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We consider propagation of light in planar optical metamaterial, which basic element is composed of two silver stripes, and it possesses strong dispersion in optical range. Our method of numerical modeling allows us to take into consideration the nonlinearity of the material and the effects of light self-action without considerable increase of the calculation time. It is shown that plasmonic resonances originating in such a structure result in multiple enhancement of local field and high sensitivity of the transmission coefficient to the intensity of incident monochromatic wave. [ABSTRACT FROM AUTHOR]

We have numerically and analytically shown that polarization singularities can emerge when a homogeneously elliptically polarized light beam undergoes self-focusing in an isotropic third-order Kerr medium without frequency and spatial dispersion (fused silica, liquids, gases etc.) In the case of axially symmetric beam the emerging C -lines have the shape of circumference with the center at the beam’s axis and they are located in the separate transversal planes in the medium. If the axial symmetry of the incident beam is broken then the even number of C -points with opposite topological charges are nucleated in the medium. They exist in a certain propagation coordinate range and then they collide and annihilate each other. [ABSTRACT FROM AUTHOR]

In this work we study numerically the quasi-solitary propagation of ultrashort elliptically polarized laser pulses in isotropic medium with cubic nonlinearity, under condition, when the frequency spectrum of the propagating light does not overlap with one-photon resonances and multi-photon non-Raman resonances. For that we use the modification of finite-difference time-domain method with auxiliary differential equation. It is shown that proper choice of initial conditions results in the formation of elliptically polarized solitary wave, which propagates then for a long distance. For the few-oscillation incident pulse its shape and the oscillation character practically do not change at distances of the order of hundreds of wavelengths, and the direction of the oscillations uniformly rotates in the course of propagation. The retardation of the nonlinear response of the medium limits the possibility of the solitary wave formation for few-cycle elliptically polarized pulses, and affects the carrier frequency shift of the incident elliptically polarized pulse. It is established that for any polarization state of the pulse its carrier frequency shift is almost proportional to the reciprocal duration of the pulse in forth degree. [ABSTRACT FROM AUTHOR]

Abstract: A principle possibility of second harmonic generation (SHG) from the surface of a chiral medium by normally incident focused fundamental beam has been shown earlier, and the key features of this phenomenon (forbidden in a planewave approximation) have been outlined in [N.I. Koroteev, V.A. Makarov, S.N. Volkov, Laser Phys. 8 (1998) 532–535]. In our work we have obtained analytical expressions, which describe the distributions of intensity and polarization in the cross-section of a second-harmonic (SH) light beam. It is found that the polarization state drastically changes along the cross-section of the signal light beam. The polarization effects concerning the transversal inhomogeneous polarization distribution were studied in detail. It is shown that the measurement of the polarization state in certain areas of the SH beam cross-section gives us quantitative information directly about the medium material constants. [Copyright &y& Elsevier]

• The canonical and angular momenta of elliptically polarized Airy beams are re-examined in the paraxial approximation. • The explicit analytical expressions for canonical momentum, spin angular momentum and orbital angular momentum are derived. • New numerical results of the canonical momentum and orbital angular momentum of Airy beams are obtained. In this comment we re-examine the problem and obtain new results for the canonical momentum density, orbital angular momentum density and spin angular momentum density of elliptically polarized Airy beams in the paraxial approximation. In contrast to the results of [1] the canonical momentum density and orbital angular momentum density do not depend on beam polarization. [ABSTRACT FROM AUTHOR]

Local field potentials (LFPs) reflect the coordinated firing of functional neural assemblies during information coding and transfer across neural networks. As such, it was proposed that the extraordinary variety of cytoarchitectonic elements in the brain is responsible for the wide range of amplitudes and for the coverage of field potentials, which in most cases receive contributions from multiple pathways and populations. The influence of spatial factors overrides the bold interpretations of customary measurements, such as the amplitude and polarity, to the point that their cellular interpretation is one of the hardest tasks in Neurophysiology. Temporal patterns and frequency bands are not exclusive to pathways but rather, the spatial configuration of the voltage gradients created by each pathway is highly specific and may be used advantageously. Recent technical and analytical advances now make it possible to separate and then reconstruct activity for specific pathways. In this review, we discuss how spatial features specific to cells and populations define the amplitude and extension of LFPs, why they become virtually indecipherable when several pathways are co-activated, and then we present the recent advances regarding their disentanglement using spatial discrimination techniques. The pathway-specific threads of LFPs have a simple cellular interpretation, and the temporal fluctuations obtained can be applied to a variety of new experimental objectives and improve existing approaches. Among others, they facilitate the parallel readout of activity in several populations over multiple time scales correlating them with behavior. Also, they access information contained in irregular fluctuations, facilitating the testing of ongoing plasticity. In addition, they open the way to unravel the synaptic nature of rhythmic oscillations, as well as the dynamic relationships between multiple oscillatory activities. The challenge of understanding which waves belong to which populations, and the pathways that provoke them, may soon be overcome. [ABSTRACT FROM AUTHOR]

The reaction of 5-formyl-4-thiocyanatopyrimidines with nitromethane was studied under various conditions. The reaction was found unexpectedly to proceed with closure of a thiophene ring to give thieno[2,3-d]pyrimidines. The use of ammonium acetate as the catalyst leads to a side reaction involving closure of an isothiazole ring to give isothiazolo[5,4-d]pyrimidines. X-ray diffraction crystallographic analysis was used to confirm the structure of thieno[2,3-d]pyrimidine. [ABSTRACT FROM AUTHOR]

Reports on the crystal and molecular structures of 2[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitroacetonitrile, determined from X-ray, synchrotron and neutron powder diffraction data using various methods. Original solution of the structures from Guinier photographs with a grid search procedure; High level of reproducibility and reliability of various powder software and equipment.