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Micrometer-sized polystyrene (PS) particles coated with poly(3,4-ethylenedioxythiophene) (PEDOT), an air-stable organic conducting polymer, have been described previously (Langmuir 1999, 15, 3469). X-ray photoelectron spectroscopy (XPS) was used to examine the surface of these coated particles. For the first time, both the conducting polymer overlayer and the steric stabilizer, poly(N-vinylpyrrolidone) (PNVP), could be identified by unique elemental markerssulfur for the PEDOT and nitrogen for the PNVP, respectively. The line shape of the C 1s core-line spectra of a latex coated with a thin PEDOT overlayer (<15 nm) closely resembled that of the uncoated PS latex. However, as the PEDOT overlayer thickness was increased, the line shape came to resemble that of bulk PEDOT. The surface specificity of XPS indicated that the particle surface becomes PEDOT-rich as the conducting polymer loading is increased. Examination of the S 2p core-line spectra revealed that the PEDOT overlayers had relatively low doping levels, which is consistent with the relatively low pressed pellet conductivities. Surprisingly, a N 1s signal could be detected even at the highest PEDOT loadings, where the PNVP stabilizer would be expected to be totally obscured. This suggested that the PEDOT is deposited within the solvated PNVP stabilizer layer (which correlates well with the observed colloidal stability of the coated particles) and that the resulting PEDOT shell might be patchy. Quantification of the surface proportion of PEDOT by XPS confirmed this, with a maximum PEDOT coverage of only 75% being achieved at high loadings. XPS examination of a PEDOTcoated, PNVP-stabilized poly(4-bromostyrene) latex, which contains unique bromine, nitrogen, and sulfur markers for the latex core, steric stabilizer, and conducting polymer components, respectively, confirmed that the PEDOT overlayers do not completely encapsulate the latex core, because bromine is always detected even for PEDOT overlayer thicknesses of 20-25 nm. On the other hand, tetrahydrofuran extraction of the latex core revealed a "broken egg-shell" morphology for the remaining PEDOT overlayer residues, suggesting a reasonable degree of structural integrity.

International audienceIn this paper, we study game dynamics and learning schemes for heterogeneous 4G networks. We introduce a novel learning scheme called cost-to-learn that incorporates the cost to switch, the switching delay, and the cost of changing to a new action and, captures the realistic behavior of the users that we have experimented on OPNET simulations. Considering a dynamic and uncertain environment where the users and operators have only a numerical value of their own payoffs as information, we construct various heterogeneous combined fully distributed payoff and strategy reinforcement learning (CODIPAS-RL): the users try to learn their own optimal payoff and their optimal strategy simultaneously. We establish the asymptotic pseudo-trajectories as solution of differential equations. Using evolutionary game dynamics, we prove the convergence and stability properties in specific classes of dynamic robust games. We provide various numerical examples and OPNET simulations in the context network selection in wireless local area networks (WLAN) and Long Term Evolution (LTE)

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In this study, composite scaffolds were prepared with polyethylene oxide (PEO)-linked gelatin and tricalcium phosphate (TCP). Chitosan, a positively charged polysaccharide, was introduced into the scaffolds to improve the properties of the artificial bone matrix. The chemical and thermal properties of composite scaffolds were investigated by Fourier transform infrared spectroscopy, thermogravimetric analyzer, differential thermal analyzer. In vitro cytotoxicity of the composite scaffold was also evaluated and the sample showed no cytotoxic effect. The morphology was studied by SEM and light microscopy. It was observed that the prepared scaffold had an open interconnected porous structure with pore size of 230-354 μm, which is suitable for osteoblast cell proliferation. The mechanical properties were assessed and it was found that the composite had compressive modulus of 1200 MPa with a strength of 5.2 MPa and bending modulus of 250 MPa having strength of 12.3 MPa. The porosity and apparent density were calculated and it was found that the incorporation of TCP can reduce the porosity and water absorption. It was revealed from the study that the composite had a 3D porous microstructure and TCP particles were dispersed evenly among the crosslinked gelatin/chitosan scaffold.

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