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
