Fatigue crack growth in ±-Zirconium phosphate/epoxy nanocomposites was investigated. A new fatigue testing technique was implemented for miniature samples. Two different methods “strength of materials and Rayleigh-Ritz - were used in determining the bending stress. The fatigue stress and fatigue life of different nanocomposite specimens were plotted in a traditional stress-life (S-N) curve. It was inferred from the S-N plot that the values obtained from both the methods compare well. The experimental results showed that fatigue life of filled epoxy nanocomposite is more than that of the unfilled epoxy composite. A model for bending stresses, ultimate strength and the number of cycles to failure was obtained to predict a component service life without conducting elaborate tests. Scanning electron examination of the fractured surfaces revealed that the crack takes a tortuous path during its propagation course, indicating crack blunting and crack deflection roles of ZrP and CSR nanofillers, which consequently improve the fracture resistance. In case of the M-ZrP-epoxy systems, delamination of ZrP platelets from surrounding epoxy matrix was proposed as the reason behind crack growth. The improved fracture resistance of these nanocomposites was attributed to the delamination of ZrP platelets and deflection of crack direction. The superior behavior of CSR-ZrP-epoxy composites was attributed to the cavitation process and void coalescence due to CSR particles delamination.

Amelogenesis imperfecta (AI) is a genetically determined enamel defect characterized by genetic and clinical heterogeneity . The prevalence and incidence of AI were established in the county of Västerbotten, northern Sweden, in 3-19-yr-olds born 1963-79, as were the mode of inheritance and clinical manifestation of AI. The distribution of the inorganic component in the enamel of AI teeth was studied as well as the surface morphology and other morphological details, and the findings were correlated to genetic and clinical data. AI was diagnosed in 79 children and adolescents (index cases). The prevalence in the study population was 1.4: 1 000. The mean yearly incidence 1963-79 was 1.3:1 000. The inheritance patterns for AI were established in 78 index cases from 51 families. Pedigree and segregation analyses suggested autosomal dominant (AD) inheritance in 3 3 families, autosomal recessive (AR) in six families, and X- linked recessive in two families; in ten families only sporadic cases were found. In one of the families with an AD inheritance pattern, X-linked dominant was a possible alternative. Examination of the families of the 78 index cases revealed 107 new cases of AI. The hypoplastic form was seen in 72% of all diagnosed cases and the hypomineralization form in 28% of the cases. A further classification of the clinical manifestations led to the identification of eight clinical variants. In 3 3 of the 51 families the same clinical variant was found in all affected members. In eight families affected members were assigned to different clinical variants. In three families with an X-linked inheritance pattern for AI, the clinical manifestation differed between women and men due to lyo- nization. Among the remaining five families, with an AD inheritance pattern for AI, variants clinically characterized by hypoplasia as well as variants characterized by hypomineralization were found in three families; in the other two families the clinical manifestation varied within the same main form of AI, i.e. hypoplasia or hypomineralization. Hypoplasia as well as hypomineralization were observed microradiographically in the enamel of most of the examined teeth. These findings were supported by scanning electron microscopy (SEM). Both clinically and microradiographically as well as by SEM, similar variants of AI were found as AD and AR traits and/or among the sporadic cases. In the families with AI as an X-linked trait the genetic hypothesis was confirmed by the clinical, microradiographic and scanning electron microscopic findings. / <p>S. 1-46: sammanfattning, s. 47-134: 5 uppsatser</p> / digitalisering@umu

Individual, well structurally characterised dislocations present in n-type silicon have been studied using the electron beam induced current (EBIC) mode of an SEM.</p>An EBIC system has been designed and constructed which includes i) phase sensitive detection, ii) computerised control of the experimental equipment and data capture and iii) a variable temperature SEM specimen stage. With this system measurements have been made of the EBIC contrast of individual segments of deformation induced dislocations produced by two stage compressive deformation at 850°C and 420°C. An experimental and theoretical analysis of EBIC signal generation in the Schottky barrier specimens used in this work is presented. This shows that the EBIC contrast measurements made may be directly correlated to the dislocation recombination strength. Contrast measurements have been made at temperatures in the range 120K to 370K and for electron beam currents from 6 x 10^-12A to 2 x 10^-9A. Several new effects have been observed. Minority carrier diffusion length measurements have also been performed in silicon containing dislocations. These show that the value obtained may depend upon experimental parameters used in a hitherto undetected manner. A new theory describing recombination of carriers at charged dislocations has been developed and this has been extended to provide a description of the variation of the EBIC contrast of dislocations with temperature, electron beam current and also the transient response of the EBIC contrast. Comparison of the theoretical predictions with the results gained experimentally shows full agreement for low temperatures or large beam currents. At high temperatures and small beam currents the theory shows the EBIC contrast will behave differently depending on the density of dislocation states present. Interpretation of the experimental results in terms of this theory allows some new insight to be gained for recombination at dislocations, and values for some of the parameters controlling recombination have been obtained.

