Multiscale modelling of thermoplastic woven fabric composites: From micromechanics to mesomechanics

The mechanical properties of woven composites can be predicted by using a multiscale modelling approach. The starting point to its application is the microscale (the level of fibres, matrix and interfaces), that allows the computation of the homogenised behaviour of the yarn. The aim of this work was to predict the yarn-level behaviour of a thermoplastic-based woven composite in order to allow the formulation of a representative constitutive model that can be used to predict ply properties at the mesoscale. To accomplish this purpose, an in situ characterisation of the microconstituents was carried out. This served to generate inputs for three different representative volume element (RVE) models that allowed predicting the yarn longitudinal, transverse and shear responses. These mechanical characteristics allowed the determination of homogenised yarn constitutive behaviour which was found to be characterised by significant non-linearity until failure, specially in transverse and shear directions.The research leading to the developments described received funding of the project ADVANSEAT; a collaborative R&D project led by Grupo Antolín, and partially supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO). C.S. Lopes also acknowledges the support of MINECO through the Ramón y Cajal fellowship (RYC-2013-14271)

Occupational exposure to nano-TiO2 in the life cycle steps of new depollutant mortars used in construction

The present work is focused on the measurement of workers exposure to nano-TiO2 in the life cycle steps of depollutant mortars. It has been done in the framework of the SCAFFOLD project, which aims at the management of potential risks arising from the use of manufactured nanomaterials in construction. Main findings can be summarized as follows: (1) The occupational exposure to nano- TiO2 is below 0.3 mg/m3 for all measured scenarios. The highest concentrations were measured during the cleaning task (in the nano- TiO2 manufacturing process) and during the application (spraying) of depollutant coatings on a wall. (2) It was found a high release of particles above the background in several tasks as expected due to the nature of the activities performed. The maximum concentration was measured during drilling and during adding powder materials (mean total particle concentration up to 5.591E+04 particles/cm3 and 5.69E+04 particles/cm3). However, considering data on total particle concentration released, no striking differences have been observed when tasks have been performed using conventional materials in the sector (control) and when using materials doped with nano-objects.European Commission's FP

Histone Acetylation-Mediated Regulation of the Hippo Pathway

The Hippo pathway is a signaling cascade recently found to play a key role in tumorigenesis therefore understanding the mechanisms that regulate it should open new opportunities for cancer treatment. Available data indicate that this pathway is controlled by signals from cell-cell junctions however the potential role of nuclear regulation has not yet been described. Here we set out to verify this possibility and define putative mechanism(s) by which it might occur. By using a luciferase reporter of the Hippo pathway, we measured the effects of different nuclear targeting drugs and found that chromatin-modifying agents, and to a lesser extent certain DNA damaging drugs, strongly induced activity of the reporter. This effect was not mediated by upstream core components (i.e. Mst, Lats) of the Hippo pathway, but through enhanced levels of the Hippo transducer TAZ. Investigation of the underlying mechanism led to the finding that cancer cell exposure to histone deacetylase inhibitors induced secretion of growth factors and cytokines, which in turn activate Akt and inhibit the GSK3 beta associated protein degradation complex in drug-affected as well as in their neighboring cells. Consequently, expression of EMT genes, cell migration and resistance to therapy were induced. These processes were suppressed by using pyrvinium, a recently described small molecule activator of the GSK 3 beta associated degradation complex. Overall, these findings shed light on a previously unrecognized phenomenon by which certain anti-cancer agents may paradoxically promote tumor progression by facilitating stabilization of the Hippo transducer TAZ and inducing cancer cell migration and resistance to therapy. Pharmacological targeting of the GSK3 beta associated degradation complex may thus represent a unique approach to treat cancer. © 2013 Basu et al

Negative responses of highland pines to anthropogenic activities in inland Spain: a palaeoecological perspective

