135 research outputs found
Dynamics of relativistic solitons
Relativistic solitons are self-trapped, finite size, electromagnetic waves of
relativistic intensity that propagate without diffraction spreading. They have
been predicted theoretically within the relativistic fluid approximation, and
have been observed in multi-dimensional particle in cell simulations of laser
pulse interaction with the plasma. Solitons were observed in the laser
irradiated plasmas with the proton imaging technique as well. This paper
reviews many theoretical results on relativistic solitons in electron-ion
plasmas.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
Nonlinear propagation of light in Dirac matter
The nonlinear interaction between intense laser light and a quantum plasma is
modeled by a collective Dirac equation coupled with the Maxwell equations. The
model is used to study the nonlinear propagation of relativistically intense
laser light in a quantum plasma including the electron spin-1/2 effect. The
relativistic effects due to the high-intensity laser light lead, in general, to
a downshift of the laser frequency, similar to a classical plasma where the
relativistic mass increase leads to self-induced transparency of laser light
and other associated effects. The electron spin-1/2 effects lead to a frequency
up- or downshift of the electromagnetic (EM) wave, depending on the spin state
of the plasma and the polarization of the EM wave. For laboratory solid density
plasmas, the spin-1/2 effects on the propagation of light are small, but they
may be significant in super-dense plasma in the core of white dwarf stars. We
also discuss extensions of the model to include kinetic effects of a
distribution of the electrons on the nonlinear propagation of EM waves in a
quantum plasma.Comment: 9 pages, 2 figure
Single-Cycle High-Intensity Electromagnetic Pulse Generation in the Interaction of a Plasma Wakefield with Nonlinear Coherent Structures
The interaction of coherent nonlinear structures (such as sub-cycle solitons,
electron vortices and wake Langmuir waves) with a strong wake wave in a
collisionless plasma can be exploited in order to produce ultra-short
electromagnetic pulses. The electromagnetic field of a coherent nonlinear
structure is partially reflected by the electron density modulations of the
incident wake wave and a single-cycle high-intensity electromagnetic pulse is
formed. Due to the Doppler effect the length of this pulse is much shorter than
that of the coherent nonlinear structure. This process is illustrated with
two-dimensional Particle-in-Cell simulations. The considered laser-plasma
interaction regimes can be achieved in present day experiments and can be used
for plasma diagnostics.Comment: 11 pages, 11 figures. Submitted to Phys. Rev.
Localized structures of electromagnetic waves in hot electron-positronplasmas
The dynamics of relativistically strong electromagnetic (EM) wave propagation
in hot electron-positron plasma is investigated. The possibility of finding
localized stationary structures of EM waves is explored. It is shown that under
certain conditions the EM wave forms a stable localized soliton-like structures
where plasma is completely expelled from the region of EM field location.Comment: 14 pages, LaTeX, 1 figure can be obtained upon request through email
to [email protected]
Ontogeny of kainate-induced gamma oscillations in the rat CA3 hippocampus in vitro
© 2015 Tsintsadze, Minlebaev, Suchkov. GABAergic inhibition, which is instrumental in the generation of hippocampal gamma oscillations, undergoes significant changes during development. However, the development of hippocampal gamma oscillations remains largely unknown. Here, we explored the developmental features of kainate-induced oscillations (KA-Os) in CA3 region of rat hippocampal slices. Up to postnatal day P5, the bath application of kainate failed to evoke any detectable oscillations. KA-Os emerged by the end of the first postnatal week; these were initially weak, slow (20-25 Hz, beta range) and were poorly synchronized with CA3 units and synaptic currents. Local field potential (LFP) power, synchronization of units and frequency of KA-Os increased during the second postnatal week to attain gamma (30-40 Hz) frequency by P15-21. Both beta and gamma KA- Os are characterized by alternating sinks and sources in the pyramidal cell layer, likely generated by summation of the action potential—associated currents and GABAergic synaptic currents, respectively. Blockade of GABA(A) receptors with gabazine completely suppressed KA-Os at all ages indicating that GABAergic mechanisms are instrumental in their generation. Bumetanide, a NKCC1 chloride co-transporter antagonist which renders GABAergic responses inhibitory in the immature hippocampal neurons, failed to induce KA-Os at P2-4 indicating that the absence of KA-Os in neonates is not due to depolarizing actions of GABA. The linear developmental profile, electrographic features and pharmacological properties indicate that CA3 hippocampal beta and gamma KA- Os are fundamentally similar in their generative mechanisms and their delayed onset and developmental changes likely reflect the development of perisomatic GABAergic inhibition
