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The global burden of obesity leads to significant morbidity and has major economic implications. In April 2018, Britain will join a growing number of countries attempting to tackle this using fiscal measures when the UK Soft Drinks Industry Levy is introduced. We review recent evidence from natural experiments of the impact of health-related food and drink taxes on consumer behaviour, and discuss the possible consequences of these approaches on purchases and health. We highlight some of the potential indirect consequences and the importance of robust prospective evaluation.
Machine learning is a lively academic discipline and a key player in the continuous pursuit for new technological developments. The editorial in the first issue of the journal Machine Learning, published in March 1986, described the discipline as that field of inquiry concerned with the processes by which intelligent systems improve their performance over time (Langley, 1986). A glossary of terms published in the same journal in 1998 refined this to: Machine Learning is the field of scientific study that concentrates on induction algorithms and on other algorithms that can be said to ‘learn’ (Kohavi and Provost, 1998).
Thomas J. Watson, the brilliant salesman who from 1914 to 1956 oversaw the remarkable growth and success of IBM, serving as both CEO and chairman, was famously quoted as saying in 1943, ‘I think there is a world market for maybe five computers.’ With more than one billion computers now in use worldwide (Virki, 2008), this quote is often referenced to illustrate how vastly their usefulness had been underestimated.No area of computer science is making progress more rapidly than machine learning, with computers being capable of tasks that were a few decades ago only mentioned in science-fiction stories. Watson brought to IBM from his previous employment his trademark motto ‘Think’. It would at the time have been reasonable for Watson to suppose that only humans could really ‘think’. While computers could surpass humans in adding, subtracting, multiplying, and dividing, they were hardly thought of as being good at human tasks, such as playing chess, which required thinking. This begs the question, ‘What is thinking?’ In February 1996 World Chess Champion Garry Kasparov took on the IBM computer Deep Blue in Philadelphia. Even with the IBM engineers allowed to reprogram the computer between games, the world champion won, but only just, losing one game, drawing two, and winning three. His victory was short-lived. The following year he played a rematch. With the score even after the first five of six games, Kasparov allowed Deep Blue to commit a knight sacrifice, which wrecked his Caro–Kann defence and forced him to resign in fewer than twenty moves.
The meaning and value of Fet's poetry have provided food for debate for over a century, but its musicality has long stood beyond question. Whatever the decision about their ultimate worth, his melodic lyrics undoubtedly call up some of the sweetest sounds of nineteenth-century Russian verse. Just as there is hardly a Russian poet who has been more widely or successfully parodied, so scarcely is there one who has been more often set to music. As a mid-century poet he had serious rivals for the favors of composers and yet defeated them all—A. K. Tolstoy, Polonsky, Mei, Grigoriev, even the redoubtable Nekrasov. His whole poetic manner seemed to impinge so far upon music itself that the composer could see immediately how the music should be written and set to work at once with the enthusiasm of any expert who suddenly finds before him a small challenge which is right in his own field.
A number of laser facilities coming online all over the world promise the capability of high-power laser experiments with shot repetition rates between 1 and 10 Hz. Target availability and technical issues related to the interaction environment could become a bottleneck for the exploitation of such facilities. In this paper, we report on target needs for three different classes of experiments: dynamic compression physics, electron transport and isochoric heating, and laser-driven particle and radiation sources. We also review some of the most challenging issues in target fabrication and high repetition rate operation. Finally, we discuss current target supply strategies and future perspectives to establish a sustainable target provision infrastructure for advanced laser facilities.
We have compiled a catalogue of H ii regions detected with the Murchison Widefield Array between 72 and 231 MHz. The multiple frequency bands provided by the Murchison Widefield Array allow us identify the characteristic spectrum generated by the thermal Bremsstrahlung process in H ii regions. We detect 306 H ii regions between 260° < l < 340° and report on the positions, sizes, peak, integrated flux density, and spectral indices of these H ii regions. By identifying the point at which H ii regions transition from the optically thin to thick regime, we derive the physical properties including the electron density, ionised gas mass, and ionising photon flux, towards 61 H ii regions. This catalogue of H ii regions represents the most extensive and uniform low frequency survey of H ii regions in the Galaxy to date.
Spectropolarimetric observations of the 10 arc second region surrounding Eta Carinae have been made in the 8-13 μm wavelength band. The observed polarization, of a few percent, is due to emission of radiation from aligned grains. The radial position angle of the polarization suggests that gas streaming is responsible for the grain alignment.
