High Dynamic-Range Radio-Interferometric Images at 327 MHz

Radio astronomical imaging using aperture synthesis telescopes requires deconvolution of the point spread function as well as calibration of the instrumental characteristics (primary beam) and foreground (ionospheric/atmospheric) effects. These effects vary in time and also across the field of view, resulting in directionally-dependent (DD), time-varying gains. The primary beam will deviate from the theoretical estimate in real cases at levels that will limit the dynamic range of images if left uncorrected. Ionospheric electron density variations cause time and position variable refraction of sources. At low frequencies and sufficiently high dynamic range this will also defocus the images producing error patterns that vary with position and also with frequency due to the chromatic aberration of synthesis telescopes. Superposition of such residual sidelobes can lead to spurious spectral signals. Field-based ionospheric calibration as well as "peeling" calibration of strong sources leads to images with higher dynamic range and lower spurious signals but will be limited by sensitivity on the necessary short-time scales. The results are improved images although some artifacts remain.Comment: to appear in Comptes Rendus Physique (2011

Understanding the gender and ethnicity attainment gap in UK higher education

In recent years the success rates of different groups of students in higher education (HE), have come under considerable scrutiny, with gender and ethnicity identified as key attributes predicting differential achievement of ‘good degrees’. A review of previous studies highlights the need for research which looks beyond ‘the deficit model’ to explain the attainment gap. This research used a mixed-methods approach to explore the academic and social experiences of students, as well as lecturers’ views on student achievement, in one UK University. Findings suggest that there are significant differences in motivation and confidence speaking English for different ethnic groups in this study, and a divergence in attendance and study time by gender – both of which may go some way to helping understand the gaps in attainment. In addition, male and BME students tended to over-estimate their likelihood of achieving a good degree outcome, compared to other groups

SJSU: Diversity University

‘San Jose State: Diversity University’ was written and designed to be a series of conversations with people who have been a part of the fabric of San Jose State. The narrative includes reflections of how they came to San Jose State, and what it was like at the time that they were, and have been here.https://scholarworks.sjsu.edu/history/1001/thumbnail.jp

Skeleton Islands of New Zealand and elsewhere

Skeleton Islands are a variety of the class of islands resulting from subsidence of dissected land, subcategory 4a of a classification of islands here offered. Such islands are characterised by development of a sprawling outline with a narrow axial ridge from which slender lateral spurs, or ribs, extend more or less at right angles. Extreme skeletonisation is associated with development before a final drowning, or redrowning, of amphitheatre heads in valleys already heading in the main divide. This may be a climatically induced change of the valley form related, in the case of the New Zealand example, Arapawa Island, to cryergic (periglacial) activity in the Pleistocene glacial ages. Kakeroma Island (Ryukyu Group), an example of a skeleton island described by W. M. Davis, has quite possibly a history different from that of Arapawa Island as regards both the development of the relief of the subsiding lands and. being in a low latitude, the possibly climatic process responsible for shaping its now submerged valley heads and thus emaciating the ribs of the island