Connections of activated hopping processes with the breakdown of the Stokes-Einstein relation and with aspects of dynamical heterogeneities

We develop a new extended version of the mode-coupling theory (MCT) for glass transition, which incorporates activated hopping processes via the dynamical theory originally formulated to describe diffusion-jump processes in crystals. The dynamical-theory approach adapted here to glass-forming liquids treats hopping as arising from vibrational fluctuations in quasi-arrested state where particles are trapped inside their cages, and the hopping rate is formulated in terms of the Debye-Waller factors characterizing the structure of the quasi-arrested state. The resulting expression for the hopping rate takes an activated form, and the barrier height for the hopping is ``self-generated'' in the sense that it is present only in those states where the dynamics exhibits a well defined plateau. It is discussed how such a hopping rate can be incorporated into MCT so that the sharp nonergodic transition predicted by the idealized version of the theory is replaced by a rapid but smooth crossover. We then show that the developed theory accounts for the breakdown of the Stokes-Einstein relation observed in a variety of fragile glass formers. It is also demonstrated that characteristic features of dynamical heterogeneities revealed by recent computer simulations are reproduced by the theory. More specifically, a substantial increase of the non-Gaussian parameter, double-peak structure in the probability distribution of particle displacements, and the presence of a growing dynamic length scale are predicted by the extended MCT developed here, which the idealized version of the theory failed to reproduce. These results of the theory are demonstrated for a model of the Lennard-Jones system, and are compared with related computer-simulation results and experimental data.Comment: 13 pages, 5 figure

Soziophysiologie: Grundlegende Prozesse der Emphathiefähigkeit

Diese Übersicht beschreibt Prozesse, welche dem komplexen Phänomen der menschlichen Empathie zugrunde liegen. Automatische, reflexartige Prozesse wie physiologische Ansteckung und Handlungsspiegelung werden über das Spiegelneuronensystem vermittelt und stellen eine Grundlage für die Weiterverarbeitung sozialer Signale dar. Im sozialen Kontakt entsteht damit auf der körperlichen Ebene eine direkte Verbindung zweier Individuen. Diese Verbindung besteht auf der gleichzeitigen Aktivierung gemeinsamer motorischer Repräsentationen. Auf implizite Art werden die so geteilten Eindrücke durch individuelle Assoziationen im limbischen und vegetativen System zu einem affektiven Zustand. Die hier beschriebenen Prozesse werden Soziophysiologie genannt. Durch kontrolliert-reflektierende, selbst-referentielle, d.h. auf die persönliche Innenwelt gerichtete (Weiter-)Verarbeitung solcher sozialen Signale, entstehen schliesslich explizite Repräsentationen des Bewusstseins von Anderen. Diese höhergradigen Prozesse nennen wir soziale Kognition. Durch das Zusammenspiel der verschiedenen Prozesse entsteht das Phänomen der menschlichen Empathiefähigkeit

"Selbstscreen-Prodrom" - ein Selbstbeurteilungsinstrument zur Früherkennung von psychischen Erkrankungen und Psychosen

OBJECTIVE: In the past years, the significance of early detection of psychoses has been increasingly recognized. Screening for the onset of disorders should focus on individuals seeking treatment in an outpatient setting and should preferably operate stepwise. Within a prospective study for the early detection of psychoses (FePsy = Früh Erkennung von PSYchosen) the self-rating instrument "Self-screen Prodrome" was developed to differentiate between healthy individuals, individuals with psychosis or an at-risk mental state for psychosis and patients with other ICD-10 diagnoses. METHOD: The "Self-screen Prodrome" was developed by taking established risk factors and early signs of disease into account. In particular, prodromes and pre-psychotic symptoms were captured. A total score and a subscale were analyzed with regard to validity and reliability. RESULTS: The total score "Self-screen Prodrome" distinguished between outpatients with a mental disorder and healthy individuals (Cut-off < or = 6; sensitivity: 85 % specificity: 91 %). Additionally the subscale distinguished between psychosis-(risk)-individuals and outpatients with other ICD-10 psychiatric diagnoses (Cut-off < or = 2; sensitivity: 85 % specificity: 39 %). CONCLUSION: The "Self-screen Prodrome" is a useful instrument that a) separates mentally ill patients from healthy individuals and b) filters individuals with a risk of developing psychoses from patients with other ICD-10 diagnoses for further screening. The next step in the early detection of psychoses for identified individuals should be a detailed psychiatric exploration by experts

