Nanodispersions containing astaxanthin were prepared by an emulsification evaporation processing technique. The influence of the processing conditions, buy DZNeP namely,
the pressure of the high-pressure homogenizer (20-90 MPa), the number of passes through the homogenizer (0-4) and the evaporation temperature (16-66 degrees C) on the physicochemical properties of the prepared astaxanthin nanodispersions were evaluated using a three-factor central composite design. Average particle size, polydispersity index (POI) and astaxanthin loss in the prepared nanodispersions were considered as response variables. The multiple-response optimization predicted that using three passes through the high-pressure homogenizer at 30 MPa for the preparation of the astaxanthin nanoemulsion and then removing the organic phase (solvent) from the system by evaporation at 25 degrees C provided astaxanthin nanodispersions with optimum physicochemical properties. (C) 2011 Elsevier Ltd. All rights reserved.”
“Objective. The goal of this investigation was to assess validity of predictive models of stress relaxation in dental polymers when applied to extended master curves generated from short time experimental data by WLF time temperature superposition method. Methods. The stress relaxation modulus changes with time at three different temperatures near the ambient body temperature were
GSK621 supplier determined for selected mono-methacrylate (PEMA and PMMA) and
dimethacrylate (bis-acryl) dental polymers. WLF time-temperature superposition procedure of logarithmic shift of the data from other temperatures to those at 37 degrees C was used to generate extended master curves of relaxation modulus changes with time. The extended data were analyzed for conformity to three different predictive models of stress relaxation including Maxwell, KWW stretched exponential function and Nutting’s power law equation. Results. Maxwell model was found to be a poor fit for the extended data in all polymers tested, but the data showed a much better fit for KWW (0.870 smaller than R-2 smaller than 0.901) and Nutting’s (0.980 smaller than R-2 smaller than 0.986) models. The non-exponential factor beta in the KWW function and the fractional JPH203 cost power exponent n in Nutting’s equation were both significantly different for PEMA based system when compared to that of PMMA and bis-acryl systems. Significance. The mean values of beta in KWW function and power exponent n in Nutting’s equation for PEMA resin is consistent with significant viscoplastic contribution to its deformation under stress unlike in PMMA and bis-acryl resin systems. This may have significant bearing for PEMA use in medium to longer term stress-bearing applications even as a temporization material. (C) 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.