Plasma System Research Articles

Контрольоване нагрівання циліндричної плазми з використанням особливостей виняткової точки

The paper proposes a method of controlled heating of a cylindrical plasma using the features of the Exceptional point. It is shown that the coupled system of plasma and dielectric waveguides is capable of generating exceptional points where their dispersion curves cross. By controlling the connection (distance) between the waveguides, it is possible to control the distribution of the electromagnetic field, both in the plasma and in the dielectric waveguides around the exceptional point. It is also shown that in the presence of dissipative losses in the plasma, the degree of heating of the plasma waveguide can be controlled by tuning the distribution and intensity of the exciting electromagnetic field in the coupled waveguide system, which gives a potential advantage among other methods of plasma heating. The results obtained in the work can be considered as an example of a new method of controlled plasma heating, which can be used to overcome the existing problems of controlled thermonuclear fusion.

Endothelial HDAC1-ZEB2-NuRD Complex Drives Aortic Aneurysm and Dissection Through Regulation of Protein S-Sulfhydration.

Aortic aneurysm and aortic dissection (AAD) are life-threatening vascular diseases, with endothelium being the primary target for AAD treatment. Protein S-sulfhydration is a newly discovered posttranslational modification whose role in AAD has not yet been defined. This study aims to investigate whether protein S-sulfhydration in the endothelium regulates AAD and its underlying mechanism. Protein S-sulfhydration in endothelial cells (ECs) during AAD was detected and hub genes regulating homeostasis of the endothelium were identified. Clinical data of patients with AAD and healthy controls were collected, and the level of the cystathionine γ lyase (CSE)/hydrogen sulfide (H2S) system in plasma and aortic tissue were determined. Mice with EC-specific CSE deletion or overexpression were generated, and the progression of AAD was determined. Unbiased proteomics and coimmunoprecipitation combined with mass spectrometry analysis were conducted to determine the upstream regulators of the CSE/H2S system and the findings were confirmed in transgenic mice. Higher plasma H2S levels were associated with a lower risk of AAD, after adjustment for common risk factors. CSE was reduced in the endothelium of AAD mouse and aorta of patients with AAD. Protein S-sulfhydration was reduced in the endothelium during AAD and protein disulfide isomerase (PDI) was the main target. S-sulfhydration of PDI at Cys343 and Cys400 enhanced PDI activity and mitigated endoplasmic reticulum stress. EC-specific CSE deletion was exacerbated, and EC-specific overexpression of CSE alleviated the progression of AAD through regulating the S-sulfhydration of PDI. ZEB2 (zinc finger E-box binding homeobox 2) recruited the HDAC1-NuRD complex (histone deacetylase 1-nucleosome remodeling and deacetylase) to repress the transcription of CTH, the gene encoding CSE, and inhibited PDI S-sulfhydration. EC-specific HDAC1 deletion increased PDI S-sulfhydration and alleviated AAD. Increasing PDI S-sulfhydration with the H2S donor GYY4137 or pharmacologically inhibiting HDAC1 activity with entinostat alleviated the progression of AAD. Decreased plasma H2S levels are associated with an increased risk of aortic dissection. The endothelial ZEB2-HDAC1-NuRD complex transcriptionally represses CTH, impairs PDI S-sulfhydration, and drives AAD. The regulation of this pathway effectively prevents AAD progression.

Remediation of atrazine-contaminated soil in a fluidized-bed DBD plasma reactor

In this study, an innovative approach combining dielectric barrier discharge (DBD) plasma and fluidized-bed techniques is proposed and employed to remediate atrazine (ATZ) contaminated soil. Compared with traditional fixed-bed plasma soil remediation system, the fluidized-bed DBD plasma soil remediation system ensures sufficient and uniform contact between the chemically reactive species and the fluidized soil particles, thereby improving the migration and infiltration of reactive species in the soil layer and achieving high-efficiency remediation of contaminated soil. The optimum removal efficiency of 91.2% and energy efficiency of 0.342 mg/kJ were achieved, respectively, after only 6 min fluidized-bed DBD plasma treatment, which were 35.5% and 38.9% higher than those in a fixed-bed DBD plasma system. The primary organic intermediates after fluidized-bed DBD plasma treatment were identified, and the toxicological evaluation of intermediates was performed. Additionally, possible degradation pathways of ATZ in the fluidized-bed DBD plasma reactor were proposed. This system may offer an ideal approach to facilitate mass transfer between chemically reactive species and contaminants on the surface of soil particles, which is expected to achieve efficient, rapid, and continuous treatment of actual contaminated soil.

