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X100管线钢在中性重碳酸盐溶液中的塑性应变腐蚀
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作者 l.y.xu 乔林锁 王金龙 《现代冶金(内蒙古)》 2015年第2期56-63,共8页
本文中用加工试验、电化学和微电化学检测及有限元分析研究了塑性应变对X100管线钢腐蚀影响的研究,施加应变增强了钢的腐蚀,弹性形变的影响是有限的,机械电化学对钢的弹性区腐蚀作用不大,但在塑性应变条件下变得明显。预应变增强了... 本文中用加工试验、电化学和微电化学检测及有限元分析研究了塑性应变对X100管线钢腐蚀影响的研究,施加应变增强了钢的腐蚀,弹性形变的影响是有限的,机械电化学对钢的弹性区腐蚀作用不大,但在塑性应变条件下变得明显。预应变增强了阳极和阴极反应,对阳极反应的影响更为明显,此外,实际在管线上塑性应力和应变的不均匀分布对钢会产生明显不同的腐蚀活性,这就是在局部开始优先腐蚀甚至开裂的原因。 展开更多
关键词 碳钢 EIS 应变影响 应力腐蚀
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Construction and optimization of boldenone synthesis from androstenedione catalyzed by a dual-enzyme system
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作者 Y.Liang H.Li +6 位作者 W.Liu l.y.xu J.X.Zhang L.Y.Chen S.L.Wang J.S.Shi Z.H.Xu 《Systems Microbiology and Biomanufacturing》 2024年第2期783-793,共11页
Boldenone is a protein-assimilating androgen steroid that can promote protein synthesis,support nitrogen storage,and enhance renal erythropoietin release.The industrial production of boldenone mainly relies on chemica... Boldenone is a protein-assimilating androgen steroid that can promote protein synthesis,support nitrogen storage,and enhance renal erythropoietin release.The industrial production of boldenone mainly relies on chemical synthesis,which has various problems,such as a complex conversion process,excessive byproducts,and serious environmental pollution.There-fore,it is of great significance to explore a new biosynthetic route.Recently,the enzymatic synthesis of steroid compounds has been performed more frequently than in the past.In this work,boldenone was produced from androstenedione(AD)in two steps by a dual-enzyme cascade of 17β-hydroxysteroid dehydrogenase(17β-HSD)and 3-sterone-Δ^(1)-dehydrogenase(KstD).The conversion efficiency of three isoenzymes of 17β-HSD from Mycobacterium sp.LY-1 for substrate AD was first analyzed.After that,the 17β-HSD2 with high selectivity and specificity for AD was screened and co-expressed with KstD3 in Escherichia coli BL21 to construct a dual-enzyme catalytic system.The results showed that the synthesis of boldenone from AD could be achieved by constructing the dual-enzyme expression system of 17β-HSD and KstD,as we determined that the concentration of boldenone reached 24.3 mg/L.To further improve the synthesis efficiency of boldenone,the expression conditions of the dual-enzyme system were optimized,and the concentration of boldenone reached 31.9 mg/L.The explora-tion of this route will provide a foundation for the efficient enzymatic synthesis of boldenone. 展开更多
关键词 BOLDENONE Dual-enzyme catalytic system 17β-HSD KstD Escherichia coli Heterologous expression
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