Josep Comas Solà, va veure l'atmosfera de Tità?

In 1907 Josep Comas Solà, director of the Fabra Observatory in Barcelona, announced that he had seen a darkening on Saturn’s satellite Titan which made him think that this celestial body had an atmosphere. If this is so, he would be the discoverer of Titan’s atmosphere. We analyse Comas’ experience in planetary observation, the instrumental characteristics and the conditions of Titan, in order to verify whether Comas could actually observe the atmosphere. We can only conclude that he could

Abandonament escolar a les Illes Balears: anàlisi de tendències

L’abandonament dels estudis és una de les problemàtiques que preocupa més els organismes educatius i institucions nacionals i internacionals.En aquest sentit, l’abandonament escolar és un problema greu a la nostra comunitat autònoma que pot di!cultar la cohesió social i posar en risc les trajectòries d’inserció social d’un nombre notable d’individus.El abandono de los estudios es una de las problemáticas que preocupa más los organismos educativos e instituciones nacionales e internacionales.En este sentido, el abandono escolar es un problema grave en nuestra comunidad autónoma que puede di!cultar la cohesión social y poner en riesgo las trayectorias de inserción social de un número notable de individuos

Marine Microbial Diversity and its role in Ecosystem Functioning and Environmental Change

Seas and oceans cover more than 70% of the Earth’s surface, host the majority of its biomass, and contribute significantly to all global cycles of matter and energy. All life on Earth most likely originated from microbes in the sea. In today’s marine ecosystems, following billions of years of evolution, microbes such as Bacteria, Archaea, viruses, fungi and protists (including microalgae), dominate the living biomass. Recent rapid developments in molecular ecology, metagenomics and ecological modelling illustrate that microbes represent the most important biological group on Earth in terms of phylogenetic and functional diversity. In addition, interdisciplinary research has uncovered new and unexpected roles of microbes in the biogeochemical cycling of carbon, nitrogen, silica and iron and many other (trace) elements in our seas and oceans. Marine microorganisms produce the organic matter and oxygen required to sustain life and facilitate the storage, transport, and turnover of key biological elements. Thus, microorganisms are the foundation of life and are of critical importance to the habitability and sustainability of our planet. (...)Peer reviewe

Continuous chip formation in metal cutting processes using the Particle Finite Element Method (PFEM)

This paper presents a study on the metal cutting simulation with a particular numerical technique, the Particle Finite Element Method (PFEM) with a new modified time integration algorithm and incorporating a contact algorithm capability . The goal is to reproduce the formation of continuous chip in orthogonal machining. The paper tells how metal cutting processes can be modelled with the PFEM and which new tools have been developed to provide the proper capabilities for a successful modelling. The developed method allows for the treatment of large deformations and heat conduction, workpiece-tool contact including friction effects as well as the full thermo-mechanical coupling for contact. The difficulties associated with the distortion of the mesh in areas with high deformation are solved introducing new improvements in the continuous Delaunay triangulation of the particles. The employment of adaptative insertion and removal of particles at every new updated configuration improves the mesh quality allowing for resolution of finer-scale features of the solution. The performance of the method is studied with a set of different two-dimensional tests of orthogonal machining. The examples consider, from the most simple case to the most complex case, different assumptions for the cutting conditions and different material properties. The results have been compared with experimental tests showing a good competitiveness of the PFEM in comparison with other available simulation tools.Peer ReviewedPostprint (published version

Small-scale mechanical response of cemented carbides: Correlation between mechanical properties and microstructure

