Long-term evolution of the three-dimensional structure of string-fluid complex plasmas in the PK-4 experiment.

Microparticle suspensions in a polarity-switched discharge plasma of the Plasmakristall-4 facility on board the International Space Station exhibit string-like order. As pointed out in [Phys. Rev. Research 2, 033314 (2020)2643-156410.1103/PhysRevResearch.2.033314], the string-order is subject to evolution on the timescale of minutes at constant gas pressure and constant parameters of polarity switching. We perform a detailed analysis of this evolution using the pair correlations and length spectrum of the string-like clusters (SLCs). Average exponential decay rate of the SLC length spectrum is used as a measure of string order. The analysis shows that the improvement of the string-like order is accompanied by the decrease of the thickness of the microparticle suspension, microparticle number density, and total amount of microparticles in the field of view. This suggests that the observed long-term evolution of the string-like order is caused by the redistribution of the microparticles, which significantly modifies the plasma conditions.

Plasmakristall-4: New complex (dusty) plasma laboratory on board the International Space Station.

New complex-plasma facility, Plasmakristall-4 (PK-4), has been recently commissioned on board the International Space Station. In complex plasmas, the subsystem of µm-sized microparticles immersed in low-pressure weakly ionized gas-discharge plasmas becomes strongly coupled due to the high (103-104 e) electric charge on the microparticle surface. The microparticle subsystem of complex plasmas is available for the observation at the kinetic level, which makes complex plasmas appropriate for particle-resolved modeling of classical condensed matter phenomena. The main purpose of PK-4 is the investigation of flowing complex plasmas. To generate plasma, PK-4 makes use of a classical dc discharge in a glass tube, whose polarity can be switched with the frequency of the order of 100 Hz. This frequency is high enough not to be felt by the relatively heavy microparticles. The duty cycle of the polarity switching can be also varied allowing to vary the drift velocity of the microparticles and (when necessary) to trap them. The facility is equipped with two videocameras and illumination laser for the microparticle imaging, kaleidoscopic plasma glow observation system and minispectrometer for plasma diagnostics and various microparticle manipulation devices (e.g., powerful manipulation laser). Scientific experiments are programmed in the form of scripts written with the help of specially developed C scripting language libraries. PK-4 is mainly operated from the ground (control center CADMOS in Toulouse, France) with the support of the space station crew. Data recorded during the experiments are later on delivered to the ground on the removable hard disk drives and distributed to participating scientists for the detailed analysis.

Assessing particle kinematics via template matching algorithms.

Template matching algorithms represent a viable tool to locate particles in optical images. A crucial factor of the performance of these methods is the choice of the similarity measure. Recently, it was shown in [Gao and Helgeson, Opt. Express 22 (2014)] that the correlation coefficient (CC) leads to good results. Here, we introduce the mutual information (MI) as a nonlinear similarity measure and compare the performance of the MI and the CC for different noise scenarios. It turns out that the mutual information leads to superior results in the case of signal dependent noise. We propose a novel approach to estimate the velocity of particles which is applicable in imaging scenarios where the particles appear elongated due to their movement. By designing a bank of anisotropic templates supposed to fit the elongation of the particles we are able to reliably estimate their velocity and direction of motion out of a single image.

Particle flows in a dc discharge in laboratory and microgravity conditions.

We describe a series of experiments on dust particles' flows in a positive column of a horizontal dc discharge operating in laboratory and microgravity conditions. The main observation is that the particle flow velocities in laboratory experiments are systematically higher than in microgravity experiments for otherwise identical discharge conditions. The paper provides an explanation for this interesting and unexpected observation. The explanation is based on a physical model, which properly takes into account main plasma-particle interaction mechanisms relevant to the described experimental study. A comparison of experimentally measured particle velocities and those calculated using the proposed model demonstrates reasonable agreement, both in laboratory and microgravity conditions, in the entire range of discharge parameters investigated.

[Stepwise treatment of a patient with seven bilateral cerebral aneurysms].

This case report describes successful multistage combined treatment of a female patent with seven bilateral cerebral aneurysms.

[Three years experience of catheter treatment of patients with acute coronary syndrome in conditions of 24-hour work of endovascular service].

In this work we have summarized 3-years experience of the treatment of acute coronary syndrome with the use of endovascular methods and presented organizational basis allowing to realize 24-hour work of the endovascular service, and algorithm of examination and treatment of patients admitted with diagnosis of acute coronary syndrome. During the analyzed period invasive interventions were carried out in 1417 patients (transluminal angioplasty - in 93, angioplasty with stenting - in 1356 patients) with mean door to balloon time 37.7 min. For stenting we used 925 standard metal stents and 584 drug eluting stents. Coronary artery bypass surgery was performed in 150 patients. Severe complications during hospital stay developed in 3% of patients. Fifteen patients died, 14 of them were admitted in a state of cardiogenic shock. Repeat coronary angiography in remote period was fulfilled in 170 patients with recurrence of angina. Restenoses were found in 31.2% of these patients, predominantly in those with implanted standard metal stents.

Formation of a boundary-free dust cluster in a low-pressure gas-discharge plasma.

An attraction between negatively charged micron-sized plastic particles was observed in the bulk of a low-pressure gas-discharge plasma under microgravity conditions. This attraction had led to the formation of a boundary-free dust cluster, containing one big central particle with a radius of about 6 microm and about 30 1 microm-sized particles situated on a sphere with a radius of 190 microm and with the big particle in the center. The stability of this boundary-free dust cluster was possible due to its confinement by the plasma flux on the central dust particle.

Particle charge in the bulk of gas discharges.

