Photopolymerization is considered an attractive alternative in many industries to traditional polymerization processes. The advantages of photopolymerization over other types of polymerization include elimination of heat sources, faster cure times, and reduction in the use of volatile organic solvents. Despite these environmental and cost-saving advantages, photopolymerizations have several limitations. Light attenuation can be a problem for systems containing pigments or fillers. The radiation source penetrates only to a shallow depth beneath the surface, limiting the thickness of strongly pigmented or filled coatings and films. Photopolymerization is also generally limited to systems with simple geometries that can be uniformly illuminated. Coatings on three-dimensional substrates, or other systems with complex geometries, are difficult to uniformly cure. These problems can be solved by "shadow cure," which is defined as the reactive diffusion of photoinitiated active centers into regions of a polymer that are unilluminated. In this contribution, the generation and subsequent spatial and temporal evolution of the active center concentrations during illumination are analyzed using the differential equations that govern the light intensity gradient and photoinitiator concentration gradient for polychromatic illumination. Reactive diffusion of the active centers during the post-illumination period is shown to result in cure of unilluminated regions. A kinetic analysis is performed by coupling the active center concentration profiles with the propagation rate equation, yielding predicted cure times for a variety of applications. This analysis is used for the evaluation of cationic shadow cure in pigmented photopolymerization systems, and systems with complex geometries. The extensive characterization of cationic systems is then applied to free-radical photopolymerization to examine the potential of shadow cure for active centers with much shorter lifetimes. An example of a free-radical photopolymerization system is characterized in which the dimensional scales are small enough to utilize the short lifetimes of the active centers. The results presented for both free-radical and cationic shadow cure indicate that the reactive diffusion of photoinitiated active centers may be used for effective cure in unilluminated regions of a photopolymer. This research will potentially allow photopolymerization to be applied in industries where it has never before been utilized.

An investigation of the initiation mechanism in the free radical copolymerisation of acrylonitrile and vinyl acetate using the aminoxyl radical trapping technique, employing 1,1 ,3,3-tetramethyl-2,3-dihydro- 1 Hisoindol-2-yloxyl is reported. Based upon the experimental results, the mechanism of initiation is suggested as proceeding via the 'free monomer' mechanism. Additionally, the effect of Lewis acids on the initiation mechanism is reported. A study of the addition of phosphorus-centred radicals to alkenes and phenylacetylene, utilising the aminoxyl radical trapping technique is reported. The results indicate a decreased rate of addition by both diphenylphosphinyl and dimethoxyphosphinyl radicals to cyclic versus acyclic alkenes. In contrast to cyclic alkenes, both these phosphorus-centred radicals add readily to the triple bond of phenylacetylene. The stereochemistry of the addition of diphenyiphosphinyl and dimethoxyphosphinyl radicals and of the aminoxyl trap is discussed. The stereochemistry of the addition of benzoyloxyl radicals to a conformationally rigid alkene, trans-a2-octalin is reported. Attempts to examine the initiation mechanism in the free radical copolymerisation of styrene/maleic anhydride and of styrene/tetracyanoethylene utilising the aminoxyl radical trapping technique are described. Also described are attempts to synthesise some new phosphorus radical initiators.

Doctor of Philosophy (PhD) / This thesis primarily details the application of high-level ab initio quantum chemistry techniques in order to understand aspects of free-radical mediated protein oxidation. Traditionally, product analysis and electron paramagnetic resonance (EPR) spectroscopy are the primary means for elucidating the chemistry of protein oxidation. However, in experiments involving relatively small proteins reacting with a controlled radical-flux, a vast array of compounds can be produced, which are often difficult to analyse. Quantum chemical techniques on the other hand, can calculate the properties of any particular species directly, without suffering from the problems associated with experiment, such as side-reactions and chain processes. The results presented in this thesis are aimed at elucidating mechanistic details of protein oxidation, which might otherwise be difficult to probe experimentally. Chapter 1 gives an overview of the free-radical hypothesis of disease and ageing. Protein-derived radicals can undergo a variety of reactions, with the particular reaction that occurs depending on numerous aspects. Many types of reactions have been identified through radiolysis experiments of amino acids, and these are detailed in this chapter. In addition, the key reactive species are characterized and their different chemistries explained. Chapter 2 details the theoretical tools used throughout this thesis. Species with unpaired electrons (radicals) present unique problems for quantum chemistry to handle, thus an appropriate choice of theoretical technique is needed. The approach taken in this thesis is to use high-level compound methods, many of which have been directly formulated to give improved results for radical species, to provide benchmark quality results by which other less demanding techniques can be assessed. During the course of this study, it became apparent there was a void in the armoury of tools that could be used for the theoretical chemistry calculations. Chapter 3 details the formulation of a new tool in an attempt to fill this gap. Historically, the formulation of this new procedure came after much of the work in this thesis had been carried out. Thus, for the study of many of the reactions of this thesis the new method has not been used. However, it is most appropriate to place its formulation after summarizing the current status of techniques in common use today. Chapters 4 and 5 detail computations carried out on models of peptides containing backbone carbon- and nitrogen-centered radicals. A number of different theoretical techniques are used in these chapters, ranging from the highly accurate and computationally intensive to the less reliable and less demanding. The highly accurate techniques are used to gauge the accuracy of the other less demanding theoretical techniques so that the latter can be used with confidence in larger systems. Not only is the choice of theoretical technique important but also the judicious choice of model is essential. With this in mind, models are incrementally built until convergence of the particular property of interest is reached. Chapters 6 and 7 detail the calculations of β-scission reactions of alkoxyl radicals, which are a particular class of reaction known to occur on peptide backbones. Alkoxyl radicals are particularly difficult for theory to describe correctly. Therefore, Chapter 6 extensively assesses and then identifies the theoretical methods needed to portray them. Chapter 7 uses the techniques identified in the previous chapter in order to predict how the preference for a particular type of β-scission reaction changes.