Qualitative analysis of nonlinear electrostatic excitations in magnetoplasma with pressure anisotropy

Abstract The nonlinear propagation of ion-acoustic (IA) electrostatic solitary waves (SWs) is investigated in a magnetized electron-ion plasma in the presence of pressure anisotropy. The energy integral equation is derived by employing the Sagdeev approach. The current approach only allows for positive potential nonlinear structures. The effect of relevant plasma parameters on the characteristics of SW structures is investigated. The current study may be significant in space and astrophysical plasma systems.

A high efficiency multi-module parallel RF inverter system for plasma induced hydrogen

Hydrogen energy plays an important role in achieving carbon neutralization, and plasma induced hydrogen is an effective production method. One challenge is how to guarantee high efficiency operation with wide power output range of the RF inverter system used to generate the plasma. In this paper, a multi-module parallel topology of a high-frequency inverter is analyzed, in which the power combining network can maintain the soft switching characteristics of the inverter modules. A control method of "ON/OFF + phase shift" is adopted to broaden the output power range of the inverter. The equivalent impedances of different modules are analyzed in detail. A four-module 13.56 MHz high-frequency inverter prototype is built and tested. The results show that the inverter can operate at high efficiency and wide output power range with efficiency improved by at least 5% compared with the traditional parameter design method without considering the effect of paralleled modules.

Opportunities of Electronic and Optical Sensors in Autonomous Medical Plasma Technologies

Low temperature plasma technology is proving to be at the frontier of emerging medical technologies with real potential to overcome escalating healthcare challenges including antimicrobial and anticancer resistance. However, significant improvements in efficacy, safety, and reproducibility of plasma treatments need to be addressed to realize the full clinical potential of the technology. To improve plasma treatments recent research has focused on integrating automated feedback control systems into medical plasma technologies to maintain optimal performance and safety. However, more advanced diagnostic systems are still needed to provide data into feedback control systems with sufficient levels of sensitivity, accuracy, and reproducibility. These diagnostic systems need to be compatible with the biological target and to also not perturb the plasma treatment. This paper reviews the state-of-the-art electronic and optical sensors that might be suitable to address this unmet technological need, and the steps needed to integrate these sensors into autonomous plasma systems. Realizing this technological gap could facilitate the development of next-generation medical plasma technologies with strong potential to yield superior healthcare outcomes.

Staphylococcus aureus Cell Wall Phenotypic Changes Associated with Biofilm Maturation and Water Availability: A Key Contributing Factor for Chlorine Resistance

Staphylococcus aureus biofilms are resistant to both antibiotics and disinfectants. As Staphylococci cell walls are an important defence mechanism, we sought to examine changes to the bacterial cell wall under different growth conditions. Cell walls of S. aureus grown as 3-day hydrated biofilm, 12-day hydrated biofilm, and 12-day dry surface biofilm (DSB) were compared to cell walls of planktonic organisms. Additionally, proteomic analysis using high-throughput tandem mass tag-based mass spectrometry was performed. Proteins involved in cell wall synthesis in biofilms were upregulated in comparison to planktonic growth. Bacterial cell wall width (measured by transmission electron microscopy) and peptidoglycan production (detected using a silkworm larva plasma system) increased with biofilm culture duration (p < 0.001) and dehydration (p = 0.002). Similarly, disinfectant tolerance was greatest in DSB, followed by 12-day hydrated biofilm and then 3-day biofilm, and it was least in the planktonic bacteria--suggesting that changes to the cell wall may be a key factor for S. aureus biofilm biocide resistance. Our findings shed light on possible new targets to combat biofilm-related infections and hospital dry surface biofilms.

