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The performance characteristics of an argon propellant Hall thruster with two types of propellant injectors, the axial and swirl injectors, were investigated. In the swirl injector, the propellant is injected in the tangential direction. At a discharge voltage of 150 V, the swirl injector achieved a higher propellant utilization efficiency (30.3%) and anode efficiency (8.8%) compared to the axial injector (26.7% and 7%, respectively). A numerical simulation quantitatively explained the reason for these differences, which shows an increase in the neutral particle density of 32.6% near the injection region and 7.8% at the exit of the hollow anode with the swirl injector. Neutral particle accommodation on the anode wall was found to be the predominant mechanism, which reduces the injection effect. [ABSTRACT FROM AUTHOR]

A fundamental equation of state in terms of the Helmholtz energy is presented for mixtures of nitrogen, oxygen, and argon at any composition. It is expressed in terms of the residual Helmholtz energy and can be used to calculate all thermodynamic equilibrium properties including vapor–liquid equilibria. The parameters of the equations for the pure-fluid and mixture contributions are fitted exclusively to molecular simulation data so that the model has a predictive character. The description of the mixture-specific reducing parameters is realized via generalized correlations of the critical parameters of the pure fluids so that an extension of the model to additional components can be implemented straightforwardly. Extensive comparisons to experimental data and the GERG-2008 reference equation of state show that the prediction of thermodynamic properties is satisfactory. [ABSTRACT FROM AUTHOR]

For many years, the recombination of excited ions of argon, Ar + ( P 1 / 2 2 ) , has been assumed negligible under ambient conditions as compared to the recombination of ground-state ions, Ar + ( P 3 / 2 2 ). This opinion was confronted with detailed experimental results that seem to clearly support it. Here, we propose a new interpretation in light of our recent calculations, which shows that the recombination efficiency is comparable for both fine-structure states. Noteworthily, in our model leading to a picture consistent with the experiment, residual dimer ions emerge from A r + ( P 1 / 2 2 ) due to non-adiabatic dynamics effects and interplay in measured data. [ABSTRACT FROM AUTHOR]

Laser diode absorption spectroscopy is used to experimentally measure Ar(1s5) metastable density and translational gas temperature within a 94 GHz microplasma. A square two-dimensional photonic crystal (PhC) at this resonance frequency serves to ignite and sustain the plasma from 20 to 200 Torr (2.7 × 103–2.7 × 104 Pa) by using millimeter wave power from 300 to 1000 mW. Metastable density within the plasma is estimated from the absorption line shape of the laser traversing the PhC. The metastable density reaches an order of 1019 m−3 at lower pressure and decreases as pressure increases. From the Lorentzian line shape of the absorption profile at 811.53 nm, the gas temperature is extracted and found to increase from 500 K at 20 Torr to 1300 K at 200 Torr. These data are analyzed and compared with a zero-dimensional plasma model and with previous experimental plasma results at 43 GHz. [ABSTRACT FROM AUTHOR]

In this work, the Yb2Si2O7 interphase was prepared on SiC fibers using the sol–gel method. The influence of sol concentration on the morphology of the interphase was discussed. After heat treatment in argon at 1200°C for 1 h, the Yb2Si2O7 was grown in situ on the fiber surface, forming an interphase layer. Then, SiCf/Yb2Si2O7/SiC minicomposites were prepared by chemical vapor infiltration (CVI). The Yb2Si2O7 interphase exhibited no changes throughout the high‐temperature preparation process and maintained stability and compatibility with the fiber and matrix. The tensile strength of SiCf/Yb2Si2O7/SiC minicomposites with Yb2Si2O7 interphase was significantly higher than SiCf/SiC minicomposites without interphase. The crack deflection, interfacial debonding, and fiber pullout were observed in the tensile fracture of the SiCf/Yb2Si2O7/SiC minicomposites. [ABSTRACT FROM AUTHOR]

Thermodynamic property data for solid argon have been analysed to construct a new fundamental equation of state (EOS) based on the Helmholtz energy. This approach is based on methodologies previously applied to solid CO2 and benzene (Trusler in J Phys Chem Ref Data 40:043105, 2011; Xiao et al. in J Phys Chem Ref Data 50:043104, 2021). The EOS is capable of predicting thermodynamic properties of solid argon up to 760 K and 6300 MPa, using temperature and cell volume as independent variables. The model incorporates the quasi-harmonic approximation with a Debye oscillator framework for vibrons, along with an anharmonic term to address deviations near the triple point. In addition to literature data, the model was regressed to new measurements of argon's solid cell volume conducted from (8 to 50) K using a high-intensity neutron diffractometer, the results of which are reported here. This new EOS achieves a high degree of accuracy in representing experimental data, with uncertainties (k = 1) estimated of 0.1 %, 0.5 %, and 0.5 % for the cell volume along the sublimation curve, along the melting curve, and in the compressed solid phase, respectively; 2 % to 10 % for the heat capacity along the sublimation curve in different temperature regions; 1 % to 10 % for the thermal expansivity on the sublimation curve; 2 % for the isothermal bulk modulus, 1 % for the isentropic bulk modulus, 0.2 % for the enthalpy of sublimation, 0.5 % to 2 % for the enthalpy of melting, 1 % for the sublimation pressure (T > 50 K), and 2 % to 5 % for melting pressure. The EOS maintains physically realistic behaviour across the range of conditions from absolute zero to high-pressure. [ABSTRACT FROM AUTHOR]

