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.

Since 1946, a major project at the Vineland Station laboratory has been one on the indirect effects of pesticides on populations of injurious arthropods in peach orchards of the Niagara Peninsula. Plant-feeding mites have been the most readily affected. This paper describes the gross changes in mite populations produced by the pesticides and considers their economic importance and the possibility of reducing their injurious effects. The controversial problem of the means whereby some pesticides, particularly DDT, promote mite increase is still under study and will be treated in later papers.

A simulation model is described for the population dynamics of the European red mite, Panonychus ulmi (Koch). The model incorporates the following features: (a) development rate is dependent on effective daily temperature; (b) division of each population component into distinct daily age classes; (c) emergence of individuals from each population component is dependent on a log-normal probability distribution, and a temperature related development vector to accumulate a measure of the temperature effect on development. Validation runs on a mini-computer in 1976 and 1977 adequately described actual population curves determined from daily orchard sampling. A model of this type which can be used with small computers should prove useful in investigating the main factors affecting the population dynamics, and control strategies for this and other pests.

DDT, parathion, and carbaryl experimentally applied in peach orchards were highly toxic to most insect and arachnid predators, including those most effective in controlling orchard mites. Azinphos-methyl appeared to be as toxic as parathion to predators in grower-sprayed orchards. Larvae of the chrysopid Chrysopa carnea Stephens and the syrphid Toxomerus geminatus (Say) were remarkably tolerant of DDT. The phytoseiid mite Typhlodromus caudiglans Schuster appeared to have developed a high degree of resistance to DDT in one orchard. Sulphur was appreciably toxic only to phytoseiids and the erythraeid Balaustium sp., and captan had little or no effect on any predator. Chemical and biological control of phytophagous mites in peach orchards cannot be integrated while the presently used insecticides are needed for the control of the oriental fruit moth, Grapholitha molesta (Busck).

At least 25 species of Carabidae were caught in pitfall traps in a DDT-sprayed Ontario peach orchard, the commonest being Pterostichus melanarius (Ill.). Harpalus pennsylvanicus (Dej.), Agonoderus lecontei Chd., Amara (Curtonotus) pennsylvanica Hayw., Anadaptus sanctaecrucis (F.) and Anisodactylus rusticus Say. Fewer P. melanarius were caught in plots where foliar sprays of DDT were used most recently, but a rather large and varied population of carabids persisted in all plots despite the application of DDT for as long as ten years.

Mortality of the European red mite, Panonychus ulmi (Koch), on peach leaves was directly related to the uniformity of distribution and amount of deposit of dicofol for up to 4 days after the spray was applied. Mite mortality decreased rapidly from the 4th to the 11th day after spraying, whereas the dicofol detected by chemical analysis decreased at a slower rate. The minimum deposit of dicofol for 100% kill of the mite, immediately after spraying, was between 0.3 and 0.8 μg/cm2, depending upon uniformity of coverage. Doubling the dose did not increase the mortality then or later. Fourteen days after spraying, the dicofol deposit on some leaves was still 0.7–0.8 μg/cm2 but there was practically no mite mortality.

Overwintering stages of the European red mite, Panonychus ulmi (Koch), and the McDaniel spider mite, Tetranychus mcdanieli McGregor, on harvested apples were destroyed with ethylene dibromide using a dosage of 6 mg/l. for 4 h at 24 °C. Some control was achieved at lower temperatures but the dosage had to be increased accordingly. No injury of the fruit occurred. Taste tests showed that flavour of the apples was not adversely affected even after treatment with 10 mg/l. for 4 h.

Different stages of the European red mite, Panonychus ulmi (Koch), were immersed in water for periods up to 48 hours. Mortality of eggs was negligible; of active stages it was low but appreciable. Immersion in water inhibited egg hatching, feeding, moulting, and oviposition. It was concluded that if the mite responds similarly under orchard conditions, frequent or prolonged wet periods would delay the buildup of a mite infestation.

The ‘clover’ mite, Bryobia praetiosa Koch, has long been known to be a complex of closely related species or biological races differing greatly in host range, life-history, and habits. Morgan and Anderson (1957) reviewed the problem and described the form occurring on fruit trees in British Columbia as a new species, B. arborea, to be known as the brown mite, and these authors (Anderson and Morgan, 1958) also published a detailed study of the life-histories and habits of this species and of the true clover mite, B. praetiosa. Although the presence of Bryobia mites on fruit trees in Eastern North America, including Ontario, has long been recognized, they have seldom received more than casual mention and no extensive study of their biology in this area appears to have been undertaken. The species has little economic importance in Ontario (Putman and Herne, 1959).

