Re: Pulse miscalibration, R1A and R1B in the fitting_main_kex.py script.Re: Pulse miscalibration, R1A and R1B in the fitting_main_kex.py script.|
Hello,
We have found useful to carry out some simulations with the same equations to figure out the influence of some parameters. You are right, the train of 180º pulses can be miscalibrated and the rf coil can be highly inhomogeneous. If the CPMG pulses differ from 180º, then the spins spend some fraction of time along the z-axis. In the case of slow tumbling proteins, the difference between R1 and R2 may become quite large. Whether the small oscillations observed for some CPMG profiles originate from imperfect 180º remains to be demonstrated. Cheers, Dominique On 16/7/13 16:35 , Edward d'Auvergne wrote: Hello, I'm now copying in the function returned by MakeFunction when a==1 into relax. I have noticed that this has the ability to handle miscalibrated pulses via the R180_3Dx() function, however the pi-pulse angle is 180 + a degrees, where a is hardcoded to 0.0 degrees. Is this a planned future feature? It is also not clear how the R1 relaxation rates for states G and E (or A and B) are used. Is the aim to have R1G (per spin), R1E (per spin), and the pulse angle (all per magnetic field strength) as optimisable parameters of the model? For the current implementation, I will just set these all to hardcoded values of zero, as neither relax nor the fitting_main_kex.py script appear to use these. Cheers, Edward |
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