Ger Koper - Academia.edu (original) (raw)

Papers by Ger Koper

The Journal of Physical Chemistry, 1995

This paper deals with the aggegation behavior of microemulsion droplets, especially water droplet... more This paper deals with the aggegation behavior of microemulsion droplets, especially water droplets covered with a monomolecular surfactant layer in oil. In the first part a picture obtained by a number of experimental techniques reported in the literature is reviewed. In the second part we propose a model that describes the aggregation of microemulsion droplets into chainlike aggregates from a thermodynamic point of view. The model is shown to be capable of explaining experimental data measured in a temary microemulsion using sodium bis(2-ethylhexyl)sulfosuccinate as surfactant quite well.

Science, 2015

Fuel-driven self-assembly of actin filaments and microtubules is a key component of cellular orga... more Fuel-driven self-assembly of actin filaments and microtubules is a key component of cellular organization. Continuous energy supply maintains these transient biomolecular assemblies far from thermodynamic equilibrium, unlike typical synthetic systems that spontaneously assemble at thermodynamic equilibrium. Here, we report the transient self-assembly of synthetic molecules into active materials, driven by the consumption of a chemical fuel. In these materials, reaction rates and fuel levels, instead of equilibrium composition, determine properties such as lifetime, stiffness, and self-regeneration capability. Fibers exhibit strongly nonlinear behavior including stochastic collapse and simultaneous growth and shrinkage, reminiscent of microtubule dynamics.

The Journal of Physical Chemistry

Potentiometric titrations of linear poly(ethylenimine) were performed in the presence of, as well... more Potentiometric titrations of linear poly(ethylenimine) were performed in the presence of, as well as in the absence of, added NaCl. In the NaCl concentration range of 0.1-1.0 M, the titration curves, with an inflexion point at beta = 0.5, have a total pH change of about 6 units and a shape which was independent of the NaCl concentration. The potentiometric behavior of LPEI in an excess of added salt is explained by taking into account the nearest-and next-nearest-neighbor interactions between charges on the LPEI chain. The experimental titration curves of LPEI solutions in 0.1 M NaCl, 0.5 M NaCl, and 1.0 M NaCl could well be described by the set of potentiometric equations derived from a statistical mechanical treatment of the dissociation equilibrium, based on the Ising model with three parameters: the intrinsic dissociation constant K0 and the excess energies epsilon(d) and epsilon(t) determined by the nearest and next-nearest-neighbor interactions, respectively. The intrinsic vis...

Lecture Notes in Physics

ABSTRACT Without Abstract

Surface and Colloid Science, 2001

ABSTRACT Binding of ions to various materials, such as small molecules, proteins, polymers, collo... more ABSTRACT Binding of ions to various materials, such as small molecules, proteins, polymers, colloid particles, and membranes, represents a central theme in basic and applied chemistry. Particularly, the case of proton binding to these substances (i.e., their acid-base behavior) has been a focus of research in many branches of chemistry since the turn of the century. One important topic in physical, analytical, and inorganic chemistry is the measurement, compilation, and prediction of acid-base properties of simple molecules or solvated metal ions.(1–8) These topics remain of much relevance for the development of new analytical techniques and tailoring of buffering or complexing agents.(7,9) Accurately known ionization constants also represent a rather stringent testing ground of our ab initio simulation capabilities of simple molecules in water.(10) Acid-base properties of proteins have been also investigated from early on.(11–14) This field has now matured into an active area of modern biochemistry with implications to the current view of protein folding, enzyme action, and photosynthesis.(15–17) Similar studies of weak polyelectrolytes were initiated in polymer science almost simultaneously(18–21) These systems represent an ongoing challenge to our understanding of acid-base equilibria.(22–25) The substantial interest in polyelectrolytes is due to their use as complexing, flocculating, or stabilizing agents, and their importance in various applications in catalysis, material engineering, biochemistry, and water purification.(26–28)

