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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.
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 aim of this study was to estimate the amount of childhood hepatitis B virus transmission in children born in the UK, a very low-prevalence country, that is preventable only by universal hepatitis B immunization of infants. Oral fluid specimens were collected from schoolchildren aged 7–11 years in four inner city multi-ethnic areas and tested for the presence of antibody to hepatitis B core antigen (anti-HBc). Those found positive or indeterminate were followed up with testing on serum to confirm their hepatitis B status. The overall prevalence of anti-HBc in children was low [0·26%, 95% confidence interval (CI) 0·14–0·44]. The estimated average annual incidence of hepatitis B was estimated to be 29·26/100 000 children (95% CI 16·00–49·08). The total incidence that is preventable only by a universal infant immunization programme in the UK was estimated to be between 5·00 and 12·49/100 000. The study demonstrates that the extent of horizontal childhood hepatitis B virus transmission is low in children born in the UK and suggests that schools in the UK are an uncommon setting for the transmission of the virus. Targeted hepatitis B testing and immunization of migrants from intermediate- and high-prevalence countries is likely to be a more effective measure to reduce childhood transmission than a universal infant immunization programme.
Application of CHG-impregnated or control (Comfort Bath; Sage) cloths applied over entire body thrice weekly.
Recruits were monitored daily for SSTI. Baseline and serial nasal and/or axillary swabs were collected to assess S. aureus colonization.
Of 1,562 subjects enrolled, 781 (from 23 platoons) underwent CHG-impregnated cloth application and 781 (from 21 platoons) underwent control cloth application. The rate of compliance (defined as application of 50% or more of wipes) at 2 weeks was similar (CHG group, 63%; control group, 67%) and decreased over the 6-week period. The mean 6-week SSTI rate in the CHG-impregnated cloth group was 0.094, compared with 0.071 in the control group (analysis of variance model rate difference, 0.025 ± 0.016; P = .14). At baseline, 43% of subjects were colonized with methicillin-susceptible S. aureus (MSSA), and 2.1% were colonized with MRSA. The mean incidence of colonization with MSSA was 50% and 61% (P = .026) and with MRSA was 2.6% and 6.0% (P = .034) for the CHG-impregnated and control cloth groups, respectively.
CHG-impregnated cloths applied thrice weekly did not reduce rates of SSTI among recruits. S. aureus colonization rates increased in both groups but to a lesser extent in those assigned to the CHG-impregnated cloth Intervention. Antecedent S. aureus colonization was not a risk factor for SSTI. Additional studies are needed to identify effective measures for preventing SSTI among military recruits.