Comparison between Eulerian diagnostics and finite-size Lyapunov exponents computed from altimetry in the Algerian basin

Transport and mixing properties of surface currents can be detected from altimetric data by both Eulerian and Lagrangian diagnostics. In contrast with Eulerian diagnostics, Lagrangian tools like the local Lyapunov exponents have the advantage of exploiting both spatial and temporal variability of the velocity field and are in principle able to unveil subgrid filaments generated by chaotic stirring. However, one may wonder whether this theoretical advantage is of practical interest in real-data, mesoscale and submesoscale analysis, because of the uncertainties and resolution of altimetric products, and the non-passive nature of biogeochemical tracers. Here we compare the ability of standard Eulerian diagnostics and the finite-size Lyapunov exponent in detecting instantaneaous and climatological transport and mixing properties. By comparing with sea-surface temperature patterns, we find that the two diagnostics provide similar results for slowly evolving eddies like the first Alboran gyre. However, the Lyapunov exponent is also able to predict the (sub-)mesoscale filamentary process occuring along the Algerian current and above the Balearic Abyssal Plain. Such filaments are also observed, with some mismatch, in sea-surface temperature patterns. Climatologies of Lyapunov exponents do not show any compact relation with other Eulerian diagnostics, unveiling a different structure even at the basin scale. We conclude that filamentation dynamics can be detected by reprocessing available altimetric data with Lagrangian tools, giving insight into (sub-)mesoscale stirring processes relevant to tracer observations and complementing traditional Eulerian diagnostics

El Yo y su cerebro. Veinticinco años después

En 1977, K. Popper y J. Eccles publicaban The Self and Its Brain. Tres años antes, en 1974, se reunían con sus esposas, a quienes dedican el libro, como invitados a la Villa Serbelloni, un paradisíaco lugar a orillas del lago de Como. Dedicaron sus días a redactar los capítulos del libro y a pasear dialogando sobre los temas. Algunas de esas sesiones peripatéticas se grabaron y publicaron en la Parte Tercera del libro. La Parte Primera es obra de K. Popper, con seis capítulos: 1.El materialismo se supera a sí mismo; 2. Los Mundos 1, 2 y 3; 3. Crítica del materialismo; 4. Algunas consideraciones en torno al yo; 5. Comentarios históricos en torno al problema del cuerpo y de la mente; 6. Sumario. J. Eccles elaboró la Parte Segunda, con ocho capítulos: 1. El cortex cerebral; 2. La percepción consciente; 3. El movimiento voluntario; 4. Los centros del lenguaje del cerebro humano; 5. Lesiones globales del cerebro humano; 6. Lesiones cerebrales limitadas; 7. La mente autoconsciente y el cerebro; 8. La memoria consciente: procesos cerebrales implicados en el almacenamiento y recuperación. En el año 2002, 25 años después, las investigaciones en las ciencias cognitivas, y particularmente en neurociencias, están proporcionando conocimientos espectaculares que exigen replantear el clásico problema mente-cuerpo, a la altura de nuestro tiempo. Estudiar la mente humana, la conciencia, la intencionalidad, el yo, es hoy tarea apasionante y lo seguirá siendo en las próximas décadas. En este proceso de comprensión y explicación de nuestra propia identidad, las diversas ciencias cognitivas nos seguirán ofreciendo respuestas que a su vez nos plantearán nuevas preguntas

Los modelos educativos. En torno a la vieja polémica Escuela Nueva frente a Escuela Tradicional.

Sin resume

Burridge-Knopoff Models as Elastic Excitable Media

We construct a model of an excitable medium with elastic rather than the usual diffusive coupling. We explore the dynamics of elastic excitable media, which we find to be dominated by low dimensional structures, including global oscillations, period-doubled pacemakers, and propagating fronts. We suggest that examples of elastic excitable media are to be found in such diverse physical systems as Burridge-Knopoff models of frictional sliding, electronic transmission lines, and active optical waveguides

La comprensión de textos. Modelo de procesamiento y estrategias de mejora.

