Search results for "HD"
showing 10 items of 4547 documents
Crust-magnetosphere coupling during magnetar evolution and implications for the surface temperature
2018
We study the coupling of the force-free magnetosphere to the long-term internal evolution of a magnetar. We allow the relation between the poloidal and toroidal stream functions - that characterizes the magnetosphere - to evolve freely without constraining its particular form. We find that, on time-scales of the order of kyr, the energy stored in the magnetosphere gradually increases, as the toroidal region grows and the field lines expand outwards. This continues until a critical point is reached beyond which force-free solutions for the magnetosphere can no longer be constructed, likely leading to some large-scale magnetospheric reorganization. The energy budget available for such events …
Long-term evolution of the force-free twisted magnetosphere of a magnetar
2017
We study the long-term quasi-steady evolution of the force-free magnetosphere of a magnetar coupled to its internal magnetic field. We find that magnetospheric currents can be maintained on long timescales of the order of thousands of years. Meanwhile, the energy, helicity and twist stored in the magnetosphere all gradually increase over the course of this evolution, until a critical point is reached, beyond which a force-free magnetosphere cannot be constructed. At this point, some large-scale magnetospheric rearrangement, possibly resulting in an outburst or a flare, must occur, releasing a large fraction of the stored energy, helicity and twist. After that, the quasi-steady evolution sho…
The force-free twisted magnetosphere of a neutron star – II. Degeneracies of the Grad–Shafranov equation
2017
We extend our previous study of equilibrium solutions of non-rotating force-free magnetospheres of neutron stars. We show that multiple solutions exist for the same sets of parameters, implying that the solutions are degenerate. We are able to obtain configurations with disconnected field lines, however, in nearly all cases these correspond to degenerate higher energy solutions. We carry out a wide parametric search in order to understand the properties of the solutions. We confirm our previous results that the lower energy solutions have up to $\sim 25\%$ more energy than the vacuum case, helicity of the order of $\sim 5$ (in some defined units), maximum twist of $\sim 1.5$ rad, and a dipo…
ROLE OF EJECTA CLUMPING AND BACK-REACTION OF ACCELERATED COSMIC RAYS IN THE EVOLUTION OF TYPE Ia SUPERNOVA REMNANTS
2012
We investigate the role played by initial clumping of ejecta and by efficient acceleration of cosmic rays (CRs) in determining the density structure of the post-shock region of a Type Ia supernova remnant (SNR) through detailed 3D MHD modeling. Our model describes the expansion of a SNR through a magnetized interstellar medium (ISM), including the initial clumping of ejecta and the effects on shock dynamics due to back-reaction of accelerated CRs. The model predictions are compared to the observations of SN 1006. We found that the back-reaction of accelerated CRs alone cannot reproduce the observed separation between the forward shock (FS) and the contact discontinuity (CD) unless the energ…
Polarized radio emission unveils the structure of the pre-supernova circumstellar magnetic field and the radio emission in SN1987A
2022
The detected polarized radio emission from remnant of SN1987A opens the possibility to unveil the structure of the pre-supernova magnetic field in the circumstellar medium. Properties derived from direct measurements would be of importance for understanding the progenitor stars and their magnetic fields. As the first step to this goal, we adopted the hydrodynamic data from an elaborated three-dimensional (3-D) numerical model of SN1987A. We have developed an approximate method for `reconstruction' of 3-D magnetic field structure inside supernova remnant on the `hydrodynamic background'. This method uses the distribution of the magnetic field around the progenitor as the initial condition. W…
Phenotyping plant root and their interaction with soil micro-organisms
2014
International audience
From Face-to-Face to Online UDeL Camps: Supporting Staff at Higher Education Institutions in Developing Universal Design for eLearning (UDeL)
2021
The TINEL Project is running a series of camps for staff at higher education institution to support them in developing inclusive eLearning. The first camp was conducted face-to-face, but the coronavirus pandemic meant that the second camp was conducted online. This created a case study in inclusive eLearning in itself and allowed us to experience and reflect on the challenges and opportunities of inclusive online teaching and learning. This paper presents the structure and content of the two camps, our reflections on moving from a face-to-face to an online situation and our elaboration how the UDL principles apply to eLearning to create Universal Design for eLearning (UDeL). We found that b…
El impacto de las estancias internacionales en el desarrollo de competencias en estudiantes de doctorado y su transferencia en diversos contextos
2019
El profesorado se enfrenta a crecientes y cambiantes demandas sociales que requieren una actualización constante de las competencias profesionales. En este sentido, el Espacio Europeo de Educación Superior (EEES) plantea la importancia del papel de la enseñanza y el aprendizaje en diversos entornos y en cooperación con el mundo laboral y de la investigación. De hecho, estas competencias pueden ser desarrolladas, entre otras posibilidades, mediante las experiencias de estancias internacionales. El objetivo de esta investigación es examinar, mediante entrevistas, el papel de las estancias en el desarrollo de las competencias de estudiantes de doctorado y su posterior transferencia al alumnado…
Transforming Finnish Higher Education : Institutional Mergers and Conflicting Academic Identities
2017
<p style="margin: 0cm 0cm 10pt;"> </p><p class="RESUMENCURSIVA">As in many other European countries also Finnish higher education system has witnessed several reforms over the past decade many of which originate in efforts to make more competitive and affordable higher education system. The aim of this paper is to describe the changes and institutional mergers in particular that have taken place in Finnish higher education and explore what kind of academic identities are constructed amid changes in Finnish higher education. The paper shows that the mergers followed the objectives set by the Finnish Ministry of Education and Culture for the structural development of the hig…
A chromatin-associated histone deacetylase from pea (Pisum sativum)
1991
Abstract A histone deacetylase activity has been found in preparation of chromatin from pea (Pisum sativum) embryonic axes. This activity readily deacetylates free histones and is somewhat specific for H2A and H2B; this property and its chromatographic behaviour allowed us to identify the enzyme with the previously described histone deacetylase HD2 (Sendra et al., Plant Mol. Biol., 11 (1988) 857). HD2 is only loosely associated to chromatin but the enzymatic activity is enhanced when chromatin adopts a folded conformation. Polyamines and divalent cations activate the enzyme, probably due to their effect on chromatin folding.