Plasma Potential Research Articles

Factors Influencing the Fluctuation Amplitude of the H− Ion Beam Extracted from an RF Wave Excited Ion Source Plasma

The beam oscillation of J-PARC ion source is being studied as AC electric field at 2 MHz ion source driving frequency can directly change the extraction characteristics of both H− ions and electrons. The internal RF antenna inducing the electric field generated two peaks of plasma production during one RF cycle as confirmed by 4 MHz modulation of Balmer-alpha (Hα) emission intensity. The coupling between the plasma production at 4 MHz and the oscillation of the local plasma potential in the vicinity of the extraction hole at 2 MHz can cause 6 MHz oscillation, which was observed in the measurement of extraction current from the ion source. Phase-delay of Hα intensities from the source plasma and those of the extraction electron current were compared with the RF input signal to the amplifier.

On double-layer and reverse discharge creation during long positive voltage pulses in a bipolar HiPIMS discharge

Time-resolved Langmuir probe diagnostics at the discharge centerline and at three distances from the target ( 35mm , 60mm , and 100mm ) was carried out during long positive voltage pulses (a duration of 500μs and a preset positive voltage of 100V ) in bipolar high-power impulse magnetron sputtering of a Ti target (a diameter of 100mm ) using an unbalanced magnetron. Fast-camera spectroscopy imaging recorded light emission from Ar and Ti atoms and singly charged ions during positive voltage pulses. It was found that during the long positive voltage pulse, the floating and the plasma potentials suddenly decrease, which is accompanied by the presence of anode light located on the discharge centerline between the target center and the magnetic null of the magnetron’s magnetic field. These light patterns are related to the ignition of a reverse discharge, which leads to the subsequent rise in the plasma and the floating potentials. The reversed discharge is burning up to the end of the positive voltage pulse, but the plasma and floating potentials have lower values than the values from the initial part of the positive voltage pulse. Secondary electron emission induced by the impinging Ar+ ions to the grounded surfaces in the vicinity of the discharge plasma together with the mirror configuration of the magnetron magnetic field are identified as the probable causes of the charge double-layer structure formation in front of the target and the ignition of the reverse discharge.

Properties of collisional plasma sheath with ionization source term and two-temperature electrons in an oblique magnetic field

A collisional magnetized plasma sheath with two groups of electrons has been studied using a fluid model including the effects of the ionization source term and the collisional force between ions and neutral atoms. Two kinds of non-Maxwellian descriptions of electron velocity distribution, non-extensive distribution and truncated distribution, are applied in the model, and the ionization effects of both kinds are considered. By applying Sagdeev potential, the modified Bohm sheath criterion is derived. The effects of ionization, magnetic field, and high-temperature electron concentration ratio on plasma sheath density, potential, sheath thickness, and ion kinetic energy are studied. In cases with high background gas density, ion density accumulates at the sheath edge position, forming a peak and manifesting as a rapid drop in the potential profile. The distribution characteristics of electrons have a significant impact on the transport properties of ions. Oscillations and non-monotonic characteristics of net charge near the sheath edge occur as the magnetic field angle increases, leading to an increase in the sheath layer width. It can be seen that in the case of a collisional sheath structure with high-temperature electrons, it is essential to consider the sheath changes induced by the ionization and the collisional force. Compared to a symmetric electron velocity distribution, the actual thickness of the sheath layer in a truncated electron distribution assumption could be significantly reduced.

Integrated grade-wise profiling analysis reveals potential plasma miR-373-3p as prognostic indicator in Prostate Cancer & its target KPNA2

