiness. But in general I would start with a known working recipe, then experiment from there. Ariel. (talk) 08:59, 15 June 2010 (UTC)

The OP undoubtably means castor sugar (also spelled caster), a very fine-grained suger used in cooking, and mentioned somewhere in the Sucrose article. 87.81.230.195 (talk) 09:13, 15 June 2010 (UTC)

There are three different types of meringue, according to this site: BBC Food: Meringues. You need to ascertain from the village store which type of meringue they make and follow the correct recipe. Cooking desserts is much more chemistry than cooking savoury food is, and if you don't follow meringue recipes then you will inevitably fail. I think the problem you had originally had was to do with failing to whisk the egg whites before adding anything else, but really you need to follow the recipe. --TammyMoet (talk) 09:35, 15 June 2010 (UTC)

Shirley Corriher list four types in Cookwise: soft, hard, Swiss, and Italian. Soft meringue, as used in lemon meringue pie, use about 2 tablespoons sugar per egg white, with sugar added gradually. Hard meringues, as used in hard meringue candies, use about ¼ cup sugar per egg white. Swiss meringue is very stiff and used for decorations/icing, and is made by beating sugar and eggs over boiling water. Italian meringue is used in puddings, and is made by drizzling a "hard-ball stage" (248F/120C) sugar syrup into well beaten egg whites. Corriher adds cornstarch to soft meringues, but omits it for hard meringues (indicating that the cornstarch keeps them from being "light"). I've never heard anyone advocate adding basic ingredients (like sodium bicarbonate), it's always slightly acidic, like cream of tartar or using a copper bowl. The acid stabilizes the foam. By adding base you may have overbeaten the whites before they set, causing them to be tough. For soft meringue, you want to beat just until the "soft peak" stage (where peaks form when you pull the beaters out of the foam, but where the the tops curl over under their own weight). For hard meringues, you beat a little further, until the "hard peak" stage (glossy peaks form, but don't curl over). Note that you don't need bicarb for leavening - the bubbles in meringue come from the whipping process, not from carbon dioxide generation. -- 174.24.195.56 (talk) 14:56, 15 June 2010 (UTC)

Make that five types - four from Shirley Corriher and the industrial meringue from the OP. Richard Avery (talk) 17:55, 15 June 2010 (UTC)

Instability of Manganese(III) fluoride

Why is manganese(III) fluoride so unstable? Manganese(III) oxide is much more stable, even though oxide is more easily oxidized than fluoride. --Chemicalinterest (talk) 11:40, 15 June 2010 (UTC)

It's not unstable (the article was misleading when it said that it will release F₂ on heating). It may well hydrolyse in moist air, but then so will most metal fluorides – that's why you must store them in polythene bottles instead of glass bottles – and hydrolysis is not what we usually mean by "unstable".

2MnF₃ + 3H₂O → Mn₂O₃ + 6HF

So, to anticipate your next question: "why do they hydrolyse?" Because the oxides are even more stable, and hydrogen fluoride is a pretty low energy molecule as well. And why are the oxides even more stable? Well the quick answer is because their lattice energy is higher. If you take the approximation of a pure ionic bond (not a very good approximation for the transition metals, but for the sake of illustration), then Coulomb's Law says that the strength of the bond is proportional to the product of the two opposing charges: so an Mn³⁺–O²⁻ ionic bond is (roughly) twice as strong as an Mn³⁺–F⁻ ionic bond. There are several other factors that come into it as well, but I'll leave you with this for starters! Physchim62 (talk) 12:03, 15 June 2010 (UTC)

Fluorides normally react with glass to form hexafluorosilicates. I thought that it spontaneously released F₂ gas, which is what I had a hard time believing. --Chemicalinterest (talk) 12:23, 15 June 2010 (UTC)

The release of F₂ is incorrect, at least at normal temperatures (all halides will decompose if you heat them strongly enough, but we're talking about thousands of degrees for most of them). As for fluorides reacting with glass to form hexafluorosilicates, the reaction is very slow in the absence of moisture: but, as you usually have a bit of moisture around when you're using these things, it is much better to store them in polythene bottles than to have a glass bottle shatter as you pick it up off the shelf! Physchim62 (talk) 12:30, 15 June 2010 (UTC)

Can you check the temp? [3] says decomposes at 600C - there's a difference between decomposes liberating F2, and melts (or boils) whilst retaining the same stoichiometry - I think the original statement may be roughly correct.87.102.18.94 (talk) 13:04, 15 June 2010 (UTC)

Also many flourides do not decompose at temperatures below that which will produce atomic fluroine - eg MnF2 - I think the difference is between 'eventually decomposes to elements' and 'decomposes with formation of a more stable flouride'87.102.18.94 (talk) 13:06, 15 June 2010 (UTC)

(it is unstable - but we need the Temp.) See also [4] and http://www.1911encyclopedia.org/Manganese - "manganic flouride".87.102.18.94 (talk) 13:11, 15 June 2010 (UTC)

Fair enough. I was going on Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 1224. ISBN 978-0-08-022057-4., which says it is "thermally stable". Physchim62 (talk) 13:39, 15 June 2010 (UTC)

It's good to at least 300C :) —Preceding unsigned comment added by 87.102.18.94 (talk) 19:30, 15 June 2010 (UTC)

They might be talking about the hydrate, (one link was) though I still think decomposition to CoF2 is likely.87.102.18.94 (talk) 17:31, 15 June 2010 (UTC)

Decomposition to MnF₂ is more plausible! ;-) Physchim62 (talk) 19:33, 15 June 2010 (UTC)

Bats, birds and convergent evolution

I remember reading once about theory of convergent evolution, and as an example, the text offered that it was much more parsimonious to speculate that insects, birds and bats (which are very different organisms) each evolved flight independently than to suggest that they had a much more recent common ancestor that evolved flight once and then split into these three lineages afterward. So I was wondering just how different bats and birds are and I came up with the following list. If anyone can add constructively to my pondering, that'd be great.

1. Bats are mammals in every sense of the word and birds are not. Perhaps this is the most glaring imparsimoneousness of the suggestion that a recent common ancestor of bats and birds produced bats that then converged perfectly with a previously existing mammal line.
2. Another likely glaring imparsimoneousness of the aforementioned speculation relates to the evolutionary timeline, with which I am altogether unfamiliar. I sort of got stuck at the Reptiliomorpha article because it seems that there's lots of bird/reptile talk but not a lot of bird mammal talk about convergence/divergence.
3. For me, it seems very difficult to discuss any physiologic/anatomic differences because I don't know how to give the proper weight to the evolutionary significance of any particular convergence/divergence, as I'm merely a freelance zoologist and not an evolutionary biologist. Mammals converged with birds with Protheria in terms of cloaca and egg-laying, so who's to say that any of the various traits we all know that separate birds from bats (beaks, etc.) count for that many parsimony points in the tally I'm trying to make?

DRosenbach ^{(Talk | Contribs)} 12:19, 15 June 2010 (UTC)

The "traditional" argument (from the days before routine DNA sequencing) comes from the structure of the skull, in particular the temporal fenestrae (openings in the side of the skull). All birds (and most modern reptiles) are diapsid, that is they have two temporal fenestrae on either side of the skull; all mammals (including bats and Protheria) are synapsid, that is they have a single temporal fenestra on each side of the skull. The appearance of temporal fenestrae dates to a bit more than 300 million years ago, long before there were any creatures that could be described as mammals or birds, and has been preserved through later fossils, so it's thought that the temporal fenestrae are a marker for evolutionary divergence. Physchim62 (talk) 12:56, 15 June 2010 (UTC)

Very helpful -- thanx! DRosenbach ^{(Talk | Contribs)} 15:41, 15 June 2010 (UTC)

If I personally were writing a textbook, I would not frame this issue in terms of parsimony -- parsimony is a useful criterion mainly when the evidence is relatively sparse. In this case we know enough to actually tell the story of how things happened -- we know for example that protostomes and deuterostomes (the superphyla containing insects and vertebrates respectively) diverged over 500 million years ago, when complex life existed only in the sea, and that synapsids and diapsids diverged over 300 million years ago, when no vertebrate could fly and even walking was pretty crude. Looie496 (talk) 16:10, 15 June 2010 (UTC)

Looie -- I think you're making my point without even realizing it. The reason why we can state "we know what happened" even though no one was there is because it makes sooooooo much sense to state proposition A and so little sense to state proposition B. Proposition A would be that synapsids and diapsids split and then much much much later, each developed their own flying organisms, while proposition B would be that the split occurred between flying and nonflying and that convergent evolution brought some initial divergents back to what appears to have been a continuous line of protostome heritage. Granted it sounds a bit odd to anyone who has even a somewhat realistic perspective of evolutionary biology, but I'd say that I meet less than 1 new person a day who would have such a grasp. On the contrary, I find that once explained, the parsimony argument will essentially state the same thing but be more palatable to the untrained mind. Thanks for your additions to the response -- it served to concretize my understanding of this matter. DRosenbach ^{(Talk | Contribs)} 20:45, 15 June 2010 (UTC)

The problem with any theory of extreme convergent evolution in which so very many attributes of mammals, birds and insects would have had to be converged - is that the flight mechanisms of birds, bats and mammals are dramatically different. If they came from common ancestors, why don't insects and bats have feathers? Why do birds use modified fore-arms to form the structure of their wings - where bats are using modified fingers and insects are using yet some other modified structure (the 'notum'). Their flight mechanisms are so spectacularly different, it's really inconceivable that these flight mechanisms evolved from some common ancestor. It's not reasonably to say that flight is a "convergent feature" of birds, bats and insects because the underlying mechanisms are not remotely similar. So there are NO features that birds, bats and insects share that are closer to each other than they are to other animals in their class. A bat's wing is much more similar to (say) a mouse's fore-feet than it is to a bird's wing. The flight muscles of an insect are not remotely related to the flight muscles that a bird use. This hypothesis is so far from being possible - it's utterly untenable. SteveBaker (talk) 22:39, 15 June 2010 (UTC)

This just keeps getting better -- Thanks Steve. DRosenbach ^{(Talk | Contribs)} 02:07, 16 June 2010 (UTC)

It doesn't address your question directly, but it's important to note that relationship markers are specifically chosen that would not generally be influenced by natural selection. Besides fenestrae, one of the favourite markers used are the foramina of the skull. While they're obviously required for blood vessels and/or nerves, their exact number and placement won't usually be exposed to evolutionary pressure. For example, if the supraorbital artery was to come of from the middle of the frontal bone instead of the supraorbital notch, it's not likely that it would exert much pressure in terms of differing levels of offspring survival. Our article doesn't mention it, but I believe the relationship between Nanotyrannus and T. rex, for example, was determined using one or more of the facial nerve foramina. The point being, of course, is that the last thing you want to use is something that will directly affect genetic survival; if you wanted to determine whether your boots and coat were made by the same manufacturer, you wouldn't try to examine the materials (those would be made to "suit the environment"), you'd check the label, which wouldn't be under that pressure. Matt Deres (talk) 16:40, 16 June 2010 (UTC)

question about the supernova

do stars makes a small explodes/core collapses before they explode as a supernovae or novae? do the information in this link means that? and if this is right, how much of time between every explode and the other? do this happen with a certain types of the supernovae? and do information in this section of the supernova article talking about the same thing? (quote: "This process repeats several times; each time the core collapses, and the collapse is halted by the ignition of a further process involving more massive nuclei and higher temperatures and pressures.") --Abbad Dira (talk) 12:34, 15 June 2010 (UTC).

For the first, it's important to note that novae and supernovae are two completely different processes that just happen to have unfortunately similar names (because, from Earth, they appear superficially similar). The APOD link refers to novae, and our article notes that "astronomers theorize... that most, if not all, novae are recurrent, albeit on time scales ranging from 1,000 to 100,000 years" (a citation is provided). So yes, they have an ongoing pattern of explosions, which probably vary in size to some extent or another.

For supernovae, what you've quoted refers to internal fusion processes, which are unrelated to externally falling matter as discussed at the nova reference. Those collapses are the result of the star exhausting its supply of fusible material at current core temperatures and pressures. When fusion ceases, the forces counterbalancing gravity cease and the core begins to collapse. That collapse leads to ever higher temperatures and pressures, until conditions are such that a heavier element becomes fusible and a new temporary balance is restored, up until a nickel-iron core forms, which leads to the supernova. The star almost certainly flares and whatnot in the buildup to the supernova, which might be characterized as explosions (see Eta Carinae for one current example), but there are no small-scale supernovae before the actual supernova. — Lomn 13:04, 15 June 2010 (UTC)

thank you very much. quote:

"The star almost certainly flares and whatnot in the buildup to the supernova, which might be characterized as explosions"

can this flares makes a notable changes in the star magnitude? and thank you again --Abbad Dira (talk) 07:35, 16 June 2010 (UTC).

Beer nutritious

Is it appropriate to call beer "nutritious" as we do in our Ale article? In what sense is "Small beer" "highly nutritious"? The Hero of This Nation (talk) 13:51, 15 June 2010 (UTC)

Lots of calories, if you consider that nutrition. --Chemicalinterest (talk) 14:36, 15 June 2010 (UTC)

If you consider Real ale, then the yeast will provide plenty of B vitamins. In years gone by, when water was in short supply if not downright poisonous, then beer would be a very useful source of nutrition, not to mention hydration. Small beer, being the drink of the poor, would have provided a large chunk of their daily nutritional requirements. Some countries classify beer as "liquid bread" (I believe that's the case in Belgium, where their licensing laws allow beer to be sold as a food), which makes sense because the ingredients are essentially the same. And of course, if you drink beers such as wheat beers, which are neither filtered nor allowed to drop clear, you're getting plenty of nutrients from the suspended sediment. --TammyMoet (talk) 14:42, 15 June 2010 (UTC)

Beer only provides some B vitamins. Chronic alcoholics go mental because their liquid diet lacks one of the B vitamins in particular, I forget which. Other consumables provide far better nutrition - for example an apple or apple juice. So beer cannot be said to be "nutritious" enough to warrant calling it so. 92.15.28.6 (talk) 23:13, 15 June 2010 (UTC)

You're thinking of pellagra, generally caused by a niacin (vitamin B₃) deficiency. Alcoholics with pellagra have typically gone so far as to have abandoned food all together. It makes sense that they would probably also prefer distilled liquors to the far more nutritious beer. – ClockworkSoul 02:44, 16 June 2010 (UTC)

It is also lacking B12 for example, and probably others. If you ranked all commonly available drinkable items according to how "nutritious" or healthy they are, then I expect beer would come towards the bottom of the list. Calling it "nutritious" is a weasel word that is meant to label it as healthy, when it is not. 92.28.251.43 (talk) 11:30, 16 June 2010 (UTC)

The context the word "nutritious" is used is small beer in medieval Europe. Small beer is thick and unfiltered. It would probably wind up near the top of your nutrition list of commonly available medieval beverages. APL (talk) 14:32, 16 June 2010 (UTC)

Especially if the rest of the list is whole milk, wine, and "the water everyone's been shitting in". :-) Matt Deres (talk) 16:44, 16 June 2010 (UTC)

I beieve milk and wine are better for you than beer. Implying that beer is germ-free is not the same as being nutritious. 92.15.14.87 (talk) 17:12, 18 June 2010 (UTC)

Quite! And also bear in mind that describing something as "nutritious" or even "highly nutritious" is very far from saying that it supplies all nutritional needs and that one could live on it with no other dietary input. Incidentally, "small beer" was so called because it had the lowest alcoholic content of the various 'grades' (usually three) available. 87.81.230.195 (talk) 17:36, 16 June 2010 (UTC)

If you put it that way, then name me any normally consumed food or drink that is not 'nutritious'? If everything is nutritious, including food in medieaval times, then should not each and every food be described as nutritious? (Water is nutritious - try not consuming any). 92.15.14.87 (talk) 17:10, 18 June 2010 (UTC)

You understand that "Small beer" has very little resemblance to the cool, refreshing beverage we now enjoy at the local pub? It was probably much too high calorie for those of us with non-physical jobs who don't get enough exercise, but I don't see why it wouldn't contain a reasonably good assortment of nutrients. Much more-so than any bottle of regular beer you might find in the supermarket.

Of course, Let's not forget that if you're a laborer in medieval times, your body needs lots of calories. Calories are a form of nutrition, and small beer would be an inexpensive way of getting them.

Perhaps you are confusing "nutritious" with "healthy"? APL (talk) 21:46, 18 June 2010 (UTC)

See the mention of weasel word above. Calling it nutritious is just an excuse for boozing, and implying its healthy covers up its bad effects. 92.15.4.168 (talk) 12:23, 19 June 2010 (UTC)

The article mentions that small beer has just enough alcohol to act as a preservative, and not enough to cause intoxication (and having drunk it throughout the day for several weeks, I can confirm this). That fact, along with the fact that small beer is unavailable as a commercial product nowadays, means calling it nutritious clearly isn't "an excuse for boozing". 81.131.37.105 (talk) 14:01, 19 June 2010 (UTC)

Immediately preceding the "highly nutritious" assertion is a sentence mentioning gruit, which shouldn't be overlooked and I think was intended to be connected. I have actually brewed and drunk small beer during a month-long 16th c. recreation; lots of herbs go into the tun (and the mash is nice to eat for breakfast). 81.131.52.194 (talk) 09:03, 19 June 2010 (UTC)

Beer is indeed more nutritious than water, and small beer is more nutritious than strong filtered beer. Though, of course, thinking of "nutritiousness" as a linear scale is a recipe for disaster, given that we need all kinds of nutrients, and not too much of any of them, and not too much alcohol either come to that. It might be better to say that beer was a valuable component of the medieval diet. 81.131.37.105 (talk) 14:01, 19 June 2010 (UTC)

Transplanted lungs

This link from Yahoo! news describes a 28 year old British cystic fibrosis patient who received a lung transplant from a deceased smoker. The British government official overseeing transplant stated that a transplant isn't a guarantee of a "brand new" organ but that smokers' lungs can function normally. If anyone out there is a doctor or nurse, researcher, student, etc. experienced with the respiratory system, how plausible are that official's comments? A "brand new" organ is not admittedly neither necessary or possible in the case of human transplants, but as a general remark, would medical science approve of transplanting a smoker's lungs? Or only if they were a really light smoker? Is a matter of degree (spectrum) or of kind?--达伟 (talk) 14:00, 15 June 2010 (UTC)

The problem as I understand is that so few lungs area available for transplant that such 'sub-optimal' organs are being used. The main issue appears to be that the recipient was not informed. Mikenorton (talk) 14:10, 15 June 2010 (UTC)

[5] from Australia mentions one of the criteria is "20 pack-years smoking". I don't know what that is but perhaps it means 1 pack a day for 20 years, or 2 packs a day for 10 year etc. It also mentions it was an uncommon reason (along with age) for rejecting lungs. There are other criteria including relating to lung function that some smokers may fail. :[6] from Australia mentions one of the criteria is "20 pack-years smoking". I don't know what that is but perhaps it means 1 pack a day for 20 years, or 2 packs a day for 10 year etc. It also mentions it was an uncommon reason (along with age) for rejecting lungs. There are other criteria including relating to lung function that some smokers may fail.

These [7] [8] [9] discuss some of the problems relating to sub-optimal organs. They also mention that the criteria are changing anyway. However I would note it's not clear whether the lungs in question were considered sub-optimal under the criteria. Presuming the donor was a light smoker say half a pack a day for 30 years then the donor may not have meet the 20 pack-years if I understood it correctly and the lung functions may have been considered sufficient. Of course those are from Australia anyway and over 10 years old.

From the refs, I gather one of the problems is that transplant authorities don't like recepients cherry-picking organs (and I can understand this). While they may support informed consent, the consent needs to be given before hand so you can't list the donor's lifestyle and potential risk factors afterhand and ask them only to find they reject the organ and then it potentially goes to waste if you can't find another recepient in time. And I would guess filling out a 50 question yes or no on all the potential risks for a profile beforehand on what they're willing to accept is way too complicated particularly given the fact you really want to patient to actually understand the risks and not just think 'well that sounds bad' so you'll need to explain to them (and even I think we've established before most people are bad at evaluating risks).

Ultimately as with many things medical, it's a delicate balancing act between too much information which will just confuse the patient and lead to what many would consider poor decision making and ensuring informed consent.

When it comes to a smokers lungs the cancer risk (similar to the e.g. HIV and Hepatitis C risks one of the refs mentioned) from a smokers lungs particularly given the immuno-suppresants that would have to be used is an obvious concern.

Nil Einne (talk) 15:24, 15 June 2010 (UTC) Nil Einne (talk) 15:24, 15 June 2010 (UTC)

On the other hand, you have to weigh up the benefits to the patient. If I had the choice of five miserable years of life with a terminal illness against ten better years of life then being killed by my transplanted organ, I know which option I'd choose! [the time-scales are only for illustration, BTW: we don't know the prognoses of this patient] Physchim62 (talk) 15:43, 15 June 2010 (UTC)

Well yes. Although I think that's obvious, otherwise the issue of sub-optimal organs wouldn't even come in to it. In this particular case, the patient doesn't seem to be happy with what happened so I presume that at least meant they weren't likely to die in a few weeks. And I presume it also meants they weren't expected to die within a few years even with a highly successful transplant with excellent lungs. But perhaps I'm presuming too much. In terms of choice it doesn't seem to have come in to it here which is the primary reason why it hit the news. But as illustrated in the refs and also in my summary paragraph (which I albeit added after your message although I didn't get an EC) this isn't that surprising and doesn't mean there was any wrongdoing. On a personal note from the very limited information available I do feel if I were in the women's circumstances I would be glad I got something but as I said there's very little information. In any case, the patient must believe they would have survived long enough to get a 'better' (by which I mean in their opinion) set of lungs. Nil Einne (talk) 15:52, 15 June 2010 (UTC)

This article gives a nice overview. In particular, "The major concern for using donors with a history of cigarette smoking is the potential for poor lung function due to the obstructive pulmonary disease and the risk of transplanting an undetected primary or metastatic cancer or for developing a malignancy in the donor lung in the years after the transplant.... There are, however, no studies that directly address how much cigarette smoke exposure a donor may have before the lungs are not safe to use for transplantation. A donor history of smoking should therefore not prevent the use of donor lungs for transplantation." Axl ¤ [Talk] 17:44, 15 June 2010 (UTC)

The official's comment: "lungs from a smoker can be working perfectly normally" certainly is plausible. The key word is "can". Axl ¤ [Talk] 17:46, 15 June 2010 (UTC)

The main thing from smoking actually is cardiovascular disease, because of what nicotine does to the endocrine system. A lot of heart attacks coincide with being a smoker... which is probably half the reason for being out of breath. John Riemann Soong (talk) 15:46, 16 June 2010 (UTC)

clump of matter

Why isn't the universe one big clump of matter surrounded by space? 71.100.13.202 (talk) 14:51, 15 June 2010 (UTC)

Because all the way back at the Big Bang, the inflationary epoch laid down the seeds of structure formation via fluctuations. We observe later evidence of this in the cosmic microwave background radiation, the anisotropies of which are explained by the Big Bang model. Or, in short, because explosions are messy, uneven things. That's a very rough approximation, but it's a fair one. Later on, dark energy and the acceleration of the expansion of the universe play a role, too. — Lomn 15:17, 15 June 2010 (UTC)

For the first real proof of this, see COBE mission. Regards, --—Cyclonenim | Chat  17:15, 15 June 2010 (UTC)

It is a very profound question, OP (you should be a scientist), and while the generally-accepted theory for the singular universe (which indeed was a big clump of matter/energy) is inflation, at this point it still like saying "it is because it is". It's a great answer for "how", but not "why". While I have no problem accepting some "philosophically tidy" explanations for the cause of the Big Bang (such as chaotic inflation), there are many layers of complexity lying beneath, and if the history of science teaches us anything, a revolution in thinking occurs when that complexity is realized to indicate something even more simple. So indeed, why isn't the universe one big clump of matter? SamuelRiv (talk) 18:50, 15 June 2010 (UTC)

I assume that by "...be a scientist..." you mean obtain a degree in science and pursue science as a career. While that is great for people who want to live in a groove it is not so good for people who want unfettered comprehension; i.e., people who can not see the forest for the trees. 71.100.13.202 (talk) 23:29, 15 June 2010 (UTC)

Anthropic principle. Why isn't always the right question.-RunningOnBrains^(talk) 20:36, 15 June 2010 (UTC)

Sorry OP71.100, I should have said "become a scientist". I assumed (perhaps unjustly) you were a wide-eyed high-school student. And as I am in physics, I am possibly the "grooviest" if I take your meaning correctly - but those are the types of questions and philosophical concerns we do have to ask ourselves, even when dealing with everyday matter.

For example, right now we are working on a stable state that appears for a large number of moving things, ie a crowd of people walking across a bridge. This new stable state was discovered mathematically two years ago, but we don't have any record of it existing because nobody thought to look for it. The question of the "forest" now is whether or not it appears everywhere simply because it should, according to our results - were we so satisfied with our understanding of stable systems ten years ago that we ignored this state, even if it appeared, as some external complexity? These questions are important. SamuelRiv (talk) 01:24, 16 June 2010 (UTC)

I'm not against having knowledge or facts but rather the assumption that a person can not obtain all of them without pursuing a degree unless of course higher education is assuring itself work by sitting on facts and knowledge. If you believe that the Sun is at the center of the solar system and the university you want to attend insists that you admit that the Earth is really at the center of the universe then knowledge and fact have nothing to do with a degree or being a scientist. Why do you think so many college kids drink alcohol and smoke pot? 71.100.13.202 (talk) 22:33, 16 June 2010 (UTC)

Definition of "Earth's surface" for purposes of defining meteorites

If a meteor falls in a big city, lands on the top of a skyscraper, and somehow survives in one piece, is it considered a meteorite? The intro to Meteorite says: "A meteorite is a natural object originating in outer space that survives impact with the Earth's surface". Do definitions generally require it to land on dirt or in water, or does anything attached to dirt or water qualify? Nyttend (talk) 15:18, 15 June 2010 (UTC)

Yes. If it landed on a skyscraper, and the skyscraper is on the surface of the Earth, then it landed on (planet) Earth. (The word Earth here does not mean soil.)--Shantavira|^{feed me} 15:58, 15 June 2010 (UTC)

I think it means it's no longer whizzing through the air. So if you caught it in mid air it counts too, as long as you slowed it down. Ariel. (talk) 19:08, 15 June 2010 (UTC)

The distinction is between objects that burn up in the atmosphere and objects that don't. Even if you float yourself in a big old blimp and manage to catch one with a kevlar oven mitt, it's still a meteorite because it didn't burn up.

You might want to coat your kevlar with asbestos, because that will be one hot rock! Googlemeister (talk) 20:00, 15 June 2010 (UTC)

Not necessarily. The linked article says in part:

"Meteorites are sometimes reported to be warm to the touch when they land, but they are never hot. Reports, however, vary greatly, with some meteorites being reported as "burning hot to the touch" upon landing,[11][12] and others forming a frost upon their surface."

