Victor Kuz - Academia.edu (original) (raw)
Papers by Victor Kuz
Physical Review B, 1985
The total-energy and pressure-volume relations are calculated nonrelativistically for Si, Ge, and... more The total-energy and pressure-volume relations are calculated nonrelativistically for Si, Ge, and a-Sn within the local-density-functional formalism, with use of first-principles nonlocal pseudopotentials. Ground-state static structural properties (total energy, lattice constant, and bulk modulus and its pressure derivative) are obtained and are in good agreement with experimental values. A prediction of these for cz-Sn from pressure determinations has not yet been reported. Its bulk modulus from both total-energy and pressure calculations is much smaller than that determined by experimental measurement. This confirms a recent theoretical prediction from other authors casting doubts on the experimental value. An assessment has been made on the advantages and disadvantages of pressure calculations over total-energy calculations and on the influence on the results of the size of all cutoff parameters and perturbative schemes used.
Nonlinear Phenomena and Complex Systems, 2004
A thermodynamic model is developed to explain the formation of a solid ridge of polystyrene spher... more A thermodynamic model is developed to explain the formation of a solid ridge of polystyrene spheres on the periphery of a sessile drop. The drop initially contains a uniform solution of water and polystyrene spheres. Evaporation creates a crater. The spheres leave the center and a ridge, whose width increases with increasing initial concentration, forms. For each equilibrium state, three contributions to the Gibbs free energy mainly control this process. One is related with the mechanical work of formation, the other with the spreading of the diameter and the last with the variation of the number of particles in the ridge. The model predicts, in agreement with the experiment, the initial and final value of the contact angles and the exponential diminution of concentration of particles with the ratio of the diameters of the ridge.
Nonlinear Phenomena and Complex Systems, 1996
A two dimensional ( 2-D ) system of bubbles in a lipid monolayer is maintained at a fixed tempera... more A two dimensional ( 2-D ) system of bubbles in a lipid monolayer is maintained at a fixed temperature and area in the liquid-gas coexistence region. From the Einstein’s fluctuation formula it is shown that the mean square relative deviation from the mean area A = ( - 2)-r 2 is proportional to the surface compressibility of this system. In the case of correlated particles, this quantity is also proportional to the integral of the particles correlation function over the area. The present model predicts a linear growth of A with time, but a constant value when the correlations are absent. From the comparison of this result with the recent experiment of Berge et al. ( Phys.Rev.A.41,6893(1990)) it can be inferred that the macroscopic transition from regular to irregular bubble pattern is due to the microscopic interaction of the surfactant particles. Changes in concentration increases the interparticles correlation, which in turn induces the experimentally observed shape transition.
Journal of Colloid and Interface Science, 1991
Abstract When a liquid surface is under a horizontal thermal gradient, the liquid starts to flow ... more Abstract When a liquid surface is under a horizontal thermal gradient, the liquid starts to flow in the direction of the applied gradient. This flow, called thermocapillary flow, is due to the surface tension temperature gradient. We study the temperature and velocity distributions at the interface by including, in the thermal boundary condition, the bulk and surface conductivity contribution. By neglecting this thermal effect we produce Levich's result. It is found that the velocity dependence on depth is a function of the thermal properties of the fluids. The surface velocity and temperature predicted here are compared with the experiment.
Journal of Colloid and Interface Science, 1989
Abstract A phenomenological thermal balance equation for a fluid-liquid interface is presented. T... more Abstract A phenomenological thermal balance equation for a fluid-liquid interface is presented. The equation contains surface properties and differences of bulk properties. In addition to recovering all the known phenomenological equations, our equation predicts the existence of heat flow due to the surface thermal gradient, surface tension gradient, and pressure difference across the interface. Also, a relation between the thermal gradient of surface tension and the surface heat coefEcients is presented.
Physical Review A, 1992
A dynamic analysis of the growth of a gas bubble system in a lipid monolayer is presented. The bu... more A dynamic analysis of the growth of a gas bubble system in a lipid monolayer is presented. The bubles are separated by thin liquid films. The two-dimensional bubble pattern has, independently of the initial gas phase covering the surface, two different regimes of growth with time. Using simple arguments, we find a differential equation which links the radius of the bubble with the width of the liquid film. According to the mechanism of thinning this film, the model predicts two different power laws for the aeral growth with time
Physical Review E, 2015
Periodical patterns of vegetation in an arid or semiarid ecosystem are described using statistica... more Periodical patterns of vegetation in an arid or semiarid ecosystem are described using statistical mechanics and Monte Carlo numerical simulation technique. Plants are characterized by the area that each individual occupies and a facilitation-competition pairwise interaction. Assuming that external resources (precipitation, solar radiation, nutrients, etc.) are available to the ecosystem, it is possible to obtain the persistent configurations of plants compatible with an equitable distribution of resources maximizing the Shannon entropy. Variation of vegetation patterns with density, critical cluster size, and facilitation distance are predicted. Morphological changes of clusters are shown to be a function of the external resources. As a final remark, it is proposed that an early warning of desertification could be detected from the coefficient of variation of the mean cluster size together with the distribution of cluster sizes.
