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May 8

Paint color matching.

When I take a chip of paint to a DIY store and have them make a matching paint - what kind of sensor do they use? Seems like a regular RGB camera wouldn't cut it...do they switch light sources? How does it actually work?

SteveBaker (talk) 02:21, 8 May 2016 (UTC)

Colorimeter?--178.107.62.251 (talk) 03:34, 8 May 2016 (UTC)

One actually can use a regular camera, for example, Sherwin-Williams has an app.[1] DMacks (talk) 04:13, 8 May 2016 (UTC)

I'm DEEPLY skeptical that a cellphone camera, with unknown lighting, could possibly, remotely, come up with a useful color match to existing paintwork - and to be fair to Sherwin-Williams, that's not what they're claiming. They suggest using colors captured in photos for "inspiration" and other such things - but they never say it's going to match...and nor would it. SteveBaker (talk) 18:00, 9 May 2016 (UTC)

Not sure how good it is, but [2] has some technical discussion. That and other sources like [3] [4] (second one is about car paint colour matching) says a spectrophotometer. One source I came across called it a Spectroradiometry, but I think photometer is more accurate for the type of machine normally used. Admitedly I wonder if spectrocolorimeter may be even more accurate for what being done, but I didn't read enough to know for sure.

Anyway I found this PR about one machine used [5] which may help find out PR about this specific machine [6], if you cut through the PR I would guess you could get some info on what's actually involved. Colour Match Navi CT-X is evidentally one device used for cars although I could find very little about it. The device mentioned in the Gizmodo link is more productive [7]. I also noticed a lot of AliBaba results e.g. [8], I would guess some stores are using products sold there.

I would also assume/hope, there must be some published science about these commercial computerised paint colour matching machines, I didn't notice any but a targeted search may work better.

Nil Einne (talk) 14:23, 8 May 2016 (UTC)

Hmmm - so according to the HowItWorks article - they shine "pure" white light onto the target then capture the reflected intensity across the visible spectrum in 10nm steps using a bunch of interference patterns. That's kinda what I thought.

SteveBaker (talk) 18:00, 9 May 2016 (UTC)

Mobile phones in walkie-talkie mode - range?

I understand that a mobile phone connecting directly to another mobile phone instead of via a cell tower would have greatly diminished range because the cell tower provides the power so that the phone doesn't have to but what would that range be? Using the hardware usually used to connect to the nearest cell tower, how far could phones talk to each other in a such a walkie-talkie mode? — Preceding unsigned comment added by 78.148.108.58 (talk) 19:52, 8 May 2016 (UTC)

This question really devolves pretty quickly when you start getting into technical details. Cellular networks are specifically designed to be asymmetric, not peer-to-peer; and this design is embodied in every detail of the hardware, from the amplifier design to the antenna design to the frequency choice to the digital and software protocols that are used. A significant limiting factor - perhaps the most significant limiting factor - is the nature of the shared channel, and if we re-architected a mobile phone for direct peer-to-peer operation, this changes everything about the communication signal quality. Every single detail of your mobile telephone's radio is defined by its mechanism for cooperatively sharing that channel with a tower and with other users. So, we simply can't answer the original question as posed - not accurately - because cellular telephone electronics don't work in this mode. If we start changing details or making approximations, we haven't got a cellular telephone anymore.

How familiar are you with radio technology? Before we start lobbing specifications at you, it might be good for you to review some basic terminology for telecommunications engineering and radio-frequency engineering.

At best, we could show you some specifications for other types of radios whose size and shape are "similar" to mobile cellular telephones. For example, a handheld VHF radiotelephone for use at aviation radio frequencies will reach one or two miles (if you're on the ground); and you might manage to reach as far as ten or twenty miles if you're at altitude - say, two miles above the ground, with a clear line of sight to your remote station. Aviation VHF is quite a bit lower frequency than the bands used by a modern mobile cellular telephone. To first-order approximation, that means that your cellular telephone will have a shorter range and will be much more limited by any obstacles (like walls, buildings, and terrain, and even humidity in the atmosphere) that block your line-of-sight.

I happened to be reading this article - on natural antennas - earlier this weekend. It's fascinating to see some cold, hard numbers - a 15 watt HF radio (which is much lower frequency and much much much much greater power than your mobile telephone) will work over a few miles through dense forest; but if you use a tree as an antenna, you can get as much as 20 or 30 dB of antenna gain. If you were in a forest and wanted to use a modern mobile cellular telephone, you'd probably have to be within a mile of the tower, or the signal would drop below usable levels.

Nimur (talk) 20:47, 8 May 2016 (UTC)

• Some cell-phone manufacturers marketed cellphones which were known for walkie-talkie modes (known as Push-to-talk). Nextel was one of the best known. --Jayron32 23:10, 8 May 2016 (UTC)

Yes, but that technology was still mediated by the centralized cellular network. There was no direct device-to-device radio link. For example, iDEN, the Motorola-branded technology that powered Boost Mobile and NexTel, was a trunk radio carrier. It has the superficial appearance of being a "walkie talkie," but that technology actually has more in common with VoIP than with a real, direct radio link. Nimur (talk) 02:42, 9 May 2016 (UTC)

TETRA (Terrestrial Trunked Radio) Mobile Stations (MS) designed for use by emergency services can communicate in direct-mode operation (DMO) in situations where network coverage is not available. DMO also includes the possibility of using a sequence of one or more TETRA terminals as relays. AllBestFaith (talk) 13:27, 9 May 2016 (UTC)

Neat! That's very similar to a lot of research into mesh networks and ad-hoc digital packet radio networks used by advanced HAM operators. But I'm pretty sure TETRA is not used in the United States by emergency services. We have a diverse set of local, state, Federal, and special-purpose services, so perhaps some organizations use it... but they are exceptions, not the rule.

Here's a pretty cool rundown of the historical and current radio technologies used by the CHP: California Highway Patrol radios, from WB6NVH. That guy has great photos, does a deep technology dive, covers current and historical systems, and even lists sources .... he even links to the authorization-legislation!

Such radios are neither "mobile phone" nor "walkie-talkie" - the preferred terminology is "Tactical Network Radio" or some variation therein.

