共查询到20条相似文献,搜索用时 15 毫秒
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On the W test for the extreme value distribution 总被引:1,自引:0,他引:1
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Modelling multivariate extreme value distributions 总被引:10,自引:0,他引:10
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Beneficial fitness effects are not exponential for two viruses 总被引:1,自引:0,他引:1
Rokyta DR Beisel CJ Joyce P Ferris MT Burch CL Wichman HA 《Journal of molecular evolution》2008,67(4):368-376
The distribution of fitness effects for beneficial mutations is of paramount importance in determining the outcome of adaptation.
It is generally assumed that fitness effects of beneficial mutations follow an exponential distribution, for example, in theoretical
treatments of quantitative genetics, clonal interference, experimental evolution, and the adaptation of DNA sequences. This
assumption has been justified by the statistical theory of extreme values, because the fitnesses conferred by beneficial mutations
should represent samples from the extreme right tail of the fitness distribution. Yet in extreme value theory, there are three
different limiting forms for right tails of distributions, and the exponential describes only those of distributions in the
Gumbel domain of attraction. Using beneficial mutations from two viruses, we show for the first time that the Gumbel domain
can be rejected in favor of a distribution with a right-truncated tail, thus providing evidence for an upper bound on fitness
effects. Our data also violate the common assumption that small-effect beneficial mutations greatly outnumber those of large
effect, as they are consistent with a uniform distribution of beneficial effects. 相似文献
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Multivariate distributions with support above the diagonal 总被引:1,自引:0,他引:1
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Markov chain models for threshold exceedances 总被引:7,自引:0,他引:7
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Bivariate extreme value theory: Models and estimation 总被引:21,自引:0,他引:21
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For Location and Scale models with Type I Censored Data the estimation of the parameters based on likelihood is analyzed. When the sample size is very small the usual procedures for inference based on the asymptotic distribution of the statistics do not function properly. We develop higher‐order asymptotic methods and their performance is investigated by Monte Carlo experiments. 相似文献
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A nonparametric estimation procedure for bivariate extreme value copulas 总被引:10,自引:0,他引:10
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动物巢区二维正态概率模型的探讨 总被引:3,自引:1,他引:2
本文根据二维正态分布的性质以及识别动物极端活动位点的技术建立了一种动物巢区二维正态概率模型。应用中,首先对动物活动位点进行二维正态分布检验,采用加权法消除了极端位点的影响。在二维正态分布条件下,动物巢区定义为由下列方程决定的椭圆区域d_β由下列方程组确定其中β为巢区所含活动位点百分比,a_i(i=1,2,…6)为常数。椭圆巢区两半轴长分别为d_β·面积为π·d_β·σ_x~2 ·椭圆的方向由坐标轴旋转角 相似文献
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极端低温分布模型在邓恩桉抗寒性标准定量化应用的研究 总被引:1,自引:0,他引:1
依据闽北建阳市1971~2005年的极端低温资料构建极值分布数学模型, 用电导率指标确定邓恩桉(Eucalyptus dunnii)优株的半致死温度,预测0~5年、5~10年和10年以上可能出现的极端临界低温分别是-7.47℃、-7.47~-8.5℃和-8.68℃。首次提出利用极端低温分布模型结合电导率指标的方法定量划分林木的抗寒性, 称为“抗寒性极端低温分布法”, 该方法可广泛应用于不同区域、树种的抗寒适应性定量评价和林木个体的抗寒适应性筛选。 相似文献
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By generating a large diversity of molecules, the immune system selects antibodies that bind antigens. Sharing the same approach, combinatorial biotechnologies use a large library of compounds to screen for molecules of high affinity to a given target. Understanding the properties of the best binders in the pool aids the design of the library. In particular, how does the maximum affinity increase with the size of the library or repertoire? We consider two alternative models to examine the properties of extreme affinities. In the first model, affinities are distributed lognormally, while in the second, affinities are determined by the number of matches to a target sequence. The second model more explicitly models nucleic acids (DNA or RNA) and proteins such as antibodies. Using extreme value theory we show that the logarithm of the mean of the highest affinity in a combinatorial library grows linearly with the square root of the log of the library size. When there is an upper bound to affinity, this “absolute maximum” is also approached approximately linearly with root log library size, reaching the upper limit abruptly. The design of libraries may benefit from considering how this plateau is reached as the library size is increased. 相似文献
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