This study explores the reasons underlying the frequent appearance of ＂marking problem＂ during the production of double-walled copper-brazed steel tubes. To this end, we compared two types of copper-coated steel str...This study explores the reasons underlying the frequent appearance of ＂marking problem＂ during the production of double-walled copper-brazed steel tubes. To this end, we compared two types of copper-coated steel strips, of which one has almost no problem during production, whereas the other has higher number of incidences of ＂marking problem＂. We analyzed the chemical composition,mechanical properties,the cross-sectional metallographs, and surface quality of the trimmed edge in both types of specimen. After the roll forming process, the bonding condition between the steel layers of the tubes before and after brazing process has also been examined. Results indicate that the chemical composition and mechanical properties of the two kinds of strips are similar; however, the edge quality of the trimmed strips is significantly different. It is believed that the irregular shape of the edge portions in the strips will be more pronounced during the bevel treatment. Consequently, smooth and tight seams cannot be guaranteed by such uneven beveled edges,which lead to higher number of incidences of ＂marking problem＂ during production.展开更多
DNA双链断裂(double-strand breaks,DSBs)修复对于保证基因组完整性以及维持细胞的平衡稳定性起着关键作用。p53结合蛋白1(p53-binding protein 1,53BP1)是针对产生的双链断裂损伤做出反应的重要调控因子。目前,研究人员对于53BP1被招...DNA双链断裂(double-strand breaks,DSBs)修复对于保证基因组完整性以及维持细胞的平衡稳定性起着关键作用。p53结合蛋白1(p53-binding protein 1,53BP1)是针对产生的双链断裂损伤做出反应的重要调控因子。目前,研究人员对于53BP1被招募到受损的染色质上的过程,以及53BP1在DSBs修复过程中阻止同源重组(homologous recombination,HR)的同时推动非同源末端连接(non-homologous end-joining,NHEJ)的过程,已经有了新的认识。并且,近期的研究结果启发科学家们提出了一种新的模型,即53BP1的招募需要直接识别DSBs特异性的组蛋白密码,而53BP1发挥作用时的通路选择则与BRCA1蛋白的拮抗作用有关。结合近年来有关53BP1的研究进展,主要综述了53BP1的结构与功能特点,其作为调控因子在DSBs修复过程中发挥的作用,以及53BP1达到有效聚集的方式。展开更多
文摘This study explores the reasons underlying the frequent appearance of ＂marking problem＂ during the production of double-walled copper-brazed steel tubes. To this end, we compared two types of copper-coated steel strips, of which one has almost no problem during production, whereas the other has higher number of incidences of ＂marking problem＂. We analyzed the chemical composition,mechanical properties,the cross-sectional metallographs, and surface quality of the trimmed edge in both types of specimen. After the roll forming process, the bonding condition between the steel layers of the tubes before and after brazing process has also been examined. Results indicate that the chemical composition and mechanical properties of the two kinds of strips are similar; however, the edge quality of the trimmed strips is significantly different. It is believed that the irregular shape of the edge portions in the strips will be more pronounced during the bevel treatment. Consequently, smooth and tight seams cannot be guaranteed by such uneven beveled edges,which lead to higher number of incidences of ＂marking problem＂ during production.
