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The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
The Molonglo Observatory Synthesis Telescope (MOST) is an 18000 m2 radio telescope located 40 km from Canberra, Australia. Its operating band (820–851 MHz) is partly allocated to telecommunications, making radio astronomy challenging. We describe how the deployment of new digital receivers, Field Programmable Gate Array-based filterbanks, and server-class computers equipped with 43 Graphics Processing Units, has transformed the telescope into a versatile new instrument (UTMOST) for studying the radio sky on millisecond timescales. UTMOST has 10 times the bandwidth and double the field of view compared to the MOST, and voltage record and playback capability has facilitated rapid implementaton of many new observing modes, most of which operate commensally. UTMOST can simultaneously excise interference, make maps, coherently dedisperse pulsars, and perform real-time searches of coherent fan-beams for dispersed single pulses. UTMOST operates as a robotic facility, deciding how to efficiently target pulsars and how long to stay on source via real-time pulsar folding, while searching for single pulse events. Regular timing of over 300 pulsars has yielded seven pulsar glitches and three Fast Radio Bursts during commissioning. UTMOST demonstrates that if sufficient signal processing is applied to voltage streams, innovative science remains possible even in hostile radio frequency environments.
The class of radio transients called Fast Radio Bursts (FRBs) encompasses enigmatic single pulses, each unique in its own way, hindering a consensus for their origin. The key to demystifying FRBs lies in discovering many of them in order to identity commonalities – and in real time, in order to find potential counterparts at other wavelengths. The recently upgraded UTMOST in Australia, is undergoing a backend transformation to rise as a fast transient detection machine. The first interferometric detections of FRBs with UTMOST, place their origin beyond the near-field region of the telescope thus ruling out local sources of interference as a possible origin. We have localised these bursts to much better than the ones discovered at the Parkes radio telescope and have plans to upgrade UTMOST to be capable of much better localisation still.
The initial results from timing observations of PSR J1141–6545, a relativistic pulsar-white dwarf binary system, are presented. Predictions from the timing baseline hint at the most stringent test of gravity by an asymmetric binary yet. The timing precision has been hindered by the dramatic variations of the pulse profile due to geodetic precession, a pulsar glitch and red timing noise. Methods to overcome such timing irregularities are briefly presented along with preliminary results from the test of the General Theory of Relativity (GR) from this pulsar.
Cerebral blood volume and metabolism of oxygen decline as part of human ageing, and this has been previously shown to be related to cognitive decline. There is some evidence to suggest that polyphenol-rich foods can play an important role in delaying the onset or halting the progression of age-related health disorders such as CVD and Alzheimer’s disease and to improve cognitive function. In the present study, an acute, placebo-controlled, double-blinded, cross-over, randomised Latin-square design study with a washout period of at least 14 d was conducted on twenty-seven, middle-aged (defined as 45–60 years) volunteers. Participants received either a 60 ml dose of Montmorency tart cherry concentrate (MC), which contained 68·0 (sd 0·26) mg cyanidin-3-glucoside/l, 160·75 (sd 0·55) mean gallic acid equivalent/l and 0·59 (sd 0·02) mean Trolox equivalent/l, respectively, or a placebo. Cerebrovascular responses, cognitive performance and blood pressure were assessed at baseline and 1, 2, 3 and 5 h following consumption. There were significant differences in concentrations of total Hb and oxygenated Hb during the task period 1 h after MC consumption (P≤0·05). Furthermore, MC consumption significantly lowered systolic blood pressure (P≤0·05) over a period of 3 h, with peak reductions of 6±2 mmHg at 1 h after MC consumption relative to the placebo. Cognitive function and mood were not affected. These results show that a single dose of MC concentrate can modulate certain variables of vascular function; however, this does not translate to improvements in cognition or mood.
Post-traumatic stress disorder (PTSD) is associated with elevated risk for metabolic syndrome (MetS). However, the direction of this association is not yet established, as most prior studies employed cross-sectional designs. The primary goal of this study was to evaluate bidirectional associations between PTSD and MetS using a longitudinal design.
A total of 1355 male and female veterans of the conflicts in Iraq and Afghanistan underwent PTSD diagnostic assessments and their biometric profiles pertaining to MetS were extracted from the electronic medical record at two time points (spanning ~2.5 years, n = 971 at time 2).
The prevalence of MetS among veterans with PTSD was just under 40% at both time points and was significantly greater than that for veterans without PTSD; the prevalence of MetS among those with PTSD was also elevated relative to age-matched population estimates. Cross-lagged panel models revealed that PTSD severity predicted subsequent increases in MetS severity (β = 0.08, p = 0.002), after controlling for initial MetS severity, but MetS did not predict later PTSD symptoms. Logistic regression results suggested that for every 10 PTSD symptoms endorsed at time 1, the odds of a subsequent MetS diagnosis increased by 56%.
Results highlight the substantial cardiometabolic concerns of young veterans with PTSD and raise the possibility that PTSD may predispose individuals to accelerated aging, in part, manifested clinically as MetS. This demonstrates the need to identify those with PTSD at greatest risk for MetS and to develop interventions that improve both conditions.
