7 research outputs found
Plasma thrombomodulin levels in lung cancer patients
No full textBackground. Thrombomodulin (TM) is a glycoprotein and besides its anticoagulant property it is accepted as an once developmental antigen. Considering these properties we hypothesised that active TMB might have a role in cancer cell behaviour
Lack of association between increased mitochondrial DNA(4977) deletion and ATP levels of sputum cells from chronic obstructive pulmonary disease patients versus healthy smokers
No full textWOS: 000397858400027PubMed ID: 26713688In this study we looked at smokers with and without chronic obstructive pulmonary disease (COPD) patients in order to evaluate the incidence of 4977 base pair (bp) mtDNA (mtDNA(4977)) deletion and mtDNA copy number in sputum cells and in peripheral blood leukocytes (PBLs) in relation to mitochondrial function and oxidative stress status. Twenty-five COPD patients who were current smokers, 22 smokers and 23 healthy nonsmokers (for only PBLs studies) participated in this study. The 4977-bp deletion was detected in all examined samples within 40 cyles of PCR amplification, using a quantitative real time PCR. The frequency of the mtDNA(4977) was significantly higher in the sputum cells of patients with COPD compared to smokers without COPD (p<0.0001). This difference was not observed in PBLs. Levels of cellular oxidative stress were significantly higher in the sputum cells of subjects with COPD than in the smoker group. However, mtDNA copy number, mitochondrial membrane potential (Delta Psi m) and cellular ATP levels in PBLs and sputum cells were not significantly different between the studied groups. The Pearson analysis revealed no correlations between the accumulation of mtDNA(4977), and intracellular ATP content and Delta Psi m values of the sputum cells, although there was a positive correlation between the increase in the percentage of deleted mtDNA(4977) and the levels of cellular oxidative stress in COPD patients (r = 0.80, p<0.0001). Our studies may suggest that the accumulation of mtDNA(4977) in the sputum cells of smokers with COPD does not seem to have an important impact on mitochondrial dysfunction in relation to ATP production and Delta Psi m when compared to those of healthy smokers.Research Fund of Istanbul University [T81/12122006]There is no conflict of interest among the author. This work was supported by the Research Fund of Istanbul University (project number: T81/12122006)
Estudo de tensões residuais e defeitos microestruturais gerados no resfriamento de compósito de matriz vítrea com partículas cristalinas de quartzo, alumina e zirconita
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência e Engenharia de MateriaisEsse trabalho tem como objetivo estudar o comportamento das propriedades mecânicas de materiais formados por uma microestrutura composta por fases cristalinas dispersas em uma fase vítrea. Para o desenvolvimento de uma matriz vítrea foi utilizado um feldspato sódico de alta pureza. Partículas cristalinas de quartzo, alumina e zirconita foram selecionadas e adicionadas à matriz para estudar o efeito dessas sobre as propriedades mecânicas dos materiais. Diferentes tamanhos de partículas e frações volumétricas das fases cristalinas foram incorporadas à matriz vítrea de feldspato sódico objetivando estudar o possível reforço e/ou geração de defeitos microestruturais. O presente trabalho foi dividido em três partes. Na primeira parte, o reforço microestrutural promovido pela geração de tensões residuais macroscópicas de compressão na superfície do material cerâmico foi simulado teoricamente. Os modelos foram comparados com os resultados experimentais obtidos pelo método de relaxação de deformação por corte incremental. Nessa parte do trabalho, mostrou-se que a velocidade de resfriamento, em altas temperaturas, influencia fortemente a geração de tensão na superfície do material. Em contrapartida, as maiores tensões residuais macroscópicas de compressão na superfície foram obtidas com uma maior fração volumétrica de fase vítrea no material. Este resultado foi vinculado à baixa difusividade térmica da fase amorfa comparada com as das fases cristalinas adicionadas. Com a simulação numérica desenvolvida foi possível determinar a faixa de temperatura na qual as tensões macroscópicas são incrementadas, faixa que foi muito próxima à temperatura de transição vítrea do vidro de albita formado pela fusão do feldspato sódico da matriz. O estudo estatístico da influência das propriedades termomecânicas do material sobre as tensões residuais macroscópicas mostrou que a variação da viscosidade da fase vítrea apresentou maior significância sobre o incremento de tensões residuais na superfície do material. Na segunda parte do trabalho, estudou-se a variação do módulo de elasticidade com a temperatura. Os resultados mostraram uma forte relação entre a curva experimental do módulo de elasticidade e a presença das partículas de quartzo na microestrutura. Para temperaturas abaixo de 573oC, nas quais o quartzo está na forma , foi obtida uma histerese entre as curvas de aquecimento e resfriamento. Os resultados mostraram uma relação entre a área da histerese e o diâmetro médio (D50) das partículas de quartzo. Por outro lado, para temperaturas acima de 573 oC, onde o quartzo está na forma , os resultados mostraram uma relação entre a variação do módulo de elasticidade do material entre 573 a 700 oC com a fração volumétrica de quartzo presente na microestrutura dos materiais cerâmicos. Essa relação entre o comportamento do módulo de elasticidade dos materiais cerâmicos com o quartzo presente na microestrutura possibilitou estimar o tamanho médio e a fração volumétrica de quartzo presente na microestrutura de um material já sinterizado. No capítulo final desse trabalho foi realizado um estudo sobre a influência das partículas cristalinas de quartzo, alumina e zirconita sobre a resistência à flexão, a tenacidade à fratura e o tamanho do defeito microestrutural. Não foi observado nenhum tipo de reforço microestrutural provocado pelas partículas cristalinas. A maior resistência e a maior tenacidade foram obtidas com a matriz vítrea pura, obtida somente a partir de feldspato sódico. Os resultados ainda mostraram que o tamanho do defeito microestrutural não apresentou relação com a velocidade de resfriamento, não sendo observada a deterioração da microestrutura com o aumento da velocidade de resfriamento utilizada.This work aims to study the mechanical behavior of ceramic materials formed by a microstructure composed by crystalline phases dispersed in amorphous glassy phase. A glass matrix was developed using high purity sodium feldspar. Crystalline particles of quartz, alumina and zircon were selected and added in matrix to study their effect on the mechanical properties. Different particle sizes and volumetric fractions were added into the glass matrix to study the microstructural reinforcement and/or deterioration. This work was divided into three parts. In the first part, the microstructural reinforcement promoted by the compressive residual stresses on surface was simulated by a mathematical model. The values predict with the model were compared to experimental results measured by deformation-relaxation method with incremental cuts. In this part, it was showed that the cooling rate, at high temperature, had influence on the stresses generation on material surface. On the other hand, the highest residual stresses were obtained with higher amounts of glass phase. This result is related with a low thermal diffusivity of the glass phase when compared to that of the crystalline phases added. The numerical simulation development allowed to determine the temperature range where the macroscopic stresses were increased. The results showed that this range was close to the transition temperature of the albite glass, formed by melting the sodium feldspar. A statistical study of the effect of thermomechanical properties on the macroscopic residual stresses showed that the viscosity variation of vitreous phase was the most significance variable for increasing the residual stresses. In the second part of this work, the dependence of elastic modulus with the temperature was studied. The results showed a strong relation between the experimental curve of elastic modulus and the presence of crystalline quartz in the microstructure. For temperatures below 573oC, where the quartz is present as phase, a hysteresis between heating and cooling was observed. The results showed that there is a relation between the hysteresis area and the quartz particle size (D50). On the other hand, for temperatures above 573oC, where the quartz is present as the phase, the results showed a relation between the elastic modulus variation (573 to 700oC) to the volumetric fraction of quartz in the microstructure. This relation between the elastic modulus behavior and the quartz in the microstructure allowed estimating the mean particle size and the volumetric fraction of quartz in a sintered ceramic material. The last part of this work was aimed to study the effect of some crystal particles as quartz, alumina and zircon on flexural strength, fracture toughness and defect size. No kind of microstructural reinforcement caused by these crystal particles was observed. Higher strength and toughness were observed for the pure glass matrix, obtained from only sodium feldspar. The results also showed that the microstructural defect size did not show any relation to the cooling rate. A microstructural deterioration by increasing the cooling rate was not observed
Fundamental Study into the Mechanics of Material Removal in Rock Cutting
No full textThe objective of this work was to understand the mechanics of material removal during rock cutting. The exact nature of the failure of the rock material at the tool tip was investigated using a single cutting tooth test rig coupled with high speed photography, for various rock-like specimens. Linear cutting tests were performed using a tungsten carbide tipped orthogonal cutting tool with three different rake angles on low and high strength simulated rocks. Statistical analysis together with high speed video analysis were supported by numerical simulation, performed using a commercially available code called ELFEN; a hybrid finite-discrete element software package
