Arrowsmith discovers implicit links between the results of two MEDLINE searches.
Basically, you enter two searches and it retrieves the list of abstracts. By applying filters to the MESH terms found in those abstracts you narrow down the list, then pick a single MESH term by which to compare the two searches. You then end up with a list of papers that matched either search but shared a common MESH term. As an example, you might choose papers that matched searches for either "immune tolerance" or "interleukin-1" but shared the common MESH term "arthritis".
There's also a separate tool (Author-ity) that identifies which MEDLINE articles are written by a particular author, even if they share the same name with another author.