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Master equations for spherical dust structures are solved numerically using the asymptotic solutions at the center of the structures for the case of absence of external ionization and small diffusions. The structures are determined by a single parameter, the external plasma flux at the surface of the structure. The equilibrium states that are possible in a limited range of this parameter are investigated numerically. It is demonstrated that in the range of existence of equilibria the structures are changing their shapes and type of distributions inside the structures. For large external fluxes the ion and dust distributions can have peaks inside the structures while for low external fluxes the dust distribution has a single maximum at the structure center. The lower is the external flux supporting the structure the larger is its size. An increase of the external flux decreases the accumulation of dust and ions at the center. The total number of dust confined by the structure is larger for larger size structures. Estimates of dust crystallization inside structures are given. The role of diffusion is calculated by perturbations and is shown to be small in all structure regions except the structure edges. In the perturbation theory we use the exact expressions of the diffusion coefficients calculated previously numerically. The regions with dust density peaks inside the structures have been calculated with two order of magnitude larger precision that allows to resolve the structure parameter dependencies inside the peaks. It is shown that although in peaks the gradients of all parameters are increased the diffusion flux is still small and that the continuity and hydrodynamic approach are applicable within an accuracy about several %-s (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Non-thermal (low-temperature) physical plasma is under intensive study as an alternative approach to control superficial wound and skin infections when the effectiveness of chemical agents is weak due to natural pathogen or biofilm resistance. The purpose of this study was to test the individual susceptibility of pathogenic bacteria to non-thermal argon plasma and to measure the effectiveness of plasma treatments against bacteria in biofilms and on wound surfaces. Overall, Gram-negative bacteria were more susceptible to plasma treatment than Gram-positive bacteria. For the Gram-negative bacteriaPseudomonas aeruginosa,Burkholderia cenocepaciaandEscherichia coli, there were no survivors among the initial 105c.f.u. after a 5 min plasma treatment. The susceptibility of Gram-positive bacteria was species- and strain-specific.Streptococcus pyogeneswas the most resistant with 17 % survival of the initial 105c.f.u. after a 5 min plasma treatment.Staphylococcus aureushad a strain-dependent resistance with 0 and 10 % survival from 105c.f.u. of the Sa 78 and ATCC 6538 strains, respectively.Staphylococcus epidermidisandEnterococcus faeciumhad medium resistance. Non-ionized argon gas was not bactericidal. Biofilms partly protected bacteria, with the efficiency of protection dependent on biofilm thickness. Bacteria in deeper biofilm layers survived better after the plasma treatment. A rat model of a superficial slash wound infected withP. aeruginosaand the plasma-sensitiveStaphylococcus aureusstrain Sa 78 was used to assess the efficiency of argon plasma treatment. A 10 min treatment significantly reduced bacterial loads on the wound surface. A 5-day course of daily plasma treatments eliminatedP. aeruginosafrom the plasma-treated animals 2 days earlier than from the control ones. A statistically significant increase in the rate of wound closure was observed in plasma-treated animals after the third day of the course. Wound healing in plasma-treated animals slowed down after the course had been completed. Overall, the results show considerable potential for non-thermal argon plasma in eliminating pathogenic bacteria from biofilms and wound surfaces.

Complex plasma is the plasma state of soft matter which consists of weakly ionized gas (plasma) and highly charged microparticles. The microparticles are large enough to be visualized individually and their dynamics can be observed with great accuracy using simple video microscopic techniques. These features allow us to perform experiments with high temporal and spatial resolutions. Furthermore, since the background gas is usually dilute, the particle dynamics of strongly coupled complex plasmas are virtually undamped, which provides a direct analogy to regular liquids and solids in terms of the atomistic dynamics. All these unique features allow complex plasma to be used as an ideal model system (complementary to other model systems in soft matter physics such as colloids, granular medium, etc.) to investigate various phenomena (e.g, phase transitions, phase separation, self-organizations, rheology, linear and nonlinear waves, transport, etc.) at the most fundamental kinetic level.

The recent tremendous progress in understanding physical plasma phenomenon, together with the development of new plasma sources has put growing focus on the application of plasmas in health care. Active plasma components, such as molecules, atoms, ions, electrons and photons, reactive species, ultraviolet radiation, optical and infrared emission and heat have the ability of activating, controlling and catalysing reactions and complex biochemical procedures. Thermal and non-thermal (i.e. cold) plasmas - both already widely established in medicine - are used for various therapeutic applications. Particularly in dermatology, plasma applications hold big potential, for example, in wound healing, such as efficient disinfection or sterilization, therapy of various skin infections or tissue regeneration. This review gives an overview on potential plasma applications in medicine - including the recent research on skin diseases - and summarizes possible interactions between plasmas and living tissue.

