The Experts below are selected from a list of 14697 Experts worldwide ranked by ideXlab platform
M. Roux - One of the best experts on this subject based on the ideXlab platform.
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Diatom-based Ionic Concentration and salinity models from the south Bolivian Altiplano (15–23 ° S
Journal of Paleolimnology, 2001Co-Authors: Florence Sylvestre, S. Servant-vildary, M. RouxAbstract:The relationship between surface sediment diatom assemblages and measured limnological variables in fifty eight lake samples from the south Bolivian Altiplano was examined by constructing a diatom-water chemistry dataset. Analysis of this dataset by canonical correspondence analysis revealed that salinity and Ionic Concentration accounted for a significant amount of the variation in the distribution of the diatom assemblages. Two methods ‘weighted-averaging regression and calibration’, and ‘by-class mean percentage table’ were used to established a transfer function for future reconstruction of past lake water salinity and Ionic Concentration in the southern Bolivian Altiplano. Weighted-averaging regression and calibration with inverse deshrinking provided a better model for the water chemistry reconstructions in this region.
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Diatom-based Ionic Concentration and salinity models from the south Bolivian Altiplano (15-23 degrees S)
Journal of Paleolimnology, 2001Co-Authors: Florence Sylvestre, S. Servant-vildary, M. RouxAbstract:The relationship between surface sediment diatom assemblages and measured limnological variables in fifty eight lake samples from the south Bolivian Altiplano was examined by constructing a diatom-water chemistry dataset. Analysis of this dataset by canonical correspondence analysis revealed that salinity and Ionic Concentration accounted for a significant amount of the variation in the distribution of the diatom assemblages. Two methods `weighted-averaging regression and calibration', and `by-class mean percentage table' were used to established a transfer function for future reconstruction of past lake water salinity and Ionic Concentration in the southern Bolivian Altiplano. Weighted-averaging regression and calibration with inverse deshrinking provided a better model for the water chemistry reconstructions in this region.
Florence Sylvestre - One of the best experts on this subject based on the ideXlab platform.
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Diatom-based Ionic Concentration and salinity models from the south Bolivian Altiplano (15–23 ° S
Journal of Paleolimnology, 2001Co-Authors: Florence Sylvestre, S. Servant-vildary, M. RouxAbstract:The relationship between surface sediment diatom assemblages and measured limnological variables in fifty eight lake samples from the south Bolivian Altiplano was examined by constructing a diatom-water chemistry dataset. Analysis of this dataset by canonical correspondence analysis revealed that salinity and Ionic Concentration accounted for a significant amount of the variation in the distribution of the diatom assemblages. Two methods ‘weighted-averaging regression and calibration’, and ‘by-class mean percentage table’ were used to established a transfer function for future reconstruction of past lake water salinity and Ionic Concentration in the southern Bolivian Altiplano. Weighted-averaging regression and calibration with inverse deshrinking provided a better model for the water chemistry reconstructions in this region.
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Diatom-based Ionic Concentration and salinity models from the south Bolivian Altiplano (15-23 degrees S)
Journal of Paleolimnology, 2001Co-Authors: Florence Sylvestre, S. Servant-vildary, M. RouxAbstract:The relationship between surface sediment diatom assemblages and measured limnological variables in fifty eight lake samples from the south Bolivian Altiplano was examined by constructing a diatom-water chemistry dataset. Analysis of this dataset by canonical correspondence analysis revealed that salinity and Ionic Concentration accounted for a significant amount of the variation in the distribution of the diatom assemblages. Two methods `weighted-averaging regression and calibration', and `by-class mean percentage table' were used to established a transfer function for future reconstruction of past lake water salinity and Ionic Concentration in the southern Bolivian Altiplano. Weighted-averaging regression and calibration with inverse deshrinking provided a better model for the water chemistry reconstructions in this region.
