1,721,002 research outputs found
Functional palladium metal films for plasmonic devices: an experimental proof
No full textPalladium-based, Inverted surface plasmon resonance substrates with functional surfaces are presented and characterized. The advantages of the use of palladium in lieu of other metals (most notably gold) are discussed and assayed experimentally. We demonstrate how the bare metal films can be functionalized by thiol chemistry or by adsorption of functional graphene sheets and how the features of the surfaces affect the performance of the substrate
EUV Polarimetry with single multilayer optical elementProceedings of SPIE
No full textA polarimetric measurement technique based on the analysis of the reflection data given by a single mirror rotated around the incidence beam axis is presented. In the extreme ultraviolet spectral region, a multilayer coated mirror must be used. The multilayer mirror must be fully characterized before the experiment. Theory demonstrates how this method allows complete determination of Stoke's parameters in case of a totally polarized beam. A simulation code has been developed in order to model the experiment in case of synchrotron radiation propagating in a bending magnet beamline and impinging a multilayer mirror. The simulation is useful to verify each time the effectiveness of the method in the different experimental conditions considered. Finally an experimental application is presented
Long-term stability of Mg/SiC multilayers
No full textMg/SiC multilayers have been selected to coat the primary and secondary mirrors of the SCORE (Sounding-rocket CORonagraphic Experiment) telescope, a part of the NASA HERSCHEL program. Their experimental reflectance at the He II 30.4 nm wavelength is twice as much that of standard Mo/Si multilayer coatings, with a large improvement of the instrument effective area. Nevertheless, their long-term stability still needs to be evaluated in order to consider them as a valuable candidate for instrumentation of a long term space mission. A study is carried out on different Mg/SiC samples designed and fabricated varying the structural parameters and/or the capping layer material and thickness, which have been monitored for four years after deposition
SiC/Mg multilayer coatings for SCORE coronagraph: long term stability analysis
No full textSiC/Mg multilayers have been used as coatings of the Sounding-rocket CORonagraphic Experiment (SCORE) telescope mirrors launched during the NASA HERSCHEL program. This materials couple has been largely studied by researchers since it provides higher performances than a standard Mo/Si multilayer; the SCORE mirrors show in fact a peak reflectance of around 40% at HeII 30.4 nm. Nevertheless, long term stability of this coating is an open problem. A study on the aging and stability of this multilayer has been carried on. SiC/Mg multilayer samples characterized by different structural parameters have been deposited. They have been measured just after deposition and four years later to verify degradation based on natural aging. Experimental results and analysis are presented
Test of a multilayer-coated EUV grating for I-IV order spectroscopic measurements of the solar corona
No full textMETIS, the Multi Element Telescope for Imaging and Spectroscopy, is a coronagraph selected by the European Space
Agency to be part of the payload of the Solar Orbiter mission. The original METIS proposal included four optical paths,
for observations in: 1) linearly polarized visible-light (590-650 nm), 2) narrow-band ultraviolet HI Lyman-alpha (121.6
nm), 3) narrow-band extreme-ultraviolet HeII Lyman-alpha (30.4 nm), 4) spectrographic mode for the HI Lyman- alpha
and He II Lyman-alpha in corona. The design, coating performances, and test activities of the grating for the
spectroscopic path are here described. The grating is optimized to work at near normal incidence and to diffract the 121.6
nm radiation at the first order and the 30.4 nm at its 4th order, consequently the two spectroscopic channels are
overlapped on the focal plane. The grating is spherical with variable-line-spaced rulings, 1800 gr/mm central density.
The selection of the spectroscopic channel to be acquired, either the 121.6 nm or the 30.4 nm, is made by a suitable filter
wheel. The grating is multilayer-coated, to have high efficiency in both the spectral channels. In this paper we describe
the tests made on a prototype with flat surface and constant groove spacing. The measures have been carried out at the
BEAR beamline at the ELETTRA Synchrotron in Trieste (Italy). The grating was initially coated by gold and
successively by a Mo-Si multilayer optimized at 30.4 nm. The efficiencies at the first and fourth order (121.6 and 30.4
nm) have been measured before and after the multilayer deposition. The quality of the multilayer deposition has been
tested by atomic force microscope measurements on the grating surface and by reflectivity measurements performed on a
test reference mirror. The experimental data are compared with numerical simulations accounting for the coating
roughness and the smoothening effect on the blaze profile after the multilayer deposition. To our knowledge, this is the
first time that such a grating configuration is proposed
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
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