Direct functionality

A catalytic enantio- and diastereoselective dihydroxylation procedure without the assistance of a directing functional group (like the allylic alcohol group in the Sharpless epox-idation) has also been developed by K.B. Sharpless (E.N. Jacobsen, 1988 H.-L. Kwong, 1990 B.M. Kim, 1990 H. Waldmann, 1992). It uses osmium tetroxide as a catalytic oxidant (as little as 20 ppm to date) and two readily available cinchona alkaloid diastereomeis, namely the 4-chlorobenzoate esters or bulky aryl ethers of dihydroquinine and dihydroquinidine (cf. p. 290% as stereosteering reagents (structures of the Os complexes see R.M. Pearlstein, 1990). The transformation lacks the high asymmetric inductions of the Sharpless epoxidation, but it is broadly applicable and insensitive to air and water. Further improvements are to be expected. [Pg.129]

Thermal shock resistance is a direct function of enamel thickness. The greater the residual compressive stress in the porcelain enamel, the greater is the resistance to thermal shock failure. Thin coatings, such as one-coat enamels or the two-coat enamels having alow expansion titania covet coat, provide excellent thermal, shock resistance. [Pg.218]

The axial-flow fan is inherently a device for moving a consistent volume of air when blade setting and speed of rotation are constant. Variation in the amount of air flow can be obtained by adjusting the blade angle of the fan and the speed of rotation. The blade angle can be either (1) permanently fixed, (2) hand-adjustable, or (3) automatically adjusted. Air delivery and power are a direct function of blade pitch angle. [Pg.1079]

PROBLEMS OF DIRECTED FUNCTIONALIZATION OF ORGANIC ANALYTICAL REAGENTS... [Pg.402]

Recirculating loss. This loss occurs because of backflow into the impeller exit of a compressor and is a direct function of the air exit angle. As the flow through the compressor decreases, there is an increase in the absolute flow angle at the exit of the impeller as seen in Figure 6-34. Part of the fluid is recirculated from the diffuser to the impeller, and its energy is returned to the impeller. [Pg.253]

Unburnt hydrocarbon (UHC) and carbon monoxide (CO) are only produced in incomplete combustion typical of idle conditions. It appears probable that idling efficiency can be improved by detailed design to provide better atomization and higher local temperatures. CO2 production is a direct function of the fuel burnt (3.14 times the fuel burnt) it is not possible to control the production of CO2 in fossil fuel combustion, the best control is the increasing of the turbine efficiency, thus requiring less fuel to be burnt for the same power produced. [Pg.392]

The equations have been expressed as proportionals however, they can be used by simply ratioing an old to a new value. To add credibility to fan law adaptation, recall the flow coefficient, Equation 5.19, The term Qj/N is used which shows a direct proportion between volume Qj and speed N. Equation 5.12 indicates the head, Hp, to be a function of the tip speed, squared. The tip speed is, in turn, a direct function of speed making head proportional to speed. Finally, the power, Wp, is a function of head multiplied by flow, from which the deduction of power, proper tional to the speed cubed, may be made. [Pg.184]

Since the throw of a jet is a function of the velocity, and since the rate of velocity decrease is dependent on the rate of induction that occurs, the quantity of air induced into the discharge from an outlet is a direct function of the perimeter of the cross section of the primary airstream. [Pg.736]

Table 13.17 lists some of the important considerations for the different fume capture techniques. From the point of view of cost effectiveness, the usual preference is source collection or a low-level hood, provided an acceptable scheme can be developed within the process, operating, and layout constraints. The cost of fume control systems is almost a direct function of the gas volume being handled. Flence, the lower volume requirements for the source capture or low-level hood approach often results in significant capital and operating cost savings for the fume control system. [Pg.1275]

In addition to the gas load, the rod and cros.shead pin bushing is subject to the inertia forces created by the acceleration and deceleration of the compressor reciprocating mass. The inertia load is a direct function of crank radius, the reciprocating weight, and speed squared. The total load imposed on the crosshead pin and bushing is the sum of the gas load and the inertia load and is referred to as the combined rod load. ... [Pg.311]

The horsepower output of a gas turbine is a direct function of flow rate across the power turbine, which is a function of air compressor speed and combustion temperature. Figure 16-13 shows the relationship between... [Pg.482]

It has been proposed dial a directed cuprate addilioti widi a carbamate or a carbonate serving as a reagenl-directing functional group may account for die stereo-clieniical outcome of diese reactions fsee models 115 and 116 in Sclieme 6.25) [39,... [Pg.201]

It was recently found that j3-PCPY can also be used as a radical initiator to obtain an alternate copolymer of MMA with styrene [35], which was only possible in the presence of Lewis acids [36,37] in the past. The kinetics of the system has been formulated as Rp a[/3-PCPY] a[MMA] (l/a[Styrene] The values of kp /k, and AE were evaluated as 1.43 x 10 L mol -s and 87 kJ/ mol, respectively, for the system. NMR spectroscopy was used to determine the structure composition and stereochemistry of copolymers. Radical copolymerization of AN with styrene [38] by using /3-PCPY as the initiator at 55-65°C also resulted in an alternate copolymer. Rp is a direct function of /3-PCPY and AN, and is inversely related to styrene. [Pg.377]

The flooding of the packing is a direct function of the a/e, therefore it is valid at constant separation to examine the performance as shown. The metal Pall rings appear to allow for a considerable increase in capacity. In fact the condition at 35.2% of flood might not be good from a contact efficiency standpoint. [Pg.315]

