Orientational order of carbon nanotube guests in a nematic host suspension of colloidal viral rods

In order to investigate the coupling between the degrees of alignment of elongated particles in binary nematic dispersions, surfactant stabilized single-wall carbon nanotubes (CNTs) have been added to nematic suspensions of colloidal rodlike viruses in aqueous solution.We have independently measured the orientational order parameter of both components of the guest-host system by means of polarized Raman spectroscopy and by optical birefringence, respectively. Our system allows us therefore to probe the regime where the guest particles (CNTs) are shorter and thinner than the fd virus host particles. We show that the degree of order of the CNTs is systematically smaller than that of the fd virus particles for the whole nematic range. These measurements are in good agreement with predictions of an Onsager-type second-viral theory, which explicitly includes the flexibility of the virus particles, and the polydispersity of the CNTs.Comment: 5 pages, 2 figure

Microemulsion nanocomposites: phase diagram, rheology and structure using a combined small angle neutron scattering and reverse Monte Carlo approach

The effect of silica nanoparticles on transient microemulsion networks made of microemulsion droplets and telechelic copolymer molecules in water is studied, as a function of droplet size and concentration, amount of copolymer, and nanoparticle volume fraction. The phase diagram is found to be affected, and in particular the percolation threshold characterized by rheology is shifted upon addition of nanoparticles, suggesting participation of the particles in the network. This leads to a peculiar reinforcement behaviour of such microemulsion nanocomposites, the silica influencing both the modulus and the relaxation time. The reinforcement is modelled based on nanoparticles connected to the network via droplet adsorption. Contrast-variation Small Angle Neutron Scattering coupled to a reverse Monte Carlo approach is used to analyse the microstructure. The rather surprising intensity curves are shown to be in good agreement with the adsorption of droplets on the nanoparticle surface

Fermi level shift in carbon nanotubes by dye confinement

International audienceDye confinement into carbon nanotube significantly affects the electronic charge density distribution of the final hybrid system. Using the electron-phonon coupling sensitivity of the Raman G-band, we quantify experimentally how charge transfer from thiophene oligomers to single walled carbon nanotube is modulated by the diameter of the nano-container and its metallic or semiconducting character. This charge transfer is shown to restore the electron-phonon coupling into defected metallic nanotubes. For sub-nanometer diameter tube, an electron transfer optically activated is observed when the excitation energy matches the HOMO-LUMO transition of the confined oligothiophene. This electron doping accounts for an important enhancement of the photoluminescence intensity up to a factor of nearly six for optimal confinement configuration. This electron transfer shifts the Fermi level, acting on the photoluminescence efficiency. Therefore, thiophene oligomer encapsulation allows modulating the electronic structure and then the optical properties of the hybrid system

Taking the steps toward sustainable livestock: our multidisciplinary global farm platform journey

International audienc

Key traits for ruminant livestock across diverse production systems in the context of climate change: perspectives from a global platform of research farms

Ruminant livestock are raised under diverse cultural and environmental production systems around the globe. Ruminant livestock can play a critical role in food security by supplying high-quality, nutrient-dense food with little or no competition for arable land while simultaneously improving soil health through vital returns of organic matter. However, in the context of climate change and limited land resources, the role of ruminant-based systems is uncertain because of their reputed low efficiency of feed conversion (kilogram of feed required per kilogram of product) and the production of methane as a by-product of enteric fermentation. A growing human population will demand more animal protein, which will put greater pressure on the Earth’s planetary boundaries and contribute further to climate change. Therefore, livestock production globally faces the dual challenges of mitigating emissions and adapting to a changing climate. This requires research-led animal and plant breeding and feeding strategies to optimise ruminant systems. This study collated information from a global network of research farms reflecting a variety of ruminant production systems in diverse regions of the globe. Using this information, key changes in the genetic and nutritional approaches relevant to each system were drawn that, if implemented, would help shape more sustainable future ruminant livestock systems

Application des reseaux de neurones au controle de procedes

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 82698 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Structures et propriétés rhéologiques de réseaux transitoires chargés par des nanoparticules de silice

Structural and rheological properties of viscoelastic fluids - transient networks filled with silica nanoparticles - have been studied. Three different viscoelastic matrices have been prepared: two connected and filled microemulsion networks with different droplet sizes (30 and 100 Å) and an aqueous telechelic tribloc copolymer gel. The two characterisation techniques, rheology and small angles neutron scattering allow us to link the rheological properties to the structure of this filled matrix. The rheological reinforcement factor of the gel is greater than the theorical predictions by Smallwood and Einstein, which apply to elastomers and dilute colloidal solutions. The structure measured by small angles neutron scattering proves that silica nanoparticles are well dispersed in the viscoelastic medium. A surfactant layer appears to be absorbed on the hydrophilic surface in the microemulsion case. This phenomenon leads to an increase of the number of active links per unit volume upon addition of silica nanoparticles. Macroscopically, this increase allows us to understand the shift of the percolation thresholds.Nous avons étudié les propriétés structurales et rhéologiques de gels viscoélastiques de réseaux transitoires connectés et chargés par des nanoparticules de silice. Trois matrices viscoélastiques ont été préparées : deux microémulsions connectées possédant des gouttelettes de taille différente (30 et 100 Å) et un gel aqueux de copolymère tribloc. Les deux techniques de caractérisation employées sont la rhéologie et la diffusion de neutrons aux petits angles, ce qui nous a permis de relier les propriétés rhéologiques à la structure de ces réseaux chargés. Le facteur de renforcement rhéologique de ces gels est supérieur aux prévisions de Smallwood et d'Einstein appliquées respectivement aux élastomères et aux solutions colloïdales diluées. D'autre part, l'investigation de la structure menée par diffusion de neutrons aux petits angles montre des particules de silice bien dispersées dans la matrice. Une couche de tensioactifs est absorbée sur la surface de la silice dans le cas des microémulsions. Ce mécanisme mène à une augmentation du nombre de liens actifs par unité de volume en présence de nanoparticules. Macroscopiquement, cette augmentation permet d'expliquer le décalage du seuil de percolation

Intégration corticale d'une stimulation viscérale nociceptive (étude en IRM fonctionnelle)

ROUEN-BU Médecine-Pharmacie (765402102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF