Estimation of geodesic tortuosity and constrictivity in stationary random closed sets

We investigate the problem of estimating geodesic tortuosity and constrictivity as two structural characteristics of stationary random closed sets. They are of central importance for the analysis of effective transport properties in porous or composite materials. Loosely speaking, geodesic tortuosity measures the windedness of paths, whereas the notion of constrictivity captures the appearance of bottlenecks resulting from narrow passages within a given materials phase. We first provide mathematically precise definitions of these quantities and introduce appropriate estimators. Then, we show strong consistency of these estimators for unboundedly growing sampling windows. In order to apply our estimators to real data sets, the extent of edge effects needs to be controlled. This is illustrated using a model for a multiphase material that is incorporated in solid oxide fuel cells.     

Linear scalar-on-surface random effects regression models

Many research fields increasingly involve analyzing data of a complex structure. Models investigating the dependence of a response on a predictor have moved beyond the ordinary scalar-on-vector regression. We propose a regression model for a scalar response and a surface (or a bivariate function) predictor. The predictor has a random component and the regression model falls in the framework of linear random effects models. We estimate the model parameters via maximizing the log-likelihood with the ECME (Expectation/Conditional Maximization Either) algorithm. We use the approach to analyze a data set where the response is the neuroticism score and the predictor is the resting-state brain function image. In the simulations we tried, the approach has better performance than two other approaches, a functional principal component regression approach and a smooth scalar-on-image regression approach.     

中国教育资源市场化与个体选择：初中课外补习效应异质性探究

本文在中国教育资源市场化的背景下,探究了初中课外补习对学业成绩的效应异质性及其对教育公平的启示。通过分析“中国教育追踪调查”（CEPS）的数据发现,从同质性效应来看,参加课外补习对于提升初中生学习成绩没有显著影响,但参与课外补习的倾向性影响其效应异质性。课外补习有助于提高倾向性处于中间水平学生的学习成绩,表明课外补习受益学生大多来自学习成绩中等的普通工薪家庭。对于倾向性较低的大多数相对弱势的家庭和倾向性较高的少数优势家庭而言,课外补习对学业成绩的作用微乎其微。研究表明,中国教育领域的市场化变革和相关政策的制定需要考虑个体教育选择的复杂性及其对教育公平所造成的深刻影响。     

Alternative estimation methods for identifying contagion effects in dynamic social networks: A latent-space adjusted approach

Contagion effects, also known as peer effects or social influence process, have become more and more central to social science, especially with the availability of longitudinal social network data. However, contagion effects are usually difficult to identify, as they are often entangled with other factors, such as homophily in the selection process, the individual’s preference for the same social settings, etc. Methods currently available either do not solve these problems or require strong assumptions. Following Shalizi and Thomas (2011), I frame this difficulty as an omitted variable bias problem, and I propose several alternative estimation methods that have potentials to correctly identify contagion effects when there is an unobserved trait that co-determines the influence and the selection. The Monte-Carlo simulation results suggest that a latent-space adjusted estimator is especially promising. It outperforms other estimators that are traditionally used to deal with the unobserved variables, including a structural equation based estimator and an instrumental variable estimator.     

医疗保险对农村居民家庭消费的影响分析--基于不同收入层级的跨地区比较

利用2009、2010农村固定观察点数据,分析了医疗保险对不同地区、不同收入层级的农村居民家庭医疗消费支出和非医疗消费支出的影响。实证结果表明：医疗保险对农村居民家庭的医疗类消费不存在显著影响,对非医疗类消费支出则存在显著的正向促进作用。分地区来看,医疗保险对东西部地区农村居民家庭医疗类消费的影响差异显著,对东中部地区农村居民家庭非医疗类消费支出的影响同样差异显著;分收入层级来看,医疗保险对家庭医疗类消费的影响在不同收入层级的农村居民家庭之间不存在显著差异,但对非医疗类消费支出的影响在不同收入层级之间差异显著。此外,商业医疗保险作为医疗保险体系的重要组成部分,对促进农村消费起到带动作用。最后,本文从加大政府补贴和完善保障机制两个方面提出政策建议以期有效降低农村居民家庭超常的预防性储蓄,促进农村居民家庭消费。     

