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41.
GODFREYB Andy 《中国科学:技术科学》2010,(4)
The evolution of the microstructure and texture with strain during compression at 150℃of the magnesium alloy AZ31 has been investigated using the electron backscattered diffraction(EBSD)technique.The initial samples were chosen to have a strong basal plane texture with the crystal c-axes perpendicular to the compression direction.The EBSD data provide evidence concerning the relative activity of both{10-12}extension twinning and slip,and suggest that non-basalc+a slip is important in samples deformed to a strain of more than 0.2.The relative contributions of the twinning and the slip during deformation have been discussed based on the results above. 相似文献
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Andy Bilson 《Systemic Practice and Action Research》1997,10(2):153-177
Constructivist family therapy offers a model for the application of Maturana's theories to practice. This paper describes key concepts of a constructivist approach and draws on family therapy to provide guidelines for applying them in an organizational setting. It offers a view of the organization as a network of conversations in which change occurs through the coconstruction of new conversations which widen or change the rational domain in which a problem occurs. 相似文献
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XuePing Ji Darren Curnoe ZhenDe Bao Andy I. R. Herries David Fink YunSheng Zhu John Hellstrom Yun Luo Paul S. C. Tacon 《科学通报(英文版)》2013,58(35):4472-4485
Three-dimensional mapping and section work undertaken by us in 2008 have identified 11 stratigraphic units at Maludong site. AMS radiocarbon dating of charcoal established an accurate and internally consistent age profile for the sequence of 17.8±0.2 ka to 13.2±0.1 ka. Archaeomagnetic analysis showed changes in externally derived pedogenically enhanced material consistent with a warming in climate between the cold period of Henrich Event 1 and the Blling-AllerCd interstadial. Human remains recovered during the 1989 excavation were derived from a deposit dating to this interstadial, or between 14.3±0.3 ka and 13.5±0.1 ka. An- thropogenic features, including burnt rocks, baked sediment and thick charcoal and ash layers, were identified and examined through archaeomagnetic analysis. Two monkey fossils are described here, one of them being reassigned from Macaca robustus to M. aft'. M. assamensis. They confirm the young age of the site and also show signs of anthropogenic alteration in the form of burning. Additional human cranial remains are reported for the first time and new data are provided for some specimens described previously. A range of new features is identified that strengthen the affinities of the Maludong remains to archaic humans. The presence of this globally unique mosaic of archaic and modern features raises important questions about human evolutionary his- tory in East Asia during the Late Upper Pleistocene. 相似文献
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Northcott PA Shih DJ Peacock J Garzia L Morrissy AS Zichner T Stütz AM Korshunov A Reimand J Schumacher SE Beroukhim R Ellison DW Marshall CR Lionel AC Mack S Dubuc A Yao Y Ramaswamy V Luu B Rolider A Cavalli FM Wang X Remke M Wu X Chiu RY Chu A Chuah E Corbett RD Hoad GR Jackman SD Li Y Lo A Mungall KL Nip KM Qian JQ Raymond AG Thiessen NT Varhol RJ Birol I Moore RA Mungall AJ Holt R Kawauchi D Roussel MF Kool M Jones DT Witt H Fernandez-L A Kenney AM Wechsler-Reya RJ Dirks P Aviv T 《Nature》2012,488(7409):49-56
Medulloblastoma, the most common malignant paediatric brain tumour, is currently treated with nonspecific cytotoxic therapies including surgery, whole-brain radiation, and aggressive chemotherapy. As medulloblastoma exhibits marked intertumoural heterogeneity, with at least four distinct molecular variants, previous attempts to identify targets for therapy have been underpowered because of small samples sizes. Here we report somatic copy number aberrations (SCNAs) in 1,087 unique medulloblastomas. SCNAs are common in medulloblastoma, and are predominantly subgroup-enriched. The most common region of focal copy number gain is a tandem duplication of SNCAIP, a gene associated with Parkinson's disease, which is exquisitely restricted to Group 4α. Recurrent translocations of PVT1, including PVT1-MYC and PVT1-NDRG1, that arise through chromothripsis are restricted to Group 3. Numerous targetable SCNAs, including recurrent events targeting TGF-β signalling in Group 3, and NF-κB signalling in Group 4, suggest future avenues for rational, targeted therapy. 相似文献
45.
