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61.
Wareham NJ Jakes RW Rennie KL Schuit J Mitchell J Hennings S Day NE 《Public health nutrition》2003,6(4):407-413
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Spielman A Andreadis TG Apperson CS Cornel AJ Day JF Edman JD Fish D Harrington LC Kiszewski AE Lampman R Lanzaro GC Matuschka FR Munstermann LE Nasci RS Norris DE Novak RJ Pollack RJ Reisen WK Reiter P Savage HM Tabachnick WJ Wesson DM 《Science (New York, N.Y.)》2004,306(5701):1473-5; author reply 1473-5
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The silica-supported transition metal hydrides (=Si-O-Si=)(=Si-O-)2Ta-H and (=Si-O-)xM-H (M, chromium or tungsten) catalyze the metathesis reaction of linear or branched alkanes into the next higher and lower alkanes at moderate temperature (25degrees to 200degreesC). With (=Si-O-Si=)(=Si-O-)2Ta-H, ethane was transformed at room temperature into an equimolar mixture of propane and methane. Higher and lower homologs were obtained from propane, butane, and pentane as well as from branched alkanes such as isobutane and isopentane. The mechanism of the step leading to carbon-carbon bond cleavage and formation likely involves a four-centered transition state between a tantalum-alkyl intermediate and a carbon-carbon final sigma-bond of a second molecule of alkane. 相似文献
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Supernatants from cultures of normal feline lymphocytes stimulated with Staphylococcus enterotoxin A showed antiviral activity, characterized as a gamma-like interferon. With the addition of inactivated feline leukemia virus, markedly less interferon was produced. The reduction in interferon production was not attributable to lowered lymphocyte viability or reduced mitogenic properties of Staphylococcus enterotoxin A and appears to be a direct retroviral effect. This finding may reflect clinically relevant events that may contribute to the development of the feline or human states of acquired immunodeficiency. 相似文献
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Hypovirulence in Endothia parasitica is caused by a cytoplasmic determinant that is transferred by hyphal anastomosis in host tissue and in culture. Transmission of this determinant affects the virulence of the fungus to the extent that host invasion by previously virulent isolates is limited. 相似文献
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Spatial Variability of Turbulent Mixing in the Abyssal Ocean 总被引:3,自引:0,他引:3
Ocean microstructure data show that turbulent mixing in the deep Brazil Basin of the South Atlantic Ocean is weak at all depths above smooth abyssal plains and the South American Continental Rise. The diapycnal diffusivity there was estimated to be less than or approximately equal to 0.1 x 10(-4) meters squared per second. In contrast, mixing rates are large throughout the water column above the rough Mid-Atlantic Ridge, and the diffusivity deduced for the bottom-most 150 meters exceeds 5 x 10(-4) meters squared per second. Such patterns in vertical mixing imply that abyssal circulations have complex spatial structures that are linked to the underlying bathymetry. 相似文献