4,185 research outputs found

    Large magnetic circular dichroism in resonant inelastic x-ray scattering at the Mn L-edge of Mn-Zn ferrite

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    We report resonant inelastic x-ray scattering (RIXS) excited by circularly polarized x-rays on Mn-Zn ferrite at the Mn L2,3-resonances. We demonstrate that crystal field excitations, as expected for localized systems, dominate the RIXS spectra and thus their dichroic asymmetry cannot be interpreted in terms of spin-resolved partial density of states, which has been the standard approach for RIXS dichroism. We observe large dichroic RIXS at the L2-resonance which we attribute to the absence of metallic core hole screening in the insulating Mn-ferrite. On the other hand, reduced L3-RIXS dichroism is interpreted as an effect of longer scattering time that enables spin-lattice core hole relaxation via magnons and phonons occurring on a femtosecond time scale.Comment: 7 pages, 2 figures, http://link.aps.org/doi/10.1103/PhysRevB.74.17240

    Goals and their associations with beliefs about success in and perceptions of the purpose of physical education

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    This is the publisher's version, also found at http://ehis.ebscohost.com/ehost/detail?vid=3&sid=f2fadc72-30ec-4818-a6be-17c24af97fd1%40sessionmgr13&hid=2&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=s3h&AN=SPH367545This study examined the relationship of students' goal orientation to their beliefs about what leads to success in physical education and perceptions of the purposes of physical education. High school students {N = 144,78 females and 66 males) completed a modified version of the Task and Ego Orientation in Sport Questionnaire and measures of beliefs and perceived purposes specific to physical education class. Results indicated that students high in task orientation were significantly more likely to believe that success is achieved through intrinsic interest/effort/cooperation than were those low in task orientation. High ego-oriented students believed that success is achieved when students possess high ability more so than low ego-oriented students. The high task/low ego students were most likely to reject the notion that success in physical education occurs when students know how to use deceptive tactics and were less likely to perceive that an important function of physical education is to provide an easy class

    Dynamic quantum clustering: a method for visual exploration of structures in data

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    A given set of data-points in some feature space may be associated with a Schrodinger equation whose potential is determined by the data. This is known to lead to good clustering solutions. Here we extend this approach into a full-fledged dynamical scheme using a time-dependent Schrodinger equation. Moreover, we approximate this Hamiltonian formalism by a truncated calculation within a set of Gaussian wave functions (coherent states) centered around the original points. This allows for analytic evaluation of the time evolution of all such states, opening up the possibility of exploration of relationships among data-points through observation of varying dynamical-distances among points and convergence of points into clusters. This formalism may be further supplemented by preprocessing, such as dimensional reduction through singular value decomposition or feature filtering.Comment: 15 pages, 9 figure

    A semi-implicit version of the MPAS-atmosphere dynamical core

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    An important question for atmospheric modeling is the viability of semi-implicit time integration schemes on massively parallel computing architectures. Semi-implicit schemes can provide increased stability and accuracy. However, they require the solution of an elliptic problem at each time step, creating concerns about their parallel efficiency and scalability. Here, a semi-implicit (SI) version of the Model for Prediction Across Scales (MPAS) is developed and compared with the original model version, which uses a split Runge-Kutta (SRK3) time integration scheme. The SI scheme is based on a quasi-Newton iteration toward a Crank-Nicolson scheme. Each Newton iteration requires the solution of a Helmholtz problem; here, the Helmholtz problem is derived, and its solution using a geometric multigrid method is described. On two standard test cases, a midlatitude baroclinic wave and a small-planet nonhydrostatic gravity wave, the SI and SRK3 versions produce almost identical results. On the baroclinic wave test, the SI version can use somewhat larger time steps (about 60%) than the SRK3 version before losing stability. The SI version costs 10%-20% more per step than the SRK3 version, and the weak and strong scalability characteristics of the two versions are very similar for the processor configurations the authors have been able to test (up to 1920 processors). Because of the spatial discretization of the pressure gradient in the lowest model layer, the SI version becomes unstable in the presence of realistic orography. Some further work will be needed to demonstrate the viability of the SI scheme in this case.UK Natural Environment Research Council as part of the G8 ICOMEX projec

    Magnetism in purple bronze Li0.9_{0.9}Mo6_6O17_{17}

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    Muon spin relaxation measurements around the 25 K metal-insulator transition in Li0.9_{0.9}Mo6_6O17_{17} elucidate a profound role of disorder as a possible mechanism for this transition. The relaxation rate 1/T11/T_1 and the muon Knight shift are incompatible with the transition to a SDW state and thus exclude it.Comment: pages 2, fig 2, The conf. on strongly correlated electron systems, SCES 2004, German