For anyone interested in some in depth research regarding LED lighting my thread Are LEDs Misunderstood has attracted some excellent minds. Here is an excerpt on UVB (note they are thinking short blasts):
I devoted most of my research to this topic, as currently there is more that we don't know about than we know for sure.
For cannabis, we are narrowing down the spectrum that works better, at least for whole grows. Except for the UV range, we know decently what we need to use, and how to vary attending to different situations.* Now we need to find optimal spectrums for each stage of development and situations as well as "tricks" allowing to affect some traits by lighting manipulation.* I think possibilities of LEDs on this are really huge and severely under researched. Blast of light of narrow wavelengths or combinations of narrow wavelengths for short periods of time have the potential of strongly affect outcomes.
Just an example: could strong blue light blasts affect in a similar way than UV? (I suspect so). Either a pair of hours a day, maybe blasts during three days each 15 days, or at the mid of veg period, then after flowering induction and finally at ripening, etc. Possibilities are almost endless. Or, does a blast of very narrow UVB (290 +-5nm, for example) have a different effect or intensity response that wide UVB or UVB+UVA irradiation?