Fabrication andin vitro characterization of three-dimensional organic/inorganic scaffolds by robocasting

International audienceA key issue for the fabrication of scaffolds for tissue engineering is the development of processing techniques flexible enough to produce materials with a wide spectrum of solubility (bioresorption rates) and mechanical properties matching those of calcified tissues. These techniques must also have the capability of generating adequate porosity to further serve as a framework for cell penetration, new bone formation, and subsequent remodeling. In this study, we show how hybrid organic/inorganic scaffolds with controlled microstructures can be built using robotic assisted deposition at room temperature. Polylactide or polycaprolactone scaffolds with pore sizes ranging between 200–500 μm and hydroxyapatite contents up to 70 wt % were fabricated. Compressive tests revealed an anisotropic behavior of the scaffolds, strongly dependent on their chemical composition. The inclusion of an inorganic component increased their stiffness but they were not brittle and could be easily machined even for ceramic contents up to 70 wt %. The mechanical properties of hybrid scaffolds did not degrade significantly after 20 days in simulated body fluid. However, the stiffness of pure polylactide scaffolds increased drastically due to polymer densification. Scaffolds containing bioactive glasses were also printed. After 20 days in simulated body fluid they developed an apatite layer on their surface

Biocomposite from polylactic acid and lignocellulosic fibers: structure-property correlations

ABSTRACT PLA biocomposites were prepared using three corncob fractions and a wood fiber as reference. The composites were characterized by tensile testing, scanning electron (SEM) and polarization optical (POM) microscopy. Micromechanical deformation processes were followed by acoustic emission measurements. The different strength of the components was proved by direct measurements. Two consecutive micromechanical deformation processes were detected in composites containing the heavy fraction of corncob, which were assigned to the fracture of soft and hard particles, respectively. The fracture of soft particles does not result in the failure of the composites that is initi-ated either by the fracture of hard particles or by matrix cracking. Very large particles debond easily from the matrix resulting in catastrophic failure at very low stresses. At sufficiently large shear stresses large particles break easily during compounding, thus reinforcement depending on interfacial adhesion was practically the same in all composites irrespectively of initial fiber characteristics

Spark plasma sintering of TiyNb1-yCxN1-x monolithic ceramics obtained by mechanically induced self-sustaining reaction

Nanometer-sized titanium-niobium carbonitride powders (TiyNb1-yCxN1-x) with different Ti/Nb atomic ratios were obtained by a mechanically induced self-sustaining reaction, and sintered by spark plasma sintering technique at 1500 degrees C for 1 min in a vacuum atmosphere. Mechanical properties such as hardness and Young's modulus were determined by nanoindentation technique and friction and wear coefficients assessed by ball-on-disk testing using alumina ball in dry sliding conditions. The fracture surface and wear tracks of samples were examined by scanning electron microscopy. Results showed that it is possible to obtain dense monolithic ceramics from the solid solution (TiyNb1-yCxN1-x) with good mechanical properties and excellent wear resistance. The optimum values of nanomechanical properties were found for the Ti0.3Nb0.7C0.5N0.5 ceramic composition, which exhibited a high hardness over 26.0 GPa and Young's modulus around 400 GPa. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.The authors would like to thank Dr. Emilio Rayon for performing the nanoindentation analysis in the Materials Technology institute (ITM) of the Polytechnic University of Valencia and to acknowledge the financial support received from Spanish Ministry of Science and Innovation for FPI grant (MAT2006-01783). This work was supported by the Spanish government under grant (MAT2010-17046), which is financed in part by the European Regional Development Fund of 2007-2013. E. Chicardi was supported by CSIC through a JAE-Pre grant, which is financed in part by the European Social Fund (ESF).Borrell Tomás, MA.; Salvador Moya, MD.; Garcia-Rocha, V.; Fernandez, A.; Chicardi, E.; Gotor, FJ. (2012). Spark plasma sintering of TiyNb1-yCxN1-x monolithic ceramics obtained by mechanically induced self-sustaining reaction. Materials Science and Engineering: A. 543:173-179. https://doi.org/10.1016/j.msea.2012.02.071S17317954

Maladies bulleuses auto-immunes : rôle du chirurgien dentiste dans la prise en charge précoce. Revue de la littérature et élaboration d'une plaquette d'information

