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排序方式: 共有26条查询结果,搜索用时 31 毫秒
1.
Heme oxygenase 1 is required for mammalian iron reutilization   总被引:1,自引:0,他引:1  
Stressed mammalian cells up-regulate heme oxygenase 1 (Hmox1; EC 1.14.99.3), which catabolizes heme to biliverdin, carbon monoxide, and free iron. To assess the potential role of Hmox1 in cellular antioxidant defense, we analyzed the responses of cells from mice lacking functional Hmox1 to oxidative challenges. Cultured Hmox1(-/-) embryonic fibroblasts demonstrated high oxygen free radical production when exposed to hemin, hydrogen peroxide, paraquat, or cadmium chloride, and they were hypersensitive to cytotoxicity caused by hemin and hydrogen peroxide. Furthermore, young adult Hmox1(-/-) mice were vulnerable to mortality and hepatic necrosis when challenged with endotoxin. Our in vitro and in vivo results provide genetic evidence that up-regulation of Hmox1 serves as an adaptive mechanism to protect cells from oxidative damage during stress.  相似文献   
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This paper addresses the robust vehicle routing problem with time windows. We are motivated by a problem that arises in maritime transportation where delays are frequent and should be taken into account. Our model only allows routes that are feasible for all values of the travel times in a predetermined uncertainty polytope, which yields a robust optimization problem. We propose two new formulations for the robust problem, each based on a different robust approach. The first formulation extends the well-known resource inequalities formulation by employing adjustable robust optimization. We propose two techniques, which, using the structure of the problem, allow to reduce significantly the number of extreme points of the uncertainty polytope. The second formulation generalizes a path inequalities formulation to the uncertain context. The uncertainty appears implicitly in this formulation, so that we develop a new cutting plane technique for robust combinatorial optimization problems with complicated constraints. In particular, efficient separation procedures are discussed. We compare the two formulations on a test bed composed of maritime transportation instances. These results show that the solution times are similar for both formulations while being significantly faster than the solutions times of a layered formulation recently proposed for the problem.  相似文献   
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A soil column experiment was made to study the effects of slaked lime (Ca(OH)2) and gypsum (CaSO4·2H2O) on soil acidity, soil solution chemistry and nutrient leaching in an acid soil from Southern China. Results showed that application of sufficient slaked lime to initially increase the pH of the topsoil by 1 unit caused an increase in pH to 5 cm deeper than the layer of application as a result of bicarbonate leaching. With leaching of Ca from slaked lime or gypsum from the topsoil to the subsoil there was a decrease in exchangeable Al in the subsoil. Surface application of slaked lime or gypsum or both decreased the activity of toxic Al and increased AlSO4 + activity in the subsoil solution. The Ca added in slaked lime or gypsum was accounted for by the increase in exchangeable Ca over the soil profile and the leaching loss. By contrast there was a negative balance of extractable sulfate and aluminum in the soil, indicating the formation of precipitates. There was little mineralisation of N and formation of NO3 - under the conditions of the experiment. The leaching of cations in this soil treated with slaked lime or gypsum was driven by the dynamics of sulfate.  相似文献   
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Six Salmonella enteritidis bacterin formulations differing in adjuvant content and whole-cell inactivation procedures were evaluated in egg-laying chickens. Chickens given S enteritidis bacterins containing modified Freund's incomplete adjuvant had greater humoral immune responses to S enteritidis than did birds given other bacterin formulations (P < 0.05). Better protection against infection by S enteritidis phage types 8, 13a, and 23 was obtained in birds vaccinated with bacterin 5. Bacterin 5 contained S enteritidis cells inactivated by 20% acetone and modified Freund's incomplete adjuvant.  相似文献   
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Design-build has been receiving much attention from both the profession and academia in recent years. However, there seems to be many differences in the way that the term is interpreted and applied. This paper reflects upon the results of a conference entitled "Designing/Building/Learning" that sought to explore the issues surrounding this topic through paper sessions, workshops, keynote addresses, and panel discussions. Hands-on approaches to pedagogy in the form of full-scale construction exercises have emerged in schools across the country, but these activities continue to resist theorizing. The Designing/Building/Learning Conference demonstrates this resistance, as well as the compelling role of design-build in education.  相似文献   
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Because of immigration to the United States, the number of persons who speak languages other than English has grown over the past several decades. In addition, many groups whose primary language is not English are exhibiting rapid population growth rates. As a result, health care providers may find they require an interpreter to communicate with patients. Guidelines are presented to facilitate the effective choice and utilization of interpreters in primary care. Suggestions are also presented to help interpreters work effectively in the health care setting.  相似文献   
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The two senior authors (PMP, RP) independently began using an identical enhanced posterior soft tissue repair after total hip replacement through a posterior approach. In the first author's experience, a dislocation rate of 4% in 395 patients before using the enhanced closure was reduced to 0% in 395 patients in whom the enhanced closure was performed. In the second author's experience, 160 total hip replacements had a dislocation rate of 6.2% before the enhanced closure whereas 124 total hip replacements had a dislocation rate of 0.8% after the enhanced closure. These results are highly statistically significant.  相似文献   
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