Practice activity trends among oral and maxillofacial surgeons in Australia

© 2004 Brennan et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.BACKGROUND: The aim of this study was to describe practice activity trends among oral and maxillofacial surgeons in Australia over time. METHODS: All registered oral and maxillofacial surgeons in Australia were surveyed in 1990 and 2000 using mailed self-complete questionnaires. RESULTS: Data were available from 79 surgeons from 1990 (response rate = 73.8%) and 116 surgeons from 2000 (response rate = 65.1%). The rate of provision of services per visit changed over time with increased rates observed overall (from 1.43 ± 0.05 services per visit in 1990 to 1.66 ± 0.06 services per visit in 2000), reflecting increases in pathology and reconstructive surgery. No change over time was observed in the provision of services per year (4,521 ± 286 services per year in 1990 and 4,503 ± 367 services per year in 2000). Time devoted to work showed no significant change over time (1,682 ± 75 hours per year in 1990 and 1,681 ± 94 hours per year in 2000), while the number of visits per week declined (70 ± 4 visits per week in 1990 to 58 ± 4 visits per week in 2000). CONCLUSIONS: The apparent stability in the volume of services provided per year reflected a counterbalancing of increased services provided per visit and a decrease in the number of visits supplied.David S Brennan, A John Spencer, Kiran A Singh, Dana N Teusner and Alastair N Gos

Radio Recombination Lines from Starbursts: NGC 3256, NGC 4945 and the Circinus Galaxy

A renewed attempt to detect radio recombination lines from external galaxies has resulted in the measurement of lines from several bright starburst galaxies. The lines are produced by hydrogen ionized by young, high-mass stars and are diagnostic of the conditions and gas dynamics in the starburst regions without problems of dust obscuration. We present here detections of the lines H91alpha and H92alpha near 8.6 GHz from the starburst nuclei in NGC 3256, NGC 4945, and the Circinus galaxy using the ATCA and VLA. Modelling the line emitting region as a collection of H II regions, we derive the required number of H II regions, their temperature, density, and distribution.Comment: 6 pages, to appear in "Proc 331. Heraeus Seminar: The Evolution of Starbursts", Bad Honnef, Germany, Aug 16 - 20, 2004, Eds: S. Huettemeister, S. Aalto, D.J. Bomans, and E. Manthe

Dust deposition rates in the Wollongong-Port Kembla area, New South Wales, Australia

Dust deposition in the Wollongong-Port Kembla region, New South Wales, Australia, arising from local industrial and mining activities, has been of major concern since the early 1960s. Reports dealing with dust deposition rates in the region have been published by different organisations where the data have been averaged for the region. This provides a general trend for the deposition rates for the whole region without considering the trends occurring in specific locations. This study was the first to examine the trends observed at 35 individual gauges to identify more localised trends in dust deposition rates in the Wollongong-Port Kembla region, and also to try and identify the contribution of some of the possible dust sources. The coverage span of the data was from 1991-2003. These data were compared with two guidelines. The results indicated that the trend for dust deposition rates in the Wollongong-Port Kembla region is, generally, decreasing, but the patterns for different gauges varied both spatially and temporally. Several factors were suspected to influence dust deposition rates, including meteorological conditions, mainly wind direction, proximity to dust sources, dust control devices installed by industry, and other nearby activities that could affect the deposition rate measurements. Deposition rates in some residential areas exceeded the guidelines for recommended action. Further speciation and characterisation analyses of dust samples are needed to confirm their sources

PKS B1400-33: an unusual radio relic in a poor cluster

We present new arcminute resolution radio images of the low surface brightness radio source PKS B1400-33 that is located in the poor cluster Abell S753. The observations consist of 330 MHz VLA, 843 MHz MOST and 1398 and 2378 MHz ATCA data. These new images, with higher surface brightness sensitivity than previous observations, reveal that the large scale structure consists of extended filamentary emission bounded by edge-brightened rims. The source is offset on one side of symmetrically distributed X-ray emission that is centered on the dominant cluster galaxy NGC 5419. PKS B1400-33 is a rare example of a relic in a poor cluster with radio properties unlike those of most relics and halos observed in cluster environments. The diffuse source appears to have had an unusual origin and we discuss possible mechanisms. We examine whether the source could be re-energized relic radio plasma or a buoyant synchrotron bubble that is a relic of activity in NGC 5419. The more exciting prospect is that the source is relic plasma preserved in the cluster gaseous environment following the chance injection of a radio lobe into the ICM as a result of activity in a galaxy at the periphery of the cluster.Comment: 26 pages, 8 figures, accepted for publication in the Astronomical Journa

VLA Observations of the "Eye of the Tornado"- the High Velocity \HII Region G357.63-0.06

The unusual supernova remnant candidate G357.7-0.1 and the compact source G357.63-0.06 have been observed with the Very Large Array at 1.4 and 8.3 GHz. The H92$\alpha$ line (8.3 GHz) was detected from the compact source with a surprising velocity of about -210 km/s indicating that this source is an \HII region, is most likely located at the Galactic center, and is unrelated to the SNR. The \HI absorption line (1.4 GHz) data toward these sources supports this picture and suggests that G357.7-0.1 lies farther away than the Galactic center.Comment: Latex, 14 pages including 4 figures. Accepted to A

The Sizes of 1720 MHz OH Masers: VLBA and MERLIN Observations of the Supernova Remnants W44 and W28

We have used the NRAO Very Long Baseline Array (VLBA) to image OH(1720 MHz) masers in the supernova remnants W28 and W44 at a resolution of 40 mas. We also used MERLIN to observe the same OH(1720 MHz) masers in W44 at a resolution of 290 x 165 mas. All the masers are resolved by these VLBA and MERLIN observations. The measured sizes range from 50 to 180 mas and yield brightness temperature estimates from 0.3--20 x 10**8 K. We investigate whether these measured angular sizes are intrinsic and hence originate as a result of the physical conditions in the supernova remnant shock, or whether they are scatter broadened sizes produced by the turbulent ionized gas along the line of sight. While the current data on the temporal and angular broadening of pulsars, masers and extragalactic soures toward W44 and W28 can be understood in terms of scattering, we cannot rule out that these large sizes are intrinsic. Recent theoretical modeling by Lockett et al. suggests that the physical parameters in the shocked region are indicative of densities and OH abundances which lead to estimates of sizes as large as what we measure. If the sizes and structure are intrinsic, then the OH(1720 MHz) masrs may be more like the OH(1612 MHz) masers in circumstellar shells than OH masers associated with HII regions. At two locations in W28 we observe the classical S-shapes in the Stokes V profiles caused by Zeeman splitting and use it to infer magnetic fields of order 2 milliGauss.Comment: 24 pages, 6 figures, accepted by Ap

Truncated-Determinant Diagrammatic Monte Carlo for Fermions with Contact Interaction

For some models of interacting fermions the known solution to the notorious sign-problem in Monte Carlo (MC) simulations is to work with macroscopic fermionic determinants; the price, however, is a macroscopic scaling of the numerical effort spent on elementary local updates. We find that the {\it ratio} of two macroscopic determinants can be found with any desired accuracy by considering truncated (local in space and time) matices. In this respect, MC for interacting fermionic systems becomes similar to that for the sign-problem-free bosonic systems with system-size independent update cost. We demonstrate the utility of the truncated-determinant method by simulating the attractive Hubbard model within the MC scheme based on partially summed Feynman diagrams. We conjecture that similar approach may be useful in other implementations of the sign-free determinant schemes.Comment: results of the actual Hubbard model simulations are adde