Most of the light visible from a falling meteor actually come from shocked and heated air. Only the outermost layer of the meteoroid itself gets heated up much, and this is then cooled both by heat exchange with the bulk of its interior (which is at outer-space temperature) and with the airflow as it drops after having slowed to terminal velocity. 87.81.230.195 (talk) 21:19, 15 June 2010 (UTC)

Am I misunderstanding something or is the quote sentence completely illogical and should be fixed? It seems like it's saying that "Meteorites are never hot, but sometimes they are burning hot". APL (talk) 14:41, 16 June 2010 (UTC)

I understood it to imply that some reports of meteorites being burning hot immediately after landing have been made, but were erroneous and based on a false assumption. However, of the three references cited in connection with this passage one is ambiguous, since it reports a meteorite being found in a hole made by a simultaneous lighting strike, one reports a small meteorite being hot to the touch within a minute of landing, and one reports a large meteorite being frost-coated. It makes some sense that the temperature might be size related. I agree that the passage needs some correction. 87.81.230.195 (talk) 17:31, 16 June 2010 (UTC)

Memory

Resolved

I asked this question before but didn't really get the type of answer I was hoping for, probably because I wasn't specific in my wording, so here goes again. What are some scientifically proven ways (techniques, foods, chemicals, etc) that improve memory? 82.43.90.93 (talk) 15:21, 15 June 2010 (UTC)

At the risk of sounding extremely stupid, have you considered revision? This is the most widely used technique to improve your recollection of a certain topic by simply repeating your study of it. If you're referring to a direct, automatic increase in memory, then I recommend reading the article on nootropics, but it's not well sourced. Regards, --—Cyclonenim | Chat  17:12, 15 June 2010 (UTC)

Have you not actually read the replies to your question on the Miscellaneous desk? --TammyMoet (talk) 17:19, 15 June 2010 (UTC)

I have read them, and as I said in my question here they aren't what I wanted. I realize my question on the Miscellaneousdesk was vague, so I've reworded my question and asked again on the science desk, hoping for a response that deals with scientifically proven methods, perhaps even with references.... 82.43.90.93 (talk) 17:52, 15 June 2010 (UTC)

He forgot. Axl ¤ [Talk] 17:48, 15 June 2010 (UTC)

Cross your fingers and say a prayer, while rubbing your lucky rabbit's foot. PMID 20511389 Rockpocket 17:59, 15 June 2010 (UTC)

There are no known methods that make memory substantially better in a general way across all situations. Stimulants such as amphetamine and caffeine improve memory while they are active, but the effects don't outlast the drug. Gaining knowledge about a domain improves memory for things in that domain, for example expert chess players have good memory for chess positions. And there are tricks such as the Method of Loci that can help in memorizing lists of arbitrary items. But there is no known treatment that makes memory "stronger" in a general way. Looie496 (talk) 18:04, 15 June 2010 (UTC)

Thank you for the informative answer :) 82.43.90.93 (talk) 18:08, 15 June 2010 (UTC)

Maybe these things will help: environmental enrichment, social stimulation, lack of social isolation [10], [11], [12]. Physical exercise, curcumin, and loads of other stuff in the nootropics article. --Mark PEA (talk) 18:16, 15 June 2010 (UTC)

So you haven't actually taken any notice of what I said, which was a practical method to improve your memory - that of writing things down and saying them out loud? It's a teaching method I have both experienced as a learner and used as a teacher. It works, otherwise I wouldn't have given it you. --TammyMoet (talk) 20:19, 15 June 2010 (UTC)

That is rote learning. What if the OP is trying to improve their memory skills so that if they were to witness a crime, they would give a reliable account of the events (as it's well documented how poor eye witness testimony is). You can't witness a crime and then ask the criminal to wait there whilst you write down what they are wearing, and say it out loud etc. --Mark PEA (talk) 21:10, 15 June 2010 (UTC)

To be honest, I don't think anyone in that situation will remember accurately everything they saw. The BBC did some research, which they aired recently, on just how unreliable witness testimony is. When I've been in those situations, I've stopped as soon as I can and wrote down what I can remember of the key points. This is an explanation of why eyewitness testimony is unreliable. http://www.open2.net/eyewitness/johanna_motzkau_witness_memory.html And another one: http://www.bbcfocusmagazine.com/feature/psychology/far-i-can-remember --TammyMoet (talk) 17:32, 16 June 2010 (UTC)

matter versus spirit

Why is matter even necessary? why isn't everything just spirit? 71.100.13.202 (talk) 15:24, 15 June 2010 (UTC)

Who says it's "necessary"? But this is way off into philosophy, and not a referenceable science question. — Lomn 15:33, 15 June 2010 (UTC)

Because every physical building block in our frame of reference is made of matter. If you figure out how to exist without being tied to matter, then it could become a debatable point. Until then, as Lomn said, it's just a matter of philosophy and maybe spirituality.

Without matter, where does 'spirit' come from? Your personality is entirely based upon matter, whether or not we understand it. Without this matter (the brain), you don't have thought or spirit. Regards, --—Cyclonenim | Chat  17:13, 15 June 2010 (UTC)

"Spirit" can be known as matter that is not understood by man. --Chemicalinterest (talk) 17:23, 15 June 2010 (UTC)

I've never heard it used in that sense, just as something that refers to our thoughts and personalities in a non-physical sense. It seems fairly evident, to scientists at least, that any/all of our thoughts are mere atomic interactions that are not understood. Regards, --—Cyclonenim | Chat  17:47, 15 June 2010 (UTC)

Even if you start with an assumption that the world is pure spirit, you find that it is governed by a number of regularities. Traced to the most fundamental level, these regularities show up as the laws of physics, such as conservation of energy, conservation of momentum, the Heisenberg Uncertainty Principle, and the principle of relativity, among others. The concept of matter can be viewed as a surrogate for these consistent regularities in our experience. Looie496 (talk) 17:33, 15 June 2010 (UTC)

Or... we can take the converse of that above and assert instead that because at the fundamental level it seems everything is described beautifully by largely a priori mathematical constructs, then no matter how we slice it the world is Rational, comprehensible, and perhaps even simply spiritual (entirely of the mind)? And wouldn't you know it, we even have an article! Definitely worth reading about and thinking about (even though I personally agree with what Looie summarized above). SamuelRiv (talk) 18:57, 15 June 2010 (UTC)

Basically: I think, therefore I am. Regards, --—Cyclonenim | Chat  20:38, 15 June 2010 (UTC)

Regards what? 71.100.13.202 (talk) 23:15, 15 June 2010 (UTC)

"Regards" is a formal way of ending a statement or later. It's like "yours sincerely" but slightly less formal. Regards, --—Cyclonenim | Chat  11:07, 16 June 2010 (UTC)

Latter-day Saints ("LDS" or "Mormons") believe that Spirit is matter-- just that it's more highly refined and mostly imperceptible.... Kingsfold (talk) 19:40, 17 June 2010 (UTC)

"Microrefineries" in the Gulf states

What would make impossible the idea of setting up small-sized refineries in which boats take in loads of crude instead of fish and get it into some kind of commercially usable format (if making gasoline is, as I already suspect, out of the question) they could make money off of? 20.137.18.50 (talk) 16:00, 15 June 2010 (UTC)

It's certainly not impossible, but rather a question of whether it's economical (or legal). Without doing research, I'd guess mostly the former: economy of scale is important to the oil industry. — Lomn 16:10, 15 June 2010 (UTC)

Keep in mind that the quantity (and concentration) of oil that is ecologically harmful is much smaller than the quantity (and concentration) of oil that is economical/profitable to collect. Otherwise, BP would be out there scooping up "every last drop" of spilled oil and selling it. Nimur (talk) 04:49, 16 June 2010 (UTC)

Carbon-based life more plentiful if system richer in Carbon?

"HD 108874 b is a gas giant announced in 2003. The orbit lies in the star's habitable zone. It is expected that any moons orbiting this planet are enriched in carbon, and are thus quite different than the silicate-rich bodies in our Solar System."

• Is a planet or planet-moon in system richer in Carbon likely to have more plentiful Carbon-based life than the average rock?? 24.78.167.139 (talk) 17:39, 15 June 2010 (UTC)

Leaving aside the fact we have no evidence of life anywhere except Earth? It's fairly obvious that if you have more carbon, you have a greater chance of carbon-based life than places where there are less carbon. At least it is to me. Regards, --—Cyclonenim | Chat  17:50, 15 June 2010 (UTC)

Well, it's obvious that you need a certain amount of carbon to support carbon-based life, but once you have that amount of carbon it isn't obvious whether more carbon would make life more likely. There is a theory that, if the conditions are suitable, life is essentially certain to arise (the main evidence for that is that life arose on Earth almost as soon as conditions were vaguely suitable, although it remained single-celled for several billion years, if memory serves). If it is certain, then the probability can't increase. --Tango (talk) 18:03, 15 June 2010 (UTC)

Sounds like a ton of observer bias in that theory, and with a sample size of about 1. Googlemeister (talk) 18:15, 15 June 2010 (UTC)

Yep. It's the best we can do, though. --Tango (talk) 20:22, 15 June 2010 (UTC)

Yes to all of the above, but we can make some assertions based on absolute chemistry. One thing that seems essential to current life is the rich variety of stable polymer compounds formed by carbon-chain-type molecules, something which does not occur to such a degree with atoms that bond preferentially on less than 4 points (so no nitrogen- or oxygen-based life on Earth). The second thing worth noting is that carbon, nitrogen, and oxygen are the first heavy elements formed in bulk in stellar fusion, at least for small-medium stars - so we don't have lithium or boron in high quantities at all, even though boron at least might form an excellent basis for polymer chemistry (??? I'm not a chemist - help me out here ???).

The alternative often given in sci-fi is silicon-based life, mostly because silicon forms in high quantities (most abundant heavy element in the Earth's crust) and bonds almost identically to carbon (right below it on the periodic table, so kinda like a heavy carbon: C++ ). However, that heaviness might be precisely what makes it a less-suitable candidate for forming life, as with weight comes decreasing electronegativity, so decreasing bond strength. I think those (again, not a chemist) are the fundamental assertions that we can make absolutely without having an example of life outside Earth. SamuelRiv (talk) 19:07, 15 June 2010 (UTC)

The issue is that silicon doesn't form pi bonds very well... it's less electronegative than hydrogen, the most abundant element in the universe. Thus Si-H bonds are considerably more activated (electron density on the outside) than C-H bonds (electron density near the middle part of the molecule). An important part of biochemistry is the ability for carbon to be both electron-donating or electron-withdrawing at the right moments, leading to rich aldol chemistry .... we don't see this with silicon. John Riemann Soong (talk) 19:23, 15 June 2010 (UTC)

Boron has a valency of 3 so, for the reasons you give, it isn't a good basis for polymers. It tends to form crystals with itself, rather than chains. --Tango (talk) 20:31, 15 June 2010 (UTC)

I wuv you guys! SamuelRiv (talk) 01:27, 16 June 2010 (UTC)

I look at the origin of life as a chemical reaction (or series of chemical reactions). In this case, more carbon would only increase the likelihood of the given reaction if carbon is the limiting reagent. If not, then more won't help, and could even hurt, if it displaces other reagents which are needed. StuRat (talk) 05:05, 16 June 2010 (UTC)

The last comment reads (If I may paraphrase) that excess Carbon can stifle the evolution of life because a certain amount of other elements need to be free. Have I got that correct? Awesome point by the way. So I coin the phrase "Diamond Desert Planet." 24.78.167.139 (talk) 05:59, 16 June 2010 (UTC)

well, keep in mind that carbon only makes up maybe 15%-20% of an organism (for humans it's 18%). The primary component, of course, is water, and the nature of a cell is to enclose a balanced environment which maintains a liquid solution of chemicals properly balanced for organic chemical reactions. Excess carbon (like other excess chemicals) is simply expelled from the cell to maintain that balance, so an environment with a great surplus of carbon materials might in fact be poisonous unless that carbon is bound up in non-water-soluble materials. --Ludwigs2 06:24, 16 June 2010 (UTC)

And to take this a bit further, I would expect that having all of the necessary ingredients for life in the same ratio as they are found in life is most likely to produce life. Thus, around 15-20% carbon would be ideal. Additional carbon might help if it displaces other elements not needed for life, but would be detrimental if it displaces other elements which are needed and in short supply on that planet. StuRat (talk) 15:15, 16 June 2010 (UTC)

Hummingbird feeders

I found a couple of interesting discussions in the archives, but nothing with regards to what I'd like to ask: Do hummingbird feeders need those plastic yellow flower parts? I ask because I have a feeder and it's hanging outside, but the plastic yellow flowers went missing (who knows what drove someone into removing them in the first place) and I'm hoping the birds can still figure out where the energy source is. – Kerαunoςcopia^◁_galaxies 18:10, 15 June 2010 (UTC)

No, at least not after the humming birds know where the feeders are. You may not attract the birds as quickly without the fake flowers or red die, but once they know where to find the nectar they don't need the visual cues. --Ludwigs2 19:25, 15 June 2010 (UTC)

You're right, they found the feeder and they couldn't care less about the flowers. The red dye is marketing BS though. The feeder is bright red, and that's obviously all they needed; I refuse to poison wildlife with the same additives we put in our own food to make our cheese look like cheese and bread look like wheat bread. It's sick. But anyway, feeder working fine, I was just curious. – Kerαunoςcopia^◁_galaxies 22:01, 15 June 2010 (UTC)

Probably a safe idea not to use it - there are plenty of allergies and side-effects that have occurred in humans due to food dyes (consider yellow #13). Since it's even harder to monitor the eggs and, umm, hyperactivity of hummingbird chicks, I'd think the sugar-plus-distilled-(tap)-water combo is safest. Good for you, OP. SamuelRiv (talk) 01:33, 16 June 2010 (UTC)

A hyperactive hummingbird sounds like it might flap so fast it's wings would fly off. :-) StuRat (talk) 04:57, 16 June 2010 (UTC)

Thanks SamuelRiv. I'll also caution against using distilled water, which could cause electrolyte imbalances. source: [13]. – Kerαunoςcopia^◁_galaxies 06:22, 16 June 2010 (UTC)

I wonder, is that something specific to hummingbirds, or is that just a retelling of the oft-repeated legend that distilled water will cause electrolyte imbalances in humans.

Of course, humans don't drink five times their body weight in bottled water... APL (talk) 14:14, 16 June 2010 (UTC)

I take it you've never been to a 2hr Hour Fitness club... --Ludwigs2 19:58, 17 June 2010 (UTC)

why doesn't centrifugation do some major damage to live cells?

The protocol I'm using to culture live HeLa cells calls for separation of the cells to be cultured from the old culture media via centrifuge ... I think at around 5000 rpm for 8 minutes. I can understand using this technique when trying to extract DNA -- we don't care about cells down the line, but live cells that are still metabolising, probably even still replicating DNA or even dividing? And HeLa cells (being cancer cells) are even all the more susceptible to metabolic or DNA damage.

Also why the emphasis on separating the cells from almost all traces of the previous buffer? Is it to prevent bacterial contamination? I mean, the cells seemed to be doing fine in the previous buffer -- or is it to induce the 'fresh serum effect'? John Riemann Soong (talk) 20:41, 15 June 2010 (UTC)

I don't know the answer to the first part of your question but I suspect it has to do with the fact that water behaves as a more viscous fluid at small scales, so that the flow of solution around cells and organelles as they move will be laminar and probably slow, thereby minimising potentially damaging shear forces. However that is just a guess. Also the fact that the cells will be almost neutrally buoyant will mean that the compressive forces on the cells will be much lower than would be expected intuitively, potentially preventing "crushing injuries" (again just an educated guess). For the second part: are you trypsinizing your cells before transfer (to detach them from the old flask), if so the trypsin needs to be removed or you will probably select for trypsin resistant cells, making future passage difficult. If you are culturing your HeLa in suspension rather than as attached cells this protocol from sigma-aldrich [14] says that centrifugation is only necessary if the previous medium has become acidic (i.e. yellow for phenol red indicator medium). I guess that this is because you need to reduce the amount of old medium added to the the new culture in this case to ensure the new culture starts at the correct pH. Some old medium is still added back in this protocol to ensure the correct growth factors are present etc. (unlikely to be an issue for HeLa cells). So my thoughts would be: for attached culture centrifugation is necessary to remove trypsin, for suspension culture centrifugation is probably not necessary but does no harm. I would say that the chance of removing bacterial contatamination by centrifugation is tiny (you could never remove all of the contaminated supernatent) and the extra handling steps probably slightly increase the risk of contamination if anything. Equisetum (talk | email | contributions) 21:38, 15 June 2010 (UTC)

OK, so you're sticking them on 5000 rpm, and it takes them eight minutes to make their way down to the end of the centrifuge tube; you're worried about the shear force... what's the shear force you put them under during the half-a-second that you squirt them out the end of a pipette then? ;-) Physchim62 (talk) 23:14, 15 June 2010 (UTC)

I may not have been very clear (actually, on reading it back I wasn't very clear ;)) but that is exactly my point - they take eight minutes because (I think) of the viscosity of the water surrounding them as well as their buoyancy, therefore shear force is not a problem. As you quite rightly point out the forces on cells will likely be much greater when pipetting than when centrifuging. Equisetum (talk | email | contributions) 23:27, 15 June 2010 (UTC)

A bit of back-of-the-envelope tells me that for any reasonably-sized benchtop centrifuge, 5000rpm will be equivalent to an rcf of about 1000-4000g, depending on rotor diameter. (And we're probably closer to the low end of that.) That sounds like a lot, until you realize that buoyancy is going to nullify a lot of that difference. The specific gravity of nucleated mammalian cells is generally on the order of 1.03 to 1.04, while the specific gravity of cell culture medium is somewhere north of 1.01 (mostly water, but topped up with salts and glucose, plus some other goodies.) That means that your cell spinning at 1000g is actually only experiencing a net force equivalent to 20-30g in air. While 20g is a lot for a human being, on the scale of a cell it's pretty negligible.

That said, unless there's a special reason why you're trying to get squeeze out all the old medium and get a really tightly packed pellet, 1000+g for a full eight minutes seems a bit excessive. I mean, 30 seconds at 300-500g is sufficient to pull down HeLa cells in a 15mL tube (unless you're using an oddly-high-density medium); I did it yesterday. TenOfAllTrades(talk) 15:06, 16 June 2010 (UTC)

Just a follow up question from the first respondent: Why exactly is 20-30g negligible on the scale of a cell? I know that it is, and it makes intuitive sense but I can't remember the precise physical reason why and that bugs me. I know that the force would be smaller according to F=ma, so force scales with mass/volume, so I guess the answer lies with what strength/resistance to deformation scales with?? Equisetum (talk | email | contributions) 20:46, 16 June 2010 (UTC)

Isolating elemental silicon

How can I isolate elemental silicon from quartz (SiO₂) without any expensive equipment? --75.25.103.109 (talk) 21:55, 15 June 2010 (UTC)

Try an aluminothermic process; react finely powdered aluminum with finely powdered silicon dioxide and ignite with a magnesium strip. PS: I think there might be something about the high melting point of silicon dioxide that would stop the reaction. --Chemicalinterest (talk) 22:10, 15 June 2010 (UTC)

You mean a 'silicon thermite' reaction - see here http://amazingrust.com/experiments/how_to/thermite.html#SiO2 or thermite

With access to an open fire (either coal, or coke, or a blacksmiths forge) mix powdered carbon (coke will do) with sand in a ceramic pot, and heat to about 2000C .. see Silicon#Production 87.102.18.94 (talk) 22:19, 15 June 2010 (UTC)

Open fires are generally not hot enough. That is why an electric arc furnace is normally used. --Chemicalinterest (talk) 10:59, 16 June 2010 (UTC)

If you use the reaction for its heat, then it is a thermite; but if you use the reaction in the extraction of metals, it is an aluminothermic reaction. --Chemicalinterest (talk) 10:58, 16 June 2010 (UTC)

Yes, it's a bit like a thermite reaction, so only do it on a small scale! Magnesium powder works better than aluminium powder in my experience. No need to ignite, just heat strongly in a covered crucible. Physchim62 (talk) 23:01, 15 June 2010 (UTC)

But how do you plan to separate the silicon from the oxides formed? Graeme Bartlett (talk) 01:58, 16 June 2010 (UTC)

Which reaction? - the silicon would be expected to be produced molten and sink to the bottom... but Alumina can be dissolved in NaOH.Sf5xeplus (talk) 02:36, 16 June 2010 (UTC)

That's one reason why magnesium is better than aluminium. With an excess of magnesium powder, you can simply dissolve the magnesium oxide (and excess magnesium) in dilute hydrochloric acid to leave elemental silicon. Not very pure silicon, mind, but enough to say that you've done it. Physchim62 (talk) 02:03, 16 June 2010 (UTC)

You can dissolve Al₂O₃ and Al powder in HCl too, just as well as Mg. --Chemicalinterest (talk) 10:58, 16 June 2010 (UTC)

reducing agents milder than NaBH4

AFAIK NaBH4 is still a little overkill... and a little pricey for some reactions with strong redox potentials. Redox-wise, are there any milder reagents that will reduce:

• chloramines into amines
• Ag(III) to Ag(0)
• peroxyethers (ROOR') into alcohols (ROH + R'OH or maybe an ether + alcohol)

Is it possible to couple the oxidation of formaldehyde to formic acid to actually reduce another aldehyde to an alcohol? (actually I'll cover this below). John Riemann Soong (talk) 22:15, 15 June 2010 (UTC)

ok I'll bite a bit:

• NaBH₄ is nearly dirt cheap at £30 for 100g, and down to 1/3 of that at kg quanties, plus the low 'molecular' weight of ~37g/mol they're practically giving it away..

Anyway - something cheaper:

• Hydrogen reduction - H₂ is cheap, but the catalysts can be expensive. Not everyone wants to work with hydrogen gas.
• Electrochemical reduction = particularily electrode generated H_{surface atom} is a nice way if you can get it to work. very cheap and safe.
  • For Ag(III) direct electrochemical reduction.
• Other cheap methods - all I can think of is acid + Zn or Fe or Sn ... (also Fe(II) and Sn(II) reductions) - you might have to do original research to see if it works. There's too many possibilities here for me to search all of them.
• For the chloramine possibly Mg reduction.87.102.18.94 (talk) 22:39, 15 June 2010 (UTC)

A rusty iron nail will do all of those reductions at negligeable cost: I can't guarantee the isolated yield after work-up, mind... Physchim62 (talk) 22:55, 15 June 2010 (UTC)

Why do you need it rusty? --Chemicalinterest (talk) 11:02, 16 June 2010 (UTC)

Because you want to keep your clean nails for hammering into things! Seriously, the role of the rust is just to make sure the reaction mixture can find it's way to some iron underneath – a "clean" metal surface usually has a good tough layer of oxide on it (this is why aluminium foil doesn't spontaneously burst nto flames) and that can slow down the reaction to the point of uselessness. Physchim62 (talk) 11:26, 16 June 2010 (UTC)

A nail dipped in HCl should contain some reactive iron on the surface rather than a passivating layer. --Chemicalinterest (talk) 13:29, 16 June 2010 (UTC)

Would ascorbic acid be good for any of them? --Chemicalinterest (talk) 11:12, 16 June 2010 (UTC)

Ascorbic acid would certainly do the silver reduction, as would glucose for that matter. Physchim62 (talk) 11:26, 16 June 2010 (UTC)

How do I activate these carbohydrate reducing agents? Do they need a catalyst? John Riemann Soong (talk) 16:34, 16 June 2010 (UTC)

Ooops, I was actually thinking Au(III)... I only started with gold recently so it's really weird for me to be using Au so often... John Riemann Soong (talk) 16:33, 16 June 2010 (UTC)

Au+++ should be easily reduced by any reducing agent, such as glucose or iron(II). --Chemicalinterest (talk) 20:59, 16 June 2010 (UTC)

using one aldehyde to reduce another aldehyde (product: alcohol and carboxylic acid)

It seems to me that aldehydes could disproportionate.

Consider the following reaction:

2 H2(CO) + HOH ----> HCOOH + CH3OH

Using standard heats of formation I think the overall reaction is -160 kJ/mol

Using acetaldehyde to produce acetic acid and ethanol, the reaction is less exothermic: -90 kJ/mol but it still seems sufficient to get a nice controlled reaction with the right catalyst. What catalyst would allow this disproportionation to occur? I assume that the reaction might be even more reactive if the formaldehyde wasn't stabilised by water but maybe dissolved in the right solvent.

Finally, is there any way to aim not for disproportionation but to actually have aldehydes reduce other carbonyl compounds? I imagine this would be quite useful. Maybe the reaction already exists? John Riemann Soong (talk) 22:32, 15 June 2010 (UTC)

You mean like the Cannizzaro reaction - as the article says for aldehydes with beta-carbon H atoms the aldol reaction predominates.87.102.18.94 (talk) 22:42, 15 June 2010 (UTC)

See also Cannizzaro_reaction#Variations for the 'finally' part .. yes.87.102.18.94 (talk) 22:43, 15 June 2010 (UTC)

The crossed Cannizzaro reaction with formaldehyde as the reducing agent is relatively common. Formaldehyde is cheap, so you can afford to throw away the formic acid by-product in a small scale synthesis. The practical problem is getting the formic acid out of the product mix. However, disproportionation is not the only self reaction that aldehydes can undergo: see paraldehyde, for example! Physchim62 (talk) 22:51, 15 June 2010 (UTC)

Something I find interesting is why aldehydes are less stable on average than alcohols or carboxylic acid derivatives, i.e. both oxidising and reducing an aldehyde is thermodynamically favourable. Are esters and carboxylic acids less electrophilic than aldehydes/ketones? I remember from electron density diagrams, esters/acids are somewhat turquoise? If so, why do some aldehydes not form stable acetals? John Riemann Soong (talk) 16:29, 16 June 2010 (UTC)

You're right...the carbonyl of an ester (or acid) is stabilized by resonance, whereas an aldehyde/ketone is not. And an aldehyde is also fairly unhindered, and the H electronics may play a role as well. So a carbonyl is still a very stable thing, but some carbonyls are much "less stabilized" by whatever makes a carbonyl stable. So some carbonyls are highly reactive and tend to form acetals given the opportunity. Formaldehyde is a pretty common case...exists as the hydrate when mixed with water, easily forms polyacetal chains and rings by itself. DMacks (talk) 18:16, 16 June 2010 (UTC)

Unknown concentration of NaOH

50.0 mL of 1.5 mol/L HCl was mixed with 40 mL of NaOH of unknown concentration. The temperature increased by 8.4 K. a) Calculate the heat of neutralisation of the reaction. b) Calculate the concentration of the NaOH used.
H = mcΔT/n
So 50*4.184*8.4/n
n?
n??
--203.22.23.9 (talk) 23:44, 15 June 2010 (UTC)

The HCl and NaOH should react in a 1:1 mole ratio. So moles of HCl = moles of NaOH. You can find the moles of HCl from the info you wrote above. That also equals the moles of NaOH. You can use that number of moles, and the volume to calculate the concentration. --Jayron32 01:40, 16 June 2010 (UTC)

Question makes no sense as asked - the assumption that moles HCl=moles NaOH is the only way to get a definate answer - but makes no sense - how could they know how much HCl to add if NaOH conc. was unknown.. We will never know.87.102.18.94 (talk) 03:32, 16 June 2010 (UTC)

No, they are given a concentration and a volume of HCl initially, to which the NaOH is added. Calculating the moles (n) of HCl is trivially easy to do. The question is easily answerable, and is of a type which most students should be able to solve in any introductory chemistry class. --Jayron32 03:35, 16 June 2010 (UTC)

If it had said neutralised or titrated then it would make sense.87.102.92.166 (talk) 14:46, 16 June 2010 (UTC)

I think "m" should be 90, i.e. 40+50. The whole thing's heating up, not just the HCl. - Jarry1250 ^{[Humorous? Discuss.]} 14:06, 16 June 2010 (UTC)

June 16

What value is associated with "low impedance"?

