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- ItemThe spin-flip scattering effect in the spin transport in silicon doped with bismuth(Bristol : IOP Publ., 2017) Ezhevskii, A.A.; Detochenko, A.P.; Soukhorukov, A.V.; Guseinov, D.V.; Kudrin, A.V.; Abrosimov, N.V.; Riemann, H.Spin transport of conduction electrons in silicon samples doped with bismuth in the 1.1•1013 - 7.7•1015 cm-3 concentration range was studied by the Hall effect measurements. The dependence of the Hall voltage magnitude on the magnetic field is the sum of the normal and spin Hall effects. The electrons are partially polarized by an external magnetic field and are scattered by the bismuth spin-orbit potential. Spin-flip scattering results in the additional electromotive force which compensates the normal Hall effect in strong magnetic fields.
- ItemBicrystalline grain boundary junctions of Co-doped and P-doped Ba-122 thin films(Milton Park : Taylor & Francis, 2014) Schmidt, S.; Döring, S.; Schmidl, F.; Kurth, F.; Iida, K.; Holzapfel, B.; Kawaguchi, T.; Mori, Y.; Ikuta, H.; Seidel, P.We prepared GB junctions of Ba(Fe0.9Co0.1)2As2 thin films on bicrystalline [00 l]-tilt SrTiO3 substrates. The junctions show clear Josephson effects. Electrical characterization shows asymmetric I-V characteristics which can be described within the resistively shunted junction (RSJ) model. A large excess current is observed. Their formal ICRN product is 20.2 μV at 4.2 K, which is decreased to 6.5 μV when taking Iex into account. Fabrication methods to increase this value are discussed. Additionally, measurements on GB junctions of BaFe2(As0.66P0.34)2 thin films on LSAT bicrystalline substrates are shown. Their symmetric RSJ/flux flow-behavior exhibits a formal ICRN product of 45 μV, whereas the excess corrected value is ll μV.
- ItemA multiwavelength study of the Stingray Nebula; properties of the nebula, central star, and dust(Bristol : IOP Publ., 2016) Otsuka, Masaaki; Parthasarathy, Mudumba; Tajitsu, Akito; Hubrig, SwetlanaWe performed a detail chemical abundance analysis and photo-ionization modeling of the Stingray Nebula (Hen3-1357, Parthasarathy et al. 1993[1]) to more characterize this PN. We calculated nine elemental abundances using collisionally excited lines (CELs) and recombination lines (RLs). The RL C/O ratio indicates that this PN is O-rich, which is supported by the detection of the broad amorphous silicate features at 9 and 18 μm By photo-ionization modeling, we investigated properties of the central star and derived the gas and dust masses. The nebular elemental abundances, the core-mass of the central star, and the gas mass are in agreement with the AGB model for the initially 1.5 M⊙ stars with the Z = 0.008.
- ItemPreparation of clay mineral samples for high resolution x-ray imaging(Bristol : Institute of Physics Publishing, 2013) Abbati, G.; Seim, C.; Legall, H.; Stiel, H.; Thomas, N.; Wilhein, T.In the development of optimum ceramic materials for plastic forming, it is of fundamental importance to gain insight into the compositions of the clay minerals. Whereas spectroscopic methods are adequate for determining the elemental composition of a given sample, a knowledge of the spatial composition, together with the shape and size of the particles leads to further, valuable insight. This requires an imaging technique such as high resolution X-ray microscopy. In addition, fluorescence spectroscopy provides a viable element mapping technique. Since the fine particle fraction of the materials has a major effect on physical properties like plasticity, the analysis is focused mainly on the smallest particles. To separate these from the bigger agglomerates, the raw material has to pass through several procedures like centrifugation and filtering. After that, one has to deposit a layer of appropriate thickness on to a suitable substrate. These preparative techniques are described here, starting from the clay mineral raw materials and proceeding through to samples that are ready to analyze. First results using high resolution x-ray imaging are shown.
- ItemOn Tetrahedralisations Containing Knotted and Linked Line Segments(Amsterdam [u.a.] : Elsevier, 2017) Si, Hang; Ren, Yuxue; Lei, Na; Gu, XianfengThis paper considers a set of twisted line segments in 3d such that they form a knot (a closed curve) or a link of two closed curves. Such line segments appear on the boundary of a family of 3d indecomposable polyhedra (like the Schönhardt polyhedron) whose interior cannot be tetrahedralised without additional vertices added. On the other hand, a 3d (non-convex) polyhedron whose boundary contains such line segments may still be decomposable as long as the twist is not too large. It is therefore interesting to consider the question: when there exists a tetrahedralisation contains a given set of knotted or linked line segments? In this paper, we studied a simplified question with the assumption that all vertices of the line segments are in convex position. It is straightforward to show that no tetrahedralisation of 6 vertices (the three-line-segments case) can contain a trefoil knot. Things become interesting when the number of line segments increases. Since it is necessary to create new interior edges to form a tetrahedralisation. We provided a detailed analysis for the case of a set of 4 line segments. This leads to a crucial condition on the orientation of pairs of new interior edges which determines whether this set is decomposable or not. We then prove a new theorem about the decomposability for a set of n (n ≥ 3) knotted or linked line segments. This theorem implies that the family of polyhedra generalised from the Schonhardt polyhedron by Rambau [1] are all indecomposable.
