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Grenoble, France

Absorption spectra of liquid water at various temperatures in the whole IR region (0<ν̃<4000cm-1) are obtained from ATR spectra recorded in the mid-IR region combined with absorption spectra measured in the FIR region. They can be accurately decomposed over two independent spectra. The spectra of the two kinds of H2O (D2O) molecules they suppose are defined as fulfilling spectroscopic constraints and as being in accordance with thermodynamic values. Their enthalpy difference He - Hg is found equal to 11.8 kJ mol-1 for ordinary water and 12.2 kJ mol-1 for heavy water. H2O (D2O) molecules of lower enthalpies Hg, greater than the enthalpy of H 2O or D2O molecules in ices by 1.3 kJ mol-1, display vibrations that resemble those of H2O (D2O) molecules in ice. Molecules with enthalpies He reorient without breaking their H-bonds as He appears greater than the potential barrier for rotations around their symmetry axes. © 2011 Elsevier B.V. All rights reserved. Source

Ravanat J.-L.,CEA Grenoble
Free Radical Research | Year: 2012

Emphasis is placed in that review article on a detailed description of the different chromatographic analytical methods that were developed for measuring cellular levels of oxidatively generated DNA lesions. The different methods are critically reviewed taking into account the advantages and limitations of the assays. Particular attention is focused on possible causes of over-or underestimation that may explain at least partly the wide range of cellular levels of lesions and in particular 8-oxo-7,8-dihydro-2′-deoxyguanosine reported in the literature. In that respect a chronological presentation of the main significant developments is provided and appears to be of particular interest to follow the technical and methodological improvements performed over the years. Finally, future possible progresses in terms of both specificity and sensitivity are presented. © 2012 Informa UK, Ltd. Source

Cayron C.,CEA Grenoble
Acta Materialia | Year: 2011

Grain boundary engineering (GBE) aims at optimizing the properties of face centred cubic materials with low stacking fault energy by creating a high content of special twin boundaries. Quantifying twinning and its parameters, such as the twin related domains (TRDs) and the related ∑3n special grain boundaries, is thus of prime importance for GBE. A method is presented in detail to treat the electron backscatter diffraction (EBSD) maps. The TRDs are automatically reconstructed, the twinning chain trees of the TRDs are determined and represented with fractal graphs, and the ∑3n grain boundaries are identified up to order n = 12. New parameters, such as the numbers of grains (Ng), the lengths of the longest chain (LLC), the twinning polysynthesism (p) and twinning anisotropy (a) factors, are also calculated. Examples have been given for two nickel superalloys, a silicon ingot, a cadmium telluride film, and a copper thin film. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

Cayron C.,CEA Grenoble
Acta Crystallographica Section A: Foundations of Crystallography | Year: 2013

A 'one-step' theory based on Pitsch distortion is proposed to explain the continuity between the orientations of the Kurdjumov-Sachs (KS), Nishiyama-Wassermann (NW) and Pitsch variants observed on the electron backscatter diffraction pole figures of martensitic alloys. The Pitsch distortion respects the hard-sphere packing of the iron atoms and implies the existence of a neutral line along the close-packed direction [110]γ = [111]α. Its principal strains are 0, -5.7 and 15.5%, well below the +12, +12 and -20% values of the Bain distortion. At the nucleation step, the distortion generates martensite that continuously deforms the austenitic matrix. Martensite continues to grow in Pitsch orientation inside the deformation field of the surrounding austenite to reach KS and NW orientations in reference to the bulk austenite. Some experimental results reported in the literature are revisited, such as the {225}γ habit planes, the sometimes observed 'twins' at the midrib, the formation of butterfly martensite, and the effect of prior plastic deformation of austenite on the transformation temperature and on variant selection mechanisms. © 2013 International Union of Crystallography Printed in Singapore - all rights reserved. Source

The microstructure of sulfonated poly(ether ether ketone) (sPEEK) membranes was investigated by combining small-angle neutron and X-ray scattering techniques (SANS and SAXS) for large and low water contents, respectively. The ion-exchange capacity, the water content and the nature of the counterion were varied for a better understanding of the membrane microstructure. SAXS and SANS contrast variation experiments reveal a significantly more complex structure than it is commonly believed with a delicate balance of the contrasts. At low water content, the structure can be depicted by the presence of small ionic clusters and larger more or less connected core-shell domains between crystallites for low values of the sulfonation degree. The first step of the swelling process corresponds to the filling without significant structural changes of the porosity created by the solvent evaporation during the casting process. The second step is associated with a major structural reorganization induced by a large increase of the membrane water content over a small range of temperature. This reorganization is attributed to an ionic domain percolation on a large scale. The third step corresponds to the swelling of lamellar ionic domains around the crystallites as revealed by the study of the dilution laws and of the structure of sPEEK ionomer dispersions. The sizes of the ribbon-like polymer particles were determined. They do not depend linearly with the membrane ion content suggesting a nonhomogeneous distribution of the ionic groups along the polymer chain during the sulfonation process associated with the semicrystalline nature of the polymers. Finally, the effect of the degradation in oxidative media on the membrane structure is shown to correspond to an increase of the membrane water content. © 2013 American Chemical Society. Source

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