586 research outputs found

    Dedication to Peter M. Williams

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    Peter M. Williams was a pioneer in the field of marine organic chemistry for thirty-five years. He died on 26 December 1994 of complicatio~ls from emphysema. We dedicate this special volume of Deep-Sea Research to his memory and as a commemoration of the vast amount of research inspired by his creativity and ideas, many of which were far ahead of their time. Research accomplishments of Peter Williams included: Performing the first isolation of individual organic compounds from seawater. Making the first determination of the stable carbon isotopic composition of dissolved and particulate organic matter in the sea. Performing the first radiocarbon dating of seawater organic matter. Serving as a leader and major contributor to an interdisciplinary study on the formation, composition and alteration of sea surface films. Publishing, over three decades, results of the most comprehensive studies to date on the distribution and cycling of dissolved organic carbon (DOC) in the world's oceans. As John Hedges aptly expressed in his letter nominating Peter Williams as a Fellow of the American Geophysical Union: "Who else can so accurately describe their research interests simply as 'Marine Chemistry'?

    The epitaxy of gold

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    Measurement of the t(t)over-bar production cross section in p(p)over-bar collisions at root s=1.96 TeV

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    We present a measurement of the top quark pair production cross section in pp̄ collisions at s=1.96TeV using 318pb-1 of data collected with the Collider Detector at Fermilab. We select tt̄ decays into the final states eν+jets and μν+jets, in which at least one b quark from the t-quark decays is identified using a secondary vertex-finding algorithm. Assuming a top quark mass of 178GeV/c2, we measure a cross section of 8.7±0.9(stat)-0. 9+1.1(syst)pb. We also report the first observation of tt̄ with significance greater than 5σ in the subsample in which both b quarks are identified, corresponding to a cross section of 10.1-1.4+1.6(stat)-1.3+2.0(syst) pb. © 2006 The American Physical Society

    Evidence for the Onset of Color Transparency in ρ0\rho^0 Electroproduction off Nuclei

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    We have measured the nuclear transparency of the incoherent diffractive A(e,eρ0)A(e,e'\rho^0) process in 12^{12}C and 56^{56}Fe targets relative to 2^2H using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced ρ0\rho^0's on a nucleus relative to deuterium, which is sensitive to ρA\rho A interaction, was studied as function of the coherence length (lcl_c), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared (Q2Q^2). While the transparency for both 12^{12}C and 56^{56}Fe showed no lcl_c dependence, a significant Q2Q^2 dependence was measured, which is consistent with calculations that included the color transparency effects.Comment: 6 pages and 4 figure

    Exclusive ρ0\rho^0 meson electroproduction from hydrogen at CLAS

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    The longitudinal and transverse components of the cross section for the epepρ0e p\to e^\prime p \rho^0 reaction were measured in Hall B at Jefferson Laboratory using the CLAS detector. The data were taken with a 4.247 GeV electron beam and were analyzed in a range of xBx_B from 0.2 to 0.6 and of Q2Q^2 from 1.5 to 3.0 GeV2^2. The data are compared to a Regge model based on effective hadronic degrees of freedom and to a calculation based on Generalized Parton Distributions. It is found that the transverse part of the cross section is well described by the former approach while the longitudinal part can be reproduced by the latter.Comment: 6 pages, 4 figure

    Systematic Review of Medicine-Related Problems in Adult Patients with Atrial Fibrillation on Direct Oral Anticoagulants

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    New oral anticoagulant agents continue to emerge on the market and their safety requires assessment to provide evidence of their suitability for clinical use. There-fore, we searched standard databases to summarize the English language literature on medicine-related problems (MRPs) of direct oral anticoagulants DOACs (dabigtran, rivaroxban, apixban, and edoxban) in the treatment of adults with atri-al fibrillation. Electronic databases including Medline, Embase, International Pharmaceutical Abstract (IPA), Scopus, CINAHL, the Web of Science and Cochrane were searched from 2008 through 2016 for original articles. Studies pub-lished in English reporting MRPs of DOACs in adult patients with AF were in-cluded. Seventeen studies were identified using standardized protocols, and two reviewers serially abstracted data from each article. Most articles were inconclusive on major safety end points including major bleeding. Data on major safety end points were combined with efficacy. Most studies inconsistently reported adverse drug reactions and not adverse events or medication error, and no definitions were consistent across studies. Some harmful drug effects were not assessed in studies and may have been overlooked. Little evidence is provided on MRPs of DOACs in patients with AF and, therefore, further studies are needed to establish the safety of DOACs in real-life clinical practice

    Reproducibility in the absence of selective reporting : An illustration from large-scale brain asymmetry research

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    Altres ajuts: Max Planck Society (Germany).The problem of poor reproducibility of scientific findings has received much attention over recent years, in a variety of fields including psychology and neuroscience. The problem has been partly attributed to publication bias and unwanted practices such as p-hacking. Low statistical power in individual studies is also understood to be an important factor. In a recent multisite collaborative study, we mapped brain anatomical left-right asymmetries for regional measures of surface area and cortical thickness, in 99 MRI datasets from around the world, for a total of over 17,000 participants. In the present study, we revisited these hemispheric effects from the perspective of reproducibility. Within each dataset, we considered that an effect had been reproduced when it matched the meta-analytic effect from the 98 other datasets, in terms of effect direction and significance threshold. In this sense, the results within each dataset were viewed as coming from separate studies in an "ideal publishing environment," that is, free from selective reporting and p hacking. We found an average reproducibility rate of 63.2% (SD = 22.9%, min = 22.2%, max = 97.0%). As expected, reproducibility was higher for larger effects and in larger datasets. Reproducibility was not obviously related to the age of participants, scanner field strength, FreeSurfer software version, cortical regional measurement reliability, or regional size. These findings constitute an empirical illustration of reproducibility in the absence of publication bias or p hacking, when assessing realistic biological effects in heterogeneous neuroscience data, and given typically-used sample sizes
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