Wetting properties and surface roughness of SU-8 can be modified by wet chemical and plasma processes. These processes result in an enhanced wettability that can be attributed to an increase of C=O and COO groups at the surface. Wet chemical etching with ceric ammonium nitrate (CAN) rendered the SU-8 surface hydrophilic. However, it also led to the accumulation of cerium species on the surface, which may interfere with biochemical reactions in the device. Surface activation could also be achieved with a low-temperature atmospheric argon plasma, which left a smooth surface. Treatment of SU-8 with oxygen plasma led to a stable hydrophilization and an increased surface roughness. Owing to oxygen plasma processing, antimony species were accumulated which could be removed with a cleaning step. In order to maintain the hydrophilization after oxygen plasma treatment for storage, or over several wetting cycles, the surface can be coated with a protein-resistant graft copolymer (PLL-g-PEG).

The effect of a levitating cloud of microparticles on the parameters of a radiofrequency (RF) plasma has been studied by means of two experimental techniques. Axial distributions of 1 s excited states of argon were measured by a self-absorption method. A correction of a standard self-absorption method for the extinction of the light by the levitating microparticles is proposed. In addition the electron temperature was estimated using the optical emission spectroscopy. Measurements at the same discharge conditions in a microparticle-free discharge and discharge, containing a cloud of levitating microparticles, revealed the non-local influence of the microparticle cloud on the discharge plasma. The most probable cause of this influence is the disturbance of the ionization balance by the levitating microparticles.

As a result of both the better understanding of complex plasma phenomena and the development of new plasma sources in the past few years, plasma medicine has developed into an innovative field of research showing high potential. While thermal plasmas have long been used in various medical fields (for instance for cauterization and sterilization of medical instruments), current research mainly focuses on application of non-thermal plasmas. Experiments show that cold atmospheric plasmas (CAPs) allow efficient, contact-free and painless disinfection, even in microscopic openings, without damaging healthy tissue. Plasmas influence biochemical processes and offer new possibilities for the selective application of individually designable medically active substances. In dermatology, new horizons are being opened for wound healing, tissue regeneration, therapy of skin infections, and probably many more diseases. First clinical trials show the efficacy and tolerability of plasma in treating infected chronic wounds. A major task will be the introduction of plasma into clinical medicine and, simultaneously, the further investigation of the mechanisms of action of plasma at the cellular level.

Experimental investigations of high voltage nanosecond pulses influence on charged dust particles in low pressure rf–plasma were carried out. Application of repetitive pulses leads to the vertical oscillations of the mi-croparticles. Evolution of the total kinetic energy for the cluster consisting of 14 particles is investigated. Flat clusters exhibit parametric instabilities of horizontal modes. In the initial phase the kinetic energy oscillates around a certain value and its amplitude grows very slowly. At a certain moment during the instability it goes into the exponential growth phase and then saturates under the effect of repetitive pulses. It is possible if the eigenfrequency is the function of height and the dust particle oscillates vertically in the non uniform electric field (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Experiments with complex plasmas in a dc discharge using the PK-4 facility will be discussed, focusing on the formation of strings corresponding to an electrorheological fluid observed in recent parabolic flight experiments.

Spokes are narrow markings across Saturn's B ring, most likely caused by a cloud of micrometer-sized particles intermittently lofted from the larger boulders in the ring. They were observed by the Voyagers, the Hubble Space Telescope, and, more recently, the Cassini spacecraft in orbit around Saturn since 2004. Several explanations have been suggested over the years for the triggering and subsequent evolution of the spokes. In general, it is expected that spokes form due to sudden short-lived changes in the plasma environment of the rings. Most recently, lightning in Saturn's atmosphere was suggested as a trigger for the spokes, based on Cassini observations of field-aligned high-energy (~100 keV) electron beams. In this paper, we examine the interaction of these beams with the ring and show that the expected amount of charge released in a lightning event could increase the surface charge density of the ring material itself to sufficiently high values to trigger spokes.

We conducted a series of experiments to study lane formation in complex plasma, using the PK-3 Plus Laboratory in the International Space Station. In our experiments, small (driven) microparticles penetrate into a cloud of large (background) particles, revealing a strong tendency toward lane formation: When the driving force is strong enough, particles of both sorts form interpenetrating lines. Typically, the lanes exhibit a considerable anisotropic structural order accompanied by an enhancement of their (unidirectional) mobility. Laning is quantified locally in terms of the anisotropic scaling index. Using a ?nematic? order parameter, the observed time-resolved lane-formation process is compared to a set of computer simulations of a binary Yukawa model with Langevin dynamics. This not only yields a best fit but also reveals a strong influence of the initial experimental conditions on the dynamics of lane formation.

