The inclusion complex of piromidic acid with dimethyl-β-cyclodextrin in aqueous solution and in the solid state

Inclusion complex formation of piromidic acid (PA) with dimethyl--cyclodextrin (DM--CD) in aqueous solution and in the solid state was confirmed by the solubility method, differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The apparent stability constant,K _c , of the complex was estimated to be 244 M^–1. The stoichiometry of the complex was given as the ratio 1:2 of PA to DM--CD. The dissolution rate of the PA/DM--CD complex was much greater than that of intact PA.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

计算单向复合材料弹性模量的新公式

根据复合材料单层的实际构造，提出了串并联组合模型，采用微观力学与宏观力学相结合的方法，推导出一组计算单向复合材料弹性模量的新公式。其优点是：Ｅ１和ｖ（１２）、Ｅ２和Ｇ（１２）的计算式形式对称，结构简单，计算容易，物理意义明确。我们把由世界上许多著名学者提出的多组预测公式和本文导出式计算所得的结果与国内外已发表的硼／环氧、碳／环氧、玻璃／环氧复合材料的实验数据相比较，结果表明：导出式比其他公式精确、更有价值，可供二程设计使用。     

Copolymerization of ethylene and 1-butene with highly active Ticl4/THF/Mgcl2, Ticl4/THF/Mgcl2/SiO2, and TiCl3.1/3AlCl3 catalysts

Highly active catalysts for copolymerization have been prepared by the precipitation of MgCl₂/ToCl₄ complex with or without high surface area silica. Copolymerization of ethylene and 1-butene has been tested by using the prepared catalysts at various concentrations of 1-butene. The catalytic activities are 20–80 kg/g Ti h. The rate of copolymerization is strongly affected by the addition of 1-butene. The decay rate of copolymerization is first order with respect to time. Analyses of copolymers with solvent extraction, DSC, IR, XRD, and NMR were performed. Ethylene reactivity ratio (k₁₁) for TiCl₄/MgCl₂/THF catalyst is calculated to be about 26 by NMR spectrum. © 1994 John Wiley & Sons, Inc.     

SPORES AND POLLEN IN CRUDE OILS AND PETROLEUM SOURCE OF TARIM BASIN

One hundred and forty-seven species of spores and pollen referred to 77 genera found in the crudeoil samples taken from four petroliferous provinces of the Tarim Basin of Xinjiang Provincehave been studied in this paper. By means of these spore and pollen fossils, the geological ages anddistribution of the petroleum source rocks of the basin are judged. Also, the principles and methodsto judge the petroleum source of a petroleum province by spore/pollen and other microfossils in crudeoils are explained.     

Catalytic wet air oxidation of oleic acid on ceria-supported platinum catalyst.effect of pH

Summary Catalytic wet air oxidation (CWAO) of oleic acid was carried out in a batch reactor on platinum supported ceria catalyst (Pt/CeO₂). Oleic acid is a water insoluble linear unsaturated fatty acid of 18 carbon atoms. To increase the homogeneity of the solution by saponification, the influence of NaOH additions in oleic acid CWAO mechanism and catalyst performances have been investigated. The oxidation of such molecule occurs by two types of mechanisms: successive carboxy-decarboxylation which leads essentially to CO₂and/or C-C bonds splitting in the alkyl chain inducing a high formation of acetic acid. With or without NaOH, the 5%Pt/CeO₂catalyst is active in the conversion of oleic acid and selective to carbon dioxide. In alkaline medium, oleic acid is initially saponified which increases the solubility of the reactant before it to be oxidized. Finally the oxidation is slightly delayed by the presence of NaOH. The catalyst characterizations show no significant difference before and after reaction.</o:p>     

A comparative study of various computational approaches in calculating the structure of pyridoxal 5'-phosphate (PLP)-dependent beta-lyase protein. The importance of protein environment

Various computational approaches, using molecular mechanics (Amber), semiempirical (AM1), density functional (B3LYP), and various ONIOM methods, have been comparatively investigated for the structure of Escherichia coli NifS CsdB protein. The structure of the entire monomer containing 407 amino acid residues and 579 surrounding water molecules has been optimized. The full geometry optimization in the "active site-only" approach (including only active site atoms) has been found to give the largest root-mean-square (RMS) deviation from the X-ray structure; a much better agreement has been achieved by keeping the atoms leading to the backbones of some amino acids frozen in their positions in the X-ray structure. The best agreement has been attained by including the surrounding protein in the calculations using the two-layer ONIOM (B3LYP:Amber) approach. The results presented in this study conclusively demonstrate the importance of the protein/active-site interaction on the active-site structure of the enzyme. The present theoretical study represents the largest system studied at the ONIOM level to date, containing 7992 atoms, including 84 atoms in the QM region and rest in the MM region.     

杂富勒烯的电子结构与性质关系的研究──Ⅱ.C_(57)X_3,C_(56)X_4(X=B、N、P)的位置异构体

用 CNDO／2方法在 586微机上计算了 C57X3C56X4（X=B、N、P）的 234个位置异构体的电子结构。在C57X3（X=B、N、P）位置异构体中，C57X3（1，2，9）（X=B、N、P）分别是最稳定的。对于C56X4（X=B、N、P）位置异构体，C56B4（1，2，9，8），C56N4（1，2，9，12）和C56P4（1，2，9，12）分别是最稳定的，但稳定性都比C60差。其氧化或还原性都比 C60好，将它们和 C60比较，与 X相距一个或两个键的 C原子电荷密度增加或减少较多，其余电或亲核反应性增加；X与 X，X与 C原子之间 Wiberg Order都减少较多，其键的强度削弱；邻近杂原子的 C与 C原子之间 Wiberg Order减少或增加很少，其键的强度稍有削弱或增强。     

不饱和类碳烯H2C(=)CLiBr的DFT研究

采用量子化学计算方法，在B3LYP／6－311G^*水平上全优化得到了不饱和类碳烯H2C＝CLiBr的平衡结构，结果表明，不饱和类碳烯H2C＝CLiBr只有两种平衡结构，对这两种平衡结构之间相互转化的过渡态进行计算，求得了转化势垒，根据计算得到的微观性质，采用统计热力学方法，研究了两种平衡结构之间相互转化的热力学性质，进而讨论了两种平衡结构在不同温度下的稳定性问题，在计算得到振动频率及强度的基础上，模拟了稳定平衡结构的红外光谱图。     

Pseudobond ab initio QM/MM approach and its applications to enzyme reactions

This perspective article mainly focuses on the development and applications of a pseudobond ab initio QM/MM approach to study enzyme reactions. The following aspects of methodology development are discussed: the approaches for the QM/MM covalent boundary problem, an efficient iterative optimization procedure, the methods to determine enzyme reaction paths, and the approaches to calculate free energy change in enzyme reactions. Several applications are described to illustrate the capability of the methods. Finally, future directions are discussed.