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Slow dynamics in an amorphous quasi-two-dimensional complex plasma, comprised of microparticles of two different sizes, was studied experimentally. The motion of individual particles was observed using video microscopy, and the self-part of the intermediate scattering function as well as the mean-squared particle displacement was calculated. The long-time structural relaxation reveals the characteristic behavior near the glass transition. Our results suggest that binary complex plasmas can be an excellent model system to study slow dynamics in classical supercooled fluids.

Objective: Ear, nose and throat infections are among the most common reasons for absence from work. They are usually caused by various bacteria like Haemophilus influenzae, Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes. Cold atmospheric plasma (CAP) can effectively eliminate even multi-resistant bacteria and has no cytotoxic or mutagenic effects on the mucosa when applied for less than 60s. Aim of the study was to evaluate the effects of CAP on common ENT bacteria and on the mucosa of the upper aerodigestive tract., Methods: The bactericidal effects of CAP against the bacteria most commonly causing ENT infections were investigated using the colony-forming units assay (CFU) on a Müller-Hinton agar plate after applying CAP for 30, 60, 90 and 120s. To evaluate the interaction of CAP with mucosal cells, 3D mini organ cultures were treated for up to 180s, after which cell viability and necrosis induction were evaluated., Results: Treatment with CAP for 60s or longer induced at least a 3-log 10 reduction in the bacterial load (> 99.9%). Treatment times shorter than 60s had only slight cytotoxic effects on cell viability and necrosis whereas treatment times above 60s showed a fast increase of cytotoxic side effects., Conclusion: CAP exhibited strong bactericidal effects on the most common ENT pathogens. Treatment times of up to 60s showed only minimal adverse reactions in healthy mucosa. CAP could be a promising new therapeutic modality for ENT infections., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In ground-based experiments with complex (dusty) plasmas, charged microparticles are levitated against gravity by an electric field, which also drives ion flow in the parent gas. Existing analytical approaches to describe the electrostatic interaction between microparticles in such conditions generally ignore the field and ion-neutral collisions, assuming free ion flow with a certain approximation for the ion velocity distribution function (usually a shifted Maxwellian). We provide a comprehensive analysis of our previously proposed self-consistent kinetic theory including the field, ion-neutral collisions, and the corresponding ion velocity distribution. We focus on various limiting cases and demonstrate how the interplay of these factors results in different forms of the shielding potential.

Complex (dusty) plasmas allow experimental studies of various physical processes occurring in classical liquids and solids by directly observing individual microparticles. A major problem is that the interaction between microparticles is generally not molecularlike. In this Letter, we propose how to achieve a molecularlike interaction potential in laboratory 2D complex plasmas. We argue that this principal aim can be achieved by using relatively small microparticles and properly adjusting discharge parameters. If experimentally confirmed, this will make it possible to employ complex plasmas as a model system with an interaction potential resembling that of conventional liquids.

Head and neck squamous cell cancer (HNSCC) is the 7th most common cancer worldwide. Despite the development of new therapeutic agents such as monoclonal antibodies, prognosis did not change for the last decades. Cold atmospheric plasma (CAP) presents the most promising new technology in cancer treatment. In this study the efficacy of a surface micro discharging (SMD) plasma device against two head and neck cancer cell lines was proved. Effects on the cell viability, DNA fragmentation and apoptosis induction were evaluated with the MTT assay, alkaline microgel electrophoresis (comet assay) and Annexin-V/PI staining. MTT assay revealed that the CAP treatment markedly decreases the cell viability for all tested treatment times (30, 60, 90, 120 and 180 s). IC 50 was reached within maximal 120 seconds of CAP treatment. Comet assay analysis showed a dose dependent high DNA fragmentation being one of the key players in anti-cancer activity of CAP. Annexin-V/PI staining revealed induction of apoptosis in CAP treated HNSCC cell lines but no significant dose dependency was seen. Thus, we confirmed that SMD Plasma technology is definitely a promising new approach on cancer treatment.

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.

