Selective attention and the auditory vertex potential. 2: Effects of signal intensity and masking noise

A randomized sequence of tone bursts was delivered to subjects at short inter-stimulus intervals with the tones originating from one of three spatially and frequency specific channels. The subject's task was to count the tones in one of the three channels at a time, ignoring the other two, and press a button after each tenth tone. In different conditions, tones were given at high and low intensities and with or without a background white noise to mask the tones. The N sub 1 component of the auditory vertex potential was found to be larger in response to attended channel tones in relation to unattended tones. This selective enhancement of N sub 1 was minimal for loud tones presented without noise and increased markedly for the lower tone intensity and in noise added conditions

Selective attention and the auditory vertex potential. 1: Effects of stimulus delivery rate

Enhancement of the auditory vertex potentials with selective attention to dichotically presented tone pips was found to be critically sensitive to the range of inter-stimulus intervals in use. Only at the shortest intervals was a clear-cut enhancement of the latency component to stimuli observed for the attended ear

Lower bounds for 1-, 2- and 3-dimensional on-line bin packing algorithms

In this paper we discuss lower bounds for the asymptotic worst case ratio of on-line algorithms for different kind of bin packing problems. Recently, Galambos and Frenk gave a simple proof of the 1.536 ... lower bound for the 1-dimensional bin packing problem. Following their ideas, we present a general technique that can be used to derive lower bounds for other bin packing problems as well. We apply this technique to prove new lower bounds for the 2-dimensional (1.802...) and 3-dimensional (1.974...) bin packing problem

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

Renormalization group study of the two-dimensional random transverse-field Ising model

The infinite disorder fixed point of the random transverse-field Ising model is expected to control the critical behavior of a large class of random quantum and stochastic systems having an order parameter with discrete symmetry. Here we study the model on the square lattice with a very efficient numerical implementation of the strong disorder renormalization group method, which makes us possible to treat finite samples of linear size up to $L=2048$. We have calculated sample dependent pseudo-critical points and studied their distribution, which is found to be characterized by the same shift and width exponent: $\nu=1.24(2)$. For different types of disorder the infinite disorder fixed point is shown to be characterized by the same set of critical exponents, for which we have obtained improved estimates: $x=0.982(15)$ and $\psi=0.48(2)$. We have also studied the scaling behavior of the magnetization in the vicinity of the critical point as well as dynamical scaling in the ordered and disordered Griffiths phases

Statistics of Lead Changes in Popularity-Driven Systems

We study statistical properties of the highest degree, or most popular, nodes in growing networks. We show that the number of lead changes increases logarithmically with network size N, independent of the details of the growth mechanism. The probability that the first node retains the lead approaches a finite constant for popularity-driven growth, and decays as N^{-phi}(ln N)^{-1/2}, with phi=0.08607..., for growth with no popularity bias.Comment: 4 pages, 4 figures, 2 column revtex format. Minor changes in response to referee comments. For publication in PR

Chemical fracture and distribution of extreme values

When a corrosive solution reaches the limits of a solid sample, a chemical fracture occurs. An analytical theory for the probability of this chemical fracture is proposed and confirmed by extensive numerical experiments on a two dimensional model. This theory follows from the general probability theory of extreme events given by Gumbel. The analytic law differs from the Weibull law commonly used to describe mechanical failures for brittle materials. However a three parameters fit with the Weibull law gives good results, confirming the empirical value of this kind of analysis.Comment: 7 pages, 5 figures, to appear in Europhysics Letter

Partially asymmetric exclusion models with quenched disorder

We consider the one-dimensional partially asymmetric exclusion process with random hopping rates, in which a fraction of particles (or sites) have a preferential jumping direction against the global drift. In this case the accumulated distance traveled by the particles, x, scales with the time, t, as x ~ t^{1/z}, with a dynamical exponent z > 0. Using extreme value statistics and an asymptotically exact strong disorder renormalization group method we analytically calculate, z_{pt}, for particlewise (pt) disorder, which is argued to be related to the dynamical exponent for sitewise (st) disorder as z_{st}=z_{pt}/2. In the symmetric situation with zero mean drift the particle diffusion is ultra-slow, logarithmic in time.Comment: 4 pages, 3 figure