Low-temperature Plasma Research Articles

Application of Low-Temperature Air Plasma for the Enhancement of Defense Fabric's Self-Cleaning Property.

Self-cleaning textiles have the potential to revolutionize the lives of people like military personnel and hikers who spend extended periods of time in the sun and have restricted access to washing facilities. This research aims to develop the self-cleaning capability of defense uniforms by utilizing air plasma treatment and applying TiO2 nanocoating. Following plasma treatment of differing durations (2, 4, 6, 8, and 10 min, respectively), a pad-dry cure method was employed to apply a TiO2 coating to each sample, while keeping other processing parameters constant. SEM, Fourier transform infrared spectroscopy, ultraviolet protection factor (UVPF), energy-dispersive X-rays, and a water contact angle test were performed in order to validate the air plasma-induced surface modification. There was a gradual escalation in the rate of TiO2 absorption with an extension of the plasma treatment duration. Afterward, the samples were stained with various organic and inorganic compounds, including oil, ink, soil, and coffee, and subsequently exposed to sunlight for a period of 6 h. The samples demonstrated an enhanced cleaning effectiveness with increasing quantities of TiO2. The reflectance value and visual assessment of washed sample showed a reduced yet still present self-cleaning characteristic. The UVPF of the samples increased gradually as the duration of plasma treatment increased due to the UV absorption properties of TiO2, as validated by measuring the band gap energy.

Enhancing the combustion of silicon nanoparticles via plasma-assisted fluorocarbon surface modification

Nanostructured silicon has great potential as an energetic material due to its high energy density, close to that of aluminum; however, its combustion kinetics are strongly affected by the presence of a native oxide layer. As the particle size is reduced, the material behavior is dominated by surface effects, highlighting the need for new approaches to fabricate silicon nanoparticles and precisely control their surface chemistry. Here, we describe the use of low-temperature plasma to nucleate and grow < 10 nm silicon particles. The resulting aerosol is passed through a second plasma reactor, to which a fluorocarbon monomer is supplied. The second plasma initiates the growth of a polymeric shell onto the silicon particles, resulting in a highly conformal coating. Chemical analysis confirms that the polymer shell is compositionally similar to polyvinylidene fluoride (PVDF). We find that the fluorocarbon shell acts as an artificial passivation layer that significantly delays the onset of oxidation in air. In addition, the direct contact between the fluorocarbon shell and silicon core lowers the ignition temperature compared to the physical mixtures of silicon nanoparticles and PVDF. It leads to a higher pressurization rate and a lower combustion time when tested in a combustion cell. This is consistent with the combustion process being initiated by the exothermic interfacial reactions between the silicon core and the fluorocarbon shell. Mass spectroscopy confirms this hypothesis because silicon fluoride is produced only for the core–shell structure, and not for a physical mixture of silicon and PVDF. This study provides an example of a new processing technique capable of controlling the interfacial chemistry of small nanoparticles with beneficial effects on their combustion.

Enhancing corrosion fatigue performance of 17-4 PH stainless steel by simultaneous aging and plasma nitriding

This study investigated the effects of simultaneous aging and low-temperature plasma nitriding on the corrosion fatigue performance of 17-4 PH stainless steel. Plasma nitriding was conducted under two temperatures of 400 and 500 °C and, for comparison, some other specimens were subjected to aging treatment at the same temperatures and times. Microstructural characterization by scanning electron microscope (FESEM) and electron backscatter diffraction (EBSD) confirmed similar structures at the core in the nitrided and aged specimens, thereby, the influence of nitrogen at the surface of 17-4 alloy could be carefully investigated. X-ray diffraction and grazing incidence X-ray diffraction (GIXRD) identified expanded martensite as the matrix within the nitrided layer, accompanied by CrN, Fe3N, and Fe4N phases. X-ray photoelectron spectroscopy (XPS) analysis revealed high nitrogen concentration, in regions very close to the surface, after nitriding at 500 °C. The N1s spectra shifted towards lower binding energies, indicating interaction between nitrogen and the matrix atoms, and the formation of nitrides in the nitrided layer. The nitrided thicknesses experienced close values at 400 °C (10 h) and 500 °C (5 h), provided at 400 °C the layer was mostly a supersaturated solid solution but at 500 °C it was composed of iron nitrides and chromium nitride. High hardness values of above 1600 HV0.1 were obtained after optimum plasma nitriding as the result of combined effects of solution strengthening induced by nitrogen atoms and the presence of dispersed nitride phases. EBSD results indicated residual stress within the nitrided layer, which would affect the corrosion fatigue resistance. Experimental findings demonstrated that both aging and plasma nitriding substantially enhanced the corrosion fatigue resistance of 17-4 PH stainless steel in 3.5 wt% NaCl. Moreover, simultaneous aging and plasma nitriding proved superior behavior in corrosion fatigue, primarily due to delayed crack initiation and improved fatigue resistance, without the risk of overaging which is detrimental to mechanical properties.

