1,720,977 research outputs found
Anisotropic propagation of Surface Plasmon Polaritons: study and exploitations
Full text linkSinusoidally patterned metallic surfaces, known as plasmonic gratings, constitute one of the principal structures which allow to achieve the coupling between an incident light beam and a Surface Plasmon Polariton mode. A variety of phenomena are available when the grating is rotated of an azimuthal angle with respect to the incidence plane.
Aim of this work is a comprehensive investigation of the propagation properties of the surface mode under this configuration, correlating the role of the anisotropy introduced by the grating to the position and shape of the plasmonic resonance dip in the reflectance spectra. Analytical models and physical interpretations are provided; both experimental and computational means are exploited in order to validate the models, including the observation of innovative effects. Thin-film coupled modes, the Long Range and Short Range Surface Plasmon Polaritons, are studied and experimentally observed in the azimuthally rotated configuration.
Special attention is paid to the role of the plasmon radiative losses, due to the scattering by the grating. Their dependence on the grating amplitude and the plasmon propagation direction is unraveled, and correlated to the width of the observed plasmonic resonances.
The outcomes of these analyses lead to the evaluation of the sensitivity and Figure of Merit achievable when the considered configurations are exploited in the framework of Surface Plasmon Resonance sensing.
The developed concepts and methods are proved to be valuable tools to predict and understand the response of actual plasmonic structures applied as sensing devices against gaseous analytes. Experimental tests of the plasmonic platforms as TNT, hydrogen and aromatic compounds sensors are reported, giving promising results. A particularly remarkable experiment is the combined exploitation of Long Range modes and azimuthally rotated configuration to sensibly enhance the performance of a xylene senso
Propagation of grating-coupled surface plasmon polaritons and cosine-Gauss beam generation
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Grating-Coupled Surface Plasmon Resonance (GC-SPR) Optimization for Phase-Interrogation Biosensing in a Microfluidic Chamber
Full text linkSurface Plasmon Resonance (SPR)-based sensors have the advantage of being label-free, enzyme-free and real-time. However, their spreading in multidisciplinary research is still mostly limited to prism-coupled devices. Plasmonic gratings, combined with a simple and cost-effective instrumentation, have been poorly developed compared to prism-coupled system mainly due to their lower sensitivity. Here we describe the optimization and signal enhancement of a sensing platform based on phase-interrogation method, which entails the exploitation of a nanostructured sensor. This technique is particularly suitable for integration of the plasmonic sensor in a lab-on-a-chip platform and can be used in a microfluidic chamber to ease the sensing procedures and limit the injected volume. The careful optimization of most suitable experimental parameters by numerical simulations leads to a 30–50% enhancement of SPR response, opening new possibilities for applications in the biomedical research field while maintaining the ease and versatility of the configuration
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
SPR Enhanced Molecular Imprinted Sol-Gel Film: a Promising Tool for Gas-Phase TNT Detection
No full textAn innovative surface plasmon resonance (SPR) approach for the detection of 2,4,6-trinitrotoluene (TNT) gas traces, obtained using an engineered molecular imprinted sol-gel film as recognition layer onto a plasmonic gold grating, is here proposed. The SPR substrate combined with the sol-gel matrix is able to trap gas phase TNT molecules from a TNT-saturated environment (4.9 ppb). Taking advantage of the azimuthally-controlled grating-coupled SPR, this sensing platform demonstrates the potentiality to detect TNT traces <1 ppb with a sensitivity of 0.47°/ppb
On the combined use of static and mobile cosmic-ray neutron sensors for monitoring spatio-temporal variability of soil water content in cropped fields
No full textThe primary aim of precision agriculture is to optimize crop yield while minimizing the usage of production inputs (in particular water and energy). This entails understanding and effectively managing the spatial variability of soil moisture within agricultural fields. This study present the performance of a combinated system of static and mobile Cosmic Rays Neutron Sensing (CRNS) probes installed in site and mounted onto a tractor for monitoring the temporal variability and mapping the spatial distribution of soil moisture in a cropped field. The use of CRNS entails different benefits, firstly, it allows for the collection of valuable information regarding soil water content in depth, reaching tens of centimeters. Moreover, the large footprint coverage, spanning approximately 5 hectares, provides a comprehensive understanding of soil moisture distribution over a significant area. The installation of CRNS probes on tractor allows for an efficient coverage of a large area and capturing dynamic changes in soil moisture over time. In order to achieve a comprehensive understanding of the soil moisture distribution, a total of four field mappings were conducted at key agronomic intervention points during the growing season of a plot cropped with tobacco
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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