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37 Describing the boundary of a heterogeneous material The properties of a highly heterogeneous material are extremely difficult to describe because of their significant spatial variation. A strategy called homogenization theory consists in obtaining a homogeneous model whose average characteristics are identical to those of the heterogeneous material. A group of French and US mathematicians has succeeded for the first time in using this strategy to describe the properties at the boundary of a heterogeneous material in greater detail. This is a remarkable mathematical feat, considering that the boundaries break up the structure of heterogeneities. Acta Mathematica September 2012 A European analytical sciences cluster in Lyon Since 2012, the Institute of Analytical Sciences has brought together all the Lyon-based players in this branch of chemistry in a new 12,000 m² facility, making this the biggest analytical sciences center in Europe. It combines cutting-edge theoretical, methodological and applied methods covering a wide range of analytical techniques. Completed in April, the facility hosts staff from CNRS, Lyon 1 University and the Ecole Normale Supérieure in Lyon. Along with IRSTEA, it makes up the new “Cité Lyonnaise de l’Environnement et de l’Analyse”. This was the biggest CNRS construction project in 2012. Governmental and regional authorities contributed significantly to its €27.4 million cost. A new characterization platform for the Aquitaine region Completed in early 2013, a new building with a total surface area of 1,700 m² hosts the PLateforme Aquitaine de CAractérisation des MATériaux (PLACAMAT). Built as an extension to the Institute of Condensed Matter Chemistry of Bordeaux (ICMCB) with a €4.2 million budget, the facility received support from CNRS and the Aquitaine Region. The platform, which is open to University laboratories and industrial partners, brings together characterization techniques such as electron microscopy, surface analyses and X-ray tomography. The resulting synergy should make it possible to develop these techniques for the benefit of novel materials R&D. How the motion of particles becomes irreversible In microphysics, the equations that describe the motion of particles are reversible, whereas phenomena that occur on everyday scales are not. But why should this be? Mathematicians have now taken a huge step forward in answering this question by showing that the dynamics of a system of particles – when described by the so-called Kac’s model and when the number of particles is very large – does indeed have the irreversibility properties of the equations that describe macroscopic phenomena. Inventiones Mathematicae September 2012 online Chemists find possible mechanism for prebiotic chemistry How did the first building blocks of life assemble on the early Earth? Two research teams from France and one from the US have shown that in an abiotic aqueous environment it is possible to obtain peptides from amino acids, even at very low concentrations, by adding to the solution a compound called cyanamide that acts as an activating agent. Cyanamide has a particularly simple structure and has been detected in the interstellar medium. It may therefore have played a key role in the development of prebiotic chemistry on Earth. Angewandte Chemie International Edition November 2012 online Microscopic view of the network of imprints left by the nucleation, growth and coalescence of microcracks when a sample of Plexiglas® breaks suddenly. Right, digital reconstruction of the network observed. Fragile materials: cracks slower than thought to propagate How fast does a crack propagate through a fragile material like glass? Surprisingly, recent experiments show that it spreads four times more slowly than predicted by current theory. The difference stems from the way in which microcracks, which form at a rate of hundreds of millions per second, grow and join up, causing the main crack to propagate. Taking this totally unexpected result into account should help to decipher and improve materials’ resistance to fracture. Proceedings of the National Academy of Sciences January 2012 2012 A year at CNRS


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