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41.
42.
In 1978 the USA used non-fuel processed mineral materials valued at over $200 billion (109). Non-fuel mineral imports caused a trade imbalance of $8 billion. Imports supplied more than half of US supplies of 20 important minerals. The US stockpile of strategic materials is valued at over $11 billion. While world reserves of most minerals are now deemed adequate until 2000, demand for high temperature and special property materials requires careful monitoring and anticipation of disruptions in vulnerable sources.  相似文献   
43.
Explicating the concept of cognitive progress means at the same time articulating an ideal of science. A desirable ideal: explain a lot and offer certainty. Working out the ideal with the “foundationalist-positivist” approach. If the question, “When is it rational to accept a theory?” is answered, “When it has sufficient inductive support,” this leads to insoluble problems. The Popperian alternative: rational theory preference despite fallibility of methods for determining truth or greater accuracy of representations. The sorts of risks for a theory differ in explanation and in prediction. Corresponding to the risks are the chances for cognitive progress. Instead of a cumulative index, itemized indication of success and failure in explanation and prediction with regard for importance of the questions at issue.  相似文献   
44.
Black carbon (BC; soot and charcoal) can be an extremely strong sorbent for organic compounds. In a previous study, sorption of d(10)-phenanthrene (d(10)-PHE) to BC in an unmodified contaminated sediment was found to be nine times less than that for BC isolated from this sediment. To find out the mechanism of this sorption attenuation (competition for BC sites between d(10)-PHE and native PAHs or blocking of BC sites by natural organic matter), we determined the effect on d(10)-PHE-BC sorption isotherms of additions of either PAHs or precipitated humic acid. Addition of humic acid did not significantly decrease BC sorption, whereas PAH additions (equal to the native PAH content in the original sediment) did, by about one order of magnitude. Therefore, competition between d(10)-PHE and the native PAHs could explain the whole attenuation of sorption to BC in unmodified sediments.  相似文献   
45.
This paper tests the hypothesis that relocation of pig production within the EU27 can reduce the external costs of nitrogen (N) pollution. The external cost of pollution by ammonia and nitrate from agriculture in the European Union (EU27) in 2008 was estimated at 61–215 billion € (0.5 to 1.8% of the GDP). Per capita it ranged from more than 1000 € in north-west EU27 to 50 € in Romania. The average contribution of pig production was 15%. Using provincial data (224 NUTS2 regions in EU27), the potential reduction of external N cost by relocation of pig production was estimated at 14 billion € (10% of the total). Regions most eligible for decreasing the pig stock were in western Germany, Flemish region, Denmark, the Netherlands and Bretagne, while Romania is most eligible for increasing pig production. Relocating 20 million pigs (13% of the total EU stock) decreased average external costs per capita from 900 to 785 € in the 13 NUTS2 regions where pigs were removed and increased from 69 to 107 € in 11 regions receiving pigs. A second alternative configuration of pig production was targeted at reducing exceedance of critical N deposition and closing regional nutrient cycles. This configuration relocates pigs within Germany and France, for example from Bretagne to Northern France and from Weser-Ems to Oberbayern. However, total external cost increases due to an increase of health impacts, unless when combined with implementation of best N management practices. Relocation of the pig industry in the EU27 will meet many socio-economic barriers and realisation requires new policy incentives.  相似文献   
46.
Ambio - Muskoxen (Ovibos moschatus) are an integral component of Arctic biodiversity. Given low genetic diversity, their ability to respond to future and rapid Arctic change is unknown, although...  相似文献   
47.
We examined how ecological and evolutionary (eco‐evo) processes in population dynamics could be better integrated into population viability analysis (PVA). Complementary advances in computation and population genomics can be combined into an eco‐evo PVA to offer powerful new approaches to understand the influence of evolutionary processes on population persistence. We developed the mechanistic basis of an eco‐evo PVA using individual‐based models with individual‐level genotype tracking and dynamic genotype–phenotype mapping to model emergent population‐level effects, such as local adaptation and genetic rescue. We then outline how genomics can allow or improve parameter estimation for PVA models by providing genotypic information at large numbers of loci for neutral and functional genome regions. As climate change and other threatening processes increase in rate and scale, eco‐evo PVAs will become essential research tools to evaluate the effects of adaptive potential, evolutionary rescue, and locally adapted traits on persistence.  相似文献   
48.
Diffuse phosphorus (P) export from agricultural land to surface waters is a significant environmental problem. It is critical to determine the natural background P losses from diffuse sources, but their identification and quantification is difficult. In this study, three headwater catchments with differing land use (arable, pasture and forest) were monitored for 3 years to quantify exports of dissolved (<0.45 µm) reactive P and total dissolved P. Mean total P exports from the arable catchment ranged between 0.08 and 0.28 kg ha?1 year?1. Compared with the reference condition (forest), arable land and pasture exported up to 11-fold more dissolved P. The contribution of dissolved (<0.45 µm) unreactive P was low to negligible in every catchment. Agricultural practices can exert large pressures on surface waters that are controlled by hydrological factors. Adapting policy to cope with these factors is needed for lowering these pressures in the future.  相似文献   
49.
Over the past few years, a great deal of interest has been focused on the use of remote sensing for resource management. This paper examines one of the most useful systems — Landsat. Included in this paper is a discussion of this remote-sensing technology, its application and its future as a tool for resources planning and management.  相似文献   
50.
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