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The Younger Dryas Impact Hypothesis (YDIH) posits that ~12,800 years ago Earth encountered the debris stream of a disintegrating comet, triggering hemisphere-wide airbursts, atmospheric dust loading, and the deposition of a distinctive suite of extraterrestrial (ET) impact proxies at the Younger Dryas Boundary (YDB). Until now, evidence supporting this hypothesis has come only from terrestrial sediment and ice-core records. Here we report the first discovery of similar impact-related proxies in ocean sediments from four marine cores in Baffin Bay that span the YDB layer at water depths of 0.5-2.4 km, minimizing the potential for modern contamination. Using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) and laser ablation ICP-MS, we detect synchronous abundance peaks of metallic debris geochemically consistent with cometary dust, co-occurring with iron- and silica-rich microspherules (4-163 [mu]m) that are predominantly of terrestrial origin with minor (<2 wt%) ET contributions. These microspherules were likely formed by low-altitude touchdown airbursts and surface impacts of comet fragments and were widely dispersed. In addition, single-particle ICP-TOF-MS analysis reveals nanoparticles (<1 [mu]m) enriched in platinum, iridium, nickel, and cobalt. Similar platinum-group element anomalies at the YDB have been documented at dozens of sites worldwide, strongly suggesting an ET source. Collectively, these findings provide robust support for the YDIH. The impact event likely triggered massive meltwater flooding, iceberg calving, and a temporary shutdown of thermohaline circulation, contributing to abrupt Younger Dryas cooling. Our identification of a YDB impact layer in deep marine sediments underscores the potential of oceanic records to broaden our understanding of this catastrophic event and its climatological impacts.

The Younger Dryas Impact Hypothesis (YDIH) posits that ~12,800 years ago Earth encountered the debris stream of a disintegrating comet, triggering hemisphere-wide airbursts, atmospheric dust loading, and the deposition of a distinctive suite of extraterrestrial (ET) impact proxies at the Younger Dryas Boundary (YDB). Until now, evidence supporting this hypothesis has come only from terrestrial sediment and ice-core records. Here we report the first discovery of similar impact-related proxies in ocean sediments from four marine cores in Baffin Bay that span the YDB layer at water depths of 0.5–2.4 km, minimizing the potential for modern contamination. Using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) and laser ablation ICP-MS, we detect synchronous abundance peaks of metallic debris geochemically consistent with cometary dust, co-occurring with iron- and silica-rich microspherules (4–163 μm) that are predominantly of terrestrial origin with minor (<2 wt%) ET contributions. These microspherules were likely formed by low-altitude touchdown airbursts and surface impacts of comet fragments and were widely dispersed. In addition, single-particle ICP-TOF-MS analysis reveals nanoparticles (<1 μm) enriched in platinum, iridium, nickel, and cobalt. Similar platinum-group element anomalies at the YDB have been documented at dozens of sites worldwide, strongly suggesting an ET source. Collectively, these findings provide robust support for the YDIH. The impact event likely triggered massive meltwater flooding, iceberg calving, and a temporary shutdown of thermohaline circulation, contributing to abrupt Younger Dryas cooling. Our identification of a YDB impact layer in deep marine sediments underscores the potential of oceanic records to broaden our understanding of this catastrophic event and its climatological impacts.

The delivery of water to the inner Solar System, including Earth, is still a debated topic. A preferential role for hydrated asteroids in this process is supported by isotopic measurements. Carbonaceous chondrite (CC) meteorites represent our main source of information about these volatile-rich asteroids. However, the destruction of weaker materials during atmospheric entry creates a bias in our CC data. The return of surface materials from the C-type asteroid 162173 Ryugu by the Hayabusa2 spacecraft provides a unique opportunity to study high-porosity, low-density, primitive materials, unrepresented in the meteorite record. We measured the bulk oxygen isotope composition from four Ryugu particles and show that they most closely resemble the rare CI (CC Ivuna-type) chondrites, but with some differences that we attribute to the terrestrial contamination of the CI meteorites. We suggest that CI-related material is widespread among carbonaceous asteroids and a more important source of Earth’s water and other volatiles than its limited presence in our meteoritic collection indicates.Oxygen isotopic measurements from the Ryugu returned sample suggest that primitive hydrated carbonaceous chondrites are an important source of early water and other volatiles to Earth, despite being underrepresented in our meteorite collection due to their preferential destruction during atmospheric entry.

Ryugu is the C-type asteroid from which material was brought to Earth by the Hayabusa2 mission. A number of individual grains and fine-grained samples analysed so far for noble gases have indicated that solar wind and planetary (known as P1) noble gases are present in Ryugu samples with concentrations higher than those observed in CIs, suggesting the former to be more primitive compared to the latter. Here we present results of analyses of three fine-grained samples from Ryugu, in one of which Xe concentration is an order of magnitude higher than determined so far in other samples from Ryugu. Isotopically, this Xe resembles P1, but with a much stronger isotopic fractionation relative to solar wind and significantly lower 36 Ar/ 132 Xe ratio than in P1. This previously unknown primordial noble gas component (here termed P7) provides clues to constrain how the solar composition was fractionated to form the planetary components. Ryugu is more primitive than carbonaceous chondrites, according to elevated noble gas concentrations. Elevated Xe and its isotopic composition further provide constraints on fractionation of the solar composition to form the early planetary components.