An experimental determination of particle charge in a bulk dc discharge plasma covering a wide range of neutral gas pressures, was recently reported [S. Ratynskaia, Phys. Rev. Lett. 93, 085001 (2004)]. The charges obtained were several times smaller than the predictions of collisionless orbital motion limited theory. This discrepancy was attributed to the effect of ion-neutral collisions. In the present paper a more detailed description of this experiment is provided and additional experimental results obtained with particles of different sizes are reported. The measurements are compared with molecular dynamics simulations of particle charging for conditions similar to those of the experiment, with other available experimental data on particle charge in the bulk of gas discharges, and with a simple analytical model accounting for ion-neutral collisions. All the considered evidence indicates that ion-neutral collisions represent a very important factor, which significantly affects (reduces) the particle charge under typical discharge conditions.

Micron-sized particle-charge measurements in an inductive rf gas-discharge plasma using gravity-driven probe grains.

A method for measuring the interactions of charged dust particles within a three-dimensional dust cloud in a plasma is presented. The measurements have been performed with the help of gravity-driven heavy charged probe particles, which moved through a dust cloud levitating at the diffuse edge of an inductively coupled rf discharge plasma. Assuming a screened Coulomb potential surrounding each particle, both the particle charge and the effective screening length were calculated from an analysis of the elastic particle interactions for 20, 30, and 50 Pa of neon pressure. The basic parameters of the bulk discharge plasma have been diagnosed with a Langmuir probe to compare the experimental data with those deriving from different theoretical approaches. The observed discrepancies are discussed.

Experimental determination of dust-particle charge in a discharge plasma at elevated pressures.

The charge of dust particles is determined experimentally in a bulk dc discharge plasma in the pressure range 20-100 Pa. The charge is obtained by two independent methods: one based on an analysis of the particle motion in a stable particle flow and another on an analysis of the transition of the flow to an unstable regime. Molecular-dynamics simulations of the particle charging for conditions similar to those of the experiment are also performed. The results of both experimental methods and the simulations demonstrate good agreement. The charge obtained is several times smaller than predicted by the collisionless orbital motion theory, and thus the results serve as an experimental indication that ion-neutral collisions significantly affect particle charging.

Photochemical effect in two-photon laser-induced fluorescence detection of carbon monoxide in hydrocarbon flames.

The CO formation as a result of the CO(2) photodissociation at 230.08 nm was observed by using the two-photon laser-induced fluorescence (LIF) method. The measurements were performed in a propane-air combustion product flow and in mixtures of CO(2) and O(2). The temperature dependence of the fluorescence signal caused by CO molecules, produced in the photodissociation of CO(2) molecules under the action of laser radiation at a wavelength of 230.08 nm, was measured at temperatures ranging from 1300 to 2000 K. It is shown that consideration of CO(2) photodissociation under the action of the probing radiation is necessary when one applies the two-photon LIF method for the measurement of small CO concentrations in high-temperature gas mixtures containing CO(2). As an example, a correction is given of the CO concentration profiles measured by the LIF method in the combustion product flow around a cooled metallic plate.

[Effects of prolonged low-intensity radiofrequency radiation in cm-range on the development of subcutaneously grafted Ehrlich's adenocarcinoma]. / Vliianie dlitel'nogo nizkointensivnogo vozdeistviia radiochastotnogo izlucheniia santimetrovogo diapazona na podkozhno privituiu adenokartsinomu Erlikha.

White mongrel male mice with subcutaneously grafted Ehrlich adenocarcinoma were exposed at week intervals to three three-day sessions of low-intensity (5 microWt/cm2) super short wave-therapy from two generators of oscillating frequency in the range of 2-18 GHz. As a result of treatment, the increase in tumour size was diminished, and the probability of its reverse development was increased, with animal lethality being decreased. During a month the recovery was increased from 0 to 50% in the first experiment and from 38.3% to 60% in the second. In the third experiment, the recurrence during a 72-day observation period was showed in none of the recovered mice.

[Radioprotective effect of low-intensity radio-frequency centimeter-band waves in lethal gamma irradiation]. / Radioprotektornoe deistvie nizkointensivnogo radiochastotnogo izlucheniia santimetrovogo diapazona voln pri smertel'nom gamma-obluchenii.

Primary investigations have been carried out to determine whether low-intensity EMR of a cm range exerts the radioprotective effect. Prior to gamma-irradiation with doses LD100/30 and LD60/30 mice were exposed for 23 h to 2-8 GHz microwaves with a swing frequency of 12-14 Hz, at energy flow density of 5 +/- 1.5 mu Wt/cm2. Survival and time of death of mice were registered during a month. With absolutely lethal doses of gamma-irradiation, the application of SHF EMR delayed the time of animal death by 2.8-4.2 days and led in one of the experiments to 20% survival of mice. With doses in non-absolutely lethal range, the pretreatment of mice with EMR increased the survival by 20% in two experiments.

[Modification of lethal radiation injury in mice by postradiation exposure to low-intensity centimeter-band radio frequency waves]. / Modifikatsiia letal'nogo radiatsionnogo porazheniia myshei postradiatsionnym nizkointensivnym radiochastotnym izlucheniem santimetrovogo diapazona.

A clearly pronounced modification of acute radiation injury of mice has been obtained by prolonged action (for up to 23 hours) of low-intensity (5 +/- 1.5 mu Wt/cm2) radiofrequency radiation in the ranges of 2-8, 8-18 and 19-27 GHz with a swing frequency of 12-14 Hz, applied immediately after exposure to lethal dose of gamma-radiation. Survival of mice and average life duration of killed mice were increased.