The Journal of Physical Chemistry, 1995

We have studied the Kelvin relation, e.g., an equilibrium between a two-component drop (in which ... more We have studied the Kelvin relation, e.g., an equilibrium between a two-component drop (in which the solute is involatile) and the vapor of the solvent component. This equilibrium and its stability have been analyzed previously, but not in a thermodynamically disciplined manner that employs the appropriate thermodynamic potential. Using the theory of the thermodynamic potential, we verify the previous conclusion

The Journal of Physical Chemistry, 1996

ABSTRACT In this paper we address the constant pressure ensemble and the volume scale that must b... more ABSTRACT In this paper we address the constant pressure ensemble and the volume scale that must be introduced in order to represent the corresponding partition function as a dimensionless integral. The volume scale or length scale problem arises quite generally when it is necessary (for whatever reason) to apply semiclassical statistical mechanical theory in configuration space alone, rather than in the full phase space of the system. We find that the length scale, derived by earlier workers concerned primarily with systems in the thermodynamic limit, is not suitable for application of the constant pressure ensemble to small systems such as clusters in nucleation theory or mesodomains in microemulsion theory. We discuss some of the well-known deficiencies of the conventional representation of the constant pressure ensemble and some which are not so well-known. Also the close connection between the constant pressure ensemble and Einstein fluctuation theory is emphasized, and we clarify the two types of fluctuation that are relevant to both developments but which are not always understood and distinguished by workers in the field. We derive the proper length scale applicable to systems of any size and remark that when it is used for small systems, the constant pressure ensemble partition function can no longer be derived from that for the canonical ensemble by simple Laplace transformation. We emphasize the fact that although the constant pressure ensemble has only found modest application in the statistical thermodynamics of macroscopic systems, it is being increasingly applied in the theory of small systems that may be conceptual rather than real, and that, for this reason, the ensemble should be placed on a firm fundamental foundation. In particular, we illustrate the relevance of the so-called “shell molecule”. Finally we apply our development to fluctuations in small systems to illustrate the qualitative and quantitative differences between small and large systems.

Chemical communications (Cambridge, England), Jan 14, 2014

We report on the production of Carbon Nano Networks (CNNs) from dense microemulsions in which cat... more We report on the production of Carbon Nano Networks (CNNs) from dense microemulsions in which catalyst nanoparticles have been synthesized. CNNs are 3D carbon networks, consisting of branches and junctions, and are mesoporous, graphitic, and conductive being suitable as electrode materials.

Langmuir : the ACS journal of surfaces and colloids, Jan 4, 2006

We report on a new method by which, for the first time, the viscoelastic properties of an adsorbe... more We report on a new method by which, for the first time, the viscoelastic properties of an adsorbed surfactant layer on a solid surface are measured. It is based on an analysis of the amplitude and the phase angle of the pressure fluctuations induced by a pulsating flow of a Newtonian surfactant solution through cylindrical pores. This method is subsequently used to determine the viscoelastic properties of an admicelle, formed when flushing surfactant solutions through nanopores, around the stick-slip transition. We find that the admicelle responds elastically for flow strengths below the transition and beyond the viscous. This is in agreement with the hypothesis formulated earlier (Cheikh, C.; Koper, G. J. M. Phys. Rev. Lett. 2003, 91, 156102).

The Journal of Physical Chemistry A, 2006

The surface temperature and surface mole fractions are calculated for a catalytic hydrogen oxidat... more The surface temperature and surface mole fractions are calculated for a catalytic hydrogen oxidation reaction over a Pt/Al 2 O 3 catalyst pellet. The thermodynamics of irreversible processes was used in order to ensure the correct introduction of coupled heat and mass transfer. Two pathways, one using the 4 × 4 resistivity matrix and the other using a simplified effective conductivity matrix, were proven to yield equivalent results. By using expressions for the thermal diffusion coefficients, heats of transfer, and the Maxwell-Stefan diffusion coefficients given in the literature, available experimental data could be reproduced. The Dufour effect was found to be negligible for the prediction of the surface temperature. Neglecting the Soret effect would increase the predicted value of the surface temperature significantlysmore than 30 K out of an average of about 400 K. It is found that the reaction rate can be used to predict the surface temperature.

