Correlation between photoluminescence and structural defects in Ca 1+x Cu 3 - X Ti 4 O 12 systems

Ca1+xCu3-xTi4O12 powders were synthesized by a conventional solid-state reaction. X-ray diffraction (XRD) was performed to verify the formation of cubic CaCu3Ti4O 12 (CCTO) and orthorhombic CaTiO3 (CTO) phases at long range. Rietveld refinements indicate that excess Ca atoms added to the Ca 1-xCu3-xTi4O12 (x = 1.0) composition segregated in a CaTiO3 secondary phase suggesting that solubility limit of Ca atoms in the CaCu3Ti4O12 lattice was reached for this system. The FE-SEM images show that the Ca 1+xCu3-xTi4O12 (0 < x < 3) powders are composed of several agglomerated particles with irregular morphology. X-ray absorption near-edge structure spectroscopy (XANES) spectra indicated [TiO5Vo z]-[TiO6] complex clusters in the CaCu3Ti4O12 structure which can be associated with oxygen vacancies (Vo z = V o x, Vo •, and Vo ••) whereas in the CaTiO3 powder, this analysis indicated [TiO6]-[TiO6] complex clusters in the structure. Ultraviolet-visible (UV-vis) spectra and photoluminescence (PL) measurements for the analyzed systems revealed structural defects such as oxygen vacancies, distortions, and/or strains in CaCu3Ti4O12 and CaTiO3 lattices, respectively. © 2012 The American Ceramic Society.

Spin squeezing and entanglement via finite-dimensional discrete phase-space description

We show how mapping techniques inherent to N2-dimensional discrete phase spaces can be used to treat a wide family of spin systems which exhibits squeezing and entanglement effects. This algebraic framework is then applied to the modified Lipkin-Meshkov-Glick (LMG) model in order to obtain the time evolution of certain special parameters related to the Robertson- Schrödinger (RS) uncertainty principle and some particular proposals of entanglement measure based on collective angular-momentum generators. Our results reinforce the connection between both the squeezing and entanglement effects, as well as allow to investigate the basic role of spin correlations through the discrete representatives of quasiprobability distribution functions. Entropy functionals are also discussed in this context. The main sequence correlations → entanglement → squeezing of quantum effects embraces a new set of insights and interpretations in this framework, which represents an effective gain for future researches in different spin systems. © 2013 World Scientific Publishing Company.

Morphotropic phase boundary and electrical properties of 1-x[Bi 0.5Na0.5]TiO3 -xBa[Zr0.25Ti 0.75]O3 lead-free piezoelectric ceramics

Lead-free solid solutions (1-x)Bi0.5Na0.5TiO 3 (BNT)-xBaZr0.25Ti0.75O3 (BZT) (x=0, 0.01, 0.03, 0.05, and 0.07) were prepared by the solid state reaction method. X-ray diffraction (XRD) and Rietveld refinement analyses of 1-x(BNT)-x(BZT) solid solution ceramic were employed to study the structure of these systems. A morphotropic phase boundary (MPB) between rhombohedral and cubic structures occured at the composition x=0.05. Raman spectroscopy exhibited a splitting of the (TO3) mode at x=0.05 and confirmed the presence of MPB region. Scanning electron microcopy (SEM) images showed a change in the grain shape with the increase of BZT into the BNT matrix lattice. The temperature dependent dielectric study showed a gradual increase in dielectric constant up to x=0.05 and then decrease with further increase in BZT content. Maximum coercive field, remanent polarization and high piezoelectric constant were observed at x=0.05. Both the structural and electrical properties show that the solid solution has an MPB around x=0.05. © 2012 Elsevier Ltd and Techna Group S.r.l.

A distributed-parameters transmission line model developed directly in the phase domain

This article shows a transmission line model developed directly in the phase domain. The proposed model is based on the relationships between the phase currents and voltages at both the sending and receiving ends of a single-phase line. These relationships, established using an ABCD matrix, were extended to multi-phase lines. The proposed model was validated by using it to represent a transmission line during short-and open-circuit tests. The results obtained with the proposed model were compared with results obtained with a classical model based on modal decomposition. These comparisons show that proposed model was correctly developed. © 2013 Taylor and Francis Group, LLC.

