Biomedical subjects

G Odriozola

Publications and source records attributed to G Odriozola.

4 recordsLinked to original sources

PubMed2003

Modeling the aggregation of partially covered particles: theory and simulation.

A theoretical model for describing the initial stages of the aggregation of partially covered colloidal particles is presented. It is based on the assumption of short-range interactions that may be modeled by a sticking probability on contact. Three types of sticking probabilities are distinguished depending on the collision type, i.e., for bare-bare, bare-covered, and covered-covered collisions. Hence, the model allows an analytical expression for the dimer-formation rate constant k(11), to be deduced as a function of the degree of surface coverage and the three sticking probabilities. The theoretical predictions are contrasted with simulated data. The observed agreement between theory and simulations shows the usefulness of the model for predicting the initial stages of this kind of aggregation processes.

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PubMed2003

Coupled aggregation and sedimentation processes: the sticking probability effect.

The influence of the sticking probability P and the drift velocity on kinetics and structure formation arising in coupled aggregation and sedimentation processes was studied by means of simulations. For this purpose, a large prism with no periodical conditions for the sedimentation direction was considered allowing for sediment formation at the prism base. The time evolution of the cluster size distribution (CSD) and weight-average cluster size (n(w)) were determined in three different regions of the prism. The cluster morphology and the sediment structure were also analyzed. We found that the coupled aggregation and sedimentation processes in the bulk are governed by P for short times, and controlled by the Péclet number Pe for long times. In the lower part of the reaction volume, where the sediment grows, the local n(w) grows at sufficiently large times analytically with an exponent of four. This behavior seems to be independent of Pe and P. The obtained results are in good agreement with the experimental data reported by C. Allain, M. Cloitre, and M. Wafra [Phys. Rev. Lett. 74, 1478 (1995)] and support the idea of a possible internal cluster rearrangement for the experiments. Finally, we discuss how the scale dependent fractal character of the sediment is related to the different stages of the aggregation process.

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PubMed2002

Constant bond breakup probability model for reversible aggregation processes.

Reversible aggregation processes were simulated for systems of freely diffusing sticky particles. Reversibility was introduced by allowing that all bonds in the system may break with a given probability per time interval. In order to describe the kinetics of such aggregation-fragmentation processes, a fragmentation kernel was developed and then used together with the Brownian aggregation kernel for solving the corresponding kinetic master equation. The deduced fragmentation kernel considers a single characteristic lifetime for all bonds and accounts for the cluster morphology by averaging over all possible configurations for clusters of a given size. It became evident that the simulated cluster-size distributions could be described only when an additional fragmentation effectiveness was considered. Doing so, the stochastic solutions were in good agreement with the simulated data.

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PubMed2000

Multiple contact kernel for diffusionlike aggregation

The Brownian kernel is usually assumed to describe pure diffusion-limited cluster-aggregation processes. In this work, we show that this assumption is correct for simulated data. For experimental data, however, significant deviations were observed although the system was aggregated at an electrolyte concentration well above the critical coagulation concentration. This indicates that residual cluster-cluster interactions are not completely absent in real experimental systems. In order to improve the description of the experimental data, we developed a kernel that considers a monomer-monomer sticking probability explicitly and accounts for the possibility of multiple monomer-monomer contacts in the cluster collision area. The proposed kernel agrees excellently with the experimental cluster-size distribution and the corresponding scaling function.

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