We report on the possibility of diffracting electrons from light waves traveling inside a dielectric medium. We show that, in the frame of reference which moves with the group velocity of light, the traveling wave acts as a stationary diffraction grating from which electrons can diffract, similar to the conventional Kapitza-Dirac effect. To characterize the Kapitza-Dirac effect with traveling light waves, we make use of the Hamiltonian Analogy between electron optics and quantum mechanics and apply the Helmholtz-Kirchhoff theory of diffraction.

We explore the propagation and transformation of electromagnetic waves through spatially homogeneous yet smoothly time-dependent media within the framework of classical electrodynamics. By modelling the smooth transition, occurring during a finite period tau, as a phenomenologically realistic and sigmoidal change of the dielectric permittivity, an analytically exact solution to Maxwell's equations is derived for the electric displacement in terms of hypergeometric functions. Using this solution, we show the possibility of amplification and attenuation of waves and associate this with the decrease and increase of the time-dependent permittivity. We demonstrate, moreover, that such an energy exchange between waves and non-stationary media leads to the transformation (or conversion) of frequencies. Our results may pave the way towards controllable light matter interaction in time-varying structures. (C) 2015 Elsevier Ltd. All rights reserved

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The developmental and behavioral disabilities remain high in children and in adults who were born preterm. In this case assessment of quality of life and development of preterm infants can be very informative and interesting. This is a prospective longitudinal (at 3, 6, 9 and 12 months) study of preterm birth and term control infants selected from pediatric polyclinics of Yerevan. The quality of life (QL) measures were done with QUALIN questionnaire and the developmental measures with Battelle Developmental Inventory. A total of 71 preterm and 105 term control infants underwent study. Among 71 preterm birth infants, who selected on the study at 3 months, 40 infant's score on the BDI was <–1 SD and 1 infants' score on the BDI was <–2 SD. However, at the age of 12 months 32 of these same children showed a BDI score >85. Parents and pediatricians reported worse QL for of preterm infants compared with control group. At same time parents of preterm infants reported better QL for their children compared with pediatricians. The lowest QL and developmental scores among preterm children were detected at 3 months. Improvement of QL and developmental score was observed in the next age groups.

In the problem of electron diffraction by a standing light wave (the Kapitza–Dirac effect), an electronic refractive index can be defined as the ratio of electron momenta in the wave field and outside it. Moreover, both kinetic and canonical electron momenta can be used for this purpose, which corresponds to the Abraham–Minkowski controversy in photonic optics. It is shown that in both cases the same expression for the electronic refractive index is obtained. This is consistent with Barnett's resolution of the Abraham–Minkowski dilemma.