1,074 research outputs found
On hemispheric differences in evoked potentials to speech stimuli
Confirmation is provided for the belief that evoked potentials may reflect differences in hemispheric functioning that are marginal at best. Subjects were right-handed and audiologically normal men and women, and responses were recorded using standard EEG techniques. Subjects were instructed to listen for the targets while laying in a darkened sound booth. Different stimuli, speech and tone signals, were used. Speech sounds were shown to evoke a response pattern that resembles that to tone or clicks. Analysis of variances on peak amplitude and latency measures showed no significant differences between hemispheres, however, a Wilcoxon test showed significant differences in hemispheres for certain target tasks
Universal Statistics of the Critical Depinning Force of Elastic Systems in Random Media
We study the rescaled probability distribution of the critical depinning
force of an elastic system in a random medium. We put in evidence the
underlying connection between the critical properties of the depinning
transition and the extreme value statistics of correlated variables. The
distribution is Gaussian for all periodic systems, while in the case of random
manifolds there exists a family of universal functions ranging from the
Gaussian to the Gumbel distribution. Both of these scenarios are a priori
experimentally accessible in finite, macroscopic, disordered elastic systems.Comment: 4 pages, 4 figure
Progressive Probabilistic Hough Transform for line detection
We present a novel Hough Transform algorithm referred to as Progressive Probabilistic Hough Transform (PPHT). Unlike the Probabilistic HT where Standard HT is performed on a pre-selected fraction of input points, PPHT minimises the amount of computation needed to detect lines by exploiting the difference an the fraction of votes needed to detect reliably lines with different numbers of supporting points. The fraction of points used for voting need not be specified ad hoc or using a priori knowledge, as in the probabilistic HT; it is a function of the inherent complexity of the input data. The algorithm is ideally suited for real-time applications with a fixed amount of available processing time, since voting and line detection is interleaved. The most salient features are likely to be detected first. Experiments show that in many circumstances PPHT has advantages over the Standard HT
Universal distribution of threshold forces at the depinning transition
We study the distribution of threshold forces at the depinning transition for
an elastic system of finite size, driven by an external force in a disordered
medium at zero temperature. Using the functional renormalization group (FRG)
technique, we compute the distribution of pinning forces in the quasi-static
limit. This distribution is universal up to two parameters, the average
critical force, and its width. We discuss possible definitions for threshold
forces in finite-size samples. We show how our results compare to the
distribution of the latter computed recently within a numerical simulation of
the so-called critical configuration.Comment: 12 pages, 7 figures, revtex
Psychological models of sporting injury: Janos Selye revisited
A recent model, the Cumulative Stress and Training Continuum Model, emphasizes the complex interactions between psychological, social and physical factors. Such an approach helps to explain how apparently non-significant factors can exert disproportionate effects on injury risk in high stress states. This presentation synthesises psychological models of injury into the same framework and explains some of the processes leading to sport injuries and syndromes characterised by unexplained underperformance. Injury in sport is something of an occupational hazard, with a reported annual incidence among athletes of 30% – 70%. Many injuries are due to human error and/or overload of performance capacities, and are therefore preventable. Most of the models draw directly or indirectly on Selye’s General Adaptation Theory, although the lax use of terminology frequently obscures this. The unique contribution of the present synthesis is that, being inclusive and holistic, it provides a unifying paradigm for research and application. To address the high incidence of injuries among athletes at the Queensland Academy of Sport, a Cognitive-Behavioural Stress Management program has been developed and is being tested. The program teaches stress management skills, including breathing optimisation, muscular relaxation, cognitive restructuring, plus recovery-related and performance-related imagery. The program is introduced over a two-week period and is also provided on MP3 players for daily utilisation. Athletes are monitored over a 10-week period using salivary cortisol and psychometric measures of perceived stress, life events, mood, and stress recovery. Injury characteristics and time lost from planned training is recorded. Pilot results will be presented
Probing the tails of the ground state energy distribution for the directed polymer in a random medium of dimension via a Monte-Carlo procedure in the disorder
In order to probe with high precision the tails of the ground-state energy
distribution of disordered spin systems, K\"orner, Katzgraber and Hartmann
\cite{Ko_Ka_Ha} have recently proposed an importance-sampling Monte-Carlo
Markov chain in the disorder. In this paper, we combine their Monte-Carlo
procedure in the disorder with exact transfer matrix calculations in each
sample to measure the negative tail of ground state energy distribution
for the directed polymer in a random medium of dimension .
In , we check the validity of the algorithm by a direct comparison with
the exact result, namely the Tracy-Widom distribution. In dimensions and
, we measure the negative tail up to ten standard deviations, which
correspond to probabilities of order . Our results are
in agreement with Zhang's argument, stating that the negative tail exponent
of the asymptotic behavior
as is directly related to the fluctuation exponent
(which governs the fluctuations
of the ground state energy for polymers of length ) via the simple
formula . Along the paper, we comment on the
similarities and differences with spin-glasses.Comment: 13 pages, 16 figure
Survival Probability for Open Spherical Billiards
We study the survival probability for long times in an open spherical
billiard, extending previous work on the circular billiard. We provide details
of calculations regarding two billiard configurations, specifically a sphere
with a circular hole and a sphere with a square hole. The constant terms of the
long-term survival probability expansions have been derived analytically. Terms
that vanish in the long time limit are investigated analytically and
numerically, leading to connections with the Riemann hypothesis
Anomalous diffusion in disordered multi-channel systems
We study diffusion of a particle in a system composed of K parallel channels,
where the transition rates within the channels are quenched random variables
whereas the inter-channel transition rate v is homogeneous. A variant of the
strong disorder renormalization group method and Monte Carlo simulations are
used. Generally, we observe anomalous diffusion, where the average distance
travelled by the particle, []_{av}, has a power-law time-dependence
[]_{av} ~ t^{\mu_K(v)}, with a diffusion exponent 0 \le \mu_K(v) \le 1.
In the presence of left-right symmetry of the distribution of random rates, the
recurrent point of the multi-channel system is independent of K, and the
diffusion exponent is found to increase with K and decrease with v. In the
absence of this symmetry, the recurrent point may be shifted with K and the
current can be reversed by varying the lane change rate v.Comment: 16 pages, 7 figure
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