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661.
Foss RD 《Journal of Safety Research》2007,38(2):185-192
Graduated driver licensing (GDL) is a concept for how to transform non-drivers into reasonably safe drivers while minimizing the risks as they learn. Several state GDL programs can be improved by moving their structures closer to an adequate implementation of that concept. The learner stage of a GDL system needs to be long enough for beginners to obtain a thorough introduction to the vagaries of driving. The second or intermediate stage needs to effectively limit exposure to known high risk conditions as novices adapt to being fully in charge of the vehicle. The benefits of GDL to date are due almost entirely to the risk-reducing conditions it implements. To improve the functioning of GDL will probably require a better understanding of teen driving than we presently have. The likelihood of further gains will be enhanced by efforts to learn more about the actual causes of teen crashes, the nature and type of teen driver exposures, and what parents do with their teens during the supervised driving stage of GDL. Without a better understanding of these, and other, phenomena it will be difficult to further reduce crashes among young beginning drivers, whether through GDL enhancements or with other approaches. 相似文献
662.
663.
M.D. Fraser V.J. TheobaldM.S. Dhanoa O.D. Davies 《Agriculture, ecosystems & environment》2011,144(1):102-106
A comparative experiment was conducted to test the extent to which grazing of rank Molinia caerulea-dominated grassland increases botanical diversity and improves animal performance. The study was carried out on an area of under-grazed Molinia-dominant pasture that had not been stocked for 20 years. Three treatments were compared from 2001 until 2008: (1) no grazing, (2) grazing by Welsh Mountain sheep and (3) grazing by Welsh Black heifers. Patterns of change in sward surface composition across the grazing season were consistent with greater consumption of Molinia by the cattle, but there was little evidence of management regime influencing changes in sward composition year-on-year. There was a significant effect of year on animal performance (P < 0.001). Although the growth rates of the heifers improved over the course of the first three years of the experiment, this performance was not sustained. In contrast, any weight changes for the sheep were positive. The results highlight the slow pace of change within upland swards, and the need to develop site-specific grazing guidelines. 相似文献
664.
M.A. Bustamante D. Said-Pullicino E. Agulló J. Andreu C. Paredes R. Moral 《Agriculture, ecosystems & environment》2011,140(1-2):80-87
The effects on different physico-chemical, chemical and biological soil properties of the incorporation of different organic materials into a calcareous vineyard soil were studied in an experiment during three growing seasons. The organic materials used were sheep manure and four composts derived from the treatment of winery and distillery wastes. A multivariate technique, factor analysis (FA), was also used for interpreting the data obtained from the samplings carried out throughout the three vine growing seasons. The application of the organic materials induced an increase in the activity of the soil microorganisms and in the soil macro and micronutrient contents, as well as a slow release of inorganic N. Through FA of the soil properties studied, three factors that explained 74.7% of the variability were established and the effects of the treatments after the whole experimental period were assessed. 相似文献
665.
666.
667.
崇明岛生态风险源分析及其防范对策研究 总被引:1,自引:0,他引:1
上海市城市总体规划(1999~2020年)中提出了要将崇明岛建成生态岛的发展目标,而保障崇明岛的生态安全,规避生态风险是实现这一目标以及实现经济可持续发展的重要内容。崇明岛地处长江的河口和经济最发达的长江三角洲,而且东邻东海,地理位置十分特殊,区域生态风险来源十分复杂。因此,深入分析崇明岛的生态风险源类型、来源和特征,是进一步开展生态风险评价和正确制定风险防范对策的基础。通过对崇明历史资料的分析和现状的评价,辨识出26种生态风险源,这些风险源按性质分可分为自然风险源和人为风险源两类,按来源分可分为来自流域、来自周边区域、来自海洋和来自岛屿内部4类;通过对风险源的发生概率、强度分析结果,结合各风险源的特点,筛选出咸水入侵、台风、暴雨、风暴潮、生物入侵为崇明岛的主要风险源,并分析了其对生态系统的干扰和危害。在上述分析的基础上,提出了具体的风险防范对策。 相似文献
668.
Application of ICP-QMS for the determination of plutonium in environmental samples for safeguards purposes 总被引:1,自引:0,他引:1
Aiming to determine the plutonium amount as well as its isotopic composition, in particular, in swipe samples for safeguards purposes, an analytical method was developed with a plutonium separation step based on extraction chromatography using 2 cm TEVA columns and detection with quadrupole ICP-MS applying an ultra-sonic nebulizer coupled with membrane desolvation system. The method was successfully applied to New Brunswick plutonium certified reference materials as well as to Lawrence Livermore National Laboratory round robin samples, based on the round robin samples provided by the Institute for Reference Materials and Measurements (Belgium), as part of the Regular European Interlaboratory Measurement Evaluation Programme (REIMEP), campaign 16 (isotopic abundances of plutonium in plutonium nitrate samples), with a total plutonium amount between 1 and 0.25 ng per sample. After the introduction of an additional separation step, it was also possible to carry out precise and accurate total plutonium, (240)Pu/(239)Pu, (241)Pu/(239)Pu and (242)Pu/(239)Pu atom ratios determination in sediment sample showing its applicability to environmental samples in general, reaching a detection limit equivalent to 5 mBq(239)Pu kg(-1). 相似文献
669.
Generic approaches to transfer 总被引:1,自引:0,他引:1
A review of methods which have been used to describe and predict transfer of radionuclides in biota was undertaken. The intent was to identify approaches that might prove useful in extending predictive estimates to other organisms and environments. Empirical approaches, such as found in the use of transfer factors, were examined. Kinetic methodologies were also presented. Allometric functions, with their ability to make broad generalizations, were also discussed. Data from several earlier radioecological assessments were tested for their potential utility in developing allometric relationships, with the result implying that such an approach might prove useful. 相似文献
670.
Alvarez-Muñoz D Lara-Martín PA Blasco J Gómez-Parra A González-Mazo E 《Environment international》2007,33(4):565-570
The presence of linear alkylbenzene sulfonates (LAS) and their degradation intermediates, sulfophenylcarboxylic acids (SPCs), with concentrations up to 100 ppb has been found in surface waters taken from the estuary of the river Guadalete (Cádiz, SW of Spain). Higher concentrations were found at the sampling site located adjacent to the discharge outlet of a wastewater treatment plant (WWTP). The concentrations decreased downstream to a few ppb as a result of dilution, sorption, and degradation processes, which were taking place along the estuary. Once the presence of both xenobiotics was confirmed in the environment, an in vivo assay was conducted to study their biotransformation and effects in the benthic fish Solea senegalensis. A flow-through system was employed, consisting of an exposure phase (120 h) with environmental levels of the surfactant (200, 500 and 800 microg/L of 2?C(10)LAS), followed by a depuration stage (72 h). The generation of SPCs has been quantified during these phases in both water and fish, with LAS biotransformation shown in all cases. The antioxidant enzymes catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), the phase II enzyme glutathione S-transferase (GST), and the phase III acid and alkaline phosphatases (AcP, ALP) were also estimated and utilized as biomarkers. 相似文献