排序方式: 共有23条查询结果,搜索用时 15 毫秒
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Identification of the transforming EML4-ALK fusion gene in non-small-cell lung cancer 总被引:1,自引:0,他引:1
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Palaeovegetation. Diversity of temperate plants in east Asia 总被引:3,自引:0,他引:3
The exceptionally broad species diversity of vascular plant genera in east Asian temperate forests, compared with their sister taxa in North America, has been attributed to the greater climatic diversity of east Asia, combined with opportunities for allopatric speciation afforded by repeated fragmentation and coalescence of populations through Late Cenozoic ice-age cycles. According to Qian and Ricklefs, these opportunities occurred in east Asia because temperate forests extended across the continental shelf to link populations in China, Korea and Japan during glacial periods, whereas higher sea levels during interglacial periods isolated these regions and warmer temperatures restricted temperate taxa to disjunct refuges. However, palaeovegetation data from east Asia show that temperate forests were considerably less extensive than today during the Last Glacial Maximum, calling into question the coalescence of tree populations required by the hypothesis of Qian and Ricklefs. 相似文献
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The role of presenilin cofactors in the gamma-secretase complex 总被引:27,自引:0,他引:27
Takasugi N Tomita T Hayashi I Tsuruoka M Niimura M Takahashi Y Thinakaran G Iwatsubo T 《Nature》2003,422(6930):438-441
Mutations in presenilin genes account for the majority of the cases of the familial form of Alzheimer's disease (FAD). Presenilin is essential for gamma-secretase activity, a proteolytic activity involved in intramembrane cleavage of Notch and beta-amyloid precursor protein (betaAPP). Cleavage of betaAPP by FAD mutant presenilin results in the overproduction of highly amyloidogenic amyloid beta42 peptides. gamma-Secretase activity requires the formation of a stable, high-molecular-mass protein complex that, in addition to the endoproteolysed fragmented form of presenilin, contains essential cofactors including nicastrin, APH-1 (refs 15-18) and PEN-2 (refs 16, 19). However, the role of each protein in complex formation and the generation of enzymatic activity is unclear. Here we show that Drosophila APH-1 (Aph-1) increases the stability of Drosophila presenilin (Psn) holoprotein in the complex. Depletion of PEN-2 by RNA interference prevents endoproteolysis of presenilin and promotes stabilization of the holoprotein in both Drosophila and mammalian cells, including primary neurons. Co-expression of Drosophila Pen-2 with Aph-1 and nicastrin increases the formation of Psn fragments as well as gamma-secretase activity. Thus, APH-1 stabilizes the presenilin holoprotein in the complex, whereas PEN-2 is required for endoproteolytic processing of presenilin and conferring gamma-secretase activity to the complex. 相似文献
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Manabu Asai 《Journal of forecasting》2013,32(5):469-480
The paper considers the return and range model with dynamic conditional correlations (DCC). The paper suggests the new specifications for the asymmetric effects on log‐volatilities and dynamic correlations, combined with long‐run dependences. The new DCC model can be estimated by the quasi‐maximum likelihood method. Empirical analysis on Nikkei 225, Hang Seng and Straits Times indices shows the daily, weekly and monthly pattern of asymmetric effects. For the period including the global financial crisis, the new DCC model provides plausible one‐step‐ahead forecasts of the VaR thresholds, and yields positive economic values of switching from other DCC models. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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The Drosophila fruitless (fru) gene product Fru has been postulated to be a neural sex determination factor that directs development of the central nervous system (CNS), thereby producing male-typical courtship behaviour and inducing male-specific muscle. Male-specific Fru protein is expressed in small groups of neurons scattered throughout the CNS of male, but not female, Drosophila. Collectively, these observations suggest that Fru 'masculinizes' certain neurons, thereby establishing neural substrates for male-typical behaviour. However, specific differences between neurons resulting from the presence or absence of Fru are unknown. Previous studies have suggested that Fru might result in sexual differences in the CNS at the functional level, as no overt sexual dimorphism in CNS structure was discernible. Here we identify a subset of fru-expressing interneurons in the brain that show marked sexual dimorphism in their number and projection pattern. We also demonstrate that Fru supports the development of neurons with male-specific dendritic fields, which are programmed to die during female development as a result of the absence of Fru. Thus, Fru expression can produce a male-specific neural circuit, probably used during heterosexual courtship, by preventing cell death in identifiable neurons. 相似文献
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USHIOMasao SUGITANIYuji TANAKAManabu 《兰州理工大学学报》2005,31(3):25-31
Automationhasgivenapowerfulmeansto solvemanyissuesinproductionindustries,e.g.up efficiency,costreduction,manpowerproblems,en vironmentproblems,etc.Automatizationofthe weldingprocesseshavebeenremarkablypro gressedduringaboutthelasthalfcenturyandit wasbasedonthetechnologicaldevelopmentsof manyconstituentssuchas,sensorsandtheirappli cationsystemsforseamtrackingandadaptivecon trol,weldingrobot,weldingmaterial,weldingpow ersource,etc.Particularlyinthelastdecade, throughtheprogressofthecompute… 相似文献
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一种新的决策支持系统开发方法——层次模型法 总被引:11,自引:0,他引:11
层次模型法是我国研究的新的决策支持系统开发方法。文章介绍了层次模型法的研究背景和研究思想。层次模型也包括应用层、任务层、功能层和物理层。文章详细介绍了其独有的任务层和功能层的实现方法。最后,文章说明了基于层次模型法的某公司年度生产经营决策支持系统的设计和开发思路。层次模范法作为通用决策支持系统生成器,具有一定的理论价值和实践价值。 相似文献
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