Search results for "Enna"
showing 10 items of 748 documents
Tunable Optical Antennas Using Vanadium Dioxide Metal-Insulator Phase Transitions
2019
Here, we investigate the possibility of exploiting the insulator-to-metal transition in vanadium dioxide (VO2) to tune and optically control the resonances of dipole nanoantennas in the visible near-infrared region. We compare the results obtained in the case of antennas completely made by VO2 with those of previous works and highlight the key role of the substrate to perform dynamical tuning. We also present a highly efficient configuration composed of dipole gold antenna loaded with VO2 and give some general guidelines to optimally exploit phase transitions to tune nanodevices.
Avicenna on Negative Judgement
2016
Avicenna’s logical theory of negative judgement can be seen as a systematic development of the insights Aristotle had laid out in the De interpretatione. However, in order to grasp the full extent of his theory one must extend the examination from the logical works to the metaphysical and psychological bases of negative judgement. Avicenna himself often refrains from the explicit treatment of the connections between logic and metaphysics or psychology, or treats them in a rather oblique fashion. Time and again he is satisfied with noting that this or that question is not proper for a logician and should be dealt with in metaphysics or psychology—without bothering to refer his reader to the …
Subjugation, freedom, and recognition in Poulain de la Barre and Simone de Beauvoir
2022
In 1949, Simone de Beauvoir cited the fairly unknown author Poulain de la Barre in an epigraph for The Second Sex (1949). When reading The Second Sex, one soon realizes that there are profound similarities between the two authors’ discussions of women’s situation. Both Poulain and Beauvoir view the subjection of women as a process that includes choice as well as force. Liberation necessarily requires overcoming opinions rooted in custom and prejudice. The article develops a comparison between the arguments of Poulain and Beauvoir in order to illuminate interesting features in the works of both authors. The focus is on similarities as well as differences. The first section examines how preju…
Optical switches with biplanemers obtained by intramolecular photocycloaddition reactions of tethered arenes.
2012
The dimerization of anthracene by a [4π + 4π] cycloaddition is one of the oldest and best known reactions in photochemistry. In the series of tethered bichromophoric arenes, this reaction type could be extended to anthracene–naphthalene, naphthalene–naphthalene and recently even to anthracene–benzene and naphthalene–benzene systems. Cyclophanes, which can be regarded as twofold or multiple tethered systems, are not discussed here. The cycloisomerizations are performed by irradiation at the long-wavelength absorption (λ > 270 nm), whereas shorter wavelengths (λ < 270 nm) lead to cycloreversions, which can be also achieved by a thermal route. The systems represent therefore a P- and T-type ph…
ChemInform Abstract: Optical Switches with Biplanemers Obtained by Intramolecular Photocycloaddition Reactions of Tethered Arenes
2013
The dimerization of anthracene by a [4π + 4π] cycloaddition is one of the oldest and best known reactions in photochemistry. In the series of tethered bichromophoric arenes, this reaction type could be extended to anthracene–naphthalene, naphthalene–naphthalene and recently even to anthracene–benzene and naphthalene–benzene systems. Cyclophanes, which can be regarded as twofold or multiple tethered systems, are not discussed here. The cycloisomerizations are performed by irradiation at the long-wavelength absorption (λ > 270 nm), whereas shorter wavelengths (λ < 270 nm) lead to cycloreversions, which can be also achieved by a thermal route. The systems represent therefore a P- and T-type ph…
Electrical control of the nonlinear properties of plasmonic nanostructures
2020
This work brings nano-electronics and nano-photonics technologies together to create an electron- plasmon device whose linear and nonlinear optical properties are electrically controlled. Here, we present the first demonstration of nonlinear photoluminescence modulation by electrical means in an uncluttered configuration. To this purpose, plasmonic nanoantennas are interfaced with elec- trical connections inducing localized regions of electron accumulation and depletion and therefore affecting the optical response. Additionally, a complete analysis of the nonlinear photoluminescence in plasmonic nanowires is carried out. The delocalization and transport of nonlinearities provided by such st…
Nonlinear photon-assisted tunneling transport in optical gap antennas.
2014
International audience; We introduce strongly coupled optical gap antennas to interface optical radiation with current-carrying electrons at the nanoscale. The transducer relies on the nonlinear optical and electrical properties of an optical gap antenna operating in the tunneling regime. We discuss the underlying physical mechanisms controlling the conversion involving d-band electrons and demonstrate that a simple two-wire optical antenna can provide advanced optoelectronic functionalities beyond tailoring the electromagnetic response of a single emitter. Interfacing an electronic command layer with a nanoscale optical device may thus be facilitated by the optical rectennas discussed here.
Fiber-based planar antennas for spectroscopy and sensing
2021
Fluorescence detection is a well-established method for spectroscopy and sensing. However, since dye molecules are dipolar light sources, a large fraction of the emitted photons can be lost. An effective approach to overcome this problem relies on a planar antenna configuration, which beams the radiation pattern of the dye into a narrow cone. A planar antenna works like a Yagi-Uda antenna, but reflector and director elements are made of thin metal films. Here, by introducing a scanning optical fiber, which incorporates the reflector or the director, we demonstrate a tunable planar antenna for spectroscopic and sensing applications. Our results show that the radiation pattern narrows down to…
Photonic controlled metasurface for intelligent antenna beam steering applications including 6G mobile communication systems
2023
This paper presents a novel metasurface antenna whose radiation characteristics can be remotely controlled by optical means using PIN photodiodes. The proposed reconfigurable antenna is implemented using a single radiating element to minimize the size and complexity. The antenna is shown to exhibit a large impedance bandwidth and is capable of radiating energy in a specified direction. The proposed antenna consists of a standard rectangular patch on which is embedded an H-tree shaped fractal slot of order 3. The fractal slot is used to effectively reduce the physical size of the patch by 75 % and to enhance its impedance bandwidth. A metasurface layer is strategically placed above the patch…
Direct energy transfer from the major antenna to the photosystem II core complexes in the absence of minor antennae in liposomes
2015
AbstractMinor antennae of photosystem (PS) II, located between the PSII core complex and the major antenna (LHCII), are important components for the structural and functional integrity of PSII supercomplexes. In order to study the functional significance of minor antennae in the energetic coupling between LHCII and the PSII core, characteristics of PSII–LHCII proteoliposomes, with or without minor antennae, were investigated. Two types of PSII preparations containing different antenna compositions were isolated from pea: 1) the PSII preparation composed of the PSII core complex, all of the minor antennae, and a small amount of major antennae (MCC); and 2) the purified PSII dimeric core comp…