From: Geoff=Howlett%BioChem%UNIMELB@muwaye.unimelb.EDU.AU
  To  : rasmb@bbri.eri.harvard.edu
  Date: Sat, 14 May 94 11:00:03 +1000

...no subject...

Hi

One possibility which seems to have been ignored re. the sloping baselines in 
the solution plateau during velocity runs is that of convection.

If the centerpiece is not aligned radially in the rotor or is faulty there 
will be continual erosion of the boundary leading to a non-flat plateau.

Simple tests include checking different cells.  If all is well the 
sedimentation coefficient for identical solutions in the same rotor but 
different cells should agree within 0.1 % or at least that used to be the 
case with schlieren optics.

Has anyone experience with difference sedimentation velocity using the XLA?  
My recollection from Howard Schachman is that it was necessary to make a few 
changes to the machine. 

Geoff Howlett