Purpose: The emulsification of silicone oil (SO) remains poorly understood. In the present study, we investigated the physical properties of unused pharmaceutical SO samples under various conditions. Moreover, clinical correlations with the patients' SO samples were assessed. Methods: Unused pharmaceutical ophthalmic SO samples and four explanted SO samples from previously vitrectomized patients with rhegmatogenous retinal detachment were analyzed. To assess the stability of SO, the samples were exposed to UV light, visible light, a green argon laser, microwave radiation, heat, and were aged. Following exposure, the samples were investigated using Fourier-transform infrared spectroscopy, optical transmittance and absorbance, and micro-viscometry measurements. Two patients underwent argon laser retinopexy while SO tamponaded the vitreous cavity postoperatively. Results: The physical properties of SO exposed to heat, UV light, microwave radiation, and aging did not change. However, SO irradiated by the green argon laser demonstrated a significant breakdown of atomic bonding and a transmittance loss. These results are consistent with the analyses of SO samples provided by patients. In those who underwent laser retinopexy, the SO exhibited clinical emulsification necessitating earlier removal, which was confirmed by physical tests. Conclusions: It may be postulated that patients exposed to the argon laser experienced more emulsification than the other two groups, leading to the earlier removal of the SO implants from the eyes. This investigation did not consider the biological effects of inflammatory biomarkers; however, it may provide valuable insights for optimizing the use of SO in ophthalmic surgery and other potential applications. [ABSTRACT FROM AUTHOR]

The dual-phase liquid argon time projection chamber is presently one of the leading technologies to search for dark matter particles with masses below 10 GeV c−2. This was demonstrated by the DarkSide-50 experiment with approximately 50 kg of low-radioactivity liquid argon as target material. The next generation experiment DarkSide-20k, currently under construction, will use 1,000 times more argon and is expected to start operation in 2027. Based on the DarkSide-50 experience, here we assess the DarkSide-20k sensitivity to models predicting light dark matter particles, including Weakly Interacting Massive Particles (WIMPs) and sub-GeV c−2 particles interacting with electrons in argon atoms. With one year of data, a sensitivity improvement to dark matter interaction cross-sections by at least one order of magnitude with respect to DarkSide-50 is expected for all these models. A sensitivity to WIMP–nucleon interaction cross-sections below 1 × 10−42 cm2 is achievable for WIMP masses above 800 MeV c−2. With 10 years exposure, the neutrino fog can be reached for WIMP masses around 5 GeV c−2. The DarkSide-20k collaboration reports the sensitivity of its detector, currently under construction, to models predicting light dark matter particles. This includes Weakly Interacting Massive Particles and particles interacting with bound electrons of argon atoms. [ABSTRACT FROM AUTHOR]

A self-consistent model of inductively coupled plasma (ICP) discharge in argon describing the main plasma parameters at medium and high pressures was formulated in the work. Numerical calculations were carried out in a wide range of discharge conditions. Deviations from the fulfillment of similarity laws for some parameters for geometrically similar discharge tubes are shown. [ABSTRACT FROM AUTHOR]

The work carried out numerical calculations to study the dynamics of plasma-chemical processes in a glow discharge in argon with small admixtures of methane CH4 at low pressures. The dynamics of changes in the main conversion products and various types of ions in the process of establishing a discharge are presented. It is shown that the time it takes for the conversion products to reach a stationary regime is about t = 8 s. The main products of methane conversion in steady state are atomic hydrogen, as well as atomic and molecular carbon. [ABSTRACT FROM AUTHOR]

The application of the entropy-driven and density-driven phase transitions for analysis of phase diagram of water and argon is discussed. The reduced coefficient of isothermal compressibility is evaluated as βr = –(dV/dP)T(Pc/Vc) (Pc and Vc are the values in the critical point). The data are presented as dependencies of βr on the reduced temperature T/Tc, pressure P/Pc, and chemical potential μ/μc. Consideration is based on the principle of corresponding states. For water, the regions with anomalous behavior associated with the entropy-driven liquid–hexagonal ice phase transition and minima observed at T = (315.3 ± 0.2) K, P = (8.30 ± 0.04) kPa, and μ = (1122 ± 5) kJ/kg. For water, the baric dependence βr(P/Pc) along the liquid–vapor equilibrium line forms a closed loop with line of the liquid–hexagonal ice equilibrium. The thermodynamic similarity of water and argon is observed at relatively large temperatures T/Tc > 0.56, pressures P/Pc > 0.00358, and chemical potentials μ/μc > 0.505. [ABSTRACT FROM AUTHOR]

In this study, we explore high harmonic generation (HHG) in pure argon (Ar) gas and a mixture of argon and helium (He). We investigate phase-matching conditions and interference effects in both single and mixed-gas systems. By varying the gas pressure in the Ar–He mixture, we optimize the harmonic spectrum, achieving a broad range from H17 to H43, corresponding to photon energies of 25 eV to 75 eV. We attribute the spectrum broadening to a cascaded HHG process: argon-generated extreme ultraviolet photons excite helium's outer electrons, which are then driven by the fundamental laser field to contribute to HHG. This finding aligns with previous studies, showing that mixing gases with low and high ionization potentials can enhance HHG. The results offer a broad HHG spectrum ideal for ultra-fast spectroscopy and high-resolution imaging applications. [ABSTRACT FROM AUTHOR]

This study investigates the ionization pressure threshold of a gas (air, helium, argon, and SF6 across a wide pressure range) filled dielectric tube when a ∼300 MW, ∼0.7 ns, 9.6 GHz high-power microwave (HPM) pulse propagates through it. The thresholds are determined as the pressure for which the energy of the transmitted HPM pulse decreases to ∼30%, which is close to the same HPM pulse's transmission coefficient when a metal rod fills the tube. These thresholds are found to be 0.4 × 105 Pa,105 Pa, 1.8 × 105 Pa, and 0.2 × 105 Pa, for air, argon, helium, and SF6, respectively. The measured intensity of the plasma light emission starts to decrease at a pressure which coincides with the pressure threshold determined by HPM pulse propagation. Additionally, at gas pressures <5 × 104 Pa, it is shown that time- and space-resolved images of the light emission display a diffused plasma which at higher pressures >105 Pa transforms into streamer like plasma. Simplified numerical simulations of a microwave discharge in air at 1 × 105 Pa and 4 × 105 Pa are consistent with the experimental plasma light observations. [ABSTRACT FROM AUTHOR]

