At present, one of the key challenges in the light-emitting diode (LED) packaging technology is light extraction due to the difference in index of refraction between LED chip and air. Silicone nanocomposites have been extensively researched for applications in LED encapsulant to reduce such difference in refractive index. It is well-known that silicone is desirable for LED encapsulant because of its optical transparency and photothermal resistance. However, not much has been accomplished to leverage the elastic properties of silicone for enabling a stretchable LED encapsulant. In this work, I aim to investigate the stretch ability of silicone/zinc oxide (ZnO) nanocomposites for LED packaging. Wurtzite ZnO nanoparticles were prepared in colloids and subjected to silane treatment. Effects of both ex situ and in situ silane treatment on the final mechanical and optical properties of the silicone/ZnO nanocomposites were examined. Silicone/ZnO nanocomposites exhibit significantly more compliant stress-strain behavior than silicone control. In particular, silicone/silane-treated ZnO nanocomposites show more serrated stress-strain curves. They also embrace higher transmittance than silicone/unmodified ZnO nanocomposites, indicating an improvement in the dispersion of the nanoparticles. It was found that the silicone/5% silane-treated ZnO nanocomposite prepared by an in situ method was able to deform over a range of up to 160%. The film made of this unique silicone/ZnO nanocomposite (~40 microns thick) exhibits transmittance >70% throughout the visible range.

No description available.

Zugl.: Göttingen, University, Diss., 2006.

