Magnetohydrodynamics dynamical relaxation of coronal magnetic fields. II. 2D magnetic X-points

We provide a valid magnetohydrostatic equilibrium from the collapse of a 2D X-point in the presence of a finite plasma pressure, in which the current density is not simply concentrated in an infinitesimally thin, one-dimensional current sheet, as found in force-free solutions. In particular, we wish to determine if a finite pressure current sheet will still involve a singular current, and if so, what is the nature of the singularity. We use a full MHD code, with the resistivity set to zero, so that reconnection is not allowed, to run a series of experiments in which an X-point is perturbed and then is allowed to relax towards an equilibrium, via real, viscous damping forces. Changes to the magnitude of the perturbation and the initial plasma pressure are investigated systematically. The final state found in our experiments is a "quasi-static" equilibrium where the viscous relaxation has completely ended, but the peak current density at the null increases very slowly following an asymptotic regime towards an infinite time singularity. Using a high grid resolution allows us to resolve the current structures in this state both in width and length. In comparison with the well known pressureless studies, the system does not evolve towards a thin current sheet, but concentrates the current at the null and the separatrices. The growth rate of the singularity is found to be tD, with 0 < D < 1. This rate depends directly on the initial plasma pressure, and decreases as the pressure is increased. At the end of our study, we present an analytical description of the system in a quasi-static non-singular equilibrium at a given time, in which a finite thick current layer has formed at the null

Meta-model Pruning

Large and complex meta-models such as those of Uml and its profiles are growing due to modelling and inter-operability needs of numerous\ud stakeholders. The complexity of such meta-models has led to coining\ud of the term meta-muddle. Individual users often exercise only a small\ud view of a meta-muddle for tasks ranging from model creation to construction\ud of model transformations. What is the effective meta-model that represents\ud this view? We present a flexible meta-model pruning algorithm and\ud tool to extract effective meta-models from a meta-muddle. We use\ud the notion of model typing for meta-models to verify that the algorithm\ud generates a super-type of the large meta-model representing the meta-muddle.\ud This implies that all programs written using the effective meta-model\ud will work for the meta-muddle hence preserving backward compatibility.\ud All instances of the effective meta-model are also instances of the\ud meta-muddle. We illustrate how pruning the original Uml metamodel\ud produces different effective meta-models

Consequences of spontaneous reconnection at a two-dimensional non-force-free current layer

Magnetic neutral points, where the magnitude of the magnetic field vanishes locally, are potential locations for energy conversion in the solar corona. The fact that the magnetic field is identically zero at these points suggests that for the study of current sheet formation and of any subsequent resistive dissipation phase, a finite beta plasma should be considered, rather than neglecting the plasma pressure as has often been the case in the past. The rapid dissipation of a finite current layer in non-force-free equilibrium is investigated numerically, after the sudden onset of an anomalous resistivity. The aim of this study is to determine how the energy is redistributed during the initial diffusion phase, and what is the nature of the outward transmission of information and energy. The resistivity rapidly diffuses the current at the null point. The presence of a plasma pressure allows the vast majority of the free energy to be transferred into internal energy. Most of the converted energy is used in direct heating of the surrounding plasma, and only about 3% is converted into kinetic energy, causing a perturbation in the magnetic field and the plasma which propagates away from the null at the local fast magnetoacoustic speed. The propagating pulses show a complex structure due to the highly non-uniform initial state. It is shown that this perturbation carries no net current as it propagates away from the null. The fact that, under the assumptions taken in this paper, most of the magnetic energy released in the reconnection converts internal energy of the plasma, may be highly important for the chromospheric and coronal heating problem

The social support in kinship foster care: a way to enhance resilience.

