Corrosion Performance of Stainless Steel Reinforcement in the Concrete Prepared with Seawater and Coral Waste and Its Ecological Effects

Durability and ecological effects of the stainless steel reinforced coral waste concrete were compared with those of the carbon steel reinforced ordinary concrete.The results showed that the corrosion current densities of the stainless steel in the coral waste concrete were less than one-tenth of those of the carbon steel in the same grade ordinary concrete.The stainless steel in the seawater coral waste concrete maintained passivation even after more than two years of immersion in 3.5%NaCl solution,while the carbon steel counterparts in the ordinary concrete were seriously corroded under the same condition.Simultaneously,the corrosion current density of the stainless steel reinforcement decreased slightly with the strength grade of the coral waste concrete.The ecological evaluation indicated that the non-renewable energy consumption and CO_(2)emission of per cubic meter of the newly constructed stainless steel reinforced coral waste concrete were 23.72%and 1.419%less than those of the carbon steel reinforced ordinary concrete with the same grade,while the aforementioned two parameters of the former material were reduced by 44.81%and 32.0%in comparison to the latter one in 50 years duration.

NirA1基因对球孢白僵菌生长、抗逆及毒力的影响

【目的】探究参与硝酸盐同化的一个特异转录因子NirA1对球孢白僵菌(Beauveria bassiana)生长、抗逆及毒力的影响。【方法】利用RT-PCR检测球孢白僵菌NirA1基因在不同培养基中的表达特征。通过构建敲除突变株ΔNirA1、超量表达OENirA1及回复互补菌株ComNirA1,解析NirA1在球孢白僵菌生长发育、逆境胁迫反应和致病昆虫中的功能。【结果】NirA1基因在营养较贫瘠的CZB培养基中表达量高于丰富培养基PDB和SDB。敲除NirA1导致了菌株在人工培养基上的生长缓慢,对NaNO_(2)和Urea的利用效率降低。RT-PCR显示,ΔNirA1中硝酸盐转运蛋白基因NrtA的表达较野生型显著下调。在CZA、PDA和1/4 SDAY培养基中,其分生孢子产量分别较野生型降低了21.6%、16.2%和25.6%。逆境胁迫分析发现,在高温(32℃),高渗(1mol/LNaCl)和H2O_(2)处理后,ΔNirA1菌落生长抑制率较野生型分别降低29.0%、25.2%及49.0%;但在添加SDS和刚果红(CR)的处理中,突变体菌落的生长抑制率分别较野生型升高34.1%和96.2%。因此,缺失NirA后,菌株对SDS和CR更加敏感,但对高温、H2O_(2)和NaCl的耐受性提高。以3龄的大蜡螟为试虫的毒力测定表明,敲除NirA1基因导致菌株的毒力提高,半致死时间较野生型提前17.4%。【结论】NirA1在球孢白僵菌生长过程中参与了氮源的利用,并在球孢白僵菌的菌落生长、分生孢子生产、胁迫反应和致病宿主过程中发挥了重要作用。