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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Crystal growth and characterization of I-IV2-V3 semiconductor compounds and alloys based thereon

Omar, Mustafa Saeed January 1985 (has links)
The existence of various ternary adamantine compounds is discussed. Normal and defect ternary adamantine compounds have been a subject of discussion, particularly from a structural point of view. Rules for the formation of adamantine compounds are explained and related to each other. A home-made DTA apparatus was operated to detect the melting point and phase change from room temperature up to 1300°C for the materials investigated. The group I-IV2-V3 compounds were the main subject of this research. CuGe2Ps and CuSi2P3 were the only compounds found to grow in this family. The first was chosen for study in more detail, mainly because of its lower melting point. CuGe2P3 was compared to other compounds, particularly structural aspects, and solid solutions were tried for twenty-two different materials. This investigation shows similarity with group I2-IV-V3 compounds, such as Cu2GeS3, and new alloys were found with Cu2GeS3. Stoichiometric Cu2GeS3 does not form good material, but alloys containing 10% CuGe2P3 produced good material with a zincblend structure. As well as alloys with ternary compounds, about 33% Ge per mole could be dissolved in CuGe2P3. This result showed similarity with the compounds Cu2GeSe3 and ZnGeAs2, which also dissolve a considerable quantity of Ge. In this investigation, only a maximum of 33% Si per mole in CuSi2P3 was prepared, although it is likely that even more Si can be dissolved. Attention was also given to AqGe2P3. Chemical analysis of single crystals grown from AgGe2P3 composition showed the existence of only the Ag6Ge10P12 compound. Single crystals were grown for all single phase materials. A new modification of the directional freeze technique was employed, which was capable of controlling the pressure and having a steep temperature gradient. This method improved the growth to produce large single crystals of cm dimensions. The CuGe2P3 crystals doped with Zn, S, Sn, Se and ZnIn were prepared. Single crystals of CuGe2P3 were also annealed with Cu-P and CuGe2P3 powder. Room temperature lattice parameters were determined for all the compounds and alloys, while variations of the lattice parameters with temperatures up to the melting point of CuGe2P3 were studied using a high temperature X-ray camera. Measurements of optical properties were not successful in this investigation, although electrical properties were successfully measured. These measurements were carried out for all materials in a single crystal form. Hall mobility and conductivity measurements were carried out from liquid nitrogen to 450 °K. Carrier concentration was very high for phosphide compounds and alloys, whilst it was lower for sulphides. Flash evaporation was used for preparing thin films of compounds CuGe2P3 and Ag6Ge10P12. Single phase films were the result for Ag6Ge10P12, whilst a particular treatment was employed for producing films of CuGe2P3 after evaporation. A final investigation of the compound CuGe2P3 was made into its lattice matching with other compounds. The p-n junctions were produced with n-type GaP, using epitaxial growth, while results were negative with CdS and Si.
2

Alterações no periodonto de proteção e ligamento periodontal em molares de ratos ubmetidos ao etanol durante a lactação: estudo Histopatológico e Histométrico

