Rheological, Mechanical and Adhesive Properties of Surfactant-Containing Systems Designed as a Potential Platform for Topical Drug Delivery

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

Structural characterization and in vivo evaluation of retinyl palmitate in non-ionic lamellar liquid crystalline system

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

Evaluation of Preservative Effectiveness of Liquid Crystalline Systems with Retynil Palmitate by the Challenge Test and D-value

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nucleação de vortices e paredes de domínio em nanoestruturas magnéticas

We report a theoretical investigation of the magnetic phases and hysteresis of exchange biased ferromagnetic (F) nanoelements for three di erent systems: exchange biased nanoparticles, exchange biased narrow ferromagnetic stripes and exchange biased thin ferromagnetic lms. In all cases the focus is on the new e ects produced by suitable patterns of the exchange energy coupling the ferromagnetic nanoelement with a large anisotropy antiferromagnetic (AF) substrate. We investigate the hysteresis of iron and permalloy nanoparticles with a square basis, with lateral dimensions between 45 nm and 120 nm and thickness between 12 nm and 21 nm. Interface bias is aimed at producing large domains in thin lms. Our results show that, contrary to intuition, the interface exchange coupling may generate vortex states along the hysteresis loop. Also, the threshold value of the interface eld strength for vortex nucleation is smaller for iron nanoelements. We investigate the nucleation and depinning of an array of domain walls pinned at interface defects of a vicinal stripe/AF bilayer. The interface exchange eld displays a periodic pattern corresponding to the topology of the AF vicinal substrate. The vicinal AF substrate consists of a sequence of terraces, each with spins from one AF subalattice, alternating one another. As a result the interface eld of neighboring terraces point in opposite direction, leading to the nucleation of a sequence of domain walls in the ferromagnetic stripe. We investigated iron an permalloy micrometric stripes, with width ranging from 100 nm and 300 nm and thickness of 5 nm. We focused in domain wall sequences with same chirality and alternate chirality. We have found that for 100nm terraces the same chiraility sequence is more stable, requiring a larger value of the external eld for depinning. The third system consists of an iron lm with a thickness of 5 nm, exchange coupled to an AF substrate with a periodic distribution of islands where the AF spins have the opposite direction of the spins in the background. This corresponds to a two-sublattice noncompensated AF plane (such as the surface of a (100) FeF2 lm), with monolayer-height islands containing spins of one sublattice on a surface containing spins of the opposite sublattice. The interface eld acting in the ferromagnetic spins over the islands points in the opposite direction of that in the spins over the background. This a model system for the investigation of interface roughness e ects. We have studied the coercicivity an exchange bias hysteresis shift as a function of the distance between the islands and the degree of interface roughness. We have found a relevant reduction of coercivity for nearly compensated interfaces. Also the e ective hysteresis shift is not proportional to the liquid moment of the AF plane. We also developed an analytical model which reproduces qualitatively the results of numerical simulations

Development and application of methods for determination of residual monomer in dental acrylic resins using high performance liquid chromatography

Two high-performance liquid chromatographic methods for determination of residual monomer in dental acrylic resins are described. Monomers were detected by their UV absorbance at 230 nm, on a Nucleosil((R)) C-18 (5 mu m particle size, 100 angstrom pore size, 15 x 0.46 cm i.d.) column. The separation was performed using acetonitrile-water (55:45 v/v) containing 0.01% triethylamine (TEA) for methyl methacrylate and butyl methacrylate, and acetonitrile-water (60:40 v/v) containing 0.01% TEA for isobutyl methacrylate and 1,6-hexanediol dimethacrylate as mobile phases, at a flow rate of 0.8 mL/min. Good linear relationships were obtained in the concentration range 5.0-80.0 mu g/mL for methyl methacrylate, 10.0-160.0 mu g/mL for butyl methacrylate, 50.0-500.0 mu g/mL for isobutyl methacrylate and 2.5-180.0 mu g/mL for 1,6-hexanediol dimethacrylate. Adequate assay for intra- and inter-day precision and accuracy was observed during the validation process. An extraction procedure to remove residual monomer from the acrylic resins was also established. Residual monomer was obtained from broken specimens of acrylic disks using methanol as extraction solvent for 2 h in an ice-bath. The developed methods and the extraction procedure were applied to dental acrylic resins, tested with or without post-polymerization treatments, and proved to be accurate and precise for the determination of residual monomer content of the materials evaluated. Copyright (c) 2005 John Wiley & Sons, Ltd.

