#3 - I like the sun, and overall styling. I like this one over #2 because of the addition of the chemistry/physics-like symbol. I do not like to mortar board (graduation hat). I do the like "movement" towards the sun that the river(?) provides. If possible, I would like to integrate multiple symbols of science - life, earth/space, chemistry, physics.
#11 - I like this one also, same comment re: the brown. Also, is there a way for the ball on the earth to be in northern California rather than New York? With the black copy (name of the conference) over the brown, it is hard to read.