A site on factor XII required for productive interactions with polyphosphate

BackgroundDuring plasma contact activation, factor XII (FXII) binds to surfaces through its heavy chain and undergoes conversion to the protease FXIIa. FXIIa activates prekallikrein and factor XI (FXI). Recently, we showed that the FXII first epidermal growth factor-1 (EGF1) domain is required for normal activity when polyphosphate is used as a surface. ObjectivesThe aim of this study was to identify amino acids in the FXII EGF1 domain required for polyphosphate-dependent FXII functions. MethodsFXII with alanine substitutions for basic residues in the EGF1 domain were expressed in HEK293 fibroblasts. Wild-type FXII (FXII-WT) and FXII containing the EGF1 domain from the related protein Pro-HGFA (FXII-EGF1) were positive and negative controls. Proteins were tested for their capacity to be activated, and to activate prekallikrein and FXI, with or without polyphosphate, and to replace FXII-WT in plasma clotting assays and a mouse thrombosis model. ResultsFXII and all FXII variants were activated similarly by kallikrein in the absence of polyphosphate. However, FXII with alanine replacing Lys73, Lys74, and Lys76 (FXII-Ala73,74,76) or Lys76, His78, and Lys81 (FXII-Ala76,78,81) were activated poorly in the presence of polyphosphate. Both have <5% of normal FXII activity in silica-triggered plasma clotting assays and have reduced binding affinity for polyphosphate. Activated FXIIa-Ala73,74,76 displayed profound defects in surface-dependent FXI activation in purified and plasma systems. FXIIa-Ala73,74,76 reconstituted FXII-deficient mice poorly in an arterial thrombosis model. ConclusionFXII Lys73, Lys74, Lys76, and Lys81 form a binding site for polyanionic substances such as polyphosphate that is required for surface-dependent FXII function.

Cathode Position Detection in a Transferred Arc Plasma Using Artificial Neural Network

In a transferred arc plasma system, the position of the cathode is difficult to detect during the smelting process as it remains inside the cylindrical anode. Real-time and accurate cathode position detection leads to efficient smelting operation with optimal use of electrical energy. In this article, a machine learning technique is proposed to accurately detect the position of the cathode in a direct current (DC) transferred arc plasma system. The measured voltage signal sampled at 20 kHz is processed using a tunable Q-factor wavelet transform (TQWT) followed by statistical features extraction and a machine learning algorithm to provide accurate cathode position information. Two different machine learning algorithms are used in this work, namely, single hidden layer neural network (SHLNN) and single-layer extreme learning machine (SELM). The output of these machine learning algorithms provides accurate position information and is also compared to the traditional voltage-related position information. The experimental signal of a 30-kW DC plasma system and cathode position detection results is shown.

Effects of Heavy Ions on the Second‐Harmonic Generation of EMIC Waves in the Inner Magnetosphere

AbstractRecent studies have reported electromagnetic ion cyclotron (EMIC) waves with nonlinear second harmonics (SHs) whose frequency and wave number are twice those of the fundamental waves (FWs). In this paper, we provide detailed analyses of the cross‐band SH generation of EMIC waves in a multi‐ion plasma. In the presence of heavy ions, EMIC wave modes can be divided into distinct wave bands according to heavy ion gyrofrequencies, and the SH can exist in a wave band different from that of the FW. The SH can be generated around or even exactly on the normal modes of the plasma system, leading to a more efficient energy transfer than that in H+‐only plasmas. The detailed parametric analysis also manifests the vital role of heavy ions in promoting SH's amplitude. Further, multiple 1‐D hybrid simulations are performed to investigate the cross‐band SH generation and validate the theoretical results. The SHs are well reproduced in simulations and the quantitative relation of frequency and wave number between the FW and the SH is well satisfied. The variations of the amplitude ratios (the SH to the FW) with fundamental frequencies are well consistent with those obtained from theoretical calculations in magnitude. Therefore, our results demonstrate the significant roles of heavy ions in the SH generation.

