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We study the onset and characteristics of vortices in complex (dusty) plasmas using two-dimensional simulations in a setup modeled after the PK-3 Plus laboratory. A small number of microparticles initially self-arranges in a monolayer around the void. As additional particles are introduced, an extended system of vortices develops due to a non-zero curl of the plasma forces. We demonstrate a shear-thinning effect in the vortices. Velocity structure functions and the energy and enstrophy spectra show that vortex flow turbulence is present that is in essence of the "classical" Kolmogorov type., 5 pages, 6 figures

Implications of the recently discovered effect of channeling of upstream extra particles for transport phenomena in a two-dimensional plasma crystal are discussed. Upstream particles levitated above the lattice layer and tended to move between the rows of lattice particles. An example of heat transport is considered, where upstream particles act as moving heat sources, which may lead to anomalous heat transport. The average channeling length observed was 15–20 interparticle distances. Other features of the channeling process are also reported.

We study effects of the particle-wake interactions on the dispersion and polarization of dust lattice wave modes in two-dimensional plasma crystals. Most notably, the wake-induced coupling between the modes causes the branches to "attract" each other, and their polarizations become elliptical. Upon the mode hybridization the major axes of the ellipses (remaining mutually orthogonal) rotate by $45^\circ$. To demonstrate importance of the obtained results for experiments, we plot spectral densities of the longitudinal and transverse waves revealing distinct fingerprints of the mixed polarization. Furthermore, we show that at strong coupling the hybrid mode is significantly shifted towards smaller wave numbers, away from the border of the first Brillouin zone (where the hybrid mode is localized for a weak coupling)., Comment: 10 pages, 6 figures

The Debye shielding of a charge immersed in a flowing plasma is an old classic problem in plasma physics. It has been given renewed attention in the last two decades in view of experiments with complex plasmas, where charged dust particles are often levitated in a region with strong ion flow. Efforts to describe the shielding of the dust particles in such conditions have been focused on the homogeneous plasma approximation, which ignores the substantial inhomogeneity of the levitation region. We address the role of the plasma inhomogeneity by rigorously calculating the point charge potential in the collisionless Bohm sheath. We demonstrate that the inhomogeneity can dramatically modify the wake, making it non-oscillatory and weaker.

Plasma therapy is a rapidly developing area of medicine, which is based on nonthermal effects of nonequilibrium ‘cold’ gas plasma. The nonthermal plasma (NTP) exerts proven microbicidal and sporicidal effects while it has relatively low toxicity for mammalian tissues. The review discusses mechanisms underlying the therapeutic effects of the ‘cold’ plasma and its selectivity toward prokaryotes. The applications of NTP in medicine and hygiene are considered.

We present a heuristic study on the correlations between harmonic space phase information and higher-order statistics. Using the spherical full-sky maps of the cosmic microwave background as an example, we demonstrate that known phase correlations at large spatial scales can gradually be diminished when subtracting a suitable best-fit (Bianchi-)template map of a given strength. The weaker phase correlations are attended by a vanishing signature of anisotropy when measuring the Minkowski functionals and scaling indices in real space with the aid of surrogate maps being free of phase correlations. Those investigations can open a new road to a better understanding of signatures of non-Gaussianities in complex spatial structures, especially by elucidating the meaning of Fourier phase correlations and their influence on higher-order statistics.

Cold atmospheric plasma (CAP) based on the Surface Micro-Discharge (SMD) technology was investigated for inactivation of different bacteria and endospores. The used technique was developed to serve as an alternative method for the decontamination of spacecraft components based on the COSPAR planetary protection policy where currently the dry heat microbial reduction method is the only applicable way to satisfy the required demands. However it is known, that dry heat can thermally damage sophisticated components installed on the device. Therefore, the development of a low temperature sterilization system is one of the high priority issues for upcoming space missions in the extraterrestrial field. In the study presented here, the vegetative bacteria Escherichia coli and Deinococcus radiodurans and several types of bacterial endospores – including Bacillus atrophaeus, Bacillus safensis, Bacillus megaterium, Bacillus megaterium 2c1 and Bacillus thuringiensis E24 – were inactivated by exposing them indirectly i.e. only to the reactive gases produced by the SMD electrode at room temperature. The results showed a 5 log inactivation for E. coli after 10 min of exposure. In contrast D. radiodurans proved to be more resistant resulting in a reduction of 3 log after exposure of 30 min. More than 6 log reductions were achieved for B. safensis, B. megaterium and B. megaterium 2c1 after 90 min of exposure. Furthermore the applicability of the used CAP system for spacecraft decontamination according to the planetary protection policy was investigated. This included also the investigation of the inactivation homogeneity by the plasma gas, the control of the temperature at the area of interest, the measurement of the O3 density in the treatment region and the detailed investigation of the effects of the exposure on different materials.

