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参照鱼类病毒性出血性败血症病毒序列,根据PCR引物设计的原则,设计巢式PCR引物,采用巢式逆转录聚合酶链反应(RT-PCR)方法,对如何快速检测鱼类病毒性出血性败血症病的方法进行了较为系统的研究,并对RT-PCR的反应条件进行了优化.结果表明,巢式RT-PCR扩增获得279bp的特异性片断,阴性对照无扩增条带.巢式RT-PCR扩增出的特异性片段经测序分析,结果证实与报道的序列完全一致.该方法最低可检测出0.1pg的鱼类病毒性出血性败血症病毒RNA.初步建立了VHSV的巢式RT-PCR检测方法,该方法灵敏、特异,可为VHSV的检测提供一个快速、有效的手段. 相似文献
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进入创新驱动发展的新时代,未取得流入地户籍的高学历流动人口成为各地竞相引进的重要资源。本文基于2017年中国流动人口动态监测数据,结合探索性空间数据分析等方法精细刻画高学历流动人口流动的空间格局,并借助嵌套Logit模型揭示其空间选择机制。结果发现：(1)中国高学历流动人口不断集聚,形成以京、沪为核心的流动网络;各城市流出的人口中高学历人才占比在空间上具有明显的“东高西低、北高南低、中部塌陷”特征,但各城市吸引的流动人口受教育水平在南北方向上的空间分异较小;高学历流动人口流动的空间依赖性显著,呈现出城市群的雏形。(2)在机制方面,个体因素对高学历流动人口的空间选择影响更大;其普遍表现出近距离、跨级别向上流动的倾向;学历越高、户籍所在地行政等级越高、50岁以下年龄越大的人才越倾向于流入一线城市。(3)城市特征变量中,经济因素变量如工资水平、第三产业占比等和地方品质变量如公共服务、高等教育、空气质量等均对高学历流动人口的空间选择具有显著的正向作用。本研究为不同城市制定人才引进政策、促进城市高质量发展提供了实证依据和科学参考。 相似文献
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The levels of variance associated with measuring the infiltration process and modelling it by means of a regression model are compared to see which approach yields the best results in terms of effort and accuracy. A nested sampling scheme has been used in the three major physiographic units of central Guyana, South America: ‘White Sands’; (Haplic and Ferralic Arenosols), ‘Brown Sands’ (Haplic Ferrasols) and ‘Laterite’ (Xanthic and Dystric Leptosols). Cluster analysis yields three sample groups that reflect the sharp landscape boundaries between the units. Multiple regression analysis shows that each unit has a different combination of soil properties that explains the variance in final infiltration rate and sorptivity satisfactorily. Nested analysis of variance indicates that clear spatial patterns with distances of variation of several hundred metres exist for final infiltration rate in White Sands and Laterite. Infiltration rate in Brown Sands and sorptivity in all units have large short-distance variabilities and high ‘noise’ levels. The correlated independent variables behave accordingly. For the majority of the soil properties, sampling at distances of 100 to 200 m results in variance levels of more than 80 per cent of the total variance, which indicates that only a detailed investigation can assess spatial variation in soil hydrological behaviour. The use of simple soil properties to predict infiltration is only possible in a very general sense and with the acceptance of high variance levels. 相似文献
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关于台风非对称结构与台风路径的数值分析 总被引：3，自引：1，他引：3
采用一个有限区域原始方程双向相互作用的移动套网格台风路径数值预报模式，对１９９２年的两个台风进行了５个个例预报试验，结果表明预报路径和实况有很好的一致性，通过对预报个例的台风非对称结构进行分析，发现非对称结构随时间变化与台风移动路径有着比较密切的联系，如能了解实际台风的非对称结构，将有助于提高台风路径预报的水平。 相似文献
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《Marine Policy》2014
Marine governance in European seas is at a crossroad aiming towards implementation of eco-system based marine management (EBMM) through integration of different EU policies or directives to protect the environment, while at the same time expected to facilitate growth and employment in support of the blue economy. This article shows that the governance landscape at the regional sea level is very complex, fragmented and faced with several dilemmas. It examines the present governance structures in the four European seas (Baltic, Black, and Mediterranean Seas and North East Atlantic Ocean). It is argued that the implementation of EBMM at the