Use of non-thermal treatment methods to ensure the quality and safety of fish and other hydrobionts. Overview of the subject field

Products of aquatic origin are among the most perishable products. Heat processing, including sterilization, drying and evaporation, can lead to undesirable changes in food products, such as a decrease in their nutritional value or deterioration in organoleptic characteristics. The purpose of the paper is to review the results of scientific research on non-thermal methods of processing fish and other aquatic organisms to inhibit bacteria, ensure microbiological safety and maintain quality. The groups of primary spoilage bacteria vary among fish, crustaceans and molluscs depending on storage conditions and duration. Non-thermal processing methods such as ultra-high pressure, irradiation, pulsed electric field and low-temperature plasma have shown significant results in inhibiting microbial growth and increasing the shelf life of aquatic products. However, uncertain processing parameters and characteristics of the technology itself can lead to adverse effects such as lipid oxidation and protein degradation during sterilization. Non-thermal processing can be used in combination with antioxidant composite coatings (membranes) to delay the oxidation of lipids and proteins and improve the physical, chemical and sensory properties of fish products. It is possible to combine several methods of non-thermal treatment, which will make it possible to compensate for the shortcomings of one technology by the action of another method of non-thermal exposure. Further scientific research should be aimed at establishing optimal processing modes, the possibility of combining non-thermal methods with other technologies, such as modified atmosphere packaging in order to determine the mechanisms of spoilage and improve the quality of storage of products of aquatic origin, as well as further industrial implementation of modern processing methods. BELROSAKAVA

Development of an Ultrasonic Nebulization System for an Inverse Low Temperature Plasma Ionization Source.

An effective nebulization and evaporation of a liquid sample, like in liquid chromatography, mass spectrometry (LC-MS) couplings, is an essential requirement for the ionization of analyte molecules in the gas phase by, for example, atmospheric pressure chemical ionization (APCI) or the novel low temperature plasma (LTP)-based ion source. These LTP-based ion sources have recently gained interest in the field of atmospheric pressure ion sources, as they can cover a wide range of polarity and molecular mass. They can be used in combination with separation techniques like liquid chromatography or used as an ambient ion source. However, commercial nebulizer systems are of course not constructed to fit to home-built LTP-based ion sources, and this was one incentive to develop a new nebulization system. Instead of an atmospheric pressure chemical ionization (APCI) nebulizer, two commercial nebulizers were disassembled and remodeled to be used as nebulizing systems in an LC-MS setup using an LTP-based ion source. Based on these results, a novel nebulizer system was subsequently developed. To further improve the degree of ionization, cones to focus the LC eluent spray on the plasma region, heating applications, and auxiliary nitrogen gas for dispersion of the solvent droplets were implemented. The LOD that could be calculated via the rule of three resulted in an average of 2.0 μg/L for the APCI-nebulizer and 41 μg/L for the USN. Both could be reduced to 1.4 and 18 μg/L, respectively, by using a TPI-configuration instead of an iLTP. The linearity was equally good for both types of nebulization devices. The final nebulizer could also be operated with a high water content and flow rates higher than those of the two previous ones, indicating an important improvement step.

