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Molar extinction coefficients of some carbohydrates viz. l-arabinose (C5H10O5), d-glucose (C6H12O6), d-mannose (C6H12O6), d-galactose (C6H12O6), d(-) fructose (C6H12O6) and maltose (C12H24O12) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a
narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter
polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying
within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well. 相似文献
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The structure of 1,3-dehydro-5-adamantyl cation and its isoelectronic boron analogue 1,3-dehydro-5-boraadamantane as well as some related adamantane systems, hitherto unknown as persistent long-lived species, were investigated by using the density functional theory (DFT) method. (13)C and (11)B NMR chemical shifts of the compounds were also calculated using the IGLO method. Stabilization of the systems due to homoconjugation is discussed. 相似文献
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GK Johri Akhilesh Tiwari Saumya Saxena Rajesh Sharma Kuldeep Srivastava Manoj Johri 《Pramana》2002,58(3):563-567
Calculations for the relative width (Δω/ω0) as a function of refractive index and relative radius of the photonic band gap for the fcc closed packed 3-D dielectric
microstructure are reported and comparison of experimental observations and theoretical predictions are given. This work is
useful for the understanding of photonic crystals and occurrence of the photonic band gap. 相似文献
4.
离子液体作为溶剂/催化剂用于卤代烃对胺的选择性烷基化反应 总被引:1,自引:0,他引:1
在三乙胺存在下,在离子液体([bmim]I和[bmim]PF6)中进行了各种卤代烃对胺类化合物中氨基的选择性烷基化反应.反应在相对温和的条件下进行,转化率和选择性优异.离子液体可以回收并重复使用. 相似文献
5.
In order to understand the mechanism by which dyes assist chromatographic detection in reverse-phase systems, absorption spectra of brilliant green and methylene blue were investigated. It is shown that dye-assisted chromatographic detection depends on the ability of the analyte to shift the monomer-dimer equilibrium of the dyes toward greater monomer concentrations. Monomers have higher molar absorptivities than dimers. Equilibrium constants and molar absorptivities for monomeric and dimeric forms of the dyes are reported. 相似文献
6.
G. K. Vemulapalli 《Foundations of Chemistry》2008,10(3):167-176
Two different models for chemical bond were developed almost simultaneously after the Schrödinger formulation of quantum theory. These are known as the valence bond (VB) and molecular orbital (MO) theories. Initially chemists preferred the VB theory and ignored the MO theory. Now the VB theory is almost dropped out of currency. The context of discovery and Linus Pauling’s overpowering influence gave the VB theory its initial advantage. The current universal acceptance of the MO theory is due to its ability to provide direct interpretation of many different types of experiments now being pursued. In current research both localized bonds and delocalized charge distributions play important roles and the MO theory has been successful in giving a good account of both. 相似文献
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<正>The square soft-edge diaphragm with round angle is designed by Matlab,and is sent to a liquid crystal spatial light modulator by the computer.In order to obtain precompensation for the following laser system, local diaphragm transmission can be adjusted by feedback signals of surface-channel charge-coupled device (SCCD).This method can reduce the diffraction effect and realize no modulation,high stability,high homogeneity,and large scale laser beam.Several parameters of soft-edge diaphragms which affect the laser beam quality are studied systematically,and the optimized values are obtained.The method can avoid the serious modulation of hard edges and provide soft-edge diaphragms of different shapes in a fast and convenient way for the large scale laser beam system. 相似文献
8.
Scott N Vemulapalli GK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,(12):2373-2377
Most of the research on solvent effects on the electronic spectra of organic molecules has been concerned with frequency shifts. Solvent induced intensity changes, however, have not received much attention. At present there is no simple, general theory that relates: (a) the solvent induced changes in electronic transition intensities to (b) the macroscopic properties of the solvent. In this article we derive an equation that provides a quantitative interpretation for the changes in the absorption intensities. We show that solvent induced intensity changes are related to van der Waals constants for solvent and solute. Absorption data, some from previous investigations, are presented to show the usefulness and limitations of the theory. 相似文献
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Central to many issues surrounding reduction in science is the relation between a physical system and its components. In this article we examine how thermodynamic theory relates properties of whole systems to properties of their components. In order to keep the analysis general, we focus our study on universal properties like volume, heat capacity, energy and temperature. In the cases examined we find that scientific explanation requires appeal to properties of components that are spatially as extensive as the whole system. We discuss some implications of our study for the purported paradigmatic reductions of heat and temperature to molecular motion. We conclude that while macro systems reduce ontologically to micro components, epistemologically the reduction of theoretical concepts in general fails. 相似文献
10.
K.K. Innes L.A. Franks A.J. Merer G.K. Vemulapalli T. Cassen J. Lowry 《Journal of Molecular Spectroscopy》1977,66(3):465-477
A detailed vibrational analysis of the 5515 Å absorption of s-tetrazine (tetra-azabenzene) vapor is attempted. More than 80% of the total intensity of the system can be accounted for by band assignments to a single allowed electronic transition, 1B3u-1Ag. The only progression-forming vibration in absorption in ν6a. Three progressions in ν′6a account for all intense cold bands. Isotopic shifts of bands lead to convincing assignments of the two excited-state vibrations upon which ν6a progressions are based, namely ν6b and ν8a. It is shown that in all probability the antisymmetric mode ν6b is prominent because of vibrational (Fermi) resonance rather than because of vibronic interactions. 相似文献
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