2010 MU dissertations - Access restricted to UM
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Item The study of dental composites containing hydroxyapatite nanofillers(University of Missouri--Columbia, 2010) Chen, Liang; Chen, Liang[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Dental composites have received widespread clinical acceptance as alternative restorative materials to dental amalgam for their better aesthetic property and less metal ion release safety concern. However, the inadequate mechanical property of dental composites is still one of the key issues, which lead to the restoration fracture, secondary caries and relatively shorter lifespan in comparison with amalgam. In order to improve the mechanical properties as well as extend the survival lifetime of dental composites, we have conducted the following studies: i) synthesis and characterization of novel single crystalline high-aspectratio hydroxyapatite (HAP) nanofibers and mass production of such nanofibers, ii) fabrication and evaluation of the dental composites containing original, glyoxylic acid modified and silanized HAP nanofibers, iii) development and evaluation of dental composites systems with acrylic acid. After systematic evaluation and in-depth analysis of the experimental results, it was concluded that: i) Impregnation of small mass fractions of the original HAP nanofibers into the BisGMA/TEGDMA dental resins (5wt%, 10wt%)/composites(2wt%, 3wt%) can substantially improve the biaxial flexural strength; ii) Glyoxylic acid modification can effectively breakdown the HAP nanofibers bundles to individual nanofibers and lead to the improvement of corresponding dental composites; the water absorption rate was not significantly changed, due to the surface of HAP nanofiber remaining hydrophilic after modification; iii) 3- MPS silanization processing can not only significantly enhance the mechanical strength by improving the interfacial bonding between nanofillers and matrix but also reduce the water absorption rate by converting the hydrophilic surface of HAP nanofibers to hydrophobic; iv) the incorporation of acrylic acid to dental composites systems can generate an amazing improvement on mechanical strength, which can reach as high as 214[plus-minus sign]14MPa. According to the experimental results and scientific findings, the silanized HAP nanofiber reinforced dental composites are very promising for clinical application. In the second part of this dissertation, HAP nanoparticles with different surface charges were successfully synthesized and their influence on cellular uptake behavior and biocompatibility of MC3T3-E1 cell lines was studied. The HAP nanoparticles with positive charge could be more easily uptaken by the MC3T3-E1 cell lines than other nanoparticles due to their attractive interaction with the negative cell membrane. The HAP nanoparticles with different dosage and different charges could all enhance cell proliferation and result in less cell membrane damage for MC3T3-E1 cell lines. Also the positive charged HAP nanoparticles have better biocompatibility compared to the other HAP nanoparticles. These results may provide an improved understanding of surface charge of functional properties of HAP nanoparticles in cells and biomedical field, which could potentially aid in application used in the gene delivery and intracellular drug delivery fields.Item Vascular smooth muscle calcium waves in isolated arterioles : interactions between intraluminal pressure and intracellular calcium handling(University of Missouri--Columbia, 2010) Ella, Srikanth Reddy; Hill, Michael A.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Arterioles, an important control element in the circulatory system regulate blood flow in part though a phenomenon known as the 'Myogenic Response'. Myogenic response of small vessels is their ability to constrict in response to increase in intraluminal pressure or conversely dilate in response to a reduction in pressure. Calcium (Ca[superscript 2+]) is an important and essential signaling element for myogenic constriction. Apart from steady elevations in smooth muscle intracellular Ca[superscript 2+] in response to agonists or intraluminal pressure, several local and temporal Ca[superscript 2+] events such as sparks, waves, flashes also exist. These temporal Ca[superscript 2+] events are differentially regulated in several vascular beds and are poorly understood. Therefore, the current project aimed to understand the effects of intraluminal pressure on arteriolar vascular smooth muscle Ca+ waves in rat cremaster muscle arterioles. The project aimed to investigate the mechanisms underlying the generation of Ca[superscript 2+] waves and postulate a possible physiological role for the Ca[superscript 2+] waves. Increases in intraluminal pressure increased the Ca[superscript 2+] wave activity, described by the number of cells exhibiting Ca[superscript 2+] waves and their frequency. Ca[superscript 2+] waves occurred due to the activation of the IP3 receptors present on the sarcoplasmic reticulum in the cells. The presence of Ca[superscript 2+] waves in the smooth muscle cells provided a general level of vascular activation, wherein the wave activity is modulated to change the temporal responses of the myogenic behaviour. Elimination of Ca[superscript 2+] waves delayed the myogenic constriction, while increased Ca[superscript 2+] wave activity fastened the myogenic constriction.