Decay instability of a lower hybrid wave

A study is made of the decay instability of a lower hybrid wave with a finite wave vector (k ₀≠0) and a large amplitude such that the oscillatory velocity of the electrons with respect to the ions cannot be neglected. It is shown that, depending on the angle between the propagation direction of the lower hybrid wave and the external magnetic field and the angle through which the wave is scattered, the decay instability is primarily governed either by the oscillatory electron motion with respect to the ions or by the nonlinear response of the plasma to the lower hybrid wave propagating in it. The role of the nonlinear frequency shift in the saturation of the lower hybrid decay instability is clarified.     

Nonlinear modulation of an extraordinary wave under the conditions of parametric decay

A self-consistent set of Hamilton equations describing nonlinear saturation of the amplitude of oscillations excited under the conditions of parametric decay of an elliptically polarized extraordinary wave in cold plasma is solved analytically and numerically. It is shown that the exponential increase in the amplitude of the secondary wave excited at the half-frequency of the primary wave changes into a reverse process in which energy is returned to the primary wave and nonlinear oscillations propagating across the external magnetic field are generated. The system of ??slow?? equations for the amplitudes, obtained by averaging the initial equations over the high-frequency period, is used to describe steady-state nonlinear oscillations in plasma.     

Nonlinear extraordinary wave in dense plasma

Conditions for the propagation of a slow extraordinary wave in dense magnetized plasma are found. A solution to the set of relativistic hydrodynamic equations and Maxwell’s equations under the plasma resonance conditions, when the phase velocity of the nonlinear wave is equal to the speed of light, is obtained. The deviation of the wave frequency from the resonance frequency is accompanied by nonlinear longitudinal-transverse oscillations. It is shown that, in this case, the solution to the set of self-consistent equations obtained by averaging the initial equations over the period of high-frequency oscillations has the form of an envelope soliton. The possibility of excitation of a nonlinear wave in plasma by an external electromagnetic pulse is confirmed by numerical simulations.     

Improved intracellular delivery of oligonucleotides by square wave electroporation

Prior studies have shown that electroporation is a simple and effective method for the introduction of oligonucleotides (ODN) into cells. In ex vivo bone marrow purging models, electroporation of ODN into cells has been associated with selective killing of human neoplastic cells while sparing hematopoietic stem cells. Prior studies used conventional electroporation methods (i.e., exponential decay) to introduce ODN into cells. Square wave electroporation allows the delivery of a more defined and regulated electrical pulse and is associated with high transfection efficiencies in a variety of systems. The current study was undertaken to determine whether square wave electroporation was more effective than exponential decay electroporation for the delivery of ODN into hematopoietic cells. Using fluorescein-tagged ODN and K562, chronic myelogenous leukemia (CML) cells, higher transfection rates were observed after square wave electroporation. In addition, c-myc antisense ODN were more effective in reducing c-myc protein when introduced by square wave electroporation, as compared with introduction by exponential decay electroporation. Square wave electroporation is thus identified as the optimal method for delivering ODN into hematopoietic cells.     

Reflectionless passage of an electromagnetic wave through an inhomogeneous plasma layer

An exactly solvable model is used as a basis to study the reflectionless passage of a transverse electromagnetic wave through an inhomogeneous plasma containing large-amplitude, small-scale (subwave-length) structures (in particular, opaque regions) that cannot be correctly described by approximate methods. It is shown that, during the reflectionless passage of an electromagnetic wave, strong wave field splashes can occur in certain plasma sublayers. The nonuniform spatial plasma density profile is characterized by a number of free parameters describing the modulation depth of the dielectric function, the characteristic sizes of the structures and their number, the thickness of the inhomogeneous plasma region, and so on. Such plasma density structures are shown to be very diverse when, e.g., a wave that is incident from vacuum propagates without reflection through a plasma layer (wave barrier transillumination). With the cubic nonlinearity taken into account, a one-dimensional problem of the nonlinear transillumination of an inhomogeneous plasma can be solved exactly.     

