1,994 research outputs found
Neutron skin of Al with Skyrme and Korea-IBS-Daegu-SKKU density functionals
Recent measurement of the parity-violating (PV) asymmetry in the elastic
electron scattering on Al target evokes the interest in the distribution
of the neutron in the nucleus. In this work, we calculate the neutron skin
thickness () of Al with nonrelativistic nuclear structure
models. We focus on the role of the effective mass, symmetry energy and pairing
force. Models are selected to have effective masses in the range
where is the nucleon mass in free space, and stiffness of the symmetry
energy is varied by choosing the slope of the symmetry energy in the range 9.4
-- 100.5 MeV. Effect of pairing force is investigated by calculating
with and without pairing, and using two different forms of the pairing force.
With nine models, we obtain fm. The result is
independent of the effective mass, symmetry energy, and the form of pairing
force. However, is negative when the pairing force is switched off, so
the pairing force plays an essential role to make positive and
constrained in a narrow range. We also calculate the PV asymmetry () in the elastic electron-Al scattering in the Born approximation at
the kinematics of the Qweak experiment. We obtain a very narrow-ranged result
(2.07 -- 2.09) . The result is consistent with
the experiment and insensitive to the effective mass, symmetry energy and
pairing force.Comment: 5 pages, 2 figure
Gravitational Lensing by Power-Law Mass Distributions: A Fast and Exact Series Approach
We present an analytical formulation of gravitational lensing using familiar
triaxial power-law mass distributions, where the 3-dimensional mass density is
given by . The deflection angle and magnification factor are
obtained analytically as Fourier series. We give the exact expressions for the
deflection angle and magnification factor. The formulae for the deflection
angle and magnification factor given in this paper will be useful for numerical
studies of observed lens systems. An application of our results to the Einstein
Cross can be found in Chae, Turnshek, & Khersonsky (1998). Our series approach
can be viewed as a user-friendly and efficient method to calculate lensing
properties that is better than the more conventional approaches, e.g.,
numerical integrations, multipole expansions.Comment: 24 pages, 3 Postscript figures, ApJ in press (October 10th
Two-gap and paramagnetic pair-breaking effects on upper critical field of SmFeAsO and SmFeAsOF single crystals
We investigated the temperature dependence of the upper critical field
[] of fluorine-free SmFeAsO and fluorine-doped
SmFeAsOF single crystals by measuring the resistive transition
in low static magnetic fields and in pulsed fields up to 60 T. Both crystals
show that 's along the c axis [] and in an -planar
direction [] exhibit a linear and a sublinear increase,
respectively, with decreasing temperature below the superconducting transition.
's in both directions deviate from the conventional one-gap
Werthamer-Helfand-Hohenberg theoretical prediction at low temperatures. A
two-gap nature and the paramagnetic pair-breaking effect are shown to be
responsible for the temperature-dependent behavior of and
, respectively.Comment: 21 pages, 8 figure
Limits of Binaries That Can Be Characterized by Gravitational Microlensing
Due to the high efficiency of planet detections, current microlensing planet
searches focus on high-magnification events. High-magnification events are
sensitive to remote binary companions as well and thus a sample of
wide-separation binaries are expected to be collected as a byproduct. In this
paper, we show that characterizing binaries for a portion of this sample will
be difficult due to the degeneracy of the binary-lensing parameters. This
degeneracy arises because the perturbation induced by the binary companion is
well approximated by the Chang-Refsdal lensing for binaries with separations
greater than a certain limit. For binaries composed of equal mass lenses, we
find that the lens binarity can be noticed up to the separations of
times of the Einstein radius corresponding to the mass of each lens. Among
these binaries, however, we find that the lensing parameters can be determined
only for a portion of binaries with separations less than times of
the Einstein radius.Comment: 5 pages, 3 figures, 1 tabl
Dynamics of fullerene coalescence
Fullerene coalescence experimentally found in fullerene-embedded single-wall
nanotubes under electron-beam irradiation or heat treatment is simulated by
minimizing the classical action for many atom systems. The dynamical trajectory
for forming a (5,5) C nanocapsule from two C fullerene molecules
consists of thermal motions around potential basins and ten successive
Stone-Wales-type bond rotations after the initial cage-opening process for
which energy cost is about 8 eV. Dynamical paths for forming large-diameter
nanocapsules with (10,0), (6,6), and (12,0) chiral indexes have more bond
rotations than 25 with the transition barriers in a range of 10--12 eV.Comment: 4 pages, 2 figures, 1 supplementary movie at
http://dielc.kaist.ac.kr/yonghyun/coal.mpeg. To be published in Physical
Review Letter
