A novel technique for wide-field polarimetry with a radiotelescope array

We report the use of the Australia Telescope Compact Array (ATCA) to conduct polarimetric observations of the sky at 5 GHz. The ATCA is normally operated as an interferometer array, but these observations were conducted in a split array mode in which the antenna elements were used as single-dishes with their beams staggered to simultaneously cover a wide area of sky with a resolution of 10 arcmin. The linearly polarized sky radiation was fully characterized from measurements, made over a range of parallactic angles, of the cross correlated signals from the orthogonal linear feeds. We describe the technique and present a polarimetric image of the Vela supernova remnant made as a test of the method. The development of the techniques was motivated by the need for wide-field imaging of the foreground contamination of the polarized component of the cosmic microwave background signal.Comment: 13 pages, 2 figures, accepted for publication in A

Radicals of 0-regular algebras

We consider a generalisation of the Kurosh--Amitsur radical theory for rings (and more generally multi-operator groups) which applies to 0-regular varieties in which all operations preserve 0. We obtain results for subvarieties, quasivarieties and element-wise equationally defined classes. A number of examples of radical and semisimple classes in particular varieties are given, including hoops, loops and similar structures. In the first section, we introduce 0-normal varieties (0-regular varieties in which all operations preserve 0), and show that a key isomorphism theorem holds in a 0-normal variety if it is subtractive, a property more general than congruence permutability. We then define our notion of a radical class in the second section. A number of basic results and characterisations of radical and semisimple classes are then obtained, largely based on the more general categorical framework of L. M\'arki, R. Mlitz and R. Wiegandt as in [13]. We consider the subtractive case separately. In the third section, we obtain results concerning subvarieties and quasivarieties based on the results of the previous section, and also generalise to subtractive varieties some results for multi-operator group radicals defined by simple equational rules. Several examples of radical and semisimple classes are given for a range of fairly natural 0-normal varieties of algebras, most of which are subtractive

A study of the occupational adjustment of the graduates of the industrial arts curriculum of South High school for a twelve year period

Any program in progressive education must recognize the fact that its main objective is to prepare individuals for effective participation in the activities of every day life. The need in education today is to more closely correlate the life of the boy in school with his life after graduation. Schools and industry have reached a point at which an evaluation of Common goals is necessary

Development of the NASA VALT digital navigation system

The research to develop and fabricate a terminal area navigation system for use in the NASA VTOL Approach and Landing Technology (VALT) program. The results of that effort are reported. The navigation system developed and fabricated was based on a general purpose airborne digital computer. A set of flight hardware units was fabricated to create the necessary analog, digital and human interface with the computer. A comprehensive package of software was created to implement the control and guidance laws required for automatic and flight director approaches that are curved in two planes. A technique was developed that enables the generation of randomly shaped lateral paths from simple input data. The lateral path concept combines straight line and elliptical-curved segments to fit a continuous curved path to the data points. A simple, fixed base simulation was put together to assist in developing and evaluating the system. The simulation was used to obtain system performance data during simulated curved-path approaches

Extent and impacts of dryland salinity

The extent and impact of dryland salinity in Western Australia was based on analysis of groundwater depth and trend and the risk of shallow watertables is derived from these two attributes. As dryland salinity is caused by shallow watertables, the risk of salinity is inferred from the risk of shallow watertables

Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells

We report a model describing the molecular orientation disorder in CH3NH3PbI3, solving a classical Hamiltonian parametrised with electronic structure calculations, with the nature of the motions informed by ab-initio molecular dynamics. We investigate the temperature and static electric field dependence of the equilibrium ferroelectric (molecular) domain structure and resulting polarisability. A rich domain structure of twinned molecular dipoles is observed, strongly varying as a function of temperature and applied electric field. We propose that the internal electrical fields associated with microscopic polarisation domains contribute to hysteretic anomalies in the current--voltage response of hybrid organic-inorganic perovskite solar cells due to variations in electron-hole recombination in the bulk.Comment: 10 pages; 4 figures, 2 SI figure

