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961.
导电混凝土材料电阻系数的研究和分析   总被引:2,自引:0,他引:2  
作者研究表明:导电混凝土电气加热蓄热冷却过程中温度(t)随时间(z)变化的客观规律可用广义吴震东方程精确描述和控制。在冬季,导电混凝土墙面、地面及水泥混凝土路面在通电加热或融雪化冰过程中的热工计算也可用广义吴震东方程精确地描述,但需要考虑0℃的冰吸热后转化为0℃的水所需的溶解热。基于这一原理建立了导电混凝土融雪化冰新的热力学微分方程及一整套精确的理论公式,其中,电功率(P)的计算与导电混凝土材料的电阻系数(ρ)密切相关,在上述的基础上对导电混凝土材料电阻系数ρ的主要影响因素,作了研究和分析。  相似文献   
962.
为中小企业融资提供担保,可以保证中小企业融到资金。但是,担保公司却承担着巨大的担保风险,必须采取措施防范融资担保风险,保证担保公司的资产不受损失,实现其良性运作。长期发挥支持中小企业融资的作用。  相似文献   
963.
终身学习是终身教育的继承和超越,是人的一切活动的核心。介绍了终身学习的内涵及特征,阐述了数字图书馆以其信息资源数字化,信息传递网络化,资源管理分布化和共事化以及提供个性化智能信息的优势,成为人们终身学习的重要场所。  相似文献   
964.
“长江三角经济带”是我国最大的经济核心区,而电力又是制约其发展的一个重要因素。论述了实施“西电东送”,对实现我国能源合理配置,改善电源结构,促进“长江三角经济带”经济发展具有深远的战略意义和作用。  相似文献   
965.
从压力降型脉动发生的机理方面作了分析,用小扰动法计算了压力降型脉动发生的界限,同时用试验数据加以验证,还比较了3种不同布置的U型管的脉动界限。  相似文献   
966.
The turnover of adenosine triphosphate (ATP) in vertebrate skeletal muscle can increase more than a hundredfold during high-intensity exercise while the content of ATP in muscle may remain virtually unchanged. This requires that the rates of ATP hydrolysis and ATP synthesis are exactly balanced despite large fluctuations in reaction rates. ATP is regenerated initially at the expense of phosphocreatine (PCr) and then mainly through glycolysis from muscle glycogen. The increased ATP turnover in contracting muscle will cause an increase in the contents of adenosine diphosphate (ADP), adenosine monophosphate (AMP) and inorganic phosphate (Pi), metabolites that are substrates and activators of regulatory enzymes such as glycogen phosphorylase and phosphofructokinase. An intracellular metabolic feedback mechanism is thus activated by muscle contraction. How muscle metabolism is integrated in the intact body under physiological conditions is not fully understood. Common frogs are suitable experimental animals for the study of this problem because they can readily be induced to change from rest to high-intensity exercise, in the form of swimming. The changes in metabolites and effectors in gastrocnemius muscle were followed during exercise, post-exercise recovery and repeated exercise. The results suggest that glycolytic flux in muscle is modulated by signals from outside the muscle and that fructose 2,6-bisphosphate is a key signal in this process.  相似文献   
967.
Primary structure of dystrophin-related protein.   总被引:29,自引:0,他引:29  
  相似文献   
968.
对感应电机定子磁通定向控制中的死区效应进行了分析与讨论,从理论上阐明了死区的存在及其对系统性能的影响。经过数学分析与理论推导,得出了死区效应对系统在低速轻载时的影响尤为显著的结论,为工程实际提供了理论依据和方法。  相似文献   
969.
Hsp90 chaperones protein folding in vitro.   总被引:31,自引:0,他引:31  
H Wiech  J Buchner  R Zimmermann  U Jakob 《Nature》1992,358(6382):169-170
The heat-shock protein Hsp90 is the most abundant constitutively expressed stress protein in the cytosol of eukaryotic cells, where it participates in the maturation of other proteins, modulation of protein activity in the case of hormone-free steroid receptors, and intracellular transport of some newly synthesized kinases. A feature of all these processes could be their dependence on the formation of protein structure. If Hsp90 is a molecular chaperone involved in maintaining a certain subset of cellular proteins in an inactive form, it should also be able to recognize and bind non-native proteins, thereby influencing their folding to the native state. Here we investigate whether Hsp90 can influence protein folding in vitro and show that Hsp90 suppresses the formation of protein aggregates by binding to the target proteins at a stoichiometry of one Hsp90 dimer to one or two substrate molecule(s). Furthermore, the yield of correctly folded and functional protein is increased significantly. The action of Hsp90 does not depend on the presence of nucleoside triphosphates, so it may be that Hsp90 uses a novel molecular mechanism to assist protein folding in vivo.  相似文献   
970.
Matter with a high energy density (>10(5)?joules per cm(3)) is prevalent throughout the Universe, being present in all types of stars and towards the centre of the giant planets; it is also relevant for inertial confinement fusion. Its thermodynamic and transport properties are challenging to measure, requiring the creation of sufficiently long-lived samples at homogeneous temperatures and densities. With the advent of the Linac Coherent Light Source (LCLS) X-ray laser, high-intensity radiation (>10(17)?watts per cm(2), previously the domain of optical lasers) can be produced at X-ray wavelengths. The interaction of single atoms with such intense X-rays has recently been investigated. An understanding of the contrasting case of intense X-ray interaction with dense systems is important from a fundamental viewpoint and for applications. Here we report the experimental creation of a solid-density plasma at temperatures in excess of 10(6) kelvin on inertial-confinement timescales using an X-ray free-electron laser. We discuss the pertinent physics of the intense X-ray-matter interactions, and illustrate the importance of electron-ion collisions. Detailed simulations of the interaction process conducted with a radiative-collisional code show good qualitative agreement with the experimental results. We obtain insights into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. Our results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions.  相似文献   
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