Does it ever explain why staking a vampire puts them to sleep? I know the sunlight thing is explained as a mystical weakness rather than a physiological one; VALKYRIE's gadget to emit light and radiation that's almost identical to sunlight might make a vamp go into fear frenzy, but won't actually ash it. But the stake thing, I'm not sure about. Is there some symbolic reason why a sharp piece of wood to the chest is significant, or is it a biological thing that "plant cells + vampire heart tissue = bad"?