1,721,000 research outputs found
Atomistic simulations of swift ion tracks in diamond and graphite
No full textWe have used molecular dynamics simulations to study ion tracks in diamond and graphite. Tracks are included using a thermal spike model, i.e. a certain number of atoms within an initial track radius are given an initial excitation energy. The total energy given to the excited atoms and the length of the track determine an "effective" stopping power dE/dx. Electronic excitations in semiconductors and semimetals like diamond and graphite can diffuse far from each other or be quenched before they couple to the lattice. This effect is included by varying the number of atoms that are effectively energized within the track. We use an initial track radius of 3 nm and we find that full amorphization of this region during the first few ps only occurs when the "effective" dE/dx is larger than 6 +/- 0.9 keV/nm for graphite and 10.5 +/- 1.5 keV/nm for diamond. Since the "effective" dE/dx depends on the electron-phonon coupling, our simulations set bounds on the efficiency of the coupling between the electronic excitations and the lattice in this highly non-equilibrium scenario. (c) 2006 Elsevier B.V. All rights reserved
High-Energy ion tracks in thin films
No full textHigh-energy ion tracks (374 MeV Au(26+)) in thin films were examined with transmission electron microscopy to investigate nanopore formation. Tracks in quartz and mica showed diffraction contrast. Tracks in sapphire and mica showed craters formed at the positions of ion incidence and exit, with a lower-density track connecting them. Direct nanopore formation by ions (without chemical etching) would appear to require film thicknesses less than 10 nm
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
Nano-hillock formation in diamond-like carbon induced by swift heavy projectiles in the electronic stopping regime: Experiments and atomistic simulations
Full text linkThe formation of surface hillocks in diamond-like carbon is studied experimentally and by means of large-scale molecular dynamics simulations with 5 × 106 atoms combined with a thermal spike model. The irradiation experiments with swift heavy ions cover a large electronic stopping range between ∼12 and 72 keV/nm. Both experiments and simulations show that beyond a stopping power threshold, the hillock height increases linearly with the electronic stopping, and agree extremely well assuming an efficiency of approximately 20% in the transfer of electronic energy to the lattice. The simulations also show a transition of sp3 to sp2bonding along the tracks with the hillocks containing almost no sp3 contribution.Fil: Schwen, D.. University of Illinois at Urbana-Champaign. Department of Materials Science and Engineering; Estados UnidosFil: Bringa, Eduardo Marcial. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Krauser, J.. Hochschule Harz; AlemaniaFil: Weidinger, A.. Helmholtz-Zentrum Berlin fur Materialien und Energie; AlemaniaFil: Trautmann, C.. GSI Helmholtzzentrum; AlemaniaFil: Hofsass, H.. Universitat Gottingen. Physikalisches Institut; Alemani
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
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