Thesis (M. S. in Interdisciplinary Materials Science)--Vanderbilt University, Aug. 2008. / Title from title screen. Includes bibliographical references.

Thesis (MSc.(Anatomy)--Faculty of Health Sciences)-University of Pretoria, 2007. / Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xxii, 212 p.; also includes graphics. Includes bibliographical references (p. 203-212). Available online via OhioLINK's ETD Center

abstract: The research of this dissertation has involved the nanoscale quantitative characterization of patterned magnetic nanostructures and devices using off-axis electron holography and Lorentz microscopy. The investigation focused on different materials of interest, including monolayer Co nanorings, multilayer Co/Cu/Py (Permalloy, Ni81Fe19) spin-valve nanorings, and notched Py nanowires, which were fabricated via a standard electron-beam lithography (EBL) and lift-off process. Magnetization configurations and reversal processes of Co nanorings, with and without slots, were observed. Vortex-controlled switching behavior with stepped hysteresis loops was identified, with clearly defined onion states, vortex states, flux-closure (FC) states, and Omega states. Two distinct switching mechanisms for the slotted nanorings, depending on applied field directions relative to the slot orientations, were attributed to the vortex chirality and shape anisotropy. Micromagnetic simulations were in good agreement with electron holography observations of the Co nanorings, also confirming the switching field of 700-800 Oe. Co/Cu/Py spin-valve slotted nanorings exhibited different remanent states and switching behavior as a function of the different directions of the applied field relative to the slots. At remanent state, the magnetizations of Co and Py layers were preferentially aligned in antiparallel coupled configuration, with predominant configurations in FC or onion states. Two-step and three-step hysteresis loops were quantitatively determined for nanorings with slots perpendicular, or parallel to the applied field direction, respectively, due to the intrinsic coercivity difference and interlayer magnetic coupling between Co and Py layers. The field to reverse both layers was on the order of ~800 Oe. Domain-wall (DW) motion within Py nanowires (NWs) driven by an in situ magnetic field was visualized and quantified. Different aspects of DW behavior, including nucleation, injection, pinning, depinning, relaxation, and annihilation, occurred depending on applied field strength. A unique asymmetrical DW pinning behavior was recognized, depending on DW chirality relative to the sense of rotation around the notch. The transverse DWs relaxed into vortex DWs, followed by annihilation in a reversed field, which was in agreement with micromagnetic simulations. Overall, the success of these studies demonstrated the capability of off-axis electron holography to provide valuable insights for understanding magnetic behavior on the nanoscale. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2010

Dans cette thèse, nous abordons les défis rencontrés lors de la caractérisation des mémoires non volatiles par microscopie en transmission in situ. Les innovations récentes menées sur les porte-objets de TEM in situ basés sur l'utilisation de puces en silicium apportent de grands avantages comparée aux précédents modèles. Cependant, cette technique reste complexe et les expériences de MET in situ sont difficiles à mener à terme. Ce manuscrit tente d'apporter de nouvelles solutions pour permettre l'observation à l'échelle atomique pendant le recuit, ou la polarisation d'un échantillon dans le MET. Ce projet a été mené à travers plusieurs améliorations effectuées au cours des différentes étapes des expériences de MET in situ. Cette thèse se focalise plus particulièrement sur les problèmes rencontrés lors de la polarisation de dispositifs de mémoires résistives de taille nanométrique. Ces travaux furent conduits à travers une étude des instruments utilisés, le développement de nouvelles méthodes de préparation d'échantillons, et une analyse de l'impact de l'imagerie électronique sur le fonctionnement d'un dispositif dans le MET.Tout d’abord, une nouvelle méthode est développée spécifiquement pour les expériences de MET in situ en température. Grâce à ces développements, la cristallisation de mémoires à changement de phase en GeTe est observée en temps réel. Ces résultats ont notamment permis d'obtenir des informations utiles pour le développement de mémoires à changement de phase de type chalcogénure. Ensuite, de nouvelles puces en silicium dédiées à la polarisation in situ sont développées et produites. Une étude est ensuite menée sur la préparation d'échantillons par FIB afin d'améliorer la qualité des contacts électriques pour la polarisation in situ, ainsi que la technique de préparation elle-même. La qualité de cette méthode est ensuite démontrée à travers des mesures quantitatives obtenues pendant la polarisation in situ d'un échantillon de référence de type jonction PN. Ces développements sont ensuite appliqués afin d’observer des dispositifs de mémoires résistives de type CBRAM en fonctionnement dans le microscope électronique en transmission. Ces résultats ont permis d'apporter de nouvelles informations sur les mécanismes de fonctionnement des mémoires résistives, ainsi que sur la technique de polarisation in situ. / In this work, we address the current challenges encountered during in situ Transmission Electron Microscopy characterization of emerging non volatile data storage technologies. Recent innovation on in situ TEM holders based on silicon micro chips have led to great improvements compared to previous technologies. Still, in situ is a particularly complicated technique and experiments are extremely difficult to implement. This work provides new solutions to perform live observations at the atomic scale during both heating and biasing of a specimen inside the TEM. This was made possible through several improvements performed at different stages of the in situ TEM experiments. The main focus of this PhD concerned the issues faced during in situ biasing of a nanometer size resistive memory device. This was made possible through hardware investigation, sample preparation method developments, and in situ biasing TEM experiments.First, a new sample preparation method has been developed specifically to perform in situ heating experiments. Through this work, live crystallization of a GeTe phase change Memory Material is observed in the TEM. This allowed to obtain valuable information for the development of chalcogenide based Phase Change Resistive Memories. Then, new chips dedicated to in situ biasing experiments have been developed and manufactured. The FIB sample preparation is studied in order to improve electrical operation in the TEM. Quantitative TEM measurements are then performed on a reference PN junction to demonstrate the capabilities of this new in situ biasing experimental setup. By implementing these improvements performed on the TEM in situ biasing technique, results are obtained during live operation of a Conductive Bridge Resistive Memory device. This allowed to present new information on the resistive memories functioning mechanisms, as well as the in situ TEM characterization technique itself.

The development of InGaN quantum dots (QDs) is both scientifically challenging and promising for applications in visible spectrum LEDs, lasers, detectors, electroabsorption modulators and photovoltaics. Such QDs are typically grown using the Stranski-Krastanov (SK) growth mode, in which accumulated in-plane compressive strain induces a transition from 2D to 3D growth. This method has a number of inherent limitations, including the unavoidable formation of a 2D wetting layer and the difficulty of controlling the composition, areal density, and size of the dots. In this research, I have developed InGaN QDs by two methods using a plasma-assisted molecular beam epitaxy reactor. In the first method, InGaN QDs were formed by SK growth mode on (0001) GaN/sapphire. In the second, I have addressed the limitations of the SK growth of InGaN QDs by developing a novel alternative method, which was utilized to grow on both (0001) GaN/sapphire and AlN/sapphire. This method relies upon the ability to form thermodynamically stable In-Ga liquid solutions throughout the entire compositional range at relatively low temperatures. Upon simultaneous or sequential deposition of In and Ga on a substrate, the adatoms form a liquid solution, whose composition is controlled by the ratio of the fluxes of the two constituents FIn/(FIn+FGa). Depending on the interfacial free energy between the liquid deposit and substrate, the liquid deposit and vapor, and the vapor and substrate, the liquid deposit forms Inx-Ga1−x nano-droplets on the substrate. These nano-droplets convert into InxGa1−xN QDs upon exposure to nitrogen RF plasma. InGaN QDs produced by both methods were investigated in-situ by reflection high-energy electron diffraction and ex-situ by atomic force microscopy, field emission scanning electron microscopy, transmission electron microscopy, high resolution x-ray diffraction, and grazing incidence small angle x-ray scattering. The optical activity and device potential of the QDs were investigated by photoluminescence measurements and the formation and evaluation of PIN devices (in which the intrinsic region contains QDs embedded within a higher bandgap matrix). InGaN QDs with areal densities ranging from 109 to 1011 cm−2 and diameters ranging from 11 to 39 nm were achieved.

No description available.