Thermal phase transition for some spin-boson models

In this work we study two different spin-boson models. Such models are generalizations of the Dicke model, it means they describe systems of N identical two-level atoms coupled to a single-mode quantized bosonic field, assuming the rotating wave approximation. In the first model, we consider the wavelength of the bosonic field to be of the order of the linear dimension of the material composed of the atoms, therefore we consider the spatial sinusoidal form of the bosonic field. The second model is the Thompson model, where we consider the presence of phonons in the material composed of the atoms. We study finite temperature properties of the models using the path integral approach and functional methods. In the thermodynamic limit, N→∞, the systems exhibit phase transitions from normal to superradiant phase at some critical values of temperature and coupling constant. We find the asymptotic behavior of the partition functions and the collective spectrums of the systems in the normal and the superradiant phases. We observe that the collective spectrums have zero energy values in the superradiant phases, corresponding to the Goldstone mode associated to the continuous symmetry breaking of the models. Our analysis and results are valid in the limit of zero temperature β→∞, where the models exhibit quantum phase transitions. © 2013 Elsevier B.V. All rights reserved.

Dissection of the role of pili and type 2 and 3 secretion systems in adherence and biofilm formation of an atypical enteropathogenic escherichia coli strain

Atypical enteropathogenic Escherichia coli (aEPEC) strains are diarrheal pathogens that lack bundle-forming pilus production but possess the virulence-associated locus of enterocyte effacement. aEPEC strain 1551-2 produces localized adherence (LA) on HeLa cells; however, its isogenic intimin (eae) mutant produces a diffuse-adherence (DA) pattern. In this study, we aimed to identify the DA-associated adhesin of the 1551-2 eae mutant. Electron microscopy of 1551-2 identified rigid rod-like pili composed of an 18-kDa protein, which was identified as the major pilin subunit of type 1 pilus (T1P) by mass spectrometry analysis. Deletion of fimA in 1551-2 affected biofilm formation but had no effect on adherence properties. Analysis of secreted proteins in supernatants of this strain identified a 150-kDa protein corresponding to SslE, a type 2 secreted protein that was recently reported to be involved in biofilm formation of rabbit and human EPEC strains. However, neither adherence nor biofilm formation was affected in a 1551-2 sslE mutant. We then investigated the role of the EspA filament associated with the type 3 secretion system (T3SS) in DA by generating a double eae espA mutant. This strain was no longer adherent, strongly suggesting that the T3SS translocon is the DA adhesin. In agreement with these results, specific anti-EspA antibodies blocked adherence of the 1551-2 eae mutant. Our data support a role for intimin in LA, for the T3SS translocon in DA, and for T1P in biofilm formation, all of which may act in concert to facilitate host intestinal colonization by aEPEC strains. ©2013, American Society for Microbiology.

Propriedades magnéticas do modelo de Ising bidimensional em uma rede bipartida de spins 1/2 e 1: um estudo de ferrimagnetismo com vacâncias

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Avaliação in vitro da translucidez de dois sistemas cerâmicos metal-free: In-Ceram x Empress 2

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Catalisadores 'PT' e 'PTSN' modificados com 'SN''O IND.2' para a oxidação eletroquímica de etanol

Pós-graduação em Química - IQ

'ZN IND.7'SB IND. 2'O IND. 12' contendo Ce(III), Pr(III) ou Eu(III): investigação de suas propriedades estruturais e ópticas para potencial aplicação como cintilador

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Cinética de sinterização do combustível nuclear 'UO IND. 2.'7%'Gd IND.2''O IND. 3': cálculo da curva mestre de sinterização

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Caracterização elétrica e microestrutural de cerâmicas varistoras de baixa tensão à base de ('SN IND.1-x''TI IND.x')'O IND.2' e 'SN''O IND.2' dopados com 'CO''O' e 'NB IND.2''O IND.5'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da segregação de dopantes no contorno de grão e sua influência nas propriedades elétricas de cerâmicas à base de 'SN''O IND.2'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da ação antinociceptiva e antiinflamátoria do 1-Nitro-2-Feniletano, principal constituinte da Aniba Canelilla