We compare first-order (refractive) ionospheric effects seen by the MWA with the ionosphere as inferred from GPS data. The first-order ionosphere manifests itself as a bulk position shift of the observed sources across an MWA field of view. These effects can be computed from global ionosphere maps provided by GPS analysis centres, namely the CODE. However, for precision radio astronomy applications, data from local GPS networks needs to be incorporated into ionospheric modelling. For GPS observations, the ionospheric parameters are biased by GPS receiver instrument delays, among other effects, also known as receiver DCBs. The receiver DCBs need to be estimated for any non-CODE GPS station used for ionosphere modelling. In this work, single GPS station-based ionospheric modelling is performed at a time resolution of 10 min. Also the receiver DCBs are estimated for selected Geoscience Australia GPS receivers, located at Murchison Radio Observatory, Yarragadee, Mount Magnet and Wiluna. The ionospheric gradients estimated from GPS are compared with that inferred from MWA. The ionospheric gradients at all the GPS stations show a correlation with the gradients observed with the MWA. The ionosphere estimates obtained using GPS measurements show promise in terms of providing calibration information for the MWA.
GLEAM, the GaLactic and Extragalactic All-sky MWA survey, is a survey of the entire radio sky south of declination + 25° at frequencies between 72 and 231 MHz, made with the MWA using a drift scan method that makes efficient use of the MWA’s very large field-of-view. We present the observation details, imaging strategies, and theoretical sensitivity for GLEAM. The survey ran for two years, the first year using 40-kHz frequency resolution and 0.5-s time resolution; the second year using 10-kHz frequency resolution and 2 s time resolution. The resulting image resolution and sensitivity depends on observing frequency, sky pointing, and image weighting scheme. At 154 MHz, the image resolution is approximately 2.5 × 2.2/cos (δ + 26.7°) arcmin with sensitivity to structures up to ~ 10° in angular size. We provide tables to calculate the expected thermal noise for GLEAM mosaics depending on pointing and frequency and discuss limitations to achieving theoretical noise in Stokes I images. We discuss challenges, and their solutions, that arise for GLEAM including ionospheric effects on source positions and linearly polarised emission, and the instrumental polarisation effects inherent to the MWA’s primary beam.
The Murchison Widefield Array is a Square Kilometre Array Precursor. The telescope is located at the Murchison Radio–astronomy Observatory in Western Australia. The MWA consists of 4 096 dipoles arranged into 128 dual polarisation aperture arrays forming a connected element interferometer that cross-correlates signals from all 256 inputs. A hybrid approach to the correlation task is employed, with some processing stages being performed by bespoke hardware, based on Field Programmable Gate Arrays, and others by Graphics Processing Units housed in general purpose rack mounted servers. The correlation capability required is approximately 8 tera floating point operations per second. The MWA has commenced operations and the correlator is generating 8.3 TB day−1 of correlation products, that are subsequently transferred 700 km from the MRO to Perth (WA) in real-time for storage and offline processing. In this paper, we outline the correlator design, signal path, and processing elements and present the data format for the internal and external interfaces.
The Murchison Widefield Array is a new low-frequency interferometric radio telescope built in Western Australia at one of the locations of the future Square Kilometre Array. We describe the automated radio-frequency interference detection strategy implemented for the Murchison Widefield Array, which is based on the aoflagger platform, and present 72–231 MHz radio-frequency interference statistics from 10 observing nights. Radio-frequency interference detection removes 1.1% of the data. Radio-frequency interference from digital TV is observed 3% of the time due to occasional ionospheric or atmospheric propagation. After radio-frequency interference detection and excision, almost all data can be calibrated and imaged without further radio-frequency interference mitigation efforts, including observations within the FM and digital TV bands. The results are compared to a previously published Low-Frequency Array radio-frequency interference survey. The remote location of the Murchison Widefield Array results in a substantially cleaner radio-frequency interference environment compared to Low-Frequency Array’s radio environment, but adequate detection of radio-frequency interference is still required before data can be analysed. We include specific recommendations designed to make the Square Kilometre Array more robust to radio-frequency interference, including: the availability of sufficient computing power for radio-frequency interference detection; accounting for radio-frequency interference in the receiver design; a smooth band-pass response; and the capability of radio-frequency interference detection at high time and frequency resolution (second and kHz-scale respectively).
The science cases for incorporating high time resolution capabilities into modern radio telescopes are as numerous as they are compelling. Science targets range from exotic sources such as pulsars, to our Sun, to recently detected possible extragalactic bursts of radio emission, the so-called fast radio bursts (FRBs). Originally conceived purely as an imaging telescope, the initial design of the Murchison Widefield Array (MWA) did not include the ability to access high time and frequency resolution voltage data. However, the flexibility of the MWA’s software correlator allowed an off-the-shelf solution for adding this capability. This paper describes the system that records the 100 μs and 10 kHz resolution voltage data from the MWA. Example science applications, where this capability is critical, are presented, as well as accompanying commissioning results from this mode to demonstrate verification.
