The implementation and use of Ada on distributed systems with high reliability requirements

The use and implementation of Ada in distributed environments in which reliability is the primary concern were investigated. In particular, the concept that a distributed system may be programmed entirely in Ada so that the individual tasks of the system are unconcerned with which processors they are executing on, and that failures may occur in the software or underlying hardware was examined. Progress is discussed for the following areas: continued development and testing of the fault-tolerant Ada testbed; development of suggested changes to Ada so that it might more easily cope with the failure of interest; and design of new approaches to fault-tolerant software in real-time systems, and integration of these ideas into Ada

The RMS Survey: 6 cm continuum VLA observations towards candidate massive YSOs in the northern hemisphere

(Abridged) Context: The Red MSX Source (RMS) survey is an ongoing multi-wavelength observational programme designed to return a large, well-selected sample of massive young stellar objects (MYSOs). We have identified $\sim$2000 MYSO candidates located throughout the Galaxy by comparing the colours of MSX and 2MASS point sources to those of known MYSOs. Aims: To identify the populations of UCHII regions and PNe within the sample and examine their Galactic distribution. Method: We have conducted high resolution radio continuum observations at 6 cm towards 659 MYSO candidates in the northern hemisphere (10\degr< l < 250\degr) using the VLA. In addition to these targeted observations we present archival data towards a further 315 RMS sources extracted from a previous VLA survey of the inner Galaxy. Results: We find radio emission towards 272 ($\sim$27% of the observed sample). Using results from other parts of our multi-wavelength survey we separate these RMS-radio associations into two distinct types of objects, classifying 51 as PNe and a further 208 as either compact or UC HII regions. Using this well selected sample of HII regions we estimate their Galactic scale height to be 0.6\degr. Conclusions: Using radio continuum and archival data we have identified 79 PNe and 391 HII regions within the northern RMS catalogue. We estimate the total fraction of contamination by PNe in the RMS sample is of order 10%. The sample of HII regions is probably the best representation to date of the Galactic population of HII regions as a whole.Comment: Accepted for publication in Astronomy and Astrophysics. 15 pages, 9 figures and 5 tables. Full versions of Tables 3, 4 and 5 and Figs. 2, 4 and 7 will only be available via CDS or the RMS website at http:/www.ast.leeds.ac.uk/cgi-bin/RMS/RMS_VLA_IMAGES.cg

On SAT representations of XOR constraints

We study the representation of systems S of linear equations over the two-element field (aka xor- or parity-constraints) via conjunctive normal forms F (boolean clause-sets). First we consider the problem of finding an "arc-consistent" representation ("AC"), meaning that unit-clause propagation will fix all forced assignments for all possible instantiations of the xor-variables. Our main negative result is that there is no polysize AC-representation in general. On the positive side we show that finding such an AC-representation is fixed-parameter tractable (fpt) in the number of equations. Then we turn to a stronger criterion of representation, namely propagation completeness ("PC") --- while AC only covers the variables of S, now all the variables in F (the variables in S plus auxiliary variables) are considered for PC. We show that the standard translation actually yields a PC representation for one equation, but fails so for two equations (in fact arbitrarily badly). We show that with a more intelligent translation we can also easily compute a translation to PC for two equations. We conjecture that computing a representation in PC is fpt in the number of equations.Comment: 39 pages; 2nd v. improved handling of acyclic systems, free-standing proof of the transformation from AC-representations to monotone circuits, improved wording and literature review; 3rd v. updated literature, strengthened treatment of monotonisation, improved discussions; 4th v. update of literature, discussions and formulations, more details and examples; conference v. to appear LATA 201

ATLASGAL - environments of 6.7 GHz methanol masers

Using the 870 micron APEX Telescope large area survey of the Galaxy, we have identified 577 submillimetre continuum sources with masers from the methanol multibeam survey in the region 280deg lt ell lt 20deg; |b| lt 1deg.5 94 per cent of methanol masers in the region are associated with submillimetre dust emission. We estimate masses for tilde450 maser-associated sources and find that methanol masers are preferentially associated with massive clumps. These clumps are centrally condensed, with envelope structures that appear to be scale-free, the mean maser position being offset from the peak column density by 0 plusmn 4 arcsec. Assuming a Kroupa initial mass function and a star formation efficiency of tilde30 per cent, we find that over two-thirds of the clumps are likely to form clusters with masses gt20 M$_?$. Furthermore, almost all clumps satisfy the empirical mass-size criterion for massive star formation. Bolometric luminosities taken from the literature for tilde100 clumps range between tilde100 and 10$^6$ L$_?$. This confirms the link between methanol masers and massive young stars for 90 per cent of our sample. The Galactic distribution of sources suggests that the star formation efficiency is significantly reduced in the Galactic Centre region, compared to the rest of the survey area, where it is broadly constant, and shows a significant drop in the massive star formation rate density in the outer Galaxy. We find no enhancement in source counts towards the southern Scutum-Centaurus arm tangent at ell tilde 315deg, which suggests that this arm is not actively forming stars.Peer reviewe

