Investigations of Advanced Coaxial Gyrotrons at IAP RAS

Main results of experimental testing of the 140 GHz/1.5 MW coaxial gyrotron are summarized. High selective properties of the coaxial cavities and a possibility to increase considerably the efficiency of a coaxial gyrotron only by applying independently an appropriate voltage on its electrodes (without any design modification) have been confirmed. Successful uses of the two-potential connection scheme for the frequency step tuning and output power modulation in a coaxial gyrotron has been also demonstrated.     

Duality Principle and New Forms of the Inverse Laplace Transform for Signal Propagation Analysis in Inhomogeneous Media with Dispersion

Doklady Mathematics - New equations for Laplace transform inversion are obtained. The equations satisfy the causality principle. The impulse response of a channel is determined in order to analyze...     

Experimental Test of the Natural Scheme of Electron Beam Energy Recovery in a Coaxial Gyrotron

It is shown that the efficiency of a coaxial gyrotron can be increased considerably by applying only independently appropriate voltages to its electrodes (without modifying design). The proposed scheme is also suitable for stepwise frequency tuning and for deep modulation of output power.     

Femtosecond midinfrared study of aggregation behavior in aqueous solutions of amphiphilic molecules

We study the spectral and orientational dynamics of HDO molecules in aqueous solutions of different concentrations of tertiary butyl alcohol (TBA) and trimethylamine-N-oxide (TMAO). The spectral dynamics is investigated with femtosecond two-dimensional infrared spectroscopy of the O-H stretch vibration of HDO:D(2)O, and the orientational dynamics is studied with femtosecond polarization-resolved pump-probe spectroscopy of the O-D stretch vibration of HDO:H(2)O. Both the spectral and orientational dynamics are observed to show bimodal behavior: part of the water molecules shows spectral and orientational dynamics similar to bulk liquid water and part of the water molecules displays a much slower dynamics. For low solute concentrations, the latter fraction of slow water increases linearly as a function of solute molality, indicating that the slow water is contained in the solvation shells of TBA and TMAO. At higher concentrations, the fraction of slow water saturates. The saturation behavior is much stronger for TBA solutions than for TMAO solutions, indicating the aggregation of the TBA molecules.     

Vector Diffraction Integrals for Solving Inverse Problems of Radio-Holographic Sensing of the Earth's Surface and Atmosphere

Vector relationships between the fields on a certain surface confining an inhomogeneous three-dimensional volume and the fields inside this volume are obtained by the Stratton–Chu method developed for the case of homogeneous media. The vector relationships allow us to solve the direct and inverse problems of determining the fields inside an inhomogeneous medium given the field on its boundary. The vector equations take into acount the polarization changes of direct and inverse waves propagated in an inhomogeneous medium. In the case of a two-dimensional homogeneous medium, the vector equations reduce to the previously obtained scalar equations used in the approximation of spherical symmetry to describe the process of backward wave propagation during the atmospheric and ionospheric radio-occultation monitoring. It is shown that the Green's function of the scalar wave equation in an inhomogeneous medium should be used as the reference signal for solving the inverse problem of radio-occultation monitoring. This validates the method of focused synthetic aperture previously used for high-accuracy retrieval of the vertical refractive-index profiles in the ionosphere and atmosphere. In this method, the reference-signal phase was determined from a model which describes with sufficient accuracy the radiophysical parameters of a refracting medium in the region of radio-occultation sensing. The obtained equations can be used for the high-accuracy solving of inverse problems of radio-holographic sensing of the Earth's atmosphere and surface by precision signals from radio-navigation satellites.     

Chemistry of pyridoxine in drug design

Russian Chemical Bulletin - Pyridoxine and its derivatives, pyridoxamine and pyridoxal, are the three main forms of vitamin B6, which play exceptionally important biological roles in living...     

Synthesis and antiadrenergic properties of β-substituted alcohols based on 6-hydroxymethylpyridoxine

An approach to the synthesis of epoxides based on 6-hydroxymethylpyridoxine acetals was developed. The epoxides obtained were involved in the ring opening reactions by nitrogen-, oxygen-, and sulfur-containing nucleophiles. Cytotoxicity and antiadrenergic properties of some synthesized compounds were studied on the models in situ and in vivo.     

Results of Studying the Daytime Polar Ionosphere by the Radio Occultation Method on Satellite-To-Satellite Paths

Radiophysics and Quantum Electronics - We analyze specific features of the radio occultation method and the possibility of using it to study the altitude profiles of electron density and the...