Typical reactions of electronic- and muonic - neutrino production on the electron in a strong magnetic field are discussed in a Weinberg model. The resulting ratio of the corresponding cross sections, which depends on the mass of the charged boson, is, in principle, encouraging as to the possibility of estimating its mass from neutron - star neutrinoluminosity experiments.
Show AbstractA balance equation is derived for determination of the average occupation number of a certain state in the forbidden band when a disordered semiconductor is illuminated by monochromatic light. The method of none quilibrium temporal Green's functions is used for the calculation. Expressions are found for the nonequilibrium single-particle functions. Perturbation theory is used to take the effects of the light into account. The conditions to be imposed on the parameters of the problem for validity of the balance equation are stated. Among other things, it is shown that the mass - operator component that fluctuates with the period of the light can be neglected if the electron - phonon interaction constant is sufficiently small.
Show AbstractAn algorithm for approximate calculation of the Green's function for nonlinear infinite - dimensional dynamic systems on the basis of series expansion of the canonical transformation that converts the nonlinear system to a linear one is described. A nonlinear wave equation with a cubic term is considered as an example.
Show AbstractThe development and testing of a continuous garnet laser with a length of multimode quartz lightguide in its resonator is reported. Optimum conditions for excitation of various transverse modes in a laser with a lightguide resonator are calculated. It is established that strong transverse - index mode selection occurs in the lightguide resonator. It is shown experimentally that small changes in the configuration of the resonator can be made to tune the laser from one transverse mode to another. A single-mode regime corresponding to the selected lightguide mode is then excited in the multimode fiber. The calculated and experimental results indicate that incorporation of a lightguide into a laser resonator is an effective way to excite a single lightguide mode in a multimode fiber.
Show AbstractThe use of a spectral method based on the fast Fourier transformation to investigate the thermal defocusing of light beams in moving media Is described. The effectiveness of the approach in problems of the diffraction and self-action of beams with complex initial intensity distributions is discussed. An example is considered.
Show AbstractThe correlation properties of syncrotron radiation are analyzed in the classical approximation with allowance for the random radial structure of the electron bunch and its relativistic and extended nature. It Is. shown that the classical treatment has limited validity for description of the coherence of hard X-radiation from a synchrotron source. The energy parameters of dynamic scattering (DS) of partially coherent Xray beams In perfect crystals are calculated. The effects of Imperfect coherence on extinction beats and the anomalous passage of waves under DS conditions are analyzed. The increase in the radius of coherent radiation due to the interference nature of DS is calculated. A method for measuring the coherence radius in the X-ray band with use of DS effects is discussed.
Show AbstractThe theory of dynamic scattering in perfect crystals is generalized to the scattering of partially coherent X - radiation. It is shown that, both the temporal and spatial incoherences have a strong influence on the course of the p rincipal effects: extinction beats are moved and anomalous transmission (the Borrman effect) deteriorates. The method of slow amplitudes is used to obtain general results that describe the transformation of the correlation functions of a scattered X-ray beam. It is shown that the coherence radius increases on dynamic scattering (in the X-ray analog of the van Zittert-Zernicke theorem). It is found that the extinction-beat smoothing effect can be used as a basis for measurement of the correlation functions; opportunities for obtaining information on the spatial and temporal correlation functions separately are examined.
Show AbstractThree basic problems that arise in signal resolution are examined: what i is the shortest angular distance between signal sources that can be resolved by a discrete array; what is the largest number of resolvable signal sources of unknown power, and what is the nature of optimum processing to resolve signal sources of unknown power that are close to one another? The results cited indicate that the resolution of an antenna array can exceed the Rayleigh limit and Is determined by the output signal/noise ratio, while the number of signals that can be resolved depends on the number of different spatial frequencies in the aperture; of the array. It is shown that in the Gaussian approximation, the optimum - processing algorithm for resolution reduces to weighted processing of estimates of the cross-correlation moments for signals from all elements of the array and makes it possible to ensure resolution near i the potential limit.
Show AbstractThe angular properties of narrow - band and band optical filters of various types for the visible, UV, and IR regions of the spectrum are investigated. The basic behavior of the properties at angles from 0 to 60° are indicated with the aid of simple relationships and a matrix procedure. Types of systems with inclination - stable transmission-band contours and minimal variation of the characteristics with angle are designated as effectively performing angled multilayer systems.
Show AbstractThe results of an observational study of the structure of boundary layers formed on a density discontinuity are discussed, and the velocity profile in the mixing zone at the density discontinuity is calculated. It is shown that the velocity profile in a mixing layer on a density discontinuity can be calculated with Prandtl's formula for the boundary of a free jet if the variation of average velocity with the local Richardson number is taken into account.
