William Zealey

High resolution H(I) observations of the western Magellanic Bridge

The 21-cm line emission from a 7 × 6d eg 2 region east of and adjoining the Small Magellanic Cloud (SMC) has been observed with the Australia Telescope Compact Array and the Parkes telescopes. This region represents the westernmost part of the Magellanic Bridge, a gas-rich tail extending ∼14 ◦ to the Large Magellanic Cloud. A rich and complex neutral hydrogen (H I) structure containing shells, bubbles and filaments is revealed. On the larger scale, the H I of the Bridge is organized into two velocity components. This bimodality, which appears to originate in the SMC, converges to a single velocity component within the observed region. A census of shell-like structures suggests a shell population with characteristics similar to that of the SMC. The mean kinematic age of the shells is ∼6 Myr, in agreement with the SMC shell population, but not with ages of OB clusters populating the Magellanic Bridge, which are approximately a factor of 3 older. In general, the projected spatial correlation of Bridge H I shells with OB associations is poor and as such, there does not appear to be a convincing relationship between the positions of OB associations and that of expanding spherical H I structures. This survey has found only one H I shell that has an identifiable association with a known Hα shell. The origin of the expanding structures is therefore generally still uncertain, although current theories regarding their formation include gravitational and pressure instabilities, high-velocity cloud collisions and ram pressure effects.

Bra-breast forces generated in women with large breasts while standing and during treadmill running: implications for sports bra design

This study aimed to determine the bra-breast forces generated in women with large breasts while these women wore different levels of breast support during both upright standing and treadmill running. The mean bilateral vertical component of the bra-breast force in standing was 11.7 ± 4.6 N, whereas during treadmill running the mean unilateral bra-breast force was 8.7 ± 6.4 N and 14.7 ± 10.3 N in the high and low support conditions, respectively. Furthermore, breast mass was significantly correlated with vertical breast displacement (R(2) = 0.62) in the high support condition. The wide range of breast masses of women with large breasts is an important consideration for designers of sports bras to ensure these bras can reduce force generation and breast discomfort by providing a high level of breast support while these women participate in physical activity.

Detection of carbon monoxide within the Magellanic Bridge

The Mopra 22-m and SEST 15-m telescopes have been used to detect and partially map a region of 12 CO(1-0) line emission within the Magellanic Bridge, a region lying between the Large and Small Magellanic Clouds (LMC and SMC, respectively). The emission appears to be embedded in a cloud of neutral hydrogen, and is in the vicinity of an IRAS source. The CO emission region is found to have a 60 µm/100 µm flux density ratio typical for 12 CO(1-0) detections within the SMC, although it has a significantly lower 12 CO brightness and velocity width. These suggest that the observed region is of a low metallicity, supporting earlier findings that the Magellanic Bridge is not as evolved as the SMC and Magellanic Stream, which are themselves of a lower metallicity than the Galaxy. Our observations, along with empirical models based on SMC observations, indicate that the radius of the detected CO region has an upper limit of ∼16 pc. This detection is, to our knowledge, the first detection of CO emission from the Magellanic Bridge and is the only direct evidence of star formation through molecular cloud collapse in this region.

Performance of Al2O3:C optically stimulated luminescence dosimeters for clinical radiation therapy applications

A commercial Optical Stimulated Luminescence (OSL) dosimetry system developed by Landauer was tested to analyse the possibility of using OSL dosimetry for external beam radiotherapy planning checks. Experiments were performed to determine signal sensitivity, dose response range, beam type/energy dependency, reproducibility and linearity. Optical annealing processes to test OSL material reusability were also studied. In each case the measurements were converted into absorbed dose. The experimental results show that OSL dosimetry provides a wide dose response range, good linearity and reproducibility for the doses up to 800cGy. The OSL output is linear with dose up to 600cGy range showing a maximum deviation from linearity of 2.0% for the doses above 600cGy. The standard deviation in response of 20 dosimeters was 3.0%. After optical annealing using incandescent light, the readout intensity decreased by approximately 98% in the first 30 minutes. The readout intensity,I, decreased after repeated optical annealing as a power law, given byI ∝ t−1.3. This study concludes that OSL dosimetry can provide an alternative dosimetry technique for use in in-vivo dosimetry if rigorous measurement protocols are established.

