Thesis (MSc. (Faculty of Health Sciences))--University of Pretoria, 2007. / Summary in English and Afrikaans. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 123-129).

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Η αντίδραση του Ni(O2CMe)2•4H2O με την 5-βρωμο-2-υδροξυβενζαλδεΰδη (LH) σε MeOH έδωσε το σύμπλοκο [NiL2(MeOH)2] (1). Η δομή του συμπλόκου επιλύθηκε με κρυσταλλογραφία ακτίνων Χ σε μονοκρύσταλλο. Το σύμπλοκο είναι μονοπυρηνικό. Το κέντρο NiII είναι 6-ενταγμένο με οκταεδρική γεωμετρία. Το ανιόν L- συμπεριφέρεται ως διδοντικός χηλικός Ο(φαινόξο), Ο(αλδεϋδικό) υποκαταστάτης. Δημιουργούνται διπλές 1D αλυσίδες μέσω δεσμών υδρογόνου, ενώ π-π αλληλεπιδράσεις τύπου θημωνιάς είναι υπεύθυνες για το σχηματισμό ενός 2D δικτύου. Μελετήθηκε το IR φάσμα του συμπλόκου σε σχέση με την γνωστή δομή του και τους τρόπους ένταξης των υποκαταστατών / The reaction of Ni(O2CMe)2•4H2O and 5-bromo-2-hydroxybenzaldehyde (LH) in MeOH has given complex [NiL2(MeOH)2] (1). Its structure has been solved by single-crystal X-ray crystallography. The complex is mononuclear. The NiII center is six-coordinate with an octahedral geometry. The anion L- behaves as a bidentate chelating O(phenoxo), O(aldehyde) ligand. Hydrogen bonds create a double 1D chain, while π-π stacking interactions result in a 2D network. The IR spectrum of the complex has been discussed in terms of its known structure and the coordination modes of the ligands.

Thesis (MScEng (Industrial Engineering))--Stellenbosch University, 2008. / In the context of intervertebral disc replacement and customized implants, human simulation studies are of great importance. Simulation models need input data. This study investigated different in vivo motion capturing methods to capture spinal kinematics that will serve as input for simulation models. Available scanning and motion capturing techniques for capturing cervical kinematics range from simple clinical methods, to expensive specialized equipment and software. With a variety of technologies comes a variety of applications. In this study the focus is on capturing the kinematics of the cervical spine. An important distinction was made between two types of motion capturing technologies: external motion capturing and internal imaging technologies. The available external motion capturing technologies pose many advantages in terms of cost, safety, simplicity, portability and producing accurate three dimensional position and orientation. However, the ability for external motion capturing technologies to give accurate information on the movements at each vertebral level is doubted by critics reasoning that the true vertebral motion is concealed by the skin and soft tissue. Although it would be ideal to use external motion capturing systems, one needs to be confident that these surface markers or sensors truly reflect the vertebral motion at each vertebral level. An empirical study was conducted to evaluate the relationship between motion captured on the skin surface and motion of the vertebrae. Twenty-one subjects received low dosage X-rays, while radio opaque markers were attached to the skin at each respective vertebral level. The motion of external markers and that of the vertebrae could be seen simultaneously on one medium. In the empirical study, two outputs were achieved. Firstly, intervertebral kinematic data, for use in further simulation studies was obtained. Secondly, the relationship between surface markers and vertebrae in different motion instances was investigated. Distance and angle parameters were constructed for vertebral prediction from skin surface markers. The causes of variation in these parameters were identified by investigating the correlations of these parameters with anthropometrical variables. Strong correlations of the parameters were observed in flexion, but in extension, especially full extension, the correlations were poor to insignificant. It was concluded that in neutral, half flexion and full flexion it is possible to predict the vertebral position from surface markers by using the parameters and anthropometrical variables. In half extension this prediction would be less accurate and in full extension alternative methods should be investigated for external motion capturing.