The dust detector system onboard Galileo records dust impacts in circumjovian space since the spacecraft has been injected into a bound orbit about Jupiter in December 1995. This is the sixth in a series of papers dedicated to presenting Galileo and Ulysses dust data. We present data from the Galileo dust instrument for the period January to December 1996 when the spacecraft completed four orbits about Jupiter (G1, G2, C3 and E4). Data were obtained as high resolution realtime science data or recorded data during a time period of 100 days, or via memory read-outs during the remaining times. Because the data transmission rate of the spacecraft is very low, the complete data set (i. e. all parameters measured by the instrument during impact of a dust particle) for only 2% (5353) of all particles detected could be transmitted to Earth; the other particles were only counted. Together with the data for 2883 particles detected during Galileo's interplanetary cruise and published earlier, complete data of 8236 particles detected by the Galileo dust instrument from 1989 to 1996 are now available. The majority of particles detected are tiny grains (about 10 nm in radius) originating from Jupiter's innermost Galilean moon Io. These grains have been detected throughout the Jovian system and the highest impact rates exceeded $\rm 100 min^{-1}$. A small number of grains has been detected in the close vicinity of the Galilean moons Europa, Ganymede and Callisto which belong to impact-generated dust clouds formed by (mostly submicrometer sized) ejecta from the surfaces of the moons (Kr\"uger et al., Nature, 399, 558, 1999). Impacts of submicrometer to micrometer sized grains have been detected thoughout the Jovian system and especially in the region between the Galilean moons., Comment: accepted for Planetary and Space Science, 33 pages, 6 tables, 10 figures

A self-consistent model of linear waves propagating in a two component dusty plasma whose constituents are positively charged dust grains and electrons is presented. Ionization and recombination processes on the dust particle surface, elastic Coulomb collisions of electrons with dust, electron-neutral collisions, dust-electron and dust-neutral collisions, as well as dust charge variations are taken into account. The relationships between the characteristic frequencies of these processes are studied. A linear dispersion relation is obtained and some limiting cases are analyzed. It is shown that Langmuir waves are damped due to electron collisions. It is also found that low frequency waves are always stable in such a system, and there exist two dust-acoustic modes: (1) the usual dust acoustic mode, similar to the ion acoustic wave in electron-ion plasmas; and (2) an acoustic mode with reduced phase velocity, associated with dust particle charge variations. The static response of electron-dust plasmas is exa...

It is shown that the interaction of dust with neutral plasma particles can lead to attractive forces between dust particles, both in the case where the distance between dust particles is less than the mean free path of neutral particles and in the case where it is greater. The expressions for attractive forces differs in the two limits only by a numerical coefficient. The additional force of dust interaction is found to be due to the neutrals created by recombination of charged plasma particles on the surface of dust particles. The influence of radiative dust cooling on dust–dust interaction is considered.

Effects of dust on the amplitude modulation of two possible types of kinetic Alfven waves, modified and dust kinetic Alfven waves, in a magnetized dusty plasma have been investigated. The appropriate nonlinear dispersion relations of the amplitude modulation predict that the carrier kinetic Alfven waves are modulationally unstable for long wave-length perturbations. It has been found that the parameter σ plays a significant role on the amplitude modulation of the waves, where σ is the ratio of the equilibrium number densities of the ions and the electrons and is a measure of the charge carried by the dust component. The maximum growth rate of the modulational instability increases with the parameter σ, whereas, the range of the perpendicular component of the modulation wavenumber K⊥ of the unstable wave remains almost constant for the case of dust kinetic Alfven waves. On the other hand, the maximum growth rate is almost constant with σ, while the range of K⊥ of the unstable wave drastically decreases for the case of modified kinetic Alfven waves.

It has been shown that under certain conditions “complex plasmas” (plasma containing ions, electrons and charged microspheres) may undergo spontaneous phase changes to become liquid and crystalline, without recombination of the charge components. Hence these systems may be regarded as new plasma states - “condensed plasmas”. Complex plasmas are of great interest from a fundamental research point of view because the individual particles of one plasma component (the charged microspheres) can be visualised and hence the plasma can be studied at the kinetic level. In this introduction the potential of complex plasmas will be presented through dedicated experiments performed in the laboratory and under microgravity conditions.

