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101.
An approach to comparing treatments based on repeated measures 总被引：1，自引：0，他引：1
102.
Pawel Sledz Heping Zheng Krzysztof Murzyn Maksymilian Chruszcz Matthew D Zimmerman Mahendra D Chordia Andrzej Joachimiak Wladek Minor 《Protein science : a publication of the Protein Society》2010,19(7):1395-1404
Surface lysine methylation (SLM) is a technique for improving the rate of success of protein crystallization by chemically methylating lysine residues. The exact mechanism by which SLM enhances crystallization is still not clear. To study these mechanisms, and to analyze the conditions where SLM will provide the optimal benefits for rescuing failed crystallization experiments, we compared 40 protein structures containing N,N-dimethyl-lysine (dmLys) to a nonredundant set of 18,972 nonmethylated structures from the PDB. By measuring the relative frequency of intermolecular contacts (where contacts are defined as interactions between the residues in proximity with a distance of 3.5 Å or less) of basic residues in the methylated versus nonmethylated sets, dmLys-Glu contacts are seen more frequently than Lys-Glu contacts. Based on observation of the 10 proteins with both native and methylated structures, we propose that the increased rate of contact for dmLys-Glu is due to both a slight increase in the number of amine-carboxyl H-bonds and to the formation of methyl C–H···O interactions. By comparing the relative contact frequencies of dmLys with other residues, the mechanism by which methylation of lysines improves the formation of crystal contacts appears to be similar to that of Lys to Arg mutation. Moreover, analysis of methylated structures with the surface entropy reduction (SER) prediction server suggests that in many cases SLM of predicted SER sites may contribute to improved crystallization. Thus, tools that analyze protein sequences and mark residues for SER mutation may identify proteins with good candidate sites for SLM. 相似文献
103.
Dominique Pelletier Nazha Selmaoui‐Folcher Thomas Bockel Thomas Schohn 《Ecology and evolution》2020,10(14):7021-7049
104.
基于Fiedler向量的基因表达谱数据分类方法 总被引：1，自引：0，他引：1
尝试将一种基于图的Fiedler向量的聚类算法引入到基因表达谱数据的肿瘤分类中来。该方法将分属不同类的所有样本通过高斯权构造Laplace完全图,经SVD分解后获得Fiedler向量,利用各样本所对应的Fiedler向量分量的符号差异来进行基因表达谱数据的分类。通过模拟数据仿真实验和对白血病两个亚型(ALL与AML)及结肠癌真实数据实验,证明了这一方法的有效性。 相似文献
105.
长白山站的研究数据库管理系统翟永华,赵士洞（中国科学院沈阳应用生态研究所１１００１５）Ｄａｔｅ－ＢａｓｅＭａｎａｇｅｍｅｎｔＳｙｓｔｅｍｉｎＣｈａｎｇｂａｉｓｈａｎＦｏｒｅｓｔＥｃｏｓｙｓｔｅｍＲｅｓｅａｒｃｈＳｔａｔｉｏｎ．￥ＺｈａｉＹｏｎｇｈｕａ... 相似文献
106.
区域生态效率(eco-efficiency)评价是考量区域可持发展的重要内容.基于物质流分析(material flow analysis, MFA)构建区域生态效率评价指标体系,并将污染物排放作为一种非期望输入引入到数据包络分析(data envelopment analysis, DEA)模型中,以江苏省(1990～2005年)为例进行生态效率分析评价.结果表明,江苏省的区域生态效率在1990～2005年期间呈现逐步上升的趋势.但是,同期的总物质投入(total material input, TMI)、物质需求总量(total material requirement, TMR)和污染物排放量也呈上升趋势.因此,江苏省社会经济发展和环境影响总体上呈现\"弱脱钩(weak de-link)\". 相似文献
107.
From an analysis of over 900 specimens of camaenid land snails, we have assembled a molecular phylogeny of 327 tips covering > 70% genera across the entire continent of Australia and including > 90% of eastern species. Our approach emphasizes sampling to identify lineage flocks from populations down to build a hierarchical gene‐by‐taxa tapestry or supermatrix dataset using three mitochondrial genes, then analysed with Markov chain Monte Carlo and fast maximum likelihood methods. Similarity amongst taxa set results suggests missing data cause only minor distortions. This is supplemented by a separate higher level 28S rDNA phylogeny for a global scale perspective. The shallow divergence of Australasian forms, and their nesting within South‐East Asian groups within the Helicoidea supergroup extending from Europe to North America, is consistent with the Solem hypothesis of Laurasian immigration of c. Miocene origin, and so being more than 400 species in 80‐plus genera spread across the continent of Australia from rainforest to desert, forms an immense radiation. There is a major distinction between eastern and western lineages, with some key exceptions. Finer scale patterns of relictual endemics indicate that many ancestral lineages were in place before the major decline and breakup of the Tertiary mesic forest realm that once dominated Gondwanan Australia, and so chart the phylogenetic turnover of ecosystem change from mesic to xeric. The various higher classification schemes proposed all founder on the sheer scale of this radiation. Of 30 polytypic genera tested, at least 18 are not monophyletic, highlighting (1) the repeated radiation of shell forms, and (2) that the current higher taxonomy is unacceptable. Here we provide a phylogenetic and biogeographically condign arrangement as the basis for future elaborations. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 531–572. 相似文献
108.
A simple test of the proportional hazards assumption 总被引：2，自引：0，他引：2
109.
三维图像的处理和操作需要将一般的断层序列插值成为具有各坐标轴一致的分辨率的体数据,而目前最常用的线性插值方法在层间距较大时会导致图像边缘模糊和出现伪影。Penney根据现有的非刚体匹配方法,提出了利用图像形变场数据的插值算法,大大提高了层间插值的质量。本文对Penney提出的算法进行了两方面的改进,在配准过程中用简单的单射性约束取代了复杂的平滑性约束,用邻域平均算法替代Penney使用的最邻近直线插值方法,并将新算法的实验结果与原算法、线性插值进行了对比,新算法在保持高质量插值的前提下提高了计算速度。该算法可以应用于精度要求比较高的体数据插值重建过程。 相似文献
110.
Yu-jiang Yuan Tong-wen Zhang Wen-shou Wei Daniel Nievergelt Anne Verstege Shu-long Yu Rui-bo Zhang Jan Esper 《Dendrochronologia》2013,31(3):192-197
Three tree-ring maximum latewood density chronologies were developed from high elevation Picea schrenkiana sites in the western Tien Shan Mountains using different detrending methods. The new chronologies extend back to the early 16th and late 17th centuries, and contain significant late spring and summer temperature signals, respectively. An assessment of varying detrending methods and band-pass filtering the chronologies revealed only slightly differing low frequency trends retained in the maximum latewood densities. The distance between sampling sites and the varying seasonality of limiting climatic factors are identified as key drivers affecting the correlation among the maximum latewood density records in the study region. The new chronologies represent reliable proxies of high elevation late spring and summer temperature variability in an area underrepresented by such data, and are ready-to-use for network analyses addressing longer-term climate variations in eastern central Asia. 相似文献