Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

In 2018 Pearson et al. published a new sequence of annual radiocarbon (14C) data derived from oak (Quercus sp.) trees from Northern Ireland and bristlecone pine (Pinus longaeva) from North America across the period 1700–1500 BC. The study indicated that the more highly resolved shape of an annually based calibration dataset could improve the accuracy of 14C calibration during this period. This finding had implications for the controversial dating of the eruption of Thera in the Eastern Mediterranean. To test for interlaboratory variation and improve the robustness of the annual dataset for calibration purposes, we have generated a replicate sequence from the same Irish oaks at ETH Zürich. These data are compatible with the Irish oak 14C dataset previously produced at the University of Arizona and are used (along with additional data) to examine inter-tree and interlaboratory variation in multiyear annual 14C time-series. The results raise questions about regional 14C offsets at different scales and demonstrate the potential of annually resolved 14C for refining subdecadal and larger scale features for calibration, solar reconstruction, and multiproxy synchronization.

One important, but overlooked, risk mitigation device that facilitated the growth of the slave trade in the eighteenth century was the increasing availability of insurance for ships and their human cargoes. In this article we explore, for the first time, the relative cost of insurance for British slave traders, the underlying processes by which this key aspect of the business of slavery was conducted, and the factors behind price and other changes over time. Comparisons are also drawn with the transatlantic slave trades of other nations. As well as analyzing the business of underwriting slave voyages, we have two other objectives. First, we explore the meaning of slave insurance from the perspective of those directly involved in the trade. Was it about insuring lives or goods? Second, we provide new estimates of the importance of the slave trade to U.K. marine insurance. Did the former drive the growth of the latter, as Joseph Inikori has claimed?

Optimising short- and long-term outcomes for children and patients with CHD depends on continued scientific discovery and translation to clinical improvements in a coordinated effort by multiple stakeholders. Several challenges remain for clinicians, researchers, administrators, patients, and families seeking continuous scientific and clinical advancements in the field. We describe a new integrated research and improvement network – Cardiac Networks United – that seeks to build upon the experience and success achieved to-date to create a new infrastructure for research and quality improvement that will serve the needs of the paediatric and congenital heart community in the future. Existing gaps in data integration and barriers to improvement are described, along with the mission and vision, organisational structure, and early objectives of Cardiac Networks United. Finally, representatives of key stakeholder groups – heart centre executives, research leaders, learning health system experts, and parent advocates – offer their perspectives on the need for this new collaborative effort.

The Caledonides of Britain and Ireland include terranes attributed to both Laurentian and Gondwanan sources, separated along the Solway line. Gondwanan elements to the south have been variably assigned to the domains Ganderia and East Avalonia. The Midland Platform forms the core of East Avalonia but its provenance is poorly known. Laser ablation split-stream analysis yields information about detrital zircon provenance by providing simultaneous U–Pb and Lu–Hf data from the same ablated volume. A sample of Red Callavia Sandstone from uppermost Cambrian Stage 3 of the Midland Platform yields a U–Pb age spectrum dominated by Neoproterozoic and Palaeoproterozoic sources, resembling those in the Welsh Basin, the Meguma Terrane of Nova Scotia and NW Africa. Initial εHf values suggest that the Neoproterozoic zircon component was derived mainly from crustal sources < 2 Ga, and imply that the more evolved Palaeoproterozoic grains were transported into the basin from an older source terrane, probably the Eburnean Orogen of West Africa. A sample from Cambrian Stage 4 in the Bray Group of the Leinster–Lakesman Terrane shows, in contrast, a distribution of both U–Pb ages and εHf values closely similar to those of the Gander Terrane in Newfoundland and other terranes attributed to Ganderia, interpreted to be derived from the margin of Amazonia. East Avalonia is clearly distinct from Ganderia, but shows evidence for older crustal components not present in West Avalonia of Newfoundland. These three components of the Appalachian–Caledonide Orogen came from distinct sources on the margin of Cambrian Gondwana.

