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排序方式: 共有385条查询结果,搜索用时 62 毫秒
381.
Uptake of 14C-2,2′,4,5,5′-pentachlorobiphenyl by appropiately adapted juvenile Atlantic salmon (Salmo salar) is more efficient from fresh water than from sea water. Concentrations of 14C-2,2′,4,5,5′-pentachlorobiphenyl in the whole body as well as in a number of organs and tissues were substantially higher in salmon exposed in fresh water. 相似文献
382.
383.
Living in groups is a widespread phenomenon in many animal taxa. The reduction of predation risk is thought to be an important cause for the formation of groups. Consequently, grouping behavior is particularly pronounced during vulnerable life stages, i.e., as juveniles. However, group living does not only provide benefits but also imposes costs on group members, e.g., increased competition for food. Thus, benefits of grouping behavior might not be evident when predation risk is absent. The adaptive significance of living and also developing in a group independent from predation risk has received relatively little attention although this might have important implications on the evolution and maintenance of group living. The first aim of the present study was to examine whether the social environment affects juvenile performance in the cichlid fish Pelvicachromis taeniatus and, secondly, whether kinship affects social behavior. Kin selection theory predicts benefits from grouping with kin. Here, we demonstrate that juveniles reared in a group grow on average faster compared to juveniles reared in isolation under standardized laboratory conditions without predation risk. Furthermore, we found significant differences in social behavior between juveniles reared in a group and reared in isolation. Fish reared in isolation were significantly more aggressive and less willing to shoal than group-reared fish. As expected, genetic relatedness influenced social behavior in group-reared fish as well: dyads of juveniles consisting of kin showed increased group cohesiveness compared to non-kin dyads. We discuss the potential benefits of group living in general and living with kin in particular. 相似文献
384.
Manfred Thönnessen 《Environmental Sciences Europe》2006,18(1):5-12
Goal and Scope
At the present, air borne particulate matter is in the focus of public and scientific interest. In this context, it makes sense to remember the buffer function of vegetation for particulate air pollutants, notwithstanding technical and traffic management measures. Since trees with large and dense crowns might be able to shade windows and minimise the turbulent dilution of pollutants, natural-scientific results and socio-scientific aspects will point to the potentials of vertical greening with creeping plants.Methods
To differentiate the endogenous and exogenous element fractions, the pollution caused by dust that covers the façade climbing creepers leaves was removed by a polyvinyl-butyrale based stripping method. The cleaning success is proven by SEM-Scans. The results of cleaned and not cleaned leaf-samples from an inner-city vertical greening for the element concentrations of Al, Cd, Co, Cr, Cu, Fe, Ni, Pb, Pt, Rh, Sb and Zn between 1991 and 1997 are shown by AAS- and ICP-MS analyses.Results and Conclusion
The results show the increasing element concentrations during the course of the separate vegetation periods. Due to the long investigation period, it is possible to detect historical aspects concerning pollution, such as the end of the use of leaded fuel and the introduction of the catalytic converters. The comparison of dust deposition data from different cities shows the relevance of the pollution filtering by vertical greenings with Japanese Creeper. The comparison of investigation results of sycamore leaves refer to entirely different filtering characteristics of the leaf-surfaces.Recommendation and Perspective
If appropriate planning and maintenance is assured, vertical greening can be a useful contribution for air pollution control and neighbourhood improvement. As selected results from a survey show, from the citizens point of view, the aesthetical and psychosocial aspects of well-being are of more relevant than ecological arguments. Therefore it seems to be wise to implement the combined fields of interest. 相似文献385.
Vigneron V Ponthieu M Barina G Audic JM Duquennoi C Mazéas L Bernet N Bouchez T 《Waste management (New York, N.Y.)》2007,27(6):778-791
Nitrified leachate recirculation has been proposed as a promising strategy for sustainable landfill management. In four test reactors, nitrate or nitrite was added (250 mg N-NO(x)(-)L(-1)) during municipal solid waste biodegradation. Nitrogen-oxides reduction reactions were monitored. Denitrification was the main nitrogen reducing reaction observed. On one hand, during the acidogenic waste degradation phase, as high amounts of volatile fatty acids (VFA) were present, nitrogen-oxides reductions were interpreted as heterotrophic denitrifications. On the other hand, denitrification reactions occurring during the late methanogenic phase were accompanied by sulphate productions and, as VFA were not detected, it was probably an autotrophic reaction. Denitrification inhibition was observed once. Ammonium concentration increased suggesting the occurrence of a dissimilatory nitrate reduction to ammonium (DNRA). Statistical treatment of analytical data revealed that only H(2)S concentration had a significant negative effect on N(2) production in our system. NO production was observed once when nitrite was injected during the acidogenic phase resulting in a total waste degradation inhibition. These results indicate that the consequences of nitrified leachate recirculation in full-scale landfills need to be carefully examined especially during the acidogenic phase or in the presence of waste containing high quantities of sulphur. 相似文献