Recursos dispoñibles e modalidades de emprego das actividades manipulativas na física

É ben sabido que unha forma de facilitar o aprendizaxe dos contidos relacionados coa Física consiste no emprego de metodoloxías activas. Entre as distintas opcións, o profesorado pode empregar as Actividades Manipulativas (AMs) que utilizan, debidamente contextualizados, materiais, obxectos, instrumentos ou montaxes experimentais tanto na aula como fora dela (Costa e Dorrío 2010). Neste obradoiro eminentemente práctico e interactivo presentamos unha visión actualizada de recursos e modalidades de utilización de AMs que permitan ao profesorado interesado continuar posteriormente a propia exploración individual

Surface roughness and refractive index changes in contact lens induced by lens care systems

Purpose: The aim of this study was to analyze the influence of different lens care systems in surface roughness and refractive index (RI) of contact lenses (CL). This information provides us with a better understanding of how care solutions affect CL materials. Methods: Several CL and three commercially available and appropriate lens care solutions were used (two polyhexamethylene biguanide and one hydrogen peroxide care systems). Lenses were immersed in the lens care systems, and then measurements with CLR 12-70 digital automated refractometer and atomic force microscopy analysis on Tapping mode were recorded. The measurements were performed before and after the lenses were immersed in each care solution. Results: Significant changes were observed on the CL materials when exposed to lens care systems. All the materials changed, to a greater or lesser extent, their roughness and RI, after being immersed in the different solutions. The water content varied between 0% (Nelfilcon A in ReNu Multiplus, Senofilcon A in AOSEPT Plus, and Methafilcon A in Solocare Aqua) and 4.1% (Hilafilcon B in Solocare Aqua) The higher change in roughness was obtained with ReNu Multiplus in the lens Comfilcon A (with an increase of 27.2 nm) and Senofilcon A (with an increase of 16.7 nm). Conclusion: This study suggests that lens care systems play an important role in surface roughness and RI of CL.Fundação para a Ciência e a Tecnologia (FCT

Stress and deformation in tubular metallic parts of auto seats

In order to assess the structural and material behaviour in particular the deformation and failure in lightweight metallic tubular structural parts of auto seats a pseudo-dynamic procedure was devised. The deformation of circular section tubes subjected to centred transversal force is assessed by rugometric and microtopographic optical inspection.(undefined

Surface charaterization of soft contact lenses by atomic force microscopy

The aim of this study is to analyze surface properties of different hydrogel and silicone-hydrogel contact lenses (CL) using Atomic Force Microscopy (AFM) Several commercial CL prepared by the same method of manufacture (cast-moulding), with different monomers composition, water content and surface treatment were used in this study. Surface roughness analysis was performed using AFM on Tapping® Mode using standard silicone tips. High quality microtopography images and surfaces roughness measurement were recorded randomly on four different CL surface locations, and the mean roughness parameters Ra and Rq being determined. CL exhibited different surface topography appearance and average roughness (Ra) with values ranging between 0.54 and 13.40nm. The highest and lowest values were observed in silicone-hydrogel CL. On what concerns microrelief maps, Lotrafilcon B exhibits typical structures with a pattern of numerous grooves with different orientations probably related to the surface treatment, Senofilcon A shows an homogeneously and smooth structure corroborating the obtained values for roughness and Comfilcon A presenting a surface with several tracks with different orientations. With respect to the hydrogel CL, Hilafilcon B exhibits a granulated appearance, Etafilcon A and Nefilcon A presenting a kind of tiny bubbles on its surface and Methafilcon A shows a smooth surface with some bumps spread on the top of it. As the CL surface is in direct contact with the ocular surface, it is critical for bacterial adhesion, so, surface properties are an important factor to be addressed. This study shows that the topography of the CL surface revealed very different characteristics, depending on the type of monomers presenting in the CL and the type of lenses. We could also observe that the same type of lenses may present different roughness values depending on the lot

Optics and children

Light and Optics are subjects that “naturally” attracts the interest and sympathy of children even from very early ages. In this communication, we present a serie of experiments and support material designed in this hands-on perspective, to be used to introduce the study of light and optics to kindergarten and early basic school students. Our hands-on investigative approach leads the students, aged 4 to 10 years, to observe the experiment and discover themselves, in a critical and active way, different aspects of light and optics. Preparing funny eye catching situations and experiments predispose the children to work, effectively, enjoying themselves while building up their self-confidence.(undefined