[RASMB] problem with interference

[Christine Wandrey]

Dear all,

yesterday I had the Beckman service on my XL-I ( in 2007 upgraded to  
Proteom Lab). He had to replace the piece on which the Monochromator  
is screwed. After screwing for more than 13 years  the thread on the  
XL-I side was damaged.

Today we wanted to run velocity to characterize a polysaccharide using  
interference. After having started the run with usual settings, the  
fringe display remained completely dark. Only when increasing the  
laser duration the fringe picture became brighter but very  
heterogeneously, bright on the top but dark for the lower fringes. I  
thought there could be something with the samples. I stopped the run  
and put in a cell only filled with water. The same problem continued.  
I took a screen/window print, see below in the word file. You see the  
heterogeneous picture.

Note, to have this figure I already had to increase the laser duration  
to 4.0 (222 ms) at best laser delay (8 hole rotor, cell with water in  
hole 4). Normally, I scan at laser durations below 1, preferably  
0.2-0.6. Note also, with the upgraded software one cannot adjust  
brightness.
Usually I use interference at 1000 rpm for absorbance experiments to  
be run at high speed to check precise cell filling. I never saw this  
problem before.

Thank you in advance for your advice.
Best,
Christine
Note, the picture was a bit deformed to make the problem more visible.



--------------------------------------------------------------------------------
PD Dr. habil. Christine Wandrey, MER
Ecole Polytechnique Fédérale de Lausanne (EPFL)
Laboratoire de Médecine Régénérative et de Pharmacobiologie (LMRP)
http://people.epfl.ch/christine.wandrey

tél.: (+41) 21 693 9661
fax: (+41) 21 693 9685
email: christine.wandrey at epfl.ch

Postal address:
EPFL-SV-IBI-LMRP
AAB 042, station 15
CH-1015 Lausanne
Switzerland



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