QMRA for Drinking Water: 2. The Effect of Pathogen Clustering in Single‐Hit Dose‐Response Models

Spatial and/or temporal clustering of pathogens will invalidate the commonly used assumption of Poisson‐distributed pathogen counts (doses) in quantitative microbial risk assessment. In this work, the theoretically predicted effect of spatial clustering in conventional “single‐hit” dose‐response models is investigated by employing the stuttering Poisson distribution, a very general family of count distributions that naturally models pathogen clustering and contains the Poisson and negative binomial distributions as special cases. The analysis is facilitated by formulating the dose‐response models in terms of probability generating functions. It is shown formally that the theoretical single‐hit risk obtained with a stuttering Poisson distribution is lower than that obtained with a Poisson distribution, assuming identical mean doses. A similar result holds for mixed Poisson distributions. Numerical examples indicate that the theoretical single‐hit risk is fairly insensitive to moderate clustering, though the effect tends to be more pronounced for low mean doses. Furthermore, using Jensen's inequality, an upper bound on risk is derived that tends to better approximate the exact theoretical single‐hit risk for highly overdispersed dose distributions. The bound holds with any dose distribution (characterized by its mean and zero inflation index) and any conditional dose‐response model that is concave in the dose variable. Its application is exemplified with published data from Norovirus feeding trials, for which some of the administered doses were prepared from an inoculum of aggregated viruses. The potential implications of clustering for dose‐response assessment as well as practical risk characterization are discussed.     

城市发展路径研究的主要观点

自20世纪80年代以来，与整个国家快速现代化的进程相一致，我国城市呈现出加速发展的趋势。为了推进我国城市沿着科学的方向快速、稳步、健康地发展，学者们从不同的视角对中国城市发展的路径提出了各自不同的观点。文章对有代表性的观点进行了梳理，并简短地陈述了从中得到的启示。     

Influence measure for the L1 regression

Because outliers and leverage observations unduly affect the least squares regression, the identification of influential observations is considered an important and integrai part of the analysis. However, very few techniques have been developed for the residual analysis and diagnostics for the minimum sum of absolute errors, L₁ regression. Although the L₁ regression is more resistant to the outliers than the least squares regression, it appears that outliers (leverage) in the predictor variables may affect it. In this paper, our objective is to develop an influence measure for the L₁ regression based on the likelihood displacement function. We illustrate the proposed influence measure with examples.     

Has the Lewis Turning Point Arrived in China?—Theoretical Analysis and International Experience

各国农业劳动力占总劳动力的比重随着各国人均GDP增长呈现先加速下降而后减 速下降的趋势, 分界点就是刘易斯转折点。跨国平行数据的回归结果表明, 刘易斯转 折点在人均GDP为3,000-4,000美元 (购买力平价2000年国际美元) 之间出现。中国的 人均GDP超越了这一水平, 但农业劳动力比重远高于该经济发展水平下的世界平均水 平, 这很可能意味着中国的农业劳动力转移仍有较大潜力。

关键词: 刘易斯转折点 劳动力转移 跨国平行数据

Using World Bank cross-country panel data to estimate the economic development level that corresponds to the Lewis turning point, we find that as GDP per capita increases, the share of rural labor in the total labor force tends to decrease first at an accelerated rate and then, after passing the Lewis turning point, at a reduced rate. Regression analysis of cross- country panel data shows that the Lewis turning point is reached when GDP per capita reaches somewhere between US$3,000 and US$4,000 dollars (PPP, constant international US dollars for the year 2000). GDP per capita in China has exceeded this level, but the proportion of rural labor in the total labor force remains much higher than the average for countries at the same level of economic development. This may imply that there is still considerable potential for rural labor transfer in China.     

The Development of Peer Interaction in Infancy: Exploring the Dyadic Processes

Peer interaction is an important component of children's social repertoires that is associated with a variety of developmental outcomes and life skills. The present study provides an in‐depth study of early dyadic peer behaviors during the infancy period, during which social competence with peers is first being developed. Results from variable‐centered analyses highlight the effectiveness of behaviors, such as offering objects to peers, and point to the importance of the social context set by a peer's prior social behavior and processes for eliciting peer responses. Findings from person‐centered analyses reveal marked individual differences in the processes through which infants are successful in eliciting responses from their peers, illustrating the presence of multiple pathways to achieving social competence with peers.     

我国劳动力供给优势减弱与劳动力转移的优化

近年来，对于我国劳动力供给优势减弱以及劳动力成本上升的问题，不少学者利用刘易斯模型分析了其原因，并提出各种促进、完善我国农村剩余劳动力转移机制的政策措施。文章仍从分析这一问题的经典模型——刘易斯模型入手，但重点借鉴了日本的成功经验，为促进我国农村剩余劳动力转移提出了一系列对策。     

Who speaks and how? Studies of voicing in the China Daily following a decade of change

This study used critical discourse analysis (CDA) to identify and unpick some of the ideas, beliefs, and attitudes encoded in newspaper texts without being explicitly stated. It uses a quantitative-qualitative approach to content analysis to compare articles published in the Chinese government-owned, English-language newspaper the China Daily in 1998 (n = 50) and 2010 (n = 50). The analysis focused on two things: the people considered by China Daily journalists to be important/interesting enough to be quoted and (through an analysis of Halliday's verbal processes) how these people's words are presented. The aim was to demonstrate the effectiveness of the approach advocated and to see whether such an approach can help answer how much the media in China has changed in response to changing times.     

Order statistics from the linear-exponential distribution,part I: increasing hazard rate case

For the linear-exponential distribution with increasing hazard rate, exact and explicit expressions for means, product moments and percentage points of order statistics are obtained. Some recurrence relations for both single and product moments of order statistics are also derived. These recurrence relations would enable one to obtain all the higher order moments of order statistics for all sample sizes from those of the lower order     

Contrasting the Gini and Zenga indices of economic inequality

The current financial turbulence in Europe inspires and perhaps requires researchers to rethink how to measure incomes, wealth, and other parameters of interest to policy-makers and others. The noticeable increase in disparities between less and more fortunate individuals suggests that measures based upon comparing the incomes of less fortunate with the mean of the entire population may not be adequate. The classical Gini and related indices of economic inequality, however, are based exactly on such comparisons. It is because of this reason that in this paper we explore and contrast the classical Gini index with a new Zenga index, the latter being based on comparisons of the means of less and more fortunate sub-populations, irrespectively of the threshold that might be used to delineate the two sub-populations. The empirical part of the paper is based on the 2001 wave of the European Community Household Panel data set provided by EuroStat. Even though sample sizes appear to be large, we supplement the estimated Gini and Zenga indices with measures of variability in the form of normal, t-bootstrap, and bootstrap bias-corrected and accelerated confidence intervals.