Conditions for formation of the double-layer structure at the interface of a complex plasma/electron-ion plasma due to the presence of strongly coupled microparticles is theoretically investigated in a weakly collisional discharge. The result is of consequence for all problems involving the coexistence of different plasma regions, the sharp plasma boundaries, void formation, etc.

Conventional electrorheological (ER) fluids consist of suspensions of microparticles in usually nonconducting fluids with a different dielectric constant. The interparticle interaction, and hence, the rheology of ER fluids, is determined by an external electric field, which polarizes grains and thus induces additional dipole-dipole coupling. The electric field plays a role of a new degree of freedom that allows us to ?tune? the interaction between particles. This makes the phase diagram of ER fluids remarkably diversified. Here, we report on the experimental investigations of ?ER plasmas,? where the control of the interparticle interaction by an externally applied electric field is due to distortion of the Debye spheres that surround microparticles in a plasma. Interactions in ER plasmas under weak ac fields are mathematically equivalent to those in conventional ER fluids. Microgravity experiments as well as molecular dynamics simulations show a phase transition from an isotropic to an anisotropic plasma states as the electric field is increased. The variational Gibbs-Bogoliubov approach allows us to recover the phase diagram of ER plasmas, which includes string fluids and anisotropic solid phases.

Summary Background Bacterial colonization of chronic wounds slows healing. Cold atmospheric plasma has been shown in vitro to kill a wide range of pathogenic bacteria. Objectives To examine the safety and efficiency of cold atmospheric argon plasma to decrease bacterial load as a new medical treatment for chronic wounds. Patients and methods Thirty-eight chronic infected wounds in 36 patients were treated in a prospective randomized controlled phase II study with 5 min daily cold atmospheric argon plasma in addition to standard wound care. The patient acted as his or her own control. Bacterial species were detected by standard bacterial swabs and semiquantitative changes by nitrocellulose filters. Plasma setting and safety had been determined in a preceding phase I study. Results Analysis of 291 treatments in 38 wounds found a highly significant (34%, P

A simple model, allowing to determine the electron temperature in a steady-state low-pressure plasma, is proposed. The model makes use of optical cross-sections and therefore takes into account direct and cascade excitation from ground and metastable states. Spectroscopic data from Mitic et al. (New J. Phys. 11, 083020 (2009)) are used to illustrate the performance of the method.

The data obtained by the Cassini Radio and Plasma Wave Science (RPWS) instrument during the shallow (17.02.2005) and the steep (14.07.2005) crossings of the E-ring revealed a considerable electron ...

The effect of confinement on the pair correlation function of microparticles whose interaction is described by a screened Coulomb potential (Yukawa potential) has been investigated by the molecular dynamics simulations. The data are used to solve the inverse problem of the reconstruction of the particle interaction potential. It has been shown that such a reconstruction is likely impossible for a strongly nonideal system (with the coupling parameter Γ > 1). For systems with Γ ≤ 1, reconstruction is possible if confinement does not lead to the strong inhomogeneity of the system of microparticles.

Complex (dusty) plasmas are composed of a weakly ionized gas and charged microparticles and represent the plasma state of soft matter. Complex plasmas have several remarkable features: Dynamical time scales associated with microparticles are ``stretched'' to tens of milliseconds, yet the microparticles themselves can be easily visualized individually. Furthermore, since the background gas is dilute, the particle dynamics in strongly coupled complex plasmas is virtually undamped, which provides a direct analogy to regular liquids and solids in terms of the atomistic dynamics. Finally, complex plasmas can be easily manipulated in different ways---also at the level of individual particles. Altogether, this gives us a unique opportunity to go beyond the limits of continuous media and study---at the kinetic level---various generic processes occurring in liquids or solids, in regimes ranging from the onset of cooperative phenomena to large strongly coupled systems. In the first part of the review some of the basic and new physics are highlighted which complex plasmas enable us to study, and in the second (major) part strong coupling phenomena in an interdisciplinary context are examined. The connections with complex fluids are emphasized and a number of generic liquid and solid-state issues are addressed. In summary, application oriented research is discussed.

