On the Reactivity of Metal and Organometallic Halides and Pseudohalides Towards Stannosiloxane (Ph3Sn-O-SiPh3)

Abstract

Interactions of HgX₂ (X = Cl, Br, I, SCN, CN, NCO), SbCl₃, TeCl₄, and PhTeCl₃ with Ph₃Sn-O-SiPh₃ at room temperature have been found to proceed with the simultaneous cleavage of Sn-O and Si-O bonds, invariably yielding Ph₂SnO, Ph₃SiX, and the corresponding organo-mercury, -antimony, and -tellurium derivatives. The course of the reactions suggests the instability of the Sn-O-M (M = Hg, Sb, Te) system.

GRAPHICAL ABSTRACT      

Orlicz Figà – Talamanca Herz algebras and invariant means

The aim of this paper is to initiate a systematic study of the Orlicz Figà – Talamanca Herz algebras on locally compact groups. We also introduce and study invariant means on the dual of these algebras.     

重复率气体火花开关绝缘恢复特性的实验研究

 在自行设计的气体火花开关上，利用双脉冲回路，对纳秒脉冲作用下N₂和H₂的绝缘恢复特性进行了实验研究。结果表明，在静态不吹气情况下，H₂的绝缘恢复时间明显比N₂短。在吹气情况下，适当的气流速度即可使绝缘恢复时间明显缩短。     

Synthesis of (−)-elemoxide,a commercially important fragrance compound

(?)-Elemoxide, a fragrant compound was synthesised using commercially available elemol in four steps with overall yield of 32%. The cyclic ether skeleton was constructed via intramolecular hydroalkoxylation using I₂ and PhSiH₃ catalytic system. Also, intramolecular oxymercuration-demercuration was employed as an alternate approach for cyclization. The various regioselective strategies involving epoxidation of alkene, reduction of epoxide and intramolecular cyclization were the highlights of the work. The key intermediate diol serves as a versatile intermediate for the synthesis of elemoxide and elemene.     

Geometry of rank 2 distributions with nonzero Wilczynski invariants

In the famous 1910 “cinq variables” paper Cartan showed in particular that for maximally nonholonomic rank 2 distributions in ?⁵ with non-zero covariant binary biquadratic form the dimension of the pseudo-group of local symmetries does not exceed 7 and among such distributions he described the one-parametric family of distributions for which this pseudo-group is exactly 7-dimensional. Using the novel interpretation of the Cartan covariant binary biquadratic form via the classical Wilczynski invariant of curves in projective spaces associated with abnormal extremals of the distributions [4, 27, 28] one can generalize this Cartan result to rank 2 distributions in ?ⁿ satisfying certain genericity assumption, called maximality of class, for arbitrary n ≥ 5.

In the present paper for any rank 2 distribution of maximal class with at least one nonvanishing generalized Wilczynski invariants we construct the canonical frame on a (2n — 3)-dimensional bundle and describe explicitly the moduli spaces of the most symmetric models. The relation of our results to the divergence equivalence of Lagrangians of higher order is given as well.     

Some thoughts about the stability and reliability of commonly used exchange–correlation functionals – coverage of dynamic and nondynamic correlation effects

 The self-interaction error (SIE) of commonly used density functional theory (DFT) exchange functionals mimics long-range (nondynamic) pair correlation effects in an unspecified way. Slater exchange suffers from a larger SIE and, therefore, covers more nondynamic correlation effects than Becke exchange, which is the reason why exchange–correlation (XC) functionals based on Slater exchange lead to stabler restricted DFT solutions than those based on Becke exchange. However, the stability of an XC functional does not guarantee higher accuracy. On the contrary, if system-specific nondynamic correlation effects have to be introduced via the form of the wave function, these will be suppressed by nondynamic correlation effects already covered by the exchange functional. Hybrid functionals suffer less from the SIE and, therefore, cover a smaller number of nondynamic electron correlation effects. Accordingly, they are better suited when nondynamic electron correlation has to be introduced by the form of the wave function. It is shown that, for example, broken-symmetry unrestricted DFT calculations are more accurate when carried out with B3LYP than BLYP contrary to claims made in the literature. Received: 8 November 2001 / Accepted: 30 January 2002 / Published online: 8 April 2002     

Synthesis of New Macrocyclic Aryl Phosphonates. X-Ray Structure and Clathration Properties

Williamson condensation of bis-o-hydroxy aryl phosphonates with dihaloalkylaryl derivatives yields the title compounds. They show interesting stereochemical aspects and some of them can be used in chiral recognitions and separations.     

10MeV LIA强流电子束的聚焦

 研究了10MeV直线感应加速器（LIA）的输出束在螺线管透镜作用下的聚焦特性。通过解非线性电子轨迹方程获得实验所需的磁场范围，并解析分析空间电荷效应、发射度、透镜球面像差和色散像差对最小焦斑直径的限制，同时，对束质心螺旋运动影响束聚焦的情况亦做了较为详细的分析。实验结果表明：在合适的螺线管聚焦磁场下，可获得直径≤6mm的电子束焦斑，与理论分析结果基本一致。     

纳秒级脉宽砷化镓激光器陈列

 报导砷化镓激光器阵列的实验结果。该阵列光束的脉宽约0.7~5ns，近场光斑面积约100mm×6mm;已被用于触发高功率电磁脉冲发生器中的半导体光导开关阵列。报导一种提高光脉冲重复率的方法—双脉冲序列法。用该方法使激光脉冲等效重复率达约100MHz；介绍一种使激光器阵列输出光斑中光能均匀分布的多光束叠加方案。     

Structure of a di-zinc complex of a bis-calix[4]arene conjugate and its sensing of cysteine among the amino acids

Abstract

A triethylene glycol di-imine locked triazole linked bis-calix[4]arene conjugate (L) and its Zn²⁺ complex [Zn₂L], were synthesised, characterised and the three-dimentional (3-D) structure of the complex was established by single crystal XRD. In this complex, the Zn²⁺ centre exhibits distorted tetrahedral geometry with N₂O₂ binding core. The complex showed selectivity towards cysteine (Cys) with greater sensitivity followed by histidine (His) among the naturally occurring amino acids studied based on fluorescence and absorption spectroscopy. The fluorescence quenching of the complex is much greater with Cys as compared to that of His. The detection limit of Cys is 650 ppb. Release of Zn²⁺ from its complex [Zn₂L] followed by its capture by –SH containing molecules was shown based on absorption and emission spectroscopy. This was also shown in one case by ¹H NMR spectroscopy.