A new representation of the interaction between an atom and an intense elliptically polarized electromagnetic field

A new representation of the interaction between a laser field and an atom is obtained. The Fourier component of the interaction is represented as a multipole expansion dependent on the force parameter of the field, a ₀=F/ω², and the degree of its ellipticity, η. This representation provides the analytical separation of the angles in the time-dependent Schrödinger equation. The stationary spherically symmetric part of the potential V ₀(r, a ₀, η) of a “field-dressed” atom is singled out. The application of the new representation to the calculation of nonlinear effects and electron scattering by an atom in a field are discussed     

The Possible Use of a Millimeter-Wave Meteoradar for Radioacoustic Sounding of the Atmosphere

The use of millimeter-wave meteoradars with amplitude modulation of radio pulses in systems of radioacoustic sounding of the atmosphere, proposed by A. L. Fabrikant, opened new opportunities in atmospheric research. However, the experimental layout and measurement technique chosen by A. L. Fabrikant are far from optimal. Even using record-power acoustic emitters, one can only perform measurements at heights not larger than 1.5-2 km. In this paper, we consider methods for optimization of the system. We propose design solutions which improve significantly (by a factor of about 10⁴) the signal-to-noise ratio in comparison with the estimates performed by A. L. Fabrikant. The influence of wind and temperature gradients on the system operation is considered. In contrast to conventional systems of radioacoustic sounding, the use of a millimeter-wave radar with a narrow radiation pattern allows one to avoid losses in efficiency due to the wind drift of the acoustic mirror. We show that the height of sounding by a system comprising a millimeter-wave radar and an acoustic emitter with standard parameters can be increased up to 10-15 km. The proposed system allows one to measure the aerosol content and the temperature and wind profiles in the atmosphere as well as to study turbulent processes during active (prestorm or thunderstorm) periods. Moreover, such a system is compact enough to be mounted on mobile platforms.     

Resonances and dichroism in the scattering of an electron in an intense laser field by the Coulomb potential

We use a new type of Hamiltonian representing the electron-proton interaction in an intense laser field for an ab initio calculation of the differential scattering cross section. We give the diagrams of the results of calculations of the shapes and widths of the resonances in the cross section of electron scattering by the “field-dressed” Coulomb potential. The resonances emerge because of re-emission of photons by the electron. We also give the angular distribution of the scattered electrons as a function of circular dichroism for different values of the laser field strength and frequency. Zh. éksp. Teor. Fiz. 116, 1241–1249 (October 1999)     

Excitation of a magnetospheric maser through modification of the Earth’s ionosphere by high-power HF radio emission from a ground-based transmitter

A method for controlled excitation of a magnetospheric maser through the production of artificial density ducts by high-power HF radio emission from the Earth’s surface has been proposed and implemented in an in-situ experiment. Artificial density ducts allow one to affect the maser resonator system and the excitation and propagation of low-frequency electromagnetic waves in a disturbed magnetic flux tube. The experimental data presented here were obtained at the mid-latitude Sura heating facility. The characteristics of electromagnetic and plasma disturbances at outer-ionosphere altitudes were measured using the onboard equipment of the DEMETER satellite as it passed through the magnetic flux tube rested on the region of intense generation of artificial ionospheric turbulence.     

Backscattering at the <Emphasis Type="Italic">E</Emphasis> and <Emphasis Type="Italic">F</Emphasis> layers for the vertical incidence of radio waves on the ionosphere

We present the results of the vertical ionosphere sounding at a frequency of 9.02 MHz using the “Sura” facility. Intense backscatter signals from meteor trails were observed at altitudes 100–130 km. Increased background of the scattered signal, which was about − 100 dB with respect to the mirror-reflected signal, was observed at altitudes of about 190–200 and 270–280 km. According to the Doppler-shift measurements of the scattered-signal frequency, the wind velocity was more than 30 m/s at altitudes 100–130 and 270–280 km and was significantly smaller in the altitude range 190–200 km. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 1, pp. 23–27, January 2009.     

