2,524 research outputs found
Gravitational waves from the Papaloizou-Pringle instability in black hole-torus systems
Black hole (BH)--torus systems are promising candidates for the central
engine of gamma-ray bursts (GRBs), and also possible outcomes of the collapse
of supermassive stars to supermassive black holes (SMBHs). By three-dimensional
general relativistic numerical simulations, we show that an
nonaxisymmetric instability grows for a wide range of self-gravitating tori
orbiting BHs. The resulting nonaxisymmetric structure persists for a timescale
much longer than the dynamical one, becoming a strong emitter of large
amplitude, quasiperiodic gravitational waves. Our results indicate that both,
the central engine of GRBs and newly formed SMBHs, can be strong gravitational
wave sources observable by forthcoming ground-based and spacecraft detectors.Comment: 4 pages, 4 figure, to be published in PR
Raman and fluorescence contributions to resonant inelastic soft x-ray scattering on LaAlO/SrTiO heterostructures
We present a detailed study of the Ti 3 carriers at the interface of
LaAlO/SrTiO heterostructures by high-resolution resonant inelastic soft
x-ray scattering (RIXS), with special focus on the roles of overlayer thickness
and oxygen vacancies. Our measurements show the existence of interfacial Ti
3 electrons already below the critical thickness for conductivity and an
increase of the total interface charge up to a LaAlO overlayer thickness of
6 unit cells before it levels out. By comparing stoichiometric and oxygen
deficient samples we observe strong Ti 3 charge carrier doping by oxygen
vacancies. The RIXS data combined with photoelectron spectroscopy and transport
measurements indicate the simultaneous presence of localized and itinerant
charge carriers. However, it is demonstrated that the relative amount of
localized and itinerant Ti electrons in the ground state cannot be deduced
from the relative intensities of the Raman and fluorescence peaks in excitation
energy dependent RIXS measurements, in contrast to previous interpretations.
Rather, we attribute the observation of either the Raman or the fluorescence
signal to the spatial extension of the intermediate state reached in the RIXS
excitation process.Comment: 9 pages, 6 figure
Evolution of equal mass binary bare quark stars in full general relativity: could a supramassive merger remnant experience prompt collapse?
We have evolved mergers of equal-mass binary quark stars, the total mass of which is close to the mass shedding limit of uniformly rotating configurations, in fully general relativistic hydrodynamic simulations, aimed at investigating the post-merger outcomes. In particular, we have identified the threshold mass for prompt black hole formation after the merger, by tracing the minimum lapse function as well as the amount of ejected material during the merger simulation. A semi-analytical investigation based on the angular momentum contained in the merger remnant is also performed to verify the results. For the equation of state considered in this work, the maximum mass of TOV solutions for which is 2.10 , the threshold mass is found between 3.05 and 3.10 . This result is consistent (with a quantitative error smaller than 1%) with the universal relation derived from the numerical results of symmetric binary neutron star mergers. Contrary to the neutron star case, the threshold mass is close to the mass shedding limit of uniformly rotating quark star. Consequently, we have found that binary quark stars with total mass corresponding to the long-lived supramassive remnant for neutron star case, could experience collapse to black hole within several times dynamical timescale, making quark stars as exceptions of the commonly accepted post-merger scenarios for binary neutron star mergers. We have suggested explanation for both the similarity and the difference, between quark stars and neutron stars
cDNA cloning and inducible expression of human multidrug resistance associated protein 3 (MRP3)1The sequence reported in this paper has been submitted to GenBank with the accession number of AB010887.1
AbstractPreviously, we cloned rat MRP3 as a candidate for an inducible transporter for the biliary excretion of organic anions [Hirohashi et al. (1998) Mol. Pharmacol. 53, 1068–1075]. In the present study, we cloned human MRP3 (1527 amino acids) from Caco-2 cells. Human MRP3 is predominantly expressed in liver, small intestine and colon; hepatic expression of MRP3 was observed in humans but not in normal rats. In HepG2 cells, the expression of MRP3 was induced by phenobarbital. These results suggest that MRP3 may act as an inducible transporter in the biliary and intestinal excretion of organic anions
Equilibrium Configurations of Strongly Magnetized Neutron Stars with Realistic Equations of State
We investigate equilibrium sequences of magnetized rotating stars with four
kinds of realistic equations of state (EOSs) of SLy (Douchin et al.), FPS
(Pandharipande et al.), Shen (Shen et al.), and LS (Lattimer & Swesty).
Employing the Tomimura-Eriguchi scheme to construct the equilibrium
configurations. we study the basic physical properties of the sequences in the
framework of Newton gravity. In addition we newly take into account a general
relativistic effect to the magnetized rotating configurations. With these
computations, we find that the properties of the Newtonian magnetized stars,
e.g., structure of magnetic field, highly depends on the EOSs.
The toroidal magnetic fields concentrate rather near the surface for Shen and
LS EOSs than those for SLy and FPS EOSs. The poloidal fields are also affected
by the toroidal configurations. Paying attention to the stiffness of the EOSs,
we analyze this tendency in detail. In the general relativistic stars, we find
that the difference due to the EOSs becomes small because all the employed EOSs
become sufficiently stiff for the large maximum density, typically greater than
. The maximum baryon mass of the magnetized stars
with axis ratio increases about up to twenty percents for that of
spherical stars. We furthermore compute equilibrium sequences at finite
temperature, which should serve as an initial condition for the hydrodynamic
study of newly-born magnetars. Our results suggest that we may obtain
information about the EOSs from the observation of the masses of magnetars.Comment: submitted to MNRA
Gravitational Waves from Chaotic Dynamical System
To investigate how chaos affects gravitational waves, we study the
gravitational waves from a spinning test particle moving around a Kerr black
hole, which is a typical chaotic system. To compare the result with those in
non-chaotic dynamical system, we also analyze a spinless test particle, which
orbit can be complicated in the Kerr back ground although the system is
integrable. We estimate the emitted gravitational waves by the multipole
expansion of a gravitational field. We find a striking difference in the energy
spectra of the gravitational waves. The spectrum for a chaotic orbit of a
spinning particle, contains various frequencies, while some characteristic
frequencies appear in the case of a spinless particle.Comment: 8 pages, 13 figures. submitted to PR
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