We present the results of an approximately 6 100 deg2 104–196 MHz radio sky survey performed with the Murchison Widefield Array during instrument commissioning between 2012 September and 2012 December: the MWACS. The data were taken as meridian drift scans with two different 32-antenna sub-arrays that were available during the commissioning period. The survey covers approximately 20.5 h < RA < 8.5 h, − 58° < Dec < −14°over three frequency bands centred on 119, 150 and 180 MHz, with image resolutions of 6–3 arcmin. The catalogue has 3 arcmin angular resolution and a typical noise level of 40 mJy beam− 1, with reduced sensitivity near the field boundaries and bright sources. We describe the data reduction strategy, based upon mosaicked snapshots, flux density calibration, and source-finding method. We present a catalogue of flux density and spectral index measurements for 14 110 sources, extracted from the mosaic, 1 247 of which are sub-components of complexes of sources.
Water supply-associated cryptosporidiosis outbreaks have decreased in England since the application of risk reduction measures to public water supplies. We hypothesized that smaller outbreaks were occurring which could be better detected by enhanced surveillance. Rolling analysis of detailed questionnaire data was applied prospectively in a population of 2·2 million in the south of England in 2009 and 2010. Detection of spatiotemporal clusters using SaTScan was later undertaken retrospectively. Together these approaches identified eight outbreaks, compared to an expectation of less than one based on national surveillance data. These outbreaks were small and associated with swimming pool use or, less commonly, direct (e.g. petting-farm) contact with animals. These findings suggest that frequent small-scale transmission in swimming pools is an important contributor to disease burden. Identification of swimming pool-level risk factors may inform preventative measures. These findings and the approaches described may be applicable to many other populations and to some other diseases.
Numerous techniques have been described to manage the skin and other soft tissues during bone-anchored hearing aid insertion. Previously, generally accepted techniques have sometimes led to distressing alopecia and soft tissue defects. Now, some surgeons are rejecting the originally described split skin flap in favour of a less invasive approach.
To investigate bone-anchored hearing aid placement utilising a single, linear incision with either no or minimal underlying soft tissue reduction.
Patients and methods:
Thirty-four adults were prospectively enrolled to undergo single-stage bone-anchored hearing aid placement with this modified technique. A small, linear incision was used at the standard position and carried down through the periosteum. Standard technique was then followed with placement of an extended length abutment. Patients were reviewed regularly to assess wound healing, including evaluation with Holgers' scale.
Only 14.7 per cent of patients had a reaction score of 2 or higher. Most complications were limited to minor skin reactions that settled with silver nitrate cautery and/or antibiotics. None required revision surgery for tissue overgrowth, and there were no implant failures.
Our results suggest this to be a simple and effective insertion technique with favourable cosmesis and patient satisfaction.
Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the southern hemisphere designed specifically to explore the low-frequency astronomical sky between 80 and 300 MHz with arcminute angular resolution and high survey efficiency. The telescope will enable new advances along four key science themes, including searching for redshifted 21-cm emission from the EoR in the early Universe; Galactic and extragalactic all-sky southern hemisphere surveys; time-domain astrophysics; and solar, heliospheric, and ionospheric science and space weather. The Murchison Widefield Array is located in Western Australia at the site of the planned Square Kilometre Array (SKA) low-band telescope and is the only low-frequency SKA precursor facility. In this paper, we review the performance properties of the Murchison Widefield Array and describe its primary scientific objectives.
Digital signal processing is one of many valuable tools for suppressing unwanted signals or inter-ference. Building hardware processing engines seems to be the way to best implement some classes of interference suppression but is, unfortunately, expensive and time-consuming, especially if several miti-gation techniques need to be compared. Simulations can be useful, but are not a substitute for real data. CSIRO’s Australia Telescope National Facility has recently commenced a ‘software radio telescope’ project designed to fill the gap between dedicated hardware processors and pure simulation. In this approach, real telescope data are recorded coherently, then processed offline. This paper summarises the current contents of a freely available database of base band recorded data that can be used to experiment with signal processing solutions. It includes data from the following systems: single dish, multi-feed receiver; single dish with reference antenna; and an array of six 22 m antennas with and without a reference antenna. Astronomical sources such as OH masers, pulsars and continuum sources subject to interfering signals were recorded. The interfering signals include signals from the US Global Positioning System (GPS) and its Russian equivalent (GLONASS), television, microwave links, a low-Earth-orbit satellite, various other transmitters, and signals leaking from local telescope systems with fast clocks. The data are available on compact disk, allowing use in general purpose computers or as input to laboratory hardware prototypes.