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901.
We measured immunoreactive inhibin in the maternal serum of 80 pregnancies with a chromosomally normal fetus and ten Down's syndrome pregnancies in the second trimester. The inhibin level in all Down's syndrome pregnancies was above the normal median; the multiple of the normal median (MoM) was 1.9. We found a statistically significant difference between the levels of inhibin in unaffected and affected pregnancies (Kolmogorov–Smirnov test: p <0.002). Using an arbitrarily chosen cut-off of 2.4 MoM, 40 per cent of Down's syndrome and 5 per cent of the normal pregnancies were found. We conclude that immunoreactive inhibin may be useful as a marker for fetal Down's syndrome. 相似文献
902.
Comparing the soil quality changes of different land uses determined by two quantitative methods 总被引:8,自引:0,他引:8
FU Bo-jie LIU Shi-liang LU Yi-he CHEN Li-ding MA Ke-ming LIU Guo-hua 《环境科学学报(英文版)》2003,15(2):167-172
Soil quality is one of the most important environmental factors in sustaining the global biosphere and developing sustainable agricultural practices.A study was initiated in Wolong Nature Reserve,Sichuan Province,China to elucidate the soil quality changes of natural secondary succession,forest planting and agricultural practices after deforestatin in the humid mountainous region.The soil qualities of six land use types(natural forestland ,grassland,shrub land,secondary index(QI) and soil deterioration index(DI).The QI values of natural forestland ,grassland,shrub land,secondary forestland,cultivated land ,reforested land were 0.8039,0.3277,0.9127,0.6881,0.0285 and 0.3183,respectively.The DI values were 0%,-14%,12%,1%,-26% and -18% respectively.Both indexes suggested that shrub land can restore soil properties.To compare the two methods more directly,a deduced index QI‘based on QI value was developed,.The results showed that DI and AI‘ had a very high linear correlation coefficient(r=0.9775) despite the values were different .Both methods were efficient in evaluating the soil quality levels and DI was a more simple way in soil quality assessment,while QI could show more ecological meanings. 相似文献
903.
林伦举 《安全.健康和环境》2002,2(11):33-34
分析了节日期间化工生产潜在的不安全因素,提出了相应的防范对策,旨在促进节日期间化工企业的安全生产工作. 相似文献
904.
Amarjot Kaur Loredana Di Consiglio Ganapati P. Patil Charles Taillie 《Environmental and Ecological Statistics》1995,2(3):239-269
In environmental assessment and monitoring, a primary objective of the investigator is to describe the changes occurring in the environmentally important variables over time. Propagation functions have been proposed to describe the distributional changes occurring in the variable of interest at two different times. McDonald et al. (1992, 1995) proposed an estimator of propagation function under the assumption of normality. We conduct a detailed sensitivity analysis of inference based on the normal model. It turns out that this model is appropriate only for small departures from normality whereas, for moderate to large departures, both estimation and testing of hypothesis break down. Non-parametric estimation of the propagation function based on kernel density estimation is also considered and the robustness of the choice of bandwidth for kernel density estimation is investigated. Bootstrapping is employed to obtain confidence intervals for the propagation function and also to determine the critical regions for testing the significance of distributional changes between two sampling epochs. Also studied briefly is the mathematical form and graphical shape of the propagation function for some parametric bivariate families of distributions. Finally, the proposed estimation techniques are illustrated on a data set of tree ring widths. 相似文献
905.
近年来遥感技术不断地拓展着应用的领域和范围,在土壤污染方面得到了广泛的关注和应用。传统土壤污染的研究存在许多弊端,需要耗费大量时间和精力。遥感技术具有建模范围大、实时性短的特点,它的出现使这些繁琐的过程更加简化。特别是近些年来图像处理手段和无人机遥感技术的发展,极大地提高了该技术的应用精度。本文从遥感技术在土壤污染状况的识别、反演、监管和风险评估等方面的应用出发,列举了遥感技术应用过程中常用的反演手段和方法,梳理了监管数据来源和监管对象。通过目前土壤污染与遥感技术结合的发展现状,较为全面地回顾了国内外遥感技术应用于土壤污染的发展历程,总结了遥感技术应用于土壤污染的各个方面的进展,并对该方面的未来发展趋势进行了展望。 相似文献
906.
结合9年来对闹得海水库水质监测及相关文献资料,评价闹得海水库营养状态,分析主要污染物变化趋势,对该水库营养状态进行分析,提出该水库富营养化防治对策。结果表明:闹得海水库9年来营养状态在中营养-中富营养之间,主要营养盐总氮、总磷及高锰酸盐指数9年间无显著变化,农业面源是该水库主要营养盐及有机物主要来源。 相似文献
907.
环境中的外部性及其内部化 总被引:5,自引:0,他引:5
在经济活动中,经济人为了使自己的收益达到最大化,他们会尽可能地使外部成本转嫁给社会,减少自己的内部成本,使社会资源的配置偏离社会的需要,所以,为了使资源的配置达到帕累托最优,就必须使外部成本内部化。内部化外部成本的经济手段有:向经济人征税、界定资源的产权和实行排污权交易制度等措施。 相似文献
908.
矿井水中微量有机污染物的深度处理 总被引:3,自引:1,他引:3
本文对华北地区某矿务局进行矿井水中微量有机污染物现状调查的基础上,结合目前国内外城市生活饮用水中微量有机污染物处理研究的资料,初步分析和介绍了矿井水中微量有机污染物的来 要污染物的种类及目前国内研究已较的处理方法,为矿井水的深度处理衣资源化提出一个新的研究方向。 相似文献
909.
For the last 6 years, sonographic signs for excessive fluid accumulation in the backs of 10- to 12-week-old fetuses have been looked for prior to transabdominal chorionic biopsy. In 1400 pregnancies, subsequent karyotype analyses revealed 28 cases of Down syndrome. In 15 ( = 54 per cent), a large fluid cushion over most of the back had been documented at the time of biopsy. Only a few chromosomally normal fetuses with the same peculiarity were observed. The cushion was also present in fetuses with trisomies 18 and 13 , and in Turner syndrome. Systematic first-trimester screening for nuchal fluid accumulation seems to be a recommended method for the detection of Down syndrome and other chromosome anomalies in young pregnant women at low risk. It compares favourably with current methods of maternal serum screening performed at 16–18 weeks which require a higher number of invasive procedures. 相似文献
910.
Dr. S. Kanokpongsakdi S. Fucharoen C. Vatanasiri V. Thonglairoam P. Winichagoon J. Manassakorn 《黑龙江环境通报》1990,10(12):809-813
In nine pregnant women at risk for fetal alpha-thalassaemia, the two affected fetuses were diagnosed by ultrasonography at 18–20 weeks' gestation. In countries with limited resources, ultrasonography provides a cost-effective method of prenatal screening for this condition. 相似文献