  We introduce a technique for showing classical knots and links are not slice.
As one application we show that the iterated Bing doubles of many algebraically
slice knots are not topologically slice. Some of the proofs do not use the
existence of the Cheeger-Gromov bound, a deep analytical tool used by
Cochran-Teichner. We define generalized doubling operators, of which Bing
doubling is an instance, and prove our nontriviality results in this more
general context. Our main examples are boundary links that cannot be detected
in the algebraic boundary link concordance group.
