On thermomagnetic instability during ionospheric modification by powerful radio waves

The possibility of excitation of thermomagnetic instability in the ionospheric F-region with an external DC electric field on exposure to waves from powerful ground-based radio transmissions is discussed. The threshold and growth rate of the instability are determined. It is shown that such instability can appear in local regions with a rather high level of plasma waves and in the high-latitude ionosphere, especially for high ionospheric-plasma drift velocities.Scientific-Research Institute of Radiophysics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 5, pp. 674–679, May, 1994.     

Vibrational spectroscopy and the intermolecular dynamics of condensed states V. Temperature dependence of intermolecular spectra of acetonitrile and benzonitrile

Intermolecular spectra are reported for acetonitrile and benzonitrile between –196 °C and 100–140 °C. Structural changes can be established from the integral intensity, peak frequencies, and effective molecular vibration frequencies. There is a polymorphic transition in crystalline acetonitrile between –50 and –60 °C, while there is a change in the structure of liquid benzonitrile in the range 0–10 °C. There are peaks in the intermolecular spectrum of benzonitrile in the liquid state.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 92–95, August, 1971.     

Mechanism for the formation of the polar wall of the main ionospheric dip

The mechanism for the formation of the polar wall of the main ionospheric dip in the electron density in the ionospheric F region has been studied. The dynamics of this wall has also been studied. A model has been developed for the precipitation of high-energy electrons in the auroral oval. This model works at an arbitrary level of geomagnetic activity. A theoretical model of the high-latitude ionosphere is used to calculate the electron density at the maximum of the F2 layer for K_p=0 and 5. As the geomagnetic activity increases to K_p=5, the polar wall of the dip shifts about 7° toward the equator. This shift is confirmed by experimental data. The model describes the experimentally established fact that the changes which occur in the gradient of the electron density at the polar wall of the dip upon a change in the level of geomagnetic activity are small. The results of the model-based calculations are compared with data from the network of vertical radiosonde stations. A qualitative and quantitative agreement is demonstrated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 88–97, October, 1993.     

Stable bonds and unstable bonds in Y(Pr)-123 system

The Pr content dependence of the bond lengths of Y–Cu, Y–O, O–O, Cu–O, Ba–Cu and Ba–O in PrBa₂Cu₃O_y are analyzed and discussed in detail. The different valence bonds can be divided into two groups: stable bonds and unstable bonds. Since the bond lengths and angles between every two ions among O2, Cu2 and O3 are very stable, we conclude that the three ions form an unchangeable triangle when the Pr doping changes. The triangle is called “fixed triangle”. This “fixed triangle” can slightly rotate around the Cu2 ions. It is just this rotation that leads to the unstable bonds. As the increase of the Pr content, the bond lengths between the two Cu(2)–O planes becomes larger and larger, the Cu(2)–O planes bend towards the Ba–O plane. The bonds lengths between the Cu(2)–O and Ba–O planes vary oppositely from those of Cu(2)–O, and become shorter and shorter. These changes connected with the superconductivity are discussed.     

Temperature anomalies in the dispersion and absorption of sound near phase transition points at low temperatures

We examined the attenuation and dispersion of sound during phase transitions with an overdamped soft mode at low temperatures. The obtained temperature and frequency dependences differ from results known at the high-temperature asymptote. The temperature anomalies are sharper. At low frequencies, the attenuation behaves like (T – T_c)^–5/2 for a critical phonon spectrum isotropic in k, and like (T–T_c)^–2 for uniaxial ferroelectrics. The presence of a temperature anomaly is characteristic also for high-frequency attenuation, behaving like (T–T_c)^–1/2 and ln(T–T_c)., respectively. We discuss briefly the results obtained from an experimental test.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 70–74, January, 1989.     

Analysis of diffuse reflection and absorption spectra of ZnO in the near-IR region

It is established that the absorption of ZnO in the near-IR region of the spectrum is determined by free electrons and chemisorbed gases. The free-electron absorption spectrum is approximated by a power function with an exponent which varies within the range 2–3, depending on the defectiveness of the specimen. Chemisorbed gases yield absorption bands at 1.37; 1.18; 1.08–1.03; 0.95–0.93; 0.85; 0.75–0.73; and 0.65–0.63 eV. The bands at 1.18 and 0.85 eV are due to chemisorbed oxygen in the states O^– and O₂ ^–, while the other bands can be attributed mainly to atomic hydrogen and OH-groups.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 86–90, July, 1988.We thank E. V. Komarov for his help in conducting the experiments.     

Radical-Recombination Luminescence of the Uranyl Nitrate Complex in the Adsorbed State

We have investigated the luminescence of uranyl nitrate molecules on the surface of powdery SiO₂ upon excitation by UV light (PhL) and hydrogen atoms (radical-recombination luminescence (RRL)). It has been found that the PhL and RRL spectra have a clearly defined vibrational structure. The luminescence peaks of the adsorbed UO₂ ^2– ion are characterized by a systematic longwave shift from the same peaks of crystalline uranyl nitrate (by 230–430 cm^–1 at 130 K). Moreover, in the adsorption centers the vibration frequencies of UO₂ ^2– are 20–80 cm smaller than in crystalline salt and the RRL bands are 150–350 cm^–1 (130 K) wider than the corresponding PhL bands.     

Estimation of the energy spectrum of cosmic ray electrons at the atmospheric depth (3.8–7.4)g.cm−2

Analytical calculations have been done to estimate the energy spectra of the secondary electrons originated from the decay of charged and neutral pions initiated on the upper atmosphere from the primary nucleon–air interactions in the energy range (4–100) GeV. The calculations are valid up to an atmospheric depth of about (3.8–7.4) g.cm^–2. The derived results are compared with the observed electron fluxes available from the balloon flight experiments of MASS2, HEAT, magnetic spectrometer system of Golden et al., instrument using scintillating fibers of Nishimura et al., and BETS.     

Mercury vapor transfer coefficients

Average effective electron-neutral diffusion coefficients are calculated for mercury vapor in the temperature range 3000–20,000°K. Electrical conductivity and electronic thermal conductivity of mercury plasma are determined over the pressure interval 0.00001–40 MPa in the second approximation of the Chapman-Enskog method.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 11–14, March, 1982.     

Bromoacyl Analogs of Pyrene–Containing Phosphatidylcholine as New Fluorescent Lipid Probes with Intramolecular Quenching

Two new derivatives of phosphatidylcholine with an intramolecularly quenched fluorescence, namely, 1––bromoundecanoyl–2–[4–(pyren–1–yl)butyroyl]–sn–glycero–3–phosphocholine (BPPhC) and 1–(9,10–dibromostearoyl)–2–[4–(pyren–1–yl)butyroyl]–sn–glycero–3–phosphocholine (DBPPhC), have been obtained by replacing acyl chains by residual pyrenebutyric and bromine–labeled fatty acids. Their structure has been verified by the ¹H–NMR method and the spectral properties have been characterized in media of different polarity with the aid of absorption and fluorescent spectroscopy. It has been established that when BPPhC and DBPPhC are included in liposomes, the intensity of their fluorescence changes markedly as a function of the physical state of the bilayer, which makes it possible to use the compounds obtained as lipid probes for investigating the properties of biological and artificial membranes.     

Characterization of Submillimeter Wave Absorbers from 200–600 GHz

This paper presents measurements of both specular and non-specular scattering from several submillimeter wave absorber materials designed for antenna testing and from low-cost carpet materials. The frequency range is 200–600 GHz in specular scattering, and 300–400 GHz in non-specular scattering measurements. The constructed bistatic test bench allows testing of the full continuous angular range of 0°–90°. The measurement results show large differences in performance of different materials. It is shown that reflectivities below –50 dB over limited angular ranges are possible with a correct alignment of the material. Also, low-cost carpet materials have lower than –15 dB reflectivities in most angles, and may be useful in non-critical parts of the antenna test range. The results can be used to optimise the absorber placement inside an antenna range, concerning both best performance and lowest cost.     