What value is associated with "low impedance"? I know that in wire, the material, gauge, and length all contribute to the impedance. I continually see references to "low impedance", but is there a quantifiable answer to the value?—Preceding unsigned comment added by Blinstedt (talk • contribs) 00:33, 16 June 2010 (UTC)

It probably depends on the application. What sort of use are thinking of? --Jayron32 01:39, 16 June 2010 (UTC)

BTW, impedance is basically resistance as applied to A/C (like sound in a speaker wire). Ariel. (talk) 01:50, 16 June 2010 (UTC)

Blinstedt's question contains a hidden error. In wire, the length and diameter, and the resistivity of the material, all influence the resistance of the wire. Resistance is the ratio of potential difference (voltage) to direct current. Impedance is the ratio of potential difference to alternating current. Inductors have significant impedance because they prevent an alternating emf from causing as high a current as would occur if the emf was steady. Capacitors have low impedance because they allow an alternating emf to drive a continuous current (albeit a sinusoidal current.) So a low-impedance circuit has high values of capacitance and/or low values of inductance, and conversely a high-impedance circuit has low capacitance and/or high values of inductance. A thick piece of copper wire might have low resistance, but when used in series with a large inductor it becomes part of a high-impedance circuit. Conversely, a thin piece of copper wire might have high resistance, but when used in series with a large capacitor it becomes part of a low-impedance circuit. Dolphin (t) 03:10, 16 June 2010 (UTC)

You are mistaken. Please read the articles: Electrical impedance, Electrical reactance.—eric 03:22, 16 June 2010 (UTC)

People often use impedance as a synonym for Electrical reactance as dolphin has, I often make this error too. and see below.87.102.18.94 (talk) 03:28, 16 June 2010 (UTC)

I'll try = for power transmission low impedence means less than 1ohm. much less. For other applications such as audio inputs and outputs the answer is a bit different.

But we need to differentiate between reactive and resistive impedance too see Electrical_impedance#Device_examples for an explanation.87.102.18.94 (talk) 03:26, 16 June 2010 (UTC)

"High" and "low" are completely relative to your application so we cannot answer the question without more information. For example, when specifying a power transformer for a substation, typically a "standard impedance" transformer has an impedance of 10% or less, whereas a high impedance transformer would be 15% or more. There is no absolute impedance value that defines "high" or "low". Zunaid 09:03, 16 June 2010 (UTC)

To give another example: in the audio world, the most common low-impedance load is a loudspeaker, which usually has a value between 4 and 150 ohms, while an input to an amplifier, typically 10 kilohms or more, is considered high impedance. There is no exact dividing line between the two. --Heron (talk) 13:27, 16 June 2010 (UTC)

The general answer is that it depends on the application. The exact threshold could be defined as the point where accounting for the exact impedance value (as opposed to approximating it as zero) causes less than a 5% error in your application. So suppose you have a 9V battery, ignoring its equivalent series resistance, and using a piece of copper wire you connect the battery to a heating element like nichrome wire which has a 10ohm resistance. The electrical power turned to heat in the heater will be (9V)^2/(10 ohm) = 8.1 Watts, assuming the resistance of the copper wire is about zero. But suppose the copper wire has a resistance of 0.26ohms, then by using the voltage divider formula and we can see that the power being transferred to the heater has decreased by 5% from our nominal value to 7.69 watts. So below 0.26ohms maybe we don't care about the value of the copper wire's resistance, and assume it is zero, and we call it "low impedance" or "negligible". But above 0.26 ohms (in this case only) ignoring the exact value will lead to a greater than 5% error. But really "low impedance" is too vague to mean anything specific. Mattski (talk) 23:51, 16 June 2010 (UTC)

In my application, I am specifically interested in draining static electricity that is built up within a DC powered device. —Preceding unsigned comment added by Blinstedt (talk • contribs) 02:29, 17 June 2010

In that case you should work out the capacitance of your device, (probably in the picofarads range) and from how long you want to discharge to a particular fraction you can calculate a resistance required. I would expect anything below 100 megaohms will do the job to discharge static. Graeme Bartlett (talk) 12:52, 17 June 2010 (UTC)

Atom with some muons

If there is an atom with a muon or two replacing the electrons, do those muons sit in the same orbital as the electron they replace, or do they have their own, non-overlapping, series? And if it's their own series, does that mean the atom would then behave chemically as something else (because the outermost electrons are in a different shell)? Ariel. (talk) 01:41, 16 June 2010 (UTC)

Did you read the article in question? The section titled "Muonic atoms" discusses the exact issue you have, as does the linked article Exotic atom#Muonic atoms and the article Muonium discusses the exact opposite (where an antimuon replaces a proton). --Jayron32 01:54, 16 June 2010 (UTC)

These articles do not however answer the question about orbitals. Graeme Bartlett (talk) 01:55, 16 June 2010 (UTC)

Ah, of course. I would suspect that the orbital organization of a muonic atom would have to be different; since a muon has 200x the mass of an electron, its angular momentum would by necessity then be different, and a key component of orbital organization is angular momentum. See quantum numbers for a brief discussion of the role of angular momentum in orbital organization, or Azimuthal quantum number for a more detailed discussion. --Jayron32 03:05, 16 June 2010 (UTC)

To first approximation, an atom with X protons and N muons replacing electrons will have the same chemistry as an atom with X-N protons and no muons (provided X >> N). The muons have an independent series of quantum numbers and occupy much tighter orbits than electron, so effectively each muon results in one proton's worth of charge being hidden from the electron cloud so that the rest of the system behaves as if the nucleus was of lower charge. Dragons flight (talk) 03:17, 16 June 2010 (UTC)

Haha Dragons, are you willing to pull out Griffiths/Shankar and go through the derivations, as my copies are in storage? SamuelRiv (talk) 09:20, 16 June 2010 (UTC)

overcharging a handycam or mobile phone battery

why do some manufacturers advice us against leaving the batteries of handycam or mobile phones connected to the chargers for too long/ What happens when you over charge a battery? Fragrantforever 06:50, 16 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

There is a message on your talk page about signing posts that you might find helpful. ;-) Caesar's Daddy (talk) 07:30, 16 June 2010 (UTC)

If you leave a battery on a charger constantly it overheats, then dries out. The charger charges it till it's full, then the extra energy just goes to waste heating up the battery. The heat eventually dries it out, and then it doesn't work anymore. Depending on the chemistry of the battery it might damage it in other ways (rechargeable batteries are pretty delicate and are easy to damage). Lithium ion batteries especially get damaged if they overcharge even a little, so all of them include limiting circuity to prevent this. Another thing that can happen is the water in the battery gets electrolyzed into hydrogen and oxygen, which then either leaks out of the battery, causes it to swell, or (hopefully) gets recombined back to water, releasing some heat in the process.

If you want to store a battery most of them are best stored in a half charged state, except for lead acid which needs to be fully charged at all times. Ariel. (talk) 09:10, 16 June 2010 (UTC)

Note that smart chargers detect when the battery is fully charged and then stop charging it. Cell phone chargers seem to do this, for example. Unfortunately, many other chargers don't and there doesn't seem to be any standard way of labeling devices so you can tell if your charger is smart or stupid. However, if the instructions include that warning, it's probably the bad type of charger, so do as they suggest. StuRat (talk) 15:08, 16 June 2010 (UTC)

Thanks for the responses, Ceaser's daddy, I do add 4 tildes ( or whatever its called) at the end of all my posts and I thout that means signing my posts, it still says unsigned entry- which prompts you to drop a comment like that with a wink. 213.130.123.12 (talk) 10:22, 16 June 2010 (UTC)

You appear to have modified your default signature in such a way that SineBot does not recognize it. (See User:SineBot#What it looks for.) If you want to keep your linkless signature, you may wish to opt out of SineBot's scrutiny. 58.147.52.243 (talk) 10:56, 16 June 2010 (UTC)

Bad idea. See Wikipedia:Signatures#Links Nil Einne (talk) 18:33, 16 June 2010 (UTC)

yawning + stretching euphoria

why do you get euphoria when yawning + stretching in the morning (or any time of day, especially if you are a feline)? 92.224.204.156 (talk) 08:35, 16 June 2010 (UTC)

I'm not sure about the stretching, but yawning is a way of getting more oxygen into your blood which would make you more alert. Regards, --—Cyclonenim | Chat  11:21, 16 June 2010 (UTC)

That's what I thought too until I read up on this recently (trying to understand contagious yawning) and found that there is actually no data to support it. As far as I can tell, stretching feels good because it reduces muscle stiffness, and yawning may be a sort of stretching of the lungs. Looie496 (talk) 14:55, 16 June 2010 (UTC)

Evolutionarily speaking, things "feel good" which are (or were) helpful for passing on our genes. Stretching helps prevent injury and thus could keep our ancestors alive long enough to reproduce. As for yawning, the benefits there are less clear. StuRat (talk) 15:03, 16 June 2010 (UTC)

Will poppy seeds in processed horse feed test false positive for Synephrine in the urine or could slippery elm bark powder contain Synephrine.

Our race horse had a pre race urine sample taken which tested positive for Synephrine. My husband has been a trainer for thirty odd years and has never had a positive swab until now. Prior to the swab, we had started using processed feed in a pellet form, that was a bonus prize from a win we had with one of our horses. I read somewhere that poppy seeds, which were profuse here in Australia at the time and visible in unprocessed feed, can give a false positive for Synephrine and suspected that this may be the cause of the positive swab. I cannot find the article now to present to the stewards inquiry. Is this true? Will poppy seeds cause this result? Also we used slippery elm bark powder, which was guaranteed to be a legal substance that was safe to use when racing. We used this to prevent/relieve stomach ulcers that can be prevalent in race horses. —Preceding unsigned comment added by Traveloz (talk • contribs) 10:23, 16 June 2010 (UTC)

I've heard of poppy seeds giving false positives for opiate tests, but not for this. Synephrine is similar structurally to neo-synephrine which can give false positives for amphetamine/methamphetamine tests, but my previous point stands: poppy seeds shouldn't be giving false positives for synephrine, but instead for opiates. I'm not sure about slippery elm bark powder. I suspect you'd need to talk to a veterinary pharmacist for a conclusive answer. Regards, --—Cyclonenim | Chat  11:20, 16 June 2010 (UTC)

Volume of a drop

I have a tap that drips about once a second. I'm wondering how much water it is wasting a year. Drop (liquid) does not say what the volume is. Do not know if tap drops are always a particular size or if they vary. 92.28.251.43 (talk) 13:41, 16 June 2010 (UTC)

You could do an experiment... just put a liquid measuring cup under the tap, and record how long it takes to reach a certain volume. Google can make the calculation easy: example. -- Coneslayer (talk) 13:47, 16 June 2010 (UTC)

Drops will vary in size, but drops from a single source like this one should be consistent with themselves. Some of the math behind this is discussed at drop (liquid). However, you don't need that to estimate how much water you're wasting. Instead, grab a measuring cup (the one with the smallest graduations you have) and place it under the leak for a set period of time (longer is better, as long as you don't overflow the cup). You can then extrapolate annual leakage based on that short term. Suppose, for instance, that you got 1/4 cup of water in one hour's time. That would become 1/4 (cup/hour) * 24 (hours/day) * 365 (days/year) / 16 (cups/gallon) for about 140 gallons of water wasted per year. You could similarly estimate the volume of an individual drop. — Lomn 13:52, 16 June 2010 (UTC)

I agree with the previous responses. The reason is that there's a fair amount of error both in estimating the volume of a drop and in estimating the time increment between them. Collecting a larger volume over a larger time period will reduce both those errors and thus give a far more accurate total. However, use a tall, narrow container to collect the water, such as a vase. This will reduce water loss from splashing and evaporation. You can then pour it into a measuring cup. StuRat (talk) 14:54, 16 June 2010 (UTC)

Is there an approximate answer for the volume of a tap drop please? 92.28.251.43 (talk) 16:14, 16 June 2010 (UTC)

http://www.google.co.uk/search?q=volume+of+water+drop&hl=en&start=10&sa=N shows that the generally used figure is 1/20ml or 0.05ml ie 20,000 drops in a litre.87.102.92.166 (talk) 16:26, 16 June 2010 (UTC)

But, as we've noted, that doesn't mean your water drops will be 1/20 ml or anything like it. However, it would be trivial to determine this experimentally. StuRat suggests an excellent method above. — Lomn 18:39, 16 June 2010 (UTC)

WolframAlpha agrees with teh 0.05ml approximation. [15]. Aaadddaaammm (talk) 09:10, 17 June 2010 (UTC)

Thank you for your replies although I'm rather dissapointed that people seem to think I'm too stupid to have thought of the measure-it-yourself method before asking the question. I am busy. I make it 1577.88 litres a year, which is a lot. Now I'll have to find my metered water bill to see how much its costing me. 92.15.14.87 (talk) 17:15, 18 June 2010 (UTC)

It would take, what, a minute to place a measuring cup under the faucet and start a timer, a minute to read the cup and timer and put them away, and a minute to plug the values into Google? That's 3 minutes of work, and I think I'm being generous with the estimates. And you'd end up with an answer that actually meant something, and wouldn't give the impression that your time is so much more important than ours. -- Coneslayer (talk) 17:29, 18 June 2010 (UTC)

You would need an extremely small measuring jug for that, since you would only collect about 60 x 0.05ml = 0.003 litres. 92.15.4.168 (talk) 12:28, 19 June 2010 (UTC)

Um, no. You go do other things while the water is collecting in the measuring cup. You don't have to stand there watching it. At the risk of again insulting your intelligence, there's a difference between "3 minutes of work" and "the process taking 3 minutes from start to completion." -- Coneslayer (talk) 19:49, 19 June 2010 (UTC)

I don't want to play thank you, a quick estimate is better for the purpose at hand. Its charming how one gets detailed descriptions of obvious. 92.15.4.168 (talk) 20:27, 19 June 2010 (UTC)

~ (Tobacco vs. other illegal, recreational drugs)

So if I wanted to trade my legal cigarette smoke for illegal recreational drugs instead, in order to maintain whatever utility I think I get from the tobacco smoking, while expressly making the trade (with concommitant justice risk) in order to reap certain comparative health benefits for the same level of utility, would I be able to do so? As for the utility part, I shall have to judge, but for the health part, I think you can help me. Viz.

• How do the health effects of tobacco use compare with the health effects of other, illegal, recreational drugs?

Specifically, what is most comparable in its effects both during consumption and in terms of deletirious health consequences? Note: because in my estimation there are something like a few million dollars of salaries going into Wikipedia shills, I would like to mention that I have absolutely no relationship with tobacco or any other drug other than being a simple consumer. 84.153.246.145 (talk) 13:57, 16 June 2010 (UTC)

I changed your useless title to one which actually identifies the question. StuRat (talk) 14:51, 16 June 2010 (UTC)

At what point did the OP mention cannabis? There are other illegal drugs which can be vaporised or smoked, so I've renamed again accordingly. Regards, --—Cyclonenim | Chat  15:02, 16 June 2010 (UTC)

OK, but please always leave the original title, both so they can use it as a search term and so everyone knows what I was talking about when I said the original title was useless. I've therefore added the original title (a single tilde), back in. StuRat (talk) 15:28, 16 June 2010 (UTC)

To answer your question, I recommend reading these links: Health effects of tobacco, effects of cannabis, heroin#Risks of use and cocaine#Effects and health issues. Of course, there are other drugs, and if you search for their articles you'll usually find either a separate article on their health effects, or a subsection discussing it. Regards, --—Cyclonenim | Chat  15:04, 16 June 2010 (UTC)

Thanks, I'm pretty sure heroin and cocaine are off the scale in terms of risk versus tobacco, though. Isn't there something comparable? (op here) 84.153.246.145 (talk) 15:35, 16 June 2010 (UTC)

This chart should help. Note, that while I personally am not so convinced it's accurate (for example I think solvents are more dangerous than alcohol), it's probably a good start. (My main objection is how the raw data was combined into a mean.) Anyway, based on it Khat seems like the best choice. Ariel. (talk) 15:52, 16 June 2010 (UTC)

And that proves your point. Khat causes severe psychosis. The Somali community in Leicester (where I used to teach) are campaigning to get it put on the banned list in the UK because it causes more social harm in that commmunity than any other drug, legal or otherwise. But you wouldn't know that from that chart! When I get chance (later on tonight) I'll try and find the research they've used in their campaign. --TammyMoet (talk) 16:31, 16 June 2010 (UTC) Here's one: http://informahealthcare.com/doi/abs/10.3109/00048679409075648 --TammyMoet (talk) 17:24, 16 June 2010 (UTC)

I wonder where chewing of Coca leaves falls on the chart? (It is not the same thing as doing concentrated cocaine.) Off the top of my head that seems like it is probably a similar trade-off as tobacco, perhaps even a bit better for one (similar physical effects, but without the obvious lung problems). It's not illegal everywhere, but it is in the United States, so that satisfies the "illegality" component. This is not medical advice in the slightest—there are probably long-term health risks associated with chewing Coca leaves, and how they stack up against long-term risk from cigarettes, I honestly don't know. --Mr.98 (talk) 17:23, 16 June 2010 (UTC)

Interesting - I wonder where this chart came from, and what it was designed to do? for instance, yes, chewing cocoa leaves should be far less dangerous that snorting concentrated cocaine. further, while cannabis ounce for ounce might be comparable to cigarettes in terms of toxins, no one smokes 20 cigarrette-sized joints a day. consumption is probably less that 1/20th that of tobacco even in the heaviest pot smokers. Hashish might be different, of course. I'm really curious about the positioning of LSD, though - LSD is entirely non-addictive and has negligible physiological effects on the body (I don't even think researchers have discovered a toxic dose level for it). It really should be down close to 0,0, though that's not a recommendation for use (LSD is not a drug that should be taken casually, because it has intense psychological ramifications). --Ludwigs2 19:15, 16 June 2010 (UTC)--Ludwigs2 19:15, 16 June 2010 (UTC)

Is it useful to read the chart as whatever has the lowest total score is the most desirable? Presumably if you were to try to replace one with another you would have to give one addiction in favor of another addiction, right? Assuming that the "dependence" is the reliance on the effect of the drug that you develop. If that is the case then isn't it more appropriate to think of it as dependence divided by harm? Since trying to replace a high-dependence, high-harm drug with a low-dependence, low-harm drug is likely to result in failure due to your body still craving the old drug? Remember, the OP did say that he was interested in the "utility" of the drug vs smoking which means he would have to supplant his cigarette addiction with whatever addiction this new drug offered. This is an interesting (if morbid) thought experiment. How about not being addicted to any drug? Why isn't that on the chart? --144.191.148.3 (talk) 19:27, 16 June 2010 (UTC)

Tobacco has an interesting feature that the physically addictive (and perhaps even beneficial) portion, nicotine, is completely separate from the unhealthy portion, called "tar". Unfortunately, current smokers seem to associate the tar with the "nicotine high", and thus aren't satisfied with no-tar cigarettes, called a psychological addiction. However, perhaps if no-tar cigarettes were provided to new smokers, or better yet, cheap nicotine patches, pills, etc., then they wouldn't ever associate tar with the "nicotine high" and therefore wouldn't crave it, with the additional benefit of eliminating or reducing the harm to others from second-hand smoke. StuRat (talk) 13:03, 17 June 2010 (UTC)

errr... nicotine is a neurotoxin - for the tobacco plant it's a built in insecticide. like any poison it can have beneficial uses, but... --Ludwigs2 20:00, 17 June 2010 (UTC)

The dose makes the poison. --Carnildo (talk) 01:36, 18 June 2010 (UTC)

Absolutely. Sure it's toxic at a high enough level, but so is iron and many other nutrients we need. So nicotine's toxicity is quite irrelevant, unless you plan to make yourself a belt out of nicotine patches. StuRat (talk) 14:19, 18 June 2010 (UTC)

Not true, it's toxic at any level and it's definitely not irrelevant. See nicotine poisoning. You can't compare an essential nutrient to a toxin. It's like comparing vitamin C and cyanide. Regards, --—Cyclonenim | Chat  16:40, 18 June 2010 (UTC)

I think StuRat meant, it's fatally toxic at a high enough level. And many, many things are toxic in high levels. Vitamin C happens to be pretty benign because it is water-soluble and thus flushes out easily, but many other vitamins—Vitamin A or Vitamin D for example—are indeed quite http://en.wikipedia.org/w/index.php?title=Wikipedia:Reference_desk/Science&action=edit&section=8toxic at high levels. Cyanide is much higher in toxicity, but that's not the point being discussed here. The point is that just about everything has a level of toxicity associated with it in large doses. As our article on Toxicity explains quite clearly: "A central concept of toxicology is that effects are dose-dependent; even water can lead to water intoxication when taken in large enough doses, whereas for even a very toxic substance such as snake venom there is a dose below which there is no detectable toxic effect." --Mr.98 (talk) 17:10, 18 June 2010 (UTC)

I do understand what you're saying, but my point is that water is usually not toxic because on a molecular basis it is good for you, not bad. Nicotine, whether just the one molecule or millions of molecules, is harmful. Just because we recover from small doses of nicotine very effectively doesn't mean that it's not toxic at those levels. Does that make sense? Regards, --—Cyclonenim | Chat  17:43, 18 June 2010 (UTC)

No, it doesn't make sense. There is nothing inherently "good" or "bad" about molecules. --Carnildo (talk) 23:38, 18 June 2010 (UTC)

Yes, there is. A molecule of water doesn't do any damage to your body, it just gets transported in and out of cells. A molecule of nicotine, on the other hand, competes with acetylcholine receptors. That can be harmful. Regards, --—Cyclonenim | Chat  10:56, 19 June 2010 (UTC)

Regrowing of human skin and its color

The other day I saw an African-American firefighter. He had suffered a serious burn on his face at some point in his life, but the skin was all grown back. However, the skin was nowhere close to the tone that the rest of his skin was so it looked like a mask. Just a white patch around his mouth and dark brown skin everywhere else on his face. I know that skin color has a lot to do with melanin, but I am wondering why it didn't grow back the same color that it was previously. Is there only so much melanin in the body? Thanks, The Reader who Writes (talk) 15:20, 16 June 2010 (UTC)

The same applies to skins of naturally paler colours - the new growth is even paler. I don't know the reason though, except to note that skin naturally grows darker as it ages and is exposed to UV. Dbfirs 15:43, 16 June 2010 (UTC)

It's likely that the burn was of a significant enough degree to damage the melanocytes which lie at the bottom of the epidermis. Bad first degree burns and all second and third degree burns cause this damage. I suspect that the burn was bad enough to prevent the repopulation of melanocytes to the area. Regards, --—Cyclonenim | Chat  16:19, 16 June 2010 (UTC)

The white patch may have been vitiligo which is known to sometimes occur in association with trauma to the skin. 86.4.183.90 (talk) 07:02, 17 June 2010 (UTC)

A display that doesn't suffer from glare

I was checking out some of the next gen display technologies like Laser TV, and Field Emission Displays. But one thing all these displays have in common is that bright sunlight creates large amounts of glare. Is there any display technology, present or future, that will not suffer from glare while delivering high definition/quality visuals? And I'm talking about broad sunlight, like if you had your laptop or whatever out in the park in the middle of the day.

