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We present the third data release from the Parkes Pulsar Timing Array (PPTA) project. The release contains observations of 32 pulsars obtained using the 64-m Parkes ‘Murriyang’ radio telescope. The data span is up to 18 yr with a typical cadence of 3 weeks. This data release is formed by combining an updated version of our second data release with $\sim$3 yr of more recent data primarily obtained using an ultra-wide-bandwidth receiver system that operates between 704 and 4032 MHz. We provide calibrated pulse profiles, flux density dynamic spectra, pulse times of arrival, and initial pulsar timing models. We describe methods for processing such wide-bandwidth observations and compare this data release with our previous release.
The objective of this study was to investigate changes in serum biomarkers of acute brain injury, including white matter and astrocyte injury during chronic foetal hypoxaemia. We have previously shown histopathological changes in myelination and neuronal density in fetuses with chronic foetal hypoxaemia at a level consistent with CHD.
Methods:
Mid-gestation foetal sheep (110 ± 3 days gestation) were cannulated and attached to a pumpless, low-resistance oxygenator circuit, and incubated in a sterile fluid environment mimicking the intrauterine environment. Fetuses were maintained with an oxygen delivery of 20–25 ml/kg/min (normoxemia) or 14–16 ml/kg/min (hypoxaemia). Myelin Basic Protein and Glial Fibrillary Acidic Protein serum levels in the two groups were assessed by ELISA at baseline and at 7, 14, and 21 days of support.
Results:
Based on overlapping 95% confidence intervals, there were no statistically significant differences in either Myelin Basic Protein or Glial Fibrillary Acidic Protein serum levels between the normoxemic and hypoxemic groups, at any time point. No statistically significant correlations were observed between oxygen delivery and levels of Myelin Basic Protein and Glial Fibrillary Acidic Protein.
Conclusion:
Chronic foetal hypoxaemia during mid-gestation is not associated with elevated serum levels of acute white matter (Myelin Basic Protein) or astrocyte injury (Glial Fibrillary Acidic Protein), in this model. In conjunction with our previously reported findings, our data support the hypothesis that the brain dysmaturity with impaired myelination found in fetuses with chronic hypoxaemia is caused by disruption of normal developmental pathways rather than by direct cellular injury.
We describe 14 yr of public data from the Parkes Pulsar Timing Array (PPTA), an ongoing project that is producing precise measurements of pulse times of arrival from 26 millisecond pulsars using the 64-m Parkes radio telescope with a cadence of approximately 3 weeks in three observing bands. A comprehensive description of the pulsar observing systems employed at the telescope since 2004 is provided, including the calibration methodology and an analysis of the stability of system components. We attempt to provide full accounting of the reduction from the raw measured Stokes parameters to pulse times of arrival to aid third parties in reproducing our results. This conversion is encapsulated in a processing pipeline designed to track provenance. Our data products include pulse times of arrival for each of the pulsars along with an initial set of pulsar parameters and noise models. The calibrated pulse profiles and timing template profiles are also available. These data represent almost 21 000 h of recorded data spanning over 14 yr. After accounting for processes that induce time-correlated noise, 22 of the pulsars have weighted root-mean-square timing residuals of
$<\!\!1\,\mu\text{s}$
in at least one radio band. The data should allow end users to quickly undertake their own gravitational wave analyses, for example, without having to understand the intricacies of pulsar polarisation calibration or attain a mastery of radio frequency interference mitigation as is required when analysing raw data files.
We describe an ultra-wide-bandwidth, low-frequency receiver recently installed on the Parkes radio telescope. The receiver system provides continuous frequency coverage from 704 to 4032 MHz. For much of the band (
${\sim}60\%$
), the system temperature is approximately 22 K and the receiver system remains in a linear regime even in the presence of strong mobile phone transmissions. We discuss the scientific and technical aspects of the new receiver, including its astronomical objectives, as well as the feed, receiver, digitiser, and signal processor design. We describe the pipeline routines that form the archive-ready data products and how those data files can be accessed from the archives. The system performance is quantified, including the system noise and linearity, beam shape, antenna efficiency, polarisation calibration, and timing stability.
At the summit of the Antarctic plateau, Dome A offers an intriguing location for future large scale optical astronomical observatories. The Gattini Dome A project was created to measure the optical sky brightness and large area cloud cover of the winter-time sky above this high altitude Antarctic site. The wide field camera and multi-filter system was installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January 2008. This automated wide field camera consists of an Apogee U4000 interline CCD coupled to a Nikon fisheye lens enclosed in a heated container with glass window. The system contains a filter mechanism providing a suite of standard astronomical photometric filters (Bessell B, V, R) and a long-pass red filter for the detection and monitoring of airglow emission. The system operated continuously throughout the 2009, and 2011 winter seasons and part-way through the 2010 season, recording long exposure images sequentially for each filter. We have in hand one complete winter-time dataset (2009) returned via a manned traverse. We present here the first measurements of sky brightness in the photometric V band, cloud cover statistics measured so far and an estimate of the extinction.