Resonant excitation of counterpropagating surface waves at a Langmuir wave decay

A study is made of the resonant excitation of surface waves via the decay of a Langmuir wave propagating perpendicularly to a plasma-dielectric interface. The excitation dynamics in the initial stage of decay instability is studied, expressions for the growth rates are obtained, and the threshold amplitude of the Langmuir wave above which parametric instability occurs is found. Published in Russian in Fizika Plazmy, 2007, Vol. 33, No. 4, pp. 346–351. The article was translated by the author.     

Electromagnetic wave in a relativistic magnetized plasma

Results are presented from a theoretical investigation of the dispersion properties of a relativistic plasma in which an electromagnetic wave propagates along an external magnetic field. The dielectric tensor in integral form is simplified by separating its imaginary and real parts. A dispersion relation for an electromagnetic wave is obtained that makes it possible to analyze the dispersion and collisionless damping of electromagnetic perturbations over a broad parameter range for both nonrelativistic and ultrarelativistic plasmas.     

Imaging of dynamic secretory vesicles in living pollen tubes of Picea meyeri using evanescent wave microscopy

Evanescent wave excitation was used to visualize individual, FM4-64-labeled secretory vesicles in an optical slice proximal to the plasma membrane of Picea meyeri pollen tubes. A standard upright microscope was modified to accommodate the optics used to direct a laser beam at a variable angle. Under evanescent wave microscopy or total internal reflection fluorescence microscopy, fluorophores localized near the surface were excited with evanescent waves, which decay exponentially with distance from the interface. Evanescent waves with penetration depths of 60 to 400 nm were generated by varying the angle of incidence of the laser beam. Kinetic analysis of vesicle trafficking was made through an approximately 300-nm optical section beneath the plasma membrane using time-lapse evanescent wave imaging of individual fluorescently labeled vesicles. Two-dimensional trajectories of individual vesicles were obtained from the resulting time-resolved image stacks and were used to characterize the vesicles in terms of their average fluorescence and mobility, expressed here as the two-dimensional diffusion coefficient D2. The velocity and direction of vesicle motions, frame-to-frame displacement, and vesicle trajectories were also calculated. Analysis of individual vesicles revealed for the first time, to our knowledge, that two types of motion are present, and that vesicles in living pollen tubes exhibit complicated behaviors and oscillations that differ from the simple Brownian motion reported in previous investigations. Furthermore, disruption of the actin cytoskeleton had a much more pronounced effect on vesicle mobility than did disruption of the microtubules, suggesting that actin cytoskeleton plays a primary role in vesicle mobility.     

Effect of a strong monochromatic electromagnetic wave with circular polarization on one-dimensional wake waves in plasma

A study is made of the excitation of wake waves by a one-dimensional bunch of charged particles in an electron plasma in the presence of an intense monochromatic pump wave with circular polarization. In the main state (in the absence of a bunch), the interaction between a pump wave and a plasma is described by the Maxwell equations and the nonlinear relativistic hydrodynamic equations for a cold plasma. The excitation of linear waves by a one-dimensional bunch is investigated against a cold plasma background. It is shown that, in a certain range of the parameter values of the bunch, pump wave, and plasma, the amplitude of the excited transverse waves grows as the energy of the bunch particles increases until the relativistic factor of the bunch reaches a certain threshold value above which the transverse wave amplitude becomes essentially independent of the bunch particle energy and grows as the intensity and frequency of the pump wave increase. The amplitude and wavelength of the longitudinal field, which is shown to depend weakly on the energy of the bunch particles, grows with increasing the pump wave intensity.     

Excitation of growing wake waves by an electron bunch in a plasma in an intense pump wave

A study is made of the excitation of wake waves by a one-dimensional electron bunch in an electron plasma in the presence of an intense monochromatic pump wave with circular polarization. In the main state (in the absence of a bunch), the interaction between a pump wave and a plasma is described by Maxwell's equations and the nonlinear relativistic hydrodynamic equations for a cold plasma. The excitation of linear waves by a one-dimensional bunch is investigated against a cold plasma background. It is shown that, in a certain range of parameter values of the bunch, pump wave, and plasma, the excitation is resonant in character and the amplitude of the excited wake waves increases with distance from the bunch.     

