\frame{ \frametitle{}
 \hspace{1em}
 \begin{centering}
 \hspace{-1cm}\includegraphics[height=3cm]{cactuslogo_structure_thorns}\\
 \Huge Cactus Structure\\
       The Thorns\\
 \end{centering}
}

\frame[containsverbatim]{ \frametitle{The Driver}
  \abspic{cactuslogo_structure_driver}{0.0}{0.7}{0.2}
  \begin{itemize}
    \item Special thorn
    \item Only one active for a run, choose at starttime
    \item The only code (almost) dealing with parallelism
    \item Other thorns access parallelism via API
    \item Underlying parallel layer transparent to application thorns
    \item Examples
     \begin{itemize}
      \item PUGH: unigrid, part of the Cactus computational toolkit
      \item Carpet: mesh refinement, \verb|http://www.carpetcode.org|
     \end{itemize}
  \end{itemize}
}

