Acknowledgments
This work was supported by Fundação para a Ciência e a Tecnologia
– FCT/MEC (Portugal) through the projects PTDC/CTM/
100244/2008 and PEst-C/EQB/LA0006/2011, and the post-doctoral
fellowships SFRH/BPD/44946/2008 (Alexandre Paiva) and SFRH/
BPD/41175/2007 (Nuno Lourenço), and by FEDER.