Biomedical subjects

T Dabros

Publications and source records attributed to T Dabros.

4 recordsLinked to original sources

PubMed1999

Analysis of Fine Bubble Attachment onto a Solid Surface within the Framework of Classical DLVO Theory.

Fine bubble attachment onto a solid surface in an impinging jet flow was analyzed within the framework of DLVO theory. The effects of hydrodynamic convection, van der Waals (VDW) interaction, electrostatic double-layer (EDL) interaction, and gravitational force on bubble attachment rate (in terms of the Sherwood number) were examined in detail. The analyses showed that due to large Peclet number and gravity number for gas bubbles the behavior of the bubble attachment is significantly different from that of colloidal particle deposition in some aspects. Specifically, it was demonstrated that within a certain range of physicochemical conditions, gas bubbles can attach onto a solid surface despite the existence of repulsive VDW interaction force and the fact that the surfaces of both the bubble and the solid collector carry the same sign of electrostatic potentials. This is attributed to the role played by the short-range attractive asymmetric EDL interaction and the strong hydrodynamic and gravity forces, without any need for the so-called hydrophobic interaction force. In addition, it was also shown that the models derived for the impinging jet system can be used to evaluate transport of fine gas bubbles onto a large particle surface, suggesting that the information extracted from the impinging jet geometry can be applied to the analysis of flotation processes. Copyright 1999 Academic Press.

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PubMed1999

Emulsification through Area Contraction.

Emulsification requiring very little input energy can be induced at an oil-water interface that is initially in a state of equilibrium. The process involves destabilization, through contraction, of local interfacial regions. For emulsification to occur, it is necessary for the interfacial structure to have no resistance to surface shearing. Such a mechanism of emulsification may have important implications for the approach to solving emulsion problems in the petroleum industry. Copyright 1999 Academic Press.

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PubMed1998

Kinetics of Particle Transport to a Solid Surface from an Impinging Jet under Surface and External Force Fields.

Based on the presented model for the impinging jet system, extensive theoretical analysis was made on particle deposition. Complete transport equations with consideration of gravity, van der Waals, and electrical double layer (EDL) interactions, as well as hydrodynamic interactions, were numerically solved. The influences of gravity, van der Waals, and electrical double layer interactions on the particle deposition rates (in terms of the Sherwood number) were presented. The results demonstrate that the asymmetric EDL interaction, which has been ignored in previous treatments, has an impact on the particle deposition rate. It was also found that the Sherwood number is strongly dependent on the characteristics of the particle-collector interaction energy profiles, such as the height of the energy barrier and the depth of the secondary energy minimum. Particularly, the effects of the height of the energy barrier and the depth of the secondary energy minimum on the Sherwood number for different Peclet numbers were discussed. In addition, a simple expression was derived for quantitatively estimating the contributions to the deposition rate due to particle diffusion, migration, and convection. With the aid of calculated particle concentration distributions, this expression can be used to understand the numerical predictions. Copyright 1998 Academic Press.

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PubMed1998

Does Equilibrium Interfacial Tension Depend on Method of Measurement?

In the presence of surfactants, the equilibrium interfacial tension (IFT) between two immiscible fluids can be very dependent on the particular technique used for measurement. This is because the partitioning of surfactants between the two bulk phases and the interface, which ultimately determines IFT, depends on geometric factors such as the volume fractions and specific interfacial areas (i.e., interfacial areas per unit volume) of the two fluids. In this work, the effect of surfactant partitioning on equilibrium IFT is demonstrated both theoretically and experimentally. A novel technique which enables direct measurement of IFT at macroemulsion droplet surfaces, with direct application to emulsion research, is demonstrated. Copyright 1998 Academic Press.

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