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排序方式: 共有338条查询结果,搜索用时 15 毫秒
31.
32.
Sinead E. Milner Maude Brossat Thomas S. Moody Curtis J. Elcoate Simon E. Lawrence Anita R. Maguire 《Tetrahedron: Asymmetry》2010,21(8):1011-1016
The kinetic bioresolution of 2-nitrocyclohexanol 1 was investigated by screening a range of hydrolases both for enantioselective transesterification and for enantioselective hydrolysis of the corresponding acetate. By appropriate choice of biocatalyst and conditions, both enantiomers of cis and trans 2-nitrocyclohexanol 1 can be accessed in enantiopure form. 相似文献
33.
We show that real model sets with real internal spaces are determined, up to translation and changes of density 0, by their
2- and 3-point correlations. We also show that there exist pairs of real (even 1D) aperiodic model sets with internal spaces that are products of real spaces and finite cyclic groups whose 2- and 3-point
correlations are identical but which are not related by either translation or inversion of their windows. All these examples
are pure point diffractive.
Placed in the context of ergodic uniformly discrete point processes, the result is that real point processes of model sets
based on real internal windows are determined by their second and third moments. 相似文献
34.
Back Cover: Formal Total Synthesis of Diazonamide A by Indole Oxidative Rearrangement (Chem. Eur. J. 31/2016)
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35.
Buck RT Clarke PA Coe DM Drysdale MJ Ferris L Haigh D Moody CJ Pearson ND Swann E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(12):2160-2167
A different approach to the synthesis of dipeptides is described based on the formation of the NHCHR1CONH-CHR2CO bond by carbenoid N-H insertion, rather than the formation of the peptide bond itself. Thus decomposition of triethyl diazophosphonoacetate catalysed by rhodium(II) acetate in the presence of N-protected amino acid amides 8 gives the phosphonates 9. Subsequent Wadsworth-Emmons reaction of 9 with aldehydes in the presence of DBU gives dehydro dipeptides 10. The reaction has been extended to a simple two-step procedure, without the isolation of the intermediate phosphonate, for conversion of a range of amino acid amides 11 into dehydro dipeptides 12 and to an N-methylamide 11 h, and for conversion of a dipeptide to tripeptide (13-->14). Direct conversion, by using methyl diazophenylacetate, of amino acid amides to phenylglycine-containing dipeptides 19 proceeds in good chemical yield, but with poor diastereoselectivity. 相似文献
36.
An automated colorimetric procedure was developed for the determination of inorganic carbon in the range 0.3–40.0 mg l-1, and then modified to handle concentrations in the range 0.01–2.00 mg l-1. The procedure entailed conversion of carbon dioxide equilibria products to carbon dioxide. By gas dialysis, a portion of this gas was dissolved in a weakly buffered alkaline phenolphthalein solution, and inorganic carbon was determined by measuring the loss in color of the indicator. Calibrations were linear within 1% full scale. When surface water samples were processed by the subject and by alternative methods, the colorimetric carbon results were lower by approximately 1% full scale. 相似文献
37.
H. Groening K. Aleklett K.J. Moody P.L. McGaughey W. Loveland G.T. Seaborg 《Nuclear Physics A》1982,389(1):80-92
Isomer ratios for the reaction 29Si(18O, p2n)44gSc, 44gSc have been deduced from activity measurements for projectile energies between 30 and 99 MeV. Statistical model calculations show that the isomer ratio dependence on projectile energy up to about 80 MeV can be adequately described by assuming a fixed ratio of quadrupole to dipole γ-ray strengths. Such a ratio of E2/E1 strengths agrees with corresponding values deduced from the literature. The values of the γ-ray strength ratios needed to fit the experimental isomer ratios are extremely sensitive to the relative amounts of quadrupole γ-ray admixture and to the presence of discrete levels other than those which conform to the yrast line. 相似文献
38.
Yuan-Fang Liu Cheng Luo K. J. Moody D. Lee G. T. Seaborg H. R. Von Gunten 《Journal of Radioanalytical and Nuclear Chemistry》1983,76(1):119-124
Two procedures are described for fast separations of berkelium from complex mixtures of reaction products arising from heavy
ion reactions, such as18O+248Cm. The first procedure uses a combination of several extraction steps with a final separation on a cation exchanger, the
second procedure starts with an anion exchange column which is followed by multiple extractions in different media. The elements
separated in the different steps were analyzed and overall decontamination factors are given. 相似文献
39.
The objective of ISLES (Inverse-Square Law Experiment in Space) is to perform a null test of Newton's law in space with a resolution of one part in 105 or better at 100 m. ISLES will be sensitive enough to detect axions with the strongest allowed coupling and probe large extra dimensions of string theory down to a few m. The experiment will be cooled to 2 K, which permits superconducting magnetic levitation of the test masses. This soft, low-loss suspension, combined with a low-noise SQUID, leads to extremely low intrinsic noise in the detector. To minimize Newtonian errors, ISLES employs a near null source, a circular disk of large diameter-to-thickness ratio. Two test masses, also disk-shaped, are suspended on the two sides of the source mass at a nominal distance of 100 m. The signal is detected by a superconducting differential accelerometer. 相似文献
40.
A ghost interface simulation technique is developed and applied to supersaturated Lennard-Jones liquid-vapor interfaces. It is shown that the surface tension decreases approximately linearly with the supersaturation ratio and that it vanishes at the spinodal. The effect leads to a curvature-dependent surface tension since, it is argued, the local supersaturation of the vapor above a droplet is greater than in the bulk due to slow diffusion in the vapor phase. An analytic approximation is given for the local supersaturation ratio, and an analytic expression for this contribution to Tolman's length is derived. The theory gives a smaller critical radius and reduces the free energy barrier to nucleation compared to classical homogeneous nucleation theory, which have important implications for the kinetics of droplet and bubble formation. 相似文献