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

Irreversibility on the Level of Single-Electron Tunneling

We present a low-temperature experimental test of the fluctuation theorem for electron transport through a double quantum dot. The rare entropy-consuming system trajectories are detected in the form of single charges flowing against the source-drain bias by using time-resolved charge detection with a quantum point contact. We find that these trajectories appear with a frequency that agrees with the theoretical predictions even under strong nonequilibrium conditions, when the finite bandwidth of the charge detection is taken into account

Gating of high-mobility two-dimensional electron gases in GaAs/AlGaAs heterostructures

We investigate high-mobility two-dimensional electron gases in AlGaAs heterostructures by employing Schottky-gate-dependent measurements of the samples' electron density and mobility. Surprisingly, we find that two different sample configurations can be set in situ with mobilities diering by a factor of more than two in a wide range of densities. This observation is discussed in view of charge redistributions between the doping layers and is relevant for the design of future gateable high-mobility electron gases

"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

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

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

Pattern formation and localization in the forced-damped FPU lattice

We study spatial pattern formation and energy localization in the dynamics of an anharmonic chain with quadratic and quartic intersite potential subject to an optical, sinusoidally oscillating field and a weak damping. The zone-boundary mode is stable and locked to the driving field below a critical forcing that we determine analytically using an approximate model which describes mode interactions. Above such a forcing, a standing modulated wave forms for driving frequencies below the band-edge, while a ``multibreather'' state develops at higher frequencies. Of the former, we give an explicit approximate analytical expression which compares well with numerical data. At higher forcing space-time chaotic patterns are observed.Comment: submitted to Phys.Rev.