Periodicals are publications that can really be published on any time frame (such as yearly, quarterly, monthly, or even weekly). Publications such as these will generally contain information that is static and on a specific genre such as music, culture, etc. Daily news, however, changes (as the name suggests) daily with respect to the daily events. These events are sometimes called “headline news.” Headline news will occur too frequently and change too much for it to be reasonably covered at lengthy intervals. As such, headline news, is most sensibly covered in daily news.
The speaker is unsettled by the raven's repetition of “Nevermore” because he believes the raven learned it from a depressed former master and intends to make him his new owner.
