1,721,057 research outputs found
Three-dimensional searching for recurrent structural motifs in databa- ses of protein structures.
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Chemical Waves
No full textIn our paper we try to describe the basic concepts
of chemical waves and spatial pattern formation
in a simple way. We pay particular attention to self-organisation
phenomena in extended excitable systems.
These result in the appearance of travelling waves,
spiral waves, target patterns, Turing structures or more
complicated structures called scroll waves, which are
three-dimensional systems. We describe the most
famous oscillating reaction, the Belousov–Zhabotinsky
(BZ) reaction, in greater detail. This is because it is of
great interest in both physical chemistry and in studies
on the evolution and sustenance of self-organising biological
systems
On chaotic graphs: A different approach for characterizing aperiodic dynamics
No full textFractal worlds with limited connectivity are the topological result of growing graphs from
chaotic series. We show how this model presents original characteristics which cannot be
detected by means of the standard network descriptors. In detail, intrinsic inaccessibility
to the fully connected configuration is demonstrated to be a universal feature associated
with this family of graphs and strictly related to the fractality of a specific ``chaotic source''.
Here we discuss the potential of our model to be a generator of fractal graphs and also a
self-consistent tool for differentiating chaotic dynamics from stochastic processes
Butterfly effect in a chemical oscillator
No full textThe strong sensitivity of aperiodic dynamics to initial conditions is one of the fingerprinting features of chaotic systems. While this dependence can be directly verified by means of numerical approaches, it is quite elusive and difficult to be isolated in real experimental systems. In this paper, we discuss a didactic and self-consistent method to show the divergent behaviour between two infinitesimally different solutions of the famous Belousov–Zhabotinsky oscillator simultaneously undergoing a transition to a chaotic regime. Experimental data are also used to give an intuitive visualization of the essential meaning of a Lyapunov exponent, which allows for a more quantitative characterization of the chaotic transient
Exergy versus emergy flow in ecosystems: Is there an order in maximazationion?
No full textFrom ecosystems theory, orientors have been derived to give a holistic view of the trend of development of ecosystems
themselves. Several principles of maximization, mainly derived from Lotka’s maximum power, are connected with these
orientors. Other authors (Jørgensen, Patten and coworkers, for example) have shown that among these orientors there are many
common aspects, both form a quantitative terms and in principle. We show how H.T. Odum’s maximum empower and
Jørgensen’s maximum exergy principles can be both valid from a practical viewpoint. As suggested by a simple experiment there
can be a time order: first the maximization of empower and then the maximization of exergy. This time sequence is also
consistent with a maximization trend in the ratio of exergy to empower
Exploring Gas Evolution Oscillators: Mechanisms and Applications
Full text linkWe review an iconic class of chemical oscillators driven by phase transition instabilities, namely Gas Evolution Oscillators (GEOs). These systems show oscillatory dynamics in the delivery of gas sustained simple reactions yielding gaseous products in a liquid mixture, due to nucleation and supersaturation phenomena. After presenting the main features and properties of these systems, we deepen the underlying mechanism through a unified picture of the various models that have been proposed to describe this kind of oscillations. We finally discuss a concrete example of how such instabilities can impact chemical processes with applied relevance
Recurrence quantifcation analysis of spatio-temporal chaotic transient in a closed unstirred Belousov-Zhabotinsky reaction
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