I just tried it out - "show_user" and "cursor" are ignored (users are always shown). 

"since" is more interesting - `since:2014-06-04` can be added to the query string `q`. Using `since=2014-06-04` has the same effect. That's probably mentioned in the api docs somewhere, but I havn't seen it there yet (admittedly I'm not known to be thorough with reading the docs ;)