Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 59-61).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 257-263).

Thesis (doctoral)--University of Göteborg, 1991. / Extra t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / On t.p. "2" is subscript. Includes bibliographical references. Also available in electronic version.

Made available in DSpace on 2014-06-11T19:28:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-04-06Bitstream added on 2014-06-13T19:16:49Z : No. of bitstreams: 1 mariscalmunoz_e_me_arafo.pdf: 3090290 bytes, checksum: 16c5f9ca343ea1d3e9b942ecb341ffbb (MD5) / A osseointegração, requisito indispensável para o sucesso dos implantes dentários, é um processo lento, caracterizado, sequencialmente, pelas etapas de adesão, diferenciação e proliferação celular, bem como pela aposição e mineralização da matriz óssea depositada por osteoblastos. Acelerar o processo de osseointegração significa reduzir o tempo de espera para a aplicação segura de uma carga funcional sobre os implantes de titânio (Ti). Sabe-se que vários fatores, tal como a topografia da superfície do Ti, influenciam diretamente o processo de osseointegração. Assim, desde que foi demonstrado que alguns padrões específicos de superfície do Ti são capazes de bio-estimular osteoblastos, favorecendo e acelerando a osseointegração, diversas técnicas de baixo custo, rápida execução e altamente reproduzíveis, tem sido propostas para tratar a superfície dos implantes. Desta maneira, o objetivo da presente pesquisa foi avaliar a capacidade de superfícies de Ti, modificadas com laser pulsado de alta potência (L) ou usinadas (U), de estimular a diferenciação e maturação de células obtidas de calvária de camundongos cultivadas sobre elas. Para isto, foram realizados ensaios laboratoriais para determinar a atividade mineralizadora das células (coloração com vermelho de alizarina e fosfatase alcalina), o metabolismo (MTT assay) e morfologia celular (MEV). A fim de melhor caracterizar a diferenciação de osteoblastos, foi realizada a reação de polimerização em cadeia (PCR) quantitativa em tempo real para analisar a expressão, pelas células cultivadas sobre as superfícies de Ti, de genes que codificam os fatores de transcrição Runx2 e Sp7 e proteínas específicas da matriz extracelular mineralizada... / The osseointegration, which plays a fundamental role in the dental implantation success, is characterized by cell adhesion, differentiation, proliferation as well as deposition and mineralization of of bone matriz by osteoblasts. To make the osseointegration process faster means reducing the period to apply a safe functional stress on the titanium (Ti) implants. A number of factors, such as the topographical surface of Ti enhances the osseointegration process. Different Ti surface treatments capable of bio-estimulating osteoblasts to accelerate the osseointegration have been evaluated. Current studies have shown that osseointegration of Ti devices is enhanced by surface roughness. In this way, the aim of the present investigation was to assess the capacity of Ti surfaces irradiated with high potency laser (L) or polished (U) to stimulate the differentiation and maturation of cells obtained from calvarian bone of mouse. Then, laboratorial protocols to evaluate the mineralizing cell activity (alizarin red assay), cell metabolism (MTT assay) as well as the morphology (SEM) of cells cultured on the Ti surfaces were carried out. To better characterize the osteoblast differentiation, the real time qPCR for expression of genes that code to the transcription factors Runx2 and Sp7 were performed. Additionaly, this protocol was also used to assess specific proteins of extracellular matrix (Spp1, Alpl, e Col1a1). The numeric data were subjected to statistical analysis. Our data demonstrated that the Ti surface L improved the osteoblast maturation capacity of calvarial osteoblasts grown over this surface. Scanning electron microscopy (SEM) revealed spheres and protrusions created by laser treatment. Laser profilometry showed a disordered surface with micrometric and/to nanometric scales features (Ra = 10.57μm). When compared to polished... