Drug-induced gingival overgrowth is a disfiguring condition that is a side effect encountered in susceptible responder patients common to three groups of drugs - immunosupressants, calcium channel blockers and anticonvulsant agents. The altered overgrown gingiva can be aesthetically displeasing but in severe cases it can cause functional problems and such patients may eventually require excision of excess tissue. The underlying mechanisms that mediate drug-induced gingival overgrowth is uncertain and the various investigations into the pathogenesis of this disease suggest that it is multifactorial. This study investigated the effects of exogenous addition of cycJosporin and amlodipine on the growth and proliferation of human gingival fibroblasts and the production of collagen by these cells. Results showed that these drugs have a direct stimulatory effect on the gingival fibroblasts of responder patients in vitro and there seems to be a synergistic effect between the two drugs. Findings of this study have important relevance as it suggests that fibroblast proliferation and collagen production must play a significant role in the pathogenesis of drug-induced gingival overgrowth. / Dissertation (MSc (Odontology))--University of Pretoria, 2006. / Dental Management Sciences / unrestricted

Conventional methods of imparting toughness to ordinarily brittle thermosetting resins involve the incorporation of a second, discreet phase. Traditionally, this phase has been either a functionalized butadiene-acrylonitrile based elastomer or an unreactive thermoplastic. This dissertation describes the preparation, characterization, and evaluation of new functionalized polysiloxane elastomer and thermoplastic modifiers and their morphological implications to the toughening and physical behavior of, principally, epoxy thermosetting systems. Secondary amine-terminated poly(dimethyl-co-diphenyl siloxane) oligomers were found to be comparable tougheners to acrylonitrile-butadiene rubbers for a bisphenol-A based epoxy resin. The system that imparted the highest toughness was comprised of statistically placed 40% diphenyl and 60% dimethylsiloxane units with Mn̅ of 5000 g/mole loaded at 15% w/w. This composition resulted in a discreet second phase consisting of l μm spherical particles which were evenly dispersed throughout the cured epoxy matrix. Amine-terminated poly(arylene ether ketone) and poly(arylene ether sulfone) thermoplastics were reacted into an EPON 828/4,4'·DDS system. However, the polyketones proved to be ineffective toughening agents due to an incompatibility resulting in macroscopic phase separation. In contrast, the functionalized polysulfones were shown to be effective toughening agents, with the resultant morphology primarily a function of percent incorporation. At ~15% w/w, the polysulfone separated as l-2μm discreet particles while a 30% loading level resulted in a bicontinuous “honeycomb” morphology. The amine endgroups were shown to be necessary in controlling morphology and maximizing toughness. The polysulfone oligomers were also incorporated into a graphite fiber reinforced epoxy composite. Although improved mechanical properties were achieved, the toughness values were not as high as predicted by the neat resin evaluation. The morphology was less definable due to the complex nature and dimensions of the carbon fiber/matrix interactions. Finally, melt processing experiments indicated that amine-terminated polysulfones may act as effective processing aids for brittle bismaleimide systems, by reacting with the BMI, possibly via a Michael addition. This results in a chain extension and higher molecular weight without premature gelation occurring. / Ph. D.

Chemical and physical changes occur during the processing of toughened thermosetting resins. A number of properties are related to the type and sequence of these changes. There is a need for the development of in-situ real-time sensors to follow these changes. Once these sensors are developed, they can be used to preferentially select networks and/or morphologies by feedback-controlled "intelligent" processing. A practical, durable, inexpensive Fourier Transform NearInfrared (FTNIR) fiber optic sensor was developed and the cure of a model toughened cyanate as well as a commercial paste adhesive was followed with this sensor In the near-infrared. The design was suitable for many applications. A mold was designed to incorporate the fiber sensor for composite applications. The growth of the normalized triazine (crosslink) peak appeared to follow second order kinetics. The normalized peak reflected chemical as well as physical changes. Analysis of the individual peaks showed significant physical effects. Conversion based on triazine concentration did not follow second order kinetics. / Ph. D.

