14,562 research outputs found

    Measured limits to contamination of optical surfaces by elastomers in vacuum

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    We have monitored the reflectivity of mirrors that were exposed to a fluoroelastomer (3M-Fluorel 2176) and a room-temperature vulcanizing silicone rubber (RTV-615) in vacuum. The 95% confidence limit on the decrease of mirror reflectivities was less than 0.35 ppm/week for Fluorel and <0.29 ppm@week for RTV-615

    On small time asymptotics for rough differential equations driven by fractional Brownian motions

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    We survey existing results concerning the study in small times of the density of the solution of a rough differential equation driven by fractional Brownian motions. We also slightly improve existing results and discuss some possible applications to mathematical finance.Comment: This is a survey paper, submitted to proceedings in the memory of Peter Laurenc

    Algebraic structure of stochastic expansions and efficient simulation

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    We investigate the algebraic structure underlying the stochastic Taylor solution expansion for stochastic differential systems.Our motivation is to construct efficient integrators. These are approximations that generate strong numerical integration schemes that are more accurate than the corresponding stochastic Taylor approximation, independent of the governing vector fields and to all orders. The sinhlog integrator introduced by Malham & Wiese (2009) is one example. Herein we: show that the natural context to study stochastic integrators and their properties is the convolution shuffle algebra of endomorphisms; establish a new whole class of efficient integrators; and then prove that, within this class, the sinhlog integrator generates the optimal efficient stochastic integrator at all orders.Comment: 19 page

    Standard Model Top Quark Asymmetry at the Fermilab Tevatron

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    Top quark pair production at proton-antiproton colliders is known to exhibit a forward-backward asymmetry due to higher-order QCD effects. We explore how this asymmetry might be studied at the Fermilab Tevatron, including how the asymmetry depends on the kinematics of extra hard partons. We consider results for top quark pair events with one and two additional hard jets. We further note that a similar asymmetry, correlated with the presence of jets, arises in specific models for parton showers in Monte Carlo simulations. We conclude that the measurement of this asymmetry at the Tevatron will be challenging, but important both for our understanding of QCD and for our efforts to model it.Comment: 26 p., 10 embedded figs., comment added, version to appear in PR

    Accelerated return to sport after osteochondral autograft plug transfer

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    Background:Previous studies have reported varying return-to-sport protocols after knee cartilage restoration procedures.Purpose:To (1) evaluate the time for return to sport in athletes with an isolated chondral injury who underwent an accelerated return-to-sport protocol after osteochondral autograft plug transfer (OAT) and (2) evaluate clinical outcomes to assess for any consequences from the accelerated return to sport.Study Design:Case series; Level of evidence, 4.Methods:An institutional cohort of 152 OAT procedures was reviewed, of which 20 competitive athletes met inclusion and exclusion criteria. All patients underwent a physician-directed accelerated rehabilitation program after their procedure. Return to sport was determined for all athletes. Clinical outcomes were assessed using International Knee Documentation Committee (IKDC) and Tegner scores as well as assessment of level of participation on return to sport.Results:Return-to-sport data were available for all 20 athletes; 13 of 20 athletes (65%) were available for clinical evaluation at a mean 4.4-year follow-up. The mean time for return to sport for all 20 athletes was 82.9 ± 25 days (range, 38-134 days). All athletes were able to return to sport at their previous level and reported that they were satisfied or very satisfied with their surgical outcome and ability to return to sport. The mean postoperative IKDC score was 84.5 ± 9.5. The mean Tegner score prior to injury was 8.9 ± 1.7; it was 7.7 ± 1.9 at final follow-up.Conclusion:Competitive athletes with traumatic chondral defects treated with OAT managed using this protocol had reduced time to preinjury activity levels compared with what is currently reported, with excellent clinical outcomes and no serious long-term sequelae.</jats:sec

    Entropy and Hausdorff Dimension in Random Growing Trees

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    We investigate the limiting behavior of random tree growth in preferential attachment models. The tree stems from a root, and we add vertices to the system one-by-one at random, according to a rule which depends on the degree distribution of the already existing tree. The so-called weight function, in terms of which the rule of attachment is formulated, is such that each vertex in the tree can have at most K children. We define the concept of a certain random measure mu on the leaves of the limiting tree, which captures a global property of the tree growth in a natural way. We prove that the Hausdorff and the packing dimension of this limiting measure is equal and constant with probability one. Moreover, the local dimension of mu equals the Hausdorff dimension at mu-almost every point. We give an explicit formula for the dimension, given the rule of attachment