The effect of low-temperature plasma pretreatment on the biodegradability of polyethylene films

ABSTRACT With the increasing focus on environmental friendliness and sustainable development, extensive research has been conducted on the biodegradation of plastics. The non-hydrolyzable, highly hydrophobic, and high-molecular-weight properties of polyethylene (PE) pose challenges for cell interaction and biodegradation of PE substrates. To overcome these obstacles, PE films were treated with low-temperature plasma before biodegradation. The morphology, surface chemistry, molecular weight, and weight loss of PE films after plasma treatment and biodegradation were studied. The plasma treatment decreased the surface water contact angle, formed C–O and C = O groups, and decreased the molecular weight of PE films. With the increased pretreatment time, the biodegradation efficiency rose to 2.6% from 0.63% after 20 days of incubation. The mechanism was proposed that the surface oxygen-containing groups formed by plasma treatment can facilitate the bio-accessibility and be further decomposed and utilised by the microbes. This study provided an effective and rapid pretreatment strategy for improving biodegradation of PE.

Plasma‐electrified synthesis of atom‐efficient electrocatalysts for sustainable water catalysis and beyond

The downsizing of metal structures to the nano and atomic level, thereby creating nanoparticle catalysts (NPCs), sub‐nanometer cluster catalysts (SNCCs) or single atom catalysts (SACs), has gained significant interest. In particular, synthesizing these types of catalysts using low temperature plasma electrified methods is an emerging field which is highly applicable to electrochemical water splitting for the sustainable production of green hydrogen. Surface modification via plasma treatment provides a route for nanoparticle immobilization or single atom trapping which ensures high atom utilization during electrolysis reactions. Plasma can also be used to create NPCs, SNCCs and SACs from various precursors as well as modify their surface properties once formed which impacts significantly on the oxygen evolution reaction and hydrogen evolution reaction. Therefore, in this review we emphasize the role that low temperature plasma electrified synthetic strategies play in electrocatalyst development for water splitting reactions and explore the crucial relationship between the electronic and coordination environment of atom efficient catalysts and their resulting catalytic activity. We also discuss methods to characterize these types of catalysts and the possibility for scaling up this technology which will be required for commercial applications.

Clinical observation of low temperature plasma ablation combined with collagenase injection in lumbar disc herniation.

To observe the effect of low temperature plasma ablation combined with collagenase injection on lumbar disc herniation. 90 patients with lumbar disc herniation admitted to the pain department of our hospital and receiving surgical treatment from April 2021 to April 2023 were included in this retrospective study, and were divided into 2 groups according to different treatment plans. One group was treated with low-temperature plasma ablation combined with collagenase injection, and the other group was treated with low-temperature plasma ablation alone. The sample size of both groups was 80 cases. Peripheral blood was collected by fasting in the morning at 5 time points before surgery, 1, 3, 7 and 14 days after surgery, and 5 mL of whole venous blood was collected by disposable vacuum blood collection device. Serum levels of pro-inflammatory factor interleukin (IL)-1α, IL-1β, IL-6, IL-8, tumor necrosis factor-α and anti-inflammatory factor IL-4, IL-10 were detected by ELISA. VAS scores were used to evaluate postoperative low back pain. ODI and Lehmann Lumbar Function Scale were used to evaluate postoperative lumbar function. The contents of IL-1α, IL-1β, IL-6, IL-8, tumor necrosis factor-α and anti-inflammatory factor IL-4, IL-10 in the cryo-plasma ablation combined with collagenase injection group were significantly lower than those in the cryo-plasma ablation group alone (P < .05). The VAS score of cryo-plasma ablation combined with collagenase injection group was significantly lower than that of cryo-plasma ablation group at 1 day and 3 months after treatment, and the difference was statistically significant (P < .05). The ODI score of cryo-plasma ablation combined with collagenase injection group was significantly lower than that of cryo-plasma ablation group at 1 day and 3 months after treatment, and the difference was statistically significant (P < .05). The Lehmann score of cryo-plasma ablation combined with collagenase injection group was significantly higher than that of cryo-plasma ablation group at 1 day and 3 months after treatment, and the difference was statistically significant (P < .05). The overall efficacy of low-temperature plasma ablation combined with collagenase injection is better than that of low-temperature plasma ablation alone. Low temperature plasma ablation combined with collagenase injection in the treatment of patients with lumbar disc herniation has less pain, faster recovery.

