Error estimation for adaptive computations on shell structures

The finite element discretization of a shell structure introduces two kinds of errors: the error in the functional approximation and the error in the geometry approximation. The first is associated with the finite dimensional interpolation space and it is present in any finite element computation. The latter is associated with the piecewise polynomial approximation of a curved surface and is much more relevant in shell problems than in any other standard 2D or 3D computation. In the shells framework, formerly the quality control of the finite element solution has been carried out using flux projection a posteriori error estimators. This technique exhibits two main drawbacks: 1) the flux smoothing averages stress components over different elements that may have different physical meaning if the tangent planes are different and 2) the error estimation process uses only the approximate solution and hence, the discretized forces and the computational mesh: the data describing the real geometry and load is therefore not accounted for. In this work, a residual type error estimator introduced for standard 2D finite element analysis is generalized to shell problems. This allows to easily account for the real original geometry of the problem in the error estimation procedure and precludes the necessity of comparing generalized stress components between non coplanar elements. This estimator is based on approximating a reference error associated with a refined reference mesh. In order to build up the residual error equation the computed solution must be represented (projected) on the reference mesh. The use of thin shell finite elements requires a proper formulation in order to preclude shear locking. Following an idea of Donea and Lamain, the interpolation of the rotations is not unique and requires a particular technique to transfer the information from the computational mesh to the reference mesh. This technique is also developed in this work and may be used in any adaptive evolution problem where the solution must be transferred from one mesh to another.Peer ReviewedPostprint (author’s final draft

The growth suppressor p27Kip1 protects against diet-induced atherosclerosis

7 páginas, 5 figuras.The molecular basis of atherosclerosis is associated with excessive proliferation of vascular cells. Previous studies have suggested an inverse correlation between the expression of the growth suppressor p27Kip1 (p27) and cellular proliferation within human atherosclerotic tissue. However, no causal link between diminished p27 expression and atherogenesis has been established. We investigated the effect of p27 inactivation on diet-induced atherogenesis. We find that p27-deficient mice challenged with a high-fat diet for 1 month remain normocholesterolemic and have essentially no visible atheromas. However, when generated in an apolipoprotein E-null genetic background that leads to severe hypercholesterolemia in response to the atherogenic diet, deletion of p27 enhances arterial cell proliferation (∼fourfold) and accelerates atherogenesis (∼sixfold) compared with apolipoprotein E-deficient mice with an intact p27 gene. Analysis of apolipoprotein E-null mice bearing only one p27 allele inactivated reveals that a moderate decrease in p27 protein expression in the setting of hypercholesterolemia is sufficient to predispose to atherogenesis. Thus, our study establishes a molecular link between decreased p27 protein expression and atherogenesis in hypercholesterolemic animals.—Díez-Juan, A., Andrés, V. The growth suppressor p27Kip1 protects against diet-induced atherosclerosis.Work in the laboratory of V.A. is supported in part by grants from the Spanish Dirección General de Educación Superior e Investigación Científica (PM97–0136, 1FD97–1035-C02–02).Peer reviewe

Del mito a la prehistoria en la historia de España. Aproximación historiográfica

Sin resume

Joseph I, “The Regenerative King”. The Josefino’s Speech on the Regeneration of Spain

