Volatiles and refratories in solar analogs: no terrestial planet connection

We have analysed very high-quality HARPS and UVES spectra of 95 solar analogs, 24 hosting planets and 71 without detected planets, to search for any possible signature of terrestial planets in the chemical abundances of volatile and refractory elements with respect to the solar abundances. We demonstrate that stars with and without planets in this sample show similar mean abundance ratios, in particular, a sub-sample of 14 planet-host and 14 "single" solar analogs in the metallicity range 0.14<[Fe/H]<0.36. In addition, two of the planetary systems in this sub-sample, containing each of them a super-Earth-like planet with masses in the range ~ 7-11 Earth masses, have different volatile-to-refratory abundance ratios to what would be expected from the presence of a terrestial planets. Finally, we check that after removing the Galactic chemical evolution effects any possible difference in mean abundances, with respect to solar values, of refratory and volatile elements practically dissappears.Comment: 2 pages, 2 figures, to appear in the proceedings of the 276th IAU Symposium "The Astrophysics of Planetary Systems

Software reference architecture for smart environments: Perception

With the increase of intelligent devices, ubiquitous computing is spreading to all scopes of people life. Smart home (or industrial) environments include automation and control devices to save energy, perform tasks, assist and give comfort in order to satisfy specific preferences. This paper focuses on the proposal for Software Reference Architecture for the development of smart applications and their deployment in smart environments. The motivation for this Reference Architecture and its benefits are also explained. The proposal considers three main processes in the software architecture of these applications: perception, reasoning and acting. This paper centres attention on the definition of the Perception process and provides an example for its implementation and subsequent validation of the proposal. The software presented implements the Perception process of a smart environment for a standard office, by retrieving data from the real world and storing it for further reasoning and acting processes. The objectives of this solution include the provision of comfort for the users and the saving of energy in lighting. Through this verification, it is also shown that developments under this proposal produce major benefits within the software life cycle.Ministerio de Economía y Competitividad TIN2009-14378-C02-01 (ARTEMISA)Junta de Andalucía TIC-8052 (Simon

An approach to a reference model for a sentient smart city

The interest about Smart City concept has in creased in recent years. In fact, Smart Cities is ex pected to improve cityzens life experience by driv ing the next digital revolution, moving from the personal area (mobile computing, smart home) to the urban area (collective computing and collective intelligence). But the development of Smart Cities is not being as fast as expected. Several problems need to be undertaken in order to achieve the ob jectives of the paradigm. This paper presents an approach to address one of these problems: to or chestrate the platform that is required for gathering information about city, store it in a model and ena ble it for exploitation. The heterogeneity of the po tential data sources available and the complexity of the information nature and structure, make it a non trivial task that have to be solved before commer cial solutions appear and provide specific and non interoperable solutions

Aceptación y uso de los sistemas e-learning por estudiantes de grado de Ecuador : el caso de una universidad estatal