What about holograms? Don't know how advanced this technology is, but in some sci fi games, and movies they use holograms as displays in their futuristic worlds. How well will they work in broad sunlight? 148.168.127.10 (talk) 15:46, 16 June 2010 (UTC)

This isn't an answer, more of a point to ponder, but how can you create a device which emits light, but doesn't reflect it back when it shines on it's surface? I would have thought any coating that prevents glare would also darken the image. Regards, --—Cyclonenim | Chat  16:21, 16 June 2010 (UTC)

My wife has read her Kindle on the beach in extremely glaring sunlight. So, that is one very anti-glare display. However, it is only black-and-white. -- kainaw™ 16:23, 16 June 2010 (UTC)

That's the answer. ePaper. Currently only available in monochrome, but color ePaper displays are in development. APL (talk) 16:33, 16 June 2010 (UTC)

I would think any reflective capable display would also work similarly. These are usually monochrome and of course also require ambient lighting to see which may be undesirable in some circumstances. One option is for a combined display which can operate in either reflective or transmissive modes like the OLPCs or Pixel Qi although these still operate in monochrome in reflective mode. Or perhaps a transflective liquid crystal display. Nil Einne (talk) 18:24, 16 June 2010 (UTC)

Conservation of energy

What's the difference/resemblance between the conservation of energy and the first law of thermodynamics? /Natox (talk) 17:05, 16 June 2010 (UTC)

Quoting from the article: "The first law of thermodynamics [is] an expression of the principle of conservation of energy." If you want to get picky, the FLoT addresses non-isolated systems by expanding the system in question until it's isolated. — Lomn 18:33, 16 June 2010 (UTC)

No difference. The 1st law of thermodynamics is The conservation of energy applyed to thermodynamic systems. Dauto (talk) 20:56, 16 June 2010 (UTC)

Spider indentification

what kind of granddaddy long legs spider is white with black spots, and has two front yellow fangs? —Preceding unsigned comment added by 71.50.164.12 (talk) 17:05, 16 June 2010 (UTC)

It's hopeless without a picture. If by granddaddy-long-legs you mean a harvestman, then many if not most of them (and there are over 200 species in US) have spotted or wavy patterns of dark gray or brown with white or beige, and some indeed have pale chelicerae and pedipalps. Leiobunum vittatum is fairly common and may fit the bill, but there are many others, too. However, granddaddy-long-legs may also refer to Pholcidae. Which is it? --Dr Dima (talk) 18:20, 16 June 2010 (UTC)

You also have to tell us where you saw it. --Sean 19:43, 16 June 2010 (UTC)

Protein percentage in muscle by mass

Hello. Can someone please tell me what is the percentage of protein in muscle by mass, or in other words, roughly how many grams of protein can I expect to find in 100 grammes of an average muscle. Thank you.--Leptictidium (mt) 18:12, 16 June 2010 (UTC)

You might find list of foods by protein content informative, but that lists muscles in an edible state, which presumably means cooked, so some protein loss might occur in that process. --Sean 19:45, 16 June 2010 (UTC)

Most meat (animal meat) is muscle, so it's the same as that. Ariel. (talk) 23:20, 16 June 2010 (UTC)

If that 100 grams of muscle is not dehydrated, then a significant amount will be water. Protein with make up most of the remaining amount. So, a ballpark guess is 90+% if dehydrated, but 50% or less if not dehydrated. --Rajah (talk) 18:01, 17 June 2010 (UTC)

Stronger reducing agent than azide

What is the strongest stable reducing agent? --Chemicalinterest (talk) 19:10, 16 June 2010 (UTC)

Under normal conditions probably lithium. The trick answer is a charged capacitor - stable form of stored electrons - any electrochemical potential you like ie will reduced Li+ Cs+ etc etc.87.102.92.166 (talk) 12:22, 17 June 2010 (UTC)

Lithium is the most electropositive, however be careful in air it can catch fire and melt. Graeme Bartlett (talk) 12:44, 17 June 2010 (UTC)

Electropositivity says this property "increases down groups" so sodium would beat lithium (and potassium beat sodium)? Lithium and sodium are pretty easy to handle without being too likely to burst into flame accidentally. Potassium starts to more strictly require inert atmosphere. DMacks (talk) 18:22, 17 June 2010 (UTC)

Lithium is the least electropositive, but it has the highest standard reduction potential, -3.0401. Azide is -3.09, HN₃ + e^- ⇌ ³/₂ N₂ + H⁺. --Chemicalinterest (talk) 11:30, 18 June 2010 (UTC)

Strongest base

There's a redirect at strongest acid but not at strongest base, so what's the strongest base? --76.77.139.243 (talk) 19:16, 16 June 2010 (UTC)

Tert-Butyllithium - It has a pKa of greater than 50 if my memory serves. Regards, --—Cyclonenim | Chat  20:00, 16 June 2010 (UTC)

We have an article about superbases. For example, swapping tBuLi to tBuK makes it stronger. DMacks (talk) 20:07, 16 June 2010 (UTC)

Kewl. What happens if you mix a superbase with a superacid? Are there any YouTube videos, like the ones of people pouring liquid oxygen on their charcoal grills? I suppose the reaction might be just boring; that would be too bad. --Trovatore (talk) 21:30, 16 June 2010 (UTC)

Even "moderately strong" bases (almost any organometallic) reacts rapidly when exposed to the air (humidity and/or CO2), don't even need any "extra" reactivity of a complementary strong acid. The reactions are extremely exothermic, but nothing visibly dramatic unless the heat is enough to boil a solvent or fracture a glass flask. Then it's nothing special, just "a flask explodes". It gets dramatic when there is air present, because there is enough energy released to ignite the solvents or the bases themselves (n-BuLi reacts with traces of moisture to form butane and heat, for example). And it's really easy to lose control or have even a small amount of material create a very dangerous situation (unlike a charcoal fire contained to a grill, or a thermite reaction in a flowerpot, for example) because of the volatile solvents involved. This accident was less than 50 mL total. DMacks (talk) 22:29, 16 June 2010 (UTC)

That's very sad. Not what I had in mind, of course. --Trovatore (talk) 22:46, 16 June 2010 (UTC)

Tert-Butyllithium is sold as a solution in an inert solvent, for example tetrahydrofuran or hexane. I once worked with someone who accidentally let a single drop of the solution fall on chem-wipe tissue and it instantly caught fire (everyone was fine). Just spraying it in the air on even a 'not humid' day (there is always some moisture) will apparently cause it to burst into flames (graduate schools can have some poor waste disposal options). Mixing it with strong acids will be very exothermic.Pmdove (talk) 02:09, 18 June 2010 (UTC)

How can I make it not possible to throw things

I don't want people throwing things in my apartment, how do I make it so you have to place things, you can't throw them (anything)? Note: I don't think I ever throw anything at all, but I would like the change to be reversible in case there is some bad consequence I didn't think of,l. Would I have to change inertia (inertial dampers?) air viscosity, or what, and how would you do it, 85.181.146.84 (talk) 19:50, 16 June 2010 (UTC)

You can't. Next question! — Lomn 20:07, 16 June 2010 (UTC)

Concur, you can't have inertial dampers because they don't exist in that sense, we're not in the Star Trek universe unfortunately. You can't change the air viscosity because you'd have to have a solid to prevent things from moving, thus you couldn't move either. You'd be encased! Regards, --—Cyclonenim | Chat  20:12, 16 June 2010 (UTC)

Get everyone out of the apartment. Close and lock the door from the outside. Throw away the key. Problem solved. --Sean 20:23, 16 June 2010 (UTC)

Move to an Earth-like planet with a gravitational field strong enough to make everyday objects impossible to lift. Don't expect to be walking anywhere. (Is such a planet possible, or would the increased gravity cause fundamental differences precluding Earthlikeness? 20:32, 16 June 2010 (UTC)Vimescarrot (talk)

Possibly. The Moon might not have had a chance to form if the gravity of the Earth was stronger than it is/was, and our Earth would not be as stable as it is now. It was on Discovery Channel a few nights ago, saying that when the Moon finally escapes orbit all sorts of apocalyptic scenarios will happen (but it doesn't matter because the next program was about 2012). If we hadn't had a moon in the first place, though, then those scenarios would have already happened and life possibly would have evolved anyway, as hardy as it is, just not in the same way. Also, we cannot preclude the possibility that throwing things may be a very welcome evolutionary feature, and the existing animals (or some of them) would evolve to do it anyway, such as by being stronger. Therefore we can envisage a world with no moon, no tides, no months to count, and populated by short squat people with massive biceps. --KägeTorä - (影虎) (TALK) 11:26, 17 June 2010 (UTC)

Invest in friends who don['t throw things. it will be worth the money in the long run. --Ludwigs2 20:31, 16 June 2010 (UTC)

This is an exercise in apartment design. Furnish your apartment with only objects that cannot practically be thrown. Areas that need small objects (Kitchens?) could be constructed so cramped that throwing items is impractical.

That's really the only answer, there's no way to adjust the laws of physics in your room in such a way that things can't be thrown, but they can still move when carried. (Otherwise you could fill the apartment with concrete, or Lucite.)APL (talk) 20:38, 16 June 2010 (UTC)

Recently while reading about ADX Florence I came across this lovely graphic: [16]. You can design your apartment to look like that: there will be no objects that are physically capable of being picked up, moved, or thrown. All furniture is made of concrete and is part of the floor. The only other item(s) are a monolithic toilet/sink. Nimur (talk) 22:35, 16 June 2010 (UTC)

Cover EVERYTHING with Velcro!!!!! SamuelRiv (talk) 01:12, 17 June 2010 (UTC)

I'm surprised no-one's mentioned punishment. It's impossible to change the laws of physics but not human behaviour. Next time anyone throws anything, give them a good kicking. In the end, they'll either mend their ways or move out. Either way, nobody's throwing stuff any more and nobody's getting a good kicking any more. Everyone wins. --KägeTorä - (影虎) (TALK) 01:46, 17 June 2010 (UTC)

You could have nets everywhere, so you have to walk through a maze of suspended nets to get anywhere. This would make throwing things pointless, as they would just get caught in a net. StuRat (talk) 03:58, 17 June 2010 (UTC)

Change the definition of "throw." It's just a linguistic problem. Bus stop (talk) 04:11, 17 June 2010 (UTC)

Fill the apartment with Jello and wear scuba gear when inside. I considered whether it would be possible to have a computer detect a 'thrown' object with cameras, but can't think of a device it could then activate to stop it from moving (a high speed jet of air doesn't seem effective.) RJFJR (talk) 17:41, 17 June 2010 (UTC)

Since we're getting silly, have the computer automatically fire a paint-ball gun at any one who throws something in the room? CS Miller (talk) 18:05, 17 June 2010 (UTC)

The telomeres of Turritopsis nutricula

I'm a layman with respect to biology, but from what I have read, the telomeres of chromosomes for most species get a little shorter with each cell division until a cell can't divide anymore. But at List of long-living organisms, it says "Turritopsis nutricula is capable of cycling from a mature adult stage to an immature polyp stage and back again. This means that there may be no natural limit to its life span." I know it's not certain whether there's a causal relationship between telomere length and aging, but limitless life span seems to necessarily imply limitless ability to divide. So does Turritopsis nutricula not lose any telomere length at all on each cell division, or does it keep adding as much as it loses, or something else? I saw the abstract at the link entitled "Telomerase activity is not related to life history stage in the jellyfish Cassiopea sp." at the bottom of Turritopsis nutricula but didn't really understand it. Thanks. 20.137.18.50 (talk) 19:59, 16 June 2010 (UTC)

I am also a biology layman but I believe telomere shortening isn't necessarily a "given" in cell division. For example I've heard cancer cells divide without telomere shortening, this is what allows them to grow out of control, because they don't "run their course". So it's not impossible to divide a cell without shortening telomeres. Maybe it's because we assume aging is "inevitable" so it must be the result of a inevitable process, so telomere shortening must be inevitable. But I think aging is quite probably just another evolved trait, so telomere shortening could very well be just another regular biological mechanism. Vespine (talk) 00:22, 17 June 2010 (UTC)

Our telomere article suggests other ways that organisms can get around this - some have circular DNA molecules that don't need telomeres to stop them destroying themselves. Others have enzymes that replace the missing telomeres so that they never run out. There seems to be a lot of complexity going on here. SteveBaker (talk) 00:36, 17 June 2010 (UTC)

The paper you reference [17] (subscription probably needed...) measured telomerase activity in this jellyfish. Telomerase is the enzyme that fixes the shortening of telomeres - in mammals it's only active in stem cells, cancer cells, etc. But this study found it active all the time in the jellyfish. They didn't check if the telomeres are actually maintained at the same length, but it's a pretty good suggestion that they are "adding as much as it loses". Aaadddaaammm (talk) 09:07, 17 June 2010 (UTC)

Just wanted to point out that telomeres can be resynthesized and maintained for a very long time. e.g. all the cells in your body divided from a cell that was created by your mother and father, and all of theirs, ... etc. all the way back to cell-1 a few billion years ago. Cheers! --Rajah (talk) 18:11, 17 June 2010 (UTC)

Number of deep sea oil rigs worldwide

How many deep sea oil rigs are there worldwide and how many are owned by which major oil companies.

I can not find this information in any Wikipedia articles.

Gary Tennison [email removed] —Preceding unsigned comment added by 70.168.154.204 (talk) 20:31, 16 June 2010 (UTC)

There are about 100,000 offshore wells (or holes, it's not clear). Does offshore mean deep sea to you? Anyway see [18], [19], [20], [21] Ariel. (talk) 21:27, 16 June 2010 (UTC)

Every week, Oil & Gas Journal [22] publishes a statistics list of countries operating offshore rigs, and estimated production figures. They also have a Production and Operations section in each issue. You can find these numbers week-by-week. They fluctuate based on the economics of operating the rigs. (It looks like the web/HTML current issue doesn't have these statistics available for free, but you might find a hard-copy in a library or research university). Correction: You can get these statistics for free by subscribing to the O&G Email Newsletter: [23] - be sure to check "OGJ Monthly Drilling & Production Report" and any others of interest to you. Nimur (talk) 22:26, 16 June 2010 (UTC)

I don't know about the world-wide numbers - I've seen figures suggesting about about 4000 wells operating in the Gulf of Mexico alone - and also numbers that say that there are 5600 oil rigs world-wide. The difficulty of sorting out what is a "rig" and what is a "well" - and what is "operating" and what isn't makes this a tough question. SteveBaker (talk) 00:34, 17 June 2010 (UTC)

Cumberland Slider Turtles

We recently had a turtle lay her eggs in our garden. We live on the North Fork of the Holston River in Tennessee. How long will it be before we see these hatch? —Preceding unsigned comment added by 173.105.80.255 (talk) 20:37, 16 June 2010 (UTC)

don't forget not to get your hopes up as these eggs are delicious for many predators. 92.229.12.200 (talk) 20:58, 16 June 2010 (UTC)

"Hatching usually takes place in the late summer or early fall but some sliders over winter as eggs and hatch in early spring." [24] "It takes 2 to 2.5 months for young to hatch." [25] "Young turtles hatch in 8-10 weeks, though occasionally they will spend the winter underground in the nest." [26] Ariel. (talk) 00:09, 17 June 2010 (UTC)

Is it fair to say that Nuclear Power plants are environmentally friendly?

Because we all know about nuclear waste. But can it be said that as long as the nuclear waste is either properly disposed of or recycled, that a nuclear power plant is enivronmentally friendly, and produces no negative impact to the environment? 148.168.127.10 (talk) 20:43, 16 June 2010 (UTC)

Yes, it is actually a lot easier to dispose of nuclear energy than it sounds. It is certainly much more environmentally friendly than fossil fuels, since a rice-grain size piece of ²³⁵U produce as much energy as three tons of coal or fourteen barrels of oil, so certainly a rice-sized piece of nuclear waste does much less damage to the environment than all the CO₂ produced by fossil fuels. --The High Fin Sperm Whale 20:51, 16 June 2010 (UTC)

Compared to the fossil-fuel alternatives, they are massively better. Nuclear waste issues really fall into two classes - the highly radioactive waste (which can be recycled and reused) - and low level stuff which is a pain to dispose of safely. However, coal-fired power plants take vast amounts of coal with background levels of radiation - and concentrate it down into ash - which ends up being fairly radioactive. It turns out that when you take out the recyclable waste from a nuclear plant - what's left is actually quite a bit LESS radioactive than the ash that comes from a coal plant...mega-watt for mega-watt that is. SteveBaker (talk) 21:54, 16 June 2010 (UTC)

it's one of those trade-offs. the normal consumption of fossil fuels is worse for the environment than the normal use of nuclear power, but nuclear power accidents are much worse than fossil fuel accidents. The entire Gulf 'deepwater horizon' debacle isn't going to be a fraction as damaging as the Chernobyl disaster. --Ludwigs2 22:00, 16 June 2010 (UTC)

Indeed, Belarus estimated the cost from the explosion to modern day to be around $250 billion. In comparison, the gulf oil leak is currently estimated to cost around $15 billion to clean up, plus whatever they decide/are forced to pay out in damages. Of course, the economical cost is yet unknown, but BP lost about $60 billion of it's value on the stock markets. Regards, --—Cyclonenim | Chat  22:16, 16 June 2010 (UTC)

You need to multiply damage by frequency to get any sort of reasonable comparison. We have had exactly one serious accident (not including early times when we didn't understand this stuff well) (3 mile island didn't cost much). How many oil leaks have there been? How many people were killed by coal mines? Nuclear is much safer. And less radioactive too - burning coal releases a TON of radiation into the air. Far more than nuclear plants do. Ariel. (talk) 22:28, 16 June 2010 (UTC)

There are really a couple environmental questions that would need to be disentangled:

• What are the "normal" environmental costs of nuclear power as it current operates?
• What are the "normal" environmental costs of nuclear power if it were done differently? (E.g., with fuel reprocessing, which would reduce the waste volume considerably, but has been halted in the U.S. since the 1970s because of plutonium economy fears)
• What are the likely costs from not totally rare accidents?
• What are the likely costs from one-in-a-million, worst-case-scenario accidents?
• And how do these costs and benefits stack up against the comparative risks and benefits from other energy generation schemes? (Fossil, renewables, increased conservation, etc.)

It's a big equation, and there are a lot of places where informed experts, acting in good faith, will disagree. And plenty more places where uninformed pundits, or people acting really in service of one agenda or another, will disagree. Even whether something Chernobyl should be taken into account at all is something well-informed people could dispute. Chernobyl was of a plant that was inherently more dangerous than any U.S. power plants, for example, and was being run in an exceptionally shoddy manner, and had basically no disaster mitigation done afterwards because of the dysfunctional nature of the Soviet bureaucracy at that time. Is it really a useful analog to making sense of nuclear power as a whole, or is it just a specific, weird, "one-in-a-million" case? Very smart and honest people would probably disagree on that.

I'm not saying, "it's unanswerable"—it is surely answerable within certain parameters. But the odds of getting a well-informed, balanced set of answers that everyone will agree upon is pretty unlikely. Even sorting out what the right questions are is a contentious activity. --Mr.98 (talk) 22:45, 16 June 2010 (UTC)

There are certainly modern nuclear plants that are inherently safe - but even in the case of Chernobyl, the human cost was immense - but the long term ecological damage is much more debatable. The lack of people around the plant means that wildlife has had a chance to rebound strongly. Most animals are too short-lived to suffer most of the longer term ill-effects of radiation that humans suffer from - and the presence of humans is vastly more damaging to their lives than the radiation problem. This paper says that numerous kinds of wildlife are thriving inside the 10km (human) exclusion zone - and doing considerably better than in the 30km zone where limited human return has been allowed.

But more to the point - over the lifespan of nuclear power, Chernobyl is actually the only significant accident we've had. Even Three Mile Island eventually ended fairly well. Contrast that to dozens of major oil spills from wrecked tankers - and many other drilling rig disasters. You might think the present spill in the gulf is bad - but it's not that much different from the Ixtoc I oil spill and way less than the Lakeview Gusher. Also, coal power has resulted in massive problems with ash tips subsiding, dams breaking and all manner of other major problems resulting in much MUCH more loss of life than Chernobyl...although not in such spectacular fashion. Only 35 people died directly at Chernobyl - and the 2% increased cancer risk for perhaps 200,000 people living near to the site adds 4,000 more deaths - but those people will die after happily living a considerable fraction of their lives, so it's not really fair to equate them. Many people lost their homes and jobs - but the Gulf Oil spill will cause similar disruption for fishermen and people in the tourist industry and destruction of the wetlands around the coast will cause more problems with storm surges and flooding in the future. But bear in mind - that's across the entire planet and over the entire lifetime of the industry! By comparison, the various oil/gas/coal industry disasters of just the last few year have killed WAY more people than Chernobyl. 6000 coal miners die every year in China alone! Sure, China's a long way away and so maybe you don't care - but Russia is also a long way away so why do you care about that?

There is absolutely no credible argument that nuclear power is more dangerous, more polluting, worse for the environment when compared to coal, oil and natural gas production. Add the lack of CO2 pollution and the consequent world-wide disaster that's about to befall us all and it's a no-brainer. We need nuclear power to cover the gap while we downscale our energy consumption, get wind, wave and solar up to speed - and maybe figure out how to do fusion in a practical manner. Nuclear clearly isn't the most desirable solution - but it's a pill we have to swallow for the eventual health of the planet.

SteveBaker (talk) 00:04, 17 June 2010 (UTC)

I used to be totally against it, but I researched it a bit and i've changed my mind over the last few years. I think the main stumbling block is the the common perception that each nuclear power plant is basically an atom bomb waiting to go off. Chernobyl is all the proof people need. But the fact is, plant technology today, is not only more advanced, it's completely different, they have fail SAFE operation now, not fail disaster like in Chernobyl, it means when stuff goes wrong, the reactions stop instead of going critical. As for the waste, plant technology now is so much more efficient it will produce less waste in the foreseeable future then we've already made and have to deal with. Vespine (talk) 01:01, 17 June 2010 (UTC)

It's worth noting that the US didn't have Chernobyl-like reactors then, either. It's not like people didn't know the risks that Chernobyl presented. — Lomn 01:12, 17 June 2010 (UTC)

Then there's my suggestion of building nuke plants deep underground where terrorists can't get at them, with cooling towers up above. They can also just push the nuclear waste further back into the cave and not worry about transporting it. StuRat (talk) 03:50, 17 June 2010 (UTC)

You mean like these: [27]? Rmhermen (talk) 07:50, 17 June 2010 (UTC)

Except for the "mini" part, perhaps. That one is apparently designed to be both unmanned and unguarded, allowing terrorists to steal the nuclear material and use it to make a dirty bomb. StuRat (talk) 12:37, 17 June 2010 (UTC)

The other significant thing to note about Chernobyl is that it didn't fail during normal operations. They were actually experimenting on one of the two reactors - seeing if shutting off all of the safety systems and cutting primary power to the coolant pumps would allow time for the backup systems to kick in. All it took was one actual failure of backup systems during the experiment to kill the system and cause a catastrophic cascade of events that lead to the ultimate disaster. That kind of experimentation on a live reactor was just a crazy thing to be doing. Read the timeline of events in our Chernobyl disaster article and you'll be horrified at the stupid risks those guys were taking. These days we could do much of that experimentation in software simulators and only do verification of those test results on the live reactor...and I'm sure that the protocols for doing that are much stricter than they were back then. These risks are highly manageable - unlike in coal mining and oil drilling where loss of life is seen as an inevitable part of the operation. SteveBaker (talk) 11:48, 17 June 2010 (UTC)

However, we should plan for the worst case scenario. Based on the Gulf oil spill, we should expect the following:

1) Like BP, any company running a nuclear reactor may lie to regulators about their ability to prevent an accident, their ability to stop an accident in progress, their ability to clean up after, and the magnitude of the accident, once it occurs.

2) Also assume that the company will ignore all safety rules and regulations.

3) Like now, government regulators can be assumed to be both incomptent and in the pockets of the industry they are supposed to be regulating, thus effectively shielding the private company from public scrutiny and criticism while providing zero regulatory control.

So, then, can we come up with a design for a nuclear plant which is still safe given these assumptions ? StuRat (talk) 12:50, 17 June 2010 (UTC)

The assumptions have actually not proven to be valid. American nuclear regulation is based on defense in depth, with the idea that while it's possible for things to go wrong, you'd need a huge number of things going wrong at the exact same time for a worst-case scenario. The one-in-a-million scenario is not necessarily the one that should bend the entire production line around it, if you can reasonably break the risk into discrete chunks. The one-in-a-thousand scenario, definitely. But in any case, there are many different designs for plants, some of which afford greater inherent protection against serious accidents than others, and I think that the years since TMI in the US have shown that regulation doesn't have to be a bust (we've never had anything even close to it happening happen again in the US, and even then, TMI didn't kill or harm even one person). --Mr.98 (talk) 14:13, 17 June 2010 (UTC)

Why do you say those assumptions aren't valid ? If it can happen in one industry (oil), it can happen in another. Multiple safeguards are good, but can also increase complacency. As in the Chernobyl case, people might reason "we don't have to worry about disabling that safeguard, there are others". I've noticed this myself, when I thought it would be a good idea to have spare car ready to use if my primary car fails. The reality, however, was that one of them would break down, and having another usable car took all pressure off me to fix that broken one, so I always had one broken-down car after that. Putting in too many safeguards can make people just ignore them entirely, like the extreme rules for passwords at EDS which resulted in everyone having such complex passwords that they wrote them down on a Post-It note and stuck it to the computer. Similarly, if people going in the front door of a secure building must undergo the equivalent of a full body cavity search, you will find the back door chained open, with no security at all.

I like the idea of inherently safe designs, like one where gravity will drop control rods into the reactor core in the event of a power failure. Unfortunately, one particularly stupid design had caps on the end of the control rods which reflected radiated particles, thus actually increasing the reaction rate when the control rods first started to lower. StuRat (talk) 14:14, 18 June 2010 (UTC)

Use thorium reactors. Thorium is much more common than uranium, and thorium's most common isotope can be used for fission as-is (unlike uranium). Thorium reactors also produce more power and have even less nuclear waste than uranium reactors. --76.77.139.243 (talk) 12:33, 17 June 2010 (UTC)

However, in the US we have an almost unlimited supply of refined uranium available from decommissioned nuclear weapons. StuRat (talk) 12:42, 17 June 2010 (UTC)

It's not true that thorium's most common isotope can be used for fission. In the presence of neutrons, it can be bred into U-233, which is fissile. This is analogous to the fact that U-238, in the presence of neutrons, can be bred into Plutonium. Both of these still require an existing neutron economy—you need uranium reactors to start the thorium cycle. In any case, in the US, there is no reprocessing currently undergone at all for civilian purposes, the reason being that in the 1970s people got concerned that if you scaled that up to very large volumes, the amount of fissile material loss inherent to the system (say, half of 1%) would result in literally thousands of kg of bomb-grade material not being accountable, and thus presenting incredible possibilities for diversion or theft for terrorist purposes. Now whether that could be overcome, or could just be lived with, is another question, but it's not simply case of dropping in a new technology and calling it a day. --Mr.98 (talk) 14:13, 17 June 2010 (UTC)

It's also unreasonable to assume that there would NEVER be another casualty in a nuclear power plant - every industry has it's disasters (9 people died in a beer industry disaster, 21 died in a Molasses catastrophy) - the key thing is to make them rare and to keep the danger to a minimum. Very few people care for very long when an oil rig explodes and kills a dozen people - but when it does that and dumps a million barrels of oil into the ocean, it's much more significant. When the Piper Alpha oil rig exploded in the North Sea - killing 150 people, it was a major news event - but there was no lasting consequences beyond the immediate families of the victims. But when the Ixtoc I oil spill spewed oil for nine months before it could eventually be shut down - that was a major problem. The fifty or so people who died in the Chernobyl disaster are not the problem - it's the spreading of radioactive dust over half of Europe that really needed to not happen. I don't doubt that we'll someday hear about disasters caused by wind farms and solar plants too - but so long as they don't have frequent or long-term or wide-spread consequences - we can be somewhat relaxed about the risks. What's happening in the Gulf of Mexico right now is firmly in the "Not reasonable" category. SteveBaker (talk) 19:00, 17 June 2010 (UTC)

Keep in mind that nuclear power doesn't just involve fissioning Uranium. You first have to mine Uranium ore, process it and enrich it, all of which must be done with energy, and may result in the burning of fossil fuels. But I suppose that this is not a concern if you have lots of uranium fuel available from nuclear bombs, as StuRat pointed out.Pmdove (talk) 02:25, 18 June 2010 (UTC)

There are lots of other things to take into account, to be sure, but in terms of its net carbon impact, it still beats the pants off of fossil fuels in terms of energy release for carbon cost. I don't know where it stands against other forms of energy, but uranium fission releases so much energy for so little mass/volume that it still probably does pretty well. --Mr.98 (talk) 17:14, 18 June 2010 (UTC)

star classification

Could a computer scan the sky and classify stars strictly according to their spectra? 71.100.13.202 (talk) 22:46, 16 June 2010 (UTC)

Well, a computerised telescope with a spectrograph attached, yes. In fact, they do. --Tango (talk) 23:02, 16 June 2010 (UTC)

Where is the classification table? 71.100.0.224 (talk) 23:13, 16 June 2010 (UTC)

You may find some useful links within the Astronomical spectroscopy article. The one appearing as "spectral types" links to the rather relevant Stellar classification article. 87.81.230.195 (talk) 23:45, 16 June 2010 (UTC)

Spectrum (correlated to temperature) vs Luminosity is plotted in the Hertzsprung-Russel diagram (along with mass which is formulated within the axes). The "fuzziness" associated in the main sequence line is due to varying element distributions when the star is formed, which is a major bit of information determined by spectrum. Drift, rotational velocity, and at the largest scales, distance, can also be determined from redshift, so there's quite - just about everything, in fact - that one can tell from the spectra alone. SamuelRiv (talk) 01:16, 17 June 2010 (UTC)

There is not a "single" catalog or database of star classifications; every research organization is free to make and use their own system for whatever research needs they have. There are several public, free-of-charge / free-to-use astronomical catalogs. For example, the high-resolution HR diagram from our HR diagram article was made with Hipparcos Catalogue data (and other data). You can access Hipparcos online, provided by Cambridge University; you can construct queries manually or see the help-files for programming your own interface. Nimur (talk) 05:40, 17 June 2010 (UTC)

