Action du n-butyllithium sur les bromo-3 halogeno-2 pyridines fluoree,chloree et bromee : Principe et etude d'une possibilite reactionnelle nouvelle : l'homotransmetallation

Apart from the common bromine-lithium exchange reaction in brominated aromatic compounds, it is possible to obtain a lithio-derivative quite different from the one usually described in such a reaction. This new reaction, which results from a special experimental conditions is called ·homotransmetalation”, and it occurs when using n-butyllithium and 3-bromo 2-halogenopyridines (1). Different behaviour is observed with the three similar compounds (1: X = F,Cl,Br). Explanations are proposed of these results. It is then possible to compare the relative stabilities of the proposed lithio-structures. It is evident that nucleophilic substitution of bromine in position 4 of the pyridine ring is easier than is usually recognised.     

Morphology and properties of cyanate ester/liquid polyurethane/silica nanocomposites

The high‐speed homogeneous shearing method was applied to prepare nanocomposites of cyanate ester (CE) with liquid polyurethane elastomer (PUR) and silica. To investigate the influence of various components on the morphology and properties of the ternary composites, the binary composites of CE/PUR and CE/silica were also involved in this article. The morphology of the cured materials of binary and ternary systems was investigated by transmission electron microscopy (TEM), and the results show that silica nanoparticles were uniformly distributed in the ternary and binary matrix. Phase separation of elastomer in composites was not observed by TEM. FTIR test and dynamic mechanical analysis (DMA) proved that chemical linking was existent between PUR and CE. Scanning electron microscopy examinations and mechanical properties tests were carried out. The results show that ternary composites displayed higher fracture toughness and impact strength compared with most of the binary systems. This suggests that the addition of PUR and nanosilica can synergistically improve the toughness of CE. DMA studies confirmed that the incorporation of silica can increase the storage modulus and T_g for CE and CE/PUR system, since there are a good adhesion and a strong hydrogen bonding between silica and polymers. The thermal property of ternary composites increases with the increase of silica nanoparticle loading. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1243–1251, 2008     

电力系统集结二阶及外部系统分割降阶法

本文对电力系统的动态结构特性及降阶方法进行了研究,提出了二阶集结及外部系统分割两种降阶方法。它们是建立在系统动态结构特性-模式-机组关联特性基础上的。前者将一个n台机的电力系统降为一个2n×2n阶的包括全部转子摇摆模式的模型,后者可用一个更低阶的模型算出与局部系统有关的全部模式。     

植物病毒病化学防治剂的探寻Ⅴ．N－（2－取代丙基）DHT的制备及抗病毒活性

合成了６个Ｎ－溴丙基，含氮杂环丙基ＤＨＴ衍生物．新化合物的水溶性、脂溶性较好，它们对烟草花叶病毒的抑制率在５０％左右     

低密度聚乙烯光引发交联机理Ⅲ.模型化合物n-C24H50的13C NMR研究

用溶液高分辨¹³C NMR谱首次研究了由二苯甲酮(BP)光引发低密度聚乙烯模型化合物直链烷烃n-C₂₄H₅₀交联所产生的H型交联点的结构特征.现已检测和鉴定了光交联样品中与H型交联点相联系的-CH,α-CH₂和β-CH₂上碳的共振谱线,其数据与H型交联点模型化合物、γ-辐射交联正烷烃和聚乙烯所得到的结果符合得很好.在40.83ppm处出现的一个新峰可指认为H型文联点的次甲碳,其相应的31.57和28.37ppm处的另外两个新峰分别指认为相邻的α-CH₂和β-CH₂上碳的共振.本工作中的定量研究表明:在真空和熔融态条件下莱外光照3-5min的样品中H型交联点的数目据估计为每10000个碳原子8.5~11.0个.     

低密度聚乙烯光引发交联机理IV.H-和Y-型交联点结构的13C NMR研究

首次用溶液高分辨¹³C NMR研究了由二苯甲酮光引发低密度聚乙烯(LDPE)交联所产生的交联结构,现已观测和鉴定了H型和Y型长链支化两类交联点。对于熔融态紫外光交联5-10s的LDPE样品,其H型和Y型交联点的浓度据估测分别为一万个碳原子中有5.7-16.9和7.6-21.6个结构单元。     

镨甘氨酸高氯酸盐的低温热容和标准生成焓的测定

合成了一种稀土镨DL α甘氨酸配合物高氯酸盐晶体.经热重、差热及元素的化学分析,确定其组成是[Pr2 (DL αGly)6 (H2O)4 ] (ClO4 )6·5H2O,纯度是99. 63%.熔点分析仪分析知其没有固定熔点. 在79~371K,用高精密全自动绝热量热仪对晶体配合物进行了热容测定,发现该配合物在低温段没有反常热容. 333K附近是该配合物的分解温区,配合物的分解温度、分解焓和分解熵分别是320. 010K、40. 714kJ/mol和127. 227J/molK.计算机拟合了在78. 939~301. 295K热容对温度的多项式方程. 在常压、298. 15K下,用具有恒温环境的反应热量计测定了配合物的标准生成焓值为-8022. 802kJ/mol.     

极端嗜盐菌冻干保藏及其质检稳定性的研究

采用优化组合保护剂冷冻干燥２０株极端嗜盐菌，于４℃冷库保存２年，经复水测定，全部菌株保持较高存活性．用ＴＥＮＳ法对其中９株菌Ｒ１，ＲＦ１，Ｊ７，Ｓ９，Ｔ４～１，Ｊ６，Ｒ６～１，Ｒ６～７和Ｒ６～５作质粒稳定性检测，含质粒的菌株ＲＦ１，Ｊ７，Ｓ９，Ｔ４～１，Ｒ６～５于４℃保存２年后，质粒稳定存在；而菌株Ｒ１，Ｊ８，Ｒ６～１和Ｒ６～７冻干保存前后均末检测到质粒．结果表明：优化组合保护剂不仅能有效地用于极端嗜盐菌的冷冻干燥保藏，还能保持宿主质粒的稳定性．     

POSITIVE SOLUTIONS AND BIFURCATION OF FULLY NONLINEAR ELLIPTIC EQUATIONS INVOLVING SUPER－CRITICAL SOBOLEV EXPONENTS

ＰＯＳＩＴＩＶＥＳＯＬＵＴＩＯＮＳＡＮＤＢＩＦＵＲＣＡＴＩＯＮＯＦＦＵＬＬＹＮＯＮＬＩＮＥＡＲＥＬＬＩＰＴＩＣＥＱＵＡＴＩＯＮＳＩＮＶＯＬＶＩＮＧＳＵＰＥＲ－ＣＲＩＴＩＣＡＬＳＯＢＯＬＥＶＥＸＰＯＮＥＮＴＳ￥ＱＵＣＨＡＮＧＺＨＥＮＧ（屈长征）（Ｉｎｓ...