192 research outputs found

    The revised NEUROGES–ELAN system: An objective and reliable interdisciplinary analysis tool for nonverbal behavior and gesture

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    As visual media spread to all domains of public and scientific life, nonverbal behavior is taking its place as an important form of communication alongside the written and spoken word. An objective and reliable method of analysis for hand movement behavior and gesture is therefore currently required in various scientific disciplines, including psychology, medicine, linguistics, anthropology, sociology, and computer science. However, no adequate common methodological standards have been developed thus far. Many behavioral gesture-coding systems lack objectivity and reliability, and automated methods that register specific movement parameters often fail to show validity with regard to psychological and social functions. To address these deficits, we have combined two methods, an elaborated behavioral coding system and an annotation tool for video and audio data. The NEUROGES–ELAN system is an effective and user-friendly research tool for the analysis of hand movement behavior, including gesture, self-touch, shifts, and actions. Since its first publication in 2009 in Behavior Research Methods, the tool has been used in interdisciplinary research projects to analyze a total of 467 individuals from different cultures, including subjects with mental disease and brain damage. Partly on the basis of new insights from these studies, the system has been revised methodologically and conceptually. The article presents the revised version of the system, including a detailed study of reliability. The improved reproducibility of the revised version makes NEUROGES–ELAN a suitable system for basic empirical research into the relation between hand movement behavior and gesture and cognitive, emotional, and interactive processes and for the development of automated movement behavior recognition methods

    Type I Superconductivity in YbSb2 Single Crystals

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    We present evidence of type I superconductivity in YbSb2 single crystals, from DC and AC magnetization, heat capacity and resistivity measurements. The critical temperature and critical field are determined to be TcT_c\approx 1.3 K and HcH_c\approx 55 Oe. A small Ginzburg-Landau parameter \kappa = 0.05, together with typical magnetization isotherms of type I superconductors, small critical field values, a strong Differential Paramagnetic Effect (DPE) signal, and a field-induced change from second to first order phase transition, confirm the type I nature of the superconductivity in YbSb2. A possible second superconducting state is observed in the radiofrequency (RF) susceptibility measurements, with Tc(2)T_{c}^{(2)}\approx 0.41 K and Hc(2)H_{c}^{(2)}\approx 430 Oe.Comment: 6 pages, 10 figure

    Avoided ferromagnetic quantum critical point: Unusual short-range ordered state in CeFePO

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    Cerium 4f electronic spin dynamics in single crystals of the heavy-fermion system CeFePO is studied by means of ac-susceptibility, specific heat and muon-spin relaxation (μ\muSR). Short-range static magnetism occurs below the freezing temperature Tg ~ 0.7 K, which prevents the system from accessing the putative ferromagnetic quantum critical point. In the μ\muSR, the sample-averaged muon asymmetry function is dominated by strongly inhomogeneous spin fluctuations below 10 K and exhibits a characteristic time-field scaling relation expected from glassy spin dynamics, strongly evidencing cooperative and critical spin fluctuations. The overall behavior can be ascribed neither to canonical spin glasses nor other disorder-driven mechanisms.Comment: 5 pages, 4 figures, accepted for publication in Physical Review Letters, Link: http://prl.aps.org/accepted/6207bYdaGef1483c419928305372ce2d4419eb96

    Interplay between Kondo suppression and Lifshitz transitions in YbRh2_2Si2_2 at high magnetic fields

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    We investigate the magnetic field dependent thermopower, thermal conductivity, resistivity and Hall effect in the heavy fermion metal YbRh2Si2. In contrast to reports on thermodynamic measurements, we find in total three transitions at high fields, rather than a single one at 10 T. Using the Mott formula together with renormalized band calculations, we identify Lifshitz transitions as their origin. The predictions of the calculations show that all experimental results rely on an interplay of a smooth suppression of the Kondo effect and the spin splitting of the flat hybridized bands.Comment: 5 pages, 4 figure

    Evidence for a Kondo destroying quantum critical point in YbRh2Si2

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    The heavy-fermion metal YbRh2_{2}Si2_{2} is a weak antiferromagnet below TN=0.07T_{N} = 0.07 K. Application of a low magnetic field Bc=0.06B_{c} = 0.06 T (c\perp c) is sufficient to continuously suppress the antiferromagnetic (AF) order. Below T10T \approx 10 K, the Sommerfeld coefficient of the electronic specific heat γ(T)\gamma(T) exhibits a logarithmic divergence. At T<0.3T < 0.3 K, γ(T)Tϵ\gamma(T) \sim T^{-\epsilon} (ϵ:0.30.4\epsilon: 0.3 - 0.4), while the electrical resistivity ρ(T)=ρ0+aT\rho(T) = \rho_{0} + aT (ρ0\rho_{0}: residual resistivity). Upon extrapolating finite-TT data of transport and thermodynamic quantities to T=0T = 0, one observes (i) a vanishing of the "Fermi surface crossover" scale T(B)T^{*}(B), (ii) an abrupt jump of the initial Hall coefficient RH(B)R_{H}(B) and (iii) a violation of the Wiedemann Franz law at B=BcB = B_{c}, the field-induced quantum critical point (QCP). These observations are interpreted as evidence of a critical destruction of the heavy quasiparticles, i.e., propagating Kondo singlets, at the QCP of this material.Comment: 20 pages, 8 figures, SCES 201