Cyclolinopeptides (CLs) are hydrophobic cyclic peptides found in flaxseed. They show immunosuppressive activity, but the biological function of these compounds is largely unknown. This thesis presents the results of studies that were conducted to determine whether CLs could act as antioxidants. In the first study, flaxseed oil was passed over a silica adsorbent column to remove polar compounds. The polar compounds were then eluted from the silica absorbant using a series of increasingly polar solvents. Individual polar fractions were then added back to the silica-treated flaxseed oil and the oxidative stability index of these samples was determined at 100 °C. A polar fraction containing mainly CLA, β/γ- and δ-tocopherol increased the induction time of silica-treated flaxseed oil from 2.3 ± 0.28 h to 3.2 ± 0.41 h. A positive effect of the polar fraction containing a mixture of CLA and CLD-CLG on the oxidative stability of oil was also observed. The antioxidant mechanism of CLs was investigated in several model systems using electron spin resonance spectroscopy. The concentration of radicals in a DMPO (5,5-dimethyl-1-pyrroline-N-oxide) radical-CLs reaction mixture was monitored. All CLs exhibited dose dependent scavenging activities. CLA–CLC reactions with DMPO-OH at a concentration of 5 mM resulted in a 24–30% decrease in electron paramagnetic resonance (EPR) signal intensity. The reaction of CLs and the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH•) revealed a more complex interaction than simple radical scavenging. Peptides (CLG and CLG") that contained both tryptophan and methionine showed stronger radical scavenging activity than did CLs containing methionine or methionine sulfoxide but not tryptophan (CLB and CLC). Irradiation of the reaction mixture of DPPH• and peptide with UV light also affected the radical scavenging behaviour. Scavenging activities of DPPH• by CLB, CLC and CLA were enhanced by light, whereas scavenging of DPPH• by the tryptophan containing peptides CLG and CLG″ was not affected. High-performance liquid chromatography with mass spectrometry (HPLC-MS) analysis of the reaction mixtures after a radical scavenging reaction was used to determine the impact of radical scavenging on the peptides. These reactions revealed new masses that were identified and characterized. It was established that DPPH• reacted with the methionine of CLB and with tryptophan in CLG and CLG, by formation of a new covalently-bonded species. Covalent linkages between these amino acids (alone or in peptides) and DPPH• have not been reported previously.

Endotoxin (lipopolysaccharide, LPS) a chemical component of cell wall of gram-negative bacteria, is an important mediator in pathogenesis of sepsis and acute respiratory distress syndrome. It causes production and release of a wide array of mediators including cytokines, chemokines, oxygen free radicals and nitric oxide from neutrophils, macrophages, endothelial cells and epithelial cells through the NF-£eB pathway. LPS increases the permeability of microcirculation, and causes the acute formation of numerous endothelial gaps among venular endothelial cells, resulting in extensive plasma leakage in the inflammatory tissue. Urethan is commonly used as an animal anesthetic for nonrecovery laboratory surgery. It is aslo an £\2-adrenoreceptor antagonist, which can suppress the activation of the cardiovascular system and reduce the angiotensin which increases the blood pressure. Urethan or its metabolites protect animals against LPS, in part, by reducing TNF-£\ release. The aims of the present study to investigate the time-course of vascular permeability in microcirculation of rat trachea, bronchus and esophagus after intravenous application of a high dose of LPS (15 mg/kg), and to reveal the role of urethan (1 g/¢V) and dimethylthiourea (DMTU, 0.375 g/¢V) in inhibition of LPS-induced plasma leakage and edema. India ink was used as a tracer dye to mark leaky microvessels after LPS application. Endothelial gaps were made visible for light microscopy by staining the borders of endothelial cells with silver nitrate. Tracheal sections were stained with toluidine blue to show the subendothelial edema formation. A high dose of LPS was administered intravenously to induce serious plasma leakage and edema and a large number of endothelial gaps formed in postcapillary and collecting venules in the rat trachea and esophagus. The peak values of plasma leakage and edema occurred 5 min after LPS (P<0.01). Urethan anesthesia significantly inhibited LPS-induced plasma leakage by 95 ¡Ó 1.7% in various parts of the respiratory tracts and inhibited edema ratio in the trachea by 57%. Urethan was also found to reduce leukocyte infiltration and the number of endothelial gaps by 46.8 ¡Ó 4.6%. DMTU pretreatment significantly inhibited plasma leakage by 88.5 ¡Ó 2.5% in the respiratory tract and inhibited edema ratio in the trachea by 89% at 5 min after LPS. It is concluded that LPS-induced increase in plasma leakage and edema correlated with the formation of endothelial gaps, and association with activation of alpha 2-adrenergic receptors and hydroxyl free radical production.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1967. / Includes bibliographical references (leaves 83-87).

