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In this paper, we show and discuss a set of cross sections for electron collisions with dimethyl ether (DME, C2H6O) obtained by the standard swarm analysis of experimental data for drift velocities and ionization coefficients measured in pure DME and its mixtures with Ar and Ne by E. Oettinger and coworkers. While the existing cross section set gave relatively good predictions for drift velocities, it proved necessary to modify the inelastic cross sections in order to achieve a better agreement with drift velocities in gas mixtures and a good agreement for the ionization coefficient. Furthermore, the derived set of cross sections was used to calculate the electron transport and rate coefficients under the influence of a constant electric field and crossed electric and magnetic DC and RF orthogonal configuration fields. The effect of the magnitude and frequency of the fields on electron transport was studied separately. Our work has resulted in a database of collision and transport data which can be used in modeling of both DC and RF discharges and plasma applications containing pure DME and its mixtures. [ABSTRACT FROM AUTHOR]

In this review, several examples of ionized gases are presented where swarm models may be employed to provide full description. Those situations include low space charge pre-breakdown, Townsend region breakdown where space charge effects may be calculated from the swarm model and used as the first order perturbation to describe oscillations and transient signal and afterglows. In addition, implications are considered for microdischarges, discharges in and close to liquids, gas-filled particle traps, thermalization of particles in living tissue, and many more. In all those situations, swarm models provide full description of the discharge, while for most other collision dominated non-equilibrium plasmas swarm physics (transport-related phenomena) provides a part of the foundation of modeling. [ABSTRACT FROM AUTHOR]

In this paper we present results for reduced ionization coefficients (α/N, N—gas density) obtained from the breakdown voltage and emission profile measurements in low-pressure dc discharges in two freons: 1,1,1,2-tetrafluoroethane (R134a) with the chemical formula CH2F–CF3 and 2,3,3,3-tetrafluoropropene (HFO1234yf) with the chemical formula CH2=CFCF3. Our results for α/N are determined from the axial emission profiles in low-current Townsend discharge and lay in the intervals of reduced electric fields E/N (E—electric field, N—gas density), from 2.7 to 5.9 kTd for R134a and from 5 to 23 kTd for HFO1234yf. We also provide a comparison of our experimental results with those from the available literature. [ABSTRACT FROM AUTHOR]

In this paper we make a parallel between the swarm method in physics of ionized gases and modeling of positrons in radiation therapy and diagnostics. The basic idea is to take advantage of the experience gained in the past with electron swarms and to use it in establishing procedures of modeling positron diagnostics and therapy based on the well-established experimental binary collision data. In doing so we discuss the application of Monte Carlo technique for positrons in the same manner as used previously for electron swarms, we discuss the role of complete cross section sets (complete in terms of number, momentum and energy balance and tested against measured swarm parameters), we discuss the role of benchmarks and how to choose benchmarks for electrons that may perhaps be a subject to experimental verification. Finally we show some samples of positron trajectories together with secondary electrons that were established solely on the basis of accurate binary cross sections and also how those may be used in modeling of both gas filled traps and living organisms. [ABSTRACT FROM AUTHOR]

The potential of plasma applications medicine, the connections to nanotechnologies and the results obtained by our group are reviewed. A special issue in plasma medicine is the development of the plasma sources that would achieve non-equilibrium at atmospheric pressure in an atmospheric gas mixture with no or only marginal heating of the gas, and with desired properties and mechanisms that may be controlled. Our studies have shown that control of radicals or chemically active products of the discharge, such as ROS (reactive oxygen species) and/or NO, may be used to control the growth of the seeds. Simultaneously, a specially designed plasma needle and other sources were shown to be efficient to sterilize not only colonies of bacteria but also planktonic samples (microorganisms protected by water) or bio films. Finally, it was shown that a plasma might induce differentiation of stem cells. Non-equilibrium plasmas may be used in detection of different specific markers in medicine. For example proton transfer mass spectroscopy may be employed in the detection of volatile organic compounds without their dissociation and thus as a technique for instantaneous measurement of the presence of markers for numerous diseases. [ABSTRACT FROM AUTHOR]

Abstract: Rate coefficients were calculated for the first time for vibrational excitation in pure HBr in both DC and RF, E and in ExB fields. We have studied the effect of the amplitude and frequency of applied fields. The calculation was based on a Monte Carlo technique. It was found that a complex behavior may develop due to sharp and very large vibrational cross sections and modulation of the energy distribution function by time-dependent fields and by magnetic field. [Copyright &y& Elsevier]

