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Search Results: 1 - 10 of 702519 matches for " C. P.;Bragan?a "
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Aspectos teóricos e práticos sobre a resistência mecanica de porcelanas
Bragana, S. R.;Bergmann, C. P.;
Ceramica , 2004, DOI: 10.1590/S0366-69132004000200012
Abstract: the properties of traditional porcelain, including its mechanical strength, are a consequence of the ceramic processing that formed the piece, and then, raw materials and their characteristics, forming process, firing atmosphere, time and temperature. these parameters determine the complexities of microstructure and phase development, which are difficult to be controlled and makes almost impossible to predict porcelain final properties. since the last century, many theories have been developed to explain the strength of porcelain, and some have recently been revised and improved due to the development of new analytical techniques. this work shows an overview on the literature, which comprises new discussions and theories about porcelain strength, including authors′ own investigations.
Microestrutura e propriedades de porcelanas
Bragana, S. R.;Bergmann, C. P.;
Ceramica , 2004, DOI: 10.1590/S0366-69132004000400003
Abstract: the microstructure of traditional porcelain sintered at different temperatures was analyzed and related to technical parameters. the morphology of the phases was investigated. quartz, primary mullite and secondary mullite were found. the results were supported with experimental data using edx and x-ray diffraction analysis. the properties of the sintered samples show to be strongly affected by vitreous phases, and this determine the quality of the ceramic pieces. the best sintering temperature was also a consequence of vitreous phase properties, like porosity. the crystalline phases were found responsible for the achieved strength .
Produ??o de porcelana de ossos e caracteriza??o de suas propriedades técnicas
Bragana, S. R.;Bergmann, C. P.;
Ceramica , 2006, DOI: 10.1590/S0366-69132006000200014
Abstract: porcelains from bone ash are widely accepted and present high market value, however, their manufacture and research are still restricted to few countries. as a great producer of cattle, brazil presents great potential for the recycling of cattle bone into ceramic materials. in this work, it was realized a comparative investigation of technical properties of a typical porcelain composition manufactured from bone ash according to english traditional composition and a traditional porcelain. the results revealed that it is more difficult to sinter bone porcelain in fast firing cycles, once it showed shorter firing intervals compared to traditional porcelains. however, the higher mechanical strength and better aesthetic qualities, especially its whiteness, make bone porcelains very attractive materials in terms of industrial applications potential.
Rocha com espodumênio como fundente para massas ceramicas tradicionais
Bragana, S. R.;Lengler, H. C. M.;Bergmann, C. P.;
Ceramica , 2010, DOI: 10.1590/S0366-69132010000300013
Abstract: a spodumene rock was used as a flux in ceramic bodies, analyzing its reactivity to other raw materials such as quartz and kaolin. the petrology properties of the pegmatite (parent rock) from which the flux is extracted was characterized. the grindability, fluxing strength and pyroplastic deformation of the spodumene rock were investigated. the influence on technological properties of the final pieces, mainly in relation to the firing temperature, phases formation and microstructure were also further analyzed. the firing behavior to other commercial flux such as albite and feldspar were then compared. the spodumene rock was considered an effective flux, capable of reducing the firing temperatures of the tested bodies by viscous flow.
Caracteriza??o tecnológica da argila plástica de Pantano Grande, RS
Cruz, R. T. da;Bergmann, C. P.;Bragana, S. R.;
Ceramica , 2012, DOI: 10.1590/S0366-69132012000100011
Abstract: the region of pantano grande, rs, brazil, is known by the quality of its kaolins. in this region, including the nearby of the cities of gravataí and viam?o, there is a plastic clay of clear firing color, but with refractory characteristic. the use of this clay is very attractive, since it is difficulty to get plastic clays at convenient distances for the ceramic industry. in this work, it was carried out the technological characterization of this clay. the firing properties have been evaluated for the temperature range 1200 oc-1400 oc, including a mixture with a refractory clay and fired at 1300 oc. it was investigated the firing behavior of mixtures with na, k, and ca fluxes, including the analysis of the mechanical strength. in this way, it was performed a complete characterization of the related clay, and highlighted its potential of application.
Análise dos transcritos da transloca??o t(9;22) em Leucemia Mielóide Cr?nica
Barboza, Luciana P.;Souza, Jamison M.;Sim?es, Felippe V.;Bragana, Iracema C.;Abdelhay, Eliana;
Revista Brasileira de Hematologia e Hemoterapia , 2000, DOI: 10.1590/S1516-84842000000200005
Abstract: chronic myelogeneous leukemia is a proliferative disease of the hematopoietic system. it is characterized by clonal expansion of a primitive pluripotent stem cell that has the capacity to differentiate into the myeloid, monocyte, megakaryocyte and erythrocyte lineage, b and t cells. under normal physiological hematopoietic conditions there is a balance between proliferation and differentiation. on the other hand, the population of hematopoietic stem cells must also undergo a self renewal process. in chronic myelogeneous leukemia stem cells, unregulated proliferation is associated with the 210kda tyrosine kinase, which is the product of the bcr/abl fusion gene, in the translocation involving chromosomes 9 and 22, a karyotype marker of chronic myelogeneous leukemia. several chimeric transcripts have been described and it has been observed that the seriousness of the clinical picture depend on the generated mrna. in the present work we analyzed 28 samples of bone marrow cells from 27 patients diagnosed with chronic myelogeneous leukemia. in all samples the translocation t(9;22) was present and they were analyzed for the presence of the fusion transcripts (b3a2 or b2a2) using rt-pcr and nested- pcr, techniques that were shown to be more sensitive for the identification of these transcripts. among the patients, 12% presented fusion b3a2, 18% showed b2a2 fusion transcript and 32% both types, b3a2 and b2a2. the presence of the transcript, b3a2, seems to be related with a platelet above 10 3 x 10 3/mm3, recognized as a worse prognostic chracteristic in patients with chronic myelogeneous leukemia.
