1,051 research outputs found
Interaction and Localization of One-electron Orbitals in an Organic Molecule: Fictitious Parameter Analysis for Multi-physics Simulations
We present a new methodology to analyze complicated multi-physics simulations
by introducing a fictitious parameter. Using the method, we study quantum
mechanical aspects of an organic molecule in water. The simulation is
variationally constructed from the ab initio molecular orbital method and the
classical statistical mechanics with the fictitious parameter representing the
coupling strength between solute and solvent. We obtain a number of
one-electron orbital energies of the solute molecule derived from the
Hartree-Fock approximation, and eigenvalue-statistical analysis developed in
the study of nonintegrable systems is applied to them. Based on the results, we
analyze localization properties of the electronic wavefunctions under the
influence of the solvent.Comment: 4 pages, 5 figures, the revised version will appear in J. Phys. Soc.
Jpn. Vol.76 (No.1
Discovery of a Wide Substellar Companion to a Nearby Low-Mass Star
We report the discovery of a wide (135+/-25 AU), unusually blue L5 companion
2MASS J17114559+4028578 to the nearby M4.5 dwarf G 203-50 as a result of a
targeted search for common proper motion pairs in the Sloan Digital Sky Survey
and the Two Micron All Sky Survey. Adaptive Optics imaging with Subaru
indicates that neither component is a nearly equal mass binary with separation
> 0.18", and places limits on the existence of additional faint companions. An
examination of TiO and CaH features in the primary's spectrum is consistent
with solar metallicity and provides no evidence that G 203-50 is metal poor. We
estimate an age for the primary of 1-5 Gyr based on activity. Assuming
coevality of the companion, its age, gravity and metallicity can be constrained
from properties of the primary, making it a suitable benchmark object for the
calibration of evolutionary models and for determining the atmospheric
properties of peculiar blue L dwarfs. The low total mass (M_tot=0.21+/-0.03
M_sun), intermediate mass ratio (q=0.45+/-0.14), and wide separation of this
system demonstrate that the star formation process is capable of forming wide,
weakly bound binary systems with low mass and BD components. Based on the
sensitivity of our search we find that no more than 2.2% of early-to-mid M
dwarfs (9.0 0.06 M_sun.Comment: 24 pages, 5 figures, accepted for publication in Ap
Distinguishing between different mechanisms of FU-Orionis-type luminosity outbursts
Aims. Accretion and luminosity bursts triggered by three distinct mechanisms:
the magnetorotational instability in the inner disk regions, clump infall in
gravitationally fragmented disks and close encounters with an intruder star,
were studied to determine the disk kinematic characteristics that can help to
distinguish between these burst mechanisms. Methods. Numerical hydrodynamics
simulations in the thin-disk limit were employed to model the bursts in disk
environments that are expected for each burst mechanism. Results. We found that
the circumstellar disks featuring accretion bursts can bear kinematic features
that are distinct for different burst mechanisms, which can be useful when
identifying the burst origin. The disks in the stellar encounter and
clump-infall models are characterized by tens of percent deviations from the
Keplerian rotation, whie the disks in the MRI models are characterized only a
few percent deviation, which is mostly caused by the gravitational instability
that fuels the MRI bursts. Velocity channel maps also show distinct kinks and
wiggles, which are caused by gas disk flows that are peculiar to each
considered burst mechanism. The deviations of velocity channels in the
burst-hosting disks from a symmetric pattern typical of Keplerian disks are
strongest for the clump-infall and collision models, and carry individual
features that may be useful for the identification of the corresponding burst
mechanism. The considered burst mechanisms produce a variety of light curves
with the burst amplitudes varying in the \Delta m=2.5-3.7 limits, except for
the clump-infall model where \Delta m can reach 5.4, although the derived
numbers may be affected by a small sample and boundary conditions. Conclusions.
Burst triggering mechanisms are associated with distinct kinematic features in
the burst-hosting disks that may be used for their identification. Abridged.Comment: Accepted for publication by Astronomy & Astrophysic
Red blood cell dispersion in 100 um glass capillaries: the temperature effect
The rheological behaviour of the red blood cells (RBCs) flowing in microvessels and microchannels depend on several effects, such as hematocrit (Hct), geometry, and temperature.
Previous in vitro studies have measured the Hct effect on the radial dispersion (Dyy) at both diluted and concentrated suspensions of RBCs. However, according to our knowledge
the effect of the temperature on RBC Dyy was never studied.
