Threshold‐free estimation of functional antibody titers of a group B streptococcus opsonophagocytic killing assay

Opsonophagocytic killing assays (OPKA) are routinely used for the quantification of bactericidal antibodies in blood serum samples. Quantification of the OPKA readout, the titer, provides the basis for the statistical analysis of vaccine clinical trials having functional immune response endpoints. Traditional OPKA titers are defined as the maximum serum dilution yielding a predefined bacterial killing threshold value, and they are estimated by fitting a dose‐response model to the dilution‐killing curve. This paper illustrates a novel definition of titer, the threshold‐free titer, which preserves biological interpretability while not depending on any killing threshold or on a postulated shape of the dose‐response curve. These titers are shown to be more precise than the traditional threshold‐based titers when using simulated and experimental group B streptococcus OPKA experimental data. Also, titer linearity is shown to be not measurable when using threshold‐based titers, whereas it becomes measurable using threshold‐free titers. The biological interpretability and operational characteristics demonstrated here indicate that threshold‐free titers are an appropriate tool for the routine analysis of OPKA data. Copyright © 2015 John Wiley & Sons, Ltd.     

Explaining inconsistencies between patients and collaterals: validity in outcome studies of coercive alcoholism treatment

This study aims to assess the consistency of replies to questionnaires mailed to patients and two kinds of collaterals, i.e., social workers and significant others, at a public treatment center with socially unstable and compulsory committed patients. It compares the quantity and kind of discrepancies between replies by patients and collaterals on outcome data concerning social situation and drinking habits. It aims to measure the amount of systematic bias among factors that may explain inconsistencies between reports, especially the factors compulsory commitment, worse outcome, frequency of contact and type of collateral. The responders generally agreed. Variables in which there was less agreement were explored in logistic regressions using ten explanatory variables. Significant relations did not exceed those expected by chance. Discrepancies were not systematic in size and kind. On a six-rank ordinal scale of alcohol use or abuse, however, patients tended to underestimate the extent of their abuse. Inconsistencies here concerned the degree but not the presence of abuse. No difference in consistency due to type of collateral was found. In conclusion, the consistency of the questionnaires was high and independent of the social situation of the patient, of compulsory commitment and of other background or treatment factors, as well as of treatment outcome and type of collateral.     

The Copula Information Criteria

We derive two types of Akaike information criterion (AIC)‐like model‐selection formulae for the semiparametric pseudo‐maximum likelihood procedure. We first adapt the arguments leading to the original AIC formula, related to empirical estimation of a certain Kullback–Leibler information distance. This gives a significantly different formula compared with the AIC, which we name the copula information criterion. However, we show that such a model‐selection procedure cannot exist for copula models with densities that grow very fast near the edge of the unit cube. This problem affects most popular copula models. We then derive what we call the cross‐validation copula information criterion, which exists under weak conditions and is a first‐order approximation to exact cross validation. This formula is very similar to the standard AIC formula but has slightly different motivation. A brief illustration with real data is given.     

基于遗传算法与模糊控制的建模方法

从实时系统的需求出发,研究利用遗传算法实现实时模糊控制的新技术,包括规则的形成、前提参数的训练,通过对比不同的训练参数规模,讨论了训练参数规模的大小与模型“范化”之间的关系。 经检验,用遗传算法生成的模糊系统模型输入变量少、规则数目少,并且误差小于多数传统算法生成的模型,整个模型的形成过程时间空间复杂度小、易于控制,且不受经验知识的约束,适用于实时系统。     

技术进步计算和经济发展研究中的势分析模型

柯布—道格拉斯生产函数(CD生产函数)是技术进步测算和经济分析的重要函数。势分析理论和方法在CD生产函数的基础上对技术进步指标的测算方法进行了改进,使之能提供更多更合理的有用信息。边际经济参数、全要素生产率和科技进步指标都是经济运行分析中的一些重要经济指标,势分析方法使之和宏观经济发展研究统一起来。     

MOSFET中1/f噪声的Hooge参数α_H

本文报道 P 沟道 MOSFET 器件中 1/f 噪声 Hooge 参数测量的部分实验结果.由加利福尼亚州的 SILICONIX 公司提供的实验样品是采用同样工艺作在同一块基片之上的.实验表明,在由非谐和状态到谐和状态过渡时,α_H 与沟道长度的平方成正比.类似的结果未曾见报道.     

指数分布参数基于不完全数据的区间估计

对不完全样本观测数据,讨论了指数分布总体参数的区间估计;给出了构造置信区间的一种方法并推导出了相应的分布密度函数表达式;并说明了该方法在样本中可能存在异常值时的应用。     

Discriminant coordinates analysis for multivariate functional data

Abstract

One of the basic statistical methods of dimensionality reduction is analysis of discriminant coordinates given by Fisher (1936 Fisher, R. A. 1936. The use of multiple measurements in taxonomic problem. Annals of Eugenics 7 (2):179–88. doi:10.1111/j.1469-1809.1936.tb02137.x.[Crossref] , [Google Scholar]) and Rao (1948). The space of discriminant coordinates is a space convenient for presenting multidimensional data originating from multiple groups and for the use of various classification methods (methods of discriminant analysis). In the present paper, we adapt the classical discriminant coordinates analysis to multivariate functional data. The theory has been applied to analysis of textural properties of apples of six varieties, measured over a period of 180?days, stored in two types of refrigeration chamber.     

Analyzing multiple vector autoregressions through matrix-variate normal distribution with two covariance matrices

Abstract

This article proposes a new approach to analyze multiple vector autoregressive (VAR) models that render us a newly constructed matrix autoregressive (MtAR) model based on a matrix-variate normal distribution with two covariance matrices. The MtAR is a generalization of VAR models where the two covariance matrices allow the extension of MtAR to a structural MtAR analysis. The proposed MtAR can also incorporate different lag orders across VAR systems that provide more flexibility to the model. The estimation results from a simulation study and an empirical study on macroeconomic application show favorable performance of our proposed models and method.