Chemical evolution of galaxies. I. A composition-dependent SPH model for chemical evolution and cooling

We describe an SPH model for chemical enrichment and radiative cooling in cosmological simulations of structure formation. This model includes: i) the delayed gas restitution from stars by means of a probabilistic approach designed to reduce the statistical noise and, hence, to allow for the study of the inner chemical structure of objects with moderately high numbers of particles; ii) the full dependence of metal production on the detailed chemical composition of stellar particles by using, for the first time in SPH codes, the Qij matrix formalism that relates each nucleosynthetic product to its sources; and iii) the full dependence of radiative cooling on the detailed chemical composition of gas particles, achieved through a fast algorithm using a new metallicity parameter zeta(T) that gives the weight of each element on the total cooling function. The resolution effects and the results obtained from this SPH chemical model have been tested by comparing its predictions in different problems with known theoretical solutions. We also present some preliminary results on the chemical properties of elliptical galaxies found in self-consistent cosmological simulations. Such simulations show that the above zeta-cooling method is important to prevent an overestimation of the metallicity-dependent cooling rate, whereas the Qij formalism is important to prevent a significant underestimation of the [alpha/Fe] ratio in simulated galaxy-like objects.Comment: 19 pages, 22 figures, 2 tables; accepted for publication in MNRA

Cross section measurements of 155,157Gd(n, γ) induced by thermal and epithermal neutrons

© SIF, Springer-Verlag GmbH Germany, part of Springer Nature 2019Neutron capture cross section measurements on 155Gd and 157Gd were performed using the time-of-flight technique at the n_TOF facility at CERN on isotopically enriched samples. The measurements were carried out in the n_TOF experimental area EAR1, at 185 m from the neutron source, with an array of 4 C6D6 liquid scintillation detectors. At a neutron kinetic energy of 0.0253 eV, capture cross sections of 62.2(2.2) and 239.8(8.4) kilobarn have been derived for 155Gd and 157Gd, respectively, with up to 6% deviation relative to values presently reported in nuclear data libraries, but consistent with those values within 1.6 standard deviations. A resonance shape analysis has been performed in the resolved resonance region up to 181 eV and 307 eV, respectively for 155Gd and 157Gd, where on average, resonance parameters have been found in good agreement with evaluations. Above these energies and up to 1 keV, the observed resonance-like structure of the cross section has been analysed and characterised. From a statistical analysis of the observed neutron resonances we deduced: neutron strength function of 2. 01 (28) × 10 - 4 and 2. 17 (41) × 10 - 4; average total radiative width of 106.8(14) meV and 101.1(20) meV and s-wave resonance spacing 1.6(2) eV and 4.8(5) eV for n + 155Gd and n + 157Gd systems, respectively.Peer reviewedFinal Accepted Versio

A Measure of Student Engagement for Serious Games and IoT

Student Engagement has been a strong topic of research for the avoidance of student drop out and the increase in grading. Serious games have highlighted benefits in engaging students, primarily through edutainment, educating via games. This article suggests a Computer Algorithm, purposed at measuring and encouraging student engagement. In addition, the algorithm accounts for sensor networks accessed both directly and through the Internet, extending its application to the Internet of Things (IoT)

Evaluation of satellite evapotranspiration estimates using ground-meteorological data available for the Flumen District into the Ebro Valley of N.E. Spain

Evapotranspiration SEBAL MEBES Meteorological data Ebro valley Water management