866 research outputs found

    RGO/Nylon-6 composite mat with unique structural features and electrical properties obtained from electrospinning and hydrothermal process

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    In this work, the reduced graphene oxide (RGO) sheets were effectively uploaded through nylon-6 fibers using combined process of electrospinning and hydrothermal treatment. Good dispersion of graphene oxide (GO) with nylon-6 solution could allow to upload GO sheets through nylon-6 fibers and facilitate the formation of spider-wave-like nano-nets during electrospinning. GO sheets present on/into nylon-6 spider-wave-like nano-nets were further reduced to RGO using hydrothermal treatment. The impregnated GO sheets into nylon-6 nanofibers and their reduction during hydrothermal treatment were confirmed by FE-SEM, TEM, FT-IR and Raman spectra. The electrical characteristics of pristine nylon-6, GO/nylon-6 and RGO/nylon-6 nanofibers were investigated and it was found that RGO/nylon-6 composite mat had better electrical conductivity than others. The formation of spider-wave-like nano-nets as well as indirect route of incorporation of RGO sheets on electrospun nylon-6 mat may open a new direction for future graphene/polymer electronics. © 2013 The Korean Fiber Society and Springer Science+Business Media Dordrecht

    Computational and experimental study of molecular interaction in a ternary liquid mixture of cyclohexylamine+ethanol+benzene

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    1072-1080In the present investigation, we undertake the study of molecular interaction in a ternary mixture of cyclohexylamine (CHA), ethanol (Eth) and benzene (B) theoretically as well as experimentally. We study the interaction between CHA dimer and complexes (Eth-CHA, B-CHA, CHA-Eth-B) theoretically using DFT (Density functional theory) in gas phase. It includes the quantum chemical calculations of interaction energy, bond length, and identification of the intermolecular interaction from structural parameter analysis and molecular orbital analysis. Further, we experimentally determine the excess thermo-acoustic parameters of the mixture. For this, we have measured the ultrasonic velocity (u) and density (ρ) of the ternary mixture of CHA+Eth+B and of pure components at 303 K, 308 K and 313 K temperature. From these experimental values of u and ρ, excess thermo-acoustic parameters have been estimated using standard relations. The variations in excess acoustic parameters with the concentration of CHA (x1) are discussed in terms of the interactions and molecular geometry of the liquid mixture. At lower concentration, weak interactions dominate while on increasing x1 strong forces between molecules take place. The strong H-bonding interaction between CHA-ethanol molecules and molar volume differences of pure components leads to interstitial accommodation of molecules. The experimentally determined excess properties behaviour is supported by the theoretical calculation

    Photoproduction of meson pairs: First measurement of the polarization observable I^s

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    The polarization observable I^s, a feature exclusive to the acoplanar kinematics of multi-meson final states produced via linearly polarized photons, has been measured for the first time. Results for the reaction g p -> p pi0 eta are presented for incoming photon energies between 970 MeV and 1650 MeV along with the beam asymmetry I^c. The comparably large asymmetries demonstrate a high sensitivity of I^s to the dynamics of the reaction. Fits using Bonn-Gatchina partial wave analysis demonstrate that the new polarization observables carry significant information on the contributing partial waves.Comment: 11 pages, 6 figures, v2 to appear in Phys. Lett.

    In-medium ω\omega mass from the Îł+Nb→π0Îł+X\gamma + Nb \to \pi^{0}\gamma + X reaction

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    Data on the photoproduction of ω\omega mesons on nuclei have been re-analyzed in a search for in-medium modifications. The data were taken with the Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility in Bonn. First results from the analysis of the data set were published by D. Trnka et al. in Phys. Rev. Lett 94 (2005) 192303 \cite{david}, claiming a lowering of the ω\omega mass in the nuclear medium by 14% at normal nuclear matter density. The extracted ω\omega line shape was found to be sensitive to the background subtraction. For this reason a re-analysis of the same data set has been initiated and a new method has been developed to reduce the background and to determine the shape and absolute magnitude of the background directly from the data. Details of the re-analysis and of the background determination are described. The ω\omega signal on the NbNb target, extracted in the re-analysis, does not show a deviation from the corresponding line shape on a LH2LH_2 target, measured as reference. The earlier claim of an in-medium mass shift is thus not confirmed. The sensitivity of the ω\omega line shape to different in-medium modification scenarios is discussed.Comment: 13 pages and 11 figures, submitted for publicatio

    Modification of the ω\omega-Meson Lifetime in Nuclear Matter

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    The photo production of ω\omega mesons on the nuclei C, Ca, Nb and Pb has been measured using the Crystal Barrel/TAPS detector at the ELSA tagged photon facility in Bonn. The dependence of the ω\omega meson cross section on the nuclear mass number has been compared with three different types of models, a Glauber analysis, a BUU analysis of the Giessen theory group and a calculation by the Valencia theory group. In all three cases, the inelastic ω\omega width is found to be 130−150MeV/c2130-150 \rm{MeV/c^2} at normal nuclear matter density for an average 3-momentum of 1.1 GeV/c. In the restframe of the ω\omega meson, this inelastic ω\omega width corresponds to a reduction of the ω\omega lifetime by a factor ≈30\approx 30. For the first time, the momentum dependent ω\omegaN cross section has been extracted from the experiment and is in the range of 70 mb.Comment: 5 pages, 4 figure

