[No abstract available] / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Dentistry. School of Oral Health Sciences, Faculty of Health Sciences, University of the Witwatersrand, South Africa Johannesburg, 2014 / Purpose: Endodontic retreatment requires the removal of the obturation material from the root canal system. Gutta percha (GP), the most commonly employed obturation material, requires mechanical instrumentation coupled with a chemical adjunct to facilitate its removal. Xylene and Eucalyptus oil are recommended as endodontic solvents due to their dissolving capacity of GP. This study sought to test the changes in the hardness and penetrability of three types of GP (Conventional, Thermafil® and Guttacore™) when exposed to these solvents, utilizing distilled water as a control. Method and materials: Textural analysis was performed to determine the hardness by testing for rigidity, and the penetrability by testing for deformation energy and resilience. These properties were tested on 81 GP cones prior to, and following solvent exposure. For each outcome variable, results were tabulated by group. Between-group differences were assessed by means of a General Linear Model, with the outcome variable as the dependent variable and the solvent, GP type and solvent-GP type interaction as the independent variables. Results: A significant decrease in rigidity and deformation energy was observed across all groups. Resilience was observed to decrease with the thermoplastic GP, Thermafil and Guttacore, but increased with conventional GP. Thermoplastic GP was more amenable to a reduction in hardness and penetration when compared with Conventional GP. A greater reduction in the hardness of Thermafil was observed with Eucalyptus oil. Conventional GP was susceptible to a significant reduction in hardness with both solvents, however its penetrability may be reduced following exposure to Xylene. Guttacore was significantly altered by both solvents. Conclusions: Considering the toxicity profile of Xylene, and the biocompatibility and antimicrobial effects of Eucalyptol, Eucalyptus oil is recommended for use during endodontic retreatment.

Thesis--PlanB (M.S.)--University of Wisconsin--Stout, 2002. / Includes bibliographical references.

Diss. (sammanfattning) Karlstad : Karlstads universitet, 2009. / Härtill 4 uppsatser.

This thesis describes an experimental study of calixarate overbased detergent oil additives, used to neutralise acidic by-products of engine combustion. Aspects of interest in this study include experimental synthesis of calixarenes and overbased detergents, physical and structural characterisation and monitoring of the synthesis process. Two types of calixarenes were prepared (6 and 8 phenolic units). A synthesis procedure of the calixarate overbased detergent was set up, basedono adaptation of existing procedures used for other classes of overbased detergents. The procedure was also modified to suit a lab-scale. 13C NMR and UV-Vis spectroscopy have provided strong evidence for a precursor of the overbased detergent. The ionisation of the surfactants (stearic acid carboxylic group, and phenolic units) was clearly established. The synthesis process was monitored at the molecular and macroscopice level. The use of 13C -labelled compounds enabled a semi-quantitative study of the concentration evolution of each chemical during the synthesis. Langmuir-t rough measurements and dynamic light scattering showed a decrease of particle size during the synthesis of the overbased detergent. The final calixarate overbased detergent was then fully characterised by these two methods. Based on the various information gathered (starting and final material characterisation, monitoring of the process),a mechanism was suggested. This involved a progressive solvation of calcium hydroxide, and breakdown of mixed calcium hydroxide and calcium carbonate.

No description available.

Thesis (Ph. D.)--Columbia University, 1941. / Vita. Bibliography: p. [30]. Also issued in print.

Thesis (Ph. D.)--Columbia University, 1937. / Vita. Diagrams 2 and 3 on leaf mounted over diagrams 2 and 3 on p. 13. "LIterature cited": p. 36.

Thesis (Ph. D.)--School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2005. Directed by Charles A. Eckert. / Charles L. Liotta, Committee Co-Chair ; Charles A. Eckert, Committee Chair ; Amyn S. Teja, Committee Member ; J. Carson Meredith, Committee Member ; Rigoberto Hernandez, Committee Member. Vita. Includes bibliographical references.