Square vortex solitons with a large angular momentum

We show the existence of square shaped optical vortices with a large value of the angular momentum hosted in finite size laser beams which propagate in nonlinear media with a cubic-quintic nonlinearity. The light profiles take the form of rings with sharp boundaries and variable sizes depending on the power carried. Our stability analysis shows that these light distributions remain stable when propagate, probably for unlimited values of the angular momentum, provided the hosting beam is wide enough. This happens if the peak amplitude approaches a critical value which only depends on the nonlinear refractive index of the material. A variational approach allows us to calculate the main parameters involved. Our results add extra support to the concept of surface tension of light beams that can be considered as a trace of the existence of a liquid of light.Comment: 6 pages, 6 figures, submitted to Phys. Rev.

Естетична ідентичність і національно-культурна традиція (Aesthetic identity and national-cultural tradition)

У статті знаходить підтвердження думка про те, що естетичні уявлення та цінності багато в чому визначають естетичні особливості національного світогляду та ідентичність. Особливої уваги заслуговує проблема трансляції в історичному часі естетичних форм і символів національної культури, а також визначення причин, які обумовили їх функціонування (життєві умови, душевні сили, духовні потреби тощо) (In the present article the thought discovers the confirmation concerning the fact that aesthetic ideas and values in a great way determine the aesthetic peculiarities of national worldview and identity. Particular attention deserves of transmission of aesthetic forms and symbols of national culture in historical time and also identification of reasons, which conditioned their functioning (living condition, spiritual strength, spiritual needs)

Comparison of Partial Floras of Communication: Tape Habitats in the Cities of the Southern Part of Udmurtia

The purpose of this study is to establish the similarities and differences between the combined partial flora of railways and highways in the cities of the southern half of Udmurtia. Studies were accomplished by the partial floras and route methods. The combined partial flora of railways contains the greatest number of species – 648.Adventive species comprise 61% of the total. As such, the abundance of the flora of railways depends on the presence of pathways of alien species (Mozhga – 485 species, Kambarka – 439, Votkinsk – 300). The flora of the city roads is represented by 512 species. The greatest variety of flora is found in the partial flora of the Kambarka highways (376 species): There are less in Votkinsk and Mozhga (348 and 350 species, respectively). The aboriginal portion (199 species, 53%) makes a significant contribution to the diversity of the partial flora of the Kambarka highways. This is due to the peculiarities of the physiographic and administrative characteristics of the cities. Keywords: partial flora, communication-tape habitats, urban flora, flora of the Udmurt Republic, invasive plant

Сорбция ионов переходных металлов на хелатных сорбентах с функциональными группами иминодипропионовой кислоты : : автореф. дис. … канд. хим. наук : 02.00.04

Научная программа «Университеты России», грант УР.05.01.438.Грант СRDF REC-005, ЕК-005-Х1, при поддержке Федерального агентства по образованию в рамках ФЦП «Научные и научно-педагогические кадры инновационной России на 2009–2013 годы» (ГК № П278 от 23 июля 2009 г.)

Twisted speckle entities inside wavefront reversal mirrors

The previously unknown property of the optical speckle pattern reported. The interference of a speckle with an oppositely moving phase-conjugated speckle wave produces a randomly distributed ensemble of a twisted entities (ropes) surrounding optical vortex lines. These entities appear in a wide range of randomly chosen speckle parameters inside the phase-conjugating mirrors regardless to an internal physical mechanism of the wavefront reversal. These numerically generated interference patterns are relevant to a Brillouin $\bf PC$-mirrors and to a four-wave mixing $\bf PC$-mirrors based upon laser trapped ultracold atomic cloud.Comment: 4 pages,3 figures, Accepted to Physical Review

Electron detachment from negative ions in bichromatic laser field

Negative ion detachment in two-colour laser field is considered within the recent modification of Keldysh model which makes it quantitatively reliable. The general approach is illustrated by calculation of angular differential detachment rates, partial rates for particular ATD (Above Threshold Detachment) channels and total detachment rates for H$^-$ ion in bichromatic field with 1:2 frequency ratio. Both perturbative and strong field regimes are examined. Polar asymmetry and phase effects are quantitatively characterized with some new features revealed. Phase effects are found to result in a huge anisotropy factor $\sim 10^3$ in the electron angular distribution in the perturbative regime.Comment: 13 pages, 8 figures in separate files which are not incorporated in the latex file of the pape

Crystallization and Preliminary X-ray Diffraction Studies on the DNA-Binding Domain of the Multidrug Transporter Activation Protein (MtaN) from Bacillus subtilis

The N-terminal DNA-binding domain of the multidrug transporter activation protein (MtaN) was crystallized by the hanging-drop vapour-diffusion method using lithium chloride as a precipitant. The crystals are orthorhombic and belong to the space group I212121, with unit-cell parameters a = 49.4, b = 67.8, c = 115.0 Å. Diffraction data have been collected at 100 K to 2.75 Å resolution at a synchrotron-radiation source

A system for studying evolution of life-like virtual organisms

BACKGROUND: Fitness landscapes, the dependences of fitness on the genotype, are of critical importance for the evolution of living beings. Unfortunately, fitness landscapes that are relevant to the evolution of complex biological functions are very poorly known. As a result, the existing theory of evolution is mostly based on postulated fitness landscapes, which diminishes its usefulness. Attempts to deduce fitness landscapes from models of actual biological processes led, so far, to only limited success. RESULTS: We present a model system for studying the evolution of biological function, which makes it possible to attribute fitness to genotypes in a natural way. The system mimics a very simple cell and takes into account the basic properties of gene regulation and enzyme kinetics. A virtual cell contains only two small molecules, an organic nutrient A and an energy carrier X, and proteins of five types – two transcription factors, two enzymes, and a membrane transporter. The metabolism of the cell consists of importing A from the environment and utilizing it in order to produce X and an unspecified end product. The genome may carry an arbitrary number of genes, each one encoding a protein of one of the five types. Both major mutations that affect whole genes and minor mutations that affect individual characteristics of genes are possible. Fitness is determined by the ability of the cell to maintain homeostasis when its environment changes. The system has been implemented as a computer program, and several numerical experiments have been performed on it. Evolution of the virtual cells usually involves a rapid initial increase of fitness, which eventually slows down, until a fitness plateau is reached. The origin of a wide variety of genetic networks is routinely observed in independent experiments performed under the same conditions. These networks can have different, including very high, levels of complexity and often include large numbers of non-essential genes. CONCLUSION: The described system displays a rich repertoire of biologically sensible behaviors and, thus, can be useful for investigating a number of unresolved issues in evolutionary biology, including evolution of complexity, modularity and redundancy, as well as for studying the general properties of genotype-to-fitness maps. REVIEWERS: This article was reviewed by Drs. Eugene Koonin, Shamil Sunyaev and Arcady Mushegian

Video resources in teaching listening skills

The article focuses on the problem of listening skills development in foreign language acquisition. The use of video resources in listening skills development is analyzed