A Aniba canelilla (H.B.K) Mez, conhecida popularmente como casca-preciosa é uma espécie da família Lauraceae que apresenta ampla distribuição na região amazônica. O chá das folhas e das cascas são utilizados na medicina popular como digestivo, carminativo e antiinflamatório. Neste estudo decidiu-se avaliar se esta atividade é devida a um de seus principais constituintes, o 1-nitro-2-feniletano. A amostra obtida por purificação do óleo essencial de Aniba canelilla possui 97,5% de 1-nitro-2-feniletano foi fornecida pelo Laboratório de Engenharia Química da UFPA. Nos modelos de nocicepção foram realizados os testes da contorção abdominal, placa quente e formalina. Enquanto que nos modelos de inflamação foram realizados a dermatite induzido pelo óleo de croton, edema de pata induzido por dextrana e carragenina e peritonite induzido pela carragenina. No teste de contorção abdominal induzido por ácido acético, o 1-nitro-2-feniletano nas doses de 15, 25 e 50 mg/kg reduziu de maneira significativa o número de contorções abdominais. No teste de placa quente (55 0,5 C), o 1-nitro-2-feniletano nas doses de 50, 100 e 200 mg/kg não induziu alterações no tempo de latência quando comparado ao grupo controle. No teste de formalina, o 1-nitro-2-feniletano nas doses de 25 e 50 mg/kg reduziu de maneira significativa o estímulo álgico na 2 fase do teste. Além disso, a antinocicepção foi revertida pela naloxona na segunda fase. Na dermatite induzida pelo óleo de croton, o 1-nitro-2-feniletano nas doses de 25 e 50 mg/kg reduziu de maneira significativa o eritema em relação ao grupo controle (inibição de 73% e 79%, respectivamente). Nos edemas de pata induzido por carragenina e dextrana, o 1-nitro-2-feniletano foi capaz de impedir o desenvolvimento do edema, nas doses de 25 e 50 mg/kg, em comparação com o grupo controle. Na peritonite induzida por carragenina, o 1-nitro-2-feniletano na dose de 25 mg/kg reduziu o número de células globais e o número de neutrófilos quando comparado ao grupo controle (inibição de 22,55% e 38,13%, respectivamente). Nossos resultados sugerem que o 1-nitro-2-feniletano tem atividade antinociceptiva e antiinflamatória, provavelmente, de origem periférica, além disso, os resultados sugerem que os receptores opióides estão envolvidos no efeito antinociceptivo do 1-nitro-2-feniletano.

X1X1X2X2/X1X2Y sex chromosome systems in the Neotropical Gymnotiformes electric fish of the genus Brachyhypopomus

Several types of sex chromosome systems have been recorded among Gymnotiformes, including male and female heterogamety, simple and multiple sex chromosomes, and different mechanisms of origin and evolution. The ₁X₁X₂X₂/X₁X₂Y systems identified in three species of this order are considered homoplasic for the group. In the genus Brachyhypopomus, only B. gauderio presented this type of system. Herein we describe the karyotypes of Brachyhypopomus pinnicaudatus and B. n. sp. FLAV, which have an X₁X₁X₂X₂/X₁X₂Y sex chromosome system that evolved via fusion between an autosome and the Y chromosome. The morphology of the chromosomes and the meiotic pairing suggest that the sex chromosomes of B. gauderio and B. pinnicaudatus have a common origin, whereas in B. n. sp. FLAV the sex chromosome system evolved independently. However, we cannot discard the possibility of common origin followed by distinct processes of differentiation. The identification of two new karyotypes with an X₁X₁X₂X₂/X₁X₂Y sex chromosome system in Gymnotiformes makes it the most common among the karyotyped species of the group. Comparisons of these karyotypes and the evolutionary history of the taxa indicate independent origins for their sex chromosomes systems. The recurrent emergence of the X₁X₁X₂X₂/X₁X₂Y system may represent sex chromosomes turnover events in Gymnotiformes.