[5l0thgn3t]

I just started my research investigation yesterday and I'm looking on sources on gold vs gold alloys in their tensile strength and flexibility. I've stumbled upon this source called "Strength Enhancement and Deformation behaviour of gold after equal-channel angular pressing." Can someone explain the the circled bits of the picture? From googling the 4N means it's 99.99% pure, but i havent found anything about the O's, A's, Bc's, Q's and drawn.