Effects of low-temperature plasma, microwave and 60Co γ-irradiation treatments on the flavor characteristics of lychee whole fruit powder

Powdering whole lychee fruit is one of the most effective methods for improving the comprehensive utilization rate of lychees. In this study, lychee whole fruit powder (LWFP) was prepared and treated with low-temperature plasma, microwave, and 60Co γ-irradiation treatments to enhance its quality. Volatile organic compounds (VOCs) were analyzed using Headspace Solid Phase Micro-extraction Gas Chromatography-mass Spectrometry (HS-SPME-GC-MS), Headspace Gas Chromatography Ion Mobility Spectrometry (HS-GC-IMS), and electronic nose (E-nose) techniques. Electronic tongue (E-tongue) analysis revealed that both sweetness and bitterness were significant taste indicators of LWFP. GC-MS analysis revealed that the predominant volatile compounds in LWFP were terpenoids and alcohols, specifically nerol, geraniol, ɑ-pinene, hexylbenzene, ɑ-caryophyllene, caryophyllene oxide, and isoamylenol. GC-IMS identified small-molecule aldehydes such as 2-methyl propanal, hexanal, propanal, and 2-methylbutanal as significant contributors to the aroma profile. Moreover, key aromatic contributors include dimethyl sulfide, 1-penten-3-one, and acetic acid. Notably, microwave treatment exerted the most significant effect on the aroma profile of lychee. In contrast, low-temperature plasma and irradiation treatments exhibited similar and consistent changes. Specifically, microwave treatment primarily increased the concentration of larger terpenoid molecules such as nerol, 1-phenylhexane, and caryophyllene oxide, whereas low-temperature plasma and irradiation had a greater impact on smaller aldehyde molecules such as hexanal and 2-methylbutanal. All treatments enriched the sweet fruity, brilliant woody, and cabbage scents of LWFP.

Using the Plasma Jet Method to Create Zinc Nanoparticles and Study Their Structural and Optical Properties as an NH3 Gas Sensor

In this work, zinc nanoparticles were prepared using the low-temperature plasma method at different times 3 min, 5 min, 7 min, 9 min, where the initial reactions of zinc lead to the formation of nanoparticles. The metal interacts with the ionized plasma under different conditions and may turn into an oxide such as exposing the sample to air and raising the temperature of the solution a few degrees as a result of high voltage and within a certain range. The atmospheric pressure plasma system acts as the cathode, while the zinc metal strip acts as the anode. A series of techniques were used, including the use of X-ray diffraction (XRD), ultraviolet-visible spectroscopy and scanning electron microscopy (FESEM). The X-ray diffraction results showed that the samples have polycrystalline structures with hexagonal and cubic structures with a time difference, and the X-ray diffraction results showed the conversion of zinc particles into zinc oxides. FESEM images reveal particle size and shape. The ZnO nanoparticles prepared by the mentioned method seem to form different nanoshapes such as starfish and mushroom nanoparticles. The UV-visible results showed that the samples had an energy gap of about 3.4 eV at a time of 3 min, and this value decreases with increasing reaction time. The appearance of zinc oxides increases gradually with the passage of time. These results provide credibility for the fabrication of ZnO nanostructures for use in future gas sensing applications, despite the inhomogeneity of particle size among ZnO particles, the sensor was also fabricated to detect nitrogen gas (NH3) with different concentrations (17.25 ppm, 46.38 ppm, 78.58 ppm). at room temperature. The ZnO sample showed the highest sensitivity (88.1%) at 7 min. The sensitivity showed different results and increased with reaction time and gas concentration. However, response and recovery time are moderate and decrease as reaction time increases.

