The role of gas infall in the evolution of disc galaxies

Spiral galaxies are thought to acquire their gas through a protracted infall phase resulting in the inside-out growth of their associated discs. For field spirals, this infall occurs in the lower density environments of the cosmic web. The overall infall rate, as well as the galactocentric radius at which this infall is incorporated into the star-forming disc, plays a pivotal role in shaping the characteristics observed today. Indeed, characterising the functional form of this spatio-temporal infall in-situ is exceedingly difficult, and one is forced to constrain these forms using the present day state of galaxies with model or simulation predictions. We present the infall rates used as input to a grid of chemical evolution models spanning the mass spectrum of discs observed today. We provide a systematic comparison with alternate analytical infall schemes in the literature, including a first comparison with cosmological simulations. Identifying the degeneracies associated with the adopted infall rate prescriptions in galaxy models is an important step in the development of a consistent picture of disc galaxy formation and evolution.Comment: 12 pages, 12 figures, MNRAS, accepte

The role of gas infall in the evolution of disc galaxies

Spiral galaxies are thought to acquire their gas through a protracted infall phase resulting in the inside-out growth of their associated discs. For field spirals, this infall occurs in the lower density environments of the cosmic web. The overall infall rate, as well as the galactocentric radius at which this infall is incorporated into the star-forming disc, plays a pivotal role in shaping the characteristics observed today. Indeed, characterising the functional form of this spatio-temporal infall in-situ is exceedingly difficult, and one is forced to constrain these forms using the present day state of galaxies with model or simulation predictions. We present the infall rates used as input to a grid of chemical evolution models spanning the mass spectrum of discs observed today. We provide a systematic comparison with alternate analytical infall schemes in the literature, including a first comparison with cosmological simulations. Identifying the degeneracies associated with the adopted infall rate prescriptions in galaxy models is an important step in the development of a consistent picture of disc galaxy formation and evolution

A Semantic Data Grid for Satellite Mission Quality Analysis

The combination of Semantic Web and Grid technologies and architectures cases the development of applications that share heterogeneous resource,, (data and computing elements) that belong to several organisations. The Aerospace domain has an extensive and heterogeneous network of facilities and institutions, with a strong need to share both data and computational resources for complex processing tasks. One such task is monitoring and data analysis for Satellite Missions. This paper presents a Semantic Data Grid for satellite missions, where flexibility, scalability, interoperability, extensibility and efficient development have been considered the key issues to be addressed

Principios de proporcionalidad y razonabilidad en la individualización fundamentación en la sentencia penal

The present investigation was developed with the purpose of determining the relationship between the principles of proportionality and reasonableness in the individualization and foundation of punishment, the study design is correlational descriptive and the applied research methods are deductive and inductive, it has been used Two reliable questionnaires for data collection. Our problem investigated is: What is the relationship between the principles of proportionality and reasonableness in the correct individualization and justification of punishment? To this end, questionnaires were carried out on proportionality and reasonableness in the individualization and justification of the sentence. Our main conclusion to achieve a good application of the principles of proportionality and reasonableness, is to base well the penalty on crimes with clear and updated objectives.La presente investigación se desarrolló con el propósito de determinar la relación entre los principios de proporcionalidad y razonabilidad en la individualización y fundamentación de la pena, el diseño de estudio es descriptivo correlacional y los métodos de investigación aplicados es el deductivo e inductivo, se ha empleado dos cuestionarios confiables para la recolección de datos. Nuestro problema investigado es ¿Qué relación existe entre los principios de proporcionalidad y razonabilidad en la correcta individualización y fundamentación de la pena? Para ello se realizaron cuestionarios a proporcionalidad y razonabilidad en la individualización y fundamentación de la pena. Nuestra conclusión principal para conseguir una buena aplicación de los principios de proporcionalidad y razonabilidad, es fundamentar bien la pena en los delitos con objetivos claros y actualizados

