A new methodology to predict damage tolerance based on compliance via global-local analysis

Over the years several design philosophies to fatigue developed in order to combine structural safety and economy to manufacturing and operating aircraft process. The safe-life approach, which consists of designing and manufacturing a safe aeronautical structure throughout its useful life, results in factors that oversize the structural elements, preventing the possibility of failure and evidently leading to high design costs. On the other hand, the approach based on the damage tolerance concept, in which it is assumed that the structure, even whether damaged, is able to withstand the actions for which it was designed until the detection of a crack due to fatigue or other defects during its operation. Here, we propose a new methodology to the damage tolerance problem in which two-dimensional global-local analysis at different levels of external requests will be made by means of compliance, aimed at finding a relationship between fatigue life and the Paris constant. Moreover, the BemCracker2D program for simulating two-dimensional crack growth is used. This methodology has been proved to be an efficient and applied alternative in the damage tolerance analysis

Instrumented indentation applied to the mechanical characterization of polyurethane derived from castor oil

Neste trabalho são investigadas as propriedades mecânicas de poliuretana derivada do óleo de mamona, utilizando a técnica de indentação instrumentada com penetradores de geometrias piramidal e esférica. Foi analisada a influência da forma do penetrador utilizado nos ensaios de indentação instrumentada para se obter valores das propriedades mecânicas de polímero derivado de óleo de mamona. Os penetradores utilizados são de pontas piramidais dos tipos Berkovich e canto de cubo e esférico de raio igual a 150 μm em um Nanoindenter XP TM com cargas aplicadas entre 1 e 200 mN. As penetrações variam de acordo com o formato do penetrador, sendo maiores para pontas agudas. A dureza e o módulo de elasticidade foram determinados, utilizando o método de Oliver e Pharr. Verificou-se que os valores medidos para a dureza são maiores para penetradores mais agudos. Os valores obtidos com a ponta piramidal Berkovich foram de 0,14 GPa para pequenas penetrações e 0,12 GPa para maiores penetrações. Já os valores obtidos com ponta canto de cubo foram 25 a 30% maiores. Isso está relacionado com os volumes das regiões que apresentam deformações plásticas elevadas, no caso de penetradores agudos comparados com os volumes das regiões que sofrem deformações viscoelásticas. A viscosidade aparente determinada, utilizando penetrador esférico em testes de força aplicada constante, é igual a (22 ± 2) × 10(12) Pa.s.The mechanical properties of polyurethane derived from castor oil, obtained by instrumented indentation technique with pyramidal and spherical indenters are reported. The influence of the indenter shape on the values of mechanical properties of the polymer was investigated. The indentations were made with pyramidal Berkovich, cube corner and a spherical indenter with radius of 150 μm in a Nanoindenter XP TM. The applied loads varied between 1 and 200 mN. The penetration depth increases for acute indenters, being higher for the cube corner tip. The hardness and elastic modulus were determined using the method of Oliver and Pharr. It was found that the measured values for hardness are higher for more acute indenters. The hardness with the pyramidal Berkovich tip was 0.14 GPa for small penetrations and 0.12 GPa for higher penetration depths. The values obtained with a cube corner tip were 25 to 30% higher. This is related to the volumes of regions with high plastic deformation in the case of acute indenters compared to the volumes of regions that present viscoelastic deformation. The apparent viscosity determined using the spherical indenter, in tests with applied constant forces, is equal to (22 ± 2) × 10(12) Pa.s.CNPqFAPES

Osteoma of external acoustic meato: report of nine cases and literature review

The osteoma of external acoustic meatus corresponds to an abnormal and benign bony growth, that is developed under the skin of the auditory canal and that can cause total or partial obstruction of the external acoustic meatus. STUDY DESIGN: Serie study. MATERIAL AND METHOD: We reported in this study nine cases of osteoma of external acoustic meatus. The patients' ages varied between 23 and 70 years old, being the average age 40,6 years. These patients were 5 of the feminine sex and 4 were of the masculine sex. RESULTS: The more common symptoms were hipoacusia, caused by the partial or total obstruction of the canal, appealing external otitis and also the accumulation of cerumen deep in the external auditory canal with difficult removal. CONCLUSION: We recommended in the presented cases surgical treatment, which had good evolution, with no recidivism.Osteoma de meato acústico externo corresponde a um crescimento ósseo anormal e benigno, que se desenvolve abaixo da pele do conduto e pode causar obstrução total ou parcial do meato acústico externo. FORMA DE ESTUDO: Estudo de série. MATERIAL E MÉTODO: Apresentamos neste estudo nove casos de osteoma de meato acústico externo. A idade dos pacientes variou de 23 anos (idade mínima) e 70 anos (idade máxima), sendo a média 40,6 anos. Desses nove pacientes, 5 eram do sexo feminino e 4 eram do sexo masculino. RESULTADO: Os sintomas mais comuns foram: hipoacusia, causada pela obstrução parcial ou total do conduto, otites externas recorrentes e também impactação de cerume de difícil remoção. CONCLUSÃO: A conduta nos casos apresentados foi cirúrgica, com boa evolução, não ocorrendo recidivas.UNIFESP-EPMHospital Paulista de OtorrinolaringologiaUNIFESP, EPMSciEL

Tympanic paragangliomas: case reports

Glomus tumors, also called paragangliomas, originate from nonchromaffin cells. The tumor is typically vascular and grows from capillary and pre-capillary vessels in-between epithelial cells. It is worth mentioning that the most common symptoms are pulsating tinnitus and hearing loss. Imaging studies (CT and MRI) are necessary for diagnosis. This paper shows five patients seen at the Hospital between 1995 and 2001 presenting glomus tympanicum. Women were most commonly affected, and the age ranged from 48 to 60 years (mean age of 50 years). The most common complaints were pulsating tinnitus and hearing loss. All patients were treated surgically.Os tumores glômicos, também chamados de paragangliomas, são formados por células não cromafins. O tumor é tipicamente vascular formado por vasos capilares e pré-capilares, interposto por células epiteliais. Para a sua abordagem inicial, deve-se ressaltar que os sintomas mais comumentes encontrados são o zumbido pulsátil e hipoacusia. A investigação através de imagem (tomografia computadorizada e ressonância magnética) se faz necessária. Apresentaremos neste trabalho 5 pacientes portadores de paragangliomas timpânicos atendidos no Hospital (de 1995 a 2001). O sexo predominante foi o feminino, a idade variou de 48 a 60 anos, com média de 50 anos. A queixa predominante foi o zumbido pulsátil e a hipoacusia. A conduta foi cirúrgica em todos os casos.Hospital Paulista de OtorrinolaringologiaUNIFESP-EPMUNIFESP, EPMSciEL

Dopamine affects the stability, hydration, and packing of protofibrils and fibrils of the wild type and variants of alpha-synuclein

Parkinson's disease (PD) is characterized by the presence of cytoplasmic inclusions composed of alpha-synuclein (alpha-syn) in dopaminergic neurons. This suggests a pivotal role of dopamine (DA) on PD development. Here, we show that DA modulates differently the stability of protofibrils (PF) and fibrils (F) composed of wild type or variants of alpha-syn (A30P and A53T) as probed by high hydrostatic pressure (HHP). While in the absence of DA, all alpha-syn PF exhibited identical stability, in its presence, the variant-composed PF acquired a greater stability (DAPFwt < DAPFA30P = DAPFA53T), implying that they would last longer, which could shed light onto why these mutations are so aggressive. When alpha-syn was incubated for long times (18 days) in the presence of DA, we observed the formation of F by electronic microscopy, suggesting that the PF trapped in the presence of DA in short times can evolve into F. The stability of F was also altered by DA. DAFwt was more labile than Fwt, indicating that the former would be more susceptible to breakage. PFA30P and DAPFA30P, when added to mesencephalic and cortical neurons in culture, decreased the number and length of neurites and increased the number of apoptotic cells. Surprisingly, these toxic effects of PFA30P and DAPFA30P were practically abolished with HHP treatment, which was able to break the PF into smaller aggregates, as seen by atomic force microscopy. These results suggest that strategies aimed at breaking and/or clearing these aggregates is promising in alleviating the symptoms of PD