Non-crystalline thin solid films are seeing increasing interest for a wide variety of applications. However, understanding structure and compositional variations in these films is an immense challenge. Conventional bulk structural or compositional characterization techniques such as X-ray diffraction often do not provide an adequate amount of information on their own. Electron microscopy is an incredibly powerful technique for structural and compositional film characterization, but is limited to inspection of only a small volume of any given sample. Rather than using one technique alone to gain information about a specimen, the greatest success is realized when these techniques are used in concert. This dissertation illustrates the idea that statistical analysis of electron microscopy data can provide information invaluable to interpreting bulk structural and compositional data from non-crystalline films. The first set of examples include demonstration of a statistical analysis method that can be applied to electron microscopy data to determine the presence of inhomogeneity along one film axis. This analysis method is applied to understanding compositional inhomogeneity that develops during formation of amorphous oxide films from aqueous solutions. Key insights are revealed that aid interpretation of bulk film X-ray characterization and possible processing conditions that lead to the compositional inhomogeneity. The second and third sets of examples describe the importance of electron microscopy analysis for structure determination in rotationally-disordered, non-epitaxial 2D heterostructures prepared from modulated elemental reactants. The second set of examples investigates the effects of nanoarchitecture on interlayer interactions and layer structure in heterostructures with interleaved BiSe and NbSe2 layers. The BiSe layers in these compounds display an interesting structural variation that impacts the overall compound properties. The structural variation is not visible using typical X-ray diffraction experiments, but analysis of electron microscopy images provides key insight into its existence. Finally, the third set of examples investigate several SnSe-containing heterostructures that provide insight into the unusual consequences of their non-epitaxial structure and film formation from modulated elemental reactants. Electron microscopy analysis, in conjunction with other characterization techniques, was invaluable for uncovering structural and compositional details within these compounds. This work contains previously published and unpublished co-authored material. / 10000-01-01

Submitted by FERNANDO AZADINHO ROSA null (rosa.fa@gmail.com) on 2016-03-17T15:23:11Z No. of bitstreams: 1 Fernando Azadinho Rosa_TESE Doutorado.pdf: 4178073 bytes, checksum: fd6bb2a00ca16ebfbbaccdcb82ec48c7 (MD5) / Approved for entry into archive by Sandra Manzano de Almeida (smanzano@marilia.unesp.br) on 2016-03-17T19:31:15Z (GMT) No. of bitstreams: 1 rosa_fa_dr_jabo.pdf: 4178073 bytes, checksum: fd6bb2a00ca16ebfbbaccdcb82ec48c7 (MD5) / Made available in DSpace on 2016-03-17T19:31:15Z (GMT). No. of bitstreams: 1 rosa_fa_dr_jabo.pdf: 4178073 bytes, checksum: fd6bb2a00ca16ebfbbaccdcb82ec48c7 (MD5) Previous issue date: 2016-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A doxorrubicina é um dos mais eficazes agentes quimioterápicos atualmente disponíveis. No entanto, seu emprego tem sido limitado por sua ação cardiotóxica principalmente quando de seu uso por período prolongado, podendo induzir cardiomiopatia iatrogênica relacionada à dose cumulativa administrada. No presente estudo, avaliou-se a ação de três fármacos (carvedilol, ciclosporina-A e sildenafil) sobre os efeitos cardiotóxicos exercidos pela doxorrubicina. Foram utilizados 45 coelhos, alocados em cinco grupos: controle, doxorrubicina (DOX), DOX + carvedilol, DOX + ciclosporina-A, DOX + sildenafil. A antraciclina foi administrada por seis semanas, e exames seriados de hematologia, bioquímica sérica, eletrocardiografia e ecocardiografia foram realizados. Ao término de oito semanas, os animais foram submetidos a eutanásia e fragmentos de miocárdio foram utilizados para realização de exames de histopatologia, imunoistoquímica e microscopia eletrônica de transmissão. Os tratamentos testados não evitaram a ocorrência de disfunção sistólica, cardiomegalia e insuficiência cardíaca congestiva nem reduziram