1,419 research outputs found

    Main results of the experiments conducted during the flight of the Kosmos-1129 Biosatellite and the status of preparation of studies on the next biosatllite

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    Experiments included studies on the biological effects of weightlessness. Space flight stress, disorientation, and physiological factors are discussed for each experimental subject. The subjects included rats, drosophila flies, and plants. Metabolic rates were monitored along with other changes in the subject's activity cycles

    Flares in Open Clusters with K2. I. M45 (Pleiades), M44 (Praesepe) and M67

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    The presence and strength of a stellar magnetic field and activity is rooted in a star's fundamental parameters such as mass and age. Can flares serve as an accurate stellar "clock"? To explore if we can quantify an activity-age relation in the form of a flaring-age relation, we measured trends in the flaring rates and energies for stars with different masses and ages. We investigated the time-domain photometry provided by Kepler's follow-up mission K2 and searched for flares in three solar metallicity open clusters with well-known ages, M45 (0.125 Gyr), M44 (0.63 Gyr), and M67 (4.3 Gyr). We updated and employed the automated flare finding and analysis pipeline Appaloosa, originally designed for Kepler. We introduced a synthetic flare injection and recovery subroutine to ascribe detection and energy recovery rates for flares in a broad energy range for each light curve. We collected a sample of 1 761 stars, mostly late-K to mid-M dwarfs and found 751 flare candidates with energies ranging from 4⋅10324\cdot10^{32} erg to 6⋅10346\cdot10^{34} erg, of which 596 belong to M45, 155 to M44, and none to M67. We find that flaring activity depends both on TeffT_\mathrm{eff}, and age. But all flare frequency distributions have similar slopes with α≈2.0−2.4\alpha \approx2.0-2.4, supporting a universal flare generation process. We discuss implications for the physical conditions under which flares occur, and how the sample's metallicity and multiplicity affect our results.Comment: 17 pages, 11 figures, appendix. Accepted to A&

    Dual models for p-form mimetic gravity and their connection to perfect fluids consisting of (p+1)-branes

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    We propose an approach that allows one to reformulate nn-dimensional pp-form mimetic gravity (including usual mimetic gravity as particular case p=0p = 0) as nonlinear (n−p−1)(n-p-1)-form electrodynamics via electric-magnetic duality. The resulting dual Lagrangian density is just the square root of the ordinary quadratic Lagrangian density of (n−p−1)(n-p-1)-form electrodynamics. By applying field transformation in the action, we show that for the arbitrary pp this dual theory transforms into the (p+1)(p+1)-brane fluid: the model of the stack of the parallel (p+1)(p+1)-branes foliating physical spacetime. As the structure of the field transformations depends on pp, the sets of solutions in these models are related differently. We prove, that for p=0p = 0 and p=n−2p = n-2 dual mimetic models describe usual particle fluid with the potential flow and to the (n−1)(n-1)-brane fluid respectively. For other values of pp not all mimetic solutions behave like that, in general, so we restrict ourselves only to the case n=4n = 4, p=1p = 1. In this case, we show, that mimetic formulation is dual to the well-known Nielsen-Olesen theory of "dual strings" and discuss the criterion indicating whether its solutions behave like string fluid.Comment: 12 page
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