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Je présenterai une revue sur les phénomènes de fracture dans les réseaux transitoires, qui représentent une classe importante de fluides viscoélastiques. Après avoir défini ce qu'est une fracture dans un fluide complexe je rappellerai les principales propriétés structurales et rhéologiques des réseaux transitoires à base polymères associatifs. Je présenterai ensuite les observations expérimentales de fracture dans ces réseaux dans différentes configurations: fractures induites par cisaillement, fractures en cellule Hele-Shaw et fractures en géométrie extensionnelle. Je tenterai aussi de montrer comment on peut étendre les concepts de fragilité ou ductilité issus de la mécanique des solides aux fluides complexes. Enfin, les différentes approches théoriques développées pour La nucléation de fractures dans les réseaux transitoires seront présentées et confrontées aux expériences

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Ref Arxiv: 1405.0291
DOI: 10.1007/jhep11(2014)040
WoS: 000344749600003
Ref. & Cit.: NASA ADS
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7 Citations
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We derive the fivebrane instanton corrections to the hypermultiplet moduli space $M_H$ of Calabi-Yau string vacua using S-duality symmetry of the type IIB formulation. The result is given in terms of a set of holomorphic functions on the twistor space of $M_H$. It contains not only all orders of the instanton expansion, but also takes into account the presence of D1-D(-1)-brane instantons. Furthermore, we provide a thorough study of the group of discrete isometries of $M_H$ and show that its closure requires a modification of certain symmetry transformations. After this modification, the fivebrane instantons are proven to be consistent with the full duality group.

Commentaires: 40 pages, 3 figures

Ref HAL: hal-00982120_v1
PMID 32261689
DOI: 10.1039/C4TB00264D
WoS: 000335225400019
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20 Citations
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Poly(l-lactic acid) (PLLA) membranes containing pharmaceutically active ionic liquids (API-ILs) have been prepared by using a simple film casting from solvent evaporation method. Several sets of membranes were prepared from two different ionic liquids namely 1-methyl-3-butyl-imidazolium ibuprofenate (C4MImIbu) and lidocainium ibuprofenate (LidIbu) with different API-IL contents. Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Wide-Angle and Small-Angle X-ray Scattering (WAXS and SAXS) revealed the strong influence of both the IL nature and content on the morphology and the crystallinity of the resulting PLLA. At 20 weight%, LidIbu was shown to act as a plasticizer for PLLA and homogeneous membranes were obtained. In contrast, at the same IL content, phase separation occurred using C4MImIbu, resulting in the formation of porous PLLA. An increase of LidIbu content to 50 weight% results also in phase separation. 1H and 1H-13C CP-MAS NMR measurements evidenced the influence of different morphologies and crystallinities on IL mobility. C4MImIbu was found to be highly mobile whereas the mobility of LidIbu was content dependent. At low percent, low mobility was observed while at higher content, two populations with respectively high and low mobility were observed. These PLLA-IL membranes were further tested as drug delivery systems. In accordance with the morphology and mobility obtained, we demonstrated that release kinetics from PLLA membranes can be tuned by the nature and the content of API-ILs. Sustainable release kinetics were obtained with API-IL acting as a plasticizer while the fastest release was obtained with API-IL acting as a porogenic agent.

Ref HAL: hal-00981498_v1
DOI: 10.1364/OE.22.008996
WoS: 000335902200017
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16 Citations
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We report on the development of an innovative class of nanowire-based Terahertz (THz) detectors in which the metamaterial properties of an antenna have been imported in the detection scheme of an overdamped plasma-wave field-effect transistor making its response resonant to THz radiation. Responsivities of ~105 V/W at 0.3THz, with noise equivalent power levels ≈10−10W/√Hz, detectivities ~2*108cm√Hz/W and quantum efficiencies ~1.2*10−5 are reached at room-temperature. The resonant nature of the detection scheme provided by the four-leaf-clover-shaped geometry and the possibility to extend this technology to large multi-pixel arrays opens the path to demanding applications for ultra-sensitive metrology, spectroscopy and biomedicine.

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Structuration and Rheological Properties of Gels made from Gluten Proteins. 9. Annual European Rheological Conference (AERC 2014)

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Ref Arxiv: 1310.0969
DOI: 10.1038/nphys2857
WoS: 000332185900021
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176 Citations
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Solid-state physics and quantum electrodynamics, with its ultrarelativistic (massless) particles, meet in the electronic properties of one-dimensional carbon nanotubes, two-dimensional graphene or topological-insulator surfaces. However, clear experimental evidence for electronic states with a conical dispersion relation in all three dimensions, conceivable for certain bulk materials, is still missing. Here, we study a zinc-blende crystal, HgCdTe, at the point of the semiconductor-to-semimetal topological transition. For this compound, we observe three-dimensional massless electrons, as certified from the dynamical conductivity increasing linearly with the photon frequency, with a velocity of about 106 m s−1. Applying a magnetic field B results in a -dependence of dipole-active inter-Landau-level resonances and spin splitting of Landau levels also following a -dependence--well-established signatures of ultrarelativistic particles but until now not observed experimentally in any solid-state electronic system.

Commentaires: http://arxiv.org/abs/1310.0969 The authors acknowledge helpful discussions with T. Brauner, R. Grill, M. Grynberg, A. A. Nersesyan, V. Novák, M. L. Sadowski and W. Zawadzki. The work has been supported by the ERC project MOMB, by EuroMagNET II under the EU Contract No. 228043, by the GDR-I project 'Semiconductor sources and detectors of THz frequencies' and by the Scientific Council of Montpellier II University. We also acknowledge the support received from the Ambassade de France en Russie for the French-Russian collaboration and exchange of PhD students.

Ref HAL: hal-00968930_v1
DOI: 10.1007/s11664-014-3035-3
WoS: 000334269500013
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The influence of SiO2 doping on the microstructure and electrical behavior of SnO2 varistors has been studied. The varistor effect was studied over a wide range from 10 9 A to 104 A. It is shown that the J(E) characteristic of SnO2 ceramics exhibits a nonlinear coefficient>100. The SiO2 doping also resulted in a sharp-abrupt upturn region in the I-V characteristic, indicating a single semiconductor junction behavior. The leakage current of the varistors is rather low, on the order of 10 10 S m 1. In the upturn region of operation where the curve departs from the nonlinear relation and approaches the value of the bulk resistivity of the material, the ceramic is characterized by a current density almost independent of the applied voltage. A very small amount of SiO2 causes large perturbations of the conventional thermionic emission observed in varistor ceramic materials.