Vortices in the presence of a nonmagnetic atom impurity in 2D XY ferromagnets

Using a model of nonmagnetic impurity potential, we have examined the behavior of planar vortex solutions in the classical two-dimensional XY ferromagnets in the presence of a spin vacancy localized out of the vortex core. Our results show that a spinless atom impurity gives rise to an effective potential that repels the vortex structure.Comment: 6 pages, 2 figures, RevTex

AE Aurigae: first detection of non-thermal X-ray emission from a bow shock produced by a runaway star

Runaway stars produce shocks when passing through interstellar medium at supersonic velocities. Bow shocks have been detected in the mid-infrared for several high-mass runaway stars and in radio waves for one star. Theoretical models predict the production of high-energy photons by non-thermal radiative processes in a number sufficiently large to be detected in X-rays. To date, no stellar bow shock has been detected at such energies. We present the first detection of X-ray emission from a bow shock produced by a runaway star. The star is AE Aur, which was likely expelled from its birthplace by the encounter of two massive binary systems and now is passing through the dense nebula IC 405. The X-ray emission from the bow shock is detected at 30" to the northeast of the star, coinciding with an enhancement in the density of the nebula. From the analysis of the observed X-ray spectrum of the source and our theoretical emission model, we confirm that the X-ray emission is produced mainly by inverse Compton upscattering of infrared photons from dust in the shock front.Comment: Accepted for publication in the Astrophysical Journal with number ApJ, 757, L6. Four figure

Many-nodes/many-links spinfoam: the homogeneous and isotropic case

I compute the Lorentzian EPRL/FK/KKL spinfoam vertex amplitude for regular graphs, with an arbitrary number of links and nodes, and coherent states peaked on a homogeneous and isotropic geometry. This form of the amplitude can be applied for example to a dipole with an arbitrary number of links or to the 4-simplex given by the compete graph on 5 nodes. All the resulting amplitudes have the same support, independently of the graph used, in the large j (large volume) limit. This implies that they all yield the Friedmann equation: I show this in the presence of the cosmological constant. This result indicates that in the semiclassical limit quantum corrections in spinfoam cosmology do not come from just refining the graph, but rather from relaxing the large j limit.Comment: 8 pages, 4 figure

Improved drought tolerance in wheat is required to unlock the production potential of the Brazilian Cerrado.

ABSTRACT Improving rainfed wheat cultivation in central Brazil, where the Cerrado biome (Brazilian savanna) is predominant, remains a bottleneck for future increases in domestic wheat production. In the Cerrado, the limited water availability during the wheat-growing season is an obstacle to increase wheat yield. To address this issue, the physiological and molecular drought response of wheat and the environmental conditions of this region must be better understood. In this review, we characterized the impact of drought on rainfed wheat production in the Cerrado. Based on the peculiarities of this environment, we suggest that certain traits should be prioritized in selection. These traits and their molecular basis are important to raise wheat yields in the Cerrado and also to improve food security in Brazil, one of the top wheat-importing countries in the world

Physical regularization for the spin-1/2 Aharonov-Bohm problem in conical space

We examine the bound state and scattering problem of a spin-one-half particle undergone to an Aharonov-Bohm potential in a conical space in the nonrelativistic limit. The crucial problem of the \delta-function singularity coming from the Zeeman spin interaction with the magnetic flux tube is solved through the self-adjoint extension method. Using two different approaches already known in the literature, both based on the self-adjoint extension method, we obtain the self-adjoint extension parameter to the bound state and scattering scenarios in terms of the physics of the problem. It is shown that such a parameter is the same for both situations. The method is general and is suitable for any quantum system with a singular Hamiltonian that has bound and scattering states.Comment: Revtex4, 5 pages, published versio

Estrutura trófica da comunidade de peixes de riachos da porção oeste da bacia do Alto Paraná.

O conhecimento ecológico de peixes de riachos brasileiros ainda possui lacunas. Apesar dos muitos estudos ictiológicos na Bacia do Alto Rio Paraná, poucos foram conduzidos em córregos da região Centro-Oeste, uma das mais ameaçadas pela expansão agropecuária. Este estudo é resultado da compilação dos dados de amostras obtidas em riachos da porção Oeste da Bacia do Alto Rio Paraná. Nosso objetivo é analisar a dieta da ictiofauna e alocar as mais abundantes em guildas tróficas. Selecionamos 343 indivíduos de 44 espécies de peixes de 35 riachos nas sub-bacias dos rios Ivinhema, Pardo e Sucuriú, além de riachos que deságuam diretamente no rio Paraná. As 22 espécies mais abundantes foram classificadas em seis grupos tróficos: insetívoros bentônicos, onívoros generalistas, insetívoros, carnívoro com tendência à piscivoria, onívoros com tendência à herbivoria e iliófago-detritívoros. A classificação trófica de cada espécie na literatura foi revisada e discutida. Diferenças na composição da dieta e inclusão em guildas entre estudos foram frequentes, o que provavelmente se relaciona ao generalismo e a plasticidade trófica típicos de peixes de riachos. Nesse contexto, sugerimos que estudos de dieta em riachos tenham escalas espaciais, temporais e ontogenéticas amplas, e que a classificação de espécies em guildas a priori não é aconselhável.bitstream/item/79842/1/BP117.pd

Shannon Meets Carnot: Generalized Second Thermodynamic Law

The classical thermodynamic laws fail to capture the behavior of systems with energy Hamiltonian which is an explicit function of the temperature. Such Hamiltonian arises, for example, in modeling information processing systems, like communication channels, as thermal systems. Here we generalize the second thermodynamic law to encompass systems with temperature-dependent energy levels, $dQ=TdS+dT$, where $$ denotes averaging over the Boltzmann distribution and reveal a new definition to the basic notion of temperature. This generalization enables to express, for instance, the mutual information of the Gaussian channel as a consequence of the fundamental laws of nature - the laws of thermodynamics

Climatização de Bananas 'Prata-Anã' e 'BRS Platina' com diferentes concetrações de etileno.

Bananas quando colhidas após sua completa maturação fisiológica, frequentemente amadurecem de forma desuniforme, por causa da diferença de idade fisiológica das pencas. O processo denominado de climatização visa à homogeneização no amadurecimento dos frutos, sem alterar a qualidade dos mesmos. O objetivo deste trabalho foi avaliar o efeito da climatização com diferentes concentrações de etileno sobre a qualidade física e química de bananas 'Prata-Anã' e 'BRS Platina'. Foram aplicadas três concentrações de etileno para as cultivares Prata-Anã e BRS Platina: 100 e 500 'L L-1 de etileno e o controle (sem etileno). Os tratamentos foram aplicados com gerador comercial de etileno (Banasil®) por 48 horas a 16°C. Após a climatização os frutos foram armazenados a 25°C até atingirem o estádio 6 de amadurecimento, quando foram avaliados. As variáveis analisadas foram: acidez titulável (AT), sólidos solúveis (SS), relação SS/AT e perda de massa. Observou-se que a aplicação de etileno, independente da concentração, não influi nos parâmetros de qualidade física e química estudados para ambas as cultivares, porém mais estudos deverão ser realizados