In this work we extend a multi term solution of the Boltzmann equation for electrons in neutral gases to consider the third-order transport coefficient tensor. Calculations of the third-order transport coefficients have been carried out for electrons in noble gases, including helium (He), neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe) as a function of the reduced electric field, E/n0 (where E is the electric field while n0 is the gas number density). Three fundamental issues are considered: (i) the correlation between the longitudinal component of the third-order transport tensor and the longitudinal component of the diffusion tensor, (ii) the influence of the third-order transport coefficients on the spatial profile of electron swarm, and (iii) the errors associated with the two term approximation for calculating the third-order transport coefficients for electron swarms in noble gases. It is found that a very strong correlation exists between the longitudinal components of the third-order transport coefficient tensor and diffusion tensor for the higher values of E/n0. The effects of the third-order transport coefficients on the spatial profile of electron swarms are the most pronounced for noble gases with the Ramsauer-Townsend minimum in the cross sections for elastic scattering. The largest errors of two term approximation are observed in the off-diagonal elements of the third-order transport coefficient tensor in Ar, Kr and Xe for the higher values of E/n0. [ABSTRACT FROM AUTHOR]

Breakdown in oxygen, in external radio-frequency (RF) electric field is analyzed by employing a Monte Carlo simulation (MCS). Results were obtained for 13.56 MHz and distance between electrodes of 15 mm. Physical background of an oxygen RF breakdown is explained by observing time-resolved spatial distributions of electron concentration, mean energy, elastic scattering rate, ionization rate and attachment. The role of attachment is investigated in cases when these processes are included and when they are not. Especially influence of the attachment is highlighted by comparing oxygen and argon breakdown-voltage curves and spatial profiles. The electron losses induced by attachment extend the motion of the electron prebreakdown swarm much closer to electrodes to achieve a greater production; hence, spatial profiles at high values of the product pd where p is the pressure and d is the gap between electrodes, become more similar to those at the minimum of the breakdown curve. The most striking difference between the breakdown curves in argon and in oxygen is in the high increase of the breakdown voltage for high pd in oxygen. [ABSTRACT FROM AUTHOR]

In this paper, we present the results for voltage–current (V–i) characteristics of dc low-pressure low to moderate current discharges in vapors of alcohols: methanol, ethanol, isopropanol, and n-butanol vapors. These electrical measurements are supported by optical recordings of axial emission profiles from low-current to high-current regimes. The voltage–current characteristics and the corresponding distribution of emission intensities were typically recorded for two pd values, in the left-hand branch of the Paschen curve (0.15 Torr cm) and in the minimum of the Paschen curves (ranging from 0.30 to 0.40 Torr cm for different alcohols selected here). In the recorded V–i characteristics, the different discharge regimes of discharge operation are easily distinguished. Axial profiles of emitted light from the low-current to high-current regimes reveal that heavy particles make up a significant contribution to excitation part in alcohol vapor discharges. In the region of transition from normal to abnormal glow in the methanol vapor discharge, sudden changes of the regime of operation were observed and several diagnostic techniques have been applied to them. [ABSTRACT FROM AUTHOR]

Abstract: In this work we present the spatial distributions and excitation coefficients for the level O I 2p33s–2p3(4S0)3p (leading to λ =777.4 nm transition), produced by dissociative excitation by electron swarms in oxygen. We used a simple parallel plate drift tube and obtained absolute emission intensities in a low-current self-sustained Townsend type discharge. The data were obtained between moderate E/N (E—electric field, N—gas density) where electrons are in equilibrium and very high E/N where electrons may not be in equilibrium with the field and where heavy particles may be the dominant contributor to the excitation. Even at moderate E/N heavy particle effects become considerable. [Copyright &y& Elsevier]

Atmospheric pressure plasmas are becoming relevant in local microbial deactivation and other combined effects of plasmas on living organisms. For this reason, our research was focussed on optimisation of atmospheric pressure plasma jet (APPJ) parameters to complete the deactivation of different bacteria strains in a medium. Different helium APPJ treatments with different discharge parameters were used, such as input voltages and gas flows. To better understand plasma properties behind complete bacteria deactivation at optimised discharge parameters, optical and electrical plasma jet diagnostics were performed, including electrical characterisation of the plasma source, optical emission spectroscopy of the plasma plume and intensified charged coupled device imaging of the discharge behaviour for every set of plasma parameters. Then, the resulting plasma liquid chemistry was assessed to establish the connections between reactive species generated in the gaseous and liquid phases. The most efficient deactivation was found for higher discharge powers and gas flow rates, and that was linked to higher densities of reactive oxygen and nitrogen species, especially hydrogen peroxide and medium solvated charges. [ABSTRACT FROM AUTHOR]

