Thesis (M. Sc.)--University of Canterbury, 2005. / Typescript (photocopy). On t.p. "n+" is superscript. "April 2005." Includes bibliographical references (leaves 135-137). Also available via the World Wide Web.

xi, 289 f. : il. / Submitted by Rodrigo Meirelles (rodrigomei@ufba.br) on 2012-04-11T13:55:26Z No. of bitstreams: 1 Lord Of Hell Dissertacao.pdf: 12296595 bytes, checksum: ffa814f3eef44bba773fe722ed7b8e13 (MD5) / Made available in DSpace on 2012-04-11T13:55:26Z (GMT). No. of bitstreams: 1 Lord Of Hell Dissertacao.pdf: 12296595 bytes, checksum: ffa814f3eef44bba773fe722ed7b8e13 (MD5) Previous issue date: 2010 / Montes Claros é uma cidade na qual acontecem diversas manifestações musicais que são representativas do que seja pertencer a esse meio. Entretanto, cada uma possui maneiras peculiares de lidar com seu contexto, o que remarca produtos musicais e contextuais variantes de comunidade para comunidade. Dessa forma, pode-se dizer que o meio do rock montesclarense é um agregado de pessoas que tem uma visão cultural comum, o que remete assim a um meio musical específico. Mas, ao contrário do que possa se pensar, o próprio contexto roqueiro é multifacetado em suas estruturas internas, ao mesmo tempo em que possui um discurso que aparenta homogeneidade, unificação. Há diversos discursos que permeiam o universo do rock em Montes Claros e pode-se dizer que o metal é uma das suas comunidades mais prolíficas, apesar de parcialmente segmentada. Surgida no contexto da cidade em meados dos anos 1990 – na cena roqueira que se articula desde finais da década de 1950 – o metal gerou uma cena rica em bandas, públicos e eventos. Considerar, então, uma banda desse meio como foco de estudo é vislumbrar as principais características que permeiam as concepções dessa cena. Este estudo aborda os principais aspectos performáticos, estilísticos e estéticos musicais da banda Vomer, atuante em Montes Claros desde 1995. Acredita-se que suas práticas musicais – que vão além do mero “tocar” – são repletas de elementos que integram o discurso metaleiro da cidade, práticas essas que são formadas por diversos processos. Esses tangem desde o consumo de materiais musicais oriundos do mainstream, ressignificados numa prática underground – o que também implica que o metal em Montes Claros é uma prática mundializada expressa no viés local –, até a sua relação com a cena musical alternativa e independente que se estabelece na cidade, além das relações sociais que afirmam, negam, enfim, negociam as concepções musicais e extramusicais da Vomer, tudo isso expresso no momento da performance. Pode-se dizer que através da performance se estabelece uma crítica cultural que mantém ou transforma a visão musical da banda. Não apenas os shows ao vivo são performances, mas também os ensaios e gravações são momentos dinâmicos de construção e negociação do que seja a Vomer. / Salvador

Electrical, forming and switching characteristics of metal-semiconductor-metal (MSM) memory switches of ion bombarded hydrogenated amorphous silicon (a-Si:H) and its alloys are presented. MSM devices for memory switching applications are known to be characterised by instabilities as well as non-uniformity and irreproducibility of the forming and switching characteristics. It is believed that the presence of defect states in the semiconductor layer plays a significant role in the observation of memory switching in these MSM devices. Gas-phase doping and current stressing of the semiconductor are some of the techniques that have been used in the past to introduce mid-gap defect states. In this work, we use for the first time, ion bombardment as a novel tool for defect introduction into the semiconductor material of the MSM devices and we compare the electrical, forming and switching characteristics of these devices to those fabricated using the previous techniques mentioned above. A significant observation is that as the density of defects is increased in the semiconductor film with increasing implantation dose, conduction in the devices changes from barrier-controlled thermionic emission to bulk controlled where carriers hop through the defect states in a Poole-Frenkel manner. This transformation eliminates problems associated with Schottky barriers such as quality of contacts, oxidation, etc. In the forming characteristics, not only do we report enhanced uniformity of the forming voltages (VF) but also the magnitude of VF is observed to vary systematically with the implantation dose used. The ON states and switching characteristics in the bombarded devices are also observed to be much more stable presumably as a result of the uniformity of the defects introduced by ion bombardment. We report also an enhanced switching ratio in the ion bombarded devices, especially after partial annealing of the bombardment induced Si dangling bond defects.