Análise dos transcritos da transloca o t(9;22) em Leucemia Mielóide Cr nica
Barboza Luciana P.,Souza Jamison M.,Sim?es Felippe V.,Bragana Iracema C.
Revista Brasileira de Hematologia e Hemoterapia , 2000,
Abstract: A leucemia mielóide cr nica é uma doen a proliferativa do sistema hematopoiético, caracterizada pela expans o clonal de uma célula tronco primitiva e pluripotente denominada "stem cell", que tem a capacidade de se diferenciar em células mielóides, monocíticas, megacariocíticas e células B e T. Em homeostase, existe um equilíbrio entre prolifera o, diferencia o e renova o das células tronco, equilíbrio este que se encontra alterado em pacientes com Leucemia mielóide cr nica, devido a uma prolifera o e diferencia o aumentada e anormal relacionada à atividade de tirosino quinase do produto do gene quimérico BCR/ABL resultante da transloca o t(9;22), que se apresenta como marcador da doen a. Vários transcritos quiméricos têm sido descritos e acredita-se que a gravidade do quadro clínico dependa do tipo de mRNA gerado. No presente trabalho analisamos 28 amostras de 27 pacientes diagnosticados com Leucemia mielóide cr nica. Todos possuíam a transloca o t(9;22) e foram analisados para a presen a dos transcritos resultantes das fus es b3a2 ou b2a2 por RT-PCR e Nested-PCR, técnicas que se mostraram mais sensíveis para a identifica o dos transcritos. Entre os pacientes, 12% apresentaram fus o b3a2, 18% possuíam fus o b2a2 e 32% possuíam os dois tipos de transcritos. A presen a de um dos tipos de transcritos, b3a2, parece estar relacionada com contagem de plaquetas acima de 1 milh o/mm3 , reconhecida como característica de mau prognóstico em pacientes com Leucemia mielóide cr nica.
Avalia??o de revestimentos para prote??o contra a descarboneta??o de tijolos refratários MgO-C durante o aquecimento de panelas de aciaria
Lima, A.N.C.;Trommer, R.M.;Zimmer, A.;Vicenzi, J.;Bragana, S.R.;Boschetti, J.;Bergmann, C.P.;
Matéria (Rio de Janeiro) , 2008, DOI: 10.1590/S1517-70762008000300008
Abstract: this work aims to evaluate the utilization of different coatings to prevent the decarburization of refractory bricks mgo-c used in ladles. this oxidation causes the loss of thickness of the bricks and the reduction of its useful live. the three types of coatings a, b e c were prepared in laboratory and then were applied on mgo-c bricks. the samples were tested at temperatures of 850oc, 950oc and 1050oc. it was verified that the three tested coatings only minimize the decarburization, since they vitrify and become effective at temperatures higher to the beginning of the oxidation temperature. moreover, it was noticed that the thickness of the decarburized layer is directly proportional to the firing temperature. the coating that presented better results was c, which showed better characteristics of flowing and viscosity. besides that, it vitrified at lower temperature comparing to coatings a and the b.
Identifica??o e avalia??o dos mecanismos de ataque da escória SiO2-CaO-Al2O3-MgO em tijolos refratários de MgO-C
Trommer, R.M.;Correia Lima, A.N.;Vicenzi, J.;Zimmer, A.;Bragana, S.R.;Bergamann, C.P.;
Matéria (Rio de Janeiro) , 2008, DOI: 10.1590/S1517-70762008000100007
Abstract: the present work has as objective to identify and to characterize the responsible mechanisms for the degradation of magnesia-carbon refractory bricks of a metallurgical ladle, due to the attack of the sio2-cao-al2o3-mgo slag. for that, mgo-c refractory bricks used in the slag line were compared with bricks after the use (post mortem). the microstructure of the interfacial region refractory brick/slag was evaluated by mineralogical analyzes (x-rays diffraction), scanning electronic microscopy (sem) and thin sections for petrography analyses (optic microscopy). it was possible to evidence that the brick post mortem presents, beyond the existing phases already in natura, new phases such as alumina, calcium silicate and gelenite, due to its reaction with the slag. the results suggest that the main way of degradation of the brick was the infiltration of the slag in the matrix and grains boundaries of the refractory brick. this causes to the pulling out of grains, compromising the original microstructure of the refractory material, diminishing its time of useful life.
Novos fundentes para produ??o da porcelana de ossos
Ballvé, M. P;Bragana, S. R;
Ceramica , 2010, DOI: 10.1590/S0366-69132010000100010
Abstract: strong fluxes were investigated in a bone china composition by applying a fast firing cycle. the technical properties of the ceramic bodies were evaluated. the conventional flux (potash feldspar) was partially replaced by strong fluxes (wollastonite or spodumene or waste glass). a comparative analysis of the data, including technical properties, microstructure, and phase's development at different firing temperature was performed. due to the utilization of these strong fluxes, a reduction of firing temperature and, simultaneously, a broad firing range was achieved. then, the main technical aspects concerning the firing of these new compositions were investigated. the final properties of the pieces were considered good for the production of bone china.
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