Sets of natural opening-mode fractures in sedimentary rocks may show a variety of types of aperture-size distributions. A frequently documented size distribution type, in the literature and in data presented here, is the power law. The emergence of power-law distributions of fracture aperture and length sizes has been simulated using various quasi-mechanical fracture-growth routines but models based on linear-elastic fracture mechanics rarely produce such patterns. I collected a fracture-size dataset of unprecedented size and resolution using core and field methods and scanning electron microscope-based cathodoluminescence (SEM-CL) images. This dataset confirms the prevalence of power laws with a narrow range of power-law exponents among fractures that contain synkinematic cement. Organized microfractures are ubiquitous in sandstones. A fracture-growth simulation I devised reproduces observed size-scaling patterns by distributing fracture-opening increments among actively growing fractures. The simulated opening increments have a uniform size, which can be specified; uniform opening size is consistent with observations of narrow ranges of micron-scale widths of opening increments within crack-seal texture in natural fractures. Thus power-law size scaling of natural fractures can be explained using non-power-law (uniform-sized) opening increments, arranged using rules designed to simulate the effects of cement precipitation during fracture opening. A fundamental shortcoming of previous models of fracture-set evolution is the absence of a test because only natural fracture end states, not growth histories, could be measured. Using a technique to constrain fracture timing based on fluid inclusion microthermometry and thermal history modeling, I tested growth models by reconstructing the opening history of a set of natural fractures in the Triassic El Alamar Formation in northeast Mexico. The natural-fracture data show that, consistent with simulations, new microscopic fractures are continually introduced during natural fracture pattern evolution. As well, larger fractures represent sites of concentrated reactivation, although smaller fractures may be reactivated after long periods of quiescence. The pattern likely arises through feedback between fracture growth and the mechanically adhesive effects of contemporaneous fracture cement deposition. The narrow range in power-law exponents documented among fractures can help improve estimates of meter-scale large-fracture spacing where limited fracture samples are available. / text

<p><font face="Times-Roman"> <p align="left">The growth of the Internet has led to many interesting developments for both educational and commercial purposes. In this project an attempt was made to use the Internet for a research purpose to facilitate the determination of the thermal stability of diffusion barriers. Another purpose of this thesis is to investigate the teaching and training use of the Internet through the development of online interactive tools and activities as well as materials. The training aspects are mentioned as it is hoped that this thesis can serve as a form of documentation of the use of the Internet, while the central part was the determination of thermal stability of TiN, TaN and TiW diffusion <font face="Times-Roman">barriers on Ag.</font></p> </font></p>

The image analysis techniques presented in the présent thesis have been developed as part of a European projeet dedicated to the development of an automatic membrane protein crystallization pipeline. A large number of samples is simultaneously produced and assessed by transmission electron microscope (TEM) screening. Automating this fast step implicates an on-fine analysis of acquired images to assure the microscope control by selecting the regions to be observed at high magnification and identify the components for specimen characterization.The observation of the sample at medium magnification provides the information that is essential to characterize the success of the 2D crystallization. The resulting objects, and especially the artificial membranes, are identifiable at this scale. These latter present only a few characteristic signatures, appearing in an extremely noisy context with gray-level fluctuations. Moreover they are practically transparent to electrons yielding low contrast. This thesis presents an ensemble of image processing techniques to analyze medium magnification images (5-15 nm/pixel). The original contribution of this work lies in: i) a statistical evaluation of contours by measuring the correlation between gray-levels of neighbouring pixels to the contour and a gradient signal for over-segmentation reduction, ii) the recognition of foreground entities of the image and iii) an initial study for their classification. This chain has been already tested on-line on a prototype and is currently evaluated.