SONTRAC: an imaging spectrometer for solar neutrons

An instrument capable of unambiguously determining the energy and direction of incident neutrons has important applications in solar physics-as well as environmental monitoring and medical/radiological sciences. The SONTRAC (SOlar Neutron TRACking) instrument is designed to operate in the neutron energy range of 20-250 MeV. The measurement principle is based on non-relativistic double scatter of neutrons off ambient protons (n-p scattering) within a block of densely packed scintillating fibers. Using this double-scatter mode it is possible to uniquely determine neutron energy and direction on an event-by-event basis. A fully operational science model of such an instrument has been built using 300 μm (250 μm active) scintillating fibers. The science model consists of a 5×5×5 cm cube of orthogonal plastic scintillating fiber layers. Two orthogonal imaging chains, employing image intensifiers and CCD cameras, allow full 3-dimensional reconstruction of scattered proton particle tracks. We report the results of the science model instrument calibration using 35-65 MeV protons. The proton calibration is the first step toward understanding the instrument response to n-p scatter events. Preliminary results give proton energy resolution of 2% (6%) at 67.5 (35) MeV, and angular resolution of 2° (4.5°) at 67.5 (35) MeV. These measurements are being used to validate detailed instrument simulations that will be used to optimize the instrument design and develop quantitative estimates of science return. Based on the proton calibration, neutron energy and angular resolution for a 10×10×10 cm version of SONTRAC is expected to be ~5% an

Gamma-Ray Observations of GRO J1655-40

The bright transient X-ray source GRO J1655-40 = XN Sco 1994 was observed by the OSSE instrument on the Compton Gamma Ray Observatory (GRO). Preliminary results are reported here. The initial outburst from GRO J1655-40 was detected by BATSE on 27 Jul 1994. OSSE observations were made in five separate viewing periods starting between 4 Aug 1994 and 4 Apr 1995. The first, third, and fifth observations are near the peak luminosity. In the second observation, the source flux had dropped by several orders of magnitude and we can only set an upper limit. The fourth observation is a weak detection after the period of maximum outburst. In contrast with other X-ray novae such as GRO J0422+32, the spectrum determined by OSSE is consistent with a simple power law over the full range of detection, about 50 - 600 keV. The photon spectral index is in the range of -2.5 to 2.8 in all of the observations. We set an upper limit on fractional rms variation \u3c5% in the frequency range 0.01 – 60 Hz. No significant narrow or broad line features are observed at any energy

Development and performance of the Fast Neutron Imaging Telescope for SNM detection

FNIT (the Fast Neutron Imaging Telescope), a detector with both imaging and energy measurement capabilities, sensitive to neutrons in the range 0.8-20 MeV, was initially conceived to study solar neutrons as a candidate design for the Inner Heliosphere Sentinel (IHS) spacecraft of NASA\u27s Solar Sentinels program and successively reconfigured to locate fission neutron sources. By accurately identifying the position of the source with imaging techniques and reconstructing the Watt spectrum of fission neutrons, FNIT can detect samples of special nuclear material (SNM), including heavily shielded and masked ones. The detection principle is based on multiple elastic neutron-proton scatterings in organic scintillators. By reconstructing n-p event locations and sequence and measuring the recoil proton energies, the direction and energy spectrum of the primary neutron flux can be determined and neutron sources identified. We describe the design of the FNIT prototype and present its energy reconstruction and imaging performance, assessed by exposing FNIT to a neutron beam and to a Pu fission neutron source

The Carrington event not observed in most ice core nitrate records

The Carrington Event of 1859 is considered to be among the largest space weather events of the last 150 years. We show that only one out of 14 well-resolved ice core records from Greenland and Antarctica has a nitrate spike dated to 1859. No sharp spikes are observed in the Antarctic cores studied here. In Greenland numerous spikes are observed in the 40 years surrounding 1859, but where other chemistry was measured, all large spikes have the unequivocal signal, including co-located spikes in ammonium, formate, black carbon and vanillic acid, of biomass burning plumes. It seems certain that most spikes in an earlier core, including that claimed for 1859, are also due to biomass burning plumes, and not to solar energetic particle (SEP) events. We conclude that an event as large as the Carrington Event did not leave an observable, widespread imprint in nitrate in polar ice. Nitrate spikes cannot be used to derive the statistics of SEPs