[RASMB] Abrupt change in intensity

[Holger Strauss]

Karl,

though I don't know what's going on, I have also observed this 
phenomenon for intensity data at different wavelengths and at 
different absolute values for the intensity (and much lower than your 
23 000 counts), so it is also machine-independent. It is not always 
present though but I couldn't find out what really causes it. 
Strangely enough, recording absorbance instead of intensity seems to 
work fine. The analysis is OK if you set the fitting limit after this 
cutoff, or if you exclude the first eighteen scans, so it really 
seems to be a cutoff and not a systematic error affecting the other 
data points.

Any more input is greatly appreciated!

Cheers, Holger

>Dear All,
>
>I have attached the raw intensity data for a recent sedimentation 
>velocity experiment.  The first 18 scans showed a baseline intensity 
>around 23000 counts (for both air and buffer).  Then for scan 19, 
>the intensity suddenly increased to around 35000 counts and 
>contained much more systematic noise.  According to the header files 
>for every scan, the wavelength was set at 260 nm.  What is going on?
>
>Thanks for any help,
>
>Karl Maluf