行波热声发动机的研究进展

热声发动机是将热能转化为声能的装置,是一种与常规机械式压缩机完全不同的新型驱动器.它没有运动部件,采用惰性气体为工质,可利用太阳能、废热等低品位能源为动力,因此具有结构简单、无污染、寿命长等优点.文章回顾了热声理论研究历程,介绍了热声现象的基本原理,重点阐述了国内外行波热声发动机的研究进展,并对行波热声发动机的应用前景进行了展望.     

环路热声发动机驱动的热声制冷系统性能分析

热声热机是一种具有高可靠性和环保特性的无运动部件热机。研究对象是一种环路行波热声发动机驱动的热声制冷机,由一个热声发动机单元和一个热声制冷机单元串联成环路组成。高效的行波热声系统要求回热器处在高声阻抗和接近行波的声场中。由于在环路系统中,声场对声阻抗的变化极为敏感,系统中两个回热器的安装位置会极大影响回热器处的声场。为了研究热声核安装位置对系统性能的影响情况,利用DeltaEC对该系统进行了数值模拟,分析了两个热声核在不同安装位置时系统的总能效系数、发动机单元的效率、制冷机单元的能效系数以及两个回热器的平均相位差和声阻抗等。根据计算结果,当制冷机单元回热器沿声功传输方向距发动机单元回热器的距离与环路总长的比值为0.24时,系统可达到最大总能效系数0.45,对应的相对卡诺能效系数是0.13。当该比值的范围在0.21~0.26时,两个回热器的平均声阻抗较大,使系统的总体性能较优。当该比值大于0.26或小于0.21时,制冷机单元回热器和发动机单元回热器的性能都会恶化,造成了系统整体性能的不佳。     

热声制冷技术的研究前沿及进展

热声制冷技术可以高效地实现从普冷到低温的广泛温区,是目前低温与制冷领域的研究热点之一。它和相关的热声发动机技术都是利用精心布置的声学管道及换热器来实现能量转换和输运,可以无任何运动部件,结构简单,可靠性高。本文介绍了中国科学院理化技术研究所制冷与低温工程中心近年来围绕该项技术进行的研究,主要包括在基础热力学理论、热声低温和普冷制冷机以及热声系统CFD模拟方面取得的一些代表性进展。     

酸度对漆树酶活性的影响

本文研究了酸度对漆树酶活性的影响，测定了不同PH值下漆树酶的活性回复率，并证明，当溶液PH值相近时，酸种类和酸浓度对漆树酶活性的影响较大，特别是酸分子的大小对漆树酶失活率的影响很明显，初步探索了上述各因素对漆树酶活性的影响机理。     

超声波对固定化辣根过氧化物酶活性影响研究

为了研究超声波对固定化酶活性的影响,以固定化辣根过氧化物酶为对象,研究了不同超声波处理条件(超声功率,超声时间)以及超声条件下催化体系的pH、温度对固定化酶活性的作用。同时对超声波处理后固定化酶活的重复利用性进行测定。结果表明,超声波处理对提高固定化酶在高温、强酸碱条件下催化活性有一定帮助,最佳处理条件为:超声波功率50 W,超声时间30 min,pH 8,温度35℃,在此条件下,与未经超声波处理相比,固定化酶活性提高了17.6%,固定化酶重复利用性增强,经7次使用后,固定化酶催化活性是未经处理的1.8倍。     

失活钒催化剂的碱处理再生

失活钒催化剂的碱处理再生在失活钒催化剂的几种再生方法中，有发展前途的是碱处理法，其实质是用碱溶液处理失活钒催化剂，得到钾或钠的钒酸盐，再制成新的催化剂。ＩＯ．Ｐ。。ｐｏ。ｏ。等人研究了失活钒催化剂在钒酸钾碱溶液里的溶解、硅胶（载体）的再沉淀及熟化和新...     

原料对石脑油加氢催化剂性能的影响

对石脑油加氢处理产品硫、氮含量严重超标现象进行了研究 ,重点探讨了原料性质对催化剂活性的影响。研究表明 :直馏石脑油中高硫、氮含量蜡质混合物组分会引起NHT催化剂中毒 ,造成催化剂失活 ,此时通过提高反应温度和压力及降低空速对硫、氮的脱除效果影响不大 ,只有限制这种高硫、氮含量蜡质混合物进入装置 ,才能保证装置产品质量合格     

Fe在固定床渣油加氢处理装置中的沉积及对装置操作的影响

对海南、茂名和齐鲁三套固定床渣油加氢装置失活催化剂的剖析数据进行对比分析,给出Fe在催化剂上和催化剂颗粒间的沉积量及相应负荷,表征了Fe在催化剂颗粒内沉积分布情况,分析了Fe与积炭沉积的关系及对装置操作的影响。     

