The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Einar Stefansson - One of the best experts on this subject based on the ideXlab platform.
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diffusion characteristics of vitreous humour and saline solution follow the stokes Einstein Equation
Graefes Archive for Clinical and Experimental Ophthalmology, 2009Co-Authors: Svanborg Gisladottir, Thorsteinn Loftsson, Einar StefanssonAbstract:Purpose The Stokes–Einstein Equation predicts that diffusion is inversely correlated with viscosity of the medium. This predicts that diffusion fluxes should be lower in vitreous humour than in saline solution with lower viscosity. We test this hypothesis, which has implications for vitrectomy.
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diffusion characteristics of vitreous humour and saline solution follow the stokes Einstein Equation
Graefes Archive for Clinical and Experimental Ophthalmology, 2009Co-Authors: Svanborg Gisladottir, Thorsteinn Loftsson, Einar StefanssonAbstract:The Stokes–Einstein Equation predicts that diffusion is inversely correlated with viscosity of the medium. This predicts that diffusion fluxes should be lower in vitreous humour than in saline solution with lower viscosity. We test this hypothesis, which has implications for vitrectomy. Diffusion cells were used, with a middle chamber filled with saline solution with different concentrations of hyaluronic acid (0 µg/ml, 30 µg/ml, 90 µg/ml and 180 µg/ml) or porcine vitreous humour, between cellophane membranes. HPLC was used to measure the concentration of the diffusing molecule, dexamethasone, and calculate the flux through the chamber filled with the various media. The diffusion coefficients were calculated, using Fick's law. Viscosity was measured with a Brookfield digital DV-I+viscometer. The diffusion coefficient for dexamethasone in vitreous humour is 0.065 ± 0.022 cm2/hour, 0.26 ± 0.12 cm2/hour for saline alone, 0.17 ± 0.04 cm2/hour for saline with 30 µg/ml hyaluronan, 0.076 ± 0.009 cm2/hour with 90 µg/ml hyaluronan, and with 180 µg/ml hyaluronan 0.072 ± 0.0018 cm2/hour (p < 0.001). The viscosity of liquid vitreous is 6.29 ± 2.3 cp, and the viscosity of saline alone is 1.01 ± 0.008 cp. For saline with 30 µg/ml of hyaluronan the viscosity is 1.04 ± 0.015, with 90 µg/ml hyaluronan is 1.06 ± 0.01, and with 180 µg/ml hyaluronan is 1.08 ± 0.014 (p < 0.001). Dexamethasone diffuses four times faster through saline solution than vitreous humour. Liquid vitreous humour is about six times more viscous than saline. The results indicate that diffusion is faster in saline solution than in vitreous humour, in accordance to the Stokes–Einstein Equation. This finding can help explain some of the physiological, pharmacological and clinical consequences of vitrectomy.
Tadashi Takayanagi - One of the best experts on this subject based on the ideXlab platform.
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entropic counterpart of perturbative Einstein Equation
arXiv: High Energy Physics - Theory, 2013Co-Authors: Jyotirmoy Bhattacharya, Tadashi TakayanagiAbstract:Entanglement entropy in a field theory, with a holographic dual, may be viewed as a quantity which encodes the diffeomorphism invariant bulk gravity dynamics. This, in particular, indicates that the bulk Einstein Equations would imply some constraints for the boundary entanglement entropy. In this paper we focus on the change in entanglement entropy, for small but arbitrary fluctuations about a given state, and analyze the constraints imposed on it by the perturbative Einstein Equations, linearized about the corresponding bulk state. Specifically, we consider linear fluctuations about BTZ black hole in 3 dimension, pure AdS and AdS Schwarzschild black holes in 4 dimensions and obtain a diffeomorphism invariant reformulation of linearized Einstein Equation in terms of holographic entanglement entropy. We will also show that entanglement entropy for boosted subsystems provides the information about all the components of the metric with a time index.
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dynamics of entanglement entropy from Einstein Equation
Physical Review D, 2013Co-Authors: Masahiro Nozaki, Tokiro Numasawa, Andrea Prudenziati, Tadashi TakayanagiAbstract:We study the dynamics of entanglement entropy for weakly excited states in conformal field theories by using anti-de Sitter/conformal field theory (AdS/CFT). This is aimed at a first step to finding a counterpart of the Einstein Equation in CFT language. In particular, we point out that the entanglement entropy satisfies differential Equations that directly correspond to the Einstein Equation in several setups of AdS/CFT. We also define a quantity called entanglement density in higher dimensional field theories and study its dynamical property for weakly excited states in conformal field theories.