Show AbstractIt is shown how the differential magnetic susceptibility ($H/σ$)($σ^2$), which is an important parameter for study of the nature of magnetic transfor -mations in amorphous and mictomagnetic materials, can be calculated by using the $|{∂σ }/{∂ H}|$_{H}={const}}$ relation. By way of example, calculated temperature curves of |δσ/σH|$(T)_{H=const}$ are presented for dilute ferrites with spinel structure: Li$_{0,2}$Zn$_{0,6}$Fe$_{2,2}$O$_{4}$ и Mg$_{1,5}$FeTi$_{0,5}$O$_{4}$.
Show AbstractExperimental studies of kinematic flow characte ristics and turbulent - fluctuation energy spectra on a model estuarine reach are described. They are compared with measurements made on the channel reach of the model. It is shown that feeding additional sediment into the stream changes the nature of the vertical distribution of turbulence intensity: it decreases in the region near the bottom and increases in the subsurface region.
Show AbstractIt is shown experimentally that detections ensitivity can be raised by 1.5 - 2 orders of magnitude when the response to external microwave radiation is registered in the reflector circuit of the generating klystron as compared to response registration in the resonator or cathode circuit. This is explained by the fact that the reflector - circuit response is as strong as that in the resonator circuit, but the noise current(for shot noise) is 3-4 orders of magnitude lower.
Show AbstractPermittivity measurements on triglycine sulfate single crystals at a frequency of 40 GHz as a function of temperature and specimen geometry are reported. In the neighborhood of the phase - transition temperature, the measures indicated the existence of a specific dependence of permittivity on specimen dimensions in the direction perpendicular to the polaraxis. The possible causes of this behavior are discussed.
Show AbstractA method, is proposed for isolating the excess emission of a thermal nitrogen plasma behind a reflected shock wave. The initial pressure of the test gas was 400 Pa in all experiments. The velocity of the incident shock wave was varied from 7.5 to 8.3 km/sec. The probing light source was a discharge in a capillary tube. A reversal effect was observed at a distance of 1.5 mm from the end of the shock tube, simultaneously at several wavelengths in the 0.42-0.52 micron band. The results indicate that an excess component of nonthermal nature is present under certain conditions in the nitrogen - plasma continuum. The values found for the emission - coefficient ratios - excess over thermal to thermal - are of the order of 0.2-0.5 in the temperature range studied.
Show AbstractThe fundamental limits on the sensitivity of the absolute dilatometer are discussed, and it is shown that temperature coefficients of expansion down to around 10$^{-18}$ deg$^{—1}$ can, in principle, be measured by using a capacitive displacement sensor.
Show AbstractData from the international atmospheric - ozone observing network are used to test for coupling between ozone content and sunspot number. Coupling is observed at latitude 5°N and is absent in other latitude belts.
Show AbstractThe operation of a space - polarization filter (SPF) that suppresses partially scattered dual - path interference in reception of a dual - path signal is analyzed in the presence of additive noise. The efficiency of the SPF is investigated as a function of the characteristics of the signal and interference fields and of the geometric dimensions of the SPF antenna system. The existence of an optimum antenna - system size Xopt≈(0,3—0,8)λ which delivers the highest SPF efficiencies, is established.
Show AbstractIt is shown by the electron - diffraction technique that the type of martensitic structure formed in aquenched Cu$_{68}$—Zn$_{15}$—Al$_{17}$ alloy correlates with the type of ordering in the initial solid solution. M18R martensite forms in a solid solution ordered in the type Fe$_3$Al(DO$_3$), and a metastable Sato structure in the case of solid - solution ordering after the type CsCl(B2). This difference in the structures of the phases that are formed relates to differences in the phonon vibrational spectrum of the original solid solution.
Show AbstractA formula is derived for the nonlinear - damping decrement of Langmuir waves in a weakly turbulent relativistic plasma, and the limit of validity of the corresponding nonrelativistic expression is indicated. The nonrelativistic formula for nonlinear damping applies even at temperatures an order of magnitude lower than the electron rest energy.
Show AbstractThe conditions of focusing of sound by a liquid sphere in water are investigated theoretically, and various patterns observed on variation of the acoustic parameters of the liquid sphere are reported. The angular and radial variations of the acoustic pressure field are investigated at various temperatures. The problem is considered without attention to losses.
Show AbstractAn energy sufficient to form elementary excitations to levels exceeding the vacuum level of the electron fluid is released on recombination of thermal defects in transition metals. The recombination emission that results from this process is responsible for the experimentally observed fine structure of the volt - ampere characteristics of vacuum diodes with single - crystaltungsten and molybdenum electrodes. Medium - waveelectro - magnetic oscillationsoccur in the diode at zero bias.
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