Uncertainty calculations in the certification of reference materials. 2. Homogeneity study

 Many reference materials undergo a batch certification, which implies that a small number of samples is taken from a batch, characterised, and these results are then assumed to be representative of all remaining samples. An important aspect in this design is the translation of the characterisation data to a single sample, as usually the laboratory will be using only one sample of the batch. This form of homogeneity is very important and can be influenced to a certain extent by well-designed sample preparation procedures. Another subsampling problem associated with many reference materials is that only a small test portion is drawn from the sample to carry out the measurement. Obviously, this test portion must be representative of the sample, otherwise the certified value is still not applicable. Both kinds of homogeneity tests are examined in the paper and evaluated using practical examples. Received: 31 May 2000 · Accepted: 29 July 2000     

拟银杏杀菌剂邻烯丙基苯酚的内吸传导作用

采用高效液相色谱技术研究了拟银杏杀菌剂邻烯丙基苯酚(绿帝)在小麦幼苗中的内吸传导及可能机制.结果表明,绿帝的内吸传导是一种受体植物主动吸收的过程.     

吸烟饮酒与血压的关系研究

研究了吸烟、饮酒与血压的关系随机抽样21-60岁健康的男女性样本1522人，通过调查问卷方法对样本的性别、年龄、文化水平、吸烟状况、喝酒状况、体育锻炼状况和个人病史等进行询问．用标准方法测量样本的血压值，在统计软件SAS9．0中，利用简单相关分析分别计算吸烟，饮酒与舒张压、收缩压之间的相关系数；利用协方差分析在校正其他因素的影响后分别比较吸烟组、饮酒组与各自的对照组之间血压的差异性．相关分析表明吸烟、饮酒均与收缩压显著正相关，协方差分析表明：吸烟组和饮酒组分别与其对照组之间的收缩压存在显著差异（P〈0．0001）．吸烟和饮酒是预测高血压危险性的有效指标.     

侧风滑跑条件下的地面涡气动特性研究

以缩比的近地面短舱进气道为研究对象,通过数值计算的方法得出侧风来流条件下地面涡的流场特征和气动特性,着重研究飞机滑跑对地面涡的影响。研究表明：在无相对滑跑时,速度比和离地间隙是影响地面涡特性的重要因素。来流速度越大,离地高度越高,地面涡的强度就越高;进气畸变主要受来流速度影响,流速越高,畸变程度越严重。有相对滑跑时,重点考虑来流速度和滑跑速度对地面涡的影响。来流速度对进气畸变影响很大,畸变指数随着风速升高而增大;滑跑速度是地面涡强度的主要影响因素,滑跑速度越高,地面涡强度越弱。     

盐水入侵现象及其对电厂取水口位置的影响分析

通过对河口盐水入侵现象的分析,结合电厂温排放的实际情况,阐述了均质水体温排水的温度分布及取水口布置的一般规律,分析了盐水入侵时电厂温排水的影响,提出了盐淡水分层中取排水位置选择应关注的问题.     

Influence of relative response factor in the determination of organic microcontaminants with isotopically labeled standards

The use of isotopically labeled internal standards in the analysis of organic microcontaminants entails the determination of relative response factors (RRFs) of the unlabeled with respect to the labeled compounds. RRFs were measured daily during 28 replicate polychlorobiphenyl (PCB) analyses on two different sets of samples. Daily RRFs allowed more precise results to be attained than those provided by mean RRFs, the latter being the mean of all the daily RRFs obtained during the same series of analyses. Analytical applications to food matrices are presented, including the PCB contamination profile of an olive oil and that found in a matrix of Italian national mean diet. Based on the latter sample, also the polycyclic aromatic hydrocarbon (PAH) daily intake of Italians is assessed. Seven PAHs are determined.     

水源热泵的应用前景及应注意的问题

介绍了水源热泵的工作原理、系统构成、对水源系统的要求和水源、水质、取水构筑物等特点和要求,指出了水源热泵设计和施工中应注意的问题。     

咖啡因对胎鼠及乳鼠睾丸生殖细胞数量的影响

为了了解咖啡因对胚胎及新生时期男性生殖系统的影响，采用低（０３ｍｍｏｌ／Ｌ）、中（０６ｍｍｏｌ／Ｌ）、高（１２ｍｍｏｌ／Ｌ）浓度咖啡因体外培养ＳＤ孕１８ｄ胎鼠、０ｄ及４ｄ乳鼠睾丸组织块，用ＨＥ染色及放射自显影方法检测咖啡因对睾丸内生殖细胞数量及其摄取３Ｈ－ＴｄＲ的影响。结果：１８ｄ胎鼠睾丸培养组织内生殖细胞数量及３Ｈ－ＴｄＲ的摄取受咖啡因影响较少；中等浓度的咖啡因在培养３周后，生殖细胞的数量、３Ｈ－ＴｄＲ的摄取才降低；而高浓度的咖啡因在培养２周后，检测指标已有下降，３周更明显。生殖细胞数量的减少往往伴随３Ｈ－ＴｄＲ摄取的降低，由此推测高浓度咖啡因长时间培养后使生殖细胞数量减少可能与抑制生殖细胞摄取３Ｈ－ＴｄＲ，从而干扰ＤＮＡ的合成有关。     

枯草芽孢杆菌与酵母培养物对奶牛产奶性能的影响研究

研究了乳牛日粮中添加不同比例枯草芽孢杆菌与酵母培养物混合制剂"畜速益"(XSY)对乳牛泌乳量及乳品质的影响。结果表明:在乳牛日粮中添加XSY,采食量、泌乳量均有显著提高,各阶段牛乳的干物质、脂肪、蛋白质和乳糖含量均有所提高,以每吨精料补充料添加1.5%XSY饲养奶牛的经济效益最佳。     

中国硒研究历史回顾（上）

过去50年中,中国微量元素科学和营养科学中最重要的发现,就是认识了硒对人体健康的重要性。在诸多微量元素中,没有哪一个元素能像硒那样对人类产生如此深刻而又广泛的影响。从硒的生物必需性、硒的生物效应两面性、硒的抗癌性、硒的延寿作用及富硒产品开发五个方面回顾了中国的硒研究历程。