The Experts below are selected from a list of 15960 Experts worldwide ranked by ideXlab platform
Shelley L Anna - One of the best experts on this subject based on the ideXlab platform.
-
diffusion limited adsorption to a Spherical geometry the impact of curvature and competitive time scales
Physical Review E, 2010Co-Authors: Nicolas J Alvarez, Lynn M Walker, Shelley L AnnaAbstract:Although the time scale governing diffusion-limited transport of soluble species from solution onto a planar Interface is well understood, the time scale governing transport onto a Spherical Interface is not. The time scales that have been proposed in the literature for Spherical Interfaces do not capture the correct asymptotic behavior for increasing bubble radius and do not capture previously reported experimental observations of the effect of concentration. This paper develops a diffusion-limited time scale that is dependent on an intrinsic length scale termed the Spherical depletion depth. The time scale is determined by considering a specific example of diffusion-limited transport of surfactant species to a water-air Interface and is verified using numerical simulations and experiments. This newly derived diffusion time scale will have a significant impact on our understanding of fundamental phenomena at Spherical fluid-fluid and fluid-solid Interfaces, especially those involving micrometer and nanometer length scales.
-
a microtensiometer to probe the effect of radius of curvature on surfactant transport to a Spherical Interface
Langmuir, 2010Co-Authors: Nicolas J Alvarez, Lynn M Walker, Shelley L AnnaAbstract:Diffusion of surfactant to a Spherical Interface depends on the radius of curvature of the Interface; the smaller the radius of curvature is, the faster the dynamics. This paper presents and validates an experimental apparatus, denoted a “microtensiometer”, to study the dependence of surfactant dynamics on radius of curvature. Dynamic surface tension is monitored for a range of bubble radii from 17 to 150 μm, and the dynamics are compared with those obtained using the classic pendant drop experiment for a nonionic surfactant at the air−water Interface. Experiments reveal that dynamic surface tension follows a diffusion-limited scaling, in which radius of curvature is a key parameter. Despite the clear scaling behavior of the experimental equilibration time, the full dynamic curve for an initially clean Interface cannot be predicted by a diffusion-limited transport model using the molecular diffusion coefficient and a single isotherm. However, the same model is shown to correctly predict compression−expans...
Nicolas J Alvarez - One of the best experts on this subject based on the ideXlab platform.
-
diffusion limited adsorption to a Spherical geometry the impact of curvature and competitive time scales
Physical Review E, 2010Co-Authors: Nicolas J Alvarez, Lynn M Walker, Shelley L AnnaAbstract:Although the time scale governing diffusion-limited transport of soluble species from solution onto a planar Interface is well understood, the time scale governing transport onto a Spherical Interface is not. The time scales that have been proposed in the literature for Spherical Interfaces do not capture the correct asymptotic behavior for increasing bubble radius and do not capture previously reported experimental observations of the effect of concentration. This paper develops a diffusion-limited time scale that is dependent on an intrinsic length scale termed the Spherical depletion depth. The time scale is determined by considering a specific example of diffusion-limited transport of surfactant species to a water-air Interface and is verified using numerical simulations and experiments. This newly derived diffusion time scale will have a significant impact on our understanding of fundamental phenomena at Spherical fluid-fluid and fluid-solid Interfaces, especially those involving micrometer and nanometer length scales.
-
a microtensiometer to probe the effect of radius of curvature on surfactant transport to a Spherical Interface
Langmuir, 2010Co-Authors: Nicolas J Alvarez, Lynn M Walker, Shelley L AnnaAbstract:Diffusion of surfactant to a Spherical Interface depends on the radius of curvature of the Interface; the smaller the radius of curvature is, the faster the dynamics. This paper presents and validates an experimental apparatus, denoted a “microtensiometer”, to study the dependence of surfactant dynamics on radius of curvature. Dynamic surface tension is monitored for a range of bubble radii from 17 to 150 μm, and the dynamics are compared with those obtained using the classic pendant drop experiment for a nonionic surfactant at the air−water Interface. Experiments reveal that dynamic surface tension follows a diffusion-limited scaling, in which radius of curvature is a key parameter. Despite the clear scaling behavior of the experimental equilibration time, the full dynamic curve for an initially clean Interface cannot be predicted by a diffusion-limited transport model using the molecular diffusion coefficient and a single isotherm. However, the same model is shown to correctly predict compression−expans...
George Jackson - One of the best experts on this subject based on the ideXlab platform.
