Dynamics of the deconfinement transition

We estimate the dissipation coefficient Γ that appears in Ginzburg-Landau-Langevin equations that describe phenomenologically the deconfinement transition in QCD. This is done through the implementation of Glauber dynamics of pure SU(3) lattice gauge theory. The coefficient Γ is extracted from the short-time exponential growth of the equal time correlation function of the order parameter. Although the absolute determination of Γ is ambiguous due to the difficulties in relating real time and Monte Carlo time, its relative temperature dependence can be obtained with much less arbitrariness. © 2007 American Institute of Physics.

Experimental study of the complex reflection coefficient of shear waves from the solid-liquid interface

The determination of the reflection coefficient of shear waves reflected from a solid-liquid interface is an important method in order to study the viscoelastic properties of liquids at high frequency. The reflection coefficient is a complex number. While the magnitude measurement is relatively easy and precise, the phase measurement is very difficult due to its strong temperature dependence. For that reason, most authors choose a simplified method in order to obtain the viscoelastic properties of liquids from the measured coefficient. In this simplified method, inconsistent viscosity results are obtained because pure viscous behavior is assumed and the phase is not measured. This work deals with an effort to improve the experimental technique required to measure both the magnitude and phase of the reflection coefficient and it intends to report realistic values for oils in a wide range of viscosity (0.092 - 6.7 Pa.s). Moreover, a device calibration process is investigated in order to monitor the dynamic viscosity of the liquid.

Microscopic and dielectric analyses of vanadium and tungsten modified barium zirconium titanate ceramics

Dielectric spectroscopy was used in this study to examine polycrystalline vanadium and tungstendoped BaZr 0.1Ti 0.90O 3 (BZT10:2V and BZT10:2W) ceramics obtained by the mixed oxide method. According to X-ray diffraction analyses, addition of vanadium and tungsten lead to ceramics free of secondary phases. SEM analyses reveal that both dopants result in slower oxygen ion motion and consequently lower grain growth rate. Temperature dependence dielectric study showed normal ferroelectric to paraelectric transition well above the room temperature for the BZT10 and BZT10:2V ceramics. However, BZT10:2W ceramic showed a relaxor-like behavior near phase transition characterized by the empirical parameter γ. Piezoelectric force microscopy images reveals that the piezoelectric coefficient is strongly influenced by type of donor dopant suggesting promising applications for dynamic random access memories and data-storage media. Copyright © 2010 American Scientific Publishers All rights reserved.

Effect of structural anisotropy on electrical and magnetic properties of polyaniline conducting films

It is shown that highly conducting films of polyaniline protonated with di-esters of sulfosuccinic and sulfophthalic acids which contain alkyl- or alkoxy-type substituents exhibit highly anisotropic structural, electrical and magnetic properties. The layered-like structure of these films can be described as consisting of polyaniline chains which are mainly oriented parallel to the plane of the film and form regular out-of-plane stacks. These stacks are separated by bilayers of the dopant anions. Accordingly, the main anisotropy observed for solution cast films implies in-plane and out-of-plane measurements. An electrical anisotropy of about 80 is found for the in-plane and out-of-plane electronic conductivities at 5 K. The temperature dependences of the in-plane and out-of-plane conductivities are qualitatively similar and have been fitted as a series combination of variable-range-hopping-type and power law contributions. A maximum is observed in the temperature dependence of the electrical anisotropy at low temperature. The films also show a clear anisotropy of magnetization whose temperature and field characteristics depend on the chemical structure of the dopant anion. © 2013 Elsevier B.V.

Synthesis, crystal structure and photoluminescence of a binuclear complex of europium(III) containing 3,5-dicarboxypyrazolate and succinate

The new europium binuclear complex [Eu2(dcpz) 2(suc)(H2O)8]·(H2O) 1.5 (dcpz = 3,5-dicarboxypyrazolate and suc = succinate) has been synthesized and structurally characterized by single crystal X-ray diffraction methods. The binuclear complex crystallizes in the triclinic space group P1̄ and consists of two lanthanide ions linked by two different bridging organic ligands. 3D supramolecular framework is constructed by hydrogen bonds. The compound shows strong red emission under UV excitation at room temperature associated to IL transitions indicating a ligand to metal energy transfer mechanism since the triplet energy level lies higher than that of europium 5D0 level. Magnetic susceptibility studies showed weak temperature dependence characteristic of the Van Vleck paramagnetism. © 2013 Elsevier Ltd. All rights reserved.

