TOPOLOGICAL DEFECTS AND HIGHEST ENERGY COSMIC AND GAMMA RAYS

In this paper we review the hypothesis that a considerable part of the cosmic ray flux observed above about 10^{19}\eV may be produced by decaying or annihilating topological defects left over from phase transitions in the early universe at grand unification energy scales (\approx10^{16}\GeV). Possible signatures of cosmic ray producing defect models are discussed which could be tested experimentally in the near future. We thereby focus on model independent universal spectral properties of the predicted particle fluxes.Comment: 11 pages of uuencoded compressed postscript, including 3 figures, to be published in Space Science Reviews

On limit behavior of a solution to boundary value problem in a plane sector

Authors study a certain boundary value problem in Sobolev-Slobodetskii spaces with integral condition in a plane excluding a ray from origin. Using auxiliary problem in outside of a convex cone and the wave factorization concept, we construct a general solution and consider transfer to limit boundary value problem. It was shown that limit boundary value problem can be solvable only if the boundary function satisfies to a certain singular functional equatio

Self-consistent model of a positive column in a glow discharge under free-flight and collisional regimes of charged-particle motion.

We consider the nonlocal theory of a positive column in a glow discharge in two cases, where the mean free path of charged particles is either greater than the discharge tube radius (the free-flight regime) or much less than the radius (the collisional regime). The great bulk of electrons, which determines the density and the discharge current in the axial direction, appears to be trapped by the radial field of a positive column. The electron flux to the wall, which compensates for the ionization in a volume, is determined by fast electrons with energies of the order of wall potential, which are able to leave in a loss cone. The electron kinetic equation, which is solved by averaging it over the radial transits for the two regimes considered, permits us to obtain the electron density and the ionization rate. Thus, we develop the theory of a positive column for the non-Boltzmann electron distribution in the radial field. Under the free-flight regime, this theory is developed by analogy with the Langmuir-Tonks one. Under the collisional regime, the spatial distribution of the potential is obtained from the ion motion equation with the ambipolar diffusion coefficient, which depends on the radial coordinate. The concrete calculations are carried out for the xenon discharge under the free-flight and collisional regimes. The theoretical calculations are compared with the results of experiments on the measurements of the electric field and the densities of metastable and resonance xenon atoms

Parametric Collective Phenomena during the Propagation of Polychromatic Laser Pulses in an Optically Dense Resonant Medium without Population Inversion

We experimentally and theoretically study the interaction of broadband polychromatic laser pulses with an optically dense resonant extended medium without population inversion. Experimental (probe field-pumping beam) measurements of the transmission and amplification spectra were carried out in the plasma of a positive neon glow-discharge column containing a large number of metastable atoms. The strong coupling in the field-matter system and the collective behavior of the atomic system in a resonant field were attributable to a high (∼10 12 cm -3) density of atoms at the lower (metastable) level of the optical transitions under consideration and to a relatively low intensity of the interacting laser beams. We observed a broadband weakening of the probe field in the absence of pumping and its strengthening in the line wings in the presence of a strong field. We develop a theoretical model for the parametric amplification of collective interactions in dense extended media based on the solution of the semiclassical Maxwell-Bloch equations for conditions under which the pumping field does not destroy the dipole interaction between atoms through probe-field photons. © 2002 MAIK "Nauka/Interperiodica"

Neural Network Calculator of Rubber Characteristics with Improved Properties

A new technique for the use of Artificial Neural Networks (ANN) for the generalization and visual presentation of the results of experimental studies is proposed. The possibility of using ANN for cases for which their use was previously considered impossible is shown. ANN calculators have been created that summarize the results of experimental studies on the effect of trans-polynorbornene and basalt fiber on the characteristics of a rubber compound based on general-purpose rubbers (isoprene SKI-3, butadiene-methylstyrene SKMS-30ARK and butadiene SKD), which also contained vulcanizing agents (N, N′-dithiodimorpholine, thiuram D), vulcanization accelerators (sulfenamide C, 2-mercapto-benzothiazole), vulcanization activators (zinc white, stearic acid), emollients (industrial oil I-12A, rosin) and antioxidants (acetonanil H, diaphene FP). The rubber mixture was prepared on laboratory rollers LB 320 160/160. Subsequently, the rubber mixture was vulcanized in a P-V-100-3RT-2-PCD press. For the resulting vulcanizates, the physical and mechanical properties and their changes were determined after daily exposure to air and in a standard SZhR-1 hydrocarbon liquid at a temperature of 100 °C. We also studied the change in the mass of vulcanizates after exposure to industrial oil I-20A and water. The dynamic parameters (modulus of elasticity and mechanical loss tangent) of vulcanizates, which characterize their noise and vibration-absorbing properties, were studied on a Metravib VHF 104 dynamic mechanical analyzer. The created ANN calculators allow solving a direct problem - interpolating the dependences of all rubber characteristics on the content of basalt fiber, as well as solving inverse problems - to determine the required content of basalt fiber to create rubber with the required performance properties. The autonomous executable modules of the calculators developed by ANN were made and can be passed to everyone

Mechanical properties of amorphous alloys ribbons prepared by rapid quenching of the melt after different thermal treatments before quenching

The mechanical properties of amorphous alloy are greatly influenced by the thermal treatment of its melt before rapid quenching. The strength and the fracture toughness of some amorphous alloys obtained after melt beating above the melt critical temperature T-CR are essentially higher than those obtained from melts that were not heated above T-CR. This difference is considered to be caused by changes in the melt atomic structure under heating above T-CR. (C) 1997 Elsevier Science S.A

Nonstationary Parametric Amplification of Polychromatic Radiation Propagating in an Extended Absorbing Resonant Medium

Amplification spectra for an optically dense resonator extended medium interacting with two-wave polychromatic laser radiation was performed. It was shown that, depending on the pumping power, its spectral composition and the characteristics of the medium, different field-substance interaction regimes were realized. The results showed that the amplification spectra of an optically dense medium reproduced all types of spectra inherent to the effect of so-called condensation of an oscillation spectrum under intracavity pumping of an optically dense medium

Coherent Light Sources under strong field-matter coupling in an optically dense resonant medium without population inversion

A new approach in the development of coherent radiation sources has been studied both theoretically and experimentally. The approach is based on the parametric excitation of collective modes of the field + matter system in two-level resonant optically dense media with strong coupling between the field and matter. Copyright © 2005 by Astro, Ltd