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We study the propagation of electromagnetic waves in nonlinear media with the polynomial dependence of the dielectric permittivity
on the intensity of the electric field. The instability of a plane wave with respect to noncollinear perturbations is studied
in a wide band of combination frequencies. The perturbation growth rate and their dependencies on angles and frequencies are
found. It is shown that waves with frequencies close to the second harmonic of the frequency of the propagating wave can increase
faster than the perturbations in the case of the well-known modulation instability. We discuss application of the developed
theory for the description of the light wave propagation in air, for which a representation of the nonlinear dielectric permittivity
in the form of the electric field polynomial is known. The results of the work can be useful in explaining the properties
of optical rogue waves.

Content Type Journal ArticlePages 1-8DOI 10.1007/s11141-011-9281-9Authors
S. N. Vlasov, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, RussiaE. V. Koposova, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia

Journal Radiophysics and Quantum ElectronicsOnline ISSN 1573-9120Print ISSN 0033-8443

We have developed and tested a gyroklystron operating with the second harmonic of the electron cyclotron frequency at a frequency
of 32.3

We propose a new method for reconstructing the spatial distribution of fluorophore in a highly scattering object from its
images obtained by the method of diffuse fluorescence tomography. This method is intended for diagnostics of the fluorophore-marked
tumors and is based on the algebraic-reconstruction principle combined with a new theoretical model and simulation of light
propagation in randomly scattering media, such as biotissues, by the Monte Carlo method. The model experiments show that for
18-mm thick objects, the developed method allows one to determine location of the geometric center of a fluorescent inhomogeneity
and its transverse and longitudinal dimensions with accuracies of up to 0.5 and 1.5 mm, respectively.

Content Type Journal ArticlePages 1-13DOI 10.1007/s11141-011-9283-7Authors
I. I. Fiks, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, RussiaM. Yu. Kirillin, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, RussiaE. A. Sergeeva, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, RussiaI. V. Turchin, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia

Journal Radiophysics and Quantum ElectronicsOnline ISSN 1573-9120Print ISSN 0033-8443

We present the results of an experimental study of the low-amplitude cardiac signals without temporal and spatial averaging.
The characteristics of the fluctuation and quasi-periodic components of the low-amplitude signals are determined statistically
reliably for the first time. The results of the studies of the periodic and quasi-periodic components obtained from the long-term
measurement data are reported. It is found that the structure of the frequency characteristics of low-amplitude signals has
pronounced temporal variability in the neighboring cardiac cycles.

Content Type Journal ArticlePages 1-8DOI 10.1007/s11141-011-9284-6Authors
G. M. Teptin, Kazan’ Federal University, Kazan’, RussiaI. A. Latfullin, Rehabilitation Center of the Situations of Emergency Ministry of the Republic of Tatarstan, Kazan’, RussiaL. E. Mamedova, Kazan’ Federal University, Kazan’, RussiaZ. F. Kim, Kazan’ Medical University, Kazan’, Russia

Journal Radiophysics and Quantum ElectronicsOnline ISSN 1573-9120Print ISSN 0033-8443

We study the correlation between variations in the solar–geophysical parameters and variations in the maximum observable frequencies
(MOF) on several ionospheric short-wave oblique-sounding paths. The basic interplanetary space parameters, whose variations
have the greatest impact on the MOF variations on specified paths, are determined. Variations in the B_x and B_z components of the interplanetary magnetic field (IMF) affect the MOFs on the Norilsk—Rostov-on-Don subauroral path. At mid-latitudes,
the influence of the IMF components B_x, B_y, and B_z is significant on the Inskip—Rostov-on-Don and Irkutsk—Rostov-on-Don paths. On the Cyprus—Rostov-on-Don low-latitude path,
the modulus of the IMF has the most pronounced effect. The density and velocity of solar wind manifest themselves in MOF variations
on all paths. The technique of MOF retrieval by a neural network on the Cyprus—Rostov-on-Don and Irkutsk—Rostov-on-Don paths
using the MOF data of the Inskip—Rostov-on-Don path is developed with allowance for the influence of the interplanetary space
parameters. The retrieval efficiency of this technique is no less than 80%.

Content Type Journal ArticlePages 1-14DOI 10.1007/s11141-011-9277-5Authors
O. M. Barkhatova, State Architectural and Building University of Nizhny Novgorod, Nizhny Novgorod, Russia

Journal Radiophysics and Quantum ElectronicsOnline ISSN 1573-9120Print ISSN 0033-8443

We present a method for calculating the dispersion characteristics of eigenmodes of metal waveguides with helical corrugations
on the inner surface, which is based on the transition to a new nonorthogonal system of coordinates. In the new coordinate
system, the problem of finding helical-waveguide modes is rigorously equivalent to the problem of finding the modes of a circular
unitradius waveguide which has an anisotropic filling and is homogenous in the longitudinal direction. To solve the equivalent
problem, we expand the field of the desired eigenmode in the modes of an empty circular unit-radius waveguide. As a result,
the problem is reduced to solving a generalized algebraic eigenvalue problem. The comparison with the results of earlier three-dimensional
calculations shows that the developed method allows one to determine characteristics of helical-waveguides with sufficient
accuracy for many important applications and requires much lower calculation costs.

Content Type Journal ArticlePages 1-11DOI 10.1007/s11141-011-9280-xAuthors
S.V. Mishakin, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, RussiaS.V. Samsonov, Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia

Journal Radiophysics and Quantum ElectronicsOnline ISSN 1573-9120Print ISSN 0033-8443