Comparing the information capacity of entangled Laguerre-Gaussian and Hermite-Gaussian modal sets in a finite-aperture system

Using a spontaneous parametric down-conversion process to create entangled spatial states, we compare the information capacity associated with measurements in the Hermite–Gaussian and Laguerre–Gaussian modal basis in an optical system of finite aperture. We show that the cross-talk imposed by the aperture restriction degrades the information capacity. However, the Laguerre–Gaussian mode measurements show greater resilience to cross talk than the Hermite–Gaussian, suggesting that the Laguerre–Gaussian modal set may still offer real-world advantages over other modal sets

Scalable distributed event detection for Twitter

Social media streams, such as Twitter, have shown themselves to be useful sources of real-time information about what is happening in the world. Automatic detection and tracking of events identified in these streams have a variety of real-world applications, e.g. identifying and automatically reporting road accidents for emergency services. However, to be useful, events need to be identified within the stream with a very low latency. This is challenging due to the high volume of posts within these social streams. In this paper, we propose a novel event detection approach that can both effectively detect events within social streams like Twitter and can scale to thousands of posts every second. Through experimentation on a large Twitter dataset, we show that our approach can process the equivalent to the full Twitter Firehose stream, while maintaining event detection accuracy and outperforming an alternative distributed event detection system

Whistler Waves in the Radiation Belt

The Van Allen Radiation Belt is a region in space populated with high-energy, electrically-charged particles trapped in earth’s magnetic field. These particles constitute a danger to spacecraft in low-earth orbit, including the ISS and its crew. Solar storms and high-altitude nuclear explosions can increase the number of particles in the radiation belt by a factor of 100, rendering many important defense and communications satellites inoperable. It is of national security interest to develop a physical understanding of remediation of energetic particles from space. One possible method to achieve this is to use electromagnetic whistler-mode waves. Using data from the Van Allen Probes, we have conducted a preliminary analysis to validate simulations developed by Dr. Anatoly Streltsov which describe the propagation of whistler waves in space. Over the next year, we plan to further validate the models. This poster will present advances in whistler-wave physics which have important applications to future projects of launching whistlers into the radiation belt

Coherent absorption of N00N states

Recent results in deeply subwavelength thickness films demonstrate coherent control and logical gate operations with both classical and single-photon light sources. However, quantum processing and devices typically involve more than one photon and nontrivial input quantum states. Here we experimentally investigate two-photon N00N state coherent absorption in a multilayer graphene film. Depending on the N00N state input phase, it is possible to selectively choose between single- or two-photon absorption of the input state in the graphene film. These results demonstrate that coherent absorption in the quantum regime exhibits unique features, opening up applications in multiphoton spectroscopy and imaging

Psychometric validation of the Coronary Revascularisation Outcome Questionnaire (CROQv2) in the context of the NHS Coronary Revascularisation PROMs Pilot.

OBJECTIVES: The Coronary Revascularisation Outcome Questionnaire (CROQ) is a patient-reported outcome measure (PROM) for coronary artery bypass surgery (CABG) and percutaneous coronary intervention (PCI). We tested the psychometric properties of a modified version (CROQv2) when administered in a National Health Service (NHS)/Department of Health (DH) funded pilot of PROMs for coronary revascularisation. DESIGN: Psychometric validation study. SETTING: 11 English hospitals in the UK taking part in the NHS/DH funded pilot of PROMs for coronary revascularisation. PARTICIPANTS: Comprehensive analyses of acceptability, reliability, validity and responsiveness were conducted independently for each of the prerevascularisation (n=2685 and n=3711) and postrevascularisation (n=869 and n=837) versions of the CROQ-CABG and CROQ-PCI, respectively. RESULTS: All versions met prespecified stringent criteria for (1) acceptability of items (missing data) and scales (missing data, floor and ceiling effects, skewness); (2) tests of scaling assumptions; (3) reliability: internal consistency (Cronbach's α, item-total correlations); (4) construct validity based on within-scale analyses (internal consistency, intercorrelations between scales, factor analysis and hypothesis testing); (5) construct validity based on comparisons with external measures (convergent and discriminant validity and hypothesis testing) and (6) responsiveness. Results were also confirmed when tests were repeated on subsamples of CABG (n=639) and PCI (n=615) patients who reported receiving help completing prerevascularisation questionnaires. CONCLUSIONS: The availability of a psychometrically robust procedure-specific tool that could be used as part of a large-scale coronary revascularisation PROMs programme to capture the patients' perspective of coronary revascularisation will enable outcomes important to patients to be routinely collected alongside clinical outcomes. The CROQ is suitable for administration by postal survey or the prerevascularisation versions can be administered in the clinical setting as in the Coronary Revascularisation PROMs Pilot

