Synthesis of C-rich dust in CO nova ourbursts

Context. Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in stellar binary systems. The material transferred onto the white dwarf piles up under degenerate conditions, driving a thermonuclear runaway. In those outbursts, about 10-7 - 10-3 Msun, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, or Al, for ONe novae) are ejected into the interstellar medium. The large concentrations of metals spectroscopically inferred in the nova ejecta reveal that the (solar-like) material transferred from the secondary mixes with the outermost layers of the underlying white dwarf. Aims. Most theoretical models of nova outbursts reported to date yield, on average, outflows characterized by O > C, from which only oxidized condensates (e.g, O-rich grains) would be expected, in principle. Methods. To specifically address whether CO novae can actually produce C-rich dust, six different hydrodynamic nova models have been evolved, from accretion to the expansion and ejection stages, with different choices for the composition of the substrate with which the solar-like accreted material mixes. Updated chemical profiles inside the H-exhausted core have been used, based on stellar evolution calculations for a progenitor of 8 Msun through H and He-burning phases. Results. We show that these profiles lead to C-rich ejecta after the nova outburst. This extends the possible contribution of novae to the inventory of presolar grains identified in meteorites, particularly in a number of carbonaceous phases (i.e., nanodiamonds, silicon carbides and graphites).Comment: 5 pages, accepted for publication in Astronomy & Astrophysic

The effect of hepatitis C virus treatment on ovarian reserve

Background: The hepatitis C treatment effect on ovarian reserve of the treated women and so on their reproductive potential attracting the attention and becoming an issue of concern. In this study, we examine the possible action of interferon and ribavirin regimen on the ovarian reserve through assessing the change of AMH level pre-and post-treatment.Methods: This study is a prospective longitudinal one, includes fifty women in childbearing period with chronic HCV infection fulfilling the criteria of attending the Egyptian national program for HCV treatment and has been referred for antiviral therapy with PEG IFN-α2a or PEG IFN-α2b, plus oral ribavirin for a total of 48 weeks. All patients were tested to AMH level at the beginning of the treatment program (the mean AMH level was 1ngml-3ngml) and retested at the end of treatment program. In addition, they examined by vaginal ultrasound to measure ovarian volume.Results: At the end of the treatment program 28% of the studied cases remain within pre treatment level of AMH & in 32% of the studied cases the level of AMH decreased where's in 40% of the studied cases the level of AMH increased.Conclusions: It is likely that interferon and ribavirin affect ovarian reserve of treated patients as a change occurs in the level of AMH in 72% of them

Equation of state for dense supernova matter

We provide an equation of state for high density supernova matter by applying a momentum-dependent effective interaction. We focus on the study of the equation of state of high-density and high-temperature nuclear matter containing leptons (electrons and neutrinos) under the chemical equilibrium condition. The conditions of charge neutrality and equilibrium under $\beta$-decay process lead first to the evaluation of the lepton fractions and afterwards the evaluation of internal energy, pressure, entropy and in total to the equation of state of hot nuclear matter for various isothermal cases. Thermal effects on the properties and equation of state of nuclear matter are evaluated and analyzed in the framework of the proposed effective interaction model. Since supernova matter is characterized by a constant entropy we also present the thermodynamic properties for isentropic case. Special attention is dedicated to the study of the contribution of the components of $\beta$-stable nuclear matter to the entropy per particle, a quantity of great interest for the study of structure and collapse of supernova.Comment: 23 pages, 15 figure

Minimally invasive, no hardware subtalar arthrodesis with autogenous posterior iliac bone graft

Sixteen patients underwent minimally invasive subtalar arthrodesis through a mini-invasive approach with posterior iliac graft between 2004 and 2006. No hardware was used to transfix the arthrodesis and partial weight bearing was allowed immediately. The primary indication for surgery was the squeal of fracture os calcis in terms of subtalar joint arthritis, loss of heel height, malalignment of the hindfoot, and pain with weight bearing. There were 12 male and 4 female patients with a mean age of 30 (range 17–52). Patients were followed up for a period of 40.8 months (range 36–48 months). The mean interval from injury to fusion was 2 (+0.6) years ranging from 6 months to 6 years post fracture. The average clinical rating scale based on the American Orthopaedic Foot and Ankle Society (AOFAS) improved from 36 preoperatively to 78 at the latest follow-up (P < 0.05). Union rate was 94%. Radiographic evaluation revealed a mean increase in calcaneal inclination of 6.25 + 8.3° (P < 0.07) and a mean increase in the lateral talocalcaneal angle of 7.42 + 10.2° (P < 0.08). Complications were graft nonunion in 1 patient and transient tendoachilles tendinitis in another. This technique can be used to decrease the morbidity associated with the late complications of os calcis fractures by aligning the hindfoot, restoring the heel height and correcting calcaneal and talar inclination. It offers the advantage of early weight bearing while avoiding hardware complications

