4,426 research outputs found
Homogenization of metasurfaces formed by random resonant particles in periodical lattices
In this paper we suggest a simple analytical method for description of
electromagnetic properties of a geometrically regular two-dimensional
subwavelength arrays (metasurfaces) formed by particles with randomly
fluctuating polarizabilities. Such metasurfaces are of topical importance due
to development of mass-scale bottom-up fabrication methods, for which
fluctuations of the particles sizes, shapes, and/or composition are inevitable.
Understanding and prediction of electromagnetic properties of such random
metasurfaces is a challenge. We propose an analytical homogenization method
applicable for normal wave incidence on particles arrays with dominating
electric dipole responses and validate it with numerical point-dipole modeling
using the supercell approach. We demonstrate that fluctuations of particles
polarizabilities lead to increased diffuse scattering despite the subwavelength
lattice constant of the array. The proposed method can be readily extended to
oblique incidence and particles with both electric and magnetic dipole
resonances.Comment: 10 pages, 5 figure
Morava K-theory and Rost invariant
We prove that inner forms of a variety of Borel subgroups have isomorphic
motives with respect to the second Morava K-theory if and only if the
corresponding Tits algebras and Rost invariants coincide. This extends Panin's
results on interrelationship of K-theory with Tits algebras to the case of
cohomological invariants of degree 3
Electronic structure of RE1-xAxMnO3 manganite films investigated by magnetic circular dichroism spectroscopy
Magnetic circular dichroism (MCD) spectroscopy was used to study the features
of the electronic structure of an epitaxial La0.7Ca0.3MnO3 film in the range of
1.2 - 4 eV. The study of the temperature behavior of the MCD spectra made it
possible to establish a correlation between the magnetooptical and transport
properties of the sample. The data obtained were analyzed in comparison with
MCD data for polycrystalline manganite films of various RE1-xAxMnO3
compositions. The MCD spectra of the films were compared with the spectra of
the off-diagonal component of the permittivity tensor calculated from the data
of the magneto-optical Kerr effect for films of the same composition. A unified
set of ground and excited electronic states characteristic of RE1-xAxMnO3
manganites in the visible and near infrared ranges has been identified. These
results are important for a qualitative theoretical description of the
electronic structure of strongly correlated magnetic oxides.Comment: 5 figures, 2 table
Грамматика безличности
The grammar of impersonality is based on the invariant impersonal categorical grammatical meaning subjectless, which is realized in specialized morphological forms and specialized syntactic structures.The grammar of impersonality is based on the invariant impersonal categorical grammatical meaning subjectless, which is realized in specialized morphological forms and specialized syntactic structures.Грамматика безличности основывается на инвариантном категориальном значении грамматической бессубъектности, которое реализуется в специализированных морфологических формах и специализированных синтаксических конструкциях
Propagation dynamics of ultrabroadband terahertz beams with orbital angular momentum for wireless data transfer
Pollen and Isotope Investigations of an Ice Core from Vavilov Ice Cap, October Revolution Island, Severnaya Zemlya Archipelago, Russia
The Vavilov Ice Cap (79°27'N, 95° 21'E) was cored during February and March of 1988. The corer passed through 457.18 m of glacier ice, 2.15 m of moraine-containing ice, and 2.28 m of underlying rocks. Structural-stratigraphical and isotope analysis show the glacier ice is of Holocene in age; the ice layer covered by frozen deposits is Pleistocene glacier ice; and the ground (ice wedge?) ice from underlying sediments was formed during the Last Interglacial. Palynological studies of this core, carried out for the first time in the Russian Arctic demonstrate that the pollen spectra have a unique pattern. It reduces the possibility of correlation between the Vavilov Ice Cape spectra and pollen spectra from other surficial deposits, because the ice retains pollen and spores brought from enormous distances. Only the upper 65 m of the core is easily dated, to the last millennium, by the presence of cereals, Plantago lanceolata, Centaurea cyanus, Cannabis pollen. That is in good agreement with the model of age distribution based upon depth. The presence of considerable amounts of Tilia cordifolia pollen, a West-European species in the upper layers suggests that summer air masses have been dominantly from the southwest during the last 500 years. The pollen data do not contradict the conclusion the Vavilov ice core is composed of a section of Holocene ice, moraine-containing ice representing the Pleistocene episode, and a ground ice formed during an earlier warm period (Last Interglacial?).Une carotte de glace prélevée en 1988 au sein de la calotte glaciaire de Vavilov (79°27'N, 95°21'E) a fait l'objet d'analyses isotopiques et palynologiques. Le sondage comprend 457,18 m de glace « pure », suivis de 2,15 m de glace chargée de sédiments et 2,28 m de roches gelés du socle. Les résultats des analyses structurales, stratigraphiques et isotopiques sont les suivants : la glace pure datée de l'Holocène, les 2,15 de la couche chargée de sédiments datent du Pléistocène, tandis que la glace présente dans les fentes du socle s'est formée au cours du dernier interglaciaire. Les spectres polliniques de cette carotte sont caractérisés par des grains de pollen d'origine lointaine préservés dans la glace. Cette constatation réduit grandement les possibilités de corrélation avec les données sédimentaires de la région, qui reflètent la composition de la végétation locale. Un âge inférieur à 1000 ans peut être attribué aux 65 m supérieurs de la carotte en raison de la présence de pollen de céréales, de Plantago lanceolata, Centaurea cyanus et de Cannabis. Cette interprétation concorde avec le modèle du taux d'accumulation de la glace. Dans la partie supérieure de la carotte, la présence en quantité considérable de Tilia cordifolia, une espèce de tilleul d'Europe de l'Ouest, laisse supposer que les masses d'air en provenance du sud-ouest ont prédominé au cours des étés des 500 dernières années. En conclusion, les données palynologiques ne contredisent pas les résultats antérieurs selon lesquels la carotte glaciaire étudiée couvre une partie de l'Holocène, que la glace contenant la moraine représente l'épisode du Pléistocène et que la glace du socle se soit formée pendant une période chaude (le dernier interglaciaire?)
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