混合振荡介质中扩散诱导的复杂时空斑图研究

在诸多化学反应中都可以发现时空斑图的存在,但是对于混合模式振荡介质中的时空动力学行为的研究却鲜有提及。本文通过一个在一个三变量模型上添加扩散相,模拟并研究了混合模式振荡介质中所对应的螺旋波时空动力学行为,并得到了例如超靶波螺旋波,超螺旋波以及半边调制螺旋波等扩散诱导的振幅调制螺旋波。     

化学振荡和时空斑图动力学研究进展

非线性化学反应体系在时间序列上主要表现为多重定态、化学振荡和化学混沌,在时空序列上主要表现为化学波和Turing斑图。化学振荡和时空斑图是典型的非线性动力学现象,该研究对于理解生物体系中的振荡和斑图现象有重要的指导意义。本文简要综述了化学振荡,化学波和Turing斑图的研究进展,并对其今后的发展方向进行了展望。     

化学波在一维BZ凝胶体系中的单向传递

研究了化学波在一维BZ凝胶中单向传递,观察到了化学波传递时空斑图,其传播距离呈现周期性变化。考察了实验参数改变对化学脉冲波动力学行为的影响,一维化学脉冲波的时空演化有助于理解生化体系中信息的传递和调制。     

超材料宽频吸波技术研究进展

超材料因其完美吸收特性成为吸波材料研究的热点,但其吸收频段窄成为限制其应用的瓶颈技术。介绍了超材料完美吸波结构,分析了其工作原理,重点综述了超材料实现宽频吸波的途径及其国内外研究现状,总结了各种宽频吸波超材料的结构和性能特点,最后对超材料吸波技术的发展趋势进行了探讨。     

超材料宽频吸波技术研究进展

超材料因其完美吸收特性成为吸波材料研究的热点,但其吸收频段窄成为限制其应用的瓶颈技术。介绍了超材料完美吸波结构,分析了其工作原理,重点综述了超材料实现宽频吸波的途径及其国内外研究现状,总结了各种宽频吸波超材料的结构和性能特点,最后对超材料吸波技术的发展趋势进行了探讨。     

Hastings-Powell化学反应扩散模型中复杂螺旋波的几何模型解释

螺旋波是化学化学反应扩散系统中最为常见的时空结构。在三变量Hastings-Powell模型的混合模式振荡区域,通过耦合扩散,得到了具有包括双臂螺旋波,和超靶波螺旋波、半边调制螺旋波以及振幅调制导致的超螺旋波等超结构螺旋波的数值模拟结果。最终设计一个几何模型来模拟螺旋波的双臂结构,增加周期性扰动来模拟双臂之间的相互作用,得到了与反应—扩散系统数值模拟相同的结果,从而证实了复杂螺旋波结构的形成模式。     

陶瓷纤维吸波材料的吸波机理及其结构设计

陶瓷纤维复合材料在结构及隐身技术中得到了广泛的应用。通过分析陶瓷纤维材料的吸波机理以及结构特性对纤维材料的电磁参数和吸波性能的影响，提出了综合不同方法来对吸波纤维进行结构设计的构思。     

吸波材料包覆研究进展在雷达波低频上的应用

通过各种包覆手段形成的核壳结构吸波材料,不仅可增强吸收剂的耐高温性、抗氧化性、抗腐蚀性性能,还能通过降低介电常数,改善阻抗匹配,大大提高吸波材料的吸波性能。对铁氧体,陶瓷、金属及其合金作为包覆的核-壳结构吸波材料的国内外研究现状进行总结,并针对目前雷达波低频1~4GHz吸波材料的研究热点,探讨包覆研究对雷达波低频吸波材料吸波性能的影响,发现适当的对吸波材料进行包覆处理,有利于提高其在雷达波低频频段的吸波特性。     

水泥基电磁波吸收材料研究进展

水泥净浆、水泥砂浆、混凝土等水泥基复合吸波材料的研究是近几年的热点问题,也是解决当前电磁辐射污染的关键技术.吸波材料的性能很大程度上取决于吸波剂本身,本文对各种水泥基材料中吸收剂的种类、数量、性能及匹配特性的研究进行了总结.同时,水泥材料结构致密,需要添加发泡聚苯乙烯(EPS)、粉煤灰、珍珠岩等透波剂来改善阻抗匹配特性.另外,还需要进行多层结构、异形表面等优化设计.在改善吸波性能的同时,还要使材料兼具力学、隔音、隔热等功能.最后,通过总结现有研究中存在的不足,提出了水泥基吸波材料进一步发展的方向.     