The scaling-index method (SIM) is a novel tool for image processing in scanning-probe microscopy. Originating from the theory of complex systems, the SIM can be used in order to extract structural information from arbitrary data sets. This method can readily be applied to the analysis of digital atomic-force microscopy (AFM) images. Especially for biomedical diagnostics, where genetic material is investigated by various microscopic methods, a reliable image segmentation based on the SIM algorithm is helpful. As a first application, AFM-images of GTG-banded human metaphase chromosomes (with G bands obtained by Trypsin using Giemsa) are compared with micrographs from conventional light microscopy by means of a scaling-index analysis. While the grey-level distributions of the optical and the AFM-images are largely different from each other, the scaling-index images are remarkably similar. Using this method, a fingerprint of an image can be produced which helps in the classification and interpretation of the measured data.

PK-4 is a multi-functional plasma discharge source. Two setups exist for operating plasma discharge experiments on parabolic flight campaigns as well as in laboratory. Another setup for use on the International Space Station ISS is planned. The plasma can be created by a dc-discharge as well as by rf-discharges, coupled inductively. There exist various possibilities to manipulate the introduced microparticles: mechanical (glass-nozzle), optical (high power laser), electrical (EM-pulse-electrode, rf-electrodes, polarity-switching) and thermal (heating coil) manipulation. Several different types of experiments have already been done with PK-4 in parabolic flights: Nozzle-Experiments (particle jets, transition between fluid and single particle behaviour), Lane-Formation (cloud collisions), Laser driven shear flow, Shock waves and solitons (excitation of shock waves applying electric pulses using the EM-electrode), String-Fluids (electro-rheological fluids), and many more.

A simple analytical approach to estimate thermodynamic properties of model Yukawa systems is presented. The approach extends the traditional Debye-H\"{u}ckel theory into the regime of moderate coupling and is able to qualitatively reproduce thermodynamics of Yukawa systems up to the fluid-solid phase transition. The simplistic equation of state (pressure equation) is derived and applied to the hydrodynamic description of the longitudinal waves in Yukawa fluids. The relevance of this study to the topic of complex (dusty) plasmas is discussed., Comment: To be published in Phys. Rev. E

Drawing on the predominant belief in colloidal science, it is frequently supposed that the interaction responsible for colloidal plasma crystals should be repulsive. This work presents a model which shows that this interaction can indeed be attractive, depending on system parameters. A long range attractive well associated with the electrostatic interaction results by accounting for both plasma grain correlations and finite value for the product of the Debye wave vector and grain radius, kDa. These results have implications for the analogous problem in colloidal science.

The motion of dust particles confined in plasma monolayer crystals is analyzed from video images, under conditions dominated by dust-neutral collisions. In these crystals, dust-neutral collisions will act as a random driving force, exciting phonons with a stochastic nature. The phonons are investigated using standard statistical tools, including both single- and multiparticle correlation functions. Single-particle correlations as obtained from the velocity autocorrelation function yield oscillations in a very narrow frequency band. Similar behaviors have previously been reported for strongly coupled one-component plasmas, and for trapped Brownian particles. Spatial correlations in the crystal lattice are studied from multiparticle correlation functions, suggesting an average wavelength slightly larger than the dimension of the crystal. Throughout the crystal, the dust velocity amplitude and polarization vary significantly, with the main variation in the radial direction out of the crystal center. This sug...

In the presence of ionization processes, a homogeneous equilibrium dust distribution often appears as a balance between plasma generation by ionization and plasma absorption by dust particles. It is shown that such equilibrium, often present in laboratory plasmas, is generally unstable against the formation of dust clumps separated by dust-free regions (dust voids). The driving force that separates an initially homogeneous dusty plasma into dust clumps and dust voids is the drag force produced by ions flowing out from the regions with reduced dust density. The lower the dust density, the lower the electron absorption by dust particles and the larger the ionization rate proportional to the electron density. An increase in the ion drag force leads to a further decrease in the dust density and, thus, drives the instability. In the nonlinear stage, the instability creates structures—dust clouds separated by dust voids. The dependence of the instability growth rate on the wavenumber (or, in other words, on the size of the dust-free and dust-containing regions) is investigated. It is shown that, for sufficiently small wavenumbers, a homogeneous distribution is always unstable. An analogy with a gravitational-like instability related to shadowing of the plasma flux by dust particles is pointed out. This effect, which is due to collective shadowing of the plasma flux, dominates the shadowing by individual dust particles discussed previously. Similar to the usual gravitational instability, perturbations with the largest scales are always unstable. Contrary to the usual gravitational instability, the largest growth rate corresponds not to the largest possible scale but to the size close to the mean free path of plasma particles colliding with dust particles. A special investigation is undertaken to determine the influence of the ion-neutral collisions on the growth rate of the instability.

