\begin{table}%t2
\caption{Surface abundances of the models presented in Sect.~4. Abundances are taken at the moment the models reach the giant region for the first time after the VLTP. Abundances from Lawlor \&
Macdonald (\cite{LM03}) are taken from models of similar metallicity ($z=0.02$).}
\label{tab:abundancias} 
%\centerline
{
\begin{tabular}{ccccccc}
\hline \hline
& H & He & C & N & O & $M^{{\rm total}}_{\rm H}/M_\odot$ \\\hline
MLT (early VLTP) & $3.7 \times 10^{-4}$ & 0.324 & 0.371 & 0.0145 & 0.217 & $3.19 \times 10^{-6}$ \\ 
MLT  ($f=0.03$) & $5\times 10^{-6} $ & 0.307 & 0.378 & 0.0129 & 0.229& $7.24 \times 10^{-9}$ \\ 
GNA ($\nabla\mu=0$) & $3.2\times 10^{-5} $ &  0.316 & 0.378 & 0.0129 & 0.221 &$2.19 \times 10^{-7}$ \\ 
GNA &  $3.3\times 10^{-5} $ &  0.316 & 0.378 &  0.0127 & 0.221  & $6.76 \times10^{-9}$ \\\hline 
Lawlor   $D/10^{-4}\dagger$&0.06  &0.57 &0.26  & --  & 0.07  &  $2 \times10^{-6}$\\ 
Lawlor   $D/10^{-3}\dagger$&0.02  &0.55 &0.28  & --  & 0.08  &  $3 \times10^{-7}$\\ 
Lawlor  $D/10^{-2}\ddagger$&0.04 &0.54 &0.28 & -- & 0.08 & -- \\ 
Herwig (1999)& -- & 0.388 & 0.362 & -- & 0.219 & $4 \times 10^{-11}$ \\ \hline
Most PG1159 pulsators & -- & 0.397  & 0.357 & 0.0139 & 0.159 & -- \\ 
PG1159-035            & -- & 0.287  & 0.516 & 0.0100 & 0.115 & -- \\ \hline 
\end{tabular}}
\medskip
$\dagger$ Abundances correspond to the moment at which the star reaches the WD~cooling track. $\ddagger$ Abundances correspond to the first~return to the giant region, where the envelope was homogeinized by mixing. In the last column the values of the total amount of~H in
the star after the VLTP are presented. Relative abundances of PG1159~stars are taken from Dreizler \& Heber (\cite{DH98}) and normalized to the total amount of~$\rm C+O+N+He$ given by the models.
\end{table}