S. Servant-vildary - One of the best experts on this subject based on the ideXlab platform.
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Diatom-based Ionic Concentration and salinity models from the south Bolivian Altiplano (15–23 ° S
Journal of Paleolimnology, 2001Co-Authors: Florence Sylvestre, S. Servant-vildary, M. RouxAbstract:The relationship between surface sediment diatom assemblages and measured limnological variables in fifty eight lake samples from the south Bolivian Altiplano was examined by constructing a diatom-water chemistry dataset. Analysis of this dataset by canonical correspondence analysis revealed that salinity and Ionic Concentration accounted for a significant amount of the variation in the distribution of the diatom assemblages. Two methods ‘weighted-averaging regression and calibration’, and ‘by-class mean percentage table’ were used to established a transfer function for future reconstruction of past lake water salinity and Ionic Concentration in the southern Bolivian Altiplano. Weighted-averaging regression and calibration with inverse deshrinking provided a better model for the water chemistry reconstructions in this region.
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Diatom-based Ionic Concentration and salinity models from the south Bolivian Altiplano (15-23 degrees S)
Journal of Paleolimnology, 2001Co-Authors: Florence Sylvestre, S. Servant-vildary, M. RouxAbstract:The relationship between surface sediment diatom assemblages and measured limnological variables in fifty eight lake samples from the south Bolivian Altiplano was examined by constructing a diatom-water chemistry dataset. Analysis of this dataset by canonical correspondence analysis revealed that salinity and Ionic Concentration accounted for a significant amount of the variation in the distribution of the diatom assemblages. Two methods `weighted-averaging regression and calibration', and `by-class mean percentage table' were used to established a transfer function for future reconstruction of past lake water salinity and Ionic Concentration in the southern Bolivian Altiplano. Weighted-averaging regression and calibration with inverse deshrinking provided a better model for the water chemistry reconstructions in this region.
Ali Nokhodchi - One of the best experts on this subject based on the ideXlab platform.
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effect of Ionic strength and ph of dissolution media on theophylline release from hypromellose matrix tablets apparatus usp iii simulated fasted and fed conditions
Carbohydrate Polymers, 2011Co-Authors: Kofi Asareaddo, Marina Levina, Ali R Rajabisiahboomi, Ali NokhodchiAbstract:Abstract The objectives of this study were to evaluate the effects of different media Ionic Concentration strengths and pH on the release of theophylline from a gel forming hydrophilic polymeric matrix. Theophylline extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC)) were evaluated in media with a pH range of 1.2–7.5, using an automated USP type III, Bio-Dis dissolution apparatus. The Ionic Concentration strength of the media was varied over a range of 0–0.4 M to simulate the gastrointestinal fed and fasted states and various physiological pH conditions. Sodium chloride was used for Ionic regulation due to its ability to salt out polymers in the midrange of the lyotropic series. The results showed that the Ionic Concentration strength had a profound effect on the drug release from the K100LV matrices. At pH 1.2 theophylline releases increased significantly within the first hour from 28% in water to 48% in the medium with Ionic strength of 0.49 M. The K4M, K15M and K100M tablets, however, withstood the effects of media to the same extend at all Ionic Concentration strengths investigated. The similarity factor f2 was calculated using drug release in water as a reference. For the K100M matrices, f2 values of 74 (pH media), 80 (0.2 M media) and 72 (0.4 M media) suggested that it was the most resilient of all the matrices studied here. DSC hydration results explained the theophylline release from their HPMC matrices. Despite an increase in the percentage of bound water for the tablets made with high viscosity polymers K4M, K15M and K100M, they were, however, resilient to the Ionic Concentration strength effects as they were still able to form a strong gel layer. This methodology can be used as a valuable tool for predicting potential Ionic effects related to in vivo fed and fasted states on drug release from hydrophilic ER matrices.
Serge Stoll - One of the best experts on this subject based on the ideXlab platform.
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Nanoparticle adsorption on a weak polyelectrolyte. Stiffness, pH, charge mobility, and Ionic Concentration effects investigated by Monte Carlo simulations.
