 2  Author
 Ariel Fernández, Oktay Sinanoglu  Requires cookie*   Title
 A Reactive System with Diffusive Transport Displaying Two Different SymmetryBreaking Dissipative Structures    Abstract
 An open reactive system is modelled by coupling the chemical kinetics to diffuse transport. This system operates far from the regime of linear irreversible thermodynamics. The kinetics correspond to a certain region in the parameter space of the Oregonator for which two symmetrybreakdowns occur: a) A periodic orbit contained in an unstable manifold of the phase space. This solution is invariant under timetranslations generated by a period. b) A spatial stationary dissipative structure. This solution is invariant under a subgroup of the space symmetry group. The initial time periodicity of the system is followed by a spatial pattern. The restriction to the center manifold in the phase space allows to reduce an infinitedimensional problem for the bifurcation of a semiflow to a finite dimensional system of ordinary differential equations. The ranges in the control concentrations for this dynamics is found in accord with the experimental values. We also demonstrate that if the vessel is stirred after the Turing pattern has emerged, the freezed wave is destroyed and the timeperiodic behavior is achieved again.   
Reference
 Z. Naturforsch. 40a, 611—618 (1985); received October 15 1984   
Published
 1985   
Keywords
 Bifurcation under a symmetry group, Center Manifold Theorem, Dissipative structure   
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3  Author
 Roland Zander, Michael Dittmann, GerhardM. Schneider  Requires cookie*   Title
 Dissipative Structures in Demixing Binary Liquid Systems    Abstract
 The demixing of a horizontal fluid layer of farcritical composition in the presence of a vertical temperature gradient can cause the formation of dissipative structures and thereby lead to a regular distribution of the precipitate. The occurrence of these convective structures is explained with the model of a RayleighBenard instability (RBI) which is driven by parallel gradients of temperature and concentration. The distribution of the precipitate is a synergetic effect of the macroscopic convective pattern and the local action of the Marangoni flow at the surfaces of the drops. If boundary conditions prohibit an RBI, the distribution of the precipitate also becomes inhomogeneous in course of time; however, in this case no regular pattern is observable and the inhomogeneities develop mainly due to the Marangoni convection near the surfaces of the larger drops that have settled at the boundary of the sample volume.   
Reference
 Z. Naturforsch. 45a, 1309—1316 (1990); received July 28 1990   
Published
 1990   
Keywords
 Fluid phase decomposition, Dissipative structures, Precipitate organization, RayleighBenard instability, Marangoni instability   
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