Physical Review Letters, 2003

We report the first observation of a stick-slip transition of surfactant solution flow through na... more We report the first observation of a stick-slip transition of surfactant solution flow through nanopores. From the experimental data, we were able to determine both the slip length and the critical wall shear stress from which slip occurs. Whereas the latter is found to increase linearly with the concentration, the former remains constant and approximately equal to 20 nm over the studied range of concentrations. We model slip to occur in the surfactant bilayer adsorbed at the nanopore wall. The stick-slip transition is then related to a reorganization of the surfactant bilayer from an entangled structure into independent layers flowing past one another, as evidenced by independent surface plasmon resonance experiments. We conclude from our analysis that surfactant solutions are always slipping in larger tubes. However, the larger the tube diameter, the smaller the relative slip contribution to the total flow.

Physica A: Statistical Mechanics and its Applications, 2003

We consider an asymmetric electrolyte between two cylindrical concentric electrodes that are unch... more We consider an asymmetric electrolyte between two cylindrical concentric electrodes that are uncharged in the absence of an applied voltage di erence. We calculate the dielectric response of this capacitor to an alternating voltage di erence. The problem is solved using both classical boundary conditions and the new boundary conditions using excess densities to describe the charge build-up near the condensator plates as given in a previous article (C. Chassagne, D. Bedeaux and G.J.M. Koper, Colloid Surf. A 210 (2002) 137.). We verify that both boundary conditions give the same results. The advantage of the new boundary conditions lies in the possibility to extend in the future the analysis to real electrodes including reactions and speciÿc ion adsorption. A comparison of the model predictions, involving no adjustable parameters with experimental dielectric spectroscopy data, is performed and excellent agreement is found.

Physica A: Statistical Mechanics and its Applications, 2007

Electrokinetic phenomena exhibiting discontinuities are described in terms of a stick-slip transi... more Electrokinetic phenomena exhibiting discontinuities are described in terms of a stick-slip transition. The flux-force equations are partially linear and in the linear regimes the coefficients satisfy Onsager's reciprocal relations. From an interpretation of existing data on ion exchange membranes we find a linear dependence of the slip length with the surface potential. We conclude that slippage offers an alternative explanation for the so-called anomalous surface conduction, as often found in electrokinetic phenomena. This would imply an enhancement of electrokinetic effects in nanopores. r

Journal of Colloid and Interface Science, 1998

In reflectometry a laser beam is reflected off the surface The kinetics of adsorption of nano-siz... more In reflectometry a laser beam is reflected off the surface The kinetics of adsorption of nano-sized silica particles on a resulting in a certain intensity of parallel and perpendicular polymer pretreated surface were followed in situ by using optical polarized light. Changes in the refractive index close to the reflectometry in a stagnation point flow setup. Conversion of the surface due to polymer or particle adsorption give rise to a reflectometric signal to the surface coverage could be performed change in the ratio of these intensities. To interpret the meausing a homogeneous slab model which was verified by determinsured change in intensity ratio upon adsorption a model is ing the particle density on SEM pictures taken in the stagnation needed. For polymers or very small particles a model can point and by comparison with a model which includes the particube used in which the adsorbed layer is treated as a homogelate nature of the layer explicitly. The effects of salt concentration

Surface Coatings International Part B: Coatings Transactions, 2005

ABSTRACT Recently, a new technique has been proposed to obtain rheological information about dens... more ABSTRACT Recently, a new technique has been proposed to obtain rheological information about dense complex fluids such as yoghurt and paint. The method, developed by Masonet al, uses the correlations in light scattered from such dispersions in order to gain information about the Brownian motion of dispersed particles in the fluid. The mean squared displacement of the Brownian particles as a function of correlation time provides information on short, long and intermediate time-scales. For small correlation times, the particle movement is mainly diffusive (random) and leads to information about the viscous response of the fluid. For long correlation times, the movement is limited due to the caging effect of neighbouring particles and leads to information about the elastic response of the fluid. The authors shall demonstrate how this technique, called diffusing wave spectroscopy, is applied to drying films of alkyd resin emulsion paints. Several benefits are apparent: the method is not invasive andin situ, no surface effect is disturbing, and actual sagging tests can be minimised.