Isotermas de sorção e cinética de secagem de sementes de pomelo

The drying of grapefruit seeds, by-products from grapefruit processing, was studied at 40, 50, 60 and 70°C and at three air velocities, 0.6, 1.0 and 1.4 m s-1. Sorption isotherms of grapefruit seeds were obtained at each temperature by the static method using saturated salt solutions. The Henderson model adequately described the sorption isotherms, over the entire temperature range. Drying rates indicated that the drying of grapefruit seeds took place under the falling rate period. Effective moisture diffusivity in grapefruit seeds ranged from 4.36 × 10-10 to 6.82 × 10-10 m2 s-1. The temperature dependence of the effective diffusivity followed an Arrhenius relationship, and the activation energies were 12.23, 11.29 and 11.79 kJ mol-1 for dried grapefruit seeds under air velocities of 0.6, 1.0 and 1.4 m s-1, respectively. Three thin-layer models were used to predict the drying curves, Page, Lewis, and Henderson-Pabis model. The Page model presented the best fit for all drying air temperatures and velocities studied.

Estudo de filmes supercondutores para aplicações em dispositivos eletrônicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Dinâmica de modelos minimalistas de solvente em reações de transferência de elétrons: aplicação à experimentos de única molécula

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo de transições de fases estruturais nos sistemas PZT e PMN-PT por espectroscopia no infravermelho e espectroscopia de impedância

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Manganita de lantânio dopada com estrôncio obtida por coprecipitação homogênea: magnetorresistência e magnetorrefletividade

Pós-graduação em Química - IQ

Propriedades dielétricas e térmicas das blendas de poliestireno com ácido oléico e poliestireno com betacaroteno

As propriedades térmicas, dielétricas e ópticas de óleos vegetais vêm sendo estudadas pelo Grupo de Física de Materiais da Amazônia (GFMA) desde 1996 no Departamento de Física da UFPA. Recentemente uma interação com o laboratório de físico-química de polímeros do instituto de química da UnB possibilitou o estudo desses óleos e seus constituintes na forma de blendas poliméricas. Neste trabalho procuramos dar nossa contribuição a este estudo e investigamos propriedades térmicas e dielétricas das blendas de poliestireno (PS) com ácido oléico (AO) e betacaroteno (BC) em função da temperatura, foram realizadas medidas da constante dielétrica e da difusividade térmica utilizando-se capacitores planos de placas paralelas e a técnica fotopiroelétrica, respectivamente. Foi calculado o momento de dipolo associado à blenda PS/AO utilizando os modelos teóricos de Debye, Onsager e Kirkwood para ajuste linear dos dados experimentais. Os resultados encontrados mostram que a transição de fase do AO se mantêm e que ela encontra-se deslocado para temperaturas mais elevadas.

Magnetoelastic couplings in the distorted diamond-chain compound azurite

We present results of ultrasonic measurements on a single crystal of the distorted diamond-chain compound azurite Cu-3(CO3)(2)(OH)(2). Pronounced elastic anomalies are observed in the temperature dependence of the longitudinal elastic mode c(22) which can be assigned to the relevant magnetic interactions in the system and their couplings to the lattice degrees of freedom. From a semiquantitative analysis of the magnetic contribution to c(22) the magnetoelastic coupling G = partial derivative J(2)/partial derivative epsilon(b) can be estimated, where J(2) is the intradimer coupling constant and epsilon(b) the strain along the intrachain b axis. We find an exceptionally large coupling constant of | G| similar to 3650 K highlighting an extraordinarily strong sensitivity of J(2) against changes of the b-axis lattice parameter. These results are complemented by measurements of the hydrostatic pressure dependence of J2 by means of thermal expansion and magnetic susceptibility measurements performed both at ambient and finite hydrostatic pressure. We propose that a structural peculiarity of this compound, in which Cu2O6 dimer units are incorporated in an unusually stretched manner, is responsible for the anomalously large magnetoelastic coupling.

Flammability limits of hydrated and anhydrous ethanol at reduced pressures in aeronautical applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

ECOLOGICAL MODELING OF TALITROIDES TOPITOTUM (CRUSTACEA: AMPHIPODA)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Extração e caracterização de amido de quinoa, cañihua e Mirabilis jalapa

Pós-graduação em Engenharia e Ciência de Alimentos - IBILCE