Environmental considerations of plastic behaviors for automobile applications
AbstractIt is well known fact that the thermo-mechanical behaviors of polymeric materials are strongly influenced by environmental factors, and, for automobiles, the mechanical properties of interior plastic structures are noticeably changed by being repeatedly exposed to environments such as sun light and rains. As the properties change, mechanical fits such as fasteners and clips in automobiles lose their tightness, creating unexpected noises. To consider Buzz, Squeak and Rattle (BSR) from initial stage of the interior design, it is very important to obtain, analyze and understand the structural behaviors of the materials under environmental changes as well as time. In this report, the mechanical property changes of the plastics for automobiles are measured to investigate the temperature and humidity effects. The samples are undergone different temperature and humidity conditions, and regularly taken out to measure the thermo-mechanical properties. The data are compared with the original samples, and analyzed for the properties change. Viscoelastic characteristics such as glass transition temperatures and storage/loss modulus were also investigate
Microlensing under Shear
We investigate the distortions due to this shear in the microlensing light
curves and in the astrometric microlensing centroid shift trajectories. As
expected, the light curve deviation increases as the shear increases and the
impact parameter decreases. Although the light curve in the presence of a small
shear is similar to the simple Paczynski curve with a slightly smaller impact
parameter, the detailed difference between the light curve with and without
shear reflects the direction and the magnitude of the shear. The centroid shift
trajectory also deviates from a simple ellipse in the presence of shear. The
distortion of the centroid shift trajectory increases as the impact parameter
decreases, and the shape of the trajectory becomes complicated when the impact
parameter becomes small enough. The magnitude of the maximum distortion depends
on the magnitude and the direction of the shear. For a source trajectory in a
given direction, the time of the maximum distortion depends mostly on the
impact parameter and hardly on the shear. It is possible to determine the
magnitude of the shear and its direction if both the time and the magnitude of
the maximum astrometric distortion are measured. The magnitude of the shear
produced by the Galactic bulge or a globular cluster falls in the range
10^{-6}--10^{-4} in normalized units. Although the actual determination of the
shear from the Galactic sub-structures will not be easy due to complications
such as binary companion, future large scale microlensing experiments may
enable us to determine the shear in some high amplification events, leading
eventually to mapping the Galactic mass distribution.Comment: 15 pages, 11 figures, ApJ accepe
Folding potential with modern nuclear density functionals and application to 16O+208Pb reaction
Double folding potential is constructed using the M3Y interaction and the
matter densities of the projectile and target nuclei obtained from four
microscopic energy density functional (EDF) models. The elastic scattering
cross sections for the 16O+208Pb system are calculated using the optical model
with the double folding potentials of the four EDF models. We focus on the
correlation between the matter densities and the behavior the double folding
potential and the elastic scattering cross sections. First, the matter and
charge densities are examined by comparing the results of the four EDF models.
There is a slight difference in the density in the internal region, but it is
negligible in the outer region. Next, we calculate the double folding potential
with the matter densities obtained from the four EDF models. Differences
between the models are negligible in the outer region, but the potential depth
in the internal region shows model dependence, which can be understood from the
behavior of matter densities in the internal region. Another point is that the
double folding potential is shown to be weakly dependent on the incident
energy. Finally, the elastic scattering cross sections have no significant
model dependence except for the slight difference in the backward angle.Comment: 17 pages, 13 figure
Occlusal reduction of unilateral molars influences change of stress-related hormones in rats
In order to investigate the change of stress-related hormones by dental occlusal reduction, we ground molars in Sprague-Dawley (SD) rats and evaluated the effect on hormone levels. Thirteen and 18 weeks after occlusal reduction, cortisol concentration was increased 2.75 and 2.17 fold respectively, whereas corticosterone concentration was slightly elevated by 31.2% and 13.5%, respectively. Body weight was slightly decreased, but feed and water intake, and blood chemistry were the same in the experimental group as in the control group. Our results suggest that unilateral molar occlusal reduction may influence cortisol and corticosterone levels and the endocrine system, leading to hormone imbalance through the body.
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