La contra revolucion imaginaria: novela y film en Mexico (1910-1965)

COSTA, S. G. A. La contra Revolucion imaginaria: novela y film en Mexico (1910-1965). Revista Mediterranea de Comunicacion, n. 1, p.71-97, 2010. Disponivel em:. Acesso em: 04 nov. 2010.

Construção de um aparato experimental para monitoramento in situ da deposição de filmes finos de titânio por magnetron sputtering

The technique of surface coating using magnetron sputtering is one of the most widely used in the surface engineering, for its versatility in obtaining different films as well as in the micro / nanometric thickness control. Among the various process parameters, those related to the active species of the plasma are of the most fundamental importance in the mechanism and kinetics of deposition. In order to identify the active species of the plasma, parameters such as gas flow, pressure and density of electric power were varied during titanium coating on glass substrate. By flowing argon gas of 10, 20, 30, 40 and 50 sccm (cubic centimeters per minute) for each gas flow a sequential scan of the electric current of 0.10, 0.20, 0.30, 0.40 , 0.50 A. The maximum value of 0.50 A was chosen based both on literature data and on limitations of the equipment. The monitoring of plasma species present during the deposition was carried out in situ by the technique of optical emission spectroscopy (OES) through the spectrometer Ocean Optics USB2000 Series. For this purpose, an apparatus was developed to adapt the OES inside the plasma reactor to stay positioned closest to the target. The radiations emitted by the species were detected by an optical fiber placed behind the glass substrate and their intensities as a function of wavelength were, displayed on a monitor screen. The acquisition time for each condition of the plain parameters was related to the minima of spectral lines intensities due to the film formed on the substrate. The intensities of different emission lines of argon and titanium were then analyzed as a function of time, to determine the active species and estimate the thickness of the deposited films. After the deposition, the coated glasses thin films were characterized by optical transmittance through an infrared laser. It was found that the thickness and deposition rate determined by in situ analysis were consistent with the results obtained by laser transmittance

Estudo numérico de escoamento turbulento em padrão anular gás-líquido em dutos verticais

Multiphase flows in ducts can adopt several morphologies depending on the mass fluxes and the fluids properties. Annular flow is one of the most frequently encountered flow patterns in industrial applications. For gas liquid systems, it consists of a liquid film flowing adjacent to the wall and a gas core flowing in the center of the duct. This work presents a numerical study of this flow pattern in gas liquid systems in vertical ducts. For this, a solution algorithm was developed and implemented in FORTRAN 90 to numerically solve the governing transport equations. The mass and momentum conservation equations are solved simultaneously from the wall to the center of the duct, using the Finite Volumes Technique. Momentum conservation in the gas liquid interface is enforced using an equivalent effective viscosity, which also allows for the solution of both velocity fields in a single system of equations. In this way, the velocity distributions across the gas core and the liquid film are obtained iteratively, together with the global pressure gradient and the liquid film thickness. Convergence criteria are based upon satisfaction of mass balance within the liquid film and the gas core. For system closure, two different approaches are presented for the calculation of the radial turbulent viscosity distribution within the liquid film and the gas core. The first one combines a k- Ɛ one-equation model and a low Reynolds k-Ɛ model. The second one uses a low Reynolds k- Ɛ model to compute the eddy viscosity profile from the center of the duct right to the wall. Appropriate interfacial values for k e Ɛ are proposed, based on concepts and ideas previously used, with success, in stratified gas liquid flow. The proposed approaches are compared with an algebraic model found in the literature, specifically devised for annular gas liquid flow, using available experimental results. This also serves as a validation of the solution algorithm

Synthesis of poly(styrene-co-methyl methacrylate)-based ionomers and their Langmuir and Langmuir-Blodgett (LB) film formation

Poly(styrene-co-methyl methacrylate) (PS-PMMA) ionomers with several degrees of sulfonation were synthesized and characterized by infrared, UV-vis, and NMR spectroscopies, elemental analysis, and differential scanning calorimetry (DSC). Stable Langmuir films could be produced with PS-PMMA with 3 and 6 mol % of sulfonation, while PS-PMMA 8% exhibited material loss to the water subphase, probably due to its higher solubility. Surface pressure and surface potential isotherms with PS-PMMA 3% spread onto salt-containing subphases pointed to a film behavior characteristic of the polyelectrolyte effect, where charge repulsion governs the film properties. The Langmuir-Blodgett films of this ionomer were successfully transferred onto various substrates, as confirmed by UV-vis and FTIR spectroscopies. Using cycling voltammetry, we show that LB films from PS-PMMA 3% can be applied in selective sensing of dopamine, even in the presence of interferents such as ascorbic acid.

