Dear Edward. I have wondered about the outcome of the theta values.
In the systemtest: Relax_disp.test_value_write_calc_rotating_frame_params_auto_analysis I have hardcoded the values of an output of theta values. But many of them are negative. If we take the article of: 3. Palmer, A.G. & Massi, F. (2006). Characterization of the dynamics of biomacromolecules using rotating-frame spin relaxation NMR spectroscopy. Chem. Rev. 106, 1700-1719 http://dx.doi.org/10.1021/cr04042875 And look at Figure 1. We see that tan(theta) = w_1 / Omega If w_1 (Spin-lock offset) is always positive, but Omega can be negative, then negative values are to be expected for w_1 / Omega. For the symmetry of atan, theta_calc = atan(-x) = - atan(x), the theta angle describing the tilted rotating frame relative to the laboratory frame should then be theta = pi + atan(-x) = pi - atan(x) = pi - abs(atan(x)) Best Troels 2014-03-13 19:51 GMT+01:00 Edward d'Auvergne <[email protected]>: > Hi, > > This is the standard way of calculating theta. Note that some of the > dispersion models in lib.dispersion do not use this code and actually > calculate a different theta value using the population averaged > spin-lock offset. > > Regards, > > Edward > > > > On 13 March 2014 19:44, Troels E. Linnet > <[email protected]> wrote: >> Follow-up Comment #34, sr #3124 (project relax): >> >> The theta calculation in relax is: >> >> # Calculate the tilt angle. >> omega1 = point * 2.0 * pi >> Delta_omega = shifts[ei][si][mi] - offsets[ei][si][mi][oi] >> Domega[ei][si][mi][oi].append(Delta_omega) >> if Delta_omega == 0.0: >> theta[ei][si][mi][oi].append(pi / 2.0) >> else: >> theta[ei][si][mi][oi].append(atan(omega1 / Delta_omega)) >> >> _______________________________________________________ >> >> Reply to this item at: >> >> <http://gna.org/support/?3124> >> >> _______________________________________________ >> Message sent via/by Gna! >> http://gna.org/ >> >> >> _______________________________________________ >> relax (http://www.nmr-relax.com) >> >> This is the relax-devel mailing list >> [email protected] >> >> To unsubscribe from this list, get a password >> reminder, or change your subscription options, >> visit the list information page at >> https://mail.gna.org/listinfo/relax-devel _______________________________________________ relax (http://www.nmr-relax.com) This is the relax-devel mailing list [email protected] To unsubscribe from this list, get a password reminder, or change your subscription options, visit the list information page at https://mail.gna.org/listinfo/relax-devel
