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关键词： 环境工程   膜分离技术   应用  

摘要： 膜分离技术与环境保护之间有着密不可分的重要关系,膜分离技术是利用外部能量以及化学位差当做动力,结合一些天然膜或是人工合成膜以及一些其他的多分组溶剂将其膜进行分离。对于一些固态或是气态的物体,膜分离技术可以有针对性地对其进行处理,从而达到一定的排放标准,这点对于我国的环境保护有着非常重要的作用。本文阐述了环境工程中膜分离技术的应用。

关键词： 反渗透膜分离技术   饮用水   水质改善  

摘要： 通过对华亭矿区生活饮用水水源地的水资源量、水质、水压状况分析,进行现状需水量探讨和远期需水量预测,采用反渗透膜分离处理技术对水质进行处理,结果表明该工艺流程在降低水中总硬度、铁、锰、钙、镁等指标的同时能有效改善水质,提升了生活饮用水的质量,满足广大群众的生活需求,更好地适应了华亭县社会、经济事业的快速发展的需要。

关键词： SMEs   Bankruptcy   Size   Discrete-time duration-dependent hazard model  

摘要： This paper investigates the extent to which the size affects the SME probabilities of bankruptcy. Using a dataset of (11,117) US non-financial firms, of which (465) filed for insolvency under chapters 7/11 between 1980 and 2013. We forecast the bankruptcy probabilities by developing four discrete-time duration-dependent hazard models for SMEs, Micro, Small, and Medium firms. A comparison of the default prediction models for medium firms and SMEs suggests that an almost identical set of explanatory variables affect the default probabilities leading us to believe that treating each of these groups separately has no material impact on the decision making process. However, comparisons between the micro and small firms with the SMEs firms strongly suggest that these categories need to be considered separately when modelling their credit risk. (C) 2015 Elsevier Inc. All rights reserved.

关键词： Rhodosporidium toruloides   ABC transporter   Carotenoids   Lipids   Extraction   Separation  

摘要： The oleaginous yeast Rhodosporidium toruloides has great biotechnological potential. It accumulates a high amount of lipids which can be used for biofuels and also produces carotenoids which are valuable in the food and pharmaceutical industry. However, the location of these two hydrophobic products in the cell membrane prohibits its efficient harvesting and separation. Here, the transporter Pdr10 was engineered into R. toruloides and cultured in two-phase media containing oil. This enabled the production and in situ export of carotenoids into the oil and concurrent separation from intracellular lipids in the cells. When Pdr10 strain was cultured in the two-phase media, carotenoids and fatty acids yield increased from 1.9 to 2.9 mu g/mg and 0.07 to 0.09 mg/mg, respectively. A total of 1.8 mu g/mg carotenoids was exported by Pdr10 strain, as compared to 0.3 mu g/mg in the wild type. In the Pdr10 strain, the composition of carotenoids and fatty acid it produced also changed. Torulene became the major carotene produced instead of torularhodin. Also, the unsaturated fatty acid C18:2 became the dominant fatty acid produced instead of the saturated C16:0, which was similar to the grape seed oil used in the two-phase media. This indicated that oil was being consumed by the cells, which was supported by the increased intracellular glycerol levels detected by gas chromatography-mass spectrometry (GC-MS). Our approach represents an easy and greener extraction method which could serve to increase the yield and facilitate separation of carotenoids and fatty acids.

关键词： 膜分离技术   环境工程   微滤   反渗透   超滤   适用性  

摘要： 膜分离技术具有工艺精简、低能高效、生产过程无化学污染及变化等显著特点,它相比于传统分离工艺更加灵活和实用.本文就围绕该技术与环境保护工程展开话题,探讨它在环境工程中的各方面具体应用,证明它之于传统分离技术的优越性.

