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排序方式: 共有501条查询结果,搜索用时 15 毫秒
21.
Andréia Dalla Vecchia Mariana Kluge Joseane V. dos Santos da Silva Juliana Comerlato Manoela T. Rodrigues Juliane D. Fleck Roger B. da Luz Thais F. Teixeira Paulo M. Roehe Roberta Capalonga Ana Beatriz Oliveira Fernando R. Spilki 《Food and environmental virology》2013,5(1):41-45
Torque teno virus (TTV) was surveyed in tap water collected in schools from three municipalities located in the south of Brazil. TTV genomes were found in 11.7 % (4/34) of the samples. TTV DNA was detected in 10.5 % (2/19) of the samples collected at the city of Caxias do Sul and in 25 % (2/8) of the samples from Pelotas. Those cities have a low rate of sewage treatment. All samples from Santa Cruz do Sul, which has nearly 92 % of its sewage treated, were negative. These results suggest that the amount of sewage treated may have an effect on the detection rates of TTV DNA in drinking water in a given urban area, showing a mild negative correlation (r = ?0.76), when comparing the percentage of sewage treatment to the detection of TTV genomes. The detection rate of TTV was also compared with Escherichia coli, showing a strong correlation (r = 0.97), indicating that TTV may be a suitable marker of fecal contamination. 相似文献
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23.
Population differences in anti-predator behaviour have been demonstrated in several species, although less is known about the genetic basis of these traits. To determine the extent of genetic differences in boldness (defined as exploration of a novel object) and shoaling within and between zebrafish (Danio rerio) populations, and to examine the genetic basis of shoaling behaviour in general, we carried out a study that involved laboratory-raised fish derived from four wild-caught populations. Controlling for differences in rearing environment, significant inter-population differences were found in boldness but not shoaling. A larger shoaling experiment was also performed using one of the populations as the basis of a North Carolina type II breeding design (174 fish in total) to estimate heritability of shoaling tendency. A narrow-sense heritability estimate of 0.40 was obtained, with no apparent dominance effects. 相似文献
24.
A global assessment of chromium pollution using sperm whales (Physeter macrocephalus) as an indicator species 总被引:1,自引:0,他引:1
John Pierce Wise Sr. Roger Payne Sandra S. Wise Carolyne LaCerte James Wise Christy Gianios Jr. W. Douglas Thompson Christopher Perkins Tongzhang Zheng Cairong Zhu Lucille Benedict Iain Kerr 《Chemosphere》2009,75(11):1461-1467
Chromium (Cr) is a well-known human carcinogen and a potential reproductive toxicant, but its contribution to ocean pollution is poorly understood. The aim of this study was to provide a global baseline for Cr as a marine pollutant using the sperm whale (Physeter macrocephalus) as an indicator species. Biopsies were collected from free-ranging whales around the globe during the voyage of the research vessel The Odyssey. Total Cr levels were measured in 361 sperm whales collected from 16 regions around the globe detectable levels ranged from 0.9 to 122.6 μg Cr g tissue−1 with a global mean of 8.8 ± 0.9 μg g−1. Two whales had undetectable levels. The highest levels were found in sperm whales sampled in the waters near the Islands of Kiribati in the Pacific (mean = 44.3 ± 14.4) and the Seychelles in the Indian Ocean (mean = 19.5 ± 5.4 μg g−1). The lowest mean levels were found in whales near the Canary Islands (mean = 3.7 ± 0.8 μg g−1) and off of the coast of Sri Lanka (mean = 3.3 ± 0.4 μg g−1). The global mean Cr level in whale skin was 28-times higher than mean Cr skin levels in humans without occupational exposure. The whale levels were more similar to levels only observed previously in human lung tissue from workers who died of Cr-induced lung cancer. We conclude that Cr pollution in the marine environment is significant and that further study is urgently needed. 相似文献
25.
Kyle Hamish Elliott Roger D. Bull Anthony J. Gaston Gail K. Davoren 《Behavioral ecology and sociobiology》2009,63(12):1773-1785
How predators vary search patterns in response to prey predictability is poorly known. For example, marine invertebrates may
be predictable but of low energy value, while fish may be of higher energy value but unpredictable at large (pelagic schools)
or small (solitary benthics) spatial scales. We investigated the search patterns of the thick-billed murre (Uria lomvia), an Arctic seabird feeding on invertebrates, pelagic fish, or benthic fish. Foraging ranges at the Coats Island colony are
generally smaller (<240 min per trip) than at larger colonies, and many birds specialize in foraging tactics and diet. Underwater
search times for benthic fish were higher than for pelagic fish or invertebrates while above-water search times for pelagic
fish were higher than for benthic fish or invertebrates. There were few stops during trips. Total trip time, flying time,
number of flights, and number of dives were intercorrelated and increased with prey energy content, suggesting that longer
trips involved fewer prey encounters due to selection of higher-quality, but rarer, prey items. Flight times were not Lévy-distributed
and seabirds may have used area-restricted searches. The high degree of specialization, apparent absence of information center
effects, and reduced above-water searching times may be linked to the relatively small colony size and the resulting short
commuting distances to feeding areas, leading to greater prey predictability. We concluded that prey predictability over various
scales affected predator search patterns. 相似文献
26.
