Nonlinear resonance reflection from and transmission through a dense glassy system built up of oriented linear Frenkel chains: two-level models

A theoretical study of the resonance optical response of assemblies of oriented short (as compared to an optical wavelength) linear Frenkel chains is carried out using a two-level model. We show that both transmittivity and reflectivity of the film may behave in a bistable fashion and analyze how the effects found depend on the film thickness and on the inhomogeneous width of the exciton optical transition.Comment: 26 pages, 9 figure

Localization properties of a one-dimensional tight-binding model with non-random long-range inter-site interactions

We perform both analytical and numerical studies of the one-dimensional tight-binding Hamiltonian with stochastic uncorrelated on-site energies and non-fluctuating long-range hopping integrals . It was argued recently [A. Rodriguez at al., J. Phys. A: Math. Gen. 33, L161 (2000)] that this model reveals a localization-delocalization transition with respect to the disorder magnitude provided . The transition occurs at one of the band edges (the upper one for and the lower one for). The states at the other band edge are always localized, which hints on the existence of a single mobility edge. We analyze the mobility edge and show that, although the number of delocalized states tends to infinity, they form a set of null measure in the thermodynamic limit, i.e. the mobility edge tends to the band edge. The critical magnitude of disorder for the band edge states is computed versus the interaction exponent by making use of the conjecture on the universality of the normalized participation number distribution at transition.Comment: 7 pages, 6 postscript figures, uses revtex

Statistics of low-energy levels of a one-dimensional weakly localized Frenkel exciton: A numerical study

Numerical study of the one-dimensional Frenkel Hamiltonian with on-site randomness is carried out. We focus on the statistics of the energy levels near the lower exciton band edge, i. e. those determining optical response. We found that the distribution of the energy spacing between the states that are well localized at the same segment is characterized by non-zero mean, i.e. these states undergo repulsion. This repulsion results in a local discrete energy structure of a localized Frenkel exciton. On the contrary, the energy spacing distribution for weakly overlapping local ground states (the states with no nodes within their localization segments) that are localized at different segments has zero mean and shows almost no repulsion. The typical width of the latter distribution is of the same order as the typical spacing in the local discrete energy structure, so that this local structure is hidden; it does not reveal itself neither in the density of states nor in the linear absorption spectra. However, this structure affects the two-exciton transitions involving the states of the same segment and can be observed by the pump-probe spectroscopy. We analyze also the disorder degree scaling of the first and second momenta of the distributions.Comment: 10 pages, 6 figure

Giant negative magnetoresistance in semiconductors doped by multiply charged deep impurities

A giant negative magnetoresistance has been observed in bulk germanium doped with multiply charged deep impurities. Applying a magnetic field the resistance may decrease exponentially at any orientation of the field. A drop of the resistance as much as about 10000% has been measured at 6 T. The effect is attributed to the spin splitting of impurity ground state with a very large g-factor in the order of several tens depending on impurity.Comment: 4 pages, 4 figure

Exploring and collecting perennial forage and grain legume crop genetic diversity in Voronezh and Tambov provinces (Results of the collecting mission, 2016)

Surveying vegetation in various areas within Russia is an important link to successful management of plant genetic resources. Species and forms of wild perennial legumes and forage grasses possess complex adaptability to local environments. The aim of VIR’s collecting mission to Voronezh and Tambov Provinces in 2016 was to replenish the preserved genetic diversity of leguminous and perennial forage crops with samples of interest for breeding for fodder and seed productivity and resistance to limiting environmental factors. The task of the collecting mission was to explore the territory and collect seeds of wild perennial forage and leguminous plants. The exploration route and collecting sites are indicated on the map. Geographical coordinates and descriptions of habitats were recorded for 38 collecting sites. During the survey of fourteen districts in Voronezh Province and two districts in Tambov Province, 169 plant samples were collected, including 140 forage plant accessions (33 species) and 29 leguminous ones (9 species). The most frequently occurring species were identified: Poa pratensis L., Melilotus officinalis (L.) Pall., Medicago falcata L., Vicia angustifolia L. and Lathyrus tuberosus L. Plants of Onobrychis arenaria (Kit.) DC. occur throughout Voronezh Province in meadow-steppe communities. Of interest are the samples of Agropyron pectinatum (Bieb.) Beauv. collected on the northern border of its area of distribution; three species of lower-growing fescue (Festuca rubra L., F. valesiaca Gaudin. and F. pseudovina Hack. ex Wiesb.); a perennial form of Medicago lupulina L.; a sample of Lotus corniculatus L. found on chalky outcrops of the Kalach Hills; red (Trifolium pratense L.), golden (T. aureum Pollich.) and strawberry (T. fragiferum L.) clovers from the valley of the Khoper River; pisiform vetch (Vicia pisiformis L.) from Kalach District and hairy vetch (V. villosa Roth) from Povorino District of Voronezh Province. The materials collected by the team were added to the holdings of VIR and are available for further study and use in breeding

