Irina G. Zakharova

The Impact of E-Learning on Adherence to Guidelines for Acute Gastroenteritis: A Single-Arm Intervention Study.

Objective E-learning is a candidate tool for clinical practice guidelines (CPG) implementation due to its versatility, universal access and low costs. We aimed to assess the impact of a five-module e-learning course about CPG for acute gastroenteritis (AGE) on physicians’ knowledge and clinical practice. Study design This work was conceived as a pre/post single-arm intervention study. Physicians from 11 European countries registered for the online course. Personal data, pre- and post-course questionnaires and clinical data about 3 to 5 children with AGE managed by each physician before and after the course were collected. Primary outcome measures included the proportion of participants fully adherent to CPG and number of patients managed with full adherence. Results Among the 149 physicians who signed up for the e-learning course, 59 took the course and reported on their case management of 519 children <5 years of age who were referred to their practice because of AGE (281 and 264 children seen before and after the course, respectively). The course improved knowledge scores (pre-course 8.6 ± 2.7 versus post-course 12.8 ± 2.1, P < 0.001), average adherence (from 87.0 ± 7.7% to 90.6 ± 7.1%, P = 0.001) and the number of patients managed in full adherence with the guidelines (from 33.6 ± 31.7% to 43.9 ± 36.1%, P = 0.037). Conclusions E-learning is effective in increasing knowledge and improving clinical practice in paediatric AGE and is an effective tool for implementing clinical practice guidelines.

Propagation of few-cycle pulses in homogeneous and nonhomogeneous media

The interaction between a few-cycle pulse and an optically extended multi-level medium is analyzed via computer simulation. The cascade mechanism behind the excitation of the medium’s high energy levels is determined and the way in which it is affected by the pulse’s absolute phase is investigated. The effect structural disordering has on the absorption spectrum of a multi-level medium is also analyzed.

Self-similar Shape Mode of Optical Pulse Propagation in de-focusing Medium with Two-Photon Absorption

We investigate the self-similar shape mode of laser pulse propagation in medium with two-photon and multi-photon absorption under action of either cubic nonlinearity or resonant nonlinearity. The annalitycal solution for laser pulse propagation under the detuning between carrier frequency of a wave packet and energy transition frequency for atom or molucule is developed. An existance of the self-similar shape mode for laser beam propagation in de-focusing medium is predicted if the nonlinear absoption takes place. This mode takes place along some distance of laser pulse propagation. We used as analytical approach for considered problem as well as computer simulation.

New additive difference method for solving semiconductor problems

Abstract We propose a new approach to the construction of conservative monotone difference schemes for two-dimensional parabolic second-order equations with divergent form of the terms with first derivatives. These equations appear in a drift diffusion model which is a classical one for describing the semiconductor processes. Using the approach proposed, we obtain a difference scheme for the equations of the drift diffusion model and prove the convergence of this scheme in the grid norm L2 at the rate of Ο(τ + h).

Numerical simulation of some optical bistability problems in semiconductor systems

The interaction of optical radiation with a semiconductor is analyzed by means of a numerical simulation. Two-dimensional effects are discussed. The influence of heat conduction on longitudinal kinks formation is considered in detail. It is shown that temperature dependence of a charge carriers lifetime can lead to periodical oscillations of electron concentration and semiconductor temperature. An influence of light-induced charge carries on switching waves is discussed. The sphere of applicability for widely known models of thermal optical bistability is determined.

Detection and identification of substances using noisy THz signal

We discuss an effective method for the detection and identification of substances using a high noisy THz signal. In order to model such a noisy signal, we add to the THz signal transmitted through a pure substance, a noisy THz signal obtained in real conditions at a long distance (more than 3.5 m) from the receiver in air. The insufficiency of the standard THz-TDS method is demonstrated. The method discussed in the paper is based on time-dependent integral correlation criteria calculated using spectral dynamics of medium response. A new type of the integral correlation criterion, which is less dependent on spectral characteristics of the noisy signal under investigation, is used for the substance identification. To demonstrate the possibilities of the integral correlation criteria in real experiment, they are applied for the identification of explosive HMX in the reflection mode. To explain the physical mechanism for the false absorption frequencies appearance in the signal we make a computer simulation using 1D Maxwells equations and density matrix formalism. We propose also new method for the substance identification by using the THz pulse frequency up-conversion and discuss an application of the cascade mechanism of molecules high energy levels excitation for the substance identification.