Progress in Colloid & Polymer Science, 1997

... The various poly(styrene) samples were obtained from Waters Associates (Milford) and 1,4 diox... more ... The various poly(styrene) samples were obtained from Waters Associates (Milford) and 1,4 dioxane was J o obtained from JT Baker. ... 1. For a review: Cates ME, Candau SJ (1990) J Phys Condens Matter 2: 6869 6892 2. Schurtenberger P, Cavaco C (1994) Lang-muir 10:100 ...

Langmuir, 2002

... 27) Haemers, S.; van der Leeden, MC; Nijman; EJ; Frens, G. Colloids Surf., A 2001, 190, 193. ... more ... 27) Haemers, S.; van der Leeden, MC; Nijman; EJ; Frens, G. Colloids Surf., A 2001, 190, 193. ... 31) Haemers, S.; Koper, GJM; van der Leeden, MC; Frens, G. Langmuir 2002, 18, 2069. ...

International Journal of Heat and Mass Transfer, 2007

For industrial paper drying, the entropy production from heat and mass transfer irreversibilities... more For industrial paper drying, the entropy production from heat and mass transfer irreversibilities was determined by combining principles of irreversible thermodynamics with information from a dryer simulator. Transport irreversibilities depend on sheet and dryer characteristics. Entropy production for multi-cylinder paper dryer sections was compared for 5 paper machines, producing 3 grades of linerboard, 2 of newsprint. The three major contributions to entropy production were evaluated: entropy production for evaporation of water, for convective heat transfer between the sheet and ambient air, and for cylinder-to-sheet heat conduction. Effects on entropy production from paper basis weight and drying cylinder steam pressure were examined. (M. Sadeghi).

The Journal of Physical Chemistry, 1995

This paper deals with the aggegation behavior of microemulsion droplets, especially water droplet... more This paper deals with the aggegation behavior of microemulsion droplets, especially water droplets covered with a monomolecular surfactant layer in oil. In the first part a picture obtained by a number of experimental techniques reported in the literature is reviewed. In the second part we propose a model that describes the aggregation of microemulsion droplets into chainlike aggregates from a thermodynamic point of view. The model is shown to be capable of explaining experimental data measured in a temary microemulsion using sodium bis(2-ethylhexyl)sulfosuccinate as surfactant quite well.

Science, 2015

Fuel-driven self-assembly of actin filaments and microtubules is a key component of cellular orga... more Fuel-driven self-assembly of actin filaments and microtubules is a key component of cellular organization. Continuous energy supply maintains these transient biomolecular assemblies far from thermodynamic equilibrium, unlike typical synthetic systems that spontaneously assemble at thermodynamic equilibrium. Here, we report the transient self-assembly of synthetic molecules into active materials, driven by the consumption of a chemical fuel. In these materials, reaction rates and fuel levels, instead of equilibrium composition, determine properties such as lifetime, stiffness, and self-regeneration capability. Fibers exhibit strongly nonlinear behavior including stochastic collapse and simultaneous growth and shrinkage, reminiscent of microtubule dynamics.

The Journal of Physical Chemistry

Potentiometric titrations of linear poly(ethylenimine) were performed in the presence of, as well... more Potentiometric titrations of linear poly(ethylenimine) were performed in the presence of, as well as in the absence of, added NaCl. In the NaCl concentration range of 0.1-1.0 M, the titration curves, with an inflexion point at beta = 0.5, have a total pH change of about 6 units and a shape which was independent of the NaCl concentration. The potentiometric behavior of LPEI in an excess of added salt is explained by taking into account the nearest-and next-nearest-neighbor interactions between charges on the LPEI chain. The experimental titration curves of LPEI solutions in 0.1 M NaCl, 0.5 M NaCl, and 1.0 M NaCl could well be described by the set of potentiometric equations derived from a statistical mechanical treatment of the dissociation equilibrium, based on the Ising model with three parameters: the intrinsic dissociation constant K0 and the excess energies epsilon(d) and epsilon(t) determined by the nearest and next-nearest-neighbor interactions, respectively. The intrinsic vis...

