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991.
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Seu R Phillips RJ Alberti G Biccari D Bonaventura F Bortone M Calabrese D Campbell BA Cartacci M Carter LM Catallo C Croce A Croci R Cutigni M Di Placido A Dinardo S Federico C Flamini E Fois F Frigeri A Fuga O Giacomoni E Gim Y Guelfi M Holt JW Kofman W Leuschen CJ Marinangeli L Marras P Masdea A Mattei S Mecozzi R Milkovich SM Morlupi A Mouginot J Orosei R Papa C Paternò T Persi del Marmo P Pettinelli E Pica G Picardi G Plaut JJ Provenziani M Putzig NE Russo F Safaeinili A Salzillo G 《Science (New York, N.Y.)》2007,317(5845):1715-1718
Mars' polar regions are covered with ice-rich layered deposits that potentially contain a record of climate variations. The sounding radar SHARAD on the Mars Reconnaissance Orbiter mapped detailed subsurface stratigraphy in the Promethei Lingula region of the south polar plateau, Planum Australe. Radar reflections interpreted as layers are correlated across adjacent orbits and are continuous for up to 150 kilometers along spacecraft orbital tracks. The reflectors are often separated into discrete reflector sequences, and strong echoes are seen as deep as 1 kilometer. In some cases, the sequences are dipping with respect to each other, suggesting an interdepositional period of erosion. In Australe Sulci, layers are exhumed, indicating recent erosion. 相似文献
994.
Genome-wide location and function of DNA binding proteins 总被引:4,自引:0,他引:4
Ren B Robert F Wyrick JJ Aparicio O Jennings EG Simon I Zeitlinger J Schreiber J Hannett N Kanin E Volkert TL Wilson CJ Bell SP Young RA 《Science (New York, N.Y.)》2000,290(5500):2306-2309
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Marrow cells derived from C57BL/6 mice form many fewer splenic colonies in irradiated C57BL/6 x C3H F1 hybrid recipients than in irradiated C57BL/6 recipients (repression of colony formation). This effect is reversed by treatment of the hybrid recipients with active antiserum to mouse thymocytes. The repression phenomenon cannot readily be explained in immunological terms; hence the effect of the antilymphocyte serum on this phenomenon may not result from immunosuppression in the usual sense. 相似文献
998.
Contract negotiations over wages are sometimes accompanied by strikes; similarly in legal contexts, settlements of damage claims may require lengthy negotiations. These and other costly delays in resolving disputes are the subject of the studies described in this article. Formulations in terms of game theory indicate that procedural features can allow delays, but the main cause may be informational disparities between the parties. Several models are described and related to data about strikes. 相似文献
999.
Jones GH Roussos E Krupp N Beckmann U Coates AJ Crary F Dandouras I Dikarev V Dougherty MK Garnier P Hansen CJ Hendrix AR Hospodarsky GB Johnson RE Kempf S Khurana KK Krimigis SM Krüger H Kurth WS Lagg A McAndrews HJ Mitchell DG Paranicas C Postberg F Russell CT Saur J Seiss M Spahn F Srama R Strobel DF Tokar R Wahlund JE Wilson RJ Woch J Young D 《Science (New York, N.Y.)》2008,319(5868):1380-1384
Saturn's moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn's magnetosphere. The Cassini spacecraft's in situ observations reveal that energetic electrons are depleted in the moon's vicinity. The absence of a substantial exosphere implies that Rhea's magnetospheric interaction region, rather than being exclusively induced by sputtered gas and its products, likely contains solid material that can absorb magnetospheric particles. Combined observations from several instruments suggest that this material is in the form of grains and boulders up to several decimetres in size and orbits Rhea as an equatorial debris disk. Within this disk may reside denser, discrete rings or arcs of material. 相似文献
1000.
Pejchal R Doores KJ Walker LM Khayat R Huang PS Wang SK Stanfield RL Julien JP Ramos A Crispin M Depetris R Katpally U Marozsan A Cupo A Maloveste S Liu Y McBride R Ito Y Sanders RW Ogohara C Paulson JC Feizi T Scanlan CN Wong CH Moore JP Olson WC Ward AB Poignard P Schief WR Burton DR Wilson IA 《Science (New York, N.Y.)》2011,334(6059):1097-1103
The HIV envelope (Env) protein gp120 is protected from antibody recognition by a dense glycan shield. However, several of the recently identified PGT broadly neutralizing antibodies appear to interact directly with the HIV glycan coat. Crystal structures of antigen-binding fragments (Fabs) PGT 127 and 128 with Man(9) at 1.65 and 1.29 angstrom resolution, respectively, and glycan binding data delineate a specific high mannose-binding site. Fab PGT 128 complexed with a fully glycosylated gp120 outer domain at 3.25 angstroms reveals that the antibody penetrates the glycan shield and recognizes two conserved glycans as well as a short β-strand segment of the gp120 V3 loop, accounting for its high binding affinity and broad specificity. Furthermore, our data suggest that the high neutralization potency of PGT 127 and 128 immunoglobulin Gs may be mediated by cross-linking Env trimers on the viral surface. 相似文献