磁场作用下向列型液晶中的分子取向短程关联

从分子统计理论的观点研究磁场对向列型液晶的作用。将向列型液晶的格胞理论推广到包含磁场作用的情况。这一理论考虑了分子取向短程关联。向列相序参数对约化温度的依赖关系和每个分子的约化内能对约化温度的依赖关系，与计算机模拟结果符合得相当好。计算了各向同性相最低过冷温度，理论结果与实验值和分子场理论的结果进行了比较。     

Interfacial tension between low molecular weight polymers from the static analysis of cylindrical drops and their break-up dynamics

A spinning drop tensiometer was used to measure the interfacial tension between the coexisting phases of mixtures of low molecular weight polypropylene glycol, M_w = 1000, and polyethylene glycol, M_w = 300, 400, or 550. Two types of experiments gave concordant interfacial tensions. First, the static analysis of the equilibrium diameter of cylindrical drops according to Vonnegut and, second, Tomotika's dynamic analysis of Rayleigh instabilities caused by a sharp decrease of the angular speed. The end-pinching process also lead to the break-up of the drops and it was characterized by a rapid expansion of the hemispherical ends followed by a slower pinching step. The pinching rate increases as the final angular speed decreases while the growth rate of Rayleigh instabilities shows no definite trends in the range 118-245 rad · s^?1. It is shown that the end-pinching of long cylindrical drops can be analyzed in terms of short fiber retraction to get the interfacial tension. © 1995 John Wiley & Sons, Inc.     

铝靶对短脉冲强激光反射率的饱和现象

计算了铝靶对S极化短脉冲强激光的反射率的饱和段，将所得结果和H．M.Milchberg的实验结果进行了对比，二者十分一致.并对此饱和现象作了物理解释，认为是由电子的热运动和相互作用所引起的．     

ps参量放大效应

本文报道用0.53μm波长超短脉冲序列泵浦角度调谐的LiNbO_3参量晶体,获得1%单程参量放大能量转换效率,并在0.8～1.6μm范围测得参量信号光和空载光波长调谐曲线.     

Hitting, returning and the short correlation function

We consider a stochastic process with the weakest mixing condition: the so called α. For any fixed n-string we prove the following results. (1) The hitting time has approximately exponential law. (2) The return time has approximately a convex combination between a Dirac measure at the origin and an exponential law. In both cases the parameter of the exponential law is λ(A)ℙ(A) where ℙ(A) is the measure of the string and λ(A) is a certain autocorrelation function of the string. We show also that the weight of the convex combination is approximately λ(A). We describe the behavior of this autocorrelation function. Our results hold when the rate of mixing decays polinomially fast with power larger than the golden number.     

抗HCV药物索菲布韦的合成与表征——本科生“夏季小学期”创新科研实践

以“抗HCV药物索菲布韦（Sofosbuvir）合成与表征”为例,介绍了南开大学本科生“夏季小学期”创新科研实践活动的具体实施情况。内容涉及抗HCV药物索菲布韦的研究背景介绍、合成与表征,以及对实验结果的讨论。实践结果表明,利用“夏季小学期”集中安排实验时间较长且复杂程度高的综合实验,可以提高学生的科研实践能力,促进理论教学与科研实践相结合,取得了良好的教学效果。     

Anchoring transitions of liquid crystals on SiO x

Anchoring transitions were observed of nematic liquid crystal (LC) mixtures on obliquely evaporated SiO _x by varying the relative abundance of two components in the mixture. Of these two components, one has a longitudinal cyano group and another has lateral cyano groups. It was also found that both temperature and SiO _x thickness variations are able to shift the anchoring transitions. The anchoring on SiO _x has two origins: long‐range van der Waals potential and short‐range surface interactions. Since the two origins have opposite preference in LC director orientation the observed transition is caused by the change of their relative strength. Thermal absorption–desorption of molecules on SiO _x surface is important in determining the strength of short‐range interactions, whereas the layer thickness and optical properties of SiO _x are dependent on the van der Waals potential. Based on previous work by de Gennes we propose a model to describe the observed phenomenon.     

Transfer of splitness with respect to a fully invariant short exact sequence in abelian categories

Abstract

We study the transfer via functors between abelian categories of the (dual) relative splitness of objects with respect to a fully invariant short exact sequence. We mainly consider fully faithful functors and adjoint pairs of functors. We deduce applications to Grothendieck categories, (graded) module categories and comodule categories.     

ANALYSIS AND EXPERIMENT ON TRANSIENT DYNAMIC RESPONSE IN FINITE MINDLIN PLATE

The transient wave propagation in the finite rectangular Mindlin plate is investigated by the analytical and experimental methods. The generalized ray method (GRM) which has been successfully applied to study the transient responses of beams, planar trusses, space frames and infinite layered media is extended to investigate the transient wave propagation and early short time transient response in finite Mindlin plate. Combining the wave solution, the shock source and the boundary conditions, the ray groups transmitted in the finite rectangular plate can be determined. Numerical simulations and experiments are performed and compared with each other. The results show that the transient wave propagation and early short time transient responses in the finite plate can be studied using the GRM. The early short time transient accelerations are very large for the finite plate subjected to the unit impulse, while the early short time transient displacements are very small. The early short time transient accelerations under the unit impulse are much larger than those under the unit step impulse. The thickness and material characteristics have remarkable effects on the early short time transient responses.