Update Micro rheology authored by jarlt's avatar jarlt
......@@ -5,15 +5,18 @@
2. Convert the DICF into an MSD
1. Get good estimates for A(q) and B(q) using the following options
* fit data with suitable model
* Estimate from g(q,tau_min) and g(q, tau_max)
* Estimate from $g(q,\tau_{min})$ and $g(q, \tau_{max})$
2. Estimate mean squared displacement as
MSD(tau; q) = -4/q^2 ln(1 - (g(q,tau)-B(q))/A(q)).
**Note:** This assumes motion in 2D (for 3D the 4 needs to be replaced by 6)
1. This can be displayed in my software by selecting 'Representation'-> 'MSD' in the 'Display & Fit' tab
2. Rather than plotting it for all tau it uses 'MSDcutoff' to suppress values too close to the noise level: if correlation has dropped by more than 'MSDcutoff' (default 85%) it is not plotted and when saving a NaN values is saved.
3. MSD(tau; q) can be saved by using 'Save as displayed' button
3. In principle this MSD should be independent of the q used to calculate it, but in practice they differ (if nothing else in the timescales/displacements they can reliably access...).
$$MSD(\tau; q) = -\frac{4}{q^2} \ln(1 - (g(q,\tau)-B(q))/A(q)).$$
**Note:** This assumes motion in 2D (for 3D the 4 needs to be replaced by 6)
1. This can be displayed in my software by selecting 'Representation'-> 'MSD' in the 'Display & Fit' tab
2. Rather than plotting it for all $\tau$ it uses 'MSDcutoff' to suppress values too close to the noise level: if correlation has dropped by more than 'MSDcutoff' (default 85%) it is not plotted and when saving a NaN values is saved.
3. MSD$(\tau; q)$ can be saved by using 'Save as displayed' button
4. In principle this MSD should be independent of the q used to calculate it, but in practice they differ (if nothing else in the timescales/displacements they can reliably access...).
3. Extract G* from MSD
1. The 'Microrheology' tab is sometimes hidden: if so, go to 'Select Movies' -> Advanced settings' -> 'Misc' and activate the 'Show u-rheo Tab?' button
......
......