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排序方式: 共有643条查询结果,搜索用时 622 毫秒
261.
Dr Jean Cazenave LABM Francois Forestier Marie Hélène Bessieres Bernard Broussin Joël Begueret 《黑龙江环境通报》1992,12(2):119-127
A polymerase chain reaction (PCR) assay has been developed for the detection of Toxoplasma gondii. The target sequence (88 bp) is part of a rDNA repetitive gene. A signal can be observed with only one parasite. It is directly and rapidly detected by electrophoresis and ethidium bromide staining. We report a prospective study of 80 documented cases of toxoplasmic seroconversions during pregnancy. The PCR assay of the amniotic fluids was compared with the current standard methods for diagnosis of fetal infection. Seventy specimens gave no PCR signal, and were negative according to prenatal tests and postnatal examinations. The presence of T. gondii was detected in ten specimens by PCR analysis. Four were confirmed by isolation of the parasite from the amniotic fluid; four by biological study of the fetal blood. For the remaining two, infection was diagnosed after birth. Together with ultrasonographic and biological data, this technique permits prenatal diagnosis within 1 day. 相似文献
262.
In this paper, a mathematical programming-based methodology is presented for the explicit inclusion of life cycle assessment (LCA) criteria as part of the strategic investment decisions related to the design and planning of supply chain networks. By considering the multiple environmental concerns together with the traditional economic criteria, the planning task is formulated as a multi-objective optimization problem. Over a long-range planning horizon, the methodology utilizes mixed integer modelling techniques to address strategic decisions involving the selection, allocation and capacity expansion of processing technologies and assignment of transportation links required to satisfy the demands at the markets. At the operational level, optimal production profiles and flows of material between various components within the supply chain are determined. As such, the formulation presented here combines the elements of the classical plant location and capacity expansion problems with the principles of LCA to develop a quantitative decision-support tool for environmentally conscious strategic investment planning. 相似文献
263.
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265.
C. Rosatelli F. Schettini G. Monni T. Tuveri M. T. Scalas A. Di Tucci G. B. Leoni Professor A. Cao 《黑龙江环境通报》1988,8(5):393-397
This report describes a couple at risk for β thalassaemia in which one spouse was heterozygous for classical high Hb A2 β-thalassaemia while the other had the compound heterozygous state for β+-thalassaemia and a β-chain variant. This variant comigrates on carboxymethyl-cellulose columns (CMC) with γ-chains, indicating that globin separation on CMC columns could not have been used for fetal diagnosis. The β-chain variant migrates separately from the other globin chains on HPLC and the respective abnormal haemoglobin can be separated by isoelectrofocusing. Oligonucleotide hybridization showed that both parents were carriers of the β+ IVS-1, nt 6 mutation. Prenatal diagnosis was successfully accomplished by oligo-nucleotide analysis on trophoblast DNA. This case indicates that an Antenatal Service should have alternative methods to CMC columns so as to carry out prenatal diagnosis of β-thalassaemia in uncommon cases. 相似文献
266.
Discrimination of the M, Z, and S alleles of α1-antritrypsin (AAT) has been carried out using in vitro gene amplification with the polymerase chain reaction (PCR). Amplification of 90 nucleotides surrounding the Z mutation site and 120 nucleotides surrounding the S mutation site dramatically improves the sensitivity and reliability of allele-specific oligonucleotide (ASO) hybridization for direct detection of these alleles. Analysis is performed using Southern blots or dot blots hybridized with 19 base oligonucleotides and differentially washed for allele specificity. Amplification of the Z and S mutation sites can be combined in one PCR to allow detection of both mutations when analysed by gel electrophoresis and Southern transfer. This technique can be performed reliably using less than 0·1 μg of genomic DNA or less than 100 amniocytes or white blood cells. This technique has been used to perform prenatal diagnosis on a chorionic villus sample (CVS) in a fetus at risk for the ZZ Pi type form of AAT deficiency. 相似文献
267.
Lassen C Hansen E Jensen AA Olendrzyński K Kołsut W Zurek J Kargulewicz I Debski B Skośkiewicz J Holtzer M Grochowalski A Brante E Poltimae H Kallaste T Kapturauskas J;Danish Cooperation for Environment in Eastern Europe 《Environmental science and pollution research international》2003,10(1):49-56
The present paper summarises the results of the project: 'Survey of Anthropogenic Sources of Dioxins and Furans in the Baltic Region'. As a part of the project, inventories have been carried out in Estonia, Latvia, Lithuania and Poland by applying the toolkit for quantification of dioxin and furan releases developed by UNEP Chemicals. The main route of direct releases to the environment is emission to air. Total emission to air from Poland was estimated at 490 (88-1,300) g I-TEQ/year, whereas the emissions from Estonia, Latvia and Lithuania were estimated as being 14 (2.4-54), 23 (2.6-63) and 17 (2.6-38) g I-TEQ, respectively. In general, the uncertainty on the estimates is very high, and recommendations regarding further development of the inventories have been made, and measures for reducing the releases have been provided. 相似文献
268.
Adaptive two-stage one-per-stratum sampling 总被引:1,自引:0,他引:1
Mary C. Christman 《Environmental and Ecological Statistics》2003,10(1):43-60
We briefly describe adaptive cluster sampling designs in which the initial sample is taken according to a Markov chain one-per-stratum design (Breidt, 1995) and one or more secondary samples are taken within strata if units in the initial sample satisfy a given condition C. An empirical study of the behavior of the estimation procedure is conducted for three small artificial populations for which adaptive sampling is appropriate. The specific sampling strategy used in the empirical study was a single random-start systematic sample with predefined systematic samples within strata when the initially sampled unit in that stratum satisfies C. The bias of the Horvitz-Thompson estimator for this design is usually very small when adaptive sampling is conducted in a population for which it is suited. In addition, we compare the behavior of several alternative estimators of the standard error of the Horvitz-Thompson estimator of the population total. The best estimator of the standard error is population-dependent but it is not unreasonable to use the Horvitz-Thompson estimator of the variance. Unfortunately, the distribution of the estimator is highly skewed hence the usual approach of constructing confidence intervals assuming normality cannot be used here. 相似文献
269.
持久性有机污染物在食物链中积累与放大研究进展 总被引:3,自引:0,他引:3
研究持久性有机污染物(Persistent organic pollutants,POPs)在食物链中的积累与放大是进行环境风险评估和有效污染控制的生态学基础.本文综述了POPs的基本特征,POPs在食物链中的生物积累与放大的机制、影响因素以及POPs在食物链中积累与放大的模型等的研究进展.国外学者对POPs在水生食物链的积累与放大方面研究较多,并提出了较为完善的预测模型,而有关POPs在陆生食物链中的生物积累与放大的研究报道较少.大部分学者并未对完整食物链进行过系统而完整的研究.与国外相比,国内学者对POPs在水生陆生食物链中的生物积累、生物放大和预测模型探讨较少.目前POPs对环境和人体健康危害越来越严重,开展对POPs在食物链中积累、放大及相关预测模型更深入更完整的研究,已成为当前生态学和环境科学研究的重点课题和前沿领域. 相似文献
270.
为有效规避冷链供应链受突发事件带来的不利影响,并强化其应急体系协同化发展,提出基于层次分析法和序参量法的应急冷链供应链协同化水平评价模型。模型以供应链协同化理论为基础,从协同化目标入手构建影响其协同化水平的测度指标体系;利用层次分析法确定评价指标的综合权重,最后运用序参量法评估冷链供应链各应急环节的协同度。结果表明:评价模型能有效评估应急冷链供应链协同化水平,可为冷链供应链应对突发事件提供参考。 相似文献