This paper presents results for effective ionisation coefficients ( α eff / N , N—gas density) obtained from the breakdown voltage and emission profile measurements in low-pressure dc discharges in vapours of alcohols: methanol, ethanol, isopropanol, and n-butanol. Our results for α eff / N are determined from the axial emission profiles in low-current Townsend discharge and lay in the interval of reduced electric field E/N (E—electric field, N—gas density), from 1 kTd to 8.8 kTd. We also give a comparison of our experimental results with those from the available literature. Our data cover the high E/N range of the standard operating conditions and in the region where other data are available we have a good agreement. [ABSTRACT FROM AUTHOR]

The results covered in this paper provide breakdown data represented by Paschen curves for methanol, isopropanol and n-butanol, along with the corresponding axial profiles of emission in Townsend regime of the discharge and including the optical emission spectra. Paschen curves were recorded in the range of pd (pressure x electrode gap) from 0.10 to 3.00 Torr cm. The optical emission spectra (OES) are recorded for wavelength range from 300 to 900 nm, for discharges in all studied alcohols. The recorded spectra enabled identification of species that participate in these discharges. All three alcohols exhibit emission from excited radicals OH (at 306.4 nm), CH (at 431.2 nm) and Hα (at 656.4 nm) produced mostly in dissociative excitation by electrons. Recorded profiles of emission enabled us to identify conditions where processes induced by heavy particles (ions and fast neutrals) are dominant in inducing emission from the discharge. [ABSTRACT FROM AUTHOR]

In this study we evaluate apoptosis time window of primary fibroblasts treated with cold atmospheric plasma (CAP), power range 0.4-1.4 W, for 30 sec, using γ-H2AX phosphorylation assay and flow cytometry. In contrast to irradiation where maximum of γ-H2AX foci appeared 30 min after irradiation and apoptosis 24 h later irrespective of radiation dose, treatment with CAP (power of 0.4 and 0.6) induces maximum of γ-H2AX foci 2 h after treatment. Apoptosis occurred in a power-dependent manner, with time shift of 2-3 h. Besides power-dependent time shift in apoptosis induction, apoptosis time window is the same and lasts for 2 h. [ABSTRACT FROM AUTHOR]

Objectives: The study aims to evaluate the effects of non-thermal atmospheric plasma (NTAP) treatments on dentin wetting and surface free energy (SFE) and compare the effects of NTAP treatment, etch-and-rinse, and self-etch protocols for application of universal adhesives. Materials and methods: Mid-coronal dentin of intact third molars was used to measure contact angles of distilled water, ethylene-glycol, and diiodomethane and calculate SFE following different NTAP preset treatments (feeding gas consisting of pure He, He + 1% O2, He + 1.5% O2), power input (1 or 3 W), and tip-to-surface distance (2, 4, or 8 mm). Contact angles of reference liquids and SFE of dentin following He + 1.5% O2 at 3-W and 4-mm treatment was compared to phosphoric acid etching. Contact angles of Single Bond Universal (SBU; 3M ESPE) and Clearfil Universal Bond (CUB; Kuraray Noritake) were measured following NTAP, etch-and-rinse, and self-etch protocols. Results: NTAP significantly reduced contact angles of reference liquids and increased dentin SFE compared to untreated dentin (p < 0.05). O2 intensified the effect of He NTAP (p < 0.05). NTAP and phosphoric acid increased dentin polarity and Lewis base surface characteristics. Phosphoric acid increased contact angles of adhesives compared to the self-etch protocol (p < 0.05). NTAP resulted in lower adhesive contact angles than phosphoric acid, the difference being statistically significant for CUB (p < 0.05). Compared to the self-etch protocol, NTAP slightly reduced CUB contact angle but not that of SBU (p > 0.05). Conclusions: He NTAP with and without O2 increased dentin wetting and SFE, surpassing the effect of phosphoric acid and lowering adhesive contact angles. NTAP produced no apparent micro-morphological changes on dentin surface comparable to acid etching. Clinical significance: NTAP treatment of dentin prior to adhesive application increases dentin wetting and surface free energy facilitating better adhesive distribution on dentin surface compared to phosphoric acid etching and similar to the "self-etch" application protocol. [ABSTRACT FROM AUTHOR]

In this work we present results of two significantly different types of plasma treatment on Paulownia tomentosa Steud. seeds. In the first type, seeds were directly treated in low‐pressure plasma and then imbibed with distilled water. In the second type, an atmospheric pressure plasma was used for obtaining plasma activated water (PAW) which is then used for imbibition of seeds. The CAT activity and protein content is evaluated during 4 d following the imbibition process, i.e., immediately after the phytochrome activation and in the 3 subsequent days. Comparison of results of treated seeds to the control group allows to correlate the enzyme activity and protein content during the initial stages of germination with plasma treatment types and treatment conditions. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET) fabric was treated in a late afterglow of plasma created by a microwave (MW) discharge in the surfatron mode, by using oxygen (O 2 ) and ammonia (NH 3 ) gases. The series of treatments using one gas or the combination of both at different treatment times were performed in order to increase the embedment of UV-responsive microcapsules that were deposited onto PET with pad-dry-cure process. Plasma in both gases was characterized by optical emission spectroscopy (OES), which showed substantial dissociation of O 2 and NH 3 molecules as well as formation of NH x radicals due to the partial dissociation of ammonia molecules. The chemically active species in the plasma afterglow changed the surface properties of PET that were analysed using X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF–SIMS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and water absorption analysis. The effectiveness of plasma treatment on embedment of UV-responsive microcapsules on PET was evaluated by UV-responsiveness, colour strength and colour depth using reflectance spectroscopy, add-on and air permeability, respectively. Treating PET by O 2 afterglow followed by a longer treatment by NH 3 afterglow increased the polymers hydrophilicity and concentration of nitrogen-rich functional groups on surface that enabled higher uptake of UV-responsive microcapsules, and consequently better responsiveness of fabric to UV radiation. The add-on of microcapsules was almost 8-times higher and the colour depth increased up to 75% for plasma treated samples. [ABSTRACT FROM AUTHOR]

In this paper, we explain the difference in sign of the flux and bulk drift velocities of a swarm of electrons in constant direct current (dc) and in radio frequency (RF) electric fields under conditions which lead to negative absolute mobility. We have studied (0.5%) F2/Ar decaying plasma. It was shown that there is a spatial separation of groups of electrons with high and low energy and as a result there is a localization of electron attachment in the region of low energy. Finally, we show that the positive value of the bulk mobility and its delay in RF fields may be explained by a wave of localized attachment that changes the center of mass of the electron swarm. [ABSTRACT FROM AUTHOR]

Previous measurements of the drift velocities, W, and the density-normalized effective ionization (multiplication) coefficients (ionization minus attachment), (α – η)/N, measured in C2H2F4 (1,1,1,2 tetrafluoroethane) and in C2H2F4–Ar mixtures have been analysed with a standard swarm procedure. As a result of this analysis a set of electron collision cross sections for the C2H2F4 molecule has been obtained. This set has been further used to calculate other transport parameters such as the characteristic energies and rate coefficients for individual processes. [ABSTRACT FROM AUTHOR]

Ionization coefficients are measured for electrons in a dc micro-discharge in argon from optical emission profiles. The micro-discharge is operated in the Townsend regime between two parallel-plate electrodes. Axial profiles of emission are obtained with sufficient resolution to provide spatial ionization coefficients. The measured coefficients agree very well with the data obtained from other sources, indicating the operation of the discharge in the Townsend regime and also that Townsend mechanisms do not need extension to describe such discharges. [ABSTRACT FROM AUTHOR]

We have developed a large-volume low-pressure cylindrical plasma reactor with a size that matches industrial reactors for treatment of textiles. It was shown that it efficiently produces plasmas with only a small increase in power as compared with a similar reactor with 50 times smaller volume. Plasma generated at 13.56 MHz was stable from transition to streamers and capable of long-term continuous operation. An industrial-scale asymmetric cylindrical reactor of simple design and construction enabled good control over a wide range of active plasma species and ion concentrations. Detailed characterization of the discharge was performed using derivative, Langmuir and catalytic probes which enabled determination of the optimal sets of plasma parameters necessary for successful industry implementation and process control. Since neutral atomic oxygen plays a major role in many of the material processing applications, its spatial profile was measured using nickel catalytic probe over a wide range of plasma parameters. The spatial profiles show diffusion profiles with particle production close to the powered electrode and significant wall losses due to surface recombination. Oxygen atom densities range from 1019 m-3 near the powered electrode to 1017 m-3 near the wall. The concentrations of ions at the same time are changing from 1016 to the 1015 m-3 at the grounded chamber wall. [ABSTRACT FROM AUTHOR]

