Weak male-driven molecular evolution in rodents

In humans and rodents the male-to-female ratio of mutation rate (alpha m) has been suggested to be extremely large, so that the process of nucleotide substitution is almost completely male-driven. However, our sequence data from the last intron of the X chromosome-linked (Zfx) and Y chromosome-linked (Zfy) zinc finger protein genes suggest that alpha m is only approximately 2 in rodents with a 95% confidence interval from 1 to 3. Moreover, from published data on oogenesis and spermatogenesis we estimate the male-to-female ratio of the number of germ cell divisions per generation to be approximately 2 in rodents, confirming our estimate of alpha m and suggesting that errors in DNA replication are the primary source of mutation. As the estimated alpha m for rodents is only one-third of our previous estimate of approximately 6 for higher primates, there appear to be generation-time effects--i.e., alpha m decreases with decreasing generation time.     

Passivation Behaviors of Super Martensitic Stainless Steel in Weak Acidic and Weak Alkaline NaCl Solutions

The passivation behaviors of super martensitic stainless steels(SMSS)were studied by polarization curves at passive potential of-0.1Vand in various NaCl solutions,electrochemical impedance spectroscopy(EIS)and Xray photoelectron spectroscopy(XPS)analysis.Electrochemical test results showed that,in alkaline solutions,passivation region width was wider,passivation current was smaller,and polarization resistance was greater;thus,the passive film of SMSS in alkaline solutions had better passivation behaviors than that in acidic solutions.The polarization curve and EIS of samples SMSS1 and SMSS2were also used to study which sample had better passivation behaviors.All results demonstrated that passive film structure of SMSS1 sample was more stable,and capacity of passive film was enhanced.The impact of alloying elements on the passive film(SMSS)passivation capability was also discussed by XPS depth profiling,and XPS depth profiling showed that the composition of the passive film was mainly composed of Fe-oxide and Cr-oxide.So the passive film structures were mixed layers of Fe-oxide and Cr-oxide.Fe oxidation product and Cr oxidation product would help to improve the protective property of passive film,which could promote the formation of a passive film structure more stably and densely.     

金属钕工业生产中氧化钕利用率的探讨

在氟化体系氧化物电解金属钕的工业产中,针对Ｍｄ２Ｏ３在熔盐中溶解度低的情况下,尤其是以氟酸铈矿提取的ｎｄ２Ｏ３为原料电解时易发生沉底现象时,采取调整熔盐配比和适当提高氧化钕利用率的方法,可改善金属钕产品的表面质量,防止熔盐夹杂,降低产品中的碳含量,并可达到减少炉渣（废旧溶盐）生成、稳定炉况生产和节能降耗的目的。