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1.
The aim of this paper is to evaluate the role that agglomeration may have on vertical boundaries in exchanges associated with high transaction costs. Transaction cost economics identifies the presence of specific assets in stages of the value chain as the main driver of vertical integration. However, under the trustworthy and shared social milieu that agglomerated spaces may confer, neighboring firms can enjoy lower opportunism risk and communication costs. Therefore, we assume that even in the presence of specific assets, physically proximate firms are more likely to remain specialized and establish market exchanges. Empirical evidence in 10,186 establishments from the Spanish meat industry confirms these hypotheses, although it is found that the moderating role of agglomeration in the relationship between asset specificity and vertical integration has a limited geographical reach. 相似文献
2.
转基因玉米转化体特异性寡核苷酸芯片测试方法的研制 总被引：2，自引：0，他引：2
根据7种转基因玉米Bt11、Bt176、Mon810、Mon863、TC1507、GA21和NK603的重组DNA结构,利用Primer premier 5.0引物设计软件分别设计转化体特异性引物,优化PCR反应条件,对引物特异性及灵敏度进行验证。结果表明,所设计引物特异性强,灵敏度达0.1%。在植物基因组与外源基因的连接区域,利用Primer premier 5.0和Oligo 6.0软件分别设计和筛选7种转基因玉米40mer oligo转化体特异性探针,制备转基因玉米的寡核苷酸芯片,并对芯片检测的特异性、重复性及检测灵敏度进行检验。证明所设计探针特异性强,灵敏度达0.01%。与PCR检测方法相比,基因芯片检测法灵敏度高、特异性强,可有效检测及鉴定多种转基因玉米,大大提高检测的准确率和效率。 相似文献
3.
Piezoelectric material was used to establish a single input/single output (SISO) model of a lifting surface with distributed piezoelectric actuators and piezoelectric sensors. The flutter equations and state space equations of piezoelectric laminated structures were also derived. MATLAB, NASTRAN and other software programs compiled by the authors also were used to analyze the flutter and dynamic characteristics. The stability of the closed loop was analyzed for the SISO. The result indicates that the control law can be employed for flutter suppression. 相似文献
4.
The development of enterprise application results in many info islands alone which have been a restricted factor for the enterprise to share information. This paper analyzes the current conditions and methods of enterprise application integration, and proposes an application integration frame based on middleware technique. This frame can overcome the shortcoming of traditional integration methods and resolve the cross-platform problem among the enterprise applications efficiently, and it also provides a way for the enterprise to develop E-commerce. 相似文献
5.
《Netherlands Journal of Sea Research》1990,25(1-2):267-278
Herring larvae hatching from spawning sites around the Scottish coast are dispersed by water currents during the weeks following hatching. Hydrographic data, observations on the distribution of caesium-137 and measurements of current velocities by moored meters and drifting buoys, suggest that larvae from offshore spawning sites around the north of Scotland should be more rapidly dispersed than those hatching in inshore areas. This has been confirmed by direct observations on the advection of herring larvae in different regions of the north western North Sea. The conclusion is that larvae hatching in inshore areas, especially in the Moray Firth, are most likely to contribute to nearby juvenile populations, whereas larvae from offshore spawning sites should be widely dispersed over the North Sea.Tagging and parasitology investigations have shown that adult herring spawning in the north-western North Sea have been widely dispersed in the North Sea and adjacent waters as juveniles (six months — one and a half years old). However, a high proportion of adult fish caught at inshore spawning sites and in the Moray Firth were found to have been recruited from more local areas. Taken together with the observations on larval drift, these observations suggest that the stock structure of herring in the northern North Sea may in part be a consequence of the physical oceanography of the area. 相似文献
6.
Rice improvement is based to an increasing extent on ever-sharper genetic analysis to the detriment of classical breeding,
which is disappearing. Analytical genetics are very promising, but they cannot replace integrated and finalized breeding.
