Simultaneous determination of cadmium and lead in wine by electrothermal atomic absorption spectrometry

A method has been developed for the direct simultaneous determination of Cd and Pb in white and red wine by electrothermal atomic absorption spectrometry (ET-AAS) using a transversely heated graphite tube atomizer (THGA) with longitudinal Zeeman-effect background correction. The thermal behavior of both analytes during pyrolysis and atomization stages were investigated in 0.028 mol l(-1) HNO3 and in 1 + 1 v/v diluted wine using mixtures of Pd(NO3)(2) + Mg(NO3)(2) and NH4H2PO4 + Mg(NO3)(2) as chemical modifiers. With 5 mug Pd + 3 mug Mg as the modifiers and a two-step pyrolysis (10 s at 400 degreesC and 10 s at 600 degreesC), the formation of carbonaceous residues inside the atomizer was avoided. For 20 mul of sample (wine + 0.056 mol l(-1) HNO3, 1 + 1, v/v) dispensed into the graphite tube, analytical curves in the 0.10-1.0 mug l(-1) Cd and 5.0-50 mug l(-1) Pb ranges were established. The characteristic mass was approximately 0.6 pg for Cd and 33 pg for Pb, and the lifetime of the tube was approximately 400 firings. The limits of detection (LOD) based on integrated absorbance (0.03 mug l(-1) for Cd, 0.8 mug l(-1) for Pb) exceeded the requirements of Brazilian Food Regulations (decree #55871 from Health Department), which establish the maximum permissible level for Cd at 200 mug l(-1) and for Pb at 500 mug l(-1). The relative standard deviations (n = 12) were typically < 8% for Cd and < 6% for Pb. The recoveries of Cd and Pb added to wine samples varied from 88 to 107% and 93 to 103%, respectively. The accuracy of the direct determination of Cd and Ph was checked for 10 table wines by comparing the results with those obtained for digested wine using single-element ET-AAS, which were in agreement at the 95% confidence level. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Morphological analysis of pits formed on Al 2024-T3 in chloride aqueous solution

It has been used a new image analysis method, based on segmentation by shape parameters, for pits morphology examination from Al 2024 aluminum-copper alloy in chloride aqueous solution. Corrosion behavior of this alloys in naturally aerated 3.5% NaCl solution has been investigated through open circuit potential measurements. Afterwards, pits have been characterized by image analysis taking density and size measurements right from corroded surfaces. Morphological investigation has been conducted for profiles, cut orthogonally from mean surface planes, and observed through light microscopy. Image analysis data could demonstrate that pits are wider than deep, evoluting for conical, quasi-conical or irregular shapes. Most pits have presented a quasi-conical morphology, but the wider ones have evoluted to an irregular shape influenced by sub-surface microstructure. Image analysis based on shape segmentation could enhance the differences on morphological behavior. (C) 2004 Elsevier B.V. All rights reserved.

Determination of iodide and idoxuridine at a glutaraldehyde-cross-linked poly-L-lysine modified glassy carbon electrode

The detection limit (about 0.017 mu g mL(-1)) for voltammetric determination of iodide (peak at +0.87 V vs. Ag/AgCl at pH 2) at a glutaraldehyde-cross-linked poly-L-lysine modified glassy carbon electrode involving oxidation to iodine was found to be several orders of magnitude lower than that for the voltammetric determination on a bare glassy carbon electrode. This method was applied successfully to the determination of iodide in two medicinal formulations. Idoxuridine was determined indirectly at the same electrode by accumulating it first at -0.8 V vs. Ag/AgCl. At this potential the C-I bond in the adsorbed idoxuridine is reduced giving iodide, which is then determined at the modified electrode. The method was successfully applied to the determination of idoxuridine in a urine sample.

The asynchronous motor one-dimensional analysis

An application of the linear machine one-dimensional analysis method to the modeling of a conventional asynchronous induction motor, considered as a particular case of linear and sectorial machines, is described. A mathematical model for the calculation of the propulsive force developed by this motor, taking into account the transversal edge effect, is derived from the application of the one-dimensional theory and presented in this paper. As an application example, an induction motor is analyzed by means of the one-dimensional theory.

An image processing method for morphology characterization and pitting corrosion evaluation

A digital image processing and analysis method has been developed to classify shape and evaluate size and morphology parameters of corrosion pits. This method seems to be effective to analyze surfaces with low or high degree of pitting formation. Theoretical geometry data have been compared against experimental data obtained for titanium and aluminum alloys subjected to different corrosion tests. (C) 2002 Elsevier B.V. B.V. All rights reserved.

