Biofuels: Problems, challenges and perspectives

Semantic Subtyping: Challenges, Perspectives, and Open Problems

Semantic subtyping is a relatively new approach to define subtyping relations where types are interpreted as sets and union, intersection and negation types have the corresponding set-theoretic interpretation. In this lecture we outline the approach, give an aperçu of its expressiveness and generality by applying it to the λ-calculus with recursive and product types and to the π-calculus. We th...

Silicon clusters: Problems, challenges and perspectives

We search for the lowest-energy structure of XAu4 (X = C, Si, Ge, Sn) clusters and calculate the photoelectron spectrum for the lowest-energy isomer of each species. The gradual destabilization of the tetrahedral geometry from C → Si → Ge → Sn, as well as the structural transition from the tetrahedral to the square planar geometry from SiAu4 to GeAu4, indicate that the change of electronic prop...

Algal biofuels: challenges and opportunities.

Biodiesel production using microalgae is attractive in a number of respects. Here a number of pros and cons to using microalgae for biofuels production are reviewed. Algal cultivation can be carried out using non-arable land and non-potable water with simple nutrient supply. In addition, algal biomass productivities are much higher than those of vascular plants and the extractable content of li...

Key issues in estimating energy and greenhouse gas savings of biofuels: challenges and perspectives

Future Prospects and Perspectives on Biofuels