It's hard to find good technical documentation on those technologies - what's left of the Motorola radio technology division is struggling to stay afloat ever since our friends at Google decided to hack the company to pieces. Most of the technology offerings are listed on the Motorola Solutions webpage - the real Motorola - and these are pretty much the full spectrum of the radios and radio network technologies that American emergency services use today.

Nimur (talk) 15:14, 9 May 2016 (UTC)

Presumably you could build a cell phone with other radios for direct communication, right? Actually isn't that already the case, as many phones these days have Wi-Fi and/or Bluetooth? Do those use the same antenna as the cell radio? I'm a programmer, and I'm fairly knowledgeable about software in general, but all that signal processing stuff is voodoo to me. Now certainly, it might not be economical to add radios to a cell phone for peer-to-peer communication. --71.110.8.102 (talk) 00:02, 10 May 2016 (UTC)

You could build such a device - but RF electronics are difficult. Like, really difficult. Like, you don't see nifty "do-it-yourself" RF electronics at the Maker Faire.

Test equipment for RF is expensive and difficult to use. Most engineers with a degree in electronics can't tell you the difference between a TDR and a VNA, let alone would they know how to use them. When enthusiast hobbyists see the price tag for the test equipment - without which it is literally impossible to build a modern radio - they gargle and guffaw and the hobby project fizzles out pretty quick, with the budget diverted to cheaper thrills like Ferraris or fast airplanes.

Radio electronics in this decade is a far cry from an amateur pursuit.

For the ultra-enthusiast who really really wants to get into RF: don't despair! Find a great research university who can afford the equipment you need, and prove that you're worthy of time-sharing their effort by being very good at math and engineering theory. An internship wouldn't hurt, either.

So, it's unlikely a hobbyist will build such a device; but if a research team or an industrial consortium settles on a standard - say, AX.25 (with all its awesome features and deal-breaking limitations), you might see some mobile handsets that start supporting it.

But for now, especially in the United States, it looks like we're going to be using centralized radio networks for the foreseeable future. You can read about our FCC's radio spectrum policy roadmap on the Radio Spectrum Allocation webpage.

Nimur (talk) 01:12, 10 May 2016 (UTC)

@Nimur: There must be something obvious about your answer I'm missing. I am under the impression that ham radio, shortwave sets, walkie-talkies, pirate radio and so forth are very common consumer hobbies on a shoestring budget. How is the situation you describe different? Wnt (talk) 02:12, 10 May 2016 (UTC)

HAM radio sets don't work with mobile telephone bands or protocols. Nimur (talk) 03:34, 10 May 2016 (UTC)

The closest that ham radio gets is probably D-STAR, which uses similar digital protocols for voice communications on the VHF and UHF Ham bands. This technology was adopted by amateurs (hams) quite a few years ago and taken up by one of the big three amateur radio manufacturers, Icom Incorporated, in Japan. It is now a well and truly established technology. Of course, it doesn't interwork with consumers' phones. Users with D-Star capable sets are, just like their non-D-Star capable cousins, able to talk direct (line of sight), or via a compatible repeater to extend the distance, or via a satellite link to communicate with other countries. Akld guy (talk) 06:22, 10 May 2016 (UTC)

A gift for the spook who has everything, the Motorola APX Transportable Base Station's “mouse-hole” exit for a power cable allows for covert closed case operations. You did not read this here. AllBestFaith (talk) 12:14, 10 May 2016 (UTC)

Driest place east of the Mississippi river

Which place in the United States east of the Missisippi river receives the lowest average annual rainfall? — Preceding unsigned comment added by 24.207.71.235 (talk) 23:09, 8 May 2016 (UTC)

I did some searches, and while I couldn't find any specific locale, This overview of Virginia climate notes that certain valleys of the Appalachian Mountains, such as the Shenandoah Valley and the New River Valley are noted for their lower-than-normal rainfall in the Eastern U.S. That may help you narrow down your searches. Such places lie in the rain shadow of the peaks of the Appalachian ridges, so that makes some sense. --Jayron32 23:16, 8 May 2016 (UTC)

Minnesota. Sagittarian Milky Way (talk) 05:13, 9 May 2016 (UTC)

Hard to tell from just that map. There are places east of the Mississippi in other states which are colored the same color as those parts of Minnesota which are also east of the Mississippi (which is only a small part of the state). --Jayron32 08:35, 9 May 2016 (UTC)

[9] At the river's northernmost point I draw a meridian to Canada. I've seen people draw the line due north from the source. Sagittarian Milky Way (talk) 16:47, 9 May 2016 (UTC)

Here's a better mean annual precipitation map of the USA, for the period 1961-1990, using downsampled NOAA data [10]. Looks like Northern MI has the largest area in the 25-30" bin east of the Mississippi. SemanticMantis (talk) 13:49, 9 May 2016 (UTC)

Huh. So "Northern Michigan" does mean the northern Lower Peninsula, not the northernmost part of Michigan. Who knew? --69.159.61.172 (talk) 23:51, 10 May 2016 (UTC)

• If someone answers this with a source, please do tell. But I exect either somewhere far up north, such a Maine, where the lack of evaporation compensates for the lack of precipitation. That, or somewhere in Long Island. μηδείς (talk) 04:46, 12 May 2016 (UTC)

• What's wrong with this:[11]? And what's so special about Long Island? It only has pine barrens cause the soil is crappy. Sagittarian Milky Way (talk) 05:27, 12 May 2016 (UTC)

May 9

pressure enough to make "oxgen glass"?

49.135.2.215 (talk) 00:53, 9 May 2016 (UTC)Like sushi

The word "glass" or "amorphous" does not appear in our article on Solid oxygen. I'm not sure any of the solid phases of oxygen are "glass" or "glass like", can't find any reference to suggest it. Vespine (talk) 02:35, 9 May 2016 (UTC)

2 2/3 quarks for "positive hole"?

49.135.2.215 (talk) 00:54, 9 May 2016 (UTC)Like sushi

Are you talking about a pair of up quarks here? More likely for you to find is 2 up quarks, and a down quark making a proton. You would have some of these in your body. Take a read of our quark article. Particles made from quarks always appear to have integer charge. Graeme Bartlett (talk) 07:39, 9 May 2016 (UTC)

proton approaching neutron?

49.135.2.215 (talk) 00:55, 9 May 2016 (UTC)Like sushi

You haven't really asked a question here, perhaps Nuclear force helps? If not, you might need to actually form a question. If you have a hard time trying to ask a question in English, you could try asking in your native language and someone might be able to translate it for you. Vespine (talk) 04:07, 9 May 2016 (UTC)

anti-proton receeding from anti-neutron?

