On Block Updating in Markov Random Field Models for Disease Mapping

Gaussian Markov random field (GMRF) models are commonly used to model spatial correlation in disease mapping applications. For Bayesian inference by MCMC, so far mainly single-site updating algorithms have been considered. However, convergence and mixing properties of such algorithms can be extremely poor due to strong dependencies of parameters in the posterior distribution. In this paper, we propose various block sampling algorithms in order to improve the MCMC performance. The methodology is rather general, allows for non-standard full conditionals, and can be applied in a modular fashion in a large number of different scenarios. For illustration we consider three different applications: two formulations for spatial modelling of a single disease (with and without additional unstructured parameters respectively), and one formulation for the joint analysis of two diseases. The results indicate that the largest benefits are obtained if parameters and the corresponding hyperparameter are updated jointly in one large block. Implementation of such block algorithms is relatively easy using methods for fast sampling of Gaussian Markov random fields ( Rue, 2001 ). By comparison, Monte Carlo estimates based on single-site updating can be rather misleading, even for very long runs. Our results may have wider relevance for efficient MCMC simulation in hierarchical models with Markov random field components.     

服务行业排队论问题分析

本文运用排队论理论对服务行业的排队现象进行了分析,较好的解决了问题。面对加入WTO,企业应把提高顾客满意度放在首位,以获得长期竞争优势。     

英语"临时语"的构成方法及修辞效果

英语“临时语”是一种偏离语言常规的“变异”(deviation)现象 ,往往产生独特的修辞效果。“临时语”的构成方法有词缀法、转化法、合成法、拼缀法、缩略法、类推法和新选七种 ,“临时语”具有简洁明快 ,加强语气 ,鲜明生动、诙谐戏谑的修辞效果     

Re-evaluating the Community Question from a German perspective

The far-reaching effects of the social systemic division of labor on the organization and contents of primary ties make the Community Question an important issue for many sociologists. This paper looks at the personal embeddedness of families in three German cities (Berlin, Hamburg, and Stuttgart) and examines the Community Question with data collected at the end of 2003. It is based on the theoretical views of Wellman [Wellman, B., 1979. The community question. The intimate networks of East Yorkers. American Journal of Sociology 84, 1201–1231], who used a network analysis perspective to conceptualize “the Community Question”. The results of this German study generally support the results of Wellman's second East York Study. However, the network structures analyzed in my study vary from the three ideal-type models. Cluster analysis shows that Wellman's typology can be replicated relatively well in Germany. In contrast to traditional discourse related to the Community Question, particular network types are not associated with low levels of social relations. Moreover, structural factors do not explain the existence of different network types. Thus, the networks are not a product of only one community model. They suggest that it is less helpful to talk about “Saved”, “Lost”, or “Liberated” communities than it is to regard communities as a mixture of strongly-knit nuclear clusters and of broader, sparsely-knit relations that provide access to different groups and their resources.     

An affine‐invariant multivariate sign test for cluster correlated data

The author presents a multivariate location model for cluster correlated observations. He proposes an affine‐invariant multivariate sign statistic for testing the value of the location parameter. His statistic is an adaptation of that proposed by Randles (2000). The author shows, under very mild conditions, that his test statistic is asymptotically distributed as a chi‐squared random variable under the null hypothesis. In particular, the test can be used for skewed populations. In the context of a general multivariate normal model, the author obtains values of his test's Pitman asymptotic efficiency relative to another test based on the overall average. He shows that there is an improvement in the relative performance of the new test as soon as intra‐cluster correlation is present Even in the univariate case, the new test can be very competitive for Gaussian data. Furthermore, the statistic is easy to compute, even for large dimensional data. The author shows through simulations that his test performs well compared to the average‐based test. He illustrates its use with real data.     

低层次产业对智力的挤出效应

低层次产业对解决低技术劳动力就业有益，但对智力资源扣科教基本设施却会带来损害。本文探讨产业发展和教育发展的关系．着重探讨低层次产业对智力资源和设施的国际挤出效应，地区挤出效应和本地挤出效应。本文同时指出低层次产业尽管对智力存在负面效应，但不应该因此否定它，并且提出在我国产业布局和地方经济发展中应遵循梯度转移的规律，谨防欠发达区低层次产业发展对智力挤出的同时对收入也形成挤出，谨防发达区因为产业层次不高对智力形成挤出．谨防欠发达区盲目发展高层次产业对低技术劳动力形成驱赶等政策建议。     

Communication of risk: health hazards from mobile phones

Summary. Possible health hazards from mobile phones arise from the use of the phones themselves and via the base stations that relay signals. Except for an increase in traffic accidents induced by the use of mobile phones in cars the evidence for a health hazard is at most indirect, but it cannot be entirely dismissed; the phones have not been widely used for sufficiently long for direct epidemiological studies to have high sensitivity for detecting any induced incidence of cancer, for example. The background and evidence are briefly reviewed and the steps taken in the UK to make information widely available described.     

Almost Consistent Estimation of Panel Probit Models with “Small” Fixed Effects

We propose four different GMM estimators that allow almost consistent estimation of the structural parameters of panel probit models with fixed effects for the case of small Tand large N. The moments used are derived for each period from a first order approximation of the mean of the dependent variable conditional on explanatory variables and on the fixed effect. The estimators differ w.r.t. the choice of instruments and whether they use trimming to reduce the bias or not. In a Monte Carlo study, we compare these estimators with pooled probit and conditional logit estimators for different data generating processes. The results show that the proposed estimators outperform these competitors in several situations.     

Neighborhood Structure,Social Organization,and Number of Short‐Term Sexual Partnerships

We examine the relationship between neighborhood structural characteristics, social organization, and the sexual partnering practices of adults. Analyses of 1990 census and 1995–1997 survey‐based data on Chicago neighborhoods and adult sexual activity reveal for men a number of neighborhood influences on sexual partnering practices. First, residential stability is negatively associated with having a short‐term sexual partner in the last year. Second, neighborhood social ties are positively associated with short‐term sexual partnering in neighborhoods with low levels of collective efficacy—the combination of cohesion and shared expectations for beneficial action among neighbors—but this effect is substantially reduced as collective efficacy increases. Moreover, neighborhood collective efficacy and social ties mediate the effect of residential stability on sexual partnering practices. Neighborhood characteristics were not associated with short‐term sexual partnering for women.     

B股与H股及红筹股之间的溢出效应与信息流动

运用向量GARCH-M模型检验了B股与H股及红筹股之间的溢出效应与信息流动.实证结果表明:红筹股对沪深市B股、H股对沪市B股的收益和波动溢出效应均显著存在,而反向的溢出效应均不显著,表明信息是从红筹股向沪深市B股、从H股向沪市B股单向流动的;深市B股与H股之间相互的收益溢出效应均存在,而波动溢出效应均不存在,信息在H股和深市B股之间的流动情况不明显;在信息流动过程中,红筹股始终处于信息领先地位.