关键词： Molybdenum compounds  

摘要： Earth-abundant MoS2 is widely reported as a promising HER electrocatalyst in acidic solutions, but it exhibits extremely poor HER activities in alkaline media due to the slow water dissociation process. Here we present a combined theoretical and experimental approach to improve the sluggish HER kinetics of MoS2 electrocatalysts through engineering the water dissociation sites by doping Ni atoms into MoS2 nanosheets. The Ni sites thus introduced can effectively reduce the kinetic energy barrier of the initial water-dissociation step and facilitate the desorption of the -OH that are formed. As a result, the developed Ni-doped MoS2 nanosheets (Ni-MoS2) show an extremely low HER overpotential of similar to 98 mV at 10 mA cm(-2) in 1 M KOH aqueous solution, which is superior to those (>220 mV at 10 mA cm(-2)) of reported MoS2 electrocatalysts.

关键词： 放线菌   分类鉴定   四氢嘧啶   异源表达   过表达  

摘要： 1,4,5,6-四氢-2-甲基-4-嘧啶羧酸(1,4,5,6-Tetrahydro-2-methyl-4-pyrimidine carboxylic acid)又称四氢嘧啶(ectoine),是一种渗透压补偿溶质。分子量142.2g/mol,分子式为C6H10N2O2,为环状氨基酸的衍生物。四氢嘧啶能够平衡渗透压的特质与其可以稳定和保护大分子如蛋白质、DNA以及酶等的功能,使其具有较高的开发利用价值。本文以吉兰泰盐湖的土壤为材料,共分离获得29株嗜盐碱放线菌。对分离获得的菌株进行16S rDNA酶切多态性分析,并对代表菌株进行16S rDNA序列测定,其中获得3株拟诺卡氏菌株。80%乙醇法抽提分离获得菌株胞内的四氢嘧啶,然后进行薄层层析定性检测相结合,快速筛选出能够生产相容性溶质四氢嘧啶的放线菌。Streptomyces pactum Act12是1株多功能放线菌株,TLC定性检测可知其能够产生相关耐盐的相容性溶质四氢嘧啶。Streptomyces pactum Act12可在NaCl范围为0～10.0%内生长,而在2.5%的NaCl浓度下,胞内的四氢嘧啶积累量达到最大值,为72.39mg/L。经过生物信息学分析:ectA、ectB和ectC基因位于Streptomyces pactum Act12中的同一个操纵子上,而大小分别为516bp、1272bp、399bp。预测ectA、ectB、ectC分别编码二氨基丁酸乙酰基转移酶(EctA)、二氨基丁酸氨基转移酶(EctB)、四氢嘧啶合成酶(EctC),其大小依次为18.8kDa(171 amino acid)、46.6kDa(423 amino acid)、14.9kDa(132 amino acid)。利用高保真酶Pfu克隆大小为2408bp的ectABC基因簇到表达载体pET-28a上并转化大肠杆菌BL21(DE3)。含pET28a-ectABC质粒的大肠杆菌BL21(DE3)在LB培养基中经0.5mmol/L IPTG在37℃诱导6h后,能够合成四氢嘧啶,但其盐耐受度未得到明显提高。四氢嘧啶合成的前体L-天冬氨酸-β-半醛,是由L-天冬氨酸在天冬氨酸激酶(Aspartokinase;Ask)和天冬氨酸半醛脱氢酶(Aspartate-semialdehyde dehydrogenase;Asd)催化下生成,Ask和Asd是四氢嘧啶合成的关键限速酶。在440种含有四氢嘧啶或羟基四氢嘧啶基因的微生物基因组中,只有约30%(132种微生物)在ectABC/D基因簇附近含有一个天冬氨酸激酶基因。在Act12全基因组中,Ask和Asd都是单拷贝,两者位置紧邻。本文将四氢嘧啶合成中的关键限速酶Ask和Asd在Streptomyces pactum Act12中过表达,以期提高Streptomyces pactum Act12的盐耐受度及四氢嘧啶的产量。

ISBN: (纸本)9787564345266

关键词： 膜分离   环境工程   污染  

摘要： 膜分离技术是指在流体中的物质在通过膜时的速率不同,进而对各种物质的渗透作用也不同,在外力的推动下实现物质的分级、分类.膜分离技术不仅是一门新兴的高科技技术,其在对环境的保护和治理中都能起到很大的作用,本文就膜分离技术进行相关的介绍,并探究其在环境工程中的各种用途.

ISBN: (纸本)9787118107951