Los modelos de conocimiento científico escolar de un grupo de docentes sobre la alimentación humana

La investigación se propuso caracterizar e interpretar los modelos de conocimiento científico escolar de un grupo de docentes sobre la alimentación humana e identificar rasgos comunes y particularidades. Se enmarca en el modelo cognitivo de ciencia escolar y el paradigma del pensamiento de profesor. El tratamiento y análisis de los datos incluyó estrategias cuantitativas y cualitativas. Se compararon las producciones de los docentes con un mapa experto y se utilizaron mapas lógicos (Thagard, 1992) para caracterizar la racionalidad de los modelos Las conclusiones muestran un fuerte recorte informativo y un predominio de interpretaciones sesgadas por el modelo escolar de salud. Aún así, se identificaron conceptos que admitían otras lecturas disciplinares, pudiendo constituir puntos de partida para la evolución de las hipótesis curriculares de los docentes

A robust closed-form estimator for the GARCH(1,1) model

In this paper we extend the closed-form estimator for the generalized autoregressive conditional heteroscedastic (GARCH(1,1)) proposed by Kristensen and Linton [A closed-form estimator for the GARCH(1,1) model. Econom Theory. 2006;22:323–337] to deal with additive outliers. It has the advantage that is per se more robust that the maximum likelihood estimator (ML) often used to estimate this model, it is easy to implement and does not require the use of any numerical optimization procedure. The robustification of the closed-form estimator is done by replacing the sample autocorrelations by a robust estimator of these correlations and by estimating the volatility using robust filters. The performance of our proposal in estimating the parameters and the volatility of the GARCH(1,1) model is compared with the proposals existing in the literature via intensive Monte Carlo experiments and the results of these experiments show that our proposal outperforms the ML and quasi-maximum likelihood estimators-based procedures. Finally, we fit the robust closed-form estimator and the benchmarks to one series of financial returns and analyse their performances in estimating and forecasting the volatility and the value-at-risk.info:eu-repo/semantics/submittedVersio

Holographic Complexity and Fidelity Susceptibility as Holographic Information Dual to Different Volumes in AdS

The holographic complexity and fidelity susceptibility have been defined as new quantities dual to different volumes in AdS. In this paper, we will use these new proposals to calculate both of these quantities for a variety of interesting deformations of AdS. We obtain the holographic complexity and fidelity susceptibility for an AdS black hole, Janus solution and a solution with cylindrically symmetry, an inhomogeneous background and a hyperscaling violating background. It is observed that the holographic complexity depends on the size of the subsystem for all these solutions and the fidelity susceptibility does not have any such dependence.Comment: Slighly updated version. Accepted for publication in Phys. Letters

Un enfoque teórico para el abordaje de temas complejos en el aula : el caso de la alimentación humana

La propuesta que se presenta forma parte de los resultados y conclusiones de una investigación sobre los modelos de conocimiento científico escolar de un grupo de docentes sobre la alimentación humana (Bahamonde, 2007). Para caracterizar dichos modelos se elaboró una construcción teórica específica que incluye una propuesta de elementos de referencia para la construcción de islotes interdisciplinarios de racionalidad, en el marco de la ciencia escolar, revisitando la idea de Fourez (1997). Se trata de un recorte curricular multirreferenciado, que permita hacer frente a la complejidad de los aprendizajes vinculados a la salud o al ambiente. Para la construcción de los islotes o modelos teóricos ad hoc se desarrolla el ejemplo de la alimentación humana

Generalized f(R,ϕ,X)f(R,\phi,X) gravity and the late-time cosmic acceleration

High-precision observational data have confirmed with startling evidence that the Universe is currently undergoing a phase of accelerated expansion. This phase, one of the most important and challenging current problems in cosmology, represents a new imbalance in the governing gravitational equations. Historically, physics has addressed such imbalances by either identifying sources that were previously unaccounted for, or by altering the gravitational theory. Several candidates, responsible for this expansion, have been proposed in the literature, in particular, dark energy models and modified gravity models, amongst others. Outstanding questions are related to the nature of this so-called "dark energy" that is driving this acceleration, and whether it is due to the vacuum energy or a dynamical field. On the other hand, the late-time cosmic acceleration may be due to modifications of General Relativity. In this work we explore a generalised modified gravity theory, namely $f(R,\phi,X)$ gravity, where $R$ is the Ricci scalar, $\phi$ is a scalar field, and $X$ is a kinetic term. This theory contains a wide range of dark energy and modified gravity models. We considered specific models and applications to the late-time cosmic acceleration.Comment: 13 pages, 1 figure; slightly revised version, displayed name corrected. arXiv admin note: text overlap with arXiv:1412.086

