Jet Source Research Articles

Biochemical evaluation of wound healing efficacy of cold plasma-conditioned media under different operational conditions

Wound healing is a dynamic and intricate biological process crucial for tissue repair and regeneration. This study explores the potential therapeutic impact of non-thermal plasma generated by a hand-held cold atmospheric pressure plasma jet (C-APPJ) source on fibroblast cells (NIH/3T3) in vitro. The sequential phases of wound healing—inflammation, cell proliferation, and tissue remodelling, were assessed in the context of cell migration and oxidative stress dynamics. Typically, plasma generates a mixture of several reactive oxygen/nitrogen (ROS/RNS) species. The present study investigates the safety and efficacy of C-APPJ under distinct operating conditions (argon (GI) and argon + nitrogen (GII)) and exposure times (1 min and 3 min). Cell viability assays confirmed the non-cytotoxic nature of the cold plasma conditioned medium. The levels of ROS/RNS and malondialdehyde (biomarker of oxidative stress) in the plasma-treated samples remained comparable with the control fibroblast cells grown in normal media, suggesting the favourable modulation of ROS by the cellular antioxidant mechanisms. Accelerated wound-closure rates from 6th hour to 24th hour in all the treated groups ranged from 38.76% to 45.66%, when compared to 34.25% in the control cells. Substantial cell migration leading to 51.59% of wound closure was recorded in the argon + nitrogen (GII) group exposed for 3 min. Taken together, the potential of cold plasma to effectively heal wounds without causing prolonged oxidative stress and chronic inflammation is implicated. These outcomes suggest scope for clinical application of C-APPJ as safe and cost-effective treatment of wounds (ulcers, burns, diabetic foot) and wound disinfection.

Flexible atmospheric brush-like microplasma jet source with needle-shaped protrusion electrode for internal surface treatment

In this paper, a flexible plasma jet source with newly designed needle-shaped protrusion (NSP) electrode capable of producing flexible atmospheric brush-like microplasma jet (FBµPJ) was developed and its application for internal surface treatment was investigated. The generator could maintain flexibility while possessing a certain degree of rigidity. Simulation and experimental results indicate that FBµPJ with NSP electrode was more efficient in generating the brush-like microplasma jets compared to conventional wire electrodes. The electrical characteristics showed that the discharge of this novel plasma source was a typical dielectric barrier discharge, and diverse oxygen-containing reactive species favorable for material surface treatment were observed. The internal surface of the silicone tube would get rougher and grafted with polar oxygen-containing functional groups after plasma treatment, and the inner surface can be transformed from hydrophobic to hydrophilic. Finally, the interfacial adhesion of the silicone tubes can be effectively enhanced by FBµPJ.

Characteristics of Foreshock Subsolar Compressive Structures

AbstractThe turbulent foreshock region upstream of the quasi‐parallel bow shock is dominated by waves and reflected particles that interact with each other and create a large number of different foreshock transients. The structures with the enhanced magnetic field, Short Large Amplitude Magnetic Structures, and density spikes named plasmoids are frequently observed. They are one of the suggested sources of transient flux enhancements or jets in the magnetosheath. Using measurements of the Magnetospheric Multiscale Spacecraft (MMS) and OMNI solar wind database between the 2015 and 2018 years, we have found that there is a category of events exhibiting both magnetic field and density enhancements simultaneously and we introduce the term “mixed structures” for them. Consequently, we divided our set of observations into three groups of events and present their comparative statistical analysis in the subsolar foreshock. Based on our results and previous research, we discuss the properties, possible origin and occurrence rates of these events under different upstream conditions and their possible relation to the jet and plasmoid formation in the magnetosheath.

Diagnostics and characterization of a novel multi gas layer RF atmospheric pressure plasma jet for polymer processing

The quest to employ cold plasma sources at atmospheric pressure in polymer processing has emerged as a potent driving force behind their development. Atmospheric pressure operation of plasma jets provides potential cost reductions as well as easier handling and maintenance. In addition, their unique advantage of remote operation allows the substrate to be placed outside the source boundaries. This latter feature makes it easier to process complex three-dimensional objects and to integrate plasma jets into existing production lines. Although conventional atmospheric pressure plasma jet (APPJ) sources have undergone significant advancements in their design and construction, they have reached their technical and technological thresholds in several domains, thereby also impeding further enhancements in material processing applications. To cope with this issue, this work introduces a promising APPJ (named MPPJ3) working in a three co-axial gas layer geometry, incorporating the capability of aerosol and shield gas introduction leading to a configuration rich in reactive plasma species with controllable size and suitable temperature for polymer processing. A parametric study on the novel MPPJ3 device is carried out and plasma characteristics, such as reactive plasma species and temperatures, are determined by means of optical emission spectroscopy (OES), laser scattering, and infrared (IR) camera imaging whereas the fluid dynamics are analyzed using computational fluid dynamics (CFDs) and Schlieren imaging. The obtained promising results clearly show the flexibility and adaptability of the MPPJ3 device for polymer processing applications.

