Magnetic-Zenith Effect

We develop a theory of the magnetic-zenith effect (MZE) observed upon the ionosphere modification by powerful radio waves. The dependences of MZE on main parameters, such as the magnetic-field inclination angle, pump-wave frequency and power, and angular width of HF beam are obtained. The optimal elevation angle of pump-wave beam is predicted. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 772–787, September 2005.     

An intracloud discharge caused by extensive atmospheric shower

The observational evidence of RB-EAS discharge in a thunderstorm atmosphere is presented. After RB-EAS discharge we name a discharge of a special type developing due to the runaway breakdown (RB) mechanism while an extensive atmosphere shower (EAS) passes through a thundercloud electric field. The observations were fulfilled at the Tien-Shan Mountain Cosmic Ray Station. The widely spread system of oscillation detectors, the special EAS trigger array and the HF radio interferometer were used for measurements.     

Gamma-ray emission from thunderstorm discharges

Fine features of gamma-ray radiation registered during a thunderstorm at Tien-Shan Mountain Cosmic Ray Station are presented. Long duration (100-600 ms) gamma-ray bursts are found. They are for the first time identified with atmospheric discharges (lighting). Gamma-ray emission lasts all the time of the discharge and is extremely non-uniform consisting of numerous flashes. Its peak intensity in the flashes exceeds the gamma-ray background up to two orders of magnitude. Exclusively strong altitude dependence of gamma radiation is found. The observation of gamma radiation at the height 4-8 km could serve as a new important method of atmospheric discharge processes investigation.     

Growth of black holes at the centers of galaxies: Absorption of stars and activity of galactic nuclei

We study the influence of supermassive black holes on the distribution of stars at the centers of galaxies. We analyze relaxation processes associated with encounters between stars and their absorption by black holes. For an isothermal distribution of stars, we obtain the growth law and estimate the current masses of black holes. The tidal disruption of stars near black holes is considered as a possible cause of the activity of galactic nuclei.     

Examination of the oxygenation state of hemoglobin in a phantom and in-vivo tissue applying absorption balancing with two and three laser wavelengths

Two-dimensional absorption measurements of hemoglobin in (i) a phantom, imitating the optical properties of tissue, and (ii) in-vivo breast tissue are reported. The method is based on quasi-simultaneous balanced absorption measurements of hemoglobin and oxygenated hemoglobin at selected wavelengths in order to minimize baseline fluctuations during spatial scanning of the sample. The method allows the detection of 0.8 cm-diameter inclusions of oxygenated hemoglobin differing by about 30% in its oxygenation state from the surrounding hemoglobin if two-wavelengths balancing is applied. However, small wavelength detunings from the optimum wavelength positions cause considerable fluctuations of the signal baseline and deteriorate the detection sensitivity, if there is an inhomogeneous distribution of another weak wavelength dependent absorber in the sample. Although the optical absorption of water is relatively small for the wavelengths applied, a considerable influence of the water on the signal baseline was observed in in-vivo measurements of the hemoglobin status in healthy breast tissue. For better compensation of interfering water absorption, a third laser wavelength was applied in order to balance the water absorption. The prospects of this new optical technique for screening of breast tumors are discussed. PACS 41.85.Ja; 42.30.Wb; 42.55.Px; 42.62.Be     

A parametric transformation at numerical integration of ODE

The initial value problem for ordinary differential equation (ODE) is investigated when the linear parametric transformation (rotation of coordinate axes) is applied. It is shown that for transformed equation the principal term of asymptotic error expansion of numerical method can be minimized by an angle of rotation. The dependence of the optimal angle φ_opt(λ)on λis plotted for the model equation solved by linear multistep methods and Runge-Kutta methods.     

Detection of extremely low lead concentrations by laser atomic fluorescence spectrometry

The possibilities of the detection of extremely low atomic concentrations by laser atomic fluorescence were examined using Pb as an example. A detection limit of 250 $\text{atoms}\text{cm}{}^3$ or 30 atoms in the analytical volume was achieved in the experiments with saturated lead vapour in an evacuated quartz cell. A detection limit of 0.05 $\text{pg}\text{ml}$ was achieved in the experiments with aqueous solutions as reference using a graphite atomizer.