Therefore , more challenges have arisen for query optimization in database grid than traditional distributed database . following this observation , the design of a query optimizer in dartgrid ii is presented , and a heuristic , dynamic and parallel query optimization approach to processing query in database grid is proposed . a set of semantic tools supporting relational database integration and semantic - based information browsing has also been implemented to realize the above vision 克服数据库网格特性所带来的困难需要为数据库网格提供全局一致的数据表达模式各结点数据模式到全局模式之间的映射方法各结点之间负载平衡和结点动态加入和退出系统的控制策略数据库网格查询优化器结构设计以及一整套适合数据库网格的查询优化算法。
Then , nap300 and 75 were fused in a similar way to phba gene encoding 3 - ketothiolase for a direct comparison . the result indicated that the two promoter ' s expression efficiency reached a peak at the same developmental stage of tobacco , which means they have the advantage of being used simultaneously for expressing different foreign genes in plant 将nap300 、 7s分别与phba基因(编码3 -酮硫裂解酶)相连，在相似表达环境中对二者功能进行比较，发现两个启动子表达模式基本相同并在同一时期达到活性高峰，因此nap300可用于改善phb合成基因在植物体内的表达调控。
This suggests that mxmybl represents a single copy gene in the genome of mains xiaojinensis . 8 expression pattern was analysed by northern blot and rt - pcr . the results showed that mxmybl mrna was expressed in root and leaf and it was strengthened expression by the treatment of fe - deficiency for three days in roots especially 8 、 northcm杂交结合rtpcr的方法对mxmybl基因在小金海棠中的表达模式进行了分析，结果如下： mxmyb在根系和叶片中均表达，缺铁处理可以加强mxmybl在根系中的表达，尤其是缺铁3天的根系表达量最强。
The results demonstrated that the expression of grp78 and grp94 was in a time specific pattern . high levels of grp78 were present in early embryo stage , and were decreased during the fetal period , increased gradually during postnatal development , and reached adult mouse after one week . but the expression of grp94 was initially observed in low levels , and raised gradually along with the development process until the later stage 结果1 .小鼠脑发育过程中分子伴侣g刊阶8 、 g刊四4的表达呈现出时间顺序性，而且二者的表达模式不同: gr即8胚胎早期表达较高，胚胎发育末期逐渐下降，出生后逐渐升高，至生后一周时达到成年鼠的水平，而‘ gr即4在发育的早期表达水平较低，发育中期逐渐升高，出生时达到高峰，出生后一直维持在较高的水平。
In order to meet this challenge , systematic and comprehensive technology needs to be developed to explore changes of gene expression profile , the functions of gene products as well as their interactions . hi this study , we reported the application of restriction display pcr ( rd - pcr ) technology to prepare large number of cdna fragments of s . cerevisiae . the reclaimed fragments were cloned into vectors to construct a cdna library 接下来的工作就是阐明酵母的基因表达模式及其基因产物的功能，为了使这项工作进行得更加顺利，必须寻找一种既系统又全面的方法，来解释酵母细胞中基因表达的模式和产物的功能以及产物之间的相互作用。
The purposes of this project were to further analyze the characteristics of their iron efficiency under iron stress , to study the physiological and molecular mechanisms of iron efficiency under iron deficiency in c . junos and m . xiaojinensis , and to analyze the spatial expression model of fcr ( ferric chelate reductase ) gene under iron stress with the hope to cast a new light on iron stress tolerance on the molecular level , to lay solid foundations for cloning fcr gene in c . junos and m . xiaojinensis , and to provide some basic data for creating new rootstocks with excellent complex characters and iron efficiency 本研究通过进一步分析香橙和小金海棠的耐缺铁特性，研究它们耐缺铁的生理原因和分子基础，并通过分析三价铁螯合物还原酶基因的空间表达模式，从分子水平上去探讨植物耐缺铁的原因，为从香橙和小金海棠中克隆三价铁螯合物还原酶基因奠定基础，并为人工创造耐缺铁的果树砧木提供基础研究数据。
Fluorometric and histochemical assay of gus activity showed that this approximate 300bp dna fragment was sufficient to direct seed - specific gene expression and the two substitution mutations in b - box led to a slight decrease in the promoter ' s expression efficiency and almost had no effect on its temporal and spatial expression pattern 尽管b盒作为高度保守区在种子特异性表达中起重要作用，位于此处的两个碱基替代型突变并未使nap300的活性明显降低，对启动子的时空表达模式也无明显影响。
