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131.
Eijsink Vincent G.H.; Vriend Gerrit; van den Burg Bertus; Venema Gerard; Stulp Ben K. 《Protein engineering, design & selection : PEDS》1990,4(1):99-104
The role of the C-terminal Leu300 in maintaining thermal stabilityof the neutral protease of Bacillus subtilis was investigated.From model building studies based on the three dimensional structureof thermolysin, the neutral protease of B.thermoproteolyticus,it was conduded that this residue is located in a hydrophobicpocket composed of residues located in the C-terminal and themiddle domain. To test the hypothesis that Leu300, by contributingto a stabilizing interaction between these domains, is importantfor enzyme stability, several neutral protease mutants wereconstructed and characterized. The thermostability of the enzymewas lowered by deleting Leu300 or by replacing this residueby a smaller (Ala), a polar (Asn) or a sterically unfavourable(He) amino acid. Thermostabiity was increased upon replacingLeu300 by Phe. These results are in agreement with model-buildingstudies. The effects on thermostability observed after mutatingthe corresponding Val318 in the thermostable neutral proteaseof B.stearothermophilus were less pronounced. 相似文献
132.
Henri Berthiaux Antonio Guttierrez Lavin Julio Bueno De Las Heras Marisol Muñiz Alvarez 《加拿大化工杂志》2007,85(2):158-170
Despite of its general use in industry, particle sedimentation is still a not well understood unit operation. Hydrodynamics is complex in essence, mainly because the possible volumes are depending on the operating conditions, which in turn has consequences on the stability of the equipment in unsteady state conditions. 相似文献
133.
Jan Willem?van?GroenigenEmail author Pieter Jan?Georgius Chris?van?Kessel Eduard W.J.?Hummelink Gerard L.?Velthof Kor B.?Zwart 《Nutrient Cycling in Agroecosystems》2005,72(1):13-25
Studies on emissions of nitrous oxide (N2O) from agricultural soils mostly focus on fluxes between the soil and the atmosphere or are limited to the atmosphere in
the topsoil. However, in soils with shallow water tables, significant N2O formation may occur closer to the groundwater. The aims of this study were (i) to determine the importance of subsoil N2O formation in a sandy soil; and (ii) to obtain a quantitative insight in the contribution of subsoil N2O to the overall losses of N2O to the environment. We applied 15N labeled fertilizer at a rate of 5.22 kg 15N ha−1; 50% as Ca(NO3)2 and 50% as NH4Cl, on a mesic typic Haplaquod seeded with potatoes (Solanum tuberosum L.), and traced soil N2O concentrations and fluxes over a one-year period. Throughout the year, total N2O and the amount of 15N recovered in soil N2O were highest in the subsoil, with a maximum concentration at 48 cm depth in mid-February of 19900 μl m−3 and 24 μg 15N m−3, respectively. The maximum concentration coincided with the highest water-filled pore space of 71%. The cumulative flux of
N2O was 446 g N2O-N ha−1, the recovery of 15N in this flux was 0.06%. During the summer, maximum fluxes followed high soil N2O concentrations. During winter, no such relation was found. We concluded that the formation of N2O was the highest in the subsoil, largely controlled by water-filled pore space rather than NO3− concentration or temperature. Although high subsoil N2O concentrations did not lead to high surface fluxes of N2O in the winter, artificial draining may lead to high indirect N2O emissions through supersaturated drainage water. 相似文献
134.
讨论节约型高校建设的现实价值以及节约型高校建设的问题和成因,从思想政治教育、科学管理、科研创新、典型示范的角度出发,论述了加强节约型高校建设的对策。 相似文献
135.
采用三主梁精细有限元模型对海南某斜拉桥的地震响应进行计算分析.进行了反应谱和几何非线性时程分析法地震响应的对比分析.计算结果表明:该桥的桥塔刚度满足要求,主梁刚度基本满足要求,主梁顺桥向的弹性约束和阻尼装置对减小顺桥向位移有一定的作用,但在罕遇地震作用下存在动力失稳的可能性,因此对主梁位移的限制应更严格,从而提高其整体的抗震性能. 相似文献
136.
烟气冷凝热能回收利用装置中烟气的分布与流动对换热起着重要作用,为优化烟气冷凝热能回收利用装置,保证烟气能够在装置中分布均匀、充分换热,分别设计两种烟气流动方式,采用CFD软件Fluent模拟了烟气冷凝热能回收利用装置中的流场及温度场,并将其分别应用于实际工程进行现场实测.结果表明,采用渐变断面设计的烟气流动方式,烟气在换热面上分布更均匀,更有利于强化换热,阻力更小,节能率比采用等高断面最大可提高3.25%,可有效降低和消除噪音. 相似文献
137.
牟艳 《山东电力高等专科学校学报》2010,13(1):35-37
本文主要论述了齐鲁文化所表现出来的和合精神、人道主义精神、厚德仁民精神、大公无私精神、自强不息精神等,对中国传统体育文化产生的重要影响。 相似文献
138.
PST ferroelectric ceramics were fabricated successfully by a two-step method, i e first, PbTiO3 and SrTiO3 were sintered respectively, then mixed and sintered together. The process and characteristics of PST ferroelectric ceramics
were introduced and researched. Their dielectric and pyroelectric characteristics are as follows dielectric constant 104 order, low dielectric loss (lower than 3.0% in the working frequency range of 1–1 000 kHz), saturation polarization intensity
10−1 C/m2 order, and pyroelectric coefficient 10−3 C/m2·K order. 相似文献
139.
由于网络中存在复杂的非线性动力学特性,基于混沌理论,采用最大Lyapunov指数对局域网络流量序列进行预测分析,能够实现较早地预测出网络流量的突变特性.首先,采用相空间重构理论,并结合C-C算法将实际测试的流量时间序列投影到重构的相空间中.然后,计算其最大Lyapunov指数并对最大可预测时间进行了分析,同时对预测算法进行了研究.最后,对实际测试的局域网流量序列分别采用点预测和区间预测方法进行了分析.仿真结果显示,采用点预测方法对流量突变可以进行有效预测,突变越剧烈预测越准确;而采用区间预测可以有效预测流量的变化趋势,但不适用于广域网环境.进一步表明此方法能有效地利用所有数据信息进行预测,预测效果准确、可靠,可广泛的用于网络拥塞和网络攻击中. 相似文献
140.
Preparation and electrochemical characterization of activated carbons by chemical-physical activation 总被引:2,自引:0,他引:2
A process was proposed based on the combination of chemical and physical activation for the production of activated carbons
used as the electrode material for electric double layer capacitor (EDLC). By material characterization and electrochemical
methods, the influences of the activitation process on the specific surface area, pore structure and electrochemical properties
of the activated carbons were investigated. The results show that specific surface area, the mesopore volume, and the specific
capacitance increase with the increase of the mass ratio of KOH to char (m(KOH)/m(char)) and the activation time, respectively. When m(KOH)/m(char) is 4.0, the specific surface area and the mesopore volume reach the maximum values, i.e. 1 960 m2/g and 0.308 4 cm3/g, and the specific capacitance is 120.7 F/g synchronously. Compared with the chemical activation, the activated carbons
prepared by chemical-physical activation show a larger mesopore volume, a higher ratio of mesopore and a larger specific capacitance.
Foundation item: Project(2007BAE12B01) supported by the National Key Technology Research and Development Program of China 相似文献