Determination and identification of polyphenols in wine using mass spectrometry techniques

Mass spectrometry is crucial for analysing physicochemical and sensory properties, including colour, astringency, taste, and flavour, predicting ageing characteristics, and addressing stability issues in wine. Polyphenols are key chemical constituents in wine that are associated with health benefits and improve circulatory conditions. Advances in mass spectrometry ionisation techniques such as matrix-assisted laser desorption and ionisation and direct analysis in real-time offer high sensitivity for identifying important polyphenolic constituents in wine. High-resolution mass spectrometry, in combination with liquid chromatography, accurately identify and quantify polyphenolic compounds, even at low concentrations, and provides the possibility for further retrospective analysis and non-targeted analysis using statistical methods of data analysis. Ambient mass spectrometry techniques such as paper spray and low-temperature plasma allow solventless analysis, determining the geographical origin, authentication, and quality control of wine samples. This review will explore the potential benefits of using mass spectrometry to identify various polyphenols and polymeric polyphenols in wine, as well as recent developments and applications. Additionally, we will discuss determining antioxidant activity and total polyphenol content in wine.

Sustainable development of fishery resources: Precipitation of protein from surimi rinsing wastewater by low-temperature plasma

This study aimed to determine the impact of low-temperature plasma (LTP) on the protein stability and composition in surimi rinsing wastewater (SRW). When SRW (300 mL) was treated with LTP at a power of 420 W and a flow rate of 1.1 L/min for 106 s, the protein precipitation was 76.04 %, the pH was close to the estimated value of the isoelectric point (pI). In comparison with the pI precipitation treatment, non-precipitated proteins in the SRW after LTP precipitation treatment showed significant changes in amino acids susceptible to oxidation but had minor changes in the hydrophobic amino acid content. LTP showed a markedly differentiated response to the different protein types in the SRW, increasing the relative amounts of several enzyme proteins in the non-precipitated protein. The combined effect of the active ingredients provided by LTP on protein conformation and hydrophobic interactions may be responsible for this ‘screening’ phenomenon.

Influence of Alkanolamine Plasmas on Poly(Ethylene Terephthalate) Fibro-Porous Biomaterial Constructs.

The development of fibrous polymer scaffolds is highly valuable for applications in tissue engineering. Furthermore, there is an extensive body of literature for chemical methods to produce scaffolds that release nitric oxide. However, these methods often use harsh chemistries and leave behind bulk waste. Alkanolamine low-temperature plasma (LTP) is unexplored and single-step processing to form nitric oxide (NO) releasing constructs is highly desirable. The major question addressed is whether it is possible to achieve single-step processing of spun polyester with alkanolamine plasma to achieve nitric oxide releasing capabilities. Herein we report the experiments, processes, and data that support the claim that it is indeed possible to produce such a bio-functional material for potential biomedical applications, especially in cardiovascular implants. Among the tested alkanolamines, monoethylamine (MEA) plasma treated biomaterial outperformed in comparison with diethanolamine (DEA) and triethanolamine (TEA) in terms of NO release and cellular response.

Preparation of a Plasma‐Induced Dendritic Cell Vaccine and its Anti‐Tumor Immunity in a Murine Model of Melanoma

AbstractDendritic cell (DC) vaccines play an important role in anti‐tumor immunotherapy. Tumor‐associated cells or cytokines in the tumor microenvironment (TME) can inhibit the antigen‐presenting function of DC. Immunogenic cell death (ICD) can enhance the uptake and presentation of tumor antigens by DC. This study investigates the maturation mechanism of DC induced by low‐temperature plasma (LTP), as well as the therapeutic and protective effects of LTP‐induced DC vaccine in a tumor model. DC2.4 that is co‐cultured with LTP‐treated B16F10 (LTP‐B16) or with these supernatants exhibited decreased phagocytic activity, increased production of cytokines (IL‐12, IL‐6, TNF‐α, and IL‐1β), and increased expression of cell surface activation markers (CD80, CD86, and MHC II). The expression of CD80+/CD86+ is decreased after pre‐treatment with TLR4 and NF‐κB (p65) inhibitors, respectively. In vivo, trials indicated that the LTP‐induced DC vaccine‐induced anti‐tumor immunity and, when combined with cisplatin, synergistically reduced tumor growth.

