Influence of cryogenic treatment on the wear characteristics of 100Cr6 bearing steel

A series of reciprocating wear tests were performed on the deep cryogenically treated and conventionally heat-treated samples of 100Cr6 bearing steel to study the wear resistance. The worn surfaces as well as the wear debris were analyzed by scanning electron microscopy. The improvement in wear resistance of the deep cryogenically treated samples ranges from 49% to 52%. This significant improvement in wear resistance can be attributed to finer carbide precipitation in the tempered martensitic matrix and the transformation of retained austenite into martensite. X-ray diffraction analysis shows that the volume fraction of retained austenite in the conventionally heat-treated samples is 14% and that of the deep cryogenically treated samples is only 3%.     

砂体非线性分布的定量研究方法

介绍了分形几何学和分形地质统计学,并以大庆榆树林油田的砂体精细定量描述为例,利用分形地质统计学方法,对大庆榆树林油田砂体的分形分布进行了定量表征,为油田开发中的砂体非线性分布的数学定量表征提供了一种比较实用和可行的方法.     

Angiotensin-converting enzyme 2 is a functional receptor for the SARS coronavirus

Spike (S) proteins of coronaviruses, including the coronavirus that causes severe acute respiratory syndrome (SARS), associate with cellular receptors to mediate infection of their target cells. Here we identify a metallopeptidase, angiotensin-converting enzyme 2 (ACE2), isolated from SARS coronavirus (SARS-CoV)-permissive Vero E6 cells, that efficiently binds the S1 domain of the SARS-CoV S protein. We found that a soluble form of ACE2, but not of the related enzyme ACE1, blocked association of the S1 domain with Vero E6 cells. 293T cells transfected with ACE2, but not those transfected with human immunodeficiency virus-1 receptors, formed multinucleated syncytia with cells expressing S protein. Furthermore, SARS-CoV replicated efficiently on ACE2-transfected but not mock-transfected 293T cells. Finally, anti-ACE2 but not anti-ACE1 antibody blocked viral replication on Vero E6 cells. Together our data indicate that ACE2 is a functional receptor for SARS-CoV.