49.135.2.215 (talk) 00:56, 9 May 2016 (UTC)Like sushi

These two make the antideuteron. But we do not have much written on this. Strong nuclear force holds them together. Graeme Bartlett (talk) 07:31, 9 May 2016 (UTC)

Water universal soluvant as v shaped molcure?

(I will not surly be back)

49.135.2.215 (talk) 01:39, 9 May 2016 (UTC)Like sushi

Water is not a universal solvent, as many substances are not water-soluble, such as oils. (Our disambiguation page does include water, but that must be because many, but not all, substances are water soluble.) StuRat (talk) 03:24, 9 May 2016 (UTC)

Under some conditions, water becomes substantially able to dissolve non-polar things too (for various reasons depending on what conditions...Accelerated Solvent Extractor, microwave irradiation, etc). DMacks (talk) 05:24, 9 May 2016 (UTC)

...which prompted me to create the accelerated solvent extraction stub. Wasn't there a template/tag for RD discussions that led to article-space improvements? DMacks (talk) 05:51, 9 May 2016 (UTC)

{{WikiProject Reference Desk Article Collaboration}} --Jayron32 12:06, 9 May 2016 (UTC)

The molecular dipole moment of water and the v shape of the molecule are indeed an important factor in water's ability to dissolve many substances. SemanticMantis (talk) 13:45, 9 May 2016 (UTC)

Also hydrogen bonding. --Jayron32 16:32, 9 May 2016 (UTC)

The old conundrum: If you had a truly universal solvent, what could you store it in? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:15, 10 May 2016 (UTC)

@Baseball Bugs: Fullerenes, apparently. That or a Penning trap. N.B. I suppose we should have expected a universal solvent would have a high heat of solution. :) Wnt (talk) 14:25, 10 May 2016 (UTC)

Pathophysiology of hemoptysis in PE

In case of PE (or pulmonary embolism) in some of the cases one of the signs is hemoptysis. I'm trying to understand how could it happen.

Here is the blood comes the vena cava and then he's coming into the right atrium >right ventricle > pulmonary artery > alveoli capillary system and then come back to the heart through: pulmonary vein > left atrium > left ventricle and leaves the heart to the aorta etc.

My question is: if the embolism is stuck in the pulmonary artery (this is the definition of PE) how can influence on the bronchial arteries which are exploded as a result of the higher pressure of the blood there and causes to hemoptysis. here is the higher pressure is found before the embolism rather than after this point of this embolism is found. I'm trying to understand this pathophysiology unsuccessfully 93.126.95.68 (talk) 03:17, 9 May 2016 (UTC)

Pulmonary emboli often present with hemoptysis as a result of ischemic pulmonary parenchymal necrosis. (source here) --Dr Dima (talk) 06:09, 9 May 2016 (UTC) In plain English, this means that when embolism cuts off circulation to (a part of) a lung, the lung tissue startts to die. This may show up as coughing up blood. --Dr Dima (talk) 06:15, 9 May 2016 (UTC)

Thank you Dr. Dima. To be honest, I still don't understand, how can it be that there is an ischemic pulmonary parenchymal necrosis, while the lungs gets blood from the aorta (through bronchial arteries) rather than from the pulmonary artery (which is the blocked one). 93.126.95.68 (talk) 23:33, 9 May 2016 (UTC)

The detailed mechanism is explained here --Dr Dima (talk) 01:29, 10 May 2016 (UTC); see also this paper --Dr Dima (talk) 01:37, 10 May 2016 (UTC)

Our pulmonary embolism article says: "Pulmonary embolism (PE) is a blockage of an artery in the lungs...", emphasis mine. --71.110.8.102 (talk) 23:54, 9 May 2016 (UTC)

Baby growth

Asking for a friend. Do human babies grow more in the first or second year of their lives after birth? Is there a time past that when humans grow even faster? Zell Faze (talk) 20:23, 9 May 2016 (UTC)

More the first year: [12]. As far as "is there a time when they grow even faster"; as a percentage, no, but possibly in terms of most weight gained in a year, but there will be considerable variation in that, depending on gender, when growth spurts hit, if they suffer from obesity, etc. StuRat (talk) 21:05, 9 May 2016 (UTC)

Just as an anecdote, you very much notice a big difference in size between a new born baby and a one year old. IMHO there is still a considerable difference in size between a one year old and a two year old. But now my son is two, there is not such a bid difference in size between him and a three year old child. Vespine (talk) 22:37, 9 May 2016 (UTC)

A "bid difference" ? So you put him up for sale each year on his birthday ? :-) StuRat (talk) 23:22, 9 May 2016 (UTC)

Allometric growth is the general concept, here applied to applied to human ontogeny. See also Human_development_(biology), infant, and toddler. SemanticMantis (talk) 14:58, 10 May 2016 (UTC)

May 10

"glider"? "holed shere"?

49.135.2.215 (talk) 00:38, 10 May 2016 (UTC)Like sushi

Do you have a question? --69.159.61.172 (talk) 04:04, 10 May 2016 (UTC)

A punctured sphere, in which the boundary is included with the sphere is homeomorphic to a disk, and if only a single point is punctured ( or boundary is not included) it is homeomorphic to a plane. Graeme Bartlett (talk) 12:19, 10 May 2016 (UTC)

Glider_(Conway's_Life) might be what you're looking for. SemanticMantis (talk) 14:55, 10 May 2016 (UTC)

Light based lifeforms

After seeing this http://phys.org/news/2013-09-scientists-never-before-seen.html, I have wondered whether anyone has proposed the possibility of life forms that are photon-based. Has anyone hypothesized about it? — Preceding unsigned comment added by 24.207.71.235 (talk) 00:41, 10 May 2016 (UTC)

If there's somewhere where something crazy "sci fi" might be speculated, a good bet is to start with Star Trek and indeed, they've played with the idea of Photonic lifeforms .But as far as I know, it hasn't gone much further than pure speculation. Vespine (talk) 00:53, 10 May 2016 (UTC)

Don't photons usually move? How would you keep it from flying apart at many miles per millisecond? Sagittarian Milky Way (talk) 01:22, 10 May 2016 (UTC)