a mortalidade ocasionada pelo tratamento com doxorrubicina. No entanto, o tratamento concomitante com carvedilol reduziu o número de animais com disfunção diastólica do ventrículo esquerdo, reduziu o número de fibras apoptóticas e a ocorrência de fibrose intersticial nos ventrículos direito e esquerdo. Os dados obtidos permitem inferir que o tratamento com carvedilol resultou em melhora em alguns dos parâmetros avaliados, sugerindo um efeito de proteção miocárdica conferido por esse agente sobre a cardiomiopatia induzida pela doxorrubicina em modelo experimental com coelhos. / Doxorubicin is one of the most effective chemotherapeutic agents currently available. However, its use has been limited by its cardiotoxic effect, especially when used for a long time, leading to iatrogenic cardiomyopathy, related to the cumulative dose administered. In the present study, the effects of three drugs (carvedilol, cyclosporin-A and sildenafil) on doxorubicin-induced cardiomyopathy were analyzed. Fourty five rabbits were allocated in four groups: control, doxorubicin (DOX), DOX + carvedilol, DOX + cyclosporin-A, DOX + sildenafil. Animals received doxorubicin for six weeks and were monitored for eight weeks by hematological and biochemical evaluations, electrocardiography and echocardiography. At week eight, animals were killed and myocardium was analyzed by histopathology, immunohistochemistry and transmission electron microscopy. Any treatment prevented the development of systolic dysfunction, cardiomegaly and heart failure or reduced mortality induced by doxorubicin. However, treatment with carvedilol reduced the number of rabbits with left ventricle diastolic dysfunction, reduced the number of apoptotic cells and the occurrence of interstitial fibrosis in both ventricles. The results showed that treatment with carvedilol improved some of the evaluated parameters, suggesting that this drug has some cardioprotective effect on doxorubicin-induced cardiomyopathy in rabbits.

Submitted by TATIANA MARIA GONÇALVES null (tati_unesp@hotmail.com) on 2016-04-01T01:09:37Z No. of bitstreams: 1 Dissertação TATIANA HOMOLOGAÇAO (2) pdf.pdf: 2109094 bytes, checksum: 0a330bb6e84a7dbf2b6ff2f896c7189d (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-04-05T14:49:04Z (GMT) No. of bitstreams: 1 goncalves_tm_me_bot.pdf: 2109094 bytes, checksum: 0a330bb6e84a7dbf2b6ff2f896c7189d (MD5) / Made available in DSpace on 2016-04-05T14:49:04Z (GMT). No. of bitstreams: 1 goncalves_tm_me_bot.pdf: 2109094 bytes, checksum: 0a330bb6e84a7dbf2b6ff2f896c7189d (MD5) Previous issue date: 2016-02-19 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Introdução: denomina-se presbifonia o conjunto de alterações nos padrões vocais consequentes ao envelhecimento da laringe, podendo cursar com sintomas de disfonia, voz fraca, trêmula e baixa. Estudos histológicos e imunohistoquímicos da presbilaringe demonstram atrofia do epitélio, da lâmina própria e do músculo vocal, além de aumento de fibras colágenas e diminuição de fibras elásticas e das proteínas não fibrosas da matriz extracelular. Os estudos de microscopia eletrônica da presbilaringe são escassos e podem acrescentar detalhes ultraestruturais importantes e auxiliar na compreensão da fisiopatologia da presbifonia. Objetivos: descrever os achados de microscopia eletrônica de varredura e transmissão da prega vocal senil. Casuística e métodos: Foram removidas 16 laringes humanas durante necrópsia e distribuídas em dois grupos: controle (n-8; idade 30 - 50 anos; 6F e 2M) e idoso (n-8; idade 75- 92 anos; 6F e 2M). As porções medianas de ambas as pregas vocais foram dissecadas, fixadas em glutaraldeído 2,5% e preparadas para exames de microscopia eletrônica de varredura e transmissão. A espessura do epitélio foi medida nas fotografias de microscopia eletrônica de varredura, com aumentos semelhantes, utilizando-se o programa de morfometria digital Scandium. Resultados: Microscopia eletrônica de varredura: Grupo controle: epitélio composto por 5 a 7 camadas de células sobrepostas, raras células em descamação, e discreta ondulação. Lâmina própria com rede uniforme de fibras colágenas e elásticas, correndo paralelamente à membrana basal. Grupo idosos: epitélio atrófico, composto por 2 a 3 células, maior número de células em descamação, junções intercelulares demarcadas por sulcos profundos. As medidas da espessura do epitélio foram menores nos grupos