Instabilities of a circularly polarized wave with trapped particles in an isotropic plasma

The structure and stability of a transverse electromagnetic wave propagating with a velocity lower than the speed of light in an unmagnetized plasma are considered. The stationary finite-amplitude wave is described by exact solutions to the Vlasov-Maxwell equations. However, unlike the well-known electrostatic analog, the Bernstein-Greene-Kruskal wave, the wave structure is determined to a large extent by the presence of trapped particles with a shear of transverse velocities, without which the existence of waves with a refraction index larger than unity is impossible. It is shown that the main origin of the wave instability is the longitudinal motion of trapped particles relative to the background plasma. Expressions for the growth rates in the main instability regimes are found under definite restrictions on the wave parameters.     

Generation of fast charged particles in plasma by a wave with a stochastically jumping phase

The interaction between charged plasma particles and an electromagnetic wave with a stochastic jumping phase is analyzed by numerical simulations. It is demonstrated that, in the course of interaction, the particle energy can increase by more than one order of magnitude. Optimal conditions for efficient interaction of charged plasma particles with a wave having a stochastically jumping phase are determined. According to the simulation results, substantial acceleration of charged plasma particles by a wave with a stochastically jumping phase takes place both at fixed time intervals between phase jumps and when these intervals are random. The influence of the wave parameters, such as the wave amplitude, the characteristic time interval between phase jumps, and the characteristic magnitude of these jumps, on the acceleration dynamics is analyzed.     

The dissipation of wind wave energy across a fringing reef at Ipan,Guam

Field observations over a fringing reef at Ipan, Guam, during trade wind and tropical storm conditions are used to assess the transformation of sea and swell energy from the fore reef to the shoreline. Parameterizations of wave breaking and bottom friction developed for sandy beaches are found to represent the observed decay in wave energy with an increased friction coefficient. These parameterizations are incorporated into the one-dimensional energy flux balance, which is integrated across the reef to assess the effects of varying tidal range, incident wave height and reef bathymetry on the sea and swell band wave height and wave setup near the shoreline. Wave energy on the reef is strongly depth-limited and controlled by the reef submergence level. Shoreline wave energy increases with incident wave height largely due to the increase in water level from breaking wave setup. Increased tidal levels result in increased shoreline energy, since wave setup is only weakly reduced. The wave height at the shore is shown to be inversely proportional to the width of the reef flat due to dissipation.     

Nonlinear broadband doubling of the extraordinary wave frequency in inhomogeneous magnetoactive plasma

The nonlinear resonance doubling of radio wave frequencies in inhomogeneous plasma is studied as applied to the ionosphere under the conditions of the phase synchronism between an extraordinary pump wave and its second harmonic. The synchronism is not related to plasma resonances, but is determined by the magnetic field and plasma electron density in the transparency region. The generation efficiency of the second harmonic of a transversely propagating wave is calculated for a wide frequency band lying higher than the lower hybrid resonance frequency. It is shown that this effect is physically analogous to the generation of the second harmonic of laser radiation in a nonlinear crystal. The generation efficiency of the second harmonic is determined for inhomogeneous ionospheric plasma in which the synchronism condition is satisfied in a limited frequency range. It is shown that this effect can be used for remote nonlinear diagnostics of the upper ionospheric plasma, in which the characteristic size of the synchronism region can reach several kilometers. It is proposed to use a combination of satellite and ground-based ion probes in experiments on transionospheric probing. Even if the frequency of the wave emitted from the satellite is lower than the critical frequency in the ionosphere, the frequency of its second harmonic can exceed the critical frequency, so that it can be recorded by a ground-based ion probe or a specially designed receiver. The reflected second-harmonic signal can also be detected at the satellite by using a broadband radio-frequency spectrometer.     