June 17

Lapping water

This video shows, in slow motion, a dog lapping up water. It seems that the dog drops his tongue in and bends it under itself to create a scoop. This is the opposite of what I expected. Is this the standard method that animals use to lap up water? Dismas|^(talk) 02:14, 17 June 2010 (UTC)

That was very interesting. I don't think the dog is doing it voluntarily. The structure of it's tongue must simply be shaped that way. I tried and I can't get my tongue to move that way, which is why it's different from what I would expect. It doesn't necessarily have to be the same for every animal, it's just however it's tongue is shaped. Ariel. (talk) 04:57, 17 June 2010 (UTC)

Cats lap water by absorbing the water with its tongue like a sponge if I recall correctly, but their tongues bend like ours, forward instead of backward like a dog's. Btw, is it really so surprising that a dog's tongue bends backwards? Whenever a dog is panting with its tongue sticking out, it's always drooping down. Our tongues don't do that. If you really want to be surprised, look at an Echidna's penis. It has four heads.148.168.127.10 (talk) 13:14, 17 June 2010 (UTC)

It was surprising that they intentionally move it that way. I thought the panting downward direction was simply because the tongue was hanging limp. Dismas|^(talk) 19:49, 17 June 2010 (UTC)

I've observed my pigs drinking by sticking their mouths in the water and sucking, so not like a dog at all. --Sean 15:43, 17 June 2010 (UTC)

What's also interesting (to me at least) is the reliance on suction for the dog to drink. I've had this happen to both of my dogs: they will approach the bowl, thirsty, lap it a few times, and then submerge their whole mouth in an attempt to drink, but in an effort to keep their nose dry they will be exhaling the whole time and only really succeed at making the water very bubbly. They will struggle with this for a few minutes at least until human intervention arrives. What has happened is there is a sizeable foreign object stuck in their teeth (usually a plastic bit of a chew toy) that stops them from making a clean seal around their tooth line, and they are completely unable to lap water in the normal fashion. Removing the object immediately remedies the problem. --144.191.148.3 (talk) 16:45, 18 June 2010 (UTC)

tuna as cat food

The cat food article says that fresh water fish may be deficient in thiamine so does tuna provide in abundance all of the nutrients a cat needs that is lactating? Also are lactating cats normally thin or should they be normal weight or a bit overweight? 71.100.0.224 (talk) 02:58, 17 June 2010 (UTC)

For questions such as these, it would be best to ask your local veterinarian. They will be the best people to tell you what your cat needs. Dismas|^(talk) 03:06, 17 June 2010 (UTC)

That is true only for a cat that someone might own. Strays and feral cats pose an entirely different situation since most likely the vet will start by asking when was the last time you brought her in. 71.100.0.224 (talk) 03:19, 18 June 2010 (UTC)

I would expect a lactating cat (hopefully female) to be normal weight or slightly over, owing to the weight of the milk itself. But cats aren't cows, so don't expect a bulging sack of milk. As for diet, a variety of foods is best to provide all the necessary nutrients. StuRat (talk) 03:40, 17 June 2010 (UTC)

Yes see your vet, but this page says tuna is OK for an occasional treat but not as an exclusive diet. While it seems relatively normal for lactating queens to be thinner, I'd be tempted to make sure she is getting good food and plenty of it to give her kittens the best start possible. --TammyMoet (talk) 09:57, 17 June 2010 (UTC)

If you mean pure tuna such as would be served to humans, then that definitely isn't a balanced diet for any cat, just as it wouldn't be for humans. Tuna cat food, on the other hand, has all the other things a cat needs. --Tango (talk) 11:54, 17 June 2010 (UTC)

Rigid airships vertical control

How do Rigid airships (e.g. Hindenburg) move vertically? Do they use elevators on the stabilizers, or do they use ballonets like modern blimps? --The High Fin Sperm Whale 04:15, 17 June 2010 (UTC)

According to Zeppelin (which is a much better article than the Rigid airship article), "A Zeppelin was steered by adjusting and selectively reversing engine thrust and by using rudder and elevator fins." under Principal characteristics section. --Jayron32 04:21, 17 June 2010 (UTC)

Altitude can be controlled using buoyancy. Release ballast to increase buoyancy and ascend, release lifting gas to decrease buoyancy and descend. Using aerodynamic control would work when moving, but would not work at very low airspeed. anonymous6494 04:27, 17 June 2010 (UTC)

I think I've seen a documentary saying they used ballonets. I could be wrong. It might have been about modern blimps. — DanielLC 04:56, 17 June 2010 (UTC)

Modern blimps do use ballonets, but do rigid airships? --The High Fin Sperm Whale 05:22, 17 June 2010 (UTC)

Carrying ballast is an expensive thing to do - it reduces payload and limits the amount of vertical travel you can do without running out of the stuff. Venting lifting gas is also a bad idea because it too limits your flight capabilities. These days they're using helium as lifting gas which is increasingly expensive stuff. In the days of the Zepplins, they used hydrogen - and that's really cheap. Ballonets are a much more elegant solution to the problem. Modern airships have to work with much tighter air traffic control requirements than the Zepplins did - and having the ability to change altitude cheaply, quickly and precisely is an important part of what they need to do to be cost-effective. I'd expect expect modern craft to carry some ballast and have at least the capability to vent gas for emergency situations - but I doubt they do either of those things routinely. SteveBaker (talk) 11:34, 17 June 2010 (UTC)

Similarly, hot air balloons only use ballast in emergencies. Routinely, they climb by firing their burner and fall by waiting, but in an emergency they can drop a sandbag or two and rise much more quickly than they could otherwise. I would imagine airships do the same - if you're about to crash, you drop ballast, but otherwise you use more efficient means. --Tango (talk) 12:01, 17 June 2010 (UTC)

Rigid airships, and semi-rigid airships, have a horizontal stabilizer (although it isn't for the purpose of longitudinal stability) and a vertical stabilizer. These two surfaces are equipped with elevators and a rudder that are operated by the pilot in a manner similar to those on a fixed-wing aircraft. The airship is a very low aspect ratio airfoil so when it is inclined to the oncoming airflow it will generate aerodynamic force for the purposes of climbing and turning. These airships are likely to have ballonets for the purpose of trimming at low speed, and the ability to carry ballast to achieve neutral buoyancy, but they generally have an empennage for the purpose of height control and maneuvering when travelling at speed. Dolphin (t) 12:19, 17 June 2010 (UTC)

The Graf Zeppelin had yet another technique: it carried two different fuels for its engines. If it was desired to make the ship gradually lighter, they would burn gasoline rather than releasing ballast. The rest of the time they would burn Blau gas, which was a flammable mixture of gases almost the same density as air. Carrying the Blau gas increased the volume of the airship but meant that it could burn fuel and hardly change its weight. --Anonymous, 18:33 UTC, June 17, 2010.

Weren't the old Zeppelins able to use thrust vectoring by tilting their airframe or engines to provide a vertical component to their thrust forces? Googlemeister (talk) 18:39, 17 June 2010 (UTC)

Yes, the Zeppelins were able to generate lift by tilting the entire airship, but the amount of lift from the engines was a tiny component of the total lift generated. Because of its shape, the Zeppelin acts like an enormous wing. --Carnildo (talk) 01:47, 18 June 2010 (UTC)

Thanks. One more question: are there any modern, or plans to build, a rigid airship? --The High Fin Sperm Whale 16:51, 17 June 2010 (UTC)

See CargoLifter. Looie496 (talk) 18:53, 17 June 2010 (UTC)

Plenty of plans, but nobody's actually building one. --Carnildo (talk) 01:47, 18 June 2010 (UTC)

See aeroscraft. They are supposed to be building it soon or now. 148.168.127.10 (talk) 13:20, 18 June 2010 (UTC)

How do they test for performance enhancing drugs in an atheletes urine?

It is a known fact that the International Olympic Committee tomtoms itself as being foolproof and rigorous when it tests the samples of athletes every year as part of any International sporting event. Be it athletics, cycling, tennis or weightlifting several ( highly decorated) sportsmen have fallen from grace following positive drug tests.

Initially they cry foul only to realise their folly later.

My question is, how are these tests done and what do they actually look for in these tests? If the tests are indeed fool proof, how did Marion Jones escape the rigorous dragnet for years and only after an internal family scuffle did she come out with her confession- till she confessed she wasnt actually stripped off or detected. Agassi had also confessed last year.

What makes the cheats stay one step ahead of the testing agencies? Is there a defective testing process being used?

And hypothetically speaking if there is one Marion Jones and a Lance Armstrong out there, there could also be other undetected cases right?--Fragrantforever 10:47, 17 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

I feel compelled to point that, despite Lance Armstrong being possibly the most tested athlete over the past 11 or so years, he has never failed a single drug test, be it urine or blood. The only person who claims he saw Armstrong injecting illegal performance enhancing drugs is Floyd Landis, who has his own agenda to pursue. --TammyMoet (talk) 11:33, 17 June 2010 (UTC)

The biggest problem is that athletes are always finding new things to take to enhance their performance, some of which are difficult to detect and perhaps not even illegal or banned. StuRat (talk) 12:25, 17 June 2010 (UTC)

it's an ongoing process, and no system is ever foolproof. Consider it as an arms race, each time a new product is developed it takes some time to develop a test to detect it. Once that test is developed some will try to find ways to evade that test, leading to a need for further testing to detect the evasions. So you see it continually escalates.

Each test will have a margin for error, so in the marginal zone athletes can legitimately challenge the results. I'm not sure which side of caution the sports authorities err on because a false positive could reasonably ruin an athletes marketability and ability to make a living.

The actual tests range from reasonably well known to highly sensitive. The most recent are the most sensitive as protecting them in this way reduces the opportunity for counter-measures to be developed.

ALR (talk) 12:30, 17 June 2010 (UTC)

You are forgetting about drugs that simply increase the concentration of something that already exists naturally in the body. Athletes simply claim "I just naturally have a high level". Another class is something that is metabolized very very fast, those are hard to detect since they leave no residue, so you have to try to measure their effects instead of the drug directly. But hard training can cause similar effects, and now you have to try to distinguish. For example a drug that increases red blood cell count - the only way to tell was that the new ones are a bit smaller than the regular ones. There was another drug that they proposed using carbon isotope testing - apparently the ratio of the drug was slightly different from the naturally produced one (I don't think they ever did test for it, and it's one that is currently undetectable). Ariel. (talk) 20:54, 17 June 2010 (UTC)

The specific instances that you mention fit into the general case that I've talked about. The naturally high defence is essentially a marginal case argument, hence some debate around where the thresholds for sanction lie.

As you illustrate, no system is inherently foolproof, there are always ways around the testing, the challenge is for the testers to keep up with that.

ALR (talk) 22:57, 17 June 2010 (UTC)

True, but it does raise questions about the rationale for the ban in the first place. Why is it fairer for an athlete to have a naturally high level of something, than for him to eat some of it? One possible answer is that the athlete's biological makeup is part of what the competition tests, which is certainly true — but then why shouldn't women compete on an equal basis against men? (Which of course in practice means no more women in most sports; exceptions would be some of the ones judged on aesthetics, and some ultra-endurance events.) --Trovatore (talk) 02:33, 18 June 2010 (UTC)

I would see the argument around why artificial performance enhancement is banned as very different from the debate about how artificial enhancement is detected. The former is a philosophical and ethical argument, the latter science and technology implementation.

Any time that one takes science and applies it to the real world there are ambiguities around thresholds and scope for practitioner interpretation discretion and challenge.

ALR (talk) 09:52, 18 June 2010 (UTC)

To be sure, it's a different argument. To my mind, though, it illustrates one of the reasons that the argument for banning them is not convincing. --Trovatore (talk) 10:22, 18 June 2010 (UTC)

To answer the first question, I believe that they inject it (the urine sample, after a bit of preparatory work) into a HPLC to look for the actual drug or one of the metabolites. The presence of a drug can be confirmed by comparing with a known sample, or through a MS detector to verify the molecular weight.Pmdove (talk) 02:40, 18 June 2010 (UTC)

The samples are tested for a wide range of contaminants, so a number of different tests are carried out on different segments of the sample.

ALR (talk) 09:52, 18 June 2010 (UTC)

Alumin(i)um

Is the correct spelling "aluminum" or "aluminium"? --76.77.139.243 (talk) 13:13, 17 June 2010 (UTC)

Aluminium#Present-day_spelling. Aaadddaaammm (talk) 13:14, 17 June 2010 (UTC)

Aluminium. But if you are American you are allowed to spell it incorrectly. DuncanHill (talk) 13:18, 17 June 2010 (UTC)

The IUPAC recognizes both as valid alternatives, but prefers aluminium. On the other hand, they only recognize "Sulfur" as the correct English language spelling of the element with an atomic number of 16. Must be some sort of American bias, and all that. Buddy431 (talk) 17:29, 17 June 2010 (UTC)

What do they say for c(a)esium? DMacks (talk) 18:19, 17 June 2010 (UTC)

From our Caesium article, both are accepted, but "caesium" is preferred. Similar to alumin(i)um I guess - British is preferred, but American is acceptable. Buddy431 (talk) 21:02, 17 June 2010 (UTC)

In the case of aluminium, given a choice, it doesn't make sense to use "um" when the "ium" form is used in 81 of 117 element names (uranium, plutonium, vanadium, potassium, sodium, magnesium, calcium, and strontium, etc). There are, however, just 4 elements that have just 'um' (lanthanum, platinum, molybdenum and tantalum). There are 8 elements that end with "on", 3 with "gen" and 5 with "ine" and 17 with no particular ending. The choice to spell sulphur with an 'f' is a part of a general spelling simplification to replace 'ph' with 'f' because they sound the same and 'f' is simpler (although Phosphorus is still using 'ph' because US spelling rules are no more uniform than those of the rest of the English-speaking world!) SteveBaker (talk) 18:44, 17 June 2010 (UTC)

On the contrary, aluminum is the more etymologically- and historically-correct spelling. It is derived from the Latin alumina, by changing feminine to neuter. The original spelling was alumium, (from "alum"), which also would have been fine, but no one uses that these days so it's not really in contention.

Beyond etymology, aluminum was also the choice of the discoverer, Humphrey Davy; discoverers' choices generally carry some weight. Unfortunately "an anonymous contributor to Quarterly Review, a British political-literary [!] journal" made the rather unfounded suggestion to add the "i", and it stuck right of the Pond. --Trovatore (talk) 18:53, 17 June 2010 (UTC)

If you are in England (and I presume most other English speaking places), "aluminium" is correct. If you are in America "aluminum" is correct. In fact, the only reason that I know that it is spelled differently (or, in response to DuncanHill, incorrectly) in England is that I have relatives there. Falconus^{p t c} 20:59, 17 June 2010 (UTC)

No incorrect or correct way; it is just the inconsistencies of English spelling. But for chemistry, the IUPAC name is recommended. --Chemicalinterest (talk) 11:33, 18 June 2010 (UTC)

Recommended — by IUPAC, I suppose. I imagine IUPAC does some good things, but their silly pronouncements on naming should just be ignored, as with those of most similar organizations. There is no particular value to spelling uniformity anyway. --Trovatore (talk) 21:08, 18 June 2010 (UTC)

Yech yah orr write un da losst puent Neel Une (tuke) 00:24, 19 Juun 2010 (UTC) (P.S. For those who can't be bothered working out what I said: "Yes you are right on the last point" Nil Einne (talk) 09:50, 19 June 2010 (UTC))

Well, that's just incomprehensible gibberish — obviously not what I was talking about. I'm talking about organizations that reprehensibly attempt to impose uniformity on usage rather than letting it evolve naturally. In English, we do not have, and will never permit, an equivalent of the Academie Francaise, and anything that looks like it needs to be smacked down. --Trovatore (talk) 00:53, 19 June 2010 (UTC)

Ah jaast speel isa divareent then ya, neh nid fah spilung uunafurmehtey liik yeah saeed. Ey min, us nah deeferent fruum waat yeah raykommund, reit? Sah nuh prubelum, yersah?

Yersa raaaght nah went Academie Francaise teel meah huaw tah speeel. Sah eye spiila huw ey wint end evuilvi niitarally fuum ward teh wurd. Yeeh pliise jan muh ta smuk duan ill whu teh muah huw teh spoel!

Ensadentohleh, isa hiupy yeah feelaw dah derskaveruh inuh Aanited Setaytes ov Umareyka liekeh Nipponium. Uoh waat...

Niil Innuh (tuuk) 09:31, 19 Juon 2010 (UTC)

In attempting to defend the indefensible, you're just being silly. --Trovatore (talk) 18:37, 19 June 2010 (UTC)

Metals used by the human body

What metals are used by the human body? (For example, iron is used in hemoglobin.) --76.77.139.243 (talk) 13:26, 17 June 2010 (UTC)

See Composition of the human body#Elemental composition. TenOfAllTrades(talk) 13:40, 17 June 2010 (UTC)

Plasma weapons

If you had a weapon that shot a stream of plasma at a target, could you use magnetic fields to change the plasma's direction if the target moved? --76.77.139.243 (talk) 13:31, 17 June 2010 (UTC)

Magnetic fields allow you to manipulate plasma, so sure, in principle, you could. However, there are drawbacks. First, as far as I can tell from a quick search, nobody is working on a "stream of plasma" weapon. Instead, plasma-based weaponry is generally related to generating powerful lasers. Second, magnetic fields lose strength exponentially with distance. To direct the stream of plasma at any significant distance, then, you're talking about needing far more energy than the plasma itself has -- so why not just use that energy as the weapon? — Lomn 14:45, 17 June 2010 (UTC)

You wouldn't just need magnetic fields to change the direction, you would need them to keep the stream contained. A stream of plasma would spread out very quickly without something to stop it. Unfortunately, the magnetic field required would be so strong that every iron object nearby would be pulled towards you very fast. --Tango (talk) 16:56, 17 June 2010 (UTC)

Looks like an ideal weapon to me. Targets the right person... --Stephan Schulz (talk) 16:59, 17 June 2010 (UTC)

It's not going to "target the right person" any better than a grounded-in-reality laser would. — Lomn 17:27, 17 June 2010 (UTC)

I think you may have misinterpreted Stephan's comment :-) --Trovatore (talk) 20:16, 17 June 2010 (UTC)

Ah, yes. I think I see now. — Lomn 20:33, 17 June 2010 (UTC)

An electric field might work better. Ariel. (talk) 20:58, 17 June 2010 (UTC)

They're the same thing, just in a different frame of reference. What's a magnetic field for the gun will be an electric field for the plasma (or a combination of the two). --Tango (talk) 21:47, 17 June 2010 (UTC)

A static electric field. It falls by r^2 (not r^5 like a magnet), and will not attract every metal object in the room. Ariel. (talk) 22:29, 17 June 2010 (UTC)

papers

can i use a extra long roller with regular size papers ?

like the roller seen here

http://www.ryomagazine.com/july/rollers.htm

but i cant get the extra long papers

Can't see why not, though you might find the ends turn out a little more loosely packed. It might help if you were to put in something at one end (say, a spare filter or two) to reduce the free 'rolling' space to regular size. 87.81.230.195 (talk) 13:57, 17 June 2010 (UTC)

Yes you can. You can even stick two or more papers together to make a longer one using the detached sticky part from another paper.83.100.250.191 (talk) 14:29, 17 June 2010 (UTC)

You'll probably get a bit of tobacco sticking out from each end, but just pinch it off with your fingers and put it back in the tin or the pouch – that's what I do rolling by hand ;-) Physchim62 (talk) 22:55, 17 June 2010 (UTC)

Antimatter

Chemically, antimatter behaves the same as matter. So could you make the antimatter version of an explosive and use it in a bomb? When the bomb detonated, it would release the energy from the explosion, and then the debris would explode again when it contacted the surrounding matter. --76.77.139.243 (talk) 16:51, 17 June 2010 (UTC)

If you could make the appropriate antimatter, then yes, that would work. However, the extra energy from the chemical reaction would be negligible compared to the energy from the matter/antimatter anihillation, so there is really no point. If you can make that much antimatter and preserve it, then just turn off the magnetic containment (or whatever) and let it touch some matter. There is no point making an explosive out of it. --Tango (talk) 17:01, 17 June 2010 (UTC)

The energy released by electrons going from some higher energy orbital to a lower energy one is really miniscule compared to the energy released by matter-antimatter destruction. Think of comparing a pressure cooker exploding versus a propane tank exploding. John Riemann Soong (talk) 17:01, 17 June 2010 (UTC)

What about if you made anti-uranium and made an atomic bomb out of it? --76.77.139.243 (talk) 17:03, 17 June 2010 (UTC)

That would only add about 0.04% to the explosion. Much more than the chemical reaction, but still not worth it. To anticipate your next question: nuclear fusion would add about 0.3% - still not worth it. --Tango (talk) 17:09, 17 June 2010 (UTC)

No I don't think it would add anything to the explosion. In a fission reaction the small amount of energy liberated comes from fissionable matter that converted to energy. In other words, matter that could have been simply annihilated with normal matter anyway. If we assume annihilation energy is 100% efficient, then you can never surpass that. Conservation of energy dictates that. Fissioning antimatter, then annihilating the products won't yield a greater blast than annihilating the input materials in the first place with equal amounts of normal matter. 148.168.127.10 (talk) 17:18, 17 June 2010 (UTC)

There's really no reason to do this. If you have the ability to make antimatter in large quantities, an antimatter weapon itself is going to be explosive enough. Adding the extra step of spreading the antimatter around first is not going to change the explosive output, I don't think. It might change the character of the explosion, at most, but even then, I am kind of dubious that it would matter (hyuk hyuk) a whole lot, in practical terms. --Mr.98 (talk) 17:10, 17 June 2010 (UTC)

Such a bomb would add absolutely no energy whatsoever to the explosion. When energy is released from a substance in any way, including the breaking and reforming of chemical bonds, the mass decreases according to E=MC². So you'd get a (comparitively tiny) bit more energy from the chemical explosion, but the antimatter-matter explosion would result in a tiny bit less energy being released. In fact, because you'd be involving less read matter in the explosion, the net result would be that less energy overall would be released! The same goes with using anti-uranium; by turning some of the antimatter mass directly into energy, you'd involve less real matter and get (slightly) less energy released. Mr. 98 is probably correct that it would probably change the character of the explosion, but from a pure energy standpoint, it's a losing proposition. Buddy431 (talk) 17:22, 17 June 2010 (UTC)

What I had in mind by suggesting a difference in character is something analogous to a thermobaric weapon. --Mr.98 (talk) 17:35, 17 June 2010 (UTC)

I think it might actually make a difference. Not in terms of energy but in terms of practicality. An anti matter bomb only works if it touches matter - but if it explodes it pushes away all the matter, significantly reducing the yield - especially if some of the anti-matter goes into space. By spreading it around first you make more matter available. Ariel. (talk) 21:03, 17 June 2010 (UTC)

I think the main difficulty here is that the antimatter is sufficiently explosive in small quantities that what one really ends up making in such a situation is just a series of antimatter bomblets or MIRVs or what have you. It's essentially a question of whether a number of "small" antimatter bombs is more effective than one "large" one. The former is undoubtedly true just based on the nature of explosions (five small nukes destroys more surface area effectively than the same material in one large nuke, because the explosion is spherical and thus the volume increases a lot quicker than the surface area). But if extraordinarily tiny (say, on the order of a gram or so) of antimatter produces around a nuke's worth of explosive anyway, you aren't really going to be blowing one piece into many smaller pieces with explosives, you're really just talking about a reentry vehicle with ten antimatter bombs on it to begin with. (Aside from the difficulties of trying to blow apart antimatter and not have it just react with the air.) --Mr.98 (talk) 21:39, 17 June 2010 (UTC)

A gram of a solid is much smaller than a gram of air, you'll have a hard time getting it all to react at once. And the initial burst will push even more air away. It might either cycle with multiple pulses, or reach a steady state where it sort of "glows/burns". I wish it was possible to test this, maybe it can be simulated with different size grains of antimatter in air. Any graduate students here looking for a project? Ariel. (talk) 22:34, 17 June 2010 (UTC)

There are no grains of antimatter available for testing. This page mentions an efficiency of about 10⁻¹⁰ for making antiprotons at CERN; this means that making one milligram of antihydrogen would take about 10¹⁰ · 10⁻³ g · c² = 9×10²⁰ joules, which is about twice the world's total annual energy consumption. Heavier elements would add another huge power of 10 to that. -- BenRG (talk) 00:08, 18 June 2010 (UTC)

Sorry, when I said simulated I meant computer simulation. Ariel. (talk) 01:56, 18 June 2010 (UTC)

Ariel, what you're saying makes no sense. Either way the whole thing explodes and that is that. Dauto (talk) 05:09, 18 June 2010 (UTC)

As has been said, there is no use whatsoever in making explosive compounds from antimatter; the energy is no larger or smaller. For that matter (pun not intended), it would probably be easiest to use a simple antiplasma for an antimatter-based explosive. Plasma can easily be confined magnetically, and being a fluid, it will react with normal matter more or less at once. A solid block of antimatter would probably "sizzle" like a drop of water on a hot plate (albeit many orders of magnitude more violently) before all of the mass is used up, with the explosion at the edge pushing normal matter away. Moreover, an antiplasma bomb could in theory be as simple as vacuum tank containing a large, shaped electromagnet, with the antiplasma confined inside its field. Detonation is as easy as cutting the magnet's power; when the confinement is broken and the first particles touch the chamber wall, it goes boom. --Link ^(t•c•m) 11:42, 18 June 2010 (UTC)

help with Gaussian fitting and airy disks

Don't know whether this belong in math or in science...

We are tracking some nanoparticles by DIC microscopy but they appear much bigger than they already are because of the diffraction limit. We kinda know how approximately big the particles are (less than 20 nm) but of course they appear around 200-300 nm big.

So as a little assignment during 'downtime', my supervisors (who are busy) have told me I can estimate the centre of the airy disk via some sort of Gaussian method and using least squares regression, down to subpixel resolution. I want to start with a 2D fitting for one image, and hopefully 3D fitting for a stack of images taken with z-scanning. Of course, the z-resolution is considerably poorer than xy resolution so the particles (if they are spheres) and up looking like elongated ellipsoids instead.

Help??? Where do I start?

(and I do suppose it is impossible to estimate 'real size' and real boundaries via Gaussian methods?)

John Riemann Soong (talk) 16:58, 17 June 2010 (UTC)

That's a pretty challenging problem, and a lot depends on the special features of your data. One place to start might be by reading the "Modeling of data" chapter of Numerical Recipes in C or one of the other Numerical Recipes books. Looie496 (talk) 17:45, 17 June 2010 (UTC)

My supervisor told me there was an already well-established method that I just had to adapt -- it was basically an extension of nonlinear regression to three dimensions. Then again, he's a PRC postdoc student just looking for his big break, so I guess many things seem simple to him.

