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291.
[reaction: see text] Ab initio and density functional theory (DFT) calculations were used to examine the mechanisms of reduction and amination of chloromethane by lithium dimethylaminoborohydride (LAB) in the gas phase. For comparison, the amination of chloromethane by lithium dimethylamide and the reduction by borane, diborane, and borohydride ions were also examined. The reduction of chloromethane by LAB occurred most readily from a conformation that allowed coordination of the lithium atom to the chloride leaving group, and the most favorable amination pathway occurred by a backside attack of the nitrogen nucleophile on chloromethane. 相似文献
292.
Monodispersed Ag2Se nanocubes and faceted nanocrystals have been synthesized by hexadecylamine (HDA) induced thermolysis of [(PPh3)3Ag2(SeC{O}Ph)2] in a mixture of TOP (tri-n-octyl phosphine) and HDA in the temperature range 95-180 degrees C. 相似文献
293.
Let Γ be a finitely generated, torsion-free, two-step nilpotent group. Let C*(Γ) denote the universal C*-algebra of Γ. We show that , where for a unital C*-algebra A, sr(A) is the stable rank of A, and where is the space of one-dimensional representations of Γ. In process, we give a stable rank estimate for maximal full algebras of operator fields over metric spaces. 相似文献
294.
An equivalent cavity approach is used to derive the oscillation condition of a distributed Bragg reflector laser. The oscillation frequencies and thresholds are determined graphically. The effect of lossy reflectors is discussed. Several advantages and potential applications of distributed Bragg reflector structures are pointed out. Experimental results on optically pumped GaAs lasers are presented. 相似文献
295.
296.
Substantially reduced Brillouin reflection has been found for CO2 laser irradiated high density gas targets. In contrast to high reflectivity (60%) previously observed for underdense hydrogen plasma, total backscatter (stimulated plus specular) is found to peak at 30% for incident intensity 5 × 1012 W/cm2 and decrease thereafter to 18% at 1013 W/cm2. Ponderomative effects are postulated to account for these observations. 相似文献
297.
The capillary electrophoretic separation of components in propolis, a commonly used natural medicine, was investigated. Optimum conditions for the separation were established. Photodiode-array detection permitted the rapid identification of the components in the samples analysed. The determination of these components, including caffeic acid, dimethylcaffeic acid, isoferulic acid and quercetin, was performed on a commercial propolis sample. 相似文献
298.
G. La Rana C. Ngô Amand Faessler L. Rikus R. Sartor M. Barranco X. Viñas 《Nuclear Physics A》1984,414(2):309-315
Hot density distributions of heavy ions generated by a modified Thomas-Fermi calculation at finite temperature are used to calculate the optical potential using the double-folding method and a complex effective energy and density-dependent interaction deduced from a realistic NN (Reid soft-core) force in nuclear matter. The real and the imaginary part of the optical potential become more attractive when the temperature increases. 相似文献
299.
J. Nemeth M. Barranco C. Ngô E. Tomasi 《Zeitschrift für Physik A Hadrons and Nuclei》1985,320(4):691-692
We have used a self-consistent time dependent Thomas-Fermi model at finite temperature to calculate the dynamical evolution of hot and compressed nuclei. It has been found that nuclei can accomodate more thermal energy than compressional energy before they break. 相似文献
300.