\[U\left(a,b,x\right)=\frac{2e^{\frac{1}{2}x}}{\Gamma\left(a\right)}\left(\sqrt{%
\frac{2}{\beta}\tanh\left(\frac{w}{2}\right)}\left(\frac{1-e^{-w}}{\beta}%
\right)^{-b}\beta^{1-b}K_{1-b}\left(2\beta a\right)+a^{-1}\left(\frac{a^{-1}+%
\beta}{1+\beta}\right)^{1-b}e^{-2\beta a}O\left(1\right)\right),\]