Dualities between finitely separated structures
  We study dualities between classes of relational topological structures, given by Hom-functors. We show that there exists a 2-element structure with infinitely many relations, which reconstructs all other structures generated by a 2-element one. As an application, we find a natural duality for the class of normal convexity structures. As another application, we give short proofs for several known dualities for classes of structures generated by a fixed 2-element structure. 
Wies{\l}aw Kubi\'s and Krzysztof Pszczo{\l}a
math.RA math.LO