A wax distribution quantification procedure using digital image analysis and fluorescence microscopy techniques was developed. The procedure was evaluated by investigating the effect that variable application rates have on wax distribution. The effect of emulsion type and application on |B strength, thickness swell, water absorption, and linear expansion of flakeboard panels were also investigated. Tests revealed that increasing the wax emulsion flow rate and application pressure had a significant affect on wax coverage. A lower amount of flake surface area was covered when the flow rate and air pressure was increased. It was also found that the presence of resin on the flakes affected wax coverage. Resin presence generally increased the wax coverage variability. The application flow rate and pressure also seemed to affect the interaction present between the resin and wax spots. The fractional coverage area of spot size classes was also significantly affected by the emulsion's application parameters. Increasing the flow rate and air pressure was shown to create more variable wax spot distributions. The presence of resin spots on the flakes was also shown to significantly affect the spot size distribution. Changes in the emulsion flow rate and application air pressure also appeared to have a significant affect on wax spot distribution. The type of wax emulsion used, as well as increased application flow rate and pressure, was shown to significantly affect both 2 hour and 24 hour water absorption (by weight). It was found that using a soap based emulsion improved the water absorption characteristics, and that increasing the emulsion's application flow rate and air pressure adversely affected the water absorption. Differences in IB strength and 24 hour thickness swell were also seen between the panels made using increased flow rate and pressure and the panels produced with standard parameters. However, due to possible influence of press malfunctions on the boards performance, conclusions about the effect of increased parameters can not be clearly drawn. No significant difference in linear expansion was seen for any of the samples tested. / Master of Science

The purpose of this research was to determine whether all-purpose flour could be partially replaced with locust bean gum (LBG) and guar gum, and produce an acceptable bread product. A pilot study determined that up to 4% gum replacement for flour was feasible. All bread treatments were evaluated objectively by standing height, texture, color, and cell size. Moisture determinations were obtained for each bread variation. Sensory quality was examined by consumer testing. The amount of heat required to break the hydrogen bonds in amylopectin, indicative of bread staling, was measured by differential scanning calorimetry (DSC) for all bread treatments. Two percent LBG replacement significantly increased standing height. Firmness of bread increased with an increase in gum; the 4% guar bread was significantly firmer. Crumb color was not significantly different for any of the five bread treatments. Crust color, however, was significantly lighter for the control in comparison to the 2 and 4% guar, and 4% LBG breads. Two percent guar produced a more even cell size distribution throughout the bread crumb. For all 5 bread formulations moistures were not significantly different. Sensory evaluation determined a significant difference between the control and 4% LBG. The 4% LBG bread was preferred, although not significantly. Both gums were found to retard bread staling and 2% LBG was the most effective in lengthening the shelf life of the bread product. Objective and sensory evaluation indicated both gums produced acceptable bread products for consumer consumption and possible use in further research. / Master of Science

The objective of this study was to develop a two-dimensional computer model for the simulation of the resin transfer molding/resin film infusion processing of advanced composite materials. This computer simulation model is designed to provide aircraft structure and tool designers with a method of predicting the infiltration and curing behavior of a composite material component. For a given specified cure cycle, the computer model can be used to calculate the resin infiltration, resin viscosity, resin advancement, heat transfer within the component/tool assembly during processing and preform compaction. Formulations of the resin flow problem are given using the finite element/control volume technique based on Darcy's Law of flow through porous media. This technique allows for the efficient numerical calculation of the advancing resin front within the preform materials. The heat transfer in the fabric preform and tooling is analyzed using a transient finite element method which included the effects of convection on the tooling surfaces. Compaction behavior of the tooling assembly is analyzed using a simplified isotropic form of the plane elasticity equations. All of these solutions were coupled together in a quasisteady state non-linear fashion inside the computer code. / Master of Science

Tall oil is a mixture of rosin acids, fatty acids, and non-acids resulting from acidification of the soaps separating out from the kraft pulp process evaporator liquor. The present uses of tall oil center chiefly around its fatty acid content, but are limited for some purposes because of the rosin content. Separation of these constituents makes each available as such. The rosin, as crystalline abietic acid, has specific possibilities as a raw material. Rosin and fatty acids are separated chiefly by distillation, although chemical means and extraction have been proposed to overcome such objections as corrosion and losses as pitch, incurred in distillation. Chlorination is used as a step in the purification of tall oil, or to produce a sticky chlorinated oil, but no separation based on the use of chlorine appears to have been proposed. It was proposed in this investigation to chlorinate the fatty acid double bonds in hopes that the properties of this product would be such as to permit of a separation. The effects of solvent, light, heat, and catalysts were studied to determine the optimum conditions for such a reaction, and the effect of chlorination upon the rosin and fatty acids, respectively, under specific conditions was determined, It was found that the use of CCl₄ solvent and ultraviolet light accelerate chlorine consumption and promote the addition of chlorine, but do not entirely stifle the substitution reaction. Rosin and fatty acid double bonds are attacked to about an equal extent under these conditions. The chlorinated oil is entirely soluble in most common solvents at room temperature. Petroleum ether insolubles increase slightly over the amount obtained from untreated oil. It is recommended that the range of chlorination conditions be extended to a more complete study of possible results, and that other chemical attacks be investigated. / Master of Science