MESQUITA, Charles Jean Gomes de. Dimensão fractal e histometria digital na avaliação dos efeitos do propranolol sobre a reação capsular ao implante de silicone. 2014. 50 f. Tese (Doutorado em Cirurgia) - Universidade Federal do Ceará. Faculdade de Medicina, Fortaleza, 2014. / Submitted by denise santos (denise.santos@ufc.br) on 2014-12-08T13:50:22Z No. of bitstreams: 1 2014_tese_cjgmesquita.pdf: 409219 bytes, checksum: faeed2fca385c9d082980d0e7e5e4eae (MD5) / Approved for entry into archive by denise santos(denise.santos@ufc.br) on 2014-12-08T13:51:21Z (GMT) No. of bitstreams: 1 2014_tese_cjgmesquita.pdf: 409219 bytes, checksum: faeed2fca385c9d082980d0e7e5e4eae (MD5) / Made available in DSpace on 2014-12-08T13:51:21Z (GMT). No. of bitstreams: 1 2014_tese_cjgmesquita.pdf: 409219 bytes, checksum: faeed2fca385c9d082980d0e7e5e4eae (MD5) Previous issue date: 2014 / Despite their popular use in breast augmentation and reconstruction surgeries, the limited biocompatibility of silicone implants can induce severe side effects, including adverse capsularcontracture (ACC), an excessive foreign body reaction that forms, by unknown reason, a tight and hard fibrous capsule around the implant. A non-surgical treatment for ACC will be desirable as revision surgery for capsulotomy or capsulectomy with implant exchange are associated with a high risk of recurrence and complications. Recently it has been shown that sympathetic denervation accelerates wound contraction and delays reepithelialization in rats. Another study demonstrated that beta-adrenoceptor blockade has antifibrotic effects in a murine model of nonsinusoidal liver fibrosis. This study examines the effects of using propranolol, a non-selective beta-adrenoceptor antangonist, to prevent capsular formation around texturized silicone prosthesis implanted in the dorsum of male guinea-pigs. Animals (n=36) were randomly distributed into two equal groups, untreated or orally treated with propranololol (10 mg/kg dissolved in daily water). Capsules and implants were removed and examined for inflammation, thickness, fibrosis progression, density of type I and III collagen and fractal dimension by histological scoring using hematoxilin-eosin stained samples, digital histometry for measuring capsular thickness, picrosirius-polarization and digital image analysis for type I and type III collagen density and fractal dimension calculation by box-counting after 7, 14 or 21 days.Propranolol significantly reduced inflammation scores in the capsular tissue as compared to untreated group. Also, the capsular content of type I and type III collagen showed a statistical difference among the groups at different time points (p< 0,0001, Kruskal-Wallis test). The type I collagen density observed at 1, 2 or 3 weeks decreased significantly compared with that found in the control group. Conversely, the density of type III collagen increased in propranolol-treated group along the time.The capsule thickness in propranolol-treated cavies was significantly thinner and exhibited higher collagen type III/type I ratios and more irregular collagen fiber alignments than control animals. The observed decrease in fractal dimension of collagen also supported the alleviation of capsular formation by propranolol usage. Taken together, these data show that propranolol efficiently delays formation (antiproliferative or citotoxity effects) and maturation (antifibrogenic effect) of capsule around textured implants. Therefore, the blockade of beta-adrenoceptors is a promising option to support future therapeutic strategies in the treatment/prevention of capsular contracture. / As mamoplastias com implante de silicone são as cirurgias plásticas mais realizadas no mundo. O organismo reage a qualquer implante, encapsulando-o. Por razões desconhecidas, algumas cápsulas tornam-se patologicamente ativas gerando uma contratura capsular adversa (CCA), fibrose constritiva que deforma a mama reduzindo o resultado estético. Esta afecção de difícil tratamento requer, em alguns casos, reintervenções cirúrgicas que não impedem a recidiva. Tratamentos adjuvantes com drogas e/ou métodos físicos apresentam respostas variáveis e frequentemente insatisfatórias. O propranolol, antagonista não seletivo de betadrenoceptores, vem sendo empregado em estudos pré-clínicos em que a resposta fibrótica é importante parâmetro de avaliação e prognóstico. A demanda por métodos quantitativos e a tradução dos dados de bancada à clínica é uma constante. Métodos tradicionais como a histo-morfometria e a picrosirius-polarização tem sua acurácia aumentada quando associados a técnicas computacionais. A análise da Dimensão Fractal (DF), metodologia não linear de mensuração, tem se mostrado útil na avaliação de imagens biológicas permitindo visualização e compreensão de detalhes imperceptíveis ao olhar humano. O objetivo desse trabalho foi associar essas tecnologias (ferramentas computacionais e recursos matemáticos) na avaliação quantitativa dos efeitos do propranolol na formação da cápsula fibrosa peri-implante. Foram implantadas no plano subcutâneo 36 minipróteses texturizadas, preenchidas com gel de silicone (20 mL), no dorso de cobaias (Cavia porcellus). Os animais foram divididos aleatoriamente em dois grupos (n=18, cada) sendo tratados ou não com propranolol (10 mg/Kg dissolvido na água de beber diária (150 mL)). Os animais foram acompanhados e sacrificados após 7, 14 ou 21 dias. Após a retirada em bloco e explantação cuidadosa da prótese, a cápsula e o tecido do peri-implante foram preparados e corados pela hematoxilina-eosina (HE) ou picrosirius-red (PSR). A inflamação foi quantificada por atribuição de escores. Microfotografias digitais das amostras coradas pelo PSR foram obtidas sob polarização de forma padronizada para mensurar a espessura da cápsula, densidade do colágeno tipo I e tipo III, índice de fibrose (densidade do colágeno/espessura capsular) e cálculo da dimensão fractal pelo método de contagem de caixas. Foi utilizada análise estatística paramétrica ou não paramétrica conforme a natureza dos dados, considerando um nível de significância P < 0,05. Não ocorreram casos de infecção, seroma, hematoma ou deslocamento do implante. Todos os animais, independentemente do grupo e do momento do sacrifício exibiam uma cápsula fibrosa. As cápsulas dos animais tratados com propranolol exibiam significantemente menor intensidade de inflamação, cápsulas menos espessas, menor índice fibrótico e menores valores de dimensão fractal do que as do grupo controle. A DF revelou correlação inversa com esses parâmetros. Em conjunto, estes achados são condizentes com a inibição da formação da cápsula pelo betabloqueio sistêmico não seletivo, sugerindo ação anti-inflamatória e antifibrogênica do Propranolol.

