Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 131-135).

Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references. Also available via World Wide Web.

Thesis ( Ph.D) -- McMaster University, 2001. / Includes bibliographical references. Also available via World Wide Web.

Thesis (doctoral)--Lund University, 1994.

No description available.

Orientador: Edison Bittencourt / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-15T12:07:07Z (GMT). No. of bitstreams: 1 Zangiacomi_MarcosHenrique_D.pdf: 1507466 bytes, checksum: 17472578194a52bea38f1fd549a47fb5 (MD5) Previous issue date: 2009 / Resumo: 0 mercado atual procura por materiais que apresentem boas propriedades ópticas, que satisfaçam os consumidores e os usuários em geral e que sejam de fácil manuseio e processabilidade. No geral, um polímero deve apresentar boas propriedades ópticas, resistência ao impacto e dureza, compatíveis com o seu uso como lentes oftálmicas. O processo de fabricação de lentes oftálmicas poliméricas por muito tempo foi feito por meio de processos térmicos (cura térmica, processo que ainda é usado), levando cerca de 20 horas ou mais na obtenção de lentes que não apresentassem problemas de trincas por diferença de propriedades no corpo da lente. Dessa forma a introdução da tecnologia de cura pela luz ultravioleta (UV) permitiu a obtenção de materiais com a mesma característica e até superiores aquelas obtidas através da cura térmica e com a vantagem da diminuição do tempo de processo, diminuindo de horas para minutos, resultando também em redução dos custos. Neste trabalho foram utilizados os monômeros e oligômeros listados a seguir: metil metacrilato de metila (MAM), 1,6-Hexanediol diacrilato (HDDMA), diacrilato uretano alifático tetrafuncional (Ebecryl 5129) e diacrilato epóxi bisfenol-A (Ebecryl 3700) e em cada formulação foi aplicado um sistema de fotoiniciadores (nomes comerciais) compostos por Darocur 1173, Irgacure 184, Irgacure 1300, Irgacure 2959 e Irgacure 250 e Irgacure 819. Os sistemas de fotoiniciadores foram formulados a base de 3% p/p sobre cada formulação, seguindo as orientações dos fornecedores e de resultados experimentais obtidos ao longo deste estudo, sendo o tempo de cura da formulação de 7 minutos. Foram analisadas as propriedades mecânicas relevantes que uma lente deve apresentar, entre elas, dureza e resistência ao impacto. Foram determinadas também as temperaturas de transição vítrea obtidas da formulação, e a resistência ao calor. Foram comparados com os diversos fotoiniciadores, e realizado um estudo inicial da cinética, bem como medidas as entalpias e conversões resultantes da polimerização na temperatura de trabalho de 100°C, utilizando-se um fotocalorímetro diferencial de varredura (DPC). / Abstract: The current market calls for materials presenting good optical properties which satisfy consumers and users in general and that can be easily handled and processed. Generally, a polymer must present good optical properties, impact resistance and hardness - all compatible in their use as ophthalmic lenses. For quite a long period of time, ophthalmic lenses manufacturing had been achieved by means of thermal processes (thermal curing), taking up to 20 hours to obtain lenses free of cracking and/or processing errors. In this manner, the introduction of ultraviolet light curing technology has allowed the production of materials with equal and even superior characteristics than those obtained through thermal curing, and with advantages in processing time (reduced from hours to minutes), as well as costs, which were also reduced. The following monomers and oligomers were utilized in this study: methyl methacrylate (MAM), 1,6-Hexanediol diacrylate (HDDMA), diacrylate tetra functional aliphatic urethane (Ebecryl 5129) and epoxy diacrylate bisphenol A (Ebecryl 3700-20 t). A system of photoinitiators composed by darocur 1173, Irgacure 184, Irgacure 1300, Irgacure 2959, Irgacure 250 and Irgacure 819 have been applied in each formulation. The photoinitiators systems have been formulated on a 3% p/p basis, following suppliers orientations and experimental results obtained throughout this study, with a 7-minute formulation curing time. The main mechanical properties a lens must present, such as acceptable harness and impact resistance, were analyzed in the study. Vitreous transition temperature, heat resistance and the evaluation of the photoinitiators in kinetics have been analyzed and studied, as well as the evolution of enthalpy during a 100°C polymerization process and formulation conversions by differential photocalorimetry distinguishing (DPC). / Doutorado / Ciencia e Tecnologia de Materiais / Doutor em Engenharia Química