Pequeñas historias de humor y de horror : usando narrativas y casos en la formación del profesorado de ciencias

En este trabajo se discute el uso de “pequeñas historias” en la formación inicial y continuada del profesorado de ciencias para todos los niveles educativos. Se presenta un proyecto de investigación e innovación didácticas dirigido a fomentar, en profesores y profesoras de ciencias, algunos procesos cognitivolingüísticos epitómicos (paradigmáticos) de las ciencias. Para tal proyecto se diseñaron dos relatos cortos basados en materiales de historia de la ciencia. Los relatos asumen un formato narrativo y se utilizan como casos de estudio; en ellos se recurre al humor y al horror como herramientas de estructuración del hilo argumental. El contenido y el formato de los relatos tiene su base en investigaciones previas acerca de la naturaleza de la ciencia; estas “pequeñas historias” pretendían construir una imagen más robusta de la ciencia como actividad profundamente humana

Depositional style and tectonostratigraphic evolution of the El Bierzo Tertiary Subbasin (Pyrenean orogen, NW Spain)

El Bierzo Tertiary sub-basin (Oligocene–Miocene, NW Spain) is a small remnant of the western Duero Basin, a nonmarine broken foreland basin developed in front of the Cantabrian Mountains (Pyrenean orogen). The alluvial infill of El Bierzo Tertiary sub-basin consists of a coarsening-upward succession from fluvial (Toral Formation) to alluvial-fan deposits (Las Médulas Formation) and reflects the uplift of the Cantabrian Mountains, in the north, and then of the related Galaico-Leoneses Mountains, in the south. These alluvial deposits show signs of having been laid down mainly by catastrophic flows (flood-dominated systems) and consist of three main depositional elements, namely, flood-plain fines, and lobe and channel conglomerates and sandstones. The vertical stacking patterns of these deposits and their relationships to the Alpine structures permit to unravel the tectonosedimentary evolution of the basin. The alluvial-plain element is the main constituent of a wide unconfined alluvial plain (Toral Formation) during the early stages of basin evolution, whereas the channel and lobe elements form a set of relatively small, laterally confined alluvial fans (Las Médulas Formation) fed first from the north and then from the south. Las Médulas deposits form two superposed units, the lower unit, cut by the Alpine thrusts, shows a progradational character, and the upper unit, which postdates most of the thrusts but not the youngest ones, displays a composite retrogradational trend. This organisation reflects the interplay between thrust emplacement and alluvial-fan sedimentation and suggests that maximum progradation took place during the climax of Alpine deformation

Cosmological perturbations in modified teleparallel gravity models: Boundary term extension

Teleparallel gravity offers a new avenue in which to construct gravitational models beyond general relativity. While teleparallel gravity can be framed in a way to be dynamically equivalent to general relativity, its modifications are mostly not equivalent to the traditional route to modified gravity. $f(T,B)$ gravity is one such gravitational theory where the second and fourth order contributions to the field equations are decoupled. In this work, we explore the all important cosmological perturbations of this new framework of gravity. We derive the gravitational propagation equation, its vector perturbation stability conditions, and its scalar perturbations. Together with the matter perturbations, we derive the effective gravitational constant in this framework, and find an interesting branching behaviour that depends on the particular gravitational models being probed. We close with a discussion on the relation of these results with other gravitational theories.Comment: 21 page

Perturbations in Non-Flat Cosmology for f(T)f(T) gravity

The study of cosmological perturbation theory in $f(T)$ gravity is a topic of great interest in teleparallel gravity since this is one of the simplest generalizations of the theory that modifies the teleparallel equivalent of general relativity. In this work, we explore the possibility of a non-flat FLRW background solution and perform perturbations for positively as well as negatively curved spatial geometries, together with a comparison to the flat case. We determine the generalized behaviour of the perturbative modes for this non-flat FLRW setting for arbitrary $f(T)$ models, when the most general homogeneous and isotropic background tetrads are used. We also identify propagating modes in this setup, and relate this with the case of a flat cosmology.Comment: 21 pagers, no figure

Accretion Processes for General Spherically Symmetric Compact Objects

We investigate the accretion process for different spherically symmetric space-time geometries for a static fluid. We analyse this procedure using the most general black hole metric ansatz. After that, we examine the accretion process for specific spherically symmetric metrics obtaining the velocity of the sound during the process and the critical speed of the flow of the fluid around the black hole. In addition, we study the behaviour of the rate of change of the mass for each chosen metric for a barotropic fluid.Comment: 10 pages, 15 figures, v2 accepted for publication in 'European Physical Journal C