On the Formation of Clouds in the Dusty Ionosphere of Mars

Dusty plasma clouds observed at altitudes of about 100 km in the mesosphere of Mars have been considered. Features of the dusty ionosphere of Mars compared to the dusty ionosphere of the Earth have been listed. The equations of the model describing self-consistently dusty plasma structures in the ionosphere of Mars have been presented. This model involves features that are important for the ionosphere of Mars but are ignored when describing the dusty plasma system in the ionosphere of the Earth. In particular, the model for Mars involves effects of deceleration of dust particles because of the adhesion of condensed molecules to them. An altitude distribution of particles constituting mesospheric clouds on Mars has been calculated with the self-consistent model. It has been shown that an important factor for the formation of dusty plasma clouds in the ionosphere of Mars is the Rayleigh–Taylor instability, which limits both the maximum size of dust particles that can form dusty plasma clouds and the maximum thickness of the dusty plasma clouds.

Clinical Observation of Low-Temperature Plasma Ablation Combined with Drug Therapy in the Treatment of Fungal Keratitis.

To observe the efficacy and prognosis of low-temperature plasma ablation + drug therapy in the treatment of fungal corneal ulcers. The present paper presents a retrospective clinical study with a subject base of 34 eyes. Patients with a fungal corneal ulcer who visited the Affiliated Eye Hospital of Nanchang University between August 2019 and December 2021 were selected as the study participants. They were found to have highly reflective fungal hyphae in the corneal stroma layer via confocal microscope examination, which were revealed to be positive on etiology examination, with the ulcer and infiltration depths ≤1/2 of the corneal thickness. The efficacy and prognosis were observed after treatment with low-temperature plasma ablation + drug therapy. A total of 34 cases (34 eyes) had clinical manifestations of corneal infiltration and corneal ulcer formation, with a corneal lesion diameter of 1.31-8.64 mm (average = 4.79 ± 2.03 mm). The average healing time of corneal ulcers was 6.2 ± 1.7 days. Among a total of 34 cases (34 eyes) in patients with fungal keratitis, the infection was controlled and the ulcers gradually healed after treatment with low-temperature plasma system + drug therapy in a total of 30 cases (30 eyes, 88%). A total of three cases (3 eyes, 9%) exhibited no clear improvement after the treatment, and the patients underwent conjunctival flap covering surgery. One case (one eye, 3%) exhibited no clear improvement after further treatment, with the patient experiencing corneal perforation and ultimately undergoing penetrating keratoplasty. Low-temperature plasma ablation + drug therapy can effectively control the progression of fungal keratitis infection, as well as significantly shorten the ulcer healing time, and is, therefore, an effective method.

Electrical equivalent model of a long dielectric barrier discharge plasma jet for endoscopy

Cold atmospheric plasmas are a known source of reactive species enabling various treatments, from the healing of chronic wounds to the treatment of surface cancers. Therapeutic endoscopic procedures require developing specific flexible tools that can be used through or alongside endoscopes. Plasma devices for endoscopy have aroused significant research interest over the past few decades, but their electrical behaviour is not yet fully understood and predictable. There is thus a clear need for a robust model that provides a way to understand and optimize future devices. In this work, for the first time, an electrical equivalent model of a long plasma source (comprising plasma generation, transport and target interaction) was designed, implemented, and validated. System parameters were estimated based on the system geometry and independent measurements. The model reliably reproduces the double ignition (in the quartz chamber and at the treatment site) observed experimentally. Simulations globally agree with measurements taken for various gas gap distances and input voltages. Internal parameters that are difficult to measure, such as the electrical charge at the gas gaps, were inferred. The model can predict leakage current in the body and current at the target site. This work provides a new understanding of endoscopic plasma systems that could be used in the future to ensure patient and operator safety.

