Merits of Modelling Multivariate Survival Data Using Random Effects Proportional Odds Model

Recently, there has been a great deal of interest in the analysis of multivariate survival data. In most epidemiological studies, survival times of the same cluster are related because of some unobserved risk factors such as the environmental or genetic factors. Therefore, modelling of dependence between events of correlated individuals is required to ensure a correct inference on the effects of treatments or covariates on the survival times. In the past decades, extension of proportional hazards model has been widely considered for modelling multivariate survival data by incorporating a random effect which acts multiplicatively on the hazard function. In this article, we consider the proportional odds model, which is an alternative to the proportional hazards model at which the hazard ratio between individuals converges to unity eventually. This is a reasonable property particularly when the treatment effect fades out gradually and the homogeneity of the population increases over time. The objective of this paper is to assess the influence of the random effect on the within‐subject correlation and the population heterogeneity. We are particularly interested in the properties of the proportional odds model with univariate random effect and correlated random effect. The correlations between survival times are derived explicitly for both choices of mixing distributions and are shown to be independent of the covariates. The time path of the odds function among the survivors are also examined to study the effect of the choice of mixing distribution. Modelling multivariate survival data using a univariate mixing distribution may be inadequate as the random effect not only characterises the dependence of the survival times, but also the conditional heterogeneity among the survivors. A robust estimate for the correlation of the logarithm of the survival times within a cluster is obtained disregarding the choice of the mixing distributions. The sensitivity of the estimate of the regression parameter under a misspecification of the mixing distribution is studied through simulation. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The importance of Quaternary records in reducing risk from tropical cyclones

Numerous late Holocene records of tropical cyclones have been collected from north-east Queensland, Australia. They are in the form of multiple sedimentary ridges paralleling the shore. The ridges are composed of coral fragments, or shell and sand or pure sand. A method to determine the intensity of the tropical cyclone responsible for deposition of the ridges at each site has been applied and the results suggest that in the majority of cases these features were deposited by very high magnitude events. The results suggest that extrapolations of long-term cyclone magnitude and frequencies from the 30- to 40-year-long instrumental record, which is the method commonly used to assess risk from this hazard, substantially underestimate the risk from this hazard. This is confirmed for the Cairns region by an 800-year-long high-resolution isotope record of tropical cyclones preserved in a limestone stalagmite. Together the sedimentary and isotope records suggest that tropical cyclone activity in north-east Queensland has been in a phase of quiescence since before European settlement of the region in approximately AD 1870. It is suggested that the incorporation of the palaeo record into risk assessments will provide a more realistic guide to the magnitude frequency relationship of tropical cyclones and help reduce risk from this hazard as a consequence.     

Under-smoothed kernel confidence intervals for the hazard ratio based on censored data

In cancer clinical trials, it is often of interest in estimating the ratios of hazard rates at some specific time points during the study from two independent populations. In this paper, we consider nonparametric confidence interval procedures for the hazard ratio based on kernel estimates for the hazard rates with under-smoothing bandwidths. Two methods are used to derive the confidence intervals: one based on the asymptotic normality of the ratio of the kernel estimates for the hazard rates in two populations and another through Fieller's Theorem. The performances of the proposed confidence intervals are evaluated through Monte-Carlo simulations and applied to the analysis of data from a clinical trial on early breast cancer.     

Down-Regulation of ZmEXPB6 (Zea mays β-Expansin 6) Protein Is Correlated with Salt-mediated Growth Reduction in the Leaves of Z. mays L.

The salt-sensitive crop Zea mays L. shows a rapid leaf growth reduction upon NaCl stress. There is increasing evidence that salinity impairs the ability of the cell walls to expand, ultimately inhibiting growth. Wall-loosening is a prerequisite for cell wall expansion, a process that is under the control of cell wall-located expansin proteins. In this study the abundance of those proteins was analyzed against salt stress using gel-based two-dimensional proteomics and two-dimensional Western blotting. Results show that ZmEXPB6 (Z. mays β-expansin 6) protein is lacking in growth-inhibited leaves of salt-stressed maize. Of note, the exogenous application of heterologously expressed and metal-chelate-affinity chromatography-purified ZmEXPB6 on growth-reduced leaves that lack native ZmEXPB6 under NaCl stress partially restored leaf growth. In vitro assays on frozen-thawed leaf sections revealed that recombinant ZmEXPB6 acts on the capacity of the walls to extend. Our results identify expansins as a factor that partially restores leaf growth of maize in saline environments.     

