Sample Size and Power Calculation in Comparing Diagnostic Accuracy of Biomarkers with Pooled Assessments

When testing of a biomarker is costly, pooling of samples becomes a useful and efficient alternative (Faraggi et al., 2003). In this paper, we develop procedures for sample size and power calculations for planning a study comparing the accuracy of biomarkers in diagnosis of diseases with pooled samples. Explicit formulas are derived for several important pooling strategies. The effects of pooling samples on sample size and power of the test are also discussed.     

肉类食品的化学性污染及其防治措施

食品安全问题已成为二十一世纪食品研究领域的一大热点,肉类食品污染引发的疾病对人类健康也构成了严重威胁。尤其化学性污染引发的中毒事件逐年呈上升趋势,本文通过肉类食品的化学性污染和种类、来源、技术提出了化学性污染的控制措施。     

化学教学强化德育功能的思考

在化学教学中强化德育功能要进一步提高对新形势下加强德育工作要求的认识 ,这也是学校教育教学规律的必然反映和化学教学改革的正确方向 ;要紧密结合教学内容 ,不失时机实施辩证唯物主义、爱国主义、社会责任感和道德观、环保意识、科学素质等方面的教育 ;要讲究渗透性、启发性、针对性、实效性、实践性等实施德育的方法 ,优化德育效果。     

水稻生长的化控技术

在我国农业现代化过程中,运用植物生长调节剂调控植物生长的化控技术已经越来越多地发挥它的作用。对不同作物及同一作物的不同生育期,所使用调节剂的种类、数量、方法均有不同变化。化控技术与良种、栽培融合形成的化控高产栽培技术体系,将推动我国农业生产再上一个新台阶。     

化学工程学研究进展与展望

化学工程学经过多年的发展,现已形成一个体系完整、研究内容丰富、研究方法先进的工程技术学科。在新的世纪,伴随着化学工程学科的发展,化学工业将会给人类创造出更多的物质财富,对社会作出更大贡献。     

兔大肠杆菌病原菌的分离鉴定与药敏试验

从重庆市几个种兔场临诊严重腹泻的病兔采集病料 ,分离出 3株菌 ,经形态学检查及生化鉴定 ,呈革兰氏阴性 ,两端钝圆的杆状 ,常规的生化结果均符合大肠杆菌特征 ,但 3株菌对棉子糖、蕈糖的分解及赖氨酸的利用上存在着差异。用青霉素G等 2 0种药物进行药敏试验 ,结果表明 :对头孢类、庆大霉素、妥布霉素、阿米卡星、壮观霉素、痢特灵等敏感 ;对麦迪霉素、强力霉素等中敏 ;而对青霉素G、四环素、链霉素等表现为耐药。其中 1号菌株对喹诺酮类、强力霉素、卡那霉素、复方新诺明等耐药 ,2号菌株对喹诺酮类、氯霉素、卡那霉素等敏感 ,而对复方新诺明、利福平等耐药 ,3号菌株对卡那霉素、氯霉素、强力霉素等敏感 ,而对利福平耐药。该试验结果表明 :在不同兔场 ,感染兔的大肠杆菌的株型不一致 ,并且对药物的敏感性也不一致。     

Sensitivity Analysis for Importance Assessment

We review briefly some examples that would support an extended role for quantitative sensitivity analysis in the context of model-based analysis (Section 1). We then review what features a quantitative sensitivity analysis needs to have to play such a role (Section 2). The methods that meet these requirements are described in Section 3; an example is provided in Section 4. Some pointers to further research are set out in Section 5.     

Properties of a class of inequality measures: A proposal for a resistant version

Summary This note explores the robustness properties of a general class of ineqyality measures which includes the Bonferroni and the Gini indexes as special cases and proposes some modifications in order to make them outlier resistant.     

Sensitivity Analysis of Model Output with Input Constraints: A Generalized Rationale for Local Methods

In this work, we introduce a generalized rationale for local sensitivity analysis (SA) methods that allows to solve the problems connected with input constraints. Several models in use in the risk analysis field are characterized by the presence of deterministic relationships among the input parameters. However, SA issues related to the presence of constraints have been mainly dealt with in a heuristic fashion. We start with a systematic analysis of the effects of constraints. The findings can be summarized in the following three effects. (i) Constraints make it impossible to vary one parameter while keeping all others fixed. (ii) The model output becomes insensitive to a parameter if a constraint is solved for that parameter. (iii) Sensitivity analysis results depend on which parameter is selected as dependent. The explanation of these effects is found by proposing a result that leads to a natural extension of the local SA rationale introduced in Helton (1993) . We then extend the definitions of the Birnbaum, criticality, and the differential importance measures to the constrained case. In addition, a procedure is introduced that allows to obtain constrained sensitivity results at the same cost as in the absence of constraints. The application to a nonbinary event tree concludes the article, providing a numerical illustration of the above findings.     

Credibility, Information Preferences, and Information Interests

The Seveso Directive of the European Union demands that information be provided to the public by companies and authorities about facts, risks, and behaviors related to hazardous facilities, in particular chemical facilities. On behalf of the Commission of the European Communities, a survey was run in five European countries on the credibility of various information sources. This article describes the results of the German study. 430 persons were interviewed with a questionnaire of 50 items, in particular about their perceptions and evaluations of technical risks, the credibility of sources of information about chemical risks, their preferences for receiving risk information from these sources, and their interests in receiving information. Major findings are great differences in credibility, differentiated information preferences, and strong information interests. Surprisingly, credibility played only a minor role with regard to the respondents'information preferences and interests.