Showing papers by "Bruno Lucas published in 2014"

TCR-Signaling Events Are Required for Maintaining CD4 Regulatory T Cell Numbers and Suppressive Capacities in the Periphery

Abstract: CD4 regulatory T cells (Tregs) can be subdivided into two subsets according to Ly-6C expression in the periphery Phenotypic analysis, imaging, and adoptive-transfer experiments of peripheral Ly-6C(-) and Ly-6C(+) Tregs reveal that the nonexpression of Ly-6C by ∼70% of peripheral Tregs depends on TCR signaling events Interestingly, Ly-6C(-) Tregs express higher surface amounts of key immunosuppressive molecules than do Ly-6C(+) Tregs and produce constitutively anti-inflammatory cytokines In line with their phenotype, Ly-6C(+) Tregs exhibit poor suppressive capacities in vitro and in vivo Finally, although Ly-6C(-) Tregs maintain their numbers with age, Ly-6C(+) Tregs gradually disappear Altogether, our data strongly suggest that both the survival and suppressive functions of peripheral CD4 Tregs rely on their ability to receive strong TCR signals

UV Photofragmentation Dynamics of Protonated Cystine: Disulfide Bond Rupture.

Abstract: Disulfide bonds (S−S) play a central role in stabilizing the native 9 structure of proteins against denaturation. Experimentally, identification of these linkages in peptide and protein structure characterization remains challenging. UV photodissociation (UVPD) can be a valuable tool in identifying disulfide linkages. Here, the S−S bond acts as a UV chromophore and absorption of one UV photon corresponds to a σ−σ* transition. We have investigated the photodissociation dynamics of protonated cystine, which is a dimer of two cysteines linked by a disulfide bridge, at 263 nm (4.7 eV) using a multicoincidence technique in which fragments coming from the same fragmentation event are detected. Two types of bond cleavages are observed corresponding to the disulfide (S−S) and adjacent C−S bond ruptures. We show that the S−S cleavage leads to three different fragmentions via three different fragmentation mechanisms. The UVPD results are compared to collision-induced dissociation (CID) and electron-induced dissociation (EID) studies.

Simple strategy to tune the charge transport properties of conjugated polymer/carbon nanotube composites using an electric field assisted deposition technique

Abstract: Work concerning the incorporation of carbon nanotubes (CNTs) in organic semiconducting polymers have now been reported by many research groups, and the electrical properties of polymer/CNT nanocomposites have been extensively studied. In this work, we present a simple procedure to tune the charge transport properties of planar organic polymer films based on poly(3-hexylthiophene) (P3HT). The polymer/CNT composites are simultaneously processed and oriented from solution using an electric field assisted orientation technique. We first study the behavior of CNTs alone during the alignment procedure and emphasize the main experimental parameters that drive their final orientation on the substrate. By quantitatively analyzing the CNT angular distribution on the substrate, we show that the dielectric constant of the solvent used to disperse and deposit the CNTs is crucial to ensure an efficient orientation, and that a dielectrophoresis-like orientation procedure occurs. The transposition of this approach to planar P3HT/CNT composites is made by investigating the electric properties in ambient conditions of aligned and non-aligned devices. Current‐voltage characteristics show a drastic increase of the composite conductivity upon addition and alignment of CNTs. Field-effect transistor charge mobilities are improved by an order of magnitude upon addition of CNT (1 wt%) in P3HT, and another decade is gained using the optimized alignment parameters, without any additional annealing. These results demonstrate the strong potentialities of our approach in the field of printed electronics and organic optoelectronics. c � 2013 Society of Chemical Industry

Flexible inverted polymer solar cells with an indium-free tri-layer cathode

Abstract: Indium tin oxide (ITO)-free inverted polymer solar cells (PSCs) have been fabricated without the need of an additional electron transport layer. The indium-free transparent electrode consists of a tri-layer stack ZnO (30 nm)/Ag (14 nm)/ZnO (30 nm) deposited on glass and plastic substrates via ion-beam sputtering. The tri-layer electrodes exhibit similar physical properties to its ITO counterpart, specifically yielding high transmittance and low resistivity (76.5% T at 550 nm, Rsq of 8 Ω/◻) on plastic substrates. The novel tri-layer electrode allows for the fabrication of inverted PSCs without the additional ZnO interfacial layer commonly deposited between ITO and the photoactive layer. This allows for the preparation of thinner plastic solar cells using less material than conventional architectures. Initial studies involving the newly realized architecture (tri-layer electrode/P3HT:PCBM/PEDOT:PSS/Ag) have shown great promise for the transition from ITO to other viable electrodes in organic electronics.

Positive temperature coefficient and High Seebeck coefficient in ZnO-P2O5/Co composites

Abstract: This article reports a study of electrical properties of new Zinc Phosphate glass/Cobalt composites (45 mol% ZnO–55 mol%P 2 O 5 ) (ZP/Co) The measurements of electrical conductivity at room temperature as a function of cobalt's concentration showed a non-conducting to conducting phase transition at percolation threshold of 27 vol% The Seebeck coefficient obtained under the same conditions, accompanies a sign, with high positive and negative values below and above the percolation threshold respectively, depicting a p- to n-type conducting phase transition, confirming the conductivity measurements Then, the measurements of electrical conductivity and Seebeck coefficient above the percolation threshold as a function of temperature showed an original conducting to insulating phase transition, called Positive Temperature Coefficient (PTC) at T = 420 K, associated to a high negative value of S ≤ − 8000 μV/K, with the highest power factor PF = σS 2 ≈ 8 × 10 − 3 W m − 1 K − 2 The thermal measurements of volume expansion confirm this transition, indicating matrix dilation around this temperature However, the thermal behavior of the electrical conductivity and Seebeck coefficient data obtained below the percolation threshold showed different mechanisms ie; Small Polaron Hopping (SPH) mechanism at high temperatures and Mott's Variable Range Hopping (VRH) at low temperatures

Composites of zinc phosphate glass/metal: New materials for thermoelectricity and solar cell devices

Abstract: This work reports a study on thermoelectricity in new composites zinc-phosphate glasses/cobalt. The obtained Seebeck coefficient (S) changes a sign from a high positive to negative values below and above the percolation threshold, respectively, showing p-n type conducting phase transition. Thus, the Seebeck coefficient measurements above the percolation threshold as function of temperature showed respectively an original conducting to insulating phase transition at T=420K, linked with a high negative value of S≤−8000µV/K, giving rise to the highest power factor PF=σS2≈8×10−3W.m−1.K−2. The thermal measurements confirm this transition and indicate a dilation of matrix around this temperature. Such materials with high Seebeck coefficient could be used as new materials for thermoelectricity applications. In addition, the p-n transition in these materials my fined useful application in p-n junction devices.