PARALLEL ADAPTIVE SIMULATION OF A PLUNGING LIQUID JET

This paper is concerned with three-dimensional numerical simulation of a plunging liquid jet. The transient processes of forming an air cavity around the jet, capturing an initially large air bubble, and the break-up of this large toroidal-shaped bubble into smaller bubbles were analyzed. A stabilized finite element method （FEM） was employed under parallel numerical simulations based on adaptive, unstructured grid and coupled with a level-set method to track the interface between air and liquid. These simulations show that the inertia of the liquid jet initially depresses the pool＇s surface, forming an annular air cavity which surrounds the liquid jet. A toroidal liquid eddy which is subse- quently formed in the liquid pool results in air cavity collapse, and in turn entrains air into the liquid pool from the unstable annular air gap region around the liquid jet.     

Discrete approximation of continuous measures and some applications

We study the best approximation (in the Kantorovich-Rubinshtein metric) of continuous measures on the straight line by measures concentrated at finitely many points. Some algorithm for obtaining these measures is constructed, and the questions of their existence and uniqueness are considered. Applications of the results to some problems of mathematical economics are studied.     

Temporal solitons in magnetooptic and metamaterial waveguides

The important topic of temporal soliton propagation in double-negative metamaterials is discussed with an emphasis upon short pulses that exhibit self-steepening controlled by the frequency dependence of the relative permittivity and permeability. In addition, magnetooptic control is included, leading to some fascinating outcomes that should have practical application. The role of self-steepening, Raman scattering, third-order dispersion and magnetooptics is thoroughly investigated, and it is shown that pulses can acquire signatures in the form of additional velocities with respect to the moving frame. The metamaterial influence upon self-steepening has such a strong frequency dependence that it can be used to combat Raman scattering. The self-steepening can change sign, and it is shown that it is possible to arrange pulses in special switching formats to organise the output times. The metamaterial influence upon bit-patterns admits an important degree of control over multi-pulse interactions, and this is combined with magnetooptics to restore patterns. The role of third-order dispersion is also presented. Again, a control of the pulse behaviour in the neighbourhood where the frequency dependence causes the group-velocity dispersion parameter to approach zero is a direct consequence of using this kind of metamaterial. Finally, a Lagrangian analysis is used to support simulations of the positions of the pulse maxima.     

Kinetics of ultrasonic release of doxorubicin from pluronic P105 micelles

The aim of this research was to measure and model the kinetics of acoustic release and subsequent re-encapsulation of Doxorubicin (DOX) from Pluronic P105 micelles. A fluorescence detection ultrasound exposure chamber was used. Experimental data showed that no significant release was observed when DOX loaded in Pluronic P105 micelles was exposed to ultrasound for less than 0.1 s at a power density of 58 mW/cm² and a frequency of 20 kHz. Above this threshold, the amount of release was shown to increase as the pulse length increased up to 0.6 s. The same experiments showed that it requires at least 0.1 s of no ultrasound for measurable re-encapsulation to occur. Release and re-encapsulation are completed within about 0.6 s of the beginning of the ON and OFF phases of pulsed ultrasound. Several physical models and their corresponding mathematical solutions were analyzed to see which most closely fit the data. The model of zero-order release with first-order re-encapsulation appears to represent data from this polymeric system better than other models. This technique has possible applications in site-specific chemotherapy.     

The role of atmospheric temperature gradients and winds for estimating the energy potential of radio-acoustic sounding systems

We present the theory of radio-acoustic sounding (RAS) of the atmosphere allowing for the dependence on temperature, altitude, and wind. For the case of a linear temperature profile, we obtained expressions for the received signal power. Since the acoustic wave front differs from the sphere if the temperature gradient is allowed for, we can introduce the notion of projector (Fresnel) and Fraunhofer regions. In the Fresnel region, the size of the diffraction spot on the earth is determined by radar antenna dimensions and the received signal power is proportional to z⁻². In the Fraunhofer region, the spot size is greater than the antenna dimensions and the power is proportional to z⁻⁶. The existing RAS facilities work in the projector region. This can be used as a basis for developing a new method of diagnostics of a large-scale inhomogeneous atmospheric structure, including wave disturbances. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 5, pp. 616–625, May, 1997.