Genevieve Obermeyer Sara M. Aschmann Roger Atkinson Janet Arey 《Atmospheric environment (Oxford, England : 1994)》2009,43(24):3736-3744
To convert gaseous carbonyls to oximes during sampling, an XAD-4 resin denuder system pre-coated with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine and followed by analysis with methane positive chemical ionization gas chromatography/mass spectrometry was used to measure carbonyls in ambient air samples in Riverside, CA. In conjunction with similar analyses of environmental chamber OH radical-initiated reactions of o- and p-xylene, 1,2,4-trimethylbenzene, ethylbenzene, 4-hydroxy-2-butanone and 1,4-butanediol, we identified benzaldehyde, o-, m- and p-tolualdehyde and acetophenone and the dicarbonyls glyoxal, methylglyoxal, biacetyl, ethylglyoxal, 1,4-butenedial, 3-hexene-2,5-dione, 3-oxo-butanal, 1,4-butanedial and malonaldehyde in the ambient air samples. As discussed, these carbonyls and dicarbonyls can be formed from the OH radical-initiated reactions of aromatic hydrocarbons and other volatile organic compounds emitted into the atmosphere, and we conclude that in situ atmospheric formation is a major source of these carbonyls in our Riverside, CA, ambient air samples. 相似文献
27.
Roger B. Long 《Journal of the American Water Resources Association》1987,23(6):1117-1124
ABSTRACT: Pressure is increasing in the western United States to reallocate water from irrigated agriculture to other competitive uses. Since water is normally allocated through water rights and not necessarily by the price system, the question of economic efficiency is a continual concern. Study results show that returns per acre-foot of water used in western irrigation are quite high and are closely tied to the livestock industry. Returns per acre-foot of water used for crops ranged from $60 to $1,500. When water was used to support livestock, returns per acre-foot ranged from $100 to $600. Clearly, losses of water supply that reduced irrigation production could also lower farm income significantly. Estimated returns also show what alternative uses would have to pay for water under competitive market conditions. Production elasticities are also shown for various states. 相似文献
28.
29.
Energy and carbon balances of wood cascade chains 总被引:1,自引:0,他引:1
In this study we analyze the energy and carbon balances of various cascade chains for recovered wood lumber. Post-recovery options include reuse as lumber, reprocessing as particleboard, pulping to form paper products, and burning for energy recovery. We compare energy and carbon balances of chains of cascaded products to the balances of products obtained from virgin wood fiber or from non-wood material. We describe and quantify several mechanisms through which cascading can affect the energy and carbon balances: direct cascade effects due to different properties and logistics of virgin and recovered materials, substitution effects due to the reduced demand for non-wood materials when wood is cascaded, and land use effects due to alternative possible land uses when less timber harvest is needed because of wood cascading. In some analyses we assume the forest is a limiting resource, and in others we include a fixed amount of forest land from which biomass can be harvested for use as material or biofuel. Energy and carbon balances take into account manufacturing processes, recovery and transportation energy, material recovery losses, and forest processes. We find that land use effects have the greatest impact on energy and carbon balances, followed by substitution effects, while direct cascade effects are relatively minor. 相似文献
30.
Ecological Modernisation in Los Angeles and Toronto 总被引:1,自引:0,他引:1
This article presents the results of a comparative study of environmental policy making in Toronto and Los Angeles. The study was intended to explain how social formations at the urban scale play an increasingly important role in constructing environmental policy and practice as articulated in docu ments, rhetoric and political actions. It is suggested that environmental policy is embedded in broader and more long-term political goals, and that ecological discourse is not only about the environment but also brings together various social projects under the environmental protection flag. The four case studies-- in Toronto, contaminated soil and the Don River were examined, and in Los Angeles air pollution and the Los Angeles River--revealed considerable vari ation but all reflected an agenda of ecological modernisation. In particular it was found that demands for maintaining or improving environmental integrity and coherence have lost legitimacy to concerns for efficiency, competitiveness, marketability, flexibility and development. Similarly, market driven regulation and an openness to civil society have played a major role in transforming policy making apparatuses. In contrast, the cases revealed that relationships between nature and society go beyond those expected in ecological modernisation theory and include both social ecology and urban ecology. 相似文献