Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method

The determination of the longitudinal spin Seebeck effect (LSSE) coefficient is currently plagued by a large uncertainty due to the poor reproducibility of the experimental conditions used in its measurement. In this work we present a detailed analysis of two different methods used for the determination of the LSSE coefficient. We have performed LSSE experiments in different laboratories, by using different setups and employing both the temperature difference method and the heat flux method. We found that the lack of reproducibility can be mainly attributed to the thermal contact resistance between the sample and the thermal baths which generate the temperature gradient. Due to the variation of the thermal resistance, we found that the scaling of the LSSE voltage to the heat flux through the sample rather than to the temperature difference across the sample greatly reduces the uncertainty. The characteristics of a single YIG/Pt LSSE device obtained with two different setups was $(1.143\pm0.007)\cdot 10^{-7}$ Vm/W and $(1.101\pm0.015)\cdot 10^{-7}$ Vm/W with the heat flux method and $(2.313\pm0.017)\cdot 10^{-7}$ V/K and $(4.956\pm0.005)\cdot 10^{-7}$ V/K with the temperature difference method. This shows that systematic errors can be considerably reduced with the heat flux method.Comment: PDFLaTeX, 10 pages, 6 figure

Natural Z′Z' model with an inverse seesaw and leptonic dark matter

We consider a model for a Z'-boson coupled only to baryon minus lepton number and hypercharge. Besides the usual right-handed neutrinos, we add a pair of fermions with a fractional lepton charge, which we therefore call leptinos. One of the leptinos is taken to be odd under an additional Z_2 charge, the other even. This allows for a natural (inverse) seesaw mechanism for neutrino masses. The odd leptino is a candidate for dark matter, but has to be resonantly annihilated by the Z'-boson or the Higgs-boson responsible for giving mass to the former. Considering collider and cosmological bounds on the model, we find that the Z'-boson and/or the extra Higgs-boson can be seen at the LHC. With more pairs of leptinos leptogenesis is possible.Comment: 29 pages, 9 figures. RGE section moved to appendix and other minor corrections applied to matched published versio

Rotating charged fluids: theorems and results for Weyl type systems

We perform a systematic study of rotating charged fluids, and extend several well known theorems regarding static Weyl-type systems which were recently compiled by Lemos and Zanchin [Phys. Rev. D 80, 024010 (2009)] to rotating and axisymmetric systems. Static Weyl-type systems are composed by static charged fluid configurations obeying the Newton-Maxwell or the Einstein-Maxwell systems of equations in which the electric potential $\phi$ and the timelike metric potential $g_{tt}\equiv - W^ 2$ satisfy the Weyl hypothesis, i.e., $W=W(\phi)$. In the present analysis, both the Newton-Maxwell and Einstein-Maxwell theories that describe non-relativistic and relativistic systems, respectively, are used to perform a detailed analysis of the general properties of rotating charged fluids rotating charged dust as well as rotating charged fluids with pressure in four-dimensional spacetimes. In comparison to the static (nonrotating) systems, two additional potentials, a metric potential related to rotation and an electromagnetic potential related to the magnetic field, come into play for rotating systems. In each case, constraints between the fluid quantities and the metric and electromagnetic potentials are identified in order to generalize the theorems holding for static charged systems to rotating charged systems. New theorems regarding equilibrium configurations with differential rotation in both the Newtonian and the relativistic theories are stated and proved. For rigidly rotating charged fluids in the Einstein-Maxwell theory, a new ansatz involving the gradient of the metric potentials and the gradient of the electromagnetic potentials is considered in order to prove new theorems. Such an ansatz leads to new constraints between the fluid quantities and field potentials, so implying new equations of state for the charged fluids

Resonant Leptogenesis in the Minimal B-L Extended Standard Model at TeV

We investigate the resonant leptogenesis scenario in the minimal B-L extended standard model(SM) with the B-L symmetry breaking at the TeV scale. Through detailed analysis of the Boltzmann equations, we show how much the resultant baryon asymmetry via leptogenesis is enhanced or suppressed, depending on the model parameters, in particular, the neutrino Dirac Yukawa couplings and the TeV-scale Majorana masses of heavy degenerate neutrinos. In order to consider a realistic case, we impose a simple ansatz for the model parameters and analyze the neutrino oscillation parameters and the baryon asymmetry via leptogenesis as a function of only a single CP-phase. We find that for a fixed CP-phase all neutrino oscillation data and the observed baryon asymmetry of the present universe can be simultaneously reproduced.Comment: 25 pages, 15 figures, version to be published in Phys. Rev.

Plataforma +precoce: simulador de sistemas de produção de novilho precoce.

