1,720,974 research outputs found
Ultratransparent glass ceramics: The structure factor and the quenching of the Rayleigh scattering
No full textGlass ceramics with nanocrystals present a transparency higher than that expected from the theory of Rayleigh scattering. This ultratransparency is attributed to the spatial correlation of the nanoparticles. The structure factor is calculated for a simple model system, the random sequential addition of equal spheres, at different volume filling factor. The spatial correlation given by the constraint that particles cannot superimpose produces a diffraction peak with a low S (q ) in its low- q tail, which is relevant for light scattering. The physical mechanism producing high transparency in glass ceramics is demonstrated to be the low density fluctuation in the number of scatterers
Phonons in supercooled liquids: a possible explanation for the Boson Peak
No full textpreprint cond-mat/030110
Transparency and long-ranged fluctuations: The case of glass ceramics
No full textGlass ceramics with nanosized crystallites shows an unexpected high transparency, which is not accounted for by the Rayleigh theory of light scattering. Simple analytic arguments ascribe this large transparency to large spatial correlations in the number distribution of the nanocrystallites. Introducing a two-dimensional lattice model that mimics the nucleation and the coarsening phenomena leading to their formation, we show that the extent of such correlations is determined by the spatially limited diffusion of the particles that form the crystallites
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
Asymptotic aging in structural glasses
Full text link© 2004 American Physical Society. We thank A. Cavagna, B. Coluzzi, L. A. Fernández, and F. Sciortino for discussions. Simulations used the full RTN3 cluster of U. Zaragoza for six months. V.M.-M. was partially supported by MCyT (Spain) (Ramón y Cajal program, FPA2001-1813 and FPA2000-0956). P.V. was supported by the ECHP programme, Contract No. HPRN-CT-2002-00307, DYGLAGEMEM.Using a nonlocal Monte Carlo algorithm, we study the aging of a fragile glass, being able to follow it up to equilibrium, down to 0.89T_(MC) (T_(MC) is the mode-coupling temperature), and up to long waiting times at lower temperatures. We show that the fluctuation-dissipation ratio is independent of the dynamics chosen and is compatible with a phase transition and that the scaling behavior of the aging part of the correlation supports the full-aging scenario.MCyT (Spain) (Ramón y Cajal program)ECHP programmeDepto. de Física TeóricaFac. de Ciencias FísicasTRUEpu
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
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