19F NMR study of relative polarities and reactivities of N-H,N-Hg,and N-Au bonds in 2-(4-fluorophenyl)benzimidazole and its PhHg and Ph3PAu derivatives in intermolecular exchange

It has been shown by the¹⁹F NMR method that the relative polarities of nitrogenelement bonds in 2-(4-fluorophenyl)benzimidazole and its PhHg and PPh₃Au derivatives increase in the order N-H19F NMR. It has been found that these reactions occur by a bimolecular associative mechanism and that the N-H bond is substantially less reactive than the N-Hg and N-Au bonds, which have identical reactivities within the limits of sensitivity of the method used.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1574–1580, August, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No. 93-03-5528).     

Spectroscopic studies of new model compounds for poly[N,N′-bis(phenoxyphenyl)pyromellitimide]

New model compounds for poly[N,N′-bis(phenoxyphenyl)pyromellitimide] have been synthesized in order to investigate the formation of imine bonds which are proposed to form during the curing process and lead to crosslinking in the bulk polymer. Raman studies show that terminal amines can react with imide carbonyls during curing to form C?N bonds. The Raman band due to C?N appears at 1656 cm^?1 and the band due to C?O closest to the imine bond is observed at 1742 cm^?1. These results are in agreement with previously published results on vapor deposited polyimide films.     

1-甲基环氧乙烷-1-丙炔醚的结构测定及其核磁图谱

以¹H-NMR谱和¹³C双自旋回波的APT脉冲序列测定文献中尚未曾发表的化合物HC≡C-CH₂-O-C^CH₃-_O-CH₂文中计算了峰强度与脉冲间隔时间的关系,讨论了各谱线的相位并区分出-CH₃、-CH₂、-CH和季碳。     

Solvent effects in the fluorination of 1,2-dichloro-1,1-difluoroethane (R-132b) to 2-chloro-1,1,1-trifluoroethane (R-133a)

Trichloroethylene has been found to act as a rate enhancing co-factor in the liquid phase, tantalum (V) halide catalyzed, fluorine-for-chlorine exchange reaction of 1,2-dichloro-1,1-difluoroethane (R-132b) to 2-chloro-1,1,1-trifluorethane (R-133a). Several trifluoromethyl substituted benzenes have also been found to be rate-enhancing solvents.     

Illuminating Molecular Processes in Living Cells

Lately, scientists have explored approaches to developing fluorescent and/or bioluminescent indicators to pinpoint cellular processes in single living cells. These analytical methods have become a key technology for visualizing and detecting what was otherwise unseen in live cells. The target signaling included second messengers, protein phosphorylations, protein–protein interactions, and protein localizations.     

N—烃氧丙酰基四氢噻唑—2—硫酮的合成

在三聚氯氰存在下由烃氧丙酸与四氢噻唑-2-硫酮反应得到N-烃氧丙酰四氢噻哇-2-硫酮(2a-i),由2a,c-h与格氏试剂反应得到烃氧乙基苯基酮(3a,c-h).产物2a-i未见报道.     

A mixed directed-undirected data structure for a parallel implementation of a domain decomposition algorithm

The choice of data structures influences the parallelization, efficiency and the manageability of a mesh refinement program. We introduce a mixed directed-undirected graph that combines both communication and scheduling needs. An inverted index is maintained for the directed graph to improve code performance and readability.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.     

一维应变压缩下TC4钛合金绝热剪切研究

 利用内径为57 mm的压缩气炮，在撞击速度为0.2~1.2 km/s（相应的靶中压力为3~15 GPa）范围内进行对称碰撞实验，以研究TC4（Ti-Al6-V4）钛合金在一维应变冲击压缩条件下的绝热剪切现象。对回收得到的受冲击样品，在扫描电镜（SEM）下进行细观金相分析。结果指出，一维应变冲击压缩条件下，TC4钛合金中绝热剪切带产生的对称碰撞速度阈值为500 m/s（相当于样品中的压力为5.87 GPa）；主剪切带与冲击方向约为45°角，带上有圆形和椭圆形两种孔洞且随碰撞速度的增大而增多和长大，这是典型的韧性损伤特征。随碰撞速度增大，产生与主剪切带成15°角的支剪切带。这些与理论预言相符。X射线能谱分析结果指出，剪切带内材料发生了(α+β)→β相的转变，是典型的相变带。剪切带的温度估算与实验提供的信息吻合。