Inhibitory effect of helium cold atmospheric plasma on cariogenic biofilms

ABSTRACT This study aimed to determine the effects of low-temperature plasma jet produced in gas helium (LTP-helium) on cariogenic biofilms composedby Streptococcusmutans, Streptococcus sanguinis and Streptococcus gordonii, and also by the combination of Candida albicans, Lactobacillus acidophilus and S. mutans. Biofilms were treated for 1, 3, 5, and 7 minutes. A 0.12% chlorhexidine solution was used as the positive control and sterile physiologic solution was the negative control. Biofilm viability was analyzed by viable cell recovery, scanning electron microscopy, and confocal laser scanning microscopy. All assays were performed intriplicate in three independent experiments. Multispecies biofilms exposed to LTP-helium had a significant reduction in viability when compared to the negative control (p < 0.0001). For biofilm formedby S. mutans, S. sanguinis, and S. gordonii, LTP treatments for 5 and 7 minutes caused similar reduction of morethan 2 log10. Also, a significant reduction in the viability of biofilms formedby C. albicans, L. acidophilus, and S. mutans was detected (p < 0.0001). In conclusion, LTP-helium reduced theviability of cariogenic biofilms with different microbial compositions, which indicates that LTP-helium is a potential tool for developing new protocols for dental caries prevention and treatment.

Clinical analysis of 21 cases of children with ectopic bronchogenic cyst

Objective: To analyze the clinical characteristics, treatment, and prognosis of ectopic bronchogenic cysts in children. Methods: A retrospective analysis was conducted on the data including the clinical characteristics, auxiliary examination and treatment of 21 children with ectopic bronchogenic cysts diagnosed pathologically at Children's Hospital Affiliated to Zhengzhou University from July 2015 to December 2023. There were 16 males and 5 females, with a male-female ratio of 3.2∶1, and the age ranged from 4 days to 8 years old (median age 2 years and 8 months). Results: Among the 21 cases of ectopic bronchogenic cysts, 11 cases were found in the pharynx, with symptoms including dyspnea (4 cases), snoring during sleep (3 cases), and choking on milk(4 cases).Ten cases were found in the head, neck or anterior chest, 5 of these cases had infection history, and 5 showed progressive mass growth.Imaging and endoscopy showed 9 patients underwent preoperative color ultrasonography revealed cystic masses with well-defined boundaries. CT examination was performed on 13 patients, which showed round or nearly round masses with homogeneous density, smooth margins, and regular cyst walls. CT attenuation values ranged from 2 to 52 Hounsfield Units (HU). Four cystic lesions were assessed via MRI, 3 cases demonstrated long T1 and long T2 signals, while 1 case had a slight short T1 and long T2 signal, with high signal intensity on fat-suppressed images. Eleven cases of pharyngopharyngeal cysts were examined by electronic nasopharyngoscopy. The cysts appeared as spherical or ovoid masses with smooth surfaces, close to or slightly light in color with the surrounding tissue, with one cyst presenting with a bluish blue in the oropharynx. All 11 pharyngeal cysts were excised using low-temperature plasma under general anesthesia and intubation assisted by a nasal endoscope. The cysts were pulled and excised as completely as possible.Ten cases of neck and anterior chest cysts were completely excised. Postoperative histopathology confirmed bronchogenic cyst. Twenty-one children were followed up postoperatively for 4 months to 7 years without recurrence, except for 1 patient who was lost to follow-up. Conclusions: Ectopic bronchogenic cysts are uncommon and lack of typical imaging and clinical features.Combination of ultrasonography, CT and MRI is recommended for cases occuered in neck and anterior chest, while electronic nasopharyngoscopy complements pharyngeal evaluations. Surgical intervention is the preferred treatment choice for this disease.

Exploring the efficacy of in-vitro low-temperature plasma treatment on single and multispecies dental cariogenic biofilms