Abstract: A Monte Carlo simulation technique is used to investigate electron transport in N2O in crossed RF electric and magnetic fields. Our work has resulted in a database of transport parameters which can be used for correct implementation in modeling RF discharges. A behavior of transport coefficients under the influence of the magnitude and the frequency of the fields was studied separately revealing some complex features in the time dependence, most notably anomalous anisotropic diffusion and time-resolved negative differential conductivity. [Copyright &y& Elsevier]

We have presented measurements of spatial profiles of electron induced emission coefficients for the 777.4 nm radiation of oxygen in low current discharges. Measurements were performed by the drift tube technique in low-current self-sustained Townsend type discharges. We have also compared results for the delay distance for electrons in oxygen calculated using Monte Carlo simulation code and results from a semi-empirical formula adjusted to fit the oxygen data. Finally, from the spatial profiles we have determined ionization coefficients. The spatial profiles of emission provide us also with information on heavy particle excitation and on the reflection of electrons from the anode. The absolutely calibrated spatial profiles of emission may be used to separate the effects of electrons and heavy particles in excitation at high E/N values and obtain the cross sections for fast neutral excitation. [ABSTRACT FROM AUTHOR]

Abstract: We analyze the experimental and calculated electron excitation coefficients for 2p 1–1s 2 (Paschen notation) transition of neon determined in parallel plate drift tube for E/N values between 20 and 3000Td (E-electric field, N-gas density, 1Td=10−21 Vm2). A null-collision Monte Carlo code was employed, representing the transport of electrons, ions and fast neutrals. The contribution of electron reflection at the anode is analyzed. A very pronounced excitation by fast neutrals was found above several kTd. [Copyright &y& Elsevier]

Simple Summary: Dendritic cells (DCs)-based anti-cancer vaccines displayed limited efficacy in clinical trials, mostly due to a lack of protocols for preparing immunogenic tumor antigens used in the vaccine. Here, a unique atmospheric pressure plasma jet was used to prepare a plasma-activated medium (PAM) which induced immunogenic cell death in tumor cells. This procedure increased the efficacy of tumor lysates in enhancing the immunogenicity of DCs according to their increased maturation, production of IL-12, and the capacity to induce cytotoxic CD8 T cells able to kill tumor cells. In contrast to the tumor lysates commonly used in DC vaccines, PAM-tumor lysates lacked the capacity to increase IL-10 production by DCs, and their potential to induce protumorogenic Th2 and regulatory T cells. Cumulatively, these results suggest that the novel method for preparing immunogenic tumor lysates with PAM could be suitable for improved DC-based immunotherapy of cancer patients. Autologous dendritic cells (DCs)-based vaccines are considered quite promising for cancer immunotherapy due to their exquisite potential to induce tumor antigen-specific cytotoxic T cells. However, a lack of efficient protocols for inducing immunogenic tumor antigens limits the efficacy of DC-based cancer vaccines. Here, we found that a plasma-activated medium (PAM) induces immunogenic cell death (ICD) in tumor cells but not in an immortalized L929 cell line or human peripheral blood mononuclear cells. PAM induced an accumulation of reactive oxygen species (ROS), autophagy, apoptosis, and necrosis in a concentration-dependent manner. The tumor lysates prepared after PAM treatment displayed increased immunogenicity in a model of human monocyte-derived DCs, compared to the lysates prepared by a standard freezing/thawing method. Mature DCs loaded with PAM lysates showed an increased maturation potential, as estimated by their increased expression of CD83, CD86, CD40, IL-12/IL-10 production, and attenuated PDL1 and ILT-4 expression, compared to the DCs treated with control tumor lysates. Moreover, in co-culture with allogeneic T cells, DCs loaded with PAM-lysates increased the proportion of cytotoxic IFN-γ+ granzyme A+ CD8+ T cells and IL-17A-producing T cells and preserved the Th1 response. In contrast, control tumor lysates-treated DCs increased the frequency of Th2 (CD4+IL-4+), CD4, and CD8 regulatory T cell subtypes, none of which was observed with DCs loaded with PAM-lysates. Cumulatively, these results suggest that the novel method for preparing immunogenic tumor lysates with PAM could be suitable for improved DC-based immunotherapy of cancer patients. [ABSTRACT FROM AUTHOR]