Paddison PJ Silva JM Conklin DS Schlabach M Li M Aruleba S Balija V O'Shaughnessy A Gnoj L Scobie K Chang K Westbrook T Cleary M Sachidanandam R McCombie WR Elledge SJ Hannon GJ 《Nature》2004,428(6981):427-431
Gene silencing by RNA interference (RNAi) in mammalian cells using small interfering RNAs (siRNAs) and short hairpin RNAs (shRNAs) has become a valuable genetic tool. Here, we report the construction and application of a shRNA expression library targeting 9,610 human and 5,563 mouse genes. This library is presently composed of about 28,000 sequence-verified shRNA expression cassettes contained within multi-functional vectors, which permit shRNA cassettes to be packaged in retroviruses, tracked in mixed cell populations by means of DNA 'bar codes', and shuttled to customized vectors by bacterial mating. In order to validate the library, we used a genetic screen designed to report defects in human proteasome function. Our results suggest that our large-scale RNAi library can be used in specific, genetic applications in mammals, and will become a valuable resource for gene analysis and discovery. 相似文献
46.
Wave acceleration of electrons in the Van Allen radiation belts 总被引:1,自引:0,他引:1
Horne RB Thorne RM Shprits YY Meredith NP Glauert SA Smith AJ Kanekal SG Baker DN Engebretson MJ Posch JL Spasojevic M Inan US Pickett JS Decreau PM 《Nature》2005,437(7056):227-230
The Van Allen radiation belts are two regions encircling the Earth in which energetic charged particles are trapped inside the Earth's magnetic field. Their properties vary according to solar activity and they represent a hazard to satellites and humans in space. An important challenge has been to explain how the charged particles within these belts are accelerated to very high energies of several million electron volts. Here we show, on the basis of the analysis of a rare event where the outer radiation belt was depleted and then re-formed closer to the Earth, that the long established theory of acceleration by radial diffusion is inadequate; the electrons are accelerated more effectively by electromagnetic waves at frequencies of a few kilohertz. Wave acceleration can increase the electron flux by more than three orders of magnitude over the observed timescale of one to two days, more than sufficient to explain the new radiation belt. Wave acceleration could also be important for Jupiter, Saturn and other astrophysical objects with magnetic fields. 相似文献
47.
Positional cloning of a quantitative trait locus on chromosome 13q14 that influences immunoglobulin E levels and asthma 总被引:20,自引:0,他引:20
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Kishimoto M Antonucci R Blaes O Lawrence A Boisson C Albrecht M Leipski C 《Nature》2008,454(7203):492-494
Quasars are thought to be powered by supermassive black holes accreting surrounding gas. Central to this picture is a putative accretion disk which is believed to be the source of the majority of the radiative output. It is well known, however, that the most extensively studied disk model-an optically thick disk which is heated locally by the dissipation of gravitational binding energy-is apparently contradicted by observations in a few major respects. In particular, the model predicts a specific blue spectral shape asymptotically from the visible to the near-infrared, but this is not generally seen in the visible wavelength region where the disk spectrum is observable. A crucial difficulty has been that, towards the infrared, the disk spectrum starts to be hidden under strong, hot dust emission from much larger but hitherto unresolved scales, and thus has essentially been impossible to observe. Here we report observations of polarized light interior to the dust-emitting region that enable us to uncover this near-infrared disk spectrum in several quasars. The revealed spectra show that the near-infrared disk spectrum is indeed as blue as predicted. This indicates that, at least for the outer near-infrared-emitting radii, the standard picture of the locally heated disk is approximately correct. 相似文献
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