Jonathan P Reid - One of the best experts on this subject based on the ideXlab platform.
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accurate prediction of organic aerosol evaporation using kinetic multilayer modeling and the stokes Einstein Equation
Journal of Physical Chemistry A, 2021Co-Authors: Stephen Ingram, Youngchul Song, David Topping, Cari S Dutcher, Grazia Rovelli, Shihao Liu, Lucy Nandy, Manabu Shiraiwa, Jonathan P ReidAbstract:Organic aerosol can adopt a wide range of viscosities, from liquid to glass, depending on the local humidity. In highly viscous droplets, the evaporation rates of organic components are suppressed to varying degrees, yet water evaporation remains fast. Here, we examine the coevaporation of semivolatile organic compounds (SVOCs), along with their solvating water, from aerosol particles levitated in a humidity-controlled environment. To better replicate the composition of secondary aerosol, nonvolatile organics were also present, creating a three-component diffusion problem. Kinetic modeling reproduced the evaporation accurately when the SVOCs were assumed to obey the Stokes-Einstein relation, and water was not. Crucially, our methodology uses previously collected data to constrain the time-dependent viscosity, as well as water diffusion coefficients, allowing it to be predictive rather than postdictive. Throughout the study, evaporation rates were found to decrease as SVOCs deplete from the particle, suggesting path function type behavior.
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transient cavity dynamics and divergence from the stokes Einstein Equation in organic aerosol
Chemical Science, 2020Co-Authors: Youngchul Song, Stephen Ingram, Robert E Arbon, David Topping, David R Glowacki, Jonathan P ReidAbstract:The diffusion of small molecules through viscous matrices formed by large organic molecules is important across a range of domains, including pharmaceutical science, materials chemistry, and atmospheric science, impacting on, for example, the formation of amorphous and crystalline phases. Here we report significant breakdowns in the Stokes–Einstein (SE) Equation from measurements of the diffusion of water (spanning 5 decades) and viscosity (spanning 12 decades) in saccharide aerosol droplets. Molecular dynamics simulations show water diffusion is not continuous, but proceeds by discrete hops between transient cavities that arise and dissipate as a result of dynamical fluctuations within the saccharide lattice. The ratio of transient cavity volume to solvent volume increases with size of molecules making up the lattice, increasing divergence from SE predictions. This improved mechanistic understanding of diffusion in viscous matrices explains, for example, why organic compounds equilibrate according to SE predictions and water equilibrates more rapidly in aerosols.
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diffusion and reactivity in ultraviscous aerosol and the correlation with particle viscosity
Chemical Science, 2016Co-Authors: Frances H Marshall, Youngchul Song, Jonathan P Reid, Rachael E H Miles, Rory M Power, Cari S DutcherAbstract:The slow transport of water, organic species and oxidants in viscous aerosol can lead to aerosol existing in transient states that are not solely governed by thermodynamic principles but by the kinetics of gas-particle partitioning. The relationship between molecular diffusion constants and particle viscosity (for example, as reflected in the Stokes-Einstein Equation) is frequently considered to provide an approximate guide to relate the kinetics of aerosol transformation with a material property of the aerosol. We report direct studies of both molecular diffusion and viscosity in the aerosol phase for the ternary system water/maleic acid/sucrose, considering the relationship between the hygroscopic response associated with the change in water partitioning, the volatilisation of maleic acid, the ozonolysis kinetics of maleic acid and the particle viscosity. Although water clearly acts as a plasticiser, the addition of minor fractions of other organic moieties can similarly lead to significant changes in the viscosity from that expected for the dominant component forming the organic matrix (sucrose). Here we highlight that the Stokes-Einstein relationship between the diffusion constant of water and the viscosity of the particle may be more than an order of magnitude in error, even at viscosities as low as 1 Pa s. We show that the thermodynamic relationships of hygroscopic response that underpin such kinetic determinations must be accurately known to retrieve accurate values for diffusion constants; such data are often not available. Further, we show that scaling of the diffusion constants of organic molecules of similar size to those forming the matrix with particle viscosity may be well represented by the Stokes-Einstein Equation, suppressing the apparent volatility of semi-volatile components. Finally, the variation in uptake coefficients and diffusion constants for oxidants and small weakly interacting molecules may be much less dependent on viscosity than the diffusion constants of more strongly interacting molecules such as water.
