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Calculations of the spectrum of eigen oscillations of an inhomogeneous ultracold plasma are presented both in the absence and in the presence of charge imbalance. The collective modes of these plasma oscillations are recorded in experiments as absorption resonances of a radio frequency electric field. It is shown that in the presence of friction of the electronic component, a discrete spectrum of plasma eigen oscillations is formed. The dependence of the frequency of these resonances on the plasma expansion time in the presence of a charge imbalance is obtained. There is good agreement with the experiments of different authors. [ABSTRACT FROM AUTHOR]

We discuss the influence of micro- and macro-fields on spectral lines of ions as it takes place for spatially inhomogeneous plasma. A distribution function of an electric field is obtained. The function accounts for inhomogeneity and non-neutrality of plasma. The results of calculations of this function for various regimes are presented. Experimental results for ultracold plasma are used to compare theory with experiment. Dependence of the absorption coefficient on the function is shown. These results may be useful for diagnostics of various types of plasmas. One of the methods of plasma diagnostics is the analysis of the influence of its electric field on the shape of the spectral lines of atoms and ions (the Stark effect). [ABSTRACT FROM AUTHOR]

We report the direct molecular dynamics simulation results of the ultracold two-component plasma expansion. Interaction between charges is described by Coulomb's law. The number of particles varies from 103 to 105. It is shown in this article that the expansion of the plasma begins with the evaporation of some of the electrons and with the transfer of their kinetic energy to the energy of the electric field. After that, the field increases the kinetic energy of the ions. An important result is the detection of the supersonic ion wave formation. On the basis of the calculation results, equations and self-similar solutions are obtained. General dependences on plasma parameters are determined, which are compared with experimental data. [ABSTRACT FROM AUTHOR]

In this Reply, we respond to the Comment by Schlitters et al. on our recent work [Phys. Rev. E 108, 045209 (2023)10.1103/PhysRevE.108.045209], where we present simulation results of ultracold Sr plasma expansion in a quadrupole magnetic field using a molecular-dynamics method. In the Comment, Schlitters et al. present their experimental results, some of which, from their point of view, contradict our simulation results and others that confirm the experiments of Gorman et al. [Phys. Rev. Lett. 126, 085002 (2021)10.1103/PhysRevLett.126.085002] and our results. In addition, Schlitters et al. also provide results that were not described in our work. Here we show that there is not a contradiction but a misunderstanding of our results. This is due to the fact that simulations allow the use of processing methods that are difficult to obtain in experiment. We also present different simulation results related to expansion velocity variations that reflect the experimental results of Schlitters et al. and provide an explanation for the origin of these variations.

We present simulation results of ultracold Sr plasma expansion in a quadrupole magnetic field by means of molecular dynamics. An analysis of plasma evolution influenced by a magnetic field is given. Plasma confinement time behavior under variation of magnetic field strength is estimated. Similarity of the time dependence of the concentration and distribution of ion velocities against the parameters of the plasma and magnetic field is established. Simulation results are in agreement with the experimental ones.

We present the results of a direct simulation of the expansion of a two-component ultracold plasma for various numbers of particles, densities, and electron temperatures. A description of the expansion process common to all plasma parameters is given. After the escape of fast electrons from the plasma cloud, the excess positive charge is localized at the outer boundary, in a narrow layer. This layer has a characteristic front shape with a sharp drop in the charge concentration. The charged layer retains the remaining electrons during the entire expansion process. As the plasma expands, the speed of movement of the charged layer becomes constant and significantly exceeds the sonic speed of ions. In addition, the dependence of the radial velocity of ions on the radius acquires a self-similar character long before the final stage of expansion. Based on the calculation results, equations and self-similar solutions are obtained. General dependencies on plasma parameters are determined, which are compared with experimental data.

Conventional controlled lung ventilation (CLV) with positive end expiratory pressure (PEEP) (Con CLV), combined high-frequency CLV (Com HF CLV) and intermittent high-frequency CLV with PEEP (Int HF CLV) have been performed in 43 patients with parenchymatous acute respiratory failure (ARF). It has been established that Int HF CLV significantly increases PaO2 in patients with focal damages of the lung parenchyma and effective compliance (Ceff) > 0.033 l/cm H2O. Com HF CLV increases significantly PaO2 and lung compliance in patients with disseminated lung damages and Ceff < 0.030 l/cm H2O and has marked consequences. Different efficacy of various types of HF CLV under study may be to some extent accounted for by different intraalveolar maximum pressure, which (as it has been shown on the lung model) is higher in Com HF CLV and lower in Con CLV and Int HF CLV.

Jet high-frequency artificial ventilation produces oscillations of some parts of the chest wall, which in its turn transmits oscillations to the lung parenchyma. It results in the mix-up of the gas in the alveolar space, which leads to the increase in the gradient of oxygen concentration on the alveolar membranes, thus, augmenting oxygen saturation of the blood. The effect is the same when oscillation artificial ventilation is performed, owing to the provocation of the oscillations amplified by the resonance in the natural acoustic circuit, formed by the adjacent parts of the chest and lung parenchyma. Derangement of the exudative adhesion to the bronchi epithelial tissue intensifies gas exchange, when the oscillations are generated in the lungs. It facilitates the removal of the exudate and lets the air into the previously obstructed parts of the lungs. Clinical studies confirm the effect of the increase in the blood oxygenation (by average 20%) at the feeding air column by pneumatic oscillations in the range of 65 Hz, when traditional artificial ventilation is performed.