Oligomerization and Polymerization of Ethylene Initiated by a Novel Ni(Ⅱ)-Based Acetyliminopyridine Complexes as Single-Site Catalysts

Novel Ni(Ⅱ)-based acetyliminopyridine complexes 1b, 2b, 3b (1-3b), which are synthesized from ligands 1a, 2a, 3a (1-3a) and [NiCl2(DME)], are suitable precursors for the catalysts that are necessary for ethylene oligomerization and polymerization reactions, activated by methylaluminoxane (MAO). The MAO-treated 1-3b presents an active catalytic center, which may oligomerize and polymerize ethylene to produce linearα-olefins and polyethylene, respectively. The molecular weight distributions of oligomers that are obtained are in good agreement with the Schulz-Flory rules for oligomers>C4. The activity of 3b-MAO complex is 6.3×107 g/(molNi·h) at 50℃. The activities and molecular weight distributions of oligomers show significant reliance on the structures of catalyst precursors.     

Synthesis of oligo(p-phenylene vinylene)-porphyrin-oligo(p-phenylene vinylene) triads as antenna molecules for energy transfer

The oligo(p-phenylene vinylene)-porphyrin-oligo(p-phenylene vinylene) (P-OPVn, n=2, 4, where n is the number of phenyl rings) and the complex with Zn²⁺ based on P-OPVn were synthesized for investigating their photophysical properties via UV-vis, voltammetry, steady-state and time-resolved fluorescence spectra. In these molecules two OPV moieties as energy donors were linked to porphyrin center by virtue of Wittig reaction. The detailed studies of photophysical properties indicate that OPV group can act as an antenna unit for effective intramolecular energy transfer.     

基于DNA的细胞膜功能化

细胞膜在细胞与外界环境间的物质运输、能量转换和信息传递等过程中起着重要作用,研究和控制细胞膜上的分子的相互作用,对理解和操控细胞的生理功能具有重要意义。脱氧核糖核酸(Deoxyribonucleic acid, DNA)分子具有精确自组装和可编程的特性,是一种研究生物膜分子相互作用的新工具。本综述中,我们概括了DNA分子修饰细胞膜的方法,随后介绍了基于DNA分子的监测、控制细胞膜分子相互作用的工作以及DNA分子介导细胞连接的研究,并分析了上述研究的局限性。最后,我们对基于DNA的细胞膜功能化研究进行总结与展望,以期促进对细胞膜功能的新认识,获得控制细胞功能的新方法。     

新显色剂噻二唑偶氮二甲氨基苯甲酸与铜(Ⅱ)显色反应的研究和应用

本文研究了噻二唑偶氮二甲氨基苯甲酸与Cu(Ⅱ)显色反应条件,确定在pH3.0～4.5范围形成蓝紫色络合物,组成比为1:1,摩尔吸光系数ε=4.55×10~4L·mol~(-1)·cm~(-1),1gβ=7.32。应用拟定的方法测定天然水中微量铜,获得满意的结果。     

Flow-injection analysis based on a membrane separation module and a bulk acoustic wave impedance sensor – determination of the volatile acidity of fermentation products

A novel flow-injection analysis (FIA) system has been developed for the rapid determination of the volatile acidity of some fermentation products like vinegars and juices. The proposed method is based on the diffusion of volatile acids, mainly acetic acid, across a PTFE gas-permeable membrane from an acid stream into an alkaline stream, and the acids trapped in the acceptor solution are determined online by a bulk acoustic wave impedance sensor based on changes in the conductivity of the solution. It exhibited a linear frequency response up to 10 mmol · L^–1 acetic acid with a detection limit of 50 μmol · L^–1, and the precision was better than 1% (RSD) at a through-put of 72 h^–1. The effects of operating voltage for the detector, cell constant of the electrode, composition of acceptor stream, flow rates and temperature on the FIA performance were also investigated. Received: 2 June 1997 / Revised: 7 July 1997 / Accepted: 12 July 1997     

非超临界干燥法制备SiO2气凝胶

应用廉价的国产硅溶胶为原料，通过凝胶过程和干燥过程条件的选择，以非超临界干燥技术最终获得了块状SiO2气凝胶.该气凝胶外观状态与应用正硅酸乙酯为原料制得的完全一致，其微观结构也相当良好，其直径和孔分布均匀.溶液的配比和pH对凝胶过程和气凝胶样品的密度有比较明显的影响，同时pH值与SiO2的粒径之间也有一定的关系.依据制备条件的变化，所得SiO2气凝胶的密度约在200～400 kg•m－3，比表面在250～300 m2•g－1之间变化，平均孔径约为11～20 nm，而孔隙率在91％左右.     

压电石英晶体在电解质水溶液中的振荡性能研究(Ⅱ)——频率、频移特性

根据两面电极浸入液体中的压电晶体等效电路模型和Pierce振荡器振荡方程的解,得到晶体在电解质溶液中的振荡频率(F_1)与溶液电导率(x)的关系式:F_1=(1/2π)(1/C_1+1/C_2)(1/X_e)[(R_e~2+X_e~2)x~2+2R_ex+1]。以自行设计的Pierce晶体振荡器。研究了晶体和主振电路参数、输入电压及检测池外壳屏蔽接地对AT切9MHz石英晶体在KCl、Na_2SO_4水溶液中的频率、相对于纯水频移随溶液电导率变化的影响规律,结果与上式相符。