The stellar metallicity gradients in galaxy discs in a cosmological scenario

Indexación: Web of ScienceContext. The stellar metallicity gradients of disc galaxies provide information on disc assembly, star formation processes, and chemical evolution. They also might store information on dynamical processes that could affect the distribution of chemical elements in the gas phase and the stellar components. Understanding their joint effects within a hierarchical clustering scenario is of paramount importance. Aims. We studied the stellar metallicity gradients of simulated discs in a cosmological simulation. We explored the dependence of the stellar metallicity gradients on stellar age and on the size and mass of the stellar discs. Methods. We used a catalogue of galaxies with disc components selected from a cosmological hydrodynamical simulation performed including a physically motivated supernova feedback and chemical evolution. Disc components were defined based on angular momentum and binding energy criteria. The metallicity profiles were estimated for stars with different ages. We confront our numerical findings with results from the Calar Alto Legacy Integral Field Area (CALIFA) Survey. Results. The simulated stellar discs are found to have metallicity profiles with slopes in global agreement with observations. Low stellar mass galaxies tend to have a larger variety of metallicity slopes. When normalized by the half-mass radius, the stellar metallicity gradients do not show any dependence and the dispersion increases significantly, regardless of the galaxy mass. Galaxies with stellar masses of around 10(10) M-circle dot show steeper negative metallicity gradients. The stellar metallicity gradients correlate with the half-mass radius. However, the correlation signal is not present when they are normalized by the half-mass radius. Stellar discs with positive age gradients are detected to have negative and positive metallicity gradients, depending on the relative importance of recent star formation activity in the central regions. Conclusions. Our results suggest that inside-out formation is the main process responsible for the metallicity and age profiles. The large dispersions in the metallicity gradients as a function of stellar mass could be ascribed to the effects of dynamical processes such as mergers, interactions and/or migration as well as those regulating the conversion of gas into stars. The fingerprints of the inside-out formation seem better preserved by the stellar metallicity gradients as a function of the half-mass radius.http://www.aanda.org/articles/aa/abs/2016/08/aa28188-16/aa28188-16.htm

Application of a meshless method in electromagnetics

Author name used in this publication: S. L. HoAuthor name used in this publication: J. M. MachadoAuthor name used in this publication: H. C. Wong2001-2002 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A modified ant colony optimization algorithm modeled on tabu-search methods

Author name used in this publication: S. L. Ho2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

The new automated daily mortality surveillance system

The experience reported in an earlier Eurosurveillance issue on a fast method to evaluate the impact of the 2003 heatwave on mortality in Portugal, generated a daily mortality surveillance system (VDM) that has been operating ever since jointly with the Portuguese Heat Health Watch Warning System. This work describes the VDM system and how it evolved to become an automated system operating year-round, and shows briefly its potential using mortality data from January 2006 to June 2009 collected by the system itself. The new system has important advantages such as: rapid information acquisition, completeness (the entire population is included), lightness (very little information is exchanged, date of death, age, sex, place of death registration). It allows rapid detection of impacts (within five days) and allows a quick preliminary quantification of impacts that usually took several years to be done. These characteristics make this system a powerful tool for public health action. The VDM system also represents an example of inter-institutional cooperation, bringing together organisations from two different ministries, Health and Justice, aiming at improving knowledge about the mortality in the population

A self-learning simulated annealing algorithm for global optimizations of electromagnetic devices

Author name used in this publication: S. L. Ho2000-2001 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A combined wavelet-element free Galerkin method for numerical calculations of electromagnetic fields

Author name used in this publication: S. L. HoAuthor name used in this publication: J. M. Machado2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A new implementation of population based incremental learning method for optimizations in electromagnetics

Author name used in this publication: S. L. Ho2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Penetração Intra-Gástrica do Tubo Conector de Banda Gástrica Colocada por Via Laparoscópica

info:eu-repo/semantics/publishedVersio

Scale Effects on the Ballistic Penetration of Graphene Sheets

AbstractCarbon nanostructures are promising ballistic protection materials, due to their low density and excellent mechanical properties. Recent experimental and computational investigations on the behavior of graphene under impact conditions revealed exceptional energy absorption properties as well. However, the reported numerical and experimental values differ by an order of magnitude. In this work, we combined numerical and analytical modeling to address this issue. In the numerical part, we employed reactive molecular dynamics to carry out ballistic tests on single, double, and triple-layered graphene sheets. We used velocity values within the range tested in experiments. Our numerical and the experimental results were used to determine parameters for a scaling law. We find that the specific penetration energy decreases as the number of layers (N) increases, from ∼15 MJ/kg for N = 1 to ∼0.9 MJ/kg for N = 350, for an impact velocity of 900 m/s. These values are in good agreement with simulations and experiments, within the entire range of N values for which data is presently available. Scale effects explain the apparent discrepancy between simulations and experiments.</jats:p

Wavelet-Galerkin method for computations of electromagnetic fields-computation of connection coefficients

Author name used in this publication: S. L. HoAuthor name used in this publication: H. C. Wong2000-2001 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe