A biosensor based on immobilization of lactate oxidase in a PB-CTAB film for FIA determination of lactate in beer samples

An amperometric lactate biosensor with lactate oxidase immobilized into a Prussian Blue (PB) modified electrode was fabricated. The advantage of using cetyltrimethylammonium bromide (CTAB) in the electrodeposition step of PB films onto glassy carbon surfaces was confirmed taking into account both the stability and sensitivity of the measurements. The biosensor was used in the development of a FIA amperometric method for the determination of lactate. Under optimal operating conditions (pH = 6.9, E = -0.1 V), the linear response of the method was extended up to 0.28 µmol L-1 lactate with a limit of detection of 0.84 mmol L-1. The repeatability of the method for injections of a 0.28 mmol L-1 lactate solution was 2.2 % (n = 18). The usefulness of the method was demonstrated by determining lactate in beer samples and the results were in good agreement with those obtained by using a reference spectrophotometric enzyme method.

Chagas Cardiomyopathy Manifestations and Trypanosoma cruzi Genotypes Circulating in Chronic Chagasic Patients

Chagas disease caused by Trypanosoma cruzi is a complex disease that is endemic and an important problem in public health in Latin America. The T. cruzi parasite is classified into six discrete taxonomic units (DTUs) based on the recently proposed nomenclature (TcI, TcII, TcIII, TcIV, TcV and TcVI). The discovery of genetic variability within TcI showed the presence of five genotypes (Ia, Ib, Ic, Id and Ie) related to the transmission cycle of Chagas disease. In Colombia, TcI is more prevalent but TcII has also been reported, as has mixed infection by both TcI and TcII in the same Chagasic patient. The objectives of this study were to determine the T. cruzi DTUs that are circulating in Colombian chronic Chagasic patients and to obtain more information about the molecular epidemiology of Chagas disease in Colombia. We also assessed the presence of electrocardiographic, radiologic and echocardiographic abnormalities with the purpose of correlating T. cruzi genetic variability and cardiac disease. Molecular characterization was performed in Colombian adult chronic Chagasic patients based on the intergenic region of the mini-exon gene, the 24S alpha and 18S regions of rDNA and the variable region of satellite DNA, whereby the presence of T. cruzi I, II, III and IV was detected. In our population, mixed infections also occurred, with TcI-TcII, TcI-TcIII and TcI-TcIV, as well as the existence of the TcI genotypes showing the presence of genotypes Ia and Id. Patients infected with TcI demonstrated a higher prevalence of cardiac alterations than those infected with TcII. These results corroborate the predominance of TcI in Colombia and show the first report of TcIII and TcIV in Colombian Chagasic patients. Findings also indicate that Chagas cardiomyopathy manifestations are more correlated with TcI than with TcII in Colombia.

Reciprocal Modulation of Cognitive and Emotional Aspects in Pianistic Performances

Background: High level piano performance requires complex integration of perceptual, motor, cognitive and emotive skills. Observations in psychology and neuroscience studies have suggested reciprocal inhibitory modulation of the cognition by emotion and emotion by cognition. However, it is still unclear how cognitive states may influence the pianistic performance. The aim of the present study is to verify the influence of cognitive and affective attention in the piano performances. Methods and Findings: Nine pianists were instructed to play the same piece of music, firstly focusing only on cognitive aspects of musical structure (cognitive performances), and secondly, paying attention solely on affective aspects (affective performances). Audio files from pianistic performances were examined using a computational model that retrieves nine specific musical features (descriptors) - loudness, articulation, brightness, harmonic complexity, event detection, key clarity, mode detection, pulse clarity and repetition. In addition, the number of volunteers' errors in the recording sessions was counted. Comments from pianists about their thoughts during performances were also evaluated. The analyses of audio files throughout musical descriptors indicated that the affective performances have more: agogics, legatos, pianos phrasing, and less perception of event density when compared to the cognitive ones. Error analysis demonstrated that volunteers misplayed more left hand notes in the cognitive performances than in the affective ones. Volunteers also played more wrong notes in affective than in cognitive performances. These results correspond to the volunteers' comments that in the affective performances, the cognitive aspects of piano execution are inhibited, whereas in the cognitive performances, the expressiveness is inhibited. Conclusions: Therefore, the present results indicate that attention to the emotional aspects of performance enhances expressiveness, but constrains cognitive and motor skills in the piano execution. In contrast, attention to the cognitive aspects may constrain the expressivity and automatism of piano performances.

