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From: Walter Stafford <STAFFORD@bbri.harvard.edu>
To : rasmb@bbri.harvard.edu
Date: Sat, 30 May 1998 18:40:50 -0400 (EDT)
dc_dt README file correction
Dear RASMBers
I have just been informed taht there is a serious typo in one of
the readme files for dcdt.
It concerns the equation for computing D from the g(s*) curve.
The term in square barckets in the numerator shoudl be squared
That section should read :
The g(s*) vs. s* curves are essentially gaussian; The standand deviation,
sigma, can be related to the diffusion coefficient:
D = [ sigma * w^2*t * Rm ]^2/[2*t] <- error was in this eq'n
where Rm, (w^2*t) and t are given in the header of the output file, Rm is
the radius of the meniscus and sigma is defined by:
g(s) = A * exp[ -0.5 * ( (s_peak - s)/(sigma) )^2 ]
Use this equation for fitting to get sigma.
The values of s and D can be substituted into the Svedberg equation to get
the molecular weight.:
M = [ R*T*s_peak ]/[ D*(1-vBar*rho)*w^2*t ]
Sorry for any inconvenience that may have caused.
Walter Stafford
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