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

Long-Term Variations of Monthly Mean Sea Level and its Relation to Atmospheric Presssure in the Mediterranean Sea

The monthly mean sea level at 19 stations and the monthly mean atmospheric pressure at 15 stations in the Mediterranean Sea are analysed to find the trend of the sea level and to identify the significant oscillations from the power spectral estimates. The results show that from the present data at Marseille, Trieste and Genova it is expected that the sea level tends to increase by 13 cm /100 years, which will affect the water budget of the area. The spectral analysis of the pressure could explain most of the oscillations in the sea level time series at 12, 6 and 4 months’ periods, except in the Adriatic Sea where the steric effect is expected to have an important contribution

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

Evolution of Massive Stars Up to the End of Central Oxygen Burning

We present a detailed study of the evolution of massive stars of masses 15, 20, 25 and 30 \msun assuming solar-like initial chemical composition. The stellar sequences were evolved through the advanced burning phases up to the end of core oxygen burning. We present a careful analysis of the physical characteristics of the stellar models. In particular, we investigate the effect of the still unsettled reaction $^{12}$C($\alpha$,$\gamma$)$^{16}$O on the advanced evolution by using recent compilations of this rate. We find that this rate has a significant impact on the evolution not only during the core helium burning phase, but also during the late burning phases, especially the shell carbon-burning. We have also considered the effect of different treatment of convective instability based on the Ledoux criterion in regions of varying molecular weight gradient during the hydrogen and helium burning phases. We compare our results with other investigations whenever available. Finally, our present study constitutes the basis of analyzing the nucleosynthesis processes in massive stars. In particular we will present a detail analysis of the {\it s}-process in a forthcoming paper.Comment: 46 pages, 15 figures. To be published in ApJ vol 611, August 10, 200

Quality Evaluation of Feed Resources at the Newly Reclaimed Area in Egypt

The objective of this study was to examine the productivity of Egyptian clover (Trifolium alexandrinum L.) interseeded with ryegrass (Lolium multiflorum) and alfalfa (Medicaga sativa L.). These species were planted in newly reclaimed land in Ismailia, Egypt under two fertilization systems; organic (OF) or chemical (CF) during winter season of (1994-1995) using a split plot design. Feeding quality of forages was evaluated by conducting digestibility trials with rams and feeding trials with growing lambs where forage was offered ad. libitum with 1% of LBW concentrate. Productivity data indicated that organic fertilization yielded significantly more DM. Chemical analysis showed that DM content with (CF) was higher than with (OF) and it was found that alfalfa had higher CP content than that of E. Clover mixture. Digestibility of nutrients was higher with (CF) than with (OF) and it was found that CP was more digested in alfalfa than the Egyptian clover mixture. TDN values for both forages were determined by proximate analysis. Group of lambs fed chemically fertilized alfalfa attained significantly better weight gain which was attributed to high forage DM intake

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

HeII Recombination Lines From the First Luminous Objects

The hardness of the ionizing continuum from the first sources of UV radiation plays a crucial role in the reionization of the intergalactic medium (IGM). While usual stellar populations have soft spectra, mini-quasars or metal-free stars with high effective temperatures may emit hard photons, capable of doubly ionizing helium and increasing the IGM temperature. Absorption within the source and in the intervening IGM will render the ionizing continuum of high-redshift sources inaccessible to direct observation. Here we show that HeII recombination lines from the first luminous objects are potentially detectable by the Next Generation Space Telescope. Together with measurements of the hydrogen Balmer alpha emission line, this detection can be used to infer the ratio of HeII to HI ionizing photons. A measurement of this ratio would shed light on the nature and emission mechanism of the first luminous sources, with important astrophysical consequences for the reheating and reionization of the IGM.Comment: ApJ published version. Due to an error in one of the references, the strength of the 1640 A line was underestimated in a previous version; this line is now brighter by a factor of 1