The extent to which endogenous free radical-scavenging defense mechanisms are involved in experimental and human diabetes was investigated in various tissues of animals with chemically-induced or spontaneous diabetes (BB Wistar rats) and in erythrocytes of patients with either Type I or Type II diabetes. Diabetes was induced in female Wistar rats using alloxan (ALX) or streptozotocin (STZ), each administered in a dose of 50 mg/kg body wt., intravenously. The present study also included a group -of animals in which body wt. loss was induced by food-deprivation for 72 h. The effects of pharmacological interventions (insulin or allopurinol (ALP)), on these processes were also investigated in chemically-induced diabetes., The activities of catalase (CAT), CuZn-superoxide dismutase (CuZn-SOD), glutathione peroxidase (GSH-PX) and glutathione reductase (GSSG-RD) as well as levels of reduced glutathione (GSH) were examined in heart, pancreas, liver and kidney as well as in erythrocytes. Erythrocytes were also examined for their susceptibility to in vitro oxidative stress induced by hydrogen peroxide (H₂0₂). Criteria studied in this regard were GSH-depletion and malondi-aldehyde (MDA) production (an index of lipid peroxidation). The results obtained showed that tissue antioxidant systems are altered in experimental diabetes and that the magnitude of the alterations increased with the degree of body weight loss. Furthermore, the duration of hypoinsulinemia might contribute to the nature of alterations in antioxidant mechanisms. The complex patterns of the alterations observed varied from one tissue to another and may be the result of compensatory increases, usually involving enzymes whose activity in the particular tissue may be limiting, and direct inhibitory effects of endogenous oxidants on the enzymatic components of tissue antioxidant systems. The ability of insulin (9-12 U/kg body wt., subcutaneously) to reverse the many similar alterations of tissue antioxidant enzymes in diabetes induced by either STZ or ALX suggests that these changes are more likely attributable to hypoinsulinemia rather than to direct effects of either diabetogenic drug. The above-mentioned effects indicate that insulin can markedly influence tissue antioxidant status. However, the reason for the persistence of decreased CuZn-SOD activity in both liver and kidney of ALX-diabetic rats after 12 wk of treatment with insulin is not clear at present, and requires further investigation to determine whether this reflects the presence of a residual deficit in tissue antioxidant processes in liver and kidney despite insulin treatment, or whether it is the result of a direct effect exerted by ALX. Acute ALP administration (50 mg/kg body wt., intraperitoneally) was associated with reductions in ketonuria and early mortality among ALX-diabetic rats, and long-term ALP treatment (1.9 mg/day in drinking water) resulted in a normalization of renal CuZn-SOD activity in these animals. Comparable (although not identical) changes in tissue antioxidant status are present in insulin-dependent spontaneously diabetic BB (ISDBB) rats and in animals made diabetic by STZ or ALX administration. Our data also demonstate that the alterations in tissue GSH levels characterizing ALX-diabetes more closely paralleled changes seen in the ISDBB rat than did those in the diabetic state induced by STZ. If the alterations in antioxidant status in uncontrolled chemically-induced diabetes are attributable to a lack of insulin, the observed changes in ISDBB rats are suggestive of sub-optimal insulin therapy in these animals. The results obtained from BB rats demonstrate two types of alterations in antioxidant status: strain-related differences (increased CAT activity in pancreas and decreased GSH levels in pancreas and liver of both ISDBB and their non-diabetic littermates (NDLM)) and diabetes-related changes (mani- fested by an increase in cardiac GSH content and increases in activities of cardiac CAT and GSSG-RD, pancreatic CuZn-SOD and GSSG-RD, and renal GSH-PX). Whether or not these "strain-related" alterations in antioxidant status increase the susceptibility of these animals to developing diabetes remains unknown. Certain alterations were observed in red cells from diabetic patients and from animals with experimental diabetes suggesting that these alterations are more likely to be diabetes-related than species-dependent. Red cells in chemically-induced and clinical diabetes showed an increased resistance to peroxide-induced depletion of GSH, an effect attributed to hyperglycemia, which results in an increased supply of NADPH through the hexose monophosphate shunt for regeneration of GSH from GSSG via the GSSG-RD system. However, the susceptibility of red cells from diabetic patients and animals to lipid peroxidative damage was increased as reflected in augmented MDA production. In addition, insulin treatment did not normalize MDA production in red cells subjected to oxidative challenge and vigorous insulin treatment in both ALX- and STZ-diabetic rats resulted in a markedly decreased MDA production in response to H₂0₂. Moreover, GSSG-RD activity of red cells was increased in both uncontrolled and insulin-treated diabetic animals as well as in diabetic patients. However, some differences in erythrocyte antioxidant enzymes were also observed in erythrocytes from diabetic subjects and animals. For example, diabetic patients showed an increased activity of CuZn-SOD, while erythrocytes from diabetic animals showed no alterations in the activity of this enzyme. Erythrocyte membrane NADH-dehydrogenase activity was increased only in diabetic patients with Type I diabetes, but not in Type II diabetes or in diabetic animals. Erythrocytes from ALX- and STZ-diabetic animals showed an increase in the activity of GSH-PX and those from NDLM BB rats showed a decrease in CAT activity, alterations that were not observed in human diabetes. Finally, as far as antioxidant defense mechanisms are concerned, our results suggest that diabetes is associated with some common alterations in these mechanisms regardless of the model (chemically-induced versus the spontaneous type of diabetes) or the species used (animal versus human diabetes). Some of these alterations seem to be influenced by the degree of diabetic control, while others are apparently independent of it. Future studies will focus on the extent to which alterations in red cells of human diabetics can be used to predict the development of long-term sequelae of the disease. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

