Re: concepts

DON MIKULECKY (MIKULECKY%VCUVAX.BITNET@letterbox.rl.ac.uk)
Fri, 29 Sep 1995 10:57:19 -0400


Don Mikulecky,MCV/VCU,Mikulecky@gems.vcu.edu writes in reply to Bruce:
I wrote,
>> The way we deal with notions of open and closed in thermodynamics is
>> quite clear and unambiguous. Three types of system are possible:
>> 1) isolated: enclosed by a "skin" through which matter and energy can
>> not pass: such systems must go to thermodynamic equilibrium.
>> 2) closed: enclosed by a skin through which energy may pass but matter
>> may not: these systems are therefore able to maintain steady states
>> away from equilibrium as long as matter can be recycled through cycles within
>> 3) open: both energy and matter can flow through. anything goes as
>> long as the first and second laws are obeyed.
>
Bruce wrote,

> Lt me get these clear. Thus nothing is isolated (except in
> the minds of physists, for purposes of approximation or the like).
> Almost no living matter is closed. Pretty well everything is open.

The notion of isolated system is one of the most widely used ideas in thermodyna
mics.
It is the basis for most of the formalism, since it mainly deals with equilibriu
m,
the end point of the dynamis after a system is isolated. Thermo thrives
on thought experiments which take a system of interest PLUS an
environment with which it can interact and isolating them. (Analogous to
limiting the universe of discourse when usin Venn diagrams in set theory).
By this ploy, conservationlaws become the dominant source if system
description through simple bookeeping.
In the 30's Onsager ventured into non-equilibrium events. His entire
effort was redone correctly by Leonardo Peusner when Network Thermodynamics
was formulated.
Prigogine , in parallel with Kedem and Katchalsky, moved non-equilibrium
thermodynamics forward into biology. Then the openness of a steady state
system and its analogy with homeostasis in physiology became widely accepted.
Prigogine and Glansdorf tried to marry dissipative and non-dissipative
processes, but basically failed. Katchalsky, Oster, and Perelson
succeded as did Peusner. The last huge step in the development of
thermodynamic reasoning was network thermodynamics. It applies to a
great number of the open systems of interest to us and has provided thoeretical
breakthroughs of great importance, including Telligen's theorem and
a metric for thermodynamics.[REF: "Applications of network thermodynamics
to problems in biomedical engineering" by Don Mikulecky, NYU Press, 1993].

>
> Also you did not mention information which may pass without effective
> transport of energy or matter (e.g. an Einstein-Podolsky-Rosen
> channel?).
>
The way one links quantum mechanics to thermodynamics is through statistical
mechanics. In the kind of large population samples required the
averaging process often looses this kind of informaton.
The only vailid link betwen "information" and thermodynamics is via
Shannon's definition and negentropy. We now know, thanks to
Meixner's paradox, that entropy is undefinable in non-linear non-equilibrium
systems, so that it has little bearing on thermodynamics in the sphere
we are working.
I hope this helps.
Regards,
Don Mikulecky