A Short and Highly Stereoselective Synthesis of Cerebrosterol

Ｃｅｒｅｂｒｏｓｔｅｒｏｌ (2 4Ｓ ｈｙｄｒｏｘｙｃｈｏｌｅｓｔｅｒｏｌ,1)ｆｏｒｍｅｄｉｎｓｍａｌｌａｍｏｕｎｔｓｉｎｈｕｍａｎａｎｄａｎｉｍａｌｂｒａｉｎ1ｆｒｏｍｃｈｏｌｅｓ ｔｅｒｏｌｉｓｉｍｐｏｒｔａｎｔｆｏｒｃｈｏｌｅｓｔｅｒｏｌｈｏｍｅｏｓｔａｓｉｓｉｎｔｈｉｓｏｒｇａｎ .Ｔｈｅｅｘｃｅｓｓｃｈｏｌｅｓｔｅｒｏｌｉｓｃｏｎｖｅｒｔｅｄｉｎｔｏ 2 4Ｓ ｈｙｄｒｏｘｙ ｃｈｏｌｅｓｔｅｒｏｌｂｙａｕｎｉｑｕｅｂｒａｉｎ ｓｐｅｃｉｆｉｃ 2 4Ｓ ｈｙｄｒｏｘｙｌａｓｅ ,ｗｈｉｃｈｃｏｕｌｄｂｅｒ…     

取向、结晶、γ辐照聚对苯二甲酸乙二醇酯(PET)驻极体的陷阱性质

 用拉伸、热处理和γ射线辐照的方法制备了一系列具有不同平面取向度、不同结晶度和不同分子链长度的PET试样.随平面取向度、结晶度和辐照剂量的增大,平均陷阱深度加深.由拉伸取向形成的结构陷阱俘获载流子能力随取向度增大而提高;由γ辐照形成的结构陷阱对俘获载流子的限制能力随辐照剂量增大而降低;由热结晶形成的结构陷阱俘获载流子能力在结晶度为20％时达到极值.提出了相应的三种陷阱模型.     

Synthesis, Characterization and Catalysis of New Pillared Anionic Clays by [GaW_(11)O_(39)M(H_2O)]~(7-)(M=Mn~(2 ),Co~(2 ) or Ni~(2 ))

ＩｎｔｒｏｄｕｃｔｉｏｎＡｎｉｏｎｉｃｃｌａｙｓ（ｌａｙｅｒｅｄｄｏｕｂｌｅｈｙｄｒｏｘｉｄｅｓ）ａｒｅｉｍｐｏｒｔａｎｔｌａｙｅｒｅｄｍａｔｅｒｉａｌｓ．Ｔｈｅｇｅｎｅｒａｌｆｏｒｍｕｌａｉｓ［Ｍ２＋（１－ｘ）Ｍｘ３＋（ＯＨ）２］ｘ＋Ａｎ－ｘ／ｎｍ...     

水合醋酸铈直接热分解制备超细氧化铈及其抛光性能

Ultra fine ceria was prepared by calcining hydrate cerium acetate. The effects of pyrolysis temperature on the particle size, morphology, specific surface area and loose packing density of ceria were investigated, and the removal rate of optical glasses polishing by ceria was determined. The results show that with the increase of pyrolysis temperature, the loose deposit density and crystallinity increases and the specific surface area decreases, however, the particle size decreases firstly and then increases, the minimum medium particle size D₅₀ is 0.47 μm at pyrolysis temperature of 1 000 ℃. The SEM images of ceria prepared by the decomposition at 800 ℃ or at 1 100 ℃ show porous powders or quasi-sphere small particles with loosely agglomeration, respectively. It was found that the removal rate varied with pyrolysis temperature in preparation of ceria and the property of glass polished. The removal rate for three kinds of glasses was in the order of ZF7> F1> K9, and the maximum value appeared at around 1 000 ℃ for ZF7 and F1, and at around 1 100 ℃ for K9.     

Anderson结构铁钼杂多酸稀土盐的合成与结构表征

制备了具有Anderson结构的铁钼杂多酸稀土盐，经元素组成分析、TG和ICP确定其通式为Ln[FeMo6O24H6](Ln^3 =La，Ce，Pr，Nd，Sm，Gd，Dy，Yb)．采用IR，UV,^95Mo-NMR，XRD等方法进行了结构表征，发现在IR光谱图上呈现出羟基和H2O的两个振动谱带，并进行了归属，表明此类杂多酸稀土盐属Anderson结构B型．借鉴TG-DTA、不同温度下的IR和XRD及水溶性实验对Ln[FeMo6O24H6]和(NH4)3[FeMo6O24H6]的热解性质研究表明，此类杂多酸稀土盐的分解温度为350～400℃．比母体酸盐的热稳定性提高了10℃．     

Study on EPR Spectra of Three Gadolinium Complexes With Noncyclic Polyether Schiff Bases

The EPR spectra of three new gadolinium complexes with noncyclic polyether Schiff bases in powder and those of these complexes in organic solvents were investigated at different temperatures. It was observed that EPR spectra of nine and four peaks of Gd(Ⅲ) complexes in polycrystalline powder and freezing samples appeared at low temperature respectively for the first time. The interpretations of these results obtained on the basis of spin Hamiltonian of s = 7/2 system are satisfactory. The correlations of EPR feature between crystal-field strength in complexes and local symmetry around Gd3+ ions were revealed. The crystal-field parameters b20 and the asymmetry parameters λ' of complexes were estimated. A series of interesting regularity and new results were obtained.     

在活化剂邻菲罗啉存在下溴酸钾氧化胭脂红褪色催化光度法测定微量铁

基于在弱硫酸介质中及活化剂邻菲罗啉存在下 ,微量铁对溴酸钾氧化胭脂红的褪色反应有强烈的催化作用 ,由此建立了催化光度法测定微量铁的方法。该方法的检出限为 1.2× 10 - 10 g·ml- 1,测定范围为 0～ 0 .2 μg/2 5ml ,催化反应的表观活化能为 15 2 .7kJ·mol- 1。方法应用于大米、水样中微量铁的测定 ,结果满意。     

钴铬水滑石的合成及表征

采用共沉淀法合成了一系列不同Co/Cr物质的量比的碳酸根型水滑石。用X－衍射、红外光谱、差热、热重、分光光度等方法对其组成和结构进行了研究。结果表明Co/Cr投料比为2到3时能形成结晶度好、纯度高的水滑石。初步推测了部分产物的组成及所含水滑石的化学式。     

聚苯胺纳米点阵列的制备和库仑台阶现象

本文制备了PANI纳米点阵列, 利用导电原子力显微镜(C-AFM)表征了其形貌和导电性能, 在室温下观察到PANI纳米点的库仑台阶(Coulomb staircase)现象, 并利用库仑阻塞效应的理论进行了初步的分析.     

反应原料组成对单分散苯乙烯微球粒径及其分布的影响

采用分散聚合工艺制备微米级单分散聚苯乙烯微球，并对分散聚合反应的内部影响因素(分散稳定剂、助稳定剂、单体、引发剂)进行了研究．结果表明，随着分散稳定剂和助稳定剂用量的增加，聚苯乙烯微球的粒径减小；随着单体和引发剂用量的增加，聚苯乙烯微球的粒径增大．分散稳定剂和单体用量是影响聚苯乙烯微球粒径分布的两个主要内部因素．