In this paper, we report the synthesis of size-controlled (6 and 18 nm) monodisperse magnetic iron oxide nanoparticles, from the pyrolysis of iron oxyhydroxide with oleic acid in high temperature solvents. Superconducting Quantum Interface Device (SQUID) measurements revealed that the iron oxide nanoparticles exhibit a superparamagnetic behavior at room temperature. In order to evaluate their potential applications as contrast agents in Nuclear Magnetic Resonance (NMR) imaging, we investigated using 1H NMR spectroscopy (at a magnetic field 4.7 T) the changes in $T_1$ and $T_2$ relaxation times in the colloidal aqueous solution at various concentration of nanoparticles. The following transverse ($r_2$) and longitudinal ($r_1$) relaxivities were found: ($r_2 = 17.85 mM^{-1}s^{-1}, r_1 = 6.90 mM^{-1}s^{-1}$) and($r_2 = 9.20 mM^{-1}s^{-1}, r_1 = 4.30 mM^{-1}s^{-1}$) for nanoparticle sizes of 18 and 6 nm, respectively. These results confirm that the synthesized nanoparticles have both high $r_1$ and $r_2$ relaxivities and thus the capacity for positive or negative contrast enhancement. This effect increaseswith the nanoparticle size. We also developed a new recognition motif of a saccharide type (mannose coating) for targeting biological models (plants) at the tissue and cellular levels in order to track the flow of the water and saccharide (which are the main drivers of plant growth) in NMR imaging. Moreover, we demonstrated that this saccharide motif provides good biocompatibility and biodistribution in a physiological medium

Novels gels from wheat gluten proteins. 3. Journée scientifique du labex NUMEV (solutions numériques, matérielles et modélisation pour l’environnement et le vivant)

Functional MRI (fMRI) allows understanding the mechanisms by which sensations induced by food cues are perceived and processed within the brain, under the influence of various external (e.g. visual stimuli) and internal factors (e.g. body state). In particular, it allows analyzing at neurophysiological level how food formulations influence their sensory qualities and the pleasure experienced. Here, we used fMRI to infer several neural correlates of the perceived salty intensity produced by rewarding food models. Subjects received different savory solutions on their tongue using an MR-compatible gustatometer. The activations were mapped from smoothed high-resolution data, an imaging protocol providing good functional sensitivity in the gustatory cortex [1]. Two primary areas for taste processing were presumed in the human brain, intercepting the operculo-insular cortex and the lesser-known postcentral gyrus. We found highly significant neural correlates of salt taste intensity at the base of the postcentral gyrus bilaterally and to a lesser extent in the insula and the overlying operculi. This finding suggests that both primary areas were involved in salt taste intensity coding in human brain, which contrasts with previous results obtained with unpleasant salty solutions. We speculate that it may result from the use of rewarding food models, making it necessary to take specific account of the stimulation context for mimicking the brain’s integration of sensory rewards during normal feeding.[1] Iranpour J, Morrot G, Claise B, Jean B, Bonny J-M. Using high resolution to improve BOLD fMRI detection in gustatory cortices. Human Brain Mapping. Submitted.

We report on room temperature electrically-induced terahertz emission from interdigitated GaN quantum well structures. The emission spectrum has been analysed in a Michelson interferometer using a 4K-Si bolometer as a terahertz detector. A resonant peak at the frequency of around 3 THz was observed in emission spectra. A threshold behaviour of the resonance with respect to applied voltage takes place. By using the proposed analytical model the measured/observed experimentally resonant behaviour of emission spectra is interpreted as a result of ungated stream-plasma instability in the channel.

Wheat endosperm is a cemented granular material composed of a binary-sized mixture ofalmost spherical starch granules bounded to one another with an amorphous proteinmatrix. The milling properties of wheat grains depend on this typical microstructure, largelycontrolled by the genetic background and the growing conditions. An original Atomic ForceMicroscopy nano-scratch methodology has been developed [1] to assess the localrheological properties of the protein matrix, the starch granules and their interface. Thedetermined relative stiffness and failure strength, together with information on the phasedistribution, were then used to construct 2D numerical samples of wheat endosperm. Thegranular structure of the sample with different granular packing was computed using aMolecular Dynamics approach. The protein matrix was added in the form of bridgesconnecting neighboring particles. The samples were then meshed using a triangular latticeof one-dimensional spring elements that were characterized by stiffness and yield force.The rheological properties of each element were set according to the location of its twonodes leading to five different elements: starch, matrix, starch-matrix, starch-starch andvoids. The samples were then subjected to an increasing uniaxial tensile stress until failureusing an iterative procedure based on conjugate gradient minimization. The LatticeElement Method, developed by Topin [2,3], was used for the simulations and a parametricstudy was performed where the protein content, the starch granular packing and thestarch-protein adhesion, suggested to be responsible of the wheat fragmentation, werevaried. The results showed that, depending on the sample porosity, the bulk elasticproperties do not follow the mixing law of diluted composites, highlighting the granularbackbone effect of percolating particles. A non-linear evolution of the bulk elastic modulusas a function of the sample porosity was also noted, with little effect of the granule solidfraction. Concerning the failure properties, the results showed that the particle volumefraction has a greater influence on the yield stress at high starch-protein adhesion and thatfor the same porosity, increasing particles volume fraction leads to higher yield stress.Finally, we noted that the yield stress strongly depends on the sample porosity at highstarch-protein adhesion and is weakly affected by the porosity at low adhesion, whateverthe particle volume fractions.

The aim of this study was to evaluate the porphyrin involvement in the red fluorescence observed in dental caries with Soprolife® light-induced fluorescence camera in treatments mode (SOPRO, ACTEON Group, La Ciotat, France) and Vistacam® camera (DÜRR DENTAL AG, Bietigheim-Bissingen, Germany). The International Caries Detection and Assessment System (ICDAS) was used to rand the samples. Human teeth cross-sections, ranked from ICDAS score 0 to 6, were examined by epi-fluorescence microscopy and Confocal Raman microscopy. Comparable studies were done with Protoporphyrin IX, Porphyrin I and Pentosidine solutions. An RGB analysis of Soprolife® images was performed using ImageJ Software (1.46r, National Institutes of Health, USA). Fluorescence spectroscopy and MicroRaman spectroscopy revealed the presence of Protoporphyrin IX, in carious enamel, dentin and dental plaque. However, the presence of porphyrin I and pentosidine cannot be excluded. The results indicated that not only porphyrin were implicated in the red fluorescence, Advanced Glygation Endproducts (AGEs) of the Maillard reaction also contributed to this phenomenon.