Geometries and properties of bimetallic phosphido-bridged complex Cp(CO)2W(μ-PPh2)W(CO)5 and Cp(CO)3W(μ-PPh2)W(CO)5

Complete geometry optimizations were carried out by HF and DFT methods to study the molecular structure of binuclear transition-metal compounds (Cp(CO)₃W(μ-PPh₂)W(CO)₅) (I) and (Cp(CO)₂W(μ-PPh₂)W(CO)₅) (II). A comparison of the experimental data and calculated structural parameters demonstrates that the most accurate geometry parameters are predicted by the MPW1PW91/LANL2DZ among the three DFT methods. Topological properties of molecular charge distributions were analyzed with the theory of atoms in molecules. (3, −1) critical points, namely bond critical point, were found between the two tungsten atoms, and between W1 and C10 in complex II, which confirms the existence of the metal–metal bond and a semi-bridging CO between the two tungsten atoms. The result provided a theoretical guidance of detailed study on the binuclear phosphido-bridged complex containing transition metal–metal bond, which could be useful in the further study of the heterobimetallic phosphido-bridged complexes.     

锑化镓的光助微刻蚀及其表面氧化物的研究

用电化学和光电化学方法研究锑化镓表面的腐蚀以及锑化镓表面氧化膜的生成和溶解，锑化镓电极在一定电势下生成的氧化膜，用俄歇能谱证明，其主要成分为难溶的氧化锑，此氧化膜的存在抑制了锑化镓的进一步腐蚀，同时亦使锑化镓的半导体光电化学性能大为减弱，通过激光微刻蚀及电子显微镜的观察，在刻蚀剂中添加酒石酸，柠檬酸和氢氟酸等试剂，可使刻蚀形得改善，实验研究了锑化镓的平带电势的测定。     

Capillary electrophoresis with amperometric detection of curcumin in Chinese herbal medicine pretreated by solid-phase extraction

In the present study, curcumin from Chinese herbal medicine turmeric was determined by capillary electrophoresis with amperometric detection (CE-AD) pretreated by a self-designed, simple, inexpensive solid-phase extraction (SPE) cartridge based on the material of tributyl phosphate resin. An average concentration factor of 9 with the recovery of > 80% was achieved when applied to the analysis of curcumin in extracts of tumeric. Under the optimized CE-AD conditions: a running buffer composed of 15 mM phosphate buffer at a pH 9.7, separation voltage at 16 kV, injection for 6 s at 9 kV and detection at 1.20 V, CE-AD with SPE exhibited low detection limit as 3 x 10(-8) mol/l (S/N = 3), high efficiency of 1.0 x 10(5) N, linear range of 7 x 10(-4) -3 x 10(-6) mol/l (r = 0.9986) for curcumin extracted from light petroleum. The method developed resulted in enhancement of the detection sensitivity and reduction of interference from sample matrix in complicated samples and exhibited the potential application for routine analysis, especially in food, because a relatively complete process of sample treatment and analysis was described.     

Theoretical analysis and computer simulation of fluorescence lifetime measurements. I. Kinetic regimes and experimental time scales

The configuration-controlled regime and the diffusion-controlled regime of conformation-modulated fluorescence emission are systematically studied for Markovian and non-Markovian dynamics of the reaction coordinate. A path integral simulation is used to model fluorescence quenching processes on a semiflexible chain. First-order inhomogeneous cumulant expansion in the configuration-controlled regime defines a lower bound for the survival probability, while the Wilemski-Fixman approximation in the diffusion-controlled regime defines an upper bound. Inclusion of the experimental time window of the fluorescence measurement adds another dimension to the two kinetic regimes and provides a unified perspective for theoretical analysis and experimental investigation. We derive a rigorous generalization of the Wilemski-Fixman approximation [G. Wilemski and M. Fixman, J. Chem. Phys. 60, 866 (1974)] and recover the 1/D expansion of the average lifetime derived by Weiss [G. H. Weiss, J. Chem. Phys. 80, 2880 (1984)].     