This article is kind of a special situation - something called a Rydberg blockade (despite the bluelink, we don't really explain that, alas). But there is a more general category of two-photon physics. There are media that slow light substantially. There are also environments like the photon sphere of a neutron star that bring it around in circles. I cannot tell you whether and certainly not how you get from such interactions to "life", however it might be defined (which is another can of worms). But I wouldn't rule it out. Wnt (talk) 02:07, 10 May 2016 (UTC)

The light is in an unusual medium that probably wouldn't occur naturally, and that in any case is made of atoms. In vacuum, there is a weak interaction between photons (mediated by virtual charged particles), so it's not necessarily impossible to build an information-processing device out of nothing but photons. It would have to be pretty large, and would probably be ruled out by the positive cosmological constant if nothing else (the cosmological constant limits the size of any object to a few tens of billions of light years across). I think people have written about this sort of thing, but a web search isn't turning up anything. It's hard to come up with good search terms. -- BenRG (talk) 06:29, 10 May 2016 (UTC)

• See Hooloovoo, a life form referenced by both Douglas Adams and Doctor Who. --Jayron32 11:17, 10 May 2016 (UTC)

Another place to look (though it's not strictly all-photonic) is self-focusing. It is believed that light beams through interstellar medium can self-focus (there's something about it here, though I remember seeing a better source). Normally this is seen as inert, i.e. a "railroad" in that source. However, if you have pulsars and such spinning away broadcasting bright beams that have self-focusing effects, who knows what manner of selective pressures and interactions occur over billions of years of travel? I doubt it would be anything too spectacular, but I suspect the interaction of the light beams and refractive indexes, with different spots pulling in light from one another and so forth, conceivably might rise to within some technical definitions of life. Wnt (talk) 12:11, 10 May 2016 (UTC)

reverse triangle measurement?

(I would not be commenting, probably)

49.135.2.215 (talk) 00:43, 10 May 2016 (UTC)Like sushi

See Trigonometry. --Kharon (talk) 01:38, 10 May 2016 (UTC)

Scalp vs. Beard Follicles

So, this is a question that came up recently, and I don't know if much work has been done on it, since it's kind of a... (I don't want to say useless) but less-important question. Have the changes in cell lines that make up the differences between scalp and beard follicles been identified? I assume it's a series of steps in differentiation that lead to very slightly changed expression of proteins, but I haven't found (so far) any studies that definitively show this.

I did find some interesting papers at this old study and this still pretty old study(the latter of which I haven't fully read since I'm not on campus) that suggest there is a difference that's probably tied to various factors. So I'm curious if this has gone any further.

Thanks, PiousCorn (talk) 04:21, 10 May 2016 (UTC)

ambiguous state diagram

this diagram is from a datasheet on a certain chip by a renowned vendor. I couldn't help but notice that the states 5 and 7 have three outgoing arrows, two of which are associated with the same inputs. so, for example, if we're in state 5 in the middle of the diagram and see {1,0}, we don't know whether to go left or right. I compared the diagram with one from a datasheet by a different vendor which was in a slightly different format, for which purpose I first had to deduct deduce guess which states are which because their numbering scheme was different than my ad-hoc one. In it, only one arrow is associated with the input {0,1}. is this a printing error (in the first diagram) or is there a deeper meaning? If it's a mistake, are such things common in technical documentation? Asmrulz (talk) 11:32, 10 May 2016 (UTC)

Please check your link to a diagram which did not open in IE 9. AllBestFaith (talk) 11:57, 10 May 2016 (UTC)

It works on Firefox. Are you sure about which input is selecting the line? Perhaps the next state to go to is selected by the numbers in the table below, and the numbers in the circles are the outputs. Graeme Bartlett (talk) 12:06, 10 May 2016 (UTC)

I find the diagram opens in Google Chrome. May we know the device because it looks like part of a CMOS 4046 PLL chip? AllBestFaith (talk) 12:28, 10 May 2016 (UTC)

The OP seems to have selected part of Figure 1 from this Motorola(?) data sheet where the state change directions for "Phase Comparator 2" are inconsistent with my own Motorola catalog from 1976. (Hint: there's no escape from the extreme left or extreme right states.) I put a question mark after Motorola because their old catalog drawing shows better care with draughtmanship than the obviously hand-sketched lines in the example belie. The same Figure in a different manufacturer's 4046 data sheet is correctly drawn and free of ambiguity. As to the question whether such mistakes are common, there is always a finite probability of error every time technical data is copied manually, that probability increases when the copy is not immediately verified and I once encountered an uncommon form of dyslexia affecting arrow directions. This was a handbook writer who persistently drew diodes the wrong way round when copying from a circuit diagram but couldn't recognize the error when it was repeatedly pointed out. AllBestFaith (talk) 14:02, 10 May 2016 (UTC)

you are entirely correct! It's from Motorola's 4046 datasheet I found here. I didn't want to "point the finger" in case it's me who doesn't get something (as a hobbyist) or there exists somewhere a newer, fixed revision (perhaps for people with institutional access to these things). There's something else I don't get. Most of the diagram is edge detection. What if I get hardware interrupts on rising edges anyway (on an ATTiny)? If I have a state table and a step() function which takes the inputs, sets the outputs and advances in the table accordingly, where do I plug it (the function, I mean)? Asmrulz (talk) 16:00, 10 May 2016 (UTC)

The only likely use for an edge-counting phase comparator is in a PLL where it keeps two equal-frequency i.e. synchronous signals locked together in phase. As long as the rising edges of the two signals arrive simultaneously, the Type 2 comparator output is high impedance which lets the controlled oscillator continue its present frequency neither increased nor decreased. (The 4046 also has a Type 1 comparator which is an XOR gate that can be used in a PLL to lock two equal-frequency Square waves in quadrature.) However you are interested in a CPU handling hardware interrupts that are necessarily asynchronous events that are not timed by or predicted by the main program flow. Historically the Zilog Z80 8-bit microprocessor offered a key feature of a duplicate set of registers which allow the processor to handle the demand of an interrupt while keeping the main program on hold. Modern computer software handles interrupts from multiple sources by using an Interrupt vector table to direct the main CPU temporarily away from the main program to a relevant Interrupt handler code. Wikipedia has articles about interrupt handling in PCs where the main hardware element is the 8259 Programmable Interrupt Controller, and in the 65xx processors. The interrupt handling capability of a particular processor has to be found from its datasheet and usually involves a state machine that is implemented in standard components for that processor. The ATtiny can handle 6 external interrupts and here is its Summary Data Sheet. Its external interrupt handling is described here on page 49. AllBestFaith (talk) 17:18, 10 May 2016 (UTC)

sorry, now I'm being ambiguous:) A PLL is what I'm trying to do. Only the first signal is asynchronous. The second signal will be from an oscillator (ideally a software NCO running on the same ATTiny.) I want to output a frequency and an integer multiple of that frequency having a (more or less periodic) pulse train of short pulses as input (from a reed switch.) I read somewhere that the type II comparator is better due to its being immune to duty cycle variations. Asmrulz (talk) 21:32, 10 May 2016 (UTC)