    Geogia Red Knot Resights report 2014

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    Expanding the Red Knot resight program to include other important staging areas along the Atlantic Coast is a stated priority of the USFWS Red Knot Spotlight Species Action Plan (2010) and the Red Knot Conservation Plan (2010). Our objectives in expanding the program into the Georgia Coast during spring migration are to: 1) estimate the population of Red Knots using the Georgia Coast as a spring stopover, 2) estimate spring stopover duration along the Georgia Coast, 3) determine the primary stopover locations and provide this information to local land managers, 4) contribute to the range-wide demographic studies and studies in migratory connectivity of the Red Knot in the Western Hemisphere, and 5) contribute data to the current listing process initiated by the US Fish and Wildlife Service. Regional population estimates and identification of major stopover sites are considered to be the highest priority for the Georgia Department of Natural Resources State Wildlife Action Plan, the Atlantic Flyway Shorebird Initiative (Winn et al. 2013), the US Shorebird Plan (Brown et al. 2001), the USFWS Red Knot Action Plan (2010) and the Western Hemisphere Shorebird Reserve Network Red Knot Conservation Plan for the Western Hemisphere (Niles et al. 2010a). Providing a population estimate for various staging areas is a stated goal of the WHSRN Red Knot Conservation Plan for the Western Hemisphere (Niles et al. 2010a), the Atlantic Flyway Shorebird Strategy, and the US FWS Red Knot Action Plan (2010). The Georgia Department of Natural Resources State Wildlife Action Plan ranks the Red Knot as a high priority species (with state status of “Rare”) and ranks research of the Red Knot as one primary conservation actions needed within the state

    Flows driven by Banach space-valued rough paths

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    We show in this note how the machinery of C^1-approximate flows devised in the work "Flows driven by rough paths", and applied there to reprove and extend most of the results on Banach space-valued rough differential equations driven by a finite dimensional rough path, can be used to deal with rough differential equations driven by an infinite dimensional Banach space-valued weak geometric Holder p-rough paths, for any p>2, giving back Lyons' theory in its full force in a simple way.Comment: 8 page

    Investigating red knot migration ecology along the Georgia coast: fall 2015 and spring 2013, 2015-16 season summaries

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    The rufa subspecies of the Red Knot (Calidris canutus) has declined significantly in the past 35 years, leading to federal listing (US Fish and Wildlife Service Federal Register Vol. 79 No. 238, 2014a) under the Endangered Species Act in the United States (16 U.S.C. 1531 et. seq) and Canada (COSEWIC 2007, SARA 2007). The determination of regional population estimates and identification of major stopover sites are considered to be the highest priority for the Georgia Department of Natural Resources State Wildlife Action Plan (2015), the Atlantic Flyway Shorebird Business Strategy (Winn et al. 2013), the US Shorebird Plan (Brown et al. 2001), the USFWS Red Knot Spotlight Species Action Plan (2010), and the Western Hemisphere Shorebird Reserve Network (WHSRN) Red Knot Conservation Plan for the Western Hemisphere (Niles et al. 2010a). The Georgia Department of Natural Resources State Wildlife Action Plan ranks the Red Knot as a high priority species (with state status of “Rare”) and ranks research of the Red Knot as one of the primary conservation actions needed within the state. A large percentage (3-6%) of Red Knots have been previously captured and tagged with unique 2 to 3 digits alpha-numeric bands. This marked population allows for mark-resight studies of migratory populations of Red Knots with no capturing involved. We detected a total of 43,686 Red Knots during daily surveys in spring 2016 along the Georgia Coast; of those, 10,029 were scanned for flags, and 1,255 individually banded Red Knots were resighted within the spring migrant population. A total of 158 marked to unmarked ratios were recorded during the field season, with an average of 3.8% of Red Knots individually marked over the course of the spring. The estimated superpopulation size for the spring 2016 season is 11,948 Red Knots (95% credible interval: 9,821 – 16,405). The mean Minimum-length-of-stay (MINLOS) for Red Knots staging in Georgia was 9.8day±11.1SD. A total of 3,805 Red Knots were detected on daily surveys during fall migration 2015; of those, 2,231 individuals were scanned for flags, and 140 individually banded Red Knots were resighted within that group. A total of 78 marked to unmarked ratios were recorded during the field season, with an average 3.4% of Red Knots banded. A total of 68 individuals were identified during the fall season, which was not enough data to analyze the population migrating through the Georgia Coast in fall 2015. We determined relative use along the Georgia Coast in spring and fall migration through a combination of aerial and ground based surveys. We created a GIS database of all encounters of Red Knots along the barrier Island chain, totaling 299 locations and 98,155 Red Knots mapped. The Georgia Coast is a major stopover area annually for rufa Red Knots in spring migration and in certain years in fall migration. The superpopulation utilizing the coast in fall migration can exceed 23,000 birds (Lyons et al. 2017 in press) and the estimates of spring migration superpopulation from this study ranges between 8,000 and 14,000 birds. The total estimated population of rufa Red Knots is 42,000 birds (Andres et al. 2012), suggesting that a high percentage of rufa knots are using the Georgia Coast in spring and in some years fall migration. There appears to be less variation in spring migration superpopulations between years than in fall migration, suggesting a more stable (but less abundant) food source for spring migrants

