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排序方式: 共有213条查询结果,搜索用时 78 毫秒
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The ascendent theory that unifies the Earth Sciences is Plate Tectonics,a regime which is unique to Earth.Other convectively active,solid silicate bodies of our... 相似文献
46.
RNA polymerase is poised for activation across the genome 总被引:2,自引:0,他引:2
Muse GW Gilchrist DA Nechaev S Shah R Parker JS Grissom SF Zeitlinger J Adelman K 《Nature genetics》2007,39(12):1507-1511
47.
Experience-dependent plasticity of dendritic spines in the developing rat barrel cortex in vivo 总被引:14,自引:0,他引:14
Do changes in neuronal structure underlie cortical plasticity? Here we used time-lapse two-photon microscopy of pyramidal neurons in layer 2/3 of developing rat barrel cortex to image the structural dynamics of dendritic spines and filopodia. We found that these protrusions were highly motile: spines and filopodia appeared, disappeared or changed shape over tens of minutes. To test whether sensory experience drives this motility we trimmed whiskers one to three days before imaging. Sensory deprivation markedly (approximately 40%) reduced protrusive motility in deprived regions of the barrel cortex during a critical period around postnatal days (P)11-13, but had no effect in younger (P8-10) or older (P14-16) animals. Unexpectedly, whisker trimming did not change the density, length or shape of spines and filopodia. However, sensory deprivation during the critical period degraded the tuning of layer 2/3 receptive fields. Thus sensory experience drives structural plasticity in dendrites, which may underlie the reorganization of neural circuits. 相似文献
48.
Genome sequencing in microfabricated high-density picolitre reactors 总被引:21,自引:0,他引:21
Margulies M Egholm M Altman WE Attiya S Bader JS Bemben LA Berka J Braverman MS Chen YJ Chen Z Dewell SB Du L Fierro JM Gomes XV Godwin BC He W Helgesen S Ho CH Ho CH Irzyk GP Jando SC Alenquer ML Jarvie TP Jirage KB Kim JB Knight JR Lanza JR Leamon JH Lefkowitz SM Lei M Li J Lohman KL Lu H Makhijani VB McDade KE McKenna MP Myers EW Nickerson E Nobile JR Plant R Puc BP Ronan MT Roth GT Sarkis GJ Simons JF Simpson JW Srinivasan M Tartaro KR Tomasz A Vogt KA Volkmer GA Wang SH Wang Y Weiner MP 《Nature》2005,437(7057):376-380
The proliferation of large-scale DNA-sequencing projects in recent years has driven a search for alternative methods to reduce time and cost. Here we describe a scalable, highly parallel sequencing system with raw throughput significantly greater than that of state-of-the-art capillary electrophoresis instruments. The apparatus uses a novel fibre-optic slide of individual wells and is able to sequence 25 million bases, at 99% or better accuracy, in one four-hour run. To achieve an approximately 100-fold increase in throughput over current Sanger sequencing technology, we have developed an emulsion method for DNA amplification and an instrument for sequencing by synthesis using a pyrosequencing protocol optimized for solid support and picolitre-scale volumes. Here we show the utility, throughput, accuracy and robustness of this system by shotgun sequencing and de novo assembly of the Mycoplasma genitalium genome with 96% coverage at 99.96% accuracy in one run of the machine. 相似文献
49.
Joel S. Schwartz 《Annals of science》2013,70(6):631-637
While Charles Darwin wrote his Observations on South America, he often sought the advice and help of other scientists in solving specific problems. Three letters that the Cambridge geologist and mathematician William Hopkins wrote to Darwin exemplify such aid. In these letters Hopkins was able to show Darwin how he could calculate the position of the sedimentary beds on the Chonos Archipelago, which Darwin had visited. In his first letter Hopkins sent a solution, part of which eluded Darwin. Darwin's letters to Hopkins have not yet been found, but two additional letters gave Darwin the solution he was looking for. 相似文献
50.
Andrew Brighouse Joel B. Dacks Mark C. Field 《Cellular and molecular life sciences : CMLS》2010,67(20):3449-3465
Spectacular increases in the quantity of sequence data genome have facilitated major advances in eukaryotic comparative genomics.
By exploiting homology with classical model organisms, this makes possible predictions of pathways and cellular functions
currently impossible to address in intractable organisms. Echoing realization that core metabolic processes were established
very early following evolution of life on earth, it is now emerging that many eukaryotic cellular features, including the
endomembrane system, are ancient and organized around near-universal principles. Rab proteins are key mediators of vesicle
transport and specificity, and via the presence of multiple paralogues, alterations in interaction specificity and modification
of pathways, contribute greatly to the evolution of complexity of membrane transport. Understanding system-level contributions
of Rab proteins to evolutionary history provides insight into the multiple processes sculpting cellular transport pathways
and the exciting challenges that we face in delving further into the origins of membrane trafficking specificity. 相似文献