de idosos do que nos controles (22163.91 ± SD 14590.41nm versus 41783.73 ± SD 2139.314 nm, respectivamente). Lâmina própria com rede densa de fibras colágenas e elásticas formando emaranhados e com distribuição irregular. Nas camadas profundas as fibras colágenas formavam verdadeira carapaça fibrótica e rígida. Microscopia eletrônica de transmissão: Grupo Controle: epitélio íntegro, com células justapostas e desmossomos entre as junções intercelulares. Membrana basal contínua e uniforme e lâmina própria contendo fibras colágenas e elásticas em arranjo frouxo e regular, e alguns fibroblastos de diferentes formatos. Grupo Idosos: células epiteliais distanciadas umas das outras e junções intercelulares alargadas. Membrana basal sem alterações, lâmina própria com predomínio de fibroblastos de formato alongado e citoplasma contendo vacúolos. Na lâmina própria havia densa rede de fibras colágenas, na qual alguns fibroblastos estavam mergulhados. Conclusões: neste estudo de microscopia eletrônica foram identificadas algumas alterações estruturais restritas às laringes dos idosos, tanto no epitélio como na lâmina própria, algumas delas com provável participação dos fibroblastos, o que reforça a importância de estudos adicionais voltados a essas células, tanto ultraestruturais como moleculares, por serem os principais precursores dos componentes da matriz extracelular. / Introduction: Presbyphonia is called the set of changes in vocal patterns consequent aging of the larynx, which can present with symptoms of dysphonia, weak voice, trembling and low. Histological and immunohistochemical studies of presbylarynx show atrophy of the epithelium, lamina propria and the vocal muscle, and increase of collagen fibers and diminution of elastic fibers and non-fibrous proteins of the extracellular matrix. The studies of electron microscopy of presbylarynx are scarce and can add significant ultrastructural details contribute to further understanding of the pathophysiology of presbyphonia. Objectives: To describe the findings of scanning and transmission electron microscopy of senile vocal folds. Methods: 16 human larynx were removed during autopsy and distributed into two groups: control (n-8; age 30-50 years; 6F and 2M) and elderly (n-8, age 75- 92 years; 6F and 2M). The median portions of the right and left vocal folds were dissected, fixed in 2.5% glutaraldehyde and prepared for examination using scanning and transmission electron microscopy respectively. The thickness of the epithelium was analyzed in the pictures of the scanning electron microscopy with similar magnification, using the Scandium morphometric digital program. Results: Scanning electron microscopy: Control Group: epithelium composed of 5-7 layers of overlapping cells, rare cells in flaking and slight ripple. Lamina propria with uniform network of collagen and elastic fibers running parallel to the basement membrane. Group Elderly: atrophic epithelium, 2 to 3 cells, with more flaking cells and intercellular junctions marked by deep grooves. The epithelial thickness was lower in elderly than controls (22163.91 ± SD 14590.41nm versus 41783.73 ± SD 2139.314 nm, respectively). Lamina propria with dense network of collagen and elastic fibers forming tangles with irregular distribution. In the deep layers of collagen fibers formed shell true fibrotic and stiff. Transmission electron microscopy: Control Group: intact epithelium, with overlapping cells and desmosomes between intercellular junctions. Continuous and smooth basement membrane and lamina propria containing collagen and elastic fibers in loose and regular arrangement, and fibroblasts of different formats. Group Elderly: epithelial cells apart from one another enlarged intercellular junctions. Basement membrane unchanged lamina propria predominantly with fibroblasts with elongated shape and cytoplasm containing vacuoles. In the lamina propria was dense network of collagen fibers, in which some fibroblasts were plunged. Conclusions: In this study of electron microscopy identified some structural changes restricted to the larynx of the elderly in both the epithelium and lamina propria, some of them with possible participation of fibroblasts. This reinforces the importance of additional studies, both ultrastructural and molecular, facing fibroblasts, because these are the main precursors of extracellular matrix components. / FAPESP: 2014/13741-1