introducción a la termodinámica de los procesos irreversibles
Prigogine afirma que la cantidad de energía en desequilibrio, óptima para lograr formación de patrones ordenadas, nunca debe ser desmesurada, pues resulta contraproducente ya que en dichos casos el sistema suele no poder ser suficientemente disipativo.
Prigogine Ilya: INTRODUCTION TO THERMODYNAMICS OF IRREVERSIBLE
PROCESSES (Interscience Publishers, 1961)
Prigogine introduced the minimum entropy principle (stable near-
equilibrium dissipative systems minimize their rate of entropy
production) to characterize living organisms.
Simple
dissipative systems ...predictably move to simple minimised states. But the
dynamical systems of animal behaviour...come to ...a detailed balance at many
and varied points....To search behaviour for explanations armed only with
optimality is not an optimum strategy for understanding." (p.221)
The form of expression this self-organization takes is not predictable in advance because the very process of self-organization is by catastrophic (in the catastrophe theory sense) change; it "flips" into new regimes. As noted earlier, one of the characteristics of catastrophic change is that systems may have several possible behavioural pathways available at a catastrophe threshold. Which pathway is followed is largely an accident of circumstances. A reductionist world view, which cannot deal with the reality of emergence and self-organization in non-equilibrium systems, cannot offer sufficient explanation of how the world works.
Prigogine introduced the minimum entropy principle (stable near-
equilibrium dissipative systems minimize their rate of entropy
production) to characterize living organisms.
Simple
dissipative systems ...predictably move to simple minimised states. But the
dynamical systems of animal behaviour...come to ...a detailed balance at many
and varied points....To search behaviour for explanations armed only with
optimality is not an optimum strategy for understanding." (p.221)
The form of expression this self-organization takes is not predictable in advance because the very process of self-organization is by catastrophic (in the catastrophe theory sense) change; it "flips" into new regimes. As noted earlier, one of the characteristics of catastrophic change is that systems may have several possible behavioural pathways available at a catastrophe threshold. Which pathway is followed is largely an accident of circumstances. A reductionist world view, which cannot deal with the reality of emergence and self-organization in non-equilibrium systems, cannot offer sufficient explanation of how the world works.
The form of expression this self-organization takes is not predictable in advance because the very process of self-organization is by catastrophic (in the catastrophe theory sense) change; it "flips" into new regimes. As noted earlier, one of the characteristics of catastrophic change is that systems may have several possible behavioural pathways available at a catastrophe threshold. Which pathway is followed is largely an accident of circumstances. A reductionist world view, which cannot deal with the reality of emergence and self-organization in non-equilibrium systems, cannot offer sufficient explanation of how the world works.
An important observation about systems that exhibit self-organization is that they exist in a situation where they get enough energy, but not too much. If they do not get sufficient energy of high enough quality (beyond a minimum threshold level), organized structures cannot be supported and self-organization does not occur. If too much energy is supplied, chaos ensues in the system, as the energy overwhelms the dissipative ability of the organized structures and they fall apart. So self-organizing systems exist in a middle ground of enough, but not too much.
The global weather, wind and ocean circulation patterns are the result of the
difference in heating at the equator relative to the poles. The general
meteorological circulation of the earth, although affected by spatial, coriolis
and angular momentum effects, is driven by gradients and the global system's
attempt to dissipate them and come to local equilibrium. Paltridge (1979) has
suggested that the earth-atmosphere, climate system configures itself into a
state of maximum dissipation and that the global distribution of clouds,
temperature and horizontal energy flows are governed by thermodynamic
dissipative processes similar to those described above. We see that the
earth-climate system, as well as other dissipative systems, do not reach a
static equilibrium state because they are open thermodynamic systems constantly
receiving a supply of external energy (i.e. from the sun), which drives them
and maintains them in a nonequilibrium organized state.
So far we have focused our discussion on simple physical systems and how
thermodynamic gradients drive self-organization. The literature is replete
with similar phenomena in dynamic chemical systems. Prigogine and the
Brussel's School and others have documented the thermodynamics and behavior of
these chemical reaction systems. Chemical gradients result in dissipative
autocatalytic reactions, examples of which are found in simple inorganic
chemical systems, in protein synthesis reactions, or phosphorylation,
polymerization and hydrolytic autocatalytic reactions.
Autocatalytic reactions systems are a form of positive feedback where the
activity of the system or reaction augments itself in the form of
self-reinforcing reactions. Consider a reaction where A catalyzes the
formation of B and B accelerates the formation of A; the overall set of
reactions is an autocatalytic or positive feedback cycle. Ulanowicz (1986)
notes that in autocatalysis, the activity of any element in the cycle engenders
greater activity in all the other elements, thus stimulating the aggregate
activity of the whole cycle. Such self-reinforcing catalytic activity is
self-organizing and is an important way of increasing the dissipative capacity
of the system. Cycling and autocatalysis is a fundamental process in
nonequilibrium systems.
The notion of dissipative systems as gradient dissipators holds for
nonequilibrium physical and chemical systems and describes the processes of
emergence and development of complex systems. Not only are the processes of
these dissipative systems consistent with the restated second law, it should
be expected that they will exist wherever there are gradients.
29.mar.2000
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Autocatalytic reactions systems are a form of positive feedback where the
activity of the system or reaction augments itself in the form of
self-reinforcing reactions. Consider a reaction where A catalyzes the
formation of B and B accelerates the formation of A; the overall set of
reactions is an autocatalytic or positive feedback cycle. Ulanowicz (1986)
notes that in autocatalysis, the activity of any element in the cycle engenders
greater activity in all the other elements, thus stimulating the aggregate
activity of the whole cycle. Such self-reinforcing catalytic activity is
self-organizing and is an important way of increasing the dissipative capacity
of the system. Cycling and autocatalysis is a fundamental process in
nonequilibrium systems.
The notion of dissipative systems as gradient dissipators holds for
nonequilibrium physical and chemical systems and describes the processes of
emergence and development of complex systems. Not only are the processes of
these dissipative systems consistent with the restated second law, it should
be expected that they will exist wherever there are gradients.
29.mar.2000
Pulsar tecla de vuelta
Glosario de Carlos von der Becke.
29.mar.2000
Pulsar tecla de vuelta
Glosario de Carlos von der Becke.
29.mar.2000
Pulsar tecla de vuelta
Glosario de Carlos von der Becke.