Evaluation of pH and Calcium Ion Release of Calcium Hydroxide Pastes Containing Different Substances

Introduction: The objective of this study was to evaluate the pH and calcium ion release of calcium hydroxide pastes associated with different substances. Methods: Forty acrylic teeth with simulated root canals were divided into 4 groups according to the substance associated to the calcium hydroxide paste: chlorhexidine (CHX) in 2 formulations (1% solution and 2% gel), Casearia sylvestris Sw extract, and propylene glycol (control). The teeth with pastes and sealed coronal accesses were immersed in 10 mL deionized water. After 10 minutes, 24 hours, 48 hours, and 7, 15, and 30 days, the teeth were removed to another container, and the liquid was analyzed. Calcium ion release was measured by atomic absorption spectrophotometry, and pH readings were made with a pH meter. Data were analyzed statistically by analysis of variance and Tukey test (alpha = 0.05). Results: Calcium analysis revealed significant differences (P < .05) for 1% CHX solution and 2% CHX gel at 10 minutes. After 24 hours, 2% CHX gel x Control and 2% CHX gel x 1% CHX solution differed significantly (P < .05). After 48 hours, there were significant differences (P < .05) for 2% CHX gel x Control and Extract x Control. No differences (P > .05) were observed among groups in the other periods. Regarding the pH, there were significant differences (P < .05) for 2% CHX gel x Control and 2% CHX gel x 1% CHX solution after 48 hours and for 2% CHX gel x Control after 15 days. In the other periods, no differences (P > .05) were observed among groups. Conclusions: All pastes behaved similarly in terms of pH and calcium ion release in the studied periods. (J Endod 2009;35:1274-1277)

Determination of the properties of an experimental glass polyalkenoate cement prepared from niobium silicate powder containing fluoride

Objectives. The purpose of this paper is to modify the conventional calcium fluoro-aluminosilicate glass, which is used in the formation of glass ionomer cements (CIGs) by the niobium addition and to study the properties of GICs obtained.Materials and methods. Sol-gel process was used to prepare the powder at lower temperature than fusion method. Glass-ceramic powder obtained in this way was used to prepare the GICs. The properties such as working and setting times, microhardness and diametral tensile strength were evaluated for the experimental GICs and a commercial luting cement.Results. The ideal powder:liquid (P:L) ratio determined to prepare the experimental GICs was equal to 1:1. The cements prepared using this ratio showed working and setting times similar to the commercial GICs. in mechanical tests it was observed that microhardness and diametral tensile strength of the experimental GICs decreased significantly with the reduction of P:L ratio. on the other hand, the results obtained in microhardness tests indicated that the presence of niobium was a positive factor.Significance. The chemical process allows the development of glass-ceramic powder at 600 degrees C which is the goal of the present paper. It was concluded that GICs containing niobium might be used in dental applications and these results encourage further researches on other compositions. (c) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Production and characterization of polygalacturonase from thermophilic Thermoascus aurantiacus on submerged fermentation

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

Flotation of blocolloids suspended in liquid phases of different compositions and pH values

The flotation capacity was determined for cells of yeasts strains belonging to the genera Hansenula, Candida and Saccharomyces. A heterogeneous group of yeasts, comprising strains from the three genera, was identified as showing high flotation capacities (degrees of flotation above 50%), which were practically not affected by variations in medium pH in both the synthetic medium and 2% molasses. Thus, the flotation capacity of the cells in this yeast group seemed strongly dependent on the liquid phase properties and/or growth medium composition, more than on the simple variation in pH of the cell suspensions. A second group of strains, belonging to the Saccharomyces genus, including also brewing yeast strains, was identified as having lower flotation capacities (degrees of flotation below 50% at pH 1.5), which showed no alterations or variations significantly affected by the medium pH. Foam volumes obtained with Saccharomyces strains were greater in synthetic media than in molasses owing to the higher air flow rates required for flotation in molasses. The flotation efficiency decreased in molasses in all cases as well as the foam volume, except in the case of Hansenula cells, which showed an increased foam volume. This was probably due to variations in product excretion by the different yeasts and/or differences in cell wall composition.

Zirconia needles synthesized inside hexagonal swollen liquid crystals

We report the synthesis of zirconia microneedles by the direct nucleation of particles inside a hexagonal swollen liquid crystal (SLC) (cell parameter a = 27 nm) prepared by mixing with the proper ratio, an aqueous solution of sulfated zirconium colloids, a cationic surfactant (cetylpyridinium chloride), cychlohexane as swelling agent with an oil over water ratio of 2.5 (vol.), and 1-pentanol as cosurfactant. After a slow crystallogenesis that can be enhanced by an initial induction step under moderate temperature, particles in the centimeter range can be obtained, with a very high shape ratio (over 100). These particles are made of crystalline octahydrate zirconium oxychloride containing pores of 20 nm diameter, aligned along the main axis of the liquid crystal, as the fingerprint of the oil cylinders present in the hexagonal phase. The morphology of these particles confirms that the shaping mechanism is based on true liquid crystal templating (TLCT). Further thermal treatment of these particles, after extraction from the SLC, leads to the crystallization of zirconia with the same needlelike morphology as the zirconium oxychloride.

