Conductivity/activation energy relationships for cement-based materials undergoing cyclic thermal excursions

The electrical conductivity of a range of concrete mixes, with and without supplementary cementitious materials (SCM), is studied through multiple cycles of heating and cooling over the extended temperature range -30/?70 C. When presented in an Arrhenius format, the experimental results display hysteresis effects at the lowtemperature end of the thermal cycle and, in those concretes containing supplementary cementitious materials at higher water/binder ratios, hysteresis effects were evident over the entire temperature range becoming more discernible with increasing number of thermal cycles. The depression in both the freezing and thawing point could be clearly identified and was used to estimate pore-neck and pore-cavity radii. A simplified approach is presented to evaluate the volumetric ratio of frozen pore water in terms of conductivity measurements. The results also show that the conductivity and activation energy of the concrete specimens were related to the water/binder ratio, type of SCM, physical state of the pore water and the thermal cycling regime

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Relating the construction and maintenance of maternal ill-health in rural Indonesia

Estimates suggest that over 350,000 deaths and more than 20 million severe disabilities result from the complications of pregnancy, childbirth or its management each year. Death and disability occur predominately among disadvantaged women in resource-poor settings and are largely preventable with adequate delivery care. This paper presents the substantive findings and policy implications from a programme of PhD research, of which the overarching objective was to assess quality of, and access to, care in obstetric emergencies. Three critical incident audits were conducted in two rural districts on Java, Indonesia: a confidential enquiry, a verbal autopsy survey, and a community-based review. The studies examined cases of maternal mortality and severe morbidity from the perspectives of local service users and health providers. A range of inter-related determining factors was identified. When unexpected delivery complications occurred, women and families were often uninformed, unprepared, found care unavailable, unaffordable, and many relied on traditional providers. Midwives in villages made important contributions by stabilising women and facilitating referrals but were often scarce in remote areas and lacked sufficient clinical competencies and payment incentives to treat the poor. Emergency transport was often unavailable and private transport was unreliable and incurred costs. In facilities, there was a reluctance to admit poorer women and those accepted were often admitted to ill-equipped, under-staffed wards. As a result, referrals between hospitals were also common. Otherwise, social health insurance, designed to reduce financial barriers, was particularly problematic, constraining quality and access within and outside facilities. Health workers and service users provided rich and explicit assessments of care and outcomes. These were used to develop a conceptual model in which quality and access are conceived of as social processes, observable through experience and reflective of the broader relationships between individuals and health systems. According to this model, differential quality and access can become both socially legitimate (imposed by structural arrangements) and socially legitimised (reciprocally maintained through the actions of individuals). This interpretation suggests that in a context of commodified care provision, adverse obstetric outcomes will occur and recur for disadvantaged women. Health system reform should focus on the unintended effects of market-based service provision to exclude those without the ability to pay for delivery care directly