Development of the PEARLS model (Particulate Exposure from Ambient to Regional Lung by Subgroup) and use of Monte Carlo simulation to predict internal exposure to 2.5 in Toronto.

Air pollution is a current and growing concern for Canadians, and there is evidence that ambient levels that meet current exposure standards may be associated with mortality and morbidity in Toronto, Canada. Evaluating exposure is an important step in understanding the relationship between particulate matter (PM) exposure and health outcomes. This report describes the PEARLS model (Particulate Exposure from Ambient to Regional Lung by Subgroup), which predicts exposure distributions for 11 age-gender population subgroups in Toronto to PM2.5 (PM with a median aerodynamic diameter of 2.5 microm or less) using Monte Carlo simulation techniques. The model uses physiological and activity pattern characteristics of each subgroup to determine region-specific lung exposure to PM2.5, which is defined as the mass of PM2.5 deposited per unit time to each of five lung regions (two extrathoracic, bronchial, bronchiolar, and alveolar). The modeling results predict that children, toddlers, and infants have the broadest distributions of exposure, and the greatest chance of experiencing extreme exposures in the alveolar region of the lung. Importance analysis indicates that the most influential model variables are air exchange rate into indoor environments, time spent outdoors, and time spent at high activity levels. Additionally, a "critical point" was defined and introduced to the PEARLS to investigate the effects of possible threshold-pathogenic phenomena on subgroup exposure patterns. The analysis indicates that the subgroups initially predicted to be most highly exposed were likely to have the highest proportion of their population exposed above the critical point. Substantial exposures above the critical point were predicted in all subgroups for ambient concentrations of PM2.5 commonly observed in Toronto after continuous exposure of 24 hours or more.     

我国大学科技园的发展势态及问题探讨

兴办大学科技园 ,把高校人才和技术优势转化为产业和经济优势 ,是推动科技成果转化和高新技术产业化、提高我国技术创新能力和国际竞争力的客观要求。我国大学科技园从借鉴、试点到全面启动 ,有许多需要认真研究和探索的问题 ,主要包括科技园的功能定位问题、科技园的建设模式问题、高等院校的资源如何更好地对科技园开放的问题、科技园的管理体制及企业运行机制问题以及国家和地方在政策和资金上对科技园的支持问题。     

Estimates of the Health Risk Reductions Associated with Attainment of Alternative Particulate Matter Standards in Two U.S. Cities

As part of its periodic re-evaluation of particulate matter (PM) standards, the U.S. Environmental Protection Agency estimated the health risk reductions associated with attainment of alternative PM standards in two locations in the United States with relatively complete air quality data: Philadelphia and Los Angeles. PM standards at the time of the analysis were defined for particles of aerodynamic diameter less than or equal to 10 microm, denoted as PM-10. The risk analyses estimated the risk reductions that would be associated with changing from attainment of the PM-10 standards then in place to attainment of alternative standards using an indicator measuring fine particles, defined as those particles of aerodynamic diameter less than or equal to 2.5 microm and denoted as PM-2.5. Annual average PM-2.5 standards of 12.5, 15, and 20 microg/m3 were considered in various combinations with daily PM-2.5 standards of 50 and 65 microg/m3. Attainment of a standard or set of standards was simulated by a proportional rollback of "as is" daily PM concentrations to daily PM concentrations that would just meet the standard(s). The predicted reductions in the incidence of health effects varied from zero, for those alternative standards already being met, to substantial reductions of over 88% of all PM-associated incidence (e.g., in mortality associated with long-term exposures in Los Angeles, under attainment of an annual standard of 12.5 microg/m3). Sensitivity analyses and integrated uncertainty analyses assessed the multiple-source uncertainty surrounding estimates of risk reduction.     