The dispersion relation for the acoustic modes in a collisional dusty plasma is derived, taking into account the particle charge variation and ionization. Short and long wavelengths are considered separately. It is shown that the coupling between the short-wavelength branches is weak, and for sufficiently small dust fraction they can be treated independently, as in the case of a fixed charge. In the long-wavelength limit, the dust-ion acoustic (DIA) and dust acoustic (DA) branches interact “through” the dust charging (DCh) branch, unlike the direct coupling obtained in the absence of charge variations.

A theory of low-frequency dust-acoustic waves in low-temperature collisional plasmas containing variable-charge impurities is presented. Physical processes such as dust-charge relaxation, ionization-recombination of the electrons and ions, electron and ion elastic collisions with neutrals and dusts, as well as charging collisions with the dusts, are taken into account. Inclusion of these processes allows a balance of the plasma particles and thus a self-consistent determination of the stationary state of the unperturbed plasma. The generalized dispersion relation describing the propagation and damping of the dust acoustic waves is derived and analyzed.

Experiments under microgravity conditions were carried out to study 'condensed' (liquid and crystalline) states of a colloidal plasma (ions, electrons, and charged microspheres). Systems with approximately 10(exp 6) microspheres were produced. The observed systems represent new forms of matter--quasineutral, self-organized plasmas--the properties of which are largely unexplored. In contrast to laboratory measurements, the systems under microgravity are clearly three dimensional (as expected); they exhibit stable vortex flows, sometimes adjacent to crystalline regions, and a central 'void,' free of microspheres.

Taking into account the statistical charge fluctuations on microspheres embedded in a low-pressure gas discharge, a stochastic differential equation for the one-dimensional dust lattice wave is derived. Using this equation, the nonstochastic differential equations for the mean particle displacement and for the second moments of the displacement and velocity are obtained. The analysis of the equation for the second moments shows that for sufficiently small gas pressure the charge fluctuations can result in exponential growth of the average energy of lattice oscillations.

It is shown that the charge distribution on the surface of a dielectric particle immersed in a supersonic plasma flow is strongly inhomogeneous, which results in the appearance of a large dipole moment. The dependences of both the charge and dipole moment of the particle on the drift velocity of the ambient plasma are calculated. It was found that under the same conditions the charge of a dielectric particle considerably exceeds the charge of a metal one.

Colloidal plasmas may “condense” under certain conditions into liquid and crystalline states, while retaining their essential plasma properties. This “plasma condensation” therefore leads to new states of matter: “liquid plasmas” and “plasma crystals.” The experimental discovery was first reported in 1994, and since then many researchers have begun to investigate the properties of condensed plasma states. In this paper we describe some of the basic physics required to understand colloidal plasmas and discuss experiments conducted to investigate the details of the interaction between the plasma particles (in particular, the interaction potential), the melting phase transition, and the thermodynamics of this new state of matter.

The Ulysses spacecraft is orbiting the Sun on a highly inclined ellipse (i = 79°). After its Jupiter flyby in 1992 at a heliocentric distance of 5.4 AU, the spacecraftreapproached the inner solar system, flew over the Suns south polar region in September 1994,crossed the ecliptic plane at a distance of 1.3 AU in March 1995, and flew over the Suns northpolar region in July 1995. We report on dust impact data obtained with the dust detector onboardUlysses between January 1993 and December 1995. We publish and analyse the complete dataset of 509 recorded impacts of dust particles with masses between 10−16 g–10−7 g. Together with 968 dust impacts from launch until the end of 1992 published earlier ( Grun et al., 1995c ), information about 1477 particles detected with theUlysses sensor between October 1990 and December 1995 is now available. The impact ratemeasured between 1993 and 1995 stayed relatively constant at about 0.4 impacts per day andvaried by less than a factor of ten. Most of the impacts recorded outside about 3.5 AU arecompatible with particles of interstellar origin. Two populations of interplanetary particles havebeen recognized: big micrometer-sized particles close to the ecliptic plane and smallsub-micrometer-sized particles at high ecliptic latitudes. The observed impact rate is comparedwith a model for the flux of interstellar dust particles which gives relatively good agreement withthe observed impact rate. No change in the instruments noise characteristics or degradation of thechanneltron could be revealed during the three-year period.

