A model for structural defects in nanomagnets

A model for describing structural pointlike defects in nanoscaled ferromagnetic materials is presented. Its details are explicitly developed whenever interacting with a vortex-like state comprised in a thin nanodisk. Among others, our model yields results for the vortex equilibrium position under the influence of several defects along with an external magnetic field in good qualitative agreement with experiments. We also discuss how such defects may affect the vortex motion, like its gyrotropic oscillation and dynamical polarization reversal.Comment: 8 pages, resubmitted to Journal of Applied Physic

A cultura da banana no Amapá.

Introdução; Solo; Seleção e preparo de mudas; Escolha e preparo de área; Época de plantio; Espacamento; Abertura de cova e plantio; Tratos culturais; Capina; Adubação; Desbaste; Desfolha; Eliminação do coração; Corte do pseudocaule após a colheita; Controle de pragas e doenças; Colheita.bitstream/item/124843/1/CPAF-AP-1999-CULTURA-DA-BANANA.pd

A mangabeira no Estado do Amapá.

Frutífera de porte médio (5 a 10 m de altura), a mangabeira (Hancornia speciosa Gomes) pertence à família das Apocináceas. Originária do Brasil ela é encontrada vegetando de forma espontânea em diversas regiões. As populações nativas de mangabeira no Estado do Amapá ocorrem em áreas de cerrado dos municípios de Macapá, Porto Grande. Ferreira Gomes e Itaubal do Piririm, e têm sido paulatinamente eliminadas, face a implantação de grandes florestadas (Pinus e Eucaliptos) e atividades agropecuárias, mesmo que incipientes por pequenos produtores.bitstream/item/124845/1/CPAF-AP-2001-A-Mangabeira-no-estado-do-amapa.pd

Cyclical Effects of Bank Capital Buffers with Imperfect Credit Markets: international evidence

This paper analyzes the cyclical effects of bank capital buffers using an international sample of 2,361 banks from 92 countries over the 1990-2007 period. We find that capital buffers reduce the bank credit supply but – through what could be “monitoring or signaling effects” – have also an expansionary effect on economic activity by reducing lending and deposit rate spreads. This influence on lending and deposit rate spreads is more pronunced in developing countries and during downturns. The results suggest that capital buffers have a counter-cyclical effect in these countries. Our data do not suggest differences in the cyclical effects of capital buffers between Basel I and Basel II.

Non-perturbative treatment of the linear covariant gauges by taking into account the Gribov copies

In this paper, a proposal for the restriction of the Euclidean functional integral to a region free of infinitesimal Gribov copies in linear covariant gauges is discussed. An effective action, akin to the Gribov-Zwanziger action of the Landau gauge, is obtained which implements the aforementioned restriction. Although originally non-local, this action can be cast in local form by introducing auxiliary fields. As in the case of the Landau gauge, dimension two condensates are generated at the quantum level, giving rise to a refinement of the action which is employed to obtain the tree-level gluon propagator in linear covariant gauges. A comparison of our results with those available from numerical lattice simulations is also provided.Comment: 21 pages, no figures, version to appear in EPJ