Biomedical subjects

T G M van de Ven

Publications and source records attributed to T G M van de Ven.

5 recordsLinked to original sources

PubMed2006

New method to determine the viscoelastic properties of admicelles around the stick-slip transition.

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).

Journal Article↗

PubMed2006

Electroviscous sphere-wall interactions.

A theoretical analysis is presented to determine the forces of interaction between an electrically charged spherical particle and a charged plane wall when the particle translates parallel to the wall and rotates around its axis in a symmetric electrolyte solution at rest. The electroviscous effects, arising from the coupling between the electrical and hydrodynamic equations, are determined as a solution of three partial differential equations, derived from Cox's general theory [R.G. Cox, J. Fluid Mech. 338 (1997) 1], for electroviscous ion concentration, electroviscous potential and electroviscous flow field. It is a priori assumed that the double layer thickness surrounding each charged surfaces is much smaller than the particle size. Using the matched asymptotic expansion technique, the electroviscous forces experienced by the sphere are explicitly determined analytically for small particle-wall distances, but low and intermediate Peclet numbers.

Journal Article↗

PubMed2006

Electroviscous cylinder-wall interactions.

A theoretical analysis is presented to determine the forces of interaction between an electrically charged cylindrical particle and a charged plane boundary wall when the particle translates parallel to the wall and rotates around its axis in a symmetric electrolyte solution at rest. The electroviscous effects, arising from the coupling between the electrical and hydrodynamic equations, are determined as a solution of three partial differential equations, derived from R.G. Cox's general theory [J. Fluid Mech. 338 (1997) 1], for electroviscous ion concentration, electroviscous potential, and electroviscous flow field. It is assumed a priori that the double layer thickness surrounding each charged surface is much smaller than the length scale of the problem. Using the matched asymptotic expansion technique, the electroviscous forces experienced by the cylinder are explicitly determined analytically for small particle-wall distances for low and intermediate Peclet numbers. It is found that the tangential force usually increases the drag above the purely hydrodynamic drag, although for certain conditions the drag can be reduced. Similarly the normal force is usually repulsive, i.e., it is an electrokinetic lift force, but under certain conditions the normal force can be attractive.

Journal Article↗

PubMed2005

Novel self-assembly of amphiphilic copolymers into nanotubes: characterization by small-angle neutron scattering.

The self-assembly into nanotubes in solution of an amphiphilic copolymer is characterized by small-angle neutron scattering (SANS). This study confirmed the shape and the size of the tubular association and the 3-D association of the tubes predicted by molecular orbital theory. Moreover, the characterization of the stability of the association has revealed that the addition of a very small amount of salt to the solution increases the size of the association. When more salt is added, the size of the association decreases, and the structure is altered. The association was found to be independent of temperature and therefore is very stable.

Chemistry↗

PubMed2005

Linear conformation of poly(styrene-alt-maleic anhydride) capable of self-assembly: a result of chain stiffening by internal hydrogen bonds.

A careful conformational analysis of poly(styrene-alt-maleic anhydride) at different pH values is presented. It is found that a strong internal hydrogen bond is formed at intermediate pH, which induces a change in the conformation of the polymer chain, which becomes linear. This linearity does not depend on the chirality of the polymer. The linearity of the chain occurs only at intermediate pH and can explain the association among the chains observed by dynamic light scattering at pH 7.

Air↗