A Cornell University study, just released has quantified the news cycle, both in television and online (in the blogosphere). Studies such as this can provide some clues regarding short period cycles (lasting days) and also provide insight from a psychological perspective (think Asimov's "psychohistory") not only in short periods, but by examination of meta-themes, the recurrence of certain types of news in a cyclical manner.

Anyway, here is the link to the article. Enjoy and it'll be interesting to see your comments!