Reduction experiments

Shaft Centers. As in roller chains, the minimum distance between shaft centers for silent chains must, in order to provide tooth clearance, be greater than half the sum of the two sprocket diameters. On large-speed reductions, experience has shown that the center distance should not be less than eight-tenths the difference in diameters of the two sprockets. 

The drag reduction experiments show that the characteristics of drag reduction are the same as Habon-G solution reported earlier The amount of drag reduction stays almost the same for the first several hours. Then the amount of drag reduction falls off to zero abruptly as shown in Fig. 1. In the figure we plot the % friction reduction against sheared time, where the % friction reduction, % FR, is defined as follows ... 

The 50.31 MHz 13C NMR spectra of the chlorinated alkanes were recorded on a Varian XL-200 NMR spectrometer. The temperature for all measurements was 50 ° C. It was necessary to record 10 scans at each sampling point as the reduction proceeded. A delay of 30 s was employed between each scan. In order to verify the quantitative nature of the NMR data, carbon-13 Tj data were recorded for all materials using the standard 1800 - r -90 ° inversion-recovery sequence. Relaxation data were obtained on (n-Bu)3SnH, (n-Bu)3SnCl, DCP, TCH, pentane, and heptane under the same solvent and temperature conditions used in the reduction experiments. In addition, relaxation measurements were carried out on partially reduced (70%) samples of DCP and TCH in order to obtain T data on 2-chloropentane, 2,4-dichloroheptane, 2,6-dichloroheptane, 4-chloroheptane, and 2-chloroheptane. The results of these measurements are presented in Table II. In the NMR analysis of the chloroalkane reductions, we measured the intensity of carbon nuclei with T values such that a delay time of 30 s represents at least 3 Tj. The only exception to this is heptane where the shortest T[ is 12.3 s (delay = 2.5 ). However, the error generated would be less than 10%, and, in addition, heptane concentration can also be obtained by product difference measurements in the TCH reduction. Measurements of the nuclear Overhauser enhancement (NOE) for carbon nuclei in the model compounds indicate uniform and full enhancements for those nuclei used in the quantitative measurements. Table II also contains the chemical... 

Storage-reduction experiments were also performed with synthetic exhaust and by reducing gases containing 3% C02 at 300°C, as well as at 350°C, and the same effects described above were observed. 

In fact, phase diagrams as in Figure 2.2 form indispensable background information for the interpretation of reduction experiments. However, one should realize that equilibrium data as in Figure 2.2 and Table 2.1 refer to the reduction of bulk compounds. Figures valid for the reduction of surface phases may be quite different. Also, traces of water present on the surface of catalyst particles or on the support represent a locally high concentration and may cause the surface to be oxidized under conditions which, interpreted macroscopically, would give rise to complete reduction. 

In the flow-injection test, mobile phase A is 0.02 M NaH2P04 in water at pH 4.7 (0.005 M NaCl for solid state AgCl reference) mobile phase B has the same composition, but at pH 7. For reductive experiments, use steel tubing for oxidative experiments, use PTFE tubing. 

Because this reaction must involve two steps, diffusion of selenate into the interlayer spaces of the green rust followed by electron transfer from Fe(ll) green rust, Johnson and Bullen (2003) interpreted this result using a two-step model similar to that discussed above. The diffusion step presumably has very little isotopic fractionation associated with it. Step 2 might be expected to involve a kinetic isotope effect similar to that observed in the HCl reduction experiments. As is discussed above, if the diffusion step is partially rate-limiting, the isotopic fractionation for the overall process should be less than the kinetic isotope effect occurring at the reduction step. This appears to be the case, as the ese(vi)-se(iv) value of 7.4%o is somewhat smaller than that observed for reduction by strong HCl (12%o). 

Ellis et al. (2003) obtained an Sse(iv)-se(o) range for Se(lV) reduction of 5.5%o to 5.7%o in three experiments with two of the three sediment slurries used for the Se(Vl) reduction experiments reviewed above. Se(lV) concentrations were 100 pmol/L and 240 nmol/L for the estuarine sediment experiments and 460 nmol/L for the wetland sediment. As with the Se(Vl) reduction experiments from this study, there was no apparent dependence on Se concentration or sediment type, though the number of experiments was small. 

