Characterizing amalgmation bases for relation, cylindric and polyadic algebras

We characterize completey (give a necessary and suffcient condition using special neat embeddings)for a relation algebra to belong to the amalgamation, strong amalgamation, and superamalgamation base of the class of representable algebras. We do the same for cylindric and polyadic algebras for all dimensions >1, infinite included. Finally, we show that we can expand our algebras by finitely many natural operations, that force the newly expanded algebras to have various forms of amalgamation properties, like quasi-projections and directed cylindrifiers.