New longitudinal mode and compression of pair ions in plasma
Positive and negative ions forming the so-called pair plasma differing in sign of their charge but asymmetric in mass and temperature support a new acoustic-like mode. The condition for the excitation of ion sound wave through electron beam induced Cherenkov instability is also investigated. This beam can generate a perturbation in the pair ion plasmas in the presence of electrons when there is number density, temperature, and mass difference in the two species of ions. Basic emphasis is on the focusing of ion sound waves, and we show how, in the area of localization of wave energy, the density of pair particles increases while electrons are pushed away from that region. Further, this localization of wave is dependent on the shape of the pulse. Considering the example of pancake and bullet shaped pulses, we find that only the former leads to compression of pair ions in the supersonic regime of the focusing region. Here, possible existence of regions where pure pair particles can exist may also be speculated which is not only useful from academic point of view but also to mimic the situation of plasma (electron positron asymmetric and symmetric) observed in astrophysical environment
Self-trapping of strong electromagnetic beams in relativistic plasmas
Interaction of an intense electromagnetic (EM) beam with hot relativistic
plasma is investigated. It is shown that the thermal pressure brings about a
fundamental change in the dynamics - localized, high amplitude, EM field
structures, not accessible to a cold (but relativisic) plasma, can now be
formed under well- defined conditions. Examples of the trapping of EM beams in
self-guiding regimes to form stable 2D solitonic structures in a pure e-p
plasma are worked out.Comment: 9 pages, 6 figure
Statistical Theory for Incoherent Light Propagation in Nonlinear Media
A novel statistical approach based on the Wigner transform is proposed for
the description of partially incoherent optical wave dynamics in nonlinear
media. An evolution equation for the Wigner transform is derived from a
nonlinear Schrodinger equation with arbitrary nonlinearity. It is shown that
random phase fluctuations of an incoherent plane wave lead to a Landau-like
damping effect, which can stabilize the modulational instability. In the limit
of the geometrical optics approximation, incoherent, localized, and stationary
wave-fields are shown to exist for a wide class of nonlinear media.Comment: 4 pages, REVTeX4. Submitted to Physical Review E. Revised manuscrip
Stable, synthetic analogs of diadenosine tetraphosphate inhibit rat and human P2X3 receptors and inflammatory pain
© 2016, © The Author(s) 2016.Background: A growing body of evidence suggests that ATP-gated P2X3 receptors (P2X3Rs) are implicated in chronic pain. We address the possibility that stable, synthetic analogs of diadenosine tetraphosphate (Ap4A) might induce antinociceptive effects by inhibiting P2X3Rs in peripheral sensory neurons. Results: The effects of two stable, synthetic Ap4A analogs (AppNHppA and AppCH2ppA) are studied firstly in vitro on HEK293 cells expressing recombinant rat P2XRs (P2X2Rs, P2X3Rs, P2X4Rs, and P2X7Rs) and then using native rat brain cells (cultured trigeminal, nodose, or dorsal root ganglion neurons). Thereafter, the action of these stable, synthetic Ap4A analogs on inflammatory pain and thermal hyperalgesia is studied through the measurement of antinociceptive effects in formalin and Hargreaves plantar tests in rats in vivo. In vitro inhibition of rat P2X3Rs (not P2X2Rs, P2X4Rs nor P2X7Rs) is shown to take place mediated by high-affinity desensitization (at low concentrations; IC50 values 100–250 nM) giving way to only weak partial agonism at much higher concentrations (EC50 values ≥ 10 µM). Similar inhibitory activity is observed with human recombinant P2X3Rs. The inhibitory effects of AppNHppA on nodose, dorsal root, and trigeminal neuron whole cell currents suggest that stable, synthetic Ap4A analogs inhibit homomeric P2X3Rs in preference to heteromeric P2X2/3Rs. Both Ap4A analogs mediate clear inhibition of pain responses in both in vivo inflammation models. Conclusions: Stable, synthetic Ap4A analogs (AppNHppA and AppCH2ppA) being weak partial agonist provoke potent high-affinity desensitization-mediated inhibition of homomeric P2X3Rs at low concentrations. Therefore, both analogs demonstrate clear potential as potent analgesic agents for use in the management of chronic pain associated with heightened P2X3R activation
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