Raman amplification of laser pulses near the threshold for plasma wave breaking

Equations are derived for the amplitudes of counter-propagating laser pulses near the threshold for plasma wave breaking, which allow one to describe laser pulses with durations on the order of the plasma oscillation period. In the quasi-monochromatic approximation, they take the form of conventional threewave equations with an additional nonlinearity for the plasma wave. The amplitudes of the amplified laser pulses estimated using these equations agree with results obtained by solving the complete equations. It is shown that Raman amplification of a weak quasi-monochromatic signal (plasma noise) in rarified plasma is significantly suppressed. At the same time, according to numerical simulations, the amplification of laser pulses with durations on the order of the plasma oscillation period is suppressed insignificantly. This result opens new prospects in the application of Raman compression of laser pulses without additional frequency modulation.     

Langmuir wave in weakly inhomogeneous relativistic plasma

The evolution of a Langmuir wave in a weakly inhomogeneous relativistic plasma with a positive density gradient is considered. It is shown that, at relativistic phase velocities, the wave evolution even at the tail of the electron distribution, where it is close to linear in the nonrelativistic case, results in the wave transformation into a hybrid of two waves with different spatial periods. Nonlinear dispersion relations for different stages of the wave evolution are derived.     

Temperature dependence of Ca2+ wave properties in cardiomyocytes: implications for the mechanism of autocatalytic Ca2+ release in wave propagation.

Digital imaging microscopy of fluo-3 fluorescence was used to study the velocity and shape of intracellular Ca2+ waves in isolated rat cardiomyocytes as a function of temperature. Decreasing the temperature from 37 to 17 degrees C reduced the longitudinal wave velocity by a factor of 1.8 and remarkably slowed the decay of [Ca2+]i in the trailing flank of a wave. Using image analysis, rise times, and half-maximum decay times of local Ca2+ transients, which characterize the processes of local Ca2+ release and removal, were determined as a function of temperature. Apparent activation energies for wave front propagation, local Ca2+ release, and local Ca2+ removal were derived from Arrhenius plots and amounted to -23, -28, and -46 kJ/mol, respectively. The high activation energy of Ca2+ removal, which arises from the activity of the sarcoplasmic reticulum (SR) Ca2+ ATPase, relative to those of longitudinal wave propagation and local Ca2+ release excludes the hypothetical mechanism of regenerative "spontaneous Ca2+ release," in which Ca2+ that has been taken up from the approaching wavefront triggers Ca2+ release at a luminal site of the SR. It is consistent, however, with the hypothesis that Ca2+ wave propagation is based on Ca(2+)-induced Ca2+ release where Ca2+ triggers release on the cytosolic face of the SR.     

Evolution of a Langmuir wave in a weakly inhomogeneous plasma in a longitudinal electric field

The spatial evolution of a Langmuir wave excited by external sources in a weakly inhomogeneous electron plasma in a longitudinal electrostatic field is considered. It is shown that, in a longitudinal electrostatic field, a Langmuir wave can only be amplified in an inhomogeneous plasma provided that the current of trapped electrons exceeds that of untrapped electrons. In this case, as the wave propagates through the inhomogeneous region where its phase velocity increases, some untrapped electrons become trapped in the wave potential wells. As a result, the current of trapped electrons increases and the wave is amplified. Moreover, in the regions where the bulk electrons are localized, the minima of the wave are amplified to a greater extent than its maxima.     

Formation of a Density Bump in a Collisionless Electrostatic Shock Wave During Expansion of a Hot Dense Plasma into a Cold Rarefied One

Plasma Physics Reports - Formation and evolution of a density bump in an electrostatic shock wave during decay of a discontinuity in a plasma characterized by the presence of hot electrons and a...     

Nonaxisymmetric wave propagation through a viscous fluid in a viscoelastic tube.

The eigensolution of a nonaxisymmetric linear wave propagation through a viscous fluid in a viscoelastic pipe is obtained. The solution can serve as a foundation for studying nonaxisymmetric blood flow. Some leading eigenvalues for two special cases are computed. The result shows that nonaxisymmetric modes decay fast during their propagation.