Photovoltaics made from organic–inorganic hybrid perovskite semiconductors are attracting significant interest due to their ability to harvest sunlight with remarkable efficiency. The presence of lead in the best performing devices raises concerns regarding their toxicity, a problem that may create barriers to commercialization. Hybrid perovskites with reduced lead content are being investigated to overcome this issue and here we evaluate bismuth as a possible lead substitute. For a series of hybrid perovskite films with the general composition CH3NH3(Pb y Bi1−y )I3−x Cl x , we characterize their optical and structural properties using UV–Vis spectroscopy, scanning electron microscopy and grazing incidence wide angle X-ray scattering. We show that they form crystalline structures with an optical band gap, around 2 eV for CH3NH3BiI3. However, preliminary solar cell tests show low power conversion efficiencies (<0.01%) due to both incomplete precursor conversion and material de-wetting from the substrate. The overall outcome is severely limited photocurrent. With current processing methods the general applicability of hybrid bismuth perovskites in photovoltaics may be limited.

Stonehenge is a site that continues to yield surprises. Excavation in 2009 added a new and unexpected feature: a smaller, dismantled stone circle on the banks of the River Avon, connected to Stonehenge itself by the Avenue. This new structure has been labelled ‘Bluestonehenge’ from the evidence that it once held a circle of bluestones that were later removed to Stonehenge. Investigation of the Avenue closer to Stonehenge revealed deep periglacial fissures within it. Their alignment on Stonehenge's solstitial axis (midwinter sunset–midsummer sunrise) raises questions about the early origins of this ritual landscape.

Objective: Despite growing adoption, the impact of prehospital initiation of therapeutic hypothermia on outcomes of cardiac arrest patients is unknown. The objective of this study was to determine if prehospital administration of cold intravenous fluids improved the time-to-target temperature.

Methods: All patients enrolled in an institutional post– cardiac arrest treatment pathway were prospectively registered into a quality assurance database. Patients undergoing cooling induction on hospital arrival were compared to those receiving a new treatment protocol initiated during the study period involving prehospital cooling with 4°C (39.2°F) normal saline. The primary outcome was the time-to-target temperature. Secondary outcomes included emergency medicine system transport time metrics, mortality, and neurologic status at discharge and 1 year.

Results: One hundred thirty-two patients were enrolled during the study period. The initial rhythm was ventricular fibrillation/tachycardia in 63% and asystole/pulseless electrical activity in 36%. Eighty patients received prehospital cooling and 52 patients did not and comprised the historical control group. Time-to-target temperatures were not significantly different between prehospital and hospital cooled groups (256 v. 271 minutes, respectively, p=0.64), nor was there any improvement in hospital survival (54% v. 50%, p=0.67), good neurologic outcome (49% v. 44%, p=0.61), or 1- year survival (49% v. 42%, p=0.46) between the two groups. Transport times were longer in the prehospital cooled group.

Conclusions: Out-of-hospital cardiac arrest patients treated with prehospital cooling before arrival at our urban hospital did not have faster time-to-target temperature or improvement in outcomes compared to patients cooled immediately on emergency department arrival. Further research is needed to determine if any benefits exist from prehospital cooling prior to its widespread adoption.

Non-invasive survey in the Stonehenge ‘Triangle’, Amesbury, Wiltshire, has highlighted a number of features that have a significant bearing on the interpretation of the site. Geophysical anomalies may signal the position of buried stones adding to the possibility of former stone arrangements, while laser scanning has provided detail on the manner in which the stones have been dressed; some subsequently carved with axe and dagger symbols. The probability that a lintelled bluestone trilithon formed an entrance in the north-east is signposted. This work has added detail that allows discussion on the question of whether the sarsen circle was a completed structure, although it is by no means conclusive in this respect. Instead, it is suggested that it was built as a façade, with other parts of the circuit added and with an entrance in the south.

Integrated non-invasive survey in the Stonehenge ‘triangle’, Amesbury, Wiltshire, has highlighted a number of features that have a significant bearing on the interpretation of the site. Among them are periglacial and natural topographical structures, including a chalk mound that may have influenced site development. Some geophysical anomalies are similar to the post-holes in the car park of known Mesolithic date, while others beneath the barrows to the west may point to activity contemporary with Stonehenge itself. Evidence that the ‘North Barrow’ may be earlier in the accepted sequence is presented and the difference between the eastern and western parts of the enclosure ditch highlighted, while new data relating to the Y and Z Holes and to the presence of internal banks that mirror their respective circuits is also outlined.