    Bisphenol A and the risk of cardiometabolic disorders: a systematic review with meta-analysis of the epidemiological evidence.

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    Published onlineResearch Support, Non-U.S. Gov'tBisphenol A (BPA) is suspected to be associated with several chronic metabolic diseases. The aim of the present study was to review the epidemiological literature on the relation between BPA exposure and the risk of cardiometabolic disorders. PubMed and Embase databases were searched up to August 2014 by two independent investigators using standardized subject terms. We included observational studies (cohort, case-control and cross-sectional studies) carried out in children or adults, measuring urinary BPA (uBPA), including at least 100 participants and published in English. The health outcomes of interest were diabetes, hyperglycemia, measures of anthropometry, cardiovascular disease (CVD) and hypertension. Data were extracted and meta-analyzed when feasible, using a random-effects model. Thirty-three studies with sample size ranging from 239 to 4811 met the inclusion criteria, including five with a prospective design. Twelve studies reported on diabetes or hyperglycemia, 16 on anthropometry, 6 on CVD and 3 on hypertension. Evidence for a positive association between uBPA concentrations and diabetes, overweight, obesity, elevated waist circumference (WC), CVD and hypertension was found in 7/8, 2/7, 6/7, 5/5, 4/5 and 2/3 of the cross-sectional studies, respectively. We were able to conduct outcome-specific meta-analyses including 12 studies. When comparing the highest vs. the lowest uBPA concentrations, the pooled ORs were 1.47 (95% CI: 1.21-1.80) for diabetes, 1.21 (95% CI: 0.98-1.50) for overweight, 1.67 (95% CI: 1.41-1.98) for obesity, 1.48 (95% CI: 1.25-1.76) for elevated WC, and 1.41 (95% CI: 1.12-1.79) for hypertension. Moreover, among the five prospective studies, 3 reported significant findings, relating BPA exposure to incident diabetes, incident coronary artery disease, and weight gain. To conclude, there is evidence from the large body of cross-sectional studies that individuals with higher uBPA concentrations are more likely to suffer from diabetes, general/abdominal obesity and hypertension than those with lower uBPA concentrations. Given the potential importance for public health, prospective cohort studies with proper adjustment for dietary characteristics and identification of critical windows of exposure are urgently needed to further improve knowledge about potential causal links between BPA exposure and the development of chronic disease.This study was funded by the National Health and Medical Research Council, Australia (NHMRC grant APP1022923). Support for FR was provided by a postdoctoral grant from CORDDIM (field of major interest of the Île-de-France Regional Council “Cardiovascular/Obesity/Kidney/Diabetes”), the French Endocrine Disruptor Research Programme (PNRPE grant) and the Scientific Mobility Program of the Embassy of France in Australia (2014). JGL is supported by National Heart Foundation of Australia/NHMRC postgraduate scholarship [586739] and the Cardiac Society of Australia and New Zealand. This work was supported in part by the Victorian Government’s OIS Program
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