This phosphotransferase [EC 2.7.2.1] catalyzes the thermodynamically favored phosphorylation of ADP to form ATP Aeq = [ATP][acetate]/ [acetyl phosphate] [ADP] = 3000). GDP is also an effective phosphoryl group acceptor. This enzyme is easily cold-denatured, and one must use glycerol to maintain full catalytic activity. Initial kinetic evidence, as well as borohydride reduction experiments, suggested the formation of an enzyme-bound acyl-phosphate intermediate, but later kinetic and stereochemicaT data indicate that the kinetic mechanism is sequential and that there is direct in-line phosphoryl transfer. Incidental generation of a metaphosphate anion during catalysis may explain the formation of an enzyme-bound acyl-phosphate. Acetate kinase is ideally suited for the regeneration of ATP or GTP from ADP or GDP, respectively. 

Reduction Experiments. NEO (100-1000 pmole) was reacted with an excess (10-1000 equivalents) of sodium borohydride, sodium cyanoborohydride or Zn/acid in buffer at pH 8-10, 3-7 or 2-5 respectively. The borohydride and cyanoborohydride reductions were performed with and without added diglyme for 2-40 hours. The Zn was used with hydrochloric, acetic, phthalic or citric acid with... 

Cell Growth. Mycelial pellets of P. chrysosporium (ATCC 24725) were produced under nitrogen limited culture conditions at 37°C using a spore inoculum (36). The pellets were grown for 72 hr at 150 rpm after which they were concentrated fourfold by decanting excess medium. They were used for reduction experiments after a 24 hr activation period (37°C, 50 rpm, under 100% O2 atmosphere). 

Reduction Experiments. The reduction experiments were carried out with 50 ml of activated pellets. The cultures were agitated at 50 rpm and 37°C. Quinones were added at a concentration of 0.2 mM. Samples of the supernatant were taken at defined intervals and their absorption measured at 288 nm and 360 nm on a Perkin-Elmer 557 Photospectrometer. 

Navier-Stokes equations to the swirl reduction experiments and isolate dimensionless numbers that can be used to apply the experiments to various pipes and discharges. 

A correlation between the catalytic qualities and the reducibility of this type of catalyst is suggested by Massoth and Scarpiello [ 205]. They performed reduction experiments both with hydrogen and with butene. Reduction may destroy the lattice, and the best catalysts appear to be those that are only superficially reduced. The effect of the introduction of Cr in the ferrites, mentioned above, is shown to be essentially due to an increase of the stability against bulk reduction. 

Interthal W, Wilski H (1985) Drag reduction experiments with very large pipes Colloid Polym Sci 263 217... 

In the course of reduction experiments of methyl 12,14-dinitrodehydroabietate 3, a new benzoxazole resin add derivative 6 was synthesized and its structure established by spectroscopic data, chemical derivatization and X-ray analysis. 

There is no standard, universal, procedure for the Birch reduction. Experiment 7.19 illustrates some of the variants which have been reported in the literature. The original Birch procedure is to add small pieces of sodium metal to a solution of the aromatic compound in a mixture of liquid ammonia and the proton source (ethanol).18 After completion of the reaction, which is usually indicated by the disappearance of the blue colour, it is quenched by the addition of ammonium chloride and the ammonia allowed to evaporate before the cautious addition of water, and isolation of the product by ether extraction. In a modified procedure a co-solvent (ether, tetrahydrofuran, etc.) is initially added to the solution of aromatic compound/liquid ammonia prior to the addition of metal lithium metal is often used in place of sodium.19a,b In general these latter procedures are used for substrates which are more difficult to reduce. Redistilled liquid ammonia is found to be beneficial since the common contaminant iron, in collodial form or in the form of its salts, has a deleterious effect on the reaction.20 A representative selection of procedures is given in Expt 7.19 for the reduction of o-xylene, anisole, benzoic acid, and 3,4,5-trimethoxybenzoic acid. 

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