Properties of the outer regions of spiral disks: Abundances, colors and ages

© 2017 International Astronomical Union. We summarize the results obtained from our suite of chemical evolution models for spiral disks, computed for different total masses and star formation efficiencies. Once the gas, stars and star formation radial distributions are reproduced, we analyze the Oxygen abundances radial profiles for gas and stars, in addition to stellar averaged ages and global metallicity. We examine scenarios for the potential origin of the apparent flattening of abundance gradients in the outskirts of disk galaxies, in particular the role of molecular gas formation prescriptions

Crocodylian diversity peak and extinction in the late Cenozoic of the northern Neotropics

Northern South America and South East Asia are today’s hotspots of crocodylian diversity with up to six (mainly alligatorid) and four (mainly crocodylid) living species respectively, of which usually no more than two or three occur sympatrically. In contrast, during the late Miocene, 14 species existed in South America. Here we show a diversity peak in sympatric occurrence of at least seven species, based on detailed stratigraphic sequence sampling and correlation, involving four geological formations from the middle Miocene to the Pliocene, and on the discovery of two new species and a new occurrence. This degree of crocodylian sympatry is unique in the world and shows that at least several members of Alligatoroidea and Gavialoidea coexisted. By the Pliocene, all these species became extinct, and their extinction was probably related to hydrographic changes linked to the Andean uplift. The extant fauna is first recorded with the oldest Crocodylus species from South America.Facultad de Ciencias Naturales y Muse

Optical pumping of a single hole spin in a p-doped quantum dot coupled to a metallic nanoparticle

The preparation of quantum states with a defined spin is analyzed in a hybrid system consisting of a p-doped semiconductor quantum dot (QD) coupled to a metallic nanoparticle. The quantum dot is described as a four-level atom-like system using the density matrix formalism. The lower levels are Zeeman-split hole spin states and the upper levels correspond to positively charged excitons containing a spin-up, spin-down hole pair and a spin electron. A metallic nanoparticle with spheroidal geometry is placed in close proximity to the quantum dot, and its effects are considered in the quasistatic approximation. A linearly polarized laser field drives two of the optical transitions of the QD and produces localized surface plasmons in the nanoparticle which act back upon the QD. The frequencies of these localized plasmons are very different along the two principal axes of the nanoparticle, thus producing an anisotropic modification of the spontaneous emission rates of the allowed optical transitions which is accompanied by local-field corrections. This effect translates into a preferential acceleration of some of the optical pathways and therefore into a fast initialization of the QD by excitation with a short optical pulse. The population transfer between the lower levels of the QD and the fidelity is analyzed as a function of the nanoparticle's aspect ratio, the external magnetic field, and the Rabi frequency of the driving field. It is also shown that the main effect of the local-field corrections is a lengthening of the time elapsed to reach the steady-state. The hole spin is predicted to be successfully cooled from 5 to 0.04 K at a magnetic field of 4.6 T applied in the Voigt geometry

Red Iberoamericana de Toxicología y Seguridad Química

La Red Iberoamericana de Toxicología y Seguridad Química RITSQ, se inicia en marzo de 2008 y desde entonces ha tenido 70.104 visitas a la página web de la misma, se han registrado 1.133 personas de 41 países y desde entonces hemos realizado y presentado 66 carteles en Reuniones, Conferencias y Reuniones donde se mantienen de forma constante los Objetivos de la RITSQ: 1. Coordinar la participación de los diferentes grupos existentes en universidades y organismos de investigación de Iberoamérica, implicados en estudios relacionados con la Toxicología, 2. Fortalecer la colaboración y el intercambio académico entre los programas de Doctorado y Maestría de diferentes países iberoamericanos que tengan como objeto el estudio y la investigación en Toxicología o áreas relacionadas, 3. Favorecer la realización de proyectos de investigación conjuntos entre docentes e investigadores de Iberoamérica, pasantías estudiantiles y eventos académicos; 4. Profundizar en el estudio de métodos de ensayo de corta y larga duración utilizados en la evaluación de la carcinogenicidad, la mutagenicidad y la toxicidad para la reproducción de sustancias y mezclas de productos químicos, 5. Desarrollar y estandarizar métodos analíticos para la identificación y determinación de biomarcadores de exposición, efecto y .susceptibilidad para sustancias y productos químicos en el hombre y el medio ambiente; 6. Aplicar métodos de evaluación del riesgo para la salud humana y el medio ambiente de sustancias y productos químicos, 7. Fomentar el intercambio científico de profesionales interesados alimentaria; y 8. Propiciar el uso de métodos alternativos a la experimentación animal (www.remanet.net).Peer reviewe