NiSi is an attractive material in the production of CMOS devices. The problem with the utilization of NiSi, is that there is no proper method of cleaning the oxide on the surface. Sputtering is the most common method used for the cleaning, but it has its own complications. Dry cleaning methods include the reactions with radicals and these processes are not well understood and are the focus of the project. Dissociated NF3 and NH3 were used as an alternative and XPS is the technique to analyze the reactions of atomic fluorine and nitrogen with the oxide on the surface. A thermal cracker was used to dissociate the NF3 and NH3 into NFx+F and NHx+H. There was a formation of a NiF2 layer on top of the oxide and there was no evidence of nitrogen on the surface indicating that the fluorine and hydrogen are the reacting species. XPS spectra, however, indicate that the substrate SiO2 layer is not removed by the dissociated NF3 and NiF2 growth process. The NiF2 over layer can be reduced to metallic Ni by reacting with dissociated NH3 at room temperature. The atomic hydrogen from dissociated ammonia reduces the NiF2 but it was determined that the atomic hydrogen from the ammonia does not react with SiO2.

NiSi and Ni(Pt)Si, and of the effects of dissociated ammonia on oxide reduction was carried out under controlled ultrahigh vacuum (UHV) conditions. X-ray photoelectron spectroscopy (XPS) has been used to characterize the evolution of surface composition. Vicinal surfaces on NiSi and Ni(Pt)Si were formed in UHV by a combination of Ar+ sputtering and thermal annealing. Oxidation of these surfaces in the presence of either O+O2 or pure O2 at room temperature results in the initial formation of a SiO2 layer ~ 7 Å thick. Subsequent exposure to O2 yields no further oxidation. Continued exposure to O+O2, however, results in rapid silicon consumption and, at higher exposures, the kinetically-driven oxidation of the transition metal(s), with oxides >35Ǻ thick formed on all samples, without passivation. The addition of Pt retards but does not eliminate oxide growth or Ni oxidation. At higher exposures, in Ni(Pt)Si surface the kinetically-limited oxidation of Pt results in Pt silicate formation. Substrate dopant type has almost no effect on oxidation rate. Reduction of the silicon oxide/metal silicate is carried out by reacting with dissociated NH3 at room temperature. The reduction from dissociated ammonia (NHx+H) on silicon oxide/ metal silicate layer shows selective reduction of the metal oxide/silicate layer, but does not react with SiO2 at ambient temperature.

The focus of the following research was to (1) understand the chemistry involved in nitriding an organosilicate glass substrate prior to tantalum deposition, as well as the effect nitrogen incorporation plays on subsequent tantalum deposition and (2) the reduction of a native oxide, the removal of surface contaminants, and the etching of a HgCdTe surface utilizing atomic hydrogen. These studies were investigated utilizing XPS, TEM and AFM. XPS data show that bombardment of an OSG substrate with NH3 and Ar ions results in the removal of carbon species and the incorporation of nitrogen into the surface. Tantalum deposition onto a nitrided OSG surface results in the initial formation of tantalum nitride with continued deposition resulting in the formation of tantalum. This process is a direct method for forming a thin TaN/Ta bilayer for use in micro- and nanoelectronic devices. Exposure to atomic hydrogen is shown to increase the surface roughness of both air exposed and etched samples. XPS results indicate that atomic hydrogen reduces tellurium oxide observed on air exposed samples via first-order kinetics. The removal of surface contaminants is an important step prior to continued device fabrication for optimum device performance. It is shown here that atomic hydrogen effectively removes adsorbed chlorine from the HgCdTe surface.