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:31:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-26Bitstream added on 2014-06-13T19:01:27Z : No. of bitstreams: 1 000737176.pdf: 2233924 bytes, checksum: be9f98eec022d58f2c75519afa00ec37 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Objetivos: Avaliar o comportamento corrosivo da liga Ti-6Al-4V em função de sua superfície polida ou condicionada por meio de duplo ataque ácido, em simulador de fluidos corporais (SFC) com diferentes concentrações de dextrose (0; 5mM; 7,5 mM e 15 mM) e lipopopolissacarídeo (LPS) (0; 0,15 μg/mL; 15 μg/mL; 150 μg/mL), usados isolados ou associados. Materiais e Métodos: Discos de liga Ti-6Al-4V (2 mm de espessura e 15 mm de diâmetro) foram confeccionados com diferentes padrões de superfície. Para o ensaio eletroquímico (n=3), testes padrões como potencial de circuito aberto, espectroscopia de impedância eletroquímica (EIE) e teste potenciodinâmico foram conduzidos em solução de fluido corpóreo (SBF) com diferentes concentrações de dextrose e LPS. As superfícies dos discos foram caracterizadas pela microscopia eletrônica de varredura (MEV), microscopia de força atômica (MFA), e por meio da rugosidade de superfície e da microdureza. Os dados quantitativos foram analisados pelo teste de correlação de Pearson e T-teste independente, com nível de significância de 5%. Resultados: Nos parâmetros de corrosão, houve forte correlação do LPS com os valores de Ipass (densidade de corrente de passivação), Cdl (capacitância) e Rp (resistência de polarização) (p<0,05) para o titânio (Ti) com tratamento de superfície por duplo ataque ácido. A associação de dextrose e LPS foi correlacionada com Icorr (densidade de corrente de corrosão) e Ipass (p<0,05). Em relação à cinética de corrosão, os grupos tratados com ácido apresentaram aumento significante nos valores de Cdl e redução nos valores de Rp (P<0,05, T-teste). Quanto à topografia, houve aumento da rugosidade de superfície para ambas as superfícies (R2=0,726, p=0,0001 para Ti polido; R2=0,405, p=0,036 para Ti ácido). A microdureza do Ti polido diminuiu (p<0,05) e do Ti ácido aumentou (p=0,0001). A MFA... / Objectives: To analyse the corrosion behavior of Ti-6Al-4V with different surfaces (machined and modified by treatment with double acid-etching), on simulator body fluids (SBF) with different concentrations of dextrose (0; 5 mM, 7.5 mM and 15 mM) and lipopolysaccharide (LPS) (0; 0.15 μg/mL; 15 μg/mL; 150 μg/mL), used isolated or in combination. Materials and Methods: Ti-6Al-4V disks (2 mm in thickness and 15 mm in diameter) were fabricated with different surfaces. For electrochemical assay (n = 3), open circuit potential, electrochemical impedance spectroscopy (EIS) and potentiodynamic tests were conducted in SBF with different concentrations of dextrose and LPS. The surfaces of the disks were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and by surface roughness and microhardness. Data were analyzed by Pearson correlation and independent t-test at a significant level of 5%. Results: For the corrosion parameters, a strong correlation of LPS with Ipass (passivation current density), Cdl (capacitance) and Rp (polarization resistance) values (P <.05) for Ti surface treated by double acid- etching was noted. The combination of dextrose and LPS was correlated with Ipass and Icorr (corrosion current density) (P <.05). Regarding the corrosion kinetics the acid-treated groups showed significant increase in Cdl values and reduced values of Rp (P <.05, T-test). In terms of topography, there was an increase in surface roughness for both surfaces (R2 = 0.726, p = 0.0001 for machined Ti, R2 = 0.405, p = 0.036 for Ti acid). The machined Ti exhibited reduction in microhardness (P <.05), while Ti acid showed increased microhardness (p = 0.0001) vs baseline. The AFM showed changes in the microstructure of Ti by increasing the thickness of surface mainly in the association of dextrose and LPS. Conclusions: The combination of dextrose ...