Also, I guess I don't need to estimate size from Gaussian methods -- I realise there's a possible approach by looking at the absorbance pattern as we scan the input light across various frequencies and use that to estimate surface energy and from that the size of the particle. John Riemann Soong (talk) 18:08, 17 June 2010 (UTC)

Also it's pretty good if I can start with 2D regression of one image rather than a stack. It'd be somewhere I can start. John Riemann Soong (talk) 18:12, 17 June 2010 (UTC)

The bottom line is that there are many algorithms available, and it's unlikely that you will be able to figure out which one your supervisor has in mind without asking. For what it's worth, here is a recent review of issues and approaches in this area. Looie496 (talk) 18:44, 17 June 2010 (UTC)

A brute force, simplistic approach is take an image I( x, y ) and compare to a Gaussian distribution $G(x,y;x_{0},y_{0},I_{0},\sigma )={I_{0} \over 2\pi \sigma ^{2}}e^{-{{(x-x_{0})^{2}+(y-y_{0})^{2}} \over 2\sigma ^{2}}}$, where fitting a point corresponds to a local minimum of $\chi ^{2}(x_{0},y_{0},I_{0},\sigma )=\int \int (I(x,y)-G(x,y;x_{0},y_{0},I_{0},\sigma ))^{2}dxdy$. As a practical matter, one can usually use simple heuristics to isolate local neighborhoods containing approximately only one particle which will improve the computational efficiency of the approach. Dragons flight (talk) 23:27, 17 June 2010 (UTC)

Well my supervisor did give me a few hints... so I know this is the approach to use. Suppose I've already isolated a neighbourhood with a single point. How do I find the parameters that will give me least squares regression for this surface?

Also, this is less of a priority, but often nanorods like to form aggregates of several particles ... can Gaussian methods be used to locate all their centres in such a case? John Riemann Soong (talk) 15:24, 18 June 2010 (UTC)

Your task is to fit the parameters of the Airy disk formula to your data. In the general case you can use gradient descent, but if you have extra information, you may be able to simplify things by eliminating some or all parameters. For example, if you are sure you have the whole disk, then the center of mass must be where the particle is located. The variance of the disk may give you another parameter. Knowing the characteristics of the lens may give you another. Regarding the second question, the viability depends on how far apart the centres are. If they are closer than the size of the central part of the Airy disk, it's very difficult. If not -- well, you basically have to use some sort of crude deconvolution to figure out how many objects there are and approximately where they are, then use some version of gradient descent to iteratively improve the parameter values. Looie496 (talk) 22:05, 18 June 2010 (UTC)

IP Address

How to trace the computer that has actually transfer my money from my acct from BANK OF INDIA ramakrishnapuram to its branches at Mumbai. —Preceding unsigned comment added by 117.195.209.175 (talk) 17:13, 17 June 2010 (UTC)

Ask the bank, or get a court or the government to order the bank to tell you. Otherwise the only way is to hack into the bank's computer network. Banks don't make that kind of information available to the public. Looie496 (talk) 18:47, 17 June 2010 (UTC)

EMP

How do you protect from an EMP? --76.77.139.243 (talk) 19:17, 17 June 2010 (UTC)

Faraday cage, although anything with an antenna is toast.

ALR (talk) 19:37, 17 June 2010 (UTC)

So stuff with an antenna can be hit through a Faraday cage? Why? --75.25.103.109 (talk) 20:17, 17 June 2010 (UTC)

A faraday cage will protect stuff inside it, however if you have something that needs an antenna, data comms kit or similar, the faraday cage will also prevent it working as it prevents the signals getting through. So you need to breach the faraday cage with the antenna, which provides a path inside.

Catch 22. You can put a sacrificial filter in between the antenna and the equipment that will protect the equipment, but the filter would need replaced afterwards.

ALR (talk) 20:29, 17 June 2010 (UTC)

You need to be in the centre of teh faraday cage to be fully shielded (see shell theorem) at the edges you aren't. EMP isn't the same as high voltage; from which the device does always protect.83.100.250.191 (talk) 20:55, 17 June 2010 (UTC)

Isn't an EMP a pretty low frequency? Faraday cages don't protect against low frequency magnetic fields - you need Mu-metal. Ariel. (talk) 21:07, 17 June 2010 (UTC)

Nuclear electromagnetic pulses have multiple phases. The most damaging phase for moderate scale equipment is the E1 pulse, which is extremely fast (faster than a lightning pulse). It's a "pulse", so it isn't really high or low frequency as is it non-repeating, but for the purposes of Faraday cages it acts like a high frequency signal. The subsequent E3 phase of a nuclear EMP is relatively low-frequency, but its effects are similar to a geomagnetic storm and hence generally only of concern to large scale electrical infrastructure. Dragons flight (talk) 22:19, 17 June 2010 (UTC)

The same kind of devices that can protect against a lightning hit can help lightning arrester, or surge filter. Using vacuum tubes instead of semiconductors can be of assistance too. Graeme Bartlett (talk) 07:14, 18 June 2010 (UTC)

In practice no system is going to protect from everything, the theoretical faraday cage and cages in practice are quite different things. As soon as one is using electronic or electrical equipment inside an enclosure one needs to consider power supply in, communications in and out, cooling either through chilled water, forced air or air circulation. Each of these has an impact on the effect of the cage, although each one also has mitigations; sacrificial filters, wire mesh across vents etc.

ALR (talk) 11:00, 18 June 2010 (UTC)

Some other methods of protection, short of cages, include shielding all wires and keeping the lengths as short as possible (as longer wires develop more of a charge), and simply using components in the circuit with more of an ability to withstand surges. StuRat (talk) 13:18, 18 June 2010 (UTC)

Screening of cables is putting them in a cage

ALR (talk) 15:48, 18 June 2010 (UTC) CEng MIET

Of course, one strategy to protect devices from a nuclear-detonation-induced EMP is to deny the nuclear device the opportunity to emit an EMP by destroying the incoming warhead with an interceptor or several dozen interceptors before it initiates a nuclear reaction. Nimur (talk) 18:08, 19 June 2010 (UTC)

(where) do humans fit in?

For a project I need to know two major differences between humans and animals two for chordates, two for mammals, and two for primates. Any advice? —Preceding unsigned comment added by 69.17.115.101 (talk) 22:29, 17 June 2010 (UTC)

I'm afraid we won't do your homework for you. As long as you know what chordates, mammals and primates are, you shouldn't have too much trouble (it gets harder as you go along, of course - there are loads of really obvious differences between humans and other chordates). One point I'll make - the way you word the question makes me wonder if you are aware that humans are primates, all primates are mammals and all mammals are chordates. Presumably your project involves differences between humans are either some other members of that group, or most other members. And presumably you are meant to come with different qualities for each group (since the differences between humans and other primates are also differences between humans and other mammals/chordates). --Tango (talk) 22:35, 17 June 2010 (UTC)

(edit conflict) Humans are animals, primates, mammals, chordates, etc. Hence there are no major differences. If you want to identify ways that humans are different from other members of the same taxanomic group, then one could come up with a variety of possibilities, though most would probably relate to human intelligence in some way. Dragons flight (talk) 22:39, 17 June 2010 (UTC)

In addition to the intelligence thing (speech, language, make tools etc) - the other biggy (with a few exceptions eg ostrichs) - is walking upright.83.100.250.191 (talk) 00:19, 18 June 2010 (UTC)

Sorry - I have to disagree on every one of those points:

1. Tools is definitely busted. Many animals use tools. Several birds will use small rocks to break open snail shells. There are fish that cut and use leaves to hide beneath when swimming in shallow water so as to avoid surface predators. Chimpanzees cut twigs and remove leaves to make tools that they can poke into anthills to get the ants out to eat. Tool use - and even tool manufacture is far from unique to humans.
2. Speech is a little more tricky. Wiktionary defines speech as "the ability to...use vocalizations to communicate". Plenty of animals communicate using sound. Birds sing to attract mates and mark territory. Whales and elephants keep their pod/herd together using vocalizations. My dog barks to tell me about intruders and whines at the back door when he wants to go outside for a pee. He has at least three or four distinctly different barks for everything from pain to warnings to frustration. Humans are not unique in using speech.
3. Language is even more tricky. Are the songs of whales "language"? They certainly have complex but fairly recognizable structures. But 'body language' is widely used throughout the animal kingdom. Again, my dog indicates that he wants to play by using a 'play bow' - where he rests the front his body on the ground with his hind end up in the air. Tail wagging comes in at least three forms - there is a wide side-to-side wag where the tip of the tail hits the flanks - which means "Welcome". There is also a circular motion which means "Happiness" and a slower side-to-side motion that means "Curiosity". I'm sure there is more to it than that - but that's enough to tell me that these are "words" in a gestural language. The dance of a honey bee is a language - the orientation of the dance tells you compass direction to newly found sources of nectar and the speed of the dance indicates distance.
4. Walking on two legs - clearly busted. Almost all birds do it all the time (not just ostriches) - so did many dinosaurs (think of T.Rex, for example). Gibbons run across the ground on two legs...so do kangaroos, springhares...there are lots of examples.

However, there is something specifically unique about human language: It seems likely though that no animals other than humans are able to use 'grammar'. This is what turns language from a mere series of words ("Play", "Welcome", "Danger!", etc) into open ended statements...we can put together words like "Dangerous Play" and convey the idea that playing is somehow a bad idea right now...but my dog can't use any combination of his play-bow and a danger bark to impart that idea. If he needs to express something new, he has to 'invent' a new word. He learned to push the end of his leash where it was hanging by the front door with his nose to say "It's time for walkies!" - and even after we moved the leash someplace else, he still goes to the same place by the front door and makes the same gesture - but without the leash being there...it's a new "word" in his gestural language. But in human languages, there are essentially no concepts which words cannot describe given enough time without the need to invent new words. Even with Basic English (which comprises just 850 words), it's quite possible to say pretty much anything you want. Wikipedia's Simple English encyclopedia has 60,000 articles - and is written almost exclusively with a 1000 word vocabulary. But even with a restricted set of words, our language is completely open-ended.

But the language of my dog is strictly limited to the number of body gestures and vocalisations he can make. He has "Words" but no "Grammar". If you do a Google search for "Animal Grammar", the few scientific studies you find are all pretty much negative about animal abilities in this regard.

SteveBaker (talk) 05:20, 18 June 2010 (UTC)

Similar to SteveBaker's comments on grammar is the inability of animals to express an abstraction. Even animals which can use complex language, such as higher primates like chimps and orangutans, lack the ability to express ideas or concepts in the abstract or hypothetical. A chimp can express a desire in the concrete, in that it can say "I want a banana", but it could not say, or likely even understand, an idea like "Maybe tomorrow I would like a banana, even if I do not today." Higher primates can be trained to use rudimentary grammar in their constructed language systems, usually they cannot constuct language to express ideas which are not firmly concrete. --Jayron32 05:38, 18 June 2010 (UTC)

For a cellular approach to differentiating humans from other animnals, see karyotype. Gandalf61 (talk) 08:28, 18 June 2010 (UTC)

I find it funny and little bit sad that we still try to differentiate our species with such highfalutin and complicated concepts like language, art, tool-use, etc. Those are inappropriate markers - it's the kind of thing philosophers come up with then they try to get involved in biology. The article needed here is anatomically modern human; the differences between humans and their closest living (chimpanzees) and extinct (Neanderthals) relatives comes down to the same kind of boring stuff used elsewhere in biology - dentition, skull morphology, etc. Matt Deres (talk) 13:38, 18 June 2010 (UTC)

Oh, sure! Absolutely. I'm merely pointing out that the classical 'markers' such as speech, tool use, tool creation, fighting wars...and a whole host of other things like that...have all been disproved as we find animals doing each of those things. Grammar is the only simple test I could imagine that wouldn't entail looking at the detailed biology - but looking at the biology is much more likely to produce certain answers than the more holistic approaches of looking at various skills an behaviors.

June 18

Angle grinder -lidl/aldi/netto

Barely a week goes by without one of the above supermarkets having an angle grinder on special offer - this confuses me as I don't consider it a household essential.. yet they still seem to sell. Question (bit of a straw poll but I hope you will humour me) - what do individuals use them for? (I mean 'household' use). Also does Walmart or whatever in the US have a similar obsession with the sale of this machine tool? Thanks.83.100.250.191 (talk) 00:03, 18 June 2010 (UTC)

I've used one to cut a long metal bolt, I also used one to trim a metal rod that was in the way of a light fixture. If you are handy, then it's a useful tool to have. And no, I have not seen any particular obsession here in the US, but that kind of thing goes in cycles. I hope they sell safety equipment with it (face shield), it can be a dangerous tool (always stay perpendicular to the rotation of the disk). Ariel. (talk) 01:44, 18 June 2010 (UTC)

I restore classic cars - angle grinders are great tools for hacking out bits of rusty sheet-metal, sawing heads off of stubbornly stuck bolts - all sorts of general metal cutting. I don't think I've ever seen one in WalMart - they might stock them, but it's just not the kind of store I'd look at when buying tools. Most of their stuff is cheap junk. SteveBaker (talk) 04:20, 18 June 2010 (UTC)

And don't forget that many men collect tools they have no use for and will never use...it's a guy thing, like women collecting shoes. StuRat (talk) 13:10, 18 June 2010 (UTC)

I find them remarkably useful for cutting bolts, rebar, plate, grinding rough metal, grinding down welds, etc. I have two, in fact, because my first one was too small for some of the work I was doing. That said, I obviously work with metals more than most people, and I wouldn't consider them a normal household implement. They're noisy and produce showers of incandescent sparks that can do bad things if they end up in your eye or in something flammable. Acroterion _(talk) 15:49, 18 June 2010 (UTC)

With the explosion of Harbor Freight and other 100% no-name import tool stores, things like this are becoming very common in the USA. Yes, you can get an angle grinder at most Wal-Mart stores (pneumatic or electric) and I wouldn't be surprised if I saw one in a rural supermarket either (if you can tell a difference between a Wal-mart and rural supermarket). What's becoming very popular is the "multi tool" (basically a vibrating dremel), the handle sits parallel to the path of vibration so you can use it for cutting, sanding, polishing, etc. As far as either of these being a "household item".... you would be surprised how many (probably bad) ideas you come up with when you have one! --144.191.148.3 (talk) 16:33, 18 June 2010 (UTC)

conservation of PH

Starting with neutral organic chemicals is it possible to turn the mixture acidic by any reaction (including bacteria etc) while keeping all reaction products in the final mixture? Ariel. (talk) 01:43, 18 June 2010 (UTC)

Probably not. Lots of compounds are highly pH sensitive. For example, amino acids can protonate or deprotonate at specific pH's. You'd need to post the specific reaction so we can check it, but the pH environment is generally very fundemental to the nature of compounds dissolved in solution. --Jayron32 01:52, 18 June 2010 (UTC)

If the solvent is ethyl acetate+water+etc then ester hydrolysis will make the solution turn acidic. A catalyst is usually needed which can be an enzyme [28] , a metal salt [29] or other things.

Is that what you meant.?83.100.250.191 (talk) 02:10, 18 June 2010 (UTC)

Or react acetic anhydride with water - the reaction products are acetic acid only.83.100.250.191 (talk) 02:19, 18 June 2010 (UTC)

Start with glucose and oxidise it to pyruvic acid. You can choose pathways where ethanol rather than CO2 is released. John Riemann Soong (talk) 15:39, 18 June 2010 (UTC)

Or even do use a CO2-producing pathway: it's soluble in water and would make the solution acidic. The extent is complete oxidation of any organic material in an enclosed container (to trap the product gases until cooled): CO2+H2O, CO2 dissolves in H2O, now you've got carbonic acid. DMacks (talk) 16:58, 19 June 2010 (UTC)

Or acyl chlorides and water. Provided you don't release so much HCl that some of it evaporates from solution of course. John Riemann Soong (talk)`

From one perspective, since the haloform reaction consumes base, it makes the solution more acidic. And the product (if you use chlorine) is chloroform and carboxylate. John Riemann Soong (talk) 17:14, 18 June 2010 (UTC)

Wine to vinegar. Physchim62 (talk) 00:39, 19 June 2010 (UTC)

Mobile phones in supermarkets

Hi. I live in the UK and I find that, almost without fail, my mobile never seems to get a signal when I am in my local supermarkets (Marks and Spencers, Sainsburys and Asda). I do not seem to get the same problem in other buildings (no matter how large) or in other shops. This has made me wonder whether there is anything about the building or contents (e.g. refrigeration units) of a supermarket that might prevent me getting a signal, or whether it might even be intentional for them to block the signal (although I can't see why). Any thoughts would be appreciated. GaryInLondon (talk) 02:40, 18 June 2010 (UTC)

There are ways to reduce or jam signals and there are businesses that do it to keep employees from using cell phones (they can only use them in the cell phone designated area). Some department stores who are worried about competitors may also jam phones and can be recognized if you start taking photographs and they ask you to stop. Ask the management. 71.100.0.224 (talk) 03:32, 18 June 2010 (UTC)

Does the building have a metal roof? Ariel. (talk) 03:46, 18 June 2010 (UTC)

Interesting; I'd like to know how widespread this practice is — in the US, radio jamming is illegal, including jamming a cell phone signal. Comet Tuttle (talk) 03:49, 18 June 2010 (UTC)

There's a difference between active jamming and natural attenuation of the signal. In the smaller traditionally-built supermarkets in rural northern England, mobile phones usually work, but I have a problem at home caused by very thick stone walls. Dbfirs 07:43, 18 June 2010 (UTC)

No problem getting a good signal in my local (large) branches of Sainsbury's and Asda, though a metal roof might well make a difference, as will the distance from the base station of course. You can find (clunky) maps of UK base stations here.--Shantavira|^{feed me} 09:11, 18 June 2010 (UTC)

I don't know about there, but supermarkets in the US are massive, with maybe a dozen aisles and fully stocked shelves between you and the outside when you're in the center, whereas the typical office building has a window within view at all times. So, the signal just has to go through more stuff. StuRat (talk) 12:59, 18 June 2010 (UTC)

I'd guess it's more to do with the distance from the base station than anything else, although a metal roof and cheap reinforced concrete construction won't help. Many UK supermarkets are built on cheap land with nothing else around but carparks, so it's hardly "hot territory" for the phone companies to ensure coverage. I can't imagine that the store is actually jamming coverage, because that costs money for no real benefit to the store. Physchim62 (talk) 01:51, 19 June 2010 (UTC)

I also don't believe that supermarkets are intentionally messing with cel-phones.

However, it's interesting as a thought experiment. I notice that many people in the supermarket call home to verify what they should buy and how much. If they weren't allowed to phone, would they buy more or less? APL (talk) 02:56, 19 June 2010 (UTC)

They'd buy less from that supermarket. 81.131.37.105 (talk) 14:19, 19 June 2010 (UTC)

As highlighted already, the Telecommunications Act prohibits interference with the EM spectrum so intentional suppression is illegal in the UK.

I'd agree with the previous points about the amount of metal in the structure interfering with the local infrastructure coverage.

ALR (talk) 19:10, 19 June 2010 (UTC)

Life on mars

Quick version: What I'd like is some old(er) sources which specifically make reference to the possibility of life on Mars, or the solar system in general, but before scientific consensus thought it was likely or possible. I specifically want to see HOW the topic is addressed. Did "science" say "it's not possible" or did they say "evidence suggests it's unlikely but more research is required". That kind of thing.

If that doesn't make enough sense, this is the "not so quick version". I'm writing an article about scientific discovery and basing it around the idea of "Life on Mars". When i was growing up, I didn't study astronomy or anything, but the impression I got from pretty much everything i ever read or heard was there was no life anywhere else in the solar system. This idea has been turned right on its head, quite recently in the scheme of things.

The point of my article is about how science constantly examines its beliefs and follows where the evidence leads. The idea that there might be life on Mars has shaken the scientific establishment but "believers" weren't persecuted and it wasn't ignored or covered up, it has been fervently pursued and is now one of the most exciting and important areas of research. I'm going to use this as contrast to the argument frequently made about science being scared of "supernatural" beliefs because they threaten the "established" beliefs of science. Vespine (talk) 05:40, 18 June 2010 (UTC)

I have to disagree with a part of what you wrote - the idea of life on Mars has not shaken up anything. Mainly because it's still just an idea - nothing has been found. (And the rock found on earth that might be from Mars doesn't count.) You'll have to wait for something to be found, and for best drama it will need to be something non-obvious, which some will say is proof of nothing, and others will say is proof, and only later will one or the other be known to be right. (That rock might turn out to be it.) It's far too early to use Mars for this. Also - it's very easy to forget about all the revolutions that turned out to be wrong, and where the establishment was right, and the "crank" was forgotten. There's a lot of selection bias going on here. Ariel. (talk) 05:59, 18 June 2010 (UTC)

The older view of course is that Mars was covered in irrigation canals and turned colors every spring as the plants sprouted. Rmhermen (talk) 06:06, 18 June 2010 (UTC)

well i disagree that "nothing" has been found. Extraterrestrial_life#Extraterrestrial_life_in_the_Solar_System several discoveries have been made, not just on Mars but several other places, which recently have made it more of a possibility. So anyway, this article makes it seem to me that the "possibility" has been considered for a long time, so where did my preconception of there being no other life in the solar system come from? I've discussed this with more then a couple of people and they all agreed with me that growing up you learned that Earth harbored the only life in the solar system.. Even watching cartoons we knew marvin the martian was a joke because there was no life on mars. Vespine (talk) 06:17, 18 June 2010 (UTC)

And? There still isn't life on Mars, nothing changed. And the link you posted says the same thing - no life (but some water). Your preconception, as you call it, is still correct as far as we know - no one has found any life. Ariel. (talk) 06:36, 18 June 2010 (UTC)

We're obviously not understanding each other. YES of course there is still no life found on Mars but now it is acknowledged as a real possibility, much more so then not too long ago. We weren't really actively looking for life on other bodies in the solar system, partly because we didn't have the technology, but partly because it seemed much less possible! Now what we've learned about extremophiles and astrobiology, it no longer seems so extremely unlikely! Not that I don't appreciate your input but if you still don't get what I'm trying to say, i don't need another reply from you telling me how wrong I am. I'm after sources specific to life in the solar system previous to say about two decades ago. Thanks.Vespine (talk) 08:58, 18 June 2010 (UTC)

Interesting - I always thought it was the reverse. After evolution, science assumed life was everywhere, including mars, and only after we got there and really looked around (i.e. now) do we no longer think there is life there. The viking missions (40 years ago) looked for life, so at least as far back as then it was thought mars had (or could have) life. And before that people looked for evidence via telescope. (And yes, we didn't understand each other. I think it's because we came from exactly opposite assumptions.) Ariel. (talk) 09:41, 18 June 2010 (UTC)

This section: Extraterrestrial life#Early_modern_period and the following one cover what you ask I think. It was pretty much assumed there was life on other planets, but when we actually got there and there was nothing, at that point the ideas started to shift the other way. Ariel. (talk) 10:00, 18 June 2010 (UTC)

Science can, and often does, entertain several conflicting theories when evidence is sparse. One sufficient evidence accumulates, we laugh at the theories that turned out to be wrong. I still like the idea (suggested long ago) that life on earth actually originated on Mars and was carried to earth by meteorites. Dbfirs 07:38, 18 June 2010 (UTC)

I disagree with the premise here. I don't think the possibility of there being life elsewhere in the solar system has changed much at all over the past 150 to 200 years - and certainly not in the last 50. But we've certainly changed where we think it might be:

• For the longest time everyone thought that Venus would be the most likely place - imagining lush swampy jungles and such like. But results from spacecraft showed Venus to be an exceptionally nasty place - and the possibility of life there was largely discounted. But recently, we've found 'extremophile' bacteria on earth, now people are starting to entertain the possibility of life on Venus once more!
• Now we're looking at icy moons far out around Jupiter and perhaps Saturn - and thinking that they are the likely places to look for life - when in the past, they'd have been considered to be completely impossible.
• The one constant through all of that was Mars - which was always considered to be a possibility for life - and is still considered a possibility today. The results we saw from the Viking survey missions of the 1970's showed much the same promise as we see today with the Mars Polar Lander with much the same tantalizing uncertainty. Our Life on Mars article has a reasonable 'history' section which explains that life on mars was stated as an explicit possibility in 1857 - and was probably thought to be a possibility by William Herschel as early as 1800.

What's really changed is that we've gone from highly speculative statements based on the appearance of the planet through a blurry telescope and horribly inaccurate estimates of surface temperatures from orbital data - to actually sending scientific instruments there and measuring things. Yes there is water on Mars - but no, there aren't any large canals flowing with water. What's also changed is our greater appreciation of how varied the conditions can be on earth and still have life flourish. I was watching a documentary the other night about how puddles of liquid CO2 exists at the bottom of some deep ocean trenches - and that there are small crabs and other animals that can live - even in close proximity to such nastiness! If that's possible - then life beneath the ice sheets of various moons of Jupiter and Saturn starts to look very much more plausible.

SteveBaker (talk) 11:40, 18 June 2010 (UTC)

That's actually some pretty good answers thanks, and some good sources. I also have recently read and watched a few things specifically about Enceladus and Europa which is what lead me to consider this question. So what I'm hearing is that probably my preconception, while growing up, that extraterrestrial life was not being expected in the solar system was a, common or not, misconception, not based on scientific consensus, but maybe just public opinion or pop culture or something. Thanks.Vespine (talk) 11:53, 18 June 2010 (UTC)

It's actually more interesting to me that the idea of life of Mars was rather quashed quite quickly in the 1960s. If you read sci fi from that era, the idea of life on Mars is presented as a not-that-far-out thing. I'm thinking of Stranger in a Strange Land, Martian Timeslip, etc. The life on Mars part of those stories are often the part that needs the least explanation. By comparison, by the late 1960s, 1970s, and so on, the idea that life would somehow actually be there seems to be quite hard to sustain, just ridiculous. Reading those stories now, and they sound quaint in their easy presumption that there could be life at all on Mars (creatures and plants and etc.), not just intelligent life. It was relatively recently that we found out that the planet was basically a dead desert, maybe with some frozen microbes hiding somewhere but that's it. --Mr.98 (talk) 13:30, 18 June 2010 (UTC)

I strongly disagree. If the scientific opinion in the late 1960's and early 1970's was that there couldn't be life on Mars, why did NASA spend a billion dollars (which would be an inflation-adjusted $5.4bn today) to send the Viking program there specifically to look for it? Those two missions launched in 1975 and must have started planning and budgeting in precisely the period you're talking about. To the contrary - scientists were rather of the opinion that they WOULD find life there - which is why the US taxpayer was convinced to spend so much. These days, comparable missions (such as the Phoenix lander and ill-fated Mars Polar Explorer) are funded on a shoe-string ($350 million). SteveBaker (talk) 14:01, 18 June 2010 (UTC)

Well, my timing might be off. But it's not too far. What I'm saying above is that in the late 1960s, it appears not to have been a big deal to assume there was life on Mars. At some point between then and, say, the 1990s, that changed. Whether that was in the mid-1970s or early-1970s or late-1970s, I don't know. --Mr.98 (talk) 16:59, 18 June 2010 (UTC)

It's possible you are talking of the time right after the Viking missions landed. When nothing was found, the idea of life on Mars become less popular. Ariel. (talk) 21:36, 18 June 2010 (UTC)

It's not even true that "nothing was found". In fact, the criteria that the designers of the mission set out for the positive detection of life by the on-board instruments were fully met - in a sense the instruments did indicate the presence of life. The flaw was in the experiment, which (it later emerged) could be fooled by non-biological processes which could plausibly be happening in Martian soil. It is most certainly NOT the case that the Viking landers proved that there was no life there - to the contrary, they produced evidence that it could be there - but sadly, due to the flaw in the tests they'd devised, the experiments didn't show that life must be there. That's not much to show for a billion dollar expenditure - but they did snap some cool photos and gather plenty of other scientific data so it wasn't a complete bust. SteveBaker (talk) 03:49, 19 June 2010 (UTC)

It's been a constant that there might be "life on mars", but the potential forms that life might take has constricted dramatically! As late as 1900 it would not have branded you as a crackpot to put forth a theory that the Martian canals were created by intelligent beings. APL (talk) 21:16, 18 June 2010 (UTC)

Also note that what people mean when they say "life" has changed. Early on, we were only concerned with intelligent life, or at least large animals. Some scum growing in a pond on some other planet wouldn't have been very interesting 100 years ago. Now that we could examine it's DNA, such scum would be extremely interesting, so there is far more interest in finding "any life" now than there was back then. StuRat (talk) 12:53, 18 June 2010 (UTC)

Radio Interference on a 'dead' radio.