Influence of film thickness on the crystallization of Ni-doped amorphous silicon samples

This work reports on the crystallization of amorphous silicon (a-Si) films doped with 1 at. % of nickel. The films, with thicknesses ranging from 10 to 3000 nm, were deposited using the cosputtering method onto crystalline quartz substrates. In order to investigate the crystallization mechanism in detail, a series of undoped a-Si films prepared under the same deposition conditions were also studied. After deposition, all a-Si films were submitted to isochronal thermal annealing treatments up to 1000 degrees C and analyzed by Raman scattering spectroscopy. Based on the present experimental results, it is possible to state that (a) when compared to the undoped a-Si films, those containing 1 at. % of Ni crystallize at temperatures similar to 100 degrees C lower, and that (b) the film thickness influences the temperature of crystallization that, in principle, tends to be lower in films thinner than 1000 nm. The possible reasons associated to these experimental observations are presented and discussed in view of some experimental and thermodynamic aspects involved in the formation of ordered Si-Si bonds and in the development of Ni-silicide phases. (c) 2008 American Institute of Physics.

Studies on the Electrocatalytic Reduction of Hydrogen Peroxide on a Glassy Carbon Electrode Modified With a Ruthenium Oxide Hexacyanoferrate Film

The electrocatalytic reduction of hydrogen peroxide on a glassy carbon (GC) electrode modified with a ruthenium oxide hexacyanoferrate (RuOHCF) was investigated using rotating disc electrode (RDE) voltammetry aiming to improve the performance of the sensor for hydrogen peroxide detection. The influence of parameters such as rotation speed, film thickness and hydrogen peroxide concentration indicated that the rate of the cross-chemical reaction between Ru(II) centres immobilized into the film and hydrogen peroxide controls the overall process. The kinetic regime could be classified as LSk mechanism, according to the diagnostic table proposed by Albery and Hillman, and the kinetic constant of the mediated process was found to be 706 mol(-1) cm(3) s(-1). In the LSk case the reaction layer is located at a finite layer close to the modifier layer/solution interface

Polymer matrix sensitizing effect on photoluminescence properties of Eu(3+)-beta-diketonate complex doped into poly-beta-hydroxybutyrate (PHB) in film form

In this work is reported the sensitization effect by polymer matrices on the photoluminescence properties of diaquatris(thenoyltrifluoroacetonate)europium(III), [Eu(tta)(3)(H(2)O)(2)], doped into poly-beta-hydroxybutyrate (PHB) with doping percentage at 1, 3, 5, 7 and 10% (mass) in film form. TGA results indicated that the Eu(3+) complex precursor was immobilized in the polymer matrix by the interaction between the Eu(3+) complex and the oxygen atoms of the PHB polymer when the rare earth complex was incorporated in the polymeric host. The thermal behaviour of these luminescent systems is similar to that of the undoped polymer, however, the T(onset) temperature of decomposition decreases with increase of the complex doping concentration. The emission spectra of the Eu(3+) complex doped PHB films recorded at 298 K exhibited the five characteristic bands arising from the (5)D(0) -> (7)F(J) intraconfigurational transitions (J = 0-4). The fact that the quantum efficiencies eta of the doped film increased significantly revealed that the polymer matrix acts as an efficient co-sensitizer for Eu(3+) luminescent centres and therefore enhances the quantum efficiency of the emitter (5)D(0) level. The luminescence intensity decreases, however, with increasing precursor concentration in the doped polymer to greater than 5% where a saturation effect is observed at this specific doping percentage, indicating that changes in the polymeric matrix improve the absorption property of the film, consequently quenching the luminescent effect.

High Solids Content, Soap-Free, Film-Forming Latexes Stabilized by Laponite Clay Platelets

High solids content film-forming poly[styrene-co-(n-butyl acrylate)] [poly(Sty-co-BuA)] latexes armored with Laponite clay platelets have been synthesized by soap-free emulsion copolymerization of styrene and n-butyl acrylate. The polymerizations were performed in batch in the presence of Laponite and a methyl ether acrylateterminated poly(ethylene glycol) macromonomer in order to promote polymer/clay association. The overall polymerization kinetics showed a pronounced effect of clay on nucleation and stabilization of the latex particles. Cryo-transmission electron microscopy observation confirmed the armored morphology and indicated that the majority of Laponite platelets were located at the particle surface. The resulting nanostructured films displayed enhanced mechanical properties.