Sin resume

Mineral carbonation of ceramic brick at low pressure and room temperature. A simulation study for a superficial CO2 store using a common clay as sealing material

This research explores the possibilities of CO2 sequestration on ceramic bricks in a short time and at surface conditions. The experiment was carried out in a specially designed reaction chamber, filled with brick wastes and sealed with common clays. The brick used were composed of quartz, wollastonite, diopside, orthoclase and anhydrite, and the common clay was a marl composed of calcite, quartz, illite, smectite and kaolinite. Experimental condition in the reaction chamber were: reaction time 5 months, pressure of CO2 0.5 bar, 4:1 solid/water ratio. The experiment was followed by XRD, XRF, BET, physical sorption by N2 and CO2, Hg porosity, TG-DTA, SEM and ICP-EOS. After the CO2 treatment, wollastonite and anhydrite were practically destroyed and some diopside and orthoclase. Calcite precipitated as new phase (up to 48 wt%), and small amount of illite was the result of orthoclase alteration. Concerning the sealing clay, the CO2 produced an increment of calcite content (from 32 to 41 wt%) and a partial destruction of smectite, particularly close to the upper part of the brick layer. These results are hopeful in relation with the possible mineral carbonation of building ceramic waste in a short time at surface conditions, and open the opportunity to use those wastes for CO2 trapping in an appropriate system, as a quarry reclamation

Inhomogeneities and caustics in the sedimentation of noninertial particles in incompressible flows

In an incompressible flow, fluid density remains invariant along fluid element trajectories. This implies that the spatial distribution of non-interacting noninertial particles in such flows cannot develop density inhomogeneities beyond those that are already introduced in the initial condition. However, in certain practical situations, density is measured or accumulated on (hyper-) surfaces of dimensionality lower than the full dimensionality of the flow in which the particles move. An example is the observation of particle distributions sedimented on the floor of the ocean. In such cases, even if the initial distribution of noninertial particles is uniform within a finite support in an incompressible flow, advection in the flow will give rise to inhomogeneities in the observed density. In this paper we analytically derive, in the framework of an initially homogeneous particle sheet sedimenting towards a bottom surface, the relationship between the geometry of the flow and the emerging distribution. From a physical point of view, we identify the two processes that generate inhomogeneities to be the stretching within the sheet, and the projection of the deformed sheet onto the target surface. We point out that an extreme form of inhomogeneity, caustics, can develop for sheets. We exemplify our geometrical results with simulations of particle advection in a simple kinematic flow, study the dependence on various parameters involved, and illustrate that the basic mechanisms work similarly if the initial (homogeneous) distribution occupies a more general region of finite extension rather than a sheet.Comment: 56 pages, 17 figure

Miradas “noir” de Barcelona: desde Vázquez Montalbán y Mendoza a Riera

La resolución de los crímenes investigados pasa a segundo plano en la novela negra española, que opta por reforzar la simbiosis entre el género policial y la crítica social. Manuel Vázquez Montalbán y Eduardo Mendoza ofrecen una visión fragmentaria de Barcelona, un retrato descarnado de la clase trabajadora, del futuro de la juventud y de la especulación. El primero, obsesionado con evitar que el progreso y la globalización arrasen con la historia de los más humildes, hace que su personaje estrella, angustiado por la crisis de valores, abandone la ciudad. Para Mendoza, Barcelona se convierte en metáfora de la conciencia política y del poder, y prefiere revelar las tensiones del progreso y del capitalismo sirviéndose de un pícaro loco y solitario carente de un código de conducta superior. Carme Riera, preocupada por la actual crisis de valores, asume la tradición novelística pero con variaciones en, por ejemplo, los paisajes, la educación, los jóvenes, la policía o los que ostentan algún estatus social, rompiendo estereotipos en su ópera prima en el género.Casting contemporary events in an incriminating light, the detective novel genre in Spain pays more attention to the social portrait than to solving the mystery. Manuel Vázquez Montalbán and Eduardo Mendoza present their readers with a fragmented world, an incriminating view of the social reality in Barcelona which focuses on the working class, the lack of hope for the youth and the exploitation by the rich and powerful. The first one, obsessed with the dynamics of the urban process, its inner tensions, and the impact of the evolution of capitalism on the historic memory of the lower classes, makes his detective leave town. Mendoza explores the relationship between the human mind and the urban environment, which turns out to be a metaphor for a site or container of power. His detective, a mad “pícaro”, refuses to follow any norm of conduct, unlike Marlow or Spade. Carme Riera, in her debut in this genre, acknowledges her predecessors, but opts to provide the reader with some new insights. Riera, concerned with today’s lack of moral and social values, breaks with a number of stereotypes, such as locations, the educational system, the youth, the police, or those with some sort of social status