Optical activity in the Drude helix model

An old classical one-particle helix model for optical activity, first proposed by Drude, is reconsidered here. The quantum Drude model is very instructive because the optical activity can be calculated analytically without further approximations apart from the Rosenfeld long wavelength approximation. While it was generally believed that this model, when treated correctly, is optically inactive, we show that it leads to optical activity when the motion of the particle is quantum mechanically treated. We also find that optical activity arises even in the classical regime at non-zero energy, while for zero energy the model is inactive, in accordance with previous results. The model is compared with other one-electron models and it is shown that its predicted optical activity is qualitatively different from those of other one-electron systems. The vanishing of optical activity in the classical zero-energy limit for the Drude model is due to the localization of the particle at the equilibrium position, whereas in the analogous model of a particle moving freely on a helix without a definite equilibrium position, optical activity does not vanish but the spectrum is rescaled. The model under study leads to interesting predictions about the optical properties of e. g. helicene derivatives

View on the history of electromagnetics of metamaterials: Evolution of the congress series of complex media

This article describes some of the paths through which electromagnetics research of complex media and metamaterials has reached the present active state. In particular, events of a period in 1990s will be illuminated during which new scientific contacts between Former Soviet Union and the West were established. The series of chiral and bianisotropic meetings between 1993 and 2006 appear as a precursor to today's series of metamaterials congresses.Non Peer reviewe

Broadband reflectionless metasheets: Frequency-selective transmission and perfect absorption

Energy of propagating electromagnetic waves can be fully absorbed in a thin lossy layer, but only in a narrow frequency band, as follows from the causality principle. On the other hand, it appears that there are no fundamental limitations on broadband matching of thin absorbing layers. However, known thin absorbers produce significant reflections outside of the resonant absorption band. In this paper we explore possibilities to realize a thin absorbing layer which produces no reflected waves in a very wide frequency range, while the transmission coefficient has a narrow peak of full absorption. Here we show, both theoretically and experimentally, that a wide-band-matched thin resonant absorber, invisible in reflection, can be realized if one and the same resonant mode of the absorbing array unit cells is utilized to create both electric and magnetic responses. We test this concept using chiral particles in each unit cells, arranged in a periodic planar racemic array, utilizing chirality coupling in each unit cell but compensating the field coupling at the macroscopic level. We prove that the concept and the proposed realization approach also can be used to create non-reflecting layers for full control of transmitted fields. Our results can have a broad range of potential applications over the entire electromagnetic spectrum including, for example, perfect ultra-compact wave filters and selective multi-frequency sensors.Comment: 9 pages, 10 figure

Політична модернізація як фактор формування демократичного іміджу України

Семченко О. А. Політична модернізація як фактор формування демократичного іміджу України / О. А. Семченко // Актуальні проблеми політики : зб. наук. пр. / редкол. : С. В. Ківалов (голов. ред..), Л. І. Кормич (заст. голов. ред..), Ю. П. Аленін [та ін.] ; МОН України ; НУ ОЮА. – Одеса : Фенікс, 2013. – Вип. 48. – С. 218-224.The article describes the role of political modernization in a democratic state image. Analyzes the nature of the concepts of «modernization», «modernized society». It is argued that the degree of development of democratic institutions has played a leading role in the dynamic characteristics of the conditional-state image

Resource and non-resource root competition among trees of different successional status

1. This study assessed the effects of resource (i.e. nutrients) and non-resource (i.e. interference for space) competition from fine roots of competing grasses on the growth, morphology and architecture of fine roots of four tree species of varying successional status: Populus deltoides × P. balsamifera (a\ud hybrid), Betula papyrifera, Acer saccharum and Fraxinus americana. We tested the general hypothesis that tree fine-roots are affected by both below-ground resource and non-resource competition from non-self plants, and the more specific hypothesis that this effect is stronger in early- successional tree species.\ud 2. The experiment was conducted in split-containers where half of the roots of tree seedlings experienced either below-ground resource competition or non-resource competition, or both, by grasses while the other half experienced no competition.\ud 3. The late-successional tree species A. saccharum and\ud F. americana were mostly affected by resource competition, whereas the early-successional P. deltoides × balsamifera\ud and B. papyrifera were strongly affected by both resource and non-resource competition. Non-resource competition reduced fine-root growth, root branching over root length (a measure of root architecture) and specific root length (a measure of root morphology) of both early-successional species.\ud 4. Synthesis. This study suggests that early-successional tree species have been selected for root avoidance or segregation and late-successional tree species for root tolerance of competition as mechanisms to improve below-ground resource uptake in their particular environments. It also\ud contradicts recent studies showing perennial and annual grasses tend to overproduce roots in the presence of non-self conspecific plants. Woody plants, required to grow and develop for long periods in the presence of other plants, may react differently to non-self root competition than perennial or\ud annual grasses that have much shorter lives

Problems and prospects of development of ecological tourism in Ireland

The paper presents the research on the development of ecological tourism in Ireland. The basic directions and problems of development of ecotourism. Income from ecotourism in the country was analyzed in the article, as well as the model for the attraction of tourists to Irelan

Electrodeposited lead dioxide coatings

Lead dioxide coatings on inert substrates such as titanium and carbon now offer new opportunities for a material known for 150 years. It is now recognised that electrodeposition allows the preparation of stable coatings with different phase structures and a wide range of surface morphologies. In addition, substantial modification to the physical properties and catalytic activities of the coatings are possible through doping and the fabrication of nanostructured deposits or composites. In addition to applications as a cheap anode material in electrochemical technology, lead dioxide coatings provide unique possibilities for probing the dependence of catalytic activity on layer composition and structure (critical review, 256 references)

Fungal diversity regulates plant-soil feedbacks in temperate grassland

Feedbacks between plants and soil microbial communities play an important role in vegetation dynamics, but the underlying mechanisms remain unresolved. Here, we show that the diversity of putative pathogenic, mycorrhizal, and saprotrophic fungi is a primary regulator of plant-soil feedbacks across a broad range of temperate grassland plant species. We show that plant species with resource-acquisitive traits, such as high shoot nitrogen concentrations and thin roots, attract diverse communities of putative fungal pathogens and specialist saprotrophs, and a lower diversity of mycorrhizal fungi, resulting in strong plant growth suppression on soil occupied by the same species. Moreover, soil properties modulate feedbacks with fertile soils, promoting antagonistic relationships between soil fungi and plants. This study advances our capacity to predict plant-soil feedbacks and vegetation dynamics by revealing fundamental links between soil properties, plant resource acquisition strategies, and the diversity of fungal guilds in soil