Chondrite barium, neodymium, and samarium isotopic heterogeneity and early Earth differentiation     

Carlson RW  Boyet M  Horan M 《Science (New York, N.Y.)》2007,316(5828):1175-1178

Isotopic variability in barium, neodymium, and samarium in carbonaceous chondrites reflects the distinct stellar nucleosynthetic contributions to the early solar system. We used 148Nd/144Nd to correct for the observed s-process deficiency, which produced a chondrite 146Sm-142Nd isochron consistent with previous estimates of the initial solar system abundance of 146Sm and a 142Nd/144Nd at average chondrite Sm/Nd ratio that is lower than that measured in terrestrial rocks by 21 +/- 3 parts per million. This result strengthens the conclusion that the deficiency in 142Nd in chondrites relative to terrestrial rocks reflects 146Sm decayand earlyplanetary differentiation processes.  相似文献   

Inflammatory arthritis. How immune system gangs up on joints     

Beckman M 《Science (New York, N.Y.)》2002,297(5587):1626-1627

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Statement on scientific publication and security     

Atlas R  Campbell P  Cozzarelli NR  Curfman G  Enquist L  Fink G  Flanagin A  Fletcher J  George E  Hammes G  Heyman D  Inglesby T  Kaplan S  Kennedy D  Krug J  Levinson R  Marcus E  Metzger H  Morse SS  O'Brien A  Onderdonk A  Poste G  Renault B  Rich R  Rosengard A  Salzburg S  Scanlan M  Shenk T  Tabor H  Varmus H  Wimmer E  Yamamoto K;Journal Editors  Authors Group 《Science (New York, N.Y.)》2003,299(5610):1149

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Pheromone reception. When in doubt, mice mate rather than hate     

Beckman M 《Science (New York, N.Y.)》2002,295(5556):782

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Soft-tissue vessels and cellular preservation in Tyrannosaurus rex     

Schweitzer MH  Wittmeyer JL  Horner JR  Toporski JK 《Science (New York, N.Y.)》2005,307(5717):1952-1955

Soft tissues are preserved within hindlimb elements of Tyrannosaurus rex (Museum of the Rockies specimen 1125). Removal of the mineral phase reveals transparent, flexible, hollow blood vessels containing small round microstructures that can be expressed from the vessels into solution. Some regions of the demineralized bone matrix are highly fibrous, and the matrix possesses elasticity and resilience. Three populations of microstructures have cell-like morphology. Thus, some dinosaurian soft tissues may retain some of their original flexibility, elasticity, and resilience.  相似文献   

Genetics. Poultry genetic resources--operation rescue needed     

Fulton JE  Delany ME 《Science (New York, N.Y.)》2003,300(5626):1667-1668

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Organic aerosol growth mechanisms and their climate-forcing implications     

Maria SF  Russell LM  Gilles MK  Myneni SC 《Science (New York, N.Y.)》2004,306(5703):1921-1924

Surface- and volume-limited chemical reactions on and in atmospheric aerosol particles cause growth while changing organic composition by 13 to 24% per day. Many of these particles contain carbonaceous components from mineral dust and combustion emissions in Africa, Asia, and North America and reveal reaction rates that are three times slower than those typically used in climate models. These slower rates for converting from volatile or hydrophobic to condensed and hygroscopic organic compounds increase carbonaceous particle burdens in climate models by 70%, producing organic aerosol climate forcings of as much as -0.8 watt per square meter cooling and +0.3 watt per square meter warming.  相似文献   

Aldrin: removal from lake water by flocculent bacteria     

W O Leshniowsky  P R Dugan  R M Pfister  J I Frea  C I Randles 《Science (New York, N.Y.)》1970,169(949):993-995

Floc-forming bacteria isolated from Lake Erie adsorb and concentrate aldrin from colloidal dispersion so that the settling of the bacterial flocs removes aldrin from the water phase. Contemporary sediments forming in Lake Erie contain aldrin and could adsorb more. The sediments consist of a conglomerate floc of bacteria, diatoms, and inorganic and detrital particles. Flocculent bacteria also adsorb microparticulates, and this adsorption capacity represents a mechanism for sediment formation and for the removal of suspended particles including aldrin from the water column.  相似文献   

Kilimanjaro ice core records: evidence of holocene climate change in tropical Africa   总被引：1，自引：0，他引：1  

Thompson LG  Mosley-Thompson E  Davis ME  Henderson KA  Brecher HH  Zagorodnov VS  Mashiotta TA  Lin PN  Mikhalenko VN  Hardy DR  Beer J 《Science (New York, N.Y.)》2002,298(5593):589-593

Six ice cores from Kilimanjaro provide an approximately 11.7-thousand-year record of Holocene climate and environmental variability for eastern equatorial Africa, including three periods of abrupt climate change: approximately 8.3, approximately 5.2, and approximately 4 thousand years ago (ka). The latter is coincident with the "First Dark Age," the period of the greatest historically recorded drought in tropical Africa. Variable deposition of F- and Na+ during the African Humid Period suggests rapidly fluctuating lake levels between approximately 11.7 and 4 ka. Over the 20th century, the areal extent of Kilimanjaro's ice fields has decreased approximately 80%, and if current climatological conditions persist, the remaining ice fields are likely to disappear between 2015 and 2020.  相似文献   

Interpreting sequences from mastodon and T. rex     

Asara JM  Garavelli JS  Slatter DA  Schweitzer MH  Freimark LM  Phillips M  Cantley LC 《Science (New York, N.Y.)》2007,317(5843):1324-1325

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