1,720,960 research outputs found
Controlling the optical properties of Gallium nanoparticles with a beam of electrons
No full textFor the first time, we show that a beam of electrons can change the optical properties of a nanoparticle film through the mechanism of controlling the structural phase coexistence in the nanoparticles. This study is motivated by a desire to understand the exciting physics of phase equilibria in metallic nanoparticles and clusters, and is stimulated by interest in the properties of metallic nanoparticles relating to their potential role in future highly integrated photonic devices, as the active elements of waveguiding and switching structures addressed by an electron beam
Nanoscale light-induced phase transformation in alpha-gallium as the source of a broadband optical nonlinearity
No full textSummary form only given. Using a tunable optical parametric oscillator we discovered that the interface between gallium and silica displays an exceptionally broadband nonlinearity. At temperatures several degrees below gallium's melting point (~30°C) the reflectivity increases by up to 40% in response to 3 ns excitation pulses at wavelengths from 440 to 700 nm. It is shown how the reflectivity change depends on the excitation fluence, and that it saturates at about 6 mJ/cm
Phase coexistence in gallium nanoparticles controlled by electron excitation
Full text linkIn gallium nanoparticles 100 nm in diameter grown on the tip of an optical fiber from an atomic beam we observed equilibrium coexistence of ?, ?, and liquid structural phases that can be controlled by e-beam excitation in a highly reversible and reproducible fashion. With 2 keV electrons only 1 pJ of excitation energy per nanoparticle is needed to exercise control, with the equilibrium phase achieved in less than a few tenths of a microsecond. The transformations between coexisting phases are accompanied by a continuous change in the nanoparticle film's reflectivity.<br/
Gigantic broadband optical nonlinearity in gallium films deposited by ultrafast laser ablation
No full textGallium-Silica interfaces have emerged as a new type of structure that combines a strong nonlinearity [1] with picosend switching-on time [2]. Here we report that the optical nonlinearity of gallium films deposited on fused silica by ultrafast pulsed laser ablation is very broadband, spanning from 480 nm to 810 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
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
- …
