Bayesian chronological analyses consistent with synchronous age of 12,835-12,735 Cal B.P. for Younger Dryas boundary on four continents.

The Younger Dryas impact hypothesis posits that a cosmic impact across much of the Northern Hemisphere deposited the Younger Dryas boundary (YDB) layer, containing peak abundances in a variable assemblage of proxies, including magnetic and glassy impact-related spherules, high-temperature minerals and melt glass, nanodiamonds, carbon spherules, aciniform carbon, platinum, and osmium. Bayesian chronological modeling was applied to 354 dates from 23 stratigraphic sections in 12 countries on four continents to establish a modeled YDB age range for this event of 12,835-12,735 Cal B.P. at 95% probability. This range overlaps that of a peak in extraterrestrial platinum in the Greenland Ice Sheet and of the earliest age of the Younger Dryas climate episode in six proxy records, suggesting a causal connection between the YDB impact event and the Younger Dryas. Two statistical tests indicate that both modeled and unmodeled ages in the 30 records are consistent with synchronous deposition of the YDB layer within the limits of dating uncertainty (∼ 100 y). The widespread distribution of the YDB layer suggests that it may serve as a datum layer.

Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago.

Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in eight studies, but unconfirmed in two others, resulting in continued dispute about their occurrence, distribution, and origin. To further address this dispute and better identify YDB spherules, we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry, morphologies, origins, and processes of formation. We investigated 18 sites across North America, Europe, and the Middle East, performing nearly 700 analyses on spherules using energy dispersive X-ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization. Twelve locations rank among the world's premier end-Pleistocene archaeological sites, where the YDB marks a hiatus in human occupation or major changes in site use. Our results are consistent with melting of sediments to temperatures >2,200 °C by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere; they are inconsistent with volcanic, cosmic, anthropogenic, lightning, or authigenic sources. We also produced spherules from wood in the laboratory at >1,730 °C, indicating that impact-related incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across ∼50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event.

Clinical and Cost-effectiveness of a Comprehensive geriatric assessment and management for Canadian elders with Cancer-the 5C study: a study protocol for a randomised controlled phase III trial.

INTRODUCTION: Geriatric assessment and management is recommended for older adults with cancer referred for chemotherapy but no randomised controlled trial has been completed of this intervention in the oncology setting. TRIAL DESIGN: A two-group parallel single blind multi-centre randomised trial with a companion trial-based economic evaluation from both payer and societal perspectives with process evaluation. PARTICIPANTS: A total of 350 participants aged 70+, diagnosed with a solid tumour, lymphoma or myeloma, referred for first/second line chemotherapy, who speak English/French, have an Eastern Collaborative Oncology Group Performance Status 0-2 will be recruited. All participants will be followed for 12 months. INTERVENTION: Geriatric assessment and management for 6 months. The control group will receive usual oncologic care. All participants will receive a monthly healthy ageing booklet for 6 months. OBJECTIVE: To study the clinical and cost-effectiveness of geriatric assessment and management in optimising outcomes compared with usual oncology care. RANDOMISATION: Participants will be allocated to one of the two arms in a 1:1 ratio. The randomisation will be stratified by centre and treatment intent (palliative vs other). OUTCOME: Quality of life. SECONDARY OUTCOMES: (1) Cost-effectiveness, (2) functional status, (3) number of geriatric issues successfully addressed, (4) grades3-5 treatment toxicity, (5) healthcare use, (6) satisfaction, (7) cancer treatment plan modification and (8) overall survival. PLANNED ANALYSIS: For the primary outcome we will use a pattern mixture model using an intent-to-treat approach (at 3, 6 and12 months). We will conduct a cost-utility analysis alongside this clinical trial. For secondary outcomes 2-4, we will use a variety of methods. ETHICS AND DISSEMINATION: Our study has been approved by all required REBs. We will disseminate our findings to stakeholders locally, nationally and internationally and by publishing the findings. TRIAL REGISTRATION NUMBER: NCT03154671.