This question may be better suited for more small-angle-oriented forum,
e.g.
http://www.saxier.org/forum/
On 08/07/2013 11:22 AM, Remec, Mark wrote:
Dear CCP4bb,
I have a few questions concerning SANS data recently collected that
I'm having trouble analyzing. The data was collected at 2 different
detector distances (4m, 2.5m) to achieve higher q-range, but I worry
that the curves don't overlap enough at intermediate q, which might
indicate a problem with the data. The links below are pictures of the
corresponding datasets, before truncating the 4m high-q data and
merging them into one. Is there a problem evident with the data, or am
I imagining a problem?
http://postimg.org/image/qb00y20qr/
http://postimg.org/image/8trbp7akj/
http://postimg.org/image/hni86axj7/
http://postimg.org/image/3sjxnu343/
http://postimg.org/image/4ysj0dgsj/
http://postimg.org/image/9ypz8bmf7/
http://postimg.org/image/m358pazb7/
http://postimg.org/image/jzuthmzib/
My second question concerns the values obtained in the analysis of the
final scattering curves. The second sample in my experiment shows
serious deviation in the values obtained for I(0) and Rg by Guinier
analysis compared to the values obtained by the P(r) analysis. In
other words, either the P(r) values match the Guinier and the P(r) fit
is terrible, or else the P(r) fit is good but doesn't match the
Guinier at all (5-10 difference in Rg, 2x difference in I(0)). I've
checked to make sure the buffer subtraction algorithm was OK, and I'm
pretty certain that the buffers were exact matches, so I don't know
how to explain this variation. There's no evidence of aggregation or
polydispersity to throw off the values, either. Does anyone know how
this can happen?
--
Oh, suddenly throwing a giraffe into a volcano to make water is crazy?
Julian, King of Lemurs
