1,720,959 research outputs found
A single nanoparticle as a femtojoule photonic switch and optical memory element
No full textWe report that a nano-aperture occupied by a single polymorphic metal nanoparticle can be used as the active elements of low energy consumption nanophotonic devices if the dielectric properties of the nano-particle can be controlled using excitation-induced structural transformations, In essence, this new opportunity relies on the fact that, in contrast to bulk solids where phase transitions are characterized by abrupt transitions between different structural forms, phase transformations in polymorphic nanoparticles proceed through a dynamic coexistence of forms - making transitions continuous and reversible. We experimentally demonstrate this new paradigm with a gallium nanoparticle and show that using very low power laser light it can be switched between five structural phases with differing dielectric properties to provide different levels of transmission through and reflection from the nano-aperture, We also present finite element numerical modeling of light propagation through a nono-aperture blocked by a nanoparticle and analyze relevant plasmonic and scattering effects
Single nanoparticle as photonic switch and optical memory element
No full textWe suggest and experimentally demonstrate a new concept for optical nanowatt switching and memory function made possible by light-induced structural transformations in a single nanoparticle
Controlling light with light via structural transformations in metallic nanoparticles
No full textReversible, light-induced structural transitions in metallic nanoparticles, taking the form of surface-driven dynamic phase coexistences, provide an optical nonlinearity suitable for controlling light with light in nanophotonic and plasmonic switching devices. Using low-power diode lasers (giving excitation powers of a few tens of nanowatts per particle) operating at telecom wavelengths, we studied this nonlinearity in gallium nanoparticles grown from atomic beam at the tip of silica optical fiber. The nonlinear response characteristics indicate the occurrence of both solid-solid and solid-liquid transitions and are consistent with an effective medium model for the optical properties of closely-packed nanoparticle films. The megahertz dynamics of light-by-light control in the particle film provide an insight into the kinetics of structural transformations in nanoparticles. Transitions between two solid phases of gallium in the nanoparticles, occurring on application and withdrawal of optical excitation, take considerably less than a microsecond. The transient characteristics of the nonlinearity associated with the solid-liquid transition are dominated by the recrystallization time, which is typically of the order of a microsecond
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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