A layer-by-layer film of chitosan in a taste sensor application

Chitosan is alternated with sulfonated polystyrene (PSS) to build layer-by-layer (LBL) films that are used as sensing units in an electronic tongue. Using impedance spectroscopy as the principle method of detection, an array using chitosan/PSS LBL film and a bare gold electrode as the sensing units was capable of distinguishing the basic tastes - salty, sweet, bitter, and sour - to a concentration below the human threshold. The suitability of chitosan as a sensing material was confirmed by using this sensor to distinguish red wines according to their vintage, vineyard, and brands.

An electrochemical sensor for (L)-dopa based on oxovanadium-salen thin film electrode applied flow injection system

An oxovanadium-salen complex (NAP-ethylene-bis(salicylidenciminato) oxovanadium) thin film deposited on a graphite-polyurethane electrode was investigated with regard to its potential use for detection of L-dopa in flow injection system. The oxovanadium(IV)/oxovanadium(V) redox couple of the modified electrode was found to mediate the L-dopa oxidation before its use in the FIA system. Experimental parameters, such as pH of the carrier solution, flow rate, sample volume injection and probable interferents were investigated. Under the optimized FIA conditions, the amperometric signal was linearly dependent on the L-dopa concentration over the range 1.0 x 10(-1) to 1.0 x 10(-4) mol L-1 (I-anodic, mu A) = 0.01 + 0.25 [L-dopa mu mol L-1]) with a detection limit (S/N = 3) of 8.0 x 10(-7) mol L-1 and a sampling frequency of 90 h(-1) was achieved. For a concentration of 1.0 x 10(-5) mol L-1 L-dopa, the R.S.D. of nine consecutive measurements was 3.7%. (c) 2006 Elsevier B.V. All rights reserved.

Electrochemical sensor for sulfite determination based on a nanostructured copper-salen film modified electrode

The electrochemical preparation described herein involved the electrocatalytic oxidation of sulfite on a platinum electrode modified with nanostructured copper salen (salen=N,N'-ethylenebis(salicylideneiminato)) polymer films. The complex was prepared and electropolymerized at a platinum electrode in a 0.1 mol L-1 solution of tetrabutylammonium perchlorate in acetonitrile by cyclic voltammetry between 0 and 1.4V vs. SCE. After cycling the modified electrode in a 0.50 mol L-1 KCI solution, the estimated surface concentration was found to be equal to 2.2 x 10(-9) Mol cm(-2). This is a typical behavior of an electrode surface immobilized with a redox couple that can usually be considered as a reversible single-electron reduction/oxidation of the copper(II)/copper(III) couple. The potential peaks of the modified electrode in the electrolyte solution (aqueous) containing the different anions increase with the decrease of the ionic radius, demonstrating that the counter-ions influence the voltammetric behavior of the sensor. The potential peak was found to be linearly dependent upon the ratio [ionic charge]/[ionic radius]. The oxidation of the sulfite anion was performed at the platinum electrode at +0.9V vs. SCE. However, a significant decrease in the overpotential (+0.45V) was obtained while using the sensor, which minimized the effect of oxidizable interferences. A plot of the anodic current vs. the sulfite concentration for chronoamperometry (potential fixed = +0.45V) at the sensor was linear in the 4.0 x 10(-6) to 6.9 x 10(-5) mol L-1 concentration range and the concentration limit was 1.2 x 10(-6) mol L-1. The reaction order with respect to sulfite was determined by the slope of the logarithm of the current vs. the logarithm of the sulfite concentration. (C) 2009 Elsevier Ltd. All rights reserved.

