Plasma Engineering toward Improving the Microwave-Absorbing/Shielding Feature of a Biomass-Derived Material.

During the past decade, ever-increasing electromagnetic pollution has excited a global concern. A sustainable resource, facile experimental scenario, fascinating reflection loss (RL), and broad efficient bandwidth are the substantial factors that intrigue researchers. This research led to the achievement of a brilliant microwave-absorbing material by treating pampas as biomass. The carbon-based microfibers attained by biowaste were treated by plasma under diverse environments to amplify their microwave-absorbing features. Moreover, a pyrolysis scenario was performed to compare the results. The reductive processes were performed by H2 plasma and carbonization. However, the CO2 plasma was performed to regulate the heteroatoms and defects. Interestingly, polystyrene (PS) was applied as a microwave-absorbing matrix. The aromatic rings existing in the absorbing medium establish electrostatic interactions, elevating interfacial polarization, and physical characteristics of PS augment the practical applications of the final product. The manipulated biomasses were characterized by Raman, X-ray diffraction, energy-dispersive spectroscopy, field emission scanning electron microscopy, and diffuse reflection spectroscopy analyses. Eventually, the microwave-absorbing features were estimated by a vector network analyzer. The plasma-treated pampas under H2/Ar blended with PS gained a maximum RL of -90.65 dB at 8.79 GHz and an efficient bandwidth (RL ≤ -10 dB) of 4.24 GHz with a thickness of 3.20 mm; meanwhile, plasma treatment under CO2 led to a maximum RL of 97.99 dB at 14.92 GHz and an efficient bandwidth of 7.74 GHz with a 2.05 mm thickness. Particularly, the biomass plasmolyzed under Ar covered the entire X and Ku bands with a thickness of 2.10 mm. Notably, total shielding efficiencies of the treated bioinspired materials were up to ≈99%, desirable for practical applications.

Metal to semiconductor switching in the AgTe monolayer via decoration with alkali metal and alkaline earth metal atoms: a first-principles perspective.

In this work, employing first-principles calculations, we systematically investigate the atomic structure and electronic and optical properties of the AgTe monolayer, as well as the impact of alkali metal (Li, Na, K) and alkaline earth metal (Be, Mg, Ca) atoms decoration. The AgTe monolayer exhibits metallic characteristics. When Li, Na, K, and Mg atoms are decorated on the AgTe monolayer, the decorated AgTe monolayers are dynamically stable. In contrast, with Be and Ca atoms, the decorated structures are found to be dynamically unstable. Interestingly, the decoration of Li, Na, and K atoms into the AgTe monolayer can open the band gaps in the decorated Li-, Na- and K-AgTe monolayers around the Fermi level, leading to the actualization of metal-to-semiconductor transitions. In contrast, the decorated Mg-AgTe monolayer maintains its metallic characteristic. The highest electron and hole mobilities are achieved in the Na-AgTe monolayer among the decorated structures, suggesting the applicability of this structure in photovoltaic applications. The optical study shows that Li-, Na- and K-decorated AgTe monolayers have improved light absorption in the visible light region. Consequently, our findings shed light on the decoration of these 2D material monolayers and can potentially enhance and motivate studies in producing these monolayers for current nanodevices and future applications.

Comparing the efficacy of plasma exeresis and cryotherapy for the treatment of seborrheic keratosis: A randomized controlled trial.

BACKGROUND: Seborrheic keratoses (SK) is a benign epithelial skin tumor and plasma exeresis is a new technique. AIMS: To compare the efficacy and safety of plasma exeresis and cryotherapy for treating SK. METHODS: This study is a randomized controlled trial (RCT). One side of each patient was randomly treated with plasma exeresis (peak-to-peak voltage of 3.44 kV and a frequency of 62.5 kHz) and the other side with cryotherapy. RESULTS: Thirty-five males were enrolled. At week 3, 37.1 % (N = 13) of lesions treated by plasma exeresis were clear, which was higher than those treated by cryotherapy 17.1% (N = 6). However, this difference was not significant (p-value: 0.06). At week 6, 16 (57.1 %) out of 28 remaining lesions, treated by plasma exeresis were clear, which was significantly higher (p-value: 0.005) than those completely cleared by cryotherapy in 6 out of 29 remaining lesions (20.7%). The mean physician assessment scale score was significantly reduced in both groups in the second follow-up (plasma group first follow-up 0.91 ± 0.89 vs. second follow-up 0.5 ± 0.64 and p-value: 0.0031; cryo group first follow-up 1.4 ± 0.84 vs. second follow-up 1.1 ± 0.72 and p-value: 0.0002). Regarding side effects, no significant difference was seen (p = 0.438). The most common complications in the plasma and cryotherapy groups were erythema (10/19, 52.63%) and hypo pigmentation (5/13, 38.46%). CONCLUSIONS: Both cryotherapy and plasma exeresis are effective. We observed a significantly higher cleared lesions treated with plasma exeresis in 6 weeks and after two sessions.

