Re: [sr #3124] Grace graphs production for R1rho analysis with R2_eff as function of Omega_eff -- March 14, 2014 - 15:59

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 <edward@xxxxxxxxxxxxx>:
> 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
> <NO-REPLY.INVALID-ADDRESS@xxxxxxx> 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
> > relax-devel@xxxxxxx
> >
> > 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