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排序方式: 共有598条查询结果,搜索用时 15 毫秒
51.
Jaser W Severin GF Jütting U Jüttner I Schramm KW Kettrup A 《Environment international》2003,28(7):633-638
Single-species tests allow the assessment of chronical effects of endocrine disruptors on organisms under laboratory conditions. In the current study, three-generation tests with Ceriodaphnia reticulata and Sida crystallina were carried out to examine the influence of the synthetic hormone 17alpha-ethinylestradiol (EE) on the reproduction of these cladoceran species. For each species, six different concentrations (10-500 microg/l EE) and two controls were tested with eight replicates for a duration of 4 weeks. The test was initiated by transferring one neonate individual into a test vessel which was incubated under standardized conditions. Every 2 days, the medium was renewed and life history parameters such as survivorship of the adults and juveniles, clutch size, first appearance and number of produced offspring were investigated. Acute toxicity tests showed that C. reticulata (EC50 (24 h) 1814 microg/l) was more sensitive towards the substance compared to S. crystallina (EC50 (24 h) >4100 microg/l). The juvenile phase of S. crystallina was significantly shorter at concentrations above 100 microg/l EE. For C. reticulata, 17alpha-ethinylestradiol caused a higher mortality of the newly hatched juveniles at EE concentrations above 200 microg/l. No effects were found for mortality of adult animals, birth rate, number of juveniles per female and net reproduction rate of S. crystallina and C. reticulata. Thus, sublethal effects on parental generation exposed to EE lead to disturbances in reproduction and to affection of their offspring. Negative consequences for the population dynamic cannot be excluded, e.g. the decrease of a population. 相似文献
52.
Review of ozone and temperature lidar validations performed within the framework of the Network for the Detection of Stratospheric Change 总被引:1,自引:0,他引:1
Keckhut P McDermid S Swart D McGee T Godin-Beekmann S Adriani A Barnes J Baray JL Bencherif H Claude H di Sarra AG Fiocco G Hansen G Hauchecorne A Leblanc T Lee CH Pal S Megie G Nakane H Neuber R Steinbrecht W Thayer J 《Journal of environmental monitoring : JEM》2004,6(9):721-733
The use of assimilation tools for satellite validation requires true estimates of the accuracy of the reference data. Since its inception, the Network for Detection of Stratospheric Change (NDSC) has provided systematic lidar measurements of ozone and temperature at several places around the world that are well adapted for satellite validations. Regular exercises have been organised to ensure the data quality at each individual site. These exercises can be separated into three categories: large scale intercomparisons using multiple instruments, including a mobile lidar; using satellite observations as a geographic transfer standards to compare measurements at different sites; and comparative investigations of the analysis software. NDSC is a research network, so each system has its own history, design, and analysis, and has participated differently in validation campaigns. There are still some technological differences that may explain different accuracies. However, the comparison campaigns performed over the last decade have always proved to be very helpful in improving the measurements. To date, more efforts have been devoted to characterising ozone measurements than to temperature observations. The synthesis of the published works shows that the network can potentially be considered as homogeneous within +/-2% between 20-35 km for ozone and +/-1 K between 35-60 km for temperature. Outside this altitude range, larger biases are reported and more efforts are required. In the lower stratosphere, Raman channels seem to improve comparisons but such capabilities were not systematically compared. At the top of the profiles, more investigations on analysis methodologies are still probably needed. SAGE II and GOMOS appear to be excellent tools for future ozone lidar validations but need to be better coordinated and take more advantage of assimilation tools. Also, temperature validations face major difficulties caused by atmospheric tides and therefore require intercomparisons with the mobile systems, at all sites. 相似文献
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Wolfgang Nentwig 《Behavioral ecology and sociobiology》1985,17(1):79-85
Summary During a 1-year-study in tropical Panama, prey of the social theridiid Anelosimus eximius was analysed at two locations and compared with the potential prey spectrum according to sweepnet catches, pitfall traps and bowl traps. Compared with other web-building spiders, A. eximius catch an unusually high number of large insects: about 90% are flying ants, beetles,lepidopterans hemipterans, cockroaches and grasshoppers. This is the result of a communal strategy to overwhelm prey. Webs are maintained commonly, and several spiders attack an entangled insect simultaneously. More spiders participate on insects that are larger and struggle more. The ability to catch large prey insects is discussed as a major driving factor for sociality in spiders. 相似文献
55.
Advanced terrestrial ecosystem analysis and modelling 总被引:1,自引:0,他引:1
Wolfgang Cramer 《Regional Environmental Change》2008,8(3):89-90
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