Fluoride glasses : synthesis and properties

The discovery of heavy metal fluoride glasses has opened new prospects for fiber optics operating beyond 2 µm with expected losses less than 10(-2) dB/Km. The main interest of fluoride glasses lies in their infrared transmission up to 8 µm in the bulk form and 4.5 µm for optical fibers. We have reported here the preparation, the glass forming systems and properties of heavy metal fluoride glasses

Optical transition probabilites and compositional dependence of Judd-Ofelt parameters of Er3+ ions in fluoroindate glass

Fluoroindate glasses containing 1, 2, 3, and 4 mol% ErF3 were prepared in a dry box under an argon atmosphere. Absorption spectra of these glasses at room temperature were obtained. The Judd-Ofelt parameters Omegalambda (lambda = 2, 4, 6) for f-f transitions of Er3+ ions as well as transition probabilities, branching ratios, radiative lifetimes, and peak cross-sections for stimulated emission of each band were determined. The concentration effect on the intensities is analyzed. The optical properties of the fluoroindate glasses doped with Er3+ ions are compared with those of other glasses described in the literature

Peak separation by derivative spectroscopy applied to ftir analysis of hydrolized silica

Reliable spectral analysis is only achieved if the spectrum is thoroughly investigated in regard to all hidden and overlapped peaks. This paper describes the steps undertaken to find and separate such peaks in the range of 3000 to 4000 cm(-1) in the case of three different infrared absorption spectra of the glass surface of hydrolyzed silica optical fibers. Peak finding was done by the analysis of the second and fourth derivatives of the digital data, coupled with the available knowledge of infrared spectroscopy of silica-water interaction in the investigated range. Peak separation was accomplished by curve fitting with four different models. The model with the best fit was described by a sum of pure Gaussian peaks. Shoulder limit and detection limit maps were used to validate the revealed spectral features

Blue and green upconversion in Er(3+)-doped fluoroindate glasses

The upconversion properties of Er3+ in fluoroindate bulk glasses (composition: 40InF3-20ZnF2-16BaF2-(20-x)SrF2-2GaF3-2NaF-xErF3 with x=1,2,3 and 4 mole %) are investigated, following F-4(9/2) excitation with a red krypton laser. A strong green and a weaker blue luminescence is observed at room temperature corresponding to emissions from the thermally coupled S-4(3/2) and H-2(11/2) bands and the H-2(9/2) level respectively. Resonant energy transfer processes involving two excited erbium ions and a two-step absorption process are proposed to explain the upconversion phenomena. The emission intensities depend on the excitation power as P(exc)n with 1.5 less-than-or-equal-to n less-than-or-equal-to 1.7 for the green and 1.6 less-than-or-equal-to n less-than-or-equal-to 1.9 for the blue emission. The decay times and the relative intensities of the luminescences are also studied as a function of Er3+ concentration

O secretariado e a modernização da administração pública: a implementação de serviços eficientes

O presente artigo pretende evidenciar a necessária mudança de paradigma no que se refere à capacidade de um profissional qualificado em secretariado, no mundo contemporâneo, bem como à necessária abrangência dos seus conhecimentos e das suas competências. Pretende-se ainda apresentar um projeto de implementação do Balcão Único de Atendimento (BUA) na Câmara Municipal de Moimenta da Beira, no sentido de adequar os seus serviços ao atual paradigma competitivo, que exige da Administração Pública uma postura moderna e dinamizadora que incremente a melhoria constante dos seus serviços, de forma a responder às exigências de eficiência, eficácia, transparência e qualidade dos seus clientes

Optical transition probabilites and compositional dependence of Judd-Ofelt parameters of Er3+ ions in fluoroindate glass

Fluoroindate glasses containing 1, 2, 3, and 4 mol% ErF3 were prepared in a dry box under an argon atmosphere. Absorption spectra of these glasses at room temperature were obtained. The Judd-Ofelt parameters Omegalambda (lambda = 2, 4, 6) for f-f transitions of Er3+ ions as well as transition probabilities, branching ratios, radiative lifetimes, and peak cross-sections for stimulated emission of each band were determined. The concentration effect on the intensities is analyzed. The optical properties of the fluoroindate glasses doped with Er3+ ions are compared with those of other glasses described in the literature

Synthesis and Structural Studies of Er3+ Containing Lead Cadmium Fluoroborate Glasses and Glass-Ceramics

A partir de resultados de experimentos de fusão e choque térmico, o domínio vítreo foi identificado no sistema PbF2-CdF2-B2O 3. Vidros puros e dopados com Er3+ foram preparados e vitrocerâmicas foram obtidas a partir de tratamentos térmicos adequados. A fase cristalina foi identificada como beta-PbF2. Estudos estruturais foram efetuados por difração e absorção de raios X e o papel desempenhado pelos átomos de Pb2+ e Cd2+ na estrutura vítrea foi estabelecido a partir destas técnicas. Os resultados sugerem que, com a cristalização, os íons Er3+ são segregados na fase cristalina.The vitreous domain was established in the PbF2-CdF2-B2O 3 system from melting and quenching experiments. Er3+ containing glasses were prepared and glass ceramics were obtained by selected heat-treatments. Lead fluoride was identified (beta-PbF2) as the crystalline phase. Structural studies were performed in some glassy and partially crystallized samples by means of X-ray Diffraction (XRD) and Extended X-ray Absorption Fine Structure (EXAFS) measurements. The role of Cd2+ and Pb2+ atoms on the glass network formation and also on the crystallization behavior was put forward by these techniques. After crystallization Er3+ atoms segregated in the crystal phase

O ensino superior nos territórios ocupados da Palestina.

O presente artigo é um documento com características essencialmente de informação sobre uma região singular do mundo - a Palestina. Mais especificamente, os Territórios Ocupados por Israel (excluindo os Montes Golan, uma parcela do território nacional sírio), frequentemente apresentados de forma parcial e, portanto, inquinada