Observations and properties of candidate high frequency GPS radio sources in the AT20G survey

We used the Australia Telescope Compact Array (ATCA) to obtain 40 GHz and 95 GHz observations of a number of sources that were selected from the Australia Telescope Compact Array 20 GHz (AT20G) survey . The aim of the observations was to improve the spectral coverage for sources with spectral peaks near 20 GHz or inverted (rising) radio spectra between 8.6 GHz and 20 GHz. We present the radio observations of a sample of 21 such sources along with optical spectra taken from the ANU Siding Spring Observatory 2.3m telescope and the ESO-New Technology Telescope (NTT). We find that as a group the sources show the same level of variability as typical GPS sources, and that of the 21 candidate GPS sources roughly 60% appear to be genuinely young radio galaxies. Three of the 21 sources studied show evidence of being restarted radio galaxies. If these numbers are indicative of the larger population of AT20G radio sources then as many as 400 genuine GPS sources could be contained within the AT20G with up to 25% of them being restarted radio galaxies.Comment: 21 pages, 24 figures, Table 1 truncated at 11 column

Microneedles: A New Frontier in Nanomedicine Delivery

This review aims to concisely chart the development of two individual research fields, namely nanomedicines, with specific emphasis on nanoparticles (NP) and microparticles (MP), and microneedle (MN) technologies, which have, in the recent past, been exploited in combinatorial approaches for the efficient delivery of a variety of medicinal agents across the skin. This is an emerging and exciting area of pharmaceutical sciences research within the remit of transdermal drug delivery and as such will undoubtedly continue to grow with the emergence of new formulation and fabrication methodologies for particles and MN. Firstly, the fundamental aspects of skin architecture and structure are outlined, with particular reference to their influence on NP and MP penetration. Following on from this, a variety of different particles are described, as are the diverse range of MN modalities currently under development. The review concludes by highlighting some of the novel delivery systems which have been described in the literature exploiting these two approaches and directs the reader towards emerging uses for nanomedicines in combination with MN

The factory and the beehive. I. Rotation periods for low-mass stars in Praesepe

Stellar rotation periods measured from single-age populations are critical for investigating how stellar angular momentum content evolves over time, how that evolution depends on mass, and how rotation influences the stellar dynamo and the magnetically heated chromosphere and corona. We report rotation periods for 40 late-K to mid-M star members of the nearby, rich, intermediate-age (∼600Myr) open cluster Praesepe. These rotation periods were derived from 200 observations taken by the Palomar Transient Factory of four cluster fields from 2010 February to May. Our measurements indicate that Praesepe's mass-period relation transitions from a well-defined singular relation to a more scattered distribution of both fast and slow rotators at ∼0.6 M ·. The location of this transition is broadly consistent with expectations based on observations of younger clusters and the assumption that stellar spin-down is the dominant mechanism influencing angular momentum evolution at 600Myr. However, a comparison to data recently published for the Hyades, assumed to be coeval to Praesepe, indicates that the divergence from a singular mass-period relation occurs at different characteristic masses, strengthening the finding that Praesepe is the younger of the two clusters. We also use previously published relations describing the evolution of rotation periods as a function of color and mass to evolve the sample of Praesepe periods in time. Comparing the resulting predictions to periods measured in M35 and NGC2516 (∼150Myr) and for kinematically selected young and old field star populations suggests that stellar spin-down may progress more slowly than described by these relations. © 2011. The American Astronomical Society. All rights reserved

Type II Supernovae as a significant source of interstellar dust

Large amounts of dust (>108M) have recently been discovered in high-redshift quasars1, 2 and galaxies3, 4, 5 corresponding to a time when the Universe was less than one-tenth of its present age. The stellar winds produced by stars in the late stages of their evolution (on the asymptotic giant branch of the Hertzsprung–Russell diagram) are thought to be the main source of dust in galaxies, but they cannot produce that dust on a short enough timescale6 (<1 Gyr) to explain the results in the high-redshift galaxies. Supernova explosions of massive stars (type II) are also a potential source, with models predicting 0.2–4M of dust7, 8, 9, 10. As massive stars evolve rapidly, on timescales of a few Myr, these supernovae could be responsible for the high-redshift dust. Observations11, 12, 13 of supernova remnants in the Milky Way, however, have hitherto revealed only 10-7–10-3M each, which is insufficient to explain the high-redshift data. Here we report the detection of 2–4M of cold dust in the youngest known Galactic supernova remnant, Cassiopeia A. This observation implies that supernovae are at least as important as stellar winds in producing dust in our Galaxy and would have been the dominant source of dust at high redshifts