Effect of sulphadimethoxine contamination on barley (Hordeum distichum L., Poaceae, Liliposida)

Animal wastes from intensive farming are generally collected for field fertilisation. They may contain drugs that can become soil pollutants. To evaluate the possible effects of such contamination in terrestrial systems, sulphadimethoxine has been subjected to laboratory tests (in vitro, synthetic medium, and soil) using seeds of barley (Hordeum distichum L.). The drug suppressed normal post-germinative development and growth of roots and leaves in both test conditions; this effect was dependent on the bioaccumulation rate, which was higher on synthetic medium than in soil. Bioaccumulation was higher in roots than foliage and this was markedly evident in soil and, in particular, in soils with a low humus content. The environmental risk of sludge application on soils and the possible contamination of food chains are discussed.     

Differences in responses of herpetobionts and geobionts to impact from the Kosogorsky Metallurgical Plant (Tula region,Russia)

The influence of the Kosogorsky Metallurgical Plant (KMP; Tula region, Russia) on the abundance and biodiversity of carabid beetles and soil macrofauna and on the trophic activity of soil biota was studied. Metal concentrations in the impact plot were many times higher than those in the control plot located on the same transect. As the transect approached KMP, both the abundance of soil invertebrates (geobionts) and trophic activity of the soil biota remained unchanged, whereas the abundance and diversity of carabids (herpetobionts) decreased drastically. It is suggested that the impact of the KMP on herpetobionts is accounted for by modification of the structure of ecosystems and that herpetobiontic and geobiontic groups of the macrofauna respond differently to this impact because of differences in the ecological mechanisms of population response.     

The first trimester ‘combined test’ for the detection of Down syndrome pregnancies in 4939 unselected pregnancies

The high detection rate (DR) for Down syndrome (DS) pregnancies which can be achieved by measuring fetal nuchal translucency (NT) early in pregnancy can be improved by combining it with placental hormones [pregnancy-associated plasma protein A (PAPP-A) and free β-human chorionic gonadotrophin (fβ-hCG)] and maternal age (‘combined test’). In this study we wanted to assess the DR using the ‘combined test’ in an unselected population of self-referred pregnant women at a false-positive rate (FPR) of about 5%. NT, PAPP-A, fβ-hCG and maternal age were measured in all women with singleton pregnancies who booked for delivery in our hospital from 1 December 1997 to 31 April 2000 and who were between 10 and 13 completed weeks of gestation [crown–rump length (CRL) 35–70 mm]. The specific DS risk was calculated using the computer program Alpha Version 5aa (Logical Medical Systems, London, UK). A total of 4939 women were tested. Out of 14 DS pregnancies that occurred during this period of time, 12 were detected with the test. A total of 246 women had a false-positive test result in a non-DS pregnancy (FPR 5.0%). This makes the ‘combined test’ by far the best test for the detection of DS pregnancies in a low-risk population. The constant increase in maternal age at the time of delivery can also lead to an improved DR if a simple age-dependant protocol for DS detection is used, but only at the price of a much higher number of amniocenteses and subsequent abortions. The DR for DS can be increased much more markedly using the ‘combined test’ with a FPR that still remains at the level as it was in the early 1970s. Copyright © 2002 John Wiley & Sons, Ltd.     

基于虚拟碰撞试验分析燃料电池轿车车身结构的安全性

在燃料电池轿车的车身结构配合动力驱动系统的改进而不断改进的过程中,需要从碰撞安全性角度去分析结构方案的优劣.本文采用虚拟正面碰撞试验方法,研究经过改进后的燃料电池轿车的半承载式车身是否满足国家被动安全法规,并通过与第1代燃料电池轿车的整车碰撞模拟结果的对比,分析车身结构改进对正面碰撞安全性的影响,从而为进一步的结构改进提供有价值的建议.     

利用umu/SOS实验评价污灌土壤的遗传毒性

利用umu/SOS显色实验评价北京市郊污水灌溉土壤中遗传毒性物质的积累,得到表征样品遗传毒性大小的β-半乳糖苷酶诱导活性(IU值).以达到阳性时诱导比率R=2(试验管IU值/对照管IU值)需要的土壤重量来反映土壤样品的相对遗传毒性.R值起初随着96孔板每孔土壤样品量的增大而增大,但在达到某一定值后呈现稳定,此时各土壤样品投加量均为每孔约含10mg土壤.用剂量效应曲线中线性段的斜率作为标准,判断出遗传毒性物质为性质相同的一类污染物,根据相关资料推测主要是由于多环芳烃类污染物积累.     

砂尘试验箱原理分析改进及相关标准探讨

结合砂尘的产生和运动机理,对砂尘试验箱的设计原理和应用特点进行了说明,着重对吹砂程中空气的温度和湿度、砂尘颗粒直径比例进行了分析,对气固两相流中颗粒浓度的均匀性进行了探讨。基于砂尘的运动特性,国内应用较普遍采用的闭式循环吹砂试验设备,无法实现砂的有效分离,导致吹砂试验箱试验过程中颗粒直径比例不满足GJB 150.12A要求。在MIL-STD-810H中,已经取消了对吹砂试验相对湿度≤30%的要求。基于吹尘和吹砂引起的不同环境效应,结合吹尘和吹砂试验设备原理和国内已有设备的现状,对现有试验方法和校准规范的完善、砂尘试验箱的改进设计提出了建议和意见。同时文中也介绍了国外开式、闭式循环、可变循环等几种不同类型的砂尘试验箱作为参考,基于砂尘试验的破坏机理提出了砂尘试验箱的分类和选型建议。     

大跨度钢结构桥架的检测鉴定及加固处理

对大跨度受腐蚀损坏的钢结构桥架进行结构可靠性检测鉴定和内力验算,根据检测鉴定结果做加固处理,保证了结构的安全稳定和生产使用需要。     

南京及邻近地区新近沉积土的动剪切模量和阻尼比的试验研究

通过对南京及其邻近地区漫滩相成因的粘土、粉质粘土、淤泥质粉质粘土、粉质粘土与粉砂互层土、粉土、粉细砂等 6类新近沉积土的自振柱试验 ,详细探讨了围压大小、剪应变水平、土的颗粒组成和结构性对这 6类新近沉积土的剪切模量G及阻尼比λ的影响。通过与Seed和Idriss建议的砂土G/Gmax～γ和λ～γ曲线变化范围的对比 ,结果表明 ,不能将粉质粘土与粉砂互层土简单地当作砂土或粉质粘土对待。通过试验和理论分析 ,给出了南京及其邻近地区 6类新近沉积土动剪切模量和阻尼比随剪应变变化的平均曲线的拟合曲线、包络线及其参数的推荐值 ,对实际工程具有一定的借鉴作用     

装修用板材的导热性能分析

导热系数是物体的重要物理指标,对四种板材的导热系数进行了测试,并对导热性能进行了分析。