BackgroundPlasma microRNAs (miRNAs) have recently garnered attention for their potential as stable biomarkers in the context of Prostate Cancer (PCa), demonstrating established associations with tumor grade, biochemical recurrence (BCR), and metastasis. This study seeks to assess the utility of plasma miRNAs as prognostic indicators for distinguishing between high-grade and low-grade PCa, and to explore their involvement in PCa pathogenesis. MethodologyWe conducted miRNA profiling in both plasma and tissue specimens from patients with varying PCa grades. Subsequently, the identified miRNAs were validated in a substantial independent PCa cohort. Furthermore, we identified and confirmed the gene targets of these selected miRNAs through Western blot analysis. ResultsIn our plasma profiling investigation, we identified 98, 132, and 154 differentially expressed miRNAs (DEMs) in high-grade PCa vs. benign prostatic hyperplasia (BPH), low-grade PCa vs. BPH, and high-grade PCa vs. low-grade PCa, respectively. Our tissue profiling study revealed 111, 132, and 257 statistically significant DEMs for the same comparisons. Notably, miR-373-3p emerged as the sole consistently dysregulated miRNA in both plasma and tissue samples of PCa. This miRNA displayed significant overexpression in plasma and tissue samples, with fold changes of 3.584 ± 0.5638 and 8.796 ± 1.245, respectively. Furthermore, we observed a significant reduction in KPNA2 protein expression in PCa. ConclusionOur findings lend support to the potential of plasma miR-373-3p as a valuable biomarker for predicting and diagnosing PCa. Additionally, this miRNA may contribute to the progression of PCa by inhibiting KPNA2 expression, shedding light on its role in the disease.

Plasma atomic layer etching of SiO2 with a low global warming potential fluorocarbon precursor (C6F6)

Reducing greenhouse gas emissions from semiconductor manufacturing has been attracting enormous interest in both industry and academia as global warming issues have increased in significance year by year. Among various strategies, the search for etch precursors that have low global warming potential is actively underway worldwide to reduce the use of conventional precursors with high global warming potential. In this paper, we explore the use of C6F6, a promising candidate to replace the widely utilized perfluorocarbon precursor C4F8, for plasma atomic layer etching (ALE) of SiO2. In situ ellipsometry results indicated that acceptable ALE characteristics were obtained with C4F8 and C6F6 each in their own specific ALE window, while C6F6 showed superior ALE performance. Investigation into the ALE performance with different precursors was then conducted based on plasma diagnostics for radical density, electron density, and plasma potential, and the results of which showed that the difference in the radical composition between precursors significantly affected the resulting ALE trends and also that the excellent ALE performance with C6F6 might originate from its significant polymeric characteristics. We expect the present findings to contribute to the wider adoption of low global warming potential precursors in the etching process.

Remote inductively coupled plasmas in Ar/N2 mixtures and implications for plasma enhanced ALD

Plasma enhanced atomic layer deposition (PEALD) is a cyclic atomic layer deposition (ALD) process that incorporates plasma-generated species into one of the cycle substeps. The addition of plasma is advantageous as it generally provides unique reactants and a substantially reduced growth temperature compared to thermal approaches. However, the inclusion of plasma, coupled with the increasing variety of plasma sources used in PEALD, can make these systems challenging to understand and control. This work focuses on the use of plasma diagnostics to examine the plasma characteristics of a remote inductively coupled plasma (ICP) source, a type of plasma source that is commonly used for PEALD. Ultraviolet to near-infrared spectroscopy and spatially resolved Langmuir probe measurements are employed to characterize a remote ICP system using nitrogen-based gas chemistries typical for III-nitride growth processes. Spectroscopy is used to characterize the relative concentrations of important reactive and energetic neutral species generated in the remote ICP as a function of gas flow rate, Ar/N2 flow fraction, and gas pressure. In addition, the plasma potential and plasma density for the same process parameters are examined using an RF compensated Langmuir probe downstream from the ICP source. The results are also discussed in terms of their impact on materials growth.

Effects of Green and Gold Kiwifruit Varieties on Antioxidant Neuroprotective Potential in Pigs as a Model for Human Adults.