Air Pollution and Mortality: Quantification and Valuation of Years of Life Lost

To analyze the loss of life expectancy (LLE) due to air pollution and the associated social cost, a dynamic model was developed that took into account the decrease of risk after the termination of an exposure to pollution. A key parameter was the time constant for the decrease of risk, for which estimates from studies of smoking were used. A sensitivity analysis showed that the precise value of the time constant(s) was not critical for the resulting LLE. An interesting aspect of the model was that the relation between population total LLE and PM2.5 concentration was numerically almost indistinguishable from a straight line, even though the functional dependence was nonlinear. This essentially linear behavior implies that the detailed history of a change in concentration does not matter, except for the effects of discounting. This model was used to correct the data of the largest study of chronic mortality for variations in past exposure, performed by Pope et al. in 1995; the correction factor was shown to depend on assumptions about the relative toxicity of the components of PM2.5. In the European Union, an increment of 1 microg/m3 of PM2.5 for 1 year implies an average LLE of 0.22 days per person. With regard to the social cost of an air pollution pulse, it was found that for typical discount rates (3% to 8% real) the cost was reduced by a factor of about 0.4 to 0.6 relative to the case with zero discount rate, if the value of a life year was taken as given; if the value of a life year was calculated from the "value of statistical life" by assuming the latter as a series of discounted annual values, the cost varied by at most +/-20% relative to the case with zero discount rate. To assess the uncertainties, this study also examined how the LLE depended on the demographics (mortality and age pyramid) of a population, and how it would change if the relative risk varied with age, in the manner suggested by smoking studies. These points were found to have a relatively small effect (compared to the epidemiological uncertainties) on the calculated LLE.     

燃烧着激情的报告——评镇江市作家的散文创

散文的活力在于贴近人民、反映现实。本文对镇江市三位散文作家的作品作了具体分析 ,指出他们的作品虽然题材不同、风格各异 ,但都将形象、情感与思想交融在一起 ,因而产生出真正的艺术力量     

刍议通俗歌曲及其创作原则

通俗歌曲内容广泛 ,贴近生活 ,深受群众喜爱。同时通俗歌曲中存在着一些思想庸俗、格调不健康、艺术水平低下的东西。我们既不能采取一概肯定任其发展的态度 ,也不能采取全盘否定的办法 ,而应吸收其精华 ,剔除其糟粕 ,注重通俗性和民族性相结合的创作原则 ,以促使它的不断完善与提高     

论贾平凹散文的审美类型

贾平凹散在当代坛具有鲜明的个性特征。为20多年来,他不断扩展散的写作内容,不断追求新的审美样式,表现出广阔的审美视野与选材能力。总括而论,贾平凹的散可以分为五个审美类型：自传类、风情类、世相类、禅思类和化类,每一种类型都相对应地承载着他的身世,他对农乡、市井群类的感悟和对民族与人类化的反思。     

论当代农民题材小说及农民形象演变

农民形象在当代文学中明显占据着重要的位置。就文学史的发展过程而言 ,农民形象的演变 ,甚至可以视作是各个文学段落的形象标志。农民形象的变化不仅体现着社会的现代化程度 ,而且也表现出农民自身作为个体的精神独立和人格解放的时代趋势。农民形象的演变 ,实际上就是中国社会、中国文化精神的发展和演化 ,农民在成长中体现了中国社会历史的崭新面貌和走向。     

论李大钊的新民观

李大钊的前期新民思想在某种程度上是对梁启超新民说的承继和发展,后期（十月革命后）,李大钊开始用唯物史观重新审视国民性改造问题,提出了“物心两面”改造的全新新民途径．但因忽视了生产力这一最终动因,其新民说带有一定的空想色彩．     

党的十六大对非公有制经济理论的创新与突破

中共十六大将发展非公有制经济与全面建设小康社会的现实目标紧密联系起来,突破了将坚持公有制的主体地位与促进非公有制经济发展相对立的传统认识误区,强调各种所有制形式应相互促进,共同发展。同时,十六大还突破传统所有制理论,确认了非公有制经济及新兴社会阶层在现阶段的重要地位和作用。强调通过理顺收入分配关系,保护私人财产及一切合法收入,在政治经济上为其健康发展提供制度保证。