用声发射监测陶瓷材料的热震损伤

介绍了声发射技术的基本原理,用声发射技术监测了莫来石－钛酸铝陶瓷材料急冷时热震损伤强度衰减及裂纹的扩展过程,结果表明：由热应力引起的微裂纹稳态扩展和失稳扩展的声发射特性与该试样热震损伤后的残余强度变化趋势是一致的。     

A Review on the Effects of Supercritical Carbon Dioxide on Enzyme Activity

Different types of enzymes such as lipases, several phosphatases, dehydrogenases, oxidases, amylases and others are well suited for the reactions in SC-CO₂. The stability and the activity of enzymes exposed to carbon dioxide under high pressure depend on enzyme species, water content in the solution and on the pressure and temperature of the reaction system. The three-dimensional structure of enzymes may be significantly altered under extreme conditions, causing their denaturation and consequent loss of activity. If the conditions are less adverse, the protein structure may be largely retained. Minor structural changes may induce an alternative active protein state with altered enzyme activity, specificity and stability.     

球孢白僵菌Snf907发酵液对番茄根结线虫病的控病效果及防御酶活性影响

研究球孢白僵菌Snf907不同浓度发酵液对番茄幼苗期南方根结线虫病(Meloidogyne incognita)的室内防效,并测得处理后番茄幼苗根内几种主要寄主防御反应酶系PAL、POD、PPO、SOD和可溶性蛋白PRO活性的动态变化.结果表明:不同浓度的发酵液对根结和卵囊的抑制率均明显高于对照,其中原液和5倍稀释液达到80%以上.不同浓度发酵液处理后番茄幼苗根部的PAL、POD、PPO、SOD活性均高于对照,PRO活性显著增加.显示了球孢白僵菌在促进植物生长方面的潜能.     

Immobilization of Lipase B from Candida antarctica in Octyl-Vinyl Sulfone Agarose: Effect of the Enzyme-Support Interactions on Enzyme Activity,Specificity, Structure and Inactivation Pathway

Lipase B from Candida antarctica was immobilized on heterofunctional support octyl agarose activated with vinyl sulfone to prevent enzyme release under drastic conditions. Covalent attachment was established, but the blocking step using hexylamine, ethylenediamine or the amino acids glycine (Gly) and aspartic acid (Asp) altered the results. The activities were lower than those observed using the octyl biocatalyst, except when using ethylenediamine as blocking reagent and p-nitrophenol butyrate (pNPB) as substrate. The enzyme stability increased using these new biocatalysts at pH 7 and 9 using all blocking agents (much more significantly at pH 9), while it decreased at pH 5 except when using Gly as blocking agent. The stress inactivation of the biocatalysts decreased the enzyme activity versus three different substrates (pNPB, S-methyl mandelate and triacetin) in a relatively similar fashion. The tryptophane (Trp) fluorescence spectra were different for the biocatalysts, suggesting different enzyme conformations. However, the fluorescence spectra changes during the inactivation were not too different except for the biocatalyst blocked with Asp, suggesting that, except for this biocatalyst, the inactivation pathways may not be so different.     

Optimization to Low Temperature Activity in Psychrophilic Enzymes

Psychrophiles, i.e., organisms thriving permanently at near-zero temperatures, synthesize cold-active enzymes to sustain their cell cycle. These enzymes are already used in many biotechnological applications requiring high activity at mild temperatures or fast heat-inactivation rate. Most psychrophilic enzymes optimize a high activity at low temperature at the expense of substrate affinity, therefore reducing the free energy barrier of the transition state. Furthermore, a weak temperature dependence of activity ensures moderate reduction of the catalytic activity in the cold. In these naturally evolved enzymes, the optimization to low temperature activity is reached via destabilization of the structures bearing the active site or by destabilization of the whole molecule. This involves a reduction in the number and strength of all types of weak interactions or the disappearance of stability factors, resulting in improved dynamics of active site residues in the cold. Considering the subtle structural adjustments required for low temperature activity, directed evolution appears to be the most suitable methodology to engineer cold activity in biological catalysts.     