--From public.pdfItem Comprehensive guidance program implementation and student success in high school : a path analysis(University of Missouri--Columbia, 2010) Kayson, Marc A., 1973-; Gysbers, Norman C.; Lapan, Richard T.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The study in this article examined the impact of comprehensive guidance program implementation in Missouri high schools on student success. Specifically, it was hypothesized that a more fully implemented guidance program would lead to lower discipline rates, higher attendance rates, and higher standardized test scores. Further, it was hypothesized that discipline rates, attendance rates, and standardized test scores would mediate the relationship between guidance program implementation and college enrollment rates. A total of 226 high school counselors from across the state of Missouri participated. Results partially supported the hypothesized relationships. Guidance program implementation did significantly predict attendance rates, discipline rates, and standardized test scores, however, only standardized test scores were found to be a significant predictor of college enrollment. Guidance program implementation was shown to have an indirect effect on college enrollment and was mediated by standardized test scoresItem Generation, collection and characterization of nanoparticles and their diffusion in arbitrary tumor and normal tissue geometry(University of Missouri--Columbia, 2010) Boddu, Sunita R., 1979-; Loyalka, S. K.; Tompson, R. V. (Robert Vaughn), 1958-[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Nanoparticles have unique electronic, optical, mechanical, magnetic and chemical properties that are significantly different from those of the bulk materials. Because of this, such particles are of interest in a range of areas for example nuclear reactor safety, cancer diagnosis and therapy. In this work we have used a spark aerosol generator to generate carbon, gold, silver, and palladium nanoparticles. We have measured the size distribution of these nanoparticles using a Scanning Mobility Particle Spectrometer. We designed a nanoparticle collection cell to collect the nanoparticles efficiently, analyzed the nanoparticles for shape and size using Tunneling Electron Microscopy (TEM) and Environmental Scanning Electron Microscopy (ESEM). We observed that the nanoparticle deposition is enhanced by thermophoresis. Nanoparticle production rate and size distribution (peak concentration size) can be conveniently controlled through the spark frequency. The particle size distribution also widens with increasing frequency which is indicative of particle coagulation. We have also explored the use of the Computational Fluid Dynamic (CFD) code FLUENT (Ansys) to compute the deposition mass fractions of carbon, gold, silver, and palladium nanoparticles in our deposition cell to elucidate the role of the thermophoresis in our sample collection. Understanding of diffusion and accumulation of nanoparticles in tissues and tumors is important in drug delivery using nanoparticles. We have explored both analytical and CFD applications in this area, and obtained useful insights.Item Adding pieces to the monocytic ehrlichiosis puzzle : treatment, etiology and protection with a canine model(University of Missouri--Columbia, 2010) McClure, Jennifer Christine, 1981-; Stich, Roger W.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Infections with Ehrlichia canis cause Canine Monocytic Ehrlichiosis (CME), a disease which causes morbidity and mortality of dogs worldwide. Currently, there are questions in the literature regarding efficacy of treatment, etiology of severe disease and whether previous infections offer protection to dogs when they are challenged. Through careful experimentation it was determined that although treatment with doxycycline successfully ameliorates disease, it is not sufficient to clear bacteria from infected dogs and therefore a different treatment regimen should be explored which would fully clear the bacteria. Furthermore, it was determined that E. canis alone could induce severe acute CME in specific pathogen free dogs. Lastly, dogs were infected with E. canis, treated and then given a homologous challenge. Although the dogs demonstrated less severe signs of disease three out of four had levels of bacteria in their blood higher than what was seen during the initial infection.