Magnetoresistive Effects in Ferromagnet-Superconductor Multilayers

We consider a nanoscale system consisting of Manganite-ferromagnet and Cuprate-superconductor multilayers in a spin valve configuration. The magnetization of the bottom Manganite-ferromagnet is pinned by a Manganite-antiferromagnet. The magnetization of the top Manganite-ferromagnet is coupled to the bottom one via indirect exchange through the superconducting layers. We study the behavior of the critical temperature and the magnetoresistance as a function of an externally applied parallel magnetic field, when the number of Cuprate-superconductor layers are changed. There are two typical behaviors in the case of a few monolayers of the Cuprates: a) For small magnetic fields, the critical temperature and the magnetoresistance change abruptly when the flipping field of the top Manganite-ferromagnet is reached. b) For large magnetic fields, the multilayered system re-enters the zero-resistance (superconducting) state after having become resistive (normal).Comment: 3 pages, 3 figures. 2004 Magnetism and Magnetic Materials Conferenc

Two-species fermion mixtures with population imbalance

We analyze the phase diagram of uniform superfluidity for two-species fermion mixtures from the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensation (BEC) limit as a function of the scattering parameter and population imbalance. We find at zero temperature that the phase diagram of population imbalance versus scattering parameter is asymmetric for unequal masses, having a larger stability region for uniform superfluidity when the lighter fermions are in excess. In addition, we find topological quantum phase transitions associated with the disappearance or appearance of momentum space regions of zero quasiparticle energies. Lastly, near the critical temperature, we derive the Ginzburg-Landau equation, and show that it describes a dilute mixture of composite bosons and unpaired fermions in the BEC limit.Comment: 4 pages with 3 figures, accepted version to PR

Evolution from BCS to BKT superfluidity in one-dimensional optical lattices

We analyze the finite temperature phase diagram of fermion mixtures in one-dimensional optical lattices as a function of interaction strength. At low temperatures, the system evolves from an anisotropic three-dimensional Bardeen-Cooper-Schrieffer (BCS) superfluid to an effectively two-dimensional Berezinskii-Kosterlitz-Thouless (BKT) superfluid as the interaction strength increases. We calculate the critical temperature as a function of interaction strength, and identify the region where the dimensional crossover occurs for a specified optical lattice potential. Finally, we show that the dominant vortex excitations near the critical temperature evolve from multiplane elliptical vortex loops in the three-dimensional regime to planar vortex-antivortex pairs in the two-dimensional regime, and we propose a detection scheme for these excitations.Comment: 4 pages with 2 figure

Topological phase transitions in ultra-cold Fermi superfluids: the evolution from BCS to BEC under artificial spin-orbit fields

We discuss topological phase transitions in ultra-cold Fermi superfluids induced by interactions and artificial spin orbit fields. We construct the phase diagram for population imbalanced systems at zero and finite temperatures, and analyze spectroscopic and thermodynamic properties to characterize various phase transitions. For balanced systems, the evolution from BCS to BEC superfluids in the presence of spin-orbit effects is only a crossover as the system remains fully gapped, even though a triplet component of the order parameter emerges. However, for imbalanced populations, spin-orbit fields induce a triplet component in the order parameter that produces nodes in the quasiparticle excitation spectrum leading to bulk topological phase transitions of the Lifshitz type. Additionally a fully gapped phase exists, where a crossover from indirect to direct gap occurs, but a topological transition to a gapped phase possessing Majorana fermions edge states does not occur.Comment: With no change in text, the labels in the figures are modifie

Fibonacci numbers, alternating parity sequences and faces of the tridiagonal Birkhoff polytope

We determine the number of alternating parity sequences that are subsequences of an increasing m-tuple of integers. For this and other related counting problems we find formulas that are combinations of Fibonacci numbers. These results are applied to determine, among other things, the number of vertices of any face of the polytope of tridiagonal doubly stochastic matrices.http://www.sciencedirect.com/science/article/B6V00-4NF4F6K-H/1/e5d0725d5317b08a025d7df94b2ca64

Light-induced protein clustering for optogenetic interference and protein interaction analysis in drosophila S2 cells

Drosophila Schneider 2 (S2) cells are a simple and powerful system commonly used in cell biology because they are well suited for high resolution microscopy and RNAi-mediated depletion. However, understanding dynamic processes, such as cell division, also requires methodology to interfere with protein function with high spatiotemporal control. In this research study, we report the adaptation of an optogenetic tool to Drosophila S2 cells. Light-activated reversible inhibition by assembled trap (LARIAT) relies on the rapid light-dependent heterodimerization between cryptochrome 2 (CRY2) and cryptochrome-interacting bHLH 1 (CIB1) to form large protein clusters. An anti-green fluorescent protein (GFP) nanobody fused with CRY2 allows this method to quickly trap any GFP-tagged protein in these light-induced protein clusters. We evaluated clustering kinetics in response to light for different LARIAT modules, and showed the ability of GFP-LARIAT to inactivate the mitotic protein Mps1 and to disrupt the membrane localization of the polarity regulator Lethal Giant Larvae (Lgl). Moreover, we validated light-induced co-clustering assays to assess protein-protein interactions in S2 cells. In conclusion, GFP-based LARIAT is a versatile tool to answer different biological questions, since it enables probing of dynamic processes and protein-protein interactions with high spatiotemporal resolution in Drosophila S2 cells.This research was funded by the National Funds through Fundação para a Ciência e a Tecnologia (FCT) under the project (PTDC/BEX-BCM/0432/2014). E.M. holds an FCT Investigator position. M.O. is supported by a fellowship from the GABBA PhD program from the University of Porto, PD/BD/105746/2014

Former des professeurs de langues par et pour l’intercompréhension: une étude en situation de formation continue

L’intercompréhension, en tant que le processus et le résultat de l’engagement communicatif des sujets, ne peut pas être réduite au domaine des compétences, notamment à celles de compréhension. Elle est d’avantage reliée aux plusieurs axes de développement d’une éducation plurilingue et interculturelle, de plus en plus valorisée dans les orientations politiques et éducatives européennes, en particulier en ce qui concerne l’enseignement des langues. Par conséquent, ce concept ne peut que jouer un rôle central dans la formation des professeurs de langues. Dans ce texte, nous décrirons un programme de formation continue de professeurs de langues (Anglais, Français et Portugais) de la région d’Aveiro (Portugal), pendant l’année scolaire 2006/2007. Ce programme de formation a eu comme but central le développement de compétences professionnelles, notamment en ce qui concerne la conception, planification, exécution et évaluation d’activités pédagogiques orientées vers une Didactique de l’Intercompréhension. Nous commencerons par présenter le plan de formation, en nous focalisant sur l’atelier « Le Professeur de Langues Interculturel – du monde virtuel au contexte scolaire » (janvier à juin2007). Nous décrirons les activités proposées et les stratégies utilisées dans le cadre de deux axes de formation parallèles et complémentaires: - l’expérimentation de situations de communication plurilingue et interculturelle, grâce à la participation à une session de la plate-forme européenne Galanet, afin de développer des compétences plurilingues et interculturelles chez les professeurs en formation; - le développement collaboratif, l’implémentation et l’évaluation de petits projets de recherche-action encadrés par une Didactique de l’Intercompréhension, en ayant en vue le développement de compétences plurilingues et interculturels chez leurs élèves. Nous analyserons ensuite les données recueillies dans les réflexions autobiographiques des professeurs à propos des expériences de formation vécues. Nous essayerons de mettre en évidence les implications de nos stratégies de formation sur leur développement professionnel

O diálogo intercultural e o espaço curricular das línguas: uma experiência no contexto de formação contínua

A escola deve contribuir para a formação de cidadãos críticos e responsáveis, preparando os alunos para viver em sociedades cada vez mais plurilingues e interculturais. Dadas as características e natureza do objecto de ensino/aprendizagem das línguas, estas assumem-se como espaços privilegiados nesta preparação, pelo que os professores devem receber formação adequada a esse desafio. Com esta intenção, desenvolvemos uma oficina de formação2, colocando professores numa dupla situação formativa, enquanto profissionais e sujeitos de linguagem, participando em trocas plurilingues e interculturais na plataforma Galanet e desenvolvendo colaborativamente projectos de investigação-acção, com o intuito de proporcionar aos seus alunos a vivência de situações potenciadoras do desenvolvimento das competências plurilingue e intercultural. Partindo das vozes dos professores e dos seus projectos de acção, pretendemos reflectir acerca da forma como esta proposta de formação favoreceu o trabalho de competências plurilingues/interculturais em contexto de sala de aula

“Papagaio colorido”? “Bola saltitante”? “Construtor de pontes”?: como é que os professores de línguas descrevem o seu papel em contextos multilingues e multiculturais?

Na era pós-moderna, as sociedades são tendencialmente multilingues e multiculturais. Esta diversidade impulsionou um intenso esforço político e educativo para implementar uma educação plurilingue e intercultural, nomeadamente em contexto europeu, que se refletiu no crescente interesse da Didática de Línguas por conceitos como intercompreensão, interculturalidade e plurilinguismo. Neste quadro, coloca-se um desafio à escola, sobretudo aos professores de línguas: formar cidadãos responsáveis, críticos, capazes de assumir o papel de mediadores interculturais, fomentando o desenvolvimento de uma competência de comunicação plurilingue e intercultural. Uma das questões que se pode colocar, face a este desafio, é a seguinte: como encaram os professores de línguas o seu papel enquanto promotores desta educação plurilingue e intercultural? Nesta comunicação, analisamos as representações de um grupo de professores de línguas (materna e estrangeiras) portugueses relativamente ao perfil e papel do professor de línguas num contexto de educação para a diversidade linguística e cultural. Propomo-nos comparar os dados relativos aos professores de Português Língua Materna com os relativos aos professores de Línguas Estrangeiras, de forma a identificar divergências e/ou convergências, assim como fatores que lhes poderão estar subjacentes, com o intuito de problematizar potenciais possibilidades e/ou constrangimentos relativamente à implementação de uma didática integrada das línguas