Defect-mediated turbulence in systems with local deterministic chaos

We show that defect-mediated turbulence can exist in media where the underlying local dynamics is deterministically chaotic. While many of the characteristics of defect-mediated turbulence, such as the exponential decay of correlations and a squared Poissonian distribution for the number of defects, are identical to those seen in oscillatory media, the fluctuations in the number of defects differ significantly. The power spectra suggest the existence of underlying correlations that lead to a different and non-universal scaling structure in chaotic media.Comment: 4 pages, 5 figure

From ballistic to Brownian vortex motion in complex oscillatory media

We show that the breaking of the rotation symmetry of spiral waves in two-dimensional complex (period-doubled or chaotic) oscillatory media by synchronization defect lines (SDL) is accompanied by an intrinsic drift of the pattern. Single vortex motion changes from ballistic flights at a well-defined angle from the SDL to Brownian-like diffusion when the turbulent character of the medium increases. It gives rise, in non-turbulent multi-spiral regimes, to a novel ``vortex liquid''.Comment: 5 pages, 4 figure

Spiral Waves in Chaotic Systems

Spiral waves are investigated in chemical systems whose underlying spatially-homogeneous dynamics is governed by a deterministic chaotic attractor. We show how the local periodic behavior in the vicinity of a spiral defect is transformed to chaotic dynamics far from the defect. The transformation occurs by a type of period doubling as the distance from the defect increases. The change in character of the dynamics is described in terms of the phase space flow on closed curves surrounding the defect.Comment: latex file with three postscript figures to appear in Physical review Letter

Sustainable Commuting @Work

Local governments are seeking effective ways to promote sustainable commuting for reducing energy consumption and improving commuters’ experience. They often use so-called “Workplace Travel Plans” as policy interventions to engage work organizations as active players, promoting sustainable commuting amongst their employees. However, it remains difficult to systematically engage work organizations and commuters in such efforts for a number of reasons, ranging from preferences to constraints that they have to deal with. We aim at providing commuters, work organizations, and public administrators with tools that facilitate this engagement. In this paper, we discuss the requirements for the design of technology supporting corresponding services for commuters and work organizations and we shortly illustrate the infrastructure that we are developing to provide such services

Release of trace contaminants during reoxidation of anoxic sediment slurries in oxic water

Polluted sediments are periodically subjected to resuspension processes resulting from natural events such as, for example, storm occurrences or extreme high waters as well as to anthropogenically induced activities such as dredging or shipping. The main part of the resuspended material is initially in an anoxic state and will be more or less quickly reoxidized in the oxic water column. The release of Cd, Cu, Zn, Pb together with the behaviour of the nutrients PO_4, SO_4, NO_3 and NH_4 during this reoxidation have been investigated in suspensions of anoxic sediment material in oxic river water under controlled pH conditions. Up to 5% of the particulate bound heavy metals were remobilized from the sediments. Different elements showed different behaviour which could be attributed to different microbial processes. The comparison of the release under different temperature conditions with poisoned suspensions illustrated the strong effect biological activity can have on the release. (orig.)Also published in: Arch. Hydrobiol. Spec. Issues Advanc. Limnol. (Feb 1996) v. 47. p. 295-305Available from TIB Hannover: RA 3251(96/E/16) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman