16 research outputs found
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
GYOTO: a new general relativistic ray-tracing code
GYOTO, a general relativistic ray-tracing code, is presented. It aims at
computing images of astronomical bodies in the vicinity of compact objects, as
well as trajectories of massive bodies in relativistic environments. This code
is capable of integrating the null and timelike geodesic equations not only in
the Kerr metric, but also in any metric computed numerically within the 3+1
formalism of general relativity. Simulated images and spectra have been
computed for a variety of astronomical targets, such as a moving star or a
toroidal accretion structure. The underlying code is open source and freely
available. It is user-friendly, quickly handled and very modular so that
extensions are easy to integrate. Custom analytical metrics and astronomical
targets can be implemented in C++ plug-in extensions independent from the main
code.Comment: 20 pages, 11 figure
Cyclical and Patch-Like GDNF Distribution along the Basal Surface of Sertoli Cells in Mouse and Hamster Testes
BACKGROUND AND AIMS: In mammalian spermatogenesis, glial cell line-derived neurotrophic factor (GDNF) is one of the major Sertoli cell-derived factors which regulates the maintenance of undifferentiated spermatogonia including spermatogonial stem cells (SSCs) through GDNF family receptor α1 (GFRα1). It remains unclear as to when, where and how GDNF molecules are produced and exposed to the GFRα1-positive spermatogonia in vivo. METHODOLOGY AND PRINCIPAL FINDINGS: Here we show the cyclical and patch-like distribution of immunoreactive GDNF-positive signals and their close co-localization with a subpopulation of GFRα1-positive spermatogonia along the basal surface of Sertoli cells in mice and hamsters. Anti-GDNF section immunostaining revealed that GDNF-positive signals are mainly cytoplasmic and observed specifically in the Sertoli cells in a species-specific as well as a seminiferous cycle- and spermatogenic activity-dependent manner. In contrast to the ubiquitous GDNF signals in mouse testes, high levels of its signals were cyclically observed in hamster testes prior to spermiation. Whole-mount anti-GDNF staining of the seminiferous tubules successfully visualized the cyclical and patch-like extracellular distribution of GDNF-positive granular deposits along the basal surface of Sertoli cells in both species. Double-staining of GDNF and GFRα1 demonstrated the close co-localization of GDNF deposits and a subpopulation of GFRα1-positive spermatogonia. In both species, GFRα1-positive cells showed a slender bipolar shape as well as a tendency for increased cell numbers in the GDNF-enriched area, as compared with those in the GDNF-low/negative area of the seminiferous tubules. CONCLUSION/SIGNIFICANCE: Our data provide direct evidence of regionally defined patch-like GDNF-positive signal site in which GFRα1-positive spermatogonia possibly interact with GDNF in the basal compartment of the seminiferous tubules
Retraction notice to:
We have become aware, through a whistle-blower complaint, of very extensive overlap between this article and International Journal of Modern Physics E., Vol. 22, No. 10, 1330022 (2013) by the same authors. A&A therefore retracts this article. The corresponding author, Grant J. Mathews, understands our decision. Ko Nakamura, Toshitaka Kajino, and Seiji Harikae were copied on the correspondence and have not objected. We have been unable to find recent contact information for Susumu Sato
-process nucleosynthesis in the MHD+neutrino-heated collapsar jet
It has been proposed that the collapsar scenario for long-duration gamma ray bursts is a possible astrophysical site for r-process nucleosynthesis. Here we present r-process nucleosynthesis calculations based upon a model for a MHD+neutrino-heated collapsar jet. We utilize a relativistic magnetohydrodynamic model that includes ray-tracing neutrino transport to describe the development of the black hole accretion disk and the neutrino heating of the funnel region above the black hole. The late time evolution of the collapsar jet is then evolved using axisymmetric special relativistic hydrodynamics. We employ representative test particles to follow the trajectories in density, temperature, entropy, and electron fraction for material flowing from the accretion disk into the jet until they are several thousand km above the black hole. The evolution of nuclear abundances from nucleons to heavy nuclei for ejected test particle trajectories was solved in a large nuclear reaction network as temperatures fall from 9 × 109 to 3 × 108 K. We show that an r-process-like abundance distribution forms in material ejected in the collapsar jet. The possibility for a signature of collapsar r-process material to be found in metal-poor stars is discussed