The acoustic modes in a collisional dusty plasma are studied, taking into account the influence of ion–neutral collisions, ion drag, and neutral friction. It is assumed that the frequency of ion–neutral collisions is greater than the frequency of ion–dust collisions. Two limiting cases of short-wavelength and long-wavelength modes are considered separately, depending on the ratio of the dust–ion acoustic frequency to the frequency of ion–neutral collisions. It is shown that for the long wavelengths coupling between the modes becomes strong, causing the appearance of the hybrid long-wavelength mode. It is also found that in the long-wavelength case there are two types of instability caused by ionization. The theoretical results are compared with the data obtained in experiments with growing particles.

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A nonlinear Schrodinger equation for the propagation of a dust-lattice wave in a one-dimensional chain of a plasma crystal is derived by using the Krylov–Bogoliubov–Mitropolsky (KBM) perturbation technique. The resulting equation is then analyzed to obtain a nonlinear dispersion relation for the wave envelope. It has been found that the dust-lattice wave is modulationally unstable for long wavelength perturbations and the modulationally unstable wave propagates as an envelope soliton. The importance of this investigation in present-day laboratory experiments for dust-plasma crystallization is pointed out.

Using the standard reductive perturbation technique, a nonlinear Schr\"odinger equation is derived to study the modulational instability of finite amplitude dust-acoustic (DA) and dust-ion-acoustic (DIA) waves against oblique perturbations (with respect to the propagation direction of the carrier waves) in an unmagnetized dusty plasma. It is shown that both the DA and DIA waves are modulationally unstable. Possible stationary states of the wave packets can appear as envelope solitons.

It is found that the nonlinear dynamics of amplitude-modulated dispersive dust lattice waves (DLW) is governed by a nonlinear Schrodinger equation. The latter exhibits that a constant amplitude carrier dust lattice wave is modulationally stable, and that the modulated DLW packet propagates in the form of either an envelope dark soliton or an envelope shock. The relevance of our theoretical investigation to simulation studies as well as to a laboratory dusty plasma experiment is pointed out.

We argue that properties of the fine-grained rims, presumably accreted by chondrules during transport subsequent to their formation, may help differentiate between chondrule production mechanisms which are “local” (at the parent body formation site) and “distant” (e.g., close to the protosun, in accretion shocks, or outside the Solar Nebula). Systematics in the thicknesses of these rims seem most compatible with local production scenarios in which chondrules deplete the dust in a confined volume prior to parent body formation.

The scaling index method was used in order to analyze atomic force microscopic images of double-stranded DNA (plasmid PUC 8) adsorbed to mica. With this algorithm, the image can be decomposed into constituents of different dimensionality, i.e., point-like, thread-like, and area-like structures, and residual noise. Special focus is on the evaluation of this method for the future automated analysis of binding events of DNA-specific proteins.

Chondrules constitute a significant fraction of primitive meteorites. Their thermal history includes rapid melting followed by cooling on timescales of minutes to hours. The mechanism underlying such extreme, short-lived thermal excursions away from the prevailing, much milder nebular equilibrium conditions has eluded understanding for many decades. Among the prime candidate mechanisms long thought to provide a possible explanation of chondrule formation is lightning—large-scale electrostatic discharges—in the protoplanetary nebula. In this paper, we explore the possible occurrence of such electrostatic discharges in the protoplanetary nebula powered by precipitation or other processes analogous to that believed to cause lightning on Earth and other planets. Our analysis incorporates charge separation in collisions of water-ice or other solid particles, and includes a self-consistent nebular electrical conductivity determined by a balance between production of free electrons and ions and loss to grain surfaces. We find that development of a large-scale electric field strong enough to produce discharges does not occur under conditions characteristic of protostellar nebulae. This is mainly a result of the fact that the high electrical conductivity of the environment and the relatively low density of solid particles combine to yield a situation in which the large scale electric fields, as well as the electric charges segregated on the particles are short circuited by the highly mobile electrons and ions. We also consider the possibility of lightning in altered nebula environments with higher than canonical dust density, such as a dust subdisk.