Lecture Notes in Physics

ABSTRACT Without Abstract

Surface and Colloid Science, 2001

ABSTRACT Binding of ions to various materials, such as small molecules, proteins, polymers, collo... more ABSTRACT Binding of ions to various materials, such as small molecules, proteins, polymers, colloid particles, and membranes, represents a central theme in basic and applied chemistry. Particularly, the case of proton binding to these substances (i.e., their acid-base behavior) has been a focus of research in many branches of chemistry since the turn of the century. One important topic in physical, analytical, and inorganic chemistry is the measurement, compilation, and prediction of acid-base properties of simple molecules or solvated metal ions.(1–8) These topics remain of much relevance for the development of new analytical techniques and tailoring of buffering or complexing agents.(7,9) Accurately known ionization constants also represent a rather stringent testing ground of our ab initio simulation capabilities of simple molecules in water.(10) Acid-base properties of proteins have been also investigated from early on.(11–14) This field has now matured into an active area of modern biochemistry with implications to the current view of protein folding, enzyme action, and photosynthesis.(15–17) Similar studies of weak polyelectrolytes were initiated in polymer science almost simultaneously(18–21) These systems represent an ongoing challenge to our understanding of acid-base equilibria.(22–25) The substantial interest in polyelectrolytes is due to their use as complexing, flocculating, or stabilizing agents, and their importance in various applications in catalysis, material engineering, biochemistry, and water purification.(26–28)

The Journal of Physical Chemistry, 1995

We have studied the Kelvin relation, e.g., an equilibrium between a two-component drop (in which ... more We have studied the Kelvin relation, e.g., an equilibrium between a two-component drop (in which the solute is involatile) and the vapor of the solvent component. This equilibrium and its stability have been analyzed previously, but not in a thermodynamically disciplined manner that employs the appropriate thermodynamic potential. Using the theory of the thermodynamic potential, we verify the previous conclusion

The Journal of Physical Chemistry, 1996

ABSTRACT In this paper we address the constant pressure ensemble and the volume scale that must b... more ABSTRACT In this paper we address the constant pressure ensemble and the volume scale that must be introduced in order to represent the corresponding partition function as a dimensionless integral. The volume scale or length scale problem arises quite generally when it is necessary (for whatever reason) to apply semiclassical statistical mechanical theory in configuration space alone, rather than in the full phase space of the system. We find that the length scale, derived by earlier workers concerned primarily with systems in the thermodynamic limit, is not suitable for application of the constant pressure ensemble to small systems such as clusters in nucleation theory or mesodomains in microemulsion theory. We discuss some of the well-known deficiencies of the conventional representation of the constant pressure ensemble and some which are not so well-known. Also the close connection between the constant pressure ensemble and Einstein fluctuation theory is emphasized, and we clarify the two types of fluctuation that are relevant to both developments but which are not always understood and distinguished by workers in the field. We derive the proper length scale applicable to systems of any size and remark that when it is used for small systems, the constant pressure ensemble partition function can no longer be derived from that for the canonical ensemble by simple Laplace transformation. We emphasize the fact that although the constant pressure ensemble has only found modest application in the statistical thermodynamics of macroscopic systems, it is being increasingly applied in the theory of small systems that may be conceptual rather than real, and that, for this reason, the ensemble should be placed on a firm fundamental foundation. In particular, we illustrate the relevance of the so-called “shell molecule”. Finally we apply our development to fluctuations in small systems to illustrate the qualitative and quantitative differences between small and large systems.

