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11.
Volatiles that are transported by subducting lithospheric plates to depths greater than 100 km are thought to induce partial melting in the overlying mantle wedge, resulting in arc magmatism and the addition of significant quantities of material to the overlying lithosphere. Asthenospheric flow and upwelling within the wedge produce increased lithospheric temperatures in this back-arc region, but the forearc mantle (in the corner of the wedge) is thought to be significantly cooler. Here we explore the structure of the mantle wedge in the southern Cascadia subduction zone using scattered teleseismic waves recorded on a dense portable array of broadband seismometers. We find very low shear-wave velocities in the cold forearc mantle indicated by the exceptional occurrence of an 'inverted' continental Moho, which reverts to normal polarity seaward of the Cascade arc. This observation provides compelling evidence for a highly hydrated and serpentinized forearc region, consistent with thermal and petrological models of the forearc mantle wedge. This serpentinized material is thought to have low strength and may therefore control the down-dip rupture limit of great thrust earthquakes, as well as the nature of large-scale flow in the mantle wedge. 相似文献
12.
A. J. Peacock K. Bowler J. H. Anstee 《Cellular and molecular life sciences : CMLS》1972,28(8):901-902
Zusammenfassung Die Präsenz einer charakteristischen Na+–K+-aktivierbaren ATPase (E.C. 3.6.1.3) wurde erstmals in einer mikrosomalen Fraktion des Enddarmes und der malpighischen Gefässe bei der WüstenschreckeScistocerca gregaria und der LaubheuschreckeJamaicana flava nachgewiesen. 相似文献
13.
大叶白麻叶化学成分的研究 总被引:1,自引:0,他引:1
从大叶白麻[poacynumhendersonii(Hookf)woodson]叶中分得2个木脂素类化舍物,经理化常数测定和光谱分析,分别鉴定为(-)-丁香脂素[(-)-Syringaresino1]和( )-松脂素-4-O-β-D-葡萄糖甙[( )-Pinoresionol-4-0-β-D-glucopyranoside]. 相似文献
14.
Possible future changes in Arctic sea ice cover and thickness, and consequent changes in the ice-albedo feedback, represent one of the largest uncertainties in the prediction of future temperature rise. Knowledge of the natural variability of sea ice thickness is therefore critical for its representation in global climate models. Numerical simulations suggest that Arctic ice thickness varies primarily on decadal timescales owing to changes in wind and ocean stresses on the ice, but observations have been unable to provide a synoptic view of sea ice thickness, which is required to validate the model results. Here we use an eight-year time-series of Arctic ice thickness, derived from satellite altimeter measurements of ice freeboard, to determine the mean thickness field and its variability from 65 degrees N to 81.5 degrees N. Our data reveal a high-frequency interannual variability in mean Arctic ice thickness that is dominated by changes in the amount of summer melt, rather than by changes in circulation. Our results suggest that a continued increase in melt season length would lead to further thinning of Arctic sea ice. 相似文献
15.
Peacock CS Seeger K Harris D Murphy L Ruiz JC Quail MA Peters N Adlem E Tivey A Aslett M Kerhornou A Ivens A Fraser A Rajandream MA Carver T Norbertczak H Chillingworth T Hance Z Jagels K Moule S Ormond D Rutter S Squares R Whitehead S Rabbinowitsch E Arrowsmith C White B Thurston S Bringaud F Baldauf SL Faulconbridge A Jeffares D Depledge DP Oyola SO Hilley JD Brito LO Tosi LR Barrell B Cruz AK Mottram JC Smith DF Berriman M 《Nature genetics》2007,39(7):839-847
Leishmania parasites cause a broad spectrum of clinical disease. Here we report the sequencing of the genomes of two species of Leishmania: Leishmania infantum and Leishmania braziliensis. The comparison of these sequences with the published genome of Leishmania major reveals marked conservation of synteny and identifies only approximately 200 genes with a differential distribution between the three species. L. braziliensis, contrary to Leishmania species examined so far, possesses components of a putative RNA-mediated interference pathway, telomere-associated transposable elements and spliced leader-associated SLACS retrotransposons. We show that pseudogene formation and gene loss are the principal forces shaping the different genomes. Genes that are differentially distributed between the species encode proteins implicated in host-pathogen interactions and parasite survival in the macrophage. 相似文献