作动器参数对结构性能的影响和调整受力状态的实施策略模拟

基于规划法研究了作动器各参数对自适应超静定桁架性能的影响。该规划法能够使结构工作状态更合理化。这一方法能够改善自适应结构的工作状态因而提高承载能力。以此为基础，研究了具有作动器的组合杆的有关参数诸如变形上限、刚度和承载力上限对于控制效果的影响。从而为作动器的合理选择提供了理论根据。对于调整作动器变形以控制结构强度的实施策略进行了模拟和分析。该策略包括3部分：1．模拟和分析了“加载、调控、卸载”重复循环直至调控的完成；2．不同作动器按比例同时放大变形直到调控实现；3．多次加载、调控同一次加载、调控结构的等价性。研究表明本文提出的使结构工作状态合理化的调控过程是安全、可靠和灵活的。     

基于结构动力修改的桩基检测方法

采用结构动力修改技术研究桩身损伤检测，将其转化为在一定约束条件下拟合桩顶频响函数的优化问题。用遗传算法加以求解。文中给出的数值模拟试验和工程应用实例，显示该方法能在较大范围内可靠地反演出桩身横截面积、桩长、波速等参数，达到检测桩身缺陷的目的，实现测试和分析一体化，使桩基检测易于进行并且结果实用可靠。     

二维正态分布函数值的一个近似算法

二维正态分布函数值的计算是估算串联结构体系失效概率上、下限的一项重要内容。目前一般常采用两种方法，即数值积分和界限法。前者因计算量大，耗时多不便实用，后者使结构体系失效率的上、下界限进一步变宽。本文给出一个计算二维正态分布函数值的近似方法。实际计算表明，本方法计算效率高，精度完全能满足工程应用要求     

具有非线性homologous变形约束的桁架结构形态分析

研究了具有非线性homologous变形约束条件的桁架结构形态分析问题。在已有的线性homologous变形约束桁架形态分析的基础上,将结构的节点分成三类:homologous变形约束节点,形状可变节点和边界点。运用Moore-Penrose广义逆矩阵性质,将基础方程组解的存在条件表示为包含形状可变节点未知坐标的非线性方程组,为采用Newton-Raphson方法求解非线性方程组,对AA (A为任意矩阵,A 为A的Moore-Penrose广义逆矩阵)求偏导数,找到了满足保型要求的形态,给出的桁架算例说明了本文方法的有效性。     

Effect of the grain size on the macroscopic response of aluminum to shock loading

Shock tests of two lots of a 1420 aluminum-lithium alloy are performed. The mean grain size is 24 μm in the first lot and 1.6 μm in the second lot obtained by the method of equal-channel angular pressing. Two characteristics of dynamic strength of the material were determined in experiments on the high-velocity impact of flat samples: threshold of dynamic stability with respect to compression on the fore front of the compression pulse and spall strength of the material. The materials of both types have an identical threshold of dynamic stability with respect to compression, whereas the spall strength of the microcrystalline alloy is 20% greater than the spall strength of the polycrystalline alloy. The reason is the consumption of energy on structure formation in the coarse-grain material in passing to a larger-scale structural level (in the case with a fine-grain material, such a structure is available in the initial state). The experiments reveal the presence of a second plastic front whose amplitude is approximately 10% of the first plastic front. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 135–146, November–December, 2007.     

基于三线性分灾模型的结构多目标抗震优化设计

基于分灾抗震设计概念,发展了基于三线性分灾模型的结构多目标优化设计方法。以防屈曲支撑为分灾构件的框架结构为例,针对分灾构件设计参数,采用多目标遗传算法进行分灾结构多目标优化设计。最终得到了分灾框架结构分灾构件用量和层间位移角等重要特性的多目标优化关系,并进行了相关讨论。结果表明,结构多目标分灾优化模型可以综合考虑结构造价和抗震性能等,并可以根据目标偏好有效地满足设计需求;分灾构件对抗震性能的作用随着震级增大而增强,使用分灾构件的结构能够更好地抵御强震的作用。     

Biopolymer Skeleton Produced by Rhizobium radiobacter: Stoichiometric Alternation of Glycosidic and Amidic Bonds in the Lipopolysaccharide O‐Antigen

The lipopolysaccharide (LPS) O‐antigen structure of the plant pathogen Rhizobium radiobacter strain TT9 and its possible role in a plant‐microbe interaction was investigated. The analyses disclosed the presence of two O‐antigens, named Poly1 and Poly2. The repetitive unit of Poly2 constitutes a 4‐α‐l ‐rhamnose linked to a 3‐α‐d ‐fucose residue. Surprisingly, Poly1 turned out to be a novel type of biopolymer in which the repeating unit is formed by a monosaccharide and an amino‐acid derivative, so that the polymer has alternating glycosidic and amidic bonds joining the two units: 4‐amino‐4‐deoxy‐3‐O‐methyl‐d ‐fucose and (2′R,3′R,4′S)‐N‐methyl‐3′,4′‐dihydroxy‐3′‐methyl‐5′‐oxoproline). Differently from the O‐antigens of LPSs from other pathogenic Gram‐negative bacteria, these two O‐antigens do not activate the oxidative burst, an early innate immune response in the model plant Arabidopsis thaliana, explaining at least in part the ability of this R. radiobacter strain to avoid host defenses during a plant infection process.     

Simultaneous Ultrasound and Heat Enhance Functional Properties of Glycosylated Lactoferrin

Protein-polysaccharide covalent complexes exhibit better physicochemical and functional properties than single protein or polysaccharide. To promote the formation of the covalent complex from lactoferrin (LF) and beet pectin (BP), we enhanced the Maillard reaction between LF and BP by using an ultrasound-assisted treatment and studied the structure and functional properties of the resulting product. The reaction conditions were optimized by an orthogonal experimental design, and the highest grafting degree of 55.36% was obtained by ultrasonic treatment at 300 W for 20 min and at LF concentration of 20 g/L and BP concentration of 9 g/L. The formation of LF-BP conjugates was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared (FTIR) spectroscopy. Ultrasound-assisted treatment can increase the surface hydrophobicity, browning index, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radicals scavenging activity of LF due to the changes in the spatial configuration and formation of Maillard reaction products. The thermal stability, antioxidant activity and emulsifying property of LF were significantly improved after combining with BP. These findings reveal the potential application of modified proteins by ultrasonic and heat treatment.     

Predicting 19F NMR Chemical Shifts: A Combined Computational and Experimental Study of a Trypanosomal Oxidoreductase–Inhibitor Complex

The absence of fluorine from most biomolecules renders it an excellent probe for NMR spectroscopy to monitor inhibitor–protein interactions. However, predicting the binding mode of a fluorinated ligand from a chemical shift (or vice versa) has been challenging due to the high electron density of the fluorine atom. Nonetheless, reliable ¹⁹F chemical-shift predictions to deduce ligand-binding modes hold great potential for in silico drug design. Herein, we present a systematic QM/MM study to predict the ¹⁹F NMR chemical shifts of a covalently bound fluorinated inhibitor to the essential oxidoreductase tryparedoxin (Tpx) from African trypanosomes, the causative agent of African sleeping sickness. We include many protein–inhibitor conformations as well as monomeric and dimeric inhibitor–protein complexes, thus rendering it the largest computational study on chemical shifts of ¹⁹F nuclei in a biological context to date. Our predicted shifts agree well with those obtained experimentally and pave the way for future work in this area.