Made available in DSpace on 2014-06-11T19:25:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-08-22Bitstream added on 2014-06-13T19:11:58Z : No. of bitstreams: 1 franca_dcc_me_araca.pdf: 2609587 bytes, checksum: 8a7904cdb64c406b06f726af6ac60fbc (MD5) / Universidade Estadual Paulista (UNESP) / No presente estudo foram utilizados 60 ratos submetidos a implantes subcutâneos de quatro elastômeros de silicone, sendo três usados em prótese bucomaxilofacial, LIM 6050, MDX 4-4210 e Silastic 732 RTV industrial e um indicado para cirurgia plástica, o Silimed. O objetivo do estudo foi avaliar os materiais em relação à compatibilidade biológica tecidual, nos tempos pós-operatórios de sete, quinze e trinta dias, quando os animais foram sacrificados e as peças processadas e coradas pela hematoxilina e eosina para análise qualitativa e quantitativa dos espécimes. Pelo estudo histomorfométrico, oito áreas de 60,11 mm2 foram analisadas, contando-se as células mesenquimais, inflamatórias mononucleares, eosinófilos e as células gigantes do tipo corpo estranho. O experimento foi desenvolvido em dois capítulos, estudando-se separadamente os silicones de uso em prótese e o Silimed. No primeiro capítulo, a análise da biocompatibilidade dos implantes subcutâneos dos elastômeros de silicone LIM 6050, MDX 4-4210 e Silastic 732 RTV industrial, observou-se biocompatibilidade aceitável em todos eles, considerando-se o fato de que sua indicação protética dependeria em especial das características físicas próprias de cada material, pela mínima reação tecidual observada, além de que em sua forma sólida é fácil a adaptação aos tecidos. No segundo capítulo, o estudo se baseou na análise das reações referentes ao implante de silicone utilizado em cirurgia plástica (Silimed), constatando-se a presença de processo inflamatório ligeiramente maior no silicone gel em relação aos outros grupos, porém com níveis aceitáveis de biocompatibilidade, confirmada pela rara presença de células gigantes do tipo corpo estranho. Todos os dados foram submetidos à análise de variância e teste de Tukey, demonstrando que todos os materiais implantados iniciaram uma resposta... / In the present study 60 rats were submitted to subcutaneous implant of four elastomers of silicon, being three of use in bucomaxillofacial prosthesis, LIM 6050, MDX 4-4210 and Silastic 732 RTV industrial and a suitable one for plastic surgery, Silimed. The objective of the study was to evaluate the materials in relation to the tissue biological compatibility, in the postoperative times of seven, fifteen and thirty days, when the animals were sacrificed and the processed pieces and stained for the hematoxilin and eosin for qualitative and quantitative analysis of the specimens. For the histomorphometric study, eight areas of 60,11 mm2 were analyzed, being counted the mesenchimal cells, inflammatory cells, eosinophile and giant cells. The experiment was developed in two chapters, being studied the use silicons separately in prosthesis and Silimed. In the first chapter, the analysis of the biocompatibility of the subcutaneous implant of the elastomers of silicon LIM 6050, MDX 4-4210 and Silastic 732 RTV industrial, acceptable biocompatibility was observed in all of them, being considered the fact that your prosthetic indication would especially depend on the own physical characteristics of each material, for the low tissue reaction observed, in addition in your solid form it is easy the adaptation to the tissues. In the second chapter, the study based on the analysis of the referring reactions to the it implants of silicon used in plastic surgery (silimed), being verified the presence of inflammatory process lightly larger in relation to the other groups, however with acceptable levels of biocompatibility confirmed by the rare presence of giant cells of the type strange body. All the data were submitted to the variance analysis and test of Tukey, demonstrating that all the implanted materials began an acceptable tissue inflammatory reaction, with tissue reactions of light intensity the moderate... (Complete abstract, click electronic address below)