For a given catalyst and feedstock, catalytic coke yield is a direct function of conversion. However, an optimum riser temperature will minimize coke yield. For a typical cat cracker, this temperature is... [Pg.135]

Functional insights based on structural relationships can only rise to the level of hypotheses, and these hypotheses must be tested by direct functional experiments. [Pg.779]

A procedure for proplnts is presented by J.W. French (Ref 27), who used both OM and EM (electron microscope) to study plastisol NC curing. He found that the cure time of plastisol NC is a logarithmic function of temp, and direct functions of chemical compn and total available surface area, as well as of particle size distribution. It should be noted that extensive use of statistics is required as a time-saving means of interpreting particle size distribution data. The current state-of-the-art utilizes computer techniques to perform this function, and in addition, to obtain crystal morphology data (Ref 62)... [Pg.144]

Long (minutes) organic acid aging times (direct function of temperature)... [Pg.661]

Eurther considering the system displayed in Fig. 18-6 the total isotopic "lightening" of the vapor is a direct function of the fraction of water mass removed from the air. This fraction in turn is a function of the net cooling of the air mass. This suggests that 3 measured at the ice core site... [Pg.469]

Scheraga-Mandelkern equations (1953), for effective hydrodynamic ellipsoid factor p (Sun 2004), suggested that [rj] is the function of two independent variables p, the axial ratio, which is a measure of shape, and Ve, the effective volume. To relate [r ] to p and Ve, introduced f, the frictional coefficient, which is known to be a direct function of p and Ve. Thus, for a sphere we have... [Pg.98]

Ionic polymers are a special class of polymeric materials having a hydrocarbon backbone containing pendant acid groups. These are then neutralized partially or fully to form salts. lonomeric TPEs are a class of ionic polymers in which properties of vulcanized rubber are combined with the ease of processing of thermoplastics. These polymers contain up to 10 mol% of ionic group. These ionomeric TPEs are typically prepared by copolymerization of a functionalized monomer with an olefinic unsamrated monomer or direct functionalization of a preformed polymer [68-71]. The methods of preparation of various ionomeric TPEs are discussed below. [Pg.115]

Our discovery that epoxides can initiate carbocationic polymerization led to the effective direct functionalization of PIBs with hydroxyl groups. Figure 7.18 shows our novel method of direct surface functionalization of SDIBSs using 4-(l,2-oxirane-isopropyl)-styrene, a new inimer. [Pg.214]

Song, J., Bodis, J., and Fhiskas, J.E. Direct functionalization of poly isobutylene by living initiation with alpha-methylstyrene epoxide, J. Polym. Set, Polym. Chem., 40, 1005, 2002. [Pg.219]

Temperature Control. While it was well known that enzyme catalysis is a direct function of temperature, little attention was paid to its control in kinetic enzyme assays until the pioneer work of Schneider and Willis (11). These workers showed that the temperature compartment of the Beckman DU spectrophotometer varied widely as a function of room temperature and of the number of times the cuvet compartment was opened. Thus, while most authors have assumed that they were conducting their assay at room temperature (i.e., a nominal 25 ) direct measurements showed that the cuvette temperature was closer to 32 C. Schneider and Willis suggested that thermospacers, hollow plates adjacent to each side of the cuvette compartment through which water at a constant temperature is circulated, be used in order to standardize clinical enzyme assay temperatures. [Pg.179]

If the vessel is a pressure vessel the optimum length to diameter ratio will be even greater, as the thickness of plate required is a direct function of the diameter see Chapter 13. Urbaniec (1986) gives procedures for the optimisation of tanks and vessel, and other process equipment. [Pg.27]

It is also important to appreciate that the behavior on decompression can markedly affect the characteristics of the finished tablets, because the structure must be strong enough to accommodate the recovery- and ejection-induced stresses. Indeed, tablet strength is a direct function of the number of surviving bonds in the finished tablet. In addition, ability to monitor... [Pg.319]

Enzyme specificity is often explained in terms of the geometric configuration of the active site of the enzyme. The active site includes the side chains and peptide bonds that either come into direct contact with the substrate or perform some direct function during catalysis. Each site is polyfunctional in that certain parts of it may hold the substrate in a position where the other parts cause changes in the chemical bonding of... [Pg.227]

Compound 129, an intensely blue compound, was obtained by direct functionalization of DDTOMe 20b with LDA and chloro(chloromethyldimethylsilane) at one of the terminal positions followed by conversion of chloride to NCS using sodium thiocyanate in acetone (Scheme 12). The other isothiocyanates were prepared via Stille coupling of mono or dibrominated rigid cores with appropriate thienyl or phenyl stannanes followed by conversion of the chlorine atom of Si(CH3)2CH2Cl attached to a phenyl group into isothiocyanate occurred in rather low yield. [Pg.654]

This result can also be applied directly to coarse particle swarms. For fine particle systems, the suspending fluid properties are assumed to be modified by the fines in suspension, which necessitates modifying the fluid properties in the definitions of the Reynolds and Archimedes numbers accordingly. Furthermore, because the particle drag is a direct function of the local relative velocity between the fluid and the solid (the interstitial relative velocity, Fr), it is this velocity that must be used in the drag equations (e.g., the modified Dallavalle equation). Since Vr = Vs/(1 — Reynolds number and drag coefficient for the suspension (e.g., the particle swarm ) are (after Barnea and Mizrahi, 1973) ... [Pg.429]

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