1,086 research outputs found
Nucleosynthesis in 2D Core-Collapse Supernovae of 11.2 and 17.0 M Progenitors: Implications for Mo and Ru Production
Core-collapse supernovae are the first polluters of heavy elements in the
galactic history. As such, it is important to study the nuclear compositions of
their ejecta, and understand their dependence on the progenitor structure
(e.g., mass, compactness, metallicity). Here, we present a detailed
nucleosynthesis study based on two long-term, two-dimensional core-collapse
supernova simulations of a 11.2 M and a 17.0 M star. We
find that in both models nuclei well beyond the iron group (up to ) can be produced, and discuss in detail also the nucleosynthesis of the
p-nuclei Mo and Ru. While we observe the production of
Mo and Mo in slightly neutron-rich conditions in both
simulations, Ru can only be produced efficiently via the
p-process. Furthermore, the production of Ru in the p-process heavily
depends on the presence of very proton-rich material in the ejecta. This
disentanglement of production mechanisms has interesting consequences when
comparing to the abundance ratios between these isotopes in the solar system
and in presolar grains.Comment: 48 pages, 19 figures, accepted for publication in: J. Phys. G: Nucl.
Part. Phy
Gravitational waves from supernova matter
We have performed a set of 11 three-dimensional magnetohydrodynamical core
collapse supernova simulations in order to investigate the dependencies of the
gravitational wave signal on the progenitor's initial conditions. We study the
effects of the initial central angular velocity and different variants of
neutrino transport. Our models are started up from a 15 solar mass progenitor
and incorporate an effective general relativistic gravitational potential and a
finite temperature nuclear equation of state. Furthermore, the electron flavour
neutrino transport is tracked by efficient algorithms for the radiative
transfer of massless fermions. We find that non- and slowly rotating models
show gravitational wave emission due to prompt- and lepton driven convection
that reveals details about the hydrodynamical state of the fluid inside the
protoneutron stars. Furthermore we show that protoneutron stars can become
dynamically unstable to rotational instabilities at T/|W| values as low as ~2 %
at core bounce. We point out that the inclusion of deleptonization during the
postbounce phase is very important for the quantitative GW prediction, as it
enhances the absolute values of the gravitational wave trains up to a factor of
ten with respect to a lepton-conserving treatment.Comment: 10 pages, 6 figures, accepted, to be published in a Classical and
Quantum Gravity special issue for MICRA200
Neutrino oscillations in magnetically driven supernova explosions
We investigate neutrino oscillations from core-collapse supernovae that
produce magnetohydrodynamic (MHD) explosions. By calculating numerically the
flavor conversion of neutrinos in the highly non-spherical envelope, we study
how the explosion anisotropy has impacts on the emergent neutrino spectra
through the Mikheyev-Smirnov-Wolfenstein effect. In the case of the inverted
mass hierarchy with a relatively large theta_(13), we show that survival
probabilities of electron type neutrinos and antineutrinos seen from the
rotational axis of the MHD supernovae (i.e., polar direction), can be
significantly different from those along the equatorial direction. The event
numbers of electron type antineutrinos observed from the polar direction are
predicted to show steepest decrease, reflecting the passage of the
magneto-driven shock to the so-called high-resonance regions. Furthermore we
point out that such a shock effect, depending on the original neutrino spectra,
appears also for the low-resonance regions, which leads to a noticeable
decrease in the electron type neutrino signals. This reflects a unique nature
of the magnetic explosion featuring a very early shock-arrival to the resonance
regions, which is in sharp contrast to the neutrino-driven delayed supernova
models. Our results suggest that the two features in the electron type
antineutrinos and neutrinos signals, if visible to the Super-Kamiokande for a
Galactic supernova, could mark an observational signature of the magnetically
driven explosions, presumably linked to the formation of magnetars and/or
long-duration gamma-ray bursts.Comment: 25 pages, 21 figures, JCAP in pres
Biermann Mechanism in Primordial Supernova Remnant and Seed Magnetic Fields
We study generation of magnetic fields by the Biermann mechanism in the
pair-instability supernovae explosions of first stars. The Biermann mechanism
produces magnetic fields in the shocked region between the bubble and
interstellar medium (ISM), even if magnetic fields are absent initially. We
perform a series of two-dimensional magnetohydrodynamic simulations with the
Biermann term and estimate the amplitude and total energy of the produced
magnetic fields. We find that magnetic fields with amplitude
G are generated inside the bubble, though the amount of
magnetic fields generated depend on specific values of initial conditions. This
corresponds to magnetic fields of erg per each supernova
remnant, which is strong enough to be the seed magnetic field for galactic
and/or interstellar dynamo.Comment: 12 pages, 3 figure
Gravitational Waves from Core Collapse Supernovae
We present the gravitational wave signatures for a suite of axisymmetric core
collapse supernova models with progenitors masses between 12 and 25 solar
masses. These models are distinguished by the fact they explode and contain
essential physics (in particular, multi-frequency neutrino transport and
general relativity) needed for a more realistic description. Thus, we are able
to compute complete waveforms (i.e., through explosion) based on
non-parameterized, first-principles models. This is essential if the waveform
amplitudes and time scales are to be computed more precisely. Fourier
decomposition shows that the gravitational wave signals we predict should be
observable by AdvLIGO across the range of progenitors considered here. The
fundamental limitation of these models is in their imposition of axisymmetry.
