168 research outputs found
Transient spatiotemporal chaos in the complex Ginzburg-Landau equation on long domains
Numerical simulations of the complex Ginzburg-Landau equation in one spatial dimension on periodic domains with sufficiently large spatial period reveal persistent chaotic dynamics in large parts of parameter space that extend into the Benjamin-Feir stable regime. This situation changes when nonperiodic boundary conditions are imposed, and in the Benjamin-Feir stable regime chaos takes the form of a long-lived transient decaying to a spatially uniform oscillatory state. The lifetime of the transient has Poisson statistics and no domain length is found sufficient for persistent chaos
Stability of Oscillating Hexagons in Rotating Convection
Breaking the chiral symmetry, rotation induces a secondary Hopf bifurcation
in weakly nonlinear hexagon patterns which gives rise to oscillating hexagons.
We study the stability of the oscillating hexagons using three coupled
Ginzburg-Landau equations. Close to the bifurcation point we derive reduced
equations for the amplitude of the oscillation, coupled to the phase of the
underlying hexagons. Within these equation we identify two types of long-wave
instabilities and study the ensuing dynamics using numerical simulations of the
three coupled Ginzburg-Landau equations.Comment: 25 pages, 7 figure
Does a Theoretical Estimation of the Dust Size Distribution at Emission Suggest More Bioavailable Iron Deposition?
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95443/1/grl28895.pd
Double-Blind, Randomized, Comparative Study of Meditoxin® Versus Botox® in the Treatment of Essential Blepharospasm
PURPOSE: To compare the efficacies and safeties of Meditoxin (Medy-Tox, Korea) and Botox in the treatment of essential blepharospasm.
METHODS: We performed a double-blind, randomized, comparative trial comparing Meditoxin and Botox for treatment of blepharospasm in 60 patients from the intention-to-treat (ITT) population and 52 patients from the per-protocol (PP) population. We analyzed the improvements in severity of spasm (SS) at four weeks post-injection as a primary efficacy outcome. Changes in eyelid closing force (CF) and functional visual status (FVS) after injection were analyzed for secondary efficacy outcomes, and adverse effects were demonstrated for the safety evaluation.
RESULTS: Improvement in SS was noted in 90.3% of the Meditoxin group and 86.2% of the Botox group. There were no significant differences between treatment groups in the changes of CF and FVS post-injection (p>0.05). Since the lower limit of the 95% confidence interval (-1.76% for ITT, -1.64% for PP) was over the -15% threshold, we determined that Meditoxin was not inferior to Botox in either the ITT or PP populations. Adverse effects developed in 16.1% of the Meditoxin group and 27.6% of the Botox group, but no serious adverse events were found in either group.
CONCLUSIONS: Meditoxin and Botox were comparable in efficacy and safety in the treatment of essential blepharospasmope
The effect of directional social cues on saccadic eye movements in Parkinson’s disease
There is growing interest in how social processes and behaviour might be affected in Parkinson’s disease. A task which has been widely used to assess how people orient attention in response to social cues is the spatial cueing task. Socially relevant directional cues, such as a picture of someone gazing or pointing to the left or the right have been shown to cause orienting of visual attention in the cued direction. The basal ganglia may play a role in responding to such directional cues, but no studies to date have examined whether similar social cueing effects are seen in people with Parkinson’s disease. In this study, patients and healthy controls completed a prosaccade (Experiment 1) and an antisaccade (Experiment 2) task in which the target was preceded by arrow, eye gaze or pointing finger cues. Patients showed increased errors and response times for antisaccades but not prosaccades. Healthy participants made most anticipatory errors on pointing finger cue trials, but Parkinson's patients were equally affected by arrow, eye gaze and pointing cues. It is concluded that Parkinson's patients have a reduced ability to suppress responding to directional cues, but this effect is not specific to social cues
Whirling Hexagons and Defect Chaos in Hexagonal Non-Boussinesq Convection
We study hexagon patterns in non-Boussinesq convection of a thin rotating
layer of water. For realistic parameters and boundary conditions we identify
various linear instabilities of the pattern. We focus on the dynamics arising
from an oscillatory side-band instability that leads to a spatially disordered
chaotic state characterized by oscillating (whirling) hexagons. Using
triangulation we obtain the distribution functions for the number of pentagonal
and heptagonal convection cells. In contrast to the results found for defect
chaos in the complex Ginzburg-Landau equation and in inclined-layer convection,
the distribution functions can show deviations from a squared Poisson
distribution that suggest non-trivial correlations between the defects.Comment: 4 mpg-movies are available at
http://www.esam.northwestern.edu/~riecke/lit/lit.html submitted to New J.
Physic
Mean flow and spiral defect chaos in Rayleigh-Benard convection
We describe a numerical procedure to construct a modified velocity field that
does not have any mean flow. Using this procedure, we present two results.
Firstly, we show that, in the absence of mean flow, spiral defect chaos
collapses to a stationary pattern comprising textures of stripes with angular
bends. The quenched patterns are characterized by mean wavenumbers that
approach those uniquely selected by focus-type singularities, which, in the
absence of mean flow, lie at the zig-zag instability boundary. The quenched
patterns also have larger correlation lengths and are comprised of rolls with
less curvature. Secondly, we describe how mean flow can contribute to the
commonly observed phenomenon of rolls terminating perpendicularly into lateral
walls. We show that, in the absence of mean flow, rolls begin to terminate into
lateral walls at an oblique angle. This obliqueness increases with Rayleigh
number.Comment: 14 pages, 19 figure
Enhancement of the emission of mineral dust aerosols by electric forces
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95661/1/grl21575.pd
Simulations of convectively-driven density currents in the Atlas region using a regional model: Impacts on dust emission and sensitivity to horizontal resolution and convection schemes
During the SAMUM field campaign in southern Morocco in May and June 2006 density currents generated by evaporative cooling after convective precipitation were frequently observed at the Sahara side of the Atlas Mountain chain. The associated strong surface cold-air outflow during such events has been observed to lead to dust mobilization in the foothills. Here a regional model system is used to simulate a density current case on 3 June 2006 and the subsequent dust emission. The model studies are performed with different parameterization schemes for convection, and with different horizontal model grid resolutions to examine to which extent the model system can be used for reproducing dust emissions in this region. The effect of increasing the horizontal model grid resolution from 14 km to 2.8 km on the strength on the density currents and thus on dust emission is smaller than the differences due to different convection parameterization schemes in this case study. While the results in reproducing the observed density current at the Atlas Mountain varied with different convection parameterizations, the most realistic representation of the density current is obtained at 2.8 km grid resolution at which no parameterization of deep convection is needed
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