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We created a series of videos for an online introductory astronomy course at the Pennsylvania State University in part to address the lack of personal presence in online courses. Based on surveys administered to the students during the semester, we found that these videos were effective in creating an instructor presence within the online course. We also found that students who perceived a strong instructor presence had a more positive attitude toward the course. Additionally, there is a correlation between the students' perceptions of how helpful a video is with how enjoyable they rated it, but no correlation between the perceived helpfulness of a video and student performance on video-specific questions, suggesting that students are not good at assessing video helpfulness. (Contains 1 table and 3 figures.)

We present the effect of video demonstrations on student performance in an online Astronomy course. We find that students who watched the videos performed better on related exam questions compared to those who did not watch the videos. We also find that students in the online course performed as well as students in a nearly identical face-to-face course on video-related questions but worse on other questions. Finally, we find that online students performed at par with face-to-face students on the Astronomy Diagnostic Test. These videos are freely available on YouTube, Google Videos, and iTunes. (Contains 3 tables and 1 figure.)

Pulsar nulling is not always a random process; most pulsars, in fact, null non-randomly. The Wald–Wolfowitz statistical runs test is a simple diagnostic that pulsar astronomers can use to identify pulsars that have non-random nulls. It is not clear at this point how the dichotomy in pulsar nulling randomness is related to the underlying nulling phenomenon, but its nature suggests that there are at least two distinct reasons that pulsars null. [ABSTRACT FROM AUTHOR]

Analyses of multiple pulse sequences of the pulsar PSR B2303+30 reveal two distinct emission modes. One mode (B) follows a steady even–odd pattern and is more intense. The second mode (Q) is characteristically weak, but has intermittent drift bands with a periodicity of approximately 3P1/cycle, and nulls much more frequently than the B mode. Both modes occur with roughly equal frequency, and their profiles have a similar single-humped form with a slight asymmetry. Our observations and analyses strongly suggest that the subpulse drift rates in both modes are linked in a series of cycles, which can be modelled as relaxing oscillations in the underlying circulation rate. [ABSTRACT FROM AUTHOR]