Chemical communications (Cambridge, England), Jan 14, 2014

We report on the production of Carbon Nano Networks (CNNs) from dense microemulsions in which cat... more We report on the production of Carbon Nano Networks (CNNs) from dense microemulsions in which catalyst nanoparticles have been synthesized. CNNs are 3D carbon networks, consisting of branches and junctions, and are mesoporous, graphitic, and conductive being suitable as electrode materials.

Langmuir : the ACS journal of surfaces and colloids, Jan 4, 2006

We report on a new method by which, for the first time, the viscoelastic properties of an adsorbe... more We report on a new method by which, for the first time, the viscoelastic properties of an adsorbed surfactant layer on a solid surface are measured. It is based on an analysis of the amplitude and the phase angle of the pressure fluctuations induced by a pulsating flow of a Newtonian surfactant solution through cylindrical pores. This method is subsequently used to determine the viscoelastic properties of an admicelle, formed when flushing surfactant solutions through nanopores, around the stick-slip transition. We find that the admicelle responds elastically for flow strengths below the transition and beyond the viscous. This is in agreement with the hypothesis formulated earlier (Cheikh, C.; Koper, G. J. M. Phys. Rev. Lett. 2003, 91, 156102).

The Journal of Physical Chemistry A, 2006

The surface temperature and surface mole fractions are calculated for a catalytic hydrogen oxidat... more The surface temperature and surface mole fractions are calculated for a catalytic hydrogen oxidation reaction over a Pt/Al 2 O 3 catalyst pellet. The thermodynamics of irreversible processes was used in order to ensure the correct introduction of coupled heat and mass transfer. Two pathways, one using the 4 × 4 resistivity matrix and the other using a simplified effective conductivity matrix, were proven to yield equivalent results. By using expressions for the thermal diffusion coefficients, heats of transfer, and the Maxwell-Stefan diffusion coefficients given in the literature, available experimental data could be reproduced. The Dufour effect was found to be negligible for the prediction of the surface temperature. Neglecting the Soret effect would increase the predicted value of the surface temperature significantlysmore than 30 K out of an average of about 400 K. It is found that the reaction rate can be used to predict the surface temperature.

Physical Review Letters, 2003

We report the first observation of a stick-slip transition of surfactant solution flow through na... more We report the first observation of a stick-slip transition of surfactant solution flow through nanopores. From the experimental data, we were able to determine both the slip length and the critical wall shear stress from which slip occurs. Whereas the latter is found to increase linearly with the concentration, the former remains constant and approximately equal to 20 nm over the studied range of concentrations. We model slip to occur in the surfactant bilayer adsorbed at the nanopore wall. The stick-slip transition is then related to a reorganization of the surfactant bilayer from an entangled structure into independent layers flowing past one another, as evidenced by independent surface plasmon resonance experiments. We conclude from our analysis that surfactant solutions are always slipping in larger tubes. However, the larger the tube diameter, the smaller the relative slip contribution to the total flow.

Physica A: Statistical Mechanics and its Applications, 2003

We consider an asymmetric electrolyte between two cylindrical concentric electrodes that are unch... more We consider an asymmetric electrolyte between two cylindrical concentric electrodes that are uncharged in the absence of an applied voltage di erence. We calculate the dielectric response of this capacitor to an alternating voltage di erence. The problem is solved using both classical boundary conditions and the new boundary conditions using excess densities to describe the charge build-up near the condensator plates as given in a previous article (C. Chassagne, D. Bedeaux and G.J.M. Koper, Colloid Surf. A 210 (2002) 137.). We verify that both boundary conditions give the same results. The advantage of the new boundary conditions lies in the possibility to extend in the future the analysis to real electrodes including reactions and speciÿc ion adsorption. A comparison of the model predictions, involving no adjustable parameters with experimental dielectric spectroscopy data, is performed and excellent agreement is found.