We investigate the dispersion property of a low-frequency electrostatic wave in a dense metallic electron-hole-ion plasma with nanoparticles. The latter are charged due to the field emission, and hence the metallic nanoparticles/nanotubes can be regarded as charged dust rods surrounded by degenerate electrons and holes, and non-degenerate ions. By using a quantum hydrodynamic model for the electrons and holes, we obtain the electron and hole number density perturbations, while the ion and dust rod number density perturbations follow the classical expressions. A dispersion relation for the low-frequency electrostatic wave in our multi-species dense metallic plasma is derived and analyzed. The possibility of exciting non-thermal electrostatic waves is also discussed.

The international research on ISS in dusty plasma (also known as complex plasma) under prolonged microgravity condition entered a new area in March 2001: The PKE-Nefedov facility (formerly called PKE 3) performed its first experiment in radio-frequency induced complex plasmas. This bilateral German–Russian research facility operated successfully in over 13 missions over 5 years until its internal resources were consumed—resulting so far in over 30 peer-reviewed scientific publications. In place of PKE-Nefedov is the next generation experiment apparatus PK 3 Plus with refined and more powerful instruments and diagnostics, which had its on-orbit commissioning in January 2006. While PK 3 Plus will further investigate the radio-frequency induced plasmas for the next few years the new PK-4 research facility is under development for investigation of direct-current induced complex plasma. Because the highly successful series of stand-alone PK experiment facilities cover only a fraction of the overall complex plasma research field the IMPACT (International Multi-User Plasma, Atmospheric and Cosmic Dust Twin) Laboratory project was initiated. The IMPF/ICAPS (IMPACT) Laboratory is the logical next step to provide a home and rallying point for the worldwide growing research efforts under microgravity conditions in the fields of dusty plasma and interactions of cosmic and atmospheric particle systems.

The motion and the equilibrium position of cylindrical particles in a radio-frequency plasma have been interpreted by dipole and quadrupole interaction in two experimental situations. Particles levitating in steady state are aligned either horizontal or vertical in accordance with the theory. However, particles have been observed tilted w.r.t. the vertical when acquiring a horizontal velocity from sailing in the ion stream. Particles in defect of charge fall on the lower electrode, mainly vertically, and build complex ldquowoodyrdquo structures.

Recent developments in the theoretical investigations of complex (dusty) plasmas – low temperature plasmas containing charged microparticles – are reviewed. The focus is mostly on important basic problems of plasmaparticle interactions, including particle charging, electric potential distribution around the particle, interparticle interactions, and the ion drag force. In particular, the importance of plasma-neutral collisions (especially ionneutral) is emphasized (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A simple hydrodynamic model is used to calculate the ion drag force acting on a small grain in highly collisional weakly anisotropic plasma. First, it is shown that as long as the grain does not absorb ions on its surface, the result from this model coincides with the highly collisional limit of the more general kinetic approach proposed by Ivlev et al. and predicts an increase of the ion drag force with ion collisionality. Next, the effect of ion absorption on the grain is investigated. It turns out that ion absorption reduces the amplitude of the ion drag force and under certain conditions the force can even reverse direction (i.e., it acts in the direction opposite to the ion drift). The physics behind this interesting effect and its possible consequences are briefly discussed. Finally, the effect of plasma production and loss in the vicinity of the grain is investigated. The most important result here is that with increasing relative ionization rate a transition from "negative" to "positive" ion drag force can occur. The transitional ionization rates have been estimated for plasma production due to electron impact ionization and two different plasma loss mechanisms (electron-ion volume recombination and ambipolar diffusion loss).

This paper surveys the present state of the art of diagnostics and removal techniques for particles suspended in plasma. Research on ldquodusty plasmasrdquo is necessary for ITER and fusion reactors of the future. The aim is to transfer the knowledge acquired in complex (dusty) plasma research and low temperature plasma community to the broad fusion community, which is being mobilized to understand/quantify this phenomenon and find solutions. The introductory style makes it accessible also to safety personnel and other interested readers with only basic knowledge of plasma. In the transfer from research to technology, we have tried to assess the applicability of the methods proposed, and we have identified further much needed R&D.

Molecular dynamics simulations are performed to analyze the dependence of the behavior of complex (dusty) plasmas in narrow three-dimensional channels on the confining potential. Dynamics of micrometer-sized particles is modeled by using Langevin thermostat and Yukawa (screened Coulomb) pair interaction potential. A detailed analysis shows that confinement strongly affects plasma crystallization characteristics and local ordering of dust grains. In particular, the formation of a new, quasi-crystalline phase induced by hard-wall confinement is revealed. Transitions between different lattice symmetries induced by changes in channel width are examined. Strong dependence of the transverse dust density profile on the shielding parameter (ratio between mean interparticle distance and screening length) can be used to manipulate the dust-grain flux in such a system.

