R e g u l a r p a p e r s

Theoretical and mathematical physics

Moscow University Physics Bulletin 2000. **55**. N 3. P. 1

A mathematical model has been proposed to describe a leukocyte activation process, which takes into account a deep-seated source and histogram stationarity. To identify the model by parameters, a uniqueness problem has been investigated; a regularizing algorithm has been developed and a mathematical experiment conducted with estimation of the error of the result depending on the error level in observed data.

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 6

Описана схема использования гибридной перенормировки в модели Янга-Миллса. Показано, что эта перенормировка позволяет избежать появления паразитных аномалий при киральных преобразованиях.

Show AbstractRadiophysics

Moscow University Physics Bulletin 2000. **55**. N 3. P. 11

A 3-mm wave band peniotron generator operating at cyclotron frequency 10th harmonic has been designed and tested. The results of calculation and optimization of the electron-optical and electrodynamic systems of the device have been presented. A distinguishing feature of the peniotron is the fact that a monohelical electron beam is formed and focused by a permanent Sm Co-magnet focusing system. Experimental data on the characteristics of the peniotron generator have been presented.

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 17

The work has revealed that when constructing a dynamic model of the process observed, the higher degrees of freedom can be taken into account in the class of third-order delay differential equations.

Show AbstractOptics and spectroscopy

Moscow University Physics Bulletin 2000. **55**. N 3. P. 21

The feasibility of high-efficiency of conversion of argon laser stimulated Raman scattering (SRS) .in com.pressed hydrogen in biharmonic pumping was demonstrated. In biharmonic pumping the peak intensity of the Stokes components was demonstrated to exceed the weak-signal emission rate more than by a factor of 100.

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 25

The order parameter-versus-temperature relationship has been determined for oriented films of a comb-shaped liquid crystal (LC) polymer from the refractometry data using the Haller extrapolation method. The effects of a local field have been analyzed using low-molecular-weight LC paraazoxyanisole as an example. Such effects were demonstrated to be of no importance when the Haller method is used.

Show AbstractSolid state physics

Moscow University Physics Bulletin 2000. **55**. N 3. P. 31

The degree of break of pulse switching curves of iron borate monocrystals has been shown to decrease as the thickness of the crystals increases. The thickness dependence of switching coefficient Sw1 for the first part of this curve obeys the hyperbolic law. The observed phenomena are qualitatively explained by a decrease in the density of energy consumed for excitation of shock magnetoelastic oscillations accompanying pulse reversal processes with crystal thickness increase.

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 34

The experimental spectrum and wave functions of the Tb, Dy, and Ho ions in the vanadate crystal field have been used to calculate all strain susceptibilities numerically and to analyze quadrupole vrdering phase transitions. A thorough description of experimental elastic constants $C^{\delta}(T)$ and $C^{\gamma}(T)$ of Tb and Dy vanadates in the tetragonal and rhombic phases, respectively, has been given, and magnetoelastic and pair quadrupole coefficients have been determined. The $B^{\epsilon}$ magnetoelastic coefficient for the zircon structure has been first estimated from acoustic measurement data.

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 39

A numerical model of an experiment in off-resonance pulsed magnetization transfer in magnetic resonance imaging has been developed through solving the Bloch-Mcconnel equations for two cross relaxation-coupled spins. A simplified analytical model oflongitudinal magnetization dynamics has been proposed with the use of stationary approximation for transverse components and the field of its appliction has been defined. Recommendations based on numerical modeling have been given to optimize the parameters of a gradient echo pulse sequence with magnetization transfer.

Show AbstractGeophysics

Moscow University Physics Bulletin 2000. **55**. N 3. P. 46

The effect of baroelectric fields on the differential streams in the interior of planets and stars is discussed. Estimates for the magnetic fields at the surface spots on the Sun are proposed.

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 51

A solution determining pressure of solitary waves on the ocean has been obtained and analyzed.

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 55

A new approach to the problem of random field spatial ergodicity with respect to the mathematical expectation during wave propagation in a free space between the ionosphere and the Earth has been considered. A possibility of replacing volume averaging by averaging over a horizontal straight line in any direction has been proved. The results obtained can be used for analyzing the propagation of waves of various nature in geophysical media.

Show AbstractAstronomy

Moscow University Physics Bulletin 2000. **55**. N 3. P. 60

A short-time increase in fluxes of solar cusmic rays (SCR) directed towards the Sun on August 20, 1991 has been considered. It is shown that this increase was caused by a loop structure of an intnplanetary magnetic field (IMF) filled with SCR particles moving towards the Sun that was passing through the neighborhood of the Earth. A large-scltle IMF structure that existed in the Earth's neighborhood on August 18-20, 1991 has been constructed.

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 64

A second approximation has been derived for the theory of motion of solar system bodies based on a universal method for computing the perturbation function. The results of processing a 30-year series of photographic observations of selected minor planets have been presented.

Show AbstractB r i e f r e p o r t s

Theoretical and mathematical physics

Moscow University Physics Bulletin 2000. **55**. N 3. P. 68

Within the framework of the method of finite-energy sum rules, an estimate of the mass of a constituent quark has been obtained with the use of the model of gluon propagator based on the renorma]ization group analysis in the one-loop approximation.

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 71

For synchronous oscillations of the van der Pol oscillator under the action of a harmonic force, the domain of bistability, in which two stable periodic solutions with different parameters can exist under the given values of the external force parameters has been examined (analytically and numerically).

Show AbstractMoscow University Physics Bulletin 2000. **55**. N 3. P. 74

Geodesic equations of motion have been integrated for massive and massless particles in gravitational fields produced by plane electromagnetic and scalar waves in Visser's theory of gravitation. It is shown that the equations describing the paths of these particles depend to a large extent on the graviton mass.

Show AbstractAtomic and nuclear physics

Moscow University Physics Bulletin 2000. **55**. N 3. P. 76

The authors discuss a new physical scheme of a $\gamma$- and X-ray bremsstrahlung source, in which photon emission is accompanied by accete·ration of electrons. The scheme ensures the yield both of soft and hard bremsstrahlung photons, with the device remaining quite compact. High efficiency of the scheme is confirmed by computer simulation.

Show AbstractSolid state physics

Moscow University Physics Bulletin 2000. **55**. N 3. P. 79

An improved high-speed photography method was used to study the formation of a quasi-static band domain structure in ferrite-garnet films upon simultaneous action of mechanical stress pulses and a pulsed magnetic field with an amplitude exceeding the saturation field value. It has been found that orientation of this structure is unambiguously determined by induced anisotropy.

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