From owner-metabolic-reg@net.bio.net Tue Jan 14 22:00:00 1997
Path: biosci!ulb.ac.be!schepers
From: schepers@ulb.ac.be (Hans Schepers)
Newsgroups: bionet.metabolic-reg
Subject: Re: Logarithmic definitions of control coefficients
Date: 15 Jan 1997 04:08:42 -0800
Organization: Universit'e Libre de Bruxelles
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>I recently made an informal poll of several colleagues about whether
>they preferred to write control coefficients and elasticities in the
>logarithmic form, i.e.
>
>dlny/dlnx
>
>or without logarithms, i.e.
>
>(x/y)(dy/dx)

To my biological viewpoint, only the fractional
form is correct, since it does not make any sence 
to take a logarithm (or any other transcendental function)
of a non-dimensionless quantity.
Of course, since we know the chain rule and the derivative
of ln(x), we can use the short-hand notation with ln(),
and use it on graphs and use it for finite steps,
but still,
conceptually, the (dy/y)/(dx/x) is the only form that makes sense!

(see http://platine.ulb.ac.be/GEPO/gepo.html#mca
for how I simulate MCA varying 9 parameters and keeping
track of the control coefficients)

-- 
Hans Schepers, Service de Chimie Physique, Universite Libre de Bruxelles
C.P. 231 Brussels 1050
e-mail: schepers@ulb.ac.be
  http://platine.ulb.ac.be

.