A Partial Likelihood Estimator of Vaccine Efficacy

A partial likelihood method is proposed for estimating vaccine efficacy for a general epidemic model. In contrast to the maximum likelihood estimator (MLE) which requires complete observation of the epidemic, the suggested method only requires information on the sequence in which individuals are infected and not the exact infection times. A simulation study shows that the method performs almost as well as the MLE. The method is applied to data on the infectious disease mumps.     

Partial Least Squares: A First-order Analysis

We compare the partial least squares (PLS) and the principal component analysis (PCA), in a general case in which the existence of a true linear regression is not assumed. We prove under mild conditions that PLS and PCA are equivalent, to within a first-order approximation, hence providing a theoretical explanation for empirical findings reported by other researchers. Next, we assume the existence of a true linear regression equation and obtain asymptotic formulas for the bias and variance of the PLS parameter estimator     

A semiparametric Bayesian model for repeatedly repeated binary outcomes

Summary.  We discuss the analysis of data from single-nucleotide polymorphism arrays comparing tumour and normal tissues. The data consist of sequences of indicators for loss of heterozygosity (LOH) and involve three nested levels of repetition: chromosomes for a given patient, regions within chromosomes and single-nucleotide polymorphisms nested within regions. We propose to analyse these data by using a semiparametric model for multilevel repeated binary data. At the top level of the hierarchy we assume a sampling model for the observed binary LOH sequences that arises from a partial exchangeability argument. This implies a mixture of Markov chains model. The mixture is defined with respect to the Markov transition probabilities. We assume a non-parametric prior for the random-mixing measure. The resulting model takes the form of a semiparametric random-effects model with the matrix of transition probabilities being the random effects. The model includes appropriate dependence assumptions for the two remaining levels of the hierarchy, i.e. for regions within chromosomes and for chromosomes within patient. We use the model to identify regions of increased LOH in a data set coming from a study of treatment-related leukaemia in children with an initial cancer diagnostic. The model successfully identifies the desired regions and performs well compared with other available alternatives.     

一类平衡阶数为负整数的非线性偏微分方程的精确解

以齐次平衡原理为基础,给出了平衡阶数为负整数时的求解非线性偏微分方程的基本方法,并对方程ut=αuuxx+βu2x+p(u-u2)进行求解,到得了它的两个不同形式的精确解。     

Optimum constant-stress life test plans for Pareto distribution under type-I censoring

The paper considers the case of constant-stress partially accelerated life testing (CSPALT) when two stress levels are involved under type-I censoring. The lifetimes of test items are assumed to follow a two-parameter Pareto lifetime distribution. Maximum-likelihood method is used to estimate the parameters of CSPALT model. Confidence intervals for the model parameters are constructed. Optimum CSPALT plans that determine the best choice of the proportion of test units allocated to each stress are developed. Such optimum test plans minimize the generalized asymptotic variance of the maximum-likelihood estimators of the model parameters. For illustration, Monte Carlo simulation studies are presented.     

Bivariate prior distributions via branching exchangeable sequences

This paper provides a novel approach to constructing bivariate prior distributions. The idea is based on the notion of partial exchangeability. In particular, in a simple extension of the exchangeable sequence, we create two dependent exchangeable sequences via a branching mechanism. This implies the existence of a bivariate prior distribution.     

An almost sure central limit theorem for self-normalized partial sums of weakly dependent random variables

Abstract

We give here an almost sure central limit theorem for self-normalized partial sums of a strictly stationary φ-mixing sequences which is in the domain of attraction of the normal law with mean zero and possibly infinite variance. Our result substantially extend a result on the almost sure central limit theorem previously obtained by Huang and Pang (2010).     

Development of measures to assess dimensions of IS operation transactions

Information Systems (IS) researchers often rely on Organization Economics models to describe and explain various IS management issues. While those models are found to be useful, measures are yet to be proposed to assess the dimensions of IS transactions. In this paper we present the results of a study that was a first effort toward this end. The focus of the study was on one type of transaction, IS operations, in a particular management context, that of outsourcing. Measures were developed for four critical dimensions of IS operation transactions: asset specificity, measurement problem, origin of the most important investment, and governance mechanism. Data from 250 large Canadian firms were used to assess the measures, using the partial least squares technique.     

对郭沫若诗歌制作道路的反思

目前 ,学术界以 2 1世纪文学史的眼光 ,要求打通中国现代当代 ,研究横跨现当代的作家。在中国现当代文学史上 ,郭沫若是一个伟大的存在 ,也是个复杂的存在。本文通过勾勒他诗歌创作态势 ,从他文艺理论的偏颇和生存境遇的状况入手 ,对郭沫若诗歌道路进行反思。这将有助于我们解说 2 0世纪中国文学的“生存境遇”及 2 0世纪中国文学的审美机制。