Development of an electrochemical sensor for determination of dissolved oxygen by nickel-salen polymeric film modified electrode

An amperometric oxygen sensor based on a polymeric nickel-salen (salen = N,N'-ethylene bis(salicylideneiminato)) film coated platinum electrode was developed. The sensor was constructed by electropolymerization of nickel-salen complex at platinum electrode in acetonitrile/tetrabutylammonium perchlorate by cyclic voltammetry. The voltammetric behavior of the sensor was investigated in 0.5 mol L-1 KCl solution in the absence and presence of molecular oxygen. Thus, with the addition of oxygen to the solution, the increase of cathodic peak current (at -0.25 V vs. saturated calomel electrode (SCE)) of the modified electrode was observed. This result shows that the nickel-salen film on electrode surface promotes the reduction of oxygen. The reaction can be brought about electrochemically, where the nickel(II) complex is first reduced to a nickel(I) complex at the electrode surface. The nickel(I) complex then undergoes a catalytic oxidation by the molecular oxygen in solution back to the nickel(II) complex, which can then be electrochemically re-reduced to produce an enhancement of the cathodic current. The Tafel plot analyses have been used to elucidate the kinetics and mechanism of the oxygen reduction. A plot of the cathodic current vs. the dissolved oxygen concentration for chronoamperometry (fixed potential = -0.25 V vs. SCE) at the sensor was linear in the 3.95-9.20 mg L-1 concentration range and the concentration limit was 0.17 mg L-1 O-2. The proposed electrode is useful for the quality control and routine analysis of dissolved oxygen in commercial samples and environmental water. The results obtained for the levels of dissolved oxygen are in agreement with the results obtained with a commercial O-2 sensor. (C) 2012 Elsevier B.V. All rights reserved.

Electrochemical investigation of the dimeric oxo-bridged ruthenium complex in aqueous solution and its incorporation within a cation-exchange polymeric film on the electrode surface for electrocatalytic activity of hydrogen peroxide oxidation

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

Film based on Y2O3: Eu3+ (5 mol% of Eu3+) for flat panel display

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

An electrochemical sensor for dipyrone determination based on nickel-salen film modified electrode

An amperometric dipyrone sensor based on a polymeric nickel-salen (salen = N,N'-ethylenebis(salicydeneiminato)) film coated platinum electrode was developed. The sensor was constructed by electropolymerization of nickel-salen complex at a platinum electrode in acetonitrile/tetrabuthylamonium perchlorate by cyclic voltammetry. After cycling the modified electrode in a 0.50 mol L-1 KCl solution, the estimated surface concentration was found to be equal to 1.29 x 10(-9) mol cm(-2). This is a typical behavior of an electrode surface immobilized with a redox couple that can usually be considered as a reversible single-electron reduction/oxidation of the nickel(II)/nickel(III) couple. A plot of the anodic current versus the dipyrone concentration for chronoamperometry (potential fixed = +0.50 V) at the sensor was linear in the 4.7 x 10(-6) to 1.1 x 10(-4) mol L-1 concentration range and the concentration limit was 1.2 x 10(-6) mol L-1. The proposed electrode is useful for the quality control and routine analysis of dipyrone in pharmaceutical formulations.

Development of Nanostructured Electrochemical Sensor Based on Polymer Film Nickel-Salen for Determination of Dissolved Oxygen

An amperometric oxygen sensor based on a polymeric nickel-salen (salen = N,N '-ethylenebis(salicydeneiminato)) film coated platinum electrode was developed. The sensor was constructed by electropolymerization of nickel-salen complex at a platinum electrode in acetonitrile/tetrabuthylamonium perchlorate by cyclic voltammetry. The voltammetric behavior of the modified electrode was investigated in 0.5 mol L-1 KCl solution in the absence and presende of molecular oxygen. A significant increased of cathodic peak current (at -0.20 vs. SCE) of the modified electrode with addition of oxygen to the solution was observed. This result shows that the nickel-salen film on the surface of the electrode promotes the reduction of oxygen. The reaction can be brought about electrochemically where in the nickel(II) complex is first reduced to a nickel(I) complex at the electrode surface. The nickel(I) complex then undergoes a catalytic oxidation by the oxygen molecular in solution back to the nickel(II) complex, which can then be electrochemically re-reduced to produce an enhancement of the cathodic current. The plot of the cathodic current versus the dissolved oxygen concentration for chronoamperometry (potential fixed = -0.20 V) at the sensor was linear in the concentration range of 3.95 to 9.20 mg L-1 with concentration limit of 0.17 mg L-1 O-2. The modified electrode proposed is useful for the quality control and routine analysis of dissolved oxygen in commercial water and environmental water samples. The results obtained for the levels of dissolved oxygen are in agreement with the results obtained with an O-2 commercial sensor. (C) 2011 Published by Elsevier Ltd.

Numerical simulation of the liquid phase in SnO2 thin film deposition by sol-gel-dip-coating

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Growth of Al2O3 thin film by oxidation of resistively evaporated Al on top of SnO2, and electrical properties of the heterojunction SnO2/Al2O3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)