Journal de Physique, 1987
Instabilities and Nonequilibrium Structures IV, 1993
We present here an alternavite derivation to that given by De Gennes, of the Hoffman-Tanner law. ... more We present here an alternavite derivation to that given by De Gennes, of the Hoffman-Tanner law. By considering that the driving force acting upon the wedge-precursor film system is proportional to the surface tension gradient and by assuming that the flow of this system is of Couette type, we find the Hoffman-Tanner law.
Physical Review E, 1994
In this Brief Report, a formula to estimate the water content of micelles is proposed. It is base... more In this Brief Report, a formula to estimate the water content of micelles is proposed. It is based on the Laplace equation and it gives a plausible explanation of the various globular shapes the micelles take at different amphiphile concentrations. The formula is applied to an aqueous solution of Triton X-100. The estimated water content, 11 water molecules per monomer, is lower than a previous reported value obtained from geometric arguments by other authors [R.
Tree Physiology, 2007
A theoretical treatment of some of the factors influencing air seeding at the pit membranes of xy... more A theoretical treatment of some of the factors influencing air seeding at the pit membranes of xylem vessels is given. Pit membrane structure, viewed as a three-dimensional mesh of intercrossing fibrils, and vulnerability to water-stressinduced air seeding are examined in the context of the Young-Laplace equation. Simple geometrical considerations of the porous membrane show that the vapor-liquid interface curvature radius is a function of fiber-fiber distance, fiber radius, wetting angle and position of the wetting line. Air seeding (maximum pressure) occurs at the minimum curvature radius, therefore air seeding is not simply determined by the fiber-fiber distance but is a function of the geometry of the pit membrane and of physicochemical quantities like surface tension and wetting angle. As a consequence of considering a wetting angle different from zero, the minimum curvature radius becomes larger than half the fiber-fiber distance. The present model considers that, for a given pressure difference at the pit membrane, all local interface curvatures are the same. In this sense, pit membranes work as variable capillary valves that allow or prevent air seeding by adjusting local curvatures and interface positions relative to the pore-forming fibers, following the pressure differences across the membranes. The theoretical prediction for the air seeding threshold is consistent with recent experimental data for angiosperm trees.
The Journal of Physical Chemistry B, 1999
A vapor pressure equation for an aerosol is presented here. The latent heat of evaporation (Claus... more A vapor pressure equation for an aerosol is presented here. The latent heat of evaporation (Clausius−Clapeyron contribution), the curvature, and the disjoining pressure effects are considered as the main contributions to the equation. Curvature (Kelvin effect) is shown to be irrelevant. Orientation of the amphiphilic molecules at the surface of the aerosol droplets generates an extra pressure. This pressure, represented here by the structural component of the disjoining pressure, contributes to the Clausius−Clapeyron equation with a nonlinear term proportional to ln T. The prediction is in agreement with a recent experimental result.
Physical Review A, 1991
The aging of a liquid surface is made evident through the surface-mass-density variation with tim... more The aging of a liquid surface is made evident through the surface-mass-density variation with time. By using the surface-mass conservation law together with the solution of the diffusion equation, we find, for dilute solutions, that surface-mass changes with time following a Volterra integro-differential equation of the second kind. The solution of this equation, for a semi-infinite fluid, together with the two-dimensional equation of state for a dilute gas, allows us to find the surface-tension variation with time. The result is compared with a recent experimental dynamic measurement of the liquid-vapor interfacial tension for aqueous solutions of a nonionic detergent.
Molecular Physics, 2012
Parallel tempering Monte Carlo simulation is carried out in systems of N attractive Hamaker spher... more Parallel tempering Monte Carlo simulation is carried out in systems of N attractive Hamaker spheres dressed with n dipolar particles, able to move on the surface of the spheres. Different cluster configurations emerge for given values of the control parameters. Energy per sphere, pair distribution functions of spheres and dipoles as function of temperature, density, external electric field, and/or the angular orientation of dipoles are used to analyse the state of aggregation of the system. As a consequence of the non-central interaction, the model predicts complex structures like self-assembly of spheres by a double crown of dipoles. This interesting result could be of help in understanding some recent experiments in colloidal science and biology.
