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121.
Résumé On a donné de la nicotine à des rats une fois par jour, pendant 10 jours. L'activité des animaux a d'abord diminué, mais après quelques administrations de la drogue, on constata une accoutumance à ces effets. L'administration terminée, l'activité a augmenté.
This work was supported by a grant from the Tobacco Research Council. 相似文献
This work was supported by a grant from the Tobacco Research Council. 相似文献
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R Sanchis-Ojeda DC Fabrycky JN Winn T Barclay BD Clarke EB Ford JJ Fortney JC Geary MJ Holman AW Howard JM Jenkins D Koch JJ Lissauer GW Marcy F Mullally D Ragozzine SE Seader M Still SE Thompson 《Nature》2012,487(7408):449-453
The Sun's equator and the planets' orbital planes are nearly aligned, which is presumably a consequence of their formation from a single spinning gaseous disk. For exoplanetary systems this well-aligned configuration is not guaranteed: dynamical interactions may tilt planetary orbits, or stars may be misaligned with the protoplanetary disk through chaotic accretion , magnetic interactions or torques from neighbouring stars. Indeed, isolated 'hot Jupiters' are often misaligned and even orbiting retrograde. Here we report an analysis of transits of planets over starspots on the Sun-like star Kepler-30 (ref. 8), and show that the orbits of its three planets are aligned with the stellar equator. Furthermore, the orbits are aligned with one another to within a few degrees. This configuration is similar to that of our Solar System, and contrasts with the isolated hot Jupiters. The orderly alignment seen in the Kepler-30 system suggests that high obliquities are confined to systems that experienced disruptive dynamical interactions. Should this be corroborated by observations of other coplanar multi-planet systems, then star-disk misalignments would be ruled out as the explanation for the high obliquities of hot Jupiters, and dynamical interactions would be implicated as the origin of hot Jupiters. 相似文献
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Peroxiredoxins are conserved markers of circadian rhythms 总被引:1,自引:0,他引:1
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S Neph J Vierstra AB Stergachis AP Reynolds E Haugen B Vernot RE Thurman S John R Sandstrom AK Johnson MT Maurano R Humbert E Rynes H Wang S Vong K Lee D Bates M Diegel V Roach D Dunn J Neri A Schafer RS Hansen T Kutyavin E Giste M Weaver T Canfield P Sabo M Zhang G Balasundaram R Byron MJ MacCoss JM Akey MA Bender M Groudine R Kaul JA Stamatoyannopoulos 《Nature》2012,489(7414):83-90
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Bottke WF Vokrouhlický D Minton D Nesvorný D Morbidelli A Brasser R Simonson B Levison HF 《Nature》2012,485(7396):78-81
The barrage of comets and asteroids that produced many young lunar basins (craters over 300 kilometres in diameter) has frequently been called the Late Heavy Bombardment (LHB). Many assume the LHB ended about 3.7 to 3.8 billion years (Gyr) ago with the formation of Orientale basin. Evidence for LHB-sized blasts on Earth, however, extend into the Archaean and early Proterozoic eons, in the form of impact spherule beds: globally distributed ejecta layers created by Chicxulub-sized or larger cratering events4. At least seven spherule beds have been found that formed between 3.23 and 3.47?Gyr ago, four between 2.49 and 2.63?Gyr ago, and one between 1.7 and 2.1?Gyr ago. Here we report that the LHB lasted much longer than previously thought, with most late impactors coming from the E belt, an extended and now largely extinct portion of the asteroid belt between 1.7 and 2.1 astronomical units from Earth. This region was destabilized by late giant planet migration. E-belt survivors now make up the high-inclination Hungaria asteroids. Scaling from the observed Hungaria asteroids, we find that E-belt projectiles made about ten lunar basins between 3.7 and 4.1?Gyr ago. They also produced about 15 terrestrial basins between 2.5 and 3.7?Gyr ago, as well as around 70 and four Chicxulub-sized or larger craters on the Earth and Moon, respectively, between 1.7 and 3.7?Gyr ago. These rates reproduce impact spherule bed and lunar crater constraints. 相似文献
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