With respect to #40, we like your use of the symbol on the outside, but we would appreciate seeing it without the red or in a different color scheme using only 2 colors. Also, we'd appreciate seeing the "prime" in all lowercase letters. Thanks for the entries!
We also like the plus sign in #39. Although, it might look better if the random lines around the circle were cleaned up a bit and made to look a little more sleek. Thanks again.