Liquid chromatography/electrospray ionization tandem mass spectrometry profiling of compounds from the infusion of Byrsonima fagifolia Niedenzu

A rapid analytical approach suitable to achieve a comprehensive characterization of the compounds present in the infusion prepared from the leaves of Byrsonima fagifolia Niedenzu (Malpighiaceae), a Brazilian plant used as an infusion to treat gastric disorders, was developed. The method was based on high-performance liquid chromatography coupled to electrospray negative ionisation multistage ion trap mass spectrometry (HPLC/ESI-ITMSn). The main ions in the ESI-ITMS spectra were attributed to a quinic acid core containing from one to five galloyl units. Quercetin derivatives containing one and two sugar moieties as well as galloyl esterification were also detected. These results indicated that HPLC/ESI-ITMSn is easily applicable to infusions of this plant and allows the rapid and direct identification of these compounds in crude plant extracts. Copyright (C) 2007 John Wiley & Sons, Ltd.

Sol-gel transition in SnO2 colloidal suspensions: viscoelastic properties

This paper describes particle aggregation process during gelation of SnO2 hydrosols. The effect of the concentration of SnO2 colloidal particles on the kinetics of gelation of hydrosols containing PVA (poly(vinyl alcohol)) was analysed by dynamic rheological measurements. The complex viscosity and the storage and loss moduli have been measured during the sol-gel transition and the results correlated to mass fractal growth, nearly linear growth models, and scalar percolation theory. The analysis of the experimental results shows that a linear aggregation occurs in the initial step of the gelation followed by a fractal growth to form a three-dimensional network. Near the gel point this physical gel exhibits the typical scaling expected from an electrical percolation analogy. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Determination of acetaldehyde in fuel ethanol by high-performance liquid chromatography with electrochemical detection

The cyclic voltammetric behavior of acetaldehyde and the derivatized product with 2,4-dinitrophenylhydrazine (DNPHi) has been studied at a glassy carbon electrode. This study was used to optimize the best experimental conditions for its determination by high-performance liquid chromatographic (HPLC) separation coupled with electrochemical detection. The acetaldehyde-2,4-dinitrophenyl.hydrazone (ADNPH) was eluted and separated by a reversed-phase column, C-18, under isocratic conditions with the mobile phase containing a binary mixture of methanol/LiCl(aq) at a concentration of 1.0 x 10(-3) M (80:20 v/v) and a flow rate of 1.0 mL min(-1). The optimum condition for the electrochemical detection of ADNPH was +1.0 V vs. Ag/AgCl as a reference electrode. The proposed method was simple, rapid (analysis time 7 min) and sensitive (detection limit 3.80 mu g L-1) at a signal-to-noise ratio of 3:1. It was also highly selective and reproducible [standard deviation 8.2% +/- 0.36 (n = 5)]. The analytical curve of ADNPH was linear over the range of 3-300 mg L-1 per injection (20 mu L), and the analytical recovery was > 99%.

Temperature and concentration dependence of density of model liquid foods

Density of binary solutions and combinations of sucrose, glucose, fructose, citric acid, malic acid, pectin, and inorganic salts were measured with an oscillating tube density meter in the temperature range from 10degrees to 60degreesC, at varying concentrations. Density can be predicted with accuracy better than 5 x 10(-5) g cm(-3) using predictive equations obtained by fitting the experimental data. Available literature values agreed well with experimental data. Relations for the excess molar volume of these solutions were derived in terms of mole fraction and temperature. A thermodynamic model for the volumetric analysis of multicomponent aqueous solutions containing electrolyte and non-electrolyte compounds was also proposed. These models can be used for prediction of density of liquid food systems, specially fruit juices and beverages, based on composition and temperature, with high accuracy and without elaborate experimental work.

Determination of aldehydes and ketones in fuel ethanol by high-performance liquid chromatography with electrochemical detection

A new methodology was developed for analysis of aldehydes and ketones in fuel ethanol by high-performance liquid chromatography (HPLC) coupled to electrochemical detection. The electrochemical oxidation of 5-hydroxymetkylfurfural, 2-furfuraldehyde, butyraldehyde, acetone and methyl ethyl ketone derivatized with 2,4-dinitrophenylhydrazine (DNPH) at glassy carbon electrode present a well defined wave at +0.94 V; +0.99 V; +1.29 V; +1.15 V and +1.18 V, respectively which are the basis for its determination on electrochemical defector. The carbonyl compounds derivatized were separated by a reverse-phase column under isocratic conditions with a mobile phase containing a binary mixture of methanol /LiClO4(aq) at a concentration of 1.0 x 10(-3) mol L-1 (80:20 v/v) and a flow-rate of 1.1 mL min(-1). The optimum potential for the electrochemical detection of aldehydes-DNPH and ketones-DNPH was +1.0 V vs. Ag/AgCl. The analytical curve of aldehydes-DNPH and ketones-DNPH presented linearity over the range 5.0 to 400.0 ng mL(-1), with detection limits of 1.7 to 2.0 ng mL(-1) and quantification limits from 5.0 to 6.2 ng mL(-1), using injection volume of 20 mu L. The proposed methodology was simple, low time-consuming (15 min/analysis) and presented analytical recovery higher than 95%.