Paul is normally a slow start and fast finish for me. This has been the opposite. Off to a flyer then found that I had the wrong first word in 11a (there is a very viable alternative) and the wrong word completely for 22d (again a viable alternative with an s as 4th letter. This didn't feel like a normal Paul to me.
Anyway, after beginning at 8am I'm still lacking in much of the SE corner. Hints for 20d if it is a very scientific word would be appreciated.