Characterisation of the Mopra Radio Telescope at 16--50 GHz

We present the results of a programme of scanning and mapping observations of astronomical masers and Jupiter designed to characterise the performance of the Mopra Radio Telescope at frequencies between 16-50 GHz using the 12-mm and 7-mm receivers. We use these observations to determine the telescope beam size, beam shape and overall telescope beam efficiency as a function of frequency. We find that the beam size is well fit by $\lambda$/$D$ over the frequency range with a correlation coefficient of ~90%. We determine the telescope main beam efficiencies are between ~48-64% for the 12-mm receiver and reasonably flat at ~50% for the 7-mm receiver. Beam maps of strong H$_2$O (22 GHz) and SiO masers (43 GHz) provide a means to examine the radial beam pattern of the telescope. At both frequencies the radial beam pattern reveals the presence of three components, a central `core', which is well fit by a Gaussian and constitutes the telescopes main beam, and inner and outer error beams. At both frequencies the inner and outer error beams extend out to approximately 2 and 3.4 times the full-width half maximum of the main beam respectively. Sources with angular sizes a factor of two or more larger than the telescope main beam will couple to the main and error beams, and therefore the power contributed by the error beams needs to be considered. From measurements of the radial beam power pattern we estimate the amount of power contained in the inner and outer error beams is of order one-fifth at 22 GHz rising slightly to one-third at 43 GHz.Comment: Accepted for publication in PAS

The RMS Survey: 13CO observations of candidate massive YSOs in the southern hemisphere

Abridged: The Red MSX Source (RMS) survey is an ongoing multi-wavelength observational programme designed to return a large, well-selected sample of massive young stellar objects (MYSOs). Here we present 13CO observations made towards 854 MYSOs candidates located in the 3rd and 4th quadrants. We detected 13CO emission towards a total of 751 of the 854 RMS sources observed (~88%). In total 2185 emission components are detected above 3$\sigma$ level. Multiple emission profiles are observed towards the majority of these sources - 455 sources (~60%) - with an average of ~4 molecular clouds along the line of sight. These multiple emission features make it difficult to assign a kinematic velocity to many of our sample. We have used archival CS (J=2-1) and maser velocities to resolved the component multiplicity towards 82 sources and have derived a criterion which is used to identify the most likely component for a further 202 multiple component sources. Combined with the single component detections we have obtained unambiguous kinematic velocities towards 580 sources (~80% of the detections). The 171 sources for which we have not been able to determine the kinematic velocity will require additional line data. Using the rotation curve of Brand and Blitz (1993) and their radial velocities we calculate kinematic distances for all components detected.Comment: Summitted to A&A, the resolution of figure 1 has been reduced, samples of Table 3 and Figure 11 are now included but the full version will only be available in the online version of the journa

Time for some changes to ICIS? Reflections on our highest-quality conference

© 2017 by the Association for Information Systems. In this commentary, we reflect on the program chair experience of ICIS 2015 to pass on some useful organizational memory for the IS community at large. We also reflect on volunteer effort required for a high-quality conference and the challenges of maintaining quality over a diverse and dispersed reviewing effort. We ask whether we can count on this volunteer effort in a changing higher education context where universities value volunteer effort or service less than promotion and tenure. We make several wide-ranging recommendations to preserve organizational memory and ensure the ongoing excellence of ICIS. Finally, we elaborate on some hard questions about whether the current conference model is fit for purpose and consider alternative models for our high-quality conference

Parasite infections in a social carnivore: Evidence of their fitness consequences and factors modulating infection load

