铌酸锂单晶光纤包层研究

通过镁离子内扩散铌酸锂单晶光纤，以改变晶纤表层的折射率，首次在国内实现了沿不同轴向生长、不同掺杂的铌酸锂单晶光纤的芯－包层波导结构。通过匹配扩散温度、扩散时间、ＭｇＯ膜厚等扩散参数及选择合适的晶纤直径，实现了晶纤具有阶跃和抛物折射率分布的包层，并对包层晶纤的模式特性进行了观察，得到低次模传输。     

Spectrum analysis of U-doped LaBr3 single crystals. Part 1: crystal-field analysis

Single crystals of U³⁺:LaBr₃ were grown by the Bridgman-Stockbarger technique. High-resolution polarized absorption spectra of the crystals were recorded at 4.2 K in the 4000-50,000 cm⁻¹ range. Sixty-four experimental crystal-field energy levels of the U³⁺ ion were fitted to a semiempirical Hamiltonian employing free-ion, one-electron crystal-field as well as two-particle correlation crystal-field (CCF) operators with an r.m.s. deviation of 28 cm⁻¹. The performed analysis of the spectra enabled the determination of crystal-field parameters and assignment of the observed 5f³→5f³ transitions. The effects of selected CCF operators on the splitting of some specific U³⁺ multiplets have been investigated and the obtained values of Hamiltonian parameters are discussed and compared with those reported in previous analyses.     

强酸阳离子交换树脂催化性能的研究

通过叔丁醇脱水生成异丁烯的反应研究对比了国内外常见种类的凝胶型和大孔型强酸阳离子交换树脂的催化性能，并对树脂的性质，预处理方法，以及其用量和再生程度等因素对树脂催化活性的影响进行了研究。在此基础上，合成了具有较高催化活性的新型大孔强酸阳离子交换树脂。     

Hydrolysis in the system LiPF6—propylene carbonate—dimethyl carbonate—H2O

¹⁹F and ³¹P NMR spectroscopy were used to study the kinetics of the hydrolysis of LiPF₆ in the homogenous solvent system propylene carbonate (PC)—dimethyl carbonate (DMC)—H₂O. It was found that the main products of the hydrolysis are HF, LiPO₂F₂ and Li₂PO₃F. The content of POF₃ and PF₅ was negligibly low. We set up a hypothesis that the main factor determining the rate of the process is the so-called ‘secondary’ catalytic effect, caused by solvated H⁺ ions.     

Crystal structure and characterization of the bis(n-benzyl-benzotriazole-n3)-dichloro Co(II) complex: CoCl2(C6H4N3CH2Ph)2

The structure of [CoCl₂(C₆H₄N₃CH₂Ph)₂] has been determined by X-ray crystallography. It is also characterized by elemental analysis, IR and electronic spectroscopy, and by thermogravimetric differential thermal analysis. It crystallizes in the monoclinic system, space group C2/c, with lattice parameters a = 16.133(3) , b = 11.355(2) , c = 15.637(3) , = 117.22(3)°, and Z = 8. The crystal structure of the title compound consists of monomeric molecules of [CoCl₂(C₆H₄N₃CH₂Ph)₂] with slightly distorted tetrahedron geometry for the CoCl₂N₂ chromophore. The thermal gravimetry (TG) data indicate that there are four decomposition steps with five endothermic peaks. The final product of the thermal decomposition is CoCl₂. Elemental analysis and the electronic and IR spectra are in agreement with the structural data.Original Russian Text Copyright © 2004 by F. Jian, H. Wang, and H. XiaoTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 723–728, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

清洁催化氧化环己烯合成己二酸反应中酸性配体的作用

 以30％H2O2为氧源，研究了Na2WO4·2H2O催化氧化环己烯制己二\r\n酸反应中的配体效应．在大多数情况下，配体的酸性越强，目标产物己\r\n二酸的产率越高．尽管一些酚类配体、L（＋）抗坏血酸和8－羟基喹啉\r\n的酸性较弱，但己二酸的产率仍然很高．这表明影响目标产物产率的因\r\n素除配体的酸效应以外，还存在配体的配位效应．邻苯二酚和对苯二酚\r\n等酚类配体的实验结果表明，反应可能是通过络合催化反应机理完成的\r\n．对酸性配体用量及对反应动力学考察结果表明，反应过程中环氧化物\r\n水解为1，2－环己二醇是整个反应的控制步骤，反应体系的酸性起到决\r\n定性的作用．     