肉桂酸类分子非线性光学效应的理论研究

计算了一系列肉桂酸（苯基丙烯酸）类化合物的二阶非线性光学系数，系统地研究了取代基的电子性质和取代位置对其非线性光学性质的影响，并且探讨了该类化合物的饱和取代效应．研究表明，该类化合物的非线性光学性质与其分子结构有着密切的关系．     

Analysis of flavonoids in <Emphasis Type="Italic">Ginkgo biloba</Emphasis> L. and its phytopharmaceuticals by capillary electrophoresis with electrochemical detection

A high-performance capillary electrophoretic (CE) method with electrochemical detection (ED) has been developed for determination of the pharmacologically active flavonoids in Ginkgo biloba L. and phytopharmaceuticals containing its extract. Epicatechin, catechin, rutin, apigenin, luteolin, and quercetin are important flavonoids in this plant. Operated in a wall-jet configuration, a 300 micro m diameter carbon-disk electrode was used as working electrode with good response to the six analytes at +1000 mV (relative to the SCE). Under the optimum conditions, the analytes were separated within 22 min in a borax buffer (pH 9.0). Excellent linearity was obtained over two orders of magnitude and detection limits (S/N=3) ranged from 1.4 x 10(-7) to 5.0 x 10(-7) g mL(-1) for all six analytes. The method was successfully used for assay of Ginkgo biloba L. and its phytopharmaceuticals after a relatively simple extraction procedure; the results obtained were satisfactory.     

Potentiometric immunosensor based on antiserum of Japanese B encephalitis immobilized in nano-Au/polymerized o-phenylenediamine film

A novel potentiometric immunosensor for detection of Japanese B encephalitis vaccine was developed by immobilizing antiserum of Japanese B encephalitis on nano-Au/polymerized o-phenylenediamine (o-PDA) film on the platinum (Pt) electrode. The performance and factors influencing the performance of the resulting immunosensor were studied. The immunosensor showed a specific response to Japanese B encephalitis vaccine in the range 1.1 × 10⁻⁸ to 2.0 × 10⁻⁶ lgpfu/ml (plaque forming unit) with a detection limit of 6 × 10⁻⁹ lgpfu/ml. The correlation coefficient is 0.9986. The incubation time, incubation temperature, pH, reproducibility and stability of the immunosensor were also studied. The present work supplied a promising test method for biological products.     

新颍Mo-Cu-Se簇合物{MoCu3Se3I}(PPh3)3O·0.5CH2Cl2的合成及晶体结构

新颍Mo-Cu-Se簇合物{MoCu₃Se₃I}(PPh₃)₃O·0.5CH₂Cl₂是由［Et₄N］₂MoSe₄、Cu(PPh₃)₂NO₃和KI在乙腈和二氯甲烷1∶1的混合溶剂中反应所得。晶体属单斜晶系，空间群P2_{1相似文献}   

铁电极上硫脲及衍生物的缓蚀作用研究

用极化曲线方法测定了硫酸溶液中硫脲及其衍生物的浓度变化对铁腐蚀电化学行为的影响，获得了腐蚀电位下缓蚀剂对阴极和阳极过程的作用系数，用ＥＨＭＯ方法对硫脲及其衍生物的结构参数进行了量化计算，分析表明，缓蚀剂对阴极和阳极过程作用系数的大小与这些参量有密切关系。     

Chemical constituents from the roots of <Emphasis Type="Italic">Polygonum bistorta</Emphasis>

Investigation of the roots of Polygonum bistorta L. afforded seven compounds including five triterpenoids, a coumarin, and a steroid, the structures of which were identified by EIMS, ¹H NMR, ¹³C NMR, DEPT, and HMBC experiments. All the compounds have been isolated from Polygonum genus for the first time. Published in Khimiya Prirodnykh Soedinenii, No. 5, pp. 463–465, September–October, 2007.