Biofabrication: an overview of the approaches used for printing of living cells

The development of cell printing is vital for establishing biofabrication approaches as clinically relevant tools. Achieving this requires bio-inks which must not only be easily printable, but also allow controllable and reproducible printing of cells. This review outlines the general principles and current progress and compares the advantages and challenges for the most widely used biofabrication techniques for printing cells: extrusion, laser, microvalve, inkjet and tissue fragment printing. It is expected that significant advances in cell printing will result from synergistic combinations of these techniques and lead to optimised resolution, throughput and the overall complexity of printed constructs

Performance-based Criteria for the Control of GCBs in Landfill Applications

International audienceWhile geosynthetic clay barriers (GCBs) are commonly used in landfill applications, it is well known that their hydraulic properties may deteriorate over time as a result of ion exchange following contact with various types of fluids (rainwater that has percolated through a landfill cover, landfill leachate, etc.). The potential for evolution of GCB hydraulic properties is typically assessed using oedopermeameter (oedometer permeability tests), but such tests are very timeconsuming and there is therefore a need for criteria that can be tested in a rapid and cost-effective fashion in order to provide information regarding the adequacy of a given product for a given application. The ongoing LIXAR2 project described herein aims at identifying such criteria and assessing to what extent they correlate with the results of oedopermeameter tests. This paper describes the project and presents some of the findings available to date. A preliminary selection of criteria includes: cation exchange capacity (CEC), proportion of smectite (which was found to be strongly correlated to CEC), proportion of exchange-site occupation by sodium, calcium carbonate content, free swelling capacity and carbon and oxygen isotope fractionation in the carbonate phase of the bentonite

Geosynthetic Clay Liner Interaction with Leachate: Correlation between Permeability, Microstructure, and Surface Chemistry

International audienceWhen a geosynthetic clay liner (GCL) containing sodium bentonite is brought into contact with fluids containing other cations, the latter may exchange with the sodium present between clay layers. This modification of clay surface chemistry may change the clay microstructure and hence its hydraulic conductivity. The influence of clay surface chemistry on microstructure and permeability, after prolonged contact between two GCLs (a natural sodium bentonite GCL and a sodium-activated calcium bentonite GCL) and different fluids in oedometer cells, was investigated using exchangeable-cation analysis, small-angle x-ray scattering, and transmission electron microscopy. Results suggest that calcium carbonate in the bentonite, formed during activation of the calcium bentonite, may redissolve during contact with a dilute permeant, releasing calcium ions that exchange with sodium in the clay. This exchange leads to obliteration of a so-called "gel" phase (beneficial in terms of low permeability) and to the development of a more permeable "hydrated-solid" phase. Sodium replacement by calcium during GCL contact with a 0.1 M CaCl2 solution was found to be virtually complete, with or without GCL prehydration with dilute water. No gel phase was observed in these samples. When in contact with real leachate, however, a gel phase appeared, especially when GCL samples were prehydrated. A correlation was observed between the level of hydraulic conductivity and the relative proportions of gel phase and clay interlayer occupation by sodium

Indicateurs de performance pour le contrôle des GSB en étanchéité d'installation de stockage de déchets

National audienceUsers of geosynthetic clay liners (GCLs) in landfill applications, need indicators that are relatively simple and cheap to measure, to help them assess whether a given product is suitable for a given application, in particular with respect to medium to long term hydraulic performance. The objective of the LIXAR2 project was to identify such indicators, based on detailed characterizations of the main GCLs used in French landfills. Results highlight in particular the diversity of composition that the term bentonite may cover and the importance of basing choices on performance indicators rather than simply on denominations such as Na-natural, Ca-activated, etc.Les utilisateurs de géosynthétiques bentonitiques (GSB) en installations de stockage de déchets (ISD) ont besoin d'indicateurs dont la mesure est relativement simple et peu coûteuse, leur permettant de contrôler l'adéquation d'un produit par rapport à une application donnée, notamment pour ce qui concerne les performances hydrauliques à moyen et à long terme. Le projet LIXAR2 a eu pour objectif d'identifier de tels indicateurs, sur la base de caractérisations détaillées des principaux GSB utilisés en ISD en France. Les résultats illustrent notamment la variabilité de composition que peut recouvrir le terme « bentonite » et la nécessité de baser les choix sur des indicateurs de performance plutôt que sur les simples dénominations « Na-naturelle », « Ca-activée », etc

Quel avenir pour les relations turco-américaines?

Remarques préliminaires : Ce guide élaboré par des praticiens de DDE décrit la démarche de gestion de projet en s'appuyant sur les différentes étapes chronologiques de l'opération et en précise les éléments clefs.En ce qui concerne les stations d'épuration, le cadre technique et réglementaire fixé par la Loi sur l'Eau est maintenant relativement bien défini . Certaines évolutions sont cependant attendues : révision duC .C.T.G. fascicule 81 titre Il, normalisation européenne.Par contre le fondement juridique de l' intervention des services de l' Etat pour le compte des collectivités locales est, a la date d'achèvement de ce guide, en plein remaniement.Le lecteur devra donc veiller à tenir compte des textes réglementaires ou normatifs ultérieurs,la construction et l'exploitation de station d'épuration doivent répondre à des exigences de plus en plus fortes, notamment en ce qui concerne la fiabilité . Ces exigences requièrent une gestion rigoureuse des projets. Le guide précise les recommandations essentielles aux divers stades de l'opération : prise de commande, procédures administratives, financement, études préalables, ordonnancement,dossiers techniques, suivi de chantier (lien avec l'exploitation, qualité, sécurité et protection de la santé),réception des travaux