Kiwifruit (KF) has shown neuroprotective potential in cell-based and rodent models by augmenting the capacity of endogenous antioxidant systems. This study aimed to determine whether KF consumption modulates the antioxidant capacity of plasma and brain tissue in growing pigs. Eighteen male pigs were divided equally into three groups: (1) bread, (2) bread + Actinidia deliciosa cv. 'Hayward' (green-fleshed), and (3) bread + A. chinensis cv. 'Hort16A' (yellow-fleshed). Following consumption of the diets for eight days, plasma and brain tissue (brain stem, corpus striatum, hippocampus, and prefrontal cortex) were collected and measured for biomarkers of antioxidant capacity, enzyme activity, and protein expression assessments. Green KF significantly increased ferric-reducing antioxidant potential (FRAP) in plasma and all brain regions compared with the bread-only diet. Gold KF increased plasma ascorbate concentration and trended towards reducing acetylcholinesterase activity in the brain compared with the bread-only diet. Pearson correlation analysis revealed a significant positive correlation between FRAP in the brain stem, prefrontal cortex, and hippocampus with the total polyphenol concentration of dietary interventions. These findings provide exploratory evidence for the benefits of KF constituents in augmenting the brain's antioxidant capacity that may support neurological homeostasis during oxidative stress.

Letter: Influence of inhomogeneous electrode biasing on the plasma parameters of inverted H2 fireballs

In this letter we present measurements of the influence on inhomogeneous electrode biasing on the basic plasma parameters of inverted fireballs in a hydrogen plasma. The measurements were performed in hydrogen because it is often used in many reactive plasmas, which are very important for technical or industrial applications. The dependence of the plasma parameters on voltages and currents on the electrodes are described in this work. It will be shown that the density profiles and the plasma potentials inside an inverted fireball can be shaped to a certain extend by asymmetric potentials on the anode.

Platelet-Rich Plasma (PRP) in the Treatment of Long COVID Olfactory Disorders: A Comprehensive Review.

Background: Long COVID has brought numerous challenges to healthcare, with olfactory dysfunction (OD) being a particularly distressing outcome for many patients. The persistent loss of smell significantly diminishes the affected individual's quality of life. Recent attention has been drawn to the potential of platelet-rich plasma (PRP) therapy as a treatment for OD. This comprehensive review aims to evaluate the effectiveness of PRP therapy in ameliorating OD, especially when associated with long-term COVID-19. Methods: We executed a comprehensive search of the literature, encompassing clinical trials and observational studies that utilized PRP in treating OD limited to COVID-19. We retrieved and comprehensively discussed data such as design, participant demographics, and reported outcomes, focusing on the efficacy and safety of PRP therapy for OD in COVID-19 patients. Results: Our comprehensive analysis interestingly found promising perspectives for PRP in OD following COVID-19 infection. The collective data indicate that PRP therapy contributed to a significant improvement in olfactory function after COVID-19 infection. Conclusions: The evidence amassed suggests that PRP is a promising and safe therapeutic option for OD, including cases attributable to Long COVID-19. The observed uniform enhancement of olfactory function in patients receiving PRP highlights the necessity for well-designed, controlled trials. Such studies would help to refine treatment protocols and more definitively ascertain the efficacy of PRP in a broader, more varied patient cohort.

Plasma–ionic liquid-assisted CO2 capture and conversion: A novel technology

The present study focused on CO2 capture, storage, and conversion through the innovative integration of plasma–ionic liquid (IL) technology. For the first time, we employed plasma-IL technology to confront climate change challenges. We utilized 1-Butyl-3-methylimidazolium chloride IL to capture and store CO2 under atmospheric pressure, and subsequently employed plasma to induce the transformation of IL-captured CO2 into CO. Furthermore, we performed computer simulations to enhance our understanding of the CO2 and CO capture processes of water and IL solutions. This comprehensive approach provides valuable insights into the potential of plasma–IL technology as a viable solution for climate change.

Miniaturized flexible micro-tube plasma ionization source for the effective ionization of non-easily ionizable pesticides in food with liquid chromatography/mass spectrometry