You are correct that the edge-counting comparator is unaffected by duty cycle variations in its inputs. But the 4046 comparators are intended to control an analog VCO (there's one inside the 4046) via a low-pass filter that ensures the loop is stable. The filter design is critical if signal purity and speed of acquiring phase lock are important. Alternatively, for a digitally controlled oscillator the article Numerically controlled oscillator may help. That would be a demanding task for a general-purpose 8-bit CPU. AllBestFaith (talk) 00:09, 11 May 2016 (UTC)

maybe I should just take the 4046 and use the MCU only as the divider in the feedback path... anyway, thanks a lot! Asmrulz (talk) 08:34, 11 May 2016 (UTC)

Thank you everyone for your answers Asmrulz (talk) 08:34, 11 May 2016 (UTC)

bullets

If a projectile flies at supersonic speed how it is then with the electrons in the electron orbit of the atomic nucleus? Do they get somehow badly disturbed or pushed out of their orbit? --Ip80.123 (talk) 15:24, 10 May 2016 (UTC)

They don't - supersonic speeds are really slow compared to the dimensions relating to the electronic binding forces. --Askedonty (talk) 15:31, 10 May 2016 (UTC)

Hypersonic speeds, however, can produce ionization. See particularly Atmospheric entry. Tevildo (talk) 16:28, 10 May 2016 (UTC)

It's the gases near the projectile or device in case of reentry which are subject to ionization, but you're right particularly that temperature is to be taken into account. --Askedonty (talk) 17:21, 10 May 2016 (UTC)

Calculations show that electrons travel at about 2,200 kilometers per second. That's less than 1% of the speed of light, but it's fast enough to get an electron around the Earth in just over 18 seconds. A very fast bullet is doing about 1200 meters per second - much slower. At that speed a bullet would take over 9 hours to go round the planet. 81.132.106.10 (talk) 16:49, 10 May 2016 (UTC)

If electrons "travel". There's problems with that. See, for example, Larmor formula#Atomic physics. Treating electrons like bullets creates major problems under classical mechanics. Treating electrons like standing waves instead is much nicer, c.f. Schrödinger equation, quantum mechanics, etc. --Jayron32 16:59, 10 May 2016 (UTC)

If the original question regards a supersonic speed of a projectile in air - then indeed that speed (and, more importantly, the acceleration that the projectile undergoes to attain that speed) is too low to substantially perturb the bound electrons, or even the conductance band electrons that are not bound to any particular atom in metal parts of the projectile. Indeed, Fermi energies in typical metals are in the ballpark of 10 eV, which corresponds to electron "velocities" of over 10⁶ m/s, compared to 10³ m/s for the projectile itself; and whatever small currents and polarization are induced (by projectile acceleration and charge carriers inertia) should, I think, be quickly dissipated under normal conditions (although I never saw this discussed in literature; I can do the math, but Wiki is not really a place for original research). By contrast, if you are talking about supersonic speed of propagation in the projectile material itself, then the situation may be different. Supersonic compression wave is called a shock wave. Depending on the strength of the shock and the properties of the material being shocked, the heating in the front of the shock wave may be sufficient to excite or ionize at least some atoms of the material. This does not happen when a bullet is fired from a conventional firearm, but when a sufficiently fast projectile (e.g. from a railgun) impacts a target then these effects may be significant. For further reading see Rankine–Hugoniot conditions. --Dr Dima (talk) 18:03, 10 May 2016 (UTC)

A more accurate depiction of electrons in an atom

Electrons in an atom aren't like little planets orbiting a star. In a sense they're both everywhere and nowhere at the same time, although they have a higher probability of being found in certain places (atomic orbitals). Things are weird at the quantum level, at least to our ape brains that are designed for keeping us alive on the African savanna. Unfortunately this "planetary" or Rutherford-Bohr model still gets displayed all the time as a depiction of "what atoms look like", often without any discussion of what's wrong with it, which puts misleading ideas in people's heads. --71.110.8.102 (talk) 04:47, 11 May 2016 (UTC)

The electrons do move at incredible speed - the speed of light times the fine structure constant, or about 1/137 c, in the bottom hydrogen orbital, and faster in proportion to nuclear charge in larger atoms. One result is that around element 137, or 173, the periodic table runs into some weirdness (see extended periodic table - the speed of the electron seems to have to be near c, and if fully ionized, nuclei create electrons and positrons from nothing, and supposedly, this means that neutral atoms of higher numbered elements can't exist. I do not understand these deductions (note the outermost electrons move far more slowly), but you can see relativistic Dirac equation.

That huge thread I have about the magnetic quantum number gives me a way to describe this. The possible position of an electron can be viewed as a standing wave, which is made up of components orbiting in opposite directions. An electron in an s orbital is just sitting in place in a smooth sphere of probability, but in a p orbital or higher they have angular momentum, so they are orbiting round and round. Or you may know they are vibrating back and forth along one axis but not know which way they are orbiting round and round, and in quantum terms, that just means you add the orbitals up into a dumbbell.

