Photoinduced effects in As-S-P glasses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structural studies of AgPO3-MoO3 glasses using solid state NMR and vibrational spectroscopies

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

Voltammetric Determination of Phosphate in Brazilian Biodiesel Using Two Different Electrodes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Multicolor up conversion emission and color tunability in Yb3+/Tm3+/Ho3+ triply doped heavy metal oxide glasses

Multicolor and white light emissions have been achieved in Yb3+, Tm3+ and Ho3+ triply doped heavy metal oxide glasses upon laser excitation at 980 nm. The red (660 nm), green (547 nm) and blue (478 nm) up conversion emissions of the rare earth (RE) ions triply doped TeO2-GeO2-Bi2O3-K2O glass (TGBK) have been investigated as a function of the RE concentration and excitation power of the 980 nm laser diode. The most appropriate combination of RE in the TGBK glass host (1.6 wt% Yb2O3, 0.6 wt% Tm2O3 and 0.1 wt% Ho2O3) has been determined with the purpose to tune the primary colors (RGB) respective emissions and generate white light emission by varying the pump power. The involved infrared to visible up conversion mechanisms mainly consist in a three-photon blue up conversion of Tm3+ ions and a two-photon green and red up conversions of Ho3+ ions. The resulting multicolor emissions have been described according to the CIE-1931 standards. (C) 2011 Elsevier B.V. All rights reserved.

Production of defects in ZBLAN, ZBLAN : Tm3+ and ZBLAN : Cr3+ glasses by ultra-short pulses laser interaction

In this work we have studied pure and thulium- and chromium-doped ZBLAN glasses irradiated by ultra-short laser pulses. A Ti:sapphire CPA system was used, producing a 500 Hz train of pulses, centered at 830 nm, with 375 mu J of energy and 50 fs of duration (FWHM). The beam was focused by a 20 Him lens, producing a converging beam with a waist of 12 pin. The absorption spectra before and after laser irradiation were obtained showing production of color centers in pure, thulium-doped and chromium-doped ZBLAN glasses. A damage threshold of 9.56 TW/cm(2) was determined for ZBLAN. (C) 2007 Elsevier Ltd. All rights reserved.

Crystallization of monoclinic WO3 in tungstate fluorophosphate glasses

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

1.5 mu m and visible up-conversion emissions in Er3+/Yb3+ co-doped tellurite glasses and optical fibers for photonic applications

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Local order around rare earth ions during the devitrification of oxyfluoride glasses

Erbium L-3-edge extended x-ray absorption fine structure (EXAFS) measurements were performed on rare earth doped fluorosilicate and fluoroborate glasses and glass ceramics. The well known nucleating effects of erbium ions for the crystallization of cubic lead fluoride (based on x-ray diffraction measurements) and the fact that the rare earth ions are present in the crystalline phase (as indicated by Er3+ emission spectra) seem in contradiction with the present EXAFS analysis, which indicates a lack of medium range structural ordering around the Er3+ ions and suggests that the lead fluoride crystallization does not occur in the nearest neighbor distance of the rare earth ion. Molecular dynamics simulations of the devitrification process of a lead fluoride glass doped with Er3+ ions were performed, and results indicate that Er3+ ions lower the devitrification temperature of PbF2, in good agreement with the experimental results. The genuine role of Er3+ ions in the devitrification process of PbF2 has been investigated. Although Er3+ ions could indeed act as seeds for crystallization, as experiments suggest, molecular dynamics simulation results corroborate the experimental EXAFS observation that the devitrification does not occur at its nearest neighbor distance. (c) 2008 American Institute of Physics.

