原位杂交中鲑鱼精DNA处理方法探究

采用机械打断/沸水浴和超声波处理两种方法对原位杂交中的封闭DNA——鲑鱼精DNA进行了断裂处理。分别探讨了不同的吹打次数、煮沸时间和超声波处理时间对鲑鱼精DNA片段大小的影响,并且对机械打断/沸水浴和超声波处理两种方法结果进行了比较分析。研究结果表明在煮沸时间20min时,吹打次数可根据所需原位杂交片段大小进行调整;超声波适宜打断时间为20min。     

Empirical likelihood‐based inference for genetic mixture models

The authors show how the genetic effect of a quantitative trait locus can be estimated by a nonparametric empirical likelihood method when the phenotype distributions are completely unspecified. They use an empirical likelihood ratio statistic for testing the genetic effect and obtaining confidence intervals. In addition to studying the asymptotic properties of these procedures, the authors present simulation results and illustrate their approach with a study on breast cancer resistance genes.     

Uncertainties in the CIIT Model for Formaldehyde-Induced Carcinogenicity in the Rat: A Limited Sensitivity Analysis–I

Scientists at the CIIT Centers for Health Research (Conolly et al., 2000, 2003; Kimbell et al., 2001a, 2001b) developed a two-stage clonal expansion model of formaldehyde-induced nasal cancers in the F344 rat that made extensive use of mechanistic information. An inference of their modeling approach was that formaldehyde-induced tumorigenicity could be optimally explained without the role of formaldehyde's mutagenic action. In this article, we examine the strength of this result and modify select features to examine the sensitivity of the predicted dose response to select assumptions. We implement solutions to the two-stage cancer model that are valid for nonhomogeneous models (i.e., models with time-dependent parameters), thus accounting for time dependence in variables. In this reimplementation, we examine the sensitivity of model predictions to pooling historical and concurrent control data, and to lumping sacrificed animals in which tumors were discovered incidentally with those in which death was caused by the tumors. We found the CIIT model results were not significantly altered with the nonhomogeneous solutions. Dose-response predictions below the range of exposures where tumors occurred in the bioassays were highly sensitive to the choice of control data. In the range of exposures where tumors were observed, the model attributed up to 74% of the added tumor probability to formaldehyde's mutagenic action when our reanalysis restricted the use of the National Toxicology Program (NTP) historical control data to only those obtained from inhalation exposures. Model results were insensitive to hourly or daily temporal variations in DNA protein cross-link (DPX) concentration, a surrogate for the dose-metric linked to formaldehyde-induced mutations, prompting us to utilize weekly averages for this quantity. Various other biological and mathematical uncertainties in the model have been retained unmodified in this analysis. These include model specification of initiated cell division and death rates, and uncertainty and variability in the dose response for cell replication rates, issues that will be considered in a future paper.     

Interpreting forensic DNA mixtures: allowing for uncertainty in population substructure and dependence

We consider the assessment of deoxyribonucleic acid (DNA) profiles from biological samples containing a mixture of DNA from more than one person. The problem has been investigated in the context of likelihood ratios by Weir and co-workers under the assumption of independent alleles in DNA profiles. However, uncertainty about independence may arise from various factors such as population substructure and relatedness. This issue has received considerable attention in recent years. Ignoring this uncertainty may seriously overstate the strength of the evidence and therefore disadvantage innocent suspects. Taking this uncertainty into account, we develop a general formula for calculating the match probabilities of DNA profiles. Thus, we extend the result derived by Weir and co-workers to the dependence situation, which is often more to the benefit of the defendant in comparison with the simple product rule result based on an independence assumption. The effect of dependence of alleles on likelihood ratio estimates can be seen in the analysis of two real data sets.     

基于最小生成树的基因分类算法

随着基因芯片技术的快速发展以及其在基因表达分析等过程中的应用,产生了大量的基因表达谱数据,如何处理和分析这些数据并从中提取出有价值的生物学信息成为一个极为重要的课题,基因分类是进行基因数据处理的常用方法。本文首先利用主成分分析法(PCA)把基因的多个属性转化为少数几个综合属性,将基因表达谱数据映射成一个带权图,并将图论的最小生成树理论引入基因分类分析方法,然后设计了基于最小生成树的基因分类算法,理论分析和仿真结果表明了该算法的可行性和有效性。     

一个评定椭圆的线轮廓度误差的方法

给出了一个按测量坐标值原则检测、最小区域原则评判椭圆轮廓的线轮廓度误差的方法,编制出程序在计算机上进行了模拟验证。结果表明,检测值与理论值符合相当好。     

Positioning and role of public relations in large Belgian organizations

This paper studies the position and role of public relations in the hierarchical structure of Belgian organizations of at least 50 employees. Empirical data was collected from a web survey (n = 750) to find out to what extent principles of excellence in public relations are applied in Belgium.     

Mixture models for matched pairs

Mixture models for matched pairs arise when the pair-specific parameter is assumed to be a random quantity. We explore the use of semiparametric maximum-likelihood methods for a family of mixture models for matched pairs. The geometry of mixture likelihoods provides insight into the properties of these models.     

Higher order asymptotic computation of Bayesian significance tests for precise null hypotheses in the presence of nuisance parameters

The full Bayesian significance test (FBST) was introduced by Pereira and Stern for measuring the evidence of a precise null hypothesis. The FBST requires both numerical optimization and multidimensional integration, whose computational cost may be heavy when testing a precise null hypothesis on a scalar parameter of interest in the presence of a large number of nuisance parameters. In this paper we propose a higher order approximation of the measure of evidence for the FBST, based on tail area expansions of the marginal posterior of the parameter of interest. When in particular focus is on matching priors, further results are highlighted. Numerical illustrations are discussed.     

一种插层聚合纳米复合材料的调堵特性研究

针对苛刻油藏条件下对调剖堵水材料性能要求越来越高的现状，利用烯丙基单体和黏土以及实验室自制的层间修饰剂、扩链剂形成插层聚合纳米复合材料CAG，研究其调堵性能。性能评价结果显示其在80～140℃条件下老化30d，断裂应力变化不大。在140℃条件下，断裂应力变化仅为3.2%；断裂应力和有效黏度基本不受实验用水矿化度的影响；在剪切速率为 10s^-1条件下，基液黏度为39.54mPa·s；在裂缝条件下的封堵强度为23.6MPa，压力梯度为0.393MPa/cm，封堵率为98%；在三层非均质岩芯中的采收率实验中，比水驱采收率增加了5%。插层聚合纳米复合材料CAG具有耐温抗盐能力强、注入压力低、封堵强度大的优点，成功地解决了调堵剂注入性能与封堵性能的矛盾，是一种具有广阔发展前景的调堵材料。