Sensorless synchronization method for thin-film direct optical broadband monitoring system

Optical monitoring systems are necessary to manufacture multilayer thin-film optical filters with low tolerance on spectrum specification. Furthermore, to have better accuracy on the measurement of film thickness, direct monitoring is a must. Direct monitoring implies acquiring spectrum data from the optical component undergoing the film deposition itself, in real time. In making film depositions on surfaces of optical components, the high vacuum evaporator chamber is the most popular equipment. Inside the evaporator, at the top of the chamber, there is a metallic support with several holes where the optical components are assembled. This metallic support has rotary motion to promote film homogenization. To acquire a measurement of the spectrum of the film in deposition, it is necessary to pass a light beam through a glass witness undergoing the film deposition process, and collect a sample of the light beam using a spectrometer. As both the light beam and the light collector are stationary, a synchronization system is required to identify the moment at which the optical component passes through the light beam.

Film thickness measurement techniques applied to micro-scale two-phase flow systems

Recently semi-empirical models to estimate flow boiling heat transfer coefficient, saturated CHF and pressure drop in micro-scale channels have been proposed. Most of the models were developed based on elongated bubbles and annular flows in the view of the fact that these flow patterns are predominant in smaller channels. In these models, the liquid film thickness plays an important role and such a fact emphasizes that the accurate measurement of the liquid film thickness is a key point to validate them. On the other hand, several techniques have been successfully applied to measure liquid film thicknesses during condensation and evaporation under macro-scale conditions. However, although this subject has been targeted by several leading laboratories around the world, it seems that there is no conclusive result describing a successful technique capable of measuring dynamic liquid film thickness during evaporation inside micro-scale round channels. This work presents a comprehensive literature review of the methods used to measure liquid film thickness in macro- and micro-scale systems. The methods are described and the main difficulties related to their use in micro-scale systems are identified. Based on this discussion, the most promising methods to measure dynamic liquid film thickness in micro-scale channels are identified. (C) 2009 Elsevier Inc. All rights reserved.

Laboratory measurements of biomarkers and individual performances in Chironomus xanthus to evaluate pesticide contamination of sediments in a river of southeastern Brazil

This study aimed at evaluating biomarkers, individual and population responses in the native Chironomus xanthus to assess the toxicity of pesticide-contaminated sediments from the Monjolinho River (Southeast Brazil). We measured cholinesterase (ChE) and glutathione S-transferase activities (GST), as biomarkers and survival, individual growth and adult emergence, as individual performances. There was no response of the ChE activity and a tendency to decreased GST activity in contaminated sites, but this was generally not statistically significant. Therefore, there was no association of the biomarker responses with exposure to sediment containing pesticides. In contrast, ash free dry mass was significantly increased and male emergence was decreased in C. xanthus exposed to the same sediments. In conclusion, the selected biomarkers were not sensitive and specific enough to detect and anticipate effects of pesticide contamination at the levels measured in the study area. Nevertheless, individual performances alterations pointed to potential pollution problems and possible ecological consequences. (C) 2010 Elsevier Inc. All rights reserved.

Polymer toughening using residue of recycled windshields: PVB film as impact modifier

In this work, poly(vinyl butyral) (PVB) film originated from the mechanical separation of windshields was tested as all impact modifier of Polyamide-6 (PA-6). The changes undergone by PVB film during the recycling process and the blend manufacturing were evaluated by thermal analyses, infrared spectroscopy and loss oil ignition. Blends of PA-6/original PVB film and PA-6/recovered PVB film were obtained in concentrations ranging from 90/10 to 60/40. The mechanical properties of the blends were investigated and explained in light of the blends morphologies, which in turns were correlated to the changes undergone by the PVB film during the recycling process. The original film presented a plasticizer content of 33 wt.%, which decreased to as low as 20 wt.%, after the recycling and blend preparation processes. The PA-6/PVB film blends presented lower values of tensile strength and Young`s modulus than Polyamide-6, but all blends presented a dramatic increase in their toughness, with a special feature for the 40 wt.%(, blend, which resulted in a super toughened material (impact strength exceeding 500 J/m). Similar results were obtained with recovered PVB film and super tough blends were also obtained. The use of recovered PVB resulted in a smaller improvement of the impact strength due to the loss of plasticizer undergone during the recycling process. The morphological observations showed that if the interparticle distance is smaller than around 0.2 mu m (critical value), the notched Izod impact strength values increase considerably and the fracture surface of blends exhibit characteristics of tough failure. (C) 2007 Elsevier Ltd. All rights reserved.

