[ed: You may have noticed site outages with increasing frequency. The good people at my alma mater of stack.nl, where this site is hosted, are looking into it.]
A second publication has resulted from the remote data-correction I did during the move. This paper is that of my long-time colleague Martin Hollamby. He is doing very interesting work on the self-assembly of small molecules in particular solvents. These molecules can self-assemble into funny shapes if the conditions are right. One such “funny” shape is the one published in this paper, which assumed the form of a toroid. Or, at least, after drying onto a HOPG surface, the dried-up shape is toroidal under AFM observation. Whether they are already toroidal under their equilibrium condition in solution was a bit of an outstanding question. We can measure this “in-soluo” morphology with SAXS and SANS, however.
Toroids are complex shapes, and give correspondingly feature-filled scattering patterns. However, since these shapes have many degrees of freedom, fitting it is not straightforward at all. Fortunately, Martin did both SAXS as well as SANS, and these two techniques highlight different regions of the shape. Using SASFit, both datasets can be fitted at the same time, reducing potential for bias as opposed to sequential fitting.
The resulting fit is of good quality, and the shape in solution has been thereby resolved. A dispersity in size or other morphological parameter has not been included in the fit. An argument can be made for including it, but the resulting instabilities would likely render fitting infeasible. For now, I congratulate Martin on his success in fitting complex shapes to combined SAXS and SANS patterns, and hope there will be many more in the future!