284 research outputs found
N-body Simulations of Satellite Formation around Giant Planets: Origin of Orbital Configuration of the Galilean Moons
As the number of discovered extrasolar planets has been increasing, diversity
of planetary systems requires studies of new formation scenarios. It is
important to study satellite formation in circumplanetary disks, which is often
viewed as analogous to formation of rocky planets in protoplanetary disks. We
investigated satellite formation from satellitesimals around giant planets
through N-body simulations that include gravitational interactions with a
circumplanetary gas disk. Our main aim is to reproduce the observable
properties of the Galilean satellites around Jupiter through numerical
simulations, as previous N-body simulations have not explained the origin of
the resonant configuration. We performed accretion simulations based on the
work of Sasaki et al. (2010), in which an inner cavity is added to the model of
Canup & Ward (2002, 2006). We found that several satellites are formed and
captured in mutual mean motion resonances outside the disk inner edge and are
stable after rapid disk gas dissipation, which explains the characteristics of
the Galilean satellites. In addition, owing to the existence of the disk edge,
a radial compositional gradient of the Galilean satellites can also be
reproduced. An additional objective of this study is to discuss orbital
properties of formed satellites for a wide range of conditions by considering
large uncertainties in model parameters. Through numerical experiments and
semianalytical arguments, we determined that if the inner edge of a disk is
introduced, a Galilean-like configuration in which several satellites are
captured into a 2:1 resonance outside the disk inner cavity is almost
universal. In fact, such a configuration is produced even for a massive disk
and rapid type I migration. This result implies the inevitability of a Galilean
satellite formation in addition to providing theoretical predictions for
extrasolar satellites.Comment: 20 pages, 9 figures, accepted for publication in Ap
Modes in Light-Cone Quantization
We investigate the light-cone quantization of theory in 1+1
dimensions with a regularization of discretized light-cone momentum .
Solving a second-class constraint associated with the mode, we show
that the mode propagates along the internal lines of Feynman diagrams
in any order of perturbation, hence our theory recovers the Lorentz invariance.Comment: 14p
Eccentricity Trap: Trapping of Resonantly Interacting Planets near the Disk Inner Edge
Using orbital integration and analytical arguments, we have found a new
mechanism (an "eccentricity trap") to halt type I migration of planets near the
inner edge of a protoplanetary disk. Because asymmetric eccentricity damping
due to disk-planet interaction on the innermost planet at the disk edge plays a
crucial role in the trap, this mechanism requires continuous eccentricity
excitation and hence works for a resonantly interacting convoy of planets. This
trap is so strong that the edge torque exerted on the innermost planet can
completely halt type I migrations of many outer planets through mutual resonant
perturbations. Consequently, the convoy stays outside the disk edge, as a
whole. We have derived semi-analytical formula for the condition for the
eccentricity trap and predict how many planets are likely to be trapped. We
found that several planets or more should be trapped by this mechanism in
protoplanetary disks that have cavities. It can be responsible for the
formation of non-resonant, multiple, close-in super-Earth systems extending
beyond 0.1AU. Such systems are being revealed by radial velocity observations
to be quite common around solar-type stars.Comment: 24 pages, 7 figures, accepted for publication in Ap
N-body simulations of planetary accretion around M dwarf stars
We have investigated planetary accretion from planetesimals in terrestrial
planet regions inside the ice line around M dwarf stars through N-body
simulations including tidal interactions with disk gas. Because of low
luminosity of M dwarfs, habitable zones (HZs) are located in inner regions. In
the close-in HZ, type-I migration and the orbital decay induced by eccentricity
damping are efficient according to the high disk gas density in the small
orbital radii. In the case of full efficiency of type-I migration predicted by
the linear theory, we found that protoplanets that migrate to the vicinity of
the host star undergo close scatterings and collisions, and 4 to 6 planets
eventually remain in mutual mean motion resonances and their orbits have small
eccentricities and they are stable both before and after disk gas decays. In
the case of slow migration, the resonant capture is so efficient that
densely-packed ~ 40 small protoplanets remain in mutual mean motion resonances.
In this case, they start orbit crossing, after the disk gas decays and
eccentricity damping due to tidal interaction with gas is no more effective.
Through merging of the protoplanets, several planets in widely-separated
non-resonant orbits with relatively large eccentricities are formed. Thus, the
final orbital configurations of the terrestrial planets around M dwarfs
sensitively depend on strength of type-I migration. We also found that large
amount of water-ice is delivered by type-I migration from outer regions and
final planets near the inner disk edge around M dwarfs are generally abundant
in water-ice except for the innermost one that is shielded by the outer
planets, unless type-I migration speed is reduced by a factor of more than 100
from that predicted by the linear theory.Comment: Accepted to ApJ. 33 pages, 9 figures, 1 tabl
Tumor-dependent secretion of close homolog of L1 results in elevation of its circulating level in mouse model for human lung tumor
Close homolog of L1 (CHL1) and its truncated form mainly play crucial roles in mouse brain development and neural functions. Herein, we newly identified that truncated form of CHL1 is produced and released from lung tumor tissue in a mouse model expressing human EML4-ALK fusion gene. Both western blot and direct ELISA analysis revealed that mouse CHL1 level in serum (including serum extracellular vesicles) was significantly elevated in EML4-ALK transgenic mice. The correlation between the tumor size and the amount of CHL1 secretion could be examined in this study, and showed a significant positive correlation in a tumor size-dependent manner. Considering these results, the measurement of circulating CHL1 level may contribute to assess a tumor progression in human lung tumor patients
Turbulence Spreading into an Edge Stochastic Magnetic Layer Induced by Magnetic Fluctuation and Its Impact on Divertor Heat Load
Turbulence spreading into the edge stochastic magnetic layer induced by magnetic fluctuation is observed at the sharp boundary region in the large helical device. The density fluctuation excited at the sharp boundary region with a large pressure gradient does not propagate into the boundary region due to the blocking of turbulence spreading by the large second derivative of the pressure gradient. Once the magnetic fluctuation appears at the boundary, the density fluctuation begins to penetrate the edge stochastic layer and the second derivative of the pressure gradient also decreases. The increase of density fluctuation in this layer results in the broadening and reduction of the peak divertor heat load. It is demonstrated that magnetic fluctuation plays a key role in controlling the turbulence spreading at the boundary of plasma which contributes to the reduction of divertor heat load
Measurement of radial profiles of density ratio of helium to hydrogen ion using charge exchange spectroscopy with two-wavelength spectrometer
Radial profiles of density ratio of helium to hydrogen ions are measured using the charge exchange spectroscopy technique with the two-wavelength spectrometer system in the large helical device. The two-wavelength spectrometer system consists of a dichroic mirror box, a spectrometer with two grating and two camera lenses, and one CCD detector. The dichroic mirror box is used to divide the light of one fiber from the plasma to two fibers, one for HeII (λ = 468.6 nm) and the other for Hα (λ = 656.3 nm), that are connected to the entrance slit of the spectrometer to eliminate the interference between the HeII and the Hα spectra on the CCD. This system provides a simultaneous measurement of helium and hydrogen ion density ratio at 8 exact same locations (8 spatial channels) with a time resolution of >40 ms in the wide range of the density ratio of 0.05–5
Pharmacological inhibition of ataxia-telangiectasia mutated exacerbates acute kidney injury by activating p53 signaling in mice
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