1,720,967 research outputs found
Extraordinary Optical Transmittance Generation on Si3N4 Membranes
No full textMetamaterials have been recently attracting increasing attention thanks to their capability to go beyond the electromagnetic and transport properties of natural materials.
Although less developed compared to plasmonic systems, phononic metamaterials offer the advantage of controlling phonon propagation and, consequently, heat transfer at a microscopic level, and strong local field enhancement in the infrared. In this work, extraordinary optical transmittance (EOT) from insulating silicon nitride (Si3N4) membranes patterned with a periodic lattice of micrometric circular holes (3, 5, 7 μm) is achieved. By performing transmittance measurements in the infrared, the coupling between an incoming electromagnetic wave and an optical phonon is obtained, triggering an increase in the transmitted intensity in an otherwise opaque phonon spectral region. This induced transparency effect can be explained in terms of a phonon-polariton generation as also demonstrated by nano-resolved infrared imaging
The Viscosity of Carbonate‐Silicate Transitional Melts at Earth's Upper Mantle Pressures and Temperatures, Determined by the In Situ Falling‐Sphere Technique
Full text linkExperimental determination of the viscosity of Na2CO3 melt between 1.7 and 4.6 GPa at 1200–1700°C. Implications for the rheology of carbonatite magmas in the Earth's upper mantle
No full textKnowledge of the rheology of molten materials at high pressure and temperature is required to understand
magma mobility and ascent rate at conditions of the Earth's interior. We determined the viscosity of nominally
anhydrous sodium carbonate (Na2CO3), an analogue and ubiquitous component of natural carbonatitic magmas,
by the in situ “falling sphere” technique at 1.7, 2.4 and 4.6 GPa, at 1200 to 1700 °C, using the Paris-Edinburgh
press. We find that the viscosity of liquid Na2CO3 is between 0.0028 ± 0.0001 Pa·s and 0.0073 ± 0.0001 Pa·s
in the investigated pressure-temperature range. Combination of our results with those from recent experimental
studies indicate a negligible dependence on pressure from 1 atm to 4.6 GPa, and a small compositional dependence
between molten alkali metal-bearing and alkaline earth metal-bearing carbonates. Based on our results,
the viscosity of Na2CO3 is consistent with available viscosity data of both molten calcite (determined at high
pressure and temperature) and Na2CO3 at ambient pressure. Molten Na2CO3 is a valid experimental analogue for
study of the rheology of natural and/or synthetic near-solidus carbonatitic melts. Estimated values of the mobility
and ascent velocity of carbonatitic melts at upper conditions are between 70 and 300 g cm−3·Pa−1·s−1 and
330–1450 m·year−1, respectively, when using recently proposed densities for carbonatitic melts. The relatively
slow migration rate allows magma-rock interaction over time causing seismic anomalies and chemical redox
exchange
Mobility of volatile-bearing magmas in oxidised planetesimals: implications for CO2 loss and storage during accretion
No full textExperimental measurements of viscosity and melt structure of CO2-bearing melts at high pressure and temperature
Full text linkExperimental viscosity measurements of basaltic and picritic melts at pressures and temperatures of Earth’s upper mantle
No full textExtraordinary optical transmittance generation on Si3N4 membranes
Full text linkMetamaterials are attracting increasing attention due to their ability to support novel and engineerable electromagnetic functionalities. In this paper, we investigate one of these functionalities, i.e. the extraordinary optical transmittance (EOT) effect based on silicon nitride (Si3N4) membranes patterned with a periodic lattice of micrometric holes. Here, the coupling between the incoming electromagnetic wave and a Si3N4 optical phonon located around 900 cm-1 triggers an increase of the transmitted infrared intensity in an otherwise opaque spectral region. Different hole sizes are investigated suggesting that the mediating mechanism responsible for this phenomenon is the excitation of a phonon-polariton mode. The electric field distribution around the holes is further investigated by numerical simulations and nano-IR measurements based on a Scattering-Scanning Near Field Microscope (s-SNOM) technique, confirming the phonon-polariton origin of the EOT effect. Being membrane technologies at the core of a broad range of applications, the confinement of IR radiation at the membrane surface provides this technology platform with a novel light-matter interaction functionality
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
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