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471.
Explanations for the evolution of multiple mating by social insect (particularly honey bee) queens have been frequently sought. An important hypothesis is that multiple mating is adaptive because it increases intracolonial genetic diversity and thereby reduces the likelihood that parasites or pathogens will catastrophically infect a colony. We tested one assumption of this model: that honey bee worker patrilines should differ in disease resistance. We used American foulbrood (caused by the bacterium Paenibacillus larvae) as a model pathogen. We found that patrilines within colonies do indeed vary in their resistance to this disease. 相似文献
472.
建筑工地事故的经济损失与最有效的安全投资(香港经验) 总被引:1,自引:2,他引:1
本文论述了对因建筑工地发生的事故而导致承包商的经济损失的一个调查情况。作者对18个建筑工地发生的618起事故进行了调查,每一个建筑工地,其安全状况指标是用总的等量损失工作日除以总的所需工作日来评价。通过这18个例证,可以得到建筑工地事故损失与安全状况指标两者之间的关系。类似的,可以获得安全投资与安全状况指标两者的关系、从这两条曲线中。承包商可以决定对建筑工地的最适宜的安全投资。建筑项目的最小安全投资为建筑总投资的0.55%。这时,在最适宜点之处安全投资要比总的事故损失大得多。 相似文献
473.
Benjamin F. McPherson Ronald L. Miller 《Journal of the American Water Resources Association》1990,26(1):67-80
ABSTRACT: The sources and distribution of nutrients in the Charlotte Harbor estuarine system were evaluated using nutrient dilution curve models. Except for ammonia, nutrient concentrations were highest and most variable in the rivers, and generally decreased with increasing salinity. Observed and theoretical dilution curves for phosphorus were generally in close agreement, which suggests conservative behavior. Phosphorus concentrations sagged below a straight line because phosphorus-rich water from the upper Peace River basin was diluted by tributaries in the lower basin. The concentrations of dissolved silica appeared to be conservative on some occasions. On other occasions, dissolved silica appeared to be removed at low salimties or released at higher salinities. Concentrations of ammonia were highly variable along the salinity gradient, presumably because of variations in ammonia regeneration and uptake. Concentrations of nitrite plus nitrate were well below conservative dilution curves, probably due to phy-toplankton uptake. At salinities greater than 20%, nitrite plus nitrate concentrations were usually at or below the detection limit and may limit phytoplankton productivity. Projected increased nitrogen loadings from urban development in the basin would favor undesirable increases in phytoplankton and benthic algal growth in waters where sufficient light is available. 相似文献
474.
Risk assessments are fast becoming an indispensable tool for both government and industry. Unfortunately, organizations required to perform risk assessments often lack the ability to either generate or critically evaluate the quality of risk assessment reports and must rely on contractors to tell them what they need and whether they have received it. The authors advocate a proactive approach to contractual risk assessment management in which a client team directs the production of the report and maintains quality control at each step in the process. 相似文献
475.
476.
Harsha Meenawat Benjamin K. Sovacool 《Mitigation and Adaptation Strategies for Global Change》2011,16(5):515-533
Bhutan, a small least developed country in the Himalayan Mountains, faces five current climate change related vulnerabilities:
landslides and flooding, deteriorating agricultural production, impoverished forests, worsening health security, and impaired
hydroelectricity generation. The country is attempting to adapt to these challenges through two globally sponsored adaptation
efforts. One is the “Reducing Climate Change-induced Risks and Vulnerabilities from Glacial Lake Outburst Floods in the Punakha-Wangdue
and Chamkhar Valleys” project, or GLOF, a 7.7 million project being funded by the Global Environment Facility, United Nations Development Program, and the government of Bhutan. Another is the GLOF Risk Reduction Project in the Himalayas, or GRRP, a7.7 million project being funded by the Global Environment Facility, United Nations
Development Program, and the government of Bhutan. Another is the GLOF Risk Reduction Project in the Himalayas, or GRRP, a
730,000 program funded by the United Nations Development Program (UNDP). These projects offer great potential for improving
infrastructural, institutional, and community resilience within Bhutan, but must also overcome a series of pernicious social,
political, and economic challenges if they are to succeed. 相似文献
477.
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479.
Benjamin Court Thomas R. Elliot Joseph Dammel Thomas A. Buscheck Jeremy Rohmer Michael A. Celia 《Mitigation and Adaptation Strategies for Global Change》2012,17(6):569-599
Stabilization of CO2 atmospheric concentrations requires practical strategies to address the challenges posed by the continued use of coal for baseload-electricity production. Over the next two decades, CO2 capture and sequestration (CCS) demonstration projects would need to increase several orders of magnitude across the globe in both size and scale. This task has several potential barriers which will have to be accounted for. These barriers include those that have been known for a number of years including safety of subsurface sequestration, pore-space competition with emerging activities like shale gas production, legal and regulatory frameworks, and public acceptance and technical communication. In addition water management is a new challenge that should be actively and carefully considered across all CCS operations. A review of the new insights gained on these previously and newly identified challenges, since the IPCC special report on CCS, is presented in this paper. While somewhat daunting in scope, some of these challenges can be addressed more easily by recognizing the potential advantageous synergies that can be exploited when these challenges are dealt with in combination. For example, active management of water resources, including brine in deep subsurface formations, can provide the additional cooling-water required by the CO2 capture retrofitting process while simultaneously reducing sequestration leakage risk and furthering efforts toward public acceptance. This comprehensive assessment indicates that water, sequestration, legal, and public acceptance challenges ought to be researched individually, but must also be examined collectively to exploit the promising synergies identified herein. Exploitation of these synergies provides the best possibilities for successful large-scale implementation of CCS. 相似文献
480.
Benjamin I. Ruttenberg 《Conservation biology》2001,15(6):1691-1699
Abstract: The Galápagos Islands harbor some of the least impacted marine ecosystems in the tropics, but there are indications that local artisanal fishing is affecting exploited marine communities. To quantify these effects, I sampled communities of fishes and sea urchins at a number of heavily fished and lightly fished sites throughout the central islands of the archipelago. Sites were selected based on information collected as part of a local fisheries monitoring study and standardized across a number of abiotic factors. Abundance and biomass of the primary target species were significantly lower in the heavily fished sites than in the lightly fished sites. Community structure also differed between heavily and lightly fished sites. Cluster analyses of the full community of fishes and a subset of nontarget fishes revealed that sites within a treatment were more similar to one another than sites between treatments. Herbivorous fishes tended to be lower in abundance and sea urchins tended to be higher in abundance in heavily fished sites, but these differences were not significant. My results are encouraging in that the direct effects of artisanal fishing are limited to the primary target species, which probably results from a high specificity of fishing gear. The differences in community structure, however, suggest that artisanal fishing also has cascading effects on noncommercial species throughout the community. An improved understanding of important ecological interactions, increased ecological and fishery monitoring, and effective precautionary management are needed to ensure that human effects in these waters remain minimal. 相似文献