New Herbig–Haro objects and giant outflows in Orion

We present the results of a photographic and CCD imaging survey for Herbig‐Haro (HH) objects in the L1630 and L1641 giant molecular clouds in Orion. The new HH flows were initially identified from a deep Ha film from the recently commissioned AAO/UKST Ha Survey of the southern sky. Our scanned Ha and broad-band R images highlight both the improved resolution of the Ha survey and the excellent contrast of the Ha flux with respect to the broad-band R. Comparative IVN survey images allow us to distinguish between emission and reflection nebulosity. Our CCD Ha ,[ S ii], continuum and I-band images confirm the presence of a parsec-scale HH flow associated with the Ori I-2 cometary globule, and several parsec-scale strings of HH emission centred on the L1641-N infrared cluster. Several smaller outflows display one-sided jets. Our results indicate that, for declinations south of 268 in L1641, parsec-scale flows appear to be the major force in the large-scale movement of optical dust and molecular gas.

Filamentary Shell Structures from the AAO/UKST Hα Survey

Here we present the first results of a search for new optical supernova remnant candidates and other filamentary objects on films produced by the Anglo-Australian Observatory/UK Schmidt Telescope Hα Survey. Sixty-one fields, or 26% of the Galactic plane survey fields, have been visually examined. This has resulted in the detection of four new large diameter filamentary structures, and the discovery of extensive new optical emission in two previously known optical supernova remnant candidates.

The Parkes-MIT-NRAO Southern Sky Survey at 4850 MHz

G. Behrens, C. Chestnut, National Radio Astronomy Observatory, Greenbank, USA B. F. Burke, A. Fletcher, Massachusetts Institute of Technology, Cambridge, USA K. S. Russell, A. Savage, UK Schmidt Telescope, Anglo-Australian Observatory, Coonabarabran NSW 2357 J . L im, A. E. Vaughan, School of Mathematics and Physics, Macquarie University, North Ryde NSW 2113 S. Cote, Mount Stromlo and Siding Spring Observatories, Private Bag Weston ACT 2611 M. Anderson, A. Hons, G. L. White, Faculty of Science and Technology, University of Western Sydney, Kingswood NSW 2747 S. Amy, A. Burgess, S. Chan, L. Cram, A. Gray, W . Walsh, D. Campbell-Wilson, Astrophysics Department, University of Sydney, NSW 2006 V. Mclntyre, P. Randall, M. Suters, W. J. Zealey, Department of Physics, University of Wollongong, Wollongong NSW 2500

The Cosmology Distinction Course in NSW

The Cosmology Distinction Course is a new one-year course to be introduced for Year 12 candidates in the 1994 Higher School Certificate examinations in NSW. It is one of three challenging courses of study that will enrich the HSC for talented students who accelerate and complete part of the HSC one year early. The courses will be taught through distance learning and will include residential seminars. They will be implemented on behalf of the Board of Studies by Charles Sturt University and the University of New England. The Cosmology Course is organised into nine modules of course work covering historical and social aspects of cosmology, observational techniques, key observations and the various models developed—Newtonian, de Sitter, Friedmann, Lemaitre, steady-state, quasi-steadystate and big bang. Assessment will be through assignments, exams and a major project. As the first Distinction Course in a scientific area, the Cosmology Course represents an exciting and important educational initiative that needs the cooperation of NSW astronomers and, in return, promises to benefit the astronomical and general scientific community in Australia.

An investigation into the source of low energy scattered radiation of significance in film dosimetry

The nature of the background optical density on films exposed to orthovoltage x-rays and electron beams has been studied for correction purposes. A higher than expected background value can be demonstrated by comparing the film scanned beam profile with water phantom ionisation scans of the same beam. A range of 3–5% increased background in the penumbral tail, with energy dependence, has been shown experimentally. Testing the assumption that this increased background is due to Cerenkov radiation produced in the film, Filmstrips were interleaved in a solid water equivalent phantom and exposed to 300kV orthovoltage x-ray beams and 5MeV to 12MeV electron beams. The film stacks were made up of single or multiple bare filmstrips, multiple filmstrips interleaved with black paper, and multiple filmstrips interleaved with overhead transparency sheet. The experimental result demonstrated that visible light was not significantly responsible for an enhanced film optical density, but rather that this was due to scattered radiation, with a complex low energy spectrum, arising from the film silver halide emulsion or base. An improved background correction technique is developed which incorporates this unexpected background value as an added component in the correction applied to the measured optical density. The resulting profiles exhibit improved agreement between film and ionization chamber measurements in the penumbra and tail regions.

Image Digitisation of Outflows and the AAO/UKST Halpha Survey

The Halpha emission-line survey of the Southern Sky to be carried out by the AAO/UKST will provide deep, high resolution images of Galactic Plane sources allowing the detection of new and existing filamentary sources such as Herbig-Haro objects. Used in conjunction with the existing ESO/SERC Southern Sky Survey Plates, the Halpha plates will provide us with the opportunity to study the morphology and environment of new and existing star forming regions.