733 research outputs found
Light-induced magnetization reversal of high-anisotropy TbCo alloy films
Magnetization reversal using circularly polarized light provides a new way to
control magnetization without any external magnetic field and has the potential
to revolutionize magnetic data storage. However, in order to reach ultra-high
density data storage, high anisotropy media providing thermal stability are
needed. Here, we evidence all-optical magnetization switching for different
TbxCo1-x ferrimagnetic alloy composition and demonstrate all-optical switching
for films with anisotropy fields reaching 6 T corresponding to anisotropy
constants of 3x106 ergs/cm3. Optical magnetization switching is observed only
for alloys which compensation temperature can be reached through sample
heating
Problematic clinical features of powered wheelchair users with severely disabling multiple sclerosis
This article is made available through the Brunel Open Access Publishing Fund. Copyright @ 2014 Informa UK Ltd.Purpose: The aim of this study is to describe the clinical features of powered wheelchair users with severely disabling multiple sclerosis (MS) and explore the problematic clinical features influencing prescription. Method: Retrospective review of electronic and case note records of recipients of electric-powered indoor/outdoor powered wheelchairs (EPIOCs) attending a specialist wheelchair service between June 2007 and September 2008. Records were reviewed by a consultant in rehabilitation medicine, data systematically extracted and entered into a computer database. Further data were entered from clinical records. Data were extracted under three themes; demographic, diagnostic, clinical and wheelchair factors. Results: Records of 28 men mean age 57 (range 37â78, SD 12) years and 63 women mean age 57 (range 35â81, SD 11) years with MS were reviewed a mean of 64 (range 0â131) months after receiving their wheelchair. Twenty two comorbidities, 11 features of MS and 8 features of disability were thought to influence wheelchair prescription. Fifteen users were provided with specialised seating and 46 with tilt-in-space seats. Conclusions: Our findings suggest that people with severe MS requiring an EPIOC benefit from a holistic assessment to identify problematic clinical features that influence the prescription of the EPIOC and further medical and therapeutic interventions
Influence of the magnetic field sweeping rate on magnetic transitions in synthetic ferrimagnets with perpendicular anisotropy
International audienc
Two-fermion relativistic bound states in Light-Front Dynamics
In the Light-Front Dynamics, the wave function equations and their numerical
solutions, for two fermion bound systems, are presented. Analytical expressions
for the ladder one-boson exchange interaction kernels corresponding to scalar,
pseudoscalar, pseudovector and vector exchanges are given. Different couplings
are analyzed separately and each of them is found to exhibit special features.
The results are compared with the non relativistic solutions.Comment: 40 pages, to be published in Phys. Rev. C, .tar.gz fil
Exact boundary conditions at finite distance for the time-dependent Schrodinger equation
Exact boundary conditions at finite distance for the solutions of the
time-dependent Schrodinger equation are derived. A numerical scheme based on
Crank-Nicholson method is proposed to illustrate its applicability in several
examples.Comment: Latex.tar.gz file, 20 pages, 9 figure
On two dimensional coupled bosons and fermions
We study complex bosons and fermions coupled through a generalized Yukawa
type coupling in the large-N_c limit following ideas of Rajeev [Int. Jour. Mod.
Phys. A 9 (1994) 5583]. We study a linear approximation to this model. We show
that in this approximation we do not have boson-antiboson and
fermion-antifermion bound states occuring together. There is a possibility of
having only fermion-antifermion bound states. We support this claim by finding
distributional solutions with energies lower than the two mass treshold in the
fermion sector. This also has implications from the point of view of scattering
theory to this model. We discuss some aspects of the scattering above the two
mass treshold of boson pairs and fermion pairs. We also briefly present a
gauged version of the same model and write down the linearized equations of
motion.Comment: 25 pages, no figure
Engineering the magnetic and magnetocaloric properties of PrVO3 epitaxial oxide thin films by strain effects
Combining multiple degrees of freedom in strongly-correlated materials such
as transition-metal oxides would lead to fascinating magnetic and
magnetocaloric features. Herein, the strain effects are used to markedly tailor
the magnetic and magnetocaloric properties of PrVO3 thin films. The selection
of appropriate thickness and substrate enables us to dramatically decrease the
coercive magnetic field from 2.4 T previously observed in sintered PVO3 bulk to
0.05 T for compressive thin films making from the PrVO3 compound a nearly soft
magnet. This is associated with a marked enhancement of the magnetic moment and
the magnetocaloric effect that reach unusual maximum values of roughly 4.86 uB
and 56.8 J/kg K in the magnetic field change of 6 T applied in the sample plane
at the cryogenic temperature range (3 K), respectively. This work strongly
suggests that taking advantage of different degrees of freedom and the
exploitation of multiple instabilities in a nanoscale regime is a promising
strategy for unveiling unexpected phases accompanied by a large magnetocaloric
effect in oxides.Comment: This paper is accepted for publication in Applied Physics Letter
Multiscale structure description of positon Emission tomography difference images
A method is presented here which aims at analyzing Positon Emission Tomography difference images . This method is based on
a explicit description of the structure of the images. Positon Emission Tomography images are used to investigate the functional
organisation of the brain, looking at the cerebral blood flow . The differences between two images from the same subject lead to th e
changes of activity between two particular states . These differences, called "functional activations", are supposed to be specific o f
a particular task . The aim is then to detect functional activations while preserving individual information, unlike classical statistica l
methods which look mainly for the average information across several subjects . We then build a 3-dimensional linear scale-spac e
from the original image. Objects are extracted at each level of scale in a fully-automatic way. Then they are linked across th e
scales to get multi-scale objects in the scale-space . A vector of measures is associated to each of these multi-scale objects in order
to characterize functional activations . We present a short study to determine the relevancy of these measures and the way the y
can be used .Nous prĂ©sentons ici une mĂ©thode d'analyse d'images de diffĂ©rence issues de la Tomographie par Emission de Positons (TEP) qui repose sur une description explicite de la structure de ces images. Les images TEP permettent, par l'intermĂ©diaire du dĂ©bit sanguin cĂ©rĂ©bral, de rendre compte de l'Ă©tat fonctionnel du cerveau. En utilisant la diffĂ©rence entre deux images d'un mĂȘme sujet, on essaye de dĂ©terminer les diffĂ©rences d'activitĂ© cĂ©rĂ©brale entre deux Ă©tats. Ces diffĂ©rences sont supposĂ©es ĂȘtre spĂ©cifiques d'une tĂąche isolĂ©e par la diffĂ©rence entre les deux Ă©tats, et nous les appellerons « activations fonctionnelles ». L'objectif est donc de caractĂ©riser les activations fonctionnelles dans ces images de diffĂ©rence, tout en prĂ©servant l'information individuelle propre au sujet, ce qui n'est pas le cas des mĂ©thodes statistiques classiques, qui s'intĂ©ressent surtout Ă l'information moyenne sur l'ensemble des sujets. Un espace d'Ă©chelles (« scale-space ») linĂ©aire tri-dimensionnel est d'abord construit Ă partir de l'image de diffĂ©rence originale, puis des objets sont extraits Ă chaque niveau d'Ă©chelle de maniĂšre entiĂšrement automatique. ces objets sont ensuites liĂ©s dans les Ă©chelles pour former d'autres objets dans le scale-space. Des mesures sont alors dĂ©finies et associĂ©es Ă chacun d'eux, afin de caractĂ©riser les activations fonctionnelles. Une Ă©tude sur la pertinence des objets dĂ©finis et l'utilisation possible des mesures associĂ©es est prĂ©sentĂ©e
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