磁性吸波碳纤维掺杂聚氨酯泡沫制备夹层结构吸波材料

通过在碳纤维表面进行磁性涂层制备出具有吸波效果的磁性涂层碳纤维,在聚氨酯中仅掺杂质量分数〈5%该纤维发泡得到吸波聚氨酯泡沫,经与透波层和反射层复合可以得到宽频和轻质的结构吸波材料。     

魔芋葡甘聚糖酶解历程反应-扩散动力学

引 言 近年来,天然多糖的酶促水解在生物能源炼制、油气开采、药物缓释、功能保健中得到广泛应用,涉及能源、资源、医药、食品等国计民生行业,其研究引起了众多学者的极大兴趣,成为各国科技战略的重要组成部分.     

Three-dimensional large eddy simulation of wave characteristics of liquid film flow in a spinning disk reactor

The waves of liquid film flow play an important role on the process intensification in spinning disk reactors (SDRs). However, the mechanism of wave formation was still unclear. In this work, a three-dimensional large eddy simulation was developed to investigate the mechanism, as well as the characteristics of waves in the SDR. Agreed with the imaging results, different wave patterns were identified as: smooth film, concentric, and spiral waves in spreading direction; sine-like and pulse-like waves in fluctuating direction. The radial and tangential relative movements among the layers of liquid film were found to dominate the formation of different wave patterns. Local average film thickness (h_avg) and local wave amplitude (Δh) ranged from 0 to 500 μm and 0 to 200 μm, respectively. The waves can improve the turbulent intensity and enlarge the specific surface area, resulting in the intensification of transfer processes.     

Spatial structures evolving from homogeneous media in immobilized enzyme systems

The detailed pattern of spatial structures for the reaction-diffusion system involving substrate-inhibited reactions on immobilized uricase enzyme was studied. Depending on the governing parameters, three basic solutions may exist and there are two kinds of possible branching, either successive primary bifurcation from a basic trivial branch or consecutive secondary bifurcation. In both cases the branching follows the sequence of symmetric → asymmetric → symmetric, and so forth. The emergence of subsequently more complex spatial structures with the increasing length of systems suggests a close similarity to gradual buildup of complex morphogenetic patterns in developmental biology.     

超声波对木薯淀粉性质及结构的影响

考察了超声波对木薯淀粉理化性质及结构的影响. 结果表明,经超声处理后淀粉表观粘度下降,凝沉增强;经超声处理2 min,淀粉糊透明度提高,抗酶解能力降低;延长超声时间则导致糊透明度下降和抗酶解能力增强. FT-IR和XRD分析结果表明,超声作用未破坏淀粉分子基团,但淀粉结晶结构遭到破坏,结晶度下降. SEM分析显示,淀粉团粒结构减弱,受侵蚀的颗粒数量增多;淀粉-碘复合物分析表明,超声波造成淀粉大量降解,破坏支链结构和淀粉长链,直链淀粉含量增加. DSC分析表明,淀粉经超声处理后糊化焓基本不变,糊化温度升高.     

Discovery of an Allosteric Ligand Binding Site in SMYD3 Lysine Methyltransferase

SMYD3 is a multifunctional epigenetic enzyme with lysine methyltransferase activity and various interaction partners. It is implicated in the pathophysiology of cancers but with an unclear mechanism. To discover tool compounds for clarifying its biochemistry and potential as a therapeutic target, a set of drug-like compounds was screened in a biosensor-based competition assay. Diperodon was identified as an allosteric ligand; its R and S enantiomers were isolated, and their affinities to SMYD3 were determined (K_D=42 and 84 μM, respectively). Co-crystallization revealed that both enantiomers bind to a previously unidentified allosteric site in the C-terminal protein binding domain, consistent with its weak inhibitory effect. No competition between diperodon and HSP90 (a known SMYD3 interaction partner) was observed although SMYD3–HSP90 binding was confirmed (K_D=13 μM). Diperodon clearly represents a novel starting point for the design of tool compounds interacting with a druggable allosteric site, suitable for the exploration of noncatalytic SMYD3 functions and therapeutics with new mechanisms of action.     

