  We use Furuta's result, usually referred to as ``10/8-conjecture'', to show
that for any compact 3-manifold $M$ the open manifold $M\times\r$ has
infinitely many different smooth structures. Another consequence of Furuta's
result is existence of infinitely many smooth structures on open topological
4-manifolds with a topologically collarable end, provided there are only
finitely many ends homeomorphic to it. We also show that for each closed spin
4-manifold there are exotic \rf's that can not be smoothly embedded into it.
