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排序方式: 共有135条查询结果,搜索用时 46 毫秒
81.
82.
A. F. Hashish N. A. Monk M. P. F. Lovell-Smith L. M. Bardwell T. M. Fiddes R. J. M. Gardner 《黑龙江环境通报》1989,9(6):427-432
Trisomy 16 detected at chorion villus sampling (CVS) may reflect the placental but not the fetal karyotype. We describe a case in which the pregnancy continued until intrauterine death at 37 weeks. Cytogenetic study of two placental samples showed 47, +16 and 46,XX; the fetus was morphologically grossly normal, but fetal tissue culture was unsuccessful. Conservative management may be appropriate when trisomy 16 is detected at CVS and the pregnancy is normal ultransonographically. 相似文献
83.
84.
珠三角地区大气中HCFC-22的浓度观测和变化趋势初步研究 总被引:4,自引:0,他引:4
通过罐采样和预浓缩-色谱/质谱方法,对珠三角地区广州城区和鼎湖山大气中HCFC-22进行了初步的观测和分析.结果表明,2005年广州城区HCFC-22年平均体积分数达到(479.5±241.4)×10-12,鼎湖山仅为(244.4±51.3)×10-12.广州城区大气HCFC-22日变化幅度夏秋季节相对较大,而鼎湖山日变化不明显;广州城区大气HCFC-22的体积分数夏秋季节高于冬春季节,鼎湖山则相反.与城区HCFC-22排放的季节性有关,夏秋季节广州城区与鼎湖山HCFC-22体积分数差别很大,冬春季节则比较接近.初步研究结果表明,广州城区和鼎湖山大气HCFC-22的体积分数呈现快速增长趋势,年增长率分别达到6.57%和7.28%,约为一些全球基准观测站(NOAA/CMDL)的1.9~2.8倍. 相似文献
85.
Through linkage creation, commodity extraction has the capacity to support local industrial production and capabilities building. Drawing on the experience of supplying inputs into the East African gold mining industry, this paper examines the constraints experienced by local suppliers arising from the purchasing procedures of large mining corporations and specialist construction companies contracted to construct these mines. Lead firms become locked-in to particular ways of working which minimise the opportunities that local suppliers have in providing products and services. After reviewing the situation for local mining suppliers in East Africa, the paper examines ways in which lead firms, the suppliers themselves and others (governments and industry associations) can better support local supplier involvement. 相似文献
86.
With the continued growth in demand for mineral resources and China's efforts in increasing investment in geological prospecting, economic impact evaluation of geological exploration becomes a research hotspot. 相似文献
87.
Financial markets recognise maximisation of expected value (E), in an essentially risk-neutral context, as the main corporate financial objective of private enterprise. This may be valid for large, integrated mining companies. Yet, most junior and middle-size exploration companies behave in a risk-averse fashion when making decisions about progressively more expensive exploration programs. From their perspective, a potential increase in expected value from either an increase in target value or related probability of discovery, or both, may not be a sufficient incentive to embark in an exploration programme if the resultant increase in expected value is accompanied by a significant increase in possible maximum loss. Risk-averse explorers may be unwilling to bear larger, albeit less probable losses, when the cost of successive exploration programmes is taken into account. The paper provides a practical methodology for such explorers to optimise the decision whether to progress to the next stage of exploration or to farm out a risky project. It uses a decision-tree model incorporating the effectiveness of the proposed exploration programme, the explorer's risk tolerance and related utility values and the probability distribution of the possible value of the exploration target. 相似文献
88.
We report on the prenatal diagnosis and ultrasonographic findings of a second-trimester fetus with jumping translocation involving chromosome 22. A 28-year-old gravida 2, partus 1, Turkish woman was referred for genetic counselling and ultrasonographic examination at 18 weeks' gestation because of a high risk of trisomy 21 in triple test. Prenatal ultrasonography showed tetralogy of Fallot with a diverticular dilatation of the pulmonary artery, flattened brow, complete absence of the right upper limb, hypospadias, oligodactyly (three digits) in left hand and in both feet, and hyperechogenic abdominal foci. Amniocentesis revealed a karyotype of 46,XY[4]/46,XY,−8,+ der(8),t(8;22)(q24.3;q11.21)[2]/45, XY,−22,−8,+ der(8)t(8;22)(q24.3;q11.21)[22]/45,XY,−22,−5,+ der(5)t(5;22)(q35.3;q11.21)[44]. A C-banding and FISH study with a specific centromeric probe (D14Z1/D22Z1) for chromosome 22 was made. In our case, partial monosomy for the regions 22q11.21→22pter, 8q24.3→8qter and 5q35.3→5qter may partially explain the fetal malformations. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
89.
90.
Jonathan P. Park John B. Moeschler Eileen Rawnsley Susan Z. Berg Doris H. Wurster-Hill 《黑龙江环境通报》1989,9(7):501-504
Prenatal diagnosis of trisomy 20 mosaicism in this case was based on cytogenetic analysis of cultured amniotic fluid cells (23/52 cells were trisomy 20 representing cells from each of four primary cultures). The pregnancy continued to term and the mosaicism was confirmed in the phenotypically normal male neonate by analysis of cultured foreskin fibroblasts (7/49 cells + 20) and placental cells 20/20 cells + 20) whereas the peripheral lymphocytes were cytogenetically normal (20/20 cells were 46,XY). This represents the first confirmation of trisomy 20 mosaicism in a phenotypically normal full-term neonate. 相似文献