Scanning Tunneling Microscope Operating as a Spin-diode

We theoretically investigate spin-polarized transport in a system composed of a ferromagnetic Scanning Tunneling Microscope (STM) tip coupled to an adsorbed atom (adatom) on a host surface. Electrons can tunnel directly from the tip to the surface or via the adatom. Since the tip is ferromagnetic and the host surface (metal or semiconductor) is non-magnetic we obtain a spin-diode effect when the adatom is in the regime of single occupancy. This effect leads to an unpolarized current for direct bias (V > 0) and polarized current for reverse (V < 0) bias voltages, if the tip is nearby the adatom. Within the nonequilibrium Keldysh technique we analyze the interplay between the lateral displacement of the tip and the intra adatom Coulomb interaction on the spindiode effect. As the tip moves away from the adatom the spin-diode effect vanishes and the currents become polarized for both V > 0 and V < 0. We also find an imbalance between the up and down spin populations in the adatom, which can be tuned by the tip position and the bias. Finally, due to the presence of the adsorbate on the surface, we observe spin-resolved Friedel oscillations in the current, which reflects the oscillations in the calculated LDOS of the subsystem surface+adatom.Comment: 11 pages, 4 figures. Submitte

Sexual Dysfunction In Epilepsy: Identifying The Psychological Variables.

In order to evaluate the psychological variables that affect sexual dysfunction (SD) in epilepsy, where compared 60 epileptics (Group 1) with 60 healthy individuals (Group 2), through the State-Trait Anxiety Inventory (Spielberger et al., 1970), Beck Depression Inventory (Beck, 1974) and Sexual Behavior Interview (Souza, 1995). Sexual dysfunction (SD), anxiety and depression were found more frequently in Group 1 than in Group 2 and were not related to sex. Variables such as the onset duration and frequency of seizures as well as the use to medication were not associated with SD. Temporal lobe epilepsy was related to SD (p = 0.035) but not to anxiety or depression. Anxiety and depression were related to SD in both groups. Perception in controlling the seizures was closely related to anxiety (p = 0) and depression (p = 0.009). We conclude that psychological factors play an important role in the alteration of sexual behavior in epileptics and that suitable attention must be given to the control of these variables.58214-2

Modelagem do processo de trilha e separação mecânica do feijão em uma colhedora de fluxo axial.

O desempenho de uma máquina colhedora de grãos está diretamente relacionado às características mecânicas dos mecanísmos de trilha e separação nela utilizados. Além disso, estes mecanismos influenciam consideravelmente as perdas de produto durante o processo. A simulação de processos tem se mostrado como uma ferramenta de grande utilidade no auxilio ao projeto de novas máquinas, ou no aprimoramento das já existentes. Este trabalho foi desenvolvido com o objetivo de implementar um modelo de simulação da trilha e separação mecânica do feijão, para uma colhedora de arrasto com sistema de trilha em fluxo axial. Testes experimentais foram conduzidos, utilizando-se uma colhedora de feijaõ para validação do modelo implementado. Comparando os resultados de eficiência de trilha e separação simulados com aqueles obtidos experimentalmente, obteve-se um desvio médio de 1,78% o que foi considerado satisfatório para aplicações em engenharia de colheita

Vacuumless kinks systems from vacuum ones, an example

Some years ago, Cho and Vilenkin, introduced a model which presents topological solutions, despite not having degenerate vacua as is usually expected. Here we present a new model with topological defects, connecting degenerate vacua but which in a certain limit recovers precisely the one proposed originally by Cho and Vilenkin. In other words, we found a kind of parent model for the so called vacuumless model. Then the idea is extended to a model recently introduced by Bazeia et al. Finally, we trace some comments the case of the Liouville model.Comment: 11 pages, 4 figure

Naturalizing the Female Body: Social Control through Reproduction

Objective: To discuss alternatives to understand how the medical sciences have reduced the female body conceptually to its biological dimension as the foundation for its social control