Split-face comparison of hydroquinone 4% plus nitrogen plasma vs. hydroquinone 4% alone in the treatment of melasma.

Treatment of skin diseases is important yet challenging. One of the most common skin diseases in women is melasma, which features acquired facial hyperpigmentation. We studied the effect of cold atmospheric nitrogen plasma on this disease. To characterize the nitrogen plasma, we obtained the relative intensity of the species and the plasma temperature and skin temperature during processing at different input powers and gas flows. Patients complaining of melasma were treated with hydroquinone on both sides of the face, and one side was randomly selected for additional nitrogen plasma therapy. Eight treatment sessions of plasma processing were provided 1 week apart, and one follow-up session was scheduled 1 month after the end of treatment. The rate of improvement was scored by a dermatologist in the eighth session and 1 month following the last session using the modified Melasma Area Severity Index (mMASI). Skin biomechanical characteristics such as melanin, cutaneous resonance running time (CRRT), transepidermal water loss (TEWL), and hydration were measured at baseline and during the fourth, eighth, and follow-up sessions. On both sides, we observed a significant decrease in both CRRT and melanin (P < 0.05). TEWL did not change on both sides, while hydration decreased significantly only on the side to which hydroquinone was applied in isolation (P < 0.05). According to clinical scores, on both sides, we had significant improvement. On the side that plasma was not applied, the percentage reduction of pigmentation (mMASI) in the eighth and follow-up sessions in comparison with the baseline was 5.49 ± 8.50% and 33.04 ± 9.17%, respectively, while on the other side, these figures were 20.57 ± 6.64% and 48.11 ± 11%. For melanin, these figures were 13.84 ± 4.84% and 18.23 ± 7.10% on the hydroquinone side and 21.56 ± 3.13% and 23.93 ± 3.02% on the other side. According to these results, nitrogen plasma can safely complement topical hydroquinone to improve clinical outcomes when treating melasma without causing stratum corneum damage or skin discomfort, though confirmatory studies are needed.

Advancements in Plasma Agriculture: A Review of Recent Studies.

This review is devoted to a topic of high interest in recent times-the use of plasma technologies in agriculture. The increased attention to these studies is primarily due to the demand for the intensification of food production and, at the same time, the request to reduce the use of pesticides. We analyzed publications, focusing on research conducted in the last 3 years, to identify the main achievements of plasma agrotechnologies and key obstacles to their widespread implementation in practice. We considered the main types of plasma sources used in this area, their advantages and limitations, which determine the areas of application. We also considered the use of plasma-activated liquids and the efficiency of their production by various types of plasma sources.

Efficacy and safety of non-thermal nitrogen plasma versus long-pulsed Nd:YAG laser for hand rejuvenation.