Efecto de la temperatura de recocido en la cristalinidad y tamaño de nanoparticulas de ZnO sintetizadas por el método Sol-Gel

Se han producido nanopartículas de ZnO a través del método Sol-Gel, evaluando el efecto de la temperatura de recocido (350, 450, 550 y 650°C) sobre su cristalinidad y tamaño.Mediciones de difracción de rayos X evidencian que, incluso sin necesidad de recocido, las nanopartículas de ZnOpresentan fase wurtzita con estructura hexagonal sin presencia de fases secundarias. La cristalinidad de las nanopartículas mejora a medida que aumenta la temperatura, produciéndose al mismo tiempo un aumento en su tamaño desde 10 hasta 30nm. Los resultados de FT-IR muestran la presencia de grupos acetato en las nanopartículas sin recocido, eliminándose con el tratamiento térmico. Mediante espectroscopiaRaman se han determinado tres bandas características del ZnO en las nanopartículas sin recocido, siendo la H más intensa la correspondiente al modo E cuya intensidad aumentó para las nanopartículas 2 recocidas a 650°C para la cual se observaron otras bandas características del ZnO. Los resultados de fotoluminiscencia muestran que las nanopartículas presentan una intensaemisión ultravioleta pero débil emisión visible, no apreciándose efecto significativo del recocido.Palabras clave: Nanoparticulas, óxido de zinc, Sol-Gel, recocido, cristalinidad.ABSTRACTZnO nanoparticles have been synthesizedby using the Sol-gel method and the effect of annealing temperature (350, 450, 550 y 650°C) on theircrystallinity and size have been evaluated. X-ray diffraction measurements evidenced thatall ZnO nanoparticles showed hexagonal wurtzite, and no secondary phases were detected. Enhancing of crystallinityand an increasing of average particle size, from 10 to 30nm, as annealing temperature increased was clearly observed. Fourier Transform Infrared results showed the presence of acetate groups on no annealed nanoparticles, which were eliminated after annealing treatment. By Raman spectroscopy three characteristic bands of ZnO have been identified in as synthesized H nanoparticles, being the most intense the corresponding to the E mode, whose intensity 2 increased for the nanoparticles annealed at 650°C for which other characteristic bands of ZnO were clearly identified. Photoluminescence spectra showed that ZnOnanoparticles present an intense ultraviolet and a weak visible emission, and no significant effect of annealing was observed.Key words: Nanoparticles, zinc oxide, Sol-Gel, annealing, crystallinit

Plasmonic effects in excitonic population transfer in a driven semiconductor–metal nanoparticle hybrid system

We have investigated the coherent transfer of excitonic populations in a semiconductor quantum dot (SQD) modulated by the surface plasmon of a metallic nanoparticle (MNP). The SQD is considered as a three-level V-type atomic system. We applied a transform-limited laser pulse field resonant with the upper atomic levels of the SQD. When the SQD is close enough to the MNP, the otherwise equally populated atomic levels can be selectively excited. Selectivity population can be achieved by two physical mechanisms: an enhancement of the Rabi frequencies that drive the optical transitions, which depends on the polarization arrangement, and a frequency shift of the optical transitions that leads to a dynamical detuning