Dislocation nucleation and dynamics were observed in a two-dimensional plasma crystal. The observations were performed in real time at an atomistic (kinetic) level. The basic stages of edge dislocation nucleation were identified and studied, from gradual pile-up of shear strain in the crystal to eventual escape of free dislocations. After nucleation, dislocations moved supersonically with respect to the shear waves and generated shear-wave Mach cones.

An atmospheric low-temperature microwave plasma torch has been developed and applied to disinfection. The size of the plasma output is relatively large (35 mm in diameter). Ar gas at a flow rate of 2.2 slm and 85 W microwave power are used. Plasma discharges are produced between the tip of each electrode and the inner surface of the cylinder. When an Escherichia coli culture is placed for 2 min at 20 mm below the torch, where the gas temperature is sufficiently cool, the bacteria are almost completely killed within a 40 mm diameter circle. The UV radiation is one of the major players responsible for killing bacteria, others being the reactive species and the charged particles.

Complex (dusty) plasmas are a unique system for studying all sorts of dynamical processes at the most elementary individual particle level. Microparticles in complex plasmas can be easily viewed and manipulated. Moreover, collective processes in the strong coupling regime can be virtually undamped (in contrast to colloidal suspensions) and hence full dynamical information can be obtained at all the relevant time scales. Therefore, investigations of dynamical phenomena in complex plasmas can provide important insights into major generic processes governing the behavior of other strong coupling particle systems. In this article we focus on the kinetics of self-organization observed in small clusters as well as extended crystals, and report on some new findings that illustrate significant interdisciplinary potential of complex plasma studies.

The research in dusty plasma, also known as complex plasma, under prolonged microgravity condition took its first steps in 1998 onboard the Russian Space Station MIR: cosmonauts Vladimir Solovyov and Pavel Vinogradov conducted the first experiments to obtain plasma–dust crystals in the ‘Plazmennyi Kristall 1’(PK-1) device using the sun as a ‘natural’ ionization source. This experiment was followed afterwards by the PK-2 already utilizing its own DC plasma generator. A major step came only three years later with the PKE-Nefedov facility (formerly called PKE-3). Launched in February 2001 and operated in over 13 missions for five consecutive years in the Russian Segment of the International Space Station ISS, this bilateral German–Russian research facility has already shown some surprising, new behavior of radio-frequency induced complex plasmas. An advanced model of PKE-Nefedov, the PK-3 Plus experiment apparatus, is getting readied to be launched to ISS on Progress Cargo spacecraft 20P. Additional developments are in progress to continue this exciting growing research field with: (a) PK-4 utilizing high voltage DC controlled plasma, and (b) IMPACT Laboratory, the European Space Agency's next generation premier research laboratory for plasma and dust physics on the ISS. The paper will provide background information of each of the complex plasma research facilities.

We demonstrate the approach of diamond growth on levitating seed particles in a rf plasma. We introduce a hot filament chemical vapor deposition (CVD) technique into the rf plasma chamber in order to obtain improved crystal growth. Firstly, we confirmed diamond nucleation on seed particles placed on a Si substrate using the hot filament CVD. The deposition conditions, namely the total pressure and the rf power, were chosen so that they correspond to particles levitation conditions. We observe that a hydrogen pre-treatment on the seed particles improves the nucleation. Secondly, we confirm the levitation of particles at high temperatures. Fine particles levitated in a plasma are particularly sensitive to thermophoretic effects due to inhomogeneities in the gas heating. Therefore, proper heating procedures are required for successful particles levitation.

Two-dimensional equilibrium configurations of the dust component of a complex plasma in narrow channels have been numerically simulated by the molecular dynamics method for various forms of the confinement potential such as the parabolic potential and potential well. The interaction between the charged dust particles is described by a screened Coulomb potential with allowance for the interaction of microparticles with a neutral gas. It has been shown that the form of the confinement potential strongly affects the local order of the microparticles in such a system.

The cometary coma consists of neutral gas, plasma, and dust grains. The dust grains can influence both the neutral and charged coma’s constituents. Usually, the presence of dust particles in a plasma results in additional losses of both electrons and ions due to the plasma recombination on the particle surfaces. Solar radiation makes the impact of dust even more complicated depending on the solar flux, the dust number density, the photoelectric properties of the dust particles, the dust particle composition, the distribution of the sizes, etc. We propose a simple kinetic model evaluating the role of dust particles in the coma plasma chemistry and demonstrate that this role can be crucial, resulting in a nontrivial behavior of both the electron and ion densities of the plasma. We show that a coma’s dust particles can be negatively as well as positively charged depending on their composition. These opposite charges of the grains can result in fast coagulation of dust particles, thus, forming complex aggregate shapes of cometary grains.