This randomized controlled study aimed to investigate the efficacy and safety of multiple treatment sessions of pulsed non-thermal atmospheric pressure nitrogen plasma compared with long-pulsed Nd:YAG laser for hand rejuvenation. To optimize the nitrogen plasma mode for rejuvenation, the relative intensity of reactive species and skin temperature was compared at different input powers and time periods. Twenty-five patients with mild-moderate photodamaged skin were recruited; one hand was randomly selected for eight weekly treatment sessions with plasma (two passes), while the other was subjected to three monthly treatments with laser (until erythema became obvious). A blinded dermatologist scored the mean wrinkle and dyschromia improvement at 1 and 2 months after the first treatment and 1 and 3 months after the last treatment. The patients' satisfaction and the biomechanical characteristics of the skin including cutaneous resonance running time (CRRT), melanin, transepidermal water loss (TEWL), and hydration were evaluated. Clinically, both methods gave rise to a similar, significant improvement in wrinkles (49.09 ± 19.18% and 39.32 ± 18.21% after plasma and laser, respectively) and dyschromia (45.00 ± 26.32% and 30.62% ± 24.99% after plasma and laser, respectively) (P < 0.05). A significant decrease in CRRT and melanin was seen following treatment with either method (P < 0.05). Notably, plasma therapy led to a significant decrease in TEWL and boosted skin hydration. This is while laser therapy augmented the TEWL and reduced skin hydration. Our findings corroborate that cold plasma is as effective and safe as long-pulsed Nd:YAG laser, with less discomfort and dryness during treatment. The protocol was approved by the Iranian Registry of Clinical Trials. IRCT20160320027109N4. Registered 9 April 2019 (This manuscript is only a part of this registered project.).

Elliptical plasma-filled waveguide as a new standard short-period undulator.

Undulators as the sources of high-brilliance synchrotron radiation are of widespread interest in new generations of light sources and free-electron lasers. Microwave propagation in a plasma-filled elliptical waveguide can be studied as a standard short-period undulator. This structure as a lucrative insertion device can be installed in the storage ring of third- and fourth-generation light sources to produce high-energy and high-brilliance synchrotron radiation. In this article, the propagation of the transverse electric modes in a plasma-filled waveguide with an elliptical cross-section is investigated, and the field components, the cut-off frequencies and the electron beam trajectory are calculated. With due consideration of the electron beam dynamics and in order to achieve a standard short-period undulator, parameters such as the dimensions of the waveguide elliptical cross-section, the microwave frequency and the plasma density are calculated.

Protein ion yield enhancement in matrix-assisted laser desorption/ionization mass spectrometry after sample and matrix low-pressure glow discharge plasma irradiation.

RATIONALE: Plasma-assisted ionization is widely used in mass spectrometry; in this study, a low-pressure glow discharge is introduced as a new method to improve the detection of large proteins, and bovine serum albumin (BSA) is used as a protein model. The treatment of analyte, matrix, and the matrix/analyte mixture is evaluated under optimal conditions. METHODS: Low-pressure radio-frequency capacitively coupled plasma (RF-CCP) treatment is utilized in the sample preparation step of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to enhance the protein MALDI ion signal. Plasma treatment can be an effective tool for enhancing the non-covalent binding of the analyte with the matrix, incorporation of the analyte into the matrix, production of matrix/analyte crystals, and analyte protonation through plasma activation, resulting in an improved MALDI ion signal. RESULTS: Fourier-transform infrared (FTIR) spectroscopy allows us to distinguish between the functional groups of plasma-treated and control samples. In addition, optical emission spectroscopy (OES) determines the plasma species, and zeta potential analysis characterizes the potential difference between plasma-treated and control samples before MALDI-TOF MS analysis. Plasma-treated BSA can provide a five-times enhancement of ion intensity. The combination of the plasma-treated analyte with the plasma-treated matrix leads to an increase in the ion intensity by a factor of 14. CONCLUSIONS: Low-pressure glow discharge plasma treatment greatly enhances MALDI ion signals, with a noticeable increase in incorporation, co-crystallization, protonation, and the concentration of the sample functional groups.

Attosecond charge migration following oxygen K-shell ionization in DNA bases and base pairs.

Core ionization of DNA begins a cascade of events which could lead to cellular inactivation or death. The created core-hole following an impulse inner-shell ionization of molecules naturally decays in the auger timescale. We simulated charge migration (CM) phenomena following an impulsive core ionization of individual DNA bases at the oxygen K-edge which occurs before Auger decay of the oxygen. Our approach is based on real-time time dependent density functional theory (RT-TDDFT). It is shown that the pronounced hole fluctuation observed around bonds of the initial core-hole results in various valence orbital migrations. Also, the same photo-core-ionized dynamics is studied for the related base pairs. We investigate the role of base pairing and H-bonding interactions in the attosecond CM dynamics. In particular, the creation of a core-hole in the oxygen involved in H-bonding leads to an enhancement of charge migration relative to the respective single bases. Importantly, the hole oscillation of the adenine-thymine base pair upon creation of a core-hole at the oxygen, which does not contribute to the donor-acceptor interactions (not H-bonded), decreases compared to the single thymine base. Understanding the detailed dynamics of the localized core-hole initiating CM process would open the way for chemically controlling DNA damage/repair in the future.

