On polar Legendre polynomials

10 pages, no figures.-- MSC2000 codes: Primary 42C05; Secondary 33C25.-- ArXiv pre-print available at: http://arxiv.org/abs/0709.4537Accepted in Rocky Mountain Journal of Mathematics.We introduce a new class of polynomials {Pn}, that we call polar Legendre polynomials, they appear as solutions of an inverse Gauss problem of equilibrium position of a field of forces with n + 1 unit masses. We study algebraic, differential and asymptotic properties of this class of polynomials, that are simultaneously orthogonal with respect to a differential operator and a discrete-continuous Sobolev type inner product.Research by first author (H.P.) was partially supported by Dirección General de Investigación, Ministerio de Ciencia y Tecnología de España, under grant MTM2006-13000-C03-02, by Comunidad de Madrid-Universidad Carlos III de Madrid, under grant CCG06-UC3M/EST-0690 and by Centro de Investigación Matemática de Canarias (CIMAC). Research by second author (J.Y.B.) was supported by CNPq-TWAS. Research by third author (W.U.) was partially supported by Centro de Investigación Matemática de Canarias (CIMAC).En prens

Snake orbits and related magnetic edge states

We study the electron motion near magnetic field steps at which the strength and/or sign of the magnetic field changes. The energy spectrum for such systems is found and the electron states (bound and scattered) are compared with their corresponding classical paths. Several classical properties as the velocity parallel to the edge, the oscillation frequency perpendicular to the edge and the extent of the states are compared with their quantum mechanical counterpart. A class of magnetic edge states is found which do not have a classical counterpart.Comment: 8 pages, 10 figure

Reducing CNN textural bias with k-space artifacts improves robustness

Convolutional neural networks (CNNs) have become the de facto algorithms of choice for semantic segmentation tasks in biomedical image processing. Yet, models based on CNNs remain susceptible to the domain shift problem, where a mismatch between source and target distributions could lead to a drop in performance. CNNs were recently shown to exhibit a textural bias when processing natural images, and recent studies suggest that this bias also extends to the context of biomedical imaging. In this paper, we focus on Magnetic Resonance Images (MRI) and investigate textural bias in the context of k -space artifacts (Gibbs, spike, and wraparound artifacts), which naturally manifest in clinical MRI scans. We show that carefully introducing such artifacts at training time can help reduce textural bias, and consequently lead to CNN models that are more robust to acquisition noise and out-of-distribution inference, including scans from hospitals not seen during training. We also present Gibbs ResUnet; a novel, end-to-end framework that automatically finds an optimal combination of Gibbs k -space stylizations and segmentation model weights. We illustrate our findings on multimodal and multi-institutional clinical MRI datasets obtained retrospectively from the Medical Segmentation Decathlon (n=750) and The Cancer Imaging Archive (n=243)

Rotating Superconductors and the London Moment: Thermodynamics versus Microscopics

Comparing various microscopic theories of rotating superconductors to the conclusions of thermodynamic considerations, we traced their marked difference to the question of how some thermodynamic quantities (the electrostatic and chemical potentials) are related to more microscopic ones: The electron's the work function, mean-field potential and Fermi energy -- certainly a question of general import. After the correct identification is established, the relativistic correction for the London Moment is shown to vanish, with the obvious contribution from the Fermi velocity being compensated by other contributions such as electrostatics and interactions.Comment: 23 pages 4 fi

Competencias docentes transversales, el método de selección MiZona-CDT

Se propone el método MiZona-CDT para seleccionar un conjunto mínimo de competencias docentes transversales en base a las competencias TIC, para facilitar el estudio de concordancias y la normalización del concepto entre las redes de instituciones de educación superior, nacionales e internacionales y sentar las bases de un sustrato común para facilitar los estudios, investigaciones y manejos administrativos. El método MiZona-CDT plantea la derivación de las competencias docentes básicas o su conjunto mínimo equivalente, a partir de las competencias transversales del perfil profesional de una universidad para sus estudiantes, resaltando la situación que el profesor debe de contar con las competencias docentes transversales, de igual o similar características a las del estudiante al que pretende formar. A partir de las investigaciones realizadas para reforzar las competencias transversales de los estudiantes utilizando el contexto digital y la competencia Uso de TIC, y derivar las demás competencias transversales escogidas, se desprende el método MIZona-CDT que permite seleccionar el conjunto mínimoThe proposed method MiZona-CDT to select a minimum set of transversal teaching competences based on ICT skills, to facilitate the study of concordances and standardization of the concept between the networks of higher education institutions, national and international and lay the foundation a common substrate to facilitate the study, research and administrative handling. The MiZona-CDT method raises the derivation of the basic teaching competences or minimum set equivalent from transversal competences of the professional profile of a university for students, highlighting the situation that the teacher must have teaching transverse competences with the same or similar characteristics of the student who intends to form. From research to enhance the transversal competences of students using the digital environment competition and Use of ICT and other transversal competences derived chosen it follows MIZona-CDT method for selecting the minimum set of teaching competences transverse as a nexus to the necessary interventions

Red conceptual como estrategia de integración de contenidos disciplinares en enseñanza de las ciencias

La enseñanza de la ciencias busca la integración disciplinar como resultado de la experiencia educativa y de teorías como las de Morín (2002); Astolfi (1992,1994) entre otros. Partiendo de allí, este trabajo expone una experiencia efectuada durante el curso Cultivo in vitro de Tejidos Vegetales, con el uso de un Organizador Gráfico, Red Conceptual (Galagovsky, 1996), el cual permite la representación de las relaciones entre las disciplinas con un enfoque integrado. Se desarrolló como una investigación-acción sobre la práctica pedagógica, utilizando entrevistas, observación, y gráficos. La red elaborada mostró una alta interrelación entre los conceptos de diversas disciplinas de las Ciencias Naturales y Sociales. Hubo consenso en que la estrategia es apropiada para integrar diversos contenidos disciplinares desde el contexto de una asignatura como campo de estudio

Estrategias para educar en valores desde los contenidos de Ciencias Naturales

El propósito de la investigación fue describir y evaluar la efectividad del programa didáctico, que orientó la ejecución del proyecto: Estrategias didácticas para educar en valores desde los contenidos de Ciencias Naturales. La investigación, de naturaleza cualitativa, se realizó con un enfoque de investigación-acción. Los informantes fueron estudiantes de la carrera docente (UPEL Maracay, Venezuela). El programa didáctico evaluado, se propone para operacionalizar los procesos de investigación necesarios para el desarrollo del proyecto, el afianzamiento de los valores del estudiante, la sensibilización hacia su papel en la educación en valores, y el entrenamiento para diseñar actividades y recursos propios de la didáctica de los valores. Los hallazgos empíricos obtenidos durante la evaluación, muestran que el programa didáctico desarrollado es efectivo

Neutron scattering study of a quasi-2D spin-1/2 dimer system Piperazinium Hexachlorodicuprate under hydrostatic pressure

We report inelastic neutron scattering study of a quasi-two-dimensional S=1/2 dimer system Piperazinium Hexachlorodicuprate under hydrostatic pressure. The spin gap {\Delta} becomes softened with the increase of the hydrostatic pressure up to P= 9.0 kbar. The observed threefold degenerate triplet excitation at P= 6.0 kbar is consistent with the theoretical prediction and the bandwidth of the dispersion relation is unaffected within the experimental uncertainty. At P= 9.0 kbar the spin gap is reduced to 0.55 meV from 1.0 meV at ambient pressure.Comment: 4 pages, 5 figure