Made available in DSpace on 2014-06-11T19:27:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2004Bitstream added on 2014-06-13T19:35:57Z : No. of bitstreams: 1 silva_kg_me_araca.pdf: 3519498 bytes, checksum: 8be3bbadc0092628ca71b9618deb19ae (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Bisco Inc., Il, Usa / O objetivo deste estudo foi avaliar o efeito da variação do pH da solução desmineralizante em modelo de ciclagem de pH na dureza de superfície, liberação de flúor e característica de superfície dos materiais restauradores: Ketac-Fil Plus, Vitremer, Fuji II LC, Freedom e Fluorofil. Foram confeccionados, para cada material, 34 corpos-de-prova que tiveram a dureza de superfície inicial (DSI) determinada após a confecção. A seguir, foram divididos em 5 grupos (n=30) de acordo com a variação de pH (4,3; 4,6; 5,0; 5,5 e 6,2) da solução desmineralizante e submetidos a períodos cíclicos em solução desmineralizante (Des-6 horas) e remineralizante (Re-18 horas) por 15 dias. Decorrido este período, verificou-se a dureza de superfície final (DSF) e a característica de superfície (n=24). As soluções armazenadas diariamente foram utilizadas para a determinação da concentração de flúor (Des+Re). As variáveis DSI, DSF e alteração de dureza de superfície (% ADS) foram submetidas à análise de variância e a liberação de flúor ao teste de Kruskal-Wallis (p<0,05). A variação do pH proporcionou relação direta quando se comparou a dureza e inversa para a liberação de flúor nos cimentos de ionômero de vidro. Para as resinas compostas modificadas por poliácidos foi verificada relação inversa para a liberação de flúor, não havendo correlação na dureza. A característica de superfície foi influenciada pela variação do pH, ficando mais evidente nos menores pHs, exceto para as resinas compostas modificadas por poliácidos. Baseados nos resultados, concluiu-se que a variação do pH da solução desmineralizante do modelo de ciclagem influenciou a liberação de flúor dos materiais testados. Essa variação alterou a dureza e a característica de superfície dos cimentos de ionômero de vidro, mas não das resinas compostas modificadas por poliácidos. / The aim of this study was to evaluate the effect of pH of the demineralizing solution in a cycling model on surface hardness, fluoride release and surface aspects of restorative materials (Ketac-Fil Plus, Vitremer, Fuji II LC, Freedom and Fluorofil). Thirty-four specimens of each material were made and surface hardness was measured. Then, the specimens were randomized in five groups (n=30), according to pH (4.3; 4.6; 5.0; 5.5; and 6.2) of the demineralizing solution and submitted to a cycling model during 15 days. The specimens remained in the demineralizing solution for 6 hours and in the remineralizing solution for 18 hours. After that, surface hardness was measured again and surface aspects were observed (n=24). Fluoride concentration was determined daily in all solutions (De+Re). Data from SMH (before and after pH-cycling) and %SMHC were analyzed by analysis of variance (p<0.05); Kruskal-Wallis test was carried out for the results of fluoride release. For glass ionomer cements, the variation of pH led to a direct relationship when hardness was compared and to an inverse relationship with regards to fluoride release. For polyacid-modified resin composites, an inverse relationship was found regarding fluoride release; no correlation was observed with regards to hardness. Surface aspect was influenced by pH variation: an acidic pH led to a greater alteration, except for polyacid-modified resin composites. It was possible to conclude that pH of the demineralizing solution did influence fluoride release from the tested materials. The pH variation altered hardness and surface aspects of glass ionomer cements, but it did not influence polyacid-modified resin composites in those analysis.

