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51.
本研究旨在分析猪源ST9型耐甲氧西林金黄色葡萄球菌(Staphylococcus aureus,MRSA)中前噬菌体的流行情况、结构特点和转导能力,探究前噬菌体在猪源MRSA流行克隆形成中的作用。基于全基因组信息,分析了近年来从我国多省分离的131株ST9型MRSA中前噬菌体的流行率、分型、亲缘关系和结构特征;选取含不同分型前噬菌体的菌株进行诱导,对诱导获得的噬菌体颗粒进行转导,测定转导子的耐药表型及体外适应性。研究结果显示:猪源ST9型MRSA的前噬菌体携带率为78.6%(103/131株),其中,63株携带完整前噬菌体序列,所有前噬菌体序列均不含耐药基因,仅2.9%(3/103株)的前噬菌体序列含毒力基因;前噬菌体谱型丰富,其整合酶分型主要为Sa2int和Sa4int;各型别前噬菌体结构同源性较高,完整前噬菌体可被诱导为长尾噬菌体;噬菌体颗粒可包装供体菌的aadD、tet(L)耐药基因并转导至受体菌中;转导子可获得卡那霉素、四环素耐药表型,体外生长能力与受体菌株无明显差异(P>0.05)。研究结果表明:猪源ST9型MRSA的前噬菌体携带率较高,谱型丰富,不携带耐药基因,部分噬菌体可包装供体菌的耐药基因转导至受体菌,产生的适应性代价小。 相似文献
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This paper analyzes the limitation of regarding the weighted average cost of capital as the optimal standard of capital structure in the traditional capital structure decision-making method, and analyzes the view that the capital structure is affected by many factors,such as earning power, long-term stability of operating, the attitudes held by owners and operators, the attitudes held by creditors and financial risk. With the example, the affecting factors of the capital structure is analyzed. The fuzzy synthetic evaluation model are employed to decision-making of the capital structure. This article also shows the key point of its application. 相似文献
54.
This article has discussed the problem of an arbitrage about an portfolio in an unequilimarket and got a determinable theorem about existence of an arbitrage about an portfolio. According to this theorem,an arbitrage about portfolio is not existing if there exists a respect martignal measure.A structural result about existence of arbitrage about an portfolio in a market is gotten. All results represent the existence of an arbitrage about an portfolio is related closely to the type of market. 相似文献
55.
According to the security investment theory of Markowitz,this paper presents aCaculation method of portfolio investment under the risk minimization,and some mathematic expres-sions of the efficient frontier for portfolio investment are conducted.Based on these,the efficientfrontier is proved as a parabola,and a practical caculation process is given. 相似文献
56.
The influence of the structure and location of dam and weir on fluid flow state in a two-strand tundish is studied, and a set of optimal structure, combining with the average residence time calculated from RTD curve, is obtained. The result indicates that the fluid flow state can be changed and the path of the fluid flow can be prolonged as well as the average residence time is improved after using dam and weir. But there are some dead zones after fluid passed through the dam and weir. Combination scheme of No. one dam and weir is better than the others. Its average residence time is 299 s and the volume fraction of dead zone is 31.0%. After the optimization of flowing control parameters in tundish, the best case is that the distance between dam and weir is 290 mm and the distance between weir and the long nozzle is 383 mm. The longest average residence time is 351 s and the minimum volume fraction of dead zone is 19.0% under the above situation. Compared with that of no dam and weir, the average residence time increases by 65 s and the dead zone volume fraction decreases by 15.0%. Based on Newton formula, the calculated results show that the inclusions with diameter larger than 17.5 μm can float up within 351 s under this optimization situation. 相似文献
57.
YANG Zhong-ren RAO Cheng ZOU Jian PENG Zhen-liane Ministry of Education Chongqing Chin 《保鲜与加工》2004,(2):32-35
Dong village is very valuable for research work because of its special regional and national character and rich cultural implication. In this paper, some information about the location, form and features of Dong village is given. Then, the relationship between the culture and the settlement is analyzed, which provides a clue for understanding Dong village and will be beneficial to creating modern human settlements. 相似文献
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高含沙水流水轮机转轮的改型与抗磨蚀研究 总被引:1,自引:2,他引:1
进行高含沙水流水轮机转轮的改型研究,关键是要从正确确定转轮设计参数和轴面流道型式入手,根据三维水力设计理论,考虑导叶与转轮匹配关系进行叶型设计,针对不同破坏机理选择强磨蚀区采用金属喷涂或非金属保护等综合措施,使水轮机在高舍沙水流中运行时出力增加、抗磨蚀能力提高。 相似文献
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