Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xii, 173 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 138-142).

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xiii, 112 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 92-94).

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 255-268). Available also in a digital version from Dissertation Abstracts.

Thesis--Auburn University, 2009. / Abstract. Includes bibliographic references (p.127-130).

Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / "May 2002." Typescript. Vita. Includes bibliographical references (leaves 237-245).

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Fuller, Thomas; Committee Co-Chair: Deng, Yulin; Committee Member: Gallivan, Martha; Committee Member: Kohl, Paul; Committee Member: Singh, Preet. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Pancreatic beta-cells secrete insulin in response to increase in blood glucose concentration with a rapid first phase and slower, sustained second phase. This secretion pattern is similar in entire pancreas, isolated islets of Langerhans and single beta-cells and it is disrupted in type 2-diabetes. Insulin stored in secretory vesicles has to undergo preparatory steps upon translocation to the plasma membrane which include docking and priming before being released by exocytosis. A better understanding of the molecules involved in these steps is required to determine the rate limiting factors for sustained secretion. Here these processes were studied in real time using total internal reflection fluorescence microscopy, which enables observation of insulin granules localized at the plasma membrane. A pool of granules morphologically docked at the plasma membrane was found to be depleted upon repeated stimulations. Recovery of the docked pool of granules took tens of minutes and became rate limiting for sustained secretion. Shorter depolarization stimuli did not deplete the docked pool and allowed rapid recovery of releasable granules. When a new granule arrived at the plasma membrane, docking was initiated by de novo formation of syntaxin/munc18 clusters at the docking site. Two-thirds of the granules which arrived at the plasma membrane failed to recruit these proteins and hence failed to dock. Priming involved recruitment of several other proteins including munc13, SNAP25 and Cav1.2 channels. Exocytosing granules were in close proximity to Ca2+ influx sites with high degree of association with Cav1.2 channels. This is because of the association of these channels to exocytosis site through syntaxin and SNAP25. During exocytosis the assembled release machinery disintegrated and the proteins at the release site dispersed. Syntaxin dispersal was initiated already during fusion pore formation rather than after release during exocytosis. This was studied using a newly developed red fluorescent probe - NPY-tdmOrange2 which was the most reliable pH sensitive red granule marker to label insulin granules. Overall these data give new insights into the molecular mechanisms involved in biphasic insulin secretion. Disturbances in the secretion at the level of granule docking and fusion may contribute to the early manifestations of type-2 diabetes.

This dissertation discusses the effect of synthesis route and ortho-position group on the thermal and transport properties of thermally rearranged polymers. Thermally rearranged polymers are polybenzoxazoles formed via the solid state rearrangement of ortho-functional polyimides. In this study, polymers were derived from 3,3'-dihydroxy-4,4'-diamino-biphenyl and 2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (HAB-6FDA). These HAB-6FDA polymers were synthesized using chemical and thermal imidization, and hydroxyl, acetate, propanoate, or pivalate ortho-position groups were considered. In these polymers, gas permeability increases as a function of conversion for all samples. The polyimide synthesis route does not affect the thermal or transport properties. However, the precursor ortho-position group strongly influences the thermal and transport properties of TR polymers. Additionally, it was determined that an increase in gas diffusivity was the primary cause of increased permeability as a function of thermal rearrangement. / text

Fouling is a major obstacle to the implementation of membranes in water purification applications. Hydrophilization of the membrane surface tends to mitigate fouling because hydrophobic interactions between foulants and the membrane are reduced. Polydopamine was deposited onto membranes to render their surfaces hydrophilic. The chemical structure of polydopamine, which was previously ambiguous, was investigated by many spectroscopic techniques. While previously thought to consist of covalently-linked monomers, polydopamine was found to be an aggregate of partly-oxidized dopamine units linked by strong, non-covalent secondary interactions. Polydopamine was also used as a platform for the molecular conjugation of other anti-fouling materials, such as poly(ethylene glycol), to the membrane surface. Membrane fouling was assessed by constant permeate flux crossflow filtration with an oil/water emulsion feed. The threshold flux--the flux at which the rate of fouling significantly increases--was determined by a well-established flux stepping technique. Membrane resistance evolution during fouling was compared for constant flux and constant transmembrane pressure operation using unmodified membranes. Below the threshold flux (slow fouling), good agreement in resistance evolution was found between the two operational modes; above the threshold flux, significant deviation was observed. The effect of polydopamine and polydopamine-g-poly(ethylene glycol) surface modifications was studied under constant flux crossflow fouling conditions. The surface modifications were found to increase the membrane resistance, resulting in higher transmembrane pressures in the modified membranes than in the unmodified membranes at fluxes below the threshold flux. Modified membranes were also compared to unmodified membranes with the same pure water permeance (same initial resistance). In this case, the modified membranes had lower transmembrane pressures during fouling than the unmodified membranes, suggesting that a preferred method of membrane surface modification is to begin with a membrane of higher permeance than required, and then surface-modify it to achieve the desired permeance. The efficacy of polydopamine and polydopamine-g-poly(ethylene glycol) surface modifications in reducing biofouling was also evaluated. Modified membranes showed reduced protein and bacterial adhesion in short-term tests, which are commonly used to assess biofouling propensity. However, long-term operation under hydrodynamic conditions mimicking those of an industrial module showed no benefit of the hydrophilic coatings in limiting biofouling. / text

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy