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Earlier, an entropy switch model (ESM) for substorm onset as a result of the development of localized inner magnetospheric interchange-ballooning instability, was suggested. Shown observations testify that the substorm onset is accompanied by the reversal and strong fluctuations in key magnetospheric parameters such as total magnetic field strength, plasma pressure, entropy, and some others. Independently, similar behavior was attributed to a thermodynamic theory, where the onset of a substorm is regarded as a consequence of global energy development in the geomagnetic tail. In the latter, the geomagnetic tail is taken as an open thermodynamic system with an infinite number of conserved energy links (CEL) to the external space environment, and the shaping of the substorm profile is ultimately controlled by the system properties of the tail. A comparison between the signatures of substorm onset in the ESM and CEL models is conducted, and correspondence between experimental data and theoretical results is discussed. [ABSTRACT FROM AUTHOR]

Nonthermal plasma has been extensively utilized in various biomedical fields, including surface engineering of medical implants to enhance their biocompatibility and osseointegration. To ensure robustness and cost effectiveness for commercial viability, stable and effective plasma is required, which can be achieved by reducing gas pressure in a controlled volume. Here, we explored the impact of reduced gas pressure on plasma properties, surface characteristics of plasma-treated implants, and subsequent biological outcomes. Implant materials were treated with plasmas under varying discharge conditions, with pre-pumping times of 10 s and 20 s, thereby modulating the pressure during plasma treatments. Through optical emission spectroscopy, we demonstrated that the 5 Torr operational condition, achieved by 20-s pre-pumping, generated a greater density of excited nitrogen species and provided more stable plasma compared to the 16 Torr condition, achieved by 10-s pre-pumping. We then assessed the surface hydrophilicity, chemical composition, protein adsorption, and osteoblast activities on plasma-treated implants compared with those of untreated controls. Our results reveal that the 5 Torr condition significantly enhances removal of carbon-based impurities and increased protein adsorption, leading to improved cell adhesion, proliferation, and differentiation. In particular, implants treated under the 5 Torr condition showed significantly higher carbon-based impurity reduction and osteoblast differentiation performance compared to those treated under the 16 Torr condition. These findings suggest that optimizing gas pressure in plasma devices is critical for effectively controlling excited nitrogen radicals, which improves plasma surface modification and enhances the biocompatibility of implant surfaces. [ABSTRACT FROM AUTHOR]

The article studies microstreams, increases in solar wind (SW) currents up to several tens of km/s, with a time scale of the order of a day. A comparative analysis of microstreams present in the polar and low-latitude SW at different heliocentric distances has been carried out. The comparison showed that the properties of microstreams in the near-Earth fast SW are qualitatively similar to the properties of microstreams present in the polar SW during periods close to solar activity minima, at heliocentric distances from 2 to 4.5 AU. At the same time, the quantitative parameters of microstreams (amplitudes of variations in radial and tangential velocity, as well as relative variations in temperature, density, and plasma pressure) show a monotonic decrease with increasing heliocentric distance, which can be interpreted as a consequence of the gradual evolution of microstreams with distance from the Sun. However, comparison with SW measurements in the low-latitude region of the heliosphere at distances of about 5 AU shows some significant differences, which indicate a more rapid evolution of microstreams in the inhomogeneous low-latitude SW. [ABSTRACT FROM AUTHOR]

The calculations by mathematical model of the RF plasma flow at a pressure of 13.3–133 Pa at Knudsen is performed. The model is based on Navier–Stokes equations together with the continuum model for electron and metastable components of the RF plasma taking into account non-maxwellian EEDF. Results of plasma flow calculations for electrons density, distributions of electron temperature and calculations of parameters of electromagnetic field are presented. [ABSTRACT FROM AUTHOR]

Predicting the gas-surface interactions of solid carbon is necessary for the design of many engineering systems that employ graphite. Experimental determination of the reaction rates improves the fidelity of those predictions. Here, we studied oxidation and nitridation of graphite by thermal and nonthermal plasma assisted processes. Experiments were conducted at a pressure of 2 kPa, higher than previous flow reactor experiments of this kind and closer to the conditions experienced in engineering applications. At these higher pressures, the limitations of mass transport and the interference between oxygen and nitrogen species become important. Reaction rates were determined from mass loss, reaction products were identified with mass spectrometry, and surface roughening was characterized by electron microscopy. [ABSTRACT FROM AUTHOR]

Measurements of heavy (M/q > 3) ions on the Phobos-2 satellite revealed that the density of these ions in the central plasma sheet of the areomagnetic tail is proportional to the proton density of the solar wind flowing around the planet. ISEE-2 ion measurements in the near-Earth plasma sheet close to the neutral line were also compared to solar wind data obtained on the ISEE-3 satellite. It was found that the density of protons in the near-Earth plasma sheet is proportional to the density of solar wind protons as well. Analysis of the magnetic and plasma pressure balance in the solar wind and inside the magnetotails of the Earth and Mars showed that the previously found correlations are the result of the necessary equality of pressures at the magnetosphere boundary and inside the magnetic tails of the planets. [ABSTRACT FROM AUTHOR]

The May 2024 super storm is one of the strongest geomagnetic storms during the past 20 years. One of the most remarkable ionospheric responses to this event over East and Southeast Asia is the complex ionospheric fluctuations following the storm commencement. The fluctuations created multiple oscillations of total electron content (TEC) embedded in the diurnal variation, with amplitudes up to 10 TECu. Along the same latitude, the fluctuations were nearly synchronized over a wide longitude span up to 35°. In the meridional direction, the fluctuations over low latitudes were the most significant and complex, which contained two main components, the poleward extending oscillations originated from the magnetic equator, and the equatorward propagating traveling ionospheric disturbances (TIDs) from high latitudes. The TIDs likely occurred around the globe. The storm‐time interplanetary electric fields penetrating into equatorial latitudes of the ionosphere and the auroral energy input were suggested to drive the poleward extending oscillations and the equatorward TIDs, respectively. Plain Language Summary: The ionospheric responses to strong geomagnetic storms are mainly in the form of global or hemispheric scale plasma density enhancement or suppression, termed as positive or negative ionospheric storms, respectively. Previous studies have also reported fine‐scale ionospheric structures during geomagnetic storms, which were manifested as wavelike fluctuations in TEC. Multiple mechanisms were proposed to be responsible for the TEC fluctuations, including the magnetospheric compression effect, storm‐time penetration electric field, refilling process linked with plasma pressure, and traveling ionospheric disturbances triggered from high latitude and polar regions. During the May 2024 super storm, complex ionospheric fluctuations consisting of two major components, that is, poleward extending fluctuations originated from the magnetic equator and equatorward traveling oscillations from high latitude and polar regions were observed over East and Southeast Asia. It is important to figure out what mechanisms could dominate the generation and evolution of complex fluctuations over specific regions. Based on the TEC continuously measured along dense observational chains, in combination with multiple other types of observations, the characteristics and possible mechanisms of the complex ionospheric fluctuations are investigated. Key Points: Complex ionospheric fluctuations consisting of poleward extending and equatorward traveling disturbances were identified during super geomagnetic stormThe poleward oscillations were synchronized over a wide longitude and driven by multiple penetrations of electric fieldsThe equatorward traveling disturbances likely occurred around the globe that could be due to auroral energy input [ABSTRACT FROM AUTHOR]

ABSTRACT We consider a two‐component asymmetric complex plasma of finite‐size macroions with charges Z$$ Z $$ (Z≫1$$ Z\gg 1 $$) and point oppositely charged microions with unit charges. System pressure is calculated within the framework of the Poisson–Boltzmann plus hole approximation by obtaining the Coulomb nonideal parts of interaction energy and Helmholtz free energy. It is shown that both the pressure and plasma isothermal compressibility are positive over the entire range of macroion concentrations. We compared pressure and isothermal compressibility in linearized approximations and in the Poisson–Boltzmann plus hole approximation where the nonlinear screening effect is taken into account and showed a significant difference for some macroions concentrations. [ABSTRACT FROM AUTHOR]

A general approach of how to construct plasma equilibrium in a tokamak with n = 1 violation of toroidal symmetry is proposed. For an arbitrary axisymmetric tokamak plasma equilibrium, there exists the small n = 1 deformation of the initial magnetic configuration that keeps the nesting of the magnetic surfaces (as in the initial configuration) and provides plasma equilibrium; such deformation and final equilibrium configuration are calculated analytically. The asymmetric analogue of the Solov'ev's equilibrium with non-degenerated plasma pressure and current density profiles is presented as an example of the application of the developed algorithm. [ABSTRACT FROM AUTHOR]

This contribution focuses on the spatial‐temporal behavior and reactive pathways of O3 produced by a surface air microdischarge in the gas and liquid phase using ultraviolet absorption spectroscopy. The findings demonstrate that mode transition from ozone to nitrogen oxide over time is observed at a constant input power higher than ~0.60 W/cm2. Due to the long‐lived characteristic and ionic wind, the perpendicular distribution of O3 is almost uniform. The maximum penetration depth is around 5 mm, and the gas–liquid mass transfer efficiency is approximately 0.4‱ at a depth of 1 mm, when the treatment time is 10 min. The mass transfer of O3 between gas and liquid phases is dominated by the liquid convention induced by ionic wind. [ABSTRACT FROM AUTHOR]

Although metallic materials have been used as load-bearing materials in dental and biomedical fields since they have good mechanical properties such as good ductility and strength, their aesthetic properties are inferior to those of ceramic or resin. To obtain aesthetically improved Ti dental devices, the formation of white titanium oxide on pure Ti dental devices was studied. Direct atmospheric pressure plasma (APP) treatment using alternating current was carried out on pure a Ti plate and wire. It was found that a titanium oxide layer with enough whiteness can be obtained on pure Ti wire using direct APP treatment. Although delamination of the titanium oxide layer was found after a bending test, the concept of functionally graded materials (FGMs) can overcome the shortcoming. [ABSTRACT FROM AUTHOR]

Atmospheric pressure plasmas generated from a helium gas with admixtures of water vapor have numerous applications in biomedicine. It is important that the chemistry of such plasmas can be tightly controlled so that they may be tailored for their intended use. In this study, computational modeling is used to vary the pulse repetition frequency of a nanosecond-pulsed, pin-to-pin He + 0.25% H 2 O discharge in the range of 1–100 kHz to determine the influence of the pulse repetition frequency on the resulting densities of reactive oxygen species and the rates of dominant reaction pathways involving them. The plasma is simulated using the 0D plasma-chemical kinetics model GlobalKin. The pulse shape is kept constant. The afterglow duration is, therefore, dependent on the repetition frequency. Analysis of the bulk plasma chemistry after the plasma has reached equilibrium shows that the peak electron density is only weakly dependent on the pulse repetition frequency. Increasing the pulse repetition frequency is shown to increase the density of H, O, and OH radicals, while the relationship between the repetition frequency and the densities of species with longer lifetimes, namely, H 2 O 2 and O 3 , is found to be more complex. These are formed throughout the afterglow, and their density depends on the availability of reactant species, the afterglow duration, and the background gas temperature. This work concludes that the pulse repetition frequency is not a simple control parameter, especially for species that are predominantly produced in the afterglow. Detailed modeling is required for accurate control of species densities using the pulse repetition frequency. [ABSTRACT FROM AUTHOR]

The social market economies of the Western world considered the provision of plasma derivatives produced from publicly owned blood services as a legitimate state commitment and, until the last decades of the 20th century, many of the relevant jurisdictions maintained state‐supported fractionation plants to convert publicly collected plasma into products for the public health system. This situation started to change in the 1990s, because of several converging factors, and currently, publicly owned/subsidized, not‐for‐profit fractionation activity has shrunk to a handful of players. However, the collection of plasma from publicly owned blood services has continued and recent developments have increased the interest of state authorities globally to increase the volume of plasma collected to increase the level of strategic independence in the supply of crucial plasma‐derived medicines from commercial market pressures, particularly the global for‐profit fractionation sector with its dominance of source plasma from paid donors in the United States. This paper reviews the development of the plasma industry and the evolution of the pressures on the supply of plasma, which has led to a situation of scarcity of key plasma‐derived medicinal products (PDMPs). [ABSTRACT FROM AUTHOR]

The programme to design plasma scenarios for the Spherical Tokamak for Energy Production (STEP), a reactor concept aiming at net electricity production, seeks to exploit the inherent advantages of the spherical tokamak (ST) while making conservative assumptions about plasma performance. This approach is motivated by the large gap between present-day STs and future burning plasmas based on this concept. It is concluded that plasma exhaust in such a device is most likely to be manageable in a double null (DN) configuration, and that high core performance is favoured by positive triangularity (PT) plasmas with an elevated central safety factor. Based on a full technical and physics assessment of external heating and current drive (CD) systems, it was decided that the external CD is provided most effectively by microwaves. Operation with active resistive wall mode (RWM) stabilization as well as high elongation is needed for the most compact solution. The gap between existing devices and STEP is most pronounced in the area of core transport, owing to high normalized plasma pressure in the latter which changes qualitatively the nature of the turbulence controlling transport. Plugging this gap will require dedicated experiments, particularly on high-performance STs, and the development of reduced models that faithfully represent turbulent transport at high normalized pressure. Plasma scenarios in STEP will also need to be such that edge localized modes (ELMs) either do not occur or are small enough to be compatible with material lifetime limits. The high current needed for a power plant-relevant plasma leads to the unavoidable generation of high runaway electron beam current during a disruption, where novel mitigation techniques may be needed. This article is part of the theme issue 'Delivering Fusion Energy – The Spherical Tokamak for Energy Production (STEP)'. [ABSTRACT FROM AUTHOR]

The formation and evolution of unconfined counter-helicity spheromaks merging have been experimentally investigated by using a magnetized coaxial plasma gun. By comparing the time-dependent photodiode signals and plasma radiation images of counter-helicity spheromaks merging and plasma jets merging, it is found that the field-reversed configuration (FRC) plasma formed by counter-helicity spheromaks merging has a distinct contour and a long maintenance time. For plasma jets merging, the resulting plasma has no discernible contours and a shorter lifetime. In addition, it is inferred from these data that stagnation heating and magnetic reconnection events occur during the counter-helicity spheromaks merging, causing a rapid rise in plasma pressure at the merging midplane and sharp kinks in the field lines near the merger region. By changing different operating parameters and observing the impact on the merger characteristics, it is suggested that the qualitative dynamics of the FRC plasma depends on the balance between the plasma pressure and the magnetic pressure. The high discharge voltage breaks the equilibrium in the merged body, while the large gas-puffed mass just weakens the compression effect of the merged body. These results give us an intuitive understanding of the counter-helicity spheromak merger process and its dependence on discharge parameters, and also provide a distinct perspective for the optimal design of FRC. [ABSTRACT FROM AUTHOR]

This paper discusses the newly discovered acoustic waves that arise from the equilibrium between the inertia of dust particles and plasma pressure. The propagation of these waves is demonstrated to be non-linear, with supersonic solitons exhibiting either a positive or negative electrostatic potential, and linear, with normal modes in a dusty plasma. Implementing the unified method and the generalized projective Ricatti equation technique, we generate a variety of optical wave structures for the governing framework. Using 3 D and 2 D dimensional illustrations, the fundamental behavior of the derived solutions is visually analyzed by choosing appropriate values for arbitrary parameters that satisfy the specified constraints. The employed methodologies are acknowledged to be a powerful and effective mechanism for creating solitary wave solutions for non-linear evolution models. [ABSTRACT FROM AUTHOR]

With the increase in technical capabilities of computer simulation in recent years, it has become feasible to quantify the degradation of fluid scale plasma and electromagnetic energies in favor of increases of internal energies. While it is understood that electromagnetic energy can be exchanged with fluid scale velocities, it is the pressure strain interaction that exchanges energy between fluid motions and internal energy. Here using simulations of both turbulence and reconnection we show that for electrons, the pressure strain and electromagnetic work are closely related and are frequently comparable when appropriate time and spatial averaging is applied. Otherwise, the instantaneous spatial averaged pressure strain and electromagnetic work are nearly equal for slowly evolving systems, like the reconnection case, while they differ significantly in rapidly evolving systems, like the turbulence case. This clarifies the relationship between these two quantities, which are each frequently used as measures of dissipation. Plain Language Summary: The electromagnetic field changes the fluid velocity of each type of plasma particle. Meanwhile, the pressure of each plasma species, interacts with nonuniform fluid velocities to produce heat. The intermediate steps are in general, complicated, but because electrons are so light, a special simplifying approximation holds, equating properly averaged electromagnetic work on electrons to the rate of increase of electron internal energy. This result may help clarify differences in how the reconnection and turbulence communities quantify "dissipation". Key Points: Time integrated volume averaged electromagnetic work does not formally or generally correspond to dissipationDue to small electron mass, time integrated volume averaged pressure strain and electromagnetic work are nearly equal for electronsDifferences between instantaneous electromagnetic work and pressure strain can be considerable, but for electrons, these average to zero [ABSTRACT FROM AUTHOR]

We present a nonlocal gyrokinetic theory for the drift‐mirror mode in high‐β $\beta $ anisotropic plasmas. Here, β $\beta $ represents the ratio of plasma pressure to magnetic pressure. The equilibrium distribution is established self‐consistently via guiding‐center Hamiltonian theory. To keep the nonuniformity and finite Larmor radius (FLR) effects on an equal footing, we derive the three‐field nonlocal eigenmode equations in Fourier space under the assumption of weak nonuniformity. It is found that the drift‐mirror mode is essentially a dissipative instability confined within the potential well due to the FLR effect. Numerical analyses demonstrate that the drift‐mirror mode originates from the coupling between shear Alfvén and mirror branch, where the ion‐sound wave component is negligible. Furthermore, the β $\beta $ threshold of this nonlocal drift‐mirror mode is significantly lower than that of the conventional drift‐mirror mode. Plain Language Summary: The drift‐mirror instability has been intensively investigated in space physics. It can be destabilized by pressure anisotropy in magnetized plasmas and result in the formation of the cavity across the field lines where the mode is confined. In this study, we investigate the linear properties of the nonlocal drift‐mirror mode by employing the electromagnetic gyrokinetic theory. The nonuniform equilibrium is self‐consistently established, with both magnetic and plasma inhomogeneities taken into account on the equal footing. An eigenmode system describing the nonlocal drift‐mirror mode is then derived in Fourier space. It is found that the drift‐mirror mode arises from the coupling between the shear Alfvén branch and the mirror branch. The ion‐sound wave branch, however, is negligible. Additionally, further numerical analyses demonstrate that the kinetic drift‐mirror mode is more easily excited than the mirror mode in uniform and fluid limits. These results provide a deeper understanding of the drift‐mirror mode. Key Points: By employing the nonlocal electromagnetic gyrokinetic theory, we present a self‐consistent description of the drift‐mirror modeIt is showed that the drift‐mirror mode is a dissipative instability confined within the potential well arising from the FLR effectThe drift‐mirror mode originates from the coupling between shear Alfvén and mirror branch, where the ion‐sound wave component is subdominant [ABSTRACT FROM AUTHOR]

A new sintering technique as a combination of ultra-fast spark plasma sintering and high-pressure sintering was employed to densify UO 2 fuel pellets. UO 2 pellets with a relative density of 97.5 % and inhibited grain growth were fabricated at 1000 °C under 150 MPa within only 4.5 min. Both short sintering time and high pressure might explain the inhibited grain growth and hence finer microstructures. UO 2 fuel pellets prepared in this work exhibit excellent mechanical properties. [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]

Plasma treatment is necessary to optimize the performance of biomaterial surfaces. It enhances and regulates the performance of biomaterial surfaces, creating an effective interface with the human body. Plasma treatments have the ability to modify the chemical composition and physical structure of a surface while leaving its properties unaffected. They possess the ability to modify material surfaces, eliminate contaminants, conduct investigations on cancer therapy, and facilitate wound healing. The subject of study in question involves the integration of plasma science and technology with biology and medicine. Using a helium plasma jet source, applying up to 18 kV, with an average power of 10 W, polymer foils were treated for 60 s. Plasma treatment has the ability to alter the chemical composition and physical structure of a surface while maintaining its quality. This investigation involved the application of helium plasma at atmospheric pressure to polyamide 6 and polyethylene terephthalate sheets. The inquiry involves monitoring and assessing the plasma source and polymer materials, as well as analyzing the impacts of plasma therapy. Calculating the mean power of the discharge aids in assessing the economic efficacy of the plasma source. Electric discharge in helium at atmospheric pressure has beneficial effects in technology, where it increases the surface free energy of polymer materials. In biomedicine, it is used to investigate cytotoxicity and cell survival, particularly in direct blood exposure situations that can expedite coagulation. Comprehending the specific parameters that influence the plasma source in the desired manner for the intended application is of utmost importance. [ABSTRACT FROM AUTHOR]

High-beta plasma equilibria are realized in a number of physical systems, from planetary magnetospheres, sunspots, and magnetic holes to fusion laboratory experiments. When plasma pressure becomes large enough to completely expel the magnetic field from its volume, the particle trajectories cannot be considered any more as circular gyro-orbits, and plasma pressure ceases to be gyrotropic. These non-gyrotropic effects require kinetic description and are actively studied for a long time in the magnetic reconnection problem. In this paper, we will show that non-gyrotropy of plasma pressure makes it possible to markedly exceed the limit β = 1 dictated by the magnetohydrodynamics for finite-size plasmas, which may be attractive for some fusion schemes such as mirror and cusp configurations. As a first step, we study how these effects manifest themselves in a simple classical problem of confining a cylindrical plasma column by a uniform vacuum magnetic field. Using particle-in-cell simulations, we show that the equilibrium of the diamagnetic bubble type with zero internal magnetic field is formed with an electron-produced current layer of sub-ion scale and found that the gas-kinetic pressure of the central plasma exceeds the pressure of the vacuum magnetic field by 15%. [ABSTRACT FROM AUTHOR]

A set of experiments using controlled, skin depth-sized plasma pressure filaments in close proximity have been carried out in a large linear magnetized plasma device. Two- and three-filament configurations have been used to determine the scale of cross field nonlinear interaction. When the filaments are separated by a distance of approximately five times the size of a single filament or less, a significant transfer of charge and energy occurs, leading to the generation of inter-filament electric fields. This has the effect of rotating the filaments and influencing the merging dynamics. Nonlinear gyrokinetic simulations using seeded filaments confirm the presence of unstable drift-Alfvén modes driven by the steep electron temperature gradient. When the filaments are within a few collisionless electron skin depths (separations twice the size of a single filament), the unstable perturbations drive the convective mixing of the density and temperature and rearrange the gradients such that they maximize in the region surrounding the filament bundle. [ABSTRACT FROM AUTHOR]

Following Greene et al. [Phys. Fluids 14, 671 (1971)] and Connor et al. [Phys. Plasmas 31, 577 (1988); Plasma Phys. Control. Fusion 34, 161 (1992); and Nucl. Fusion 33, 1533 (1993)], the Grad-Shafranov equation for an axisymmetric tokamak plasma equilibrium is solved via an expansion in the, supposedly small, inverse aspect-ratio of the plasma, ϵ. The displacements of equilibrium magnetic flux-surfaces due to plasma shaping are assumed to be O (ϵ) smaller than the minor radii of the surfaces, but no other restriction is placed on the nature of the shaping. The solution of the Grad-Shafranov equation is matched to a vacuum solution that extends to infinity, and consists of an expansion in toroidal functions. The external poloidal magnetic field generated by a finite set of discrete external poloidal magnetic field-coils is calculated, and incorporated into the toroidal function expansion. In this manner, the shape of a large aspect-ratio tokamak plasma is directly related to the currents flowing in the external poloidal field-coils. Finally, a pedestal in the plasma pressure, and the associated spike in the bootstrap current, are incorporated into the model. [ABSTRACT FROM AUTHOR]

The problems of laser-induced fluorescence (LIF) measurements in a partially saturated regime with spatially dependent laser intensity in the sample (caused by absorption) are analyzed. The obtained equations are tested by means of LIF of free tellurium atoms in a plasma of an atmospheric pressure dielectric barrier discharge (DBD) by comparing fluorescence and absorption measurements. The results show a high reliability of LIF measurements. [ABSTRACT FROM AUTHOR]