Hence, the main purpose of the present work is to investigate the effect of the temperature on the RBC Dyy. In vitro human blood was pumped through a 100 μm glass capillary and by using a confocal micro-PTV system the RBC Dyy was calculated at two different temperatures, i.e., 25ºC and
37ºC.This study was supported in part by the following grants: Grant-in-Aid for Scientific Research (S) from the Japan Society for the Promotion of Science (JSPS; no 19100008), Grant-in-Aid for Science and Technology (PTDC/SAL-BEB/108728/2008, PTDC/SAU-BEB/105650/2008 and PTDC/EME-MFE/099109/2008) from the Science and Technology Foundation (FCT) and COMPETE, Portugal. We also acknowledge the support from the 2007 Global COE Program “Global NanoBiomedical Engineering Education and Research Network’
Linear response theory in the continuum for deformed nuclei: Green's function vs. time-dependent Hartree-Fock with the absorbing-boundary condition
The continuum random-phase approximation is extended to the one applicable to
deformed nuclei. We propose two different approaches. One is based on the use
of the three dimensional (3D) Green's function and the other is the
small-amplitude TDHF with the absorbing-boundary condition. Both methods are
based on the 3D Cartesian grid representation and applicable to systems without
any symmetry on nuclear shape. The accuracy and identity of these two methods
are examined with the BKN interaction. Using the full Skyrme energy functional
in the small-amplitude TDHF approach, we study the isovector giant dipole
states in the continuum for O-16 and for even-even Be isotopes.Comment: 15 pages, 8 figure
First Detection of NaI D lines in High-Redshift Damped Lyman-alpha Systems
A Near-infrared (1.18-1.35 micron) high-resolution spectrum of the
gravitationally-lensed QSO APM 08279+5255 was obtained with the IRCS mounted on
the Subaru Telescope using the AO system. We detected strong NaI D 5891,5897
doublet absorption in high-redshift DLAs at z=1.062 and 1.181, confirming the
presence of NaI, which was first reported for the rest-frame UV NaI
3303.3,3303.9 doublet by Petitjean et al. This is the first detection of NaI D
absorption in a high-redshift (z>1) DLA. In addition, we detected a new NaI
component in the z=1.062 DLA and four new components in the z=1.181 DLA. Using
an empirical relationship between NaI and HI column density, we found that all
"components" have large HI column density, so that each component is classified
as DLA absorption. We also detected strong NaI D absorption associated with a
MgII system at z=1.173. Because no other metal absorption lines were detected
in this system at the velocity of the NaI absorption in previously reported
optical spectra (observed 3.6 years ago), we interpret this NaI absorption
cloud probably appeared in the line of sight toward the QSO after the optical
observation. This newly found cloud is likely to be a DLA based upon its large
estimated HI column density. We found that the N(NaI)/N(CaII) ratios in these
DLAs are systematically smaller than those observed in the Galaxy; they are
more consistent with the ratios seen in the Large Magellanic Cloud. This is
consistent with dust depletion generally being smaller in lower metallicity
environments. However, all five clouds of the z=1.181 system have a high
N(NaI)/N(CaII) ratio, which is characteristic of cold dense gas. We tentatively
suggest that the host galaxy of this system may be the most significant
contributor to the gravitational-lens toward APM 08279+5255.Comment: 22 pages, 6 Postscript figures, 3 tables, ApJ in press (Vol.643, 2
June 2006
Diagnosing 0.1–10 au Scale Morphology of the FU Ori Disk Using ALMA and VLTI/GRAVITY
We report new Atacama Large Millimeter/submillimeter Array Band 3 (86–100 GHz; ~80 mas angular resolution) and Band 4 (146–160 GHz; ~50 mas angular resolution) observations of the dust continuum emission toward the archetypal and ongoing accretion burst young stellar object FU Ori, which simultaneously covered its companion, FU Ori S. In addition, we present near-infrared (2–2.45 μm) observations of FU Ori taken with the General Relativity Analysis via VLT InTerferometrY (GRAVITY; ~1 mas angular resolution) instrument on the Very Large Telescope Interferometer (VLTI). We find that the emission in both FU Ori and FU Ori S at (sub)millimeter and near-infrared bands is dominated by structures inward of ~10 au radii. We detected closure phases close to zero from FU Ori with VLTI/GRAVITY, which indicate the source is approximately centrally symmetric and therefore is likely viewed nearly face-on. Our simple model to fit the GRAVITY data shows that the inner 0.4 au radii of the FU Ori disk has a triangular spectral shape at 2–2.45 μm, which is consistent with the H2O and CO absorption features in a 10−4 M ⊙ yr−1, viscously heated accretion disk. At larger (~0.4–10 au) radii, our analysis shows that viscous heating may also explain the observed (sub)millimeter and centimeter spectral energy distribution when we assume a constant, ~10−4 M ⊙ yr−1 mass inflow rate in this region. This explains how the inner 0.4 au disk is replenished with mass at a modest rate, such that it neither depletes nor accumulates significant masses over its short dynamic timescale. Finally, we tentatively detect evidence of vertical dust settling in the inner 10 au of the FU Ori disk, but confirmation requires more complete spectral sampling in the centimeter bands
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