Hybrid functional calculations of the Al impurity in silica: Hole localization and electron paramagnetic resonance parameters

We performed first-principle calculations based on the supercell and cluster approaches to investigate the neutral Al impurity in smoky quartz. Electron paramagnetic resonance measurements suggest that the oxygens around the Al center undergo a polaronic distortion which localizes the hole being on one of the four oxygen atoms. We find that the screened exchange hybrid functional successfully describes this localization and improves on standard local density approaches or on hybrid functionals that do not include enough exact exchange such as B3LYP. We find a defect level at about 2.5 eV above the valence band maximum, corresponding to a localized hole in a O 2p orbital. The calculated values of the g tensor and the hyperfine splittings are in excellent agreement with experiment.Comment: 5 pages, 2 figures, 1 tabl

HI Emission and Absorption in the Southern Galactic Plane Survey

We present preliminary results from the Southern Galactic Plane Survey (SGPS) Test Region and Parkes data. As part of the pilot project for the Southern Galactic Plane Survey, observations of a Test Region (325.5 deg < l < 333.5 deg; -0.5 deg < b < 3.5 deg) were completed in December 1998. Single dish observations of the full survey region (253 deg < l < 358 deg; |b| <1 deg) with the Parkes Radio Telescope were completed in March 2000. We present a sample of SGPS HI data with particular attention to the smallest and largest scale structures seen in absorption and emission, respectively. On the large scale, we detect many prominent HI shells. On the small scale, we note extremely compact, cold clouds seen in HI self-absorption. We explore how these two classes of objects probe opposite ends of the HI spatial power spectrum.Comment: 9 pages, 3 embedded postscript & 4 jpeg figures. Presented at the Astronomical Society of Australia, Hobart, Tasmania, July 4-7 2000. To appear in PASA Vol. 18(1

Two Large HI Shells in the Outer Galaxy near l=279 degrees

As part of a survey of HI 21-cm emission in the Southern Milky Way, we have detected two large shells in the interstellar neutral hydrogen near l=279 deg. The center velocities are +36 and +59 km/s, which puts the shells at kinematic distances of 7 and 10 kpc. The larger shell is about 610 pc in diameter and very empty, with density contrast of at least 15 between the middle and the shell walls. It has expansion velocity of about 20 km/s and swept up mass of several million solar masses. The energy indicated by the expansion may be as high as 2.4 X 10^53 ergs. We estimate its age to be 15 to 20 million years. The smaller shell has diameter of about 400 pc, expansion velocity about 10 km/s and swept up mass of about 10^6 solar masses. Morphologically both regions appear to be shells, with high density regions mostly surrounding the voids, although the first appears to have channels of low density which connect with the halo above and below the HI layer. They lie on the edge of the Carina arm, which suggests that they may be expanding horizontally into the interarm region as well as vertically out of the disk. If this interpretation is correct, this is the first detection of an HI chimney which has blown out of both sides of the disk.Comment: 21 pages, 14 jpeg figures, accepted for publication in A

Use of detailed kinetic mechanisms for the prediction of autoignitions

This paper describes how automatically generated detailed kinetic mechanisms are obtained for the oxidation of alkanes and how these models could lead to a better understanding of autoignition and cool flame risks at elevated conditions. Examples of prediction of the occurrence of different autoignition phenomena, such as cool flames or two-stage ignitions are presented depending on the condition of pressure, temperature and mixture composition. Three compounds are treated, a light alkane, propane, and two heavier ones, n-heptane and n-decane

The Southern Galactic Plane Survey: The Test Region

The Southern Galactic Plane Survey (SGPS) is a project to image the HI line emission and 1.4 GHz continuum in the fourth quadrant of the Milky Way at high resolution using the Australia Telescope Compact Array (ATCA) and the Parkes Radio Telescope. In this paper we describe the survey details and goals, present lambda 21-cm continuum data, and discuss HI absorption and emission characteristics of the SGPS Test Region (325.5 deg < l < 333.5 deg; -0.5 deg < b < +3.5 deg). We explore the effects of massive stars on the interstellar medium (ISM) through a study of HI shells and the HI environments of HII regions and supernova remnants. We find an HI shell surrounding the HII region RCW 94 which indicates that the region is embedded in a molecular cloud. We give lower limits for the kinematic distances to SNRs G327.4+0.4 and G330.2+1.0 of 4.3 kpc and 4.9 kpc, respectively. We find evidence of interaction with the surrounding HI for both of these remnants. We also present images of a possible new SNR G328.6-0.0. Additionally, we have discovered two small HI shells with no counterparts in continuum emission.Comment: 17 pages, 7 embedded EPS figures, 10 low-res jpeg figures, uses emulateapj5.sty. Accepted for publication in the Astrophysical Journal. Version with all full resolution figures embedded is available at http://www.astro.umn.edu/~naomi/sgps/papers/SGPS.ps.g

