Molecular Hydrogen Emission from Protoplanetary Disks

We have modeled self-consistently the density and temperature profiles of gas and dust in protoplanetary disks, taking into account irradiation from a central star. Making use of this physical structure, we have calculated the level populations of molecular hydrogen and the line emission from the disks. As a result, we can reproduce the observed strong line spectra of molecular hydrogen from protoplanetary disks, both in the ultraviolet (UV) and the near-infrared, but only if the central star has a strong UV excess radiation.Comment: 19 pages, accepted for publication in Astronomy and Astrophysic

National and Regional Estimates of the Prevalence of Opiate and/or Crack Cocaine use 2008-09: A summary of key findings

<p>This report summarises the results of a follow-up study to a three year project to estimate the prevalence of ‘problem drug use’ (defined as use of opiates and/or crack cocaine) nationally (England only), regionally and locally. The follow-up was carried out two years after the final sweep of the original project, so could therefore be considered as ‘sweep 5’. An overview of the national and regional estimates are presented in this report, as are comparisons with the estimates produced by the third (2006-07) sweep of the study. Estimates for 2007-08 are not available as a study was not commissioned for that year.</p> <p>Information about the number of people who use illicit drugs such as heroin, other opiates or crack cocaine is key to formulating effective policies for tackling drug-related harm as these drugs are associated with the highest levels of harm. It also helps inform service provision at the local level and provides a context in which to understand the population impact of interventions to reduce drug-related harm.</p> <p>Direct enumeration of those engaged in a largely covert activity such as the use of class A drugs is difficult and standard household survey techniques tend to underestimate the extent of such activity. Indirect techniques making use of various data sources offer a more reliable way of calculating prevalence estimates for the use of opiates and/or crack cocaine. The estimates presented in this report are derived using two indirect measurement techniques: the capture-recapture method (CRC ); and the multiple indicator (MIM ) method. These methods are described in detail in Hay et al., 2006 and Hay et al., 2007a. Methodological developments throughout the course of the previous three sweeps are discussed elsewhere (Hay et al., 2007b, Hay et al., 2008). The individuals covered by this study were people aged 15 to 64 and resident in each DAT area, and known to be using heroin, methadone, other opiate drugs or crack cocaine.</p&gt

Chemistry in AGB stars: successes and challenges

Emission and absorption line observations of molecules in late-type stars are a vital component in our understanding of stellar evolution, dust formation and mass loss in these objects. The molecular composition of the gas in the circumstellar envelopes of AGB stars reflects chemical processes in gas whose properties are strong functions of radius with density and temperature varying by more than ten and two orders of magnitude, respectively. In addition, the interstellar UV field plays a critical role in determining not only molecular abundances but also their radial distributions. In this article, I shall briefly review some recent successful approaches to describing chemistry in both the inner and outer envelopes and outline areas of challenge for the future.Comment: To appear in the refereed proceedings of the 11th Pacific Rim Conference on Stellar Astrophysics held in Hong Kong, Dec.14-17, 2015, Sun Kwok (editor). 10 pages, 2 figure

CCH <i>N</i> = 4-3 emission from dense interstellar clouds

The authors have searched for N = 4 - 3 rotational line emission from the ethynyl radical CCH, at 349 GHz toward a number of galactic molecular clouds. They have detected emission from ten giant molecular clouds and have derived CCH column densities on the order of 1014 - 1015cm-2. They find that CCH emission arises from dense gas, n(H2) ~ 104 - 105cm-3, but not from very dense material, n(H2) > 106cm-3, nor from hot gas such as the "hot core" region in Orion

Supporting security-oriented, collaborative nanoCMOS electronics research

Grid technologies support collaborative e-Research typified by multiple institutions and resources seamlessly shared to tackle common research problems. The rules for collaboration and resource sharing are commonly achieved through establishment and management of virtual organizations (VOs) where policies on access and usage of resources by collaborators are defined and enforced by sites involved in the collaboration. The expression and enforcement of these rules is made through access control systems where roles/privileges are defined and associated with individuals as digitally signed attribute certificates which collaborating sites then use to authorize access to resources. Key to this approach is that the roles are assigned to the right individuals in the VO; the attribute certificates are only presented to the appropriate resources in the VO; it is transparent to the end user researchers, and finally that it is manageable for resource providers and administrators in the collaboration. In this paper, we present a security model and implementation improving the overall usability and security of resources used in Grid-based e-Research collaborations through exploitation of the Internet2 Shibboleth technology. This is explored in the context of a major new security focused project at the National e-Science Centre (NeSC) at the University of Glasgow in the nanoCMOS electronics domain

Sulphur-bearing molecules in AGB stars I: The occurrence of hydrogen sulfide

Through a survey of (sub-)millimetre emission lines of various sulphur-bearing molecules, we aim to determine which molecules are the primary carriers of sulphur in different types of AGB stars. In this paper, the first in a series, we investigate the occurrence of H$_2$S in AGB circumstellar envelopes and determine its abundance, where possible. We have surveyed 20 AGB stars with a range of mass-loss rates and of different chemical types using the APEX telescope to search for rotational transition lines of five key sulphur-bearing molecules: CS, SiS, SO, SO$_2$ and H$_2$S. Here we present our results for H$_2$S, including detections, non-detections and detailed radiative transfer modelling of the detected lines. We compare results based on different descriptions of the molecular excitation of H$_2$S and different abundance distributions, including those derived from chemical modelling results. We detected H$_2$S towards five AGB stars, all of which have high mass-loss rates of $\dot{M}\geq 5\times 10^{-6}M_\odot$ yr$^{-1}$ and are oxygen-rich. H$_2$S was not detected towards the carbon or S-type stars that fall in a similar mass-loss range. For the stars in our sample with detections, we find peak o-H$_2$S abundances relative to H$_2$ between $4\times 10^{-7}$ and $2.5\times 10^{-5}$. Overall, we conclude that H$_2$S can play a significant role in oxygen-rich AGB stars with higher mass-loss rates, but is unlikely to play a key role in stars of other chemical types or the lower mass-loss rate oxygen-rich stars. For two sources, V1300 Aql and GX Mon, H$_2$S is most likely the dominant sulphur-bearing molecule in the circumstellar envelope.Comment: 14 pages, 7 figures, accepted in A&

Large scale grain mantle disruption in the Galactic Center

We present observations of C2H5OH toward molecular clouds in Sgr A, Sgr B2 and associated with thermal and non-thermal features in the Galactic center. C2H5OH emission in Sgr A and Sgr B2 is widespread, but not uniform. C2H5OH emission is much weaker or it is not detected in some molecular clouds in both complexes, in particular those with radial velocities between 70 and 120 km/s. While most of the clouds associated with the thermal features do not show C2H5OH emission, that associated with the Non-Thermal Radio Arc shows emission. The fractional abundance of C2H5OH in most of the clouds with radial velocities between 0 and 70 km/s in Sgr A and Sgr B2 is relatively high, of few 1e-8. The C2H5OH abundance decreases by more than one order of magnitude (aprox. 1e-9) in the clouds associated with the thermal features. The large abundance of C2H5OH in the gas-phase indicates that C2H5OH has formed in grains and released to gas-phase by shocks in the last aprox. 1e5 years.Comment: In press in Astrophysical Journal Letters 7 pages, 1 table, 1 figur