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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 3568-3581 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The global interaction between the spatial average of the autocatalytic variable in a reactive (catalytic, electrochemical, gel) medium and a surrounding mixed fluid in a continuously fed vessel may induce a rich structure of spatiotemporal patterns that would not exist otherwise. Patterns may form when the local kinetics are either excitable, oscillatory, or bistable and the reaction rate ascends with reactant concentration. Thus, a local change in the surface reaction rate may affect the reactant concentration in the surrounding well-mixed vessel, so that it arrests moving fronts on the surface. External control of the average temperature (or rate) of a catalytic ribbon by electrical heating is another form of interaction between a spatial average of a local oscillator and a space-independent variable that induces pattern formation. We study various patterns and bifurcations that can develop in a ring or a ribbon due to global interaction using a simple cubic kinetic expression. The predominant pattern on a catalytic ring is a rotating pulse. Other patterns, such as antiphase oscillations and crossing pulses, similar to those found previously on a controlled catalytic ribbon, may coexist for a sufficiently strong interaction. Several of the transitions between regions with qualitatively different patterns are via global bifurcation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4688-4696 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Global interaction refers to a nonlocal mode of information exchange (coupling) between the local states on a surface. Global interaction may produce a very rich class of spatiotemporal patterns. A system has an inversion symmetry if both φ(x,y,λ) and φ(−x,−y,−λ) are solutions. Here x and y are the two dynamic variables of the system and λ is a global control variable. The presence of inversion symmetry sharpens the distinction among the various motions and leads to bifurcation scenarios which have not been found in its absence. A heteroclinic connection between two inversion symmetric saddle foci leads to many shifts between back-and-forth and unidirectional pulse branches of solutions. The scenario by which the periodic orbits gain and lose stability via period-increasing or saddle-node bifurcations is similar to one predicted by Glendining for a system described by three ordinary differential equations having inversion symmetry. The dynamic features are robust and rather insensitive to the functional form of the kinetic expression.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 9573-9581 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This work analyzes spatiotemporal patterns that exist in a one-dimensional isothermal fixed-bed reactor with bistable or oscillatory kinetics. The model accounts for an oscillator with a diffusing activator and immobile inhibitor. Patterns emerge due to self-induced gradients of the fluid phase and the patterns are different from those reported for uniform excitable or oscillatory media. Pattern selection is determined by the phase planes spanned by the reactor and the ratio of the two slowest time scales: front residence time and period of oscillations. The main sustained spatiotemporal patterns in the bed were classified as parallel bands, oscillatory fronts (or sticking fronts), and split bands. Parallel bands represent a periodic sequence of pulses and appear when the bed spans the oscillatory domain. Split-band patterns appear when new fronts are generated inside the reactor but they cannot propagate due to refractory trail of the previous pulse. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 10612-10619 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the process of pattern selection in a catalytic ribbon or disk subject to global interaction. The diffusion-reaction system, xt−Δx=f(x,y)−〈f(x,y)〉; yt=ε(−αx−y), with a quintic source function f(x,y)=−x(x2−1)(x2−a2)+y, qualitatively describes the behavior of catalytic or electrochemical oscillations subject to control or gas-phase mixing and the kinetics describes a system with two simultaneous or consecutive reactions. This model shows a richer class of solutions than the extensively studied one with a cubic source function (f=−x3+x+y) since f(x)=0 is tristable and for a wide separation of time scales the system admits, without global interaction, coexistence of a stable and oscillatory states. Also the reaction-diffusion equation with a quintic source may admit one large and two small fronts and their domains of existence and stability are mapped. Under global interaction the system exhibits all the patterns unveiled with the "cubic kinetics," along with multifront patterns and new patterns at the border of instability of the large front. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 289-298 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A novel problem, of diffusion resistance in porous particles that catalyze kinetically unstable reactions, is introduced, analyzed and simulated in order to unveil the possible spatiotemporal patterns in the direction perpendicular to the surface. Pore-diffusion resistance is a core problem in chemical reaction engineering. The present problem is described mathematically by three variables: a very-fast and long-ranged pore-phase concentration, a fast and diffusing autocatalytic surface species (activator) and a slow and localized surface activity. Unlike homogeneous models of pore disfussion resistance, in which instabilities emerge only with strong diffusion resistance, the present model exhibits oscillatory or excitable behavior even in the absence of that resistance. Patterns are generated by self-imposed concentration gradients. A detailed kinetic model of a simple but reasonable reaction mechanism is analyzed, but the qualitative results are expected to hold in other similar kinetics. The catalyst particle is a three-dimensional system and it may exhibit symmetry-breaking in the directions parallel to the surface due to interaction between the fast diffusion of a fluid-phase reactant and the slow solid-phase diffusivity of the activator. A thin catalyst can be described then by a one-dimensional reaction-diffusion system that admits patterned solutions. We point out this possibility, but refer to another work that investigates such patterns in the general framework of patterns due to interaction of surface reaction and diffusion with gas-phase diffusion and convection. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 8165-8174 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A condensed model that captures the main features of high- or low-pressure catalytic oscillators is used to simulate spatiotemporal patterns in a catalytic disk or square. This model includes a single autocatalytic variable (activator), a slowly changing and localized inhibitor, and a very fast and highly diffusive variable that provides the long-range interaction. The extremely rich plethora of patterns is classified according to their symmetries, capitalizing on the inversion symmetry of the model. The simpler case of the bistable system (with no inhibitor) exhibits a very high sensitivity to initial conditions that leads to large multiplicity of stationary patterns. The effect of the parameter that defines the system stability (oscillatory, excitable, or bistable) is investigated, in the three variable model, either by using the same initial conditions for all simulations or, in an "experimental mode," by stepping up or down the parameter. Patterns on a disk may be classified as circular, like stationary or oscillatory or moving (inwards or outwards) target pattern, rotating patterns, like stationary or oscillatory or moving spiral waves, and other patterns. Successive bifurcations, with changing parameter, reduce the system to states with lower symmetries and to asymmetric or even chaotic motions. Motions on a square are similar to those on a disk and include target-like pattern, propagating pulses, and oscillating or breathing stationary pulses. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 94 (1990), S. 5889-5896 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 5727-5735 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 27 (1988), S. 1152-1157 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 26 (1987), S. 786-794 
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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