Identical in situ dust detectors are flown on board the Galileo and Ulysses spacecraft. They record impacts of micrometeoroids in the ecliptic plane at heliocentric distances from 0.7 to 5.4 AU and in a plane almost perpendicular to the ecliptic from -79 deg to +79 deg ecliptic latitude. The combination of both Ulysses and Galileo measurements yields information about the radial and latitudinal distributions of micron- and sub-micron-sized dust in the Solar System. Two types of dust particles were found to dominate the dust flux in interplanetary space. Interplanetary micrometeoroids covering a wide mass range from 10^-16 to 10^-6 g are recorded mostly inside 3 AU and at latitudes below 30 deg. Interstellar grains with masses between 10^-14 and 10^-12 g have been positively identified outside 3 AU near the ecliptic plane and outside 1.8 AU at high ecliptic latitudes (>50 deg). Interstellar grains move on hyperbolic trajectories through the planetary system and constitute the dominant dust flux (1.5 x 10^-4 m^-2 sec^-1) in the outer Solar System and at high ecliptic latitudes. To compare and analyze the Galileo and Ulysses data sets, a new model is developed based on J. Geophys. Res. 98, 17029-17048, Divine's (1993, ``five populations of interplanetary meteoroids'' model. Both models describe the interplanetary meteoroid environment in terms of dust populations on distinct orbits. Taking into account the measured velocities and the effect of radiation pressure on small particles (described by the ratio of radiation pressure force to gravity, beta), we define four populations of meteoroids on elliptical orbits and one population on hyperbolic orbit that can fit the micrometeoroid flux observed by Galileo and Ulysses. Micrometeoroids with masses greater than 10^-10 g and negligible radiation pressure (beta = 0) orbit the Sun on low to moderately eccentric orbits and with low inclinations (

Dust measurements have been obtained with the dust detector onboard the Galileo spacecraft inside a distance of about 60RJ from Jupiter (Jupiter radius, RJ = 71,492 km) during two periods of about 8 days around Galileo's closest approaches to Ganymede on 27 June and on 6 Sept 1996. The impact rate of submicrometer-sized particles fluctuated by a factor of several hundred with a period of about 10 hours, implying that their trajectories are strongly affected by the interaction with the Jovian magnetic field. Concentrations of small dust impacts were detected at the times of Ganymede closest approaches that could be secondary ejecta particles generated upon impact of other particles onto Ganymede's surface. Micrometer-sized dust particles, which could be on bound orbits about Jupiter, are concentrated in the inner Jovian system inside about 20RJ from Jupiter.

The detailed study of crystals and the dynamics of the melting process in two and three dimensions is a fundamental and interesting research topic, which is important for increasing our knowledge of solid state physics. In natural crystals, structure information can be obtained principally by Bragg-scattering of neutrons, electrons or photons on the crystal, followed by an analysis in Fourier space. Dynamical aspects cannot be investigated in these systems. Recently, a new crystalline system was discovered whose properties are such that the melting transition can be investigated in great detail — the ‘plasma crystal’. This article presents the results of such an investigation and shows evidence for the existence of intermediate phases between the solid, liquid and gaseous phases. The observed ‘structured’ phase transition may be specific for plasma crystals but, alternatively, it may indicate the existence of intermediate stages in the melting transition more generally.

The internal structures of most periodic crystalline solids contain defects. This affects various important mechanical and thermal properties of crystals. Since it is very difficult and expensive to track the motion of individual atoms in real solids, macroscopic model systems, such as complex plasmas, are often used. Complex plasmas consist of micrometer-sized grains immersed into an ion-electron plasma. They exist in solidlike, liquidlike, and gaseouslike states and exhibit a range of nonlinear and dynamic effects, most of which have direct analogies in solids and liquids. Slabs of a monolayer hexagonal complex plasma were subjected to a cycle of uniaxial compression and decompression of large amplitudes to achieve plastic deformations, both in experiments and simulations. During the cycle, the internal structure of the lattice exhibited significant rearrangements. Dislocations (point defects) were generated and displaced in the stressed lattice. They tended to glide parallel to their Burgers vectors under load. It was found that the deformation cycle was macroscopically reversible but irreversible at the particle scale.

A novel mechanism of the formation of compact dusty clouds in astrophysical environments is discussed. It is shown that the balance of collective forces operating in space dusty plasmas can result in the effect of dust self-confinement, generating equilibrium spherical clusters. The distribution of dust and plasma density inside such objects and their stability are investigated. Spherical dusty clouds can be formed in a broad range of plasma parameters, suggesting that this process of dust self-organization might be a generic phenomenon occurring in different astrophysical media. We argue that compact dusty clouds can represent condensation seeds for a population of small-scale, cold, gaseous clumps in the diffuse interstellar medium. They could play an important role in regulating its small-scale structure and its thermodynamical evolution.

Network analysis was used to study the structure and time evolution of driven three-dimensional complex plasma clusters. The clusters were created by suspending micron-size particles in a glass box placed on top of the rf electrode in a capacitively coupled discharge. The particles were highly charged and manipulated by an external electric field that had a constant magnitude and uniformly rotated in the horizontal plane. Depending on the frequency of the applied electric field, the clusters rotated in the direction of the electric field or remained stationary. The positions of all particles were measured using stereoscopic digital in-line holography. The network analysis revealed the interplay between two competing symmetries in the cluster. The rotating cluster was shown to be more cylindrical than the nonrotating cluster. The emergence of vertical strings of particles was also confirmed.