Principal limitation of standard THz time-domain spectroscopy method of the detection and identification of substance and way of its overcoming

We demonstrate principal limitations of standard Time Domain Spectroscopy based on a broadband THz pulse for the detection and identification of substance using paper napkins as a sample. To avoid these limitations we propose a new high effective algorithm for this purpose. We demonstrate its applicability in realistic and simulated situation for various substances under consideration. The interaction of a THz pulse with a disordered layered structure was simulated in order to show the influence of the disordered layers on the spectral characteristics of the transmitted and reflected signals. Spectral characteristics of these signals were analyzed in a direct comparison with the spectrum of the incident pulse as well as by means of Spectral Dynamics Analysis method and integral correlation criteria. The efficiency of the detection and identification method, based on integral correlation and likeness criteria, is confirmed on the basis of computer simulation. To demonstrate the possibilities of the integral correlation criteria in real experiment, they were applied for the identification of explosive HMX in the reflection mode.

Conservative finite-difference scheme for the problem of THz pulse interaction with multilevel layer covered by disordered structure based on the density matrix formalism and 1D Maxwell’s equation

On the basis of the Crank-Nicolson method, we develop a conservative finite-difference scheme for investigation of the THz pulse interaction with a multilevel medium, covered by a disordered layered structure, in the framework of the Maxwell-Bloch equations, describing the substance evolution and the electromagnetic field evolution. For this set of the partial differential equations, the conservation laws are derived and proved. We generalize the Bloch invariant with respect to the multilevel medium. The approximation order of the developed finite-difference scheme is investigated and its conservatism property is also proved. To solve the difference equations, which are nonlinear with respect to the electric field strength, we propose an iteration method and its convergence is proved. To increase the computer simulation efficiency, we use the well-known solution of Maxwell’s equations in 1D case as artificial boundary condition. It is approximated using Cabaret scheme with the second order of an accuracy. On the basis of developed finite-difference scheme, we investigate the broadband THz pulse interaction with a medium covered by a disordered structure. This problem is of interest for the substance detection and identification. We show that the disordered structure dramatically induces an appearance of the substance false absorption frequencies. We demonstrate also that the spectrum for the transmitted and reflected pulses becomes broader due to the cascade mechanism of the high energy levels excitation of molecules. It leads to the substance emission at the frequencies, which are far from the frequency range for the incident pulse spectrum. Time-dependent spectral intensities at these frequencies are weakly disturbed by the disordered cover and, hence, they can be used for the substance identification.

Planar spatiotemporal solitons in a quadratic nonlinear medium

The averaged Lagrangian method has been used to derive an analytical solution in the form of planar light bullets for the system of equations describing the second-harmonic generation in a medium with anomalous dispersion. The stability of this solution is confirmed by the simulation for different relations between the nonlinearity, diffraction, and dispersion in the cases of input pulses at both frequencies and at only the fundamental frequency.

Self-similar mode of optical pulse propagation in a medium with non-instantaneous multi-photon absorption

We develop an analytical approach for finding of self-similar shape of an optical pulse at its propagation in a medium with non-instantaneous nonlinear absorption. The main feature of such pulse shape is asymmetric. Moreover, this mode of optical pulse propagation takes place only for a chirped pulse in contrast to well-known soliton solution of nonlinear Schrödinger equation (or set of such equations). Therefore, we discuss a new type of self-similar mode of laser pulse propagation: self-similar chirped pulse. An existence of this pulse takes place for certain distance of its propagation. We derive a relation between the problem parameters and shape of pulse and its chirp which are necessary for an occurrence of the self-similar mode for optical pulse propagation in a medium under consideration. The developed solution is confirmed by computer simulation results.