Pulsed electric fields (PEFs) are widely recognized as a non-thermal, selective physical therapy with wide clinical application in tumor ablation. The pulse width determines how electrical energy is distributed across plasma membrane to intracellular organelles. However, under an engineering-defined equal-dose condition (N·E2·tp), which serves as a practical control parameter rather than a measure of true cellular energy absorption, systematic and comparable experimental characterization of cellular and subcellular responses across pulse widths from the microsecond to nanosecond range remains limited. In this study, PEFs with pulse widths ranging from 100 μs to 50 ns were applied under equal-dose constraints, and cellular responses were evaluated using transmission electron microscopy (TEM), multi-organelle fluorescence imaging, and flow cytometry. The results indicate that pulse-width-dependent effects were observed under a fixed pulse-number, dose-equalized framework in which electric field strength varied across conditions. Structural and functional changes were observed in multiple organelles, including the nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus. Notably, nanosecond pulses were more effective in inducing mitochondrial membrane potential loss and increasing the proportion of apoptotic or non-viable cells. These findings demonstrate that, under equal-dose conditions, pulse width is a key temporal parameter governing PEF-induced biological effects, indicating that identical dose constraints do not necessarily result in equivalent biological responses. This work provides experimental foundation for parameter selection and optimization in PEF-based biomedical applications.
High-temperature superconducting (HTS) spherical tokamaks face stringent space constraints, particularly at the inboard side, where excessive toroidal field (TF) coil inner-leg thickness limits space for other components like the central solenoid (CS) and shielding. To resolve this conflict, this study develops a genetic algorithm (GA) framework to optimize TF coil contours, minimizing their inner-leg thickness. Rigorous enforcement of TF coil safety constraints—electromagnetic, thermal, and mechanical—and plasma performance requirements is maintained throughout. Integrated rapid semi-analytical models evaluate key parameters during optimization: magnetic fields, quench temperature rise, and Tresca stress. Applied to the Compact Tokamak Based Repetitive Fusion Reactor-1 (CTRFR-1) HTS spherical tokamak, the GA optimization reduced TF coil inner-leg thickness by 18 mm. This space reclamation enables a 26% increase in CS flux generation capacity at a engineering current density of 100 A/mm2. Crucially, finite element analysis (FEA) validated that critical thresholds were maintained: toroidal field ripple below 1%, peak loading factor (J/Jc) below 0.6, maximum quench temperature under 150 K, and peak von Mises stress under 600 MPa. This approach successfully resolves the space-performance conflict in spherical tokamaks, achieving significant CS enhancement while fully preserving TF operational safety and plasma performance. The work establishes an efficient multiphysics optimization framework for designing next-generation spherical tokamaks that fully leverage HTS capabilities within their unique geometry.
Abstract – In the study a geomagnetic storm forecasting data mining model is created with the help of key solar wind and interplanetary magnetic field (IMF) parameters that are optimized based on their features. The suggested model makes use of high-resolution solar wind plasma and IMF measurements retrieved in the OMNI database, and the disturbance storm time (Dst) index is used as the main measure of the strength of geomagnetic storms. A strategy of feature optimization is adopted to determine the most geoeffective parameters to predict the computational efficiency and reliability of predictive power, such as solar wind speed, proton density, total vertical magnetic field strength and southward component of IMF (Bz). Weakly correlated and redundant features are automatically removed in order to simplify the model without decreasing forecast accuracy. An optimized feature subset is then applied to the data to form a predictive model based on data mining that has the potential to learn the nonlinear relationships between the upstream solar wind conditions and geomagnetic response. The performance of the models is measured by standard statistical measures and compared to non-optimized baseline models. These findings indicate that the proposed methodology has a better forecasting accuracy at a much lower cost of computation, thus it can be used in near real-time space weather forecasting. The results indicate that feature selection is also vital in space weather prediction and that the majority of the geomagnetic disturbances are due to IMF orientation and solar wind dynamics. The suggested model offers a stable and effective framework of the operational geomagnetic storm forecasting and leads to the creation of well-grounded data-driven space weather forecasting systems. Keywords: Geomagnetic storms, Space weather forecasting, Data mining, Feature optimization, Solar wind, Interplanetary magnetic field, Dst index.
A bubble discharge reactor, termed CHIEF (concentrated high-intensity electric field), was investigated to elucidate how reactor configuration, liquid conductivity, and bubble properties (size, deformation, polarization, and water vapor content) govern electric field distribution, streamer dynamics, and plasma chemistry. Experiments revealed that increasing liquid conductivity enhances conduction current and Joule heating within the orifice, leading to thermal instability at the bubble boundary, a decrease in neutral gas density, and an increase in the reduced electric field. Collectively, these effects lower the applied voltage required for streamer initiation, providing a mechanistic basis for leveraging conduction current to facilitate plasma formation. COMSOL simulations showed that the electric field around and inside a deformed air bubble is highly non-uniform, whereas nanobubbles and microbubbles exhibit minimal electric-field enhancement. Experimental analysis, optical emission spectroscopy (OES), and BOLSIG+ calculations were used to investigate the reaction pathways of nitrogen fixation in air bubble discharges. The highest NOx production rate of 10.09 µmol min−1 was achieved using a 6.0 mm orifice length with a solution conductivity of 140 µS cm−1. The effects of water molecules on streamer initiation, plasma chemistry, and discharge characteristics were analyzed using OES, BOLSIG+ calculations, and simulations. This study provides mechanistic insights into plasma–liquid interactions for atmospheric nitrogen fixation and proposes a sustainable electrosynthesis approach using only air, water, and electricity to produce liquid nitrogen fertilizer.
Cross-field electron transport in partially magnetised plasmas arises from collective, nonlinear instability dynamics that remain only partially understood despite their importance to a wide range of E × B plasma devices. In systems such as Hall thrusters, azimuthal instabilities strongly affect electron confinement and spectral energy distribution, motivating efforts to examine how external modulation may influence these effects. Here, one-and two-dimensional particle-in-cell simulations are employed to investigate how an axially applied oscillatory electric field modifies the instability spectra and the associated cross-field electron transport. The simulations adopt local slab idealisations of an E × B discharge designed to isolate modulation–instability coupling mechanisms and the conclusions should be interpreted within this controlled modelling framework. The simulations show that the plasma response depends sensitively on modulation frequency and amplitude. Notably, modulation near 40 MHz diminishes the amplitude of the electron cyclotron drift instability and reduces axial electron transport by up to 30 %, while modulation near the electron cyclotron frequency leads to spectral broadening and enhanced transport. Bicoherence analysis of the azimuthal electric field fluctuations indicates nonlinear coupling among instability modes, suggesting that modulation reshapes energy pathways, thereby explaining the observed spectral variations. We further show that modulation modifies the phase alignment between azimuthal-electric-field and electron-density fluctuations, in turn directly affecting the observed suppression or amplification of electron transport across modulation regimes. The results provide quantitative evidence of how external modulation can alter instability characteristics in E × B plasmas and point to strategies for controlling electron transport in cross-field plasma technologies, such as Hall thrusters and magnetrons.
In this study, we present a theoretical analysis of the shear viscosity ( η ) in three‐dimensional dusty plasmas (DPs) through molecular dynamics simulations under the influence of an external electric field ( E ). The Green‐Kubo formula is applied to compute η across various values of E , Coulomb coupling, and screening parameters. The simulation results of η at zero E (= 0.0) are compared with existing data and discuss the applicability of the Green‐Kubo formula. It is found that this method provides overestimations but is still applicable to approximation investigations of η in cooled liquid states of DPs. Further, our investigations reveal that η is anisotropic when applied to E . The results of anisotropic η in DP liquids identify three distinct regimes. The first is a slight decrease in η , indicating the presence of repulsive interactions at low E values. The second is a rapid increase, suggesting strong, attractive interactions at intermediate E values. The third shows relatively stable behavior, indicating saturation at high E values. The obtained values of η as a function of normalized temperature follow the temperature scaling law. Furthermore, dust particles align along the z ‐axis and form clusters; the number and size of the clusters depend on the strength of the E . We show that using the Green‐Kubo relation with a wake potential in DPs provides reliable and accurate predictions of E impact on η . These results enhance understanding of the anisotropic η and electrorheological properties of DPs, offering valuable insights into structural transitions influenced by the E .
The EXL‐50U spherical torus has been proposed as a platform for validating the physics and engineering solutions associated with proton‐boron‐11 (p‐ 11 B) fusion. However, B ions, due to their high charge state and substantial mass, can cause significant erosion of divertor targets. In this work, an integrated framework composed of the ITCD and EMC3‐EIRENE codes is employed to conduct a predictive study of target erosion and subsequent impurity transport in the EXL‐50U device. The background plasma and B impurity information, including plasma density, temperature, and particle flux, are simulated with the EMC3‐EIRENE code. It is shown that B impurities have a stronger sputtering capability than hydrogen (H). Though the particle flux of B ions is much lower than that of H, the larger sputtering yield of B ions causes the erosion levels to be even higher than those of H. Based on this, the erosion/deposition dynamics of C impurities and the transport of eroded C particles are studied by the ITCD code. The simulation results indicate that B particles deposited on the C substrate offer only limited protective effects, meaning the C target primarily remains in an erosion‐dominated regime in EXL‐50U.
We present the physics design and engineering architecture for a stochastic adaptive spheromak reactor designed for aneutronic proton–boron (p–11B) fusion. Building upon the unified statistical reconnection model, we utilize a stochastic-adaptive control strategy to force the plasma into a ‘Hard-Lock’ limit cycle. This regime exploits two non-equilibrium effects: (1) by moving beyond passive confinement, we describe a ‘Hard-Lock’ state where magnetic lattice formation suppresses turbulent transport losses according to a τE ∝ B2, and (2) resonant alpha-dynamo recovery, where fusion products directly recharge the magnetic flux. Numerical simulations of the complete reactor cycle—including rigorous accounting for Bremsstrahlung, synchrotron radiation, and auxiliary housekeeping power—demonstrate a stable operating point with an ion temperature Ti ≈600 keV, an electron temperature Te ≈65 keV, and an engineering gain Qeng > 5. Using Langevin dynamics modified for the high inertia of boron ions, we show that a stochastic-adaptive controller, based on Wirtinger calculus, can synchronize these heating pulses to bypass the Bremsstrahlung power limit, providing a pathway to net-energy aneutronic fusion. We describe the required superconducting magnet systems, direct energy converters, and the triple-loop control architecture necessary to realize this regime.
Silicon nanocrystals (Si NCs) have attracted considerable interest over the last 30 years because of their distinctive size-dependent luminescence and their potential for incorporation into established silicon-based technologies. In contrast to bulk silicon, an indirect-bandgap material characterized by suboptimal light emission, Si NCs exhibit effective photoluminescence due to quantum confinement, surface state engineering, and exciton recombination processes. The emission characteristics may be adjusted across the visible and near-infrared spectra by manipulating nanocrystal dimensions, surface passivation, and the surrounding dielectric environment. Recent advancements in synthetic methodologies such as chemical vapor deposition (CVD), plasma-based procedures, and solution-phase-based processes have facilitated precise control of Si NC shape, crystallinity, and surface chemistry, thereby improving luminescence efficiency and stability. Furthermore, advances in theoretical modeling have enhanced our understanding of carrier dynamics, defect-mediated processes, and energy transfer mechanisms in Si NCs. These advancements have broadened the use of Si NCs, including in light-emitting devices, bioimaging, photovoltaics, photonics, and quantum technologies. This review summarizes the core mechanisms regulating luminescence in Si NCs, describes recent developments in Si NC synthesis and surface engineering, examines emerging applications, and identifies challenges and future research trajectories essential for converting laboratory advancements in Si NCs into practical technologies.
Michael Ikechukwu Okeke, Justina Ebele Okeke, Paul Anaeto Oraekie
The Korteweg-de Vries equation is a nonlinear PDE that is used to describe most physical systems involving dispersion, such as wave propagation, fluid dynamics, and plasma physics. In the light of the influence of coriolis effect on waves, the study of the Geophysical Korteweg-de Vries (GKdV) equation is examined. The Lie point symmetries and conservation laws of the equation are constructed and with the Lie point symmetries, a symmetry analysis is performed to reduce the equation to an integrable form. Numerical solutions of the reduced equation were considered for the travelling wave (periodic wave) of the GKdV equation for the parameters (for the coriolis effect) and (for the velocity of the wave). To examine the coriolis effect on free flow in oceans, the dynamical system analysis is applied on the GKdV equation. From the study, it is revealed that travelling wave velocity and coriolis factor have significant effects on the transmission of the periodic wave solution of the GKdV equation. The results obtained stands as a motivation to extend the method to some other nonlinear evolution equations.
This study investigates the enhancement of terahertz radiation from free-flowing water jets subjected to an ion-exchange softening process, in which divalent cations (Ca2+, Mg2+) are replaced by monovalent sodium ions (Na+). Our experiments utilize a femtosecond laser focused on free-flowing jets of both tap water and purified water, before and after the softening treatment. Measured terahertz emission intensities demonstrate notable increases of up to 1.19× for softened tap water and 1.08× for softened purified water. This enhancement is attributed to reduced collision frequencies in the transient plasma formed upon laser irradiation, as monovalent ions exhibit higher mobility and lower ion-ion correlation compared to their divalent counterparts. We validate these observations through conductivity measurements and a Drude-based analysis of laser-driven electron dynamics. These findings underscore that controlling water hardness provides a straightforward approach for optimizing liquid-based terahertz sources through ultrafast plasma engineering, while also highlighting the significant role of ion composition in laser-liquid interactions.
Incomplete spark discharge is known to generate oscillating bubbles and intense shockwaves in saline water, but the electroacoustic process is still not well understood. We develop a phenomenological model and describe the electroacoustic process, with a revised plasma resistance equation and a simple water resistance model. The simulation results agree well with experimental results under different charging voltages and capacitances, including the load electrical waveforms, bubble dynamics, and acoustic waves. Furthermore, the model can successfully calculate the electrical energy consumed in the plasma channel. The simulation results indicate that the energy efficiency decreases with increasing charging voltage, but increases with the increase of the charging capacitance. We also found that the shockwave peak and width increase as power-law functions of the discharge energy. In addition, the shockwave peak is more sensitive to the charging voltage, whereas the shockwave width is influenced by the charging capacitance more obviously. Finally, the proposed model confirms again that hydraulic efficiency and electroacoustic efficiency decrease when the charging voltage increases, but they increase with increasing capacitance. Overall, the phenomenological model is practical and this work helps in developing incomplete-discharge sparker sources applied in oceanic seismic explorations.
Plasma-based CO2 conversion is an emerging power-to-X technology, with the potential to recycle carbon emissions on Earth and produce fuel and life-support consumables in-situ for the human exploration of Mars. In this work, we present a zero-dimensional chemical kinetic modeling framework using ZDPlasKin to simulate nanosecond repetitively pulsed (NRP) discharges in pure CO2, enabling systematic exploration of reactor performance across pressure, temperature, and pulse repetition frequency (PRF) conditions relevant for integrated systems. A reduced chemical mechanism tailored for NRP discharges enabled long-timescale simulations (1–10 s) while still capturing key vibrational energy exchanges. The results of the simulations link the temporal dynamics between pulse and interpulse chemistry to the overall reactor performance. At atmospheric pressure, increasing the PRF reduces CO recombination between pulses and improves conversion without an energy efficiency penalty. Conversion reaches saturation when the overall rate of CO production during the pulse is equal to the rate of CO recombination between pulses. Higher temperatures, which may be required for membrane-based oxygen separation, increase recombination rates and result in lower saturation values of conversion compared to lower temperatures. Additionally, small changes in the maximum reduced electric field strength, influencing total energy coupling, have a strong influence on conversion and efficiency. At low pressures, recombination is negligible, and conversion scales linearly with frequency. These results inform strategies for co-optimizing plasma operating conditions, supporting the engineering and design of CO2 plasma reactors for both terrestrial and space-based applications.
A collaborative effort between Texas Tech University and the University of New Mexico is studying the ways to suppress or minimize outgassing from anode materials in the context of high-power microwave devices. Outgassing can lead to plasma formation with several deleterious effects such as anode-cathode gap closure with impedance collapse, pulse shortening, phase shifts, reductions in system efficiency, and degradation in the longevity and reliability of HPM systems. Here, a possible solution strategy based on quasi-isentropic compression (QIC) is probed with quantitative predictions based on molecular dynamics (MD) simulations. Using copper with hydrogen gaseous impurity as an example anode, our results show that a strong and short pressure ramp applied at one surface can lead to a herding of hydrogen atoms towards the opposite face as well as lead to an initial outgassing and neutral load reduction. Such gaseous impurity gathering could then be used for driving off the impurities by additional surface treatment and cleaning. Additionally, it is shown that upon compression, the surface becomes denser and resistant to subsequent diffusive uptake of hydrogen adsorbates, thus affecting a surface seal. Similar analysis could be applied to other gases (or gas mixtures) as well such as mitigating outgassing of oxygen, CO and CO2 in metals.
The corona discharge phenomenon has been of great interest, and it is widely used in practical applications. By coupling the fluid dynamics equations and the Poisson equation, the negative corona discharge between a plane and an ellipsoidal electrode is modeled in this article. The mechanism of ring mode discharge is, for the first time, systematically investigated through numerical simulation. The relationship between the mode of first discharge and electrode-plane setup conditions, such as various cathode shapes, applied voltages, and gap distances, is analyzed. The position where ring mode discharge occurs is correlated with the maximal electric field intensity during the discharge, which is generated by a combination of boundary charge and volume charge in the domain. It is found that in some cases, the discharge pulses can all be in ring mode. The first discharge tends to be in ring mode when the absolute value of applied voltage is lower, the semiaxis ratio $a/b$ is larger, or the gap distance is longer. This study provides important insights for optimizing the design of electrodes and improving the efficiency of discharge in applications such as electrostatic precipitators, plasma devices, aero-engines, and other devices utilizing corona discharge.
The space-time fractional non-linear Phi-4 equation is a significant equation to describes the fission and fusion process that ensued in chemical kinematics, solid-state physics, astrophysical fusion plasma, plasma physics, and electromagnetic interactions, etc. The Phi-4 non-linear partial differential equation is reshaped utilizing the three different fractional-order derivatives and constructed transformations corresponding to every fractional-order derivative to convert the partial differential equation into an ordinary differential equation. A new extended direct algebraic equation method was successfully applied to extract the solitons solutions. The solitons solutions are developed with the exponential, trigonometric, rational, and hyperbolic functions including different unknown constant parameters. The graphical interpretations of obtained solutions are also depicted by allocating the feasible values to unknown constant parameters. The proposed scheme is an effective and functional scientific technique to investigate different fractional systems and models in engineering and physics referenced to real physical problems.
Abstract Recent developments in sources of low-temperature atmospheric plasma have expanded their applications in medicine, leading to the establishment of the field of “plasma medicine”. In the first half of this paper, the clinical studies conducted to date on wound treatments using low-temperature atmospheric plasmas are summarized. In the second half, several issues in plasma medicine are discussed from the viewpoint of plasma engineering. A comparison of different plasma sources and the monitoring of plasma conditions are highlighted. Moreover, the necessity of developing standards in order to expand the application of low-temperature atmospheric plasmas in medicine is discussed.
Arc splitting is one of the most important processes in accomplishing a power interruption by multiplying the number of voltage drops. During arc-plate interaction, the arc roots erode and vaporize the metals which significantly alters the gas composition and plasma properties, such as the radiation absorption coefficient. In this work, we perform a 3D computational study of arc splitting in a circuit breaker. In order for the study to be systematic, the metal vaporization, species transport, and radiative heat transfer are integrated into the magnetohydrodynamics modeling with some special considerations. Firstly, the simulation considers the ferromagnetic effect of steel plates. Secondly, the metal-vapor-enhanced radiation is numerically implemented by the discrete ordinate method with consideration given to the banded radiation spectrum. Thirdly, the simulation model incorporates a near-electrode layer to implement the voltage drop and imposes additional heat flux on the arc spots. The simulation results show that the metal vaporization not only influences the arc dynamics (via Stefan flow) but also enhances the local radiation intensity. Besides, due to the ferromagnetic effect, the magnetic field increases dramatically during arc splitting. However, the self-induced magnetic force has quite a different influence on the motion of sub-arcs, which prevents even and concurrent arc splitting. This simulation reveals that the magnetic-field-induced uneven splitting can be compensated by the enhanced pressure wave or externally applied transversal magnetic field. This study is expected to explore more applications in simulating arc interruption and improve the design of highly-efficient circuit breakers.