More than 40 species of insects and arachnids attack Panonychus ulmi (Koch), Tetranychus urticae Koch, T. canadensis (McGregor), Bryobia arborea Morgan and Anderson, or Aculus cornutus (Banks) in peach orchards of the Niagara Peninsula. The most effective predators attacking P. ulmi are Typhlodromus caudiglans Schuster, Haplothrips faurei Hood, Stethorus punctillum Weise, and Chrysopa spp. Peach orchards lack the predatory mirids characteristic of apple orchards. A condition, presumably disease, caused heavy mortality in one year. Endemic densities of P. ulmi are maintained in that state by predators, chiefly T. caudiglans, that subsist to a considerable extent on other sources of food, whereas epidemics of P. ulmi are reduced largely by other predators, chiefly H. faurei and S. punctillum, that increase in numbers by feeding on the mite during its period of rapid population growth but exert their greatest effect later in the season by destroying the winter eggs.

A cottony scale of the genus Pulvinaria has been present in the peach orchards of the Niagara Peninsula of Ontario for many years. It has usually been referred to Pulainaria amygdali Ckll., but Phillips (1955) showed that it is almost undoubtedly P. vitis (L.). Ross and Caesar (1928) reported that it was generally distributed in the area as early as 1926, but only a few orchards were heavily infested. Subsequently only minor infestations were reported until about 1945. From 1946 to 1954 numerous orchards were heavily infested, but since 1954 the scale has been less important although it is widely distributed and sporadic infestations still occur.

In peach orchards undisturbed by pesticides and where phytophagous mites were at endemic densities, spring populations of Typhlodromus caudiglans were small and remained so during early summer until phytophagous mites, especially Aculus cornutus, began to increase. T. caudiglans reached maximal densities in September. In such orchards T. caudiglans appears to be an important factor in maintaining Panonychus ulmi at low density levels. On trees where DDT applied the previous year had caused P. ulmi to build up and which could be repopulated by T. caudiglans from neighbouring trees, the predator increased very rapidly but appeared to reach an upper limit of density fixed by intrinsic factors, possibly cannibalism. Under these conditions T. caudiglans could not bring P. ulmi to endemic densities in one season, though it appeared to slow the mite’s rate of increase and to reduce its maximal seasonal density.

The relative toxicity of Kelthane (1,1-bis (p-chlorophenyl) -2,2,2-trichloroethanol), and parathion to Phytoseiulus persimilis Athias-Henriot and its prey, Tetranychus urticae K. (= telarius (L.)), was determined using a Potter Spray Tower. Parathion was found to be far more toxic to P. persimilis than was Kelthane. The LD50 values for Kelthane were 0.051% and 0.29% for T. urticae and P. persimilis respectively, and for parathion were 0.050% and 0.0044% respectively. The LD95 values bore a similar relationship to each other. The two materials were equally toxic to T. urticae. Therefore, use of Kelthane rather than parathion in an environment where P. persimilis and T. urticae were interacting would favour the beneficial species. The statistical aspects of the test method are discussed.

Peach shoot volatiles were attractive to mated female oriental fruit moth, Cydia molesta (Busck), in a dual choice arena. No preference was observed between leaf odours from the principle host plant, peach, and the secondary host plant, apple. Twenty-two compounds were identified in headspace volatiles of peach shoots using gas chromatography–mass spectrometry. Green leaf volatiles accounted for more than 50% of the total emitted volatiles. A bioassay-assisted fractionation using different sorbent polymers indicated an attractant effect of compounds with a chain length of 6–8 carbon atoms. The major compounds of this fraction were tested either singly or in combinations for behavioural response of females. Significant bioactivity was found for a three-component mixture of (Z)-3-hexen-1-yl acetate, (Z)-3-hexen-1-ol and benzaldehyde in a 4:1:1 ratio. This synthetic mixture elicited a similar attractant effect as the full natural blend from peach shoots as well as the bioactive fraction.

Mycotic aneurysms of the extracranial carotid arteries are extremely rare. A case is reported of a false aneurysm of the left external carotid artery. This developed secondary to cervical lymphadenitis which did not settle with high dose antibiotic therapy. The diagnosis was made on investigation with carotid doppler ultrasound and confirmed with computerized tomography. Digital subtraction angiography was performed to highlight the vascular anatomy. In addition percutaneous balloon catheter control of blood flow in the external carotid artery was used as an adjunct to surgical management.

Recurrent epistaxes after head injury may rarely be dueto a traumatic intracavernous carotid artery pseudoaneurysm. The headinjury is usually associated with fracture of the skull base and the epistaxes are severe with the first episode generally occurring one to three months after the initial trauma. We present a case which illustrates the role of high resolution computed tomography (CT) scanningand also magnetic resonance angiography (MRA) in achieving the diagnosis.