The plasma-material interaction and evolution mechanism of a solitary crater governs the nature of the surface, either plain or textured, created through the electrical discharge micromachining (EDMM) process. Therefore, it is indispensable to understand the fundamentals of a single crater evolution, which involves melt pool hydrodynamics and material vaporization under intense plasma pressure. The plasma pressure during the workpiece heating phase alters the vaporization phenomenon and melt ejection, warranting an in-depth understanding. In light of this, the current work proposes a two-dimensional (2-D) multiphysics numerical model of the melt pool hydrodynamics during EDMM. The model incorporates thermal evolution along with the effects of active plasma pressure during the heating phase of the substrate with the help of a coupled thermo-fluidic model. The simulation results reveal the predominant role of plasma pressure on the crater morphology evolution, plasma flushing efficiency (PFE) and recast layer thickness (RLT). The predicted single crater profile is validated using single-spark experiments with reasonable agreement. Thereafter, the formation mechanism of a single crater has been extended to multi-crater creation for textured surface generation. [Display omitted] • A multiphysics model of the EDMM implementing plasma pressure is developed. • Maximum liquid-vapour interface temperature increases with active plasma pressure. • Plasma pressure plays a major role in determining crater morphology, PFE and RLT. • The predicted crater dimensions match the single-machined crater on Ti-6Al-4 V. • Single crater model is extended to multi-crater formation for surface texturing. [ABSTRACT FROM AUTHOR]

Modeling and forecasting the dynamics of complex systems, such as moderate pressure capacitively coupled plasma (CCP) systems, remains a challenge due to the interactions of physical and chemical processes across multiple scales. Historically, optimization for a given application would be accomplished via a design of experiment (DOE) study across the various external control parameters. Machine learning (ML) techniques show the potential to "forecast" process conditions not tested in a traditional DOE study and thereby allow better optimization and control of a plasma tool. In this article, we have used standard DOE as well as ML predictions to analyze I-V data in a moderate-pressure CCP system. We have demonstrated that supervised regression ML techniques can be a useful tool for extrapolating data even when a plasma system is undergoing a transition in the heating mode, in this case from the alpha to gamma mode. Classification analysis of control parameters is another possible application of ML techniques that can be deployed for system control. Here, we show that given a large set of measured data, the models can identify the gas ratio in the feed gas as well as correctly identify the operating pressure and electrode gap in almost all the cases. [ABSTRACT FROM AUTHOR]

In the present study, the influence of the solar wind dynamic pressure on the plasma and magnetic pressures of the magnetosphere is studied. We use 11‐year Time History of Events and Macroscale Interactions during Substorms (THEMIS) instruments for plasma and magnetic field measurements in the magnetosphere and the OMNI database for solar wind dynamic pressure and IMF data. We focus on the effects of the solar wind dynamic pressure (PSW) and consider only times in which the interplanetary magnetic field (IMF) components are within ±5 nT. We find that the plasma pressure inside the magnetosphere follows the solar wind dynamic pressure and that an increase in PSW also influence the day‐night pressure asymmetry. Our analysis also reveals the existence of ion and electron drifts from midnight toward the dusk and dawn sectors, respectively. We observe a local magnetic pressure minimum located near a plasma pressure maximum at around 11 RE on the nightside. Comparing the effect of PSW on both plasma and magnetic pressures, we observe trends which are consistent with the diamagnetic properties of plasmas. In general, the distribution of plasma pressure within the Earth's magnetosphere is an important criterion for evaluating the magnetostatic equilibrium and electric current system. The outcome of this study should provide additional methodologies for the characterization of key plasma characteristics within the magnetosphere. Plain Language Summary: Magnetospheric activity and space weather are driven by the interaction of the solar wind and the Earth's magnetic field. The solar wind dynamic pressure and interplanetary magnetic field (IMF) are two important factors that affect the behavior of the Earth's magnetosphere. The interaction between these two factors are complex and can have significant effects on our planet. Based on 11‐year plasma and magnetic field measurements, obtained from THEMIS satellites, we investigated the effect of solar wind dynamic pressure on the plasma and magnetic pressures within the Earth magnetosphere. In this study, we show that changes in the plasma pressure within the magnetosphere are linked to variations in the solar wind dynamic pressure. Our findings confirm that the plasma pressure inside the magnetosphere is mainly controlled by the solar wind dynamic pressure, which can be attributed to pressure balance. Overall, the distribution of plasma pressure within the Earth's magnetosphere is a key parameter for evaluating the magnetostatic equilibrium and electric current system. Our results are expected to offer scientists additional methodologies for characterizing main plasma parameters in the magnetosphere. Key Points: Increase in solar wind dynamic pressure leads to increase in plasma and magnetic pressures in the magnetosphereLarger solar wind dynamic pressure make the plasma pressure more symmetric around the EarthObservations reveal a local magnetic pressure minimum located near a plasma pressure maximum around 11RE on the nightside [ABSTRACT FROM AUTHOR]

Higher blood pressure variability (BPV) predisposes to cognitive decline. To investigate underlying mechanisms, we measured 24-h ambulatory BPV, nocturnal dipping and orthostatic hypotension in 518 participants with vascular cognitive impairment, carotid occlusive disease, heart failure, or reference participants. We determined cross-sectional associations between BPV indices and plasma biomarkers of neuronal injury (neurofilament light chain) and Alzheimer's disease (phosphorylated-tau-181 and Aβ42/Aβ40). None of the BPV indices were significantly associated with any of the biomarkers. Hence, in patients with diseases along the heart-brain axis, we found no evidence for an association between BPV and selected markers of neuronal injury or Alzheimer's disease. [ABSTRACT FROM AUTHOR]

Summary: Plasma‐induced finishing of coatings – Modification and removal of baked‐on siliconized coatings on glass substrates Baked‐on siliconized (BOS) coatings represent outstanding media for the generation of chemically largely inert and biologically harmless surfaces with low friction. However, for eventual subsequent stable and long‐term joining or gluing, a locally selective removal or modification and adaption of such coatings may become necessary in several cases. In the present study it is shown that BOS coatings can be converted into glass‐like and almost carbon‐free layers by using a low‐temperature plasma at atmospheric pressure. This conversion is accompanied by a reduction in layer thickness of approximately 50 %. As a result, the adhesion of glues on the plasma treated BOS coating is notably increased. [ABSTRACT FROM AUTHOR]

