999 resultados para charge migration


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The electrical and electroluminescence (EL) properties at room and high temperatures of oxide/ nitride/oxide (ONO)-based light emitting capacitors are studied. The ONO multidielectric layer is enriched with silicon by means of ion implantation. The exceeding silicon distribution follows a Gaussian profile with a maximum of 19%, centered close to the lower oxide/nitride interface. The electrical measurements performed at room and high temperatures allowed to unambiguously identify variable range hopping (VRH) as the dominant electrical conduction mechanism at low voltages, whereas at moderate and high voltages, a hybrid conduction formed by means of variable range hopping and space charge-limited current enhanced by Poole-Frenkel effect predominates. The EL spectra at different temperatures are also recorded, and the correlation between charge transport mechanisms and EL properties is discussed.

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The possible coexistence of ferromagnetism and charge/orbital order in Bi3/4Sr1/4MnO3 has been investigated. The manganite Bi0.75Sr0.25MnO3, with commensurate charge balance, undergoes an electronic transition at TCO~600 K that produces a longrange modulation with double periodicity along a and c axis, and unusual anisotropic evolution of the lattice parameters. The previously proposed ferromagnetic properties of this new ordered phase were studied by magnetometry and diffraction techniques. In zero field the magnetic structure is globally antiferromagnetic, ruling out the apparition of spontaneous ferromagnetism. However, the application of magnetic fields produces a continuous progressive canting of the moments, inducing a ferromagnetic phase even for relatively small fields (H<<1 T). Application of pulsed high fields produces a remarkable and reversible spin polarization (under 30 T, the ferromagnetic moment is ~3 ¿B/Mn, without any sign of charge order melting). The coexistence of ferromagnetism and charge order at low and very-high fields is a remarkable property of this system.

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La Suisse compte plus de 280'000 personnes âgées de plus 55 ans issues de la migration, sans compter les personnes naturalisées. Ce nombre élevé et croissant de migrants vieillissants s'inscrit dans un contexte de vieillissement de la population. Plusieurs études menées au niveau national et qui portaient sur les communautés italienne, espagnole et ex-yougoslave ont mis en évidence une importante vulnérabilité sociale et sanitaire au sein de ces groupes de populations. Cette fragilité socio-sanitaire résulte souvent d'un parcours migratoire difficile. A l'état de santé fragilisé des migrants s'ajoutent des risques accrus de pauvreté et un danger d'isolement dû à leur intégration limitée dans la société locale. En effet, une grande partie de ces personnes maîtrisent peu la langue du pays d'accueil, ce qui a entre autres pour conséquence une méconnaissance du système social et sanitaire suisse. Les migrants vieillissants s'appuient donc essentiellement sur leur réseau de proches pour les aider à faire face aux difficultés quotidiennes. Sur la base des différents constats résumés de manière succincte ci-dessus et pour répondre à cette problématique, l'Entraide Protestante Suisse (EPER) a mis sur pied en 2006, un premier projet destiné à ce public dans le canton de Zurich et a démarré un projet similaire dans le canton de Vaud en 2012. Le projet pilote de l'EPER " Age et Migration " consiste à proposer aux migrants âgés de plus 55 ans du canton de Vaud des activités pouvant contribuer à améliorer leurs conditions de vie. Ce projet vise aussi à faciliter l'accès à diverses informations et prestations relatives à l'âge et à la santé. Il permet également de lutter contre l'isolement en proposant diverses activités de socialisation.

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Calcium hydroxyapatite crystal deposition is a common disorder, which sometimes causes acute pain as calcifications dissolve and migrate into adjacent soft tissue. Intraosseous calcium penetration has also been described. We illustrate the appearance of these lesions using a series of 35 cases compiled by members of the French Society of Musculoskeletal Imaging (Société d'Imagerie Musculo-Squelettique, SIMS). The first group in our series (7 cases) involved calcification-related cortical erosions of the humeral and femoral diaphyses, in particular at the pectoralis major and gluteus maximus insertions. A second group (28 cases) involved the presence of calcium material in subcortical areas. The most common site was the greater tubercle of the humerus, accompanying a calcifying tendinopathy of the supraspinatus. In addition, an extensive intramedullary diffusion of calcium deposits was observed in four of these cases, associated with cortical erosion in one case and subcortical lesions in three cases. Cortical erosions and intraosseous migration of calcifications associated with calcific tendinitis may be confused with neoplasm or infection. It is important to recognize atypical presentations of hydroxyapatite deposition to avoid unnecessary investigation or surgery.