Index: [thread] [date] [subject] [author]
  From: Walter Stafford <>
  To  :
  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

Index: [thread] [date] [subject] [author]