The biomechanical aspects related to the adaptation of fixed prostheses over implants are directly associated to treatment success. Therefore, the aim of this study was to evaluate the presence of microgaps in the union formed by the abutment and the inner connection of Cone Morse dental implant. The study was composed by two groups. The first group (n:16) used materials (dental implant and abutment) of the same manufacturer, Neodent® (Curitiba-PR, Brazil). The second group (n:16) used materials from different manufacturers, where the dental implant was Neodent® (Curitiba-PR, Brazil), and the abutment was Singular®(Parnamirim-RN, Brazil). The sets were sent to scanning electron microscope (SEM), where it was taken the measurements of microgaps formed between the implant connection and the abutment. The results obtained were submitted to statistical (Mann-Whitney-U) evaluating dispersion measurements and central tendency of values (standard and mean deviation). In group 1 the average found was 5,69μm and standard deviation (SD) was 8,46μm. Group 2 showed average of 1,24μm and SD: 0,44μm. The group formed by dental implant and abutment from the same manufacturer showed a greater data dispersion, with greater microgap values, compared to the group formed by the set implant-abutment of different manufacturers. It was concluded that, based on the measurements taken on SEM, the group formed by implant and abutment of different manufactures showed lower values of microgaps, and, therefore, a better in vitro adaptation. / Os aspectos biomecânicos relacionados à adaptação da prótese sobre o implante dentário estão diretamente associados ao sucesso do tratamento. Assim, o objetivo deste trabalho foi avaliar a presença de microgaps na união formada pelo abutment e a conexão interna do implante dentário do tipo Cone Morse. O estudo foi composto de dois grupos onde no primeiro grupo (n:16) foram utilizados materiais (implante dentário e abutment) do mesmo fabricante, Neodent® (Curitiba-PR, Brasil). No segundo grupo (n:16) foram utilizados materiais de fabricantes diferentes, sendo o implante da marca Neodent® (Curitiba-PR, Brasil) e o componente protético da marca Singular®(Parnamirim-RN, Brasil). Os conjuntos foram levados ao microscópio eletrônico de varredura (MEV), sendo realizadas as mensurações do microgap formado entre a conexão do implante e o componente protético. Os resultados obtidos foram submetidos à análise estatística (Mann-Whitne-U) avaliando-se medidas de dispersão e tendência central dos valores (desvio padrão e média). No grupo 1 a média encontrada foi de 5,69μm e o desvio padrão (DP) foi de 8,46μm. O grupo 2 apresentou média de 1,24μm e o DP: 0,44μm. O grupo formado por implante e componente protético do mesmo fabricante apresentou maior dispersão dos dados, com valores maiores para o microgap, comparando-se com o grupo formado pelo conjunto implante-abutment de marcas diferentes. Concluiu-se que, com base nas mensurações realizadas no MEV, o grupo formado por implante e abutment de diferentes fabricantes apresentou menores valores de microgap e consequentemente uma melhor adaptação in vitro.

