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排序方式: 共有85条查询结果,搜索用时 15 毫秒
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Joe Leigh Simpson James L. Mills George G. Rhoads George C. Cunningham Howard J. Hoffman Mary R. Conley 《黑龙江环境通报》1991,11(8):641-648
No clear answer concerning whether multivitamin/folate supplementation prevents neural tube defects (NTDs) is provided by three studies in the United States. All these studies are occurrence in nature, no recurrence studies having been conducted. The Atlanta Birth Defects Study is subject to pronounced memory and recall biases, the length between event and interview being as long as 16 years. In a second study (Boston University), objections can be raised to certain aspects of the experimental design, and the claim that 22 per cent of women started vitamins sufficiently early after pregnancy diagnosis to influence NTD formation is suspicious. Our NICHD case control study of 541 women in California and Illinois revealed no evidence for multivitamins or folic acid preventing NTDs. U.S. public policy-makers face difficulties in applying results of recurrence or occurrence studies in high-risk areas to low-risk areas in the U.S. 相似文献
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BRENT J. SEWALL AMY L. FREESTONE MOHAMED F. E. MOUTUI NASSURI TOILIBOU ISHAKA SAÏD SAINDOU M. TOUMANI DAOUD ATTOUMANE CHEIKH M. IBOURA 《Conservation biology》2011,25(4):688-696
Abstract: Systematic conservation assessment (an information‐gathering and prioritization process used to select the spatial foci of conservation initiatives) is often considered vital to conservation‐planning efforts, yet published assessments have rarely resulted in conservation action. Conservation assessments may lead more directly to effective conservation action if they are reoriented to inform conservation decisions. Toward this goal, we evaluated the relative priority for conservation of 7 sites proposed for the first forest reserves in the Union of the Comoros, an area with high levels of endemism and rapidly changing land uses in the western Indian Ocean. Through the analysis of 30 indicator variables measured at forest sites and nearby villages, we assessed 3 prioritization criteria at each site: conservation value, threat to loss of biological diversity from human activity, and feasibility of reserve establishment. Our results indicated 2 sites, Yiméré and Hassera‐Ndrengé, were priorities for conservation action. Our approach also informed the development of an implementation strategy and enabled an evaluation of previously unexplored relations among prioritization criteria. Our experience suggests that steps taken to ensure the closer involvement of practitioners, include a broader range of social data, encourage stakeholder participation, and consider the feasibility of conservation action can improve the relevance of assessments for conservation planning, strengthen the scientific basis for conservation decisions, and result in a more realistic evaluation of conservation alternatives. 相似文献
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This paper examines the importance of the correlation between hydraulic conductivity (K) and degradation rate constant (k) during the transport of reactive contaminants in heterogeneous aquifers. We simulated reactive transport in an ensemble of two-dimensional heterogeneous aquifers. Two sets of transport simulations were conducted: one in which a perfect positive correlation was assumed between ln(K) and ln(k), and one in which a perfect negative correlation was assumed. We found that the sign of the correlation has important consequences for the contaminant transport. Qualitatively, a negative correlation leads to significantly more pronounced "fingering" of the contaminant plume than does a positive correlation, with potentially important consequences for downgradient receptors. Quantitatively, the expected behavior (as quantified by the contaminant mass remaining in the aquifer) is statistically different between the positive and negative cases: on average, more contaminant mass persists when K and k are negatively correlated. Also, the negative correlation leads to more variability between realizations of the ensemble, whereas a positive correlation induces relatively little variability between realizations. We discuss the implications of these findings for the management of contaminated aquifers. 相似文献
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Conservation in a Region of Political Instability: Bwindi Impenetrable Forest, Uganda 总被引:1,自引:0,他引:1
A. Hamilton A. Cunningham † D. Byarugaba ‡ and F. Kayanja‡ 《Conservation biology》2000,14(6):1722-1725
Abstract: Bwindi Impenetrable is the most important forest in Uganda for conservation of biodiversity. It contains over half the world's mountain gorillas. It is surrounded by densely populated agricultural land and lies within a region of political instability. Gazetted as a forest reserve in 1932, little forest now remains outside its boundaries. Transformation of nearby communal swampland to farmland, much owned by a few individuals, shows the probable fate of Bwindi if it had not been declared a protected area. Widespread illegal logging and other activities were among reasons why the status of the forest was raised to national park in 1991. This resulted in local resentment, fed by inadequate consultation and concern about the local people's loss of access to resources. Fires were set in the forest and threats made against the gorillas. Three schemes to provide benefits from the existence of the forest to communities and involve them in park management were then instituted: agreements allowing controlled harvesting of resources in the park, receipt of some revenue from tourism, and establishment of a trust fund partly for community development. Tension between people and park has been reduced. This case demonstrates the importance of protected areas and community involvement in such circumstances. Community support is especially critical, as here, when resources available to park managers are limited and political instability endemic. 相似文献
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Silvestre García de Jalón Ana Iglesias Ruth Cunningham Juan I. Pérez Díaz 《Regional Environmental Change》2014,14(3):1229-1242
Agricultural water management needs to evolve in view of increased water scarcity, especially when farming and natural protected areas are closely linked. In the study site of Doñana (southern Spain), water is shared by rice producers and a world heritage biodiversity ecosystem. Our aim is to contribute to defining adaptation strategies that may build resilience to increasing water scarcity and minimize water conflicts among agricultural and natural systems. The analytical framework links a participatory process with quantitative methods to prioritize the adaptation options. Bottom-up proposed adaptation measures are evaluated by a multi-criteria analysis (MCA) that includes both socioeconomic criteria and criteria of the ecosystem services affected by the adaptation options. Criteria weights are estimated by three different methods—analytic hierarchy process, Likert scale and equal weights—that are then compared. Finally, scores from an MCA are input into an optimization model used to determine the optimal land-use distribution in order to maximize utility and land-use diversification according to different scenarios of funds and water availability. While our results show a spectrum of perceptions of priorities among stakeholders, there is one overriding theme that is to define a way to restore part of the rice fields to natural wetlands. These results hold true under the current climate scenario and even more so under an increased water scarcity scenario. 相似文献
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B. R. Hubble Stanley Siegel L. H. Fuchs H. R. Hoekstra B. Tani P. T. Cunningham 《Journal of the Air & Waste Management Association (1995)》2013,63(4):343-346
Abstract Inspection and maintenance programs for motor vehicles in the United States increasingly use loaded mode mass emissions testing (IM240). A method was developed to predict mass emission rates and mass emission changes, particularly from repair benefits, using a low-cost, portable four-gas non-dispersive infrared (NDIR) vehicle exhaust gas analyzer. A single vehicle was tested several times with the analyzer while on the dynamometer and undergoing successive repairs. Excellent correlations for CO and HC were observed. Five vehicles were measured using an on-road driving loop before and after emissions-related repairs, while another three vehicles were tested with no repairs performed. The on-road concentration data used to guide the repair process were converted to grams per gallon; when divided by estimated miles per gallon, this gave grams per mile emissions for comparison to IM240. Correlation coefficients (r2) of 0.87 for CO and 0.76 for HC were achieved for the 13 tests. The linear correlations between IM240 and emissions measured by this method would allow repair facilities to perform a relatively inexpensive test for diagnostic purposes and to estimate repair effectiveness without the need for a dynamometer. 相似文献