Curi, Viviane 29 November 2010 (has links)
Made available in DSpace on 2016-01-26T12:51:28Z (GMT). No. of bitstreams: 1 vivianecuri_tese.pdf: 3356542 bytes, checksum: 3e315d421d5b2c78bdb72380eb601099 (MD5) Previous issue date: 2010-11-29 / Alcoholism is a public health problem worldwide, involving thousands of men and women, bringing serious consequences as a disease in all organs of the human body, especially the stomach, liver, heart and brain. The consumption of alcoholic beverages for infants and mothers have attracted the attention of researchers in recent decades, with significant. Objective: This study aimed to evaluate the effects of ethanol in the junctional epithelium, adamantine epithelium, epithelium of attached gingiva and periodontal ligament of the upper first molar of the rat, during lactation. Materials and Methods: To this end, we used mice with a day of postnatal life, whose mothers received 20% ethanol in drinking water and rats whose mothers do not received ethanol during the entire lactation. After 21 days, the chicks were sacrificed with anesthetic overdose (Hypnol 3%). The heads were separated and fixed in a solution of "alfac" (alcohol 80% -85 ml, 10 ml of formalin and acetic acid 5-ml), embedded in paraffin and frontal serial sections were stained with hematoxylin and eosin. The cuts were focused light microscope (100x) fitted with a camera lucida. The nuclei of cells from tissue fragments were designed on paper with increased end of 1000x. and 50 nuclei of each structure were outlined with black pencil for later measurement of larger (D) and smaller (d)diameters. Once determined the diameters were estimated karyometric following parameters: geometric mean diameter ratio D / d, perimeter, area, volume, relationship between volume and area, eccentricity, shape coefficient and contour índex. This work also was done using a grid printed on paper. The images were drawn on the grid. In order to assess the volumes and cell cytoplasm, the nucleus / xxiv cytoplasm ratio, the numerical cell density, relation to the external surface / basal layer, the thickness of epithelial layers and the density of the surface was sometimes used the count of the points and sometimes the number of intersections and applied to stereological equations appropriate for each of these variables. All data collected were submitted to non-parametric statistics (Wilcoxon-Mann-Whitney). Results: Histologically, the superior maxillar molar tooth of the rat treated with ethanol was not erupted or partially eruído; the junctional epithelium was reduced and the adamant epithelium was in full function and consists of high palisade cells. The epithelium of attached gingiva was more slender and composed of smaller cells. In the Periodontal ligament was possible to observe bigger and disorganizedfibers. The nuclei of the epithelia studies have shown decreased values after Karyometry, for larger and smaller medium diameters, volume, area, perimeter, and the relation V / A. Stereologically could be observed in the junctional epithelium, adamantine and the attached gingiva, less voluminous cell with scarce cytoplasm leading to a greater number of cells per mm3 of tissue. The disorganized periodontal ligament showed larger fibers with smaller number per mm3. Conclusion: In this study, ethanol resulted in a framework of epithelial hypotrophy, indicating a direct action on the junctional and adamantineepithelium, epithelium of attached gingiva and periodontal ligament. / O alcoolismo é um problema de saúde pública mundial, envolvendo milhares de homens e mulheres, trazendo conseqüências graves como doença em todos os órgãos do corpo do humano, em especial o estômago, o fígado, o coração e o cérebro. O consumo de bebidas alcoólicas por lactantes e lactentes vem despertando a atenção dos pesquisadores, nas últimas décadas, com achados significantes. Objetivo: Este trabalho teve como objetivo avaliar os efeitos do etanol no epitélio juncional, epitélio adamantino, epitélio da gengiva inserida e ligamento periodontal do primeiro molar superior do rato, durante a lactação. Materiais e Métodos: Para tal, foram utilizados ratos com um dia de vida pós-natal, cujas mães receberam etanol a 20% na água do bebedouro e ratos cujas mães não receberam o etanol, durante toda a lactação. Ao final de 21 dias, os filhotes foram sacrificados com sobredosagem anestésica (Hypnol a 3%). As cabeças foram separadas e fixadas em solução de alfac (álcool 80%-85 ml, formalina-10 ml e ácido acético-5 ml), incluídas em parafina e os cortes frontais seriados foram corados com hematoxilina e eosina. Os cortes foram focalizados ao microscópio de luz (100x) munido de uma câmara clara. Os núcleos das células dos tecidos estudados foram projetados sobre papel com aumento final de 1000x. e 50 núcleos de cada estrutura foram contornados com lápis preto para posterior medição dos diâmetros maior (D) e menor (d). Uma vez determinados os diâmetros, foram estimados os seguintes parâmetros cariométricos: diâmetro geométrico médio, relação entre D/d, perímetro, área, volume, relação entre volume e área, xxi excentricidade, coeficiente de forma e índice de contorno. Neste trabalho também, foi utilizada uma grade impressa sobre papel. As imagens obtidas foram desenhadas sobre a grade. Com a finalidade de se avaliar os volumes citoplasmáticos e celular, a relação núcleo/citoplasma, a densidade numérica celular, a relação superfície externa/ camada basal, a espessura das camadas epiteliais e a densidade da superfície, foi utilizada ora a contagem de pontos ora o número de intersecções e aplicadas às equações estereológicas apropriadas para cada uma dessas variáveis. Todos os dados colhidos foram submetidos à estatística não-paramétrica (teste de Wilcoxon-Mann-Whitney). Resultados: Histologicamente, o dente molar do maxilar superior do rato tratado com etanol não estava erupcionado ou então, parcialmente erupcionado; o epitélio juncional estava reduzido e o epitélio adamantino presente estava em plena função e constituído de células altas em paliçada. O epitélio da gengiva inserida era mais delgado e constituído de células menores. No ligamento periodontal foi possível observar fibras desorganizadas e maiores. Os núcleos dos epitélios estudados mostraram valores diminuídos, após cariometria, para os diâmetros maior, menor e médio; volume, área, perímetro e relação V/A. Estereologicamente foi possível observar, nos epitélios juncional, adamantino e da gengiva inserida, células menos volumosas com citoplasma mais escasso levando a um maior número de células por mm3 de tecido. O ligamento periodontal desorganizado mostrou fibras mais volumosas e com menor número por mm3. Conclusões: Neste estudo, o etanol ocasionou um quadro de hipotrofia epitelial, indicando uma xxii ação direta nos epitélios juncional e adamantino, epitélio de gengiva inserida bem como no ligamento periodontal.

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