Correlating point-referenced radon and areal uranium data arising from a common spatial process

Summary.  Because exposure to radon gas in buildings is a likely risk factor for lung cancer, estimation of residential radon levels is an important public health endeavour. Radon originates from uranium, and therefore data on the geographical distribution of uranium in the Earth's surface may inform about radon levels. We fit a Bayesian geostatistical model that appropriately combines data on uranium with measurements of indoor home radon in the state of Iowa, thereby obtaining more accurate and precise estimation of the geographic distribution of average residential radon levels than would be possible by using radon data alone.     

Book Reviews

Books reviewed: S. Moolgavkar, D. Krewski, L. Zeise, E. Cardis, and H. Møller, Quantitative Estimation and Prediction of Human Cancer Risks Jacqueline Karnell Corn, Environmental Public Health Policy for Asbestos in Schools: Unintended Consequences Andrew Ford, Modeling the Environment. An Introduction to System Dynamics Modeling of Environmental Systems James Hamilton and W. Kip Viscusi, Calculating Risks? The Spatial and Political Dimensions of Hazardous Waste Policy Sharon M. Friedman, Sharon Dunwoody, and Carol L. Rogers, Communicating Uncertainty: Media Coverage of New and Controversial Science     

一种分布式实时嵌入式系统的调度分析算法

针对现有的基于Petri网的调度分析算法存在的不足,提出了一种适合于分布式实时嵌入式系统的调度分析算法。该算法使用相对的触发域判定调度序列中的变迁是否可以调度;通过引入并行间隔,记录了调度序列中的并行变迁的相对执行时间;在计算调度长度时,使用并行间隔作为并行变迁的执行时间,从而得到了正确的调度分析结果。     

Flexible Bayesian Modelling for Survival Data

The analysis of failure time data often involves two strong assumptions. The proportional hazards assumption postulates that hazard rates corresponding to different levels of explanatory variables are proportional. The additive effects assumption specifies that the effect associated with a particular explanatory variable does not depend on the levels of other explanatory variables. A hierarchical Bayes model is presented, under which both assumptions are relaxed. In particular, time-dependent covariate effects are explicitly modelled, and the additivity of effects is relaxed through the use of a modified neural network structure. The hierarchical nature of the model is useful in that it parsimoniously penalizes violations of the two assumptions, with the strength of the penalty being determined by the data.     

陕西城市等级结构及西安城市区位特征——基于因子分析方法的证明

运用因子分析方法,以2004年的相关统计数据为依据,对陕西省中心城市的综合实力进行了测定,得到“跳跃式”的陕西省城市等级结构分布图；通过把西安与国内其它25个省会城市及4个直辖市的综合实力进行比较,显示出“承上不启下”的“孤岛型”的西安城市区位特征；认为陕西城市建设的重点是发展数个大城市,西安城市发展的方向是做强,而不是做大；在发挥西安“承东启西”功能的同时,高度重视培植西安“承上启下”的功能,重视培植西安与陕西省内城市乡村的辐射力及向心力。     

Modelling and estimating heavy-tailed non-homogeneous correlated queues: Pareto-inverse gamma HGLM with covariates

Evidence of communication traffic complexity reveals correlation in a within-queue and heterogeneity among queues. We show how a random-effect model can be used to accommodate these kinds of phenomena. We apply a Pareto distribution for arrival (service) time of individual queue for given arrival (service) rate. For modelling potential correlation in arrival (service) times within a queue and heterogeneity of the arrival (service) rates among queues, we use an inverse gamma distribution. This modelling approach is then applied to the cache access log data processed through an Internet server. We believe that our approach is potentially useful in the area of network resource management.     

再次发生SARS疫情的情况模拟分析

通过定义评估SARS疫情状态的标志性参数，给出对SARS疫情发展进行预测的统计模型，并利用该模型对再次发生SARS疫情的情况进行模拟分析，指出社会公共卫生体系把握应对时机的基本期限。论文的研究结果表明，只要坚持采取早发现、早报告、早隔离、早治疗的措施，完善发烧排查的制度，就完全有可能把SARS疫病的流行趋势遏止在萌芽状态，从而避免再次出现恶性的疫病流行过程。     

Simulation Modeling of Anthrax Spore Dispersion in a Bioterrorism Incident

Recent events have increased awareness of the risk posed by terrorist attacks. Bacillus anthracis has resurfaced in the 21st century as a deadly agent of bioterrorism because of its potential for causing massive civilian casualties. This analysis presents the results of a computer simulation of the dispersion of anthrax spores in a typical 50-story, high-rise building after an intentional release during a bioterrorist incident. The model simulates aerosol dispersion in the case of intensive, small-scale convection, which equalizes the concentration of anthrax spores over the building volume. The model can be used to predict the time interval required for spore dispersion throughout a building after a terrorist attack in a high-rise building. The analysis reveals that an aerosol release of even a relatively small volume of anthrax spores during a terrorist incident has the potential to quickly distribute concentrations that are infectious throughout the building.     

论三星堆青铜雕塑的艺术个性

3000年前的三星堆青铜艺术以独立的雕塑艺术个性语言,完成了自成体系的造型方法和特殊工艺的手段,这些已发掘的大量青铜人物雕塑是极有研究价值的国宝级青铜器,它代表了中国青铜时代最有艺术特色的典范。本文对其艺术造诣和科学工艺进行分析,并提出三星堆青铜雕塑突出的艺术个性和美学价值。     

Reassessing Benzene Cancer Risks Using Internal Doses

Human cancer risks from benzene exposure have previously been estimated by regulatory agencies based primarily on epidemiological data, with supporting evidence provided by animal bioassay data. This paper reexamines the animal-based risk assessments for benzene using physiologically-based pharmacokinetic (PBPK) models of benzene metabolism in animals and humans. It demonstrates that internal doses (interpreted as total benzene metabolites formed) from oral gavage experiments in mice are well predicted by a PBPK model developed by Travis et al. Both the data and the model outputs can also be accurately described by the simple nonlinear regression model total metabolites = 76.4x/(80.75 + x), where x = administered dose in mg/kg/day. Thus, PBPK modeling validates the use of such nonlinear regression models, previously used by Bailer and Hoel. An important finding is that refitting the linearized multistage (LMS) model family to internal doses and observed responses changes the maximum-likelihood estimate (MLE) dose-response curve for mice from linear-quadratic to cubic, leading to low-dose risk estimates smaller than in previous risk assessments. This is consistent with the conclusion for mice from the Bailer and Hoel analysis. An innovation in this paper is estimation of internal doses for humans based on a PBPK model (and the regression model approximating it) rather than on interspecies dose conversions. Estimates of human risks at low doses are reduced by the use of internal dose estimates when the estimates are obtained from a PBPK model, in contrast to Bailer and Hoel's findings based on interspecies dose conversion. Sensitivity analyses and comparisons with epidemiological data and risk models suggest that our finding of a nonlinear MLE dose-response curve at low doses is robust to changes in assumptions and more consistent with epidemiological data than earlier risk models.