The dietary regime of detritivorous fish from the River Jacaré Pepira, Brazil

The diet of detritivorous fish was analysed at four distinct habitats in a tropical river during the wet and dry seasons. Two methodologies were used to determine the diet of the fish: (1) the direct analysis of the stomach contents; and (2) the use of stable carbon isotopes. Both methods indicated food partitioning among the fish. The stomach contents showed what the fish had ingested when captured and the 13C isotope indicated what it had assimilated over a long period of time. The 13C isotope suggested the existence of sectional differences in the feeding of the detritivorous fish along the river. Plants employing the C4 photosynthesis pathways seem to have little influence on the diet of these fish. This method proved to be more appropriate for the detection of the main food sources of the captured fish.

Thermoeconomic analysis of a cogeneration system of a university campus

In this paper, a thermoeconomic analysis method based on the First and the Second Law of Thermodynamics and applied to analyse the replacement of an equipment of a cogeneration system is presented. The cogeneration system consists of a gas turbine linked to a waste boiler. The electrical demand of the campus is approximately 9 MW but the cogen system generates approximately one third of the university requirement as well as 1.764 kg/s of saturated steam (at 0.861 MPa), approximately, from a single fuel source. The energy-economic study showed that the best system, based on pay-back period and based on the maximum savings (in 10 years), was the system that used the gas turbine M1T-06 of Kawasaki Heavy Industries and the system that used the gas turbine CCS7 of Hitachi Zosen, respectively. The exergy-economic study showed that the best system, which has the lowest EMC, was the system that used the gas turbine ASE50 of Allied Signal. © 2002 Elsevier Science Ltd. All rights reserved.

Antibiofilm activity, pH and solubility of endodontic sealers

Aim: To evaluate antibiofilm activity against Enterococcus faecalis, pH and solubility of AH Plus, Sealer 26, Epiphany SE, Sealapex, Activ GP, MTA Fillapex (MTA-F) and an experimental MTA-based Sealer (MTA-S). Methodology: Sealer samples were manipulated and stored for 2 or 7 days. Prepared sealers were evaluated by a modified direct contact test (DCT) for 5 h, 10 h or 15 h with biofilm previously induced on bovine dentine for 14 days. In the control group, the biofilm was not exposed to the sealers. The number of colony-forming units (CFU mL-1) in the remaining biofilm was determined. Sealer solubility was assessed by the percentage of mass loss after 15 h of immersion in distilled water. Sealer pH was measured at 5 h, 10 h and 15 h. Statistical analysis was performed using Kruskal-Wallis and Dunn or anova and Tamhane's T2 tests, at 5% significance. Results: At 2 days post-manipulation, the DCT showed that Sealapex and MTA-F were associated with a reduction in the number of bacteria in all 3 contact periods evaluated, compared with the control group (P < 0.05). At 7 days, Sealapex had the greatest antibiofilm action at 10 h and 15 h. Sealapex had the highest pH values 2 and 7 days post-manipulation. Regarding the solubility, at 2 days the highest values were observed for MTA-F, MTA-S, Sealapex and Activ GP (P < 0.05). At 7 days, MTA-S and MTA-F had greater solubility than the other materials (P < 0.05). AH Plus had the lowest solubility for both post-manipulation periods (P < 0.05). Conclusion: Sealapex and MTA-F were associated with a reduction in the number of bacteria in biofilms and had greater solubility. The high solubility and pH may be related to the antibacterial activity of these materials. © 2012 International Endodontic Journal.

Modelagem do escoamento transiente ao longo de trocadores de calor tubo capilar-linha de sucção

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efetividade de corte das pontas do sistema CVDentUS: estudo in vitro

Pós-graduação em Odontologia - FOAR

Utilização de bulked segregant analysis na identificação de marcadores ligados a genes que controlam a resistência à ferrugem (Puccinia psidii Winter) em Eucalyptus sp

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Detecção eletroquímica de furfural e hidroximetilfurfural em bagaço de cana-de-açúcar utilizando cromatografia líquida de alta eficiência

Pós-graduação em Química - IQ

Diferenciação entre os estágios agudo e crônico na infecção toxoplásmica pelo método de aglutinação direta modificado e pesquisa do agente no leite de ovelhas naturalmente infectadas por Toxoplasma gondii

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

Detecção e classificação de distúrbios de tensão usando redes neurais ARTMAP Euclidiana modificada com treinamento continuado

Pós-graduação em Engenharia Elétrica - FEIS

Desenvolvimento e seleção de sensores para avaliação de refrigerantes em língua eletrônica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)