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排序方式: 共有883条查询结果,搜索用时 15 毫秒
481.
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
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High-rate clarification (HRC) processes are well suited for enhanced primary treatment of wet-weather flows in combined sewer systems. Suspended solids removal in excess of 75% of influent concentrations can be achieved consistently. Chemical oxygen demand and five-day biochemical oxygen demand removal are better than 60%. However, although optimal treatment could be achieved in a matter of minutes when the units were started full, a delay of up to one-half hour was observed when the units were started empty. Operational strategies that minimize this effect need to be developed in full-scale tests before HRC processes can be implemented with confidence in wet-weather-only facilities. 相似文献
484.
Diagnosing Units of Conservation Management 总被引:15,自引:0,他引:15
Species-oriented conservation programs attempt to analyze and maintain intra-specific variation in order to maximally preserve biological diversity. The "evolutionarily significant unit" has become an operational term for a group of organisms that should be the minimial unit for conservation management. No generally accepted definition for this term exists that would be the basis for the evaluation of these units in practical conservation situations. Currently, taxonomic decisions in species conservation are mostly based on the biological species concept. But the universal application of criteria of reproductive isolation or phenetic similarity to delimit conservation units is problematical. We favor a definition for evolutionarily significant units based on patterns of variation. In the theoretical framework of the phylogenetic species concept, conservation units are delimited by characters that diagnose clusters of individuals or populations to the exclusion of other such clusters. Characters are used for cladistic analysis to infer hypotheses of the phylogenetic relationships of individuals, and differentiated populations are diagnosed using population aggregation analysis. Characters can be based on genetic, morphological, ecological, or behavioral information, provided they are inferred to be heritable. The use of cladistics and population aggregation analysis has the potential to make the evaluation of evoluntionarily significant units objective and testable, an important consideration in politically controversial cases. Our cladistic approach is demonstrated by the evaluation of potential conservation units in the endangered tiger beetles Cicindela dorsalis and C. puritana . 相似文献
485.
Sandra Kim Tiam Xavier Libert Soizic Morin Patrice Gonzalez Agnès Feurtet-Mazel Nicolas Mazzella 《Environmental monitoring and assessment》2014,186(6):3931-3939
The Morcille River located in the Beaujolais vineyard area (Eastern France) is subjected to strong vine-growing pressure leading to the contamination by a range of herbicides and fungicides of the surrounding freshwater environment. Particularly high concentrations of norflurazon, desmethyl norflurazon and tebuconazole were recorded in spring 2010 at the downstream site of the river. Despite their occurrence in rivers, scarce toxicity data are available for these products, in particular in the case of desmethyl norflurazon (main norflurazon degradation product). Furthermore, the toxicity data are generally available only for single compounds and are issued from single species toxicity tests, leading to a lack of ecological relevance. Consequently, this study was undertaken to evaluate the toxic effects of norflurazon, desmethyl norflurazon and tebuconazole singly and in a ternary mixture on fluvial biofilm. Toxicity tests were performed in microplates for 48 h. Photosynthetic endpoints were measured using pulse amplitude-modulated fluorometry; diatom densities and taxonomic composition were determined. After 48 h of exposure, significant effects on optimal quantum yield (F v/F m) for desmethyl norflurazon and mixture were observed. 相似文献
486.
Hérivaux Cécile Rey-Valette Hélène Rulleau Bénédicte Agenais Anne-Laurence Grisel Marianne Kuhfuss Laure Maton Laure Vinchon Charlotte 《Regional Environmental Change》2018,18(6):1815-1828
Regional Environmental Change - This article proposes an innovative approach to assess the benefits of adapting to sea level rise (SLR) in a coastal area on a regional scale. The valuation... 相似文献
487.
Rapidly developing countries like India face numerous challenges related to social and environmental sustainability, which are associated with their fast economic growth and rising energy demand, climate change, and widening disparities between the rich and the poor. Recently, a number of claims have been made in the literature that the prospects of alternative development pathways in emerging economies in Asia are becoming more likely, and that these economies might even leapfrog Western initiatives. This paper contributes by reporting on the five most visible and established initiatives in the area of off-grid PV solar energy in India, specifically homing in on the innovative business models that are evolving. We develop a new typology of upscaling dimensions in order to analyze these five initiatives. They are found to be quite successful, but have difficulty in terms of reaching the poorest of the poor (deep upscaling) and bringing about required institutional change (institutional upscaling). 相似文献
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