- ItemAnalysis of Arc Processes in Multi-chamber Arrester for Lightning Protection at High-voltage Overhead Power Lines(Praha : Czech Technical University in Prague, Faculty of Electrical Engineering, Department of Physics, 2017) Murashov, I.V.; Frolov, V.Y.; Uhrlandt, D.; Gortschakow, S.; Ivanov, D.V.; Sivaev, A.D.Nowadays multi-chamber arresters are widely distributed as devices of lightning protection of overhead power lines. A mathematical modelling of processes in the discharge chamber of multichamber arrester is necessary to carry out in order to improve its breaking capacity. A three-dimensional mathematical transient model of thermal, gas-dynamic and electromagnetic processes taking place in the discharge chamber of multi-chamber arrester is presented in the article. Basic assumptions, model equations, a computational domain and the boundary conditions are described. Plasma turbulence is taken into account. The results of the calculation i.e. distributions of plasma temperature and overpressure in the discharge chamber at different time points are shown. The analysis of the results was carried out. It is shown that the presence of cavities in the electrodes design promotes electric arc extinction in the discharge chamber of multi-chamber arrester.
- ItemAtomic processes in bicircular fields(Bristol : IOP Publ., 2016) Odžak, S.; Hasović, E.; Becker, W.; Milošević, D.B.We investigate laser-assisted electron-ion recombination (LAR), high-order harmonic generation (HHG) and above-threshold ionization (ATI) of argon atoms by a bicircular laser field, which consists of two coplanar counter-rotating circularly polarized fields of frequencies rω and sω. The energy of soft x rays generated in the LAR process is analyzed as a function of the incident electron angle and numerical results of direct recombination of electrons with Ar+ ions are presented. We also present the results of HHG by a bicircular field and confirm the selection rules derived earlier for inert-gas atoms in a p ground state. We show that the photoelectron spectra in the ATI process, presented in the momentum plane, as well as the LAR spectra exhibit the same discrete rotational symmetry as the applied field.
- ItemCharacterization of L21 order in Co2FeSi thin films on GaAs(Bristol : Institute of Physics Publishing, 2013) Jenichen, B.; Hentschel, T.; Herfort, J.; Kong, X.; Trampert, A.; Zizak, I.Co2FeSi/GaAs(110) and Co2FeSi/GaAs(-1-1-1)B hybrid structures were grown by molecular-beam epitaxy (MBE) and characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The films contain inhomogeneous distributions of ordered L21 and B2 phases. The average stoichiometry could be determined by XRD for calibration of the MBE sources. Diffusion processes lead to inhomogeneities, influencing long-range order. An average L21 ordering of up to 65% was measured by grazing-incidence XRD. Lateral inhomogeneities of the spatial distribution of long-range order in Co2FeSi were imaged using dark-field TEM with superlattice reflections and shown to correspond to variations of the Co/Fe ratio.
- ItemLongtime behavior for a generalized Cahn-Hilliard system with fractional operators(Messina : Accademia Peloritana dei Pericolanti, 2020) Colli, Pierluigi; Gilardi, Gianni; Sprekels, JürgenIn this contribution, we deal with the longtime behavior of the solutions to the fractional variant of the Cahn-Hilliard system, with possibly singular potentials, that we have recently investigated in the paper Well-posedness and regularity for a generalized fractional Cahn-Hilliard system. More precisely, we study the ω-limit of the phase parameter y and characterize it completely. Our characterization depends on the first eigenvalues λ1≥0 of one of the operators involved: if λ1>0, then the chemical potential μ vanishes at infinity and every element yω of the ω-limit is a stationary solution to the phase equation; if instead λ1=0, then every element yω of the ω-limit satisfies a problem containing a real function μ∞ related to the chemical potential μ. Such a function μ∞ is nonunique and time dependent, in general, as we show by an example. However, we give sufficient conditions for μ∞ to be uniquely determined and constant.
- ItemAttosecond time delays in C60 valence photoemissions at the giant plasmon(Bristol : IOP Publ., 2015) Barillot, T.; Magrakvelidze, M.; Loriot, V.; Bordas, C.; Hervieux, P.-A.; Gisselbrecht, M.; Johnsson, P.; Laksman, J.; Mansson, E.P.; Sorensen, S.; Canton, S.E.; Dahlström, J.M.; Dixit, G.; Madjet, M.E.; Lépine, F.; Chakraborty, H.S.We perform time-dependent local density functional calculations of the time delay in C60 HOMO and HOMO-1 photoionization at giant plasmon energies. A semiclassical model is used to develop further insights.