Question: how to plot Sigma(R30)?

Hi,

I am trying to plot this function Sigma(R30) but I get failed to do so. Any one would like to try to help me out?

The attached maple sheet contains the asymptotic solution of the huge equation in .txt file. 

thx.

 20110819_doodles2.mws

20110818_section4-5a.txt

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