Orientador: Regina Maria Puppin-Rontani / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-15T22:54:34Z (GMT). No. of bitstreams: 1 Pacheco_LarissaFerreira_M.pdf: 2738346 bytes, checksum: a45f65b512f358ab0bd0c6efb39313e0 (MD5) Previous issue date: 2010 / Resumo: A utilização de materiais restauradores unidos ao substrato dentinário tem sido um desafio que vem sendo superado nos últimos anos. Pesquisas têm conseguido aperfeiçoar a união dos materiais ao substrato dentinário, porém, a maioria dos estudos utiliza dentina hígida, uma vez que a utilização da dentina após remoção de cárie, isto é o substrato dentinário afetado pela cárie torna as pesquisas de difícil execução. Dentre os principais motivos destaca-se a difícil seleção de lesões similares, sendo, portanto um desafio para os pesquisadores pela variabilidade encontrada nos resultados não se alcançando a devida evidência científica para a aplicação das técnicas de união. A fim de aprimorar os estudos sobre este tipo de substrato, o objetivo deste estudo foi avaliar diferentes modelos de produção de cárie: modelo biológico e modelo in situ, comparando-os quanto a microdureza e profundidade de cárie à lesão de dentes extraídos com cárie. Foram utilizados 15 terceiros molares, compreendendo 5 dentes extraídos com cárie (cárie oclusal de profundidade média - C, grupo controle), 10 dentes eram hígidos, dos quais 5 foram utilizados para o modelo de produção de cárie in situ (IS) e 5 para o modelo biológico (MB). De todos os dentes foram obtidos blocos de dentina de 4x4x2 mm. Os blocos de dentina hígida foram analisados quanto à microdureza de superfície (SMH) e depois submetidos ao processo de cárie artificial. Após o desafio cariogênico, os blocos dos 3 grupos (C, IS, e MB) foram seccionados longitudinalmente ao centro obtendo-se dois hemi-blocos um dos quais foi submetido à análise da microdureza longitudinal (CSMH), e o outro à análise em Microscopia Eletrônica de Varredura (MEV). A microdureza longitudinal foi medida em 4 colunas com 8 pontos diferentes (com distância de 20µm entre as cinco indentações iniciais e 100µm entre as três finais), obtendo-se uma média de medidas por bloco. Os hemi-blocos restantes foram submetidos à análise em MEV para verificação da profundidade da lesão (X25 e X200), que foi medida na região mais profunda de cada uma delas. Os dados obtidos na análise da microdureza de superfície e longitudinal da lesão foram submetidos ao teste t, ANOVA e teste de Tukey, respectivamente (p<0,05). E os dados obtidos na análise de profundidade da lesão pelo MEV foram submetidos a ANOVA e teste de Tukey (p<0,05). Os resultados da microdureza de superfície após a produção de cárie mostrou que houve diferença significante entre os modelos de produção de cárie biológico e in situ, sendo que o modelo biológico não diferiu da lesão de cárie natural. Na microdureza longitudinal o modelo in situ apresentou nenhuma diferença estatística da cárie natural, mas o menor valor de CSMH foi observado na cárie produzida pelo modelo biológico. Na análise do MEV a lesão de cárie em dentina produzida pelo modelo biológico e a dentina cariada naturalmente tiveram profundidades similares, e o modelo in situ apresentou a menor profundidade de lesão de cárie. Baseado nos resultados obtidos neste estudo, foi concluido que os dois métodos de produção de cárie mostraram características similares ao da lesão de cárie natural em dentina nos diferentes testes realizados: microdureza de superfície e longitudinal, e Microscopia Eletrônica de Varredura. / Abstract: The use of restorative materials attached to the dentin substrate has been a challenge that has been overcome in the last years. Research has been able to improve the bonding between the materials and dentin substrate, however, the most studies use sound dentin, since the use of dentin after caries remove, such as dentin substrate affected make research difficult to perform. Among the main reasons stand the difficult selection of similar lesions, and, therefore a challenge to the researchers for the variability found in the results not reaching the proper scientific evidence for the application of bonding techniques. In order to improve the researches about this specific substrate, the aim of this study was to evaluate different models to produce caries, using the biological model, and the in situ model, comparing them about the cross-sectional microhardness and caries depth with the natural carious lesion, thus, extract teeth with caries dentin. Were used 15 third molars, including 5 teeth with natural caries (occlusal caries with average depth- CN), 10 teeth were sound, which 5 were used for the in situ production model of caries (IS) and 5 for the biological model (MB). Of all the teeth were obtained dentin samples with 4x4x2mm. Sound dentin samples were submitted to surface microhardness analysis and after to artificial caries process. After the cariogenic challenge, samples of the three groups (CN, IS, e MB) were cross sectioned to the center obtaining two sections which one was submitted cross-sectional microhardness analysis (CSMH) and the other to Scanning Electron Microscopy (SEM). Samples were analyzed as cross-section hardness in 4 columns with 8 different points (with a distance of 20µm between the first five indentations and 100µm between the last three) obtaining average measures for sample. The rest of sections were submitted to analysis by SEM to check the depth of the lesion, which was measured in the deepest region of each one. The data obtained by microhardness analysis and the depth lesion by SEM were submitted to ANOVA 2 criteria and t test, and ANOVA and Tukey test, respectively (p<0,05). Results of surface microhardness after to artificial caries process showed significantly difference between biological model and in situ model, and the biological model had no difference to natural caries. In the cross-sectional microhardness in situ model present no statistically difference from natural caries, but the lowest CSMH was observed for biological model of caries producing. SEM analysis, the artificial carious dentin lesions produced by biological model and natural carious dentin had similar depth, and the in situ model had the lowest depth of carious lesion. Based on the obtained results of this study it was concluded that both methods showed similar characteristics to natural caries dentin but concerning different tests: surface and cross-sectional microhardness, and scanning electron microscopy. / Mestrado / Odontopediatria / Mestre em Odontologia

This paper investigates noise characteristics of detector preamplifier in electron scanning microscopes. Various preamplifiers are measured and the lowest noise level amplifier with good level of speed is used. Further measurement of individual levels of amplifier is done and proposed the most suitable way how to achieve the total amplification. By detailed measuring of amplifier structure are found all unpleasant factors that affect the image quality. On the basis of these dates amplifier hardware is adjusted, software solutions to improve image quality designed and model control implemented, which directly controls active elements of preamplifier so that noise for given amplification was the lowest and reached required amplification.