The glass transition is investigated in three dimensions for single and double Yukawa potentials for the full range of control parameters. For vanishing screening parameter, the limit of the one-component plasma is obtained; for large screening parameters and high coupling strengths, the glass-transition properties cross over to the hard-sphere system. Between the two limits, the entire transition diagram can be described by analytical functions. Unlike other potentials, the glass-transition and melting lines for Yukawa potentials are found to follow shifted but otherwise identical curves in control-parameter space.

The Debye shielding of a charge immersed in a flowing plasma is an old classic problem. 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 nonoscillatory and weaker.

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 nonzero 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.

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.

Cold atmospheric plasma (CAP) has the potential to interact with tissue or cells leading to fast, painless and efficient disinfection and furthermore has positive effects on wound healing and tissue regeneration. For clinical implementation it is necessary to examine how CAP improves wound healing and which molecular changes occur after the CAP treatment. In the present study we used the second generation MicroPlaSter ß® in analogy to the current clinical standard (2 min treatment time) in order to determine molecular changes induced by CAP using in vitro cell culture studies with human fibroblasts and an in vivo mouse skin wound healing model. Our in vitro analysis revealed that the CAP treatment induces the expression of important key genes crucial for the wound healing response like IL-6, IL-8, MCP-1, TGF-ß1, TGF-ß2, and promotes the production of collagen type I and alpha-SMA. Scratch wound healing assays showed improved cell migration, whereas cell proliferation analyzed by XTT method, and the apoptotic machinery analyzed by protein array technology, was not altered by CAP in dermal fibroblasts. An in vivo wound healing model confirmed that the CAP treatment affects above mentioned genes involved in wound healing, tissue injury and repair. Additionally, we observed that the CAP treatment improves wound healing in mice, no relevant side effects were detected. We suggest that improved wound healing might be due to the activation of a specified panel of cytokines and growth factors by CAP. In summary, our in vitro human and in vivo animal data suggest that the 2 min treatment with the MicroPlaSter ß® is an effective technique for activating wound healing relevant molecules in dermal fibroblasts leading to improved wound healing, whereas the mechanisms which contribute to these observed effects have to be further investigated.

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.

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.

Over the past few years, the application of cold atmospheric plasma (CAP) in medicine has developed into an innovative field of research of rapidly growing importance. One promising new medical application of CAP is cancer treatment. Different studies revealed that CAP may potentially affect the cell cycle and cause cell apoptosis or necrosis in tumor cells dependent on the CAP device and doses. In this study, we used a novel hand-held and battery-operated CAP device utilizing the surface micro discharge (SMD) technology for plasma production in air and consequently analysed dose-dependent CAP treatment effects on melanoma cells. After 2 min of CAP treatment, we observed irreversible cell inactivation. Phospho-H2AX immunofluorescence staining and Flow cytometric analysis demonstrated that 2 min of CAP treatment induces DNA damage, promotes induction of Sub-G1 phase and strongly increases apoptosis. Further, protein array technology revealed induction of pro-apoptotic events like p53 and Rad17 phosphorylation of Cytochrome c release and activation of Caspase-3. Interestingly, using lower CAP doses with 1 min of treatment, almost no apoptosis was observed but long-term inhibition of proliferation. H3K9 immunofluorescence, SA-ß-Gal staining and p21 expression revealed that especially these low CAP doses induce senescence in melanoma cells. In summary, we observed differences in induction of apoptosis or senescence of tumor cells in respond to different CAP doses using a new CAP device. The mechanism of senescence with regard to plasma therapy was so far not described previously and is of great importance for therapeutic application of CAP., (© 2013 John Wiley & Sons A/S.)

A self-consistent microscopic approach to calculate non-equilibrium pair correlations in strongly interacting driven binary mixtures is presented. The theory is derived from the many-body Smoluchowski equation for interacting Brownian particles by employing Kirkwood's superposition approximation as a closure relation. It is shown that the pair correlations can exhibit notable anisotropy and a strong tendency to laning in the driving direction. Furthermore, there are strong indications that pair correlations are characterized by a long-range decay along the drive. The theoretical results are in good quantitative agreement with the complementary Brownian dynamics computer simulations.