In this article, we have studied the potential of flexible microtube plasma (FμTP) as ionization source for the liquid chromatography high-resolution mass spectrometry detection of non-easily ionizable pesticides (viz. nonpolar and non-ionizable by acid/basic moieties). Phthalimide-related compounds such as dicofol, dinocap, o-phenylphenol, captan, captafol, folpet and their metabolites were studied. Dielectric barrier discharge ionization (DBDI) was examined using two electrode configurations, including the miniaturized one based on a single high-voltage (HV) electrode and a virtual ground electrode configuration (FμTP), and also the two-ring electrode DBDI configuration. Different ionization pathways were observed to ionize these challenging, non-easily ionizable nonpolar compounds, involving nucleophilic substitutions and proton abstraction, with subtle differences in the spectra obtained compared with APCI. An average sensitivity increase of 5-fold was attained compared with the standard APCI source. In addition, more tolerance with matrix effects was observed in both DBDI sources. The importance of the data reported is not just limited to the sensitivity enhancement compared to APCI, but, more notably, to the ability to effectively ionize nonpolar, late-eluting (in reverse-phase chromatography) non-ionizable compounds. Besides o-phenylphenol ([M − H]-), all the parent species were efficiently ionized through different mechanisms involving bond cleavages through the effect of plasma reagent species or its combination with thermal degradation and subsequent ionization. This tool can be used to figure out overlooked nonpolar compounds in different environmental samples of societal interest through non-target screening (NTS) strategies.

The effects of emicizumab on in vitro coagulation and fibrinolysis parameters in patients with disseminated intravascular coagulation with and without addition of anti-FVIII antibody.

Emicizumab (Emi) is used as haemostatic prophylaxis for patients with haemophilia A (PwHA). Disseminated intravascular coagulation (DIC) is a condition characterized by persistent systemic activation of coagulation, but there is yet no information on coagulation and fibrinolysis potentials in Emi-treated PwHA with DIC. To examine the effect of Emi on coagulation and fibrinolysis potentials in HA-model DIC plasmas. Plasma from a patient with sepsis-DIC (seven patients) was treated with anti-factor (F)VIII monoclonal antibody (HA-model DIC plasma) and incubated with Emi (50µg/mL). The plasma was then assessed using clot-fibrinolysis waveform analysis (CFWA). Coagulation and fibrinolysis parameters were expressed as ratios relative to normal plasma (|min1|-ratio and |FL-min1|-ratio, respectively). In case 1, coagulant potential was slightly high and fibrinolytic potential was extremely low, presenting a coagulant-dominant state (|min1|-ratio/|FL-min1|-ratio: 1.1/.38). In cases 2-5, fibrinolytic potential was not suppressed, but there were marked hypercoagulant potentials, indicating relative coagulant-dominant states. In case 6, coagulant and fibrinolytic potentials were increased but well balanced (|min1|-ratio/|FL-min1|-ratio: 1.38/1.28). In case 7, both potentials were severely deteriorated in not only CFWA but also the thrombin/plasmin generation assay. The addition of Emi into the HA-model DIC plasmas increased |min1|-ratio values in all cases, but the coagulant potentials did not exceed the initial ones (DIC plasma before treatment with anti-FVIII antibody). The presence of Emi in the HA-model DIC plasma improved coagulation potentials, but did not increase coagulation potentials beyond those of DIC plasma in non-HA states.

The level of blood neutrophils primary reactive oxygen species production in Graves’ disease patients undergoing conservative therapy with thiamazole.

Background. Conservative therapy with thiamazole in Graves’ disease helps to reduce the level of oxidative stress by restoring euthyroidism and the total reactive antioxidant potential of plasma. However, until now, in patients with Graves’ disease, the radical-producing ability of neutrophils remains unexplored at the initial stage of free radical conversion at different durations of drug-induced euthyroidism, which seems significant in revealing the mechanisms of disease recurrence. The aim is to study the level of production of primary reactive oxygen species in peripheral blood neutrophils depending on the duration of drug — induced euthyroidism in patients with Graves’ disease. Materials and methods. A single-center, prospective, controlled study was conducted with the participation of patients with laboratory-confirmed Graves’ disease. Subgroups of patients with Graves’ disease were formed depending on the duration of achieved drug-induced euthyroidism with continuous conservative therapy with thiamazole. The level of ROS production in peripheral blood neutrophils was determined by chemiluminescence. The assessment of spontaneous and zymosan-induced chemiluminescence was carried out for 90 minutes on a 36-channel chemiluminescence analyzer BLM-3607 (Medbiotech LLC, Krasnoyarsk). Results. The study included 102 Graves’ disease women with an average age of 47.54 ± 15.47 years. Of these, 75 (73.5 %) with relapse and 27 (26.47 %) with newly diagnosed disease. The total synthesis of (S) primary ROS increased statistically significantly relative to the control values in the examined patients with a duration of the euthyroid state of 5–8 and 9–12 months. It was found that in patients with Graves’ disease with stable drug-induced euthyroidism for 5–8 and 9–12 months, the S index of zymosan-induced lucigenin-dependent chemiluminescence of neutrophils increased statistically significantly, respectively, by 10.7 and 7.4 times relative to the control values. Conclusion. The restoration and maintenance of drug-induced euthyroidism for more than 12 months against the background of conservative thiamazole therapy in patients with Graves’ disease reduces the load of systemic oxidative stress on the immune system. However, the high total production of primary ROS in neutrophils of patients with Graves’ disease in a state of drug-induced euthyroidism with conservative thiamazole therapy may play a significant role in disconnecting the functioning of the NADPH oxidase complex and determine the functional capabilities of neutrophils in case of disease recurrence.

