Paramagnetic Centers
Mostrando 1-12 de 51 artigos, teses e dissertações.
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1. Dating stalagmite from Caverna do Diabo (Devil´S Cave) by TL and EPR techniques
ABSTRACT A cylindrical fragment of stalagmite from Caverna do Diabo, State of São Paulo, Brazil, has been studied and dated by thermoluminescence and electron paramagnetic resonance techniques. The thermoluminescence glow curves of stalagmite samples and subsequently gamma irradiated, have shown rise of three peaks at 135, 180 and 265 °C. From electron par
An. Acad. Bras. Ciênc.. Publicado em: 2016-12
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2. Estudos das propriedades estruturais e ópticas de vidros teluritos / Studies of the structural and optical properties of the tellurite glasses
Vidros teluritos são considerados fortes candidatos para aplicações em lasers e óptica não linear devido a importantes características, como o elevado índice de refração, baixa energia de fônons, baixa temperatura de transição vítrea e sua fácil preparação. Neste trabalho foram produzidas amostras dos sistemas vítreos TeO2- ZnO-Na2O, TeO2-Nb
Publicado em: 2011
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3. Pequenos polarons ligados e centros de cor em topázio
In the present work we studied the color beneficiation processes of colorless topaz, an abundant gemstone in Brazil. Blue topaz is the most internationally traded gemstone in the gem and market, reaching about 100 million carats per year. Almost 100% of blue topaz received some treatment to improve the color that, generally, involves some type of irradiation
Publicado em: 2010
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4. Investigation of structural, electronic and magnetica properties of Ca2-xLaxFelrO6, Sr2-xLaxFelrO6 e TbMnO3 oxides / Investigação as propriedades estruturais, eletronicas e magneticas dos oxidos Ca2-xLaxFelrO6, Sr2-xLaxFelrO6 e TbMnO3
For many decades the transition metal oxides are subject of great scientific interest because of the wide variety of interesting physical properties and their potential technological applications. More recently, for example, oxides of transition metals with multiferroic properties have been considered as potential magneto-electronic devices. Many transition
Publicado em: 2010
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5. Luminescence and paramagnetic centers in antigorite and Lizardite, two menbers of serpentine group: a comparative study / Estudo comparativo entre as propriedades dos centros luminescentes e paramagnéticos da antigorita e da lizardita do grupo da SERPENTINA: `Mg IND.3´[Si IND.2´`O IND.5´]`(OH) IND.4´
In this work, we are describing crystals luminescent properties of Antigorite (monoclinic, Mg3-x[Si2O5](OH)4-2x) and Lizardite (triclinic, Mg3[(Si,Fe)2O5](OH)4). They were studied simultaneously applying several techniques, like: Thermoluminescence (TL), Optical Absorption (OA), Electron Paramagnetic Resonance (EPR), X-rays diffraction and Inductively Couple
Publicado em: 2008
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6. Caracterização de Ametistas Naturais
This research intends to investigate the formation of color in samples of natural amethyst from different origins after submitting them to gamma irradiation, as well to develop an identification method of uncolored crystals with potential for development of color. The techniques of infrared spectroscopy, ultraviolet-visible spectroscopy and atomic emission s
Publicado em: 2008
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7. Thermoluminescence, electron paramagnetic resonance and color centers properties of diopside / Propriedades de termoluminescência, de ressonância paramagnética eletrônica e de centros de cor de diopsídio
Diopside of chemical formula, CaMgSi2O6, a natural silicate mineral has been investigated concerning its Thermoluminescence (TL), Electron Paramagnetic Resonance (EPR) and Reflectance properties. Synthetic, pure or doped diopside, produced in the laboratory, has been investigated. Samples annealed at 600 `GRAUS´ C for one hour, to eliminate previously induc
Publicado em: 2007
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8. Glycymeris Longior shells, an alternative gamma radiation reference detector
Gamma irradiation of biogenic calcium carbonate, from fossil shells of species Glycymeris Longior, results in the formation of CO2 - centers, as measured by electron paramagnetic resonance spectroscopy. The spectral line intensity increases linearly with increasing dose, without distortion, up to 50Gy. Fitting of the data yields the equation, Dose[Gy]=-0.8(0
Brazilian Journal of Physics. Publicado em: 2006-03
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9. Centros de cor, centros paramagnéticos e centros de luminescência dependentes de defeitos pontuais em zirconita / Color center, paramagnetic center and luminescence center due the defect point in zircon
In the present work the investigation of some properties of Thermoluminescence (TL), Electronic Paramagnetic Resonance (EPR) and Optical Absorption (OA) of two samples of zircon (of brown color) from Minas Gerais, but the unknown exact origin, were carried out. The glow curves of thermoluminescence emission have shown the presence of 4 TL peaks at 140, 215,
Publicado em: 2005
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10. Chelates complexes of oxovanadium (IV): potentials insulin mimetics. / Quelato complexos de oxovanádio (IV): potenciais mimetizadores de insulina.
Based on studies of another studies that explored the capacity of oxovanadium(IV) ion to mimic insulin, we had the idea to contribute with this line of research. For this, our choice of ligands was trans - 1,2 diamineciclohexane - N,N,N`,N` - tetraacétic (CDTA) and ethilenediaminetetraacétic (EDTA) acids, to synthesize the [VO(CDTA)], Na2[VO(EDTA)] and [(V
Publicado em: 2004
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11. Defect centers in a-SiNx: electronic and structural properties
By combining ab initio methods and interatomic potentials, we investigated the electronic and the structural properties of amorphous silicon nitride. Our results show the trends on the electronic band structure of SiNx (0.5 < x < 1.8) as the nitrogen content changes, and are in good agreement with the experimental data.Hydrogenation of the systems was found
Brazilian Journal of Physics. Publicado em: 2002-06
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12. Caracterização de impurezas estruturais e de centros de defeitos relacionados ao A1 e OH quartzo natural
Characterization of lattice impurities and study of AI and H defects centers have conducted on natural quartz through a variety of experiments. For this purpose, about thirty samples of natural quartz were assembled from fourteen mines with known localities in Brazil. "The concentrations of Al, Fe , Li, Na e K have evaluated by atomic absorption spectroscopy
Publicado em: 1992