The unique combination of hardness, toughness and wear resistance exhibited by heterogeneous hard materials (e.g. cemented carbides, PCD composites, PcBN systems and generic hard coating/substrate combinations) has made them preeminent material choices for extremely demanding applications, such as metal cutting/forming tools or mining bits, where improved and consistent performance together with high reliability are required. The remarkable mechanical properties of these materials results from a two-fold effectiveness associated with their intrinsic composite character. On the one hand in terms of composite nature: combination of completely different phases (hard, brittle and soft, ductile constituents) with optimal interface properties. On the other hand as related to composite assemblage: two interpenetrating-phase networks where toughening is optimized through different mechanisms depending on the relatively different chemical nature among them. In particular, this presentation is focused on WC-Co hardmetals, as reference hard material. Large number of studies has been reported, mainly focused on the mechanical behavior of this composite. On the other hand, information on the small-scale mechanical response of these materials is rather scarce. This is particularly true regarding experimental data and analysis on the influence of phase nature, crystal orientation (anisotropy) and interfacial adhesion strength on hardness, deformation and/or damage mechanisms. It is clear that knowledge of these issues is crucial not only to improve the performance of hardmetals but also to develop ceramic-metal composites beyond WC-Co systems. A systematic micro- and nanomechanical study of the mechanical response of several microstructurally different WC-Co grades is presented. In doing so, nanoindentation technique is implemented and corresponding deformation/damage mechanisms are also investigated. In general, five different approaches are followed to accomplish the main goal of this research: (1) assessment of intrinsic hardness values and main deformation mechanisms as a function of crystal orientation for the carbide phase at room temperature (RT) and also at high temperature (from RT to 600 ºC), (2) determination of effective hardness and flow stress of the metallic binder through massive nanoindentation and statistical analysis, (3) evaluation of the Hall-Petch parameters for the WC-Co as a function of a microstructural parameter (mean free path) by using the methodology presented above, (4) correlation of the microstructure with the hardness and elastic modulus map by using high indentation speed tests, and (5) study of the stress-strain response by means of ex/in-situ compression of micropillars. It is found that WC-Co composites are strongly anisotropic in terms of hardness at the small scale (microstructure), being the WC hardness for the basal plane about 20-30% higher than for the prismatic and pyramidal planes. It implies consideration of carbides with different crystal orientations as distinct phases for statistical analysis of massive nanoindentation data. Implementation of such testing/analysis protocol indicates a flow stress for the constrained Co-based binder of about 2.6-3.5 GPa. By plotting of the experimentally data as a function of the binder mean free path results in a Hall-Petch strengthening relationship. Finally, the compression of micropillars points out that main deformation mechanisms are located in the metallic binder although close to the strong interface exhibited by these materials

La qualitat educativa a l'ESO. Anàlisi multivariable d'una selecció d'indicadors educatius

A partir de l’estudi sobre l’eficàcia del sistema educatiu de les Illes Balears durant el període 2001-2008 en l’educació secundària obligatòria, realitzat pel grup GIFES de la UIB (Orte, Ballester, Pascual, Oliver 2009), en aquest capítol recollim una visió dels factors principals que poden ajudar en la presa de decisions per millorar el sistema educatiu. En l’estudi original, l’anàlisi de l’èxit o del fracàs —concretat en l’obtenció o no del títol de Graduat en Educació Secundària— el duguérem a terme a nivells macro i micro, i en vàrem analitzar les polítiques, la legislació, les inversions i els recursos; també, i a partir del model contextual de sistemes i tenint en compte una perspectiva d’anàlisi territorial, vàrem analitzar els indicadors procedents dels subsistemes que estan implicats en el sistema escolar i en el familiar.A partir del estudio sobre la eficacia del sistema educativo de las Islas Baleares durante el periodo 2001- 2008 en la educación secundaria obligatoria, realizado por el grupo GIFES de la UIB (Orte, Ballester, Pascual, Oliver 2009), en este capítulo recogemos una visión de los factores principales que pueden ayudar en la toma de decisiones para mejorar el sistema educativo. En el estudio original, el análisis del éxito o del fracaso —concretado en la obtención o no del título de Graduado en Educación Secundaria— lo llevamos a término a niveles macro y micro, y analizamos las políticas, la legislación, las inversiones y los recursos; también, y a partir del modelo contextual de sistemas y teniendo en cuenta una perspectiva de análisis territorial, analizamos los indicadores procedentes de los subsistemas que están implicados en el sistema escolar y en el familiar

Registres ornitològics

Abstract not availabl

Neutrino masses from operator mixing

We show that in theories that reduce, at the Fermi scale, to an extension of the standard model with two doublets, there can be additional dimension five operators giving rise to neutrino masses. In particular there exists a singlet operator which can not generate neutrino masses at tree level but generates them through operator mixing. Under the assumption that only this operator appears at tree level we calculate the neutrino mass matrix. It has the Zee mass matrix structure and leads naturally to bimaximal mixing. However, the maximal mixing prediction for solar neutrinos is very sharp even when higher order corrections are considered. To allow for deviations from maximal mixing a fine tuning is needed in the neutrino mass matrix parameters. However, this fine tuning relates the departure from maximal mixing in solar neutrino oscillations with the neutrinoless double beta decay rate.Comment: 11 pages, 1 figure, revte

Registres ornitològics

Abstract not availabl