Magnetic Properties of the Metamagnet Ising Model in a three-dimensional Lattice in a Random and Uniform Field

By employing the Monte Carlo technique we study the behavior of Metamagnet Ising Model in a random field. The phase diagram is obtained by using the algorithm of Glaubr in a cubic lattice of linear size $L$ with values ranging from 16 to 42 and with periodic boundary conditions.Comment: 4 pages, 6 figure

Scattering by linear defects in graphene: a continuum approach

We study the low-energy electronic transport across periodic extended defects in graphene. In the continuum low-energy limit, such defects act as infinitesimally thin stripes separating two regions where Dirac Hamiltonian governs the low-energy phenomena. The behavior of these systems is defined by the boundary condition imposed by the defect on the massless Dirac fermions. We demonstrate how this low-energy boundary condition can be computed from the tight-binding model of the defect line. For simplicity we consider defect lines oriented along the zigzag direction, which requires the consideration of only one copy of Dirac equation. Three defect lines of this kind are studied and shown to be mappable between them: the pentagon-only, the zz(558) and the zz(5757) defect lines. In addition, in this same limit, we calculate the conductance across such defect lines with size L, and find it to be proportional to k_FL at low temperatures.Comment: Major revision relative to version v1; http://prb.aps.org/abstract/PRB/v86/i21/e21420

Phenomenological study of the electronic transport coefficients of graphene

Using a semi-classical approach and input from experiments on the conductivity of graphene, we determine the electronic density dependence of the electronic transport coefficients -- conductivity, thermal conductivity and thermopower -- of doped graphene. Also the electronic density dependence of the optical conductivity is obtained. Finally we show that the classical Hall effect (low field) in graphene has the same form as for the independent electron case, characterized by a parabolic dispersion, as long as the relaxation time is proportional to the momentum.Comment: 4 pages, 1 figur

Resposta do arroz irrigado a adubação residual e aos níveis de adubação em solo de várzea.

Informações sobre o efeito residual da adubação na produção de arroz irrigado em solos de várzeas no Brasil, são escassas. Conduziu-se um experimento de campo, durante três anos consecutivos, para se avaliar o efeito residual da adubação e de níveis de adubação aplicados no sulco de plantio sobre a produção de arroz irrigado em um solo Glei Pouco Húmico (Inseptissolo) de várzea, período em que a produção de matéria seca da parte aérea e de grãos foi significativamente afetada pela adubação no sulco e não pela adubação residual. As produções máximas de matéria seca e de grãos foram obtidas com o tratamento T7 (efeito residual da adubação média + adubo verde + 75 kg N ha-1, 90 kg P2O5 ha-1 e 60 kg K2O ha-1). O tratamento T4 (efeito residual da adubação média + 50 kg N ha-1, 60 kg P2O5 ha-1 e 40 kg K2O ha-1) não foi diferente significativamente em comparação com o tratamento T7; enquanto entre os componentes da produção o número de panículas por m² e o peso de 1.000 grãos foram significativamente afetados pelos tratamentos, por outro lado, a acumulação da maioria dos nutrientes na parte aérea e nos grãos foi significativamente afetada pelos tratamentos

Scattering by linear defects in graphene: a tight-binding approach

We develop an analytical scattering formalism for computing the transmittance through periodic defect lines within the tight-binding model of graphene. We first illustrate the method with a relatively simple case, the pentagon-only defect line. Afterwards, more complex defect lines are treated, namely the zz(558) and the zz(5757) ones. The formalism developed, only uses simple tight-binding concepts, reducing the problem to matrix manipulations which can be easily worked out by any computational algebraic calculator.JNBR was supported by Fundacao para a Ciencia e a Tecnologia (FCT) through Grant No. SFRH/BD/44456/2008. NMRP was supported by Fundos FEDER through the Programa Operacional Factores de Competitividade-COMPETE and by FCT under project no. PEst-C/FIS/UI0607/2011. NMRP acknowledges both the hospitality and the funding from the Graphene Research Centre at the National University of Singapore, where this work was completed

Disorder Induced Localized States in Graphene

We consider the electronic structure near vacancies in the half-filled honeycomb lattice. It is shown that vacancies induce the formation of localized states. When particle-hole symmetry is broken, localized states become resonances close to the Fermi level. We also study the problem of a finite density of vacancies, obtaining the electronic density of states, and discussing the issue of electronic localization in these systems. Our results also have relevance for the problem of disorder in d-wave superconductors.Comment: Replaced with published version. 4 pages, 4 figures. Fig. 1 was revise

Localized states at zigzag edges of bilayer graphene

We report the existence of zero energy surface states localized at zigzag edges of bilayer graphene. Working within the tight-binding approximation we derive the analytic solution for the wavefunctions of these peculiar surface states. It is shown that zero energy edge states in bilayer graphene can be divided into two families: (i) states living only on a single plane, equivalent to surface states in monolayer graphene; (ii) states with finite amplitude over the two layers, with an enhanced penetration into the bulk. The bulk and surface (edge) electronic structure of bilayer graphene nanoribbons is also studied, both in the absence and in the presence of a bias voltage between planes.Comment: 4 pages, 5 figure

Ganho de fitomassa e acúmulo de N atmosférico em plantas de feijão-caupi inoculadas com rizóbio.

Este trabalho teve como objetivo verificar o ganho de matéria seca e o acúmulo de N na parte aérea de plantas de feijão-caupi [Vigna unguiculata (L.) Walp] inoculadas com estirpes de rizóbio específicas