Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Not available / text

Thesis (M App Sc) -- University of South Australia, 1992

Thesis (B.S.)--Butler University, 2009. / Includes bibliographical references.

No / Aqueous solutions of hen egg lysozyme (3% w/v) were dispersed and precipitated by a homogenous mixture of supercritical carbon dioxide-ethanol using the Solution Enhanced Dispersion by Supercritical fluid (SEDS) process. The effects of different working conditions, such as temperature, pressure and the flow rates of the solution and ethanol, on the particle-formation process were studied The morphology, particle size and size distribution and biological activity of the protein were determined The precipitates were examined with high-sensitivity differential scanning calorimetry (HSDSC) and high-performance cation-exchange chromatography Particle size measurements showed the precipitates to be aggregates with primary particles of size 1-5 ¿m. The similarity of HSDSC data for unprocessed and processed samples indicated that the different physical forces that stabilise the native form of lysozyme are unchanged after SEDS processing. From FT-Raman spectroscopic studies secondary structural changes were observed in certain SEDS-produced lysozyme, with most processed samples displaying a slightly more disordered secondary structure than the unprocessed sample However, SEDS samples produced at 200 bar and 40 C exhibited negligible disturbance Thus the SEDS process utilising aqueous solution was able to bring about size reduction of lysozyme with minimal loss of biological activity.

Choosing the right solvent is critical for many industrial applications. A useful property for selection of solvents is their solubility parameters. This concept of solubility parameters is central to this thesis and has been used in two different case studies of material treatment applications. Silicone rubber (crosslinked poly(dimethyl siloxane), PDMS) has many favorable material properties making it useful in biomedical devices. However, a limiting aspect of its material properties is a hydrophobic surface. The aim of this work was to prepare a hydrophilic PDMS material while retaining the transparency of the material. To do this, PDMS was combined with a hydrophilic polymer, polyvinylpyrrolidone (PVP) in an interpenetrating polymer network (IPN). A two-step IPN synthesis method was developed and it was found that the solvent used for polymerization of PVP had a significant influence on the water-wettability and the transparency of the PVP/PDMS IPN. Several different analytical techniques were used for determining the degree of phase separation in the PVP/PDMS IPN. It was found, by using microscopy techniques, that the PVP phase domains varied between 200 nm up to a few micrometers, and the size of the phase domains was correlated to the solvent used for polymerization of the IPN. The second topic for which solvent effects were explored was for the use of mesoporous silica particles as potential drug delivery devices. In the present work a drug molecule, ibuprofen, was loaded into mesoporous silica particles using different solvents, and in addition adsorption isotherms were established in each solvent. The maximum loading of ibuprofen in the mesoporous material was achieved when using a nonpolar solvent, in particular liquid carbon dioxide was successfully used. One of the advantages of using liquid carbon dioxide is that no solvent residues are left in the final material, which is important for pharmaceutical applications. Furthermore, it was concluded that ibuprofen was stored in an X-ray amorphous form in the mesoporous particles. Release studies in water showed a rapid release of ibuprofen from the mesoporous silica particles, while the dissolution of samples with crystalline ibuprofen was slower. This was verified to be an effect of a larger exposed ibuprofen area in the ibuprofen-loaded mesoporous silica particles, and it was concluded that the intrinsic dissolution rate for the samples were identical.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20338号 / 工博第4275号 / 新制||工||1662(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 石田 毅, 教授 林 為人, 准教授 奈良 禎太 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

As feature sizes in semiconductor devices become smaller and newer materials are incorporated, current methods for photoresist and post plasma etch residue removal face several challenges. A cleaning process should be environmentally benign, compatible with dielectric materials and copper, and provide residue removal from narrow and high aspect ratio features. In this work, sub-critical CO2 based mixtures have been developed to remove the etch residues; these mixtures satisfy the above requirements and can potentially replace the two step residue removal process currently used in the integrated circuit (IC) industry. Based on the chemical nature of the residue being removed, additives or co-solvents to CO2 have been identified that can remove the residues without damaging the dielectric layers. Using the phase behavior of these additives as a guide, the composition of the co-solvent was altered to achieve a single liquid phase at moderate pressures without compromising cleaning ability. The extent of residue removal has been analyzed primarily by x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Various techniques such as attenuated total reflection - Fourier transform infrared (ATR-FTIR) spectroscopy, angle-resolved XPS (ARXPS), and interferometry were used to probe the interaction of cleaning fluids with residues. Model films of photoresists and plasma deposited residues were used to assist in understanding the mechanism of residue removal. From these studies, it was concluded that residue removal takes place primarily by attack of the interface between the residue and the substrate; a solvent rinse then lifts these residues from the wafer. It has been shown that transport of the additives to the interface is enhanced in the presence of CO2. From positronium annihilation lifetime spectroscopy (PALS) studies on a porous dielectric film, it has been shown that these high pressure fluids do not cause significant changes to the pore sizes or the bonding structure of the film. Hence, this method can be used to remove post etch residues from low-k dielectric films.