But why don't the electrons fly out? Because electron charge, nuclear charge, is an unimaginably powerful force! We see lightning spark across the sky from tiny inhomogeneities in the number of protons and electrons. But in an atom, the charge difference is absolute, and they are absurdly close together. It's an inverse square law, so in outer orbitals they are less close together - the difference between knocking electrons out with a photon of ultraviolet light versus one of infrared. And so they move more slowly there. Wnt (talk) 10:38, 11 May 2016 (UTC)

Multiple births

Let's say that a woman has multiple births: triplets or more. Is it possible that some of those siblings are identical "twins", but some are fraternal "twins"? Or does it have to be all "one or the other"? Thanks. Joseph A. Spadaro (talk) 16:57, 10 May 2016 (UTC)

Read the Wikipedia article titled Multiple births, specifically the section Multiple birth#Triplets and see if that doesn't answer your question. --Jayron32 17:00, 10 May 2016 (UTC)

Let me check that out. Thanks. Joseph A. Spadaro (talk) 17:04, 10 May 2016 (UTC)

No, actually that didn't answer my question. (But -- on a side note -- I never knew that Elisabeth Kübler-Ross was a triplet.) Let me clarify my question. Say a woman has 8 babies. Can Baby 1 and 2 be identical twins (identical only to each other)? And Baby 3 and 4 and 5 are fraternal triplets? And Baby 6 and 7 are identical twins to each other (but not identical to Baby 1 and 2)? Different permutations like that? Or are all 8 going to be completely identical or completely fraternal? Thanks. Joseph A. Spadaro (talk) 17:08, 10 May 2016 (UTC)

From the first sentence of the section I directed you to: "Identical triplets come from a monozygotic pregnancy, three fetuses from one egg. The commonest set, strictly fraternal triplets, comes from a polyzygotic pregnancy of three eggs. Between these types, triplets that include an identical (monozygotic) pair of siblings plus a fraternal sibling are the result of a dizygotic pregnancy, where one zygote divides into two fetuses and the other doesn't. The Kübler triplets (see Elisabeth Kübler-Ross) were of this type." That is, the answer is "all possible variations can exist". --Jayron32 18:05, 10 May 2016 (UTC)

Here's [13] a study on triplets that says "65.8% of the sets were thought to contain both identical and fraternal siblings." The authors then say detailed genetics will be presented in a future study, and I don't time to look that up right now. But at 65.8 percent, even with a lot of error, it sounds like the answer to your question in is "yes" - in triple and higher multiple births in humans, some groups can be monozygotic while other groups came from a different zygote, all in the same litter. SemanticMantis (talk) 17:26, 10 May 2016 (UTC)

Yes. It's statistically unlikely just because identical twins aren't that likely and neither are triplets or higher - but there is nothing to prevent it from happening. SteveBaker (talk) 17:28, 10 May 2016 (UTC)

I see now that this is actually made clear for n=3 at Multiple_birth#Triplets. It is not the case that all n babies would have to be either all fraternal or all identical - they can be mixed and matched. For n>3, the section on quadruplets also makes it clear that all-identical quadruplets are much rarer than general quadruplets, and clearly states (though without explicit reference) that other combinations (4F, 2F-2I, 1F-3I, 2I-2I) are all possible. SemanticMantis (talk) 17:33, 10 May 2016 (UTC)

If you want to get freaky, take a look at superfecundation. 91.155.193.199 (talk) 18:13, 10 May 2016 (UTC)

The percentage of surfactants in my washing up detergent

The ingredients on many cleaning products give a range of surfactants instead of a fixed percentage. Are they doing this because they want to give us 15% and tell us we're getting 15-30% or is the manufacturing process just so hit and miss than they're not sure how much anionic surfactants we're getting? — Preceding unsigned comment added by 78.148.108.58 (talk) 21:45, 10 May 2016 (UTC)

More probably because a group of chemistry students, testing the product using different methods will get a range as the result, not a stable quantity. See Surface tension, Gibbs isotherm (definition of surface excess), Hydrophilic-lipophilic balance. -Askedonty (talk) 22:32, 10 May 2016 (UTC)

Why should students' results matter? Surely a business producing cleaning products knows what they're putting in and can employ a graduate if necessary?? --78.148.108.58 (talk) 23:51, 10 May 2016 (UTC)

You can guess that the head of laboratory agrees with your analysis and they already applied the strategy. The point is that they want to give numbers regarding efficiency and so it's not only about measuring grains, because the substance will behave differently according to conditions (see Gibbs isotherm, aso ). So far as I remember they are doing so also as a way of strongly marking the boundary between their field and all the various food industries, this was considered an important point in the past 60's-70's, so the reference to students, as safety conducts in the industry and this more than in one way do start with them. --Askedonty (talk) 07:38, 11 May 2016 (UTC)

• Under European rules, the ingredients of a washing up liquid need to be listed, but for trade secrets reasons, they don't have to give the exact formula. Instead, they can simply label them in bins of "less than 5%", "5% to 15%", "15% to 30%" and "more than 30%". See Guidelines on the implementation of the Detergents Regulation, page 11. Smurrayinchester 08:10, 11 May 2016 (UTC)

@Smurrayinchester: What I don't get is why this subterfuge is useful. I would think by now that some intro chemistry classes around the world (if no one more commercially interested) would make a point of analyzing brands and publishing best guesses about the ingredients. It seems like a public-interest thing, and a potential geek hobby. Wnt (talk) 12:45, 11 May 2016 (UTC)

And anyone with the right screwdriver and a pair of pliers can take apart an iPhone, but Apple still keeps its plans super-secret. No reason to make the task of reverse engineering any easier than it has to be. Smurrayinchester 13:22, 11 May 2016 (UTC)

2 Dinosaur questions

1. What was the difference between a pterodactyl and a pteranodon? 2. are birds living dinosaurs? 50.68.120.49 (talk) 22:00, 10 May 2016 (UTC)

Is this a homework question? The 1st question was very easy to answer just by reading a little of the articles. The second question is also very easy to answer with a simple google search. Is there something specific you are having trouble understanding? Vespine (talk) 22:28, 10 May 2016 (UTC)

I somehow doubt this is a homework question as it wouldn't ask about 1 in a dinosaur assignment. This isn't any easier to find in our articles than half the other questions around here...

1) Neither are dinosaurs, so this is not a dinosaur question. They are two different genera of pterosaur. It is sort of like the difference between humans and chimpanzees. We are both in the hominid family, but we are different genera and species. I think they may also have been in different families, putting them further apart. Are you looking for more phylogeny differences?