Objeto: El objetivo de esta investigación fue adaptar el Modelo de Aceptación de la Tecnología (TAM) para predecir el uso y la intención de uso de los sistemas e-learning entre los estudiantes de grado de una universidad estatal en Ecuador, con la intención de mejorar el entendimiento de los factores que puedan potenciar el uso de estos sistemas y facilitar la aplicación de políticas para incrementar los beneficios que éstos aportan al proceso de enseñanza y aprendizaje. Diseño/metodología/enfoque: El análisis tiene fundamento epistemológico en lo empírico-inductivo, basado en la observación de la percepción. En base a la revisión de la literatura científica sobre la evaluación y aceptación de los sistemas e-learning, se ha adaptado el modelo al caso de Ecuador y se ha elaborado un cuestionario con 52 ítems basado en escalas de Likert. El instrumento fue enviado por correo electrónico a 600 estudiantes de grado de una universidad estatal en Ecuador, respondiendo satisfactoriamente 423 de ellos. Se realizaron comprobaciones de validez y fiabilidad del modelo de ecuaciones estructurales por mínimos cuadrados parciales (PLS), con el soporte del software estadístico SmartPLS. Aportaciones y resultados: Los resultados indican que todas las hipótesis del TAM se cumplen en el contexto ecuatoriano, al momento de evaluar la aceptación de los sistemas e-learning entre los estudiantes de grado de una universidad estatal. El principal aporte fue identificar que el entretenimiento percibido, la influencia social y la auto-eficacia computacional, tienen un efecto directo sobre los dos constructos principales del TAM, facilidad de uso percibida (PEOU) y utilidad percibida (PU). También se encontró que la satisfacción (S) recibe una elevada influencia directa de PU y a su vez S influye en el uso de los sistemas e-learning, siendo el primero un aporte específico de este estudio. El soporte técnico reflejó no tener influencia sobre los constructos fundamentales del TAM. Limitaciones: La investigación fue realizada a los estudiantes de grado en una sola universidad estatal categoría B de Ecuador, siendo la realidad de este país más compleja, al existir cuatro categorías con características distintas. Tampoco se han considerado la edad, género, estudiantes de posgrado, condición socio económica, entre otras características de los estudiantes que puede afectar la investigación. Implicaciones prácticas: La identificación de los factores que influyen en la aceptación y uso de los sistemas e-learning, contribuirá a crear y mejorar los entornos de enseñanza aprendizaje para los estudiantes universitarios. Permitiendo explotar con mayor eficiencia los beneficios de estas herramientas tecnológicas, adaptándolas a las políticas de gestión de las instituciones de educación superior. Originalidad / Valor añadido: Este artículo presenta datos empíricos sobre el uso y aceptación de los sistemas e-learning en los estudiantes de una determinada universidad de Ecuador. No se evidencian estudios similares en el país y el modelo puede ser considerado para futuros estudios de alcance nacional.Postprint (published version

Temperature-dependent properties of 147-and 309-atom iron-gold nanoclusters

The properties of several Au-N and AuN-xFex nanoclusters are obtained by means of classical molecular dynamics calculations. In particular we study the configurations Au-147, Au134Fe13, Au-309, and Au254Fe55, which correspond to icosahedral magic numbers, for both the gold and the iron. We investigate the melting and freezing processes, atomic diffusion, hardness, vibration spectra, and specific heat of these nanoclusters. All the data obtained point toward the stability of the AuN-xFex system, with the gold atoms on the outside of the iron core

p-Type semiconducting properties in lithium-doped MgO single crystals

The phenomenally large enhancement in conductivity observed when Li-doped MgO crystals are oxidized at elevated temperatures was investigated by dc and ac electrical measurements in the temperature interval 250-673 K. The concentration of ([Li]^{0}) centers (Li^{+} ions each with a trapped hole) resulting from oxidation was monitored by optical absorption measurements. Both dc and ac experiments provide consistent values for the bulk resistance. The electricalconductivity of oxidized MgO:Li crystals increases linearly with the concentration of ([Li]^{0}) centers. The conductivity is thermally activated with an activation energy of (0.70 +/- 0.01) eV, which is independent of the ([Li]^{0}) content. The \textit{standard semiconducting} mechanism satisfactorily explains these results. Free holes are the main contribution to band conduction as they are trapped at or released from the ([Li]^{0})-acceptor centers. In as-grown MgO:Li crystals, electrical current increases dramatically with time due to the formation of ([Li]^{0}) centers. The activation energy values between 1.3 and 0.7 eV are likely a combination of the activation energy for the creation of ([Li]^{0}) centers and the activation energy of ionization of these centers. Destruction of ([Li]^{0}) centers can be induced in oxidized crystals by application of an electric field due to Joule heating up to temperatures at which ([Li]^{0}) centers are not stable.Comment: LaTeX, 20 pages, 9 Encapsulated Postscript Format Figures, use the version 4.0 of REVTEX 4 macro packag