843 research outputs found

    Excerpt from Jaki\u27s Tale

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    We cooked macaroni and cheese. It was the perfect time to have a girls’ night. Candace loved to stir the block of butter, milk and packaged cheese in the pot once I finished draining it. “Okay,” she grunted. “It’s done, Mommy.” She walked over to the sink and washed her hands. I plucked a noodle from the pot and licked the cheese from my fingertips. “Get the lemonade,” I told her. I picked up the pot and separated it into three bowls while Candace filled two glasses with lemonade. “Grab some napkins.” “I got them,” she answered. “Come on. It’s starting!” “Okay, okay.” I scraped out the last of the macaroni and tossed the pot in the sink. I quickly picked up two bowls of macaroni. “Do you have forks?” I called, skidding across the foyer in my socks. “Yeah!” Candace answered from the living room. Candace knelt on the floor in front of the coffee table. The TV displayed the first episode of the Gilmore Girls marathon

    A new multi-gas constrained model of trace gas non-homogeneous transport in firn: evaluation and behaviour at eleven polar sites

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    Insoluble trace gases are trapped in polar ice at the firn-ice transition, at approximately 50 to 100 m below the surface, depending primarily on the site temperature and snow accumulation. Models of trace gas transport in polar firn are used to relate firn air and ice core records of trace gases to their atmospheric history. We propose a new model based on the following contributions. First, the firn air transport model is revised in a poromechanics framework with emphasis on the non-homogeneous properties and the treatment of gravitational settling. We then derive a nonlinear least square multi-gas optimisation scheme to calculate the effective firn diffusivity (automatic diffusivity tuning). The improvements gained by the multi-gas approach are investigated (up to ten gases for a single site are included in the optimisation process). We apply the model to four Arctic (Devon Island, NEEM, North GRIP, Summit) and seven Antarctic (DE08, Berkner Island, Siple Dome, Dronning Maud Land, South Pole, Dome C, Vostok) sites and calculate their respective depth-dependent diffusivity profiles. Among these different sites, a relationship is inferred between the snow accumulation rate and an increasing thickness of the lock-in zone defined from the isotopic composition of molecular nitrogen in firn air (denoted d15N). It is associated with a reduced diffusivity value and an increased ratio of advective to diffusive flux in deep firn, which is particularly important at high accumulation rate sites. This has implications for the understanding of d15N of N2 records in ice cores, in relation with past variations of the snow accumulation rate. As the snow accumulation rate is clearly a primary control on the thickness of the lock-in zone, our new approach that allows for the estimation of the lock-in zone width as a function of accumulation may lead to a better constraint on the age difference between the ice and entrapped gases

    Atmospheric CO2 over the last 1000 years: A high-resolution record from the West Antarctic Ice Sheet (WAIS) Divide ice core

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    We report a decadally resolved record of atmospheric CO2 concentration for the last 1000 years, obtained from the West Antarctic Ice Sheet (WAIS) Divide shallow ice core. The most prominent feature of the pre‐industrial period is a rapid ∼7 ppm decrease of CO2 in a span of ∼20–50 years at ∼1600 A.D. This observation confirms the timing of an abrupt atmospheric CO2 decrease of ∼10 ppm observed for that time period in the Law Dome ice core CO2 records, but the true magnitude of the decrease remains unclear. Atmospheric CO2 variations over the time period 1000–1800 A.D. are statistically correlated with northern hemispheric climate and tropical Indo‐Pacific sea surface temperature. However, the exact relationship between CO2 and climate remains elusive due to regional climate variations and/or uneven geographical data density of paleoclimate records. We observe small differences of 0 ∼ 2% (0 ∼ 6 ppm) among the high‐precision CO2 records from the Law Dome, EPICA Dronning Maud Land and WAIS Divide Antarctic ice cores. However, those records share common trends of CO2 change on centennial to multicentennial time scales, and clearly show that atmospheric CO2 has been increasing above preindustrial levels since ∼1850 A.D

    Challenges and practical recommendations for successfully recruiting inactive, statin-free older adults to clinical trials

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    Objectives: To outline the challenges and provide practical recommendations for recruiting inactive, statin-free older adults to facilitate feasible study designs. Data was obtained from a double-blind randomised-controlled clinical trial investigating the effects of acipimox versus placebo on muscle function and metabolism in older (65-75 years), inactive, statin-free males. The initial recruitment target was 20 volunteers within 12 months (November 2016-November 2017). Results: Recruitment occurred via the Exeter 10,000 database containing 236 'eligible' males, a Facebook campaign reaching > 8000 ≥ 65 years old males, 400 directly-addressed letters to ≥ 66 year old males, > 1500 flyers distributed within the community, > 40 emails to local community groups, 4 recruitment talks, 2 magazine adverts and 1 radio advert. Widespread recruitment efforts reaching > 120,000 people led to the recruitment of 20 volunteers (18 completed the clinical trial) within a 25-month timeframe, highlighting the challenge of the timely recruitment of inactive, statin-free older adults for clinical trials. We recommend recruitment for future clinical trials should take a multi-pronged approach from the outset, prioritising the use of volunteer databases, Facebook campaigns and delivering recruitment talks.This article is freely available via Open Access. Click on the Publisher URL to access it via the publisher's site.This work was supported by a grant from Dunhill Medical Trust (R492/0516) and the NIHR Exeter CRF. CS Deane is a funded Medical Research Council Skills Development Fellow (MR/T026014/1). The funders had no role in study design, data analysis or outcome of the study.published version, accepted versio
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