The use of electrostatic probes as a diagnostic tool of the dust particles in the tokamak edge plasmas is investigated. Probe measurements of electrostatic fluctuations in the scrape-off layer of t ...

Previous considerations of dust acoustic waves is demonstrated to be inconsistent - the required equilibrium state for perturbations was not defined since balance of plasma fluxes was neglecting. The self-consistent treatment shows that plasma flux perturbations are accompanying any collective waves propagating in dusty plasmas and can play an important role in wave dispersion, wave damping and can create instabilities. This is illustrated by the derivation of dispersion relation for dust acoustic modes taking into account the plasma flux balances and plasma flux perturbations by waves. The result of this approach shows that the dust acoustic waves with linear dependence of wave frequency on the wave number exist only in restricted range of the wave numbers. Only for wave numbers larger than some critical wave number for low frequency modes the frequency can be have approximately a linear dependence on wave number and can be called as dust acoustic wave but the phase velocity of these waves is different from that which can be obtained neglecting the flux balance and depends on grain charge variations which are determined by the balance of fluxes. The presence of plasma fluxes previously neglected is the main typical feature of dusty plasmas. The dispersion relation in the range of small wave numbers is found to be mainly determined by the change of the plasma fluxes and is quite different from that of dust acoustic type, namely it is found to have the same form as the well known dispersion relation for the gravitational instability. This result proves in general way the existence of the collective grain attractions of negatively charged grains for for large distances between them and for any source of ionization. The attraction of grains found from dispersion relation of the dust acoustic branch coincides with that found previously for pair grain interactions using some models for the ionization source. For the existing experiments the effective Jeans length for such attraction is estimated to be about 8 – 10 times larger than the ion Debye length and the effective gravitational constant for the grain attraction is estimated to be several orders of magnitude larger than the usual gravitational constant. The grain attraction at large inter-grain distances described by the gravitationlike grain instability is considered as the simplest explanation for observed dust cloud clustering, formation of dust structures including the plasma crystals. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

PK-4 is an experiment designed to investigate complex plasmas in a combined dc/RF discharge under microgravity conditions on board of the International Space Station. The dc discharge is produced in a glass tube with a length of 35 cm and a diameter of 3 cm. In addition, an RF discharge can be applied by external RF coils. The setup is especially suited for studying the liquid phase of the complex plasmas, e.g., flow phenomena such as turbulence or nozzles, and forces acting on the microparticles. Experiments in the laboratory and in parabolic flights have been used to determine the charge of the microparticles as well as the ion drag force acting on them

It is shown that purely growing magnetic fields in a two-component dusty plasma can e generated due to the equilibrium drift of positive and negative dust grains. For this purpose, a linear dispersion relation has been derived by using the hydrodynamic equations for the charged dust fluids, the Maxwell equation and Faraday' law. The dispersion relation admits a purely growing instability, the growth rate of which is proportional to the equilibrium streaming speeds of positive and negative dust grains. A possible physical explanation for the instability is offered. Applications of our investigation to magnetic fields in the thin Martian environments, interplanetary spaces and dense molecular clouds are mentioned.

Crystallization waves in the dusty component of a complex plasma, which were recently observed experimentally, have been investigated numerically. The evolution of the system of charged microparticles whose interaction between each other is described by a screened Coulomb potential (Yukawa potential) has been numerically simulated using the molecular dynamics method. It has been shown that the process of the formation and propagation of a crystallization wave in such a system is fundamentally three-dimensional. Analysis of the local structure of dust particles behind the crystallization wave front indicates the coexistence of different types of the crystal lattice including the metastable phase, i.e., a nonequilibrium phase transition.

International audience; In an argon plasma of 20W rf discharge at a pressure of 1.38 Pa, a stable highly ordered monolayer of microparticles is suspended. We observe spontaneous particle pairing when suddenly reducing the gas pressure. Special types of dynamical activity, in particular, entanglement and cooperative movements of coupled particles have been registered. In the course of the experiment first appeared single vertical pairs of particles, in further they gradually accumulated causing melting of the entire crystal. To record pairing events, the particle suspension is side-view imaged using a vertically extended laser sheet. The long-lasting pre-melting phase assured the credible recording and identification of isolated particle pairs. The high monolayer charge density is crucial to explain the spontaneous pairing events observed in our experiments as the mutual repulsion between the particles comprising the monolayer make its vertical extend thicker. (C) 2015 AIP Publishing LLC.