December 2008

Editor: Sara Tui Miles, Assistant Editor: Kimberly Brown, Head Designer: Trinity Cotton, Photography: Daniela Brown, Illustrator: Trent Malycha, Designer: Calvin Chuang, Nursing Representative: Ernie Koh, Director of Student Services: Kevin Judge. Printed in Australia.https://research.avondale.edu.au/jacaranda/1052/thumbnail.jp

December 2007

Editor: Sara Tui Miles, Layout & Design: Elijah Roussos and Annalise Fehlberg, Literary Liaison: Stephanie Arnold, Staff Advisor: Donna Pinter, Photographer: Sarah Fischer and Daniela Brown, Marketing: Jodine Davis, Banquet Organiser: Jody Donovan, Nursing Representative: Ernie Koh. Printed in Australia.https://research.avondale.edu.au/jacaranda/1051/thumbnail.jp

Observations and Simulations of Whistler Waves in the Van Allen Radiation Belts

When the first American satellite, Explorer I, was launched into space in 1958 it inadvertently discovered one the most significant features of our local space environment: the Van Allen Radiation Belts. This region contains highly energetic protons and electrons from the sun which become trapped in the Earth’s magnetic field. These particles are extremely hazardous for spacecraft, causing damage to electronics and endangering astronauts on the International Space Station. Certain natural or artificial events, such as solar coronal mass ejections or high-altitude nuclear explosions, can enhance the radiation belts and decrease satellite lifetimes by orders of magnitude. Therefore, there is a strong motivation to develop a means by which to deplete the radiation and protect our assets in space from this threat. We present one promising remediation mechanism based on the interactions between these particles and very-low-frequency electromagnetic waves known as whistlers. One important property of whistler waves is that they can be guided along narrow inhomogeneities of plasma density called ducts. We have analyzed several events of ducted whistlers observed by the Van Allen Probes satellites and reproduce them with numerical simulations based on whistler theory. We demonstrate quantitative agreement between our simulations and the observations, indicating that our model successfully explains the existing satellite observations and can be used to predict the results from future experiments of launching whistler waves into the radiation belts from ground stations and space-based transmitters

Ducting of Whistler Waves in the Van Allen Radiation Belts

Whistler waves are electromagnetic waves in the very-low-frequency range which propagate in the near-earth space plasma environment, specifically within a region called the Van Allen Radiation Belts. This region contains many highly energetic particles which pose a significant threat to spacecraft in Earth orbit, including the International Space Station. Whistler waves are particularly interesting because they can interact with the energetic particles and precipitate them out of the Van Allen Radiation Belts. One important characteristic of whistlers is that they can become trapped inside enhancements or depletions of the ambient plasma density. We compare wave and particle observations from the Van Allen Probes spacecraft to results from a numerical simulation developed to model the wave propagation physics. By using the observed conditions as inputs to the simulation, we can reproduce the ducted waves with good, quantitative agreement. The results from this study will be important for future experiments of launching whistler waves into the Van Allen Radiation Belts from ground antennae or space vehicles