The Variables and Slow Transients Survey (VAST) on the Australian Square Kilometre Array Pathfinder (ASKAP) is designed to detect highly variable and transient radio sources on timescales from 5 s to $\sim\!5$ yr. In this paper, we present the survey description, observation strategy and initial results from the VAST Phase I Pilot Survey. This pilot survey consists of $\sim\!162$ h of observations conducted at a central frequency of 888 MHz between 2019 August and 2020 August, with a typical rms sensitivity of $0.24\ \mathrm{mJy\ beam}^{-1}$ and angular resolution of $12-20$ arcseconds. There are 113 fields, each of which was observed for 12 min integration time, with between 5 and 13 repeats, with cadences between 1 day and 8 months. The total area of the pilot survey footprint is 5 131 square degrees, covering six distinct regions of the sky. An initial search of two of these regions, totalling 1 646 square degrees, revealed 28 highly variable and/or transient sources. Seven of these are known pulsars, including the millisecond pulsar J2039–5617. Another seven are stars, four of which have no previously reported radio detection (SCR J0533–4257, LEHPM 2-783, UCAC3 89–412162 and 2MASS J22414436–6119311). Of the remaining 14 sources, two are active galactic nuclei, six are associated with galaxies and the other six have no multi-wavelength counterparts and are yet to be identified.

Marteilia refringens causes marteiliosis in oysters, mussels and other bivalve molluscs. This parasite previously comprised two species, M. refringens and Marteilia maurini, which were synonymized in 2007 and subsequently referred to as M. refringens ‘O-type’ and ‘M-type’. O-type has caused mass mortalities of the flat oyster Ostrea edulis. We used high throughput sequencing and histology to intensively screen flat oysters and mussels (Mytilus edulis) from the UK, Sweden and Norway for infection by both types and to generate multi-gene datasets to clarify their genetic distinctiveness. Mussels from the UK, Norway and Sweden were more frequently polymerase chain reaction (PCR)-positive for M-type (75/849) than oysters (11/542). We did not detect O-type in any northern European samples, and no histology-confirmed Marteilia-infected oysters were found in the UK, Norway and Sweden, even where co-habiting mussels were infected by the M-type. The two genetic lineages within ‘M. refringens’ are robustly distinguishable at species level. We therefore formally define them as separate species: M. refringens (previously O-type) and Marteilia pararefringens sp. nov. (M-type). We designed and tested new Marteilia-specific PCR primers amplifying from the 3’ end of the 18S rRNA gene through to the 5.8S gene, which specifically amplified the target region from both tissue and environmental samples.

The cold, dry, and stable air above the summits of the Antarctic plateau provides the best ground-based observing conditions from optical to sub-millimetre wavelengths to be found on the Earth. Pathfinder for an International Large Optical Telescope (PILOT) is a proposed 2 m telescope, to be built at Dome C in Antarctica, able to exploit these conditions for conducting astronomy at optical and infrared wavelengths. While PILOT is intended as a pathfinder towards the construction of future grand-design facilities, it will also be able to undertake a range of fundamental science investigations in its own right. This paper provides the performance specifications for PILOT, including its instrumentation. It then describes the kinds of projects that it could best conduct. These range from planetary science to the search for other solar systems, from star formation within the Galaxy to the star formation history of the Universe, and from gravitational lensing caused by exo-planets to that produced by the cosmic web of dark matter. PILOT would be particularly powerful for wide-field imaging at infrared wavelengths, achieving near diffraction-limited performance with simple tip–tilt wavefront correction. PILOT would also be capable of near diffraction-limited performance in the optical wavebands, as well be able to open new wavebands for regular ground-based observation, in the mid-IR from 17 to 40 μm and in the sub-millimetre at 200 μm.

Arthropod population densities were evaluated from nests of colonial ring-billed gulls (Larus delawarensis). Each nest was considered as being an island microhabitat in which a measurable population was concentrated. Despite significantly greater numbers of arthropods in larger than in smaller gull nests, population densities per nest dry weight were similar.

Mites collected from 69 Larus delawarensis Ord nests on Granite Island, Lake Superior, northwestern Ontario, during the summers of 1972 and 1973 showed phenological relationships with the breeding cycle of the gulls. The populations of five selected mite genera varied in relation to nest initiation, egg laying, and egg hatching periods of the gulls. Moisture within the nests significantly affected mite population densities, whereas nest density did not.