The noble gas argon is one of the most promising neuroprotective agents for hypoxic-reperfusion injuries of the brain. However, its effect on traumatic injuries has been insufficiently studied. The aim of this study was to analyze the effect of the triple inhalation of the argon-oxygen mixture Ar 70%/O2 30% on physical and neurological recovery and the degree of brain damage after traumatic brain injury and to investigate the possible molecular mechanisms of the neuroprotective effect. The experiments were performed in male Wistar rats. A controlled brain injury model was used to investigate the effects of argon treatment and the underlying molecular mechanisms. The results of the study showed that animals with craniocerebral injuries that were treated with argon inhalation exhibited better physical recovery rates, better neurological status, and less brain damage. Argon treatment significantly reduced the expression of the proinflammatory markers TNFα and CD68 caused by TBI, increased the expression of phosphorylated protein kinase B (pAKT), and promoted the expression of the transcription factor Nrf2 in intact animals. Treatment with an argon-oxygen breathing mixture after traumatic brain injury has a neuroprotective effect by suppressing the inflammatory response and activating the antioxidant and anti-ischemic system. [ABSTRACT FROM AUTHOR]

Recently (2024), the NA61/SHINE collaboration has presented new experimental data on , , proton, and antiproton productions in central 40Ar + 45Sc collisions at the laboratory momenta Plab = 13–150 A GeV/c and has compared these data with predictions of popular theoretical models. It turned out that the models poorly describe the data in the entire energy range. In this work, it has been suggested for the first time that nucleons participating in non-diffractive collisions cannot diffractively dissociate in subsequent nucleon–nucleon collisions. This idea has been implemented in the Geant4 FTF model. Good description of the data, including the first NICA BM@N data on meson production in the collisions of 40Ar nuclei with various nuclei at an energy of 3.2 A GeV, has been achieved. [ABSTRACT FROM AUTHOR]

The primary objective of this study was to investigate the pharmacokinetics of inhaled argon in young pigs using mechanical ventilation. Also a physiologically based model of argon pharmacokinetics (PBPK) is validated with human data for xenon from the literature and the new data from juvenile pigs. The inherent difficulty in performing pharmacokinetics studies of argon makes the use of the PBPK model especially relevant. The model is used to investigate argon pharmacokinetics for adult and neonate applications. Juvenile pigs (n = 4) were anesthetized, submitted to endotracheal intubation, and mechanical ventilation using a conventional ventilator. Argon inhalation was achieved by switching the animal from the first mechanical ventilator (with air/oxygen) to a second one that was supplied with 75% argon and 25% oxygen from premixed gas cylinders. This administration yielded blood samples that were analyzed using a quadrupole based technique for determining argon concentration. The range of blood:gas partition coefficient corresponding to the average measured Cmax of 190–872 μM is 0.005–0.022. Based on the average curve, T1/2= 75 seconds. The PBPK is shown to be in general agreement with the experimental data in pigs. Inhaled argon administration exhibited an on-off nature such that AUC was proportional to administration time. Confidence in the PBPK model and the remarkably robust and stable on-off nature of argon pharmacokinetics, notwithstanding intersubject variability and comorbidity, suggests that inhaled argon could readily be applied to any treatment regime. [ABSTRACT FROM AUTHOR]

This work studied the rovibrational absorption spectral line-shape parameters of the P(1)–P(10) and R(0)–R(9) lines for Hydrogen fluoride perturbed by argon in the 0–0, 1–0, and 2–0 vibrational bands at 20–1000 K. A dataset of beyond-Voigt line-shape parameters (pressure broadening and shifting parameters, their speed dependencies, and the complex Dicke parameters) has been theoretically determined for the first time from generalized spectroscopic cross-section calculated by the full quantum scattering calculations. Then these parameters were employed to predict the line shape and asymmetry based on the partially-correlated speed-dependent hard-collision and the partially-correlated quadratic-speed-dependent hard-collision profiles. The effect of each parameter on the line shape and line asymmetry was further studied, which revealed that the beyond-Voigt effects were indispensable to accurately describe the line shape contour. Our results are in good agreement with the available experimental observations and provide a comprehensive set of theoretical references for further experimental measurements. [ABSTRACT FROM AUTHOR]

Diode-pumped rare gas lasers (DPRGLs) have the potential for high-energy laser output with high beam quality. The metastable concentration >1014 cm−3 and pump intensity >10 kW/cm2 are required in developing high-power and efficient DPRGLs. However, the kinetics of 1s and 2p levels (Paschen notation) under these conditions is unclear yet, particularly regarding the adverse effects of interference energy levels (e.g., 1s4 and 2p1–2p8). This study addresses this gap by measuring the number densities of 1s and 2p levels in a diode-pumped plasma jet metastable argon laser. The experiment was conducted with a much higher number density of 1014 cm−3 and a higher pump intensity of 12 kW/cm2 than our previous works. The results indicate that the adverse effect of 1s4 accumulation could be partially compensated, and the relative population distribution of 2p energy levels remained unchanged. However, the high gas temperature (>1000 K) caused a significant negative impact of high 2p levels (2p1–2p8), and the air environment weakened the effect of He collision relaxation. [ABSTRACT FROM AUTHOR]