"Resins" is a class of compounds believed to play an important role in the conversion processes of coal and coal-related materials into oils. Methods currently used to isolate this fraction, generally lack reproducibility and yield impure and strongly overlapping fractions which do not reflect the actual group-type distribution in the liquid fuel. A separation method based on liquid column chromatography was developed, which divides liquid fuels into eight distinct and minimally overlapping chemical classes: five non-polar (saturated, mono-, di-, tri-, and polynuclear aromatics), one intermediate polar (resins) and two polar (asphaltenes and asphaltols) fractions. Chemical characterization of "resins fractions," derived from two alternative fuels (coal-derived liquid and sugarcane bagasse), was achieved by first subjecting them to acid-base-neutral separation, followed by analysis of each subfraction by GC/MS. Identification of the eluted components was carried out utilizing a library search system, by comparing retention times (indices) of 150 model compounds believed to exist in liquid fuels, on two fused silica capillary columns (Carbowax 20 M and SE-54), and by mass spectral interpretation. GC/MS results indicate that "resins" are mainly composed of weakly acidic (phenols, indanols, naphthols), mildly basic (benzoquinolines, chloroanilines, etc.), neutral-nitrogen (indoles and carbazoles), and oxygen (carbonyl) compounds, and are free of hydrocarbons. / Ph. D.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Com o objetivo de preservar as propriedades e otimizar o encapsulamento do Ãleo essencial de Lippia sidoides (OELS), foi preparado nanopartÃculas de quitosana e goma carregadas com OELS via spray-drying, usando gomas nativas da regiÃo do Nordeste brasileiro. As gomas foram extraÃdas dos exsudatos das Ãrvores da Anacardium Occidentale (goma do cajueiro), Sterculia striata (goma do chichÃ) e Anadenanthera macrocarpa (goma do angico). As nanopartÃculas foram caracterizadas por espectroscopia na regiÃo do infravermelho (FTIR) e na regiÃo do UV/VIS, tamanho de partÃculas e potencial zeta, anÃlise tÃrmica (TGA/DSC), e cromatografia gasosa (GC-MS). O espectro do FTIR mostrou as principais bandas da quitosana e das gomas, em 1550 e em 1647 cm-1. Observou-se diferentes propriedades nas nanopartÃculas em funÃÃo do tipo de matriz utilizada. As partÃculas produzidas apresentaram tamanho de 17 a 800 nm, onde a matriz de goma do cajueiro produziu as partÃculas maiores, e a matriz de goma do chichà as partÃculas menores. O potencial zeta variou de -40 mV a +30 mV, onde houve maior variaÃÃo quando utilizou-se a matriz com goma do chichÃ. A anÃlise tÃrmica evidenciou os eventos de perda de massa para as amostras, onde atà 200 ÂC as amostras perdem no mÃximo 20% da sua massa inicial. O encapsulamento do OELS variou entre 6 e 16 %, onde as matrizes com goma do cajueiro e do chichà apresentaram os maiores valores. As amostras com goma do cajueiro apresentaram boa estabilidade de encapsulamento apÃs 12 meses, onde o teor de Ãleo encapsulado nÃo se alterou. A anÃlise por cromatografia gasosa mostrou que o Ãleo encapsulado nÃo apresentou em sua composiÃÃo diferenÃa significativa à do Ãleo inicial, encapsulando os principais componentes. A liberaÃÃo do OELS pelas matrizes foi relativamente lenta, onde entre 60 e 100% do Ãleo foi liberado em 48 horas. O estudo cinÃtico da liberaÃÃo do OELS indicou que a liberaÃÃo segue o modelo de Higuchi, com a liberaÃÃo pelas amostras variando entre fenÃmenos fickianos e nÃo-fickianos. / Aiming to preserve the properties and optimize the encapsulation of the Lippia sidoides essential oil (LSEO), this work reports on the preparation of chitosan-gum nanoparticles loaded with LSEO by spray-drying, using gums extracted from native trees of northeast of Brazil. The gums used were extracted from exudates of Anacardium Occidentale tree (Cashew gum), Sterculia striata trees (Chichà gum) and Anadenanthera macrocarpa trees (Angico gum). Samples were characterized by FTIR and UV/VIS spectroscopy, particle size and zeta potential, thermal analysis (TGA/DSC) and gas chromatography (GC-MS). The FTIR spectrum showed the main bands of chitosan and gums, in 1550 and 1647 cm-1. Particle sizes ranged from 17 nm to 800 nm, where the angico gum matrix presented the smallest sizes and cashew gum matrix the larger sizes. The zeta potential varied from -40 mV +30 mV, where chichà gum matrix presented the biggest variation. Thermal analysis showed the events of mass loss for the samples, where up to 200 C there are a maximum of 20% mass lost compared to the initial mass. The encapsulation of LSEO ranged between 6 and 16%, where the cashew gum and chichà gum matrixes presented the highest values. Cashew gum samples showed good encapsulation stability after 12 months, where the encapsulated oil content has not changed. The encapsulated oil did not present significant difference in its composition to the initial oil, encapsulating the key components. The release of LSEO from the matrixes was relatively slow, where between 60 and 100% of the oil was released in 48 hours. The kinetic study of LSEO release indicated that the release followed the Higuchi model, with the release by the samples varying between fickians and non-fickians phenomena.

