19 research outputs found
R-Process Nucleosynthesis in MHD Jet Explosions of Core-Collapse Supernovae
We investigate -process nucleosynthesis during the magnetohydrodynamical
(MHD) explosion of supernova in a massive star of 13 . Contrary to
the case of the spherical explosion, jet-like explosion due to the combined
effects of the rotation and magnetic field lowers the electron fraction
significantly inside the layers above the iron core. We find that the ejected
material of low electron fraction responsible for the -process comes out
from the silicon rich layer of the presupernova model. This leads to the
production up to the third peak in the solar -process elements. We examine
whether the fission affects the -process paths by using the full nuclear
reaction network with both the spontaneous and -delayed fission
included. Moreover, we pay particular attention how the mass formula affects
the -process peaks with use of two mass formulae. It is found that both
formulae can reproduce the global abundance pattern up to the third peak though
detailed distributions are rather different. We point out that there are
variations in the -process nucleosynthesis if the MHD effects play an
important role in the supernova explosion.Comment: 19 pages with 7 figures, submitted to Ap
Thermodynamic properties of nuclear "pasta" in neutron star crusts
Equilibrium phase diagrams for neutron star matter at subnuclear densities
are obtained at zero temperature. Spherical, rod-like and slab-like nuclei as
well as spherical and rod-like nuclear bubbles are taken into account by using
a compressible liquid-drop model. This model is designed to incorporate
uncertainties in the nuclear surface tension and in the proton chemical
potential in a gas of dripped neutrons. The resultant phase diagrams show that
for typical values of these quantities, the phases with rod-like nuclei and
with slab-like nuclei occur in the form of Coulomb lattice at densities below a
point where the system becomes uniform. Thermal fluctuations leading to
displacements of such nuclei from their equilibrium positions are considered
through explicit evaluations of their elastic constants; these fluctuations can
be effective at destroying the layered lattice of slab-like nuclei in the
temperature region typical of matter in the neutron star crust.Comment: 37 pages and 10 postscript figures. Nuclear Physics A (accepted
On the Importance of the Equation of State for the Neutrino-Driven Supernova Explosion Mechanism
By implementing widely-used equations of state (EOS) from Lattimer & Swesty
(LS) and H. Shen et al. (SHEN) in core-collapse supernova simulations, we
explore possible impacts of these EOS on the post-bounce dynamics prior to the
onset of neutrino-driven explosions. Our spherically symmetric (1D) and axially
symmetric (2D) models are based on neutrino radiation hydrodynamics including
spectral transport, which is solved by the isotropic diffusion source
approximation. We confirm that in 1D simulations neutrino-driven explosions
cannot be obtained for any of the employed EOS. Impacts of the EOS on the
post-bounce hydrodynamics are more clearly visible in 2D simulations. In 2D
models of a 15 M_sun progenitor using the LS EOS, the stalled bounce shock
expands to increasingly larger radii, which is not the case using the SHEN EOS.
Keeping in mind that the omission of the energy drain by heavy-lepton neutrinos
in the present scheme could facilitate explosions, we find that 2D models of an
11.2 M_sun progenitor produce neutrino-driven explosions for all the EOS under
investigation. Models using the LS EOS are slightly more energetic compared to
those with the SHEN EOS. The more efficient neutrino heating in the LS models
coincides with a higher electron antineutrino luminosity and a larger mass that
is enclosed within the gain region. The models based on the LS EOS also show a
more vigorous and aspherical downflow of accreting matter to the surface of the
protoneutron star (PNS). The accretion pattern is essential for the production
and strength of outgoing pressure waves, that can push in turn the shock to
larger radii and provide more favorable conditions for the explosion.
[abbreviated]Comment: 21 pages, 22 figures, accepted for publication in Ap
Enhanced production of nitric oxide, reactive oxygen species, and pro-inflammatory cytokines in very long chain saturated fatty acid-accumulated macrophages
<p>Abstract</p> <p>Background</p> <p>Deterioration of peroxisomal β-oxidation activity causes an accumulation of very long chain saturated fatty acids (VLCSFA) in various organs. We have recently reported that the levels of VLCSFA in the plasma and/or membranes of blood cells were significantly higher in patients with metabolic syndrome and in patients with coronary artery disease than the controls. The aim of the present study is to investigate the effect of VLCSFA accumulation on inflammatory and oxidative responses in VLCSFA-accumulated macrophages derived from X-linked adrenoleukodystrophy (X-ALD) protein (ALDP)-deficient mice.</p> <p>Results</p> <p>Elevated levels of VLCSFA were confirmed in macrophages from ALDP-deficient mice. The levels of nitric oxide (NO) production stimulated by lipopolysaccharide (LPS) and interferon-γ (IFN-γ), intracellular reactive oxygen species (ROS), and pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interluekin-6 (IL-6), and interleukin-12p70 (IL-12p70), were significantly higher in macrophages from ALDP-deficient mice than in those from wild-type mice. The inducible NO synthase (iNOS) mRNA expression also showed an increase in macrophages from ALDP-deficient mice.</p> <p>Conclusion</p> <p>These results suggested that VLCSFA accumulation in macrophages may contribute to the pathogenesis of inflammatory diseases through the enhancement of inflammatory and oxidative responses.</p
Effects of fenofibrate on lipid profiles, cholesterol ester transfer activity, and in-stent intimal hyperplasia in patients after elective coronary stenting
Enhanced production of nitric oxide, reactive oxygen species, and pro-inflammatory cytokines in very long chain saturated fatty acid-accumulated macrophages
Impacts of Collective Neutrino Oscillations on Supernova Explosions
By performing a series of one- and two-dimensional (1-, 2D) hydrodynamic
simulations with spectral neutrino transport, we study possible impacts of
collective neutrino oscillations on the dynamics of core-collapse supernovae.
To model the spectral swapping which is one of the possible outcome of the
collective neutrino oscillations, we parametrize the onset time when the
spectral swap begins, the radius where the spectral swap occurs, and the
threshold energy above which the spectral interchange between heavy-lepton
neutrinos and electron/anti-electron neutrinos takes place, respectively. By
doing so, we systematically study how the neutrino heating enhanced by the
spectral swapping could affect the shock evolution as well as the matter
ejection. We also investigate the progenitor dependence using a suite of
progenitor models (13, 15, 20, and 25 ). We find that there is a
critical heating rate induced by the spectral swapping to trigger explosions,
which significantly differs between the progenitors. The critical heating rate
is generally smaller for 2D than 1D due to the multidimensionality that
enhances the neutrino heating efficiency. For the progenitors employed in this
paper, the final remnant masses are estimated to range in 1.1-1.5. For
our 2D model of the progenitor, we find a set of the oscillation
parameters that could account for strong supernova explosions (
erg), simultaneously leaving behind the remnant mass close to .Comment: accepted for publication in ApJ; 14 pages, 18 figures; quality of
some figures reduce