The importance of microwave device reliability and performance for microscale devices motivates a more fundamental understanding of breakdown mechanisms in this regime. Microwave breakdown theories predict breakdown when electron production balances electron loss. Electron production depends strongly on the ionization rate ν i ; however, previous studies either used the measured ν i in macroscale gaps or the empirical formula for DC voltage, inaccurately predicting ν i in microscale gaps. Alternatively, this work characterizes ν i in microwave microplasmas by using particle-in-cell simulations. We calculated ν i in argon gas at atmospheric pressure for 2–10 μm gaps under AC fields ranging from 1 to 1000 GHz. The behavior of ν i may be separated into two regimes by defining a critical frequency f c r that depends on the amplitude of the applied voltage, gap distance, and pressure. For frequency f < f c r , the electrodes collect the electrons during each cycle and the electron number oscillates with the electric field, causing ν i / f to roughly scale with the reduced effective field E e f f / p. For f > --> f c r , the phase-space plots indicate that the electrons are confined inside the gap, causing the electron number to grow exponentially and v i / p to become a function of E e f f / p. These results elucidate the ionization mechanism for AC fields at microscale gap distances and may be incorporated into field emission-driven microwave breakdown theories to improve their predictive capability. [ABSTRACT FROM AUTHOR]

The second-order optical nonlinearity (SON) of thermally poled fused silica was shown for the first time to be significantly improved by the implantation of multi-energy boron (B) ions, and the outcomes were compared with those obtained from the implantation of multi-energy argon (Ar) ions. Second-harmonic (SH) signals in both samples grew roughly linearly as the poling temperature rose. Samples with Ar implants showed a greater increase in SH signal with rising poling temperature. A qualitative explanation for the formation of χ (2) in poled samples can be found in a model of charge hopping and migration through defects. The diminished SH signal in the B-implanted sample is probably caused by the negative charge trapping layer, as well as by B 2 α and E ′ center defects. [ABSTRACT FROM AUTHOR]

High-temperature annealing (HTA) is one of the most promising techniques to produce high-quality, cost-efficient AlN templates for further epitaxial growth of AlGaN devices. Unfortunately, the yield of this process seems to be limited due to the restricting face-to-face configuration that is typically used, in which contaminations of the template surface can occur easily. A high yield is crucial for process transfer into industry. Indeed, templates that are annealed in open-face configuration suffer from surface degradation due to excessive AlN evaporation during the course of the annealing process. To highlight the physics that are restricting the open-face approach of the process, sublimation behavior of AlN at temperatures and atmospheres typically used in HTA processes has to be examined. In this study, we use the Knudsen effusion mass spectrometry technique to confirm the previously published results on equilibrium partial pressures of species above AlN. Based on the experimentally determined data and further AlN sublimation experiments, the apparent sublimation coefficient of AlN in N2 and Ar atmospheres at HTA process conditions can be derived. Despite N2 having a stabilizing effect on AlN during HTA, the still high decomposition rates of several hundred nanometers per hour can explain the excessive damage that is typically observed if AlN/sapphire templates are annealed in an open-face configuration. Finally, based on theoretical considerations, a strategy to reduce the sublimation of AlN during HTA in open-face configuration is suggested. [ABSTRACT FROM AUTHOR]

This paper is devoted to the experimental study of the characteristics of a continuous optical discharge (COD) sustained by high power continuous wave laser radiation at a wavelength λ = 1.08 μ m in high pressure argon. New data on the COD threshold laser power dependence of argon pressure in the range 20–50 bar is obtained. The COD threshold laser power is shown to be in good agreement with the data obtained by other authors and theoretical evaluations provided the contribution of plasma energy loss due to thermal radiation is taken into account properly. The maximum plasma temperature was estimated to be 20–21 kk or higher, favorable to obtain high UV spectral radiance. A study of the convective plume oscillations around COD in argon has been carried out. It is found that in the pressure range 25–35 bars the growth of the laser radiation power leads to a decrease in convection oscillation frequency from 33 to 29 Hz, while the radius of the convective plume grows accordingly. The oscillation frequency ν and characteristic radius of the convective plume r 0 were found to obey the similarity relation ν = 0.5 g / 2 r 0 previously established in experiments with COD in xenon. These results are promising for using COD in argon as a high brightness broadband UV radiation source. [ABSTRACT FROM AUTHOR]

The thermodynamic constraints of steel deoxidation are discussed based on calculated [%Me]–[%O] diagrams for different deoxidizing elements in pure Fe and five examples of steel grades, highlighting the influence of alloying on the equilibria. The role of deoxidation product oxides is considered with special emphasis on the activity of SiO2 and the possibility of utilizing slags with a very low aSiO2 to amplify the deoxidizing power of silicon. This effect was verified for SiCr spring steel and 18Cr8Ni stainless steel. The results indicate a strong reduction in equilibrium oxygen content. Different means for industrial implementation of this principle are discussed. The conventional steel/slag equilibration via gas stirring is tested in practice. As potentially more efficient methods, slag powder injection (argon, lance) and cored wire injection combined with argon bubbling are studied. In such treatments, specific tailored slag additives can be used for divergent steel grades to optimize steel cleanliness and inclusion engineering. [ABSTRACT FROM AUTHOR]

Chemiluminescence of OH∗ is commonly employed as an optical indicator for the combustion process. It is widely recognized that the generation of OH∗ in hydrogen flames is primarily governed by the reaction H + O + M=>OH∗+M. In this study, the time histories of OH∗ chemiluminescence from the A→X band around 308 nm were recorded behind reflected shock waves for stoichiometric and lean H 2 /O 2 mixtures highly diluted in argon over the temperature range of 1130–3150 K and at the pressure of approximately 0.9 atm. Based on the time histories of OH∗ chemiluminescence, the best-fit reaction rate coefficient for the reaction H + O + M=>OH∗+M was determined as k = 3.17 × 1027exp(-121968 cal mol−1/RT) + 2.25 × 1017exp(-4246 cal mol−1/RT) cm6 mol−2 s−1 over the temperature range studied. Furthermore, by using the current rate coefficient in mechanism predictions, the predicted time histories and relative peak intensities of OH∗ chemiluminescence are in good agreement with experimental results reported in literature. • The time histories of OH∗ chemiluminescence up to 3150K are recorded. • The rate coefficient for H + O + M=>OH∗+M is determined. • The OH∗ sub-mechanism with the fitted rate coefficient has been verified. [ABSTRACT FROM AUTHOR]