Physical cold atmospheric surface microdischarge (SMD) plasma operating in ambient air has promising properties for the sterilization of sensitive medical devices where conventional methods are not applicable. Furthermore, SMD plasma could revolutionize the field of disinfection at health care facilities. The antimicrobial effects on Gram-negative and Gram-positive bacteria of clinical relevance, as well as the fungus Candida albicans, were tested. Thirty seconds of plasma treatment led to a 4 to 6 log(10) CFU reduction on agar plates. C. albicans was the hardest to inactivate. The sterilizing effect on standard bioindicators (bacterial endospores) was evaluated on dry test specimens that were wrapped in Tyvek coupons. The experimental D(23)(°)(C) values for Bacillus subtilis, Bacillus pumilus, Bacillus atrophaeus, and Geobacillus stearothermophilus were determined as 0.3 min, 0.5 min, 0.6 min, and 0.9 min, respectively. These decimal reduction times (D values) are distinctly lower than D values obtained with other reference methods. Importantly, the high inactivation rate was independent of the material of the test specimen. Possible inactivation mechanisms for relevant microorganisms are briefly discussed, emphasizing the important role of neutral reactive plasma species and pointing to recent diagnostic methods that will contribute to a better understanding of the strong biocidal effect of SMD air plasma.

Non-thermal plasma (NTP) is a flow of partially ionized argon gas at an ambient macroscopic temperature and is microbicidal for bacteria, viruses and fungi. Viability of the Gram-negative obligate intracellular bacterial parasite Chlamydia trachomatis and its host cells was investigated after NTP treatment. NTP treatment of C. trachomatis extracellular elementary bodies (EBs) diminished the concentration of infectious bacteria by a factor of 9×10(4), as established by the parallel infection of murine fibroblast McCoy cells with treated and control EBs. NTP treatment of infected McCoy cells caused disruption of membrane-restricted vacuoles (inclusions), where C. trachomatis intracellular reticulate bodies (RBs) multiply, and a 2×10(6)-fold reduction in the concentration of infectious bacteria. When the samples were covered with magnesium fluoride glass to obstruct plasma particles and UV rays alone were applied, the bactericidal effect was reduced 1.4×10(1)-fold and 5×10(4)-fold for EBs and RBs, respectively. NTP treatment caused the viability of host McCoy cells to diminish by 19%. Therefore, the results obtained demonstrated that (i) both extracellular and intracellular forms of C. trachomatis are sensitive to NTP treatment; (ii) the reduction in concentration of infectious bacteria after NTP treatment of infected cells is superior to the reduction in viability of host cells; and (iii) the effect of NTP on intracellular bacteria does not depend on UV rays.

The fundamental higher-order Landau plasma modes are known to be generally heavily damped. We show that these modes for the ion component in a weakly ionized plasma can be substantially modified by ion-neutral collisions and a dc electric field driving ion flow so that some of them can become unstable. This instability is expected to naturally occur in presheaths of gas discharges at sufficiently small pressures and thus affect sheaths and discharge structures.

Many effects and factors can influence the efficiency of a rocket plasma probe. These include payload charging, solar illumination, rocket payload orientation and rotation, and dust impact induced secondary charge production. As a consequence, considerable uncertainties can arise in the determination of the effective cross sections of plasma probes and measured electron and ion densities. We present a new method for calibrating mesospheric rocket plasma probes and obtaining reliable measurements of plasma densities. This method can be used if a payload also carries a probe for measuring the dust charge density. It is based on that a dust probe's effective cross section for measuring the charged component of dust normally is nearly equal to its geometric cross section, and it involves the comparison of variations in the dust charge density measured with the dust detector to the corresponding current variations measured with the electron and/or ion probes. In cases in which the dust charge density is significantly smaller than the electron density, the relation between plasma and dust charge density variations can be simplified and used to infer the effective cross sections of the plasma probes. We illustrate the utility of the method by analysing the data from a specific rocket flight of a payload containing both dust and electron probes.

