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排序方式: 共有150条查询结果,搜索用时 31 毫秒
81.
M McDonald M Bayliss BA Benson RJ Foley J Ruel P Sullivan S Veilleux KA Aird ML Ashby M Bautz G Bazin LE Bleem M Brodwin JE Carlstrom CL Chang HM Cho A Clocchiatti TM Crawford AT Crites T de Haan S Desai MA Dobbs JP Dudley E Egami WR Forman GP Garmire EM George MD Gladders AH Gonzalez NW Halverson NL Harrington FW High GP Holder WL Holzapfel S Hoover JD Hrubes C Jones M Joy R Keisler L Knox AT Lee EM Leitch J Liu M Lueker D Luong-Van A Mantz DP Marrone JJ McMahon J Mehl SS Meyer ED Miller 《Nature》2012,488(7411):349-352
In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous 'cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these 'cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2?×?10(45)?erg?s(-1)) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers. 相似文献
82.
Twisted gastrulation (TSG) is involved in specifying the dorsal-most cell fate in Drosophila embryos, but its mechanism of action is poorly understood. TSG has been proposed to modify the action of Short gastrulation (SOG), thereby increasing signalling by the bone morphogenetic protein (BMP) Decapentaplegic. SOG, an inhibitor of BMP signalling, is in turn inactivated by the protease Tolloid. Here we identify Tsg gene products from human, mouse, Xenopus, zebrafish and chick. Expression patterns in mouse and Xenopus embryos are consistent with in vivo interactions between Tsg, BMPs and the vertebrate SOG orthologue, chordin. We show that Tsg binds both the vertebrate Decapentaplegic orthologue BMP4 and chordin, and that these interactions have multiple effects. Tsg increases chordin's binding of BMP4, potentiates chordin's ability to induce secondary axes in Xenopus embryos, and enhances chordin cleavage by vertebrate tolloid-related proteases at a site poorly used in Tsg's absence; also, the presence of Tsg enhances the secondary axis-inducing activity of two products of chordin cleavage. We conclude that Tsg acts as a cofactor in chordin's antagonism of BMP signalling. 相似文献
83.
对江西三处嫩毛竹自然制浆过程中的化学成分变化进行了测定,得知在此过程中,嫩竹木素下降50%~70%;半纤维素下降20%~30%;纤维素含量相对提高25%~45%。不同的土法制浆工艺得到不同质量的纸张,其化学成分也有明显差异。同时在实验室模拟了嫩竹发酵过程,对其化学成分变化进行了监测。结果表明,经2.5%石灰液浸泡嫩竹70d(室温),木素含量下降45%左右,半纤维素变化很小;用天然水浸泡嫩竹70d(室温),半纤维素略有下降,木素则几乎没变,先用石灰水预浸3周,再改用自选的芽抱菌液浸泡嫩竹,经1周就达制浆水平,木素下降59%。还对分析方法做了些探索。 相似文献
84.
H. W. Cho L. Prilipko H. Y. Meltzer C. Keller 《Cellular and molecular life sciences : CMLS》1977,33(2):166-167
Summary Creatine phosphokinase activity was found in human lymphocytes. Only MM type of the enzyme was detected in lymphocytes and polymorphonuclear leukocytes.Supported by U.S.P.H.S. MH 16 127. H.Y.M. is recipient of RCSA MH 47 808. 相似文献
85.
86.
Lysozyme refolding at high concentration by dilution and size—exclusion chromatography 总被引:6,自引:0,他引:6
This study of renaturation by dilution and size exclusion chromatography (SEC) addition of urea to improve yield as well as the initial and final protein concentrations showed that although urea decreased the rate of lysozyme refolding, it could suppress protein aggregation to sustain the pathway of correct refolding at high protein concentration; and that there existed an optimum urea concentration in renaturation buffer. Under the above conditions, lysozyme was successfully refolded from initial concentration of up to 40 mg/mL by dilution and 100 mg/mL by SEC, with the yield of the former being more than 40% and that of the latter being 34.8%. Especially, under the condition of 30 min interval time, i.e. tau > 2(t(R2) - t(R1)), the efficiency was increased by 25% and the renaturation buffer could be recycled for SEC refolding in continuous operation of downstream process. 相似文献
87.
ByeongSeob You DongWook Lee SangHun Eo SookKyung Cho HaeYoung Bae 《重庆邮电大学学报(自然科学版)》2007,19(3):318-322
For spatial based decision making such as choice of best place to construct a new department store, spatial data warehousing system is required more and more previous spatial data warehousing systems; however, provided decision making of nonspatial data on a map and so those cannot support enough spatial based decision making. The spatial aggregations are proposed for spatial based decision making in spatial data warehouses. The meaning of aggregation operators for applying spatial data was modified and new spatial aggregations were defined. These aggregations can support hierarchical concept of spatial measure. Using these aggregations, the spatial analysis classified by nonspatial data is provided. In case study, how to use these aggregations and how to support spatial based decision making are shown. 相似文献
88.
1. Introduction A manufactured item usually has some characteristics, which are required to have some values for the proper functioning of the item. These characteristics are referred to as quality characteristics and the ideal value for each quality characteristic is called a target value. Usually, a range of values containing the target value are specified for each quality characteristic of the item, within which the item is classified as non-defective. Otherwise, the item is defective. A s… 相似文献
89.
Isolation of cDNA clones encoding the 20K non-glycosylated polypeptide chain of the human T-cell receptor/T3 complex 总被引:35,自引:0,他引:35
The antigen receptor on human T lymphocytes consists of two variable immunoglobulin-like glycoproteins, alpha and beta, which occur in association with three invariable T3 membrane proteins. In humans two of these proteins, T3-gamma and T3-delta, are glycoproteins of relative molecular mass (Mr) 25,000 (25K) and 20,000 (20K), respectively, while the third, T3-epsilon, is a 20K non-glycosylated protein. On the surface of murine T cells, a non-glycosylated protein dimer composed of 17K subunits (T3-zeta) is found associated with the T-cell receptor alpha and beta chains and the three T3-like polypeptide chains. It is generally accepted that major histocompatibility complex-restricted antigen recognition is a function of the alpha-beta heterodimer. This has led to the postulation that the proteins of the T3 complex are involved in the signal transduction that immediately follows antigen recognition via the antigen receptor. Events believed to be involved in early T-cell activation, such as rapid increases in phosphatidylinositol turnover and free intracellular calcium, can be triggered by antibodies directed against either the T3 complex or the clonotypic receptor. We have previously reported our findings on the cloning of the complementary DNA and genomic structure encoding both the human and murine 20K glycoprotein, T3-delta (refs 11-13). We now present our results on the cloning of the cDNA encoding the human 20K non-glycosylated chain, T3-epsilon. 相似文献
90.
Klesert TR Cho DH Clark JI Maylie J Adelman J Snider L Yuen EC Soriano P Tapscott SJ 《Nature genetics》2000,25(1):105-109