Local electronic structure, optical bandgap and photoluminescence (PL) properties of Ba(Zr0.75Ti0.25)O3 powders

Ba(Zr0.75Ti0.25)O3 (BZT-75/25) powders were synthesized by the polymeric precursor method. Samples were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) techniques. Their electronic structures were evaluated by first-principle quantum mechanical calculations based on density functional theory at the B3LYP level. Their optical properties were investigated by ultraviolet-visible (UV-Vis) spectroscopy and photoluminescence (PL) measurements at room temperature. XRD patterns and Rietveld refinement data indicate that the samples have a cubic structure. XANES spectra confirm the presence of pyramidal [TiO5] clusters and octahedral [TiO6] clusters in the disordered BZT-75/25 powders. EXAFS spectra indicate distortion of Ti-O and Ti-O-Ti bonds the first and second coordination shells, respectively. UV-Vis absorption spectra confirm the presence of different optical bandgap values and the band structure indicates an indirect bandgap for this material. The density of states demonstrates that intermediate energy levels occur between the valence band (VB) and the conduction band (CB). These electronic levels are due to the predominance of 4d orbitals of Zr atoms in relation to 3d orbitals of Ti atoms in the CB, while the VB is dominated by 2p orbitals related to O atoms. There was good correlation between the experimental and theoretical optical bandgap values. When excited at 482 nm at room temperature, BZT-75/25 powder treated at 500 C for 2 h exhibited broad and intense PL emission with a maximum at 578 nm in the yellow region. © 2013 Elsevier Ltd. All rights reserved.

CaCu3Ti4O12 thin films with non-linear resistivity deposited by RF-sputtering

Calcium copper titanate, CaCu3Ti4O12, CCTO, thin films with polycrystalline nature have been deposited by RF sputtering on Pt/Ti/SiO2/Si (100) substrates at a room temperature followed by annealing at 600 °C for 2 h in a conventional furnace. The CCTO thin film present a cubic structure with lattice parameter a = 7.379 ±0.001 Å free of secondary phases. The observed electrical features of CCTO thin films are highly dependent on the [CaO12], [CaO 4], [CuO11], [CuO11Vx 0] and [TiO5.VO] clusters. The CCTO film capacitor showed a dielectric loss of 0.40 and a dielectric permittivity of 70 at 1 kHz. The J-V behavior is completely symmetrical, regardless of whether the conduction is limited by interfacial barriers or by bulk-like mechanisms. © 2013 Elsevier B.V. All rights reserved.

Study of exclusive two-photon production of W+W- in pp collisions at √s=7 TeV and constraints on anomalous quartic gauge couplings

A search for exclusive or quasi-exclusive W+W- production by photon-photon interactions, pp → p(*)W +W-p(*), at √s=7 TeV is reported using data collected by the CMS detector with an integrated luminosity of 5.05 fb-1. Events are selected by requiring a μ ±e∓ vertex with no additional associated charged tracks and dilepton transverse momentum p T(μ ±e∓) > 30 GeV. Two events passing all selection requirements are observed in the data, compared to a standard model expectation of 2.2 ± 0.4 signal events with 0.84 ± 0.15 background. The tail of the dilepton p T distribution is studied for deviations from the standard model. No events are observed with p T > 100 GeV. Model-independent upper limits are computed and compared to predictions involving anomalous quartic gauge couplings. The limits on the parameters α0,C W/λ2 with a dipole form factor and an energy cutoff Λcutoff = 500 GeV are of the order of 10-4. © 2013 CERN for the benefit of the CMS collaboration.

Caracterização estrutural e biofísica de duas proteínas relacionadas: β-1,3-1,4-glicanase de Bacillus subtilis 168 e α-L-arabinofuranosidase termoestável de Thermotoga petrophila RKU-1

Pós-graduação em Biofísica Molecular - IBILCE

Efeitos da terapia fotodinâmica sobre cepas de Candida isoladas de pacientes submetidos à antibioticoterapia prolongada

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Aplicação do eletrocapilaridade na manipulação de microgotas

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

Impacto do tratamento térmico com baixa umidade sobre as características físico-químicas e reológicas de amidos de mandioca, araruta e mandioquinha-salsa

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação clínico-laboratorial de cães com doença renal crônica sob tratamento com o antioxidante N-acetilcisteína

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização dos resíduos do processameto de mandioca para produção de bio-etanol e sua utilização na alimentação de aves

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Teoria quântica do campo escalar real com autoacoplamento quártico - simulações de Monte Carlo na rede com um algoritmo worm

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Crescimento da nanoapatita na liga Ti-30Ta, para aplicações odontológicas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Freqüência de isolamento de Campylobacter em gatos com e sem diarréia e sensibilidade a antimicrobianos das estirpes isoladas

Pós-graduação em Medicina Veterinária - FMVZ

Efeito do aumento da concentração de dióxido de carbono do ar sobre a murcha de ceratocystis em mudas clonais de eucalipto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)