    K^0 pi^0 Sigma^+ and K^*0 Sigma^+ photoproduction off the proton

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    The exclusive reactions Îłp→K∗0ÎŁ+(1189)\gamma p \to K^{*0} \Sigma^+(1189) and Îłp→K0π0ÎŁ+(1189)\gamma p \to K^{0} \pi^{0}\Sigma^+(1189), leading to the p 4π0\pi^{0} final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5 GeV. The experiment has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were combined to a photon detector system of almost 4π\pi geometrical acceptance. Differential and total cross sections are reported. At energies close to the threshold, a flat angular distribution has been observed for the reaction Îłp→K0π0ÎŁ+\gamma p\to K^{0} \pi^{0}\Sigma^+ suggesting dominant s-channel production. Σ∗(1385)\Sigma^*(1385) and higher lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions of the reaction Îłp→K∗0ÎŁ+\gamma p \to K^{*0}\Sigma^+ indicates a tt-channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical predictions.Comment: 11 pages, 13 figures, submitted to EPJ

    High statistics study of the reaction Îłp→p  2π0\gamma p\to p\;2\pi^0

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    The photoproduction of 2π0\pi^0 mesons off protons was studied with the Crystal Barrel/TAPS experiment at the electron accelerator ELSA in Bonn. The energy of photons produced in a radiator was tagged in the energy range from 600\,MeV to 2.5\,GeV. Differential and total cross sections and pπ0π0p\pi^0\pi^0 Dalitz plots are presented. Part of the data was taken with a diamond radiator producing linearly polarized photons, and beam asymmetries were derived. Properties of nucleon and Δ\Delta resonances contributing to the pπ0π0p\pi^0\pi^0 final state were determined within the BnGa partial wave analysis. The data presented here allow us to determine branching ratios of nucleon and Δ\Delta resonances for their decays into pπ0π0p\pi^0\pi^0 via several intermediate states. Most prominent are decays proceeding via Δ(1232)π\Delta(1232)\pi, N(1440)1/2+πN(1440)1/2^+\pi, N(1520)3/2−πN(1520)3/2^-\pi, N(1680)5/2+πN(1680)5/2^+\pi, but also pf0(500)pf_0(500), pf0(980)pf_0(980), and pf2(1270)pf_2(1270) contribute to the reaction.Comment: 28 pages, 17 figures, 7 table

    Quasi-free photoproduction of eta-mesons of the neutron

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    Quasi-free photoproduction of eta-mesons off nucleons bound in the deuteron has been measured with the CBELSA/TAPS detector for incident photon energies up to 2.5 GeV at the Bonn ELSA accelerator. The eta-mesons have been detected in coincidence with recoil protons and recoil neutrons, which allows a detailed comparison of the quasi-free n(gamma,eta)n and p(gamma,eta)p reactions. The excitation function for eta-production off the neutron shows a pronounced bump-like structure at W=1.68 GeV (E_g ~ 1 GeV), which is absent for the proton.Comment: accepted for publication in Phys. Rev. Let

    Measurement of polarisation observables in Ks0ÎŁ+K^0_s\Sigma^+ photoproduction off the proton

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    The reaction γ p→KS0 Σ+\gamma \, p \rightarrow K^0_S\,\Sigma^+ is studied in the photon energy range from threshold. Linearly polarised photon beams from coherent bremsstrahlung enabled the first measurement of photon beam asymmetries in this reaction up to EÎł=2250E_\gamma = 2250 MeV. In addition, the recoil hyperon polarisation was determined through the asymmetry in the weak decay ÎŁ+→pπ0\Sigma^+ \rightarrow p \pi^0 up to EÎł=1650E_\gamma = 1650 MeV. The data are compared to partial wave analyses, and the possible impact on the interpretation of a recently observed cusp-like structure near the K∗K^* thresholds is discussed.Comment: 6 pages, 5 figures. References [8,9,10,11] which were not on the original submission are now include

    Measurement of the Beam Asymmetry ÎŁ\Sigma in the Forward Direction for pi0 Photoproduction

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    Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector for photon energies between 0.92 and 1.68~GeV at the electron accelerator ELSA. The beam asymmetry~ÎŁ\Sigma has been extracted for 115∘<Ξc.m.<155∘115^\circ < \theta_{\rm c.m.} < 155^\circ of the π0\pi^0~meson and for Ξc.m.<60∘\theta_{\rm c.m.} < 60^\circ. The new beam asymmetry data improve the world database for photon energies above 1.5~GeV and, by covering the very forward region, extend previously published data for the same reaction by our collaboration. The angular dependence of ÎŁ\Sigma shows overall good agreement with the SAID parameterization.Comment: 11 pages, 10 figures, published in Phys. Rev. C, included LEPS data and MAID 2007 predictions for comparison with our dat
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