tert-Butyl 2-methyl-2-(4-methyl­benzo­yl)propanoate

The title compound, C16H22O3, is bent with a dihedral angle of 75.3 (1)° between the mean planes of the benzene ring and a group encompassing the ester functionality (O=C—O—C). In the crystal, the mol­ecules are linked into infinite chains held together by weak C—H⋯O hydrogen-bonded inter­actions between an H atom on the benzene ring of one mol­ecule and an O atom on the ketone functionality of an adjacent mol­ecule. The chains are arranged with neighbouring tert-butyl and dimethyl groups on adjacent chains exhibiting hydro­phobic stacking, with short C—H⋯H—C contacts (2.37 Å) between adjacent chain

MWAX: A New Correlator for the Murchison Widefield Array

We describe the design, validation, and commissioning of a new correlator termed "MWAX" for the Murchison Widefield Array (MWA) low-frequency radio telescope. MWAX replaces an earlier generation MWA correlator, extending correlation capabilities and providing greater flexibility, scalability, and maintainability. MWAX is designed to exploit current and future Phase II/III upgrades to MWA infrastructure, most notably the simultaneous correlation of all 256 of the MWA's antenna tiles (and potentially more in future). MWAX is a fully software-programmable correlator based around an ethernet multicast architecture. At its core is a cluster of 24 high-performance GPU-enabled commercial-off-the-shelf compute servers that together process in real-time up to 24 coarse channels of 1.28 MHz bandwidth each. The system is highly flexible and scalable in terms of the number of antenna tiles and number of coarse channels to be correlated, and it offers a wide range of frequency / time resolution combinations to users. We conclude with a roadmap of future enhancements and extensions that we anticipate will be progressively rolled out over time.Comment: Accepted for publication in PASA. 22 pages, 14 figures, 2 table

Gridded and direct Epoch of Reionisation bispectrum estimates using the Murchison Widefield Array

We apply two methods to estimate the 21~cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly-spaced triangles of antenna tiles, as well as an estimate based on data gridded to the $uv$-plane. The direct and gridded bispectrum estimators are applied to 21 hours of high-band (167--197~MHz; $z$=6.2--7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and variance for point source foregrounds are derived. We compare the output of these approaches, the foreground contribution to the signal, and future prospects for measuring the bispectra with redundant and non-redundant arrays. We find that some triangle configurations yield bispectrum estimates that are consistent with the expected noise level after 10 hours, while equilateral configurations are strongly foreground-dominated. Careful choice of triangle configurations may be made to reduce foreground bias that hinders power spectrum estimators, and the 21~cm bispectrum may be accessible in less time than the 21~cm power spectrum for some wave modes, with detections in hundreds of hours.Comment: 19 pages, 10 figures, accepted for publication in PAS

Improved Techniques for the Surveillance of the Near Earth Space Environment with the Murchison Widefield Array

In this paper we demonstrate improved techniques to extend coherent processing intervals for passive radar processing, with the Murchison Widefield Array. Specifically, we apply a two stage linear range and Doppler migration compensation by utilising Keystone Formatting and a recent dechirping method. These methods are used to further demonstrate the potential for the surveillance of space with the Murchison Widefield Array using passive radar, by detecting objects orders of magnitude smaller than previous work. This paper also demonstrates how the linear Doppler migration methods can be extended to higher order compensation to further increase potential processing intervals.Comment: Presented at the 2019 IEEE Radar Conference in Boston earlier this yea

The Murchison Widefield Array: the Square Kilometre Array Precursor at low radio frequencies

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.Comment: Submitted to PASA. 11 figures, 2 table

Permeating the social justice ideals of equality and equity within the context of Early Years: challenges for leadership in multi-cultural and mono-cultural primary schools

The ideology and commitment of social justice principles is central to Early Years practice, however, the term social justice in education is complex and remains contested. This paper explores the ideology of social justice through links between equality and equity and how it is embedded within Early Years, and what remain the potential challenges for leadership. Interviews in English multi-cultural and mono-cultural primary schools were conducted. Findings showed that the ideology of social justice, equality and equity was interpreted differently. Multi-cultural schools appear to use a greater variety of activities to embed social justice principles that involved their diverse communities more to enrich the curriculum. In mono-cultural schools leadership had to be more creative in promoting equality and equity given the smaller proportion of their diverse pupil and staff population. Tentative conclusions suggest that the vision for permeating equality and equity in Early Years, at best, is at early stages