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A denitrifying bacterium was isolated from activated sludge after enrichment on 4‐chlorophenol under anoxic, denitrifying conditions, and the microbial degradation of 4‐chlorophenol by this bacterium, with nitrate as the only electron acceptor, was investigated. The bacterium was capable of degrading up to 5 mM 4‐chlorophenol with stoichiometric release of chloride under denitrifying conditions. Anaerobic degradation of 4‐chlorophenol was dependent on nitrate as an electron acceptor. Nitrate (10 mM) severely inhibited the growth by the toxic effect of the accumulated nitrite. The optimum nitrate concentration for cell growth and chlorophenol degradation was 6 mM. 相似文献
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Outreach nurseries are favored conservation and social forestry tools globally, but, as with many integrated conservation
and development programs (ICDPs), they do not always produce anticipated results. A synopsis of the experience of South African
practitioners is provided in this study of 65 outreach nurseries. South African outreach nurseries frequently include financial
objectives, creating additional challenges in simultaneously attaining conservation and socioeconomic goals. Progress was
hindered by biophysical problems (e.g., lack of water, poor soils, etc.) as well as the harsh socioeconomic conditions facing
most communities in which nurseries had been established. Attaining financial viability was challenging. Business management
skills were often restricted, and few viability studies included adequate market research. Costs to community participants
were usually high, and benefits were limited. Conservation objectives were frequently lost in the struggle to attain financial
viability. The management of social processes also proved challenging. Although small scale and relatively straightforward
compared with many ICDPs, nurseries usually require substantial institutional support, including a range of technical, business,
and development services. Project time frames need to be reconsidered, as practitioners estimate that it takes 5–10 years
for nurseries to start meeting objectives, and donors and implementing agencies often operate on 2–3-year project cycles.
Detailed viability studies are essential, incorporating a social probe and an assessment of potential impacts of projects
on community participants. Progress needs to be continuously evaluated to enable institutions and community participants to
adapt to changing conditions as well as ensure that the spectrum of objectives are being achieved. 相似文献
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We investigated the behavioral effects of exposure to waterborne phytoestrogens in male fighting fish, Betta splendens. Adult fish were exposed to a range of concentrations of genistein, equol, beta-sitosterol, and the positive control 17beta-estradiol. The following behaviors were measured: spontaneous swimming activity, latency to respond to a perceived intruder (mirror reflection), intensity of aggressive response toward a perceived intruder, probability of constructing a nest in the presence of a female, and the size of the nest constructed. We found few changes in spontaneous swimming activity, the latency to respond to the mirror, and nest size, and modest changes in the probability of constructing a nest. There were significant decreases, however, in the intensity of aggressive behavior toward the mirror following exposure to several concentrations, including environmentally relevant ones, of 17beta-estradiol, genistein, and equol. This suggests that phytoestrogen contamination has the potential to significantly affect the behavior of free-living fishes. 相似文献
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用大型底栖动物和ODP系统评价珠江的有机污染 总被引:1,自引:2,他引:1
采用大型底栖动物需氧有机体百分率ODP(oxygen demander percentage)法对广州珠江前航道、西航道和流溪河的下游段进行河流有机污染评价.结果显示:底栖动物需氧类群密度在三河段间分布确有显著性差异,并根据其ODP可以判断流溪河水质相对较好,水质级别为中国地表水环境质量标准(EQSSW)Ⅳ级,西航道和前航道水质级别都为Ⅴ级.通过测试,这一方法能成功地应用在珠江及流溪河,且该法可以较好地匹配于EQSSW五级评价系统,初步认为ODP系统可以成为一个较好的河流水质生物监测方法.图3表4参13 相似文献
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Ethan D. Clotfelter 《Behavioral ecology and sociobiology》1997,41(3):193-201
Parental investment by red-winged blackbirds (Agelaius phoeniceus) in response to natural and experi‐mental parasitism by brown-headed cowbirds (Molothrus ater), and in response to freeze-dried, female cowbird mounts presented near redwing nests during the egg-laying period was measured.
Two measures of redwing parental investment were used: nest defense effort toward a model predator, and rate of feeding nestlings.
There were no significant differences in levels of parental investment among unparasitized nests, naturally parasitized nests,
or experimentally parasitized nests. Similarly, parental investment did not differ between redwings that were exposed to the
cowbird mount and those that were not exposed to the mount, or among redwings exposed to the cowbird mount at different distances
from the nest. This suggests that red-winged blackbirds do not recognize when they have been parasitized, and hence do not
associate parasitism with a decrease in their parentage, or that parentage is not an important predictor of parental investment
in this species.
Received: 24 January 1997 / Accepted after revision: 7 June 1997 相似文献
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