卟啉酞菁模型化合物光致电子转移研究

本文采用时间相关单光子计数对卟啉酞菁ＴＴＰ－（ＣＨ２）ｎ－Ｐｃ模型化合物的光致电子转移进行了研究，发现激发Ｐｃ时，呈现单指数衰减，ｎ＝４时电子转移速率减小，活化能，重排能增加，电子转移效率下降，电子转移反应△ＧＣＳ与电荷分离活化络合物衰变速率ＫＣＴ，按以下规律：△Ｇ＾（５）ＣＳ〉△＾（３）ＣＳ〉△＾（４）ＣＳ〉△＾（２）ＣＳ，ｋ＾（２）ＣＳ〉ｋ＾（３）ＣＳ〉ｋ＾（４）ＣＳ〉ｋ＾（５）ｃｓ。其△Ｇ＾     

分子手性的温度效应：D-丙氨酸的变温X衍射和中子衍射研究

利用X衍射（300, 270, 250 K）和中子衍射（300, 260, 250, 240 K）研究D-氨酸单晶在静态的和动力学的变温过程中的结构特征以及考证Salam预言的由D到L构型转变的可能性. 实验发现丙氨酸晶体的空间群P212121对称性没有改变. 实验结果否定了构型相变的可能，但是发现在~250 K有一个微小的、连续的对称性破缺发生. 晶体分子振动产生的环电流模型可以用来解释D-和L-丙氨酸单晶直流磁化率和天然旋光角相反的现象， 与之相关的中子衍射数据进一步揭示了变温过程中αC－H(2), N－H(1), N－H(4), N－H(6) 键长的不同变化. 中子衍射还显示了质子移动所导致的动力学无序，来源于分子内氨基和羧基形成的氢键和分子间αC－H和氨基形成的氢键，从而产生的晶格扭曲和NH³⁺的扭转. 实验结果表明Salam预言相变不是传统意义的结构相变，而是由于温度效应导致了在相变点附近分子的宇称破缺能差（PVED）增大，然后通过氨基酸分子的隧道效应扩大了宇称破缺能差的影响，这一研究为生命现象中快速的均一手性形成提供了非线性机理的合理解释.     

Molecular Basis of the Dynamic Strength of the Sialyl Lewis X—Selectin Interaction

The selectins are Ca²⁺‐dependent cell adhesion molecules that facilitate the initial attachment of leukocytes to the vascular endothelium by binding to a carbohydrate moiety as exemplified by the tetrasaccharide, sialyl Lewis X (sLeX). An important property of the selectin‐sLeX interaction is its ability to withstand the hydrodynamic force of the blood flow. Herein, we used single‐molecule dynamic force spectroscopy (DFS) to identify the molecular determinants within sLeX that give rise to the dynamic properties of the selectin/sLeX interaction. Our atomic force microscopy (AFM) measurements revealed that the unbinding of the selectin/sLeX complexes involves overcoming at least two activation barriers. The inner barrier, which determines the dynamic response of the complex at high forces, is governed by the interaction between the Fuc residue of sLeX and a Ca²⁺ ion chelated to the lectin domain of the selectin molecule, whereas the outer activation barrier can be attributed to interactions involving the sialic acid residue of sLeX. Due to their steep inner activation barriers, the selectin‐sLeX complexes are less sensitive to high pulling forces. Hence, besides its contribution to the bond energy, the Ca²⁺ ion also grants the selectin–sLeX complexes a tensile strength that is crucial for the selectin‐mediated rolling of leukocytes.     

Photophysical aspects of single-molecule detection by two-photon excitation with consideration of sequential pulsed illumination.

An important goal in single molecule fluorescence correlation spectroscopy is the theoretical simulation of the fluorescence signal stemming from individual molecules and its autocorrelation function. The simulation approaches developed up to now are based exclusively on continuous-wave (cw) illumination and consequently on cw-excitation. However, this approximation is no longer valid in the case of two-photon excitation, for which pulsed illumination is usually employed. We present a novel theoretical model for the simulation of the fluorescence signal of single molecules and its autocorrelation function with consideration of the time dependence of the excitation flux and thus of all illumination-dependent photoprocesses: two-photon excitation, induced emission and photobleaching. Further important characteristics of our approach are the consideration of the dependence of the photobleaching rate on illumination and the low intersystem-crossing rates of the studied coumarins. Moreover, using our approach, we can predict quantitatively the effect of the laser pulse width on the fluorescence signal of a molecule, that is, the contributions of the photobleaching and saturation effects, and thus we can calculate the optimal laser pulse width. The theoretical autocorrelation functions were fitted to the experimental data, and we could ascertain a good agreement between the resulting and the expected parameters. The most important parameter is the photobleaching constant sigma, the cross section of the transition Sn<--S1, which characterises the photostability of the molecules independent of the experimental conditions. Its value is 1.7 x 10(-23) cm2 for coumarin 153 and 5 x 10(-23) cm2 for coumarin 314.