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热处理作用下碳钢氢腐蚀裂纹愈合规律 总被引:2,自引:0,他引:2
对含氢腐蚀裂纹的碳钢进行再热处理后,SEM观察表明,氢蚀裂发生了不同程度的愈合,实验结果表明:长度约为10μm的碳钢氢蚀裂纹完全愈合的热处理条件下是从室温到1000℃热循环5次,共10h,氢蚀裂纹的愈合机制是热扩散,发生氢蚀裂纹愈合的动力是氢蚀气泡或裂纹长大导致的塑性变 能E8。在铁、碳和氢原子扩散都足够快的情况下,氢蚀裂纹愈合的条件是E8大于裂纹愈合所必须克服的表面张力能。 相似文献
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Dyhrman ST Chappell PD Haley ST Moffett JW Orchard ED Waterbury JB Webb EA 《Nature》2006,439(7072):68-71
The factors that control the growth and nitrogen fixation rates of marine diazotrophs such as Trichodesmium have been intensively studied because of the role that these processes have in the global cycling of carbon and nitrogen, and in the sequestration of carbon to the deep sea. Because the phosphate concentrations of many ocean gyres are low, the bioavailability of the larger, chemically heterogeneous pool of dissolved organic phosphorus could markedly influence Trichodesmium physiology. Here we describe the induction, by phosphorus stress, of genes from the Trichodesmium erythraeum IMS101 genome that are predicted to encode proteins associated with the high-affinity transport and hydrolysis of phosphonate compounds by a carbon-phosphorus lyase pathway. We show the importance of these genes through expression analyses with T. erythraeum from the Sargasso Sea. Phosphonates are known to be present in oligotrophic marine systems, but have not previously been considered to be bioavailable to marine diazotrophs. The apparent absence of genes encoding a carbon-phosphorus lyase pathway in the other marine cyanobacterial genomes suggests that, relative to other phytoplankton, Trichodesmium is uniquely adapted for scavenging phosphorus from organic sources. This adaptation may help to explain the prevalence of Trichodesmium in low phosphate, oligotrophic systems. 相似文献
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在一个小型固定床反应器上对流化床煤燃烧温度下N_2O均相和多相生成机理进行了试验研究。研究表明,NH_3氧化形成的N_2O量很少,其主要产物是NO,当增加O_2浓度时,N_2O略有增加,在950℃左右时,N_2O量最大,而在880℃时,NO量最大。焦炭直接燃烧能形成一定量的N_2O,NO能在焦炭表面还原成N_2O,氧化性气氛下,焦炭的还原能力降低。最后,对煤焦生成N_2O的多相反应机理进行了讨论。 相似文献
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急性肝功能衰竭的猪动物模型 总被引:3,自引:0,他引:3
目的:建立一个比较接近人类条件的急性肝衰竭模型。用于人工肝脏治疗的疗效和安全性的测试。方法:以右旋半乳糖来制造猪肝衰竭的大型动物模型,分组3组给药,剂量分别为0.5、1和0.75g/kg。观察其临床表现、生理生化指标和病理改变。结果:3组实验都能引出与人的临床和生化指标变化相伫的肝功能衰竭的表现,以0.75g/kg组最为理想。结论:以0.75g/kg的半乳糖胺制造的急性肝功能衰竭的猪动物模型,符合人工肘脏研究对动物模型的要求。 相似文献
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