La invasión napoleónica de España a principios de 1808 inauguró uno de los periodos más convulsos de su historia. Las abdicaciones de la familia Borbón y la entronización de José Bonaparte exacerbaron los ánimos de los españoles. En medio de este contexto de guerra, sin embargo, José I emprendió un ambicioso plan de reformas para regenerar la monarquía. La política, la economía o la educación fueron algunas de las esferas renovadas. El servicio de propaganda josefino, en gran medida controlado por Napoleón, pronto difundió una imagen legitimadora de José I como “rey regenerador”. La crítica a la gestión de la casa Borbón formaba parte de la misma estrategia, pero la respuesta de la propaganda antibonapartista y, sobre todo, la desconfianza del pueblo, frustraron los planes josefinos.The Napoleonic invasion of Spain in 1808 supposed one of the most turbulent periods in its history. The abdications in the Bourbon family and Joseph Bonaparte’s enthronement exacerbated the minds of Spaniards. Within this context of war, however, Joseph I undertook an ambitious reform plan to regenerate the monarchy. Politics, the economy, and the education were some of the renewed areas. Joseph’s propaganda service, largely controlled by Napoleon, soon spread a legitimizing image of Joseph I as “King regenerator”. Part of the same strategy consisted in criticizing the Bourbon’s management; however, the response of the anti-Bonapartist propaganda and, mainly, the distrust of the people frustrated Joseph’s plans

Generalized parametric solutions in Stokes flow

The final publication is available at Springer via https://doi.org/10.1016/j.cma.2017.07.016Design optimization and uncertainty quantification, among other applications of industrial interest, require fast or multiple queries of some parametric model. The Proper Generalized Decomposition (PGD) provides a separable solution, a computational vademecum explicitly dependent on the parameters, efficiently computed with a greedy algorithm combined with an alternated directions scheme and compactly stored. This strategy has been successfully employed in many problems in computational mechanics. The application to problems with saddle point structure raises some difficulties requiring further attention. This article proposes a PGD formulation of the Stokes problem. Various possibilities of the separated forms of the PGD solutions are discussed and analyzed, selecting the more viable option. The efficacy of the proposed methodology is demonstrated in numerical examples for both Stokes and Brinkman models.Peer ReviewedPostprint (author's final draft

Components of Oral Language and Handwriting Development in Early Age

Durante las últimas décadas han sido muchas las investigaciones que se han centrado en el estudio de las relaciones entre el lenguaje oral y escrito. Actualmente existe acuerdo en que las habilidades del lenguaje oral están involucradas en el acceso al lenguaje escrito. No obstante, falta determinar con mayor claridad las relaciones que los componentes del lenguaje oral presentan en la adquisición del lenguaje escrito en los inicios de este aprendizaje. El propósito del presente trabajo ha sido doble, por un lado, analizar las relaciones existentes entre los distintos componentes del lenguaje oral y el aprendizaje de la escritura en las primeras edades, y por otro, acercarnos al conocimiento sobre el modo en que estas relaciones se manifiestan en el desarrollo evolutivo del alumnado. Además se ha atendido al estudio de cómo esas relaciones se desarrollan en función del género del alumnado. Se ha empleado un diseño correlacional que nos ha permitido esclarecer las relaciones existentes entre las variables estudiadas, así como conocer en mayor medida los factores que explican el aprendizaje de nuestro sistema de escritura. En el estudio han participado 166 alumnos de diferentes centros públicos y concertados con edades comprendidas entre los 4 y los 6 años. Los resultados ponen de manifiesto que los distintos componentes del lenguaje oral se relacionan con el aprendizaje de la escritura y que lo hacen bajo un modelo de desarrollo, a la vez que se observan diferencias de género durante el proceso de aprendizaje del sistema de escritura en las primeras edades.In recent decades there has been considerable research focusing on the relationship between oral and handwritten language. Currently, there is agreement that oral language skills are involved in access to written language. However, the relationship between oral language and written language acquisition at the early stages of this learning process has yet to be determined clearly. The purpose of this study is twofold: Firstly, analyze the relationship between the various components of oral language and the learning of writing in the early ages, and secondly, gain knowledge about how these relationships manifest in the evolutionary development of students. Also, how these relationships develop according to the gender of the students, is addressed. A correlational design was employed that allows for the elucidation of relationships between the variables examined, as well as for increased awareness of the factors that explain the learning of our handwriting system. The study involved 166 students, from different public and subsidized schools, aged between 4 to 6 years. Results show that various components of oral language relate to the process of learning handwriting at a development model, while also noting gender differences during the learning process of handwriting system at an early age