Physical Review B, 1985
The total-energy and pressure-volume relations are calculated nonrelativistically for Si, Ge, and... more The total-energy and pressure-volume relations are calculated nonrelativistically for Si, Ge, and a-Sn within the local-density-functional formalism, with use of first-principles nonlocal pseudopotentials. Ground-state static structural properties (total energy, lattice constant, and bulk modulus and its pressure derivative) are obtained and are in good agreement with experimental values. A prediction of these for cz-Sn from pressure determinations has not yet been reported. Its bulk modulus from both total-energy and pressure calculations is much smaller than that determined by experimental measurement. This confirms a recent theoretical prediction from other authors casting doubts on the experimental value. An assessment has been made on the advantages and disadvantages of pressure calculations over total-energy calculations and on the influence on the results of the size of all cutoff parameters and perturbative schemes used.
Nonlinear Phenomena and Complex Systems, 2004
A thermodynamic model is developed to explain the formation of a solid ridge of polystyrene spher... more A thermodynamic model is developed to explain the formation of a solid ridge of polystyrene spheres on the periphery of a sessile drop. The drop initially contains a uniform solution of water and polystyrene spheres. Evaporation creates a crater. The spheres leave the center and a ridge, whose width increases with increasing initial concentration, forms. For each equilibrium state, three contributions to the Gibbs free energy mainly control this process. One is related with the mechanical work of formation, the other with the spreading of the diameter and the last with the variation of the number of particles in the ridge. The model predicts, in agreement with the experiment, the initial and final value of the contact angles and the exponential diminution of concentration of particles with the ratio of the diameters of the ridge.
Nonlinear Phenomena and Complex Systems, 1996
A two dimensional ( 2-D ) system of bubbles in a lipid monolayer is maintained at a fixed tempera... more A two dimensional ( 2-D ) system of bubbles in a lipid monolayer is maintained at a fixed temperature and area in the liquid-gas coexistence region. From the Einstein’s fluctuation formula it is shown that the mean square relative deviation from the mean area A = ( - 2)-r 2 is proportional to the surface compressibility of this system. In the case of correlated particles, this quantity is also proportional to the integral of the particles correlation function over the area. The present model predicts a linear growth of A with time, but a constant value when the correlations are absent. From the comparison of this result with the recent experiment of Berge et al. ( Phys.Rev.A.41,6893(1990)) it can be inferred that the macroscopic transition from regular to irregular bubble pattern is due to the microscopic interaction of the surfactant particles. Changes in concentration increases the interparticles correlation, which in turn induces the experimentally observed shape transition.
Journal of Colloid and Interface Science, 1991
Abstract When a liquid surface is under a horizontal thermal gradient, the liquid starts to flow ... more Abstract When a liquid surface is under a horizontal thermal gradient, the liquid starts to flow in the direction of the applied gradient. This flow, called thermocapillary flow, is due to the surface tension temperature gradient. We study the temperature and velocity distributions at the interface by including, in the thermal boundary condition, the bulk and surface conductivity contribution. By neglecting this thermal effect we produce Levich's result. It is found that the velocity dependence on depth is a function of the thermal properties of the fluids. The surface velocity and temperature predicted here are compared with the experiment.
Journal of Colloid and Interface Science, 1989
Abstract A phenomenological thermal balance equation for a fluid-liquid interface is presented. T... more Abstract A phenomenological thermal balance equation for a fluid-liquid interface is presented. The equation contains surface properties and differences of bulk properties. In addition to recovering all the known phenomenological equations, our equation predicts the existence of heat flow due to the surface thermal gradient, surface tension gradient, and pressure difference across the interface. Also, a relation between the thermal gradient of surface tension and the surface heat coefEcients is presented.
Physical Review A, 1992
A dynamic analysis of the growth of a gas bubble system in a lipid monolayer is presented. The bu... more A dynamic analysis of the growth of a gas bubble system in a lipid monolayer is presented. The bubles are separated by thin liquid films. The two-dimensional bubble pattern has, independently of the initial gas phase covering the surface, two different regimes of growth with time. Using simple arguments, we find a differential equation which links the radius of the bubble with the width of the liquid film. According to the mechanism of thinning this film, the model predicts two different power laws for the aeral growth with time
Physical Review E, 2015
Periodical patterns of vegetation in an arid or semiarid ecosystem are described using statistica... more Periodical patterns of vegetation in an arid or semiarid ecosystem are described using statistical mechanics and Monte Carlo numerical simulation technique. Plants are characterized by the area that each individual occupies and a facilitation-competition pairwise interaction. Assuming that external resources (precipitation, solar radiation, nutrients, etc.) are available to the ecosystem, it is possible to obtain the persistent configurations of plants compatible with an equitable distribution of resources maximizing the Shannon entropy. Variation of vegetation patterns with density, critical cluster size, and facilitation distance are predicted. Morphological changes of clusters are shown to be a function of the external resources. As a final remark, it is proposed that an early warning of desertification could be detected from the coefficient of variation of the mean cluster size together with the distribution of cluster sizes.