The observation is presented of naturally occurring pairing of particles and their cooperative drift in a two-dimensional plasma crystal. A single layer of plastic microspheres was suspended in the plasma sheath of a capacitively coupled rf discharge in argon at a low pressure of 1 Pa. The particle dynamics were studied by combining the top-view and side-view imaging of the suspension. Cross analysis of the particle trajectories allowed us to identify naturally occurring metastable pairs of particles. The lifetime of pairs was long enough for their reliable identification., 5 pages, 4 figures

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. 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., Comment: 9 pages, 7 figures

An influence of a high-voltage (3-17 kV) 20 ns pulse on a weakly-ionized low-pressure (0.1-10 Pa) capacitively-coupled radiofrequency (RF) argon plasma is studied experimentally. The plasma evolution after pulse exhibits two characteristic regimes: a bright flash, occurring within 100 ns after the pulse (when the discharge emission increases by 2-3 orders of magnitude over the steady-state level), and a dark phase, lasting a few hundreds \mu s (when the intensity of the discharge emission drops significantly below the steady-state level). The electron density increases during the flash and remains very large at the dark phase. 1D3V particle-in-cell simulations qualitatively reproduce both regimes and allow for detailed analysis of the underlying mechanisms. It is found that the high-voltage nanosecond pulse is capable of removing a significant fraction of plasma electrons out of the discharge gap, and that the flash is the result of the excitation of gas atoms, triggered by residual electrons accelerated in the electric field of immobile bulk ions. The secondary emission from the electrodes due to vacuum UV radiation plays an important role at this stage. High-density plasma generated during the flash provides efficient screening of the RF field (which sustains the steady-state plasma). This leads to the electron cooling and, hence, onset of the dark phase.

Summary form only given. Since the discovery of the bactericidal action of cold atmospheric plasma (CAP) researchers also wanted to know its effects on human cells. As there are a huge number of the different used plasma devices the results have a wide range. Several studies on wound healing and other diseases were started and had already first results. But to learn more about mechanisms which are involved and influenced, experiments have to be done in cell cultures. As most of the laboratories are working with cancer cell lines in their cell cultures it was consequential to test the effect of CAP on them. And of course there are again certain distinctions in the behaviour of for example brain tumour cells and ovarian cancer cells. There were some publications in which it is described that CAP can selectively kill cancer cells. Controls were cell lines that are declared as “normal”. But in this context “normal” means only “not cancer cells”. This cell lines are also immortalised for the convenient use in cell cultures and remain an artificial model that cannot be transferred 1:1 to real organisms. In cooperation with the department of Dermatology we were able to establish a primary culture model of human dermal fibroblast of ex vivo skin samples. This is a first step to discover the effects of CAP on cells that were not immortalised or modified otherwise. First results of the CAP treatment of ex vivo human dermal fibroblasts in the bactericidal range of CAP are presented. Cell viability and apoptosis were substance of investigation as well as cell cycle distribution and cell migration.

Objectives: Chronic infected wounds are both socioeconomic and medical problem. Combating bacterial resistance is on of the greatest challenges in the 21st century. In previous reports, 2 min and 5 min cold argon plasma treatments led to a significant reduction in bacterial load in chronic wounds of various causes in patients, regardless of the bacterial species. The observed bactericidal effect of plasma therapy relies on the synergy of reactive oxygen and nitrogen species, charged particles, electric fields, and UVR. This study evaluates the effect of CAPs on wound healing in vivo. Methods: Hard-to-heal chronic wounds of various types in 70 patients (Group A) were treated with cold argon atmospheric plasma for 3-7 minutes. The wound size before and after a course of treatment was compared for plasma-treated and control wounds. Subgroup analyses were performed for all chronic venous ulcers (n=29, Group B) and 5 min plasma treatment of chronic venous ulcers (n=18, Group C). Results: Retrospective analysis of Group A revealed a 10.4 % reduction in width of plasma treated wounds compared to 4.2 % in the control (p=0.270). Length reduced by 8.2 % compared to 5.1% respectively (p=0.068). In Group B a significantly greater reduction in width (17.9 %, p=0.03) was measured in plasma-treated ulcers compared to controls (0 %). However changes in length were not significantly different (9.1 % vs. 8.9 %, p=0.46). The Group C sub analysis showed a highly significant reduction in width (14.6 % vs. 0 %, p=0.008) with plasma treatment but not in ulcer length (2.7 % vs. 8.4 %, p=0.352). Conclusions: This study demonstrates for the first time that plasma treatment can actually accelerate wound healing in a range of chronic wounds, but particularly chronic venous ulcers.

