Predicted Infant Exposure to Tetrachloroethene in Human Breastmilk

Based on a variety of maternal occupational and residential inhalation exposure scenarios, estimates of infant exposure to the dry-cleaning solvent tetrachlorothylene (perchloroethylene, PCE) in breastmilk were made. Physiologically based pharmacokinetic (PBPK) modeling indicates that infants may be exposed to elevated levels of PCE in breastmilk due to their mothers' inhalation of PCE. The PBPK-predicted breastmilk PCE concentrations agree very well with measured concentrations, where available. Based on this analysis, infants may be exposed to this workplace chemical via breastmilk at doses corresponding to rather high levels of risk. Predicted breastmilk doses provide the infant with little margin of exposure to doses associated with adverse health effects. In addition, the estimated increased cancer risks associated with these infant exposures are large under certain exposure scenarios. The actual concentrations of PCE in breastmilk of exposed mothers can only be known with certainty if monitoring is conducted. Due to the widespread exposure potential, monitoring studies should be undertaken so that the appropriate risk management alternatives can be better evaluated.     

元明清时期西北水利的理论与实践

西部开发的关键是如何解决水资源的短缺。总结历史上西北水利的理论与实践 ,对于今日西部开发中最关键的水资源问题的解决 ,具有借鉴价值。元朝在陕西省兴元路和泾渠都设置了河渠司 ,河渠司制定“分水”、“用水则例” ,统一管理分配渠系内的水资源 ;明清时期 ,由于西北华北干旱气候的日益严重 ,农学家徐光启、王心敬等对水的自然循环系统和水旱的周期认识更加深入 ,分别提出了旱田用水五法和井利说 ,这对于在河渠水利不足时扩大农田水利的给水源 ,起到了积极的推动作用     

Poverty and its persistence: a comparison of natives and immigrants in Sweden

This paper analyzes poverty and its persistence in Sweden using a large panel with detailed income information obtained from tax registers. As opposed to many commonly used household panels, the features of the data utilized in this paper allow us to study native-immigrant differences in poverty. We use a hazard rate model based on multiple spells that accounts for unobserved heterogeneity and endogenous initial conditions. The empirical results suggest that there is negative duration dependence in both exit and entry hazard rates. Moreover, the transition rates are significantly affected by immigrant status, educational attainment, labor market conditions, age, and family status.

基于SWOT定量分析的无水港发展战略研究

无水港是新兴的物流基础设施,能加快内陆地区对外开放的步伐。选取晋江无水港为研究对象,运用SWOT定性分析方法对影响无水港战略选择的重要因素进行识别和筛选,通过SWOT定量分析各要素,建立发展战略决策四边形。在此基础上,讨论晋江无水港应采取的发展战略。研究结果为我国目前无水港企业所面临的重要战略决策问题,提供了一种客观有效的研究思路和解决方案。     

干散货航运即期费率和远期费率的动态引导关系——基于不同船型运输市场的月度经验数据

利用干散货航运市场2002—2010年的月度数据,通过ECM模型对3种主要干散货船型的即期费率和远期费率之间的动态引导关系进行实证研究。结论表明：不同船型的即期运费之间、远期运费之间均不存在协整关系;同一船型的即期运费与远期运费之间存在协整关系;Capsize型船舶的即期运费引导远期运费,Panamax型船舶的即期运费和远期运费双向引导,而Handymax型船舶的远期运费引导即期运费;各类船型的即期费率和远期费率之间呈正相关关系,且船型越大,两者之间的弹性越高。     

The Value of Improved National Exposure Information for Perchloroethylene (Perc): A Case Study for Dry Cleaners

Opportunities to improve our information about risk continue to arise and lead decision makers to indirectly address the issue of the value of improved information through resource allocation decisions. Statistical decision analysis techniques provide an analytical framework for valuing information explicitly in the context of regulatory decision making. This paper provides estimates of the value of improved national estimates of perchloroethylene (perc) exposure from U.S. dry cleaners in the context of EPA's recently promulgated National Emissions Standard for Hazardous Air Pollutants (NESHAP) with emphasis on exposure information. Consistent with the NESHAP decision, we relied on EPA's technology and economic assessments. In this first cut analysis, estimates of the exposures of workers, consumers of dry cleaning services, and the general public are probabilistically characterized to reflect uncertainty about exposure and potency. We consider the net benefits of the different control options by assessing the associated changes in the total annual population risks and valuing them in monetary terms, with no constraints placed on maximum individual risks. The results suggest that the expected value of perfect information (EVPI) about potency exceeds the EVPI about exposure. Sensitivity analyses demonstrate how the choices of the valuation parameters and distributions used to characterize uncertainty in the model affect the estimates of the value of information.     

晚稻旱育秧综合配套技术研究

通过五元二次回归旋转组合设计试验，明确了影响洞庭湖区晚稻生产的主要因素，依次为播种量（X1），2．1叶期喷施效唑（X4）移栽叶龄（X2），分蘖期施纯氮（X5）等，建立了五元二次目标函数模型，提出了适应洞庭湖区一季晚稻和双季晚稻的五套优化综合配套技术，探讨了二因素对产量影响显著的交互效应。     

Generalized Additive Modelling of Mixed Distribution Markov Models with Application to Melbourne's Rainfall

The paper considers the modelling of time series using a generalized additive model with first-order Markov structure and mixed transition density having a discrete component at zero and a continuous component with positive sample space. Such models have application, for example, in modelling daily occurrence and intensity of rainfall, and in modelling numbers and sizes of insurance claims. The paper shows how these methods extend the usual sinusoidal seasonal assumption in standard chain-dependent models by assuming a general smooth pattern of occurrence and intensity over time. These models can be fitted using standard statistical software. The methods of Grunwald & Jones (2000) can be used to combine these separate occurrence and intensity models into a single model for amount. The models are used to investigate the relationship between the Southern Oscillation Index and Melbourne's rainfall, illustrated with 36 years of rainfall data from Melbourne, Australia.     

Reemployment Probability and Multiple Unemployment Spells: A Partial-Likelihood Approach

An extended version of the mixed-proportional-hazards model is used to study the determinants of the conditional probability of reemployment of long-term unemployed young persons sampled in the first stage of the Australian National Longitudinal Survey. The survey data facilitate an econometric comparison between the effect of different factors on the conditional reemployment probability of those in their first unemployment spell with those who have experienced multiple spells. The article uses Cox's partial-likelihood approach. The empirical results support the hypothesis of lagged-duration dependence in that the length of previous job experience or the duration of previous unemployment is found to be an important determinant of reemployment probability. The results strongly suggest that fitting a common duration model to data from different spells involves a major misspecification.     

粗颗粒土混合料最大干密度及压实度研究

通过表面振动与振动台两种方法进行粗颗粒混合料最大干密度测试，试验结果表明：同一种土湿土法做出的最大干密度明显要大于干土法所测的最大干密度，表面振动仪法的振密效果要优于振动台法的振密效果。通过高速铁路路基施工现场压实后路基干密度与室内最大干密度测试结果对比，发现既有路基施工工艺可以达到以表面振动法测试得到最大干密度的95%压实度。