Since the last century, it has been known that inert gases can cause a range of physiological effects. The biological activity of inert gases is an extremely multifaceted phenomenon. Despite the similarity of most physical and chemical characteristics, they differently influence many organs and tissues by interacting with a variety of protein targets. Xenon, krypton, and argon are now known to be capable of altering the functional state of the central nervous system and correcting some psychoemotional disorders. In addition, noble gases act on the processes of apoptosis and cellular stress response, affect the immune status and various homeostatic parameters. The cytoprotective effects of helium on the cardiovascular and respiratory systems have also been convincingly demonstrated. Thus, inert gases are currently being considered as potential tools to correct various diseases. This review analyzes literature data on the physiological effects of inert gases, as identified in biomedical studies on patients, as well as in cell culture and in vivo models. Each chapter is dedicated to a particular gas of this group, starting from the most studied. For each of the inert gases (helium, neon, argon, krypton, xenon, and radon), the physiological activity, possibility of being used in medicine, and some known mechanisms of its action are considered. Moreover, the existing data are critically analyzed, and the key gaps to be filled in future research are highlighted. [ABSTRACT FROM AUTHOR]

The study aims to comprehend the behavior of nitrogen in the argon oxygen decarburization (AOD) process during the production of nitrogen‐alloyed stainless steels, where the precise adjustment of nitrogen content plays a crucial role in enhancing productivity. Furthermore, the objective is to investigate the rate of change in nitrogen content when blowing a mixture of nitrogen and argon, instead of using pure nitrogen or argon alone. Hence, both nitrogenation and denitrogenation cases are examined, and kinetic models are developed. While solution thermodynamics can predict the final nitrogen content, the kinetics are influenced by the gas flow rate, steel temperature and composition, and levels of the surface active elements in the steel. By integrating a previously developed thermodynamic equilibrium equation with the kinetic models, nitrogen contents in the range of 0.150–0.400% can be reliably predicted. Consequently, the equations can be applied to predict nitrogen content during both the nitrogenation and denitrogenation stages in the reduction and desulfurization phases of the AOD process. [ABSTRACT FROM AUTHOR]

Wood–plastic composites (WPCs) combine the properties of plastics and lignocellulosic fillers. A particular limitation in their use is usually a hydrophobic, poorly wettable surface. The surface properties of materials can be modified using ion implantation. The research involved using composites based on polyethylene (PE) filled with sawdust or bark (40%, 50%, and 60%). Their surfaces were modified by argon ion implantation in three fluencies (1 × 1015, 1 × 1016, and 1 × 1017 cm−2) at an accelerating voltage of 60 kV. Changes in the wettability, surface energy, and surface colour of the WPCs were analysed. It was shown that argon ion implantation affects the distinct colour change in the WPC surface. The nature of the colour changes depends on the filler used. Implantation also affects the colour balance between the individual variants. Implantation of the WPC surface with argon ions resulted in a decrease in the wetting angle. In most of the variants tested, the most significant effect on the wetting angle changes was the ion fluence of 1 × 1017 cm−2. Implantation of the WPC surface also increased the surface free energy of the composites. The highest surface free energy values were also recorded for the argon ion fluence of 1 × 1017 cm−2. [ABSTRACT FROM AUTHOR]

To investigate the impact of energy release of reactive material on its damage effect, a modified test chamber was developed to conduct vented chamber tests and penetration tests in both air and argon environments of Al/Ti and Al/TI/W reactive projectiles. The deformation volumes obtained from the scanning results were employed to characterize the damage effect of the reactive materials on multi-spaced plate targets. Several key results include the following: Despite its lower energy density, the Al/Ti/W composite exhibits higher energy release efficiency than the Al/Ti composite. This is attributed to the lower strength of the material, causing it to fragment into finer debris upon impact, thereby facilitating easier ignition and reaction. The Al/Ti/W projectiles induce a significant deformation volume in the plates during penetration tests but exhibit a decrease in penetrative capacity. This phenomenon is attributed to the mechanical characteristics of the Al/Ti/W materials rather than the energy release upon impact. The deflagration of reactive materials during impact does not significantly enhance the structural damage of the target, at least at impact velocities below 1200 m/s. [ABSTRACT FROM AUTHOR]

The original Rosenfeld–Tarazona (RT) scaling of the excess energy in simple dense fluids predicts a ∝ T 3 / 5 thermal correction to the fluid Madelung energy. This implies that the excess isochoric heat capacity scales as C v ex ∝ T − 2 / 5 . Careful examination performed in this paper demonstrates that the exponent − 2 / 5 is not always optimal. For instance, in the Lennard-Jones fluid in some vicinity of the triple point, the exponent − 1 / 3 turns out to be more appropriate. The analysis of the specific heat data in neon, argon, krypton, xenon, and liquid mercury reveals that no single value of the exponent exists, describing all the data simultaneously. Therefore, we propose a generalized RT scaling in the form C v ex ∝ T − α , where α is a density- and material-dependent adjustable parameter. The question concerning which material properties and parameters affect the exponent α and whether it can be predicted from general physical arguments requires further investigation. [ABSTRACT FROM AUTHOR]

In this paper, the dissolution behavior of crystal-originated particle (COP) in 300 mm Czochralski silicon under argon annealing was investigated. The latex sphere equivalent size distributions of defects along the depth direction in silicon wafers annealed under different conditions were quantified utilizing chemical–mechanical polishing and localized light scattering inspection. The interstitial oxygen concentration profiles were quantified by secondary ion mass spectrometry, and the distributions of oxygen precipitation within annealed wafers were obtained based on peak analysis. Furthermore, the classical theoretical model was employed to elucidate the depth-dependent dissolution of COP. Based on the initial COP sizes and oxygen concentrations, the relationship between COP sizes and depth after annealing was calculated. The depth distributions of defects obtained by combining the dissolution of COP from calculation with the changes of oxygen precipitation were found to be highly consistent with the measurement results. These findings could enhance the understanding of the mechanism of COP dissolution, which contributes to the production of defect-free silicon wafers for nanometre-scale integrated circuits. [ABSTRACT FROM AUTHOR]

