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111.
J. M. West D. G. Haigh P. J. Hooker E. J. Rowe 《Cellular and molecular life sciences : CMLS》1991,47(6):549-552
Summary A major concern in the geological containment of radioactive wastes is the speed of movement of radionuclides from the repository, after their eventual leaching and release, into the geosphere and finally into the biosphere. Radionuclide sorption onto the host rock is an important retarding mechanism. Experimental evidence shows that the presence of microbes in this environment influences the sorption capabilities of the host rock. Their presence can decrease the amount of retardation of137Cs, a common radionuclide in radioactive waste, by the solid phase. Sorption methods and data analysis procedures are presented and the implications for radioactive waste disposal assessments are discussed. 相似文献
112.
Zusammenfassung In verschiedenen Lagen der Mucosa und der Submucosa des Pylorusteils des Schweinemagens wurden Mastzellen gezählt und der Histamingehalt berechnet. Der hohe Histamingehalt lässt sich durch die entsprechend hohe Mastzellenzahl erklären. Die Mastzellenzahl fällt in der angrenzenden Mucosa steil ab, doch bleibt der Histamingehalt gleich hoch. Es ist möglich, dass in diesem Gewebe neben den Mastzellen auch das metachromatische Mucin der unteren Mucosa Histamin bindet. 相似文献
113.
Tomasko MG Archinal B Becker T Bézard B Bushroe M Combes M Cook D Coustenis A de Bergh C Dafoe LE Doose L Douté S Eibl A Engel S Gliem F Grieger B Holso K Howington-Kraus E Karkoschka E Keller HU Kirk R Kramm R Küppers M Lanagan P Lellouch E Lemmon M Lunine J McFarlane E Moores J Prout GM Rizk B Rosiek M Rueffer P Schröder SE Schmitt B See C Smith P Soderblom L Thomas N West R 《Nature》2005,438(7069):765-778
The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent. 相似文献
114.
Nearly a century after the true nature of galaxies as distant 'island universes' was established, their origin and evolution remain great unsolved problems of modern astrophysics. One of the most promising ways to investigate galaxy formation is to study the ubiquitous globular star clusters that surround most galaxies. Globular clusters are compact groups of up to a few million stars. They generally formed early in the history of the Universe, but have survived the interactions and mergers that alter substantially their parent galaxies. Recent advances in our understanding of the globular cluster systems of the Milky Way and other galaxies point to a complex picture of galaxy genesis driven by cannibalism, collisions, bursts of star formation and other tumultuous events. 相似文献
115.
B. Perez de Gracia A. R. Rhoads W. L. West 《Cellular and molecular life sciences : CMLS》1980,36(7):824-825
Summary Alloxan diabetes caused a decrease in cyclic AMP phosphodiesterase in all affected rat tissues. Cyclic GMP phosphodiesterase activity was, however, decreased in adipose and liver, but increased in heart and uterus.This research was supported by U.S. Public Health Service grant RO1-AM19364-O1 and MARC training grant No. 1-TO2-GMO50000. 相似文献
116.
The concept of electron localization has long been accepted to be essential to the physics of the quantum Hall effect in a two-dimensional electron gas. The exact quantization of the Hall resistance and the zero of the diagonal resistance over a range of filling factors close to integral are attributed to the localization of electronic states at the Fermi level in the interior of the gas. As the electron density is changed, charging of the individual localized states may occur by single-electron jumps, causing associated oscillations in the local electrostatic potential. Here we search for such a manifestation of localized states in the quantum Hall regime, using a scanning electrometer probe. We observe localized potential signals, at numerous locations, that oscillate with changing electron density. In general, the corresponding spatial patterns are complex, but well-defined objects are often seen which evidently arise from individual localized states. These objects interact, and at times form a lattice-like arrangement. 相似文献
117.
West GB Savage VM Gillooly J Enquist BJ Woodruff WH Brown JH 《Nature》2003,421(6924):713; discussion 714
118.
119.
Interleukin 21 and its receptor are involved in NK cell expansion and regulation of lymphocyte function 总被引:64,自引:0,他引:64
Parrish-Novak J Dillon SR Nelson A Hammond A Sprecher C Gross JA Johnston J Madden K Xu W West J Schrader S Burkhead S Heipel M Brandt C Kuijper JL Kramer J Conklin D Presnell SR Berry J Shiota F Bort S Hambly K Mudri S Clegg C Moore M Grant FJ Lofton-Day C Gilbert T Rayond F Ching A Yao L Smith D Webster P Whitmore T Maurer M Kaushansky K Holly RD Foster D 《Nature》2000,408(6808):57-63
Cytokines are important in the regulation of haematopoiesis and immune responses, and can influence lymphocyte development. Here we have identified a class I cytokine receptor that is selectively expressed in lymphoid tissues and is capable of signal transduction. The full-length receptor was expressed in BaF3 cells, which created a functional assay for ligand detection and cloning. Conditioned media from activated human CD3+ T cells supported proliferation of the assay cell line. We constructed a complementary DNA expression library from activated human CD3+ T cells, and identified a cytokine with a four-helix-bundle structure using functional cloning. This cytokine is most closely related to IL2 and IL15, and has been designated IL21 with the receptor designated IL21 R. In vitro assays suggest that IL21 has a role in the proliferation and maturation of natural killer (NK) cell populations from bone marrow, in the proliferation of mature B-cell populations co-stimulated with anti-CD40, and in the proliferation of T cells co-stimulated with anti-CD3. 相似文献
120.