Resummation of infrared divergences in the free-energy of spin-two fields

We derive a closed form expression for the sum of all the infrared divergent contributions to the free-energy of a gas of gravitons. An important ingredient of our calculation is the use of a gauge fixing procedure such that the graviton propagator becomes both traceless and transverse. This has been shown to be possible, in a previous work, using a general gauge fixing procedure, in the context of the lowest order expansion of the Einstein-Hilbert action, describing non-interacting spin two fields. In order to encompass the problems involving thermal loops, such as the resummation of the free-energy, in the present work, we have extended this procedure to the situations when the interactions are taken into account.Comment: 12 pages, 25 figure

Sex and the preimplantation embryo: implications of sexual dimorphism in the preimplantation period for maternal programming of embryonic development.

201

O perfil da indústria de laticínios na Zona da Mata e Campo das Vertentes de Minas Gerais.

Cenário econômico mundial; Cenário econômico brasileiro; Cenário macroeconômico regional: Zona da Mata e Campo das Vertentes; Evolução do setor lácteo brasileiro.bitstream/item/132488/1/Livro-O-perfil-da-industria-de-laticinios.pd

Brazilian embryo industry in context: pitfalls, lessons, and expectations for the future.

Proceedings of the 31st Annual Meeting of the Brazilian Embryo Technology Society (SBTE); Cabo de Santo Agostinho, PE, Brazil, August 17th to 19th, 2017. Abstract

Possible chiral phase transition in two-dimensional solid 3^3He

We study a spin system with two- and four-spin exchange interactions on the triangular lattice, which is a possible model for the nuclear magnetism of solid $^3$He layers. It is found that a novel spin structure with scalar chiral order appears if the four-spin interaction is dominant. Ground-state properties are studied using the spin-wave approximation. A phase transition concerning the scalar chirality occurs at a finite temperature, even though the dimensionality of the system is two and the interaction has isotropic spin symmetry. Critical properties of this transition are studied with Monte Carlo simulations in the classical limit.Comment: 4 pages, Revtex, 4 figures, to appear in Phys.Rev.Let

Robust and fault tolerant control of wheeled mobile robots in formation

Este artigo trata de controle robusto e controle tolerante a falhas de movimentos coordenados de robôs móveis com rodas. O controle robusto é baseado em controle H∞ não linear por realimentação da saída. O controle tolerante a falhas é baseado em controle H∞ por realimentação da saída de sistemas lineares sujeitos a saltos Markovianos para garantir estabilidade da formação quando um dos robôs é perdido durante o movimento coordenado. A coordenação é realizada em função de um lider e qualquer robô da formação pode assumir a liderança de maneira aleatória. Os robôs móveis trocam informações de acordo com um grafo de comunicação direcionado (dígrafo), definido a-priori.This paper deals with robust and fault tolerant controls of wheeled mobile robots (WMRs) in formation. The robust approach is based on output feedback nonlinear H∞ control. The fault tolerant approach is based on output feedback H∞ control of Markovian jump linear systems to ensure stability of the formation when one of the robots is lost during the coordinated motion. The coordination is performed with the robots following a leader, and any robot of the formation can assume the leadership randomly. The mobile robots exchange informations according to a pre-specified communication directed graph (digraph)

Efeito da temperatura de carbonização sobre características espectroscópicas dos carvões de duas espécies de bambu.

O objetivo desse trabalho foi caracterizar carvões vegetais de bambu nativo e exótico, com pirólise em diferentes temperaturas, com espectroscopia infravermelha a fim de descrever propriedades relevantes a sua função no solo como condicionador e investigar a possibilidade de quantificação desses materiais em solos.Apresentação oral - graduação

Magnetization plateau in a two-dimensional multiple-spin exchange model

We study a multiple-spin exchange model on a triangular lattice, which is a possible model for low-density solid 3He films. Due to strong competitions between ferromagnetic three-spin exchange and antiferromagnetic four-spin one, the ground states are highly degenerate in the classical limit. At least 2^{L/2}-fold degeneracy exists on the L*L triangular lattice except for the SO(3) symmetry. In the magnetization process, we found a plateau at m/m_{sat}=1/2, in which the ground state is "uuud state" (a collinear state with four sublattices). The 1/2-plateau appears due to the strong four-spin exchange interaction. This plateau survives against both quantum and thermal fluctuations. Under a magnetic field which realizes the "uuud" ordered state, a phase transition occurs at a finite temperature. We predict that low-density solid 3He thin films may show the 1/2-plateau in the magnetization process. Experimental observation of the plateau will verify strength of the four-spin exchange. It is also discussed that this magnetization plateau can be understood as an insulating-conducting transition in a particle picture.Comment: 10 pages, RevTeX, 12 figures, added a reference and corrected typos, to be published in Phys.Rev.B (01 APR 99