The Panel on Food Additives and Flavourings (FAF) provides a scientific opinion re‐evaluating the safety of the two food additives argon (E 938) and helium (E 939). Argon (Ar) and helium (He) are two noble gases, highly stable single atoms. Their chemical inertness is well known. Their physicochemical properties have served as a basis for their previous evaluations by SCF and JECFA, which have considered the use of these food additives safe even in the absence of a toxicological evaluation. No business operator or other interested party provided information in response to the call for data published by EFSA to support the re‐evaluation of these two food additives with respect to their identity and specifications, manufacturing process (including the identification and quantification of potential impurities) and how they are applied to food to exert their technological function. One business operator replied to the call for data issued by EFSA reporting use levels of E 938 as a packaging gas in one food category. Based on their physicochemical properties, both gases are considered by the Panel to be of low toxicological concern when used as food additives. No information was available on the potential presence of impurities of toxicological concern resulting from the manufacturing process(es) applied to the production of the food additives E 938 and E 939. The Panel however noted that a minimum purity of 99.0% is required to comply with existing specifications. The Panel concluded that the use of argon (E 938) and helium (E 939) as food additives does not raise a safety concern. The Panel recommended an amendment of the existing EU specifications to introduce the respective CAS numbers. [ABSTRACT FROM AUTHOR]

We interpret the recent MicroBooNE data on neutral-current single π 0 production on argon with the hypothesis that this process occurs via Delta excitation. We calculate the flux-integrated total cross section with our RPA-based model which allows for a simultaneous description of Delta-mediated resonant and coherent pion production. We also discuss the ratio between the two exclusive measurements with one proton and zero protons in the final state. [ABSTRACT FROM AUTHOR]

Narrowly divergent high-energy electron beam is experimentally demonstrated during the interaction of terawatt Ti:Sa laser radiation with a nitrogen gas-cluster jet at gas pressure corresponding to the boundary of the condensation region. A collimated electron beam with an energy of up to 10 MeV and a divergence of 10 mrad at a plasma concentration of ~1019 cm–3 is obtained. The use of nitrogen instead of argon or krypton significantly improves the spatial (divergence) and energy (charge and spectrum shape) properties of the generated electron beam. The formation of clusters in a supersonic jet is observed and their composition is thermodynamically analyzed. [ABSTRACT FROM AUTHOR]

For muscovite in ancient Proterozoic and Archean terranes, quantitative modelling of age spectrum morphology shows that a significant plateau segment does not form in an age spectrum unless there was rapid cooling that either began before and continued through, or which initiated at, the time given by the plateau age. Further, the modelling shows that a well-developed plateau is not preserved unless such rapid cooling continues until ambient temperatures are reached that are <∼220–200 °C. It thus follows that the age of a well-developed plateau segment in a muscovite age spectrum is an accurate constraint on when the rock was first exhumed to (and/or last cooled at) shallow crustal levels. In a sample held at a higher ambient temperature, argon continues to be lost from the lattice at a significant rate, well past the time of so-called 'isotopic closure' predicted by application of Dodson's formula. Parametric modelling shows that monotonic cooling paths do have a well-defined point, at which isotopic closure takes place, but to form an age plateau: (1) the rate of cooling must be rapid; and (2) cooling must continue at the same or similar rates, until temperatures are reached that are low enough to inhibit significant further loss of argon to the environment. Quantitative modelling shows how Dodson's formula begins to fail once ambient temperatures rise above these numerically computed values for isotopic closure. Yet these numerically computed closure temperatures are far below the nominal closure temperature for muscovite, typically quoted as ∼ 350–400 °C. Therefore, these results have significant implications for models that utilise closure temperatures based on estimates using Dodson's formula, when attempting to invert thermochronological datasets to obtain constraints on the temperature–time path. KEY POINTS: Quantitative modelling of age spectrum morphology can constrain possible temperature–time (T–t) paths because the shape of the age spectrum itself provides considerable information. Well-formed age plateaux developed in argon spectra from muscovite imply very rapid cooling towards ambient temperatures of ∼ 220–200 °C, which are well below the nominal closure temperatures for this mineral, typically quoted as 150–200 °C higher. There are multitudinous circumstances in which Dodson's formula fail badly, when used to produce an estimate of closure temperature. Successful applications of this formula requires fast cooling to have continued to relatively low ambient temperatures. T–t paths should not be constructed by joining the dots provided by age estimates linked to closure temperatures inferred using Dodson's formula since such T–t paths may be counter to the mathematics underlying the concept of isotopic closure. [ABSTRACT FROM AUTHOR]

Effects of the propellant, propellant mass-flow rate, and discharge voltage on the characteristics of the plume of small Hall thrusters are studied using a particle-in-cell Monte Carlo collisions program. It is shown that with the same discharge voltage and mass flow, the divergence angle of the xenon plume is smaller than that of argon and is not linearly dependent on the propellant mass flow rate. Moreover, the effect of the discharge voltage on the plume divergence angle can be significant. As the discharge voltage increases from 100 to 300 V, the plume divergence angle decreases, but in the range 300–400 V, it increases with the discharge voltage. The obtained data can be useful for the design and improving the efficiency of Hall thrusters. [ABSTRACT FROM AUTHOR]