Occurrence of symbiotic fungi and rhizospheric phosphate solubilization in weeds

Estudos sobre a ecologia de organismos envolvidos no processo de produção são necessários para o desenvolvimento de uma agricultura sustentável, e hoje, a sustentabilidade está intimamente ligada à rentabilidade de produção. Objetivou-se com este trabalho verificar a ocorrência de fungos micorrízicos arbusculares em plantas daninhas de lavouras brasileiras e avaliar o potencial de solubilização de fosfato inorgânico da microbiota associada. 36 espécies de plantas daninhas foram avaliadas quanto à ocorrência de micorrizas, e 11 foram selecionadas para avaliação do potencial de solubilização total e relativa de fosfato. Todas as espécies apresentaram colonização por micorrizas, inclusive um exemplar da família Brassicaceae, geralmente enquadrada como não micorrizada. Na maioria das espécies, os tipos morfológicos de arbúsculos e enovelados de hifas foram observados, sendo os enovelados mais comuns entre as gramíneas. Fungos endofíticos do tipo dark septate foram visualizados na maioria das plantas. As plantas daninhas apresentaram distintos potenciais de solubilização de P na rizosfera. Amaranthus retroflexus, Bidens pilosa e Leonotis nepetaefolia apresentaram elevados valores de solubilização relativa de fosfato. Este é o primeiro relato de micorrizas e da atividade de solubilização de fosfato em plantas daninhas no Brasil.

Stabilization of fluoroindate glasses by magnesium fluoride and other heavy metal fluorides

Their extended transparency in the IR makes them attractive for use as optical fibers for CO laser power delivery and optical amplification. This paper firstly describes the spectacular stabilizing effect of MgF2 on the binary system InF3-BaF2. The investigation of the InF3-BaF2-MgF2 system led to samples up to 5mm in thickness. Further optimization of this system was achieved by incorporation of limited amounts of other fluorides and resulted in increased resistence to devitrification. The second approach of this work was concerned to the investigation of the pseudo-ternary system InF3-GdF3-GaF3 at constant concentrations of ZnF2-SrF2-BaF2-NaF. Several compositions were studied in this system. The samples presented a better thermal stability when compared to other families of fluoride glasses. Therefore, these glasses seem to be very promising for the fabrication of special optical fibers. Thermal data are reported.

New compositions of fluoroindate glasses with higher chemical resistance

In this paper, glasses in the systems In-Ba-Mg and In-Ba-Zn-Sr-Mg were water leachead at 80ºC showing surface degradation after 72 hours of leaching. The extent of such degradation is determined by the solubility and the concentration of the elemental fluorides that constitute the glasses. The formation of a layer of crystallized phases on the surface of the samples was observed. Small weight losses were registered and the absence of water on the glass matrix after the attack suggested that the use of MgF2 in the systems studied can lead to better results against moisture corrosion when compared to other fluoride glasses such as the fluorozirconates.

Effects of nitrate and phosphate availabilities on growth, photosynthesis and pigment and protein contents in colour strains of Hypnea musciformis (Wulfen in Jacqu.) J.V. Lamour. (Gigartinales, Rhodophyta)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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

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

Millet seeds mixed with phosphate fertilizers

O tamanho reduzido das sementes de milheto dificulta sua semeadura uniforme, principalmente para os produtores que não possuem semeadoras apropriadas. Assim, a mistura das sementes com os fertilizantes fosfatados vem sendo utilizada para facilitar a semeadura. Entretanto, o período de contato pode provocar prejuízos na germinação e no vigor. Avaliou-se a qualidade fisiológica das sementes de milheto submetidas a diferentes períodos de contato (0, 6, 12, 24, 48, 72, 96 e 120h) com os fertilizantes superfosfato simples (SFS) e superfosfato triplo (SFT), em um experimento em delineamento inteiramente casualizado em esquema fatorial 8x2 (n=4). Os atributos químicos e físicos dos fertilizantes foram previamente determinados. Foi utilizada a proporção de 1 kg de sementes para 2,5 kg de fertilizante. Após manutenção da mistura em saco plástico no laboratório, as sementes foram separadas dos fertilizantes e submetidas à determinação de umidade, germinação, primeira contagem e condutividade elétrica. Paralelamente, na casa de vegetação, em caixas plásticas contendo terra, determinou-se a emergência e o índice de velocidade de emergência, sem e com a manutenção dos fertilizantes. Porque apresentam resíduos ácidos, tanto SFS como SFT afetaram de maneira semelhante e negativamente a germinação e o vigor das sementes de milheto em mistura, na medida em que se aumentou o período de contato.

Sintering of tin oxide and its applications in electronics and processing of high purity optical glasses

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