The evaluation of efficacy of atmospheric pressure plasma in diabetic ulcers healing: A randomized clinical trial.

The aim of this study is to evaluate the efficacy and safety of cold atmospheric plasma (CAP) as a novel therapy for diabetic foot ulcers. This was an investigator-blinded, randomized controlled trial of 14 weeks (6 weeks of treatment and 8 weeks of follow-up). Twenty patients with diabetic foot ulcers were divided into two groups: the control group receiving standard wound care and the plasma group, which received CAP twice a week for six consecutive weeks in addition to standard wound care. The ulcer size, amount of exudate, and wound grading were determined weekly. Cold plasma was produced by applying a high voltage (4.5 kV) and a high frequency (22 kHz) to helium gas. Exudate from wounds treated with CAP showed a significant reduction in the third week after complete treatment (p = 0.039). The wound grading of the ulcers improved by the sixth week (p = 0.019), and the sizes of ulcers significantly decreased in the plasma group at the end of the treatment period (p = 0.007). In this randomized clinical trial, CAP was an effective treatment option for diabetic foot ulcers in terms of wound surface reduction and antibacterial effects.

Lévy noise-driven escape from arctangent potential wells.

The escape from a potential well is an archetypal problem in the study of stochastic dynamical systems, representing real-world situations from chemical reactions to leaving an established home range in movement ecology. Concurrently, Lévy noise is a well-established approach to model systems characterized by statistical outliers and diverging higher order moments, ranging from gene expression control to the movement patterns of animals and humans. Here, we study the problem of Lévy noise-driven escape from an almost rectangular, arctangent potential well restricted by two absorbing boundaries, mostly under the action of the Cauchy noise. We unveil analogies of the observed transient dynamics to the general properties of stationary states of Lévy processes in single-well potentials. The first-escape dynamics is shown to exhibit exponential tails. We examine the dependence of the escape on the shape parameters, steepness, and height of the arctangent potential. Finally, we explore in detail the behavior of the probability densities of the first-escape time and the last-hitting point.

Effect of oxidative stress on cystine transportation by xC‾ antiporter.

We performed computer simulations to investigate the effect of oxidation on the extracellular cystine (CYC) uptake by the xC- antiporter. The latter is important for killing of cancer cells. Specifically, applying molecular dynamics (MD) simulations we studied the transport of CYC across xCT, i.e., the light subunit of the xC- antiporter, in charge of bidirectional transport of CYC and glutamate. We considered the outward facing (OF) configuration of xCT, and to study the effect of oxidation, we modified the Cys327 residue, located in the vicinity of the extracellular milieu, to cysteic acid (CYO327). Our computational results showed that oxidation of Cys327 results in a free energy barrier for CYC translocation, thereby blocking the access of CYC to the substrate binding site of the OF system. The formation of the energy barrier was found to be due to the conformational changes in the channel. Analysis of the MD trajectories revealed that the reorganization of the side chains of the Tyr244 and CYO327 residues play a critical role in the OF channel blocking. Indeed, the calculated distance between Tyr244 and either Cys327 or CYO327 showed a narrowing of the channel after oxidation. The obtained free energy barrier for CYC translocation was found to be 33.9kJmol-1, indicating that oxidation of Cys327, by e.g., cold atmospheric plasma, is more effective in inhibiting the xC- antiporter than in the mutation of this amino acid to Ala (yielding a barrier of 32.4kJmol-1). The inhibition of the xC- antiporter may lead to Cys starvation in some cancer cells, eventually resulting in cancer cell death.

Transport of cystine across xC- antiporter.

