Enhanced twin pregnancy detection within an open neural tube defect and down syndrome screening protocol using free-beta hCG and AFP

We have applied our multimarker approach of maternal serum alpha-fetoprotein (AFP) and free-beta human chorionic gonadotropin (hCG) for Down syndrome screening to multiple gestations to assess its efficacy for improved detection of twin and triplet pregnancies. This study matched 225 cases of twin pregnancy and 39 cases of triplet pregnancy each with ten singleton pregnancies based on gestational week, race, time to receive sample, time of year of sample, and geographical area. The ratios of the MOM for each group at the tenth, 50th, and 90th percentiles were compared by the Wilcoxon test. Risks for twins were calculated using Bayes' rule, the age-related incidence of twins, and the levels of AFP and free-beta hCG. The tenth, 50th, and 90th percentiles of free-beta hCG MOMs in twin and triplet cases were 0.85, 1.99, and 4.51, and 1.38, 2.78, and 4.07, respectively. For AFP, the MOMs at these percentiles were 1.26, 1.91, and 2.99, and 2.02, 2.68, and 5.30, respectively. The twin and triplet distributions for each marker were statistically significantly different from the singleton distributions (P<0.0001) and from each other (P=0.0012). At a twin risk cut-off of 1 in 50, 77.4 per cent of all twin gestations can be detected in a second-trimester AFP and free-beta hCG screening protocol with 5.1 per cent of singleton pregnancies falsely identified as at risk for twins. Our dual marker protocol for mid-trimester pregnancy screening combining AFP and free-beta hCG can identify over 77 per cent of twin pregnancies in women less than 35 years of age. This benefit may contribute to an improved outcome of pregnancy by early detection of multiple gestation.     

涕灭威在植物和土壤中的移动与分布

报道了涕灭威在花生、棉花、柑橘和土壤中的吸收、运转和分布。结果表明，涕灭威及其代谢物在柑橘叶子中的残留４０ｄ达到最高峰（３．４４９ｐｐｍ），可食部位的残留范围为０－０．０８９ｐｐｍ，低于美国ＥＰＡ规定的ＭＲＬ。涕灭威在土壤中降解较快，半衰期约１周。收获时土壤中的检出范围为０－０．１５７ｐｐｍ。涕灭威及其代谢物水溶性很强，且具有渗透和扩散性，因此使用不当可能造成地下水污染。     

鄂西的硒资源及其开发战略研究

湖北省西南部有二叠系茅口组富硒碳质硅质岩和碳质页岩广泛出露。岩石、土壤和富硒土壤上生长的玉米含硒量最高分别达到8.390、354和40(mg/kg)。作者对这一硒资源的价值进行了评估,并对其开发战略进行了探讨。     

江苏省丹阳市水稻土自然生产潜力的初步研究

本文借助作物生长模型与模糊数学的方法对江苏省丹阳市的两种种植制度的土壤自然生产潜力进行了初步的分析研究。结果表明,模拟的小麦/玉米-晚稻种植制度的气候生产潜力比小麦-单季稻高3000kg/ha 左右。指出丹阳的小麦生产应以挖掘、提高土壤自然生产潜力为主,而单季稻的生产则应以提高品种的气候生产潜力为方向。     

海河流域土壤中氮的分布特征

对海河流域不同土壤类型中各形态氮的含量分布、水平及其垂直变化进行探讨,研究了在一定条件下土壤中氮的自然富集、增减途径、自然循环环境及分布特征,为研究该区氮的库存量、流通量以及自然循环奠定基础.     

竞争吸附方程的修正和应用

以竞争吸附的一般模式为基础,修正了竞争吸附方程。研究了不同实验条件下修正竞争吸附方程的变化形式,为改进实验设计提供了理论依据。修正竞争吸附方程应用于描述pH对土壤吸附钴的影响,取得了满意的结果。     

四川盆地土壤微量元素生态类型研究

本研究从生态学观点出发,根据土壤缺乏微量元素的临界值指标,探究了四川盆地土壤微量元素的生态类型,按其土壤供给有效态微量元素的丰缺程度,将本区土壤微量元素分为五种生态类型:严重缺乏、缺乏、适中、丰富和很丰富。统计结果表明,四川盆地各类土壤的微量元素生态类型特点为:有效硼含量很低,普遍严重缺硼;有效锌含量亦低,近半数土壤缺锌;多数土壤有效锰含量丰富,仅少部分土壤供锰不足;有效铜和铁的含量丰富。     

油田行业"三废"综合利用研究

介绍了国家“三废”综合利用方面的政策，结合油田行业资源综合利用现状，提出如何进一步开展油田行业“三废”综合利用工作，并更好地利用国家资源利用税收方面的优惠政策，开拓油田行业“三废”综合利用渠道，推动“三废”综合利用，争取得到最大限度的减免税额。     

Effects of bifenthrin on Daphnia magna during chronic toxicity test and the recovery test

IntroductionWiththedevelopmentandapplicationofnewpesticide ,insecticidehasgreatlyreducedtheharmofpesttocrops .Bifenthrinisaneffectivepyrethroidinsecticideandacaricideagainstawiderangeofinsectpests ,anditisverypoisonoustomammal,aquatic .Thisinsecticideiswi…     

网络计划在液化气球罐内外部检验过程中的应用

在以工期考虑为重点的V-3002B液化气球罐内外部检验过程中，引用现代管理中网络计划技术关键路线法，为加快芳烃厂压力容器检验提供了科学的依据。本文总结和介绍了网络计划技术在芳烃厂贮运车间V-300亚球罐内外部检验过程应用情况。