This paper analyses how social support enhances family resilience in kinship foster families by involving the families in an educational group programme. Sixty-two kinship foster families from Spain participated in the research. The data were collected before the programme (interviews) and after the programme (interviews and focus groups), and it was analysed by content analysis with the program Atlas.ti. The results show that the factors that contribute most to the development of family resilience are (i) feeling able to look for solutions when faced with problems; (ii) an increase of their network of formal support; (iii) being able to offer support to other foster families; and (iv) feeling that the support they give to parents' foster children is socially recognized

Quality procedures and ABP proposal in the subject of Pharmaceutical Management and Planning

Se diseña e implanta convenientemente una propuesta de aprendizaje basada en problema (ABP), donde el alumno se enfrente a una problemática real, consistente en incrementar la rentabilidad en una farmacia, y la presentación de la solución como procedimientos normalizados de trabajo (PNT). Objetivo: diseño y caracterización de la propuesta ABP en Gestión y Planificación Farmacéutica, dando a conocer la metodología desarrollada a la comunidad académica y contrastar los resultados con el fin de mejorarla. Metodología: incluye etapas del diseño detalladas y se determinan las repercusiones en la enseñanza. Se recogen las opiniones de los alumnos con cuestionario con ítems referentes a aspectos generales de la asignatura y datos específicos del ABP. Conclusiones: El ABP mejorar los resultados los alumnos, siendo la opinión favorables tanto en los aspectos generales como en cuestiones específicas del caso problema, incluso en los alumnos con puntuación más bajas que reconocen el interés del ABP en el contexto de la asignatura. Son mejorables la documentación y recursos tecnológicos utilizados.We implant a proposal for a Learning Based on Problems (LBP) methodology, where students are facing a real problem, in how to increase the profitability of a pharmacy, and the presentation of the solution as standard operating procedures (SOPs). Objective: To design and characterize the proposal PEL (Pharmaceutical Management and Planning), publicizing the methodology developed for the academic community and contrast the results to improve it. Methodology: includes detailed design stages and determining the impact on teaching. It also reflects the opinions of students with questionnaire items concerning general aspects of the subject and specifics of PBL. Conclusions: The PBL improve students’ results, being the favorable opinion in both the general and specific issues of the case problem.Este trabajo ha sido subvencionado dentro de la Convocatoria de Ayudas para la Divulgación de Proyectos de Investigación, Innovación y Mejora de la Actividad Docente, del II Plan Propio de Docencia, de la Universidad de Sevila

Polyacrylamide networks. Kinetic and structural studies by high field H-NMR with polymerization in situ

The crosslinking polymerization of acrylamide (AA) and N,N′-methylene-bis-acrylamide (BA) in aqueous solution at 22°C has been studied by H.R. H-NMR spectroscopy. The initial comonomer mixture was placed inside the NMR spectrometer probe head and the polymerization was followed for 10 hr. This procedure allows measurement of the instant composition of the residual comonomer mixture even during and after gelation and therefore to calculate the composition of the formed copolymer or network. When the reaction was finished, the structure of the most mobile part of the network was also analyzed

Magnetohydrodynamics dynamical relaxation of coronal magnetic fields. I. Parallel untwisted magnetic fields in 2D

Context. For the last thirty years, most of the studies on the relaxation of stressed magnetic fields in the solar environment have onlyconsidered the Lorentz force, neglecting plasma contributions, and therefore, limiting every equilibrium to that of a force-free field. Aims. Here we begin a study of the non-resistive evolution of finite beta plasmas and their relaxation to magnetohydrostatic states, where magnetic forces are balanced by plasma-pressure gradients, by using a simple 2D scenario involving a hydromagnetic disturbance to a uniform magnetic field. The final equilibrium state is predicted as a function of the initial disturbances, with aims to demonstrate what happens to the plasma during the relaxation process and to see what effects it has on the final equilibrium state. Methods. A set of numerical experiments are run using a full MHD code, with the relaxation driven by magnetoacoustic waves damped by viscous effects. The numerical results are compared with analytical calculations made within the linear regime, in which the whole process must remain adiabatic. Particular attention is paid to the thermodynamic behaviour of the plasma during the relaxation. Results. The analytical predictions for the final non force-free equilibrium depend only on the initial perturbations and the total pressure of the system. It is found that these predictions hold surprisingly well even for amplitudes of the perturbation far outside the linear regime. Conclusions. Including the effects of a finite plasma beta in relaxation experiments leads to significant differences from the force-free case