On my journey to work in an urban environment, there is a specific spot where I get the sound of interference from my car radio speakers. It is a sort of clicking sound and is the typical sort of noise that one is used to hearing on occasions if a police car drives past, or there is known radio/electrcial activity nearby. My question arises because this happens when my car radio is TURNED OFF.

I have thought about this over several days, trying to work out how it happens and what processes are going on. But I always come up against the same problem . . . If there is no electrical current through my radio, what is generating the noise from my speakers?

I hope you can help. —Preceding unsigned comment added by 194.223.35.225 (talk) 07:12, 18 June 2010 (UTC)

Inductance? Dismas|^(talk) 07:23, 18 June 2010 (UTC)

What about the various beeps and bells your car makes? Are those piped through the speakers? Ariel. (talk) 07:23, 18 June 2010 (UTC)

Well it actually doesn't make many but I always assumed that those warning beep noises came directly from elsewhere - or how would I hear them if I had no car radio? Am I wrong? Are my speakers actually turned on while the radio itself is turned off? —Preceding unsigned comment added by 194.223.35.225 (talk) 07:28, 18 June 2010 (UTC)

It depends on the car, some have a dedicated speaker, others use the existing speakers. I think using the speakers is more common - it's easy to test, just make it beep and listen for where it comes from. Ariel. (talk) 09:43, 18 June 2010 (UTC)

On many (most?) cars speakers come standard. Radios are an option, but the speakers are difficult to install once the car has been assembled, so they get installed at the factory. APL (talk) 06:04, 19 June 2010 (UTC)

The interference is probably generated in your speaker coils by a large electromagnetic field. You could probably reproduce the effect at home by connecting a transformer to a household battery near to the car speakers. Dbfirs 07:31, 18 June 2010 (UTC)

Aaaah yes, of course: An electromagnetic field could be the energy that powers my speakers while also creating the souind. Thanks to both of you for showing me how this can happen. —Preceding unsigned comment added by 194.223.35.225 (talk) 08:00, 18 June 2010 (UTC)

You don't even need a strong electromagnetic field. Take any low-impedence speaker, grab a nine-volt battery, and hold a coin over the leads of the battery. When you generate a spark, you should hear the spark through the speaker. You have just made a basic radio. David E. Hughes performed these experiments in the 1870's, unfortunately he was basically ignored at the time, as no one saw any application for this novelty. We could easily have had broadcast radio several decades earlier had his work not been dismissed. Radio-frequency induction can occur with just about any speaker, and sometimes for unknown reasons, speakers can just start making sounds. Pay it no mind. --Jayron32 06:16, 19 June 2010 (UTC)

I was once in my kitchen with my boom box plugged in, but turned off, when it said, loudly, "How ya doin', good buddy ?". After I peeled myself off the ceiling, I realized it was just a stray CB transmission. StuRat (talk) 12:43, 18 June 2010 (UTC)

Poorly maintained CB radios are notorious for this sort of thing. (However I have to assume that modern digital units don't often have this problem.)

When I was growing up a neighbor (Briefly) had a CB that we could hear on just about everything we owned that had a speaker. Very strange. Intuitively you would think that this level of interference is impossible, but apparently it's not. APL (talk) 06:26, 19 June 2010 (UTC)

breasts full of milk

Can cats who have had their kittens taken away and have breasts full of milk die or be injured by the absence of nursing or else what happens to the milk? 71.100.0.224 (talk) 11:16, 18 June 2010 (UTC)

Very unlikely. I don't know about cats, but in humans (and cats are likely to be the same) the back-pressure eventually shuts down the milk production, and the lack of lactation does not stimulate any more milk production. It eventually gets reabsorbed. It hurts though - it can hurt a lot. See Breast engorgement which also discusses what you asked. Ariel. (talk) 11:30, 18 June 2010 (UTC)

Of course for most animals losing all their young even in a litter wouldn't generally be that uncommon an occurence. For the mother to not be able to survive this is needless to say unlikely Nil Einne (talk) 20:44, 18 June 2010 (UTC)

Why are there no Herring Gulls in Hampshire?

In my local area (Southampton, UK), seagulls are very common, it being near the coast, however, it is only the small gulls (Black-headed gulls I believe). When I go to coastal areas in other parts of the UK, there are always loads of the huge Herring Gulls...but for some reason, there do not appear to be any in Hampshire, which surprises me, as these gulls are usually common in urban areas, as they are well-fed by litter louts. We do have wheeliebins as opposed to black bags (the large gulls enjoy ripping those open) and waste in incinerated rather than going to landfill sites (another favourite haunt of gulls) now but I'm not sure that is the reason. The WP article on Herring Gulls shows they are found in every coastal area of Great Britain but I am not sure if there are other areas of the UK that don't have them.

GaryReggae (talk) 11:21, 18 June 2010 (UTC)

The lack of a local landfill and the presence of wheelie bins is certainly a possibility, IMO. Herring Gulls, as well as being longer and taller, are also far more 'substantial' birds - and need to eat a lot, for their size. Perhaps they are unable to eke out a living on discarded food items found in the streets? Has the sea been fished out where you are, as a matter of interest? If so, that's another possibility. Herring Gulls do prefer to feed their chicks on fresh fish. Strangely, the HG is actually declining as a species in the UK, despite the urban colonies in certain areas exhibiting massive yearly growth... --Kurt Shaped Box (talk) 17:13, 18 June 2010 (UTC)

Another possibility is that the Southampton herring gulls are all on the Isle of Wight! Southampton is actually quite a way from the open sea, so maybe the larger gulls have stayed closer to the open water, leaving the smaller gulls to pick up the urban food that's still available. Physchim62 (talk) 00:36, 19 June 2010 (UTC)

Immunosuppression drugs -> skin like tissue paper?

About 20 years ago, my grandmother had a kidney transplant and, as a result of the immune suppression drugs that she takes, her skin is extremely delicate and very slight knocks or abrasions will remove it. Recently, while alighting from a motorcar, her ankle was caught in the seat-belt and the resulting pressure created a wound. Apparently, when her hosieries were removed at the hospital, her skin was in the mesh of her tights. I am not seeking medical advice; she is now receiving daily care from the NHS. I would like to know whether this is a known condition and whether it has a name? Is it a rare reaction to immunosuppression? --78.150.225.204 (talk) 13:51, 18 June 2010 (UTC)

Skin thinning and easy bruising are common side effects of corticosteroids (source), which are a widespread and very powerful class of immune suppressants. The medical term is skin atrophy. I personally have some nasty scars from when I was on prednisone. --Sean 14:56, 18 June 2010 (UTC)

Sodium bromide as salt substitute

Would sodium bromide be a good salt substitute? --Chemicalinterest (talk) 15:29, 18 June 2010 (UTC)

This link discusses an incident where sodium bromide was taken instead of sodium chloride (by accident). I'm not sure whether that toxicity is caused because there was too much sodium bromide, or if it's because NaBr itself is toxic. Regards, --—Cyclonenim | Chat  17:51, 18 June 2010 (UTC)

The Bromide article discusses some of the toxicity/biochemistry of this ion. DMacks (talk) 18:36, 18 June 2010 (UTC)

Salt substitutes normally replace the sodium metal cation not the chlorine halide anion. The usual substitutes are calcium, potassium or possibly magnesium, all of which are needed in human biology. This is to reduce the chance of hypernatremia, excessive sodium levels (natrium is the old name for sodium, its the source for sodium's symbol, Na). Excessive chlorine levels is hyperchloremia, which appears to be asymptomatic. As bromine is a sedative, it shouldn't be used. Selenium and iodine are toxic in more than trace amounts. The common polyatomic ions like nitrate or sulfate are also poisonous. Phosphate is probably safe. CS Miller (talk) 13:22, 19 June 2010 (UTC)

Windmill on an airplane

There was previously some discussion about whether net energy would be harvested from having a windmill on a car. Would a windmill on an airplane harvest energy in a steady wind? I imagine it could do so when the wind was gusting, due to the accelerating wind acting against the inertia of the plane. 92.15.14.87 (talk) 17:31, 18 June 2010 (UTC)

As mentioned in the other thread, the ram air turbine is a windmill that pops up if all the engines fail, and it generates emergency power so the pilot can at least have some flight instruments to read, and try to control the plane. But in ordinary flight, a windmill would create drag on the aircraft, and the aircraft's engines will have to use more energy to overcome this drag than the amount of energy the windmill can generate. This occurs regardless of whether the aircraft is flying into the wind or with the wind. It's a net loss, which is why you don't see windmills on airplanes. (Last point of clarification: The ram air turbine generates extra drag, too, but if the engines have all failed then you have much bigger things to worry about than the little windmill's extra drag.) Comet Tuttle (talk) 17:44, 18 June 2010 (UTC)

I meant steady wind and steady level flight also - no diving. What about on a glider? 92.15.14.87 (talk) 18:04, 18 June 2010 (UTC)

No net power can be harvested this way - there is no such thing as a free lunch. But if your glider needs electrical energy - then a windmill will rob you of some kinetic energy (and therefore make you lose height faster and ultimately glide less far) - but if you need electricity to power instruments or whatever, then that might be a trade-off that you're prepared to make. SteveBaker (talk) 18:39, 18 June 2010 (UTC)

A windmill on a glider will produce a less efficient glider. If you need juice for electronics, solar panels are a more elegant solution, given the big long wing surface. With the widespread introduction of large lithium-ion batteries, battery-powered electric propulsion is becoming possible, allowing self-launching and extended flight for gliders, but that's a windmill in reverse. Basically, any harvesting of energy via a windmill on any moving object will come at a cost of worse performance or higher energy consumption, all things being otherwise equal. Acroterion _(talk) 18:43, 18 June 2010 (UTC)

As mentioned in the other thread (and still true here), it's not necessarily true that adding a windmill will make your aircraft less efficient. It could add more drag than the power it produces, but it could also add less than that; it could even reduce the drag. What it can't do is give you enough power to preserve your steady-state flight without any other power source. That would be a perpetual motion machine. (In the case of a ground-based vehicle, though, even that's not true, because you can extract arbitrary amounts of energy from the motion of the air relative to the ground.) -- BenRG (talk) 19:11, 18 June 2010 (UTC)

One thing to consider that might be getting overlooked in some of the above... the speed of the wind relative to the ground is pretty unimportant. An airplane in flight is moving pretty fast through the air. So the effective wind is backwards relative to the plane, at whatever speed the plane's airspeed is at the moment. So you don't need to worry whether the wind will run out - there will always be wind, as long as the plane is moving fast enough to sustain flight. Friday (talk) 19:17, 18 June 2010 (UTC)

You can not harvest energy from a steady wind, you can only harvest it from a changing wind, or a wind that is different from something else (like the ground). See Dynamic soaring for a dramatic example. Ariel. (talk) 21:32, 18 June 2010 (UTC)

When we are flying, we have airspeed and ground speed. Whether we are flying into the wind or with the wind, we still fly at the same airspeed, and as far as the aircraft is concerned, that's all that's relevant. Therefore, assuming steady wind and steady level flight (we call that "straight and level"), the airplane will always be flying x miles per hour in relation to the air moving around it. In that respect, the airplane is already using (or fighting against) all of the wind energy available to it. If it's flying with the wind, it tracks faster along the ground (ground speed). If it's flying against the wind, it tracks slower. Adding a fan at that point would cause more drag, and slow the aircraft down (or cause it to require more power). Falconus^{p t c} 22:02, 18 June 2010 (UTC)

Some of the early biplanes like the de Havilland Tiger Moth and de Havilland Dragon Rapide had small wind driven generators to provide electrical power. MilborneOne (talk) 15:54, 19 June 2010 (UTC)

Does abstinence cure any addiction?

Addiction of no matter what - sex, drugs, gambling. The idea behind it is that if you stay clean for a long time, your body will reset the addiction. --Quest09 (talk) 17:33, 18 June 2010 (UTC)

I'm not sure you can say abstinence cures addiction because usually people who abstain for years from, say, alcohol after becoming alcoholics can relapse on the first drink years later. If it was a cure, this wouldn't happen. Instead, it's just staying away from what weakens you. With respect to drugs, it's going to depend on the type of addiction: psychological or physical? Psychological addictions should be easier to remove by abstinence, but physical addictions often require weaning off the substance rather than a complete halt. Regards, --—Cyclonenim | Chat  17:47, 18 June 2010 (UTC)

Some would say yes, you can quit anything cold turkey if you have the willpower. Others would say no, you never truly cure an addiction unless you replace it with something else. There is probably a little truth in each, but since addiction is such a multi-faceted problem, there is no clear answer to your question. All we really know is what we have observed of the process, we don't have clear evidence of addiction at work inside the body, aside from chemical changes which are only a small part of the process. --144.191.148.3 (talk) 17:49, 18 June 2010 (UTC)

A distinction must be made between physiological dependence (Physical dependence), in which the balance of neuroactive chemicals in the brain is altered directly by the substance abuse, and behavioral addiction, in which the the balance of neuroactive chemicals in the brain has not necessarily been externally perturbed. In either case the etiology, the symptoms, the treatment, and the results vary greatly, so nothing general can be said without overgeneralizing the things grossly. --Dr Dima (talk) 18:17, 18 June 2010 (UTC)

My Google search for abstinence cure addiction found http://health.howstuffworks.com/addiction.htm/printable. I did not find there a definitive answer to your question, but I did find some interesting information.—Wavelength (talk) 02:53, 19 June 2010 (UTC)

This might be a language / definition problem. Does "cured" imply "permanently cured"? During the period of abstinence, by definition, one is not participating in the activity. This could be labeled "temporarily cured" (insofar as the person is not participating in the activity). But there is always the possibility of relapse. "Addiction" is subject to interpretation: broadly speaking, we can sub-categorize it into "physiological" and "psychological" dependence. The "cure" for addiction can be interpreted subjectively and may span these categories. For example, detoxification following a drug or alcohol addiction is typically the first step in treatment. For certain drugs, total "cold-turkey" abstinence techniques may actually be less effective than other methods (often a surrogate substance is used to help alleviate withdrawal symptoms - e.g., Opioid Replacement Therapy). Details depend on the type and circumstances of physical dependence. But "detox" is not the same as "cured" - it is obvious that relapse is a serious issue, because addiction has a significant psychological component, independent of physiological/chemical dependence. In the medical or psychological community, this problem of definition is sidestepped by using more precise terms. For example, a patient is classified based on the type of dependence, rather than simply saying that they are "addicted". This helps decide what kind of treatment is preferred. It is pretty rare (at least in the modern institution of psychology) to say that anybody is ever "cured" of a psychological issue, including addiction or substance abuse problems, because "cure" implies some kind of certainty that relapse will not happen. People who undergo treatment for addiction have various strategies to reduce the probability of relapse - again, based on the type of addiction and the circumstances, this might include total abstinence. Nimur (talk) 18:33, 19 June 2010 (UTC)

'natural' alkyl halides?

Are there any natural alkyl halides produced by living organisms? Would I see ever see chlorine substituted on a random amino acid in a protein for instance? John Riemann Soong (talk) 18:11, 18 June 2010 (UTC)

I don't know any specific complex natural alkyl (sp³) halides off-hand, but maybe follow the links and refs in the "Occurrence" and "Biosynthesis" sections of our haloalkane article? DMacks (talk) 18:31, 18 June 2010 (UTC)

See also Organochloride#Natural_occurrence not much info, or Encylo..Britanica better. Not suprisingly things that live in salt water are a common source.

eg http://www.google.co.uk/search?hl=en&q=asparagopsis+taxiformis&meta= (mentioned in the britannica article) aka Limu kohu

There's a nice example of thr type of thing found here google books:Invitation to organic chemistry By A. William Johnson page 113, with both alkyl and alkenyl halide (carbon-iodide bonds are also common - but most I've seen are attached to benzene or similar)

If you want more then I recommend trying using google scholar http://scholar.google.co.uk/ (searching "natural product" + bromine/halogen , with marine/algae etc to narrow seems to work..) if you don't use scholar search returns a lot of results about metal halide lights for marine aquariums...

eg this worth reading (and lots more) turns up easily with aromatic, akenyl and alkyl halides.

Alternatively hunt down and marry a marine biochemist.. :) 87.102.32.15 (talk) 19:21, 18 June 2010 (UTC)

As for halogens in amino acids - I was going to say not likely - since most examples I know of tend to appear to be the result of electrophilic attack on double bonds eg terpene like compounds etc .. but no: [30] halogenated tyrosines found in marine animals - spongin in sponges and gorgonin in Gorgonians this time - again marine creatures.87.102.32.15 (talk) 19:49, 18 June 2010 (UTC)

For an sp3 halogenated amino acid look into "barbamide" structure- contains a trichloromethyl group that is thought to derive from a halogenated leucine [31], there are probably thousands of other examples.87.102.32.15 (talk) 21:01, 18 June 2010 (UTC)

Thyroxine is not an alkyl halide, but is a halo-organic formed naturally in the human body. Physchim62 (talk) 00:29, 19 June 2010 (UTC)

Amino acids in a vegan diet

Do vegans have any deficiency of particular amino acids in their diets, or do they have all of them? Thanks 92.15.14.87 (talk) 18:18, 18 June 2010 (UTC)

According to our article Legume: "Legumes contain relatively low quantities of the essential amino acid methionine. To compensate, some vegetarian cultures serve legumes along with grains, which are low in the essential amino acid lysine, which legumes contain. Thus a combination of legumes with grains forms a well-balanced diet for vegetarians." SteveBaker (talk) 18:29, 18 June 2010 (UTC)

Yeah, rice and beans, aside from being tasty, is likely to have the amino acids you need, all together in one meal. You can get all essential amino acids from plant material, but you have to know what you're doing. Whereas you can be an uneducated meat eater and easily get them all. Friday (talk) 18:45, 18 June 2010 (UTC)

Vegans who don't go to any special effort are most likely to be short on lysine, but as the other replies pointed out, eating legumes is a good solution. Soy protein in particular has nearly the same quality as beef protein, so vegans who eat lots of soy products don't need to worry about this. (There may be other issues with eating lots of soy, though.) Looie496 (talk) 21:37, 18 June 2010 (UTC)

While this is not something I've looked into myself very well, I saw something a few week back while researching for another answer. I can't seem to find the particular source (well one of the ones I did find may be it, but I seem to recall something that I didn't see in any of the sources I provided). But sources (some of these may be a bit biased but their citations and info seems resonable to me) like Protein combining, Vegetarian nutrition, [32], [33] [34] [35] [36] (unsure about this source, comment on tryptophan doesn't appear correct) suggest while you do want a balanced diet, it is rather hard to get insufficient essential amino acids even on a vegetarian or vegan diet provided you have sufficient calorific intake.

Even if you only eat potatoes, you could easily get essential amino acids in sufficient quantities (sources say 6-8 large potatoes), although your diet is likely to be deficient in other areas (and I find it doubtful many people in the developed world would choose such a diet not counting those who eat mostly chips of either kind of course). Rice seems a bit more iffy 7.5 cups of cooked rice seems quite a lot then again if it's the only thing your eating you may need that much to fulfill you calorific intake.

In any case, note there is no need to combine proteins in one meal to ensure sufficient protein intake or balanced protein intake, simply get enough thoroughout the day. Body builders and others who want a high protein diet obviously need to take a bit more care to ensure their protein intake isn't limited by a small intake of one essential amino acid.

But in summary although getting amino acids in sufficient quantities seems to be a common concern, from what I can tell it's not really generally that big a deal, even without great effort most vegetarians and vegans who have access to a resonable set of foods won't usually won't end up deficienct even without making much of an effort. Nil Einne (talk) 22:51, 18 June 2010 (UTC)

Natural sea salt

Is natural sea salt any healthier than artificial salt? --75.25.103.109 (talk) 21:07, 18 June 2010 (UTC)

When you say artificial salt, do you mean to refer to a salt substitute? If not, I think sodium chloride is sodium chloride and it doesn't matter from whence it is derived, whether sea or flats. DRosenbach ^{(Talk | Contribs)} 21:26, 18 June 2010 (UTC)

(after ec)The term "artificial salt" is pretty meaningless. Sea salt contains sodium chloride (table salt) plus other stuff, depending where it came from. See Sea_salt#Taste_and_health. My understanding is, there is no evidence that sea salt is healthier than any other salt. Many people consume too much sodium, and eating sea salt won't change that. There is a widely held superstition that "natural" things are healthier than "artificial" things, but the people who go around believing such things usually can't explain what they even mean by those terms. A grizzly bear is very natural indeed but should not be considered safe. Friday (talk) 21:27, 18 June 2010 (UTC)

(ec2) That depends on the rest of your diet. It contains a lot more minerals other than sodium and chloride, but if you get adequate amounts of them from the other things you eat, it might not make much of a difference. Looie496 (talk) 21:28, 18 June 2010 (UTC)

(ec again!) Have you read Sea_salt#Taste_and_health? Sea salt contains some iodine which we need in our diet but standard table salt does not. As already mentioned, they are both almost entirely sodium chloride so there is little difference. 86.7.19.159 (talk) 21:30, 18 June 2010 (UTC)

You got that backwards - table salt usually has iodine added, and sea salt contains no significant iodine. Friday (talk) 21:33, 18 June 2010 (UTC)

Seaweed does, though. Kind of a lot of it if I recall correctly. No real relationship with sea salt, of course, except that you could argue that the saltiness in seaweed is sea salt, and you might expect the same type of consumer to eat it. --Trovatore (talk) 21:36, 18 June 2010 (UTC)

Iodine is not added to salt in the UK. Sea food is a source of iodine, especially seaweed. 92.15.4.168 (talk) 13:40, 19 June 2010 (UTC)

To my knowledge no one is artificially manufacturing salt. It would be a very expensive process, and salt is pretty cheap. Most table salt comes from salt mines where workers dig up giant deposits of salt from parts of the ocean that dried up eons ago. APL (talk) 21:51, 18 June 2010 (UTC)

Around here, most table salt comes from evaporation. They have big shallow ponds carved out of San Francisco Bay. The salt article doesn't seem to have a breakdown of how much is evaporated, versus mined, worldwide.

Even though it's evaporated from seawater, it's not ordinarily marketed as "sea salt". I don't know whether there are any special rules to qualify the product as "sea salt" or not. --Trovatore (talk) 23:04, 18 June 2010 (UTC)

I didn't realize that. I thought that all salt that came from evaporation was sold as "Sea Salt". I wonder what the difference is. It would be hilarious if it were just marketing. That is, the same salt, from the same source, sold as both table salt and sea salt, for different prices. APL (talk) 03:02, 19 June 2010 (UTC)

Sea salt is generally unpurified. Table salt, whether it is mined or evaporated from ocean water, goes through a purification process to be almost pure sodium chloride. So, if you take sea water, evaporate the water, and then use the leftover crystals directly, that's "sea salt". If you take that sea salt, further purify it and remove all the non-sodium chloride impurities, you have "table salt". --Jayron32 05:12, 19 June 2010 (UTC)

Assuming 'artificial salt' means refined rock salt (ie the mined type) there is difference that rock salt is very old and was laid down before man made polution, whereas sea salt has the potential to be polluted by more recent man made discharges. In practice I have no idea if this is a factor or whether there is regulation of sea salt purity.87.102.32.15 (talk) 22:55, 18 June 2010 (UTC)

So sea salt is sodium chloride with some contaminants, whereas table salt is slightly purer sodium chloride with different contaminants. Gandalf61 (talk) 09:16, 19 June 2010 (UTC)

You would be healthier adding no salt at all to your food. It's very likely that you get more than enough salt or sodium hidden in the processed foods you eat. I think the recently reduced UK target for salt consumption is 4g per day, but the true optimum is belived to be about 2.3g per day as far as I recall. I suggest you try estimating and adding up your total salt or sodium intake per day (from the nutritional information given on processed foods where available etc) - you will almost certainly have an unpleasant surprise. 92.15.4.168 (talk) 13:33, 19 June 2010 (UTC)

Organic Materials

what are the molecular components from which organic materials are constructed?Sadiehyde (talk) 21:50, 18 June 2010 (UTC)

See functional group. --Chemicalinterest (talk) 21:57, 18 June 2010 (UTC)

Blossoms and leaves: coming and going

As I recall from my experience, spring blossoms on some deciduous trees appear first at the extremities and drop off last from the extremities, and spring leaves appear first at the extremities and autumn leaves drop off last from the extremities. To what extent is my memory correct? What is the scientific (possibly biochemical) reason for the blossoms and leaves behaving in those ways?—Wavelength (talk) 22:58, 18 June 2010 (UTC)

How much sunlight and shade do the extremeties see versus the interior branches? TenOfAllTrades(talk) 23:11, 18 June 2010 (UTC)

Apparently, they see more sunlight and less shade, but I do not know how much, either in absolute measurements or in relation to the amounts seen by the interior branches.—Wavelength (talk) 23:23, 18 June 2010 (UTC)

The distribution of plant hormones might have something to do with it eg Auxins I would guess that they dominate at growing tips and diffuse to the 'interior parts'. Also see Plant hormone - .. - Abscisic acid seems to be involved (in some cases) - though I'm not sure if it's causal (or the mechanism by which it is produced at growing tips..) . Maybe someone else can expand on this.87.102.32.15 (talk) 23:17, 18 June 2010 (UTC)

By the way I can't actually confirm what you remember - and there are growing tips all over the plant branches (potentially).. so .dunno. 87.102.32.15 (talk) 00:27, 19 June 2010 (UTC)

Neither do I believe that deciduous trees in general lose their blossom or leaves in this way. Richard Avery (talk) 14:16, 19 June 2010 (UTC)

Why is the speed of light relative to an observer constant regardless of the velocity of the source of light or of the observer?