Испарение метастабильной жидкости из полости через бинарную систему капилляров

The porous materials as a totality of interrelated pores are examined. The high-temperature liquid vaporization through longitudinal channels from united internal volume is investigated. The analytical expression of the liquid evaporation velocity at adjacent pores is obtained.Разработана термометрическая модель, представляющая собой шаг периодической структуры, состоящей из полостей, связанных между собой микро- или макрокапиллярами. Исследована кинетика испарения перегретых жидкостей из сферического объема через бинарную систему одноуровневых капилляров. Теоретически оценены размеры полостей, при наличии которых в материале осушение нагреванием оказывается малоэффективным

TARGET SUBSIDIES AS A FILM SCREENING DEVELOPMENT TOOL IN RUSSIAN REGIONS

Execution of protectionist measures by the state in the film screening field is a significant for the entire film industry as a whole, as the state of the Russian film screening affects both distribution and film production. The implementation process of the state program to provide subsidies for the cinemas modernization cinemas in small and medium-sized Russia cities has been examined. The current program results, their importance for the regional film screening and the Russian film industry have been analyzed. The special socio-economic conditions of the subsidized theaters functioning have been highlighted. The two-level system organization for further activities subsidized cinemas support is proposed and a measures set to achieve the state program goals for the long term have been offered

Pulsars versus Dark Matter Interpretation of ATIC/PAMELA

In this paper, we study the flux of electrons and positrons injected by pulsars and by annihilating or decaying dark matter in the context of recent ATIC, PAMELA, Fermi, and HESS data. We review the flux from a single pulsar and derive the flux from a distribution of pulsars. We point out that the particle acceleration in the pulsar magnetosphere is insufficient to explain the observed excess of electrons and positrons with energy E ~ 1 TeV and one has to take into account an additional acceleration of electrons at the termination shock between the pulsar and its wind nebula. We show that at energies less than a few hundred GeV, the flux from a continuous distribution of pulsars provides a good approximation to the expected flux from pulsars in the Australia Telescope National Facility (ATNF) catalog. At higher energies, we demonstrate that the electron/positron flux measured at the Earth will be dominated by a few young nearby pulsars, and therefore the spectrum would contain bumplike features. We argue that the presence of such features at high energies would strongly suggest a pulsar origin of the anomalous contribution to electron and positron fluxes. The absence of features either points to a dark matter origin or constrains pulsar models in such a way that the fluctuations are suppressed. Also we derive that the features can be partially smeared due to spatial variation of the energy losses during propagation.Comment: 23 pages, 15 figures, 1 table; v2: minor corrections, references added; v3: 20 pages, 10 figures, 1 table, major changes in presentation, main conclusions unchanged; v4: minor correction

Simulation of interaction of oriented J aggregates with resonance laser radiation

The interaction of laser radiation with single J aggregates of cyanine dyes is theoretically analyzed and numerically simulated. The quantum mechanical calculations of the equilibrium geometry and the energies and intensities of the lowest singlet electronic transitions in pseudoisocyanine chloride and its linear (chain) oligomers are fulfilled. The data of these calculations can serve as parameters of the analyzed model of interaction of J aggregates with radiation in the oneparticle density matrix approximation. This model takes into account relaxation processes, the annihilation of excitations at neighboring molecules, and inho mogeneous broadening. Assuming that the inhomogeneous broadening is absent, calculations demonstrate the existence of spatial bistability, molecular switching waves, and dissipative solitons. The effect of the inhomogeneous broadening and the radiation intensity on the effective coherence length in linear (chain) J aggregates is analyzedComment: 8 pages, 8 figure