X射线荧光光谱法测定橄榄岩主次痕量元素

本文采用熔融玻璃片和粉末压片法制样，用理论ａ系数和散射线内标法校正元素间的效应，     

Damage-Bone Remodelling Theory: An Extension to Anisotropic Damage

Everyday activities damage bone, and this damage is normally repaired in a continuous remodelling process. When an imbalance in this remodelling process occurs, bones may become more susceptible to fracture. This paper is concerned with a derivation of: (a) the general rule for bone remodelling in interaction with anisotropic damage and (b) the associated thermodynamic restrictions. The procedure of Coleman and Noll, utilizing the Clausius–Duhem inequality is used and is provided as basis for a consistent formulation of bone remodelling involving a chemical reaction and mass transfer between two constituents in presence of microcracks. It is hoped that this work provides a rational basis for the practical use of such theoretical results.     

Matrix isolation study of the photochemical reaction of cyclohexane and cyclohexene with CrCl2O2

The matrix isolation technique, combined with infrared spectroscopy, has been used to characterize the products of the photochemical reactions of cyclohexane and cyclohexene with CrCl₂O₂. While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, strong product bands were noted following irradiation with light of λ > 300 nm. The irradiation was shown to lead to oxygen atom transfer, forming complexes between cyclic alcohol derivatives and CrCl₂O, although complexes between ring expansion products and CrCl₂O could not be ruled out. This latter result could arise from C-C bond activation and oxygen atom insertion into a C-C bond. For the cyclohexene system, the cyclohexanone-CrCl₂O complex was also observed. The identification of the complexes was further supported by isotopic labeling (²H) and by density functional calculations at the B3LYP/6-311G++(d,2p) level.     

Nicht-radiative Desaktivierung von Molekülen: III. Theoretische Bestimmung der inneren Konversion von ausgewählten 1,3-Diketonato-Borkomplexen unter Berücksichtigung des Akzeptor- und Promotorverhaltens

Summary Taking as a basis the completely-optimized S₀ and S₁ molecular geometries of selected 1,3-diketonato boron complexes the rate constants of internal conversion and fluorescence are determined theoretically. It is shown that the consideration of the accepting as well as promoting modes is essential to get a more substantiated insight into the photophysics of these compounds. An analysis of the significant modes is given.

     

Theoretically Calculated Deformation Density of Small Molecules

Analysis of the theoretical electron deformation density based on EHMO and ab initio calculations has been applied to the simple molecules F₂, H₂O and SO₂ The effects from varied basis sets for such deformation density were sought. The accumulation of electron density between the bonded atoms calculated from EHMO and ab initio methods with STO-3G is generally under-estimated. Such phenomena are significantly improved by using split-valence basis sets e.g. 3–21G and 4–31G. The addition of d polarization functions is apparently important for the sulfur atom in sulfur-related bonding. 3–21G or 3–21G^* basis sets were found to provide not only valuable deformation density distributions of molecules but also comparable orbital energy states with respect to the experimental values.     

Chromatographic terminal band lengths

A terminal band length is defined here as the length of a dispersed solute band as it emerges from the chromatographic column. The number of terminal band lengths per column can be used in the same way that the number of theoretical plates per column is used to measure and compare chromatographic efficiencies, but with greater insight since the proposed unit of measure is an easily visualized, real entity. In addition, the height equivalent to a theoretical plate (HETP) can be regarded as a ratio of the terminal band lenght to sixteen times the number of equivalent terminal band lengths that could be contained in tandem in the column. This concept offers another approach to understanding the meaning of the term, HETP. The terminal band length of a series of homologues is constant and independent of retention time above a certain solute molecular size and column capacity ratio. Within those conditions the correlation between the recorded peak width and retention time during isothermal analysis occurs primarily as a result of change in solute velocity.     

(ZnS)6~12团簇三阶非线性光学性质的理论研究

在TDDFT/Lanl2DZ+6-31G*水平下对(ZnS)6~12半导体团簇的三阶非线性光学性质进行了计算, 并用态求和(SOS)方法得到静态三阶宏观极化率χ(3)和0~2.5 eV范围内输入光子能量对三阶微观极化率γ的动态行为. 结果表明, (ZnS)6~12的χ(3)值比其它半导体团簇的略好. 且(ZnS)7和(ZnS)11分别在1.6和2.0 eV处出现了很大的γ值, 为-2.38×10-33和1.26×10-33 esu. 在此输入光子能量处激发, 它们将会产生很强的三阶非线性光学效应.     

A theoretical investigation of the mechanism for the reaction between a quebrachitol derivative and N3−

The reaction between a mesylated compound and sodium azide was previously studied experimentally at a temperature of 140 °C using dimethylformamide as a solvent. The product was assigned on the basis of the analysis of the NMR spectra. In this work semiempirical (AM1 and PM3), ab initio (Hartree–Fock and MP2) and density functional theory (BLYP functional) quantum mechanical calculations, using continuum models for describing the solvent effect, were carried out for this process to better understand the reaction mechanism. Three distinct mechanisms involving a carbocation and epoxide intermediates, and a transition-state structure for direct attack of the N₃ ⁻ species to the reactant were investigated. The theoretically calculated preferred reaction pathway passing through an epoxide intermediate agrees nicely with the experimental proposal, providing a good example of where theoretical calculations can be of great help to definitively elucidate the reaction mechanism. Received: 10 July 2001 / Accepted: 20 December 2001 / Published online: 8 April 2002