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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.
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.
The Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the mid-west of Western Australia, a location chosen for its extremely low levels of radio frequency interference. The MWA operates at low radio frequencies, 80–300 MHz, with a processed bandwidth of 30.72 MHz for both linear polarisations, and consists of 128 aperture arrays (known as tiles) distributed over a ~3-km diameter area. Novel hybrid hardware/software correlation and a real-time imaging and calibration systems comprise the MWA signal processing backend. In this paper, the as-built MWA is described both at a system and sub-system level, the expected performance of the array is presented, and the science goals of the instrument are summarised.
We contrast the current, clinically based framework for behavior disorder against a life course framework, as an alternative structure upon which to map the variations in onset and stability of clinical symptomatology known to take place in adult life. This alternative developmental framework is used as a base around which to understand known variations in rates of alcohol abuse/dependence over the life course and to review existing schemes for the evaluation of developmental variation in “caseness.” From this work, it was proposed that symptom structure be regarded as a mass of greater or lesser breadth, with properties of extensiveness in time and life course invasiveness, as a function of where in the life course the symptomatology first emerged, and the degree to which the mass sustained itself in developmental time. This framework guided the construction of a time-based measure of alcohol related symptomatology, called the Lifetime Alcohol Problems Score (LAPS). The LAPS discriminated among a variety of alcohol-specific and nonalcohol-specific measures of alcohol-related difficulty, including diagnosis of alcohol dependence, having been in treatment, level of other psychopathology, and measures of family disorganization. The measure has potential applicability for prospective studies, and in estimating clinical prognosis. The utility of the paradigm as a framework within which to conceptualize the emergence, ebb, and flow of other behavior disorders is also discussed.
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