Mode of access: World Wide Web. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 94-111). / Electronic reproduction. / Also available by subscription via World Wide Web / xv, 111 leaves, bound ill. (some col.) 29 cm

Aliphatic polyesters prepared by the ring opening polymerization of lactones and lactides, are versatile polymers having good hydrolyzability, mechanical properties and biocompatibility. These characteristics make them a leading material in biomedical and pharmaceutical industries as a resorbable implant and a vehicle for controlled drug delivery. An extensive research effort has been made to develop new initiators, catalysts for the ring opening polymerization of cyclic esters. Many effective initiators based on alkali metals, metal oxides have been developed for anionic polymerization of lactones. The main objectives of this project were to develop a novel catalyst by utilizing fully biocompatible and non-toxic reagents for the synthesis of polycaprolactone (PCL) by ring opening polymerization of cyclic esters at reasonably low temperature and a synthesis of hybrid silica nano-composite for biomedical applications and its characterization. Silica and dry calcium hydride reagents were used to successfully prepare heterogeneous catalysts for the ring opening polymerization of cyclic ester monomer å-caprolactone at reasonably low temperature of 100 oC. Two kinds of catalyst were prepared with non-functionalized and silane functionalized silica. The GP silane functionalized silica catalyst showed higher activity and higher product yield as compared to non-functionalized catalyst during polymerization at the same temperature. The in-situ polymerization kinetics of both reactions was studied using Raman spectroscopy. A silica based nano-composite was also synthesized which has a potential application in bone tissue engineering and possible drug delivery. The synthesized polyester and hybrid silica nano-composite were characterized with different analytical techniques to confirm required product formation.

The wettability of titania is an important factor in numerous industrial and natural processes. It is, as for most oxide surfaces, mainly determined by the density of hydroxyl groups (titanols). / The influence of external stimuli - heat and UV light - on the surface of titania was investigated with a number of surface-sensitive techniques: secondary ion mass spectroscopy, atomic force microscopy, streaming potential and contact angle measurements. Measurements were done in parallel on silica. / Thesis (PhDApSc(MineralsandMaterials))--University of South Australia, 2005.

Hydrophobic colloidal suspensions are common in nature and industry. DLVO theory has been used to model the interactions between colloidal particles for decades, however the origin of long-ranged attractive forces observed between hydrophobic colloids remains the subject of much debate. In an effort to understand these forces and improve the prediction of colloidal stability, the colloidal stability of synthetic silica and titania was studied at various concentrations of dissolved gas, KCl electrolyte and pH. / Thesis (PhD)--University of South Australia, 2003

Thesis (PhDBiomedicalScience)--University of South Australia, 2001.

This study is primarily concerned with the adsorption characteristics of ethyl(hydroxyethyl)cellulose (EHEC), a water soluble polymer with many pharmaceutical appliations. / Thesis (PhD in AppSc)--University of South Australia, 2001.

This study is primarily concerned with the adsorption characteristics of ethyl(hydroxyethyl)cellulose (EHEC), a water soluble polymer with many pharmaceutical appliations.

Deposition of amorphous silica (SiO2) and calcium oxalate (CaOx) on the calandria tubes of juice evaporators cause serious processing problems in Australian cane sugar mills. The removal of these deposits by mechanical and chemical means is a timeconsuming and costly experience. The cost of downtime and chemical cleaning can be several million dollars per year for the Australian sugar industry. The interactions between CaOx and SiO2 have not been investigated previously because conventional studies only address fouling by individual components. The present work evaluates their interactions using two experimental approaches: batch tests for assessing kinetic and thermodynamic behaviour, and fouling-loop experiments for examining composite fouling behaviour under different operating conditions. The above two approaches were employed both in the absence and in the presence of sugar to elucidate the effect of sugar on composite fouling mechanisms and to determine the controlling species responsible for composite fouling. The composite fouling experiments were performed in a novel closed-loop circulation system simulating the effect of feed composition of successive stages of evaporation cycle in a single run. In addition, the fouling-loop system was operated in a constant composition mode to study the effects of thermal hydraulic conditions on composite fouling. The combined information obtained from both the batch and fouling-loop tests in this study offer a unique insight into the mechanisms of composite fouling of CaOx and SiO2. Some of the highlights of the obtained results are as follows: ??? Identification of a complex interactive process in calcium oxalate monohydrate ??? silica (COM-SiO2) systems by investigation of the kinetics and thermodynamics of COM-SiO2 coprecipitation in water and sugar solutions, and an understanding of the mechanisms of these interactions; ??? Development of a novel fouling-loop system, which is simple, efficient and cost effective for the study of the effect of juice composition on scale formation in various stages of juice evaporation; ??? Elucidation of composite fouling mechanisms, e.g., a feed composition dependent fouling mechanism is proposed; ??? Isolation and verification of the existence of certain species in composite deposits, which is known to be thermodynamically unstable. In other words, it is established that calcium oxalate trihydrate is stable under certain conditions; ??? Evaluation of the role of thermal hydraulic operating parameters in determining the characteristics of subcooled flow boiling heat transfer and in determining the strength of the composite deposit; ??? Development and validation of an empirical model to predict the subcooled flow boiling heat transfer coefficients in water and sugar solutions; ??? Development of an analytical model incorporating the effects of operating parameters for COM and SiO2 composite fouling in sugar solutions. This model predicted the experimental data better than available models. Results of this work are significant, not only because they have made a valuable contribution to advance the fundamental understanding of heat exchanger fouling, but also because they may play a key role in the development of scale control and removal strategies to minimize the composite fouling in Australian sugar mill evaporators. For example it was found that, in order to effectively minimize the rate of composite fouling and reduce the scale tenacity, it would be necessary to control thermal hydraulic operating conditions, especially the fluid velocity, and to adjust the initial CaOx/SiO2 supersaturation ratio to the optimum value. To achieve the optimal CaOx/SiO2 ratio, certain device can be developed to sequentially measure oxalic acid and SiO2 concentrations in juice so that the correct proportions of chemicals can be added. Model simulations of the composite fouling rate may also effectively and economically provide comparative and relevant information essential for process optimisation and evaporator design

This thesis covers the construction and characterisation of microlasers based on whispering gallery modes in ytterbium-doped microsphere resonators. The microlasers were made by drawing and fusing Yb-doped silica optical fibre into microspheres of approximately 100 μmin diameter using CO2 laser-induced melting. Access to whispering gallery modes was accomplished using a prism coupled to the evanescent field of the internal cavity modes. Microspheres with Q-factors of up to 10^7 were made using this technique. CW multimode lasing was observed at 1050 nm, with a pump threshold required for lasing estimated to be of the order of 100 μW for a 900 nm pump. Both TE and TM modes were identified in the laser emission and the ability to selectively excite each mode family (TE or TM) is shown to be directly controlled by the pump. Pulsed lasing was also observed at 975 nm and 1050 nm.

Hydrophobic colloidal suspensions are common in nature and industry. DLVO theory has been used to model the interactions between colloidal particles for decades, however the origin of long-ranged attractive forces observed between hydrophobic colloids remains the subject of much debate. In an effort to understand these forces and improve the prediction of colloidal stability, the colloidal stability of synthetic silica and titania was studied at various concentrations of dissolved gas, KCl electrolyte and pH. / Thesis (PhD)--University of South Australia, 2003