To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
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.
Word production variability is widespread in speech, and rates of variant production correlate with many factors. Recent research suggests mental representation of both canonical word forms and distinct reduced variants, and that production and processing are sensitive to variant frequency. What factors lead to frequency-weighted variant representations? An experiment manipulated following context and word repetition for final t/d words in read, narrative English speech. Modeling the experimentally generated data statistically showed higher final-segment deletion in tokens followed by consonant-initial words, but no evidence of increased deletion with repetition, regardless of context. Deletion rates were also higher the greater a word's cumulative exposure to consonant contexts (measured from distributional statistics), but there was no effect of word frequency. Token effects are interpreted in terms of articulation processes. The type-level context effect is interpreted within exemplar and usage-based models of language to suggest that experiences with word variants in contexts register as frequency-weighted representations.
Gilliland et al. (2000) have reported HST photometric observations of 34000 stars in the globular cluster 47 Tuc, showing an absence of close-in giant planets in that cluster relative to their frequency in the solar neighborhood. Here we describe the methods of time-series analysis that were used to search the 47 Tuc data for transits by giant extrasolar planets, and the means by which these methods were validated.
The public health burden of alcohol is unevenly distributed across the life course, with levels of use, abuse, and dependence increasing across adolescence and peaking in early adulthood. Here, we leverage this temporal patterning to search for common genetic variants predicting developmental trajectories of alcohol consumption. Comparable psychiatric evaluations measuring alcohol consumption were collected in three longitudinal community samples (N = 2,126, obs = 12,166). Consumption-repeated measurements spanning adolescence and early adulthood were analyzed using linear mixed models, estimating individual consumption trajectories, which were then tested for association with Illumina 660W-Quad genotype data (866,099 SNPs after imputation and QC). Association results were combined across samples using standard meta-analysis methods. Four meta-analysis associations satisfied our pre-determined genome-wide significance criterion (FDR < 0.1) and six others met our ‘suggestive’ criterion (FDR <0.2). Genome-wide significant associations were highly biological plausible, including associations within GABA transporter 1, SLC6A1 (solute carrier family 6, member 1), and exonic hits in LOC100129340 (mitofusin-1-like). Pathway analyses elaborated single marker results, indicating significant enriched associations to intuitive biological mechanisms, including neurotransmission, xenobiotic pharmacodynamics, and nuclear hormone receptors (NHR). These findings underscore the value of combining longitudinal behavioral data and genome-wide genotype information in order to study developmental patterns and improve statistical power in genomic studies.
Develop and implement an effective program for hazard analysis and control of waterborne pathogens at a multicampus hospital with clinics.
A longitudinal study. Several-year study including analysis of results from monitoring and tests of 26 building water systems.
Outpatient and inpatient healthcare facilities network.
The hazard analysis and critical control point (HACCP) process was used to develop a water management program (WMP) for the hospital campuses. The HACCP method systematically addressed 3 questions: (1) What are the potential waterborne hazards in the building water systems of these facilities? (2) How are the hazards being controlled? (3) How do we know that the hazards have been controlled? Microbiological and chemical tests of building water samples were used to validate the performance of the WMP; disease surveillance data further validated effective hazard control.
Hazard analysis showed that waterborne pathogens were generally in good control and that the water quality was good in all facilities. The hospital network has had several legionellosis cases that were identified as presumptive hospital acquired, but none was confirmed or substantiated by water testing in follow-up investigations. Building water system studies unrelated to these cases showed that pressure tanks and electronic automatic faucets required additional hazard control.
Application of the HACCP process for long-term building water systems management was practical and effective. The need for critical control point management of temperature, flow, and oxidant (chlorine) residual concentration was emphasized. The process resulted in discovery of water system components requiring additional hazard control.
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.
Radiation damage experiments are being performed with pyrochlore and zirconolite in support of the disposition of surplus weapons-ready Pu. Pyrochlore becomes amorphous in approximately 1 year from the alpha recoil damage of ∼ 1018 alphas/g from the decay of 238Pu. The dissolution rate of 238Pu-bearing ceramics increases with increasing radiation damage as measured in a 3 d MCC-1 test at 90°C. Over the same period, zirconolite retains substantial crystallinity albeit with broadened diffraction peaks. The dissolution rate also increases with increasing radiation damage.
In this work, an electron spin resonance study of NH3-nitrided, N2O-nitrided, and N2O-grown oxides yields information relating the process history, point defect structure, and electrical behavior. NH3-nitridation is responsible for the introduction of bridging nitrogen centers, high capture cross section neutral electron traps, while N2O-processed dielectrics never exhibit these defects. In addition, structural changes at the interface due to nitridation result in observable differences in the interfacial defects.
Electromigration and stress migration are important reliability concerns in the semiconductor industry. Relative and absolute assessments of lifetimes generally rely on the accelerated testing of ‘standard’ test structures. However, the sensitivity to various important electromigration phenomena is found to depend strongly on the type of test structure. Two common structures for electromigration testing are (i) a long line with large pads at either end and (ii) a more realistic interconnect line with W-studs at the line end. The effects of (a) different flux divergences at the line end, (b) interfacial diffusion, and (c) Cu-depletion generally result in different lifetimes for the two types of test structures under the same testing conditions. In this paper, we compare void growth rates and mean times to failure for both types of test structure taking these effects into account. Our results are used to explain differences in MTF values reported in the literature for different test structures.
Recent work in thermal stress induced voiding in passivated lines has focussed on the isothermal, quasi-steady state growth of existing voids. In this work, the transient growth and shrinkage of voids during the thermal cycling of narrow, passivated lines was studied. Analysis of experimental data for passivated lines demonstrates the quick buildup and evolution of a backstress at the grain boundary during heating and cooling. This backstress greatly reduces the driving force for void growth at higher temperatures and must be accounted for in stress induced void growth models for the case of appreciably varying temperatures in short time scales.
Strongly non uniform Fe depth distributions have been observed in AI(0.13 at% Fe) thin films deposited at temperatures of 350ºC and above. The concentration of Fe is uniform in depth at a deposition temperature of 300ºC but is increasingly enhanced toward the substrate interface at 450ºC. Subsequent annealing produces only a slight redistribution of Fe. The Fe is primarily present as precipitates smaller than 100 nm. A model of grain boundary diffusion of Fe and precipitate formation and grain growth is proposed to explain the observed behavior.