Made available in DSpace on 2014-06-11T19:23:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-03-08Bitstream added on 2014-06-13T19:50:17Z : No. of bitstreams: 1 antonio_sg_me_bauru.pdf: 3160547 bytes, checksum: 9d2a5b8b4f185ebe13b3880b18a9443c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os espinélios têm como sua fórmula unitária geral (A1-iBi)[AiB2-i]O4 (0 =i =1), em que os parênteses são os sítios tetraédricos, os colchetes representam os sítios octaédricos e i é o grau de inversão que representa a distribuição dos cátions na rede cristalográfica. Para i igual a 1 o espinélio é chamado de inverso e tem os cátions distribuídos nos sítios tetraédrico e octaédrico de acordo com a fórmula (B)[AB]O4 e igual a 0 o espinélio é chamado de normal com a fórmula (A)[B2]O4, e para 0 < i < 1 os cátions A e B estão distribuídos entre os dois sítios randomicamente e são chamados de parcialmente invertidos ou mistos. As propriedades desses materiais dependem dos tipos de cátions e do grau de inversão. Neste trabalho utilizamos o processo de combustão, o qual tem sido apresentado como um método eficiente para a produção de partículas nanométricas, para a obtenção do sistema Ni1-d Co d Fe2O4 (d = 0; o; u; ; 1). Os materiais resultantes foram caracterizados usando o método de Rietveld para determinar a distribuição dos cátions nos sítios tetraédrico e octaédrico. Análises de espectroscopia Mössbauer foram utilizadas para corroborar os resultados obtidos pelo Método de Rietveld. A principal variável para promover a síntese de óxidos por reação de combustão e otimizá-la é a razão combustível/oxidante, que foram variadas de 1X (estequiométrica), 1,5X e 2X (dobro) e estabelecida o dobro para o desenvolvimento do trabalho. Observamos também, indicações que a razão combustível/oxidante deve variar para cada estequiometria (d ), e que o Co e Ni ocupam apenas os sítios octaédricos. O método de Rietveld e a luz síncrotron permitiram a determinação da estequiometria em cada composição, e os cálculos de microdeformação mostram a existência de flutuação composicional. / The spinels have the general unity formulae (A1-iBi)[AiB2-i]O4 (0 =i =1), where () represents the tetrahedral sites, [ ] represents the octahedral sites and i is the degree of inversion that represents the distribution of cations in the crystal lattice. For i equal to 1 it is the inverted spinel (B)[AB]O4 and i = 0 it is the normal spinel (A)[B2]O4, and for 0 < i < 1 the cations A and B are randomly distributed between the two sites. The properties of these materials depend on the types of cations and the degree of inversion. In this work we use the combustion process, which has been presented as an efficient method for the production of nanometrics particles, for the attainment of the system Ni1-d Co d Fe2O4 (d = 0; o; u; ; 1). The resulting materials were characterized using the Rietveld Method (RM) to determine the cations distribution in the tetrahedral and octahedral sites. Analyses of Mössbauer spectroscopy carried through by E. Miola and H. Rechenberg had been also used to corroborate the results obtained using Rietveld Method. The main variable to promote the oxide synthesis through combustion reaction is the fuel/oxidant ratio that, in this work, varied from stoichiometric (ratio = 1) up to two times (ratio = 2). We observe that the ratio varies from one stoichiometry to another(d ), and that Co and Ni occupy only the octahedral sites. We observe, also, that the procedure is not yet adjusted to get itself homogeneous material, since the materials present particles with very varied sizes and degree of agglomeration. The Rietveld method and the synchrotron light allowed the determination of the stoichiometry for each composition.

Revestimentos de zinco obtidos por imersão a quente têm sido amplamente utilizados em estruturas expostas em solos, águas naturais e atmosfericamente, devido a excelente resistência em meios de baixa agressividade. Nessas aplicações, as arestas de corte ficam expostas e estão mais susceptíveis à corrosão. Objetivando relacionar a microestrutura dos revestimentos com técnicas de microssondas eletroquímicas, para melhor entender os processos corrosivos de aços galvanizados, buscou-se uma nova metodologia para ampliar as fases e obter uma estrutura em camadas. Para a caracterização da morfologia dos revestimentos obtidos pelo processo de galvanização por imersão a quente (galvanized, galvannealed e galvalume) utilizou-se microscopia óptica e eletrônica de varredura com microanálise. Para verificar e analisar os mecanismos de corrosão das fases presentes nos revestimentos de zinco de forma localizada empregou-se a técnica de varredura por eletrodo vibratório (SVET) e microcélula capilar (MEC), e de forma complementar, para identificar os produtos de corrosão formados utilizou-se micro difração de raios X (μ-DRX). Os resultados demonstraram que a metodologia empregada neste estudo é adequada para avaliar as fases de forma individual ou conectadas galvanicamente, e assim identificar as fases mais ativas durante os processos corrosivos. Os resultados obtidos por microcélula complementam os mapeamentos de densidade de corrente obtidos por eletrodo vibratório, mostrando que os intermetálicos permanecem estáveis após os ensaios e a região mais ativa é o revestimento não intemperizado (polido) próximo à interface aço/revestimento. O revestimento que apresentou melhor resistência à corrosão em soluções contendo cloreto foi o Zn55Al. O espectro μ-XRD para o revestimento galvanized, indica a presença das fases zincita e Fe-α sobre o aço IF (interstitial free), mostrando que sob condições de OCP a superfície de aço IF foi protegida pelo revestimento apesar da sua grande área. Esta precipitação pode ainda proteger áreas de aço expostas aonde o revestimento foi danificado por arranhões ou na aresta de corte. / Hot-dip zinc coatings have been widely used in structures exposed to soils, natural water and atmosphere due to their excellent resistance in low aggressive media. In such applications, the cutting edges are exposed and more susceptible to corrosion. In order to correlate the microstructure of the coating with electrochemical microprobe techniques, a new methodology was developed to amplify the size of the phases and to obtain a layered structure. Optical microscopy and scanning electron microscopy were used to characterize the morphology of the coatings obtained by the hot dip galvanization process (galvanized, galvannealed e galvalume). Scanning vibrating electrode technique (SVET) and capillary microcell (MEC) were used to identify and study the corrosion mechanisms of the phases present in zinc coatings. The corrosion products were identified by X-ray micro-diffraction (μ-XRD). The results demonstrated that the methodology employed in this study is adequate to evaluate the phases individually or galvanically connected, thus identifying the most active phases during the corrosive processes. The results obtained by microcell complement the current density mappings obtained by vibrating electrode, showing that the intermetallics remain stable after the analysis and the most active region is the not wedered coating near the steel/coating interface. The coating that showed the best corrosion resistance in solutions containing chloride was the Zn55Al. The μ-XRD spectrum for the galvanized coating indicates the presence of zincite and Fe-α on the IF steel (interstitial free), showing that under OCP conditions the IF steel surface was protected by the coating despite its large area. This precipitation can further protect exposed steel areas where the coating has been damaged by scratches or at the cutting edge.