Dear Nick,
If you're happy to keep on using xia2, you can just put both of the
data sets in a single directory and run
xia2 -3dii /heres/where/the/data/went
And wait a little while.
To comment on your analysis of the statistics: inside xia2 the scaling
is switched off as far as possible in the XDS CORRECT step and is
instead done with XSCALE, which will scale several data sets at the
same time. The data are then merged with Scala. I have found that data
scaled with XSCALE will always give lower residuals than the same data
(say from INTEGRATE.HKL) scaled with Scala or Aimless. I suspect that
this relates to the parametrisations used - Scala (and I assume
Aimless) use an analytical model with a small number of parameters,
XDS and XSCALE use a numerical approach with rather more parameters. I
will leave discussion of which way is best to the experts :o)
On the subject of overloads, the 2^20 limit is an absolute limit -
however there is a more real (and lower) limit which is written in the
image headers, which relates to the count rate dead time correction -
if the pixel count exceeds this threshold then the correction becomes
less reliable. Typically though this is quite a large number, and is
usually not met, though I should include this in the xia2 / XDS
running code.
If you'd like any help specifically with fiddling the xia2 run please
feel free to contact me off list - at Diamond we also have facilities
for remotely reprocessing the data which may help to make things a
little quicker and would save moving the data around.
Best wishes,
Graeme
On 7 February 2012 17:36, Nicholas Keep n.k...@mail.cryst.bbk.ac.uk wrote:
We have a high and low res pass on a crystal that is going to around 1.2 A
on the pilatus at Diamond.
We tried to scale them together using the xds CORRECT files from the xia2
-3dii runs (gives best results as far as we can see comparing xia2.html
files) through aimless via ccp4i interface.
The combined dataset looks worse (based on merging statistics at lower
resolutions) than the individual particular at low res.(Compared to scala
xia2 runs).
XDS does not record the pilatus as having overloads even on the high res
pass using the correct detector parameters
http://xds.mpimf-heidelberg.mpg.de/html_doc/detectors.html
What I wanted to do was limit the resolution of the two runs ie to use low
res between 100-2.5 beyond which completeness plummets and then the highres
between 8 and 1.2. Aimless does not seem to allow me to do that at least by
the ccp4i interface- is this then bad practice? I guess I could run a
utility to remove the resolutions I don't want.
The one effect that makes me wonder if the lowres is better data, and worth
combining, ie there is some overload in the high res, is that it goes from
30-8 mean I/SIGI whereas the high res has I/SIGI of 15 in most of the low
res shells and then slowly falls off to 2.0 at 1.2 angstrom.
Am intending to carry on just using the hires pass.
Any comments?
I think Phil is in NZ and not looking at email hence putting this to the
whole community
--
Prof Nicholas H. Keep
Executive Dean of School of Science
Professor of Biomolecular Science
Crystallography, Institute for Structural and Molecular Biology,
Department of Biological Sciences
Birkbeck, University of London,
Malet Street,
Bloomsbury
LONDON
WC1E 7HX
email n.k...@mail.cryst.bbk.ac.uk
Telephone 020-7631-6852 (Room G57 Office)
020-7631-6800 (Department Office)
Fax 020-7631-6803
If you want to access me in person you have to come to the crystallography
entrance
and ring me or the department office from the internal phone by the door