Made available in DSpace on 2014-06-11T19:33:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-03-15Bitstream added on 2014-06-13T18:45:01Z : No. of bitstreams: 1 almussa_afm_dr_arafo.pdf: 1982978 bytes, checksum: 078c30ee2ec08d13b4ca6d31af723b59 (MD5) / Determinar in vivo e in vitro o efeito do tempo sobre as propriedades mecânicas de molas helicoidais fechadas de níquel-titânio. Métodos: Três artigos científicos foram redigidos e utilizados para a avaliação dos propósitos apresentados. Resultados: No artigo 1 (in vivo), o tempo e a ativação influenciaram significantemente a taxa de superelasticidade (SE) e a força média do platô clínico superelástico (FP) quando o perfil total das molas foi avaliado (p<0,001). Foi detectada uma interação significante entre tempo e ativação nas variáveis taxa de SE (p<0,001) e FP (p=0,013). No artigo 2 (in vitro), o tempo influenciou significantemente a FP e a taxa de SE quando o perfil total das molas foi avaliado (p<0,001). A ativação influenciou significantemente a taxa de SE (p<0,001), não influenciando a FP (p=0,218). Foi detectada uma interação significante entre tempo e ativação na variável taxa de SE (p=0,020), o que não ocorreu na variável FP (p=1,00). No artigo 3 (in vivo), o uso clínico e a ativação influenciaram significantemente a deformação das molas (p<0,001). Foi detectada interação significante entre os fatores tempo e ativação na variável deformação (p<0,001). Conclusões: Após 6 meses de uso clínico, as molas apresentaram diminuições significantes nas taxas de SE em até 52%, nas FP em até 88% e aumento da deformação em até 1,26 mm. Laboratorialmente, os efeitos nas FP foram maiores nos dois primeiros meses e depois se estabilizaram, já as taxas de SE não apresentaram diferenças nos dois meses iniciais, aumentando nos seguintes. Desta forma, a reutilização das molas avaliadas neste estudo seria desaconselhada. / Determine in vivo and in vitro the time effect on the mechanical properties of nickel-titanium closed coil springs. Materials and Methods: Three research papers were written and analyzed for the evaluation of the aims presented. Results: In first paper (in vivo), time and the activation significantly affected superelasticity (SE) rate and the average force of the superelastic clinical plateau (FP) when the total profiles of the springs were evaluated (p<0,001). A significant interaction between time and activation was detected for the SE rate (p<0,001) and FP (p=0,013) variables. In second paper (in vitro), time significantly affected FP and SE rate when the total profiles of the springs were evaluated (p<0,001). Activation significantly affected the SE rate (p<0,001), but not the FP (p=0,218). A significant interaction between time and activation was detected for the SE rate variable (p=0,020), but not for the FP variable (p=1,00). In third paper (in vivo), the clinical use and activation significantly affected the springs deformation (p<0,001). A significant interaction between time and activation was detected for the deformation variable (p<0,001). Conclusions: After six months of active clinical use, the analyzed springs presented a significant decay on their SE rates up to 52%, on FP up to 88% and increase in deformation up to 1,26 mm. In the in vitro study, the effects on FP were higher in the first two months and then stabilized, and the SE rates didn’t differ in the two initials months, increasing in the following. This way, reuse of the springs evaluated in this study would be inadvisable.

Orientador: Wirley Gonçalves Assunção / Co-orientador: Valentim Adelino Ricardo Barão / Banca: Idelmo Rangel Garcia Júnior / Banca: Maria Cristina Rosifini Alves Rezende / Banca: Paulo Martins Ferreira / Banca: Maria da Gloria Chiarello de Mattos / Resumo: Objetivos: Avaliar o comportamento corrosivo da liga Ti-6Al-4V em função de sua superfície polida ou condicionada por meio de duplo ataque ácido, em simulador de fluidos corporais (SFC) com diferentes concentrações de dextrose (0; 5mM; 7,5 mM e 15 mM) e lipopopolissacarídeo (LPS) (0; 0,15 μg/mL; 15 μg/mL; 150 μg/mL), usados isolados ou associados. Materiais e Métodos: Discos de liga Ti-6Al-4V (2 mm de espessura e 15 mm de diâmetro) foram confeccionados com diferentes padrões de superfície. Para o ensaio eletroquímico (n=3), testes padrões como potencial de circuito aberto, espectroscopia de impedância eletroquímica (EIE) e teste potenciodinâmico foram conduzidos em solução de fluido corpóreo (SBF) com diferentes concentrações de dextrose e LPS. As superfícies dos discos foram caracterizadas pela microscopia eletrônica de varredura (MEV), microscopia de força atômica (MFA), e por meio da rugosidade de superfície e da microdureza. Os dados quantitativos foram analisados pelo teste de correlação de Pearson e T-teste independente, com nível de