Journal de Physique, 1987
Instabilities and Nonequilibrium Structures IV, 1993
We present here an alternavite derivation to that given by De Gennes, of the Hoffman-Tanner law. ... more We present here an alternavite derivation to that given by De Gennes, of the Hoffman-Tanner law. By considering that the driving force acting upon the wedge-precursor film system is proportional to the surface tension gradient and by assuming that the flow of this system is of Couette type, we find the Hoffman-Tanner law.
Physical Review E, 1994
In this Brief Report, a formula to estimate the water content of micelles is proposed. It is base... more In this Brief Report, a formula to estimate the water content of micelles is proposed. It is based on the Laplace equation and it gives a plausible explanation of the various globular shapes the micelles take at different amphiphile concentrations. The formula is applied to an aqueous solution of Triton X-100. The estimated water content, 11 water molecules per monomer, is lower than a previous reported value obtained from geometric arguments by other authors [R.
Tree Physiology, 2007
A theoretical treatment of some of the factors influencing air seeding at the pit membranes of xy... more A theoretical treatment of some of the factors influencing air seeding at the pit membranes of xylem vessels is given. Pit membrane structure, viewed as a three-dimensional mesh of intercrossing fibrils, and vulnerability to water-stressinduced air seeding are examined in the context of the Young-Laplace equation. Simple geometrical considerations of the porous membrane show that the vapor-liquid interface curvature radius is a function of fiber-fiber distance, fiber radius, wetting angle and position of the wetting line. Air seeding (maximum pressure) occurs at the minimum curvature radius, therefore air seeding is not simply determined by the fiber-fiber distance but is a function of the geometry of the pit membrane and of physicochemical quantities like surface tension and wetting angle. As a consequence of considering a wetting angle different from zero, the minimum curvature radius becomes larger than half the fiber-fiber distance. The present model considers that, for a given pressure difference at the pit membrane, all local interface curvatures are the same. In this sense, pit membranes work as variable capillary valves that allow or prevent air seeding by adjusting local curvatures and interface positions relative to the pore-forming fibers, following the pressure differences across the membranes. The theoretical prediction for the air seeding threshold is consistent with recent experimental data for angiosperm trees.
The Journal of Physical Chemistry B, 1999
A vapor pressure equation for an aerosol is presented here. The latent heat of evaporation (Claus... more A vapor pressure equation for an aerosol is presented here. The latent heat of evaporation (Clausius−Clapeyron contribution), the curvature, and the disjoining pressure effects are considered as the main contributions to the equation. Curvature (Kelvin effect) is shown to be irrelevant. Orientation of the amphiphilic molecules at the surface of the aerosol droplets generates an extra pressure. This pressure, represented here by the structural component of the disjoining pressure, contributes to the Clausius−Clapeyron equation with a nonlinear term proportional to ln T. The prediction is in agreement with a recent experimental result.
Physical Review A, 1991
The aging of a liquid surface is made evident through the surface-mass-density variation with tim... more The aging of a liquid surface is made evident through the surface-mass-density variation with time. By using the surface-mass conservation law together with the solution of the diffusion equation, we find, for dilute solutions, that surface-mass changes with time following a Volterra integro-differential equation of the second kind. The solution of this equation, for a semi-infinite fluid, together with the two-dimensional equation of state for a dilute gas, allows us to find the surface-tension variation with time. The result is compared with a recent experimental dynamic measurement of the liquid-vapor interfacial tension for aqueous solutions of a nonionic detergent.
Molecular Physics, 2012
Parallel tempering Monte Carlo simulation is carried out in systems of N attractive Hamaker spher... more Parallel tempering Monte Carlo simulation is carried out in systems of N attractive Hamaker spheres dressed with n dipolar particles, able to move on the surface of the spheres. Different cluster configurations emerge for given values of the control parameters. Energy per sphere, pair distribution functions of spheres and dipoles as function of temperature, density, external electric field, and/or the angular orientation of dipoles are used to analyse the state of aggregation of the system. As a consequence of the non-central interaction, the model predicts complex structures like self-assembly of spheres by a double crown of dipoles. This interesting result could be of help in understanding some recent experiments in colloidal science and biology.