Upconversion ultraviolet random lasing in Nd 3+ doped fluoroindate glass powder

An upconversion random laser (RL) operating in the ultraviolet is reported for Nd 3+ doped fluoroindate glass powder pumped at 575 nm. The RL is obtained by the resonant excitation of the Nd 3+ state 2G 7/2 followed by energy transfer among two excited ions such that one ion in the pair decays to a lower energy state and the other is promoted to state 4D 7/2 from where it decays emitting light at 381 nm. The RL threshold of 30 kW/cm 2 was determined by monitoring the photoluminescence intensity as a function of the pump laser intensity. The RL pulses have time duration of 29 ns that is 50 times smaller than the decay time of the upconversion signal when the sample is pumped with intensities below the RL laser threshold. © 2011 Optical Society of America.

Nilpotent orbits and codimension-2 defects of 6d N = (2, 0)theories

We study the local properties of a class of codimension-2 defects of the 6d N = (2, 0) theories of type J = A, D, E labeled by nilpotent orbits of a Lie algebra $g, where g is determined by J and the outer-automorphism twist around the defect. This class is a natural generalization of the defects of the six-dimensional (6d) theory of type SU(N) labeled by a Young diagram with N boxes. For any of these defects, we determine its contribution to the dimension of the Higgs branch, to the Coulomb branch operators and their scaling dimensions, to the four-dimensional (4d) central charges a and c and to the flavor central charge k. © 2013 World Scientific Publishing Company.

Note on linearized new massive gravity in arbitrary dimensions

By means of a triple master action we deduce here a linearized version of the new massive gravity (NMG) in arbitrary dimensions. The theory contains a 4th-order and a 2nd-order term in derivatives. The 4th-order term is invariant under a generalized Weyl symmetry. The action is formulated in terms of a traceless ημνΩμνρ=0 mixed symmetry tensor Ωμνρ=-Ωμρν and corresponds to the massive Fierz-Pauli action with the replacement e μν=∂ρΩμνρ. The linearized 3D and 4D NMG theories are recovered via the invertible maps Ωμνρ=Ïμνρβhβμ and Ωμνρ=ÏμνργδT [γδ]μ respectively. The properties h μν=hνμ and T[[γδ]μ]= 0 follow from the traceless restriction. The equations of motion of the linearized NMG theory can be written as zero curvature conditions ∂νTρμ-∂ρT νμ=0 in arbitrary dimensions. © 2013 American Physical Society.

A combined theoretical and experimental study of electronic structure and optical properties of β-ZnMoO4 microcrystals

In this paper, a combined theoretical and experimental study on the electronic structure and photoluminescence (PL) properties of beta zinc molybdate (β-ZnMoO4) microcrystals synthesized by the hydrothermal method has been employed. These crystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, Fourier transform Raman (FT-Raman) and Fourier transform infrared (FT-IR) spectroscopies. Their optical properties were investigated by ultraviolet-visible (UV-Vis) absorption spectroscopy and PL measurements. First-principles quantum mechanical calculations based on the density functional theory at the B3LYP level have been carried out. XRD patterns, Rietveld refinement, FT-Raman and FT-IR spectra showed that these crystals have a wolframite-type monoclinic structure. The Raman and IR frequencies experimental results are in reasonable agreement with theoretically calculated results. UV-Vis absorption measurements shows an optical band gap value of 3.17 eV, while the calculated band structure has a value of 3.22 eV. The density of states indicate that the main orbitals involved in the electronic structure of β-ZnMoO4 crystals are (O 2p-valence band and Mo 4d-conduction band). Finally, PL properties of β-ZnMoO4 crystals are explained by means of distortions effects in octahedral [ZnO6] and [MoO6] clusters and inhomogeneous electronic distribution into the lattice with the electron density map. © 2013 Elsevier Ltd. All rights reserved.

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.

Fotoperíodo na reprodução de Betta splendens

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo experimental de sistemas de drenagem externa do líquido cefalorraquidiano

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Embriogênese somática e transformação genética de soja via biobalística

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Potencial de linhagens experimentais de milho (Zea mays L.) para produção de híbridos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação de superelasticidade e deformação das molas fechadas de níquel-titânio sob diferentes ativações

Pós-graduação em Ciências Odontológicas - FOAR

Ciclo de muda e metabolismo durante o desenvolvimento larval do camarão-da-amazônia Macrobrachium amazonicum (Heller, 1862)

Pós-graduação em Aquicultura - FCAV

Estresse oxidativo e lipoperoxidação devido à anemia induzida por perda aguda de sangue em ovinos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Monitoramento do processo de densificação de compósitos termoestruturais de carbono reforçado com fibras de carbono por tomografia computadorizada e resistividade elétrica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Detecção e identificação de Diaporthe phaseolorum var. meridionalis em sementes de soja por PCR

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

Harmonic superspace from the Ad'S IND. 5' × 'S POT. 5' pure spinor formalism

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