Further progress will require counterpart three-dimensional models.Comment: 10 pages, 5 figure
Axisymmetric simulations of magneto--rotational core collapse: dynamics and gravitational wave signal
We have performed a comprehensive parameter study of the collapse of
rotating, strongly magnetized stellar cores in axisymmetry to determine their
gravitational wave signature based on the Einstein quadrupole formula. We use a
Newtonian explicit magnetohydrodynamic Eulerian code based on the relaxing-TVD
method for the solution of the ideal MHD equations, and apply the
constraint-transport method to guarantee a divergence--free evolution of the
magnetic field. We neglect effects due to neutrino transport and employ a
simplified equation of state. The pre--collapse initial models are polytropes
in rotational equilibrium with a prescribed degree of differential rotation and
rotational energy (~ 1 % of the gravitational energy). The initial magnetic
fields are purely poloidal the field strength ranging from 10^10 G to 10^13 G.
The evolution of the core, whose collapse is initiated by reducing the gas
pressure by a prescribed amount, is followed until a few ten milliseconds past
core bounce.
The initial magnetic fields are amplified mainly by the differential rotation
of the core giving rise to a strong toroidal field component. The poloidal
field component grows by compression during collapse, but does not change
significantly after core bounce if (abbreviated)Comment: 34 pages, 25 figures, accepted for publication in A&A. Minor changes
in the main text, additional appendix on numerical convergence. Figure
quality reduced to match arXiv file size requirement
Brucella abortus invasion of osteocytes modulates connexin 43 and integrin expression and induces osteoclastogenesis via receptor activator of NF-ÎșB ligand and tumor necrosis factor alpha secretion
Osteoarticular brucellosis is the most common localization of human active disease. Osteocytes are the most abundant cells of bone. They secrete factors that regulate the differentiation of both osteoblasts and osteoclasts during bone remodeling. The aim of this study is to determine if Brucella abortus infection modifies osteocyte function. Our results indicate that B. abortus infection induced matrix metalloproteinase 2 (MMP-2), receptor activator for NF-ÎșB ligand (RANKL), proinflammatory cytokines, and keratinocyte chemoattractant (KC) secretion by osteocytes. In addition, supernatants from B. abortus-infected osteocytes induced bone marrow-derived monocytes (BMM) to undergo osteoclastogenesis. Using neutralizing antibodies against tumor necrosis factor alpha (TNF-α) or osteoprotegerin (OPG), RANKL's decoy receptor, we determined that TNF-α and RANKL are involved in osteoclastogenesis induced by supernatants from B. abortus-infected osteocytes. Connexin 43 (Cx43) and the integrins E11/gp38, integrin-α, integrin-ÎČ, and CD44 are involved in cell-cell interactions necessary for osteocyte survival. B. abortus infection inhibited the expression of Cx43 but did not modify the expression of integrins. Yet the expression of both Cx43 and integrins was inhibited by supernatants from B. abortus-infected macrophages. B. abortus infection was not capable of inducing osteocyte apoptosis. However, supernatants from B. abortus-infected macrophages induced osteocyte apoptosis in a dose-dependent manner. Taken together, our results indicate that B. abortus infection could alter osteocyte function, contributing to bone damage.Fil: Pesce Viglietti, AyelĂ©n Ivana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de InmunologĂa, GenĂ©tica y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de InmunologĂa, GenĂ©tica y Metabolismo; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de ClĂnicas General San MartĂn; ArgentinaFil: Arriola Benitez, Paula Constanza. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de InmunologĂa, GenĂ©tica y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de InmunologĂa, GenĂ©tica y Metabolismo; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de ClĂnicas General San MartĂn; ArgentinaFil: Gentilini, Maria Virginia. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de InmunologĂa, GenĂ©tica y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de InmunologĂa, GenĂ©tica y Metabolismo; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de ClĂnicas General San MartĂn; ArgentinaFil: Velasquez, Lis Noelia. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Fossati, Carlos Alberto. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de Estudios InmunolĂłgicos y FisiopatolĂłgicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Estudios InmunolĂłgicos y FisiopatolĂłgicos; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Ciencias BiolĂłgicas; ArgentinaFil: Giambartolomei, Guillermo Hernan. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de InmunologĂa, GenĂ©tica y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de InmunologĂa, GenĂ©tica y Metabolismo; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de ClĂnicas General San MartĂn; ArgentinaFil: Delpino, MarĂa Victoria. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de InmunologĂa, GenĂ©tica y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de InmunologĂa, GenĂ©tica y Metabolismo; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de ClĂnicas General San MartĂn; Argentin
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