蛋白质多态解折叠行为与稳定性Ⅱ:酶的多态解折叠行为

基于结构基元模型,进一步假设,由n个结构基元组成的蛋白酶,其活性中心由na(na?n)个结构基元组成,酶活性仅与组成活性中心的结构基元相关.由此,推导出适合于蛋白酶解折叠研究的变性曲线、解折叠结构基元平均自由能、物种分布等表达式.本文以盐酸胍诱导的卵清溶菌酶解折叠为例,通过荧光方法测定的溶菌酶解折叠曲线,得出卵清溶菌酶由2个结构基元组成,结构基元平均自由能?G0element(H2O)为48.47 kJ/mol.物种分布表明,酶活性随盐酸胍浓度的变化仅仅反映的是结构基元1(?-片结构域)的解折叠,而结构基元2(?-螺旋结构域)的解折叠反映在3.8~5.0 mol/L盐酸胍浓度范围内.结构基元模型既可描述蛋白酶多态解折叠的谱学行为,又可解释蛋白酶活性的两态性质.     

Ab Initio Study of the Mechanism of Forming a Spiro-Si-heterocyclic Ring Compound Involving Ge from Cl_2Ge=Si:and Formaldehyde

The X2Ge=Si:(X = H, Me, F, Cl, Br, Ph, Ar···) is a new species. Its cycloaddition reaction is a new area for the study of silylene chemistry. The mechanism of cycloaddition reaction between singlet Cl2Ge=Si: and formaldehyde has been investigated with CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction pathways. The reaction rule presented is that the two reactants firstly form a four-membered Ge-heterocyclic ring silylene through the [2+2] cycloaddition reaction. Owing to the 3p unoccupied orbital of Si: atom in the four-membered Ge-heterocyclic ring silylene and the π orbital of formaldehyde forming a π→p donor-acceptor bond, the four-membered Ge-heterocyclic ring silylene further combines with formaldehyde to form an intermediate. Because the Si: atom in intermediate shows sp3 hybridization after transition state, the intermediate isomerizes to a spiro-Si-heterocyclic ring compound involving Ge via a transition state. Simultaneously, the ring strain of the four-membered Ge-heterocyclic ring silylene makes it isomerize to a twisted four-membered ring product. The research result indicates the laws of cycloaddition reaction between X2Ge=Si:(X = H, Me, F, Cl, Br, Ph, Ar···) and the asymmetric π-bonded compounds, which are significant for the synthesis of small-ring and spiro-Si-heterocyclic ring compound involving Ge. The study extends the research area and enriches the research content of silylene chemistry.     

Elasto-plastic buckling and post-buckling analysis of sandwich plates with functionally graded metal-metal face sheets and interfacial damage简

Based on the elasto-plastic theory, considering the effect of spherical stress tensor on the elasto-plastic deformation and using the slicing treatment to deal with the plasticity of functionally graded coatings, the elasto-plastic increment constitutive equations of the sandwich plates with functionally graded metal-metal face sheets can be derived. Applying the weak bonded theory to the interfacial constitutive relation and taking into account the geometric nonlinearity, the nonlinear increment differential equilibrium equations of the sandwich plates with functionally graded metal-metal face sheets are obtained by the minimum potential energy principle. The finite difference method and the iterative method are used to obtain the post-buckling path. When the effect of geometrical nonlinearity of the plate is ignored, the elasto-plastic critical buckling load of the sandwich plates with functionally graded metal-metal face sheets can be solved by the Galerkin method and the iterative method. In the numerical examples, the effects of the interface damages, the induced load ratio, the functionally graded index, and the geometry parameters on the elasto-plastic post-buckling path and the elasto-plastic critical buckling load are investigated.     

解析CAF失效机理及分析方法

随着电子产品的快速发展,电子设备更是朝着轻、薄、小的方向发展,使得印制电路板CAF问题成为影响产品可靠性的重要因素。通过介绍CAF失效原理,及CAF失效分析方法,为加工商提供CAF效应分析和改善的依据。     

一种适用于开关电源的内部供电电路设计

本文提出了一种适用于开关电源的内部供电电路。该电路采用齐纳二极管的稳压原理,将开关电源的高输入电压稳压输出5V,供模拟模块和数字模块使用,简化了以往采用基准和低压差线性稳压器(LDO,Low Dropout Regulator)供电的设计方法。本电路基于0.35 um BCD工艺,对所设计电路进行了仿真验证。仿真结果表明,该电路在-40℃~125℃应用环境温度范围内都能够实现高精度的输出电压,具有较强的稳定性。     

Analysis of Trapping Force and Torque for Fiber-optical Trap by the Finite-differential Time-domain (FDTD) Method

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　ＳｉｎｃｅＡｓｈｋｉｎｅｔａｌ.[1] ｐｒｏｐｏｓｅｄｔｈｅｏｐｔｉｃａｌｔｒａｐｐｉｎｇｏｆｄｉｅｌｅｃｔｒｉｃｐａｒｔｉｃｌｅｓｂｙａｓｉｎｇｌｅ ｂｅａｍｇｒａｄｉｅｎｔｆｏｒｃｅｔｒａｐ ,ｏｐｔｉｃａｌｔｗｅｅｚｅｒｓｔｅｃｈｎｏｌｏｇｙａｒｏｕｓｅｄｔｈｅｉｎｔｅｒｅｓｔｏｆｒｅｓｅａｒｃｈｅｒｓ,ｈｏｗｅｖｅｒｔｈｅｉｒａｔｔｅｎｔｉｏｎｗａｓｃｏｎｃｅｎｔｒａｔｅｄｏｎｈｉｇｈＮＡｍｉｃｒｏｌｅｎｓｔｗｅｅｚｅｒｓ.Ｏｐｔｉｃａｌｔｒａｐｐｉｎｇｔｅｃｈｎ…     

光学相干性综合实验

利用双频光栅剪切干涉法，CCD摄像机采集剪切干涉条纹图，用自行设计的软件对图像进行处理，可定量测量光场的时空相干性以及梯度折射率透镜的像差。     

掺钕聚甲基丙烯酸甲酯的光谱性质

研究了三价钕离子在钕螯合物掺杂的聚甲基丙烯酸甲酯(PMMA)中的吸收光谱和发射光谱。根据Judd-Ofelt理论,从吸收光谱计算了钕离子在PMMA中的光学跃迁的强度参量Ω2、Ω4和Ω6(Ω2=28.99×10-20cm2,Ω4=5.29×10-20cm2,Ω6=3.82×10-20cm2)。用强度参量计算了钕离子激发态(4F3/2)的辐射跃迁几率(2221.54s-1)和辐射寿命(450.14μs),同时计算了4F3/2→4IJ',跃迁的受激发射截面σij和荧光分支比β。分析表明,Nd(DBM)3Phen掺杂的PMMA可望用于激光放大器件。     

呼叫中心接入方式的创新与实现

本文回顾了呼叫中心（Call Center)技术的发展，重点介绍了作者在呼叫中心接入方式（电话、图文电话、微机终端、Web、可视终端、传真、手机）方面的研究成果，并给出了实现方案。     

入侵检测技术研究综述

入侵检测是信息安全保障的关键技术之一。本文综述了入侵检测系统的最新研究进展,包括基本概念、模型、方法等,讨论了该领域尚存在的问题及今后的发展趋势。