2) That does seem to be the scientific consensus, yes. See evolution of birds. --OuroborosCobra (talk) 22:34, 10 May 2016 (UTC)

Birds are dinosaurs, but pterosaurs are not, despite the name! The article on Pteranodon places it in Pterodactyloidea, i.e. it is a pterodactyl; the term is used more broadly but inaccurately to refer to other pterosaurs, but not birds/dinosaurs. It is widely believed flight evolved independently in birds and pterosaurs. Wnt (talk) 10:53, 11 May 2016 (UTC)

Pterodactyl and Pterodactyloidea are not synonymous; one is a specific genus within a family and order, the other is a given order (or suborder). A pteranodon is not a oterodactyl, but it is a pterodactyloidea. --OuroborosCobra (talk) 11:51, 11 May 2016 (UTC)

@OuroborosCobra: I see pterodactyl redirects to Pterodactylus. Nonetheless, as explained at Pterodactyloidea, the term is used more broadly to include that group. "Pterodactyl" is, after all, a near common name generally used for a broad group of animals, and an interpretation that limits it to just one species seems contrary to this. Wnt (talk) 12:41, 11 May 2016 (UTC)

It may help to step back a bit and consider how organisms are classified:

1) The traditional way was to group similar species in to genra, genera into families, and so forth. The main ranks were species, genus, family, order, class, phylum, and kingdom. To answer your first question: pterodactyl and pteranodon were separate genera, in separate families, within the order Pterosauria. This means they were not dinosaurs, because "dinosaurs" was a super-order made of two other orders. Dinosaurs and pterosaurs are closely related, but are different enough to be considered different.

(But if you just want a basic descriptive answer: Pterodactyl was about the size of a parrot, Pteranodon was about the size of a hang glider (and had a bony crest on the back of its head)).

2) Under the old Linnaean scheme, birds are not dinosaurs. Birds are a class, which is a higher rank than dinosaurs. This is despite them being directly descended from them (and more specifically, from a specific group of them). And this is where the Linnaean system starts to break down and give some silly results. Also, I mentioned that dinosaurs are a super order. People like neat classifications, but Nature doesn't. There are all sorts of animals and groups of animals that are too different to fit into one of the classic ranks, but too similar to be spilt between higher ranks. So you end up with a whole mess of sub/super/infra groups.

For this reason, a lot of scientists now prefer to ignore the old ranks completely, and group things into unranked Clades, defined by ancestry. Under this scheme, birds are a type of dinosaur, because anything descended from a dinosaur is by definition also a dinosaur. This can take a bit of getting used to, but when you consider that there is no clear point when "obvious" dinosaurs turn into "obvious" birds, but rather a gradual transition with a lot of dinosaurs that look rather bird-like (including ones that were not ancestors of birds), and a lot of early birds that still had many "traditional" dinosaur features, it starts to make sense. (Consider for example: most of the relatives and ancestors of T. rex had feathers. See also Deinonychus and Velociraptor. Or more generally, Feathered_dinosaur. Iapetus (talk) 12:24, 11 May 2016 (UTC)

To add a perspective to Iapetus's excellent answer, imagine that you're standing in a forest 68 million years ago. Many of the creatures you can see around you are dinosaurs. Some of the species you see are big reptilian looking things, some are similar but with feathers (T. Rex itself may have had feathers when juvenile), some are smaller with feathers but are not birds, some other very similar and related ones are birds looking quite similar to modern birds, and it's obvious (both from casual inspection and from any anatomical and genetic analyses you care to do) that there are no major differences between the "non-birds" and the "birds": the "birds" are just some of the varieties of these smaller feathered dinosaurs. (Then a T. rex eats you.) This is not so obvious today because in the present time we only see the birds around us, not any of the very similar small feathered dinosaurs, or any of the less bird-like dinosaurs: if we could see the latter also we'd realise more easily that the birds were and are just a particular subset of dinosaurs. {The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 13:54, 11 May 2016 (UTC)

All of that and no one has actually mentioned the MAIN difference between Pterodactylus and Pteranodon. A pterodactyl grew to have a wingspan of about 1m, while a Pteranodon grew to an average wingspan of almost 6m! Vespine (talk) 22:44, 11 May 2016 (UTC)

Birds in general are not always living dinosaurs a clear counter example can be seen here: https://www.youtube.com/watch?v=npjOSLCR2hEGr8xoz (talk) 22:48, 11 May 2016 (UTC)

When I visited Glen Rose, Texas - where one may visit Dinosaur Valley State Park and to put your hand into a for-real dinosaur footprint (PICTURE) on the same day watch Emu's feet (PICTURE) at the nearby Fossil Rim Wildlife Center - it's hard not to believe that the animals are related. SteveBaker (talk) 01:57, 12 May 2016 (UTC)

May 11

Lightning strike

In a thunderstorm, is it (relatively) safe to be outside in an area with lots of high-rise buildings close together? Because intuitively, it follows that these could act as lightning rods, but how effective is it in practice? 2601:646:8E01:515D:F88D:DE34:7772:8E5B (talk) 01:24, 11 May 2016 (UTC)

I don't know, maybe? I think it suffices to say you shouldn't rely on high-rises protecting you, as lightning can do all kinds of wacky things depending on what path(s) it wants to take. People have been struck by lightning inside buildings through openings (windows, doors, chimneys). Also the current can travel along the ground, which means that even if the bolt "misses" you, you can still get a nasty shock if you're nearby. --71.110.8.102 (talk) 04:51, 11 May 2016 (UTC)

Safe regions are discussed in Lightning Rod#Lightning protection system design. --catslash (talk) 09:19, 11 May 2016 (UTC)

It should be relatively safe inside such buildings; their metallic skeletons would likely act as a Faraday cage. --Jayron32 11:04, 11 May 2016 (UTC)

That assumes the electricity can actually get to the frame, which would mean going through cement/concrete, which is a good electrical insulator (it needs to be, or it will corrode, see electrical resistivity measurement of concrete). StuRat (talk) 17:40, 11 May 2016 (UTC)

The lightning just made it through a mile and a half of air. A few centimeters of cement isn't going to do jack. The lightning more than exceeds the breakdown voltage of the cement, meaning it tears through it like it isn't there. --Jayron32 20:11, 11 May 2016 (UTC)

How many percents of proteins and fats are taken by our bodies?