IntroductionFewer than half of all people in the USA have a documented advance care plan (ACP). Hospitalisation offers an opportunity for physicians to initiate ACP conversations. Despite expert recommendations, hospital-based physicians (hospitalists) do not routinely engage in these conversations, reserving them for the critically ill.The objective of this study is to test the effect of a novel behavioural intervention on the incidence of ACP conversations by hospitalists practicing at a stratified random sample of hospitals drawn from 220 US acute care hospitals staffed by a large, nationwide acute care physician practice with an ongoing ACP quality improvement initiative.Methods and analysisWe developed Hopewell Hospitalist, a theory-based adventure video game, to modify physicians\" attitudes towards ACP conversations and to increase their motivation for engaging in them. The planned study is a pragmatic stepped-wedge crossover phase III trial, testing the efficacy of Hopewell Hospitalist for increasing ACP conversations. We will randomise 40 hospitals to the month (step) in which they receive the intervention. We aim to recruit 30 hospitalists from up to eight hospitals each step to complete the intervention, playing Hopewell Hospitalist for at least 2 hours. The primary outcome is ACP billing for patients aged 65 and older managed by participating hospitalists. We hypothesise that the intervention will increase ACP billing in the quarter after dissemination, and have 80% power to detect a 1% absolute increase and 99% power to detect a 3.5% absolute increase.Ethics and disseminationDartmouth’s Committee for the Protection of Human Subjects has approved the study protocol, which is registered on clinicaltrials.gov. We will disseminate the results through manuscripts and the trials website. Hopewell Hospitalist will be made available on the iOS Application Store for download, free of cost, at the conclusion of the trial.Trial registration numberNCT04557930.

Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth’s water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but the meteorite record is biased: only the strongest types survive atmospheric entry and are then modified by interaction with the terrestrial environment. Here we present the results of a detailed bulk and microanalytical study of pristine Ryugu particles, brought to Earth by the Hayabusa2 spacecraft. Ryugu particles display a close compositional match with the chemically unfractionated, but aqueously altered, CI (Ivuna-type) chondrites, which are widely used as a proxy for the bulk Solar System composition. The sample shows an intricate spatial relationship between aliphatic-rich organics and phyllosilicates and indicates maximum temperatures of ~30 °C during aqueous alteration. We find that heavy hydrogen and nitrogen abundances are consistent with an outer Solar System origin. Ryugu particles are the most uncontaminated and unfractionated extraterrestrial materials studied so far, and provide the best available match to the bulk Solar System composition. The sample taken from carbonaceous asteroid Ryugu and brought back to Earth by the Hayabusa2 spacecraft contains outer Solar System-derived materials uncontaminated by terrestrial processes. Even CI carbonaceous chondrites, despite their closeness to solar abundances, are not pristine.

Motivated by the need to understand the dynamics of relationship formation and dissolution over time in real world social networks we develop a new longitudinal model for transitions in the relationship status of pairs of individuals ('dyads'). We first specify a model for the relationship status of a single dyad and then extend it to account for important interdyad dependences (e.g. transitivity—'a friend of a friend is a friend') and heterogeneity. Model parameters are estimated by using Bayesian analysis implemented via Markov chain Monte Carlo sampling. We use the model to perform novel analyses of two diverse longitudinal friendship networks: an excerpt of the Teenage Friends and Lifestyle Study (a moderately sized network) and the Framingham Heart Study (a large network).

Background: Prior research identified variations in care experiences across Medicare health plans (Medicare Advantage [MA]), but the relative amount of variation in MA and traditional fee-for-service (FFS) Medicare is unknown. Objectives: Compare variation and correlations of beneficiary reports of care experiences across geographic areas in MA and FFS. Methods: Using the 2001 to 2004 Medicare CAHPS surveys, we analyzed 14 measures of care experiences and preventive services reported by 433,092 MA beneficiaries (82% response rate) and 244,731 in FFS (69% response rate). We estimated hierarchical regression models with random effects for state, hospital referral region, and plan, adjusting for respondent characteristics. We examined the relative variation in FFS and MA scores across areas and among individual MA plans, the correlation between FFS and MA scores across areas, and variability relative to average MA-FFS differences in scores. Results: Although MA and FFS scores are highly correlated, variation is greater in MA than FFS across states and local areas for almost all measures. MA plan variation within areas accounts for 25% to 50% of explained MA variation. MA-FFS differences are smaller than the standard deviations of differences across areas for 10 of 14 measures. Conclusions: Relative performance between MA and FFS may differ across areas and locally between individual plans and FFS. Quality improvement initiatives should address local system factors that affect both MA and FFS, and identify organizational factors that make some MA plans more successful in improving quality.

What do Christians do with the Bible? How do theyùindividually and collectivelyùinteract with the sacred texts? Why does this engagement shift so drastically among and between social, historical, religious, and institutional contexts? Such questions are addressed in a most enlightening, engaging, and original way inThe Social Life of Scriptures. Contributors offer a collection of closely analyzed and carefully conducted ethnographic and historical case studies, covering a range of geographic, theological, and cultural territory, including: American evangelicals and charismatics; Jamaican Rastafarians; evangelical and Catholic Mayans; Northern Irish charismatics; Nigerian Anglicans; and Chinese evangelicals in the United States. The Social Life of Scripturesis the first book to present an eclectic, cross-cultural, and comparative investigation of Bible use. Moreover, it models an important movement to outline a framework for how scriptures are implicated in organizing social structures and meanings, with specific foci on gender, ethnicity, agency, and power.