The hour-long, gradual phase of solar flares is well observed across the electromagnetic spectrum, demonstrating many multiphase aspects, where cold condensations form within the heated post-flare system, but a complete 3D model is lacking. Using a state-of-the-art 3D magnetohydrodynamic simulation, we identify the key role played by the Lorentz force through the entire flare lifespan, and show that slow variations in the post-flare magnetic field achieve the bulk of the energy release. Synthetic images in multiple passbands closely match flare observations, and we quantify the role of conductive, radiative, and Lorentz force work contributions from flare onset to decay. This highlights how the non-force-free nature of the magnetic topology is crucial to trigger Rayleigh–Taylor dynamics, observed as waving coronal rays in extreme ultraviolet observations. Our C-class solar flare reproduces multiphase aspects such as post-flare coronal rain. In agreement with observations, we find strands of cooler plasma forming spontaneously by catastrophic cooling, leading to cool plasma draining down the post-flare loops. As there is force balance between magnetic pressure and tension and the plasma pressure in gradual-phase flare loops, this has potential for coronal seismology to decipher the magnetic field strength variation from observations. [ABSTRACT FROM AUTHOR]

The possibility of production of metal powder of grade "EOS Stainless Steel PH 1" by electrolyte-plasma spraying of finished products manufactured by selective laser melting is considered. The sample is sprayed by gas-discharge plasma at atmospheric pressure in an electrode configuration, where the metal cathode is the sprayed product and the electrolytic anode is a 3% NaCl solution in purified tap water. The current-voltage characteristics of the discharge, the surface temperature of the electrodes, the topography and the elemental composition of the powder are determined. [ABSTRACT FROM AUTHOR]

The discharge properties of post‐cathode plasma generated by grid electrode discharge were investigated. Post‐cathode plasma is the plasma, generated in an open discharge, at the other side of the cathode that is different from the electrode gap. Based on the unique electron transport, discharge chamber parameters were adjusted to compare their impact on the electron density of the post‐cathode plasma. The peak of the electron flow in the grid cathode hole and the peak of the post‐cathode plasma thickness appear in the same diameter of the grid electrode holes, which shows the crucial influence of the electron transport within the grid cathode on the post‐cathode plasma. The study also investigated the combined effects of cathode thickness and gas pressure on post‐cathode plasma thickness. The findings suggest that the primary factor influencing post‐cathode plasma thickness is the electron transport within the grid cathode. [ABSTRACT FROM AUTHOR]

Plasma technology is increasing its applications in the textile industry for conferring surface functionalities through greener processes. In this study, plasma treatments are studied to improve the wettability of mycelium-based material, an emerging material with a lot of potential in the near future. The plasma effect was characterized by assessing the added functionality (wettability) and inspecting surface modifications with different techniques, such as scanning electron microscopy (SEM) and X-Ray photoelectron spectroscopy (XPS). Low pressure plasma (LPP) treatments were successfully applied into the mycelium-based material and optimal power of discharge and treatment time were set for this material (750 W, 17.5 min). With the optimized LPP treatments, the water absorption capacity of mycelium-based material was improved by 2000% and some surface morphological modifications were observed by SEM analysis. On the other hand, XPS analysis demonstrated how the plasma treatment changes the surface composition. [ABSTRACT FROM AUTHOR]

Interactions at the interface between atmospheric pressure plasmas and liquids are being investigated to address applications ranging from nanoparticle synthesis to decontamination and fertilizer production. Many of these applications involve activation of droplets wherein the droplet is fully immersed in the plasma and synergistically interacts with the plasma. To better understand these interactions, two-dimensional modeling of radio frequency (RF) glow discharges at atmospheric pressure operated in He with an embedded lossy dielectric droplet (tens of microns in size) was performed. The properties of the sheath that forms around the droplet were investigated over the RF cycle. The electric field in the bulk plasma polarizes the dielectric droplet while the electron drift in the external electric field is shadowed by the droplet. The interaction between the bulk and sheath electric fields produces a maximum in E/N (electric field/gas number density) at the equator on one side of the droplet where the bulk and sheath fields are aligned in the same direction and a minimum along the opposite equator. Due to resistive heating, the electron temperature Te is maximum 45° above and below the equator of the droplet where power deposition per electron is the highest. Although the droplet is, on the average, negatively charged, the charge density on the droplet is positive on the poles and negative on the equator, as the electron motion is primarily due to diffusion at the poles but due to drift at the equator. [ABSTRACT FROM AUTHOR]

The paper is dedicated to the numerical study of the dependence of plasma antenna resonance wavelengths on pressure. The study was carried out by simulating a RF capacitively coupled plasma with the Comsol Multiphysics software in one- dimensional formulation. Based on the calculated electric current in the plasma, the directional pattern and axial distribution of the electromagnetic field were found by solving Maxwell's equations in a 2D formulation. The results showed that one of the advantages of plasma antennas is the transmission of waves at significantly longer wavelengths compared to metal antennas of similar geometry. [ABSTRACT FROM AUTHOR]

A theory of the three-wave coupling of triplets of tearing modes in toroidal pinches [i.e., either reversed field pinches (RFPs) or tokamaks] was proposed by R. Fitzpatrick [Phys. Plasmas 6, 1168 (1999)]. However, this theory only applies to toroidal pinches with negligible equilibrium plasma pressure gradients. Such a limitation is particularly inappropriate to RFPs. This paper generalizes the analysis of R. Fitzpatrick [Phys. Plasmas 6, 1168 (1999)] in order to take the equilibrium pressure gradient into account. However, for the sake of simplicity, a stepped pressure profile, rather than a continuous profile, is employed. In the limit in which the number of steps becomes very large, the results obtained from the generalized theory are presumably equivalent to those that would have been achieved using a continuous pressure profile. The generalized theory is used to investigate the formation of the characteristic toroidally localized pattern of phase-locked m = 1 and m = 0 tearing modes in RFP plasmas that is known as the "slinky" pattern. The incorporation of the equilibrium plasma pressure into the analysis is found to be of crucial importance when determining the properties of the pattern. This is the case because the plasma pressure controls the number of unstable m = 1 and m = 0 tearing modes, and also significantly affects the strength of three-wave coupling, as well as the phase relation between the phase-locked m = 1 and m = 0 modes. [ABSTRACT FROM AUTHOR]

