Production, by co-grinding in a media mill, of porous biodegradable polylactic acid-apatite composite materials for bone tissue engineering

This paper presents the results of a study of the production of porous biodegradable composite materials by co-grinding, followed by scaffolding. Dry powders of polylactic acid and nanocrystalline carbonated apatite, analogous to bone mineral were co-ground in a tumbling ball mill in order to disperse the mineral filler within the polymer. Porous scaffolds were then made by hot moulding the mixture of the two components along with a pore-forming agent which was subsequently eliminated by washing. The mechanical resistance of the scaffolds was evaluated in order to determine the best operating conditions to produce implants offering optimised properties for use as bone substitutes. It was shown that 30 wt.% of filler and 70 wt.% of pore-forming agent produce scaffolds which are sufficiently porous and resistan

Influence of Moisture on the Electrical Properties of XLPE Insulation

During their operating service, insulated power cables can be exposed to wet environment. The presence of moisture in cables surroundings may affect the properties of the used insulation material for instance, XLPE widely employed in MV and HV power cables insulation and therefore the reliability of the insulated cables. In order to examine the influence of wet aging conditions on the performances of XLPE insulated cables,samples (plates moulded from granules HFDE 4201-EC) of the same insulation material were exposed during 5600 hours to wet environment inside a cell simulating moisture. The XLPE material used in the present investigation is employed as insulation for medium voltage (MV) cables (18 / 30 kV). This work presents the results of the effect of aging under wet conditions on the electrical properties of XLPE. The goal of this paper was to investigate the eventual degradation of XLPE insulation under humidity effect by characterization techniques. For this purpose, measurements of dielectric losses factor, relative permittivity, volume resistivity and dielectric strength were performed

An oracle based method to compute a coupled equilibrium in a model of international climate policy

This paper proposes a computational game-theoretic model for the international negotiations that should take place at the end of the period covered by the Kyoto protocol. These negotiations could lead to a self-enforcing agreement on a burden sharing scheme given the necessary global emissions limit that will be imposed when the real extent of climate change is known. The model assumes a non-cooperative behavior of the parties except for the fact that they will be collectively committed to reach a target on total cumulative emissions by the year 2050. The concept of normalized equilibrium, introduced by J.B. Rosen for concave games with coupled constraints, is used to characterize a family of dynamic equilibrium solutions in an m-player game where the agents are (groups of) countries and the payoffs are the welfare gains obtained from a Computable General Equilibrium (CGE) model. The model deals with the uncertainty about climate sensitivity by computing an S-adapted equilibrium. These equilibria are computed using an oracle-based method permitting an implicit definition of the payoffs to the different players, obtained through simulations performed with the global CGE model GEMINI-E

An Oracle method to couple climate and economic dynamics

This paper deals with an oracle method to couple economic and climate models. The approach permits a dialogue between two models pertaining to two different scientific domains, the climate module being a fully-coupled ocean-atmosphere-ice model, whereas the economic module is an adaptation of the neo-classical optimal economic growth paradigm. The paper explains how the Analytic Centre Cutting Plane Method (ACCPM) is implemented to integrate in the optimal economic growth model a constraint on climate change that is computed from the climate model runs. Several experiments show the usefulness of the approach to build new types of integrated assessment meta-model

Production par co-broyage de matériaux composites poreux biodégradables à usage orthopédique

L’article présente les résultats d’une étude sur la production de matériaux composites poreux biodégradables par co-broyage suivi d’une mise en forme. De l’acide polylactique et une apatite nanocristalline carbonatée analogue au minéral osseux, sous forme de poudres, ont été cobroyés dans un broyeur à boulets afin de disperser la charge minérale dans le polymère. Des implants poreux ont ensuite été réalisés en moulant à chaud le mélange des deux constituants et un agent porogène qui a ensuite été éliminé par lessivage. La résistance mécanique des implants a enfin été caractérisée. Il a été montré que des pourcentages de 30 % de charge et 70 % d’agent porogène permettent de produire des implants suffisamment poreux et résistants

Phosphates du Protérozoïque supérieur dans la chaîne des Dahomeyides (circa 600 Ma) de la région de Bassar (Nord-Togo, Afrique de l'Ouest)

Les phosphates de Bassar (nord du Togo) sont situés dans la partie tectonisée de la couverture du craton ouest-africain, et plus précisément dans les schistes de l'unité structurale de l'Atacora de la chaîne des Dahomeyides. Les roches phosphatées se présentent comme des intercalations d'épaisseur variables (< 30 m). Elles sont généralement constituées de pellets d'apatite plus ou moins pure et recristallisée enrobés dans une matrice essentiellement phosphatée. Ce gisement s'ajoute notamment aux indices d'Aloub Djouana et de Pagala et démontre ainsi une extension fort intéressante des phosphates précambriens dans les unités tectonisées au front des Dahomeyide