\begin{table}%t4
\caption{Electron density derived from the
          \ion{Mg}{viii} 338.983/313.743~\AA\  
          line ratio in the selected segments.
          The lower limit and the upper limit are 
          indicated with "ll'' and~"ul'', respectively.}
\label{table:segments_Ne}
%\centering
\par
\begin{tabular}{ll}
\hline  \hline
Segment & $\log~N_{\rm e}$ \\
\hline
1(0)   & $7.3_{\rm ll}^{+0.5}$ \\
2(1)   & $6.9_{\rm ll}^{+0.6}$ \\
3(4)   & $7.4_{\rm ll}^{+0.5}$ \\
4(7L)  & $\rm 8.0_{-0.6}^{+1.7}$ \\
5(7U)  & $8.2_{-0.6}^{\rm ul}$ \\
6(8L)  & $7.4_{\rm ll}^{+0.5}$ \\
7(8U)  & $\rm 7.6_{-0.9}^{+0.5}$ \\
8(9)   & $8.3_{-0.6}^{\rm ul}$ \\
\hline
\end{tabular}
\end{table}