Magnetic Miniband Structure and Quantum Oscillations in Lateral Semiconductor Superlattices

We present fully quantum-mechanical magnetotransport calculations for short-period lateral superlattices with one-dimensional electrostatic modulation. A non-perturbative treatment of both magnetic field and modulation potential proves to be necessary to reproduce novel quantum oscillations in the magnetoresistance found in recent experiments in the resistance component parallel to the modulation potential. In addition, we predict oscillations of opposite phase in the component perpendicular to the modulation not yet observed experimentally. We show that the new oscillations originate from the magnetic miniband structure in the regime of overlapping minibands.Comment: 6 pages with 4 figure

Local prediction of turning points of oscillating time series

For oscillating time series, the prediction is often focused on the turning points. In order to predict the turning point magnitudes and times it is proposed to form the state space reconstruction only from the turning points and modify the local (nearest neighbor) model accordingly. The model on turning points gives optimal prediction at a lower dimensional state space than the optimal local model applied directly on the oscillating time series and is thus computationally more efficient. Monte Carlo simulations on different oscillating nonlinear systems showed that it gives better predictions of turning points and this is confirmed also for the time series of annual sunspots and total stress in a plastic deformation experiment.Comment: 7 pages, 5 figures, 2 tables, submitted to PR

Peeling Bifurcations of Toroidal Chaotic Attractors

Chaotic attractors with toroidal topology (van der Pol attractor) have counterparts with symmetry that exhibit unfamiliar phenomena. We investigate double covers of toroidal attractors, discuss changes in their morphology under correlated peeling bifurcations, describe their topological structures and the changes undergone as a symmetry axis crosses the original attractor, and indicate how the symbol name of a trajectory in the original lifts to one in the cover. Covering orbits are described using a powerful synthesis of kneading theory with refinements of the circle map. These methods are applied to a simple version of the van der Pol oscillator.Comment: 7 pages, 14 figures, accepted to Physical Review

Occupation, social support and quality of life in persons with schizophrenic or affective disorders

Abstract. : Background: : Most people suffering from severe mental illness (SMI) lack paid employment. This study investigates the relationship between work status and objective as well as subjective quality of life (QoL) in people with SMI. Methods: : The sample consists of 261 subjects (102 women, 159 men) aged 35 (men) and 38 (women) years on average, of whom 158 suffer from a schizophrenic disorder (ICD-10: F2) and 103 were diagnosed as having an affective disorder (ICD-10: F3). Subjective QoL was assessed with the WHOQOL-BREF scale. Results: : Subjects with an occupation in general have a larger social network at their disposal and receive more social support. With regard to income, few (12%) of the subjects with a job on the open labour market live below the poverty level, but many (28-38%) of those engaged in sheltered or other work-like activities do. Occupation ameliorates satisfaction with life domains referring to social integration (social relationships, environment), whereas the individual's well-being (psychological, physical) is hardly affected. Social support is an important mediator of the relationship between occupation and subjective QoL. Income is weakly and negatively related to subjective QoL. Conclusion: : Supportive relationships to colleagues at the workplace mainly explain the better subjective QoL of SMI people with an occupation.When designing specific employment possibilities for people with SMI, we should take notice of the social support dimension at the workplace. Mentally ill people have a substantial poverty risk, even when they are working. In particular, payment for sheltered work should be ameliorate

Network synchronization of groups

In this paper we study synchronized motions in complex networks in which there are distinct groups of nodes where the dynamical systems on each node within a group are the same but are different for nodes in different groups. Both continuous time and discrete time systems are considered. We initially focus on the case where two groups are present and the network has bipartite topology (i.e., links exist between nodes in different groups but not between nodes in the same group). We also show that group synchronous motions are compatible with more general network topologies, where there are also connections within the groups