The toroidal dipole is a peculiar electromagnetic excitation that can not be presented in terms of standard electric and magnetic multipoles. A static toroidal dipole has been shown to lead to ...violation of parity in atomic spectra and many other unusual electromagnetic phenomena. The existence of electromagnetic resonances of toroidal nature was experimentally demonstrated only recently, first in the microwave metamaterials, and then at optical frequencies, where they could be important in spectroscopy analysis of a wide class of media with constituents of toroidal symmetry, such as complex organic molecules, fullerenes, bacteriophages, etc. Despite the experimental progress in studying toroidal resonances, no direct link has yet been established between microscopic toroidal excitations and macroscopic scattering characteristics of the medium. To address this essential gap in the electromagnetic theory, we have developed an analytical approach for calculating the transmissivity and reflectivity of thin slabs of materials that exhibit toroidal dipolar excitations.
The toroidal dipole is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles. While the electric dipole can be understood as a pair of opposite charges and the ...magnetic dipole as a current loop, the toroidal dipole corresponds to currents flowing on the surface of a torus. Toroidal dipoles provide physically significant contributions to the basic characteristics of matter including absorption, dispersion and optical activity. Toroidal excitations also exist in free space as spatially and temporally localized electromagnetic pulses propagating at the speed of light and interacting with matter. We review recent experimental observations of resonant toroidal dipole excitations in metamaterials and the discovery of anapoles, non-radiating charge-current configurations involving toroidal dipoles. While certain fundamental and practical aspects of toroidal electrodynamics remain open for the moment, we envision that exploitation of toroidal excitations can have important implications for the fields of photonics, sensing, energy and information.
High-index dielectric materials are in great demand for nanophotonic devices and applications, from ultrathin optical elements to metal-free sub-diffraction light confinement and waveguiding. Here we ...show that chalcogenide topological insulators are particularly apt candidates for dielectric nanophotonics architectures in the infrared spectral range, by reporting metamaterial resonances in chalcogenide crystals sustained well inside the mid-infrared, choosing Bi
Te
as case study within this family of materials. Strong resonant modulation of the incident electromagnetic field is achieved thanks to the exceptionally high refractive index ranging between 7 and 8 throughout the 2-10 μm region. Analysis of the complex mode structure in the metamaterial allude to the excitation of circular surface currents which could open pathways for enhanced light-matter interaction and low-loss plasmonic configurations by coupling to the spin-polarized topological surface carriers, thereby providing new opportunities to combine dielectric, plasmonic and magnetic metamaterials in a single platform.
Engaging strongly resonant interactions allows dramatic enhancement of functionalities of many electromagnetic devices. However, resonances can be dampened by Joule and radiation losses. While in ...many cases Joule losses may be minimized by the choice of constituting materials, controlling radiation losses is often a bigger problem. Recent solutions include the use of coupled radiant and sub-radiant modes yielding narrow asymmetric Fano resonances in a wide range of systems, from defect states in photonic crystals and optical waveguides with mesoscopic ring resonators to nanoscale plasmonic and metamaterial systems exhibiting interference effects akin to electromagnetically-induced transparency. Here we demonstrate theoretically and confirm experimentally a new mechanism of resonant electromagnetic transparency, which yields very narrow isolated symmetric Lorentzian transmission lines in toroidal metamaterials. It exploits the long sought non-trivial non-radiating charge-current excitation based on interfering electric and toroidal dipoles that was first proposed by Afanasiev and Stepanovsky in J. Phys. A Math. Gen. 28, 4565 (1995).
The approach used for solving of the task concerned, corresponds to an early design stage of the floating crane. The floating crane size is defined and the optimum trim system is proposed in this ...paper. The scheme of the declined arm of the crane, allowed to calculate and construct cargo and geometrical characteristics of the load-lifting device. Preliminary tests of the vessel's stability at carrying out cargo operations have shown satisfactory results.
We show that subterahertz transmission of the superconducting metamaterial, an interlinked two-dimensional network of subwavelength resonators connected by a continuous superconducting wire loop, can ...be dynamically modulated by passing electrical current through it. We have identified the main mechanisms of modulation that correspond to the suppression of the superconductivity in the network by magnetic field and heat dissipation. Using the metamaterial fabricated from thin niobium film, we were able to demonstrate a transmission modulation depth of up to 45% and a bandwidth of at least 100 kHz. The demonstrated approach may be implemented with other superconducting materials at frequencies below the superconducting gap in the THz and subterahertz bands.
Antioxidant cytoprotective properties of mexidol have been studied under the influence of argon and helium gas-discharge cold plasma of atmospheric pressure on
Paramecium caudatum
cell culture. It ...has been shown that mexidol exhibits strong antioxidant properties and practically completely eliminates the negative effects of oxidative stress, retaining almost 100% of the initial number of cells. The data obtained demonstrate a wide range of behavioral responses of cells of
Paramecium caudatum
, which confirms their practical value as model objects for pharmacological and toxicological studies, and the use of gas-discharge cold plasma makes it possible to exclude the direct oxidative effect of hydrogen peroxide (the standard model of oxidative stress) on the studied drugs and to increase the reliability of toxicological studies.
The novel DC arc plasmatrons, with tungsten rod cathodes and nozzle anodes, and ways of their application are described in this article. The initial successful device was a T-plasmatron with a T-form ...of its gas-flow channels. Its specific anode erosion rate was lowered by four orders of magnitude, as compared with traditional arc plasmatrons. The result of a specific anode design, arranging technological gas and plasma-forming gas interactions, decreased this parameter to 4·10−10 g/C. This plasmatron was used in several technological processes, including cleaning the flow of Diesel engine exhaust, etching, and depositing different materials. After these experiments, the A-plasmatron was created, which had a generally axisymmetric form with a three-times greater ability for technological gas activation as compared with the T-plasmatron. The A-plasmatron was also used in the above-mentioned technological processes and demonstrated higher possibilities for each process. The extremely clean plasma flow of this plasmatron was studied using integral and local plasma diagnostic results, which have indicated its acceptable application for several processes, including the rather effective and interesting biomedical interactions with human wounds, vegetables, white straw crops and their products.
PDF
