$M$-theory Compactification and Two-brane/Five-brane Duality
  We discuss various dual {\it pairs} of $M$-theory compactifications. Each pair consists of a compactification in which the two-brane plays the crucial role in relation to a string theory and a compactification in which the five-brane takes center stage. We show that in many examples such dual pairs are interchanged by the {\it same} duality transformation in each case. 
B.S.Acharya (Queen Mary and Westfield College, London)