Some stellarators tend to benefit from favourable average magnetic curvature for trapped particles when the plasma pressure is sufficiently high. This so-called maximum- $J$ property has several positive implications, such as good fast-particle confinement, magnetohydrodynamic stability and suppression of certain trapped-particle instabilities. This property cannot be attained in quasisymmetric stellarators, in which deeply trapped particles experience average bad curvature and therefore precess in the diamagnetic direction close to the magnetic axis. However, quasi-isodynamic stellarators offer greater flexibility and allow the average curvature to be favourable and the precession to be reversed. We find that it is possible to design such stellarators so that the maximum- $J$ condition is satisfied for the great majority of all particles, even when the plasma pressure vanishes. The qualitative properties of such a stellarator field can be derived analytically by examining the most deeply and the most shallowly trapped particles, although some small fraction of the latter will inevitably not behave as desired. However, through numerical optimisation, we construct a vacuum field in which 99.6 % of all trapped particles satisfy the maximum- $J$ condition. [ABSTRACT FROM AUTHOR]

Investigation of the processes involved in the synthesis of magnesium oxide and zinc oxide powders using the thermal effects of an atmospheric-pressure glow discharge plasma in an inert gas flow are described. The discharge operates in a repetitively pulsed mode with pulse repetition rate of several tens of kilohertz and pulse duration up to 12 μs, discharge current of 600 mA and voltage up to 300 V. These parameters lead to thermal erosion of magnesium or zinc inserts in a molybdenum crucible. The chemical and phase composition of the erosion products were determined using TEM/EDS and X-ray diffraction analysis, and the composition of the plasma was assessed by optical emission spectrometry. This experimental approach allows fabrication of powders of these metal oxides with characteristic particle size 10–50 nm, and the formation of coatings of these materials in a one-step process. [ABSTRACT FROM AUTHOR]

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In light of the adopted green policies and strategies, thermal plasmas are gaining interest as a potential solution to electrify the industry, particularly for endothermic processes, for their tunable enthalpy and the absence of direct CO2 emissions. However, the majority of industrial applications of thermal plasma technologies are at atmospheric or lower pressure, whether for material processing, waste treatment, gasification, assisted combustion or in electric arc furnaces. Very little information exists on thermal plasmas at pressures above 1 bar, with the majority of academic publications using either analytical or numerical methodologies. The main experimental high-pressure plasma studies conducted date back to the 1960s, the 1970s and 1980s mainly in the US and the EU for aerospace applications, in addition to gas blast circuit breaker and underwater welding applications. However, these systems operate only for a few milliseconds to a few minutes at most. The interest in operating plasma systems at high-pressure is on one hand to reduce the volume of the facilities, and therefore, global costs, and on the other hand, is of practical necessity such as the case of underwater welding and in aerospace application where plasma technology plays a role in duplicating the conditions to which a vehicle is exposed to in atmospheric entry/reentry. This paper reports a thorough literature review on all high-pressure plasma arc studies available to date, including journal articles, books, and declassified reports. The findings of the studies are classified into four categories: DC and AC technologies, electrical characteristics, thermodynamics and heat transfer, and electrode erosion. The gaps and limitations are identified, and the main hypotheses are formulated, (re)opening the way for future high-pressure thermal plasma studies. Operating thermal plasma systems at high pressure could have considerable economic benefits, and thus, leading to competitive pricing for electrified high temperature processes, but faces many challenges. [ABSTRACT FROM AUTHOR]

The use of fused silica material is crucial in various scientific applications; however, its chemical inertness and brittle nature pose challenges to machining and fabrication processes. The present study introduced a dynamic plasma flow system for medium-pressure plasma processing of fused silica substrate to address this issue. The results indicate that the new plasma flow system can significantly enhance the material removal rate compared to existing systems, with a 300% increase in material removal rate. Importantly, this process enables a sustained linear material removal rate, essential for long process durations. Despite the higher material removal rate, there is no deterioration in surface finish observed, and in fact, an improvement in surface integrity is noted after plasma processing. Confocal Raman microscopy characterization further confirms this improvement, revealing reduced stress-induced defect peaks compared to a confined plasma system. [ABSTRACT FROM AUTHOR]

Background: Recent observational studies suggest higher blood pressure (BP) variability (BPV) is associated with Alzheimer's disease (AD) biomarkers amyloid-beta (Aβ) and tau. Less is known about relationships in interventional cohorts with strictly controlled mean BP levels. Objective: Investigate the longitudinal relationship between BPV and change in plasma AD biomarkers under standard versus intensive BP treatment. Methods: In this post hoc analysis of the SPRINT trial, 457 participants (n = 206 in standard group, n = 251 in intensive group) underwent repeated BP measurement between baseline and 12-months follow-up, and venipuncture at baseline and median (IQR) 3.5 (3.0–4.0) years later to determine plasma AD biomarkers total tau and Aβ1–42:Aβ1–40 ratio. BPV was calculated as tertiles of variability independent of mean. Linear mixed models investigated the effect of BPV×time on AD biomarker levels. Results: Higher BPV was associated with increased levels of total tau in the standard group (β [95% CI] 1st versus 3rd tertiles of BPV: 0.21 [0.02, 0.41], p = 0.035), but not in the intensive group (β [95% CI] 1st versus 3rd tertiles of BPV: −0.02 [−0.19, 0.16], p = 0.843). BPV was not associated with Aβ 1–42:Aβ 1–40 ratio in either group. Mean BP was not associated with biomarkers. Conclusions: Higher BPV was associated with increased plasma total tau under standard BP treatment. Findings add new evidence to prior observational work linking BPV to AD pathophysiology and suggest that, despite strict control of mean BP, BPV remains a risk for pathophysiological change underlying risk for AD. [ABSTRACT FROM AUTHOR]

