Escape statistics for systems driven by dichotomous noise. I. General theory

Previous results on first-passage-time statistics for systems driven by dichotomous noise are extended in order to cover the escape from regions including fixed points of the stochastic flow. For such regions a treatment splitting the escape through one or the other boundary is required. The obtained escape probabilities and mean exit times are relevant for the complete characterization of stochastic systems undergoing bifurcations.     

Escape statistics for systems driven by dichotomous noise. II. The imperfect pitchfork bifurcation as a case study

We use the general results for the escape probabilities and mean exit times obtained in an accompanying paper to analyze in detail a nonlinear system presenting an imperfect (subcritical) pitchfork bifurcation. We redraw the bifurcation diagram to show the effect of the noise. To avoid spurious results we introduce the concept ofextinction level as the minimum possible value for the system, and discuss its effect on the bifurcation diagram.     

Effects of Adsorbed Polyaniline on Redox Processes on As(2)O(3) Surfaces

Polyaniline deposited on As(2)O(3) surface resulted in a new material, which was characterized by infrared spectoscopy, thermogravimetry, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and cyclic voltammetry. The mass percentage of polymer deposited on oxide surface is approximately 13%. The scanning electron microscopy images as well as the X-ray diffraction patterns provided conclusive evidence that the oxide surface is coated by the polymer. The cyclic voltammograms of the polyaniline adsorbed on As(2)O(3) surface showed that the adsorbate exerts remarkable effects on redox processes on this oxide. The pure oxide exhibited two oxidation/reduction peaks at 0.25/-0.06 and 0.47/-0.25 V attributed tentatively to the processes As(2)O(3)(s)+6H(+)+6e(-)=2As(s)+3H(2)O and As(s)+3H(+)+3e(-)=AsH(3)(g), respectively. The polyaniline-coated sample exhibited a better-defined voltammogram in which the first oxidation peak of the oxide had its intensity increased about four times. Copyright 2000 Academic Press.