regional sea level is characterized by a highly fragmented European governance system where there is lack of coordination between relevant DGs within the European Commission, between EU, International organisations, Regional Sea Conventions and the Member States and between sectoral governance arrangements that should provide sectoral management measures that support EBMM. The article develops suggestions for a nested governance system in which institutions, policies, laws and sectors are nested into a tiered, internally consistent and mutually re-enforcing planning and decision-making system. Developing institutional interaction and soft modes of governance between the EU, the Regional Sea Conventions, Member States and the governance arrangements of the different marine sectors will be crucial in evolving towards such a nested governance system for EBMM. Moreover, there is no one size fits all approach in implementing EBMM, which means that for each European Sea a context-dependent nested governance system should be developed. 相似文献
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采用PCR-DGGE方法,对2011年夏季北极王湾表层海水及沉积物细菌的群落分析结果表明,沉积物中的细菌多样性指数高于海水。深水站位(S1和S3)的沉积物细菌群落不但与浮游细菌群落存在差异,并且与浅水站位(S5)也存在差异。位于湾口、湾内的浮游细菌群落组成也存在一定差异。测序结果显示,王湾海洋细菌的多样性组成包括α-变形细菌、γ-变形细菌、δ-变形细菌、放线菌、拟杆菌及厚壁菌等类群。基于定量PCR方法的检测结果表明,位于湾口、湾内的浮游细菌丰度相似,但湾内玫瑰杆菌支系的丰度明显低于湾口。研究结果表明,与湾口相比,王湾湾内的细菌群落受陆源性淡水输入的影响明显,不但表现在细菌群落的多样性组成上,也表现在某些特定细菌类群的数量分布上。 相似文献
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This paper explores variant space-time models for log-transformed West Nile virus (WNv) mosquito data, which explicitly account for both local environmental conditions and complex dependent structures. Four space-time models take various forms to accommodate correlated structure in space and time, nested data, and nonstationarity. The average WNv mosquito abundance is captured by a global trend across all four models, but different model assumptions are imposed on the stochastic component of the proposed models: a simple multivariate linear regression model with independent and identical errors, a site-specific linear mixed model with temporally correlated errors, a week-specific linear mixed model with spatially correlated errors, and a local space-time kriging model. In a case study, the predictive performance of the four models was assessed using data collected in 2007 and 2008 for the Greater Toronto Area by the mosquito surveillance program of Ontario Ministry of Health and Long-term Care: the local space-time kriging model outperforms others, but closely followed by a site-specific linear mixed model with temporal correlation. Our findings suggest that the predictive accuracy of space-time WNv mosquito abundance models can be enhanced by explicitly taking into account spatiotemporal correlation, nonstationarity, and the data collection procedure, such as surveillance design, based on sound understanding of mosquito behavior and population dynamics. 相似文献
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基于WRF模式对青藏高原一次强降水的模拟 总被引：4，自引：0，他引：4
为了了解新一代中尺度数值预报模式WRF中各参数化方案组合、嵌套技术的使用对青藏高原降水模拟结果的影响,利用WRF模式对2004年10月5—6日青藏高原一次强降水过程进行了模拟试验;对各微物理方案和积云参数化方案组合进行了模拟和对比评分,对嵌套技术的使用进行了对比分析,主要分析了不同行星边界层方案选择对降水模拟的影响。结果表明,WRF模式基本能够重建此次强降水过程的中心、强度及降水范围,Eta-Ferrier云微物理方案和Betts-Miller-Janjic积云参数化方案的组合在此次模拟降水过程中是最优的,采用嵌套技术的模拟结果要优于不采用嵌套技术的结果;行星边界层方案的合理选择能够明显提高降水模拟的效果。 相似文献
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