Enabling robust assessment of QTc prolongation in early phase clinical trials

Since the implementation of the International Conference on Harmonization (ICH) E14 guideline in 2005, regulators have required a “thorough QTc” (TQT) study for evaluating the effects of investigational drugs on delayed cardiac repolarization as manifested by a prolonged QTc interval. However, TQT studies have increasingly been viewed unfavorably because of their low cost effectiveness. Several researchers have noted that a robust drug concentration‐QTc (conc‐QTc) modeling assessment in early phase development should, in most cases, obviate the need for a subsequent TQT study. In December 2015, ICH released an “E14 Q&As (R3)” document supporting the use of conc‐QTc modeling for regulatory decisions. In this article, we propose a simple improvement of two popular conc‐QTc assessment methods for typical first‐in‐human crossover‐like single ascending dose clinical pharmacology trials. The improvement is achieved, in part, by leveraging routinely encountered (and expected) intrasubject correlation patterns encountered in such trials. A real example involving a single ascending dose and corresponding TQT trial, along with results from a simulation study, illustrate the strong performance of the proposed method. The improved conc‐QTc assessment will further enable highly reliable go/no‐go decisions in early phase clinical development and deliver results that support subsequent TQT study waivers by regulators.     

Decomposition of the main effects and interaction term by using orthogonal polynomials in multiple non symmetrical correspondence analysis

The multiple non symmetric correspondence analysis (MNSCA) is a useful technique for analyzing a two-way contingency table. In more complex cases, the predictor variables are more than one. In this paper, the MNSCA, along with the decomposition of the Gray–Williams Tau index, in main effects and interaction term, is used to analyze a contingency table with two predictor categorical variables and an ordinal response variable. The Multiple-Tau index is a measure of association that contains both main effects and interaction term. The main effects represent the change in the response variables due to the change in the level/categories of the predictor variables, considering the effects of their addition, while the interaction effect represents the combined effect of predictor categorical variables on the ordinal response variable. Moreover, for ordinal scale variables, we propose a further decomposition in order to check the existence of power components by using Emerson's orthogonal polynomials.     

Substance‐dependent women becoming mothers: breaking the cycle of adverse childhood experiences

Parenting may be particularly challenging for substance‐dependent mothers who have grown up with parents who themselves had substance use disorders (SUDs). The aim of this study was to explore how substance‐dependent mothers describe their childhood experiences with substance‐abusing parents and the association between these earlier experiences and their own role as caregivers. Using purposeful sampling, mothers admitted for 1 year to a family ward at a substance abuse clinic were approached. Through in‐depth, qualitative interviews, nine substance‐dependent mothers described their lives in the form of present, past and future tense. The findings indicate that substance‐dependent women, who have experienced SUDs in their families of origin, face several major challenges when they become mothers. Some describe having lived their whole lives ‘on the edge of society'. This makes their rehabilitation process more complex. All mothers work to abstain from substances, process traumatic experiences and integrate their family into society. They need help to build supportive social networks and to establish a safe and predictable family environment for themselves and their children. The therapeutic implications of these findings will be discussed.     

Mortality among elder abuse victims in rural Malaysia: A two-year population-based descriptive study

Our study aims at describing mortality among reported elder abuse experiences in rural Malaysia. This is a population-based cohort study with a multistage cluster sampling method. Older adults in Kuala Pilah (n = 1,927) were interviewed from November 2013 to May 2014. Mortality was traced after 2 years using the National Registration Department database. Overall, 139 (7.2%) respondents died. Fifteen (9.6%) abuse victims died compared to 124 (7.0%) not abused. Mortality was highest with financial abuse (13%), followed by psychological abuse (10.8%). There was a dose-response relationship between mortality and clustering of abuse: 7%, 7.7%, and 14.0% for no abuse, one type, and two types or more, respectively. Among abuse victims, 40% of deaths had ill-defined causes, 33% were respiratory-related, and 27% had cardiovascular and metabolic origin. Results suggest a link between abuse and mortality. Death proportions varied according to abuse subtypes and gender.