Médecine. Chirurgie dentaireRésumé : Les maladies bulleuses auto-immunes constituent un groupe hétérogène de pathologies, certes peu fréquentes mais de pronostic variable, pouvant dans certains cas engager le pronostic vital. Elles sont caractérisées par l’existence d’une auto-immunité dirigée contre différents constituants assurant la cohésion entre les kératinocytes ou entre le derme et l’épiderme. Elles sont scindées en deux groupes : les dermatoses bulleuses intra-épithéliales et les dermatoses bulleuses sous-épithéliales. Le diagnostic qui repose sur la clinique, l’histologie mais également sur différents examens immunologiques est parfois difficile à poser mais doit être le plus précoce possible afin de permettre une prise en charge adéquate. Le niveau d’information des odontologistes concernant ces maladies bulleuses nécessite d’être amélioré. Dans une première partie, une revue de la littérature nous permettra de réaliser une synthèse de l’étiopathogénie des aspects cliniques, anatomopathologiques et immunologiques ainsi que des différentes thérapeutiques proposées à l’heure actuelle. Nous axerons plus particulièrement notre travail sur le les dermatoses bulleuses auto-immunes dont l’atteinte au niveau buccal est préférentielle. Dans un second temps, nous mettrons en évidence le rôle que peut jouer le chirurgien-dentiste dans ces maladies, rôle de diagnostic précoce avant tout, mais aussi d’orientation et thérapeutique. Enfin, une dernière partie sera consacrée à la réalisation d’une plaquette à visée informative destinée aux praticiens dans leur pratique quotidienne au cabinet.Summary : Autoimmune bullous diseases are an heterogeneous group. Although they are rare, they have a variable prognosis and can be life-threatening in some cases. They are characterized by existence of autoimmunity directed against different components ensuring the cohesion between dermis and epidermis.They are divided into two groups : intraepithelial bullous diseases and subepithelial bullous diseases. The diagnosis is complex to make as it is based simultaneously on clinical, histological, and different immunological examinations. It should be made as early as possible to allow an appropriate management. The level of knowledge of the dentists about these bullous disease can be improved. In a first part, a review of the literature will allow us to make a synthesis of the etiopathogenesis of the clinical, pathological and immunological aspects as well as the different therapeutics that are currently available. In particular, we will focus on the autoimmune bullous diseases with a preferential oral involvement. In a second part, we will hightlight the role played by the dentists in these disease, particularly in the early diagnosis, but also in the orientation and the treatment. Finally, the last part we be dedicated to the creation of an informative brochure that dentists can use in their daily practice

La restauration des tourbières affectées par l'extraction de tourbe et les reboisements : les exemples du système tourbeux de Gourgon et de la tourbière bombée de Vérines dans les Monts du Forez (Massif Central, France)

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Hot pressed titanium nitride obtained from SHS starting powders: Influence of a pre-sintering heat-treatment of the starting powders on the densification process

International audienceSynthesis of titanium nitride (TiN) powders by the self propagating high temperature synthesis (SHS) process is economically appealing. This chemical reaction allows producing fine grains powders with a high specific surface area (12 m2/g). After a thermal treatment above 1000 °C under argon atmosphere, the physical and microstructural characteristics of the powders are drastically modified: density increases and specific surface decreases. Powders morphology and heat treatment influence are investigated by transmission electron microscopy. Observations reveal a regular nanocrystalline layer, surrounding the particles. After heat treatment, this layer disappears from grains surface and powders undergo important morphological changes. The behavior of these special ceramic powders during the sintering stage by the hot press process is investigated. Bulk specimens obtained are characterized from a physical, microstructural and mechanical point of view and the beneficial effect of the heat treatment on starting powder is explained. Bulk specimens processed in the optimum conditions reach a relative density superior to 98%, a microhardness of 1790 Hv and a Young modulus of 430 MPa

Benefits of adaptative multi-paddock grazing – implementation in French livestock production systems

International audienceThe beef industry and livestock production systems are at the centre of debates questioning GHG emissions and the environment more generally. To improve sustainability and to highlight the contributions of the beef sector has thus become a national and international goal of involved actors. Along with other solutions, grazing management techniques, such as adaptive multi-paddock grazing (AMP), have been suggested to provide services related to production, carbon sequestration, biodiversity, landscape, farmers’ workloads and many other aspects at the farm level. Though, a number of studies have compared different grazing systems around the world (e.g. rotational vs continuous), only few have performed integral multicriteria analyses. Hence, there is urgent need to assess advantages and disadvantages of climate-smart grazing practices based on common and comparable indicators (e.g. ecosystem services). In the present study, we will compare three different grazing systems including AMP, implemented in 27 commercial farms on three pedo-climatic regions. For each grazing system we examine grassland production (quantity and quality), carbon sequestration, biodiversity, and technical-economic results. This work will provide relevant information for grazing management aiming to achieve desired environmental and economic goals, and will put forward interesting grazing systems to meet multiple challenges (services)