The primary aim of this study was to investigate the impact of treatment with low-temperature plasma (LTP) for varying exposure durations on a multispecies cariogenic biofilm comprising C. albicans, L. casei, and S. mutans, as well as on single-species biofilms of L. casei and C. albicans, cultured on hydroxyapatite discs. Biofilms were treated with LTP-argon at a 10 mm distance for 30 s, 60 s, and 120 s. Chlorhexidine solution (0.12%) and NaCl (0.89%) were used as positive (PC) and negative controls (NC), respectively. Argon flow only was also used as gas flow control (F). Colony-forming units (CFU) recovery and confocal laser scanning microscopy (CLSM) were used to analyze biofilm viability. LTP starting at 30 s of application significantly reduced the viability of multispecies biofilms by more than 2 log10 in all treated samples (p < 0.0001). For single-species biofilms, L. casei showed a significant reduction compared to PC and NC of over 1 log10 at all exposure times (p < 0.0001). In the case of C. albicans biofilms, LTP treatment compared to PC and NC resulted in a significant decrease in bacterial counts when applied for 60 and 120 s (1.55 and 1.90 log10 CFU/mL, respectively) (p < 0.0001). A significant effect (p ≤ 0.05) of LTP in single-species biofilms was observed to start at 60 s of LTP application compared to F, suggesting a time-dependent effect of LTP for the single-species biofilms of C. albicans and L. casei. LTP is a potential mechanism in treating dental caries by being an effective anti-biofilm therapy of both single and multispecies cariogenic biofilms.

Analysis of an induced Langmuir wave by ponderomotive forces and its applicability for plasma diagnostics

We present a numerical study on the electron and ion density perturbation in low-temperature plasmas driven by the frequency detuning of two intense laser beams. Our study is performed in the hydrodynamic regime, which becomes applicable when the plasma grating period induced by the beating of the laser beams is greater than the Debye length and collective processes such as plasma oscillations can be excited. Our findings show a resonance in electron density perturbation as the frequency detuning approaches a value consistent with the Bohm–Gross dispersion relation in low- and high-pressure plasmas. We discuss the potential of this resonance as a diagnostic tool for precisely measuring electron temperature and density in low-temperature plasmas through coherent scattering.

A birdcage resonant antenna for helicon wave generation in TORPEX.

A birdcage resonant helicon antenna is designed, mounted, and tested in the toroidal device TORPEX. The birdcage resonant antenna is an alternative to the usual Boswell or half-helical antenna designs commonly used for ∼10 cm diameter helicon sources in low temperature plasma devices. The main advantage of the birdcage antenna lies in its resonant nature, which makes it easily operational even at large scales, an appealing feature for the TORPEX device whose poloidal cross section is 40cm in diameter. With this antenna, helicon waves are shown to be launched and sustained throughout the whole torus of TORPEX. The helicon waves can be launched at low power on a pre-existing magnetron-generated plasma with little effect on the density profiles. The birdcage antenna can also be used alone to produce plasma, which removes the constraint of a narrow range of applied magnetic fields required by the magnetron, opening the way to a new range of studies on TORPEX with the external magnetic field as a control parameter.

Low-temperature plasma jet treatment generates reactive oxygen species in solution that leads to peptide oxidation and protein aggregation

Abstract Low-temperature plasma (LTPs) jets are FDA-approved medical devices to remove cancerous tissue and aid in wound healing. However, reports on their reaction with proteins are conflicting, ranging from fragmentation, oxidation, aggregation, or a combination thereof. In this study we bridge the gap between plasma-treatment of short peptides to proteins at physiologically relevant concentrations. The LTP in this study is based on a helium dielectric barrier discharge (DBD) that forms a plasma-jet, which is directed at the solution without direct contact with the plasma, and results in the formation of reactive oxygen species (ROS) OH• and O2•- in solution. The longer the solution is treated, the more solution-phase ROS form. Treating peptide- and protein-containing solutions leads to extensive oxidation. The ROS led to the same oxidative modifications for peptide M with increasing chain length (9, 18, 37, 76 amino acids), which could be identified with high-resolution mass spectrometry. Oxidized species M+xO led to conformational changes such as compaction and elongation, while the unmodified peptide M remained unaltered, as found by ion mobility spectrometry and size exclusion chromatography. For proteins at high concentration, insoluble aggregates formed and could be identified by UV/Vis light scattering and atomic force microscopy. The formation of aggregates is dependent on the amino acid chain length, the peptide concentration, and the time for aggregate formation. These findings highlight the importance of both peptide chain length and concentration in determining the fate of peptides following the exposure to LTP, while also offering valuable insights for the field of plasma medicine. &amp;#xD;