Biomedical subjects

Graeme J Jameson

Publications and source records attributed to Graeme J Jameson.

3 recordsLinked to original sources

PubMed2006

An improved collision efficiency model for particle aggregation.

A generalized geometric model is presented which describes the collision efficiency factor of aggregation (the probability of a binary particle or aggregate collision resulting in adhesion) for systems comprised of two oppositely charged species. Application of the general model to specific systems requires calculation of the area of each species available for collision with a second species. This is in contrast to previous models developed for polymer-particle flocculation that are based on the fractional surface coverage of adsorbed polymer. The difference between these approaches is suggested as an explanation for previously observed discrepancies between theory and observation. In the current work the specific case of oppositely charged nondeformable spherical particles (heteroaggregation) is quantitatively addressed. The optimum concentration of oppositely charged particles for rapid aggregation (maximum collision efficiency) as a function of relative particle size is calculated and an excellent correlation is found with data taken from literature.

Journal Article↗

PubMed2005

Bi-modal hetero-aggregation rate response to particle dosage.

The rate of flocculation of cationic polystyrene latex (PSL) particles by smaller, anionic PSL particles has been measured using a low-angle static light scattering technique. The rate of aggregate growth has been investigated as a function of particle size ratio and relative concentration of each particle species (for a constant dose of cationic particles). Contrary to many previous reports, two peaks in the flocculation rate were observed as a function of dose. It is speculated that the peak observed at the lower particle concentration coincides with the dose yielding maximum constant collision efficiency in the steady-state regime, a condition which is attained only after complete adsorption of the smaller particles onto the larger particle species. The peak at the higher particle concentration is believed to be related to the maximum collision rate constant upon reaching the steady-state regime, the value of which corresponds to maximum degree of aggregation and therefore the maximum mean collision efficiency prior to reaching this condition. From classical collision kinetics, the rate of aggregate growth may be represented as being proportional to the product of the collision rate constant and collision efficiency at any given time. Given then that the maximum value of these two variables coincides with different particle concentrations, the product of the response of each to particle dosage can in some cases yield a net bi-modal aggregation rate response to particle dosage.

Journal Article↗

PubMed2002

The effect of molecular weight of nonadsorbing polymer on the structure of depletion-induced flocs.

This work explores the structural compactness of depletion-induced particle flocs with respect to the molecular weight of nonadsorbing polymer flocculants. Small-angle static light scattering was used to monitor the structural characteristics of the flocs, which were formed by the addition of nonadsorbing poly(acrylic acids) to a stable colloidal polystyrene latex dispersion. It was found that the floc mass fractal dimension, considered to be a measure of structural compactness, was dependent upon both the molecular weight and the concentration of the polyacid. In particular, reducing the molecular weight of the polymer at a fixed polyacid concentration resulted in higher mass fractal dimensions, despite the highly polydisperse nature of the polymer samples. This structural behavior was attributed to the lower particle sticking efficiencies upon collision. This reduced sticking ability is the result of the shallowing in the secondary potential energy well with decreasing polymer chain length, which was directly supported by atomic force microscopy data. Our results suggest that the formation of a shallower attraction well with a lower molecular weight nonadsorbing polymer is the result of the insufficiency of the increased osmotic pressure to counter-balance the short-ranged nature of the depletion interaction.

Acrylic Resins↗