Extracellular cystine (CYC) uptake by xC- antiporter is important for the cell viability. Especially in cancer cells, the upregulation of xC- activity is observed, which protects these cells from intracellular oxidative stress. Hence, inhibition of the CYC uptake may eventually lead to cancer cell death. Up to now, the molecular level mechanism of the CYC uptake by xC- antiporter has not been studied in detail. In this study, we applied several different simulation techniques to investigate the transport of CYC through xCT, the light subunit of the xC- antiporter, which is responsible for the CYC and glutamate translocation. Specifically, we studied the permeation of CYC across three model systems, i.e., outward facing (OF), occluded (OCC) and inward facing (IF) configurations of xCT. We also investigated the effect of mutation of Cys327 to Ala within xCT, which was also studied experimentally in literature. This allowed us to qualitatively compare our computation results with experimental observations, and thus, to validate our simulations. In summary, our simulations provide a molecular level mechanism of the transport of CYC across the xC- antiporter, more specifically, which amino acid residues in the xC- antiporter play a key role in the uptake, transport and release of CYC.

CO2 conversion in a dielectric barrier discharge plasma by argon dilution over MgO/HKUST-1 catalyst using response surface methodology.

Metal-organic frameworks (MOFs) as carbon dioxide adsorption in combination with metal oxides have shown catalyst application in CO2 conversion. Herein, the MgO/HKUST-1 catalyst is synthesized to direct conversion of CO2 upon dilution by argon in a cylindrical dielectric barrier discharge (DBD) reactor. A water-cooling circulation adjusts the reactor temperature, and aluminum powder is used as a high-voltage electrode. The effect of the discharge power, feed flow rate, CO2 fraction, and their interaction in plasma and plasma catalyst method on CO2 conversion (R1), effective CO2 conversion (R2), and energy efficiency (R3) is evaluated by central composite design (CCD) based on response surface methodology. The Analysis of Variance (ANOVA) results demonstrate that the quadratic regression model describes CO2 conversion and effective CO2 conversion, and the reduced cubic model describes energy efficiency. The results indicate that the method (plasma, plasma catalyst) and discharge power on R1 and R2 have a considerable effect. Also, the method and CO2 fraction on R3 have the greatest impact, respectively. In the plasma and plasma catalyst method maximum CO2 conversion is 12.3% and 20.5% at a feed flow rate of 80 ml/min, CO2 fraction of 50%, and discharge power of 74 W.

Development and characterization of a spark plasma device designed for medical and aesthetic applications.

Cold atmospheric plasma devices have shown high potential to be useful for different medical applications. In this study, it has been tried to develop and characterize a cold atmospheric spark plasma device that can be used safely as a tool for medical and aesthetic applications. The schematic of the device is presented in the paper, and the signals of each block are also tested. A special handpiece for this device is designed to make the device as safe as possible. The device's properties that can impose a risk to users' health have been under consideration. The device's electrical properties have been tested, and results show that the electrical current of the device is below the safety thresholds and can be used safely. The radiation power of the device also has been tested. It is shown that the time needed for the radiation power to reach the danger threshold is much longer than the treatment time. The device will not impose any risk regarding radiation from the UV spectrum. Optical emission spectroscopy is also used to investigate the neutral and charged species that are the by-products of electrical discharge. The presence of NOx and OH locally in the discharge can be helpful for various medical applications. This paper presents one of the first studies conducted to investigate the engineering aspect and the immunometry of the spark plasma that can be used in medicine and other purposes.

Parametric investigation and RSM optimization of DBD plasma methods (direct & indirect) for H2S conversion in the air.

Hydrogen sulfide (H2S) is known as a harmful pollutant for the environment and human health, and its emission control is a high priority. Non-thermal plasma is an effective technology in this field. In this study, for the first time, the performance of direct and indirect H2S plasma conversion methods was compared, optimized, and modeled with the CCD method. H2S was diluted in zero air, and the study investigated the effect of discharge power, relative humidity, total flow rate, initial H2S concentration, and their interactions. ANOVA results showed that the models for H2S conversion efficiency and energy yield were significant and efficient. The direct method achieved a maximum conversion efficiency of 56 % and energy yield of 3.43 g/kWh, while the indirect method produced 68 % conversion efficiency and 1.59 g/kWh energy yield. According to the process optimization results, the direct conversion method is more optimal than the indirect conversion method due to the presence of active species and high-energy electrons in the plasma treatment, and it is a better choice if there are suitable working conditions.

