\begin{table}%t4
\caption {\label{tab_alpha}Main characteristics of the $\alpha$-enhanced mixtures described
  in text. }
%\centerline
 {\begin{tabular}{ccccccccccccc}
\hline
\hline
$[\alpha/{\rm Fe}]$ & {\it Mixture} & $f_{\rm C}$ & $g_{\rm C}$ & $f_{\rm N}$ & $g_{\rm N}$ 
& $f_{\rm O}$ & $g_{\rm O}$ & $f_{\rm Fe-group}$ & $g_{\rm Fe-group}$ & $f_Z$  & $g_Z$ \\
\hline
0.2 & $A$ & 0.714 & 0.721 & 0.714 & 0.721 & 1.131 & 1.143 & 0.714 & 0.721 & 1.000 & 0.990 \\ 
    & $B$ & 1.000 & 0.982 & 1.000 & 0.982 & 1.041 & 1.022 & 0.657 & 0.645 & 1.000 & 1.018 \\
    & $C$ & 0.714 & 0.721 & 0.714 & 0.721 & 1.131 & 1.143 & 0.714 & 0.721 & 1.392 & 1.387 \\ 
0.4 & $A$ & 0.491 & 0.500 & 0.491 & 0.500 & 1.233 & 1.256 & 0.491 & 0.500 & 1.000 & 0.982 \\
    & $B$ & 1.000 & 0.970 & 1.000 & 0.970 & 1.060 & 1.037 & 0.426 & 0.413 & 1.000 & 1.031 \\
    & $C$ & 0.491 & 0.500 & 0.491 & 0.500 & 1.233 & 1.256 & 0.491 & 0.500 & 2.004 & 2.000 \\
0.6 & $A$ & 0.329 & 0.336 & 0.329 & 0.336 & 1.308 & 1.339 & 0.329 & 0.336 & 1.000 & 0.977 \\
    & $B$ & 1.000 & 0.962 & 1.000 & 0.962 & 1.087 & 1.046 & 0.273 & 0.263 & 1.000 & 1.039 \\
    & $C$ & 0.329 & 0.336 & 0.329 & 0.336 & 1.308 & 1.339 & 0.329 & 0.336 & 2.950 & 2.972 \\
0.8 & $A$ & 0.215 & 0.222 & 0.215 & 0.222 & 1.360 & 1.398 & 0.215 & 0.222 & 1.000 & 0.973 \\
    & $B$ & 1.000 & 0.957 & 1.000 & 0.967 & 1.099 & 1.052 & 0.174 & 0.167 & 1.000 & 1.045 \\
    & $C$ & 0.215 & 0.222 & 0.215 & 0.222 & 1.360 & 1.398 & 0.215 & 0.222 & 4.392 & 4.513 \\
\hline
\end{tabular}}
\par
\smallskip
 The variation factors of~C, N, O, and Fe-group elements, defined by Eqs.~(\protect{\ref{eq_figi}})
 for abundances either in mass fraction or in mass fraction, 
are indicated together with the quantities  $f_Z=Z/Z_{\rm ref}$ and $g_Z=\varepsilon_{Z}/\varepsilon_{Z_{\rm ref}}$. 
The reference solar composition is GS98.
\end{table}