2,023 research outputs found

    Durability performance of concrete bridge piers made with metakaolin and latex mixes

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    Requirements for assessment of structural performance based on a combination of concrete strength and reinforcement cover seems to be insufficient to provide adequate durability of reinforced and prestressed concrete structures. Under these circumstances, the construction industry is expected to generalize the use of higher quality concrete with an enhanced or even high performance. This paper summarizes the main results of several tests to assess the durability performance of different concretes used in the construction of a new highway bridge in the north of Portugal. In this report, only the metakaolin and latex results are discussed. The durability performance was evaluated with tests based on capillary absorption, permeability to oxygen and water as well as chloride diffusivity and electrical resistivity. The results demonstrated that the use of metakaolin and latex improve the resistance against chloride penetration, while the effect on water and oxygen permeability is not so clear.Auto-Estradas do Norte (AENOR), Portugal. Community’s Sixth Framework Programme - Research Project “Sustainable Bridges” (FP6-PLT-01653)

    Terapia Celular Cardíaca com Células Mesenquimatosas

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    Cardiovascular disease is among the main causes of mortality and morbidity worldwide. Despite significant advances in medical and interventional therapy, the prognosis of conditions such as ischemic heart disease is still dismal. There is thus a need to investigate new therapeutic tools, one of which is stem cell therapy. Hematopoietic stem cells are the most studied type, and the fact that their biology is relatively well understood has led to their being used in preclinical research and clinical trials. However, the results of some of these studies have been controversial, which has opened the way for studies on other cell types, such as mesenchymal stem cells. These cells have immunomodulatory properties which suggest that they have therapeutic potential in cardiology. In the present article, the authors review the state of the art regarding mesenchymal stem cells, from basic and translational research to their use in clinical trials on ischemic heart disease, heart failure and arrhythmias, and discuss possible future uses

    Modelling of bond between galvanized steel rebars and concrete

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    In reinforced concrete structures, it is extremely difficult to ensure that steel bars will be not subject, either in a lower or higher extent, to the corrosion effect. The application of hot dip galvanized rebar is an economic and effective way of protecting reinforced concrete against corrosion. This protective technique has an influence, which should not be disregarded, on the performance of the rebar’s coating, its behaviour and, fundamentally, the bond between concrete and galvanized rebar. With the aim of studying the bond behaviour between galvanized steel rebar and concrete, an experimental program was carried out by means of direct pullout tests. To predict the full pullout response, an analytical cohesive interface model was developed to obtain the bond stressslip relationship. To account for the interfacial bond, a nonlinear bond stress-slip law was used. In the present work the numerical method and mathematical tools are detailed and its performance is assessed. Hence, the parameters that define the local bond stress slip relationship are obtained by a fitting procedure between the simulated pullout curve and the experimental one. Finally, the obtained local bond law relationship is compared to the one proposed by the CEB-FIP Model Code

    Cardiac Extension of Renal Cell Carcinoma

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    Apresenta-se o caso de um homem de 62 anos de idade com um episódio de dispneia súbita que motivou estudo ecocardiográfico, o qual revelou uma massa na aurícula direita. A avaliação posterior demonstrou tratar-se de extensão de neoplasia do rim direito. A massa tumoral foi removida através duma abordagem multidisciplinar, com cirurgia torácica e abdominal. O estudo anatomopatológico mostrou tratar-se de um carcinoma de células renais

    Caracterização de paredes tradicionais de tabique

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    Neste artigo discutem-se aspectos construtivos relacionados com as paredes divisórias tradicionais de tabique, de forma a contribuir para um conhecimento mais aprofundado sobre este tipo de elementos, que são parte integrante de um estilo de construção marcante no panorama do património construído português que imperou até inícios do século XX. Informação relativa aos materiais utilizados e às soluções construtivas adoptadas é fornecida e descrita. Simultaneamente, algumas propriedades físicas avaliadas também são apresentadas com a intenção de auxiliar processos de reabilitação e outros trabalhos de investigação que visem o estudo de soluções construtivas alternativas de paredes divisórias, tendo em conta que o tabique pode ser uma técnica construtiva sustentável, económica e versátil

    Simulation in Information Systems: Potential of the vulnerability theory

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    Systems simulation has been widely used in the last decades in order to analyze the impact of different scenarios in several areas, and its application to information systems in no exception. Analyzing information systems through simulation models is simultaneously much more affordable; it is required a smaller amount of resources and it is less disruptive with the real system. Since information systems are becoming a cornerstone for our society, a failure in these systems can have a huge impact. The theory of vulnerability identifies failures in which small damage can have disproportionate impact consequences in terms of the functionality of the whole system. This paper discusses the use of the theory of vulnerability in information system simulation

    Numerical simulation of galvanized rebars pullout

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    The usage of rebars in construction is the most common method for reinforcing plain concrete and thus bridging the tensile stresses along the concrete crack surfaces. Usually design codes for modelling the bond behaviour of rebars and concrete suggest a local bond stress – slip relationship that comprises distinct reinforcement mechanisms, such as adhesion, friction and mechanical anchorage. In this work, numerical simulations of pullout tests were performed using the finite element method framework. The interaction between rebar and concrete was modelled using cohesive elements. Distinct local bond laws were used and compared with ones proposed by the Model Code 2010. Finally an attempt was made to model the geometry of the rebar ribs in conjunction with a material damaged plasticity model for concrete

    Infective Endocarditis Complicated by Large Aortic Pseudoaneurysm after Cardiac Surgery

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    A 66-year-old female with Streptococcus viridans aortic and tricuspid infective endocarditis develops, during the course of antibiotic therapy, rupture of a right coronary sinus of Valsalva aneurysm to the right ventricle. An urgent cardiac surgery is preformed with implantation of a mechanical aortic prosthesis and a right coronary sinus plasty. Six months later a huge aortic pseudoaneurysm is diagnosed and she is submitted to a second uneventful surgery. A review is done for the significant features with discussion of diagnosis and therapy
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