-
surface thermodynamics of planar cylindrical and Spherical vapour liquid Interfaces of water
Journal of Chemical Physics, 2015Co-Authors: Gabriel V Lau, Ian J Ford, Patricia A Hunt, Erich A Muller, George JacksonAbstract:The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar Interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid Interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derived for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and Spherical fluid Interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the Spherical Interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a Spherical Interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and Spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 A, below which the tension is found to decrease again. In the case of Spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 A; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large system sizes for both the cylindrical and Spherical cases. Estimates of the entropic and energetic contributions are also evaluated for the planar and cylindrical geometries and their magnitudes are in line with the expectations of our simple analysis.
M Tachiya - One of the best experts on this subject based on the ideXlab platform.
-
a model for diffusive transport through a Spherical Interface probed by pulsed field gradient nmr
Biophysical Journal, 1998Co-Authors: William S Price, Alexander V Barzykin, Kikuko Hayamizu, M TachiyaAbstract:Abstract In biological systems, because of higher intracellular viscosity and/or the restriction of the diffusion space inside cells, the (apparent) diffusion coefficient of an intracellular species (e.g., water) is generally smaller than when it is in the extracellular medium. This difference affects the spin-echo signal attenuation in the pulsed field gradient NMR experiment and thus affords a means of separating the intracellular from the extracellular species, thereby providing a basis for studying transmembrane transport. Such experiments have commonly been analyzed using the macroscopic model of Karger (see Adv. Magn. Reson . 21:1–89 (1988)). In our previous study, we considered a microscopic model of diffusive transport through a Spherical Interface using the short gradient pulse approximation ( J. Magn. Reson. A114:39–46 (1995)). The spins in the external medium were modeled with the "partially absorbing wall" condition or as having a small but finite lifetime. In the present paper, we extend our treatment to the case in which there is no limitation upon the lifetime in either medium. We also consider a simple modification of Karger's model that more properly accounts for the restricted intracellular diffusion. Importantly, it was found that the exact solution within the short gradient pulse approximation developed here and the modified Karger model are in close agreement in the (experimentally relevant) long-time limit. The results of this study show that when there is no limitation upon the lifetime of the transported species in either phase, the spin-echo attenuation curve is very sensitive to transport.
Lynn M Walker - One of the best experts on this subject based on the ideXlab platform.
-
diffusion limited adsorption to a Spherical geometry the impact of curvature and competitive time scales
Physical Review E, 2010Co-Authors: Nicolas J Alvarez, Lynn M Walker, Shelley L AnnaAbstract:Although the time scale governing diffusion-limited transport of soluble species from solution onto a planar Interface is well understood, the time scale governing transport onto a Spherical Interface is not. The time scales that have been proposed in the literature for Spherical Interfaces do not capture the correct asymptotic behavior for increasing bubble radius and do not capture previously reported experimental observations of the effect of concentration. This paper develops a diffusion-limited time scale that is dependent on an intrinsic length scale termed the Spherical depletion depth. The time scale is determined by considering a specific example of diffusion-limited transport of surfactant species to a water-air Interface and is verified using numerical simulations and experiments. This newly derived diffusion time scale will have a significant impact on our understanding of fundamental phenomena at Spherical fluid-fluid and fluid-solid Interfaces, especially those involving micrometer and nanometer length scales.
-
a microtensiometer to probe the effect of radius of curvature on surfactant transport to a Spherical Interface
Langmuir, 2010Co-Authors: Nicolas J Alvarez, Lynn M Walker, Shelley L AnnaAbstract:Diffusion of surfactant to a Spherical Interface depends on the radius of curvature of the Interface; the smaller the radius of curvature is, the faster the dynamics. This paper presents and validates an experimental apparatus, denoted a “microtensiometer”, to study the dependence of surfactant dynamics on radius of curvature. Dynamic surface tension is monitored for a range of bubble radii from 17 to 150 μm, and the dynamics are compared with those obtained using the classic pendant drop experiment for a nonionic surfactant at the air−water Interface. Experiments reveal that dynamic surface tension follows a diffusion-limited scaling, in which radius of curvature is a key parameter. Despite the clear scaling behavior of the experimental equilibration time, the full dynamic curve for an initially clean Interface cannot be predicted by a diffusion-limited transport model using the molecular diffusion coefficient and a single isotherm. However, the same model is shown to correctly predict compression−expans...