This section contains models for very specific tasks:
The first two are useful for achieving an empirical fit of the sedimentation data only. This can be useful if the main goal is to get a good estimate of the time-invariant noise.
* fit sedimentation time offset
The last one is a model for time-dependent sedimentation coefficients and molar masses. This may be useful not only if the sedimenting macromolecules undergo some (e.g. conformational) change during sedimentation, but mostly if the analysis window is restricted so that the composition and the weight-average changes because of selective sedimentation of some species.