[ccp4bb] (yet again a) Postdoc position in Berkeley

2019-11-08 Thread Petrus Zwart
Dear All, We have two postdoc positions open in LBNL's  Center for Advanced Mathematics in Energy Research Applications (CAMERA; https://www.camera.lbl.gov/) to work on a diverse set of problems in managing, cleaning and interpreting biophysical data ranging from microscopy to crystallography. 

Re: [ccp4bb] [3dem] Which resolution?

2020-02-16 Thread Petrus Zwart
Hi All, How is the 'correct' resolution estimation related to the estimated error on some observed hydrogen bond length of interest, or an error on the estimated occupancy of a ligand or conformation or anything else that has structural significance? In crystallography, it isn't really (only in

Re: [ccp4bb] [3dem] Which resolution?

2020-03-12 Thread Petrus Zwart
Hi Jacob, On Thu, Mar 12, 2020 at 9:13 AM Keller, Jacob wrote: > I would think the most information-reflecting representation for > systematic absences (or maybe for all reflections) would be not I/sig but > the reflection's (|log|) ratio to the expected intensity in that shell > (median

Re: [ccp4bb] 2fofc maps from refmac twinned refinement - clarify?

2020-04-29 Thread Petrus Zwart
I am not quite sure how it is done in Refmac, but in phenix it works as follows - difference maps are gradient maps for a least squares target and they do not contain any amplitude contamination from twinning. - Fo type maps are computed either via classic detwinning (solving the linear

Re: [ccp4bb] Strange Pseudosymmetry Effects

2020-05-27 Thread Petrus Zwart
Hi Jessica, If you see spots and they fit a lattice, you should use them. Use the b=10 solution in P1 that you have with 3 models (or two if one is iffy) and use that as a start model for MR in b=20 and start searching for the rest. Alternatively, use the b=10 model with stuff that looks decent

Re: [ccp4bb] Twin law definition in REFMAC5

2020-07-07 Thread Petrus Zwart
On Mon, Jul 6, 2020 at 10:33 PM Petr Kolenko wrote: > Dear Eleanor, > The unit cell parameters are 117.385 155.506 155.611 90.00 90.00 > 90.00, as you expected. The twin law was recognized using phenix.xtriage. > If I refine the structure using phenix.refine with no twin law and the >

Re: [ccp4bb] Nonlinearities and Thresholds

2022-03-10 Thread Petrus Zwart
Hi Jacob, What you describe sounds a lot like a phase transition. For instance, in random graph methods, one often observes a sharp increase in the largest connected component at a defined sparsity level. This phenomenon has application in data analysis, machine learning, etc etc. Predicting

Re: [ccp4bb] outliers

2022-11-08 Thread Petrus Zwart
Hi James, This is what you need. https://en.wikipedia.org/wiki/Generalized_extreme_value_distribution The distribution of a maximum of 1k random variates looks like this, and the (fitted by eye) analytical distribution associated with it seems to have a decent fit - as expected. [image: