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1.
Neutron diffraction provides an experimental method of directly locating hydrogen atoms in proteins, a technique complimentary to ultra-high-resolution [1, 2] X-ray diffraction. Three different types of neutron diffractometers for biological macromolecules have been constructed in Japan, France and the United States, and they have been used to determine the crystal structures of proteins up to resolution limits of 1.5-2.5 A. Results relating to hydrogen positions and hydration patterns in proteins have been obtained from these studies. Examples include the geometrical details of hydrogen bonds, H/D exchange in proteins and oligonucleotides, the role of hydrogen atoms in enzymatic activity and thermostability, and the dynamical behavior of hydration structures, all of which have been extracted from these structural results and reviewed. Other techniques, such as the growth of large single crystals, the preparation of fully deuterated proteins, the use of cryogenic techniques, and a data base of hydrogen and hydration in proteins, will be described.  相似文献   
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应用粒子群算法从已知数据中确定置信测度和似然测度   总被引:1,自引:1,他引:1  
应用粒子群算法确定置信测度和似然测度,针对2种模糊测度的特点,对基本粒子群算法进行改进.通过与基本粒子群算法和遗传算法的分析和比较,验证了改进算法的有效性和高效性.  相似文献   
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A deeper understanding of models is sought in considering what models do, rather what they are. This distinction emphasizes how two different modeling strategies, as they pursue different purposes, do invest in different options, in particular in regard to rigor and immediate empirical relevance. The analysis focuses therefore on the services expected from models by the scientists who construct them: models are sought for how they contribute to exploring and testing the context in which they operate. In a forthcoming Part II these general considerations will be anchored in the presentation of specific case studies.  相似文献   
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The characteristics of artificial life are emergence and dynamic interaction with the environment, and food-chain phenomenon appears to be an important and widespread phenomenon in the living system. According to those ideas above, the local action rules of artificial life are defined, and a novel artificial-life algorithm named food-chain algorithm is proposed. Food-chain algorithm achieves optimization computation by mimicking the evolution of natural ecosystem and the information processing mechanism of natural organisms. In the article, the definition, ideology, and flow of food-chain algorithm and the energy rules of artificial-life metabolism and the transformation rules of movement range of artificial-life individuals are discussed. Compared with real-coded genetic algorithm by standard functions, food-chain algorithm is more predominant in function optimization. Furthermore, food-chain algorithm has lifelike traits, for example, autonomy, evolution, and self-adaptive, and it is fit to deal with the optimization problems of lifelike systems.  相似文献   
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汽车排气系统的振动和噪声是影响乘坐舒适性的因素之一。为研究排气消声器结构模态和声腔模态对消声器降噪性能的影响规律,建立声学有限元模型计算壳体结构模态和声腔模态,并分析各自振型模态和固有频率之间的关系。结果表明:在低频率范围内,壳体结构模态和声腔模态的固有频率发生耦合共振,导致降噪效果不佳;增加消声器外壳壁厚可提升结构固有频率,降低排气系统振动和辐射噪声水平。  相似文献   
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 为了纠正多单元中β 射频超导腔在制造过程中由于加工误差和焊接收缩引起的场频率偏移,参照超导腔特性和场平滑度调谐原理设计了多单元超导腔场平滑度调谐器,根据超导腔场平滑度的测试要求搭建了测试系统,并将调谐器用于多单元中β射频超导腔场平滑度的调制过程。测试和实验结果表明:多单元中β 射频超导腔场平滑度调谐器可以成功用于超导腔场平滑度的调制。  相似文献   
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采用固相萃取/超声辅助萃取-超高效液相色谱-质谱联用技术,建立了一种适用于市政污水厂污水和污泥中15种典型抗生素的同步测定方法.污水样品经过滤、酸化及固相萃取柱富集净化;污泥样品用体积比为3 ∶ 1的McIlvaine缓冲液-乙腈和Mg( NO3 )2-NH3·H2 O超声提取后经固相萃取柱富集净化.以体积分数为0. ...  相似文献   
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