Little attention has been paid to improving participatory rice breeding methods for subsequent integration into sustainable
cropping systems. Special methodological initiatives are required to ensure the success of this breeding-agronomy integration.
This integration of inexpensive breeding methods has increased the biodiversity of rice: low temperature and drought tolerant
upland rice varieties for mountain areas, and polyvalent varieties, which have the ability to grow in both rainfed or irrigated
conditions, they are perfectly adapted to improved cropping systems and to beneficiaries’ needs and preferences. These preliminary
results on this integration demonstrate that the present approach is relevant. 相似文献
7.
Leonie Rooke Susan H. Steele Pilar Barcelo Peter R. Shewry Paul A. Lazzeri 《Euphytica》2003,129(3):301-309
Transgene integration, inheritance and expression were studied in six transgenic wheat (Triticum aestivum) lines produced by co-bombardment with two plasmids containing marker genes and genes encoding HMW subunits of wheat glutenin,
respectively. Transgene insertion number ranged from 1 to approximately 15. Within a transgenic locus the majority of plasmid
copies were found at dispersed genomic sites separated by intervening DNA. However, evidence was obtained for the arrangement
of introduced plasmid copies as concatamers and for plasmid truncation and rearrangement. Transgenes were frequently located
in genetically unlinked chromosome sites, resulting in independent segregation of loci among progeny. In two lines this gave
rise to progeny containing only the gene of interest. Transgenes were inherited in the T1 generation as a dominant trait although Mendelian segregation ratios were not always observed. No evidence of co-suppression
of
endogenous HMW subunits was observed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
The pattern and level of separation among ethnic groups continues to change, and there are certainly more mixed neighborhoods both in cities and suburbs than two decades ago. The immigration flows of the past decade have substantially altered the ethnic mix and neighborhood mixing. In addition, multi‐ethnic individuals themselves are altering the level of mixing among racial and ethnic groups. The research in this article shows that those who report themselves of more than one race have high levels of residential integration both in central cities and suburbs. These residential patterns can be interpreted as further evidence of tentative steps to a society in which race per se is less critical in residential patterning. The level of integration, for Asian mixed and black mixed is different and substantially higher than for those who report one race alone. The research in this article builds on previous aggregate studies of mixed‐race individuals to show substantial patterns of integration in California's metropolitan areas. 相似文献
9.
新农村建设背景下城乡一体化发展的路径审视 总被引：1，自引：0，他引：1
推进城乡一体化发展是当前新农村建设的重要任务之一。当前,城乡一体化发展中存在着一些制约因素。户籍制度制约了城乡一体化,城乡一体化规划与土地使用缺乏规范,城乡二元分割格局还没有彻底打破,城市化水平偏低致使城市吸纳力不强,农村集体土地流转的法律规定不完善,城市边缘区的科学规划水平不高。为此,应积极推进户籍制度改革,优化城乡产业结构和布局,建立城乡统一市场,积极推进制度创新,正确处理政府与市场的关系,加快中心城市的现代化,推进农村地区的城镇化,推进城乡经济的高度发展,加快城乡生态一体化建设。 相似文献
10.
Jiaping Wu 《Asia Pacific viewpoint》2008,49(2):244-253
Abstract: With the increase of global integration, the peri‐urban area (PUA) of megacities in Asia has become a favourite destination for foreign direct investment (FDI). This paper uses the PUA of Shanghai as a case study to investigate the impact of global forces on the urban expansion of the city, and the link between urban growth and sustainable development in this mega‐urban context. Shanghai has grown impressively during the past two decades in terms of economic and physical transformation. Much of this transformation has rested on the unbridled exploitation of land and other environmental resources in its peri‐urban area. This is characterised by the designation of development zones and the concentration of manufacturing FDI, resulting in dispersed growth and environmental degradation. The disruption of the physical environment, combined with the concentration of the urban poor in these areas (in particular ‘temporary migrants’), has turned the PUA into a potential crisis point threatening the social and economic development of the city. 相似文献
11.
