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.     

中西典型思维方式与汉英文字音形意关联

文章指出文字与民族思维方式跨文化研究中的不足 ,扼要分析了潜在的成因 ,着重探讨比较了中西民族典型思维 (西方二元分析思维与汉民族整体思维 )在西方字母文字 (以英文为例 )与汉字音、形两大物质特性与意义概念结合上的反映 ,认为正确对待文字与思维之间的客观关联 ,不仅能从新的角度审视文字功能 ,而且有利于我们从中认识和挖掘各民族历史文化的深厚积淀 ,促进跨文化交流的全面开展     

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.     

矩阵非奇异性判定

本文利用矩阵块对角占优的性质,给出矩阵非奇异的一个判定条件     

对参加“步步高杯“全国女排联赛运动队拦网状况的比较研究

通过对2004~2005和2005~2006两个赛季的女子“步步高杯”全国联赛中的拦网状况分析和研究,指出了栏网存在的主要问题,并提出了合理化的建议。     

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.     

A spatiotemporal auto-regressive moving average model for solar radiation

Summary.  To investigate the variability in energy output from a network of photovoltaic cells, solar radiation was recorded at 10 sites every 10 min in the Pentland Hills to the south of Edinburgh. We identify spatiotemporal auto-regressive moving average models as the most appropriate to address this problem. Although previously considered computationally prohibitive to work with, we show that by approximating using toroidal space and fitting by matching auto-correlations, calculations can be substantially reduced. We find that a first-order spatiotemporal auto-regressive (STAR(1)) process with a first-order neighbourhood structure and a Matern noise process provide an adequate fit to the data, and we demonstrate its use in simulating realizations of energy output.     

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.