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排序方式: 共有866条查询结果,搜索用时 15 毫秒
861.
862.
Campana S Mangano V Blustin AJ Brown P Burrows DN Chincarini G Cummings JR Cusumano G Della Valle M Malesani D Mészáros P Nousek JA Page M Sakamoto T Waxman E Zhang B Dai ZG Gehrels N Immler S Marshall FE Mason KO Moretti A O'Brien PT Osborne JP Page KL Romano P Roming PW Tagliaferri G Cominsky LR Giommi P Godet O Kennea JA Krimm H Angelini L Barthelmy SD Boyd PT Palmer DM Wells AA White NE 《Nature》2006,442(7106):1008-1010
Although the link between long gamma-ray bursts (GRBs) and supernovae has been established, hitherto there have been no observations of the beginning of a supernova explosion and its intimate link to a GRB. In particular, we do not know how the jet that defines a gamma-ray burst emerges from the star's surface, nor how a GRB progenitor explodes. Here we report observations of the relatively nearby GRB 060218 (ref. 5) and its connection to supernova SN 2006aj (ref. 6). In addition to the classical non-thermal emission, GRB 060218 shows a thermal component in its X-ray spectrum, which cools and shifts into the optical/ultraviolet band as time passes. We interpret these features as arising from the break-out of a shock wave driven by a mildly relativistic shell into the dense wind surrounding the progenitor. We have caught a supernova in the act of exploding, directly observing the shock break-out, which indicates that the GRB progenitor was a Wolf-Rayet star. 相似文献
863.
Schawinski K Khochfar S Kaviraj S Yi SK Boselli A Barlow T Conrow T Forster K Friedman PG Martin DC Morrissey P Neff S Schiminovich D Seibert M Small T Wyder TK Bianchi L Donas J Heckman T Lee YW Madore B Milliard B Rich RM Szalay A 《Nature》2006,442(7105):888-891
Detailed high-resolution observations of the innermost regions of nearby galaxies have revealed the presence of supermassive black holes. These black holes may interact with their host galaxies by means of 'feedback' in the form of energy and material jets; this feedback affects the evolution of the host and gives rise to observed relations between the black hole and the host. Here we report observations of the ultraviolet emissions of massive early-type galaxies. We derive an empirical relation for a critical black-hole mass (as a function of velocity dispersion) above which the outflows from these black holes suppress star formation in their hosts by heating and expelling all available cold gas. Supermassive black holes are negligible in mass compared to their hosts but nevertheless seem to play a critical role in the star formation history of galaxies. 相似文献
864.
Scherer SE Muzny DM Buhay CJ Chen R Cree A Ding Y Dugan-Rocha S Gill R Gunaratne P Harris RA Hawes AC Hernandez J Hodgson AV Hume J Jackson A Khan ZM Kovar-Smith C Lewis LR Lozado RJ Metzker ML Milosavljevic A Miner GR Montgomery KT Morgan MB Nazareth LV Scott G Sodergren E Song XZ Steffen D Lovering RC Wheeler DA Worley KC Yuan Y Zhang Z Adams CQ Ansari-Lari MA Ayele M Brown MJ Chen G Chen Z Clerc-Blankenburg KP Davis C Delgado O Dinh HH Draper H Gonzalez-Garay ML Havlak P Jackson LR Jacob LS 《Nature》2006,440(7082):346-351
Human chromosome 12 contains more than 1,400 coding genes and 487 loci that have been directly implicated in human disease. The q arm of chromosome 12 contains one of the largest blocks of linkage disequilibrium found in the human genome. Here we present the finished sequence of human chromosome 12, which has been finished to high quality and spans approximately 132 megabases, representing approximately 4.5% of the human genome. Alignment of the human chromosome 12 sequence across vertebrates reveals the origin of individual segments in chicken, and a unique history of rearrangement through rodent and primate lineages. The rate of base substitutions in recent evolutionary history shows an overall slowing in hominids compared with primates and rodents. 相似文献
865.
Okada A Charron F Morin S Shin DS Wong K Fabre PJ Tessier-Lavigne M McConnell SK 《Nature》2006,444(7117):369-373
In the spinal cord, sonic hedgehog (Shh) is secreted by the floor plate to control the generation of distinct classes of ventral neurons along the dorsoventral axis. Genetic and in vitro studies have shown that Shh also later acts as a midline-derived chemoattractant for commissural axons. However, the receptor(s) responsible for Shh attraction remain unknown. Here we show that two Robo-related proteins, Boc and Cdon, bind specifically to Shh and are therefore candidate receptors for the action of Shh as an axon guidance ligand. Boc is expressed by commissural neurons, and targeted disruption of Boc in mouse results in the misguidance of commissural axons towards the floor plate. RNA-interference-mediated knockdown of Boc impairs the ability of rat commissural axons to turn towards an ectopic source of Shh in vitro. Taken together, these data suggest that Boc is essential as a receptor for Shh in commissural axon guidance. 相似文献
866.
Bin Zhang Se Hun Chung Susan Barker Duncan Craig Roger J.Narayan Jie Huang 《自然科学进展(英文版)》2021,31(2):180-191
There has been increasing interest over recent years in the application of three-dimensional(3 D) printing technologies in the biomedical field. One such method is Direct Ink Writing(DIW); this approach has the potential advantage of allowing room-temperature deposition of materials, presented as an ink, to build complex architectures. DIW offers the ability to process biomaterials containing temperature-sensitive components. Due to the fabrication principles of DIW, there are specific rheologic... 相似文献