Vanadium pentoxide thin films deposited by the thermionic vacuum arc plasma

The Vanadium pentoxide (V2O5) thin films were deposited on glass substrates by a Thermionic vacuum arc (TVA) plasma system. The structural, elemental, surface morphological, and optical properties of the deposited thin films were investigated in detail using X-ray diffraction (XRD), Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), Ultraviolet-visible (UV–VIS) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), and atomic force microscopy (AFM). In this study, the V2O5 thin films deposited on the glass substrates were produced at three different arc powers at fixed cathode filament current and deposition time, and all characteristics of the deposited thin films were analyzed separately for these three arc powers. The thicknesses of the V2O5 thin films deposited at arc powers of 80, 280, and 640 W were measured as 92, 98, and 204 nm, respectively. The main objective of the research is to show that V2O5 thin films can be deposited by the TVA with the features specified by the technology, which cannot be arranged easily in other methods. While all the deposited thin films have an amorphous structure and roughness as small as 0.4 – 1.8 nm, the arc power did not cause any different bonding in the atomic structure. The transmittance of each film, in the spectral range of 300 to 900 nm, was measured and the optical energy band gap (Eg) was calculated for three films deposited at various arc powers and found to be 3.84, 3.42, and 3.20 eV for the direct allowed transitions respectively.

Signatures of an energetic charged body streaming in a plasma.

A charged body moving in a plasma can excite a variety of linear and nonlinear waves in the form of trailing wakes, fore-wake shocks, and precursor solitons. These structures can further interact with the background plasma to create secondary effects that can serve as signatures of the passage of the charged body. Using particle-in-cell simulations, we carry out a basic investigation of the dynamics of a plasma system that is being traversed by an energetic charged body. Using two different shapes of this charged source, namely, an idealized infinite length planar source and a two-dimensional thin rectangular source, we examine the differences in the nature of the excited wave structures and their consequent impact on the background plasma. Our simulations reveal interesting features such as the dependence of the precursor speeds on the total charge on the driving source, local particle trapping, and energization of the trapped particles in various regions along the traversal path leading to the formation of energetic charged beamlets. Our basic findings could find practical applications such as in analyzing the trajectories of charged objects like space debris orbiting in the ionosphere.

Low-Temperature H2/D2 Plasma–W Material Interaction and W Dust Production for Fusion-Related Studies

In this paper, results concerning hydrogen and deuterium plasma (RF, 13.56 MHz) interactions with tungsten surfaces, were reported. We used the Hollow-Cathode (HC) configuration for plasma–tungsten surface interaction experiments, along with the collection of tungsten dust, at different distances. Further on, the plasma-exposed tungsten surfaces and the collected dust were morphologically analyzed by contact profilometry, scanning electron microscopy, and energy dispersive spectroscopy measurements, along with chemical investigations by the X-ray photoelectron spectroscopy technique. The results showed that exposing the tungsten surfaces to the hydrogen plasma induces surface erosion phenomena along with the formation of dust and interconnected W structures. Herein, the mean ejected material volume was ~1.1 × 105 µm3. Deuterium plasma facilitated the formation of blisters at the surface level. For this case, the mean ejected material volume was ~3.3 × 104 µm3. For both plasma types, tungsten dust within nano- and micrometer sizes could be collected. The current study offers a perspective of lab-scaled plasma systems, which are capable of producing tungsten fusion-like surfaces and dust.

Large amplitude electrostatic solitary waves in anisotropic plasma

The propagation of nonlinear ion-acoustic solitary waves (IASWs) is investigated in a magnetized anisotropic electron ion plasma with Cairns distributed electrons. The ions are warm and exhibit pressure anisotropy due to the external magnetic field. The energy integral equation for the wave potential is derived via Sagdeev approach. The effect of various physical plasma parameters (nonthermality, ion pressure anisotropy) on the characteristics of IASWs is investigated in detail. The present investigation could be of interest to space and astrophysical plasma systems having ion pressure anisotropy, for instance, in the magnetosphere and near earth magnetosheath.

