ORCID Profile
0000-0003-4944-2216
Current Organisation
University of Queensland
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Publisher: American Astronomical Society
Date: 06-07-2023
Abstract: We present highly s led photometry of the supernova (SN) 2023ixf, a Type II SN in M101, beginning 2 days before its first known detection. To gather these data, we enlisted the global Unistellar Network of citizen scientists. These 252 observations from 115 telescopes show the SN’s rising brightness associated with shock emergence followed by gradual decay. We measure a peak M V = − 18.18 ± 0.09 mag at 2023 May 25 21:37 UTC in agreement with previously published analyses.
Publisher: Springer Science and Business Media LLC
Date: 26-04-2018
DOI: 10.1007/S41114-018-0012-9
Abstract: We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and $$90\\%$$ 90 % credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5– $$20~\\mathrm {deg}^2$$ 20 deg 2 requires at least three detectors of sensitivity within a factor of $$\\sim 2$$ ∼ 2 of each other and with a broad frequency bandwidth. When all detectors, including KAGRA and the third LIGO detector in India, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.
Publisher: American Astronomical Society
Date: 13-12-2017
Publisher: IOP Publishing
Date: 21-09-2012
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-05-2023
Abstract: When confined within an optical cavity light can exert strong radiation pressure forces. Combined with dynamical backaction, this enables important processes, such as laser cooling, and applications ranging from precision sensors to quantum memories and interfaces. However, the magnitude of radiation pressure forces is constrained by the energy mismatch between photons and phonons. Here, we overcome this barrier using entropic forces arising from the absorption of light. We show that entropic forces can exceed the radiation pressure force by eight orders of magnitude and demonstrate this using a superfluid helium third-sound resonator. We develop a framework to engineer the dynamical backaction from entropic forces, applying it to achieve phonon lasing with a threshold three orders of magnitude lower than previous work. Our results present a pathway to exploit entropic forces in quantum devices and to study nonlinear fluid phenomena such as turbulence and solitons.
Publisher: Springer Science and Business Media LLC
Date: 11-01-2011
DOI: 10.1038/SC.2010.186
Abstract: Cross-sectional survey. To determine the employment outcomes of persons with spinal cord injury (SCI) and to investigate the impact of various demographic, injury-related and work-related variables on these outcomes. People living with SCI in Malaysia who are members of a disability support organization. A total of 84 members of the Malaysian Spinal Injury Association, who have had traumatic SCI for at least 2 years and were between 15 and 64 years of age at the time of study, were interviewed through phone using a questionnaire to identify the association between demographic, injury-related and work-related variables and employment outcomes. The return to work rate in this study was 57.1% (employed at the time of study). The overall employment rate after SCI was 76.2% (worked at some point after injury). Those who were younger at time of injury (<20 years of age), able to drive a modified vehicle, independent in personal care and mobility were positively related to being employed. On the other hand, being hospitalized in the preceding 1 year and receiving financial incentives were negatively related to employment. Functional independence, especially ability to drive, was strongly associated with return to work and should be one of the priority goals of comprehensive rehabilitation of persons with SCI. The negative impact of recent hospitalization as well as financial compensation needs to be probed further.
Publisher: American Astronomical Society
Date: 18-12-2017
Publisher: Springer Science and Business Media LLC
Date: 16-10-2017
DOI: 10.1038/NATURE24471
Abstract: On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817-a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first 'multi-messenger' astronomical observation. Such observations enable GW170817 to be used as a 'standard siren' (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic 'distance ladder': the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements, while being completely independent of them. Additional standard siren measurements from future gravitational-wave sources will enable the Hubble constant to be constrained to high precision.
Publisher: IOP Publishing
Date: 12-04-2017
Publisher: American Physical Society (APS)
Date: 16-11-2020
Publisher: American Physical Society (APS)
Date: 26-01-2015
Publisher: Optica Publishing Group
Date: 14-07-2020
DOI: 10.1364/OE.397478
Abstract: Brillouin systems operating in the quantum regime have recently been identified as a valuable tool for quantum information technologies and fundamental science. However, reaching the quantum regime is extraordinarily challenging, owing to the stringent requirements of combining low thermal occupation with low optical and mechanical dissipation, and large coherent phonon-photon interactions. Here, we propose an on-chip liquid based Brillouin system that is predicted to exhibit large phonon-photon coupling with exceptionally low acoustic dissipation. The system is comprised of a silicon-based “slot” waveguide filled with superfluid helium. This type of waveguide supports optical and acoustical traveling waves, strongly confining both fields into a subwavelength-scale mode volume. It serves as the foundation of an on-chip traveling wave Brillouin resonator with an electrostrictive single photon optomechanical coupling rate exceeding 240 kHz. Such devices may enable applications ranging from ultra-sensitive superfluid-based gyroscopes, to non-reciprocal optical circuits. Furthermore, this platform opens up new possibilities to explore quantum fluid dynamics in a strongly interacting condensate.
Publisher: Wiley
Date: 04-10-2016
Publisher: Springer Science and Business Media LLC
Date: 10-02-2020
Publisher: American Astronomical Society
Date: 16-10-2017
Publisher: SAGE Publications
Date: 08-2014
Abstract: Feet displacement is recognized to be an important element in standing and is also linked to postural instability in elderly people with diabetes. This study investigates standing balance in diabetic patients in four asymmetric feet displacements. Quiet standing balance was investigated using the Biodex Balance System in 18 diabetic patients and compared with 18 control elderly subjects. The four standing conditions, namely, comfortable feet position, preferred feet position with a stance width of 17 cm and 15° angle between the medial borders, feet side by side, and heel side by side with a 30° angle between medial edges of feet were evaluated (i.e. eyes opened, eyes closed). The overall stability was calculated by measuring anterior–posterior and medial–lateral indices in standing conditions. Differences among feet positions were compared using an analysis of variance and the independent t-test. The diabetic patients were unstable in the medial–lateral direction when standing with feet side by side versus heel side by side with a 30° angle between medial edges of feet ( p = 0.012 and 0.011, respectively), while in controls the anterior–posterior stability scores between standing in preferred foot position with stance width of 17 cm and 15° angle between the medial borders versus feet side by side, and heel side by side with a 30° angle between medial edges of feet versus preferred foot position with stance width of 17 cm and 15° angle between the medial borders had significant difference ( p 0.05). The anterior–posterior stability scores of diabetic subjects with feet side by side versus comfortable foot position ( p = 0.047) and heel side by side with a 30° angle between medial edges of feet versus comfortable foot position ( p = 0.016) when they closed their eyes during the test had significant difference. Results confirmed that diabetic patients have greater instability in the medial–lateral direction when the base of support reduces and visual clue has an important role in standing balance.
Publisher: American Astronomical Society
Date: 07-04-2017
No related grants have been discovered for Andreas Sawadsky.