The Galactic Distribution of Large HI Shells

We report the discovery of nineteen new HI shells in the Southern Galactic Plane Survey (SGPS). These shells, which range in radius from 40 pc to 1 kpc, were found in the low resolution Parkes portion of the SGPS dataset, covering Galactic longitudes l=253 deg to l=358 deg. Here we give the properties of individual shells, including positions, physical dimensions, energetics, masses, and possible associations. We also examine the distribution of these shells in the Milky Way and find that several of the shells are located between the spiral arms of the Galaxy. We offer possible explanations for this effect, in particular that the density gradient away from spiral arms, combined with the many generations of sequential star formation required to create large shells, could lead to a preferential placement of shells on the trailing edges of spiral arms. Spiral density wave theory is used in order to derive the magnitude of the density gradient behind spiral arms. We find that the density gradient away from spiral arms is comparable to that out of the Galactic plane and therefore suggest that this may lead to exaggerated shell expansion away from spiral arms and into interarm regions.Comment: 25 pages, 20 embedded EPS figures, uses emulateapj.sty, to appear in the Astrophysical Journa

Medical students’ and doctors’ attitudes towards older patients and their care in hospital settings: a conceptualisation

Background: despite assertions in reports from governmental and charitable bodies that negative staff attitudes towards older patients may contribute to inequitable healthcare provision for older patients when compared with younger patients (those aged under 65 years), the research literature does not describe these attitudes in any detail. Objective: this study explored and conceptualised attitudes towards older patients using in-depth interviews. Methods: twenty-five semi-structured interviews with medical students and hospital-based doctors in a UK acute teaching hospital were conducted. Participants were asked about their beliefs, emotions and behavioural tendencies towards older patients, in line with the psychological literature on the definition of attitudes (affective, cognitive and behavioural information). Data were analysed thematically. Results: attitudes towards older patients and their care could be conceptualised under the headings: (i) beliefs about older patients; (ii) older patients’ unique needs and the skills required to care for them and (iii) emotions and satisfaction with caring for older patients. Conclusions: our findings outlined common beliefs and stereotypes specific to older patients, as opposed to older people in general. Older patients had unique needs concerning their healthcare. Participants typically described negative emotions about caring for older patients, but the sources of dissatisfaction largely related to the organisational setting and system in which the care is delivered to these patients. This study marks one of the first in-depth attempts to explore attitudes towards older patients in UK hospital settings

Analysis of lesion localisation at colonoscopy: outcomes from a multi-centre U.K. study

Background: Colonoscopy is currently the gold standard for detection of colorectal lesions, but may be limited in anatomically localising lesions. This audit aimed to determine the accuracy of colonoscopy lesion localisation, any subsequent changes in surgical management and any potentially influencing factors. Methods: Patients undergoing colonoscopy prior to elective curative surgery for colorectal lesion/s were included from 8 registered U.K. sites (2012–2014). Three sets of data were recorded: patient factors (age, sex, BMI, screener vs. symptomatic, previous abdominal surgery); colonoscopy factors (caecal intubation, scope guide used, colonoscopist accreditation) and imaging modality. Lesion localisation was standardised with intra-operative location taken as the gold standard. Changes to surgical management were recorded. Results: 364 cases were included; majority of lesions were colonic, solitary, malignant and in symptomatic referrals. 82% patients had their lesion/s correctly located at colonoscopy. Pre-operative CT visualised lesion/s in only 73% of cases with a reduction in screening patients (64 vs. 77%; p = 0.008). 5.2% incorrectly located cases at colonoscopy underwent altered surgical management, including conversion to open. Univariate analysis found colonoscopy accreditation, scope guide use, incomplete colonoscopy and previous abdominal surgery significantly influenced lesion localisation. On multi-variate analysis, caecal intubation and scope guide use remained significant (HR 0.35, 0.20–0.60 95% CI and 0.47; 0.25–0.88, respectively). Conclusion: Lesion localisation at colonoscopy is incorrect in 18% of cases leading to potentially significant surgical management alterations. As part of accreditation, colonoscopists need lesion localisation training and awareness of when inaccuracies can occur