This paper will discuss the structure-property model developed that correlates the tensile modulus to the elastic properties and angular distribution of constituent graphitic layers for carbon fiber derived from a polyethylene precursor. In addition, a high-temperature fiber tensile device was built to enable heating of carbon fiber bundles at a variable rate from 25 °C to greater than ∼2300 °C, while simultaneously applying a tensile stress. This capability combined with synchrotron wide-angle x-ray diffraction (WAXD), enabled observation in situ and in real time of the microstructural transformation from different carbon fiber precursors to high-modulus carbon fiber. Experiments conducted using PAN- and PE-derived fiber precursors reveal stark differences in their carbonization and high-temperature graphitization behavior.
Healthcare-associated outbreaks and pseudo-outbreaks of rapidly growing mycobacteria (RGM) are frequently associated with contaminated tap water. A pseudo-outbreak of Mycobacterium chelonae–M. abscessus in patients undergoing bronchoscopy was identified by 2 acute care hospitals. RGM was identified in bronchoscopy specimens of 28 patients, 25 of whom resided in the same skilled nursing facility (SNF). An investigation ruled out bronchoscopy procedures, specimen collection, and scope reprocessing at the hospitals as sources of transmission.
To identify the reservoir for RGM within the SNF and evaluate 2 water system treatments, hyperchlorination and point-of-use (POU) membrane filters, to reduce RGM.
A comparative in situ study of 2 water system treatments to prevent RGM transmission.
An SNF specializing in care of patients requiring ventilator support.
RGM and heterotrophic plate count (HPC) bacteria were examined in facility water before and after hyperchlorination and in a subsequent 24-week assessment of filtered water by colony enumeration on Middlebrook and R2A media.
Mycobacterium chelonae was consistently isolated from the SNF water supply. Hyperchlorination reduced RGM by 1.5 log10 initially, but the population returned to original levels within 90 days. Concentration of HPC bacteria also decreased temporarily. RGM were reduced below detection level in filtered water, a 3-log10 reduction. HPC bacteria were not recovered from newly installed filters, although low quantities were found in water from 2-week-old filters.
POU membrane filters may be a feasible prevention measure for healthcare facilities to limit exposure of sensitive individuals to RGM in potable water systems.
Most studies of third nerve palsy (TNP) antedate computerized imaging and focus primarily on chart review of referral outpatients.
To compare a large contrasting population, I reviewed 1400 personally-examined municipal hospital inpatients with TNPs seen over 37 years.
TNPs were bilateral in 11%, complete in 33%, without other neurological signs (isolated) in 36%, and associated with recurrent cranial neuropathies in 7%. Third nerve damage occurred in the subarachnoid space in 32%, the cavernous sinus in 23%, the brainstem in 14%, as a nonlocalized peripheral neuropathy in 18% and at an uncertain location in 13%. Causes were trauma (26%), tumor (12%), diabetes (11%), aneurysm (10%), surgery (10%), stroke (8%), infection (5%), Guillain-Barre and Fisher syndromes (5%), idiopathic cavernous sinusitis (3%), benign self-limited (2%), miscellaneous (4%), and unknown (3%). Local causes, besides an abundance of trauma, included six cases involving cysticercosis, four with wound botulism, and one with coccidiomycotic meningitis. Of 234 patients with diabetes, microvascular ischemia was the cause of TNP in only two-thirds (five had aneurysms) and 53% of those with diabetic microvascular ischemia had pupillary involvement—often bilateral, suggesting concomitant autonomic neuropathy. Only 2% of aneurysms spared the pupil. Apainful onset occurred with 94% of aneurysm and 69% of diabetic cases.
Bilateral TNPs, multiple cranial neuropathies, and accompanying neurological signs were common among our inpatients, as were causes rare in outpatient settings such as severe trauma, transtentorial herniation, midbrain strokes, and the Guillain-Barre syndrome. Few cases remained undiagnosed and nondiabetic ischemia was rare.
To fabricate a high-efficiency polycrystalline thin-film tandem cell, the most critical work is to make a high-efficiency top cell (>15%) with high bandgap (Eg=1.5-1.8 eV) and high transmission (T>70%) in the near-infrared (NIR) wavelength region. The CdTe cell is one of the candidates for the top cell, because CdTe state-of-the-art single-junction devices with efficiencies of more than 16% are available, although its bandgap (1.48 eV) is slightly lower for a top cell in a dual-junction device. In this paper, we focus on the development of an ultra-thin, low-bandgap CuxTe transparent back-contact to produce high-efficiency CdTe cells with high NIR transmission. We have achieved an NREL-confirmed 13.9%-efficient CdTe transparent solar cell with an infrared transmission of ~50% and a CdTe/CIS polycrystalline mechanically stacked thin-film tandem cell with an NREL-confirmed efficiency of 15.3%.
Some designs are sufficiently creative that they are considered to be
inventions. The invention process is typically characterized by a singular
moment when the prevailing thinking concerning a long-standing problem is,
in a “flash of genius,” overthrown and replaced by a new
approach that could not have been logically deduced from what was
previously known. This paper discusses such logical discontinuities using
an example based on the history of one of the most important inventions of
the 20th century in electrical engineering, namely, the invention of
negative feedback by AT&T's Harold S. Black. This 1927 invention
overthrew the then prevailing idiom of positive feedback championed by
Westinghouse's Edwin Howard Armstrong. The paper then shows how this
historically important discovery can be readily replicated by an automated
design and invention technique patterned after the evolutionary process in
nature, namely, genetic programming. Genetic programming employs Darwinian
natural selection along with analogs of recombination (crossover),
mutation, gene duplication, gene deletion, and mechanisms of developmental
biology to breed an ever improving population of structures. Genetic
programming rediscovers negative feedback by conducting an evolutionary
search for a structure that satisfies Black's stated high-level goal
(i.e., reduction of distortion in amplifiers). Like evolution in nature,
genetic programming conducts its search probabilistically without resort
to logic using a process that is replete with logical discontinuities. The
paper then shows that genetic programming can routinely produce many
additional inventive and creative results. In this regard, the paper
discusses the automated rediscovery of numerous 20th-century patented
inventions involving analog electrical circuits and controllers, the
Sallen–Key filter, and six 21st-century patented inventions. In
addition, two patentable new inventions (controllers) have been created in
the same automated way by means of genetic programming. The paper
discusses the promising future of automated invention by means of genetic
programming in light of the fact that, to date, increased computer power
has yielded progressively more substantial results, including numerous
human-competitive results, in synchrony with Moore's law. The paper
argues that evolutionary search by means of genetic programming is a
promising approach for achieving creative, human-competitive, automated
design because illogic and creativity are inherent in the evolutionary
As a result of the Agenda 2000 increase in the Special Beef Premium and introduction of a slaughter premium for bulls, there is renewed interest in bull beef production especially from low value Holstein-Friesian calves. To evaluate the economics of such a production system further information is required on responses to supplementary concentrates with silage and duration of the finishing period.
Graded-band-gap CuIn1−xGaxSe2 (CIGS) absorbers with Ga/Ga+In value in the 20%-30% range have a demonstrated efficiency of 18.8%. For CdS-containing devices, the shortcircuit current density (Jsc) has almost reached its expected maximum. However, the open-circuit voltage of CIGS solar cells is limited by the surface microstructure and chemistry. In this work, we examine the microstructural properties and chemistry of CIGS. We also attempted to correlate the above observations and device performance.
Although GaN has been grown mainly by metal organic chemical vapour deposition (MOCVD), molecular beam epitaxy (MBE) offers the advantages of lower growth temperatures and a more flexible control over doping elements and their concentrations . We are growing GaN by MBE on sapphire substrates, using a GaN buffer layer to reduce the misfit strain, thus improving the structural quality of the epilayer. The quality of the GaN epilayers (in terms of their photoluminescence, mobility and structure) has been investigated as a function of the buffer layer thickness and annealing time.
The investigation showed that increasing the buffer layer thickness improved the mobility of the material because the defect density in the GaN epilayer decreased. Optical characterisation showed that the ratio of the donor band exciton (DBE) peak (3.47eV) to the structural peak (3.27eV) in the photoluminescence spectrum, measured at 10K, increased with decreasing defect density. The unwanted structural peak can be considered to originate from a shallow donor to a shallow acceptor transition, which is clearly related to the structural defects in GaN. Thus by increasing the buffer layer thickness and annealing time the structural quality, mobility and photoluminescence improves in the GaN epilayers.
Structural characterisation by transmission electron microscopy (TEM) showed that the observed increase in the DBE to structural peak ratio in the photoluminescence spectra could be correlated with a decrease in the density of stacking faults in the GaN epilayers. The detailed structure of these stacking faults was investigated by dark field and high resolution TEM. Their effect on the electrical and optical behaviour of GaN may be assessed by determining the local change in the dielectric function in the vicinity of individual stacking faults.
In this paper we describe our research efforts directed towards the understanding of the CdS/CuInGaSe2junctions and, specifically, the interaction of the chemical bath with the CuInGaSe2 (CIGS). We find that Cd and S diffuse into the absorber during the CdS growth. Heating the absorbers in Cd partial baths resuled in a significant improvement in the ZnO/CIGS device properties. Photoluminescence measurements indicate that the effect of Cd is very similar to that of CBD CdS.
Cu(In, Ga)Se2 (CIGS) solar cells are under investigation for 1-sun and concentrator applications. Design criteria are examined and reveal that only grid design modifications are required. In the special case where cell width dimensions are 4–5 cm, an interdigitated design removes the back contact as a loss mechanism. Processing issues relating to the intrinsic ZnO layer are critical to optimal and reproducible cell performance. 1-sun and 20 sun performance of 17.7% are reported for different cells. The latter represents a 2.9% absolute improvement over the 1-sun control measurement. 20% performance is therefore a realistic goal. CIGS-based cells represent a viable concentrator technology.