关于城轨制动系统中梯形螺纹零件的数控车削加工方法及应用

在国内梯形螺纹的加工主要是车削、成套丝锥、拉削加工等方法。以城轨踏面制动单元中套筒螺母的Tr22x16/P8非标梯形螺纹为例,介绍数控车削加工梯形螺纹的工艺原理、刀具方案、数控程序,确保螺纹加工精度、表面质量。

人肺腺癌染色体8p21～p22杂合性缺失精细作图

目的 在染色体 8p2 1 8p2 2界定发生于中国人肺腺癌的杂合性缺失 (LOH)的最小区域 ,为定位克隆肺腺癌相关抑癌基因提供线索。方法 利用 32例肺腺癌患者肿瘤组织检测位于 8p2 1～p2 2的 17个微卫星多态性标记的LOH频率 ,并且探讨各位点LOH与病理分级和临床分期的关系。结果 在 32例肺腺癌患者组织中有 31例 (96 6 7% )存在至少 1个位点的LOH ;主要集中于 3个区域 :位于 8p2 2的D8S2 5 4～ 2 6 1、D8S182 7～ 1731以及D8S1135。所检测位点中仅D8S2 6 1位点的LOH发生频率与肺腺癌分期呈正相关 (P <0 0 5 )。结论 8p2 2区域可能存在位于D8S2 5 4～ 2 6 1,D8S1135和D8S182 7～ 1731的。

Cloning, tissue expression pattern characterization and chromosome localization of human peptide methionine sulfoxide reductase cDNA

Oxidation and reduction of some amino acids are one of the molecular mechanisms for regulating the function of proteins. The oxidation of methionine (Met) to methionine sulfoxide (Met(O)) results in decreasing or loss of the biological activity of related proteins. It was found that peptide methionine sulfoxide reductase (msrA) can reduce Met(O) to Met and therefore restored the biological function of the oxidized proteins. To reveal the methionine oxidation-reduction mechanism in human body, in this study, the cDNA sequence of bovine msrA was used as an information-probe to screen the human EST database. Based on a contig assembled from homologous ESTs, a 1 256-bp human MSRA cDNA was cloned from several human cDNA libraries. The cDNA contains an open reading frame (ORF) of 705 bp in length, which encodes 235 amino acid residues. Homology comparison revealed that human MSRA shares 88% and 61% identities with bovine and Escherichia coli msrA protein respectively. Expression pattern analysis revealed a