A New Model for The Formation of Mini Black Holes

A new model different from the Hawking model is suggested to describe the formation of mini (primordial) black holes. It is based on an idea that the fluids, which fill in the universe at the beginning just after the big bang, are separated into mini clusters, moving with supersonic velocities and colliding with each other under the forces of gravitational attractions. We show that between the time era from 10^–43 to 10^–8 sec. about 36 various generations of mini black holes with masses ranging in the interval 10^–5—10^–30 gm are possible.     

Relativistic calculations of inelastic collisions between electrons and atoms

The Feynman S-matrix formalism is used to consider the inelastic collisions of electrons with a hydrogen atom. The two leading Feynman diagrams are calculated, and the 1s-2s transition is treated in detail. Results are given for scattering amplitudes at energies of 1.0–8.0 (atomic units) and for various scattering angles, as well as the differential cross sections for direct scattering in the energy region 1.36–118.5 keV. On the basis of comparison with nonrelativistic calculations, we conclude that relativistic effects are appreciable and increase with energy. Total cross sections are calculated in both nonrelativistic and relativistic approximations. The difference between them increases with energy and is 15–20% for energies of 20–50 keV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 7–12, August, 1977.     

General intense electron beams by means of a contracted arc discharge

Two types of contracted arc discharge are investigated with a view to generating intense electron beams over a wide pressure range (1–10^–3 Pa). For an arc discharge with a hollow cathode and anode, an electron beam corresponding to a current of up to 300 A and a pulse length of 25 µsec is obtained at a pressure of 1–10^–1 Pa in the accelerating gap with an accelerating voltage of up to 15 kV. At pressures of 10^–2–10^–3 Pa, emitting plasma is created by a low-pressure arc discharge on the basis of a Penning cell. Three discharge systems operating in parallel are used to increase the working life of the cathode and improve the current density distribution of the beam. An electron beam of diameter 200 mm with a current of up to 125 A and a pulse length of 50 µsec is obtained.Institute of High-Power Electronics, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshkikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 76–82, March, 1994.     

Calculation and study of the IR absorption spectrum of hydantoin

The IR absorption spectrum of hydantoin has been obtained in the range 400–3500 cm^–1, and the normal-vibration frequencies are calculated on the basis of the mechanical model. The spectrum is interpreted.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 6, pp. 116–120, June, 1969.     

Infrared absorption and far-infrared diffuse reflection spectra in Pb-doped Bi?Sr?Ca?Cu?O high-temperature superconductor

In this paper we study the room-temperature infrared transmission spectra (400–1600cm^–1) and far-infrared diffuse reflection spectra (50–450cm^–1) in Pb-doped Bi–Sr–Ca–Cu–O (2223) single phase (Tc=107k, sp1), multiphase (Tc=110k, sp2) and nonsuperconducting samples (sp3). The spectral features in superconductor are totally different from those in nonsuperconductor, which show the different crystal structure. The correlation existing between a factor group analysis of the phonons in (2223) and (2212) compounds affords a tentative assignment of ir-active modes in Pb-doped (2223) single phase by comparison with reported data in (2212) materials. The Cu–O stretching E_u vibration (605cm^–1) of CuO₂ layers is the characteristic vibrational mode related perovskitelike crystal structures. Two phonon coupling effect emerges in the infrared transmission spectra in Pb-doped superconductor. The Ca–O vibration A_2u (254cm^–1) might be related to superconductivity of Bi-based family.     

Experimental pressure dependence of the accelerated current in the chamber of the sirius synchrotron

An experimental study of the dependence of the accelerated charge in the synchrotron on the vacuum-chamber pressure is reported. The results are compared with calculations; in the pressure range 5 · 10^–6–2 · 10^–5 torr, the experimental and calculated results agree well.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 2, pp. 31–35, February, 1969.The authors thank P. P. Krasnonosen'kikh for assistance in the experiments and G. P. Fomenko for discussion of the results.     

Charge transport and accumulation in liquid crystals

Charge carrier formation mechanisms in liquid crystals and their contribution to conductivity in the voltage range 0.1–10 V and field action times of 0–300 sec are compared. Values of accumulated charge are calculated corresponding to the processes of carrier separation within the volume, injection from the electrode, and molecular dissociation under electric field action.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 9–12, July, 1989.