The whole relativity thing depends on this phenomenon, so it would be interesting to know WHY this is the case.––220.253.96.217 (talk) 23:31, 18 June 2010 (UTC)

Because that explanation best fits the universe we observe. At some point, questions of "why" regarding fundamentals are philosophical rather than scientific. — Lomn 01:17, 19 June 2010 (UTC)

The two parts of this have two different answers. The reason it remains constant regardless of the velocity of the source is basically the same as the reason waves generated by a boat traveling through water remain constant regardless of the velocity of the boat. But the reason it remains constant regardless of the velocity of the observer is much deeper: it is a result of the Einstein equations for special relativity, which say that when an observer moves, the basic laws of physics only remain valid if time is rescaled, and the amount of rescaling is exactly what is needed to keep the apparent speed of light constant. Looie496 (talk) 01:28, 19 June 2010 (UTC)

Modern physics rejects Looie496's assertion that the reason the speed of light remains constant regardless of the velocity of the source is basically the same as the reason waves generated by a boat traveling through water remain constant regardless of the velocity of the boat. Looie496's presumption that there exists a medium (water) that light travels in is the old Luminiferous aether theory that has been disproven since 1887 by the Michelson–Morley experiment, Cuddlyable3 (talk) 11:27, 19 June 2010 (UTC) small tweak

Relativity does not presume that there is no such thing as space. Light as viewed in special relativity consists of oscillating electric and magnetic fields, and those fields are defined in spatial coordinates. Maxwell's equations for electromagnetic fields produce an oscillation that propagates across space according to the wave equation, which is the same equation that governs the propagation of waves across the surface of a body of water. Looie496 (talk) 17:08, 19 June 2010 (UTC)

The whole relativity thing depends on that only if you chose to follow the historical aproach (which most introductory books do) and postulate the constancy of the speed of light and get everything else from there. Alternately you could postulate, for instance, the Lorentz transformations and get everything else from there (including the constancy of the speed of light which is not a postulate on that approach). You might ask now why does the universe obey the Lorentz transformations? Well, it is a matter of space-time symmetries. The Lorentz transformations obey a set of symmetries which are generalizations of space rotations. Asking why the universe obeys Lorentz covariance (That's the technical name of the symmetry) is simmilar to asking why the universe is isotropic and homogeneous. The answer of couse is that's simply the way it is and we know that from empirical obsergations. There is no why. Dauto (talk) 03:11, 19 June 2010 (UTC)

I think it's important to distinguish "we don't know why, or even if there is a why" from "there is no why". The former would be a much more justified statement. --Trovatore (talk) 03:19, 19 June 2010 (UTC)

I think the latter is the better statement. Dauto (talk) 15:52, 19 June 2010 (UTC)

Why do you think that? Of course, it's a stronger statement, and we want to make the strongest statements we can justify. But I don't see that you have any justification for it whatsoever. --Trovatore (talk) 18:51, 19 June 2010 (UTC)

I agree with Trovatore. Lorentz invariance could easily end up having an explanation (in terms of some sort of pregeometry). -- BenRG (talk) 18:58, 19 June 2010 (UTC)

While we're mincing words, "it is a result of the Einstein equations for special relativity..." This is accurate, but it is phrased in such a way that it sounds like one day Einstein just decided that he should write some equations to make the speed of light constant in all frames. The way the universe works is not a consequence of Einstein, or any other scientist's equations. The universe works the way it does - and Einstein's equations happen to explain this particular detail in a simpler and more consistent way than any other explanation. Universal principles are not a "consequence" of our mathematical effort to represent them. Instead of attributing this fact to the equations, we should say "if this fact were not true, there would be an inconsistency in the universe because of the way that electromagnetic waves work. This inconsistency was first resolved mathematically by Einstein." Nimur (talk) 18:40, 19 June 2010 (UTC)

If you're asking why we believe it: testing. If you're asking why it's true, special relativity explains it. — DanielLC 06:30, 19 June 2010 (UTC)

...And if you're asking "why it is the way it is instead of working out some other way", that answer lies at some level in either philosophy or religion. The most agnostic answer to the "big why" is probably the Anthropic principle which is a type of logical tautology. The Anthropic Principle states that the laws of the universe exist the way they do because we are observing them. To state it another way, the fact that humans exist to observe the universe is predicated on the fact that the laws of the universe cannot exist in any way other than what we are observing, because if they were different, the universe under THOSE laws could not have produced humans to observe them. Or, to put it a third way, if the universe obeyed different laws, it would not have produced an intelligent life form to ponder the universe. So the answer to "why" could just be that if it were different, it wouldn't exist in a way to allow us to observe those differences. --Jayron32 06:52, 19 June 2010 (UTC)

That's a pretty "extreme" statement of the strong anthropic principle" - as you have phrased it, Jayron, you discount the possibility of a null space within which certain physical laws could differ while still providing a universe suitable for intelligent life. Nimur (talk) 18:48, 19 June 2010 (UTC)

I agree. E.g., there is a formal description of Jayron32's brain, therefore any algorithm that aims to simulating it, defines the laws of physics of a a universe in which he lives. Count Iblis (talk) 19:16, 19 June 2010 (UTC)

Paper cuts vs. "normal" cuts

I've seemed to notice that paper cuts have more pain to them than your average minor cut, and a kid in my scout troop who accidentaly sliced his finger with a knife (almost bad enough for stitches) said it hurt less than some paper cuts he's gotten. What causes paper cuts to hurt worse than other "normal" cuts? Ks0stm ^(T•C•G) 23:49, 18 June 2010 (UTC)

From Paper cut: "Paper cuts can be surprisingly painful as they can stimulate a large number of skin surface pain receptors (nociceptors) in a very small area of the skin. Because the shallow cut does not bleed very much, the pain receptors are left open to the air, ensuring continued pain. This is exacerbated by irritation caused by the fibers in the paper itself, which may be coated in chemicals such as bleach. Additionally, most paper cuts occur in the fingers, which have a greater concentration of sensory receptors than the rest of the body."[37] Ariel. (talk) 00:15, 19 June 2010 (UTC)

semiconductor doping

If silicon chips are doped with arsenic, why doesn't touching them poison you? --75.25.103.109 (talk) 23:55, 18 June 2010 (UTC)

1. No one ever touches them. The part you see is a plastic cover, the silicon is inside.
2. There is a VERY tiny amount.
3. The arsenic is tightly bound in the silicon, and will not come out just because it's touched.

Ariel. (talk) 00:13, 19 June 2010 (UTC)

You don't get arsenic poison by touching a piece of arsenic elemental anyway; you get it by touching then ingesting, inhaling fumes or the volatile compounds such as arsenic trichloride, or intentional poisoning. --Chemicalinterest (talk) 10:58, 19 June 2010 (UTC)

The amounts are tiny, and by the time an electronic chip gets to you, the consumer, it is virtually impossible for any arsenic to be chemically active or in any way exposed to you. Arsenic would be tightly bound inside the semiconductor crystal lattice - see doping (semiconductor) - and the concentrations would be insignificantly small. Inside a semiconductor fab, arsenic gas may be released into an ion implantation chamber. This is usually an airtight device (hermetically sealed vacuum chamber). Arsine and Arsenic trifluoride are commonly released into the chamber. "Since these gases are all highly toxic or otherwise hazardous, additional input purging and trapping systems are needed to ensure that the all of the source gas is removed from the system before wafer loading or removal." Arsenic breaks out from these "extremely toxic" gases at high temperatures inside the ion implanting device. It then diffuses into the substrate (and is therefore deeply buried inside the silicon ("deep" can mean nearly 1 micron - but we can safely say that no arsenic will "rub off" the chip. (Microchip Manufacturing, Chp. 11 "Diffusion Sources"). Occasionally, an epitaxial layer will intentionally be doped with arsenic, but even during the processing, the gas is introduced in amounts of around 20-100 parts per million (relative to the already near-vacuum conditions inside the chamber). Again, safety devices are supposed to flush the chambers and input plumbing to ensure that the gas is totally purged before anybody is exposed to the wafers. At least one study has been published to investigate the effects of prolonged exposure to arsenic for people who work in the silicon fabs (factories) (and also, copper smelters, who are exposed to even higher concentrations because arsenic occurs naturally in copper ores). Here is Biological monitoring of arsenic exposure of gallium arsenide- and inorganic arsenic-exposed workers, (1989). It was found that these workers had "far higher" concentrations of arsenic than a control-group, but it seems that there was no conclusive evidence that even this elevated level of arsenic was unsafe. Nimur (talk) 19:08, 19 June 2010 (UTC)

June 19

Ammonia

What's a chemical which decomposes ammonia but which is harmless to humans? --75.25.103.109 (talk) 00:30, 19 June 2010 (UTC)

Sodium bicarbonate: it reacts to form sodium ammonium carbonate, which is harmless. --Chemicalinterest (talk) 00:49, 19 June 2010 (UTC)

sodium ammonium carbonate doesn't really exist - carbonate is too basic - so it will deprotonate ammonium.

A mild dilute acid will convert ammonia to a salt - eg citric acid will form ammonium citrate - which will get rid of the ammonia smell, but does not decompose the ammonia.87.102.32.15 (talk) 02:36, 19 June 2010 (UTC)

It only deprotonates ammonia partially, so there is still a little odor. Try reacting smelly vinegar with smelly ammonia to produce the faintly odored ammonium acetate. --Chemicalinterest (talk) 10:54, 19 June 2010 (UTC)

Urine contains urea, which breaks down into ammonia. See also the urea cycle. Of course, in high enough concentrations, any substance can be harmful to humans. Nimur (talk) 19:12, 19 June 2010 (UTC)

Vague definitions of harmful aren't needed here; he is obviously asking whether something that is not very toxic. --Chemicalinterest (talk) 20:09, 19 June 2010 (UTC)

Production of carbon tetrachloride

Can carbon tetrachloride be made by burning a candle in chlorine gas? In oxygen it forms carbon dioxide. --Chemicalinterest (talk) 00:54, 19 June 2010 (UTC)

Based on the article you linked, specifically the section on synthesis and the chlorination article it cites, one can generate CCl₄ through oxidation reactions using chlorine gas. However, those references suggest that one must use more specific reactants and conditions than simply applying heat to a candle in a chlorine gas atmosphere to obtain the desired products in substantial quantities. -- Scray (talk) 04:06, 19 June 2010 (UTC)

I would imagine that, if you burned a candle in chlorine gas, you would get all sorts of chlorinated products (including some carbon tetrachloride). To get a good yield of pure(ish) carbon tetrachloride, you would need a more specific reaction, such as the chlorination of methane mentioned in the article. Physchim62 (talk) 11:47, 19 June 2010 (UTC)

Potato Chips

How do potato chips companies get their chips crisp, even when they are the baked kind? When I thinly slice mine and cook whether it is frying or baking they come out like au gratin potatoes? —Preceding unsigned comment added by 71.137.252.51 (talk) 03:38, 19 June 2010 (UTC)

I don't think you can do the baked kind at home -- they actually powder the potatoes and mix them with other stuff to get something that will be crispy when baked. For the fried ones, it's simply a matter of frying them for a long time at a relatively low oil temperature -- there's an amazing amount of water in potatoes and you have to get it all out or your chips will be soggy. Looie496 (talk) 05:00, 19 June 2010 (UTC)

I haven't made potato chips, but when I fry French Fries, I get them quite hard and crispy. My method is to have plenty of oil to completely, really really submerge whatever you're frying (aka deep frying). Then you have to get the oil really really hot. You should have it on maximum heat on your stove's largest flame (if you have different sizes) and test the oil by dropping a single drop of water into it. If the water does not sizzle IMMEDIATELY when it hits the surface of the deep oil, you have to wait for the oil to get hotter. (when it's not hot enough, the drop of water will fall in, and only a moment or two later cause a reaction. you have to then wait for the oil to get hotter.) Once the oil is really really hot, so that a drop of water sizzles onto it (you should be testing every minute or two), you drop on whatever you're deep-frying, in this case potato chips: STAND BACK! It will splutter and sizzle like hell when you put the stuff in. But then it will settle down (you keep it on maximum heat) and just fry. You should be frying for about 4-8 minutes, you can stir occasionally, the oil won't pop out at you (juts don't get any water in it), all of this is on your stove's maximum heat, and you check that it's done by the color: your chips shoudl be "golden brown". When they are, turn off the heat and carefully remove the chips onto a kitchen towel (bounty, etc) or you can strain them with a strainer, leaving them oilier. Now, one thing is a little bit of oil will be all over your stove, so don't remove the pan until you've turned off the flame (and, if it's an electric stove, waited for it to cool) as it could ignite the oil - this happened to me. That's about it. So, my advice is really the opposite of the advice to "cook slowly for a long time". Then again, I haven't fried chips yet, so who knwos if this will work :) 92.229.14.159 (talk) 12:03, 19 June 2010 (UTC)

Harold McGee's On Food and Cooking explains both styles of cooking them. He says factory made crisps are cooked at a consistent, high temperature (~170C) for 3..4 minutes (they're on a submerged conveyor). Home cooked crisps (and factory made "kettle chips") are made in batches, with the oil starting at ~120C and rising to 175C in 8..10 minutes. He explains how the differences in the water and protein behaviour in these two environments account for the kettle chips being harder; this latter method largely resembles the double-frying method that's commonly used for making fully-fledged Belgian fries (example). As that recipe I cited notes, don't dump in such a massive lot of slices that the oil temperature plummets - use small to medium sized batches. In general, different cultivars have different water and starch content, so experimenting with locally available types is a good idea. It's very common to dry the cut potato before frying (to reduce spitting and promote rapid caramelisation) and for some cultivars people wash the cut slices before drying (to reduce excess starch) - I've heard of people who towel dry the cut slices and them leave them out for a couple of hours to really dry out (but overdo this and they'll burn, or disintegrate and contaminate the oil). -- Finlay McWalter • Talk 14:17, 19 June 2010 (UTC)

sperm sorting

I just want to ask a question about sperm sorting. I am not great with negotiating computers so I hope I am doing this right. I understand sperm sorting can be used to determine sex. I am wondering if it would also work to help males with balanced chromosome translocations. Up to 60% of an affected male's sperm will produce miscarriages. Since sex determination looks at the chromosomes or in some way sorts the x from the y sperm, I thought it might work for this too. Any help you can give me will be much appreciated. —Preceding unsigned comment added by Sallygartner (talk • contribs) 04:23, 19 June 2010 (UTC)

Have you read the obvious article Sperm sorting? Nil Einne (talk) 10:27, 19 June 2010 (UTC)

Yes, I have read the article. This does not specifically say it would help with chromosome problems. —Preceding unsigned comment added by Sallygartner (talk • contribs) 15:27, 19 June 2010 (UTC)

Well the article explains how sex sorting works which you seemed confused about. The sperm are dyed and given a different charge depending on amount of dye absorbed (which varies because of the differing amounts of DNA the dye binds to).

So if the sperm have a differing DNA complement, e.g. lack part of one or more chromosome (nullisomy), you may be able to detect them in this way (in particular if the X sperm have what seems a complete complement), but if the sperm chromosomes contain balance translocations, the DNA complement will be the same. [38] seems to discuss this somewhat although you'd need a subscription.

The article also mentions "DNA damage in sperm cells may be detected by using Raman spectroscopy. [1] It is not specific enough to detect individual traits, however.[1]" From the ref [39] it doesn't appear this will help with balanced translocations much since it's detecting DNA damage.

Nil Einne (talk) 16:05, 19 June 2010 (UTC)

This procedure exposes spermatozoa to a fluorescent dye (Hoechst 33342) and ultraviolet light? Both of those seem like things that could cause chromosomal or genetic damage. This issue seems to have been brought up letters to the journal Human Reproduction. This 2005 article states in its title, Hoechst 33342 stain and u.v. laser exposure do not induce genotoxic effects in flow-sorted boar spermatozoa, but I'm unconvinced. Nimur (talk) 19:22, 19 June 2010 (UTC)

why do gas (petrol) stations have the same characteristic roof over the filling area?

Why do gas (petrol) stations all have the characteristic roof (or covering) over the filling area. Specifically, it is flat, held up on pilons, and of a rectangular or other very "square" (right angled corners) footprint. There are many types of roofs on many buildings, but only gas stations have this type as a rule - why? Thank you. 92.229.14.159 (talk) 12:10, 19 June 2010 (UTC)

Maybe they are mass produced. --Chemicalinterest (talk) 12:12, 19 June 2010 (UTC)

Well this one [40] doesn't. Anyway while I don't know the specific answer to the question I would guess there are some considerations for a petrol station that many other buildings lack, in particular they need high roofs both to accomodate large vehicles and I presume to ensure fumes don't get trapped. The roofs also likely need a degree of fire resistance and perhaps resistance to the petrol (and probably some diesel) fumes. And they do need roofs so people can fill their cars up without getting wet and perhaps for other reasons. Ultimately it may be tradition and the lack of any real advantage to do something else as much as anything. Nil Einne (talk) 15:28, 19 June 2010 (UTC)

The roofs are serving the same purpose, so it's not surprising they use the same design. It's probably the best design for the job. It needs to be open on two sides for the vehicles to get in and out and it is beneficial for it to be open on the 3rd side as well for ventilation. That gives them two options for holding it up, columns or a cantilevered design. The former is far easier and there are no real disadvantages, so naturally they choose that. They have a choice between a flat roof or a sloping roof. Flat roofs are easier and cheaper, and clearly work, so naturally they choose flat roofs. Everyone (with a few exceptions, either due to different priorities or a different starting point) that designs petrol stations goes through the same thought process and naturally gets the same result. --Tango (talk) 16:01, 19 June 2010 (UTC)

Major gas (petrol) brands aim to provide a distinctive recognizable "welcoming" forecourt for self service. This corporate styling exercise includes a brand logo, pumps, card reader and uniform prefabricated roofs that provide shelter and lighting. Cuddlyable3 (talk) 16:29, 19 June 2010 (UTC)

I (op) don't buy these answers. They lead, perhaps, to the current design, but the current would be the second-to-last step following the above reasoning: the last step would be to add a sloping roof, so that the rain can roll off, instead of accumulating. Why isn't there such a slope? You can make it with $75 of corrugated sheet metal. There has to be something else. 92.229.14.11 (talk) 19:41, 19 June 2010 (UTC)

Spindle cell rhabdomyosarcoma

What is the outlook for metastatic spindle cell rhabdomyosarcoma? —Preceding unsigned comment added by 64.223.235.196 (talk) 13:47, 19 June 2010 (UTC) I am not asking for medical advice, just info. —Preceding unsigned comment added by 70.16.107.144 (talk) 14:10, 19 June 2010 (UTC)

Not sure if this will answer your question: "Two types of ERMS, botryoid and spindle cell rhabdomyosarcomas, tend to have a better prognosis (outlook) than the more common forms." Taken from this page. --TammyMoet (talk) 15:28, 19 June 2010 (UTC)

but does that apply to cases that have metastasized —Preceding unsigned comment added by 70.16.107.144 (talk) 16:15, 19 June 2010 (UTC)

I think that crosses the line into medical advice. Ask your oncologist. --TammyMoet (talk) 16:57, 19 June 2010 (UTC)

We understand that you are just looking for information, but honestly there is no way anyone on the Ref Desk can intelligently answer what the prognosis would be for any given person's metastatic cancer. There are simply too many variables. There is some information in the soft tissue sarcoma article, and this reference discusses factors associated with prognosis in metastatic rhabdomyosarcoma, but your best option (as usual) is to ask a physician. --- Medical geneticist (talk) 19:36, 19 June 2010 (UTC)

Simulator

I need to simulate a microprocessor based system. The system would have some external devices interfaced to the microprocessor. What are the software that can do this type of a simulation ? —Preceding unsigned comment added by 218.248.80.62 (talk) 14:05, 19 June 2010 (UTC)

Nisan and Schocken's The Elements of Computing Systems has a free multi-layered simulator (here) which has both hardware level simulation and a simulated CPU. People have designed various components in the book's HDL (a simplified counterpart of VHDL), which the forum should be able to help you find. -- Finlay McWalter • Talk 14:28, 19 June 2010 (UTC)

Something from Category:Electronic circuit simulators might help. DMacks (talk) 16:51, 19 June 2010 (UTC)

The Computing Ref Desk would be a better place for this question, but in short, what you are hoping to do is to create an emulator. There is software available to use as a starting point, but I'm not very familiar with it. Looie496 (talk) 17:43, 19 June 2010 (UTC)

Radioactive minerals on other planets?

Has any attempt been made to find commercially exploitable radioactive minerals on any of the moons or planets of our solar system? Solar powered robots and rail-guns could parachute this back to Earth for atomic power. What about Mercury- could its high density mean that dense minerals such as Uranium might exist there?[Trevor Loughlin]80.1.88.6 (talk) 14:36, 19 June 2010 (UTC)

No attempt has been made. There's vanishingly little possibility that it would yield product at a lower cost than on earth. --Tagishsimon (talk) 14:40, 19 June 2010 (UTC)

Why would anybody do that when uranium still is a fairly common element on earth? Dauto (talk) 15:26, 19 June 2010 (UTC)

Something like Uranium is best found on the Earth - it's already here in great quantities. The closest serious idea to what you describe is finding Helium-3 on the Moon (deposited there by solar wind) for use in nuclear fusion (we need to invent a fusion reactor that actually produces more energy than it uses for that to be useful, of course). Apart from Helium-3, there isn't much on the Moon that we can't get easier on Earth, so most ideas about exploiting resources of the Moon are about either using them on the Moon or in space. There are lots of ideas about asteroid mining, including sending resources back to Earth - it's much cheaper (in terms of energy requirement) to get resources from an asteroid to Earth than from another planet (or even the Moon) to Earth, due to weaker gravity. --Tango (talk) 16:16, 19 June 2010 (UTC)

Purpose of Addiction

Why can the body become addicted to certain substances and what purpose does this serve? Addictions don't seen to benefit the body in any way. So why does the body crave something? Here I'm talking about physical addictions, not psychological ones. Thanks! Stripey the crab (talk) 14:53, 19 June 2010 (UTC)

You probably want to read Substance_dependence#Pathophysiology, such as the Role of dopamine subsection. --Tagishsimon (talk) 14:58, 19 June 2010 (UTC)

The neurotransmitter Dopamine is closely associated with reward-seeking behaviors including basic desires for survival such as sex, eating and family, without which none of us would be alive. It is also involved pathologically in physical addictions. Human neurobiology has not evolved enough to be fool-proof. Cuddlyable3 (talk) 15:57, 19 June 2010 (UTC)

Expanding on that, I think the original poster has as a premise the idea that everything in the body has some purpose, which is untrue. The human body has various weird properties that don't serve a great purpose; they just didn't interfere with our ancestors enough to stop them from being able to breed. See the "Evolutionary baggage" section of Evolution of the eye, or see Recurrent laryngeal nerve, a nerve that runs from your brain to your voice box to control it, but it idiotically goes down into your chest cavity first and then loops back up. Comet Tuttle (talk) 16:02, 19 June 2010 (UTC)

Right, addictions are malfunctions of the biological reward system caused by putting substances into the body that it is not equipped to handle. They don't have a purpose any more than the breakdown of a car after you put water into the gas tank has a purpose. Looie496 (talk) 16:49, 19 June 2010 (UTC)

See [41], in real life turkeys won't come across heads stuck onto sticks to make love with. We're little different, evolution hasn't fitted us to resist all drugs purified in a laboratory where analogues have a useful purpose in the brain. Dmcq (talk) 19:00, 19 June 2010 (UTC)

It maybe because we are creatures of habit, and we resist change. MacOfJesus (talk) 19:31, 19 June 2010 (UTC)

Experiments in quantum mechanics?

What aspects of quantum mechanics have actually been experimentally verified?

If that's a contentious question with a debatable answer, where might one find a list of the most well-known experiments of quantum mechanics? 96.255.178.76 (talk) 15:56, 19 June 2010 (UTC)

If I may add the contra-positive: what open questions still exist in quantum mechanics that have not been experimentally verified? Zunaid 16:20, 19 June 2010 (UTC)

The double-slit experiment is a famous one that demonstrates wave-particle duality, which is a fundamental feature of quantum mechanics. Pretty much all of quantum mechanics has been experimentally verified - that's a requirement to be considered a scientific theory. --Tango (talk) 16:25, 19 June 2010 (UTC)

Many of these experiments are still open to contending interpretations. Cuddlyable3 (talk) 16:35, 19 June 2010 (UTC)

Indeed. Things like the Copenhagen interpretation aren't theories, they are interpretations of theories. Theories have evidence for them, interpretations don't (once you get significant evidence for an interpretation over the others, that interpretation just becomes part of the theory and you stop using the word "interpretation"). --Tango (talk) 16:40, 19 June 2010 (UTC)

Spin (physics) has been confirmed experimentally - so much so that it's used in NMR spectroscopy , Electron paramagnetic resonance spectroscopy, as well as Magnetic resonance imaging. The Stern–Gerlach experiment is the classic experiment. These are examples of quantisation of spin.

Quantum tunnelling is an example of an experimentally obtained results that are explained in terms of a quantum mechanical wavefunction. I'm not aware of other explanations - but that doesn't mean they don't exist - 'QM' represents a good theoretical basis for this phenonoma though.83.100.252.174 (talk) 16:52, 19 June 2010 (UTC)

The list is too long even to summarize. Our article on Theoretical and experimental justification for the Schrödinger equation is probably the best resource here as far as I can see, but it is written at a pretty advanced level. (The Schrödinger equation is the basic mathematical formulation of quantum mechanics). Looie496 (talk) 16:54, 19 June 2010 (UTC)

Quantum mechanics is a rather wide umbrella term that can cover any theory in physics which is based on the principles of the wave function, gauge symmetry and quantum field theory. We have quantum mechanical theories of three of the four fundamental forces - electromagnetism, the strong force and the weak interaction. All of these have been extensively tested. In particular, the quantum theory of electromagnetism, quantum electrodynamics, has been verified to a higher degree of precision than any other theory in physics, I think. These quantum theories together make up the Standard Model of particle physics. A confirmation of the existence of the Higgs boson would fill one of the few experimental gaps in this model. However, what we lack is a quantum mechanical theory of gravity. There are various candidate theories, but each of these is either inconsistent with known facts, too vague to be testable, or not testable with current technology. Gandalf61 (talk) 16:55, 19 June 2010 (UTC)

Quantum mechanics (like special relativity) is a simple set of rules that one requires one's physical theories to follow. It's not a physical theory by itself. A theory that follows the rules might be called "quantum" (or "relativistic"). The basic quantum-mechanical (and relativistic) rules are ludicrously well confirmed; basically every high-energy physics experiment in the last century tests these rules. As for individual quantum theories, it depends on the theory; it's the same as asking "how well has physics been tested?".

Gauge symmetry is not an intrinsically quantum idea. It happens that the most famous gauge theory (the Standard Model) is also quantum, but Maxwell's electrodynamics is a U(1) gauge theory, and the equivalence principle in general relativity is related to the gauge principle. -- BenRG (talk) 18:26, 19 June 2010 (UTC)

An experiment proposed by David Deutsch in which an observer is able to reversibly forget the outcome of a measurement, while not forgetting that the measurment was performed, thus disproving the Copenhagen Interpretation (because the measured system would be back in the original state, rather than its wavefunction having irreversibly collapsed because of the measurement), has not yet been performed. Count Iblis (talk) 16:58, 19 June 2010 (UTC)

David Deutsch's Request for a Photon Experiment Cuddlyable3 (talk) 17:12, 19 June 2010 (UTC)

As far as I can tell that page was not written by Deutsch but by some random Internet crank. Deutsch himself is also kind of crankish. -- BenRG (talk) 18:26, 19 June 2010 (UTC)