Point Interactions from Flux Conservation
  We show that the physical requirement of flux conservation can substitute for the usual matching conditions in point interactions. The study covers an arbitrary superposition of $\delta$ and $\delta'$ potentials on the real line and can be easily applied to higher dimensions. Our procedure can be seen as a physical interpretation of the deficiency index of some symmetric, but not self-adjoint operators. 
Luis J. Boya and E.C.G. Sudarshan