Energy dependence of a vortex line length near a zigzag of pinning centers

A vortex line, shaped by a zigzag of pinning centers, is described here through a three-dimensional unit cell containing two pinning centers positioned symmetrically with respect to its center. The unit cell is a cube of side $L=12\xi$, the pinning centers are insulating spheres of radius $R$, taken within the range $0.2\xi$ to $3.0\xi$, $\xi$ being the coherence length. We calculate the free energy density of these systems in the framework of the Ginzburg-Landau theory.Comment: Submitted to Braz. Jour. Phys. (http://www.sbfisica.org.br/bjp) 11 pages, 6 figures, 1 table, LaTex 2

Ample subvarieties and rationally connected fibrations

Under some positivity assumptions, extension properties of rationally connected fibrations from a submanifold to its ambient variety are studied. Given a family of rational curves on a complex projective manifold X inducing a covering family on a submanifold Y with ample normal bundle in X, the main results relate, under suitable conditions, the associated rational connected fiber structures on X and on Y. Applications of these results include an extension theorem for Mori contractions of fiber type and a classification theorem in the case Y has a structure of projective bundle or quadric fibration.Comment: 27 pages; v2: minor changes and corrections following the referee's comments. v3: few typos corrected. To appear in Math. An

Metabolic syndrome and the immunological affair with the blood-brain barrier

Copyright © 2015 Mauro, De Rosa, Marelli-Berg and Solito. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms

Paramagnetic excited vortex states in superconductors

We consider excited vortex states, which are vortex states left inside a superconductor once the external applied magnetic field is switched off and whose energy is lower than of the normal state. We show that this state is paramagnetic and develop here a general method to obtain its Gibbs free energy through conformal mapping. The solution for any number of vortices in any cross section geometry can be read off from the Schwarz - Christoffel mapping. The method is based on the first order equations used by A. Abrikosov to discover vortices.Comment: 14 pages, 7 figure

Vanishing of the upper critical field in Bi_2Sr_2CaCu_2O_{8+\delta} from Landau-Ott scaling

We apply Landau-Ott scaling to the reversible magnetization data of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ published by Y. Wang et al. [\emph{Phys. Rev. Lett. \textbf{95} 247002 (2005)}] and find that the extrapolation of the Landau-Ott upper critical field line vanishes at a critical temperature parameter, T^*_c, a few degrees above the zero resistivity critical temperature, T_c. Only isothermal curves below and near to T_c were used to determine this transition temperature. This temperature is associated to the disappearance of the mixed state instead of a complete suppression of superconductivity in the sample.Comment: 3 figure

Verification of Magnitude and Phase Responses in Fixed-Point Digital Filters

In the digital signal processing (DSP) area, one of the most important tasks is digital filter design. Currently, this procedure is performed with the aid of computational tools, which generally assume filter coefficients represented with floating-point arithmetic. Nonetheless, during the implementation phase, which is often done in digital signal processors or field programmable gate arrays, the representation of the obtained coefficients can be carried out through integer or fixed-point arithmetic, which often results in unexpected behavior or even unstable filters. The present work addresses this issue and proposes a verification methodology based on the digital-system verifier (DSVerifier), with the goal of checking fixed-point digital filters w.r.t. implementation aspects. In particular, DSVerifier checks whether the number of bits used in coefficient representation will result in a filter with the same features specified during the design phase. Experimental results show that errors regarding frequency response and overflow are likely to be identified with the proposed methodology, which thus improves overall system's reliability

Effect of the boundary condition on the vortex patterns in mesoscopic three-dimensional superconductors - disk and sphere

The vortex state of mesoscopic three-dimensional superconductors is determined using a minimization procedure of the Ginzburg-Landau free energy. We obtain the vortex pattern for a mesoscopic superconducting sphere and find that vortex lines are naturally bent and are closest to each other at the equatorial plane. For a superconducting disk with finite height, and under an applied magnetic field perpendicular to its major surface, we find that our method gives results consistent with previous calculations. The matching fields, the magnetization and $H_{c3}$, are obtained for models that differ according to their boundary properties. A change of the Ginzburg-Landau parameters near the surface can substantially enhance $H_{c3}$ as shown here.Comment: 7 pages, 4 figures (low resolution

Effects of boundaries in mesoscopic superconductors

A thin superconducting disk, with radius $R=4\xi$ and height $H=\xi$, is studied in the presence of an applied magnetic field parallel to its major axis. We study how the boundaries influence the decay of the order parameter near the edges for three-dimensional vortex states.Comment: To appear in Physica C as a special issue of M2S-HTS

Uma metodologia de apoio à seleção de softwares educativos para o ensino de matemática

En virtud del intenso desarrollo de productos de software educativos hoy, la selección de esos productos por los maestros ha se tornado una tarea cada vez más difícil. Argumentamos en este trabajo que mismo existiendo innúmeras estrategias de evaluación ellas no son efectivamente aplicadas para realizar una selección basada en la comparación de los rasgos de los productos de software evaluados. En este sentido, presentamos un nuevo abordaje para la evaluación de productos de software educativo. En este abordaje proponemos una metodología que tiene como objectivo principal permitir la selección de productos de software educativo que tengan rasgos funcionales semejantes, por medio del uso de métricas definidas por el propio evaluador y que son basadas en la teoría de los campos conceptuales y formalizadas utilizando la técnica de puntos de casos de uso.Em virtude ao intenso desenvolvimento de produtos de software educativo atualmente, a seleção desses produtos pelos professores tem se tornado uma tarefa cada vez mais difícil. Argumentamos nesse trabalho que mesmo existindo inúmeras estratégias de avaliação elas não são efetivamente aplicadas para realizar uma seleção baseada na comparação das características dos produtos de software avaliados. Nesse sentido, apresentamos uma nova abordagem para a avaliação de produtos de software educativo. Nessa abordagem propomos uma metodologia que tem como objetivo principal permitir a seleção de produtos de software educativo que possuam características funcionais semelhantes, através da utilização de métricas definidas pelo próprio avaliador e que são baseadas na teoria dos campos conceituais e formalizadas utilizando a técnica de pontos de casos de uso.Due to the intense product development educational software currently, the selection of these products by the teachers has become an increasingly difficult task. We argue in this paper that even though there are numerous assessment strategies they are not effectively applied to filter based on the comparison of the characteristics of software products evaluated. In this sense, we present a new approach for the evaluation of educational software products. In this approach we propose a methodology that aims to allow the selection of educational software products that have similar functional characteristics through the use of metrics defined by the evaluator itself and that are based on the theory of conceptual fields and formalized using the point technique use cases