Large Area Maskless Photopolymerization (LAMP) is a technology being developed to fabricate integrally-cored ceramic molds for the investment casting of turbine airfoils. In LAMP, ultraviolet (UV) light in the form of bitmap images is projected from a spatial light modulator (SLM) onto a photocurable ceramic material system (PCMS). Exposed and unexposed regions are determined through black and white portions of the bitmaps, respectively. UV light induces photopolymerization and the formation of an insoluble solidified network. Three-dimensional structures are built layer-by-layer through sequential application and curing of PCMS layers of 100 micron thickness. To date, ceramic molds fabricated using LAMP have been successfully implemented in investment casting of single-crystal turbine airfoils without internal cooling schemes. Two particularly important challenges for the fabrication of airfoil molds with internal cooling passages are: (a) fabrication of unsupported structures in the mold geometry and; (b) mitigation of internal stresses that arise during layer-by-layer build-up due to volumetric shrinkage during photopolymerization. Unsupported geometries arise in nearly every cored airfoil mold and often in a location where support structures cannot be easily removed after fabrication. Internal stresses generated by volumetric shrinkage can lead to cracking during binder burnout (BBO), sintering and casting. This thesis aims to simultaneously address these challenges through the investigation of grayscale exposure to control the degree of monomer conversion during photopolymerization of single and multiple layers. The effective intensity of the UV light incident on the monomer system can be reduced by selectively turning off pixels within the nominally "white" or "on" regions of the projected bitmaps, effectively producing an exposure with a lower light intensity. In an effort to reduce internal stresses in the mold, the grayscale exposure can be tuned to create regions of uncured or partially cured monomer within the mold geometry to reduce the connectivity between cured regions and thus reduce the net effect of volumetric shrinkage. Grayscale exposure can also be used to generate support structures with a low degree of polymerization to create a gel state beneath and surrounding the unsupported segments of the mold, which can be washed away after completion of mold fabrication. In order to successfully utilize grayscale techniques in LAMP, the cure depth must be predicted. This is accomplished through cure depth measurements at different exposure times to develop a "working curve." In addition, the degree of monomer conversion and its relation to cure depths resulting from grayscale exposure must be understood. Measurements of the degree of conversion are obtained through Fourier Transform Infrared spectroscopy (FTIR). Empirical models are developed and compared to theoretical predictions. Also, the scattering length pixelation model is introduced as a technique to predict the light intensity distribution within the PCMS for exposure patterns at multiple length scales. Results from these grayscale investigations are then applied to LAMP and the effectiveness of grayscale to fabricate unsupported geometries and internal stresses from volumetric shrinkage is discussed.