One hundred and seven unrelated Danish patients considered to be manic-depressive according to strict diagnostic, symptomatic and course criteria were typed for antigens of the HLA system, the major histocompatibility system in man. Preliminary results from the first 47 patients had previously been reported to suggest a positive association between manic-depressive disorders and HLA-A3, HLA-B7, and HLA-Bw16 and a negative association between such disorders and HLA-B8. Results from the extended series provide confirmatory evidence that there is a positive association between manic-depressive disorders and HLA-Bw16 and also strongly suggest a positive association between HLA-B7 and such disorders. HLA typing may prove to be a useful way of identifying sub-groups of manic-depressive patients for other biological studies. The associations described provide a potential lead for formulating hypotheses about the nature of the biological mechanisms which predispose to manic-depressive disorders.

The microstructural evolution of AlxGa1-xN films grown by metalorganic vapor phase epitaxy on 6H-SiC (0001) was studied by means of X-ray diffraction, atomic force microscopy and transmission electron microscopy in conjunction with energy dispersive X-ray spectroscopy. A significant spatial variation of composition was found in 100 nm thick layers the nature of which could be traced back to the initial stage of film formation. Upon nucleation two phases are formed: a wetting layer and isolated islands of high and low aluminum content, respectively. The observed results are discussed in terms of strain and growth rates.

Tertiary structure in globular RNA folds can create local environments that lead to pKa perturbation of specific nucleotide functional groups. To assess the prevalence of functionally relevant adenosine-specific pKa perturbation in RNA structure, we have altered the nucleotide analog interference mapping (NAIM) approach to include a series of α phosphorothioate-tagged adenosine analogs with shifted N1 pKa values. We have used these analogs to analyze the hairpin ribozyme, a small self-cleaving/ligating RNA catalyst that is proposed to employ a general acid-base reaction mechanism. A single adenosine (A10) within the ribozyme active site displayed an interference pattern consistent with a functionally significant base ionization. The exocyclic amino group of a second adenosine (A38) contributes substantially to hairpin catalysis, but ionization of the nucleotide does not appear to be important for activity. Within the hairpin ribozyme crystal structure, A10 and A38 line opposite edges of a solvent-excluded cavity adjacent to the 5′-OH nucleophile. The results are inconsistent with the model of ribozyme chemistry in which A38 acts as a general acid–base catalyst, and suggest that the hairpin ribozyme uses an alternative mechanism to achieve catalytic rate enhancement that utilizes functional groups within a solvent-excluded cleft in the ribozyme active site.

Tertiary structure in globular RNA folds can create local environments that lead to pKa perturbation of specific nucleotide functional groups. To assess the prevalence of functionally relevant adenosine-specific pKa perturbation in RNA structure, we have altered the nucleotide analog interference mapping (NAIM) approach to include a series of α phosphorothioate-tagged adenosine analogs with shifted N1 pKa values. We have used these analogs to analyze the hairpin ribozyme, a small self-cleaving/ligating RNA catalyst that is proposed to employ a general acid-base reaction mechanism. A single adenosine (A10) within the ribozyme active site displayed an interference pattern consistent with a functionally significant base ionization. The exocyclic amino group of a second adenosine (A38) contributes substantially to hairpin catalysis, but ionization of the nucleotide does not appear to be important for activity. Within the hairpin ribozyme crystal structure, A10 and A38 line opposite edges of a solvent-excluded cavity adjacent to the 5′-OH nucleophile. The results are inconsistent with the model of ribozyme chemistry in which A38 acts as a general acid–base catalyst, and suggest that the hairpin ribozyme uses an alternative mechanism to achieve catalytic rate enhancement that utilizes functional groups within a solvent-excluded cleft in the ribozyme active site.

Tertiary structure in globular RNA folds can create local environments that lead to pKa perturbation of specific nucleotide functional groups. To assess the prevalence of functionally relevant adenosine-specific pKa perturbation in RNA structure, we have altered the nucleotide analog interference mapping (NAIM) approach to include a series of α phosphorothioate-tagged adenosine analogs with shifted N1 pKa values. We have used these analogs to analyze the hairpin ribozyme, a small self-cleaving/ligating RNA catalyst that is proposed to employ a general acid-base reaction mechanism. A single adenosine (A10) within the ribozyme active site displayed an interference pattern consistent with a functionally significant base ionization. The exocyclic amino group of a second adenosine (A38) contributes substantially to hairpin catalysis, but ionization of the nucleotide does not appear to be important for activity. Within the hairpin ribozyme crystal structure, A10 and A38 line opposite edges of a solvent-excluded cavity adjacent to the 5′-OH nucleophile. The results are inconsistent with the model of ribozyme chemistry in which A38 acts as a general acid–base catalyst, and suggest that the hairpin ribozyme uses an alternative mechanism to achieve catalytic rate enhancement that utilizes functional groups within a solvent-excluded cleft in the ribozyme active site.