In order to produce cold plasma at atmospheric pressure, a multi-channel RF, of (1, 2, 3, and 4 MHz) frequencies, plasma jet system is developed using argon as the working gas. This system consists of two parts, a multi-channel power supply (of a power of 100 W) and a plasma jet. A strong electric field is created that ionizes and excites argon ions. The I-V characteristics of the system and the electron temperature and density for different powers (20, 50, 70, and 80 W), gas flow rates (10, 20, 30, and 40 sccm) (standard centimeter cubic per minute) at different frequencies (1, 2, 3, and 4 MHz) are studied, using the optical emission spectroscopy method. This system can be used in medical applications and material treatment with high efficiency. [ABSTRACT FROM AUTHOR]

Matrix isolation infrared spectroscopy was used to characterize a 1:1 complex of methanol (CH3OH) and benzene (C6H6). Co-deposition experiments with CH3OH and C6H6 were performed at 17–20 K using nitrogen and argon as the matrix gases. Several new infrared peaks in the co-deposition spectra were observed near the fundamental absorptions of the CH3OH and C6H6 parent molecules and these new peaks have been attributed to CH3OH–C6H6 complexe. Experiments were also performed with isotopic CD3OD and C6D6 and the corresponding infrared peaks of the isotopologue complexes have also been observed. Theoretical calculations were performed for the CH3OH–C6H6 complex using the M06-2X, ωB97X-D, MP2, and CCSD(T) methods with the aug-cc-pVDZ and aug-cc-pVTZ basis sets. Full geometry optimizations followed by vibrational frequency calculations were performed for several initial starting geometries and three stable minima were found for the CH3OH–C6H6 complex. The first has the CH3OH above the C6H6 ring with the OH hydrogen interacting with the π cloud of the ring (H–π complex), the second has the CH3OH above the C6H6 ring with the OH oxygen interacting with one or two of the C–H bonds of the ring (CH–O 1 complex), and the third has the CH3OH towards the side of the C6H6 ring with the OH oxygen interacting with two of the C–H bonds of the ring (CH–O 2 complex). The H–π complex structure is predicted to be the lower energy structure by ∼8 kJ/mol compared to the two CH–O structures. Comparing the theoretically predicted infrared spectra for the optimized CH3OH–C6H6 complex structures to the experimentally observed infrared peaks in argon and nitrogen matrices, it is concluded that in the argon matrices only the H–π complex structure is being observed, whereas in the nitrogen matrices the H–π complex and CH–O 1 complex structures are being observed. [ABSTRACT FROM AUTHOR]

Isotopic (2H and 15N) labelling and IR absorption spectroscopy have been used to study UV-induced transformations of cyanoacetylene in cryogenic noble gas matrices. The results obtained indicate that all observed isomerization processes involve single, isolated molecules of the precursor. No photoproducts have been found that would imply the recombination of fragments originating from different molecules. [ABSTRACT FROM AUTHOR]

The paper describes a method for the synthesis of silicon-carbon nanotubes in an argon arc. The evaporation of carbon and silicon atoms was carried out from crystalline silicon placed in the well of a graphite anode. An electric arc was ignited at the boundary between graphite and crystalline silicon. The experiment took place in argon at a pressure of 500 Torr. The deposits on the surface of the molybdenum cathode were silicon-carbon nanotubes with diameters of the order of 11–17 nm and lengths of the order of 1 μm. [ABSTRACT FROM AUTHOR]

The paper investigates the change in the structure of fur sheepskin leather tissue at its modification by non-equilibrium low-temperature plasma before tanning and fattening processes in modes that increase mechanical parameters of fur. High-frequency capacitive low-temperature plasma treatment in argon gas medium was used for modification of fur sheepskin leather tissue. The results of research of physical and mechanical characteristics of fur sheepskin, such as tensile strength, elongation are given. It is established that plasma modification of fur sheepskin in argon medium at a power of 2000 W contributes to the increase of physical and mechanical characteristics up to 42%. [ABSTRACT FROM AUTHOR]

Short pulses of millimeter wave (MMW) radiation at 43 GHz create microplasma within a photonic crystal for pressures from 40 to 600 Torr (1.3 × 103–8.0 × 104 Pa). Gas breakdown occurs within a photonic crystal, which acts as an electromagnetic resonator to create a strong initial electric field. The time response of the argon metastable density is experimentally determined during the pulse and in the afterglow using laser absorption. The metastable density overshoots the steady-state condition at the beginning of the pulse and during the afterglow. Modeling is presented to understand these observations. The overproduction of argon 1s5 at the beginning of each pulse is due to a concurrent overshoot in the MMW electric field within the photonic crystal. This field overheats the plasma electrons and enhances the production of excited states. The burst of argon metastables observed in the afterglow is due to the pooled energy of the plasma stored in electrons, ions, and excited states of argon. Understanding metastable production is an important intermediate step to ionization and is also critical in the study of diode-pumped rare gas lasers. [ABSTRACT FROM AUTHOR]

Utilizing alternative propellants has been recognized as a strategy to reduce the total cost of propellants in electric propulsion-based missions. The aim of this study is to quantify the Hall effect thruster (HET) performance and operating characteristics using a Kr–Ar mixture to enable mission designers to evaluate the impact on mission and spacecraft design. We present the performance and plume plasma properties of the P5 5 kW-class HET operated with a Kr–Ar mixture with Ar volumetric flow rate fractions from 0 to 100%. The thruster is characterized at discharge power levels of 2.6 kW and 4.1 kW at constant discharge current and voltage over the range of Ar fractions. Despite higher ionization energy and lower mass of Ar, the thruster exhibited a similar level of thrust within 2% when comparing the pure Kr and 26%-Ar mixture cases. The derived ion energy distribution functions and analytical modeling suggest that the characteristic length for the ionization region is extended as the Ar fraction increases. The increased residence time of Kr at the extended ionization region and background energetic electrons from the ionized Ar neutrals are considered to cause this enhanced ionization of the injected Kr neutrals. This leads to a 6% higher Kr ion density at the 26%-Ar case even at the 16% less injected Kr neutral density than in the pure Kr case. The enhanced Kr ionization and generated Ar ions in the 26%-Ar case consequently led to a comparable thrust with that of the pure Kr case. The study indicates that mixing Ar with approximately 26% volumetrically with Kr can provide a similar or even higher thrust performance at the same discharge power. This will be particularly advantageous for various space missions that require high impulses by reducing the total cost of the propellant. [ABSTRACT FROM AUTHOR]