s-Process Nucleosynthesis in Advanced Burning Phases of Massive Stars

We present a detailed study of s-process nucleosynthesis in massive stars of solar-like initial composition and masses 15, 20,25, and 30 Msun. We update our previous results of s-process nucleosynthesis during the core He-burning of these stars and then focus on an analysis of the s-process under the physical conditions encountered during the shell-carbon burning. We show that the recent compilation of the Ne22(alpha,n)Mg25 rate leads to a remarkable reduction of the efficiency of the s-process during core He-burning. In particular, this rate leads to the lowest overproduction factor of Kr80 found to date during core He-burning in massive stars. The s-process yields resulting from shell carbon burning turn out to be very sensitive to the structural evolution of the carbon shell. This structure is influenced by the mass fraction of C12 attained at the end of core helium burning, which in turn is mainly determined by the C12(alpha,gamma)O16 reaction. The still present uncertainty in the rate for this reaction implies that the s-process in massive stars is also subject to this uncertainty. We identify some isotopes like Zn70 and Rb87 as the signatures of the s-process during shell carbon burning in massive stars. In determining the relative contribution of our s-only stellar yields to the solar abundances, we find it is important to take into account the neutron exposure of shell carbon burning. When we analyze our yields with a Salpeter Initial Mass Function, we find that massive stars contribute at least 40% to s-only nuclei with mass A 90, massive stars contribute on average ~7%, except for Gd152, Os187, and Hg198 which are ~14%, \~13%, and ~11%, respectively.Comment: 52 pages, 16 figures, accepted for publication in Ap

The Molecular Hydrogen Deficit in Gamma-Ray Burst Afterglows

Recent analysis of five gamma-ray burst (GRB) afterglow spectra reveal the absence of molecular hydrogen absorption lines, a surprising result in light of their large neutral hydrogen column densities and the detection of H$_2$ in similar, more local star-forming regions like 30 Doradus in the Large Magellanic Cloud (LMC). Observational evidence further indicates that the bulk of the neutral hydrogen column in these sight lines lies 100 pc beyond the progenitor and that H$_2$ was absent prior to the burst, suggesting that direct flux from the star, FUV background fields, or both suppressed its formation. We present one-dimensional radiation hydrodynamical models of GRB host galaxy environments, including self-consistent radiative transfer of both ionizing and Lyman-Werner photons, nine-species primordial chemistry with dust formation of H$_2$, and dust extinction of UV photons. We find that a single GRB progenitor is sufficient to ionize neutral hydrogen to distances of 50 - 100 pc but that a galactic Lyman-Werner background is required to dissociate the molecular hydrogen in the ambient ISM. Intensities of 0.1 - 100 times the Galactic mean are necessary to destroy H$_2$ in the cloud, depending on its density and metallicity. The minimum radii at which neutral hydrogen will be found in afterglow spectra is insensitive to the mass of the progenitor or the initial mass function (IMF) of its cluster, if present.Comment: 12 pages, 7 figures, accepted for Ap

Equation of state for β\beta-stable hot nuclear matter

We provide an equation of state for hot nuclear matter in $\beta$-equilibrium by applying a momentum-dependent effective interaction. We focus on the study of the equation of state of high-density and high-temperature nuclear matter, containing leptons (electrons and muons) under the chemical equilibrium condition in which neutrinos have left the system. The conditions of charge neutrality and equilibrium under $\beta$-decay process lead first to the evaluation of proton and lepton fractions and afterwards of internal energy, free energy, pressure and in total to the equation of state of hot nuclear matter. Thermal effects on the properties and equation of state of nuclear matter are assesed and analyzed in the framework of the proposed effective interaction model. Special attention is dedicated to the study of the contribution of the components of $\beta$-stable nuclear matter to the entropy per particle, a quantity of great interest for the study of structure and collapse of supernova.Comment: 28 pages, 18 figure