Svanborg Gisladottir - One of the best experts on this subject based on the ideXlab platform.
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diffusion characteristics of vitreous humour and saline solution follow the stokes Einstein Equation
Graefes Archive for Clinical and Experimental Ophthalmology, 2009Co-Authors: Svanborg Gisladottir, Thorsteinn Loftsson, Einar StefanssonAbstract:Purpose The Stokes–Einstein Equation predicts that diffusion is inversely correlated with viscosity of the medium. This predicts that diffusion fluxes should be lower in vitreous humour than in saline solution with lower viscosity. We test this hypothesis, which has implications for vitrectomy.
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diffusion characteristics of vitreous humour and saline solution follow the stokes Einstein Equation
Graefes Archive for Clinical and Experimental Ophthalmology, 2009Co-Authors: Svanborg Gisladottir, Thorsteinn Loftsson, Einar StefanssonAbstract:The Stokes–Einstein Equation predicts that diffusion is inversely correlated with viscosity of the medium. This predicts that diffusion fluxes should be lower in vitreous humour than in saline solution with lower viscosity. We test this hypothesis, which has implications for vitrectomy. Diffusion cells were used, with a middle chamber filled with saline solution with different concentrations of hyaluronic acid (0 µg/ml, 30 µg/ml, 90 µg/ml and 180 µg/ml) or porcine vitreous humour, between cellophane membranes. HPLC was used to measure the concentration of the diffusing molecule, dexamethasone, and calculate the flux through the chamber filled with the various media. The diffusion coefficients were calculated, using Fick's law. Viscosity was measured with a Brookfield digital DV-I+viscometer. The diffusion coefficient for dexamethasone in vitreous humour is 0.065 ± 0.022 cm2/hour, 0.26 ± 0.12 cm2/hour for saline alone, 0.17 ± 0.04 cm2/hour for saline with 30 µg/ml hyaluronan, 0.076 ± 0.009 cm2/hour with 90 µg/ml hyaluronan, and with 180 µg/ml hyaluronan 0.072 ± 0.0018 cm2/hour (p < 0.001). The viscosity of liquid vitreous is 6.29 ± 2.3 cp, and the viscosity of saline alone is 1.01 ± 0.008 cp. For saline with 30 µg/ml of hyaluronan the viscosity is 1.04 ± 0.015, with 90 µg/ml hyaluronan is 1.06 ± 0.01, and with 180 µg/ml hyaluronan is 1.08 ± 0.014 (p < 0.001). Dexamethasone diffuses four times faster through saline solution than vitreous humour. Liquid vitreous humour is about six times more viscous than saline. The results indicate that diffusion is faster in saline solution than in vitreous humour, in accordance to the Stokes–Einstein Equation. This finding can help explain some of the physiological, pharmacological and clinical consequences of vitrectomy.
R P Woodard - One of the best experts on this subject based on the ideXlab platform.
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hartree approximation to the one loop quantum gravitational correction to the graviton mode function on de sitter
Journal of Cosmology and Astroparticle Physics, 2013Co-Authors: P J Mora, N C Tsamis, R P WoodardAbstract:We use the Hartree approximation to the Einstein Equation on de Sitter background to solve for the one loop correction to the graviton mode function. This should give a reasonable approximation to how the ensemble of inflationary gravitons affects a single external graviton. At late times we find that the one loop correction to the plane wave mode function u(η,k) goes like GH{sup 2}ln (a)/a{sup 2}, where a is the inflationary scale factor. One consequence is that the one loop corrections to the ''electric'' components of the linearized Weyl tensor grow compared to the tree order result.
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hartree approximation to the one loop quantum gravitational correction to the graviton mode function on de sitter
arXiv: General Relativity and Quantum Cosmology, 2013Co-Authors: P J Mora, N C Tsamis, R P WoodardAbstract:We use the Hartree approximation to the Einstein Equation on de Sitter background to solve for the one loop correction to the graviton mode function. This should give a reasonable approximation to how the ensemble of inflationary gravitons affects a single external graviton. At late times we find that the one loop correction to the plane wave mode function $u(\eta,k)$ goes like $G H^2 \ln(a)/a^2$, where $a$ is the inflationary scale factor. One consequence is that the one loop corrections to the "electric" components of the linearized Weyl tensor grow compared to the tree order result.