\begin{table}%t2
%\centering
\par
\caption {\label{tab_frac}Positron escape and survival fractions (in \%) as a function of parent nucleus, ejecta mass and transport scheme.}
\begin{tabular}{ccccc}
\hline\hline
\noalign{\smallskip}
\celltspace Ejecta mass & Transport & $^{56}$Ni & $^{44}$Ti \cellbspace \\
\hline
\celltspace 2 & Free & 0.4 & 97.4 \cellbspace \\
\celltspace 2 & Trapped & $<$$ 10^{-2}$ & 90.8 \cellbspace \\
\celltspace 4 & Free & $<$$ 10^{-2}$ & 94.8 \cellbspace \\
\celltspace 4 & Trapped & $<$$ 10^{-2}$ & 79.7 \cellbspace \\
\celltspace 6 & Free & $<$$ 10^{-2}$ & 92.3 \cellbspace \\
\celltspace 6 & Trapped & $<$$ 10^{-2}$ & 69.0 \cellbspace \\
\celltspace 8 & Free & $< $$10^{-2}$ & 90.0 \cellbspace \\
\celltspace 8 & Trapped & $<$$ 10^{-2}$ & 59.2 \cellbspace \\
\hline
\end{tabular}
\end{table}