Effect of cerium (IV) ions on the anticorrosion properties of siloxane-poly(methyl methacrylate) based film applied on tin coated steel

This work investigates the influence of the addition of cerium (IV) ions on the anticorrosion properties of organic-inorganic hybrid coatings applied to passivated tin coated steel. In order to evaluate the specific effect of cerium (IV) addition on nanostructural features of the organic and inorganic phases of the hybrid coating, the hydrolytic polycondensation of silicon alkoxide and the radical polymerization of the methyl methacrylate (MMA) function were induced separately. The corrosion resistance of the coatings was evaluated by means of linear polarization, Tafel type curves and electrochemical impedance measurements. The impedance results obtained for the hybrid coatings were discussed based on an electrical equivalent circuit used to fit the experimental data. The electrochemical results clearly showed the improvement of the protective properties of the organic-inorganic hybrid coating mainly when the cerium (IV) was added to the organic phase solution precursor, which seemed to be due to the formation of a more uniform and densely reticulated siloxane-PMMA film. (C) 2010 Elsevier Ltd. All rights reserved.

Performance of a solar energy powered falling film evaporator with film promoter

A solar energy powered failing film evaporator with film promoter was developed for concentrating diluted solutions (industrial effluents). The procedure proposed here does not emit CO(2), making it a viable alternative to the method of concentrating solutions that uses vapor as a heat source and releases CO(2) from burning fuel oil in a furnace, in direct opposition to the carbon reduction agreement established by the Kyoto protocol. This novel device consists of the following components: a flat plate solar collector with adjustable inclination, a film promoter (adhering to the collector), a liquid distributor, a concentrate collector. and accessories. The evaporation rate of the device was found to be affected both by the inclination of the collector and by the feed flow. The meteorological variables cannot be controlled, but were monitored constantly to ascertain the behavior of the equipment in response to the variations occurring throughout the day. Higher efficiencies were attained when the inclination of the collector was adjusted monthly, showing up to 36.4% higher values than when the collector remained in a fixed position. (c) 2008 Elsevier Ltd. All rights reserved.

Corrosion resistant and adsorbent plasma polymerized thin film

Adsorbent and corrosion resistant films are useful for sensor development. Therefore, the aim of this work is the production and characterization of plasma polymerized fluorinated organic ether thin films for sensor development. The polymerized reactant was methyl nonafluoro(iso)butyl ether. Infrared Spectroscopy showed fluorinated species and eventually CO but CH(n) is a minor species. Contact angle measurements indicated that the film is hydrophobic and organophilic but oleophobic. Optical microscopy reveals not only a good adherence on metals and acrylic but also resistance for organic solvents, acid and basic aqueous solution exposure. Double layer and intermixing are possible and might lead to island formation. Quartz Crystal Microbalance showed that 2-propanol permeates the film but there is no sensitivity to n-hexane. The microreactor manufactured using a 73 cm long microchannel can retain approximately 9 X 10(-4) g/cm(2) of 2-propanol in vapor phase. Therefore, the film is a good candidate for preconcentration of volatile organic compounds even in corrosive environment. (C) 2009 Elsevier B.V. All rights reserved.

Single step process for particles surface modification or thin film composite production

Adsorbent materials and composites are quite useful for sensor development. Therefore, the aim of this work is the surface modification of particulates and/or composite formation. The material was produced by plasma polymerization of HMDS (hexamethyldisilazane) in a single step. SEM analysis shows good surface coverage of particulates with a plasma polymerized film formed by several clusters that might increase adsorption. Particles (starch. 5 5 mu m) recovered with HMDS films show good properties for retention of medium-size Organic molecules, such as dye. Thin films formed by a mixture of particles and plasma polymerized thin film HMDS species were obtained in a single step and can be used for retention of organic compounds, in liquid or gaseous phase. (C) 2009 Elsevier B.V. All rights reserved.