Optimal group symmetric localized molecular orbitals

Summary The concept and generating method of optimum group symmetric localized molecular orbitals (OSLMOs) are proposed. The OSLMOs have strong points of orthogonality, equivalence and symmetry, and they are simultaneously as close to the classical VB structure as possible. By using the OSLMOs as one-electron orbitals the multiconfigurational correlation calculations are reduced. The scheme is also a valuable popularization and development to hybridization theory.     

PU/MOMMT纳米复合材料的制备与研究

纳米复合材料由于其纳米尺寸效应，表面效应以及纳米粒子与基体界面间强的相互作用，具有优于相同组分常规复合材料的力学、热学等性能，引起了人们的广泛关注。用纳米材料改性聚合物，制备纳米复合材料是获得高性能高分子复合材料的重要方法。1998年以来，Pinnavaia等首先制备了聚氨酯，蒙脱土（PU／MMT）纳米复合材料，研究了有机蒙脱土在聚醚中的分散性。其后Chen等将聚羟基己内酯/蒙脱土（PCL／MMT）纳米复合材料加入到PCL和二苯基甲烷-4，4＇-二异氰酸酯（MDI）合成的预聚体与1，4-丁二醇扩链反应后的溶液中，制备了PU／MMT纳米复合材料。少量PCL／MMT的引入可使复合材料的综合性能大幅提高。     

Solid-phase synthesis and spectral properties of 2-alkylthio-6H-pyrano[2,3-f]benzimidazole-6-ones: a combinatorial approach for 2-alkylthioimidazocoumarins

The solid-phase synthesis of 2-alkylthio-6H-pyrano[2,3-f]benzimidazole-6-ones (2-alkylthioimidazocoumarins) is described. 7-Fluoro-4-methyl-6-nitro-2-oxo-2H-1-benzopyran-3-carboxylic acid was coupled to Rink amide resin via its carboxyl group. The resin-bound scaffold then underwent aromatic nucleophilic substitution with primary amines, followed by reduction of the nitro group with tin (II) chloride. Subsequent cyclization of the o-dianilino intermediates with thiocarbonyldiimidazole (TCD) afforded resin-bound 1,3-dihydro-2-thioxo-6H-pyrano[2,3-f]benzimidazole-6-ones, which were then S-alkylated with alkyl halides in the presence of N,N-diisopropylethylamine (DIEA). The desired products were obtained in good yield with high purity after trifluoroacetic acid cleavage. The unique spectral properties of 2-alkylthioimidazocoumarins indicate that they may be useful in photodynamic therapy.     

高锌试样中痕量锗的吸光光度法测定

建立了高锌试样中痕量锗的快速光度分析方法,显色条件为8×10~(-5)mol·L~(-1)SAF 0.8g·L~(-1)OP 2.4mol·L~(-1)盐酸,λ_(max)为510nm,锗浓度在0.05～5μg/25ml范围内符合比耳定律,摩尔吸光系数为1.3 ×10~5.     

聚氨酯/蒙脱土纳米复合材料的制备与性能研究

纳米复合材料由于其纳米尺寸效应 ,表面效应以及纳米粒子与基体界面间强的相互作用 ,具有优于相同组分常规复合材料的力学 ,热学等性能 ,引起了人们的广泛关注 .用纳米材料改性聚合物 ,制备纳米复合材料是获得高性能高分子复合材料的重要方法 ,采用较多的是插层复合法 ,可分为两类 ,一是单体预先插层于层状结构填料的晶片层间 ,然后聚合 ;二是聚合物溶液或熔体直接插层于层状结构填料的晶片层间 .聚氨酯 (PU)是由多异氰酸酯与多元醇通过加聚反应而形成的高聚物 ,其重复结构单元是氨基甲酸酯链段( R2 OCONHR1NHCOO) .PU弹性体具有耐磨…     

稀土在汽车尾气净化催化剂中的作用

通过对稀土在汽车尾气净化催化剂中的作用综述,阐明随着贵金属资源的日趋耗竭和越来越严格的排放法规在全世界范围的推行,稀土在高性价比汽车尾气净化催化剂中必将扮演越来越重要的角色,发挥其它元素甚至贵金属元素都无法取代的作用.     

PROMOTERS IN THE CATALYST SYSTEM FOR METHANOL CARBONYLATION TO METHYL FORMATE

在一个机械搅拌式反应器中，在反应温度为６０～９０℃，压力为３～６ＭＰａ条件下试验了几种不同类型的化合物作为甲醇催化羰化合成甲酸甲酯碱金属醇碱催化剂的助催化剂。结果发现，在甲醇羰化制甲酸甲酯反应中，是助催化剂的极性而不是碱性起着重要的作用。同时证明，强极性非质子型化合物对该羰化反应具有良好的助催效果，乙腈则是一个例外。     

Studies on injector pump-ultrasonic nebulizer feeding sample system for MPT-AES

The feeding-sample system used by microwave plasma torch atomic emission spectroscopy (MPT-AES) is the pneumatic nebulization system; its efficiency, however, is not good. A newly built injector pump-ultrasonic nebulizer combination feeding-sample system has been designed. Its performance was tested and compared with that of the pneumatic nebulization system. It can be concluded that the newly built feeding-sample system can increase the spectral line intensity by about two to three times and decrease the detection limit by about 2 to 10 times. Moreover, this newly built system can reduce the time taken washing the sample cell from 30 min or so to about 10 min. __________ Translated from Journal of JiLin University(Science edition), 2005, 43(4)(in Chinese)     

低功率微波等离子体炬原子发射光谱法的研究——超声雾化进样测定金、银、铂、铑、钯

本文提出一种测定贵金属元素的微波等离子体炬原子发射光谱法(MPTAES)。采用自制的超声雾化微量进样装置进样,以氩气为工作气体,探讨了观察高度,微波功率、体系介质、氩气流量和共存元素对被测元素发射信号的影响。选用合适的分析线和MPT光源的工作参数,其方法的检出限分别为5.8(Au)、0.5(Ag)、12(Pt)、1.6(Rh)和t 1.0ng/ml(Pd)。实际样品中金和银的测定结果是令人满意的。