We demonstrate that the melting curves of various model systems of interacting particles collapse to (or are located very close to) a universal master curve on a plane of appropriately chosen scaled variables. The physics behind this universality is discussed. An equation for the emerging "universal melting curve" is proposed. The obtained results can be used to approximately predict melting of various substances in a wide range of conditions.

Analyzing three approximate methods to locate liquid-solid coexistence in simple systems, an observation is made that all of them predict the same functional dependence of the temperature on density at freezing and melting of the conventional Lennard-Jones (LJ) system. The emerging equations can be written as T=Aρ(4)+Bρ(2) in normalized units. We suggest to determine the values of the coefficients A at freezing and melting from the high-temperature limit, governed by the inverse 12th power repulsive potential. The coefficients B can be determined from the triple point parameters of the LJ fluid. This produces freezing and melting equations which are exact in the high-temperature limit and at the triple point and show remarkably good agreement with numerical simulation data in the intermediate region., (© 2011 American Institute of Physics.)

We put forward an approximate method to locate the fluid-solid (freezing) phase transition in systems of classical particles interacting via a wide range of Lennard-Jones-type potentials. This method is based on the constancy of the properly normalized second derivative of the interaction potential (freezing indicator) along the freezing curve. As demonstrated recently it yields remarkably good agreement with previous numerical simulation studies of the conventional 12-6 Lennard-Jones (LJ) fluid [S.A.Khrapak, M.Chaudhuri, G.E.Morfill, Phys. Rev. B 134, 052101 (2010)]. In this paper, we test this approach using a wide range of the LJ-type potentials, including LJ n-6 and exp-6 models, and find that it remains sufficiently accurate and reliable in reproducing the corresponding freezing curves, down to the triple-point temperatures. One of the possible application of the method--estimation of the freezing conditions in complex (dusty) plasmas with "tunable" interactions--is briefly discussed.

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 bacteria Pseudomonas aeruginosa, Burkholderia cenocepacia and Escherichia coli, there were no survivors among the initial 10(5) c.f.u. after a 5 min plasma treatment. The susceptibility of Gram-positive bacteria was species- and strain-specific. Streptococcus pyogenes was the most resistant with 17 % survival of the initial 10(5) c.f.u. after a 5 min plasma treatment. Staphylococcus aureus had a strain-dependent resistance with 0 and 10 % survival from 10(5) c.f.u. of the Sa 78 and ATCC 6538 strains, respectively. Staphylococcus epidermidis and Enterococcus faecium had 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 with P. aeruginosa and the plasma-sensitive Staphylococcus aureus strain 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 eliminated P. aeruginosa from 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.

Ensembles of particles with a spherically symmetric repulsive Yukawa interaction and additional dipole-dipole interaction induced by an external field exhibit numerous solid-solid phase transitions controlled by the magnitude of the field. Such interactions emerge most notably in electro- and magnetorheological fluids and plasmas. We propose a simple variational approach based on the Bogoliubov inequality for determining equilibrium solid phases. Phase diagrams for several regimes are calculated and compared with previously performed Monte Carlo and molecular dynamics simulations.

Momentum transfer in complex plasmas (systems consisting of ions, electrons, neutrals, and charged macroscopic grains) is investigated assuming an interaction potential between the charged species of the screened Coulomb (Yukawa) type. Momentum transfer cross sections and rates are derived. Applications of the results are discussed; in particular, we classify the possible states of complex plasmas in terms of the momentum transfer due to grain-grain collisions and its competition with that due to interaction with the surrounding medium. The resulting phase diagrams are presented.

Fluid flow around an obstacle was observed at the kinetic (individual particle) level using "complex (dusty) plasmas" in their liquid state. These "liquid plasmas" have bulk properties similar to water (e.g., viscosity), and a comparison in terms of similarity parameters suggests that they can provide a unique tool to model classical fluids. This allows us to study "nanofluidics" at the most elementary-the particle-level, including the transition from fluid behavior to purely kinetic transport. In this (first) experimental investigation we describe the kinetic flow topology, discuss our observations in terms of fluid theories, and follow this up with numerical simulations.