As a typical liquid-like thermoelectric material, Cu2 Se not only has good electrical transport performance, but also has low lattice thermal conductivity. Nanoengineering is an effective method to achieve high thermoelectric properties for thermoelectrics. However, nanoscale Cu2 Se particles are extremely easy to be oxidized in the process of synthesizing, thus affecting its thermoelectric performance. In order to study the effect of powder reduction on the thermoelectric performance of Cu2 Se, nano-sized Cu2 Se powders were synthesized by hydrothermal method. Hydrogen argon mixed gas ( hydrogen volume fraction of 5%) and pure argon were used to purge the powders, respectively. Cu2 Se bulk materials with density above 95% were prepared by spark plasma sintering. The results show that the oxygen content of Cu2 Se bulk is significantly reduced after powder reduction, and there is a 41% decrease in thermal conductivity at 800 K, with a 16% increase in ZT value. [ABSTRACT FROM AUTHOR]

Melt pool dynamics in metal additive manufacturing (AM) is critical to process stability, microstructure formation, and final properties of the printed materials. Physics-based simulation, including computational fluid dynamics (CFD), is the dominant approach to predict melt pool dynamics. However, the physics-based simulation approaches suffer from the inherent issue of very high computational cost. This paper provides a physics-informed machine learning method by integrating the conventional neural networks with the governing physical laws to predict the melt pool dynamics, such as temperature, velocity, and pressure, without using any training data on velocity and pressure. This approach avoids solving the nonlinear Navier-Stokes equation numerically, which significantly reduces the computational cost (if including the cost of velocity data generation). The difficult-to-determine parameters' values of the governing equations can also be inferred through data-driven discovery. In addition, the physics-informed neural network (PINN) architecture has been optimized for efficient model training. The data-efficient PINN model is attributed to the extra penalty by incorporating governing PDEs, initial conditions, and boundary conditions in the PINN model. [ABSTRACT FROM AUTHOR]

Efficient handling of high heat flux on the plasma‐facing components, particularly the divertor targets, poses a significant challenge for the Chinese Fusion Engineering Testing Reactor (CFETR) with fusion power of Gigawatt. This work investigates the divertor plasma detachment of CFETR with a standard ITER‐like divertor geometry by neon (Ne) or argon (Ar) impurity seeding using UEDGE code. The cross‐field drifts terms are switched off, and fluid neutral models and a "fixed‐fraction" impurity model are applied to enable efficient simulations for the study of CFETR detachment. In order to reduce the heat load on the divertor targets below the acceptable level (<10 MW/m2), the impurity fraction (f), pumping speed (S), and upstream density are varied to identify the suitable operations window during Ne seeding. The effects of Ne and Ar impurities on the plasma detachment are compared. It is found that with the power across the core‐edge interface PSOL = 200 MW and separatrix density of 2.8 ×$$ \times $$ 1019m−3$$ {\mathrm{m}}^{-3} $$, Ne impurity fraction ≥1.7%, and Ar impurity fraction ≥0.24% can achieve the partial detachment. Achieving similar total radiation power (˜148 MW), the Ne fraction is 2.3% and the Ar fraction is 0.24%. Moreover, the simulation results indicate that Ar exhibits better power radiation efficiency and core compatibility compared with Ne. [ABSTRACT FROM AUTHOR]

A linear plasma device (LPD) module has been developed under the BOUT++ framework to simulate plasma transport in the MPS‐LD. However, previously, the LPD module used a simplistic neutral particle model that only includes particle density and velocity, which prevents the full understanding of the plasma‐neutrals interactions. In this work, we further optimize the neutral model by using a more complete neutral fluid model containing the continuity equation, momentum equation, and energy equation. The reactions such as charge exchange, excitation, and radiation collisions are included. Since the neutral particle source is mainly provided by particle recycling from the target, a particle recycling model is employed, which includes both fast reflection and slow thermal release. The upgraded LPD module is applied to simulate the argon (Ar) discharge experiment of MPS‐LD, and the benchmark against experiment measurement and SOLPS‐ITER simulation results are presented. Good agreements are obtained, showing the validation of the upgraded module. After that, the impact of particle recycling on Ar plasma is investigated. It is found that a higher recycling coefficient (R) promotes the achievement of high‐density plasma at the target. The recycled Ar atoms change target plasma pressure as well as plasma‐neutral collisions, which both contribute to plasma momentum loss, thus promoting the rollover of ion flux to the target. [ABSTRACT FROM AUTHOR]

The problems associated with the formation of an external cluster flow that we previously discovered, which is formed in the external field of a traditional supersonic jet and called the cluster wake, are discussed. The reasons for the long-term anomalous glow of the cluster wake are studied. The results of a spectral study of the induced radiation of a supersonic clustered argon flow in the region of particle excitation (on an electron beam) and beyond are presented. The anomalies in the glow of a traditional spindle-shaped jet and a flow of heavy clusters are discussed. The possible causes of the observed anomalous phenomena are presented based on the above comparisons of the results obtained. The role of the energy exchange between clusters and the background gas in the afterglow of a cluster wake is established. The wavelengths and corresponding transitions in ArI and ArII that are responsible for the anomalous emission are determined. The lifetimes of particles in the excited state in the central part and on the periphery of the clustered flow are determined. [ABSTRACT FROM AUTHOR]