Prostaglandin and acyl chain effects on glutamate dehydrogenase activity

Prostaglandins A₁ (PGA₁), A₂, B₁, B₂, E₁, E₂, F_1α, F_2α, and 19 esterified natural fatty acids were tested as effectors of beef liver glutamate dehydrogenase (L-glutamate: NAD(P)⁺, oxidoreductase [deaminating], EC 1.4.1.3). All prostaglandins tested are found to activate the enzyme initially, but only PGA₂>PGB₂≥PGA₁ cause a subsequent time-dependent loss (not inhibition) of NADH oxidation activity. Both PGA₁ and PGA₂ desensitize glutamate dehydrogenase to allosteric activation by ADP, whereas PGA₂ and PGB₂ desensitize to allosteric inactivation by GTP. Preincubation of enzyme with diethylstilbestrol prevents the initial activation by the PG. Of the methyl esters, only prostaglandin precursors inactivated the enzyme. Simultaneous desensitization to the ADP and GTP allosteric effects resulted. Multiple esterification to glycerol or phospholipids enhanced the action of linoleoyl and diminished the action of linolenoyl chains. Preincubation of the PGA with glutathione or cysteine prevents the inactivation; i.e., the sulfhydryl binding region of the prostaglandin must be free for enzyme to be inactivated. Sulfhydryl reagents also protect the enzyme from the effects of the unsaturated acyl chains, and pHMB mimics acyl protection against GTP allosteric inactivation. Where the lipid effector is active against sulfhydryl groups, the desensitizations to the ADP and GTP allosteric effectors are reciprocal. The initial activation, subsequent inactivation and desensitization to ADP and GTP are all characteristic of binding in the estrogen-specific effector site, suggesting this site as the target for PG and acyl action. In the PGA₂ activation, the effect is found to be amplified by the cooperativity of the enzyme at 1 PG molecule/6 molecules of GDH. We conclude from the action of the PG and structural analogs that the initial activation of glutamate dehydrogenase is caused by α,β-unsaturated monoketo cyclopental structures. GTP inhibition is blocked primarily by diketo structures which eventually inactivate the enzyme. ADP activation is blocked by sulfhydryl binding of the unsaturated cyclopental keto structure of the PG. Appearance of a 270 nm absorbance simultaneous to the acyl effects on the enzyme suggests that conjugated unsaturations are responsible for the precursor's qualitatively similar action to that of the PG.     

Covalent Allosteric Inhibitors of Akt Generated Using a Click Fragment Approach

Akt is a protein kinase that has been implicated in the progression of cancerous tumours. A number of covalent allosteric Akt inhibitors are known, and based on these scaffolds, a small library of novel potential covalent allosteric imidazopyridine-based inhibitors was designed. The envisaged compounds were synthesised, with click chemistry enabling a modular approach to a number of the target compounds. The binding modes, potencies and antiproliferative activities of these synthesised compounds were explored, thereby furthering the structure activity relationship knowledge of this class of Akt inhibitors. Three novel covalent inhibitors were identified, exhibiting moderate activity against Akt1 and various cancer cell lines, potentially paving the way for future covalent allosteric inhibitors with improved properties.     

Specific Modulation of Protein Activity by Using a Bioorthogonal Reaction

Unnatural amino acids with bioorthogonal reactive groups have the potential to provide a rapid and specific mechanism for covalently inhibiting a protein of interest. Here, we use mutagenesis to insert an unnatural amino acid containing an azide group (Z) into the target protein at positions such that a “click” reaction with an alkyne modulator (X) will alter the function of the protein. This bioorthogonally reactive pair can engender specificity of X for the Z‐containing protein, even if the target is otherwise identical to another protein, allowing for rapid target validation in living cells. We demonstrate our method using inhibition of the Escherichia coli enzyme aminoacyl transferase by both active‐site occlusion and allosteric mechanisms. We have termed this a “clickable magic bullet” strategy, and it should be generally applicable to studying the effects of protein inhibition, within the limits of unnatural amino acid mutagenesis.     

Linker insertion mutagenesis based on IS21 transposition: isolation of an AMP-insensitive variant of catabolic ornithine carbamoyltransferase from Pseudomonas aeruginosa

The bacterial insertion sequence IS21 when repeated in tandemefficiently promotes non-replicative cointegrate formation inEscherichia coli. An IS21–IS21 junction region which hadbeen engineered to contain unique SalI and BglII sites closeto the IS21 termini was not affected in the ability to formcointegrates with target plasmids. Based on this finding, anovel procedure of random linker insertion mutagenesis was devised.Suicide plasmids containing the engineered junction region (pME5and pME6) formed cointegrates with target plasmids in an E.colihost strain expressing the IS21 transposition proteins in trans.Cointegrates were resolved in vitro by restriction with SalIor BglII and ligation; thus, insertions of four or 11 codons,respectively, were created in the target DNA, practically atrandom. The cloned Pseudomonas aeruginosa arcB gene encodingcatabolic ornithine carbamoyltransferase was used as a target.Of 20 different four-codon insertions in arcB, 11 inactivatedthe enzyme. Among the remaining nine insertion mutants whichretained enzyme activity, three enzyme variants had reducedaffinity for the substrate ornithine and one had lost recognitionof the allosteric activator AMP. The linker insertions obtainedillustrate the usefulness of the method in the analysis of structure–functionrelationships of proteins.