The journal of physical chemistry. B, 2006Co-Authors: Serge Ulrich, Marianne Seijo, And Abohachem Laguecir, Serge StollAbstract:Monte Carlo simulations have been used to study two different models for a weak linear polyelectrolyte in the presence of nanoparticles: (i) a rodlike and (ii) a flexible polyelectrolytes. The use of simulated annealing has made it possible to simulate a polyelectrolyte chain in the presence of several nanoparticles by improving conformation sampling and avoiding multiple minima problems when dense conformations are produced. Nanoparticle distributions along the polymer backbone were analyzed versus the Ionic Concentration, polyelectrolyte stiffness, and nanoparticle surface charge. Titration curves were calculated and the influences of the Ionic Concentration, solution pH, and number of adsorbed nanoparticles on the acid/base polyelectrolyte properties have been systematically investigated. The subtle balance of attractive and repulsive interactions has been discussed, and some characteristic conformations are presented. The comparison of the two limit models provides a good representation of the stiffn...
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Polyelectrolyte–particle complex formation. Polyelectrolyte linear charge density and Ionic Concentration effects. Monte Carlo simulations
Colloid & Polymer Science, 2002Co-Authors: Marcin Brynda, Pierre Chodanowski, Serge StollAbstract:The influence of the linear charge density (LCD) of a polyelectrolyte on its adsorption on an oppositely charged colloidal particle is investigated by Monte Carlo simulations. Adsorption characteristics are studied at different linear charge densities and Ionic Concentrations and for a given polyelectrolyte/particle size ratio so that particle curvature has full effect. The isolated polyelectrolyte goes through a smooth transition from a collapsed structure to an extended rod-like conformation with increasing the linear charge density in the low Ionic Concentration regime. In the high Ionic Concentration regime, the polyelectrolyte is less sensitive to the increase in the linear charge density and adopts a coil conformation. We found that complex formation is promoted by decreasing the Ionic Concentration and increasing the linear charge density and that large changes in the polymer dimensions are observed at the adsorption–desorption limit. By adjusting the linear charge density and Ionic strength, we demonstrate that the adsorption–desorption limit corresponds to a sharp transition from non-adsorbed to adsorbed conformations and that the mean adsorption energy per monomer has to be less than –0.4 kT to achieve adsorption. We calculated that the linear charge density at the adsorption–desorption limit is related to the Debye-Huckel length according to LCDcrit ~κ 2. At small values of the linear charge density and low Ionic strength (no adsorption is observed at high Ionic strength), a large amount of monomers are present in loops and tails. By increasing LCD, the amount of monomers in trains reaches a maximum value and the polyelectrolyte adopt flat conformation at the surface of the particle.
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Polyelectrolyte adsorption on charged particles: Ionic Concentration and particle size effects—A Monte Carlo approach
The Journal of Chemical Physics, 2001Co-Authors: Pierre Chodanowski, Serge StollAbstract:The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and Ionic Concentration on the adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on polyelectrolyte adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a polyelectrolyte/particle complex and the conformations of the adsorbed polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers...
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polyelectrolyte adsorption on charged particles Ionic Concentration and particle size effects a monte carlo approach
Journal of Chemical Physics, 2001Co-Authors: Pierre Chodanowski, Serge StollAbstract:The complexation between a charged polymer and an oppositely charged spherical particle is investigated using Monte Carlo simulations. Electrostatic interactions are described in the Debye–Huckel approximation. The influence of particle size and Ionic Concentration on the adsorption/desorption limit, interfacial structure of the adsorbed layer, amount of adsorbed polymer, and the overcharging issue is investigated. Attention is focused on polyelectrolyte adsorption on small spherical particles whose surface curvature effects are expected to limit the amount of adsorbed monomers, large particles that allow the polyelectrolyte to spread to the same extent as on a flat surface, and particles whose radius is close to the polyelectrolyte radius of gyration so that the chain can completely wrap around it. The formation of a polyelectrolyte/particle complex and the conformations of the adsorbed polyelectrolyte are found to result from two competing effects: the electrostatic repulsions between the chain monomers...