There are substantial individual differences in parasite composition and infection load in wildlife populations. Few studies have investigated the factors shaping this heterogeneity in large wild mammals or the impact of parasite infections on Darwinian fitness, particularly in juveniles. A host's parasite composition and infection load can be shaped by factors that determine contact with infective parasite stages and those that determine the host's resistance to infection, such as abiotic and social environmental factors, and age. Host–parasite interactions and synergies between coinfecting parasites may also be important. We test predictions derived from these different processes to investigate factors shaping infection loads (fecal egg/oocyte load) of two energetically costly gastrointestinal parasites: the hookworm Ancylostoma and the intracellular Cystoisospora, in juvenile spotted hyenas (Crocuta crocuta) in the Serengeti National Park, in Tanzania. We also assess whether parasite infections curtail survival to adulthood and longevity. Ancylostoma and Cystoisospora infection loads declined as the number of adult clan members increased, a result consistent with an encounter‐reduction effect whereby adults reduced encounters between juveniles and infective larvae, but were not affected by the number of juveniles in a clan. Infection loads decreased with age, possibly because active immune responses to infection improved with age. Differences in parasite load between clans possibly indicate variation in abiotic environmental factors between clan den sites. The survival of juveniles (<365 days old) to adulthood decreased with Ancylostoma load, increased with age, and was modulated by maternal social status. High‐ranking individuals with low Ancylostoma loads had a higher survivorship during the first 4 years of life than high‐ranking individuals with high Ancylostoma loads. These findings suggest that high infection loads with energetically costly parasites such as hookworms during early life can have negative fitness consequences

The RMS survey: near-IR spectroscopy of massive young stellar objects

Near-infrared H- and K-band spectra are presented for 247 objects, selected from the Red MSX Source (RMS) survey as potential young stellar objects (YSOs). 195 (∼80 per cent) of the targets are YSOs, of which 131 are massive YSOs (L BOL > 5×10 3 L ⊙ , M > 8 M ⊙ ). This is the largest spectroscopic study of massive YSOs to date, providing a valuable resource for the study of massive star formation. In this paper, we present our exploratory analysis of the data. The YSOs observed have a wide range of embeddedness (2.7 < A V < 114), demonstrating that this study covers minimally obscured objects right through to very red, dusty sources. Almost all YSOs show some evidence for emission lines, though there is a wide variety of observed properties. The most commonly detected lines are Brγ, H 2 , fluorescent Fe ii, CO bandhead, [Fe ii] and He i 2-1 1 S- 1 P, in order of frequency of occurrence. In total, ∼40 per cent of the YSOs display either fluorescent Fe ii 1.6878 μm or CO bandhead emission (or both), indicative of a circumstellar disc; however, no correlation of the strength of these lines with bolometric luminosity was found. We also find that ∼60 per cent of the sources exhibit [Fe ii] or H 2 emission, indicating the presence of an outflow. Three quarters of all sources have Brγ in emission. A good correlation with bolometric luminosity was observed for both the Brγ and H 2 emission line strengths, covering 1 < L BOL < 3.5 × 10 5 L ⊙ . This suggests that the emission mechanism for these lines is the same for low-, intermediate- and high-mass YSOs, i.e. high-mass YSOs appear to resemble scaled-up versions of low-mass YSOs. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

The statistics of triggered star formation: an overdensity of massive YSOs around Spitzer bubbles

We present a detailed statistical study of massive star formation in the environment of 322 Spitzer mid-infrared bubbles by using the RMS survey for massive Young Stellar Objects (YSOs). Using a combination of simple surface density plots and a more sophisticated angular cross-correlation function analysis we show that there is a statistically significant overdensity of RMS YSOs towards the bubbles. There is a clear peak in the surface density and angular cross-correlation function of YSOs projected against the rim of the bubbles. By investigating the autocorrelation function of the RMS YSOs we show that this is not due to intrinsic clustering of the RMS YSO sample. RMS YSOs and Spitzer bubbles are essentially uncorrelated with each other beyond a normalised angular distance of two bubble radii. The bubbles associated with RMS YSOs tend to be both smaller and thinner than those that are not associated with YSOs. We interpret this tendency to be due to an age effect, with YSOs being preferentially found around smaller and younger bubbles. We find no evidence to suggest that the YSOs associated with the bubbles are any more luminous than the rest of the RMS YSO population, which suggests that the triggering process does not produce a top heavy luminosity function or initial mass function. We suggest that it is likely that the YSOs were triggered by the expansion of the bubbles and estimate that the fraction of massive stars in the Milky Way formed by this process could be between 14 and 30%.Comment: 12 pages, 8 figures. Accepted by MNRAS. This version incorporates minor suggestions by the referee. A version with higher resolution Figure 1 is available upon reques