Film forming solutions based on gelatin and poly(vinyl alcohol) blends: Thermal and rheological characterizations

The objective of this work was to study the theological and thermal properties of film forming solutions (FFS) based on blends of gelatin and poly(vinyl alcohol) (PVA). The effect of the PVA concentration and plasticizer presence on the flow behavior, and viscoelastic and thermal properties of FFS was studied by steady-shear flow and oscillatory experiments, and also, by microcalorimetry. The FB presented Newtonian behavior at 30 degrees C, and the viscosity was not affected neither by the PVA concentration nor by the plasticizer. All FFS presented a phase transition during tests applying temperature scanning. It was verified that the PVA affected the viscoelastic properties of FFS by dilution of gelatin. This behavior was confirmed by microcalorimetric analysis. The behaviors of the storage (G`) and loss (G ``) moduli as a function of frequency of FFS obtained at 5 degrees C were typical of physical gels; with the G` higher than the G ``. The strength of the gels was affected by the PVA concentration. (C) 2009 Elsevier Ltd. All rights reserved.

Order and disorder in fiction labyrinths: the librarians` representations in some contemporary cultural productions

This paper, first result of a larger research, proposes a query about some aspects of social representation of libraries and librarians, as they appear in literary and cinematographic productions. Little by little, this query, which arose from purposes of organizing catalogues, revealed elements that established different series, in which the narrative genre (literary or cinematographic) has no relevance to either libraries or librarians` representations. The presence of these elements seems to show some expectations and utopias in relation to the common knowledge, independently from narratives being located in the past, in the present or in the future, stimulating reflection on some medieval and baroque traditions about the library universe and its main characters, the librarians. The cinematographic material selected for research was The time machine, Farenheit 451, The day after tomorrow, Star Wars - episode II and the novels Martin Eden, The man without qualities, The time machine and La sombra del viento.

Development and Evaluation of a Novel pH Indicator Biodegradable Film Based on Cassava Starch

A pH indicator film based on cassava starch plasticized with sucrose and inverted sugar and incorporated with grape and spinach extracts as pH indicator sources (anthocyanin and chlorophyll) has been developed, and its packaging properties have been assessed. A second-order central composite design (2(2)) with three central points and four star points was used to evaluate the mechanical properties (tensile strength, tensile strength at break, and elongation at break percentage), moisture barrier, and microstructure of the films, and its potential as a pH indicator packaging. The films were prepared by the casting technique and conditioned under controlled conditions (75% relative humidity and 23 degrees C), at least 4 days before the analyses. The materials were exposed to different pH solutions (0, 2, 7, 10, and 14) and their color parameters (L*, a*, b*, and haze) were measured by transmittance. Grape and spinach extracts have affected the material characterization. Film properties (mechanical properties and moisture barrier) were strongly influenced by extract concentration presenting lower results than for the control. Films containing a higher concentration of grape extract presented a greater color change at different pH`s suggesting that anthocyanins are more effective as pH indicators than chlorophyll or the mixture of both extracts. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1069-1079,2011

Numerical simulation of the liquid phase in SnO(2) thin film deposition by sol-gel-dip-coating

The fluid flow of the liquid phase in the sol-gel-dip-coating process for SnO(2) thin film deposition is numerically simulated. This calculation yields useful information on the velocity distribution close to the substrate, where the film is deposited. The fluid modeling is done by assuming Newtonian behavior, since the linear relation between shear stress and velocity gradient is observed. Besides, very low viscosities are used. The fluid governing equations are the Navier-Stokes in the two dimensional form, discretized by the finite difference technique. Results of optical transmittance and X-ray diffraction on films obtained from colloidal suspensions with regular viscosity, confirm the substrate base as the thickest part of the film, as inferred from the numerical simulation. In addition, as the viscosity increases, the fluid acquires more uniform velocity distribution close to the substrate, leading to more homogenous and uniform films.

Nanostructured copper thin film used for catalysis

Catalytic properties of copper thin films deposited in small channels and cavities were tested using Raman microscopy and mass spectroscopy (MS) techniques, mainly. The catalytic surface conditions were addressed visually and chemically by optical microscopy and X-ray photoelectron spectroscopy (XPS), respectively. The experimental conditions of present work induced copper oxidation; eventually a number of carbon species and graphite remained on the catalytic surface. Quartz crystal microbalance and mass spectroscopy data support both adsorption and catalysis phenomena. MS showed CO2 formation during n-hexane heating process but not to 2-propanol, probably due to redox reactions. XPS of copper surface present in the cavity after catalysis tests detected Cu2O and a range of possible carbon species. The adsorption and catalytic performance of copper films deposited in cavities and microchannels were quite similar. A simple miniaturized device for microanalysis was proposed. (C) 2007 Elsevier B.V. All rights reserved.