In most of the tribological experiments studying friction and wear behaviour, the contact interface is hidden. The present work attempts to overcome this hidden-interface problem by carrying out real-time tribological experiments inside Transmission Electron Microscope (TEM). This is achieved by developing an in situ TEM triboprobe which can carry out nanoscale indentation, sliding and reciprocating tests on an electron transparent sample inside TEM. A novel in situ TEM triboprobe is developed by characterising the individual components involved in the development. Coarse positioning of a sharp probe is achieved using inertial sliders. Fine motion of the probe is controlled using a 4-quadrant tube piezoceramic. This triboprobe is capable of carrying out high stiffness tribological experiments inside TEM. The interface is viewed at high resolutions in real time during the experiments using a movie rate CCD camera. In indentation experiments a sharp probe is brought into contact with the sample surface. During indentation of Aluminium alloy tribolayer, it has been observed that the cracks originate from subsurface and propagate to the surface causing delamination-like material removal. Indentation experiments on protruding silicon particle in Aluminium-Silicon (Al-Si) alloy shows that initial deformation is elastic. Once the load is increased, the particle starts indenting the soft aluminum matrix, and results in sinking of the particle into the aluminium matrix. Once the particle starts sinking, the increase in the displacement causes the generation of a crack and the propagation of this crack results in the fracture of the particle. The sliding experiments inside TEM allowed the direct visualization of asperity level interaction during sliding. The preliminary experimental results of nanoscale sliding experiments carried out using an AFM tip as the sample. The adhesive instability is observed as snap-in and snap-out events. The snap-out distance seems to depend on the local geometry of the contact. To simulate reciprocating wear, a sharp diamond probe is brought into contact with Al-Si alloy and reciprocated sinusoidally at 0.5Hz. At lower loads no wear is observed. However, when the normal load is increased, material starts getting removed in thin slivers, and most of the wear debris generated get swept away from the track. Some wear debris get entrapped in between the sliding surfaces; subsequently they join to form larger wear particles. The trapped particles generated during the test act like rollers and a significant increase in the stroke-length is observed accompanying the rolling action of the particle. The phenomena like agglomeration and dissociation of the wear particles has also been observed. Repeated deformation of the trapped particles leads to the formation of tiny liquid drop on some of the wear debris. The liquid consists of gallium which comes from the sample preparation technique. The interaction between the liquid droplets has been studied by carrying out liquid-bridge pulling experiments. Liquid gallium gets cooled with time during tensile pulling of the droplets. A nano-filament is formed between the droplets during pulling. After some time, the droplet gets solidified and coalescence of droplets does not take place. Further frictional heating was necessary to form the bridge again. The in situ TEM triboprobe, which allow the tribological processes to be observed dynamically under high resolutions, is a power full tool in detecting fundamental tribological interactions.

The aim of this thesis is to investigate the methodology of three dimensional chemical imaging of nanoparticles through the use of scanning transmission electron microscope (STEM) – energy dispersive X-ray (EDX) spectroscopy. In this thesis, an absorption correction factor is derived for spherical nanoparticles that can correct X-ray absorption effects. Quantification of EDX spectra of nanoparticles usually neglects X-ray absorption within the nanoparticle but may lead to erroneous results, thus an absorption correction is important for accurate compositional quantification. The absorption correction presented is verified through comparison with experimental data of Au X-ray peaks in spherical Au nanoparticles and is found to agree excellently. This absorption correction allows accurate compositional quantification of large ( > 100 nm) particles with STEM-EDX.Three dimensional chemical mapping is achievable through the use of EDX spectroscopy with electron tomography. Here, the methodology of STEM-EDX tomography is fully explored, with a focus on how to avoid artefacts introduced through detector shadowing and low counts per pixel. A varied-time acquisition scheme is proposed to correct for detector shadowing that is shown to provide a more constant intensity over a series of projections, allowing a higher fidelity reconstruction. The STEM-EDX tomography methodology presented is applied to the study of AgAu nanoparticles synthesized by the galvanic replacement reaction. The elemental distribution as a function of the composition of the as-synthesized nanoparticles is characterised and a reversal in the element segregated to the surface of the nanoparticles is found. The composition at which the reversal takes place is shown to correlate with a peak in the catalytic yield of a three component coupling reaction. It is hypothesized that a continuous Au surface results in the optimum catalytic conditions for the reaction studied, which guides the use of galvanically prepared AgAu nanoparticles as catalysts.

Magister Chirurgiae Dentium (MChD)