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排序方式: 共有181条查询结果,搜索用时 15 毫秒
91.
将Luo和Woolliams模型中的混合正态分布推广到混合对数正态分布.先用矩量法得到各参数的估计值,再将此估计值作为EM(Expectation Maximization)算法迭代的初值进行迭代,将矩量估计和极大似然估计结合起来,提高了EM算法的收敛速度并使修改后的模型更符合生物学事实. 相似文献
92.
根据重组近交系(RIL)群体的遗传特性,由矩估计,获得了该类群体中分子标记(ML)与数量性状座位(QTL)间重组率估计、以及QTL基因型数量表现的均值和方差估计的理论公式与方法. 相似文献
93.
Bartek Wierzba 《哲学杂志》2013,93(6):611-623
This paper concerns interdiffusion in a diffusion couple and determination of the Kirkendall plane. The “entropy density” model is proposed in which the entropy is used to predict the position of the Kirkendall plane in a multicomponent system. It is shown that the marker position depends on the drift velocity and pressure field only. Application of the model is presented for ternary CoFeNi diffusion couples of three various initial compositions. The concentration profiles and entropy densities are calculated for each diffusion couple. The positions of the Kirkenadl planes are determined and compared with those obtained by velocity-curve and trajectory methods. 相似文献
94.
Sona KrizkovaOndrej Zitka Vojtech Adam Rene Kizek Michal MasarikMarie Stiborova Tomas EckschlagerGrace J. Chavis 《Trends in analytical chemistry : TRAC》2011,30(11):1819-1832
Matrix metalloproteinases (MMPs) are involved in many physiological and pathological processes. Due to their ability to cleave and to remodel components of surrounding tissues, MMPs may affect cell migration, differentiation, growth, inflammatory processes, neovascularization, wound healing, apoptosis, the uterine cycle and many other actions within the body, including those needed for tumorigenesis and other diseases.MMPs can therefore be used as potential markers for detecting various cancers, neurodegenerative, and immune and cardiovascular diseases. Numerous MMP assays were developed for clinical and research purposes, but far more attention has been devoted to understanding their biological functions.Due to differences in methodology, results obtained in various laboratory settings are difficult to compare because of the lack of standards and analytical methods of validation. Limits of detection of particular methods used for identifying MMPs are also disputable.Enzymatic, immunochemical and fluorimetric methods are particularly suitable for clinical use. In-vivo imaging methods offer many potential advantages in cancer research and diagnostics. Other methods are subject to investigation [e.g., phage display, multiple-enzyme/multiple-reagent assay system (MEMRAS) and activity-based profiling]. 相似文献
95.
Xiao-Ye Jin Wei Cui Chong Chen Yu-Xin Guo Yong-Wei Tao Qiong Lan Ting-Ting Kong Bo-Feng Zhu 《Electrophoresis》2020,41(3-4):235-245
A biogeographic estimate of a certain population can not only discern population substructure in the whole genome association study, but also provide informative clues for forensic investigations when obtained DNA genotypes do not find a match in the available forensic DNA database. In this study, 100 ancestry informative single nucleotide polymorphisms (AISNPs) were first presented to differentiate three continental ancestries (African, East Asian and European). Ultimately, forty-two AISNPs were chosen from the 100 AISNPs. Distinguishing power of the 100 and 42 AISNPs for differentiating continental populations was further evaluated with population cluster analyses. Results indicated both of AISNP sets could efficiently differentiate 11 training populations from the three continents. Further validation of 42 AISNPs in testing population set indicated these 42 AISNPs performed well for ancestry inferences of these testing individuals. Ancestry components of Uyghur group were assessed by comparing with different continental populations based on these 42 AISNPs. Results revealed that East Asian populations contributed more ancestry components to the studied Uyghur group than European populations. In conclusion, our study is expected to provide more AISNP markers and enrich extant reference database. 相似文献
96.
ZHANG Hai-tao LI Zhuo ZHANG Jun-bo ZHANG Yang YE Jian-nong CHU Qing-cui ZHANG Mei-jiang 《高等学校化学研究》2013,29(5):850-853
An electrophoretic method was developed for the determination of several important catecholamine markers, namely norepinephrine, epinephrine, dopamine, metanephrine, vanillylmandelic acid and homovanillic acid in urine samples. Under the optimum conditions, the six marker compounds could be well separated with the major coexisting interference compound uric acid within 24 min at a separation voltage of 16 kV in a borate running buffer (80 mmol/L, pH=9.48). Highly linear response can be obtained over three orders of magnitude for the above markers with the low limits of detection ranging from 1.0 ng/mL to 5.0 ng/mL(S/N=3). The proposed capillary electrophoresis with amperometric detection(CE-AD) method has been used to simultaneously determine the six catecholamine markers in urine samples of healthy volunteers and patients suffering from different diseases avoiding redundant measurements and high assay cost; and the electrochemical profiles can suggest more diagnostic information of multiple diseases, which provides a promising and convenient entry into primary diagnoses of several clinical diseases. 相似文献
97.
The fluorescence behavior of a calix[6]arene with a dansyl group as fluorescence marker (C6-DA) was investigated with respect to the inclusion properties of alkaloids as atropine and cocaine. A strong hypsochromic shift of the fluorescence band and a strong increase in fluorescence intensity is connected with the interaction of atropine to the lower rim of the C6-DA. The fluorescence increase is saturated at an atropine concentration above the 1:1 complex formation. Addition of cocaine to the complexed atropine-C6-DA leads to a decrease of the fluorescence intensity which could be explained by an exchange mechanism of the complexed molecules. The complexation of the atropine (the “belladonna effect”) is interpreted by electrostatic interaction (proton transfer from the carboxylic group to the nitrogen) with important contribution from hydrogen bonding by the guest OH-group. 相似文献
98.
建立了阿胶中马、牛、羊、猪、骆驼、鹿皮源成分的检测方法。通过比对驴皮和马皮、牛皮、猪皮、羊皮、骆驼皮、鹿皮胶原蛋白的序列,采用蛋白酶切技术和高分辨质谱技术发现理论的各杂皮胶原蛋白特征肽。同时建立三重四极杆质谱筛查方法,以含0.1%(v/v)甲酸的乙腈溶液和0.1%(v/v)甲酸水溶液作为流动相,梯度洗脱,电喷雾离子源(ESI)正离子扫描模式,多反应监测。15批阿胶样品检出了杂皮源成分。该方法操作简便,专属性强,可用于阿胶中杂皮源成分的鉴别,并已成功用于阿胶日常打假监督抽验工作。 相似文献
99.
100.