High entropy alloy MoNbTaVW synthesized by metal-oxide reduction in a microwave plasma

A unique approach was used to synthesize the high entropy alloy MoNbTaVW via reduction of metal-oxide precursors in a microwave plasma. The metal-oxides underwent ball milling and consolidation before plasma annealing at 1800 °C for 1 h with hydrogen as feedgas. X-ray diffraction, scanning electron microscopy/energy dispersive x-ray analysis, and Vickers hardness testing reveal characteristics of the high-entropy alloy. This includes a predominantly single-phase body-centered cubic structure, homogeneous distribution of all five metals, and 6.8 ± 0.9 GPa hardness, comparable with other reports for the same five-metal high entropy alloy configuration. Localized microwave plasma particle sintering is evident from the microstructure. These results highlight the promising potential of microwave plasma as a fast, economical, and flexible processing tool for high entropy alloys.

Study of ionization equilibrium taking into account the depression of ionization potential in a dense degenerate plasma

Study of ionization equilibrium taking into account the depression of ionization potential in a dense degenerate plasma

Measurement of a force imparted to a magnetic nozzle by electron diamagnetism

An electron-beam plasma source consisting of a hot filament is installed near the throat of the magnetic nozzle immersed in a vacuum chamber. The low plasma potential of about 5 V is formed over the region of the measurement in the weakly ionized and partially magnetized argon plasma expanding along a magnetic nozzle; an electric field is much smaller than a pressure gradient, providing a force balance between the electron pressure and the magnetic pressure. This condition leads to a negligible electron E×B drift current and nearly pure diamagnetism. Measurement of the force exerted on the magnetic nozzle is performed by attaching only the solenoid to a pendulum thrust balance, clearly demonstrating the presence of the force induced by the purely diamagnetic current, which is the major contributor to the thrust generation in the magnetic nozzle plasma thruster. This indicates that the thrust can be generated only by the electrons expanding in the magnetic nozzle.

Laboratory observation of electron energy distribution near three-dimensional magnetic nulls

The acceleration of electrons near three-dimensional (3D) magnetic nulls is crucial to the energy conversion mechanism in the 3D magnetic reconnection process. To explore electron acceleration in a 3D magnetic null topology, we constructed a pair of 3D magnetic nulls in the PKU Plasma Test (PPT) device and observed acceleration of electrons near magnetic nulls. This study measured the plasma floating potential and ion density profiles around the 3D magnetic null. The potential wells near nulls may be related to the energy variations of electrons, so we measured the electron distribution functions (EDFs) at different spatial positions. The axial variation of EDF shows that the electrons deviate from the Maxwell distribution near magnetic nulls. With scanning probes that can directionally measure and theoretically analyze based on curve fitting, the variations of EDFs are linked to the changes of plasma potential under 3D magnetic null topology. The kinetic energy of electrons accelerated by the electric field is 6 eV ( ) and the scale of the region where accelerating electrons exist is in the order of serval electron skin depths.

Plasma electron characterization in electron chemical vapor deposition

Recently, a novel approach of depositing metallic films with chemical vapor deposition (CVD), using plasma electrons as reducing agents, has been presented and is herein referred to as e-CVD. By applying a positive substrate bias to the substrate holder, plasma electrons are drawn to the surface of the substrate, where the film growth occurs. In this work, we have characterized the electron flux at the substrate position in terms of energy and number density as well as the plasma potential and floating potential when maintaining an unbiased and a positively biased substrate. The measurements were performed using a modified radio frequency Sobolewski probe to overcome issues due to the coating of conventional electrostatic probes. The plasma was generated using a DC hollow cathode plasma discharge at various discharge powers and operated with and without precursor gas. The results show that the electron density is typically around 1016 m−3 and increases with plasma power. With a precursor, an increase in the substrate bias shows a trend of increasing electron density. The electron temperature does not change much without precursor gas and is found in the range of 0.3–1.1 eV. Introducing a precursor gas to the vacuum chamber shows an increase in the electron temperature to a range of 1–5 eV and with a trend of decreasing electron temperature as a function of discharge power. From the values of the plasma potential and the substrate bias potential, we were able to calculate the potential difference between the plasma and the substrate, giving us insight into what charge carriers are expected at the substrate under different process conditions.

Comparative assessment of direct and indirect cold atmospheric plasma effects, based on helium and argon, on human glioblastoma: an in vitro and in vivo study

Recent research has highlighted the promising potential of cold atmospheric plasma (CAP) in cancer therapy. However, variations in study outcomes are attributed to differences in CAP devices and plasma parameters, which lead to diverse compositions of plasma products, including electrons, charged particles, reactive species, UV light, and heat. This study aimed to evaluate and compare the optimal exposure time, duration, and direction-dependent cellular effects of two CAPs, based on argon and helium gases, on glioblastoma U-87 MG cancer cells and an animal model of GBM. Two plasma jets were used as low-temperature plasma sources in which helium or argon gas was ionized by high voltage (4.5 kV) and frequency (20 kHz). In vitro assessments on human GBM and normal astrocyte cell lines, using MTT assays, flow cytometry analysis, wound healing assays, and immunocytochemistry for Caspase3 and P53 proteins, demonstrated that all studied plasma jets, especially indirect argon CAP, selectively induced apoptosis, hindered tumor cell growth, and inhibited migration. These effects occurred concurrently with increased intracellular levels of reactive oxygen species and decreased total antioxidant capacity in the cells. In vivo results further supported these findings, indicating that single indirect argon and direct helium CAP therapy, equal to high dose Temozolomide treatment, induced tumor cell death in a rat model of GBM. This was concurrent with a reduction in tumor size observed through PET-CT scan imaging and a significant increase in the survival rate. Additionally, there was a decrease in GFAP protein levels, a significant GBM tumor marker, and an increase in P53 protein expression based on immunohistochemical analyses. Furthermore, Ledge beam test analysis revealed general motor function improvement after indirect argon CAP therapy, similar to Temozolomide treatment. Taken together, these results suggest that CAP therapy, using indirect argon and direct helium jets, holds great promise for clinical applications in GBM treatment.

Assessment of urine CCL2 as a potential diagnostic biomarker for acute kidney injury and septic acute kidney injury in intensive care unit patients

Acute kidney injury (AKI) is a prevalent and serious condition in the intensive care unit (ICU), associated with significant morbidity and mortality. Septic acute kidney injury (SAKI) contributes substantially to AKI cases in the ICU. However, current diagnostic methods have limitations, necessitating the exploration of novel biomarkers. In this study, we investigated the potential of plasma and urine CCL2 levels as diagnostic markers for AKI and SAKI in 216 ICU patients. Our findings revealed significant differences in plasma (p < 0.01) and urine CCL2 (p < 0.0001) levels between AKI and non-AKI patients in the ICU. Notably, urine CCL2 demonstrated promising predictive value for AKI, exhibiting high specificity and sensitivity (AUC = 0.8976; p < 0.0001). Furthermore, we observed higher urine CCL2 levels in SAKI compared to non-septic AKI (p < 0.001) and urine CCL2 could also differentiate SAKI from non-septic AKI (AUC = 0.7597; p < 0.0001). These results suggest that urine CCL2 levels hold promise as early biomarkers for AKI and SAKI, offering valuable insights for timely intervention and improved management of ICU patients.