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Extensive measurements of low-energy positive ions and electrons were made throughout the Jupiter encounter of Voyager 1. The bow shock and magneto-pause were crossed several times at distances consistent with variations in the upstream solar wind pressure measured on Voyager 2. During the inbound pass, the number density increased by six orders of magnitude between the innermost magnetopause crossing at approximately 47 Jupiter radii and near closest approach at approximately 5 Jupiter radii; the plasma flow during this period was predominately in the direction of corotation. Marked increases in number density were observed twice per planetary rotation, near the magnetic equator. Jupiterward of the Io plasma torus, a cold, corotating plasma was observed and the energylcharge spectra show well-resolved, heavy-ion peaks at mass-to-charge ratios A/Z* = 8, 16, 32, and 64.  相似文献   
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Although island attributes such as size and accessibility to colonizing organisms can influence community structure, the consequences of these for ecosystem functioning are little understood. A study of the suspended soils of spatially discrete epiphytes or treetop "islands" in the canopies of New Zealand rainforest trees revealed that different components of the decomposer community responded either positively or negatively to island size, as well as to the tree species that the islands occurred in. This in turn led to important differences between islands in the rates of ecosystem processes driven by the decomposer biota. This system serves as a model for better understanding how attributes of both real and habitat islands may affect key ecosystem functions through determining the community structure of organisms that drive these functions.  相似文献   
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Nematode populations of seven soils with grazed pasture were sampled monthly for 12–36 months and two of the soils received irrigation; a total of 46 nematode genera were identified from the 13 site-years. Diversity, evenness, richness and similarity of the faunae were assessed. Diversity was not related to pasture productivity and evenness was negatively correlated with the abundance (16–44%) of the dominant genus. Genera present were 21–35, but varied from 21 to 27 in one soil during 3 yr. In this group of soils under pasture Czekanowski's similarity coefficient showed replicated sampling within a soil generally yielded nematode faunae more similar to each other than to faunae in other soils, while analysis of variance showed genera to be more influenced by site than month.  相似文献   
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Testacea were observed ingesting nematodes in the litter horizons of native forests in New Zealand. Nematodes were most commonly attacked from the tail end but some specimens were attacked at mid-body. Nematodes with damaged tails were recovered in greatest numbers from the highest, wettest site sampled. Nebela (Apodera) vas (Certes, 1989) and Difflugia sp. (possibly lanceolata Penard, 1890) were the predators; both species were redescribed using light and scanning electron microscopy and morphometry. Most damaged nematodes were Ironus sp. but Clarkus, Tobrilus, Iotonchus, Cobbonchus, Dorylaimus and Plectus were also attacked. Literature on testacean feeding strategies was reviewed briefly.  相似文献   
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The effects of elevated CO2 on rhizosphere processes, including the response of soil faunal populations and community structure, have so far received little attention. We report on significant responses in the soil fauna of ryegrass/white clover swards to both increasing CO2 from 350 to 750 μl · l–1 and, to a period of 60 days when some of the turves were subject to drought, in a controlled climate growth room experiment. The nematodes which increased were predominantly Enoplia, including dorylaimids, alaimids and trichodorids. This accords with both the doubling of Alaimus under elevated CO2 conditions reported in a similar experiment and with the common association of Enoplia with less disturbed habitats. The most marked decrease was in the bacterial-feeding Rhabditis (Secernentea). The increase in omnivorous and predacious nematodes may have been responsible for the decrease in populations of bacterial-feeding nematodes. However, in contrast to their standing crops, the turnover rate of bacterial-feeding nematodes and soil microbial biomass probably increased as a result of increased grazing by these omnivorous and predacious nematodes. Increases in earthworm and enchytraeid populations were related to increased below-ground productivity reported for the same trial. Received: 30 September 1996  相似文献   
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This article looks at the existing evidence-base by which veterinary surgeons can make welfare-focused treatment choices. Narrative and structured reviews were conducted. Papers were categorised under headings based on (1) themes in the UK Animal Welfare Act (AWA 2006) - behaviour, environment, nutrition, company and health; (2) iatrogenic harm induced by treatment; (3) decision-making methods, and (4) the subjects' context (e.g. home versus laboratory). There is more information available about 'overt' problems (e.g. acute disease), than 'covert' issues (e.g. chronic pain, lack of company and obesity). Forty of 109 papers covered pain, suffering, injury and disease, compared to 69 across four other themes in the AWA. Twelve papers were identified as focusing on welfare assessment and clinical decision-making. Veterinary surgeons should consider each of the five welfare themes described in the AWA in both veterinary practice and in determining veterinary research priorities.  相似文献   
10.
There remains a lack of a clear overarching policy framework for decision‐making in pest control programmes. In comparison, ethical principles have been extensively developed for scientific procedures, such as those underlying the UK's Animals (Scientific Procedures) Act 1986. This paper assesses the extent to which the principles and methodology underlying the act and secondary guidance could be used to provide principles of rodent management. Useful principles include that any programme has a legitimate purpose; that methods are used only if the harms are outweighed by the benefits; that harms are minimised by refinement, replacement and reduction and that there is personal responsibility. The usefulness and implications for pest control of each principle and the overall approach are discussed. Copyright © 2009 Society of Chemical Industry  相似文献   
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