Inactivation of SARS-CoV-2 on Surfaces by Cold-Plasma-Generated Reactive Species.

A Cold Atmospheric Plasma (CAP) apparatus was designed and developed for SARS-CoV-2 killing as evaluated by pseudotyped viral infectivity assays. The reactive species generated by the plasma system was fully characterized by using Optical Emission Spectroscopy (OES) measurement under given conditions such as plasma power, flow rate, and treatment time. A variety of reactive oxygen species (ROS) and reactive nitrogen species (RNS) were identified from plasma plume with energies of 15-72 eV in the frequency range between 500-1000 nm. Systematic virus killing experiments were carried out, and the efficacy of CAP treatment in reducing SARS-CoV-2 viral infectivity was significant following treatment for 8 s, with further enhancement of killing upon longer exposures of 15-120 s. We correlated killing efficacy with the reactive species in terms of type, intensity, energy, and frequency. These experimental results demonstrate effective cold plasma virus killing via ROS and RNS under ambient conditions.

Oxygen-mediated dielectric barrier discharge plasma for enhanced degradation of chlorinated aromatic compounds

Chlorinated aromatic compounds (CACs), a kind of refractory pollutants, pose a potential risk to the environment and human health. Herein, dielectric barrier discharge (DBD) plasma is employed to enhance the degradation of 2,4-dichlorophenol (2,4-DCP) from water, and O2 is the most efficient working atmosphere with totally 2,4-DCP degradation in 40 min. O3, ·OH, ·O2– and 1O2 are the main active species responsible for the degradation, while the contribution of hydrated electrons and reactive nitrogen species is almost negligible. Moreover, highly efficient o-Nitrochlorobenzene (o-NCB) and chlorobenzene (CB) degradation and mineralization are also achieved in DBD/O2 process. All the CACs are completely degraded in 60 min following the degradation rate order of CB > 2,4-DCP > o-NCB, which almost follows the order of ionization potential values. The mineralization efficiencies of CB, 2,4-DCP and o-NCB reach 61.14 %, 70.50 % and 92.77 % in DBD/O2 process, respectively, which are 1.74,1.15 and 1.28 times higher than that in DBD process alone. Based on theoretical calculation and intermediates analysis, three common degradation pathways are proposed including hydroxylation, dechlorination and ring-opening. Soil remediation experiments further indicate the high efficiency and promising perspective of DBD/O2 process in CACs contaminated soil treatment. This work is instructive to elucidate the importance of O2 atmosphere in the degradation of CACs by DBD plasma system and provides an alternative way for removing CACs from water and soil.

Liquid plasma as a treatment for cutaneous wound healing through regulation of redox metabolism

The skin functions as the outermost protective barrier to the internal organs and major vessels; thus, delayed regeneration from acute injury could induce serious clinical complications. For rapid recovery of skin wounds, promoting re-epithelialization of the epidermis at the initial stage of injury is essential, wherein epithelial keratinocytes act as leading cells via migration. This study applied plasma technology, which has been known to enable wound healing in the medical field. Through in vitro and in vivo experiments, the study elucidated the effect and molecular mechanism of the liquid plasma (LP) manufactured by our microwave plasma system, which was found to improve the applicability of existing gas-type plasma on skin cell migration for re-epithelialization. LP treatment promoted the cytoskeletal transformation of keratinocytes and migration owing to changes in the expression of integrin-dependent focal adhesion molecules and matrix metalloproteinases (MMPs). This study also identified the role of increased levels of intracellular reactive oxygen species (ROS) as a driving force for cell migration activation, which was regulated by changes in NADPH oxidases and mitochondrial membrane potential. In an in vivo experiment using a murine dorsal full-thickness acute skin wound model, LP treatment helped improve the re-epithelialization rate, reaffirming the activation of the underlying intracellular ROS-dependent integrin-dependent signaling molecules. These findings indicate that LP could be a valuable wound management material that can improve the regeneration potential of the skin via the activation of migration-related molecular signaling within the epithelial cell itself with plasma-driven oxidative eustress.