Transformation-associated recombination between diverged and homologous DNA repeats is induced by strand breaks

Rearrangements within plasmid DNA are commonly observed during transformation of eukaryotic cells. One possible cause of rearrangements may be recombination between repeated sequences induced by some lesions in the plasmid. We have examined the mechanisms of transformation-associated recombination in the yeast Saccharomyces cerevisiae using a plasmid system which allowed the effects of physical state and/or extent of homology on recombination to be studied. The plasmids contain homologous or diverged (19%) repeats of the URA3 genes (from S. cerevisiae or S. carlsbergensis) separated by the genetically detectable ADE2 colour marker. Recombination during transformation for covalently closed circular plasmids was over 100-fold more frequent than during mitotic growth. The frequency of recombination is partly dependent on the method of transformation in that procedures involving lithium acetate or spheroplasting yield higher frequencies than electroporation. When present in the repeats, unique single-strand breaks that are ligatable, as well as double-strand breaks, lead to high levels of recombination between diverged and identical repeats. The transformation-associated recombination between repeat DNAs is under the influence of the RAD52 and RAD1 genes.     

Fuzzy divergence, probability measure of fuzzy events and image thresholding

A new measure called divergence between two fuzzy sets is introduced along with a few properties. Its application to clustering problems is indicated and applied to an object extraction problem. A tailored version of the probability measure of a fuzzy event is also used for image segmentation. Both parametric and non-parametric probability distributions are considered in this regard.     

高功率CO_2激光束发散角的测量

理论和实验研究了高功率CO_2激光器的光束发散角测量。对三种不同测量方法进行了理论分析,给出了相应公式和计算曲线。     

Predicting the number of accidents at a road junction

We consider a model, within a Bayesian framework, which can be used to predict the number of accidents occurring at a road junction in a given period of time. The predictions are based on measurements of the traffic flows as well as on covariates which describe important features of the junctions. Various approximate and estimative methods, which use Gibbs sampling, posterior normality and Laplace approximations, are considered and compared. Procedures to assess the importance of the different covariates through the use of the Kullback-Leibler measure of divergence are also developed.     

确定KrF激光光束品质的光楔法

运用光楔对发散角较大、光束品质不够好的ＫｒＦ激光光束进行了分光测量，测量了ＫｒＦ激光光束的一维能量分布和远场发散角；具体计算了ＫｒＦ激光光束剖面的能量密度分布的均匀性。     

氟硅酸铵处理KL沸石对有关指标的影响

用（ＮＨ４）２ＳｉＦ６处理了ＫＬ沸石。结果表明：无ＮＨ４Ａｃ缓冲剂时，所得样品具有较多的中间孔，但孔分布不集中；加入ＮＨ４Ａｃ作为缓冲剂，或延长反应时间，所制备的样品不仅可获得较高的结晶度，而且孔分布集中程度也得到明显改善。但无论如何，中间孔的孔质及孔分布集中程度均远不如一次合成的ＭＣＭ－４１中孔材料。     

对Riemann重新安排定理证明中“注”的证明

针对菲赫金哥尔茨著《微积分学教程》第二卷第二分册中Ｒｉｅｍａｎｎ定理证明中的“注”（第３１４页）所提及条件收敛级数重排后发散的情形，分三种情形给予推证．     

多棒串接固体激光器输出光束发散角的研究

分析了输出耦合镜和热透镜效应对激光器输出高斯光束发散角的影响.首先对等间距腔型和对称腔型双棒串接固体激光器输出高斯光束的发散角进行了比较,然后分别计算和讨论了单棒、双棒和三棒对称腔型固体激光器输出多模高斯光束发散角与热焦距的关系.     

基于三层平板理论的LDA快轴发散角特性研究

以三层平板理论为基础,得出半导体激光器阵列(LDA)快轴方向发散角的简化模型,从该模型中可以看出,对LDA的快轴发散角的影响因素主要有:单个发光单元的波导结构(包括有源层厚度、折射率)、波长和bar间距.通过仿真给出了LDA快轴发散角在这几个主要因素影响下的变化趋势.为了解LDA快轴发散角特性以及它的应用提供了理论支持.     

Classifying densities using functional regression trees: Applications in oceanology

The problem of building a regression tree is considered when the response variable is a probability density function. Splitting criteria which are well adapted to measure the dissimilarity between densities are proposed using the Csiszár's f-divergence. The comparison between performances of trees constructed with various criteria is tackled through numerical simulations. Afterwards, a tree is constructed to predict the size distribution of a zooplankton community using a set of explanatory environmental variables. Functional PCA is used in order to interpret the main modes of variation of the size spectra around the predicted density in each terminal node. Finally, a bagging procedure is used to increase the accuracy of the tree-based model.