883 resultados para Preparation and characterisation of xanthates
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Solid-state compounds Ln-4Cl-BP, where Ln represents lighter trivalent lanthanides and 4Cl-BP is 4-chlorobenzylidenepyruvate, were prepared. Thermogravimetry, derivative thermogravimetry (TG and DTG), differential scanning calorimetry (DSC) and other methods of analysis were used to characterize and to study the thermal behaviour of these compounds.
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Some new compounds of cinnamic acid with lighter trivalent lanthanides were prepared in the solid state. The compounds have general formula ML3·H2O, where L is cinnamate (C6H5-CH=CH-COO-) and M is La, Ce, Pr, Nd or Sm. Thermogravimetry, derivative thermogravimetry, differential scanning calorimetry, infrared absorption spectra and X-ray diffraction powder patterns were used to characterize and to study the thermal stability and thermal decomposition of these compounds.
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Several years of total ozone measured from space by the ERS-2 GOME, the Earth Probe TOMS, and the ADEOS TOMS, are compared with high-quality ground-based observations associated with the Network for the Detection of Stratospheric Change (NDSC), over an extended latitude range and a variety of geophysical conditions. The comparisons with each spaceborne sensor are combined altogether for investigating their respective solar zenith angle (SZA) dependence, dispersion, and difference of sensitivity. The space- and ground-based data are found to agree within a few percent on average. However, the analysis highlights for both GOME and TOMS several sources of discrepancies: (i) a SZA dependence with TOMS beyond 80° SZA; (ii) a seasonal SZA dependence with GOME beyond 70° SZA; (iii) a difference of sensitivity with GOME at high latitudes; (iv) a difference of sensitivity to low ozone values between satellite and SAOZ sensors around the southern tropics; (v) a north/south difference of TOMS with the ground-based observations; and (vi) internal inconsistencies in GOME total ozone. © 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.
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Trichilia catigua A. Juss. - Meliaceae has been traditionally used as a tonic and digestive medicine. Some Brazilian pharmaceutical firms use this species to produce phytopharmaceuticals and alcoholic beverages. The aim of this work is to determine its geographical distribution and characterise the environments where catuaba is found in the state of Paraná, in order to support the domestication strategy for the agricultural production of this species. Based on the literature, botanical collections and field observations it was established, that five species of the genus occurring in Paraná, which were identified as T casaretti, T catigua, T claussenii, T elegans, T pallida and another supposed to be T pattens. Trichilia catigua occurs within a wide but defined strip in the state. By evaluating data of climate; soil types; natural vegetation formations; mean, maximum and minimum temperatures; relative humidity; rainfall; altitudes and evapotranspiration the strip may be localised above latitude 25° in the central and Eastern regions of the state and above latitude 26° in South-western Parana. In general, T catigua was found to occur on fertile, organic-matter-rich soils and predominantly under forest canopies.
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OBJECTIVE: To evaluate the influence of cavity design and photocuring method on the marginal seal of resin composite restorations. METHOD AND MATERIALS: Seventy-two bovine teeth were divided into 2 groups: group 1 received box-type cavity preparations, and group 2 received plate-type preparations. Each group was divided into 3 subgroups. After etching and bonding, Z250 resin composite (3M Espe) was applied in 2 equal increments and cured with 1 of 3 techniques: (1) conventional curing for 30 seconds at 650 mW/cm2; (2) 2-step photocuring, in which the first step was performed 14 mm from the restoration for 10 seconds at 180 mW/cm2 and the second step was performed in direct contact for 20 seconds at 650 mW/cm2; or (3) progressive curing using Jetlite 4000 (J. Morita) for 8 seconds at 125 mW/cm2 and then 22 seconds at 125 mW/cm2 up to 500 mW/cm2. The specimens were thermocycled for 500 cycles and then submitted to dye penetration with a 50% silver nitrate solution. Microleakage was assessed using a stereomicroscope. Data were analyzed using analysis of variance and Tukey test (5% level of significance). RESULTS: A statistically significant difference was found between groups when a double interaction between photocuring and cavity preparation was considered (P = .029). CONCLUSIONS: No one type of cavity preparation or photocuring method prevented micro-leakage. The plate-type preparation showed the worst dye penetration when conventional and progressive photocuring methods were used. The best results were found using the 2-step photocuring with the plate-type preparation.
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Crystalline terbium-doped indium hydroxide structures were prepared by a rapid and efficient Microwave-Assisted Hydrothermal (MAH) method. Nanostructures were obtained at a low temperature. FE-SEM images confirm that these samples are composed of 3D nanostructures. XRD, optical diffuse reflectance and photoluminescence (PL) measurements were used to characterize the products. Emission spectra of terbium-doped indium hydroxide (In(OH)3:xTb 3+) samples under excitation (350.7 nm) presented broad band emission referent to the indium hydroxide matrix and 5D4 → 7F6, 5D4 → 7F 5, 5D4 → 7F4, and 5D4 → 7F3 terbium transitions at 495, 550, 590 and 627 nm, respectively. Relative intensities of the Tb 3+ emissions increased as the concentration of this ion increased from 0, 1, 2, 4 and 8 mol%, of Tb3+, but the luminescence is drastically quenched for the In(OH)3 matrix. © 2012 Elsevier B.V. All rights reserved.
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Incluye Bibliografía
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Contiene un análisis del cuestionario utilizado para efectuar el estudio sobre preparación, publicación e impresión de materiales educacionales para el Caribe, y algunas respuestas entregadas por los países de la región.
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Incluye Bibliografía
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O trabalho foi conduzido em área de expansão de cana-de-açúcar da Usina Vale do Paraná, no município de Suzanápolis - SP, na região do noroeste paulista. Foi utilizada a variedade de cana RB92-5345, espaçamento de 1,5 m entre linhas, em ARGISSOLO VERMELHO. O trabalho objetivou avaliar a produtividade em cana-planta e 1ª cana-soca e alguns atributos químicos de solo, em função dos métodos de preparo do solo e aplicação ou não de gesso. O delineamento experimental utilizado foi o de blocos ao acaso, com seis tratamentos, fatorial 3x2, e seis repetições. Os tratamentos principais foram preparos de solo com três equipamentos: arado de aivecas, escarificador e grade pesada, e dois tratamentos secundários com aplicação de 1 t ha-1 de gesso e sem gesso. Após cada colheita da cana, o solo foi caracterizado quanto aos indicadores de fertilidade nas camadas de 0,0-0,15; 0,15-0,30 e 0,30-0,45 m. As diferenças dos atributos químicos do solo, devido aos métodos de preparo ocorridas na cana-planta, não perduraram até a colheita da 1ª cana-soca e também não influenciaram na produtividade da cultura. A gessagem proporcionou maiores valores de ATR e produtividade de TCH, para cana-planta e 1ª cana-soca, respectivamente, confirmando a hipótese inicial.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)