Radiogenic p-isotopes from type Ia supernova, nuclear physics uncertainties, and galactic chemical evolution compared with values in primitive meteorites

The nucleosynthesis of proton-rich isotopes is calculated for multi-dimensional Chandrasekhar-mass models of Type Ia supernovae (SNe Ia) with different metallicities. The predicted abundances of the short-lived radioactive isotopes 92Nb, 97, 98Tc, and 146Sm are given in this framework. The abundance seeds are obtained by calculating s-process nucleosynthesis in the material accreted onto a carbon-oxygen white dwarf from a binary companion. A fine grid of s-seeds at different metallicities and 13C-pocket efficiencies is considered. A galactic chemical evolution model is used to predict the contribution of SN Ia to the solar system p-nuclei composition measured in meteorites. Nuclear physics uncertainties are critical to determine the role of SNe Ia in the production of 92Nb and 146Sm. We find that, if standard Chandrasekhar-mass SNe Ia are at least 50% of all SN Ia, they are strong candidates for reproducing the radiogenic p-process signature observed in meteorites.Peer reviewedFinal Accepted Versio

Theoretical determination of surface roughness during high-speed milling and grinding

Аналитически установлено, что высокоскоростное фрезерование располагает значительными технологическими возможностями с точки зрения уменьшения шероховатости поверхности при одновременном увеличении производительности обработки. Установлено также, что при шлифовании уменьшение шероховатости поверхности связано с уменьшением производительности. Наиболее прогрессивным методом шлифования, обеспечивающим одновременно увеличение производительности и уменьшение шероховатости поверхности, является глубинное шлифование с небольшой скоростью детали, которое характеризуется меньшей производительностью по сравнению с высокоскоростным фрезерованием.The paper presents the results of theoretical studies of the surface roughness during milling and grinding. It is shown that high-speed milling has significant technological capabilities in terms of reducing surface roughness, because cutting data parameters are included in the calculated dependencies obtained to determine surface roughness with higher degrees than during grinding. This applies in particular to the speed of rotation of the cutter. Therefore, with its increase, it becomes possible to significantly reduce the surface roughness while increasing the processing capacity, which opens up broad prospects for the practical use of high-speed milling. It is established that during grinding, a decrease in surface roughness is associated with a decrease in productivity, and this reduces the efficiency of processing. The most progressive method of grinding, providing b oth an increase in productivity and a reduction in surface roughness, is deep-grinding at a low speed of the part. However, it is characterized by lower productivity in comparison with high-speed milling

The s Process: Nuclear Physics, Stellar Models, Observations

Nucleosynthesis in the s process takes place in the He burning layers of low mass AGB stars and during the He and C burning phases of massive stars. The s process contributes about half of the element abundances between Cu and Bi in solar system material. Depending on stellar mass and metallicity the resulting s-abundance patterns exhibit characteristic features, which provide comprehensive information for our understanding of the stellar life cycle and for the chemical evolution of galaxies. The rapidly growing body of detailed abundance observations, in particular for AGB and post-AGB stars, for objects in binary systems, and for the very faint metal-poor population represents exciting challenges and constraints for stellar model calculations. Based on updated and improved nuclear physics data for the s-process reaction network, current models are aiming at ab initio solution for the stellar physics related to convection and mixing processes. Progress in the intimately related areas of observations, nuclear and atomic physics, and stellar modeling is reviewed and the corresponding interplay is illustrated by the general abundance patterns of the elements beyond iron and by the effect of sensitive branching points along the s-process path. The strong variations of the s-process efficiency with metallicity bear also interesting consequences for Galactic chemical evolution.Comment: 53 pages, 20 figures, 3 tables; Reviews of Modern Physics, accepte

Tungsten isotopic compositions in stardust SiC grains from the Murchison meteorite: Constraints on the s-process in the Hf-Ta-W-Re-Os region

We report the first tungsten isotopic measurements in stardust silicon carbide (SiC) grains recovered from the Murchison carbonaceous chondrite. The isotopes 182W, 183W, 184W, 186W and 179Hf, 180Hf were measured on both an aggregate (KJB fraction) and single stardust SiC grains (LS+LU fraction) believed to have condensed in the outflows of low-mass carbon-rich asymptotic giant branch (AGB) stars with close-to-solar metallicity. The SiC aggregate shows small deviations from terrestrial (=solar) composition in the 182W/184W and 183W/184W ratios, with deficits in 182W and 183W with respect to 184W. The 186W/184W ratio, however, shows no apparent deviation from the solar value. Tungsten isotopic measurements in single mainstream stardust SiC grains revealed lower than solar 182W/184W, 183W/184W, and 186W/184W ratios. We have compared the SiC data with theoretical predictions of the evolution of W isotopic ratios in the envelopes of AGB stars. These ratios are affected by the slow neutron-capture process and match the SiC data regarding their 182W/184W, 183W/184W, and 179Hf/180Hf isotopic compositions, although a small adjustment in the s-process production of 183W is needed in order to have a better agreement between the SiC data and model predictions. The models cannot explain the 186W/184W ratios observed in the SiC grains, even when the current 185W neutron-capture cross section is increased by a factor of two. Further study is required to better assess how model uncertainties (e.g., the formation of the 13C neutron source, the mass-loss law, the modelling of the third dredge-up, and the efficiency of the 22Ne neutron source) may affect current s-process predictions.Comment: Accepted for Publication on The Astrophysical Journal 43 pages, 2 tables, 7 figure

