景天属植物耐非生物胁迫研究进展

景天属植物作为园林绿化的重要植物材料已被广泛应用。了解其对非生物胁迫逆境的适应性,对在生态园林城市的建设和环境修复中景天品种的选择和利用具有重大意义。现综述了近年来我国在景天属植物耐高温、低温、干旱、涝、酸、盐、光和重金属等非生物胁迫研究方面的进展,对存在的问题及今后的发展方向提出了一些建议。     

地熊蜂为重庆地区设施番茄授粉的效果研究

为评价地熊蜂在重庆地区设施番茄的授粉效果,在重庆市荣昌区龙舌嘴村开展授粉效果比较试验,分析地熊蜂授粉对设施番茄产量、果实品质及畸形果率的影响。试验结果显示,经地熊蜂授粉的设施番茄平均产量为2 206.44 kg/667 m2,与未授粉组相比显著提高了104.95%,授粉组的单果质量、果纵径、果最大横径、可溶性固形物含量、VC含量及总糖含量显著高于未授粉组。由此,认为地熊蜂适宜为重庆地区设施番茄授粉,且能够显著提高重庆地区设施番茄的产量与品质。     

Association between porpoise presence and fish choruses: implications for feeding strategies and ecosystem-based conservation of the East Asian finless porpoise

The associations between feeding activities and environmental variables inform animal feeding tactics that maximize energetic gains by minimizing energy costs while maximizing feeding success. Relevant studies in aquatic animals, particularly marine mammals, are scarce due to difficulties in the observation of feeding behaviors in aquatic environments. This data scarcity concurrently hinders ecosystem-based fishery management in the context of small toothed-cetacean conservation. In the present study, a passive acoustic monitoring station was deployed in an East Asian finless porpoise habitat in Laizhou Bay to investigate potential relationships between East Asian finless porpoises and their prey. The data revealed that porpoises were acoustically present nearly every day during the survey period. Porpoise detection rates differed between spring and autumn in concert with activities of fish choruses. During spring, fish choruses were present throughout the afternoon, and this was the time when porpoise vocalizations were the most frequently detected. During autumn, when fish choruses were absent, porpoise detection rates decreased, and diurnal patterns were not detected. The close association between fish choruses and finless porpoise activities implies an “eavesdropping” feeding strategy to maximize energetic gains, similar to other toothed cetaceans that are known to engage similar feeding strategies. Underwater noise pollution, particularly those masking fish choruses, could interrupt finless porpoises’ feeding success. Fisheries competing soniferous fishes with finless porpoise could impact finless porpoise viability through ecosystem disruption, in addition to fishing gear entanglement.     

国内外致泻大肠埃希氏菌O157:H7的检测标准比较及建议

致泻大肠埃希氏菌O157:H7（STEC O157:H7）是大肠埃希氏菌中致病性最严重的一种食源性致病菌,主要存在于牛肉、牛奶、水果及其制品中,对身体健康造成很大危害,甚至引发死亡。食品中STEC O157:H7检测尤为重要。本文对国内外STEC O157:H7的检测标准进行比较,提出我国标准在样品前处理、快速筛选方法的应用等方面需要加强,以便为该菌快速准确检测提供帮助,实现与国际标准化体系建设接轨,满足实验室检测需要。     

猪源ST9型耐甲氧西林金黄色葡萄球菌中前噬菌体的流行状况与转导分析

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。     

Dynamics of Actin Polymerization

The process of actin polymerization and depolymerization have some relation with its function,the activation of such process is compatible to its functions. The polymerization progress is divided into four steps: The first step is the activation of the monomer actin. The nucleation of actin nucleus forms in the second step which limits the polymerization speed. The elongation of the F-actin filaments happens in the following step. In the last step, a steady-state is attained, the length of the filament does not change because the polymerizing rate in the barbed end is the same with the depolymerizing rate in the pointed end. Some factors which affect the polymerizing process, such as nucleotide, actin related proteins are discussed. The aim is to know more about how to assemble the complicated system with biomacromolecule and what to function.     

Water model study on flow optimization of five streams L-type tundish

In this paper, the water model method is used to optimize the flow behavior of asymmetrical five streams L-type tundish in a steelmaking plant. The results show that the optimization plan is set up with turbulence suppressor T+ vice guide wall D2+ main guide wall with three holes (D1a) which consists of top two holes with 25° inclination and one hole with 30° inclination below. With this plan, the time which the colorants reach to the outlets increases, the difference of response time in all outlets decreases, the peak concentration of the RTD reduces, the existence time of high concentration liquid steel extends, and the ratio of dead zone in each streams reduces.     

Behavior and Design of High-strength Bolt in Tensile Connection

The tensile strength of high strength bolt is affected by many factors, including prying force. The prying force can result in the increment of bolt force, for which the connection failed ahead of time. Several methods are presented for calculating the prying force. In the China's "Code for Design of Steel Structure" (GB50017), there is no formula for calculation of prying force and a factor of 0.8 is considered in formula for tensile strength of bolt for taking the prying force into account. It is proposed that the design value of tensile resistance for high strength bolt should be increased.     

Exploring Harmonious Protection of Land Resources in City Construction

Urbanization in China is at an essential point in its transformation from the initial stage to accelerating stage. With quick expansion of city scale and large occupation of land for urban construction, the contradiction between land resource shortage and people's living needs becomes more and more prominent. It has great affection on the grand plan of China's sustainable development of economy and society. How to adjust the relations between the development of urban construction and protect the land resource, promote the rational use of urban land, perfect and complete the protection system of land resource for improving the efficiency of urban land use. In order to conserve land resource and find a sustainable way for development of people's living and environment construction, the above mentioned problems are the most important issue for urban construction and important subject of this paper.