Potential exposures and risks from beryllium-containing products.

Beryllium is the strongest of the lightweight metals. Used primarily in military applications prior to the end of the Cold War, beryllium is finding new applications in many commercial products, including computers, telecommunication equipment, and consumer and automotive electronics. The use of beryllium in nondefense consumer applications is of concern because beryllium is toxic. Inhalation of beryllium dust or vapor causes a chronic lung disease in some individuals at concentrations as low as 0.01 microg/m3 in air. As beryllium enters wider commerce, it is prudent to ask what risks this might present to the general public and to workers downstream of the beryllium materials industry. We address this question by evaluating the potential for beryllium exposure from the manufacturing, use, recycle, and disposal of beryllium-containing products. Combining a market study with a qualitative exposure analysis, we determine which beryllium applications and life cycle phases have the largest exposure potential. Our analysis suggests that use and maintenance of the most common types of beryllium-containing products do not result in any obvious exposures of concern, and that maintenance activities result in greater exposures than product use. Product disposal has potential to present significant individual risks, but uncertainties concerning current and future routes of product disposal make it difficult to be definitive. Overall, additional exposure and dose-response data are needed to evaluate both the health significance of many exposure scenarios, and the adequacy of existing regulations to protect workers and the public. Although public exposures to beryllium and public awareness and concern regarding beryllium risks are currently low, beryllium risks have psychometric qualities that may lead to rapidly heightened public concern.     

Assessing accuracy of a continuous screening test in the presence of verification bias

Summary.  In studies to assess the accuracy of a screening test, often definitive disease assessment is too invasive or expensive to be ascertained on all the study subjects. Although it may be more ethical or cost effective to ascertain the true disease status with a higher rate in study subjects where the screening test or additional information is suggestive of disease, estimates of accuracy can be biased in a study with such a design. This bias is known as verification bias. Verification bias correction methods that accommodate screening tests with binary or ordinal responses have been developed; however, no verification bias correction methods exist for tests with continuous results. We propose and compare imputation and reweighting bias-corrected estimators of true and false positive rates, receiver operating characteristic curves and area under the receiver operating characteristic curve for continuous tests. Distribution theory and simulation studies are used to compare the proposed estimators with respect to bias, relative efficiency and robustness to model misspecification. The bias correction estimators proposed are applied to data from a study of screening tests for neonatal hearing loss.     

论国际资本流动与金融危机的关系--兼析加入WTO后不断加剧的国际资本流动给我国带来的风险

20世纪90年代以来,各种类型的金融危机频繁爆发,对危机国乃至世界经济产生了巨大的影响。这些危机不但使国际学术界和各国政府都高度重视,而且也掀起了探索、研究金融危机的热潮。从国际资本流动的机制和国际资本流动的规模这两个角度,探析了国际资本流动与金融市场动荡和金融危机的关系,并分析了国际资本的充分流动,可能给加入WTO后的我国带来的风险与影响。     

关于高等学校教师流动的探讨

高校教师是高层次的教学、文化和科技工作者 ,在市场经济体制下必然成为各用人单位争取引进的对象。高校教师的流动具有频繁性、方式的多样性、失衡性等特点。究其原因有需要因素、环境因素和文化因素。采取协调、控制和顺应高校教师需要 ,创新激励机制 ,发挥人才市场导向功能等对策 ,可以促进高校教师合理流动     

一次计数抽样检验的风险分析

利用抽样检验特征曲线 ,分析了一次计数抽样检验中N ,n ,Ac3个参数的改变对生产者风险和消费者风险的影响     

简论诗的意象运动

诗的意象运动的动力源在于情感 ,是情的流动引起包括情与理两端的意的流动 ,又是情和意的流动造成象的跃动。因为情和意如气体或液体呈线型流动 ,像如固体作块状跃动 ,所以在诗的意象运动中 ,往往出现象断而意连的状况。     

递推法求一元n次实系数多项式函数的完全等价n次Bezier参数曲线

用递推方法论证了至少存在一条n次Bezier参数曲线与一元n次实数多项式函数完全等价。同时给出了将一元n次实纱多项式转换为完全等价的n次Bezier参数曲线的方法。     

二维浅水流动的涡运动学特性及动力学特征

建立了二维浅水流动的旋涡诱导速度公式，在已知旋涡场和胀量场时，由该表达式可确定流动速度场，对比分析了二维浅水流动中的涡运动与可压缩流动中涡运动的异同点。     

关于加快发展现代物流业的思考

加快发展我国物流产业 ,可以全面提升我国企业的国际竞争实力。搞好现代物流业对我国的经济发展具有重要作用。通过分析物流的基本涵义以及现代物流的发展趋势 ,提出在我国入世之后 ,应如何全面提高我国物流管理水平的重要性 ,以及在当前物流发展中存在的问题。     

一阶非线性中立型方程解的渐近性与振动性

本文研究一类具有交系数和多偏差的一阶非线性中立型微分方程解的渐近性与振动性