30,143 research outputs found

    Large exchange bias after zero-field cooling from an unmagnetized state

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    Exchange bias (EB) is usually observed in systems with interface between different magnetic phases after field cooling. Here we report an unusual phenomenon in which a large EB can be observed in Ni-Mn-In bulk alloys after zero-field cooling from an unmagnetized state. We propose this is related to the newly formed interface between different magnetic phases during the initial magnetization process. The magnetic unidirectional anisotropy, which is the origin of EB effect, can be created isothermally below the blocking temperature.Comment: including supplementary information, Accepted by Physical Review Letter

    Heavy Quark diffusion from lattice QCD spectral functions

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    We analyze the low frequency part of charmonium spectral functions on large lattices close to the continuum limit in the temperature region 1.5T/Tc31.5\lesssim T/T_c\lesssim 3 as well as for T0.75TcT \simeq 0.75T_c. We present evidence for the existence of a transport peak above TcT_c and its absence below TcT_c. The heavy quark diffusion constant is then estimated using the Kubo formula. As part of the calculation we also determine the temperature dependence of the signature for the charmonium bound state in the spectral function and discuss the fate of charmonium states in the hot medium.Comment: 4 pages, Proceedings for Quark Matter 2011 Conference, May 23-28, 2011, Annecy, Franc

    Coulomb effects on the formation of proton halo nuclei

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    The exotic structures in the 2s_{1/2} states of five pairs of mirror nuclei ^{17}O-^{17}F, ^{26}Na-^{26}P, ^{27}Mg-^{27}P, ^{28}Al-^{28}P and ^{29}Si-^{29}P are investigated with the relativistic mean-field (RMF) theory and the single-particle model (SPM) to explore the role of the Coulomb effects on the proton halo formation. The present RMF calculations show that the exotic structure of the valence proton is more obvious than that of the valence neutron of its mirror nucleus, the difference of exotic size between each mirror nuclei becomes smaller with the increase of mass number A of the mirror nuclei and the ratios of the valence proton and valence neutron root-mean-square (RMS) radius to the matter radius in each pair of mirror nuclei all decrease linearly with the increase of A. In order to interpret these results, we analyze two opposite effects of Coulomb interaction on the exotic structure formation with SPM and find that the contribution of the energy level shift is more important than that of the Coulomb barrier for light nuclei. However, the hindrance of the Coulomb barrier becomes more obvious with the increase of A. When A is larger than 34, Coulomb effects on the exotic structure formation will almost become zero because its two effects counteract with each other.Comment: 9 pages, 6 figures. One colum

    Hydrogen production by sorption-enhanced steam reforming of glycerol

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    Catalytic steam reforming of glycerol for H(2) production has been evaluated experimentally in a continuous flow fixed-bed reactor. The experiments were carried out under atmospheric pressure within a temperature range of 400-700 degrees C. A commercial Ni-based catalyst and a dolomite sorbent were used for the steam reforming reactions and in situ CO(2) removal. The product gases were measured by on-line gas analysers. The results show that H(2) productivity is greatly increased with increasing temperature and the formation of methane by-product becomes negligible above 500 degrees C. The results suggest an optimal temperature of approximately 500 degrees C for the glycerol steam reforming with in situ CO(2) removal using calcined dolomite as the sorbent, at which the CO(2) breakthrough time is longest and the H(2) purity is highest. The shrinking core model and the 1D-diffusion model describe well the CO(2) removal under the conditions of this work

    Three realizations of quantum affine algebra Uq(A2(2))U_q(A_2^{(2)})

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    In this article we establish explicit isomorphisms between three realizations of quantum twisted affine algebra Uq(A2(2))U_q(A_2^{(2)}): the Drinfeld ("current") realization, the Chevalley realization and the so-called RLLRLL realization, investigated by Faddeev, Reshetikhin and Takhtajan.Comment: 15 page

    Mesoscopic Kondo effect of a quantum dot embedded in an Aharonov-Bohm ring with intradot spin-flip scattering

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    We study the Kondo effect in a quantum dot embedded in a mesoscopic ring taking into account intradot spin-flip scattering RR. Based on the finite-UU slave-boson mean-field approach, we find that the Kondo peak in the density of states is split into two peaks by this coherent spin-flip transition, which is responsible for some interesting features of the Kondo-assisted persistent current circulating the ring: (1) strong suppression and crossover to a sine function form with increasing RR; (2) appearance of a "hump" in the RR-dependent behavior for odd parity. RR-induced reverse of the persistent current direction is also observed for odd parity.Comment: 7 pages,6 figures, to be published by Europhys. Let
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