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

The case for using lumbar drainage intraoperatively to help curb the number of iatrogenic CSF leaks

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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

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

As línguas na internacionalização da Universidade de Aveiro

Partindo da análise de documentos que revelam a missão, objectivos e vectores estratégicos da Universidade de Aveiro, apresentamos um estudo com o qual se pretende compreender o papel que as línguas desempenham nas estratégias de internacionalização definidas pela instituição

As línguas na investigação científica: práticas e discursos na Universidade de Aveiro

Considerando que Instituições de Ensino Superior são espaços onde o conhecimento científico é produzido e disseminado, apresenta-se um estudo de caso da Universidade de Aveiro, Portugal, que pretende descrever práticas e discursos institucionais relativamente à utilização das línguas na investigação científica. Para descrição das práticas, foram recolhidos e analisados Relatórios Anuais das Unidades de Investigação da Universidade de Aveiro. Para acesso aos discursos institucionais, foram entrevistados oito atores institucionais, responsáveis pela investigação científica e pelo governo e coordenação da instituição. Os resultados apontam para uma convergência entre as práticas investigativas e os discursos institucionais relativamente ao papel e estatuto que as diferentes línguas adquirem na investigação científica: a língua inglesa surge, tanto nas práticas como nos discursos, como primordial para o processo de internacionalização da ciência; por outro lado, as outras línguas são percecionadas enquanto barreiras a essa internacionalização e ao sucesso científico-profissional do investigador.Considering Higher Education Institutions as settings where scientific knowledge is produced and disseminated, a case study with the University of Aveiro, Portugal, will be presented which aimed at describing institutional practices and discourses concerning the use of languages in scientific research. In order to identify practices within scientific research, documentary analysis of the Annual Reports of the Research Units of the University of Aveiro was carried out. In order to access institutional discourses, eight actors responsible for scientific research and management at the University of Aveiro were interviewed. The results underline that there is a convergence between research practices and the institutional discourses concerning the role and status that different languages have in scientific research: English is, both in practices and discourses, a primordial asset in science internationalisation process; on the other hand, other languages are perceived as barriers to that internationalisation and to researchers’ scientific acknowledgement.Considérant les institutions d’enseignement supérieur comme des espaces où les connaissances scientifiques sont produites et diffusées, on présentera une étude de cas au sein de l’Université de Aveiro, Portugal, qui vise à décrire les discours et les pratiques institutionnels concernant l’utilisation des langues dans la recherche scientifique. Pour une description des pratiques nous avons recueilli et analysé des rapports annuels des unités de recherche de l’Université d’Aveiro. Pour accéder aux discours institutionnels nous avons interrogé huit acteurs institutionnels, responsables de la recherche scientifique et du gouvernement et de l’institution de coordination. Les résultats montrent une convergence entre les pratiques d’enquête et les discours institutionnels concernant le rôle et le statut qu’ acquièrent différentes langues dans la recherche scientifique: la langue anglaise se positionne, à la fois dans la pratique et dans le discours comme un élément central dans le processus d’internationalisation de la science; en revanche, les autres langues sont perçues comme des obstacles à cette internationalisation et au succès scientifique et professionnel du chercheur

Language education at the University of Aveiro before and after Bologna: practices and discourses

Higher education plays a fundamental role in the construction of a European citizenship that demands the development of plurilingual competences. Although the Bologna Process highlights that development (relating it to mobility, employability and lifelong learning), language education does not seem to be a priority in the agenda of higher education institutions (Tudor 2006).In the context of curricular restructuring required by the Bologna Process, this article presents a case study of the University of Aveiro (UA), Portugal, which set out to describe institutional practices and discourses concerning the use and function of languages in undergraduate and postgraduate education in two academic years (2002–2003 and 2007–2008, before and after the restructuring). In order to identify practices, we analysed the programmes of all language courses.This allowed us to identify the languages and language courses offered, as well as the degree programmes into which they are integrated. In order to access institutional discourses, we interviewed seven actors responsible for training and management at the UA (Rectors, Vice-Rectors, the Head of the Department of Languages and Cultures, The Erasmus Programme Coordinator, and the President of the Students’ Union). The results show that the Bologna Process has had a limiting effect on language education: fewer language courses are offered and fewer degree programmes include them. This converges with the institutional actors’ discourses, since they do not recognize the institution’s responsibility to develop students’ plurilingual competences and tend to value only the instrumental role of English

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