Several series of novel diamido, diamino and diimino ligands containing different spacers and heterocyclic donors have been synthesised. The spacers include the flexible biphenyl, the rigid 1,1 O-phenanthroline and various acyclic moieties, while the heterocyclic donors comprise pyridine, imidazole or benzimidazole groups. These ligands have been designed to complex copper and act as biomimetic models of the active site of the enzyme, tyrosinase, and their complexes with copper, cobalt, nickel and platinum have been analysed using microanalytical, IR, UV-Visible and cyclic voltammetric techniques. Attempted reduction of the biphenyl-based diimino ligands resulted in an unexpected intramolecular cyclisation affording azepine derivatives, the structures of which were elucidated with the aid of single crystal X-ray analysis of cobalt and nickel complexes. Computer modelling methods have been used to explore the conformational options of the copper complexes, and to assess the accessibility of the dinuclear copper site to substrate molecules. Computer modelling has also been used, in conjunction with the available analytical data, to visualise the possible structures of selected ligands and complexes. The copper complexes, although predominantly polymeric, were evaluated as biomimetic catalysts using 3,5-di-t-butylphenol and 3,5-di-t-butylcatechol as substrates. Some of the complexes clearly displayed biomimetic potential, exhibiting both phenolase and catecholase activity.

No description available.

Metal-on-metal (MM) bearings have been considered as an alternative to conventional metal-on-polyethylene (MPE) bearings because of their lower volumetric wear, but concern exists due to potential metal hypersensitivity. Metal hypersensitivity reactions have been thought to be T cell-mediated delayed type hypersensitivity (DTH) reaction. However some of the MM periprosthetic tissues show the presence of B- and plasma cells, as well as massive fibrin exudation, which are not characteristic of a DTH reaction. Therefore, the exact nature of the hypersensitivity reaction(s) MM implants remains unclear. The present study aimed to compare the phenotypes of lymphocytes from the peripheral blood and synovial fluid of patients with failed MM and MPE implants, and from volunteers with no implant (peripheral blood only). Results in peripheral blood showed differences in the T-cell populations depending on the implant type. This included differences in the proportions of T-helper and T-cytotoxic cells, and T-cells expressing IFN-g. Results in synovial fluid showed a significant difference between MM and MPE groups for the B-cells. Both groups depicted a predominance of T-cell lymphocytes in synovial fluid and overall larger proportions of memory cells than in peripheral blood, but group sizes were rather small. Overall, T-cell cytokine expression (analyzed in peripheral blood only because of the limited number of synovial fluid samples) did not exhibit characteristics of a DTH reaction and the proportions of memory lymphocytes did not indicate activation of a specific subset in the MM group. Nevertheless, group sizes still remain to be increased.

Thesis (M. Sc. (Chemistry)) --University of Limpopo, 2019. / Metal alloys are one of few materials that are capable of acting as catalyst precursors in Sabatier reactions, reducing poisonous CO2 gas into different useful hydrocarbons. However, optimal reduction of CO2 through these materials takes place at relatively elevated temperatures due to poisoning-intolerance and deterioration of hydrogen absorption/desorption kinetics resulting from the surface chemical action of electrophilic gases at lower or room temperature. This work presents results of the feasibility study focused on improving hydriding kinetics and poisoning-tolerance, which are prerequisites properties that a material should possess to be a suitable catalyst precursor for Sabatier reaction, of the metal hydride (MH) materials. The studies in this work included: (i) element substitution and (ii) surface modification procedure. The substrate alloys investigated had the compositions LaNi4.8-xSnx and TiMn1.52, where x was 0.2. The activation performances of the materials were estimated by measurement of H2 absorption kinetics in the absence of vacuum heating, after long-term exposure to air. The presence of oxide layers on the alloy surface resulted in the deterioration of H sorption kinetics for the parent alloys. To overcome impurity effects, surface-modification technique through autocatalytic palladium deposition was employed. The activation performances and kinetics of the surface-modified were found to be superior to that of the unmodified AB2 and AB5 alloys. Based on this observation, it was seen that surface-modified MH materials based on the alloy substrate and Pd nanostructured coatings may be utilised as catalysts precursors for CO2 reduction into hydrocarbons.

A study was performed involving the leaching characteristics of three synthetically-generated metal finishing sludges. Three precipitates (one hydroxide, two sulfide-based) containing varying concentrations of cadmium, copper, lead, nickel and zinc were dewatered and subjected to an EPA-regulated limits. The sludge generated from an insoluble sulfide process exhibited the fewest parameters in violation (two), while the soluble sulfide sludge had one metal in compliance and the hydroxide sludge had none. On a metal-by-metal basis, the lead and copper exhibited the greatest capacity to withstand resolubilization in a low pH (5) environment. Nickel and zinc were present at the highest leachate concentrations in all three sludges. Cadmium extraction concentrations varied. In conjunction with this study, a montmorillonite clay was combined with each sludge on a mass ration basis to discern metal attenuating effects under a low pH environment. The presence of the clay served to reduce metal leachate rates for two of the three sludge-types tested. However, neither sludge-type exhibited leachate concentrations below federally regulated limits. On a metal by metal basis, lead and copper were attenuated to the highest degree, nickel and zinc the lowest. The presence of clay in copper and lead-dominant sludges may serve to lower extract concentrations for both metals and possibly provide an opportunity to have the sludge(s) declared non-hazardous. Conversely, sludges consisting predominantly of nickel and/or zinc would require disposal in a secure landfill.

