1,703 research outputs found
Generation of powerful terahertz emission in a beam-driven strong plasma turbulence
Generation of terahertz electromagnetic radiation due to coalescence of
upper-hybrid waves in the long-wavelength region of strong plasma turbulence
driven by a high-current relativistic electron beam in a magnetized plasma is
investigated. The width of frequency spectrum as well as angular
characteristics of this radiation for various values of plasma density and
turbulence energy are calculated using the simple theoretical model adequately
describing beam-plasma experiments at mirror traps. It is shown that the power
density of electromagnetic emission at the second harmonic of plasma frequency
in the terahertz range for these laboratory experiments can reach the level of
1 with 1% conversion efficiency of beam energy losses to
electromagnetic emission
Second harmonic electromagnetic emission of a turbulent magnetized plasma driven by a powerful electron beam
The power of second harmonic electromagnetic emission is calculated for the
case when strong plasma turbulence is excited by a powerful electron beam in a
magnetized plasma. It is shown that the simple analytical model of strong
plasma turbulence with the assumption of a constant pump power is able to
explain experimentally observed bursts of electromagnetic radiation as a
consequence of separate collapse events. It is also found that the
electromagnetic emission power calculated for three-wave interaction processes
occurring in the long-wavelength part of turbulent spectrum is in
order-of-magnitude agreement with experimental results
Nonlinear dispersion of stationary waves in collisionless plasmas
A nonlinear dispersion of a general stationary wave in collisionless plasma
is obtained in a non-differential form from a single-particle
oscillation-center Hamiltonian. For electrostatic oscillations in nonmagnetized
plasma, considered as a paradigmatic example, the linear dielectric function is
generalized, and the trapped particle contribution to the wave frequency shift
is found analytically as a function of the wave amplitude .
Smooth distributions yield , as usual. However,
beam-like distributions of trapped electrons result in different power laws, or
even a logarithmic nonlinearity, which are derived as asymptotic limits of the
same dispersion relation
Infestation by Ips amitinus (Eichhoff, 1872), Its Associated Fungi, and Butt Rots in Stands of Pinus sibirica in South-Western Siberia
: In 2019, the bark beetle Ips amitinus (native to central Europe) was identified in southwestern Siberia at a distance exceeding 2500 km east of its previously known easternmost location in the European part of Russia. In Siberia, its invasive populations are characterised by high abundance and harmfulness. Here, I. amitinus accomplishes primary attacks on standing vital trees of Pinus sibirica with a lethal outcome. This invasion has already resulted in massive dieback in stands of pine over a large geographic territory. By, 2021, the invaded area was estimated to cover at least 31,200 km2 . The objectives of this study were to investigate fungi associated with/vectored by I. amitinus in its invasive area in south-western Siberia and wood decay fungi that cause root and butt rots to P. sibirica. This led to the following conclusions: (i) DNA analysis of sixty adult beetles of Ips amitinus collected from P. sibirica in south-west Siberia revealed the presence of 143 fungal taxa; (ii) species richness was significantly higher in beetles collected from dead branches than from (more recently infested) dying branches; (iii) fungal communities were >90% dominated by yeasts, among which the most common were Nakazawaea holstii, Kuraishia molischiana, and N. ambrosiae; (iv) entomopathogenic Beauveria bassiana s.l. was the most common fungus isolated from dead/mycosed beetles of I. amitinus, followed by Lophium arboricola and four Ophiostoma spp.; and (v) Heterobasidion parviporum was the most common decay fungus detected, which was causing heart rot in stems of P. sibirica
Methodological basis of the regional systems socio-economic profile using survey method
The author's method of creating social and economic portrait of regional systems is offered. In its basis assessment by experts of economic indicators system allowing to open comprehensively tendencies of the region economic development is offered. Handling of results is performed by a ball method with use of concordance coefficient and Pearson's criterion. The technique also includes population poll with use of economic activity indexes: consumer moods, usefulness of conditions for large purchases, independence worthiness, manpower mobility. Their use shows forecasts of the population concerning level of living and economy of the region in general, consumer opportunities, labor potential and migratory moods. In total use of methods of expert poll and the population allow to constitute a social and economic portrait of the region on the basis of which to develop strategies of its development
Recombination limited energy relaxation in a BCS superconductor
We study quasiparticle energy relaxation at sub-kelvin temperatures by
injecting hot electrons into an aluminium island and measuring the energy flux
from electrons into phonons both in the superconducting and in the normal
state. The data show strong reduction of the flux at low temperatures in the
superconducting state, in qualitative agreement with the presented
quasiclassical theory for clean superconductors. Quantitatively, the energy
flux exceeds that from the theory both in the superconducting and in the normal
state, possibly suggesting an enhanced or additional relaxation process
Parameters of Hardening of Platinum-Palladium Alloys with Alloy Additions in View of Baushinger Effect
- …