Petra P. Beličev

A novel mobile transtelephonic system with synthesized 12-lead ECG

The problem of synthesizing the standard 12-lead electrocardiogram (ECG) from the signals recorded using three special ECG leads is studied in detail. The implementation of that concept into the design of a new mobile ECG transtelephonic system is presented. The system has two separate units: a stationary diagnostic-calibration center and a mobile ECG device with integrated electrodes. The patient records by himself three special leads with the mobile ECG recorder and sends data via cellular phone to the personal computer in the diagnostic center where standard 12-lead ECG is numerically reconstructed on the base of the patient transformation matrix previously calculated into the calibration process. The experimental study shows high accuracy of the reconstructed ECG.

Analysis of tunneling times in absorptive and dispersive media

Tunneling times in absorptive and dispersive media are considered, as are the relations between them. Group delay and dwell time are used as the most appropriate tunneling time characterizations. A general expression that relates these two quantities, valid for all linear media (with both positive and negative index of refraction), is derived, but particular attention is given to negative index metamaterials. The example of a nonmagnetic, lossless medium with dispersive surroundings was chosen to illustrate the derivation of self-interference time. Existence of the Hartman effect and negative group delay in a certain range of frequencies, in metamaterials, is numerically verified.

Composite localized modes in discretized spin–orbit-coupled Bose–Einstein condensates

We introduce a discrete model for binary spin-orbit-coupled (SOC) Bose-Einstein condensates (BEC) trapped in a deep one-dimensional optical lattice. Two different types of the couplings are considered, with spatial derivatives acting inside each species, or between the species. The discrete system with inter-site couplings dominated by the SOC, while the usual hopping is negligible, \textit{emulates} condensates composed of extremely heavy atoms, as well as those with opposite signs of the effective atomic masses in the two components.\ Stable localized composite states of miscible and immiscible types are constructed. The effect of the SOC on the immiscibility-miscibility transition in the localized complexes, which emulates the phase transition between insulating and conducting states in semiconductors, is studied.

Dynamics of dark solitons localized at structural defect in one-dimensional photonic lattices with defocusing saturable nonlinearity

We investigated the influence of the structural defect placed inside uniform photonic lattice on existence and dynamics of dark spatially localized defect modes. Depending on the strength of the defect and considering the lattice with defocusing saturable nonlinearity, we found two different types of dark solutions to exist. Their stability and dynamical properties are shown to be affected by the defect as well.

Observation of discrete gap solitons in one-dimensional waveguide arrays with alternating spacings and saturable defocusing nonlinearity.

We consider, both experimentally and theoretically, the existence and stability of localized, symmetric, and antisymmetric gap solitons (GSs) in binary lattices of identical waveguides but with alternating spacings. Furthermore, the properties of surface GSs at the boundary of the lattice are explored.

Linear and nonlinear light propagation at the interface of two homogeneous waveguide arrays

We investigate linear and nonlinear light propagation at the interface of two one-dimensional homogeneous waveguide arrays containing a single defect of different strength. For the linear case and in a limited region of the defect size, we find trapped staggered and unstaggered modes. In the nonlinear case, we study the dependence of power thresholds for discrete soliton formation in different channels as a function of defect strength. All experimental results are confirmed theoretically using an adequate discrete model.

Observation of linear and nonlinear strongly localized modes at phase-slip defects in one-dimensional photonic lattices

We investigate light localization at a single phase-slip defect in one-dimensional photonic lattices, both numerically and experimentally. We demonstrate the existence of various robust linear and nonlinear localized modes in lithium niobate waveguide arrays exhibiting saturable defocusing nonlinearity.

Light propagation in binary kagome ribbons with evolving disorder

By introducing evolving disorder in the binary kagome ribbons, we study the establishment of diffusive spreading of flat band states characterized by diffractionless propagation in regular periodic ribbons. Our numerical analysis relies on controlling strength and rate of change of disorder during light propagation while tailoring binarism of the kagome ribbons in order to isolate the flat band with the gap from the rest of the ribbons eigenvalue spectrum and study systematically its influence on diffusion. We show that the flat band plays a dominant role in the establishment of the diffusion for a given strength and rate of change of disorder, whereas the rest of the ribbons eigenvalue spectrum induces only quantitative differences in the light spreading regimes. Due to the universality of studied phenomena, our findings may be of interest in various disordered physical systems with flat spectral bands, ranging from photonics to ultracold matter systems and plasmonics.

Modeling of tunneling times in anisotropic non-magnetic metamaterials

Tunneling times in an anisotropic structure composed of alternately placed layers of two linear, dispersive and absorptive materials are analyzed in this paper. For such a structure, a general expression for the relation between the two most common tunneling time definitions, namely the dwell time and the group delay, is obtained. Numerical calculations are performed for a new type of semiconductor metamaterial. The results show a peak position frequency mismatch between the dwell time and the group delay, and between the dwell time and the absorption.

Tunneling times in dispersive and third-order nonlinear optical metamaterials

Investigating the propagation of electromagnetic radiation in linear and nonlinear materials (with third-order nonlinearity), we derived a general expression for the dwell time valid for all linear media, as well as its relation with the group delay. The obtained results indicate that, for a nonmagnetic lossless material, the group delay reduces to the sum of the dwell time and the self-interference time. Calculations confirmed the occurrence of the Hartman effect in negative-refractive-index metamaterials (the dwell time saturates with increasing obstacle length), as well as the negative group delay in a certain spectral regime. Analysis of the Goos-Hanchen shift, in case of an obstacle made of negative-refractive-index metamaterial embedded in a dielectric with saturable nonlinearity, showed that there is no impact on the dwell time, while various effects on the group delay may be achieved, including its reduction or even preservation for nonzero incident angles.