This has been a point of confusion
Here are the conventions used in a few of the classic SAXS text vs. recent
reviews:
--
I believe Guinier actually used the variable u in his thesis, but must have
changed at some point (I don't have it handy to check at the moment).
Guinier
The most extreme degree of confusion (or at least of requirement for fast
mental arithmetic) I have come across in relation to this topic is the habit
of small-molecule crystallographers working on accurate density studies to
characterise the resolution limit of their datasets by quoting the