significância de 5%. Resultados: Nos parâmetros de corrosão, houve forte correlação do LPS com os valores de Ipass (densidade de corrente de passivação), Cdl (capacitância) e Rp (resistência de polarização) (p<0,05) para o titânio (Ti) com tratamento de superfície por duplo ataque ácido. A associação de dextrose e LPS foi correlacionada com Icorr (densidade de corrente de corrosão) e Ipass (p<0,05). Em relação à cinética de corrosão, os grupos tratados com ácido apresentaram aumento significante nos valores de Cdl e redução nos valores de Rp (P<0,05, T-teste). Quanto à topografia, houve aumento da rugosidade de superfície para ambas as superfícies (R2=0,726, p=0,0001 para Ti polido; R2=0,405, p=0,036 para Ti ácido). A microdureza do Ti polido diminuiu (p<0,05) e do Ti ácido aumentou (p=0,0001). A MFA ... / Abstract: Objectives: To analyse the corrosion behavior of Ti-6Al-4V with different surfaces (machined and modified by treatment with double acid-etching), on simulator body fluids (SBF) with different concentrations of dextrose (0; 5 mM, 7.5 mM and 15 mM) and lipopolysaccharide (LPS) (0; 0.15 μg/mL; 15 μg/mL; 150 μg/mL), used isolated or in combination. Materials and Methods: Ti-6Al-4V disks (2 mm in thickness and 15 mm in diameter) were fabricated with different surfaces. For electrochemical assay (n = 3), open circuit potential, electrochemical impedance spectroscopy (EIS) and potentiodynamic tests were conducted in SBF with different concentrations of dextrose and LPS. The surfaces of the disks were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and by surface roughness and microhardness. Data were analyzed by Pearson correlation and independent t-test at a significant level of 5%. Results: For the corrosion parameters, a strong correlation of LPS with Ipass (passivation current density), Cdl (capacitance) and Rp (polarization resistance) values (P <.05) for Ti surface treated by double acid- etching was noted. The combination of dextrose and LPS was correlated with Ipass and Icorr (corrosion current density) (P <.05). Regarding the corrosion kinetics the acid-treated groups showed significant increase in Cdl values and reduced values of Rp (P <.05, T-test). In terms of topography, there was an increase in surface roughness for both surfaces (R2 = 0.726, p = 0.0001 for machined Ti, R2 = 0.405, p = 0.036 for Ti acid). The machined Ti exhibited reduction in microhardness (P <.05), while Ti acid showed increased microhardness (p = 0.0001) vs baseline. The AFM showed changes in the microstructure of Ti by increasing the thickness of surface mainly in the association of dextrose and LPS. Conclusions: The combination of dextrose ... / Doutor

Dissertation submitted in fulfilment of the requirements for the degree Master of Technology: Mechanical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2014 / The research described in this dissertation investigates the feasibility of casting inlet valves for an internal combustion engine using Ti6Al4V alloy. The engine valves operate in an extreme environment under high thermal cycles – this requires a material that can withstand such exposures. Ti6Al4V is the most common titanium alloy with high temperature creep and fatigue resistant behaviour, however, it is not all positive. Ti6Al4V alloy also yields many difficulties with respect to processing especially when the material is cast. It is therefore important to gain a thorough understanding of the pouring and solidification characteristics of this material. The main focus of this work was to investigate and optimise feeding and geometrical parameters to produce valves that are free from defects, especially porosity. An in depth analyses of the parameters that influenced the casting quality was performed, and it was found that casting orientation, inlet feeder geometry, initial and boundary conditions all played a vital role in the final results. These parameters were individually investigated by performing detailed numerical simulations using leading simulation software for each of these cases. For each case, a minimum of ten simulations was performed to accurately determine the effect of the alteration on casting soundness and quality. Furthermore, the relationships (if any) were observed and used in subsequent optimised simulations of an entire investment casting tree. The change of geometric orientation and inlet feeder diameter and angle showed distinct relationships with occurrence of porosity. On the other hand, alteration in the pouring parameters, such as temperature and time, had negligible effect on occurrence or position of porosity in the valve. It was found that investigating individual parameters of simple geometry and then utilising these best-fit results in complex geometry yielded beneficial results that would otherwise not be attainable.