3种ELISA试剂盒对牛新孢子虫血清抗体比较检测

用瑞典Svanova公司、美国IDEXX公司和美国VMRD公司生产的3种检测新孢子虫血清抗体ELISA试剂盒对来自澳大利亚牛血清（41份）、新西兰牛血清（40份）、乌拉圭牛血清（30份）和中国新疆牛血清（46份）进行了同步检测和比较分析,并以其中2个试剂盒检测结果均为阳性或阴性的血清为真阳性或真阴性,对另1个试剂盒在诊断相对敏感性和相对特异性方面进行了比较评估。结果表明,3个试剂盒的诊断相对敏感性和诊断相对特异性分别为：85.7%和92.5%（Svanova）、95.8%和98%（IDEXX）、88.5%和98%（VMRD）。3个试剂盒都具有较好的重复性,检测低限相近。在对样品的检测中,IDEXX与VMRD两个试剂盒检测符合率较高,但对不同国家的样品检测符合率差别较大。     

标准化对我国出口贸易的影响

在标准主导国际竞争的时代,标准化已成为影响国际贸易的重要变量。本文选取1991-2010年的样本数据,在利用单位根检验对变量平稳性考察的基础上,采用协整检验方法对我国国家标准增量、外商直接投资额、人民币汇率和我国出口贸易额等变量的长期均衡进行了分析并作了误差修正和Granger因果检验。结果表明,外商直接投资额和人民币汇率与我国出口贸易存在正相关,而我国国家标准增量在短期内对我国出口贸易具有抑制作用,在长期内则对我国出口贸易具有促进作用。     

中国股票市场换月效应及其成因的实证研究

本文以上证指数和深成指数为研究对象,用ARMA—GARCH模型就换月效应在我国沪深两市的存在性及其成因进行了实证检验,结果发现换月效应在样本研究期间的沪深两个市场普遍存在,采用滚动样本检验进行的稳健性分析也支持这一结论。为了研究换月效应的成因,本文根据我国基金业的发展特征构造了相关的假设检验,结果发现我国股市的换月效应在证券投资基金出现之后显著增强,而在之后基金业较为规范的一个时期换月效应又有所减弱,表明窗饰假说对我国股票市场换月效应具有相当大的解释力。     

兵团产业结构与经济规模关系的实证分析

产业结构的演进与经济规模扩大之间具有密切的联系。本文基于协整理论和格兰杰因果关系检验理论,利用1980年-008年的时间序列数据对兵团产业结构与经济规模间的关系进行实证分析。研究结果表明,兵团产业结构与经济规模之间存在着长期稳定的均衡关系,二者之间互为因果关系。     

全球主要石油市场间的信息溢出效应分析

本文选取了全球主要的石油市场组合,以均值、方差、分位数为代理变量,运用Granger因果检验方法研究了市场的信息溢出效应。在过滤掉了均值因果关系后,着重分析了不同市场组合的波动溢出效应,判断了市场间的信息流向。在波动溢出分析的基础上,又进一步检验了极端上涨和极端下跌时的风险溢出关系,提出了非对称风险溢出的概念,并将其应用于石油市场。实证结果表明信息大多从信息效率高的市场流向信息效率低的市场,上涨侧的信息传递速度比下跌侧更高,强风险溢出证据是普遍的。对波动溢出与风险溢出的比较表明,风险溢出继承了波动溢出的大多数特征,表明方差Granger因果关系的存在是风险溢出的主要原因,二者的差异表明高阶矩存在的因果关系也可以导致风险溢出。     

Impact of the Fast Track Land Reform Programme (FTLRP) on agricultural production: A tobacco success story in Zimbabwe?

The study ascertained the impact of the Fast Track Land Reform Programme (FTLRP) in Zimbabwe on tobacco production. The Chow Test, Vector Error Correction Model (VECM) and the Vector Error Granger-Causality Test were applied. The results reveal that there was a structural break in tobacco sales in the year 2000. Furthermore, in the long-run, area under tobacco production had a positive impact whilst number of tobacco producers had a negative impact on tobacco sold pre-FTLRP. Post-FTLRP, area of tobacco and number of tobacco producers had negative impact. In addition, the FTLRP induced an 8.94 % increase in the speed of adjustment in correcting the long-run equilibrium in tobacco sales. In the short-run, the FTLRP caused a percentage increase in the area of tobacco production and number of tobacco producers to induce a 0.65 % and 0.76 % increase in the tobacco sales, respectively. Area of tobacco production and number of tobacco producers Granger-caused tobacco sales in the pre-FTLRP period. Post-FTLRP, the number of tobacco growers Granger-caused tobacco sales. It is concluded that the FTLRP had an impact on tobacco sales, mainly through the number of tobacco growers. The study recommends the specialisation and training of the new farmers to improve productivity.     

The long breadth of cities: revisiting worldwide urbanization patterns, 1950–2030

ABSTRACT

A comparative analysis of population dynamics worldwide contributes to profile distinctive demographic and economic trajectories of urban growth, discriminating processes of settlement concentration or dispersion under sequential cycles of urbanization. However, a wide-ranging characterization of urban cycles based on demographic dynamics worldwide is still missing. The present work is aimed at filling such a gap analysing long-term changes (1950–2030) in annual population growth rate of 1691 urban agglomerations with more than 300,000 inhabitants in 74 world countries. Results of this study indicate that metropolitan growth worldwide was associated with largely variable rates of population growth, highly positive before 2000 and progressively reducing over recent decades. Despite important differences at continental (and country) scale, demographic expansion of urban agglomerations showed two contrasting phases with a break point in the 1980s denoting a progressive reduction in spatial heterogeneity of population growth rates and a moderate slowdown in demographic dynamics. Intensity of urban expansion and spatial heterogeneity in population growth rates across metropolitan agglomerations evidences a trade-off between fast and slow demographic dynamics. These findings can be better understood to support theories of sequential city growth, making a suitable contribution to policy making, especially in countries where urban population is expanding more rapidly.     

浅析电子喷油器常用的检测方法

气车电控汽油喷射系统已经成为汽油车的标准配置。文章介绍了电子喷油器的常见故障、产生的原因及检测方法。     

Labour market recruiting with intermediaries

We consider a Rothschild–Stiglitz–Spence labour market model and employ a centralised mechanism to coordinate the efficient matching of workers to firms. This mechanism can be thought of as operated by a recruitment agency, an employment office or head hunter. In a centralised descending-bid, multi-item procurement auction, workers submit wage-bids for each job and are assigned stable jobs as equilibrium outcome. We compare this outcome to independent, sequential hiring by firms and conclude that, in general, a stable assignment can only be implemented if firms coordinate to some extent.      

对基于价值无差异的资产定价模型的实证检验——兼解释股权高溢价之谜

陈小悦和孙力强（2007）在价值无差异的基础上建立了一套全新的定价模型,本文采用股票市场的数据对该模型进行了实证检验,模型检验的同时也是对股权溢价之谜进行解释。研究结果表明,本文的定价模型在美国、中国内地和中国香港三个市场的检验都取得了良好的效果,即市场风险溢价均值都向模型的理论值收敛,实际风险溢价与理论值差异很小且不显著,采用该模型可以准确地描述股票市场组合收益率与风险的关系,并对股权溢价之谜做出合理的解释。