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61.
In addition to the usual fixed costs, we introduce variable costs in a community's effort to cooperate in extracting from a common pool resource. Using a standard supervision mechanism, these variable costs are shown to be an increasing function of individual members' incentives to default. The model explains why we frequently observe communities that all cooperate and have relatively similar resource endowments, and yet achieve very different levels of extraction.  相似文献   
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Environmental Science and Pollution Research - Pharmaceuticals, such as dipyrone (DIP), paracetamol (PCT), and propranolol (PPN), are widely used analgesics and beta-blockers with the greatest...  相似文献   
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The goal of this study is to evaluate the impact of the inoculum to substrate ratio (I/S) on the anaerobic degradation potential of municipal solid waste (MSW). Reconstituted MSW samples were thus incubated under batch anaerobic conditions and inoculated with an increasing amount of inoculum originating from a mesophilic sludge digester. I/S tested values were 0 (no inoculum added), 0.015, 0.03, 0.06, 0.12, 0.25, 1, 2 and 4 (gVMinoculum/gVMwaste). The results indicate that the apparent maximal rate of dissolved organic carbon accumulation is reached at I/S = 0.12. Under this level, the hydrolysis process is limited by the concentration of biomass and can thus be described as first order kinetics phenomena with respect to biomass for I/S ratios below 0.12. The maximum methane production rate and the minimal latency are reached at a ratio of 2. In addition to that, both methane signature and ARISA show a shift in the methanogenic populations from hydrogenotrophic to acetoclastic.  相似文献   
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This study investigated antioxidant status of animals given aqueous extract of Morinda morindoides leaves using the levels of reduced glutathione, total-thiol, vitamin C, and vitamin E as well as malondialdehyde concentrations as indices, and its in vitro antioxidant capacity. Thirty rats divided into five groups were used. Group A served as control and were administered distilled water while groups B, C, D, and E were given 100, 200, 400, and 800 mg per kilogram body weight of water-extracted constituents of M. morindoides for 28 days. Total phenolic compounds amounted to 83.6 ± 5.9 mg g?1 gallic acid equivalent, while total flavonoid content was 9.5 ± 0.9 mg g?1 pyrocathecol equivalent. Malondialdehyde in plasma was significantly decreased in a dose-dependent manner, ranging from 21% in groups B and C to 84% in groups D and E. Vitamins C and E were significantly increased, in group E by 91% and 17% compared with control. Total thiols and glutathione in plasma were significantly increased, with group E having 2.5-fold and 4.2-fold higher values than control.  相似文献   
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Each year thousands of people are treated in emergency departments and trauma centers for alcohol-related injuries, including those sustained in drinking driving crashes. Emergency departments and trauma centers provide an opportunity to screen for alcohol use problems and intervene with injured or high-risk drivers to reduce future alcohol-related traffic and injury risk. Recently physicians have expressed interest in exploring screening and intervention for alcohol use problems in these venues as a means of improving clinical care. This article reviews the literature that has examined screening and brief interventions in acute care settings to reduce future alcohol consumption and alcohol-related injury. The methodological and practical issues inherent in conducting these studies as well as in actual practice are discussed. The chaotic environment of acute care, the large numbers of patients required to be screened to obtain an adequate study sample, and high attrition rates make study in these settings difficult at best and are methodological problems that should be addressed in future research. A basic question that has not been adequately answered by research to date is whether reduction in alcohol consumption will translate to reduced alcohol-related harm, such as driving while impaired, or injurious or fatal crashes. Long-term studies that assess records-based outcomes in addition to alcohol-consumption levels are needed.  相似文献   
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