Hi,
We (Pierre-Yves Savard and I) have found a problem with the
structure.create_diff_tensor_pdb() function.
If you use either results.read() or diffusion_tensor.init() to load a diffusion
tensor and, then, display it, it is fine, except for the ellipsoid where some
weird things happen...
Indeed, with the ellipsoid, you get a weird shaped tensor, depending on the
angles input. With angles set to 0, the tensor is fine. With alpha and beta set
to non-zero values, the shape of the tensor changes drastically as it becomes
completely flat. With gamma set to a non-zero value, the shape is fine, with
the tensor just turned around the Dz axis...
I submitted a bug report and attached 7 files:
tensor.pdb
With all angles set to 0.
tensor__angles__alpha_90.pdb
With alpha = 90 degrees.
tensor__angles__beta_90.pdb
With beta = 90 degrees.
tensor__angles__gamma_90.pdb
With gamma = 90 degrees.
tensor__angles__all_90.pdb
With all angles set to 90 degrees.
tensor__angles__all_45.pdb
With all angles set to 45 degrees.
tensor__angles__45_0_45.pdb
With all angles set to 45, 0 and 45 (alpha, beta and gamma, respectively).
As you will see, the tensor is fine if both alpha and beta are equal (files:
tensor__angles__all_45.pdb and tensor__angles__all_90.pdb), but weird shaped
when alpha and beta are not equal (tensor__angles__45_0_45.pdb)...
These observations were made with the subversion repository. I verified with
relax-1.3.1 / relax-1.3.2 / relax-1.3.3 and the same problem arises... so the
problem as been there for a long time...
Shouldn't the tensor always keep a symmetric shape, with angles only changing
the orientation, not the shape..?
Thanks for help.
Séb :)
-- Sébastien Morin PhD Student S. Gagné NMR Laboratory Université Laval
& PROTEO Québec, Canada
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