O setor pecuário brasileiro passa por uma evolução em seu modelo de produção, a partir de tecnologias de diversas naturezas. Neste cenário, a adoção de inovações computacionais tem figurado como diferencial para a obtenção de competitividade de mercado, produção de melhor qualidade e melhoria da rentabilidade. No âmbito das Tecnologias da Informação e Comunicação (TICs) os simuladores têm se destacado como ferramentas que permitem ao produtor rural aprimorar seus processos, auxiliando na tomada de decisões gerencias, desenvolvimento de projetos, avaliação do uso de recursos e do impacto ambiental, dentre outros. Analisando o contexto da utilização de softwares simuladores na área de concentração de sistemas de produção de bovinos de corte, foi possível observar que há muitos desafios e oportunidades e que, apesar de existirem vários softwares para este propósito, ainda existe espaço para novos trabalhos que objetivem principalmente levar esta possibilidade de uso aos produtores e técnicos rurais. Neste sentido, o objetivo deste trabalho foi desenvolver um software capaz de simular sistemas melhorados de produção de gado de corte e gerar indicadores econômicos, físicos e ambientais a partir de parâmetros de produção, reprodução, consumo, compras, rebanho, área, equipe, tempo e emissões. Ao final do desenvolvimento, foi criado um modelo para verificar os cálculos realizados pelo simulador, cujos resultados foram verificados por pesquisadores da Embrapa Gado de Corte e Embrapa Pantanal. Espera-se que a construção desta ferramenta proporcione a produtores rurais e técnicos a possibilidade de simularem sistemas de produção melhorados que possam ser replicados nas propriedades rurais, elevando a produtividade, a qualidade e a sustentabilidade da pecuária de corte.Dissertação (Mestrado em Computação Aplicada) - Faculdade de Computação, Universidade Federal do Mato Grosso do Sul, Campo Grande. Orientadora: Débora Maria Barroso Paiva, UFMS. Coorientadores: Rodrigo da Costa Gomes, Embrapa Gado de Corte; Fernando Rodrigues Teixeira Dias, Embrapa Pantanal

Ground state optimization and hysteretic demagnetization: the random-field Ising model

We compare the ground state of the random-field Ising model with Gaussian distributed random fields, with its non-equilibrium hysteretic counterpart, the demagnetized state. This is a low energy state obtained by a sequence of slow magnetic field oscillations with decreasing amplitude. The main concern is how optimized the demagnetized state is with respect to the best-possible ground state. Exact results for the energy in d=1 show that in a paramagnet, with finite spin-spin correlations, there is a significant difference in the energies if the disorder is not so strong that the states are trivially almost alike. We use numerical simulations to better characterize the difference between the ground state and the demagnetized state. For d>=3 the random-field Ising model displays a disorder induced phase transition between a paramagnetic and a ferromagnetic state. The locations of the critical points R_c(DS), R_c(GS) differ for the demagnetized state and ground state. Consequently, it is in this regime that the optimization of the demagnetized stat is the worst whereas both deep in the paramagnetic regime and in the ferromagnetic one the states resemble each other to a great extent. We argue based on the numerics that in d=3 the scaling at the transition is the same in the demagnetized and ground states. This claim is corroborated by the exact solution of the model on the Bethe lattice, where the R_c's are also different.Comment: 13 figs. Submitted to Phys. Rev.

Grapevine virus diseases: economic impact and current advances in viral prospection and management.

Grapevine (Vitis spp.) is a major vegetative propagated fruit crop with high socioeconomic importance worldwide. It is susceptible to several graft-transmitted agents that cause several diseases and substantial crop losses, reducing fruit quality and plant vigor, and shorten the longevity of vines. ] The vegetative propagation and frequent exchanges of propagative material among countries contribute to spread these pathogens, favoring the emergence of complex diseases. Its perennial life cycle further accelerates the mixing and introduction of several viral agents into a single plant. Currently, approximately 65 viruses belonging to different families have been reported infecting grapevines, but not all cause economically relevant diseases. The grapevine leafroll, rugose wood complex, leaf degeneration and fleck diseases are the four main disorders having worldwide economic importance. In addition, new viral species and strains have been identified and associated with economically important constraints to grape production. In Brazilian vineyards, eighteen viruses, three viroids and two virus-like diseases had already their occurrence reported and were molecularly characterized. Here, we review the current knowledge of these viruses, report advances in their diagnosis and prospection of new species, and give indications about the management of the associated grapevine diseases. Index terms: Vegetative propagation, plant viruses, crop losses, berry quality, next-generation sequencing. VIROSES EM VIDEIRAS: IMPACTO ECONÔMICO E RECENTES AVANÇOS NA PROSPECÇÃO DE VÍRUS E MANEJO DAS DOENÇAS DE ORIGEM VIRAL A videira (Vitis spp.) é propagada vegetativamente e considerada uma das principais culturas frutíferas por sua importância socioeconômica mundial. Ela é suscetível a vários agentes transmitidos por meio da enxertia, os quais causam diversas doenças e significativas perdas na produtividade e produção, redução na qualidade dos frutos, no vigor da planta e na longevidade dos vinhedos. A propagação vegetativa e o frequente intercâmbio de material propagativo entre países contribuem para a disseminação destes patógenos, favorecendo a emergência de doenças complexas. Seu ciclo de vida perene acelera ainda mais a mistura e a introdução de vários agentes virais em uma mesma planta. Atualmente, aproximadamente 65 vírus pertencentes a diferentes famílias foram reportados infectando videiras, embora nem todos causem doenças economicamente relevantes. As viroses do enrolamento da folha, complexo do lenho rugoso, degenerescência e mancha-das-nervuras da videira são as quatro principais desordens que têm importância econômica mundial. Além disso, novas espécies e estirpes virais foram identificadas e associadas a limitações economicamente importantes para a produção de uvas. Em vinhedos brasileiros, dezoito espécies virais, três viroides e duas doenças semelhantes a viroses já tiveram sua ocorrência reportada e foram molecularmente caracterizados. Aqui, nós revisamos o conhecimento atual dessas viroses, os recentes avanços na diagnose e prospecção viral, e fornecemos recomentações sobre o manejo das viroses da videira. Termos para indexação: Propagação vegetativa, vírus de plantas, redução da produtividade e produção, qualidade das bagas, sequenciamento de nova geração

REPRESENTAÇÕES SOCIAIS DOS ADOLESCENTES ACERCA DA VIOLÊNCIA DOMÉSTICA

Com o objetivo de analisar as representações sociais dos adolescentes sobre a violência doméstica realizou-se esta pesquisa qualitativa junto a 18 alunos de escolas de ensino médio em Passo Fundo - RS, com técnicas projetivas e entrevistas semi-estruturadas, evidenciando-se a representação da violência como um fenômeno presente na sociedade, ancorada no consumo de drogas, na defesa pessoal com porte de armas e na conduta anti-social. A violência doméstica é representada como uma atitude de fuga e defesa, maléfica, intencional e impune e como uma banalização legitimada. Essas representações ancoram-se na sensação de abandono e rejeição, cuja superação deverá ser buscada de forma multidimensional para a internalização de novas práticas e condutas socialmente aceitas

The Effect of Glass Thickness on Stress in Vacuum Glazing

Heat transfer through multiple pane windows can be reduced by creating a vacuum pressure less than 0.1 Pa between the glass panes, with low emittance coatings on one or more of the internal surfaces. Fabrication of vacuum glazing (VG) requires the formation of a hermetic seal around the periphery of the glass panes together with an array of support pillars between the panes to prevent them from touching under atmospheric pressure. Atmospheric pressure and temperature differentials induce stress which can affect the integrity of the glazing. Several parameters define the stresses in VG including the glass thickness, pillar specifications, glazing dimensions and edge seal configuration. Inherent stresses in VG can result in fractures in the glass panes and failure of the edge seal. In this study, stress in VG with different glass thicknesses is theoretically studied using Finite Element Modelling (FEM). Based on the finding in this study, suggestions are made to address problems resulting from the use of thinner glass panes in the fabrication of VG. This can lead to the development of high performance, light and thin VG

Simulation of tillage systems impact on soil biophysical properties using the SALUS model

A sustainable land management has been defined as the management system that allows for production, while minimizing risk, maintaining quality of soil and water. Tillage systems can significantly decrease soil carbon storage and influence the soil environment of a crop. Crop growth models can be useful tools in evaluating the impact of different tillage systems on soil biophysical properties and on the growth and final yield of the crops. The objectives of this paper were i) to illustrate the SALUS model and its tillage component; ii) to evaluate the effects of different tillage systems on water infiltration and time to ponding, iii) to simulate the effect of tillage systems on some soil biophysical properties. The SALUS (System Approach to Land Use Sustainability) model is designed to simulate continuous crop, soil, water and nutrient conditions under different tillage and crop residues management strategies for multiple years. Predictions of changes in surface residue, bulk density, runoff, drainage and evaporation were consistent with expected behaviours of these parameters as described in the literature. The experiment to estimate the time to ponding curve under different tillage system confirmed the theory and showed the beneficial effects of the residue on soil surface with respect to water infiltration. It also showed that the no-tillage system is a more appropriate system to adopt in areas characterized by high intensity rainfal