How many percents of proteins and fats are taken by our bodies? For example if it's written on some food that it contains 20g proteins and 5g fats, does it say that our body take all this proteins and fats and store them or use them? or it says that this is the maximum value that the body can take from it but in fact it can be less significantly (of course I'm not talking about exceptions or pathological cases, but generally)93.126.95.68 (talk) 06:49, 11 May 2016 (UTC)

The values shown in the nutritional content show the amount that actually exists in the food. The ability of the human body to absorb nutrients depends on the specific nutrient in question, the makeup of the food (most especially the fiber content, with higher amounts of fiber impeding absorption), and miscellaneous personal factors. It's generally estimated the human body or its microbiota consumes about 95% of the nutrients you eat [14]. What I haven't been able to find is an estimate of how many calories are burned by your microbiota instead of being absorbed by your own body. Someguy1221 (talk) 10:13, 11 May 2016 (UTC)

So that ref goes (eventually) to here [15], presenting a research bulletin of the USDA from 1899. If you download the PDF, there is a big warning saying that it is an archived document, and that we should "not assume content reflects current scientific knowledge". Now, I don't necessarily think that 95% figure has changed much, but we probably can and should find a more contemporary ref :) SemanticMantis (talk) 14:07, 11 May 2016 (UTC)

The efficiency may depend on how much you eat. If you eat excess protein, your body dumps amino acids (broken down proteins) out in urine. Not sure what happens if you eat excess fats. StuRat (talk) 17:37, 11 May 2016 (UTC)

• Two points. First, if all the microbiota in your body were to cease to exist, you'd suddenly find yourself cadaverous, unable to engage in the symbiotic metabolic biome they provided, and would be like a reef that had lost all its bilateria. In other words, you are your own human framework, with all its inhabitants.

• As for fat, look up Olestra. I'm not sure whether there's a means of extruding fat per say, fat metabolism will help her. And you could always have a series of fatty meals, then boil the turds to see what floats to the top. μηδείς (talk) 04:31, 12 May 2016 (UTC)

Loud as a refrigerator

Our Wind power#Environmental effects says, "Wind turbines generate some noise. At a residential distance of 300 metres (980 ft) this may be around 45 dB, which is slightly louder than a refrigerator." Louder than a refrigerator at what distance? Is there a standard distance at which the loudness of a refrigerator is measured? Here is the reference for that statement. It gives db(A) values for various machinery, but with no indication of how close to those items the values apply. -- ToE 18:58, 11 May 2016 (UTC)

I can't think of a science more habitually dishonest than the estimation of noise. Even computer science, whose practitioners each year become more beholden to large corporations, still is not so bad as "scientific" statements about the planned noise of an industrial project.

The first lie is A-weighting itself. There are people who claim to be unable to hear noise below a certain frequency, whose perceptions influenced this curve; nonetheless, the infrasound has effects on them. Moreover, the curve details perception, but not penetration. Low frequency noise will come straight through the walls and pillows in a way that high frequencies won't, and there's no weighting for that. There is a different weighting used in Europe that is also bad, but not this bad. Another trick routinely used makes multiplication a suspect practice: instead of simply going by the decibel scale, which details the actual 10-fold differences in intensity, they instead have surveyed some people in a room at some time and gotten them to say that one sound "is about twice as loud" as the other, and then use this mistaken subjective estimation to claim that their company's sound is a lesser multiple of whatever than it is. So when they say "slightly", they could mean several-fold actual difference in sound level! And of course, as you noticed, the sound of a refrigerator does depend on the distance, and on the refrigerator, and when they don't tell you what parameters they used, it's fairly safe to assume the worst. And believe me, people who care about noise will go to great lengths to avoid the noise of a refrigerator! Wnt (talk) 20:39, 11 May 2016 (UTC)

Minor Sound volumes in the open are very dependent on wind direction and additionally 300 metres is very close to a wind generator. In Bavaria, Germany the minimal distanct to the closest settlement must be 10 times its height including the wings but atleast 2000 metres. Strangely this grafic on your source only reaches till 500 metres. Also the volume seems to high at the start. I doubt you would have any trouble talking to someone next to you even on top of one of these turbines but you will shurely have that next to an lawnmower that is used as comparrison in this grafic. That seems completely exaggerated. --Kharon (talk) 04:52, 12 May 2016 (UTC)

Norse pineapples

Jeopardy! just claimed that the Norse gods drank pineapple mead. Pineapple notes that the plant is native to South America and that Columbus, 1493, was responsible for first taking it to the Old World. Is or was "pineapple" also used to refer to an Old World plant or other substance? The article also notes that the term was previously used as a reference to pine cones, but I can't imagine creating an alcoholic beverage from pine tar or anything else present in pine cones. Nyttend (talk) 23:52, 11 May 2016 (UTC)

The question does not have to be parsed "the Norse Gods drank pineapple mead", and in fact does not state that. The statement instead means "I drank the pineapple type of this drink, which the Norse Gods also drank." Pineapple mead exists. Norse Gods Drank mead. It only states those facts, both of which are true. It does not say the Norse Gods drank pineapple mead. --Jayron32 00:21, 12 May 2016 (UTC)

With reference to the idea that you can't make an alcoholic drink using anything from a pine, bear in mind that Greek Retsina is a drink made using resin of the Aleppo Pine to flavour it. 81.132.106.10 (talk) 08:14, 12 May 2016 (UTC)

May 12

Percentage of Muslims that self-identify as British-first or muslim first

Out of Muslims living in Great Britain,what percentage of them identify as Muslim-first, and what percentage identify as British-first? — Preceding unsigned comment added by 70.180.208.48 (talk) 03:00, 12 May 2016 (UTC)

In other words, how many people identify as "Britons who are Muslim", and how many are "Muslims who are British" — is that what you're asking? Nyttend (talk) 03:50, 12 May 2016 (UTC)

Yes — Preceding unsigned comment added by 70.180.208.48 (talk) 04:08, 12 May 2016 (UTC)

In a recent survey 17% said their Muslim identity was more important than their British identity, 6% said their British identity was more important than their Muslim identity, and 76% said they were both equally important to them. http://survation.com/new-polling-of-british-muslims/ 81.132.106.10 (talk) 08:21, 12 May 2016 (UTC)

For which person is more easier to lift his hands?

For which person is more easier to lift his hands, to someone thin or for someone muscular? I think that for the thin it's more easier because for the muscular guy he needs to carry heavy muscles = more weight. But I'm not sure about that. 93.126.95.68 (talk) 09:32, 12 May 2016 (UTC)