Carbon tetrachloride (CCl4) is a hepatotoxicant known to elevate alanine aminotransferase (ALT) and other liver enzyme levels, and cause lipid peroxidation, as well as centrilobular necrosis. A number of poly ADP-ribose polymerase (PARP) inhibitors were administered via intraperitoneal (i.p.) injections to male ICR mice as cotreatments at various time intervals relative to the CCl4. Aminophylline, a water soluble complex consisting of two molecules of theophylline bridged by ethylene diamine, was administered one-half hour, one hour and two hours after CCl4. The levels of ALT in the serum, as well as malondialdehyde and its equivalent markers of oxidative damage in the liver, were significantly reduced by aminophylline, relative to those in mice receiving only CCl4. The hepatoprotective effects of aminophylline were confirmed via the examination of histopathologic samples from the livers of mice receiving aminophylline in conjunction with CCl4 as opposed to those administered CCl4 alone. The potential benefit to society as a result of this research is that aminophylline, which has already been approved by the Food and Drug Administration (FDA), could potentially be administered in the event of an overexposure to CCl4 or similar halocarbons to minimize the free radical-mediated hepatotoxicity resulting from overexposure.

Doctor of Philosophy (PhD) / This thesis primarily details the application of high-level ab initio quantum chemistry techniques in order to understand aspects of free-radical mediated protein oxidation. Traditionally, product analysis and electron paramagnetic resonance (EPR) spectroscopy are the primary means for elucidating the chemistry of protein oxidation. However, in experiments involving relatively small proteins reacting with a controlled radical-flux, a vast array of compounds can be produced, which are often difficult to analyse. Quantum chemical techniques on the other hand, can calculate the properties of any particular species directly, without suffering from the problems associated with experiment, such as side-reactions and chain processes. The results presented in this thesis are aimed at elucidating mechanistic details of protein oxidation, which might otherwise be difficult to probe experimentally. Chapter 1 gives an overview of the free-radical hypothesis of disease and ageing. Protein-derived radicals can undergo a variety of reactions, with the particular reaction that occurs depending on numerous aspects. Many types of reactions have been identified through radiolysis experiments of amino acids, and these are detailed in this chapter. In addition, the key reactive species are characterized and their different chemistries explained. Chapter 2 details the theoretical tools used throughout this thesis. Species with unpaired electrons (radicals) present unique problems for quantum chemistry to handle, thus an appropriate choice of theoretical technique is needed. The approach taken in this thesis is to use high-level compound methods, many of which have been directly formulated to give improved results for radical species, to provide benchmark quality results by which other less demanding techniques can be assessed. During the course of this study, it became apparent there was a void in the armoury of tools that could be used for the theoretical chemistry calculations. Chapter 3 details the formulation of a new tool in an attempt to fill this gap. Historically, the formulation of this new procedure came after much of the work in this thesis had been carried out. Thus, for the study of many of the reactions of this thesis the new method has not been used. However, it is most appropriate to place its formulation after summarizing the current status of techniques in common use today. Chapters 4 and 5 detail computations carried out on models of peptides containing backbone carbon- and nitrogen-centered radicals. A number of different theoretical techniques are used in these chapters, ranging from the highly accurate and computationally intensive to the less reliable and less demanding. The highly accurate techniques are used to gauge the accuracy of the other less demanding theoretical techniques so that the latter can be used with confidence in larger systems. Not only is the choice of theoretical technique important but also the judicious choice of model is essential. With this in mind, models are incrementally built until convergence of the particular property of interest is reached. Chapters 6 and 7 detail the calculations of β-scission reactions of alkoxyl radicals, which are a particular class of reaction known to occur on peptide backbones. Alkoxyl radicals are particularly difficult for theory to describe correctly. Therefore, Chapter 6 extensively assesses and then identifies the theoretical methods needed to portray them. Chapter 7 uses the techniques identified in the previous chapter in order to predict how the preference for a particular type of β-scission reaction changes.

Thesis (Ph.D.)--McMaster University (Canada), 1992. / Source: Dissertation Abstracts International, Volume: 54-12, Section: B, page: 6173. Adviser: J. Warkentin.

Thesis (Ph.D)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2010. / Committee Chair: Wine, Paul; Committee Member: Huey, Greg; Committee Member: Mulholland, James; Committee Member: Nenes, Athanasios; Committee Member: Weber, Rodney. Part of the SMARTech Electronic Thesis and Dissertation Collection.