The method to polygon' intersection is applied in computational geometry, computer graphics, GIS, evaluation of geo-hazards and civil engineering. Based on the node state of polygon, the authors propose the method and algorithm of polygon' intersection, the key to which is node operation. This method's concept is simple; and it is easy to computer program's implementation. It avoids to singular problem of Boolean Operation, and is easy to solve the problem of overlapping side and sides intersecting in node of polygon. For the arbitrary way of intersecting of arbitrary solid polygon, this method is accurate and general. 相似文献
12.
13.
菜地硝酸盐累积现状、影响及其解决出路 总被引：2，自引：1，他引：1
蔬菜是人们日常生活中不可缺少的副食品,但其是一种易富集硝酸盐的作物,而蔬菜体内硝酸盐的累积对人体健康有危害作用。大量研究表明,氮肥过量施用造成土壤硝酸盐积累是蔬菜硝酸盐含量超标的主要原因,各国学者曾先后采用不同的方法,从不同角度来研究硝酸盐产生的途径及解决办法,但大多研究比较分散,本文总结了菜地硝酸盐累积的现状以及对地下水、蔬菜、大气、人体的影响,并就此提出了选育低硝酸盐累积量的蔬菜品种、科学的栽培管理措施等解决方法。 相似文献
14.
Alan H. Schulman 《Euphytica》2007,158(3):313-321
Molecular markers play an essential role today in all aspects of plant breeding, ranging from the identification of genes
responsible for desired traits to the management of backcrossing programs. The emergence of marker systems has, for the last
30 years, closely tracked developments in biochemistry and molecular biology. Following the demonstration that retrotransposons
are ubiquitous, active, and abundant in plant genomes, markers were developed that are based on the insertional polymorphism
they create upon replication. They virtually all exploit the joint that is formed, during retrotransposon integration, between
genomic DNA and the long terminal repeats at either end of retrotransposon. The various retrotransposon marker systems differ
in the nature of the second primer used in the amplification reactions. All except one of these marker methods is dominant
(RBIP is co-dominant). Hence, the availability of effective means to generate doubled haploid populations through gametophytic
embryogenesis is valuable for the efficient use of these markers. Over the last eight years, retrotransposon-based markers
have been developed for crop species and trees across the plant kingdom, as well as for fungi and insects. Many retrotransposons
features make them appealing as the basis of molecular marker systems. They are usually dispersed throughout the genome and
produce large genetic changes at the point of insertion that can be detected with family-specific amplification primers. The
ancestral state of a retrotransposon insertion is known, and subsequent changes at the locus are not subject to homoplasy.
Retrotransposon markers are useful in accelerating backcrossing programs, tagging genes of interest, tracking germplasm, verifying
and producing pedigrees, and examining crop evolution. 相似文献
15.
《Soil Technology》1991,4(4):319-327
Because of the very low soil solution ionic strengths in highly weathered soils, clay particles can be readily dispersed under the impact of raindrops. The clay fraction of many soils is dispersible under the combined effects of mechanical disturbance and low electrolyte concentration. This clay dispersion results in fine particle segregation at the soil surface, with clay particles moving into and blocking soil pores resulting in the formation of a highly impervious crust which reduces infiltration. Because the clay is dispersed, the particles usually orient themselves in a laminar fashion as they settle. As a result, runoff is substantially increased, giving rise to soil erosion. The crusts formed in this manner often have very high strengths which prevent or substantially reduce crop emergence. The formation of such crusts can be prevented by the application of relatively low rates of by-product gypsum such as phosphogypsum on the soil surface which produces sufficient electrolyte in solution during raindrop impact to maintain the clay particles in a flocculated condition. The results of a number of experiments in which different soils were treated with phosphogypsum are discussed to illustrate the effects of electrolyte concentration, level of sodium and other factors on the formation of surface crusts and the consequent runoff and erosion. As a result of the application of phosphogypsum to the soil surface, a laminar orientation of clay particles at the surface is prevented, which allows a much greater proportion of the rainfall to enter the soil. Any crusts formed are thus much weaker and do not reduce seedling emergence. This type of crust formation can also be prevented by reducing raindrop impact through the use of mulches. This phenomenon occurs on many soils not normally considered to suffer from chemically-induced physical problems, which points to the importance of considering chemical as well as physical processes in the evaluation of potential runoff and erosion. 相似文献
16.
DNA-RAPDs detect genetic variation and paternity in Malus 总被引：1，自引：0，他引：1
Summary DNA amplification fingerprinting using arbitrary primer(s) was applied to the identification of Malus species. Highly variable DNA fragment patterns were clearly detected by polyacrylamide gel electrophoresis of the amplified extension products, although three sports of Delicious exhibited the same fingerprint as the original cultivar. The fingerprinting of two triploid apple cultivars suggested that the parent contributing the 2n gamete was the female. We applied this fingerprinting to paternity analysis of an apple cultivar of which the pollen parent was unknown. By using 5 arbitrary primers and RFLP analysis of the amplified products, one cultivar was singled out for paternity among six putative candidates. 相似文献
17.
By analyzing the main issues in tobacco industrial information system constructing in the past time, it is determined that CIMS technique used for implementing tobacco industrial integrated management. An integrated support-guarantee system based on tobacco industrial CIMS integration pattern is presented for tobacco industrial CIMS, which consists of industrial integration support system for data integrating, application services integrating and business processes integrating of industrial CIMS, and industrial integration guarantee system for supporting system running safely in high efficiency by providing guaranteed mechanism of standardization system and security system. In the practical application, the content of CIMS is extended from traditional manufacturing factory to total tobacco industry, And industrial integration dada center is the support-guarantee system which offers three functions of standardization management system, information security management system, and industrial integration support system, provide the service for tobacco industrial integrated management. 相似文献
18.
19.
利用过氧化物同工酶对云南红壤区的几种紫花苜蓿杂交组合进行初步筛选,以期为该地区紫花苜蓿的引种驯化工作提供理论依据,从而获得有价值的杂交后代。对各杂交组合亲本及其后代的过氧化物酶酶谱表现分析结果表明,杂交过程中发生了过氧化物酶位点的遗传重组,从而在F1代产生了酶谱表现与亲本不同和相同的两类个体;亲本及其后代有3条共有酶带;亲本中,爱博、射手2个栽培种比野生种和AC-3的酶谱表现好;过氧化物酶的遗传背景差异较大的杂交组合有可能通过遗传物质的交流产生有利的性状重组,对其进行筛选,可获得有价值的育种材料。 相似文献
20.
转mCherry基因水稻的遗传分析及T-DNA整合位点的研究 总被引：1，自引：0，他引：1
为了建立转基因水稻的高通量遗传分析系统,本研究以粳稻成熟胚诱导的愈伤组织为受体材料,潮霉素磷酸转移酶(HPT)为抗性筛选标记,通过农杆菌介导的方法将红色荧光蛋白基因mCherry导入水稻。在水稻转化愈伤组织、转化植株(T0)和转基因后代(T1)均检测到红色荧光,证实mCherry在转基因水稻中稳定表达。139个独立转化株系的遗传分析表明,mCherry在转基因后代表现多种遗传模式,54%的转基因株系呈单位点遗传。TAIL-PCR进一步验证转基因整合到水稻基因组。根据T-DNA整合位点DNA序列分析结果,T-DNA左边界发生碱基缺失、增加和替换,右边界只发生碱基缺失,说明左边界比右边界有更多的碱基变异类型。此外,对T2代植株mCherry和HPT的转录水平进行实时定量逆转录PCR分析,结果表明,mCherry和HPT转录水平因T-DNA在水稻基因组中的整合位置而变化,表现位置效应。本研究在mCherry荧光蛋白和其它相关方法的基础上,为转基因水稻遗传及分子分析建立了一个高效的流程体系。 相似文献