Orientador: Inez Valeria Pagotto Yoshida / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T17:10:27Z (GMT). No. of bitstreams: 1 Kaneko_ManuelaLimaQueirozdeAndrade_D.pdf: 13306082 bytes, checksum: 41561d4cea7b176be2c3dd7f2fa2f1d9 (MD5) Previous issue date: 2009 / Resumo: Neste trabalho foram preparados compósitos de silicona reforçados com argila montmorillonita natural (MT) e orgânica (MT-O). Os compósitos foram obtidos por adição direta das argilas (MT ou MT-O) em goma de silicona de altíssima massa molar (~10 g/mol), que foi reticulada para formar borracha, ou por adição de ¿masterbatches¿ argila/fluido de silicona na matriz de silicona. Previamente à preparação dos ¿masterbatches¿ avaliou-se o efeito de 3 fluidos de silicona: poli(dimetilsiloxano) de terminais ¿Si(CH3)2OH, PDMS-OH, poli(dimetilsiloxano-co-3-óxido de etilenopropilmetilsiloxano), PDMS-POE e poli(dimetilsiloxano-co-metilaminoetilaminopropilsiloxano, PDMS-NH2), na modificação das argilas, selecionando-se aquele que promoveu um maior efeito na expansão das lamelas para a obtenção dos ¿masterbatches¿. Para isto foram preparadas dispersões argila/fluido estudando-se as características morfológicas dessas dispersões por espalhamento de raios X em baixo e alto ângulo utilizando detector bidimensional (SAXS/WAXS-2D). As análises de SAXS/WAXS-2D mostraram que os fluidos PDMS-POE e PDMS-NH2 apresentaram forte tendência de expansão das lamelas das argilas, diferente do PDMS-OH. O fluido PDMS-POE se mostrou mais adequado para a preparação dos compósitos e foi então selecionado para a preparação dos ¿masterbatches¿. Os compósitos preparados via ¿masterbatch¿ ou por adição direta da argila foram caracterizados por medidas de intumescimento em tolueno, difração de raios X, espalhamento de raios X em baixo e alto ângulo, microscopia eletrônica de varredura, microscopia eletrônica de transmissão e ensaios mecânicos sob tração. Os compósitos preparados com os ¿masterbatches¿ apresentaram maior intumescimento em tolueno do que os preparados por adição direta das argilas, indicando que a presença do PDMS-POE aumenta a quantidade de solvente admitida no material. Os ensaios mecânicos mostraram que o compósito preparado com o ¿masterbatch¿ da argila orgânica, PDMS/MB2:5, carregado com apenas 5 phr da MT-O, apresentou praticamente a mesma resistência à tração do que o compósito de PDMS carregado com 30 phr da MT-O, obtido por adição direta da argila no polímero. Além disto, o PDMS/MB2:5 apresentou um aumento de 126% no alongamento na ruptura em relação ao PDMS/MT-O:30. O desempenho mecânico do PDMS/MB2:5 foi atribuído à dispersão nanométrica da argila na matriz de silicona. Por outro lado, no compósito preparado com o ¿masterbatch¿ da MT, PDMS/MB1:5, a argila não se dispersou adequadamente e as propriedades mecânicas obtidas (particularmente, resistência à tração e alongamento na ruptura) não foram satisfatórias. Essa diferença de comportamento foi atribuída aos diferentes arranjos do PDMS-POE entre as lamelas das argilas MT e MT-O. No ¿masterbatch¿ com a MT-O, a parte apolar do PDMS-POE deve se localizar, preferencialmente, no interior das lamelas da argila, resultando em uma dispersão mais eficiente da MT-O, devido à ação lubrificante do fluido do silicona entre as lamelas da argila. A inversão desse arranjo no ¿masterbatch¿ com a MT resulta em uma pobre dispersão da argila no PDMS/MB1:5 / Abstract: In this study, silicone composites were prepared with natural (MT) or organomodified (MT-O) montmorillonite clays. The composites were obtained by direct addition of the clays (MT or MT-O) to a high molar mass poly(dimethylsiloxane)-gum (~10 g/mol), which was than crosslinked to form rubber, or by addition of clay/silicone fluid masterbatches into the silicone matrix. Previously to the preparation of the masterbatches, the effect of 3 silicone fluids: (poly(dimethylsiloxane) with ¿Si(CH3)2OH end groups, PDMS-OH, poly(dimethylsiloxane-co-3-ethylenepropylmethylsiloxane oxide), PDMS-PEO, and a poly(dimethylsiloxane-co-aminoethylaminopropylmethylsiloxane), PDMS-NH2) into the clays was studied. The most appropriate silicone fluid, which promoted the greatest effect in the separation of the clay layers, was selected in order to prepare the masterbatches. For this purpose, clay/fluid dispersions were prepared and the morphological characteristics of these dispersions were studied by small angle/wide angle X-ray scattering using a two-dimensional imaging plate detector (SAXS/WAXS-2D). The SAXS/WAXS-2D analisis indicated that the PDMS-POE and the PDMS-NH2 showed greater tendencies to swell the galleries of the clays than the PDMS-OH fluid. The PDMS-PEO was the most appropriate fluid and it was selected to prepare the masterbatches. The composites prepared via masterbatch or by direct clay addition were characterized by swelling measurements in toluene, X-ray diffraction, small angle/wide angle X-ray scattering, scanning electron microscopy, transmission electron microscopy and tensile tests. The composites prepared via masterbatch showed higher toluene swelling than the composites prepared by direct addition, indicating that the presence of the PDMS-POE enchances the solvent amount into the material. The tensile tests showed that the composite with the MT-O masterbatch, PDMS/MB2:5, filled only with 5 phr of O-MT, improved the tensile strength as much as that one obtained with the composite filled with 30 phr of O-MT clay, PDMS/MTO: 30, prepared by direct clay addition. Moreover, the elongation at break was improved at least 126% in comparison to that of the PDMS/MT-O:30. The mechanical performance of PDMS/MB2:5 was attributed to the nanometric dispersion of the clay layers into the silicone matrix. On the other hand, the clay did not disperse well in the composite prepared with the MT masterbatch, PDMS/MB1:5, and the mechanical properties of the this composite (especially, tensile strenght and elongation at break) were not satisfactory.The difference in these behaviours was atribuited to the PDMS-POE arrange between the MT and MT-O clay layers. In the MT-O masterbatch, the PDMS-POE apolar chains should be mainly located inside the clay layers, resulting in an efficient clay dispersion, due to the lubricating effect of the silicone fluid between the layers. The inversion of this arrange in the MT masterbatch results in a poor dispersion of the clay into PDMS/MB1:5 / Doutorado / Físico-Química / Doutor em Ciências

