1,720,955 research outputs found
Multi-model estimate of direct and indirect radiative impact of aviation aerosols
No full textAircraft emissions may perturb the global amount and the size distribution of atmospheric aerosols in two ways: (a) direct emission of ultrafine black carbon (BC) soot and sulphuric acid particles in aircraft plumes and (b) release of gas phase SO2, later dispersed on large atmospheric scales and oxidized in H2SO4 by the OH radical. Direct particle emissions are estimated to account for 4–15% of the overall aircraft emitted sulphur. These direct particle emissions do not significantly change aerosol mass and extinction but may substantially increase surface area density (SAD) in the Northern Hemisphere UTLS. Release of gas phase SO2, on the other hand, may increase the net production of H2SO4, thus enhancing the sulphate mass in the accumulation mode and consequently, the direct RF. It also may increase the gas phase contribution to SAD, in the range of 25% of the change produced by direct plume particle emission. The University of L’Aquila climate-chemistry coupled model (ULAQ-CCM) has calculated the accumulation of sulphate aerosols and BC and their globally averaged direct radiative forcing (RF) at the NCEP tropopause with temperature adjustment and in total sky conditions, i.e. -3.3 W/m2 and +1.1 W/m2, respectively (with forcing efficiencies of -140 W/g-SO4 and +2300 W/g-BC, respectively).
The increase of BC in the upper troposphere due to aviation emissions may trigger formation of ice cloud particles (i.e. aviation ‘soot-cirrus’). The formation of background upper tropospheric ice particles is produced by homogeneous and heterogeneous freezing of supercooled aerosols. The ULAQ-CCM considers the basic physical processes that eventually determine the number of ice crystals Ni forming during an adiabatic ascent, including the link of Ni on temperature and updraft speed. In normal conditions the homogeneous freezing mechanisms dominates, but under significant local emissions of BC from aircraft the competition of heterogeneous and homogeneous freezing mechanisms becomes important. In the parameterization used for the formation of aviation soot-cirrus particles in a model grid-box, the change of ice crystals number concentration ∆Ni-HET is calculated as a function of ∆NBC and PHET, where ∆NBC is the change of soot particles due to aviation emissions, assuming a 1% non-hydrophobic fraction of the particles that may act as ice nuclei. PHET, in turn, is the probability that heterogeneous freezing may occur at given grid-box in the model, calculated as the probability to have ice super-saturation for a given temperature (RHICE › 100%) and taking into account water vapour transport due to subgrid vertical updraft velocity. The ULAQ-CCM calculates a +4.9 W/m2 indirect RF of BC, through formation of soot-cirrus (with forcing efficiency of +5 W/g-ice). Uncertainties in this model calculation of soot cirrus RF are however rather large.
The feedback of aviation-produced sulphate aerosol SAD on heterogeneous NOx chemistry represents another significant indirect radiative impact of aviation aerosols, via O3 and CH4 changes produced by the aerosol induced NOx perturbation. Here the physical and chemical approaches and the final calculations are much more robust than for upper tropospheric ice. In this case the results of the University of Oslo models (i.e. UiO-CTM2 and UiO-CTM3) have been used together with those from the ULAQ-CCM used in CTM mode, with the following results: -0.8 ± 0.2 W/m2 and +0.5 ± 0.1 W/m2, for O3 and CH4, respectively, where the error bar is obtained from the three models dispersion. The net aviation-aerosol RF calculated in this study accounts to -2.2 W/m2 (direct) and +4.6 W/m2 (indirect, including soot-cirrus) or -0.3 W/m2 (indirect, not including soot-cirrus), that is (in total) +2.4 W/m2 (including soot-cirrus) or -2.5 W/m2 (not including soot-cirrus). Taking into account that the non-CO2 aviation RF of gas species as calculated in the ULAQ-CCM (i.e. O3 and CH4 from aviation NOx changes and stratospheric H2O) accounts to +9.0 W/m2, the net aerosol impact represents a relative correction of the radiative forcing equal to +27% (including soot-cirrus) and -28% (not including soot-cirrus)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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