<p> Metal contamination from anthropogenic activities is of great concern due to the associated detrimental effects on ecosystem health. An increase in metal concentrations in the dissolved phase creates greater ecosystem impacts. Thus, the relative extent of metal distribution between sediment and dissolved compartments, and an understanding of the factors that control this partitioning is key to assessing metal impacts. In this thesis, metal concentrations were determined for a suite of 12 metals (Cr, Mn, Co, Cu, Sn, Ag, As, Ni, Zn, Cd, Se and Fe) associated with three compartments, dissolved, surficial bed sediment and suspended particulate matter (SPM) in Hamilton Harbour, Ontario. Due to highly dynamic interactions of anthropogenic impacts that may work together to affect metal distributions as well as processes that occur over small or rapid scales, a high-resolution temporal and spatial scale was used to evaluate these metal distributions over a seasonal timeframe. </p> <p> Concentrations of metals amongst sediment fractions indicated that sediment metal uptake was largely controlled by the concentration of the sediment associated amorphous and crystalline oxyhydroxide fractions accounting for up to 90% of total sediment bound metal, even though the oxyhydroxides only accounted for a maximum of 23% of the total sediment mass for both surficial bed sediment and SPM compartments. The formation and dissolution of amorphous oxyhydroxides is commonly a microbially mediated process. Thus, these results underscore the important role of oxyhydroxides and the microbial processes that contribute to their formation and dissolution m controlling metal dynamics, and likely metal impacts in Hamilton Harbour. </p> <p> Metal partitioning was found to be both spatially and temporally variable for all compartments, temporally ranging 0.5 to 4 orders of magnitude for a given element; indicating highly dynamic metal exchanges between sediment and solution compartments and fluctuating distributions over the time and spatial scales examined. </p> <p> The suite of variables that are considered to control metal distribution between dissolved and sediment compartments, and thus impact metal toxicity (i.e., temperature, pH, specific conductivity, oxidation-reduction potential, dissolved organic carbon concentration, SPM concentration (for SPM associated metals only), fraction concentrations i.e. g carbonate /g solid, g amorphous oxyhydroxide I g solid, etc., and dissolved metal concentrations) did not constrain the variability in observed metal distribution behaviour, indicating that other factors in this system, such as hydrodynamic disturbances associated with shipping traffic and channelized water currents, as well as specific point source metal discharges, may play a larger role in determining metal partitioning in Hamilton Harbour, compared to less anthropogenically, impacted systems. Furthermore, no one master variable defming metal partitioning between the dissolved and sediment compartments was found, rather relationships controlling metal distribution behavior were site, compartment, sediment fraction and element specific highlighting the challenges for the development of a Harbour-wide management plan for priority metal contaminants. The results presented in this thesis, show that it is necessary to consider metal, site and compartment specific conditions as well as fully addressing temporal variability in metal behaviour. In addition, the results of this thesis point to the need to address hydrodynamic disturbance and point source influences on metal behaviour in Hamilton Harbour and likely extend to other multi-impacted metal contaminated systems. </p> / Thesis / Master of Science (MSc)

The theme of this work is the observation and understanding of the effects of pore functionalization on adsorption properties of stable Metal-Organic Frameworks (MOFs). Over the first two sections of this work, sets of materials with representative pore sizes and functional groups are studied for adsorption properties. Observed trends are used to identify the best pore properties achievable via functionalization for adsorption systems. The third section of this work provides perspective on MOF materials and proposes target pore features for an efficient adsorbent for carbon dioxide capture from flue gas. First, the highly stable UiO-66 series of materials was selected for a pure-component adsorption study. The selectivity and capacity for CO2 can be best enhanced with the smallest, most polar functional group, such as an amino group, but significantly enhance water adsorption. Large, non-polar groups do not yield a completely hydrophobic material, but may be useful for humid gas separations as pore filling with water is inhibited. Next, a breakthrough study was conducted using CO2:CH4 and CO2:N2 mixtures on a set of stable MOFs. UiO-66-NH2 and UiO-66-DM, where DM=dimethyl, outperform predictions based on published isotherms and have dynamic CO2:CH4 selectivity comparable to zeolite NaY. UiO-66-DM may be a good candidate for further study due to the combination of partial hydrophobicity and good selectivity. Finally, by combining a review of literature with observations made in this work, a perspective on MOFs as efficient humid gas separation materials is provided. The presence of water vapor prevents use of current high performance adsorbents, but several MOF pore features show promise for these separations. The designable nature of MOFs allows for targeted design of size-matched pores and single-molecule traps which can selectively or cooperatively adsorb CO2 in the presence of water. Also, many MOF materials would be well suited for advanced pressure swing adsorption cycles and engineered sorbents, which enables greater material utilization and system efficiency.