Chemical modification of a nanocrystalline TiO(2) film for efficient electric connection of glucose oxidase

A novel biosensor for glucose was prepared by adsorption of 1,1`-bis(4-carboxybenzyl)-4,4`-bipyridinium di-bromide compound (H(2)BpybcBr(2)) onto the surface of a nanocrystalline TiO(2) film deposited onto FTO glasses, which was used as a platform to assemble the enzyme glucose oxidase to the electrode surface. The H(2)BpybcBr(2)/TiO(2)/FTO modified electrode was characterized by scanning electron microscopy, X-ray fluorescence image, cyclic voltammograms and spectroelectrochemical measurements. The immobilization of GOD on functionalized TiO(2) film led to stable amperometric biosensing for glucose with a linear range from 153 mu mol L(-1) to 1.30 mmol L(-1) and a detection limit of 51 mu mol L(-1). The apparent Michaelis-Menten constant (K(m)) was estimated to be 3.76 mmol L(-1), which suggested a high enzyme-substrate affinity. The maximum electrode sensitivity was 1.25 mu A mmol L(-1). The study proved that the combination of viologen mediators with TiO(2) film retains the electrocatalytic activity of the enzyme, and also enhances the electron transfer process, and hence regenerating the enzyme in the reaction with glucose. (C) 2010 Elsevier Inc. All rights reserved.

Flow injection analysis using carbon film resistor electrodes for amperometric determination of ambroxol

Flow injection analysis (FIA) using a carbon film sensor for amperometric detection was explored for ambroxol analysis in pharmaceutical formulations. The specially designed flow cell designed in the lab generated sharp and reproducible current peaks, with a wide linear dynamic range from 5 x 10(-7) to 3.5 x 10(-4) mol L-1, in 0.1 mol L-1 sulfuric acid electrolyte, as well as high sensitivity, 0.110 A mol(-1) L cm(-2) at the optimized flow rate. A detection limit of 7.6 x 10(-8) mol L-1 and a sampling frequency of 50 determinations per hour were achieved, employing injected volumes of 100 mu L and a flow rate of 2.0 mL min(-1). The repeatability, expressed as R.S.D. for successive and alternated injections of 6.0 x 10(-6) and 6.0 x 10(-5) mol L-1 ambroxol solutions, was 3.0 and 1.5%, respectively, without any noticeable memory effect between injections. The proposed method was applied to the analysis of ambroxol in pharmaceutical samples and the results obtained were compared with UV spectrophotometric and acid-base titrimetric methods. Good agreement between the results utilizing the three methods and the labeled values was achieved, corroborating the good performance of the proposed electrochemical methodology for ambroxol analysis. (C) 2008 Elsevier B.V. All rights reserved.

The characterisation of the protective film formed by benzotriazole on the 90/10 copper-nickel alloy surface in H2SO4 media

The nature of the protective film formed by benzotriazole (BTAH) on the surface of the 90/10 CuNi alloy in deaerated 0.5 mol L-1 H2SO4 solution containing Fe(III) ions as oxidant was investigated by weight-loss, calorimetric measurements, and by surface-enhanced Raman spectroscopy (SERS). The SERS measurements show that the protective film is composed by the [Cu(I)BTA](n), polymeric complex and that the BTAH molecules are also adsorbed on the electrode surface. A modification of the BET isotherm for adsorption of gases ill solids is proposed to describe the experimental results obtained from weight-loss experiments that suggest an adsorption in multilayers. Electrochemical studies of copper and nickel in 0.5 mol L-1 H2SO4 in presence and absence of BTAH have also been made as an aid to interpret the results. The calculated adsorption free energy of the cuprous benzotriazolate on the surface of the alloy is in accordance with the value for pure copper. (C) 2007 Elsevier Ltd. All rights reserved.

Effect of polyol excess on the electrical property of vegetable-polyurethane film

Freestanding castor oil-based polyurethane (PU) film was obtained using spin-coating method. The effect of polyol content was analysed by means of thermally stimulated depolarisation current and AC dielectric measurements techniques. Two relaxation peaks were observed in the temperature range of -40 to 60 degrees C for PU with different polyol contents. The presence of polyol excess provides a shift to lower temperature of the a relaxation and the decrease in the activation energy of the transition in this region might be attributed to the plasticising effect of the polyol. The peak at higher temperature is due to the Maxwell-Wagner-Sillars relaxation, which also shifts in the low temperature direction as the polyol content is increased.