Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 155-170).

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Elbio Dagotto, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Sept. 21, 2004). Includes bibliographical references.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 64-66). Also available in electronic version.

As conventional oil reserves deplete and more efficient refining technologies emerge, the use and transportation of heavy fuel oils such as dilbit is rising. Despite the risk of accidental dilbit spills, the fate and behaviour in aquatic systems is largely unknown. The objective of this thesis was to develop new approaches and insights to directly address knowledge gaps surrounding the fate and behaviour of diluted bitumen (dilbit) in freshwater systems. During the summers of 2017 and 2018, a large-scale collaborative field study was conducted at the International Institute for sustainable Development’s – Experimental Lakes Area (IISD-ELA), a world-renowned freshwater research station located in Northwestern Ontario, Canada. First, two tank-based dilbit spill simulations were carried out at oil:water ratios of 1:8000 and 1:800 v/v (Chapter 2). Here I examined the physical fate and behaviour of dilbit spilled onto the water’s surface for 11 days. In this chapter I provide, for the first time, experimental evidence of dilbit physically sinking after 8 days of environmental weathering in land-based tanks containing natural lake water. Building on the findings of chapter 2, the remaining four chapters focus on a series of 70-d long experimental dilbit spills carried out in limnocorrals (10 m diameter x 1.5 m depth) installed directly in a freshwater lake. Chapter 3 provides, to our knowledge, the most detailed temporal account to date of dilbit submergence in freshwater at multiple oil:water ratios. In Chapter 4 I provide the rates at which over 100 individual hydrocarbons are depleted over time from the dilbit slicks and apply diagnostic ratios to postulate which weathering processes are responsible for the observed depletions. As predicted, evaporation, dissolution, and photooxidation are prominent weathering processes whereas biodegradation is not. I then describe both the short- and long-term behaviour of these compounds as they partition from the dilbit slick to the air, water, and sediments of the limnocorrals in Chapter 5. While the concentrations of polycyclic aromatic hydrocarbons (PAHs) were elevated in the water columns of each treatment, they were orders of magnitude lower than concentrations that pose a toxicological risk. The same was true for all sediment samples except those that were in direct contact with sunken dilbit. This suggests that the major threat of dilbit spills from an ecotoxicological point of view is the dilbit-laden sediments produced by submergence. Finally, I demonstrated the successful application of a mass transfer model to predict the dissolution trends of the highly toxic benzene, toluene, ethylbenzene, and o,m,p-xylene (BTEX) compounds following the dilbit spills. In Chapter 7 I detail the implications and conclusions for each chapter and the thesis as a whole. I also describe areas where future research is needed. In the end, the conclusions of this thesis were: 1) dilbit has the propensity to sink following spills in freshwater, 2) prominent weathering processes include evaporation, dissolution, and photooxidation, 3) our regression design allowed for important relationships between contamination and spill size to be realized, 4) sunken dilbit poses a toxicological threat to aquatic biota, and 5) mass transfer models can accurately predict BTEX dynamics in the water column following a dilbit spill.

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-17Bitstream added on 2014-06-13T20:21:45Z : No. of bitstreams: 1 leite_dmg_dr_bauru.pdf: 3640633 bytes, checksum: adf6650360687a658c11b1cc1b69b693 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A recente busca por semicondutores magnéticos diluídos com propriedades magnéticas de interesse motivou este trabalho de crescimento de filmes de Ga1-xMnxN pelas técnicas de sputtering e epitaxia da fase de vapor de organometálicos (MOVPE). Os filmes são caracterizados estruturalmente por medidas de difração de raio X e microscopia eletrônica de transmissão, opticamente por transmitância óptica e espalhaçamento Raman, e magneticamente por medidas magnetização versus campo aplicado e versus temperatura. As principais diferenças entre os filmes de GaMnN preparados por sputerring e MOVPE referem-se à microestrutura e ao conteúdo de Mn: os primeiros são policristalinos e apresentam conteúdo de Mn até 9%, enquanto os últimos são monocristalinos com concentração de Mn até 1%. A alta concentraçao de Mn nos filmes crescidos por sputtering é possivelmente responsável pelo surgimento coletivo destes íons de Mn nas medidas magnéticas. Esse comportamento coletivo se identifica a partir de contribuição paramagnética de domínios isolados com alto vapor de momento magnético, o que se mostra consistente com a microestrutura apresentada por estes filmes. A alta concentração de Mn nos filmes preparados por sputtering também se mostra responsável por intensa absorção óptica abaixo da energia do gap, sendo esta relacionada a transições eletrônicas entre os estados localizados do Mn e as bandas de valência e condução do GaN. O contraste entre as propriedades dos filmes de GaMnN produzidos por sputtering e por MOVPE possibilita então um entendimento mais abrangente dos aspectos da incorporação de Mn no GaN e suas respectivas características estruturais, ópticas e magnéticas. Esse entendimento é importante para delinear a otimização deste material visando propriedades magnéticas de interesse / The current search for dilluted magnetic semiconductors with interesting magnetic properties has motivated the present work on growing GaMnN films by sputerring and metalorganic vapor phase epitaxy (MOVPE) techniques. The films are characterized by X-ray diffraction, transmission electron microscopy, optical transmission, Raman scattering, and by magnetization measurements. The main differece between the GaMnN grown by sputtering and those grown by MOVPE relates to their microstructure (polycrystalline/monocrystalline) and Mn content (up to 9%/1% respectively). The high Mn content in GaMnN samples grown by sputtering is probably responsible for a collective response on the magnetic measurements. This collective Mn response is identified as a high magnetic moment contribution which is consistent with sample microstructure. In the sputtered samples, the high Mn content is also responsible for strong subbandgap optical absorption related to eletronic transitions involving Mn states and the valence and conduction bands of GaN. The comparison between the properties of GaMnN films grown by different techniques is important in order to get a better understanding about the Mn incorporation in GaN. This understanding been important to define the next steps regarding the optimization of this material

No description available.

Thesis (Ph.D.)--Tufts University, 1998 . / Adviser: Yaacov Shapira. Submitted to the Dept. of Physics. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph. D., Material Sciences and Engineering)--University of Idaho, January 2008. / Major professor: Keith A. Prisbrey. Includes bibliographical references (leaves 85-90). Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 194-209).

Orientador: José Humberto Dias da Silva / Banca: Carlos Frederico de Oliveira Graeff / Banca: Antonio Ricardo Zanatta / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: A recente descoberta de propriedades ferromagnéticas em alguns semicondutores magnéticos diluídos (DMS) trouxe a esta classe de materiais um grande potencial para aplicações em dispositivos de controle de spin. Um DMS é basicamente formado por um semicondutor dopado por íons magnéticos, os quais têm o papel de criar um momento magnético local e também, em algumas situações, de introduzir portadores livres no material. Entre os DMSs conhecidos, o 'GA IND.1-x'MN IND.XN' surge como o mais forte candidato a aplicações práticas por apresentar até o momento a mais alta temperatura de transição ferromagnética ('T IND.C' 'DA ORDEM DE' 400 k). Até o presente, os filmes de 'GA IND.1-x'MN IND.XN' com propriedades ferromagnéticas relatados na literatura foram preparados por epitaxia por feixe molecular (MBE). Neste trabalho, descrevemos a preparação de filmes nanocristalinos de 'GA IND.1-x'MN IND.XN' com diferentes conteúdos de Mn (0,00 'MENOR' x 'MENOR' 0,18) pela técnica de RF-magnetron sputtering reativo. Analisamos os efeitos da incorporação de Mn na estrutura e nas propriedades ópticas destes filmes através de medidas de difração de raios-X e de absorção óptica entre o ultravioleta (6,5 eV) e infravermelho próximo (1,4 eV). Os resultados apontam um aumento do parâmetro de rede e do índice de refração, uma diminuição do gap ótico e um aumento da densidade de estados de defeitos no interior do gap conforme se aumenta o conteúdo de Mn nos filmes de 'GA IND.1-x'MN IND.XN' preparados por sputtering. Estes resultados são semelhantes aos reportados para a incorporação de Mn em filmes monocristalinos de 'GA IND.1-x'MN IND.XN' com propriedades ferromagnéticas preparados por MBE. / Abstract: The recent discoveries related to the ferromagnetic properties in some diluted magnetic semiconductors (DMS) have attracted considerable attention on this class of material due to their potential application on spin control devices. A DMS is basically formed by a semiconductor doped with magnetic ions with the purpose of creating local magnetic moments and, in some situations, to introduce free carriers in the material. Among the known DMSs, 'GA IND.1-x'MN IND.XN' is the one with the highest ferromagnetic transition temperature ('T IND.C' 'DA ORDEM DE' 400 k), and it is consequently on of the stronger candidates for practical applications. Until now, the 'GA IND.1-x'MN IND.XN' films with ferromagnetic properties described in the literature were prepared by molecular beam epitaxy (MBE). In this work, we report the preparation of nanocrystalline 'GA IND.1-x'MN IND.XN' films (0,00 'MENOR' x 'MENOR' 0,18) by reactive RF-magnetron sputtering technique. We analyzed the Mn incorporation effects on structure and optical properties of the films by X-ray diffraction measurements and optical absorption between UV (6,5 eV) and near infrared (1,4 eV). The results show the increase of the lattice parameters and of the refractive index, a decrease of the optical gap and a increase of defect states in the gap when Mn concentration is increased. These results are similar to those reported for Mn incorporation in monocrystalline 'GA IND.1-x'MN IND.XN' films prepared by MBE with ferromagnetic properties. / Mestre