Synthesis and magnetic properties of an iron 1,2-bisthienyl perfluorocyclopentene photochromic coordination compound

The coordination compound Fe(BM-4-PTP)₂(NCS)₂⋅2MeOH (1) including the photoisomerizable ligand BM-4-PTP (1,2-bis(2′-methyl-5′-(pyrid-4″-yl)thien-3′-yl)perfluorocyclopentene) was obtained as an orange powder. The powder turns blue upon photocyclization of the 1,2-bisthienyl photochromic ligand induced by UV light irradiation at room temperature. Photocycloreversion is obtained by visible light irradiation of the material in the solid state. The orange and blue powders were investigated over the temperature range (5-293 K) and pressure range (1 bar-12 kbar) by magnetic susceptibility measurements and variable temperature ⁵⁷Fe Mössbauer spectroscopy. The photo-induced colour change is accompanied by a distinct magnetic variation at room temperature. Potentialities of this functional optical material for display and data recording are introduced.     

Finite element simulation of low-density thermally bonded nonwoven materials: Effects of orientation distribution function and arrangement of bond points

A random and discontinuous microstructure is one of the most characteristic features of a low-density thermally bonded nonwoven material, and it affects their mechanical properties significantly. To understand their effect of microstructure on the overall mechanical properties of the nonwoven material, discontinuous models are developed incorporating random discontinuous structures representing microstructures of a real nonwoven material. Experimentally measured elastic material properties of polypropylene fibres are introduced into the models to simulate the tensile behaviour of the material for its both principle directions: machine direction and cross direction. Additionally, varying arrangements of bond points and schemes of fibres’ orientation distribution are implemented in the models to analyse the respective effects.     

The structure of monomeric components of self-assembling CXCR4 antagonists determines the architecture of resulting nanostructures

Self-assembling peptides play increasingly important roles in the development of novel materials and drug delivery vehicles. Understanding mechanisms governing the assembly of nanoarchitectures is essential for the generation of peptide-based nanodevices. We find that a cone-shaped derivative of the second transmembrane domain of CXCR4 receptor, x4-2-6 self-assembles into nanospheres, while a related cylindrical peptide, x4-2-9 forms fibrils. Stronger intermolecular interactions in nanospheres than in fibrils result in slow rates of particle disassembly and protection against proteolytic degradation.     

用于持续电源应用的热插拔连接器

目前,许多公司要求其通讯、监控、存储或控制用的电子系统不得失效。电信和公用事业公司显然首当其冲采纳了这一主张。但是,将电气系统的停工时间保持到绝对低程度的要求使得现在即使很小的公司在其计算机特别是电源系统结构中均采用了备用功能。 N 1 备用系统允许现场替换失效的程序存储单元(PSU),而不必关闭整个系统。这种方法不仅能确保效率更高、停工时间更少,而且符合产业发展趋势,如日益采用模块式叠层系统和更小的产品占用面积等。此外,如果系统可以重新设置且不需要关闭,则现场维护和日常系统升级会更简单且破坏性更小。 持续电源应用,即允许现场替换电源装置同时保持完整的正常运行时间,全都基于某种形式的“热插拔”或“热替换”连接器系统,而这两个术语经常被混淆。二者均消除了系统停工时间,但热替换系统是一种先断后插的技术,在这种技术中,电流只是在插合过程的最后阶段触发流动,而实际的热插拔接触件结构允许系统和界面连接器带电插拔而不中断电流。设计“热插拔”接触件是为了在这种带电条件下保持机械强度和电导率,并能够经受住在插合过程中发生的可能具有破坏性的电弧放电。当选择最适合应用的技术时,考虑到有多少空间供互连系统占用是同样重要的。热替换技...     

Electrically controlled light scattering in FLC cells

Abstract— Three types of light‐scattering effects distinguished by physical mechanisms were studied in detail in monomeric ferroelectric liquid‐crystal (FLC) compositions at different boundary conditions and electrical pulse regimes. The total time of the scattering switching on and switching off is less than 150, 250, and 500 μsec at ±50 V for different scattering types in helix and non‐helix FLCs. They are quite fast, and FLC cells are quite transparent and were used in a stack of 30–100 light‐scattering shutters for a volumetric screen of a 3‐D display.     

Stability of natural convection between spherical shells: energy theory

The energy stability problem with respect to axisymmetric disturbances of the natural convection in the narrow gap between two spherical shells under the earth gravity is discussed. The results are compared with the results of the linear stability analysis for the same problem. The problem is solved for different fluids with Pr=0-100 and different radius ratios η=0.9,0.925,0.95. With the aid of the variational principle Euler-Lagrange equations are received, which have the form of an eigenvalue problem, that is solved by means of Galerkin-Chebyshev spectral method. The convergence problem and the dependence of the critical stability parameter on Prandtl number are discussed. The calculations show that there is a big difference between critical numbers for energy and linear stability theories for the small Prandtl numbers. For large Prandtl numbers this difference is very small.     

对法国电信经营管理的体会

今年６月，笔者参加了黑龙江省邮电管理局赴法国电信局高级管理培训班，对法国电信的经营管理，网络运行管理系统进行了全面的参观学习有关专家全面系统地介绍了法国电信的经营管理情况，中法双方进行了经验交流。     

Gearing optimization

We consider an optimization problem that arises in machine-tool design. It deals with optimization of the structure of gearbox, which is normally represented by a graph. The edges of such a graph correspond to pairs of gear-wheels and the vertices stand for velocities. There is a designated input vertex and a set of output vertices. The problem is to create a graph with given number of output vertices while minimizing the total number of vertices. We present an integer programming formulation of this problem and propose an efficient solution in the special case of regular graphs. The author gratefully acknowledges the support of DIMAP—the Center for Discrete Mathematics and its Applications at the University of Warwick.