1,720,974 research outputs found
Second harmonic optical vortex generation in air
No full textWe demonstrate second harmonic vortex generation in atmospheric pressure air using tightly focused femtosecond laser beam. The average second harmonic power is two orders of magnitude higher compared to previous reports
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
Travelling-wave parametric conversion of microjoule pulses with LBO
No full textWe report on the travelling-wave parametric generation which employs a temperature-tuned LBO crystal pumped by a ≈ 1 ps dye-laser source. Pulses of good spatial quality, tunable from 0.8 to 2 μm, are obtained with pump pulses of a few microjoules. Temporally structured pump pulses allow for the lower thresholds and the shorter time durations
High power, subpicosecond, 750-1770 nm tunable pulses from travelling wave parametric generator
No full textTransform limited subpicosecond pulses have been obtained by parametric conversion of the second harmonic of a short pulse generated by a Nd:glass laser system. The arrangement consists of a KDP followed by a BBO respectively with type II and type I phase-matching, pumped in a travelling wave configuration without any spectral selecting element between them. It provides tunability from 750 to 1770 nm with pulses as short as 0.6 ps. Pulse energies above 50 μJ, with a total conversion efficiency of 13%, have been achieve
Visible pulses of 100 fs and 100 μJ from an upconverted parametric generator
No full textUpconversion by sum-frequency and second-harmonic generation of pulses from a Ti:sapphire-pumped parametric generator provides 50-120 μJ, sub-100 fs, bandwidth-limited pulses at 470-700 n
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
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