Numerical investigation of the effects of classical phase space structure on a quantum system with decoherence

We present a detailed numerical study of a chaotic classical system and its quantum counterpart. The system is a special case of a kicked rotor and for certain parameter values possesses cantori dividing chaotic regions of the classical phase space. We investigate the diffusion of particles through a cantorus. A quantum analysis confirms that the cantori act as barriers. We numerically estimate the classical phase space flux through the cantorus per kick and relate this quantity to the behavior of the quantum system. We introduce decoherence via environmental interactions with the quantum system and observe the subsequent increase in the transport of quantum particles through the boundary.     

Robust Optimal Stopping-Time Control for Nonlinear Systems

Abstract. We formulate a robust optimal stopping-time problem for a state-space system and give the connection between various notions of lower value function for the associated games (and storage function for the associated dissipative system) with solutions of the appropriate variational inequality (VI) (the analogue of the Hamilton—Jacobi—Bellman—Isaacs equation for this setting). We show that the stopping-time rule can be obtained by solving the VI in the viscosity sense and a positive definite supersolution of the VI can be used for stability analysis.     

Mikro-Elementaranalyse

Ohne Zusammenfassung     

PH-Bestimmungsmethoden

Ohne Zusammenfassung     

Eine objektive Untersuchung der A11ison schen magneto-optischen Analysenmethode

Ohne Zusammenfassung     

Melanin‐Containing Films: Growth from Dopamine Solutions versus Layer‐by‐Layer Deposition

Films formed by oxidation of dopamine are of interest for functionalisation of solid–liquid interfaces owing to their versatility. However, the ability to modulate the properties of such films, for example, permeability to ionic species and the absorption coefficient, is urgently needed. Indeed, melanin films produced by oxidation of dopamine absorb strongly over the whole UV/Vis part of the electromagnetic spectrum and are impermeable to anions even for a film thickness as low as a few nanometers. Herein we combine oxidation of dopamine to produce a solution containing dopamine–melanin particles and their alternating deposition with poly(diallyldimethylammonium chloride) to produce films which have nearly the same morphology as pure dopamine–melanin films but are less compact, more transparent and more permeable to ferrocyanide anions.     

Impedance spectroscopy measurements to study physio-chemical processes in lime-based composites

The conduction and dielectric behaviour of two different grades of natural hydraulic lime is presented over the frequency range 1 Hz–1 MHz, with measurements taken over the initial six months after gauging with water. Samples containing embedded electrodes were exposed to both a natural atmosphere (20°C and 65% relative humidity) and a natural atmosphere with a carbon dioxide concentration maintained at 400 ppm which was used to accelerate the carbonation process. A decrease in relative dielectric permittivity and rise in conductivity, with increasing frequency, was observed at all stages over the time-scale presented. When plotted in the complex plane, the impedance featured a bulk response comprising two depressed semicircles and a low frequency spur, the latter being associated with the electrode/sample interface. The complex impedance plot, together with the application of an equivalent circuit model, indicated a dual arc feature with carbonation and hydration contributing to bulk impedance response. This study demonstrates the applicability of electrical property measurements to monitor the combined processes of hydration and carbonation in this group of materials.