“…The resulting process B α behaves like standard Brownian motion when away from the "interface" at zero, but its sample paths are skewed, namely P(B α t > 0 B α 0 = 0) = α for all t 0. While skew Brownian motion has many interesting and sometimes unexpected properties, it is of particular relevance to recent physical experiments involving diffusive transport in heterogeneous media in the presence of a single membrane; e.g., see [6,12,21,15,24,30,5,18,25,2]. The mathematical theory underlying applications to a single interface rests largely on the foundations for skew Brownian motion as developed by [13,11,31,22,18,1].…”