Thesis (M.App.Sc.) - Carleton University, 2002. / Includes bibliographical references (p. 72-87). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Hong Kong, 1994. / Photocopy of original typescript. Includes bibliographical references.

Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 132-139). Also available in electronic format on the Internet.

Thesis (M.S.)--Brigham Young University. Dept of Physics and Astronomy, 2007. / Includes bibliographical references (p. 89-94) and index.

Thesis (doctoral)--Université Pierre et Marie Curie, 1978. / Cover title. Includes bibliographical references (leaves 223-231).

A manutenção da morfologia normal do endotélio da córnea é um importante indicador da integridade funcional. A reparação endotelial frente a um trauma, em coelhos, ocorre por migração, hipertrofia e mitose celular. Objetivou-se comparar a morfologia das células do endotélio, da região periférica perincisional à região central, da córnea de coelhos (Oryctolagus cuniculus) em diferentes períodos pós-operatórios. Foram designados três grupos, com 5 animais cada, para avaliação pós-operatória, sendo G1 (7 dias); G2 (15 dias) e G3 (45 dias). Trinta bulbos dos olhos de coelhos, da raça Nova Zelândia, foram submetidos à incisão de córnea clara uniplanar com 3,2 mm. Ao fim dos períodos determinados, procedeu-se a avaliação da morfologia endotelial valendose da microscopia eletrônica de varredura. Realizaram-se seis eletromicrografias de varredura, de cada região da córnea, com aumento de 1000 vezes. Para análise do percentual do número de lados celular, foram analisadas 100 células endoteliais. Na região periférica perincisional, avaliada ao 7° dia de pós-operatório, foram encontradas células com 6 lados (47,8%), 5 lados (31,3%), 7 lados (13,9%), 3 lados (0,1%), 4 lados (4,9%), 8 lados (1,8%) e 9 lados (0,2%). Na avaliação ao 15° dia de pós-operatório, observaram-se células com 6 lados (45,6%), 5 lados (32,6%), 7 lados (17,4%), 4 lados (1,7%) e 8 lados (2,7%). No 45° dia de pós-operatório, verificou-se a presença de células com 6 lados (57%), 5 lados (24%), 7 lados (17,2%), 4 lados (0,1%), 8 lados (1,6%) e 9 lados (0,1%). Na área central, ao 7° dia de pós-operatório, detectaram-se células com 6 lados (75,6%), 5 lados (13,3%), 7 lados (10,8%) e 8 lados (0,3%). Na avaliação, ao 15° dia de pós-operatório, foi possível observar células com 6 lados (78,9%), 5 lados (11,5%) e 7 lados (9,6%). No 45° dia de pós-operatório identificaram-se células com 6 lados (74,8%), 5 lados (13,6%) e 7 lados (11,6%). Os resultados demonstraram que na região periférica perincisional ocorreu diminuição das células com seis lados e aumento do número de células com cinco e sete lados. Na região central manteve-se o padrão regular de hexagonalidade das células endoteliais nos diferentes períodos pós-operatórios. Conclui-se que houve alteração na morfologia das células endoteliais, da região periférica perincisional comparada à região central, da córnea de coelhos nos diferentes períodos pós-operatórios. / The maintenance of the normal corneal endothelium morphology is an important indicator of its functional integrity. In rabbits, endothelial repair in the event of traumas is made through cell migration, hypertrophy and mitosis. The purpose of this study was to compare the morphology of endothelial cells of the perincisional area with the central area of the cornea of rabbits (Oryctolagus cuniculus), in different post-operative periods. Three groups containing 5 animals each were designed for post-operative evaluation: G1 (7 days); G2 (15 days) and G3 (45 days). The clear cornea of thirty New Zealand rabbits was subjected to a single-planed incision of 3.2 mm. At the end of the established periods, a morphological evaluation of the endothelium was carried out using scanning electron microscopy. Six scanning electron micrographs of each corneal area were performed using a magnification of 1000 x. One hundred endothelial cells were analyzed to obtain the cell side count percentage. In the perincisional peripheral area, which was evaluated at the 7 post-operative day, 6-sided (47.8%), 5-sided (31.3%) and 7-sided (13.9%) cells were found, in addition to, 3-sided cells (0.1%), 4-sided cells (4.9%), 8-sided cells (1.8%) and 9-sided cells (0.2%). In the evaluation made on the 15th post-operative day, 6-sided (45.6%), 5-sided (32.6%) and 7-sided (17.4%) cells were observed, as well as 4-sided (1.7%) and 8-sided cells (2.7%). On the 45th postoperative day, the presence of 6-sided (57%), 5-sided (24%), 7-sided (17.2%), 4-sided (0,1%), 8-sided (1.6%) and 9-sided cells (0.1%) was verified. On the 7th post-operative day, 6-sided (75.6%), 5-sided (13.3%), 7-sided (10.8%) and 8-sided cells (0.3%) were observed in the central area .Upon evaluation made on the 15th post-operative day, it was possible to observe 6-sided (78.9%), 5-sided (11.5%) and 7-sided (9.6%) cells. Results have shown that there was a reduction of six-sided cells and an increase in the number of five and seven-sided cells in the perincisional peripheral area. The regular hexagonal standard of the endothelial cells was maintained in the central area in different post-operative periods. In comparison to the central area, there was a morphological alteration of the endothelial cells of the peripheral perincisional area in different post-operative periods of the cornea of rabbits.

Made available in DSpace on 2014-06-11T19:32:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-20Bitstream added on 2014-06-13T19:02:32Z : No. of bitstreams: 1 volanti_dp_dr_araiq.pdf: 1844353 bytes, checksum: 8213435ede38e29d8f618a9b95eeb7c7 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O trabalho que se apresenta centra-se no estudo investigativo do crescimento de cristais de óxido de cobre (II), CuO, com cristais organizados em diferentes formas semelhantes à ouriços-do-mar, fibras, e nanobastões, com controle fino da morfologia e cristalizados pelo método hidrotérmico assistido por micro-ondas. Esses materiais foram previamente caracterizados por difração de raios X (DRX), medida de área de superfície específica, espectroscopia de fotoelétrons excitados por raios X, microscopia eletrônica de varredura de alta resolução e de transmissão, além de espectroscopia de absorção de raios X próxima à borda de absorção (XANES), e outras. Pelas técnicas de microscopia combinadas foi possível caracterizar detalhadamente os materiais sintetizados, como sua estrutura, forma, tamanho, composição química, direção de crescimento, etc. Os óxidos obtidos foram testados quanto suas propriedades catalíticas na reação de desidrogenação do etanol – atividade, seletividade, frequência de reação. A originalidade do trabalho é que ao compreender as relações entre a morfologia do cristal e a estrutura da superfície dos óxidos nanoestruturados será possível obter catalisadores mais sensíveis, seletivos e com maior atividade catalítica. Ademais, foram realizados experimentos in situ de redução e reoxidação a temperatura programada, monitorada por XANES e DRX, resolvidos no tempo e na temperatura. Assim obteve-se uma projeção semiquantitativa de diferentes espécies de clusters de cobre (Cu2+, Cu+, e/ou Cu0). Esses resultados sugerem particularidades intrínsecas devido às diferentes morfologias no estado ativo nas cinéticas de redução e reoxidação. Em suma, foi desenvolvida uma rota sintética rápida e eficaz para sintetizar estruturas de CuO com diversas morfologias. Os materiais foram... / The present work goal the crystal growth of copper (II) oxide (II), CuO, with in different particles assembly. Herein, we report results of three distinct controlled CuO morphologies, urchin-like, fiber-like and nanorods, with fine control of morphology and crystallized by microwave assisted hydrothermal method. These materials were previously characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, surface area determination, scanning electron microscopy high-resolution and transmission electron microscopy, and absorption spectroscopy, X-ray absorption near edge (XANES), and others. The entire sequence of the crystallization procedure of CuO was monitored by field emission scanning electron microscopy in combination with transmission electron microscopy combined was possible to characterize in detail the materials synthesized, and its structure, shape, size, chemical composition, direction of growth, etc. The oxides obtained were tested for their catalytic properties in the reaction of dehydrogenation of ethanol – activity, selectivity, turnover frequency. The originality of this work is that by understanding the relationships between morphology and crystal structure of the surface oxides of nanostructured catalysts will be possible to obtain more sensitive and more selective catalytic activity. Copper-based catalysts obtained by microwave-assisted morphosynthesis were correlated with the dehydrogenation of ethanol. The degree of reduction and reoxidation was monitored using time-resolved in situ XANES and XRD during TPR under H2 and TPO under O2. A semiquantitative estimation of the different chemical forms (Cu2+, Cu+, and/or Cu0) was obtained. The results suggest intrinsic particularities due to different morphologies at the active state in reduction kinetics. In summary, we developed a rapid... (Complete abstract click electronic access below)