This note corrects an error in our paper “A Galois correspondence for reduced crossed products of unital simple $\text{C}^{\ast }$-algebras by discrete groups”, http://dx.doi.org/10.4153/CJM-2018-014-6. The main results of the original paper are unchanged.

Let a discrete group $G$ act on a unital simple $\text{C}^{\ast }$-algebra $A$ by outer automorphisms. We establish a Galois correspondence $H\mapsto A\rtimes _{\unicode[STIX]{x1D6FC},r}H$ between subgroups of $G$ and $\text{C}^{\ast }$-algebras $B$ satisfying $A\subseteq B\subseteq A\rtimes _{\unicode[STIX]{x1D6FC},r}G$, where $A\rtimes _{\unicode[STIX]{x1D6FC},r}G$ denotes the reduced crossed product. For a twisted dynamical system $(A,G,\unicode[STIX]{x1D6FC},\unicode[STIX]{x1D70E})$, we also prove the corresponding result for the reduced twisted crossed product $A\rtimes _{\unicode[STIX]{x1D6FC},r}^{\unicode[STIX]{x1D70E}}G$.

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.

KMOS is a cryogenic infrared spectrograph fed by twentyfour deployable integral field units that patrol a 7.2 arcminute diameter field of view at the Nasmyth focus of the ESO VLT. It is well suited to the study of galaxy clusters at 1 < z < 2 where the well understood features in the restframe V-band are shifted into the KMOS spectral bands. Coupled with HST imagining, KMOS offers a window on the critical epoch for galaxy evolution, 7-10 Gyrs ago, when the key properties of cluster galaxies were established. We aim to investigate the size, mass, morphology and star formation history of galaxies in the clusters. Here we describe the instrument, discuss the status of the observations and report some preliminary results.

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.

In this paper we consider near inclusions $A\,{{\subseteq }_{\gamma }}\,B$ of ${{\text{C}}^{*}}$ -algebras. We show that if $B$ is a separable type $\text{I}$ ${{\text{C}}^{*}}$ -algebra and $A$ satisfies Kadison's similarity problem, then $A$ is also type $\text{I}$ . We then use this to obtain an embedding of $A$ into $B$ .

Around the world large quantities of sludge wastes derived from nuclear energy production are currently kept in storage facilities. In the UK, the British government has marked sludge removal as a top priority as these facilities are nearing the end of their operational lifetimes. Therefore chemical understanding of uranium uptake in Mg-rich sludge is critical for successful remediation strategies. Previous studies have explored uranium uptake by the calcium carbonate minerals, calcite and aragonite, under conditions applicable to both natural and anthropogenically perturbed systems. However, studies of the uptake by Mg-rich minerals such as brucite [Mg(OH)2], nesquehonite [MgCO3·3H2O] and hydromagnesite [Mg5(CO3)4 (OH)2·4H2O], have not been previously conducted. Such experiments will improve our understanding of the mobility of uranium and other actinides in natural lithologies as well as provide key information applicable to nuclear waste repository strategies involving Mg-rich phases. Experiments with mineral powders were used to determine the partition coefficients (Kd) and coordination of UO22+ during adsorption and co-precipitation with brucite, nesquehonite and hydromagnesite. The Kd values for the selected Mg-rich minerals were comparable or greater than those published for calcium carbonates. Extended X-ray absorption fine structure analysis results showed that the structure of the uranyl-triscarbonato [UO2(CO3)3] species was maintained after surface attachment and that uptake of uranyl ions took place mainly via mineral surface reactions.

The potential of bio-dielectrics for thin film transistor applications was explored via the incorporation of titanium dioxide (TiO2) nanoparticles, rutile form, a high dielectric constant (ε) ceramic, in the deoxyribonucleic acid (DNA) bio-polymer. The DNA-ceramic hybrid films were fabricated from stable suspensions of the TiO2 nanoparticles in viscous, aqueous DNA solutions. Dielectric characterization revealed that the incorporation of TiO2 in DNA resulted in enhanced dielectric constant (14.3 at 1 kHz for 40 wt % TiO2) relative to that of DNA in the entire frequency range of 1 kHz-1 MHz. Variable temperature dielectric measurements, in the 20-80°C range, of the DNA-TiO2 films revealed that the ceramic additive stabilizes DNA against large temperature dependent variations in both ε and the dielectric loss factor tan δ. The bulk resistivity of the DNA-TiO2 hybrid films was measured to be two to three orders of magnitude higher than that of the control DNA films, indicating their potential for utilization as insulating dielectrics in transistor and capacitor applications.

In the fusion irradiation environment, helium created by transmutation will play an important role in the response of structural materials to neutron radiation damage. Recently we have developed a new 3-body potential to describe the Fe–He interaction in an Fe matrix. We have used this potential to investigate the equilibrium state of He bubbles embedded into the bcc Fe matrix. We have investigated bubble size, He content and temperature effects. It was found that the equilibrium He content is rather low and at a room temperature it is ~0.38 to 0.5 He per vacancy for bubble diameters from 1 to 6 nm. At constant bubble size, the equilibrium He/vacancy ratio decreases with temperature increase. For bubbles of 6 nm diameter it goes down as low as ~0.25 at 900K. The results are compared with the capillarity model often used for estimating the equilibrium pressure of He bubbles.