Clinical studies suggest radiation dose and dose rate cause increased failure of medical implants however, little evidence supports this claim and due to the complexity of an in vivo environment, separating variable implants is difficult. Before beginning to understand material changes in vivo, a systematic study of silicone and polyurethane exposed to radiation is needed to verify whether radiation is a major variable contributing to material changes. This research fills a gap within the current literature by investigating low dose therapeutic radiation and varying dose rates at sterilization dose and answers questions on whether radiation in an aqueous environment alone is enough to significantly alter material properties. This is the first research to apply a water environment to therapeutic doses and the first to investigate a range of dose rates for clinical applications. Biomedical grade silicone and polyurethane films will be exposed to both types of radiation in an aqueous environment separately and analyzed for changes. The limited current literature combined with standards for biomedical devices will be used to characterize changes seen in materials. The first strategy used to explore the compliance of biomedical grade polymers employs low doses of therapeutic radiation ranging between 0 Gy and 80 Gy. Analysis of these low doses results in confirming cellular, mechanical and chemical stability of silicone and polyurethane. The second strategy used to investigate silicone and polyurethane exposed materials to 25 kGy (sterilization dose) of gamma irradiation at varying dose rates (3.2 - 833 Gy/min). Results from these studies conclude that varying the dose rate causes slight changes in both materials but not significant enough to alter bulk material properties. In conclusion, the results from this research reveal that both silicone and polyurethane maintain their stability at low doses and varying dose rates of irradiation while in an aqueous environment. This indicates that increased failure rates seen in silicone and polyurethane materials in vivo when exposed to radiation cannot be contributed to radiation alone. With the highly complex environment medical devices are exposed to in vivo, each variable that may contribute to failure should be investigated individually before combining to fully understand the mechanisms of material failure. This study indicates that the environment may play a larger role in material change and there is a need for updates to medical device standards. / PHD / Clinical studies suggest radiation dose and dose rate cause increased failure of medical implants however, little evidence supports this claim and due to the complexity of a human environment, separating factors contributing to failure is difficult. Before beginning to understand material changes, a study of silicone and polyurethane exposed to radiation is needed to verify whether radiation is a major variable contributing to material changes. The results from this research reveal that both silicone and polyurethane maintain their stability at low doses and varying dose rates of irradiation while in water environment. This indicates that increased failure rates seen in silicone and polyurethane materials in clinical settings when exposed to radiation cannot be contributed to radiation alone. With the highly complex environment medical devices are exposed, each factor that may contribute to failure should be investigated individually before combining to fully understand the mechanisms of material failure. This study indicates that the environment may play a larger role in material change and there is a need for updates to medical device standards.

Scanning electrochemical microscopy is a method that incorporates an ultramicroelectrode capable of facilitating electrochemical reactions paired with an XYZ positioning system capable of micron-level movements. This study investigates the corrosion behavior of structural transition joint clad material that contains steel, pure aluminum, and an aluminum alloy blast welded into a single joint. This study will characterize the corrosion response of the structural transition joint and identify the galvanic activity measured between its layers. High-temperature coatings in this study are designed to be used effectively up to 1400?F. In this study, we characterized several commercial high-temperature coatings exposed to different levels of heat. General trends of decreasing barrier performance were observed with the exception when these coatings are exposed to their rated temperature limit of 1400?F, at which the barrier increased slightly, indicated by their low-frequency impedance modulus. The cause is a combination of sintering and oxide formation.

No description available.

No description available.