Physica A: Statistical Mechanics and its Applications, 2007

Electrokinetic phenomena exhibiting discontinuities are described in terms of a stick-slip transi... more Electrokinetic phenomena exhibiting discontinuities are described in terms of a stick-slip transition. The flux-force equations are partially linear and in the linear regimes the coefficients satisfy Onsager's reciprocal relations. From an interpretation of existing data on ion exchange membranes we find a linear dependence of the slip length with the surface potential. We conclude that slippage offers an alternative explanation for the so-called anomalous surface conduction, as often found in electrokinetic phenomena. This would imply an enhancement of electrokinetic effects in nanopores. r

Journal of Colloid and Interface Science, 1998

In reflectometry a laser beam is reflected off the surface The kinetics of adsorption of nano-siz... more In reflectometry a laser beam is reflected off the surface The kinetics of adsorption of nano-sized silica particles on a resulting in a certain intensity of parallel and perpendicular polymer pretreated surface were followed in situ by using optical polarized light. Changes in the refractive index close to the reflectometry in a stagnation point flow setup. Conversion of the surface due to polymer or particle adsorption give rise to a reflectometric signal to the surface coverage could be performed change in the ratio of these intensities. To interpret the meausing a homogeneous slab model which was verified by determinsured change in intensity ratio upon adsorption a model is ing the particle density on SEM pictures taken in the stagnation needed. For polymers or very small particles a model can point and by comparison with a model which includes the particube used in which the adsorbed layer is treated as a homogelate nature of the layer explicitly. The effects of salt concentration

Surface Coatings International Part B: Coatings Transactions, 2005

ABSTRACT Recently, a new technique has been proposed to obtain rheological information about dens... more ABSTRACT Recently, a new technique has been proposed to obtain rheological information about dense complex fluids such as yoghurt and paint. The method, developed by Masonet al, uses the correlations in light scattered from such dispersions in order to gain information about the Brownian motion of dispersed particles in the fluid. The mean squared displacement of the Brownian particles as a function of correlation time provides information on short, long and intermediate time-scales. For small correlation times, the particle movement is mainly diffusive (random) and leads to information about the viscous response of the fluid. For long correlation times, the movement is limited due to the caging effect of neighbouring particles and leads to information about the elastic response of the fluid. The authors shall demonstrate how this technique, called diffusing wave spectroscopy, is applied to drying films of alkyd resin emulsion paints. Several benefits are apparent: the method is not invasive andin situ, no surface effect is disturbing, and actual sagging tests can be minimised.

Progress in Colloid & Polymer Science, 1997

... The various poly(styrene) samples were obtained from Waters Associates (Milford) and 1,4 diox... more ... The various poly(styrene) samples were obtained from Waters Associates (Milford) and 1,4 dioxane was J o obtained from JT Baker. ... 1. For a review: Cates ME, Candau SJ (1990) J Phys Condens Matter 2: 6869 6892 2. Schurtenberger P, Cavaco C (1994) Lang-muir 10:100 ...

Langmuir, 2002

... 27) Haemers, S.; van der Leeden, MC; Nijman; EJ; Frens, G. Colloids Surf., A 2001, 190, 193. ... more ... 27) Haemers, S.; van der Leeden, MC; Nijman; EJ; Frens, G. Colloids Surf., A 2001, 190, 193. ... 31) Haemers, S.; Koper, GJM; van der Leeden, MC; Frens, G. Langmuir 2002, 18, 2069. ...

International Journal of Heat and Mass Transfer, 2007

For industrial paper drying, the entropy production from heat and mass transfer irreversibilities... more For industrial paper drying, the entropy production from heat and mass transfer irreversibilities was determined by combining principles of irreversible thermodynamics with information from a dryer simulator. Transport irreversibilities depend on sheet and dryer characteristics. Entropy production for multi-cylinder paper dryer sections was compared for 5 paper machines, producing 3 grades of linerboard, 2 of newsprint. The three major contributions to entropy production were evaluated: entropy production for evaporation of water, for convective heat transfer between the sheet and ambient air, and for cylinder-to-sheet heat conduction. Effects on entropy production from paper basis weight and drying cylinder steam pressure were examined. (M. Sadeghi).