<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content="text/html; charset=us-ascii" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 8.00.6001.19170"></HEAD>
<BODY>
<DIV dir=ltr align=left><SPAN lang=EN>
<P><FONT face=Arial><FONT color=#0000ff><FONT size=2>Anna, I have a somewhat
different view <SPAN class=244212816-26012012>from the others </SPAN>about
the cause of th<SPAN class=244212816-26012012>is</SPAN> problem. <SPAN
class=244212816-26012012>Noise that shows up only at certain radii and
independent of wavelength is characteristic of a mechanical motion issue with
the slit assembly. I'm not at all clear why the slit assembly motion
problem occurs only at low temperatures, but the characteristics of the noise
itself are exactly what one expects for this sort of problem. Usually these
problems are caused by a burr or some dirt getting between the slit assembly and
the gold-plated ring that caps the PMT. Occasionally the thin foil piece in
which the slit is formed comes partially un-glued from the body of the slit
assembly and catches on the PMT ring cap at certain radial
positions.</SPAN></FONT></FONT></FONT></P>
<P><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=244212816-26012012>John</SPAN></FONT></FONT></FONT></SPAN></P>
<P>
<HR tabIndex=-1>
</P>
<P><FONT size=2 face=Tahoma><B>From:</B> rasmb-bounces@rasmb.bbri.org
[mailto:rasmb-bounces@rasmb.bbri.org] <B>On Behalf Of </B>anna
vitlin<BR><B>Sent:</B> Thursday, January 26, 2012 4:33 AM<BR><B>To:</B>
<B>Subject:</B> [RASMB] Radial-dependent noise in Beckmann
XL-I<BR></FONT><BR></P></DIV>
<DIV></DIV>
<DIV dir=ltr>
<DIV>Hello,</DIV>
<DIV> </DIV>
<DIV>We have a Beckmann XL-I running a An-60 Ti rotor. </DIV>
<DIV>When running sedimentation velocity experiments at 4 deg. we have noticed
protein-independent, time-independent, radial-dependent noise, consistently
between 6.2 and 6.4 Radius. </DIV>
<DIV>This phenomenon occurs using different cell assemblies, different
wavelengths and different velocities but does not occur at 20 deg. </DIV>
<DIV>Has anyone detected behavior like this and how do we troubleshoot it?</DIV>
<DIV>Should we call for service?</DIV>
<DIV> </DIV>
<DIV>Thank you</DIV>
<DIV>Anna Vitlin </DIV>
<DIV>Tel-Aviv university</DIV></DIV></BODY></HTML>