Cold plasma as a new anticancer agent is described by Freund I et al. i [25] The anticancer effect of oxidized saline generated using a spark discharge is investigated using CT26 colorectal cancer cells I in vitro i and I in vivo i and compared against oxidized saline generated by the well-investigated medical plasma jet I kINPen i . In summary, atmospheric plasmas play an important role in many current and emerging fields, including plasma medicine, agriculture, plasma processing, catalysis, and aerospace engineering. Plasma generated in contact with liquid is charactered by Ng I et al i .[35] It is shown that the plasma can be tailored to tune the composition of plasma-functionalized liquids. The significant effect of radiation trapped photon emission on ionization wave dynamics demonstrates the need to consider these effects in plasma reactors where self-absorbed radiation is typically ignored. [Extracted from the article]

Indium nitride nanostructures have been formed by atmospheric and sub-atmospheric pressure plasma nitridation of molten indium. By nitriding the molten indium metal layer with Ar-10%N2 atmospheric pressure plasma at 435 K, micrometer-sized particles (0.7–4 μm) made up by agglomeration of nanoparticles (5–50 nm) and a variety of nanostructures (nanowires, microrods, and hollow microtubes) with various diameters (60–700 nm) have been formed, as observed by scanning electron microscopy. Transmission electron microscope observations show that these structures are composed of wurtzite type indium nitride nanocrystals (5–20 nm). By nitriding the molten indium metal with N2 sub-atmospheric pressure plasma at 673 K, hexagonal crystallites having facets (40–200 nm) have been grown to pile up. It is found that high quality indium nitride crystallites of wurtzite type single crystals can be grown at a relatively low growth temperature of 673 K, as revealed by transmission electron microscopy and Raman spectroscopy. Based on the experimental results, the main active nitrogen species for indium nitride formation are assumed to be nitrogen atoms and formation mechanisms of indium nitride nanoparticles and nanowires have been discussed. [ABSTRACT FROM AUTHOR]

A novel model is developed for atomic oxygen surface kinetics in silica-like walls, introducing a plasma-induced surface modification, which may impact intermediate pressure plasma reactors. The model is the first to reproduce experimental measurements in an oxygen glow discharge operating in the pressure range between 0.27 mbar (0.2 Torr) and 4 mbar (3 Torr), showing a decrease with pressure of the O recombination probability on Pyrex between 0.27 mbar and 1 mbar. The numerical simulations suggest that a modification is induced by the production and destruction of metastable chemisorption sites at the surface. As such, the Langmuir–Hinshelwood (L-H) and Eley-Rideal (E-R) recombination mechanisms take place involving not only physisorption and stable chemisorption sites, but also metastable chemisorption sites, produced by the impact of fast O2 ions and neutrals. The presence of metastable sites can be reversed by increasing the plasma pressure. [ABSTRACT FROM AUTHOR]

In recent years, atmospheric-pressure plasma jets have emerged as valuable tools in many application areas, including material modification, environmental remediation and biomedicine. Understanding the discharge characteristics of these plasma jets under various operating conditions is crucial for optimizing process outcomes. This paper presents a two-dimensional fluid model for numerical simulation to study the variation in electron density within an atmospheric-pressure helium plasma jet under different operating conditions. The investigated parameters include helium gas flow rate, voltage amplitude, needle-to-ring discharge gap, and relative permittivity of the dielectric tube. The results reveal that the peak electric field and electron density initially occur at the wall of the dielectric tube and subsequently shift towards the head of the propagating jet. Gas flow rate has minimal impact on the electron density throughout the plasma jet, whereas increasing the needle-to-ring discharge gap significantly decreases the average electron density within the jet. In addition, an increase in the voltage amplitude and the relative permittivity of the dielectric tube enhances the electric field within the discharge space, thereby increasing the electron density in the plasma jet. These findings underscore the importance of understanding the correlation between electron density and operating conditions to precisely control plasma jets and enhance material treatment effectiveness for specific applications. [ABSTRACT FROM AUTHOR]

The present paper discusses about a new method developed for determining the quality of BWR and PHWR core components with respect to chemistry viz; determination of alloying elements as well as impurities using Radio Frequency Glow Discharge Optical Emission Spectrometer (RF GD-OES). Various experimental parameters of Glow discharge plasma such as forward power, Argon gas pressure inside plasma chamber, pre-integration time and integration time have been optimized using "Single parameter alternative method". The method has been validated using Certified Reference Materials (CRMs) and also by comparing with other techniques such as AAS and ICP-AES using statistical tests like F-test & t-test. [ABSTRACT FROM AUTHOR]

In recent years, cold plasma treatment has emerged as a promising method to positively impact early seed growth. This study aimed to investigate the effects of cold plasma treatment on millet seeds with ambient air plasma discharge at pressures of 100 Pa and power ranging from 40 to 250 W. Results indicated that cold plasma treatment significantly increased radicle length by up to 112.5% (250 W) after 48 h and up to 57% (120 W) after 72 h compared to nontreated plants. The study also found that cold plasma treatment influenced electron transport during the primary phase of photosynthesis, with the effect varying with the power of discharge. However, high levels of discharge resulted in a significantly higher chlorophyll synthesis. These results suggest that cold plasma treatment may be used to reduce plant stress and improve growing properties. [ABSTRACT FROM AUTHOR]

The basic goal of magnetic confinement is to maintain plasma in an equilibrium state for an extended period using a magnetic field configuration. The plasma equilibrium configuration significantly affects the confinement efficiency and stability of the magnetic confinement device, and we anticipate that the equilibrium discharge of the Trimyx Galatea magnetic trap device will operate in an optimal configuration. The Grad–Shafranov equation, a mathematical model of two-dimensional magneto-fluid static equilibrium of the Trimyx Galatea magnetic trap, was established. Numerical calculations were performed under the conditions of a given magnetic field configuration and plasma pressure distribution and the evolution laws of the distinctive parameters of the equilibrium configuration were determined under different plasma confinement settings. The magnetic specific volume coupling model was further developed to demonstrate the mechanism of the influence of the magnetic trap magnetic field on the plasma confinement efficiency and properties. [ABSTRACT FROM AUTHOR]