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991.
为解决既有建构筑物地基基础加固工程所面临的施工条件有限、工期紧张以及沉降控制严格等问题,基于南京某复杂运营供水结构加固工程,提出了一种后注浆静压复合桩(PSCP)加固技术.采用数值分析的方法,结合现场观测数据,对加固过程和长期沉降进行评价,并对比分析了桩长、桩径、反力梁高度等参数对加固效果的影响.结果表明:PSCP桩具... 相似文献
992.
We investigated the pathophysiology of neurofibromatosis-1 (NF1) in Drosophila melanogaster by inactivation or overexpression of the NF1 gene. NF1 gene mutants had shortened life spans and increased vulnerability to heat and oxidative stress in association with reduced mitochondrial respiration and elevated reactive oxygen species (ROS) production. Flies overexpressing NF1 had increased life spans, improved reproductive fitness, increased resistance to oxidative and heat stress in association with increased mitochondrial respiration and a 60% reduction in ROS production. These phenotypic effects proved to be modulated by the adenylyl cyclase/cyclic AMP (cAMP)/protein kinase A pathway, not the Ras/Raf pathway. Treatment of wild-type D. melanogaster with cAMP analogs increased their life span, and treatment of NF1 mutants with metalloporphyrin catalytic antioxidant compounds restored their life span. Thus, neurofibromin regulates longevity and stress resistance through cAMP regulation of mitochondrial respiration and ROS production, and NF1 may be treatable using catalytic antioxidants. 相似文献
993.
He XC Yin T Grindley JC Tian Q Sato T Tao WA Dirisina R Porter-Westpfahl KS Hembree M Johnson T Wiedemann LM Barrett TA Hood L Wu H Li L 《Nature genetics》2007,39(2):189-198
Intestinal polyposis, a precancerous neoplasia, results primarily from an abnormal increase in the number of crypts, which contain intestinal stem cells (ISCs). In mice, widespread deletion of the tumor suppressor Phosphatase and tensin homolog (PTEN) generates hamartomatous intestinal polyps with epithelial and stromal involvement. Using this model, we have established the relationship between stem cells and polyp and tumor formation. PTEN helps govern the proliferation rate and number of ISCs and loss of PTEN results in an excess of ISCs. In PTEN-deficient mice, excess ISCs initiate de novo crypt formation and crypt fission, recapitulating crypt production in fetal and neonatal intestine. The PTEN-Akt pathway probably governs stem cell activation by helping control nuclear localization of the Wnt pathway effector beta-catenin. Akt phosphorylates beta-catenin at Ser552, resulting in a nuclear-localized form in ISCs. Our observations show that intestinal polyposis is initiated by PTEN-deficient ISCs that undergo excessive proliferation driven by Akt activation and nuclear localization of beta-catenin. 相似文献
994.
Aquatic ecosystems require ecological water allocation to prevent from being damaged by natural disasters and undue exploitation. This paper discusses and estimates the ecological water requirements (EWRs) of typical areas in the Huaihe Basin to determine rational allocations of water resources and pro- mote regional improvements of the ecological environment. The main river course, including Hongze Lake and Nansi Lake, was selected as the study subject. Calculational methods for the river and lake EWRs were based on the reasonableness of the results and data availability. The monthly guarantee rate method was used to calculate monthly, flood period, non-flood period, and annual EWRs for the main river course and the main tributaries at two different guarantee rates. The minimum water level method was used to calculate annual EWRs for Hongze Lake and the upper and lower Nansi Lake of 1.521×10^9 m^3, 0.637×10^9 m^3, and 0.306×10^9 m^3. The results were used to evaluate the rationality of the quantity of water resources allocated to ecological uses in the Huaihe Basin during 1998-2003. The result shows that the present water resource allocations in the Huaihe Basin cannot satisfy the basic ecological requirements for some years, especially years with less precipitation. 相似文献
995.
术语的命名有损于汉语环境吗? 总被引:1,自引:1,他引:0
术语的命名应与汉语环境相适应乃国人之共识,原无可非议.但制定科技术语除应考虑其与汉语环境相适外,还应遵循科学性、系统性、单义性、国际性、简明性、习惯性(约定俗成)等多项原则,此外还应考虑到修辞、音节等各个方面,如果片面强调其中之一而不顾其他,必将局限于一隅而忽视全局,给科技术语工作带来不利.<术语命名须应对汉语环境>[1](以下简称<汉语环境>)一文中对防火墙、以太网等术语提出的异议恰好表明了该文中的众多论点是不够全面的. 相似文献
996.
Application of rough graph in relationship mining 总被引:1,自引:0,他引:1
Based on the definition of class shortest path in weighted rough graph,class shortest path algorithm in weighted rough graph is presented,which extends classical shortest path algorithm.The application in relationship mining shows effectiveness of it. 相似文献
997.
Tong Kai Guo Jianning Chinese Academy of Space Technology P. O. Box Beijing P. R. China 《系统工程与电子技术(英文版)》1993,(3)
The paper describes the development of mobile communication first and then points out that it is necessary for China to develop satellite mobile communication after comparing the cellular mobile communication with the satellite mobile communication. After comparing the geostationary satellite system with the low earth orbit satellite mobile communication system, as well as the single beam with the multi-beams, both used in satellite mobile communication, we suggest that China, according to its economic status and level of satellite technology, should develop a geostationary multi-beams satellite for its domestic mobile communication. 相似文献
998.
999.
聚落演变中的社会心理研究 总被引:1,自引:0,他引:1
城市与乡村是聚落存在与发展的两种基本的模式.但是在乡村不断地消减,城市不断扩张的当下,城市化困境越发突出.城市人的困境并非只是经济问题、社会问题,更是自然问题与心理问题.因此,厘定聚落演变的社会心理特征,从人的主体性角度指导聚落发展的根本动力,为走出城市化困境提供哲学层面的指导. 相似文献
1000.
主要讨论了几本复杂性著作和复杂性的《涌现》专业杂志1999-2005年各期文献表现出的研究趋势,基于文献,我们认为复杂性研究存在三个重要的趋势:(1)复杂性研究的形上形下两级化趋势明显;(2)复杂性研究的科学之维与人文之维扩展趋势明显,甚至出现了艺术学科和神学领域的复杂性问题研究;(3)复杂性研究隐喻与超越隐喻的方法论两级化趋势也很明显,希望超越隐喻的呼声渐高。 相似文献