Waist-to-hip ratio versus body mass index as predictors of fitness in women

The claim that men prefer women with low waist-to-hip ratios (WHR) has been vigorously disputed. We examine self-report data from 359 primiparous Polish women (with normal singleton births and healthy infants) and show that WHR correlates with at least one component of a woman’s biological fitness (her first child’s birth weight, a variable that significantly affects infant survival rates). However, a woman’s Body Mass Index (BMI) is a better predictor of her child’s neonatal weight in small-bodied women (<54 kg). The failure to find a preference for low WHR in some traditional populations may thus be a consequence of the fact that, even in western populations, body mass is a better predictor of fitness in those cases characterized by low maternal body weight. Boguslaw Pawłowski Ph.D., D.Sc., is a researcher and lecturer in biological anthropology at the University of Wrocław, Poland. His research interests focus on mechanisms of human evolution (with special attention to the evolution of subcutaneous fat tissue distribution) and human mate choice. Robin Dunbar Ph.D., FBA is British Academy Research Professor of Evolutionary Psychology at the University of Liverpool, England, and co-Director of the British Academy Centenary Research Project. His research interests focus on the evolutionary and environmental determinants of social and reproductive strategies, with particular references to humans, nonhuman primates, and ungulates.     

某私营木制家具制造企业2004 年与2010 年职业病危害因素检测 与评价报告比较和分析

目的:通过比较2个年份职业病危害因素检测与评价报告,评估职业病防治工作的效果。方法:选取两份有代表性的报告,比较和分析职业病危害防护设施的安装、个人防护用品发放与使用、警示标示以及各项检测结果的合格率。结果:该企业2010年各项调查指标相比2004年明显提高。结论:该企业各项职业病防治工作效果显著,劳动环境明显改善,但仍需注意噪声、木粉尘的危害。     

Risk and ethics in biological control

All introduced natural enemies present a degree of risk to nontarget species. Since most biological control programs use relatively host-specific natural enemies, the risk to nontarget species is generally very low, particularly from biological control of weeds, which uses extensively tested and validated host-specificity testing procedures to predict risk. However, many of the published comments about risks of biological control are superficial or misleading, often inappropriately lumping risk from all taxa of agents as “the risk of biological control,” and ignore the potential benefits, rather than dealing with species-by-species risk and benefits. Particularly confounding accurate predictions is the common mixing of parameters of hazard and exposure in discussions of risk. In this paper, traditional risk analysis techniques are discussed and adapted for biological control. How people perceive risk is the key to understanding their attitude to risk. Some of the criticisms of biological control relating to inadequate post-release monitoring are valid and the ethical responsibilities of biological control scientists in this area are also discussed. Biological control scientists should address objectively the criticisms of biological control, continue to review and adjust current host-specificity testing procedures and make appropriate changes. This process will result in better science, ultimately delivering more focused programs, and altering the perception of risk from biological control agents by objective observers.     

Genotoxicity risk assessment: a proposed classification strategy

Recent advances in genetic toxicity (mutagenicity) testing methods and in approaches to performing risk assessment are prompting a renewed effort to harmonize genotoxicity risk assessment across the world. The US Environmental Protection Agency (EPA) first published Guidelines for Mutagenicity Risk Assessment in 1986 that focused mainly on transmissible germ cell genetic risk. Somatic cell genetic risk has also been a risk consideration, usually in support of carcinogenicity assessments. EPA and other international regulatory bodies have published mutagenicity testing requirements for agents (pesticides, pharmaceuticals, etc.) to generate data for use in genotoxicity risk assessments. The scheme that follows provides a proposed harmonization approach in which genotoxicity assessments are fully developed within the risk assessment paradigm used by EPA, and sets out a process that integrates newer thinking in testing battery design with the risk assessment process. A classification strategy for agents based on inherent genotoxicity, dose-responses observed in the data, and an exposure analysis is proposed. The classification leads to an initial level of concern for genotoxic risk to humans. A total risk characterization is performed using all relevant toxicity data and a comprehensive exposure evaluation in association with the genotoxicity data. The result of this characterization is ultimately used to generate a final level of concern for genotoxic risk to humans. The final level of concern and characterized genotoxicity risk assessment are communicated to decision makers for possible regulatory action(s) and to the public.     

Effects of Nutrition on Desiccation Tolerance and Virulence of Colletotrichum truncatum and Alternaria alternata Conidia

The promising mycoherbicides Colletotrichum truncatum and Alternaria alternata were grown respectively in liquid and solid semi-defined media. C. truncatum conidia produced in a medium with a C:N ratio of 5:1 showed higher desiccation tolerance (survival during storage) at 15% relative humidity and 25°C, greater germination on the host leaf and greater disease expression on Sesbania exaltata than those produced in media with C:N ratios of 15:1 or 40:1. Similar results were obtained with conidia of A. alternata produced on a medium with a C:N ratio of 15:1. Conidia washed with 0.9% (w/v) NaCl produced higher tolerance to desiccation, and greater disease incitement, than unwashed conidia of C. truncatum or conidia washed with water. In contrast, washing had no positive effect on desiccation tolerance in A. alternata .