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I see. I guess it would only make sense, if any, in very few cases, like
if there is a six-fold NCS parallel to a crystallographic 2-fold or
4-fold, i.e. if the non-crystallographic axis runs parallel to a
crystallographic one of lower symmetry (if the inverse is true, then
Phoebe's point about reflections being already crystallographically
related would apply).
Thank you for your explanation, Ethan.
Cheers,
Miguel
En/na Ethan Merritt ha escrit:
> On Friday 29 December 2006 13:36, Miguel Ortiz-Lombardia wrote:
>> I have a related question: how this procedure (thin resolution
>> shells) compares to select a subset of reflections for the test set
>> and then, knowing the NCS operators, extend the test set by including
>> their NCS-related reflections?
>
> Other than special cases, such as the case of a 2-fold NCS parallel to
> a crystallographic 6(1) screw already mentioned, the NCS operator
> does not map integral hkl values onto other integral hkl values.
> Thus the contamination of one particular Rfree reflection is due to
> contributions from multiple Rwork reflections in the shell.
>
- --
Miguel Ortiz Lombardía
Centro de Investigaciones Oncológicas
C/ Melchor Fernández Almagro, 3
28029 Madrid, Spain
Tel. +34 912 246 900
Fax. +34 912 246 976
e-mail: [EMAIL PROTECTED]
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Et ainsi ne pouvant faire que ce qui est juste fût fort, on a fait que
ce qui est fort fût juste.
Blaise Pascal, Pensées
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