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861.
文章根据从事电力工程地下水环境影响评价的方法,介绍了电力工程地下水评价,探讨了电力工程地下水评价等级的评价,分析了前电力工程地下水环境影响评价实践中存在的技术问题,对地下水评价过程中的评价等级划分、项目所在区地质环境现状调查、水文地质试验及参数计算、地下水污染源确定及影响预测、污染防治措施的确定等方面构建出电力工程地下水环境影响评价的整体框架,提出了地下水环境影响评价的整体思路,并以完成审批的电力工程为例进行了分析和探讨. 相似文献
862.
Reed F. Noss 《Conservation biology》2003,17(5):1270-1275
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József Gábor Joó Artúr Beke Csaba Papp Ernő Tóth-Pál Ákos Csaba Zsanett Szigeti Zoltán Papp 《黑龙江环境通报》2007,27(10):912-921
Objective This study was conducted to evaluate the major demographic details, diagnostical and clinical features, as well as the risk of recurrence of cases with the major types of neural tube defects (NTD). We also examined the efficiency of ultrasonography based on autopsy examinations during 26 years. Methods The investigations were made into the sample of 743 NTD diagnosed between 1 January 1976 and 31 December 2002. A computerized database was used to sum up the available information about the individual cases; in addition to surveying the couples' major demographic details, we also had the opportunity to collect detailed information about the history, diagnostics (ultrasound) and outcome of the pregnancies as well as the results of the autopsies during the investigation. Results In the 743 cases of NTD, maternal and paternal median ages turned out to be 23.7 years (±5.22 years) and 28.7 years (±5.81 years), respectively. The male:female ratio was 0.78. Comparable samples of anencephaly and spina bifida allowed for the conclusion that a positive genetic history was equally often found while a positive obstetrical history was almost twice as common in anencephaly. The sensitivity of the maternal serum-alpha fetoprotein (AFP) screening test is the highest in anencephaly and lowest in encephalocele. While the majority of cases of anencephaly were diagnosed before the 24th gestational week, examples of diagnosing spina bifida and encephalocele at a later time could also be found. Among the associated malformations other than those of the central nervous system special mentioning should be made of fetal pyelectasia, cleft palate as well as diaphragmatic herniation. No pathological karyotypes were found in association with encephalocele or spina bifida, but anencephaly was accompanied with trisomy 21 and trisomy 18 in one case each. Anencephaly was found to have the highest risk of recurrence in both nervous system malformations and malformations other than those of the nervous system. Sonography proved to be the most reliable method in cases of enecephalocele. Conclusion The respective median values of maternal and paternal age show that aetas has no role in the occurrence of NTDs. NTDs are more common among girls. Positive genetic, obstetrical and medical findings are of great importance in the incidence of NTDs. Although reliable to only a limited extent, maternal serum-AFP tests are considered to be useful and necessary in screening NTDs, while sonography is the gold standard method in recognizing these frequent malformations. The knowledge of the eventual associated malformations is mainly important in certain cases of spina bifida, which may also yield a good post-natal prognosis. Our data obtained from the sample of 26 years also confirm that the periconceptional administration of folic acid reduces the incidence and risk of recurrence of NTDs. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
866.
植物群落是植物在自然因素综合作用下形成的一个有机体,是植物群体发展的自然属性.在不同的生态环境条件下产生了不同的群落类型.地处中亚热带丘陵地的株洲,地带性典型植物群落是常绿阔叶林,是以各类常绿树种为优势的植被类型.但是随着历史变迁,人类频繁活动,此类群落已不复存在,以人工群落和次生群落取而代之,其主要群落类型有青冈栎群落、石栎群落、苦槠、青冈栎群落、樟树群落、冬青群落、山杜英群落等12种.园林绿化作为人工群落,其园林植物选择和配置,设计建造人工群落都要遵循天然群落发生、发展规律及模拟其结构特征才能实现园林绿化低成本、高效益、高生产力、高生物量的总体目标.因此,开展对城郊区现有天然林的调查是非常必要的.其结果直接用于城市绿地系统规划和人工模拟地带性植物造景. 相似文献
867.
对处于4种不同状态下的"热得快"从宏观形貌和微观形貌进行比较、观察和分析;同时系统地分析了"热得快"金属管表面形貌特征和电热丝表面形貌特征形成的机理和主要影响因素。结果表明:不同状态下"热得快"金属管宏观形貌特征存在差异,但容易受到火场复杂条件的影响,不能对火灾前"热得快"所处的状态进行定性;通过扫描电子显微镜(SEM)分析技术观察"热得快"电热丝的微观形貌的差异,可以直观快捷地识别"热得快"在火灾前所处的状态,为"热得快"火灾残留物的鉴定提供一种新的鉴定依据和技术方法。 相似文献
868.
Arzarello M Marcolini F Pavia G Pavia M Petronio C Petrucci M Rook L Sardella R 《Die Naturwissenschaften》2007,94(2):107-112
Some flint lithic artifacts were discovered in the fissure fillings of the well-known Pirro Nord site (Apulia, Southern Italy).
The lithic industry, composed by three cores and some flakes, has been found to be associated to an Early Pleistocene vertebrate
fossil assemblage. The fossil association contains a wide range of micromammals, including Allophaiomys ruffoi and Episoriculus gibberodon and large mammals including Bison degiulii and Equus altidens together with African elements as the gelada baboon Theropithecus and the saber-toothed cat Megantereon whitei. It defines the latest Villafranchian chronological unit (Pirro Nord Faunal Unit) in the Western European mammal biochronology.
The lithic industry of Pirro Nord represents the oldest occurrence of the genus Homo in Europe as it is attributable to a chronological interval between 1.3 and 1.7 Ma. This supports the hypothesis that the
genus Homo, with Oldowaian technology, extended its range in Europe, probably from western Asia, during the first half of the Early
Pleistocene. The new discovery from Pirro Nord changes the chronology of the first arrival of hominids in Europe and offers
new perspectives in the debate about the human dispersal in the Early Pleistocene. 相似文献
869.
Natural regeneration and the height-age structure of small-leaved linden (Tilia cordata Mill.) under a forest canopy were studied with regard to specific features of forest typology on the Ufa Plateau. For the first time, the height-age structure of linden undergrowth was analyzed by an anatomical method, which allowed accurate determination of the actual plant age and linear increment. The results of this analysis made it possible to reveal three periods in the development of linden undergrowth with respect to the linear growth rate and abundance of plants. More successful regeneration of linden was observed in open elements of relief. 相似文献
870.