We show that the kinetics of a molecular motor fueled by ATP and operating between a deactivated and an activated state can be derived from the principles of non-equilibrium thermodynamics applied to ...the mesoscopic domain. The activation by ATP, the possible slip of the motor, as well as the forward stepping carrying a load are viewed as slow diffusion along a reaction coordinate. Local equilibrium is assumed in the reaction coordinate spaces, making it possible to derive the non-equilibrium thermodynamic description. Using this scheme, we find expressions for the velocity of the motor, in terms of the driving force along the spacial coordinate, and for the chemical reaction that brings about activation, in terms of the chemical potentials of the reactants and products which maintain the cycle. The second law efficiency is defined, and the velocity corresponding to maximum power is obtained for myosin movement on actin. Experimental results fitting with the description are reviewed, giving a maximum efficiency of 0.45 at a myosin headgroup velocity of 5 × 10
−7
m s
−1
. The formalism allows the introduction and test of meso-level models, which may be needed to explain experiments.
A thermodynamic non-linear rate theory for molecular motors is developed, relating measured variables to the efficiency of muscular contraction.
In earlier work a systematic extension of the van der Waals square gradient model to nonequilibrium one-component systems was given. In this work the focus was on heat and mass transfer through the ...liquid-vapor interface as caused by a temperature difference or an over- or underpressure. We will give an extension of this approach to multicomponent nonequilibrium systems in the systematic context of nonequilibrium thermodynamics. An explicit expression for the pressure tensor is derived valid also for curved surfaces. It is shown how the Gibbs relation should be modified in the interfacial region, in both equilibrium and nonequilibrium. The two-dimensional isotropy of a curved interface is discussed. Furthermore, we give numerically obtained profiles of the concentration, the mole fraction, and the temperature, which illustrate the solution for some special cases.
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We present a mathematical procedure for the determination of the driving force distribution in a chemical reactor that has minimum lost work for a given production rate. It is shown how the path of ...minimum lost work is determined from knowlegde of reaction kinetics, using the reaction A → B as an example. The normal chemical reaction has a nonlinear relation between the rate, r, and the driving force, −A/T, where A is the affinity and T is the absolute temperature. Minimum lost work is obtained when A/T + r d(A/T)/dr is constant. This criterion is converted into a more practical criterion for the operating temperature along the reactor. The inverse operating temperature should be parallel to the inverse equilibrium temperature, when the enthalpy of reaction is constant.
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•We extend the ‘Small System Method’ for CO2 gas on a graphite surface.•Chemical potential, activity coefficient and enthalpy of CO2 (ads) are obtained from molecular dynamics simulations.•Two ...distinct layers of CO2 are in equilibrium.
We find by examination of density profiles that carbon dioxide adsorbs on graphite in two distinct layers. We report the activity coefficient, entropy and enthalpy for CO2 in each layer using a convenient computational method, the Small System Method, thereby extending this method to surfaces. This opens up the possibility to study thermodynamic properties for a wide range of surface phenomena.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Thermodynamic equilibrium for adsorption means that the chemical potential of gas and adsorbed phase are equal. A precise knowledge of the chemical potential is, however, often lacking, because the ...activity coefficient of the adsorbate is not known. Adsorption isotherms are therefore commonly fitted to ideal models such as the Langmuir, Sips or Henry models. We propose here a new procedure to find the activity coefficient and the equilibrium constant for adsorption which uses the thermodynamic factor. Instead of fitting the data to a model, we calculate the thermodynamic factor and use this to find first the activity coefficient. We show, using published molecular simulation data, how this procedure gives the thermodynamic equilibrium constant and enthalpies of adsorption for CO
2
(g) on graphite. We also use published experimental data to find similar thermodynamic properties of CO
2
(g) and of CH
4
(g) adsorbed on activated carbon. The procedure gives a higher accuracy in the determination of enthalpies of adsorption than ideal models do.
Thermodynamic equilibrium for adsorption means that the chemical potential of gas and adsorbed phase are equal.
Using a method introduced by Albano et al (Albano, A. M.; Bedeaux, D.; Vlieger, J. Phys. A 1979, 99, 293. Albano, A. M.; Bedeaux, D.; Vlieger, J. Phys. A 1980, 102, 105), we derive an exact analytic ...expression for the dipolar coefficient of a charged sphere in an electrolyte as a function of the frequency which is valid for all double layer thicknesses and is given both for low and for high zeta potentials. The expression is found to have the same form as the expression for a sphere surrounded by a multiple of shells of different complex conductivities. One shell can then be attributed to the double layer and another to a diffusion layer. Including a Stern layer in the model subsequently adds another shell with associated complex dielectric permittivity.
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Thermodynamic equilibrium for adsorption means that the chemical potential of gas and adsorbed phase are equal. A precise knowledge of the chemical potential is, however, often lacking, because the ...activity coefficient of the adsorbate is not known. Adsorption isotherms are therefore commonly fitted to ideal models such as the Langmuir, Sips or Henry models. We propose here a new procedure to find the activity coefficient and the equilibrium constant for adsorption which uses the thermodynamic factor. Instead of fitting the data to a model, we calculate the thermodynamic factor and use this to find first the activity coefficient. We show, using published molecular simulation data, how this procedure gives the thermodynamic equilibrium constant and enthalpies of adsorption for CO sub(2)(g) on graphite. We also use published experimental data to find similar thermodynamic properties of CO sub(2)(g) and of CH sub(4)(g) adsorbed on activated carbon. The procedure gives a higher accuracy in the determination of enthalpies of adsorption than ideal models do.
Thermodynamic equilibrium for adsorption means that the chemical potential of gas and adsorbed phase are equal. A precise knowledge of the chemical potential is, however, often lacking, because the ...activity coefficient of the adsorbate is not known. Adsorption isotherms are therefore commonly fitted to ideal models such as the Langmuir, Sips or Henry models. We propose here a new procedure to find the activity coefficient and the equilibrium constant for adsorption which uses the thermodynamic factor. Instead of fitting the data to a model, we calculate the thermodynamic factor and use this to find first the activity coefficient. We show, using published molecular simulation data, how this procedure gives the thermodynamic equilibrium constant and enthalpies of adsorption for CO 2 (g) on graphite. We also use published experimental data to find similar thermodynamic properties of CO 2 (g) and of CH 4 (g) adsorbed on activated carbon. The procedure gives a higher accuracy in the determination of enthalpies of adsorption than ideal models do.
Electrically induced birefringence experiments were performed on dispersions consisting of sulfate latex nanospheres of two different sizes and charges dispersed in an electrolyte solution, at ...various ionic strengths. The induced birefringence was found to have an important contribution increasing as a quadratic power law of the volume fraction of the spheres. This shows that interparticle interactions play a role in the observed birefringence. The data were analyzed, using a theory from Hafkenscheid and Vlieger Physica 75 (1974) 57, in terms of the changes of the interparticle separations in the directions parallel and perpendicular to the applied electric field.
Electrically induced birefringence experiments were performed on dispersions consisting of sulfate latex nanospheres of two different sizes and charges dispersed in an electrolyte solution, at various ionic strengths. The induced birefringence was found to have an important contribution increasing as a quadratic power law of the volume fraction of the spheres. This shows that interparticle interactions play a role in the observed birefringence. The data were analyzed, using a theory from Hafkenscheid and Vlieger Physica 75 (1974) 57, in terms of the changes of the interparticle separations in the directions parallel and perpendicular to the applied electric field.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK