Browsing by Author "Costa, M."
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- Effect of the size reduction on the bulk tensile and double cantilever beam specimens used in cohesive zone modelsPublication . Costa, M.; Viana, G.; Canto, C.; Silva, L.F.M. da; Bane, M.D.; Chaves, F.; Campilho, Raul; Fernandes, A.A.Cohesive zone elements used in finite element analysis are a reliable way to design and predict the behaviour of the joint. The characterisation of the traction separation law used in these models is done using tensile and fracture tests, and the parameters of such laws depend on humidity and temperature. Water diffusion tests are therefore necessary, which are dependent on specimen geometry, meaning a bigger specimen takes longer to fully saturate. To solve this problem and increase the efficiency of the ageing process, smaller tensile bulk and double cantilever beam (DCB) specimens are necessary. Another advantage of smaller DCB specimens is that they can be tested in smaller high-temperature chambers, where normal DCB specimens do not fit. Smaller geometries of the bulk tensile and DCB tests are analysed, and a proposed geometry for each test is shown to produce very satisfactory results, validating the use of these specimens.
- Elucidating the mechanisms Involved in the cytotoxicity induced by marine cyanobacteria strains against the RKO colon carcinoma cell linePublication . Freitas, S.; Urbatzka, R.; Osório, H.; Costa, M.; Barros, Piedade; Vasconcelos, V.; Martins, RosárioCyanobacteria are known to synthesize secondary metabolites that may have potential as drugs for the treatment of human diseases such as cancer. Previous studies on marine cyanobacteria isolated from the Portuguese coast revealed strains of the picoplanktonic genera Cyanobium and Synechocystis as potential sources of anticancer compounds. The ethyl acetate fraction of the strains Cyanobium sp. LEGE06113 and the Synechocystis salina LEGE06155 was found to reduce cell viability of cancer cell lines. This work aimed to elucidate the mechanisms involved in the cytotoxicity of this strains in the colon adenocarcinoma cell line RKO by employing real-time PCR (RT-PCR) for genes involved in cell cycle and apoptosis, by flow cytometry for cell cycle and by two-dimensional gel electrophoresis for protein expression. RT-PCR results revealed differences in mRNA expression of genes CCNB1 (cell cycle) and BCL-2 (apoptosis). Flow cytometry results revealed a decrease in the G0/G1 and S phase and increased its number in the G2/M phase, which is in accordance with the lower expression of CCNB1. The proteomic results demonstrated different protein patterns comparing treatment groups with control. Proteins differentially regulated in exposed RKO cells were involved in cell cycle regulation, apoptosis, cell structure, protein regulation and cell metabolism. Although several of these proteins were identified in cells exposed to both cyanobacterial extracts, the data provides an indication that the cytotoxicity is induced by different toxic mechanisms in LEGE06113 and LEGE06155 fractions.
- Ensaios preliminares para caracterização de um solo sujeito a fogo controladoPublication . Meira Castro, Ana C.; Albergaria, José Tomás; Meixedo, João Paulo; Delerue-Matos, Cristina; Vivas, António; Ferreira, F.; Costa, M.; Freitas, A.; Ribeiro, S. R.No presente trabalho são apresentados os resultados obtidos num estudo realizado na região do Norte de Portugal, onde uma equipa multidisciplinar, em estreita cooperação com a Autoridade Florestal Nacional, estudou as variações de pH e teores de humidade e matéria natural orgânica do solo antes e após a execução de um fogo controlado. Foi avaliada também a evolução destes parâmetros nos 90 dias seguintes após a queimada no sentido de estudar o nível de recuperação natural dos solos. Deste estudo foi possível concluir-se que o fogo controlado causou um aumento do pH do solo e uma redução no teor de humidade. Relativamente à recuperação natural dos solos, foi verificada uma recuperação parcial das características do solo não se tendo atingido, ao fim de 90 dias, os valores observados antes da acção do fogo. Os trabalhos de monitorização/ avaliação prosseguirão com periodicidade trimestral.
- Powered smart textile-based exoskeleton for human support movementPublication . Ferreira, C.; Fertuzinhos, A.; Silva, R.; Ramalho, M.; Vale, B.; Silva, J.; Costa, L.; Oliveira, C.; Ramôa, A.; Aguiar, F.; Pilastri, A.; Matta, A.; Dias, P.; Sampaio, R.; Machado, D.; Costa, M.; Roças, A.; Madureira, P.; Moreira, Juliana; Pereira, J. R.; Pereira, C.; Pereira, F. B.Industrial environments require people’s physical efforts related to excessive force, poor posture, and repetitive tasks that increase the risk of developing musculoskeletal diseases. Due to the high prevalence of postural complaints and consequent global health burdens, a significant demand has been conducted to build and implement powered lower and upper limb devices for human enhancement, considering the working layout/position, anthropometric and ergonomic data to generate valuable information for posture correction guidance.
- Validation of a methodology for post-construction Energy Yield Assessment of an operational wind farmPublication . Costa, M.; Rocha, T.; Mendonça, J.; Pilão, R.; Pinto, P.The uncertainty associated with the prospective Energy Yield Assessment (EYA) of a wind farm may be reduced by re estimating the energy yield after it enters normal operation. This study aims to validate a simple methodology for conducting post-construction EYA of an operational wind farm. The proposed methodology derives a linear relationship between a historical source of wind speed data and the observed wind farm production on a monthly basis. In a first stage, the impact of different data sources on the accuracy of the Long-Term energy yield estimate was assessed. Results suggest that the determination coefficient R 2 is a reliable indicator for selecting the most adequate source of historical wind speed data to be used in the Long-Term energy yield estimate. In a second stage, the model was validated from a statistical point of view by testing the premises of the linear regression model, namely the significance of the linear correlation (ANOVA test), and normally-distributed (Shapiro-Wilk test), non-self-correlated (Durbin-Watson), homoscedastic (Breusch-Pagan test) residuals. Results show these premises are verified for most test cases, indicating that the model is statistically robust that the model is statistically robust for most test cases.