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51.
Beck CB 《Science (New York, N.Y.)》1960,131(3412):1524-1525
Characters of two Upper Devonian genera, Archaeopteris, often considered to be a fern, and Callixylon, classified with the gymnosperms, have been recognized in a single specimen. 相似文献
52.
Multilineage potential of adult human mesenchymal stem cells 总被引:7,自引:0,他引:7
Pittenger MF Mackay AM Beck SC Jaiswal RK Douglas R Mosca JD Moorman MA Simonetti DW Craig S Marshak DR 《Science (New York, N.Y.)》1999,284(5411):143-147
Human mesenchymal stem cells are thought to be multipotent cells, which are present in adult marrow, that can replicate as undifferentiated cells and that have the potential to differentiate to lineages of mesenchymal tissues, including bone, cartilage, fat, tendon, muscle, and marrow stroma. Cells that have the characteristics of human mesenchymal stem cells were isolated from marrow aspirates of volunteer donors. These cells displayed a stable phenotype and remained as a monolayer in vitro. These adult stem cells could be induced to differentiate exclusively into the adipocytic, chondrocytic, or osteocytic lineages. Individual stem cells were identified that, when expanded to colonies, retained their multilineage potential. 相似文献
53.
Beck CB 《Science (New York, N.Y.)》1963,141(3579):431-433
A specimen identified as Ginkgophyton (Psygmophyllum) with a structurally preserved stem of gymnospermic organization has been collected from a late Devonian stratum in New York. 相似文献
54.
Creutzfeldt-Jakob disease (spongiform encephalopathy): transmission to the chimpanzee 总被引:48,自引:0,他引:48
C J Gibbs D C Gajdusek D M Asher M P Alpers E Beck P M Daniel W B Matthews 《Science (New York, N.Y.)》1968,161(839):388-389
Biopsy material taken from the brain of a patient with CreutzfeldtJakob disease with status spongiosus induced a similar fatal encephalopathy in a chimpanzee 13 months after inoculation. 相似文献
55.
Chalcocite Oxidation and Coupled Carbon Dioxide Fixation by Thiobacillus ferrooxidans 总被引:1,自引:0,他引:1
The reaction of cell suspensions of Thiobacillus ferrooxidans with pulverized chalcocite (Cu(2)S) in a Warburg manometric apparatus resulted in oxygen uptake accompanied by increased solubilization of copper and fixation of carbon dioxide. Since the only detectable oxidized products were cupric ions and the more oxidized form of the sulfide mineral, that is, digenite or covellite, the apparent source of energy for the carbon dioxide fixation was provided by the oxidation of the cuprous copper of the chalcocite. 相似文献
56.
Battista JR Cox MM Daly MJ Narumi I Radman M Sommer S 《Science (New York, N.Y.)》2003,302(5645):567-8; author reply 567-8
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Beck JW Edwards RL Ito E Taylor FW Recy J Rougerie F Joannot P Henin C 《Science (New York, N.Y.)》1992,257(5070):644-647
Seasonal records of tropical sea-surface temperature (SST) over the past 10(5) years can be recovered from high-precision measurements of coral strontium/calcium ratios with the use of thermal ionization mass spectrometry. The temperature dependence of these ratios was calibrated with corals collected at SST recording stations and by (18)O/(16)O thermometry. The results suggest that mean monthly SST may be determined with an apparent accuracy of better than 0.5 degrees C. Measurements on a fossil coral indicate that 10,200 years ago mean annual SSTs near Vanuatu in the southwestern Pacific Ocean were about 5 degrees C colder than today and that seasonal variations in SST were larger. These data suggest that tropical climate zones were compressed toward the equator during deglaciation. 相似文献