Palaeoecological evidence indicates that highland pines were dominant in extensive areas of the mountains of Central and Northern Iberia during the first half of the Holocene. However, following several millennia of anthropogenic pressure, their natural ranges are now severely reduced. Although pines have been frequently viewed as first-stage successional species responding positively to human disturbance, some recent palaeobotanical work has proposed fire disturbance and human deforestation as the main drivers of this vegetation turnover. To assess the strength of the evidence for this hypothesis and to identify other possible explanations for this scenario, we review the available information on past vegetation change in the mountains of northern inland Iberia. We have chosen data from several sites that offer good chronological control, including palynological records with microscopic charcoal data and sites with plant macro- and megafossil occurrence. We conclude that although the available long-term data are still fragmentary and that new methods are needed for a better understanding of the ecological history of Iberia, fire events and human activities (probably modulated by climate) have triggered the pine demise at different locations and different temporal scales. In addition, all palaeoxylological, palynological and charcoal results obtained so far are fully compatible with a rapid human-induced ecological change that could have caused a range contraction of highland pines in western Iberia

Análisis del comportamiento a impacto-indentación de materiales poliméricos mediante el método de elementos finitos

El objetivo de este trabajo consiste en predecir la respuesta de materiales poliméricos sometidos a impacto-indentación mediante el programa de elementos finitos Abaqus/Explicit. En primer lugar se ha empleado un modelo de material resultante de un método de caracterización del polipropileno a impacto-tracción propuesto en trabajos previos. De los resultados se deduce que el comportamiento del material es sensible al tipo de solicitación. En consecuencia, se ha caracterizado el polipropileno también bajo impacto-indentación. El módulo de elasticidad se ha obtenido mediante la aplicación de un modelo reológico. El resto de parámetros del modelo se han obtenido mediante diseño de experimentos. Se ha comprobado que las mejores correlaciones se obtienen mediante un modelo que presenta un máximo en la zona de respuesta plástica. Se concluye que para obtener mejores correlaciones es imprescindible emplear un modelo de material que describa su comportamiento en la descarga.Peer Reviewe

Análisis del comportamiento a impacto-indentación de materiales poliméricos mediante el método de elementos finitos

El objetivo de este trabajo consiste en predecir la respuesta de materiales poliméricos sometidos a impacto-indentación mediante el programa de elementos finitos Abaqus/Explicit. En primer lugar se ha empleado un modelo de material resultante de un método de caracterización del polipropileno a impacto-tracción propuesto en trabajos previos. De los resultados se deduce que el comportamiento del material es sensible al tipo de solicitación. En consecuencia, se ha caracterizado el polipropileno también bajo impacto-indentación. El módulo de elasticidad se ha obtenido mediante la aplicación de un modelo reológico. El resto de parámetros del modelo se han obtenido mediante diseño de experimentos. Se ha comprobado que las mejores correlaciones se obtienen mediante un modelo que presenta un máximo en la zona de respuesta plástica. Se concluye que para obtener mejores correlaciones es imprescindible emplear un modelo de material que describa su comportamiento en la descarga.Peer ReviewedPostprint (published version

Análisis del comportamiento a impacto-indentación de materiales poliméricos mediante el método de elementos finitos

El objetivo de este trabajo consiste en predecir la respuesta de materiales poliméricos sometidos a impacto-indentación mediante el programa de elementos finitos Abaqus/Explicit. En primer lugar se ha empleado un modelo de material resultante de un método de caracterización del polipropileno a impacto-tracción propuesto en trabajos previos. De los resultados se deduce que el comportamiento del material es sensible al tipo de solicitación. En consecuencia, se ha caracterizado el polipropileno también bajo impacto-indentación. El módulo de elasticidad se ha obtenido mediante la aplicación de un modelo reológico. El resto de parámetros del modelo se han obtenido mediante diseño de experimentos. Se ha comprobado que las mejores correlaciones se obtienen mediante un modelo que presenta un máximo en la zona de respuesta plástica. Se concluye que para obtener mejores correlaciones es imprescindible emplear un modelo de material que describa su comportamiento en la descarga.Peer Reviewe