Simulation and experimental study of a cold atmospheric pressure plasma and comparison of efficiency in boosting recombinant Endoglucanase II production in Pichia pastoris.

Recombinant proteins are essential in various industries, and scientists employ genetic engineering and synthetic biology to enhance the host cell's protein production capacity. Stress response pathways have been found effective in augmenting protein secretion. Cold atmospheric pressure plasma (CAP) can induce oxidative stress and enhance protein production. Previous studies have confirmed the applicability of CAP jets on Phytase and green fluorescent protein (GFP) production in Pichia pastoris hosts. This study investigates the effect of CAP treatment on another valuable recombinant protein, Endoglucanase II (EgII), integrated into the Pichia pastoris genome. The results demonstrated that plasma induction via two different ignition modes: sinusoidal alternating current (AC) and pulsed direct current (DC) for 120, 180, and 240 s has boosted protein secretion without affecting cell growth and viability. The AC-driven jet exhibited a higher percentage increase in secretion, up to 45%. Simulation of plasma function using COMSOL software provided a pattern of electron temperature (Te) and density distribution, which determine the plasma cocktail's chemistry and reactive species production. Furthermore, electron density (ne) and temperature were estimated from the recorded optical spectrum. The difference in electron properties may explain the moderately different impressions on expression capability. However, cell engineering to improve secretion often remains a trial-and-error approach, and improvements are, at least partially, specific to the protein produced.

The FEDBD plasma's quantitative investigation of skin parameters: Skin elasticity, thickness, density, tissue oxygenation, perfusion, and edema.

This study used the FEDBD plasma device for skin rejuvenation in animal samples. There were two groups of six male Wistar rats. Before starting the treatment, immediately after the treatment, the fourth week, and the tenth week of follow-up, biometric tests were performed, including moisture level, evaporation from the skin surface, erythema and melanin, skin elasticity and firmness with an MPA9 device and cutometer. The thickness and density of the epidermis and dermis, an essential indicator in rejuvenation, were evaluated with a skin ultrasound device. Also, the level of oxygen, perfusion, and interstitial water (edema) was checked using a Tivita tissue hyperspectral camera at a depth of 6 mm of the skin.

Plasma pyrolysis feasibility study of Spent Caustic waste to hydrogen production.

Spent caustic is a used industrial caustic whose chemical content puts it in the special waste category. The disposal of this waste and the production of value-added products from it has attracted the attention of researchers not only to solve environmental problems but also to take advantage of its byproducts. This research has experimentally proved the transferred thermal plasma technology as a practical method feasible for the disposal of spent caustic. In this study, the applied voltage, electrical current, and feed rate are variable parameters, and others are kept constant. GC analysis showed H2 as the main product, which is environmentally beneficial. The percentage of hydrogen production of approximately 74% is a promising result, considering the difficulty of achieving such a high percentage of hydrogen.

Rapid cold plasma synthesis of cobalt metal-organic framework/reduced graphene oxide nanocomposites for use as supercapacitor electrodes.

Metal-organic frameworks (MOFs) are recognized as a desirable class of porous materials for energy storage applications, despite their limited conductivity. In the present study, Co-MOF-71 was fabricated as a high-performance supercapacitor electrode at ambient temperature using a fast and straightforward, one-pot cold plasma method. A supercapacitor electrode based on Co-MOF@rGO was also synthesized by adding reduced graphene oxide (rGO) during processing to increase the capacitance retention and stability after 4000 cycles from 80 to 95.4%. The Co-MOF-71 electrode provided a specific capacitance (Cs) of 651.7 Fg-1 at 1 Ag-1, whereas the Co-MOF@rGO electrode produced a Cs value of 967.68 Fg-1 at 1 Ag-1. In addition, we fabricated an asymmetric device (Co-MOF@rGO||AC) using Co-MOF-rGO as a high-rate positive electrode and activated carbon (AC) as a negative electrode. This hybrid device has a remarkable specific energy and power density. The combination of MOFs with reduced graphene oxide (rGO) in a cold plasma environment resulted in the formation of a three-dimensional nanostructure composed of nanosheets. This nanostructure exhibited an increased number of electroactive sites, providing benefits for energy storage applications.