Half-lives of neutron-rich Cd 128-130

R. Dunlop et al. ; 6 págs.; 7 figs.; 1 tab. ; Rapid CommunicationsThe β-decay half-lives of Cd128-130 have been measured with the newly commissioned GRIFFIN γ-ray spectrometer at the TRIUMF-ISAC facility. The time structures of the most intense γ rays emitted following the β decay were used to determine the half-lives of Cd128 and Cd130 to be T1/2=246.2(21) ms and T1/2=126(4) ms, respectively. The half-lives of the 3/2+ and 11/2- states of Cd129 were measured to be T1/2(3/2+)=157(8) ms and T1/2(11/2-)=147(3) ms. The half-lives of the Cd isotopes around the N=82 shell closure are an important ingredient in astrophysical simulations to derive the magnitude of the second r-process abundance peak in the A∼130 region. Our new results are compared with recent literature values and theoretical calculations. ©2016 American Physical SocietyThis work has been partially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Research Chairs Program. I.D. and R.C.-F. are supported by NSERC Discovery Grants SAPIN-2014-00028 and RGPAS 462257-2014. A.J. acknowledges financial support by the Spanish Ministerio de Ciencia e Innovación under contract FPA2011-29854-C04 and the Spanish Ministerio de Economía y Competitividad under contract FPA2014- 57196-C5-4-P. S.L.T acknowledges financial support from the U.S. National Science Foundation under contract NSF- 14-01574. E.P.-R. acknowledges financial support from the DGAPA-UNAM under the PASPA program. The GRIFFIN spectrometer was funded by the Canada Foundation for Innovation, TRIUMF, and the University of Guelph. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada.Peer Reviewe

Nuclear Physics Experiments with Ion Storage Rings

In the last two decades a number of nuclear structure and astrophysics experiments were performed at heavy-ion storage rings employing unique experimental conditions offered by such machines. Furthermore, building on the experience gained at the two facilities presently in operation, several new storage ring projects were launched worldwide. This contribution is intended to provide a brief review of the fast growing field of nuclear structure and astrophysics research at storage rings.Comment: XVIth International Conference on Electro-Magnetic Isotope Separators and Techniques Related to their Applications, December 2--7, 2012 at Matsue, Japa

High-resolution measurement of the time-modulated orbital electron capture and of the β+\beta^+ decay of hydrogen-like 142^{142}Pm60+^{60+} ions

The periodic time modulations, found recently in the two-body orbital electron-capture (EC) decay of both, hydrogen-like $^{140}$Pr$^{58+}$ and $^{142}$Pm$^{60+}$ ions, with periods near to 7s and amplitudes of about 20%, were re-investigated for the case of $^{142}$Pm$^{60+}$ by using a 245 MHz resonator cavity with a much improved sensitivity and time resolution. We observed that the exponential EC decay is modulated with a period $T = 7.11(11)$s, in accordance with a modulation period $T = 7.12(11)$ s as obtained from simultaneous observations with a capacitive pick-up, employed also in the previous experiments. The modulation amplitudes amount to $a_R = 0.107(24)$ and $a_P = 0.134(27)$ for the 245 MHz resonator and the capacitive pick-up, respectively. These new results corroborate for both detectors {\it exactly} our previous findings of modulation periods near to 7s, though with {\it distinctly smaller} amplitudes. Also the three-body $\beta^+$ decays have been analyzed. For a supposed modulation period near to 7s we found an amplitude $a = 0.027(27)$, compatible with $a = 0$ and in agreement with the preliminary result $a = 0.030(30)$ of our previous experiment. These observations could point at weak interaction as origin of the observed 7s-modulation of the EC decay. Furthermore, the data suggest that interference terms occur in the two-body EC decay, although the neutrinos are not directly observed.Comment: In memoriam of Prof. Paul Kienle, 9 pages, 1 table, 5 figures Phys. Lett. B (2013) onlin

How the Replica-Symmetry-Breaking Transition Looks Like in Finite-Size Simulations

Finite-size effects in the mean-field Ising spin glass and the mean-field three-state Potts glass are investigated by Monte Carlo simulations. In the thermodynamic limit, each model is known to exhibit a continuous phase transition into the ordered state with a full and a one-step replica-symmetry breaking (RSB), respectively. In the Ising case, Binder parameter g calculated for various finite sizes remains positive at any temperature and crosses at the transition point, while in the Potts case g develops a negative dip without showing a crossing in the g>0 region. By contrast, non-self averaging parameters always remain positive and show a clear crossing at the transition temperature in both cases. Our finding suggests that care should be taken in interpreting the numerical data of the Binder parameter, particularly when the system exhibits a one-step-like RSB.Comment: 7 pages, 8 figure