Anomalous attenuation of extraordinary waves in the ionosphere heating experiments

Multiple scattering of radio waves by artificial random irregularities HF-induced in the ionosphere F region may cause significant attenuation of both ordinary and extraordinary waves together with common anomalous absorption of ordinary waves due to their non-linear conversion into plasma waves. To demonstrate existence and strength of this effect, direct measurements of attenuation of both powerful pump wave and weak probing waves of extraordinary polarization have been carried out during an experimental campaign on September 6, 7 and 9, 1999 at the Sura heating facility. The attenuation magnitude of extraordinary waves reaches of 1-10 dB over a background attenuation caused by natural irregularities. It is interpreted in the paper on the base of the theory of multiple scattering from the artificial random irregularities with characteristic scale lengths of 0.1-1 km. Simple procedure for determining of irregularity spectrum parameters from the measured attenuation of extraordinary waves has been implemented and some conclusions about the artificial irregularity formation have been obtained.Comment: 17 pages, 9 figure

The Radiation Transfer at a Layer of Magnetized Plasma With Random Irregularities

The problem of radio wave reflection from an optically thick plane monotonous layer of magnetized plasma is considered at present work. The plasma electron density irregularities are described by spatial spectrum of an arbitrary form. The small-angle scattering approximation in the invariant ray coordinates is suggested for analytical investigation of the radiation transfer equation. The approximated solution describing spatial-and-angular distribution of radiation reflected from a plasma layer has been obtained. The obtained solution has been investigated numerically for the case of the ionospheric radio wave propagation. Two effects are the consequence of multiple scattering: change of the reflected signal intensity and anomalous refraction.Comment: 22 pages, 4 figure

On the implementation of some methods applied to optimization design problems

It is shown that in optimization problems arising during electronic circuit design constraints often may be represented as a direct product of some sets from different spaces which in general may have different dimensions. Taking into account this form of valid set makes it possible a decomposition of the optimization problem of large dimension. It is also shown that in man-machine decision support systems implemented on parallel computers it is possible to branch the optimization algorithm in order to reduce computing time. The efficiency of the approach is demonstrated by using a modification of gradient and subgradient projection methods for electronic circuit design

Ultrastructure of oocytes and female copulatory organs of Acoela

The ultrastructure of oocytes in four species of Acoela ( Archaphanostoma agile, Otocelis rubropunctata, Symsagittifera japonica, and Amphiscolops sp.) and that of female copulatory organs of S. japonica and Amphiscolops sp. are described for the first time. According to the similarity of the reproductive apparatus structure, the sister relationships between the families Sagittiferidae and Convolutidae are confirmed. The ultrastructure of oocytes and specific features of oogenesis are proposed to be useful in phylogenetics of Acoela