The thermal expansion coefficients of glass-forming Zr-based alloys were measured in the melt, the undercooled liquid and the glassy/crystalline state. Due to the high reactivity of the liquid material the experiments were performed containerlessly in an electrostatic levitator. We used an optical method where the samples were imaged with a high-resolution CCD- camera and the volume of the samples was evaluated by digital image processing. The coefficients of thermal expansion in the liquid and in the solid state could be determined from the volume versus temperature curves. The results can be compared with measurements in the electromagnetic levitation facility TEMPUS performed under microgravity conditions in the mission MSL-1 and ground based DMA-measurements. The thermal expansion data can be interpreted in terms of the free volume model.

InGaN layers grown by molecular beam epitaxy are investigated in terms of their compositional homogeneity using transmission electron microscopy and cathodoluminescence spectroscopy performed with high spatial resolution. Strong fluctuations of the indium content were found in bulklike layers, which could be partially reduced by modulating the indium flux during growth, i. e. by nominally growing a short period GaN/InGaN superlattice. For indium compositions above x ≅ 0.1 this approach fails. Strained InGaN in quantum wells exhibits lateral fluctuations on an atomic scale and on a scale of several hundred nanometers. The results are discussed in view of the origin of inhomogeneous indium incorporation.

InGaN layers grown by molecular beam epitaxy are investigated in terms of their compositional homogeneity using transmission electron microscopy and cathodoluminescence spectroscopy performed with high spatial resolution. Strong fluctuations of the indium content were found in bulk-like layers, which could be partially reduced by modulating the indium flux during growth, i. e. by nominally growing a short period GaN/InGaN superlattice. For indium compositions above x ≠ 0.1 this approach fails. Strained InGaN in quantum wells exhibits lateral fluctuations on an atomic scale and on a scale of several hundred nanometers. The results are discussed in view of the origin of inhomogeneous indium incorporation.

This study was performed to assess the survival times of the Provox™ valve in the Manchester area. Thirty-nine patients from four hospitals, representing 81 valve failures, were studied. The effects of the timing of the tracheo-oesophageal puncture, previous radiotherapy, and the presence and timing of cricopharyngeal myotomy on valve life were analysed. Regression analysis using an extension of the Cox model to allow strata showed that the lifetime of the first valve only is adversely affected by previous radiotherapy. The other covariates do not have a statistically significant effect on valve survival. The median valve survival is 4.5 months, (range one to 12 months). A small percentage of valve users with particularly frequent valve failures may require additional support and prolonged anti-fungal therapy.

The effects of both temperature and atmosphere on the resulting morphological features of the polar faces of single crystal ZnO were investigated and characterized by atomic force microscopy (AFM). In studies where ZnO was thermally processed in flowing oxygen at atmospheric conditions within the temperature range of 500°C to 900°C for 30 minutes, the Znsurface (i.e., (000 1)) showed a tendency to reconstruct with increasing temperature until terraces became evident at 900°C. Terrace heights were as small as 0.9 nm. In contrast, the O-surface (i.e., (000 ī)) was observe to change very little during the O2-atmoshere, thermal treatment and remained comparatively rougher than the Zn-surface. ZnO samples which were thermally processed under high vacuum (i.e., 5 × 10-7 Torr) conditions exhibited a more dramatic contrast. The vacuum annealed Zn-surface was observed to develop very smooth surface features (Roughness = 0.09 nm) at annealing temperatures within the 700 – 800°C range. In contrast, and as expected, the O-surface roughness increased due to surface reduction reactions. In addition to these findings, it is noted that AFM measurements may be utilized as a convenient method to distinguish between the two polar surfaces of ZnO.

Aluminum nitride was deposited on the Zn- and O- surfaces from 700 to 850°C by pulsed laser evaporation. X-ray diffraction indicated that the AIN was c-axis oriented with no interface reaction products detected between the ZnO substrate and AIN film.

In a study of 23 diabetic men complaining of impotence, completion of physical tests, self-report psychometric testing, a rating of marital intimacy, and a semistructured interview revealed that, of ten patients found to be at risk of psychogenic impotence secondary to marital or psychiatric morbidity, five were thought to have adequate erectile response and to have a psychogenic component to their problem. This seems to show high sensitivity, if not specificity, of the selfreport questionnaires.

Eight ring-ditches and several stretches of pit alignment have been excavated between 1981 and 1985, as part of the investigation of an extensive cropmark complex on a gravel terrace in the Upper Severn valley at Four Crosses, northern Powys. Excavation of the ring-ditches, which form part of a more scattered barrow cemetery, has revealed a long and complex pattern of development of barrow types and burial forms in the period between the Middle Neolithic and the Middle Bronze Age. This is compared with the recently published sequence from the neighbouring upland barrow cemetery at Trelystan, and subdivided into four hypothetical phases. There is evidence of activity in the vicinity of some of the sites in the Iron Age, Romano-British, and possibly the early post-Roman period.