多元素专用肥对油松幼苗几种酶活性影响的研究

对3年生油松幼苗4种不同施肥处理下超氧化物歧化酶活性、过氧化物酶活性和多酚氧化酶活性的动态变化进行了测定,探讨了施肥对上述3种酶活性的影响及其机理。结果表明,多元素油松专用肥明显提高超氧化物歧化酶活性和过氧化物酶活性,对增强油松的抗性有重要作用;而对多酚氧化酶活性影响则不甚明显。     

Effects of Acrylamide on the Activity and Structure of Human Brain Creatine Kinase

Acrylamide is widely used worldwide in industry and it can also be produced by the cooking and processing of foods. It is harmful to human beings, and human brain CK (HBCK) has been proposed to be one of the important targets of acrylamide. In this research, we studied the effects of acrylamide on HBCK activity, structure and the potential binding sites. Compared to CKs from rabbit, HBCK was fully inactivated at several-fold lower concentrations of acrylamide, and exhibited distinct properties upon acrylamide-induced inactivation and structural changes. The binding sites of acrylamide were located at the cleft between the N- and C-terminal domains of CK, and Glu232 was one of the key binding residues. The effects of acrylamide on CK were proposed to be isoenzyme- and species-specific, and the underlying molecular mechanisms were discussed.     

六种活性污泥酶活测定及条件优化

活性污泥的生物降解能力与其酶活性相关。在各种涉及活性污泥的环境工程和生物降解分析测试过程中,快速测定活性污泥的酶活性有助于各种活性污泥的生物降解能力分析和实时监测,对于监控降解过程有着重要意义。文章选择6种与生物降解直接相关的活性污泥酶进行测定方法的研究,从反应体系的pH、反应温度、反应时间、反应终止方法和污泥浓度等4个方面对L-亮氨酸氨基肽酶(L-AP)、棕榈酸脂酶(LIP)、磷酸酯酶(PPA)、α-葡萄糖苷酶(α-GLC)、磷酸酶(APA)和脱氢酶(DHA)的酶活测定条件进行优化,结果显示,L-AP最适反应pH为7.4,PPA、APA和DHA反应最适pH为7.9,LIP和a-GLC最适pH为8.4。6种酶活的最适反应温度均为37℃。a-GLC适合反应时间为90 min,其余酶活为60 min。L-AP、LIP、PPA、a-GLC和APA反应终止方法为高温加热,DHA反应的产物萃取剂为乙醇:二甲基甲酰胺=1:1。在优化测定条件的基础上提出一种快速测定6种与生物降解相关的酶活方法,用该方法测定采自4个不同污水处理厂的活性污泥的酶活,除了LIP外,发现工业污水处理厂的活性污泥酶活普遍要高。优化后的测定方法方便快捷,对仪器设备要求低,更能直接、真实反映活性污泥的生物降解活性。     

The effect of oxygen upon the kinetics of enzyme inactivation: In vitro investigations using glutamine synthetase

The relationship between enzyme inactivation and the concentration of oxygen in the reaction environment was studied using glutamine synthetase. Batch incubations of the enzyme were conducted under different oxygen partial pressures in a mixed-function oxidase model system. Enzyme activity was monitored using a transferase reaction assay. Studies showed that oxygen was necessary for inactivation to occur. Furthermore, for oxygen partial pressures up to 61kPa, the rate of inactivation increased linearly with partial pressure. Rates of inactivation ranged from 0.0172+/?0.0038 min^-1 at 15 kPa to 0.0591+/?0.0045 min^-1 at 61 kPa. However, at partial pressures of 61, 81, and 101 kPa, rates of inactivation were statistically identical.     

木瓜蛋白酶还原半合成酶

以木瓜蛋白酶作为模板,用四种N基取代基不同的吡啶盐对其活性中心的Cys-25进行修饰,得到与天然木瓜蛋白酶具有不同催化能力的半合成酶。在循环剂的存在下,将四种半合成酶应用于苯甲醛的催化还原。探索了其最适pH值和温度,并根据催化结果的不同,结合修饰剂在木瓜蛋白酶活性中心的结合情况,讨论了修饰剂与木瓜蛋白酶催化活性中心的其他基团的相互作用力,对其催化能力的影响。     

印楝素对黄粉虫生长发育、能量储存及相关消化酶的影响

[目的]为了解印楝素对鞘翅目昆虫生长发育和繁殖的影响及其作用机理,以黄粉虫末龄幼虫为试材,开展了印楝素对黄粉虫代谢过程中几种主要储能物质及其相关酶影响研究。[方法]食料浸药后饲喂试虫,称其体质量,采用紫外分光光度法等测定了黄粉虫储能物质及中肠消化酶的生物活性。[结果]随着浸药质量浓度增加,黄粉虫体质量增量下降且龄期延长;可溶性总蛋白、糖原和脂质合成减少;胰蛋白酶、淀粉酶和脂肪酶活性均有下降,而体外试验检测上述3种酶没有发现其活性发生显著变化。[结论]印楝素在体内能够间接降低黄粉虫消化酶的活性,导致储能物质减少,从而明显抑制黄粉虫的生长发育。