    Interplay between unconventional superconductivity and heavy-fermion quantum criticality: CeCu2_2Si2_2 versus YbRh2_2Si2_2

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    In this paper the low-temperature properties of two isostructural canonical heavy-fermion compounds are contrasted with regards to the interplay between antiferromagnetic (AF) quantum criticality and superconductivity. For CeCu2_2Si2_2, fully-gapped d-wave superconductivity forms in the vicinity of an itinerant three-dimensional heavy-fermion spin-density-wave (SDW) quantum critical point (QCP). Inelastic neutron scattering results highlight that both quantum critical SDW fluctuations as well as Mott-type fluctuations of local magnetic moments contribute to the formation of Cooper pairs in CeCu2_2Si2_2. In YbRh2_2Si2_2, superconductivity appears to be suppressed at T 10T\gtrsim~10 mK by AF order (TNT_N = 70 mK). Ultra-low temperature measurements reveal a hybrid order between nuclear and 4f-electronic spins, which is dominated by the Yb-derived nuclear spins, to develop at TAT_A slightly above 2 mK. The hybrid order turns out to strongly compete with the primary 4f-electronic order and to push the material towards its QCP. Apparently, this paves the way for heavy-fermion superconductivity to form at TcT_c = 2 mK. Like the pressure - induced QCP in CeRhIn5_5, the magnetic field - induced one in YbRh2_2Si2_2 is of the local Kondo-destroying variety which corresponds to a Mott-type transition at zero temperature. Therefore, these materials form the link between the large family of about fifty low-TT unconventional heavy - fermion superconductors and other families of unconventional superconductors with higher TcT_cs, notably the doped Mott insulators of the cuprates, organic charge-transfer salts and some of the Fe-based superconductors. Our study suggests that heavy-fermion superconductivity near an AF QCP is a robust phenomenon.Comment: 30 pages, 7 Figures, Accepted for publication in Philosophical Magazin

    Quantum Tricritical Points in NbFe2_2

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    Quantum critical points (QCPs) emerge when a 2nd order phase transition is suppressed to zero temperature. In metals the quantum fluctuations at such a QCP can give rise to new phases including unconventional superconductivity. Whereas antiferromagnetic QCPs have been studied in considerable detail ferromagnetic (FM) QCPs are much harder to access. In almost all metals FM QCPs are avoided through either a change to 1st order transitions or through an intervening spin-density-wave (SDW) phase. Here, we study the prototype of the second case, NbFe2_2. We demonstrate that the phase diagram can be modelled using a two-order-parameter theory in which the putative FM QCP is buried within a SDW phase. We establish the presence of quantum tricritical points (QTCPs) at which both the uniform and finite qq susceptibility diverge. The universal nature of our model suggests that such QTCPs arise naturally from the interplay between SDW and FM order and exist generally near a buried FM QCP of this type. Our results promote NbFe2_2 as the first example of a QTCP, which has been proposed as a key concept in a range of narrow-band metals, including the prominent heavy-fermion compound YbRh2_2Si2_2.Comment: 21 pages including S

    Ferromagnetic Quantum Criticality in the Quasi-One-Dimensional Heavy Fermion Metal YbNi4P2

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    We present a new Kondo-lattice system, YbNi4P2, which is a clean heavy-fermion metal with a severely reduced ferromagnetic ordering temperature at T_C=0.17K, evidenced by distinct anomalies in susceptibility, specific-heat, and resistivity measurements. The ferromagnetic nature of the transition, with only a small ordered moment of ~0.05mu_B, is established by a diverging susceptibility at T_C with huge absolute values in the ferromagnetically ordered state, severely reduced by small magnetic fields. Furthermore, YbNi4P2 is a stoichiometric system with a quasi-one-dimensional crystal and electronic structure and strong correlation effects which dominate the low temperature properties. This is reflected by a stronger-than-logarithmically diverging Sommerfeld coefficient and a linear-in-T resistivity above T_C which cannot be explained by any current theoretical predictions. These exciting characteristics are unique among all correlated electron systems and make this an interesting material for further in-depth investigations.Comment: 14 pages, 6 figure

    Channelling figurativity through narrative : the paranarrative in fiction and non-fiction

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    Contrary to wide-spread assumptions, metaphor in narrative is not a pre-established, extra-textual form appearing in different instances of discourse, but rather an event resulting from a strategic distribution of information in the narrative process. Hence, the appeal to conceptual cultural knowledge is to be considered as a consequence, and not as a prerequisite of metaphor interpretation. By means of the concept of the paranarrative, we highlight the rhetorical interconnectedness of metaphor with other figures of speech (such as metonymy) and we explore the narrative integration of diacritic forms of indirectness. In order to illustrate the terminology that can address these focal concerns, the paper discusses the relation between tropes and narrative, via selected examples from narrative texts (both fictional and non-fictional) written by Juli Zeh, Herta Müller, Jürgen Nieraad, and Siddhartha Mukherjee. As their common denominator, these examples channel through narrative figurative domains considered to be known intuitively to wit: personifications; iconic pars pro toto references to concentration camps; and metaphors for cancer in disease biographies
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