Particle collisions and coalescence in fluids

Coagulation, in the physical context, is looked upon here first from the fundamental perspective of collision and coalescence of individual particles. A Monte Carlo technique is used to investigate the particle size distribution in a suspension of coagulating particles when one or more collision mechanisms operate. The effect of interparticle forces - hydrodynamic, van der Waals' and electrostatic - on the collision probability of the particles is examined. The results obtained are used to evaluate the well-known dynamic equilibrium hypothesis according to which an equilibrium particle size distribution is assumed to exist under the action of a given collision mechanism. It is shown that dimensional analysis cannot, in general, be used to predict steady state particle size distributions, mainly because of the strong dependence of the interparticle forces on the sizes of the interacting particles. The insight into particle kinetics thus gained from the Monte Carlo simulation of collision processes is used to develop a numerical simulation of a rectangular settling basin. The computer model follows the spatial and temporal development of the influent particle size distribution towards the outlet of the tank, accounting for all of the basic kinetics of particle collision and coalescence processes and including transport processes such as particle settling, advection, resuspension and turbulent mixing. The influence of the particle size-density relationship and floc deaggregation by turbulent shearing are also modeled. Of necessity, modeling of some of these processes has been somewhat empirical since the physical and biochemical nature of the flocs are unique to a particular suspension and their determination requires experimental work. The results of the simulations performed indicate that the particle size-density relationship, the collision efficiencies between flocs and the influent particle size distribution are of major importance to the performance of the sedimentation basin. Clearly, further modifications, Improvements and trials are needed in order to use the model for the design of new facilities. Nevertheless, the computer model may serve as a guide for selection of several design and operation variables for the successful treatment of a particular waste or the selective removal of pollutants whose concentration depends on the shape of the effluent particle size distribution

Microgravity coagulation and particle gel formation

VIII+192hlm.;24c

Hydroxyapatite Nanoparticles and Nanobiocomposite Scaffold for Protein Adsorption and Release

Spherical, rod and fibrous hydroxyapatite (HA) nanoparticles synthesize through a common co-precipitation technique and fabricate macroporous HA-gelatin nanobiocomposite scaffolds for protein adsorption/release study. Three fundamental processing parameters such as solution pH, temperature and Ca/P ratio synchronize the morphology and crystallinity of nano HA from identical precursors Ca(CH3COO)2 and KH2PO4. Dispersion study illustrates the HA nanoparticle suspension stability phenomenon in aqueous media. Rod shaped HA exhibits relatively better bovine serum albumin (BSA) protein adsorption efficacy with compare to other two morphologies. In aqueous media, one gram nanorod HA particle adsorb 28 mg BSA within a time frame of 48 h and subsequently 75 wt.% release after 96 h in phosphate buffer solution. Low temperature freeze casting of homogenous aqueous slurry of HA nanoparticles, gelatin and biocompatible polyvinyl alcohol binder develops nano HA – gelatin nanobiocomposite macroporous scaffolds. Freeze casted nanorod HA-gelatin macroporous (70 vol.%) scaffold demonstrate highest yield compressive strength of ~2 MPa compare to other scaffolds prepared from spherical and fibrous HA because of high surface area and the effective anchoring. An optimum cryogenic treatment time at 77K promotes the mechanical response of this low strength scaffold and designates as cryo-treated hydroxyapatite–gelatin macroporous scaffold (CHAMPS). CHAMPS has a high degree of interconnected pores of 50-200 μm in size, compressive strength up to 5.6 MPa and larger strain failure up to 25%. L929 mouse fibroblast cell interaction supports the cytotoxicity and cell adherence behaviour with CHAMPS. Porous scaffold exhibits bioactivity in simulated body fluid (SBF) solution through preferable deposition of carbonated apatite layer around the pores. Biodegradation of scaffold in tris-HCl solution reveals a slow but systematic decrease in weight over incubation up to 7 days. Importantly, the excellent adsorption (upto 50 wt.%) and release (upto 60 wt.% of adsorbed protein) of BSA within 48 h has been uniquely attributed to the inherent porous microstructure of the CHAMPS. Protein adsorption behaviour for both of the particles and scaffolds follow the classical Langmuir isotherm. The extensive micro-computed tomography (micro-CT) analysis establishes cancellous bone-like highly interconnected and complex porous architecture of the protein loaded and original CHAMPS. Overall, the present study provides an assessment of the interaction of protein with HA nanoparticles and their cryotreated HA-gelatin scaffold in vitro to support as drug delivery media and tissue engineering, respectively

Electrification by liquid dielectric flow

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.Includes bibliographical references.by Steven Marc Gasworth.Ph.D