Human norovirus (NoV) is the most frequent cause of epidemic nonbacterial acute gastroenteritis worldwide. We investigated the impact of nonthermal or cold atmospheric pressure plasma (CAPP) on the inactivation of a clinical human outbreak NoV, GII.4. Three different dilutions of a NoV-positive stool sample were prepared and subsequently treated with CAPP for various lengths of time, up to 15 min. NoV viral loads were quantified by quantitative real-time reverse transcription PCR (RT-qPCR). Increased CAPP treatment time led to increased NoV reduction; samples treated for the longest time had the lowest viral load. From the initial starting quantity of 2.36 × 104 genomic equivalents/ml, sample exposure to CAPP reduced this value by 1.23 log10 and 1.69 log10 genomic equivalents/ml after 10 and 15 min, respectively (P < 0.01). CAPP treatment of surfaces carrying a lower viral load reduced NoV by at least 1 log10 after CAPP exposure for 2 min (P < 0.05) and 1 min (P < 0.05), respectively. Our results suggest that NoV can be inactivated by CAPP treatment. The lack of cell culture assays prevents our ability to estimate infectivity. It is possible that some detectable, intact virus particles were rendered noninfectious. We conclude that CAPP treatment of surfaces may be a useful strategy to reduce the risk of NoV transmission in crowded environments. Importance Human gastroenteritis is most frequently caused by noroviruses, which are spread person to person and via surfaces, often in facilities with crowds of people. Disinfection of surfaces that come into contact with infected humans is critical for the prevention of cross-contamination and further transmission of the virus. However, effective disinfection cannot be done easily in mass catering environments or health care facilities. We evaluated the efficacy of cold atmospheric pressure plasma, an innovative airborne disinfection method, on surfaces inoculated with norovirus. We used a clinically relevant strain of norovirus from an outbreak in Germany. Cold plasma was able to inactivate the virus on the tested surfaces, suggesting that this method could be used for continuous disinfection of contaminated surfaces. The use of a clinical strain of norovirus strengthens the reliability of our results as it is a strain relevant to outbreaks in humans., Importance Human gastroenteritis is most frequently caused by noroviruses, which are spread person to person and via surfaces, often in facilities with crowds of people. Disinfection of surfaces that come into contact with infected humans is critical for the prevention of cross-contamination and further transmission of the virus. However, effective disinfection cannot be done easily in mass catering environments or health care facilities. We evaluated the efficacy of cold atmospheric pressure plasma, an innovative airborne disinfection method, on surfaces inoculated with norovirus. We used a clinically relevant strain of norovirus from an outbreak in Germany. Cold plasma was able to inactivate the virus on the tested surfaces, suggesting that this method could be used for continuous disinfection of contaminated surfaces. The use of a clinical strain of norovirus strengthens the reliability of our results as it is a strain relevant to outbreaks in humans.

Cold atmospheric plasma (CAP) has been gaining increasing interest as a new approach for the treatment of skin diseases or wounds. Although this approach has demonstrated promising antibacterial activity, its exact mechanism of action remains unclear. This study explored in vitro and in vivo whether CAP influences gene expression and molecular mechanisms in keratinocytes. Our results revealed that a 2 min CAP treatment using the MicroPlaSter ß in analogy to the performed clinical studies for wound treatment induces expression of IL-8, TGF-ß1, and TGF-ß2. In vitro and in vivo assays indicated that keratinocyte proliferation, migration, and apoptotic mechanisms were not affected by the CAP treatment under the applied conditions. Further, we observed that antimicrobial peptides of the ß-defensin family are upregulated after CAP treatment. In summary, our results suggest that a 2 min application of CAP induces gene expression of key regulators important for inflammation and wound healing without causing proliferation, migration or cell death in keratinocytes. The induction of ß-defensins in keratinocytes describes an absolutely new plasma strategy. Activation of antimicrobial peptides supports the well-known antibacterial effect of CAP treatment, whereas the mechanism of ß-defensin activation by CAP is not investigated so far.

PK-4 is an experiment designed to investigate complex plasmas (low-temperature plasmas containing microparticles, e.g. dust grains) in a combined dc/rf discharge under microgravity conditions on board of the International Space Station. Within the 35th and 36th ESA parabolic flight campaigns first experiments under microgravity conditions in a specially designed experiment set-up have been performed. The particle flow inside the tube, the appearance of dust waves, and lane formation in interpenetrating particle clouds have been observed.

The dust detector system on board the Galileo spacecraft recorded dust impacts in circumjovian space during the craft's orbital mission about Jupiter. This is the eighth 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 1997-December 1999 when the spacecraft completed 21 revolutions about Jupiter. In this time interval data were obtained as high resolution realtime science data or recorded data during 449 days (representing 41% of the entire period), or via memory readouts during the remaining times. Because the data transmission rate of the spacecraft was very low, the complete data set (i.e. all parameters measured by the instrument during impact of a dust particle) of only 3% (7625) of all particles detected could be transmitted to Earth; the other particles were only counted. Together with the data of 2883 particles detected during, Galileo's interplanetary cruise and 53 53 particles detected in the jovian system in 1996, complete data of 15 861 particles detected by the Galileo dust instrument from 1989 to 1999 are now available. The majority of the detected particles were tiny grains (about 10 nm in radius), most of them originating from Jupiter's innermost Galilean moon Io. They were detected throughout the jovian system and the highest impact rates exceeded 100 min(-1) (C21 orbit; 01 July 1999). With the new data set the times of onset, cessation and a 180 degrees shift in the impact direction of the grains measured during 19 Galileo orbits about Jupiter are well reproduced by simulated 9 nm particles charged up to a potential of +3 V, confirming earlier results obtained for only two Galileo orbits (Horanyi, M., Grun, E., Heck, A., 1997. Modeling the Galileo dust measurements at Jupiter. Geophys. Res. Lett. 24, 2175-2178). Galileo has detected a large number of bigger particles mostly in the region between the Galilean moons. The average radius of 370 of these grains measured in the 1996-1999 period is about 2 mu m (assuming spherical grains with density 1 g cm(-3)) and the size distribution rises steeply towards smaller grains. The biggest detected particles have a radius of about 10 mu m. (c) 2006 Elsevier Ltd. All rights reserved. (Less)

The purpose of this study was to obtain different structure measures as the three-dimensional (3D)-based scaling index method (SIM) and standard two-dimensional (2D) bone histomorphometric parameters from high-resolution (HR) magnetic resonance (MR) images of the distal radius and to compare these parameters with bone mineral density (BMD) in their diagnostic performance to differentiate postmenopausal patients with and without vertebral fractures. Axial HR-MR images of the distal radius were obtained at 1.5 T in 40 postmenopausal women (17 with osteoporotic spine fractures and 23 controls). Trabecular microarchitecture analysis was performed using the new structure measure % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % WGTbWaaSbaaSqaaiaadcfacaGGOaGaeqySdeMaaiykaaqabaaaaa!3C7B! $$m_{{P(\alpha )}}$$ , derived from the SIM, as well as standard morphological 2D parameters. BMD of the spine was obtained using quantitative computed tomography (QCT). Receiver operating characteristic (ROC) analyses were used to determine diagnostic performance in differentiating both groups. Results were validated by bootstrapping techniques. Significant differences between both patient groups were obtained using % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % WGTbWaaSbaaSqaaiaadcfacaGGOaGaeqySdeMaaiykaaqabaaaaa!3C7B! $$m_{{P(\alpha )}}$$ , 2D parameters, and spine BMD (p

Although it is relatively straightforward to measure the atomic structure of crystals, the detailed dynamics of crystal growth (including the evolution of self-organization, structure formation, and the associated kinetic and thermodynamic development) remains one of the most important topics of solid-state physics1,2,3. Very little is known, for instance, about the evolutionary paths of crystal structure development, and the structural complexity of the surface down to atomic dimensions and its change with time. This is, to a large extent, due to the lack of suitable systems that can be studied at the appropriate length- and timescales. Here, we report experimental observations of a crystallization front propagating in a supercooled region of a three-dimensional fluid complex plasma. The structure and evolution of the front are analysed using kinetic measurements of individual microparticle dynamics. It is found that the fluid–crystalline transition is accompanied by short-lived ‘nano’-crystallites in the fluid and ‘nano’-droplets in the crystalline phases, that the surface structure is scale-free (fractal) in the experimentally accessible regime (2–10 lattice distances) and that crystal growth follows a universal self-organization pattern at the particle level, leading to oscillations in the surface roughness.

A dust void is a dust-free region in dusty plasma. Theory demonstrates that the void results from the balance of the electrostatic and plasma (such as the ion drag) forces acting on a dust particle. In dusty plasma experiments, physical properties of the void show clear dependence on the power input into the plasma (in particular, its size increases with the increase of the applied power). Here, the theory and numerical results are presented for such a dependence.

The plasma cloud mechanism of spoke formation in Saturn's rings, proposed by Goertz and Morfill in 1983, is revisited in the light of new data and the criticisms raised by Farmer and Goldreich [Farmer, A.J., Goldreich, P., 2005. Icarus. This issue]. It is concluded that the plasma cloud model satisfies all available observational and physical constraints.