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排序方式: 共有111条查询结果,搜索用时 265 毫秒
61.
Detection of human influence on twentieth-century precipitation trends 总被引:18,自引:0,他引:18
Zhang X Zwiers FW Hegerl GC Lambert FH Gillett NP Solomon S Stott PA Nozawa T 《Nature》2007,448(7152):461-465
Human influence on climate has been detected in surface air temperature, sea level pressure, free atmospheric temperature, tropopause height and ocean heat content. Human-induced changes have not, however, previously been detected in precipitation at the global scale, partly because changes in precipitation in different regions cancel each other out and thereby reduce the strength of the global average signal. Models suggest that anthropogenic forcing should have caused a small increase in global mean precipitation and a latitudinal redistribution of precipitation, increasing precipitation at high latitudes, decreasing precipitation at sub-tropical latitudes, and possibly changing the distribution of precipitation within the tropics by shifting the position of the Intertropical Convergence Zone. Here we compare observed changes in land precipitation during the twentieth century averaged over latitudinal bands with changes simulated by fourteen climate models. We show that anthropogenic forcing has had a detectable influence on observed changes in average precipitation within latitudinal bands, and that these changes cannot be explained by internal climate variability or natural forcing. We estimate that anthropogenic forcing contributed significantly to observed increases in precipitation in the Northern Hemisphere mid-latitudes, drying in the Northern Hemisphere subtropics and tropics, and moistening in the Southern Hemisphere subtropics and deep tropics. The observed changes, which are larger than estimated from model simulations, may have already had significant effects on ecosystems, agriculture and human health in regions that are sensitive to changes in precipitation, such as the Sahel. 相似文献
62.
Zhifeng Li Xiaoping Yang Nathan J.DeYonker Xianyan Xu Zhen Guo Cunyuan Zhao 《科学通报(英文版)》2014,59(21):2597-2607
Nonclassical single electron hydrogen,sodium and lithium bonds(SEHBs,SENaBs and SELiBs)between single electron acceptors X–A(A=H,Na,Li;X=CN,HCC,HO,NC,CF3)and neutral radicals BY2(Y=H,OH,CH3)and have been systematically investigated by high level theoretical methods,such as second-order Mφller-Plesset perturbation theory(MP2),spin-component-scaled MφllerPlesset theory(SCS-MP2),the coupled cluster method with perturbative triples(CCSD(T)),and the correlation consistent composite approach(ccCA).Binding energies have been corrected for zero-point vibrational effects and(when applicable)basis set superposition error.The quantum theory of atoms in molecules(AIM)and natural bond orbital(NBO)analyses were also employed to qualitatively characterize the single electron bond interactions.The stabilization energy was partitioned via the localized molecular orbital energy decomposition analysis(LMOEDA)method,and both electrostatic and exchange interactions were seen to be major driving forces for the complex stabilization.Interestingly,the sum of the energy contributors of exchange(EEX),repulsion(EREP),polarization(EPOL),dispersion(EDIS)is close to zero and the changes in the interaction energy follow the trend of the electrostatic energy(EES).We observe several linear relationships among the optimized intermolecular parameters and the interaction energies of the various complexes. 相似文献
63.
64.
The developmental transcriptome of Drosophila melanogaster 总被引:2,自引:0,他引:2
Graveley BR Brooks AN Carlson JW Duff MO Landolin JM Yang L Artieri CG van Baren MJ Boley N Booth BW Brown JB Cherbas L Davis CA Dobin A Li R Lin W Malone JH Mattiuzzo NR Miller D Sturgill D Tuch BB Zaleski C Zhang D Blanchette M Dudoit S Eads B Green RE Hammonds A Jiang L Kapranov P Langton L Perrimon N Sandler JE Wan KH Willingham A Zhang Y Zou Y Andrews J Bickel PJ Brenner SE Brent MR Cherbas P Gingeras TR Hoskins RA Kaufman TC Oliver B Celniker SE 《Nature》2011,471(7339):473-479
65.
66.
Identification and analysis of functional elements in 1% of the human genome by the ENCODE pilot project 总被引:2,自引:0,他引:2
ENCODE Project Consortium Birney E Stamatoyannopoulos JA Dutta A Guigó R Gingeras TR Margulies EH Weng Z Snyder M Dermitzakis ET Thurman RE Kuehn MS Taylor CM Neph S Koch CM Asthana S Malhotra A Adzhubei I Greenbaum JA Andrews RM Flicek P Boyle PJ Cao H Carter NP Clelland GK Davis S Day N Dhami P Dillon SC Dorschner MO Fiegler H Giresi PG Goldy J Hawrylycz M Haydock A Humbert R James KD Johnson BE Johnson EM Frum TT Rosenzweig ER Karnani N Lee K Lefebvre GC Navas PA Neri F Parker SC Sabo PJ 《Nature》2007,447(7146):799-816
67.
Recent evidence indicates that growing blood-vessel sprouts consist of endothelial cells with distinct cell fates and behaviours; however, it is not clear what signals determine these sprout cell characteristics. Here we show that Notch signalling is necessary to restrict angiogenic cell behaviour to tip cells in developing segmental arteries in the zebrafish embryo. In the absence of the Notch signalling component Rbpsuh (recombining binding protein suppressor of hairless) we observed excessive sprouting of segmental arteries, whereas Notch activation suppresses angiogenesis. Through mosaic analysis we find that cells lacking Rbpsuh preferentially localize to the terminal position in developing sprouts. In contrast, cells in which Notch signalling has been activated are excluded from the tip-cell position. In vivo time-lapse analysis reveals that endothelial tip cells undergo a stereotypical pattern of proliferation and migration during sprouting. In the absence of Notch, nearly all sprouting endothelial cells exhibit tip-cell behaviour, leading to excessive numbers of cells within segmental arteries. Furthermore, we find that flt4 (fms-related tyrosine kinase 4, also called vegfr3) is expressed in segmental artery tip cells and becomes ectopically expressed throughout the sprout in the absence of Notch. Loss of flt4 can partially restore normal endothelial cell number in Rbpsuh-deficient segmental arteries. Finally, loss of the Notch ligand dll4 (delta-like 4) also leads to an increased number of endothelial cells within segmental arteries. Together, these studies indicate that proper specification of cell identity, position and behaviour in a developing blood-vessel sprout is required for normal angiogenesis, and implicate the Notch signalling pathway in this process. 相似文献
68.
<授时历>受外来影响很少,不是因为中国人不喜欢外国人,也不是因为中国人对外来的专业知识不感兴趣,而是蒙古统治者的统治政策造成了这个结果.忽必烈及其后继者限制不同种族人员之间的知识交流,好让自己享有多种选择的特权,而不使不同种族的臣民联手反抗.尽管元初设有回回司天监,但回回天文学家与汉族天文学家之间没有什么交流. 相似文献
69.
Nathan M. Smith 《西北部美国博物学家》2011,34(4)
A noosed female Crotophytus collaris bicinclores Smith and Tanner voiced an alarm similar to that of C. wislizeni. 相似文献
70.
Immune (gamma) interferon produced by a human T-lymphoblast cell line 总被引:15,自引:0,他引:15