Cold atmospheric plasma science is an innovative upcoming technology for the medical sector. The plasma composition and subsequent effects on cells, tissues and pathogens can vary enormously depending on the plasma source, the plasma settings and the ambient conditions. Cold atmospheric plasmas consist of a highly reactive mix of ions and electrons, reactive molecules, excited species, electric fields and to some extent also UV radiation. In the last year, this partly ionized gas has been demonstrated to have a broad antimicrobial activity, while resistance and resistance development are unlikely. Furthermore, recent research has indicated that plasmas also have a strong influence on various cell lines and cell functions, including anticancer properties. This review summarizes the major plasma designs available and their main benefits, as well as assessing possible risks of this new technology.

Experimental evidence is presented for a scale-free transition from an unordered to an ordered state in a 2D complex plasma that differs from the KTHNY theory of phase transitions in 2D systems. The transition is characterized by the formation and growth of ordered domains. A fractal relationship is found between the domain areas and domain boundary lengths, which can be explained by a recent theoretical model. The experimental findings are supported by a molecular dynamics simulation of a 2D particle system.

A two-dimensional plasma crystal was melted by suddenly applying localized shear stress. A stripe of particles in the crystal was pushed by the radiation pressure force of a laser beam. We found that the response of the plasma crystal to stress and the eventual shear melting depended strongly on the crystal's angular orientation relative to the laser beam. Shear stress and strain rate were measured, from which the spatially resolved shear viscosity was calculated. The latter was shown to have minima in the regions with high velocity shear, thus demonstrating shear thinning. Shear-induced reordering was observed in the steady-state flow, where particles formed strings aligned in the flow direction., Comment: 7 pages, 8 figures, submitted to Physical Review E

In order to test for non-Gaussianities with respect to scale-dependencies we use so-called surrogate maps, in which possible phase correlations of the Fourier phases of the original WMAP data and simulations, respectively, are destroyed by applying a shuffling scheme to the maps. A statistical comparison of the original maps with the surrogate maps then allows to test for the existence of higher order correlations in the original maps, also and especially on well-defined Fourier modes. Using Minkowski functionals as an image analysis technique we calculate the deviation between the original data and 500 surrogates for different hemispheres in the sky and find ecliptic hemispherical asymmetries between northern and southern ecliptic sky. We find strong deviations from Gaussianity in the WMAP data when considering the low-l range with l = [2,20]. The analysis technique of the scaling indices leads to a slightly lower deviation. Although the underlying foreground reduction methods of the maps differ from each other, we find similar results for the WMAP 7yr ILC map and the WMAP 7yr (needlet-based) NILC map in the low-l range. Our results point once more to a cosmological nature of the signal. For a higher l range with l = [120,300] the results differ between the two image analysis techniques and between the two maps which makes an intrinsic nature of the signal on this l range less likely. When we decrease the size of the analysed sky regions for the low-l study, we do not find signatures of NG in the northern sky. In the south we find individual spots which show deviations from Gaussianity. In addition, we investigate non-Gaussian CMB simulations that depend on the f_NL parameter of the local type. These simulations cannot account for the detected signatures on the low-l range., Comment: 13 pages, 10 figures, accepted for publication in MNRAS

Glioblastoma (GBM) is the most common and aggressive brain tumor in adults. Despite multimodal treatments including surgery, chemotherapy and radiotherapy the prognosis remains poor and relapse occurs regularly. The alkylating agent temozolomide (TMZ) has been shown to improve the overall survival in patients with malignant gliomas, especially in tumors with methylated promoter of the O6-methylguanine-DNA-methyltransferase (MGMT) gene. However, intrinsic and acquired resistance towards TMZ makes it crucial to find new therapeutic strategies aimed at improving the prognosis of patients suffering from malignant gliomas. Cold atmospheric plasma is a new auspicious candidate in cancer treatment. In the present study we demonstrate the anti-cancer properties of different dosages of cold atmospheric plasma (CAP) both in TMZ-sensitive and TMZ-resistant cells by proliferation assay, immunoblotting, cell cycle analysis, and clonogenicity assay. Importantly, CAP treatment restored the responsiveness of resistant glioma cells towards TMZ therapy. Concomitant treatment with CAP and TMZ led to inhibition of cell growth and cell cycle arrest, thus CAP might be a promising candidate for combination therapy especially for patients suffering from GBMs showing an unfavorable MGMT status and TMZ resistance.