79 research outputs found

    Uma Reflexão sobre Didática na Educação Básica: o apostilamento no 4.º ano

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    Este trabalho descreve como a lógica adultocêntrica, que há muito rege as relações escolares, pode comprometer a didática e suas metodologias, em especial o apostilamento. O aporte teórico se baseia no pragmatismo de Dewey e Peirce, fundamentando as análises das linguagens que se interpenetram na elaboração dos conteúdos. Abordam-se exercícios de uma apostila do 4.º ano do ensino fundamental, vendida em nível nacional, relativos às disciplinas de geografia e matemática. As asserções obtidas revelam que a experiência infantil foi pouco considerada, o que explica em parte o desinteresse das crianças pelos discursos pedagógico-científicos, tais como aparecem nas apostilas. Como resposta possível ao problema, propõe-se o encontro entre as subjetividades docente e discente

    Nanomechanical and tribological characterization of the MPC phospholipid polymer photografted onto rough polyethylene implants

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    International audienceGrafting biomimetic polymers onto biomaterials such as implants is one of the promising approaches to increase their tribological performance and biocompatibility and to reduce wear. In this paper, poly(2-methacryloyloxyethyl phosphorylcholine) (p(MPC)) brushes were obtained by photografting MPC from the rough surface of ultra high molecular weight polyethylene (UHMWPE) joint implants. Such substrates have a high roughness (Ra ∼ 650 nm) which often has the same order of magnitude as the brush thickness, so it is very difficult to estimate the vertical density profile of the grafted content. The quality of the p(MPC) grafting was evaluated through a wide range of characterization techniques to reveal the effectiveness of the grafting: atomic force microcopy (AFM) imaging and force spectroscopy, contact angle, SEM/EDX, and confocal microscopy. After testing the methods on smooth glass substrate as reference, AFM nano-indentation proves to be a reliable non destructive method to characterize the thickness and the mechanical properties of the p(MPC) layer in liquid physiological medium. Tribological measurements using a homemade biotribometer confirm that, despite heterogeneity thickness (h = 0.5-6 μm), the p(MPC) layer covers the roughness of the UHMWPE substrate and acts as an efficient lubricant with low friction coefficient and no wear for 9 h of friction
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