Molecular Dynamics Simulation of Sub‐Transition for Polyethersulfone

Molecular dynamics (MD) simulations of a polyethersulfone (PES) chain are carried out in the amorphous state by using the Dreiding 2.21 force field at four temperatures. Two types of molecular motion, i.e. rotations of phenylene rings and torsions of large segments containing two oxygen atoms, two sulfur atoms, and five phenylene rings on the backbone, are simulated. The modeling results show that the successive phenylene rings should be in‐phase cooperative rotations, whereas the successive large segments should be out‐of‐phase cooperative torsions. By calculating the diffusion coefficient for the phenylene ring rotations, it is found that this rotation contributes to the β‐transition of PES.     

Monte Carlo Simulation of Phase Behavior of Polymer Blends with Special Interactions

The phase behavior of A–B-random copolymer/C-homopolymer blends with special interaction was studied by a Monte Carlo simulation in two dimensions. The interaction between segment A and segment C was repulsive, whereas it was attractive between segment B and segment C. The simulation results showed that the blend became two large co-continuous phase domains at lower segment-B component compositions, indicating that the blend showed spinodal decomposition. With an increase of the segment-B component, the miscibility between the copolymer and the polymer was gradually improved up to being miscible. In addition, it was found that segment B tended to move to the surface of the copolymer phase in the case of a lower component of segment B. On the other hand, it was observed that the average end-to-end distances (h) for both copolymer and polymer changed slowly with increasing segment-B component of the copolymer up to 40%, thereafter they increased considerably with increasing segment B component. Moreover, it was found that the h of the copolymer was obviously shorter than that of the homopolymer for the segment-B composition region from 0% to 80%. Finally, a phase diagram showing I phase and II phase regions under the condition of constant temperature is presented.     

BN纳米带几何结构和电子性质第一性原理研究

本文采用第一性原理研究了不同带宽下BN纳米带的几何结构与电子性质。研究结果表明：随着带宽的增大,BN纳米带边缘发生形变,键角增大,B-B键键长增大,当带宽约为1.7nm时,B-B键发生断裂;电子性质研究表明：随带宽减小,最高占据轨道(HOMO)/最低非占据轨道(LUMO)能隙减小。对电子态密度(DOS)及赝能隙分析表明：BN纳米带带宽越小在费米能级处DOS越大,且赝能隙越小,这和GNR比较相似,说明BN纳米带越窄电子越容易从价带向导带跃迁。     

Virtually Nilpotent Groups with (almost) All Localizations Trivial

A group G is generically trivial if and only if, for all prime numbers p the localization of G with respect to p is trivial. Taking off from a theorem of Casacuberta and Castellet , we prove that a virtually nilpotent group E is generically trivial if and only if E is perfect. Inspired by this result, we introduce the concept of almost generically trivial groups. Those are groups G such that, for only finitely many primes p the localization of G with respect to p is not trivial. We prove that a virtually nilpotent group E with finitely generated abelianization is almost generically trivial if and only if the abelianization of E is finite.     

Macroscopic Approach to Quantum Optics

This paper investigates how an approach alternative to the canonical quantization schemes may be used to describe Quantum Optics phenomena. By utilizing the approach pioneered by Keldysh, we derive equations for the time dependent correlation functions of the quantized optical fields. These contain the coupling to matter in linear and nonlinar response functions which replace the material parameters of phenomenological macroscopic theories. We present these results as alternatives to existing theoretical methods in Quantum Optics. The paper presents the general formulation of the theory, derives the equations in some specific cases relating to non‐linear optics, and solves some illustrative special cases. We regain known results but also some additional terms deriving from the quantum fluctuations of the material media.     

重频XeF蓝绿激光技术

 利用表面放电光泵浦技术,研制了重频XeF(C-A)激光器,运行频率达到10 Hz。研究了运行频率、气体流量对激光输出能量稳定性的影响,分析了影响输出稳定性的主要因素,实验结果表明,提高气流量可有效改善重频输出能量的稳定性。同时,还给出了优化实验条件下不同运行频率连续20个脉冲较为理想的输出结果。运行频率分别为1,2,5 Hz时,输出能量稳定性较好,输出能量大于4.0 J;气流量大于53 L/s时,10 Hz重频运行的输出稳定性已显著提高,平均输出能量也达到1.8 J。     

CCN蛋白家族研究进展

CCN蛋白家族包含多个成员,它们结构相似,富含半胱氮酸。作为分泌蛋白,CCN蛋白能够促进细胞生长、细胞粘附、细胞迁移;诱导细胞凋亡;并调控肿瘤生长、血管发生和软骨内骨化。由于CCN蛋白在癌症和其它疾病预测或／和诊断中的重要性,成为近几年研究的热点。本文将简述近几年在CCN蛋白领域的研究进展。     

Nonisothermal crystallization kinetics of poly(β-hydroxybutyrate)

Kinetics of nonisothermal crystallization of poly(β-hydroxybutyrate) from melt and glassy states were performed by differential scanning calorimetry under various heating and cooling rates. Several different analysis methods were used to describe the process of nonisothermal crystallization. The results showed that both Avrami treatment and a new method developed by combining the Avrami equation and Ozawa equation could describe this system very well. However, Ozawa analysis failed. By using an evaluation method, proposed by Kissinger, activation energies have been evaluated to be 92.6 kJ/mol and 64.6 kJ/mol for crystallization from the glassy and melt state, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1305–1312, 1998