Rotational detection of the silicon-carbon chains H2C3Si and HSiCCH

The rotational spectra of two new silicon-bearing carbon chains, H2C3Si and HSiCCH have been detected by means of Fourier-transform microwave spectroscopy in a supersonic jet source equipped with an electrical discharge. On the basis of measurements between 10 and 42GHz, precise spectroscopic constants have been determined for both molecules. Along with H29SiCCH and H30SiCCH, which were detected in natural abundance, several other rare isotopic species of HSiCCH were observed using samples enriched in carbon-13 and D. From this isotopic data, a precise semi-experimental equilibrium structure was derived and compared with a re-evaluated semi-experimental equilibrium structure of the parent silylene SiH2; the deuterium isotopic measurements also provide important clues as to the formation pathway of HSiCCH in our discharge. Because other small Si-bearing chains have been detected in the circumstellar envelope of the evolved carbon star IRC+10216, both chains may be of astronomical interest.

Plasma-Activated Media Produced by a Microwave-Excited Atmospheric Pressure Plasma Jet Is Effective against Cisplatin-Resistant Human Bladder Cancer Cells In Vitro.

Media exposed to atmospheric pressure plasma (APP) produce reactive oxygen and nitrogen species (RONS), with hydrogen peroxide (H2O2), nitrite (NO2-), and nitrate (NO3-) being among the most detected species due to their relatively long lifetime. In this study, a standardized microwave-excited (ME) APP jet (APPJ) source was employed to produce gaseous RONS to treat liquid samples. The source was a commercially available plasma jet, which generated argon plasma utilizing a coaxial transmission line resonator at the operating frequency of 2.45 GHz. An ultraviolet-visible spectrophotometer was used to measure the concentrations of H2O2 and NO3- in plasma-activated media (PAM). Three different types of media (deionized water, Hank's balanced salt solution, and cell culture solution Dulbecco's modified eagles medium [DMEM]) were utilized as liquid samples. Among these media, the plasma-treated DMEM was observed to have the highest levels of H2O2 and NO3-. Subsequently, the feasibility of using argon ME-APPJ-activated DMEM (PAM) as an adjuvant to enhance the therapeutic effects of cisplatin on human bladder cancer cells (T-24) was investigated. Various cancer cell lines, including T-24 cells, treated with PAM were observed in vitro for changes in cell viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. A viability reduction was detected in the various cancer cells after incubation in PAM. Furthermore, the study's results revealed that PAM was effective against cisplatin-resistant T-24 cells in vitro. In addition, a possible connection between HER expression and cell viability was sketched.

Numerical investigation of terahertz wave driven electron acceleration generated from gas jet

We have investigated the dependence of the acceleration efficiency for three different proposed direct terahertz wave driven electron accelerator setups, including ionization in a gas jet source. We have numerically simulated and optimized the ionization processes using Particle-In-Cell code (EPOCH) and pointed out its crucial effect on the accelerating mechanism. Supposing two single-cycle terahertz driving pulses with 1 mJ energy per pulse we characterized the different accelerator arrangements. The main properties of the predicted electron beams with the average kinetic energy of 27 keV can be adapted to the requirements of different applications in the fC-pC charge range.

Solar Active Region Coronal Jets. III. Hidden-onset Jets

Solar quiet- and coronal-hole region coronal jets frequently clearly originate from erupting minifilaments, but active-region jets often lack an obvious erupting-minifilament source. We observe a coronal-jet-productive active region (AR), AR 12824, over 2021 May 22 0–8 UT, primarily using Solar Dynamics Observatory (SDO) Atmospheric Imaging Array (AIA) EUV images and SDO/Helioseismic and Magnetic Imager magnetograms. Jets were concentrated in two locations in the AR: on the south side and on the northwest side of the AR’s lone large sunspot. The south-location jets are oriented so that we have a clear view of the jets’ origin low in the atmosphere: their source is clearly minifilaments erupting from locations showing magnetic flux changes/cancelations. After erupting a projected distance ≲5″ away from their origin site, the minifilaments erupt outward onto far-reaching field as part of the jet’s spire, quickly losing their minifilament character. In contrast, the northwest-location jets show no clear erupting minifilament, but the source site of those jets are obscured along our line of sight by absorbing chromospheric material. EUV and magnetic data indicate that the likely source sites were ≳15″ from where the we first see the jet spire; thus, an erupting minifilament would likely lose its minifilament character before we first see the spire. We conclude that such AR jets could work like non-AR jets, but the erupting-minifilament jet source is often hidden by obscuring material. Another factor is that magnetic eruptions making some AR jets carry only a harder-to-detect comparatively thin (∼1″–2″) minifilament “strand.”

Laminar Swirling Wall Jets

The problem of determining the characteristics of a laminar swirling wall jet of an incompressible fluid is considered. Numerical solutions of the Navier–Stokes equations are obtained in the stationary and non-statitonary formulations. It is shown that the jet characteristics obey a self-similar law at large distances from the jet source, as in the case of a three-dimensional laminar non-swirling jet, but in our case the jet propagates at a certain angle to the initial direction of jet blowing. With a large swirling of flow in the jet, regions of recirculation flow appear and the jet flow becomes unsteady.

Development of cold atmospheric pressure plasma jet sources for biomedical application

Development of cold atmospheric pressure plasma jet sources for biomedical application

Deciphering Solar Coronal Heating: Energizing Small-scale Loops through Surface Convection

The solar atmosphere is filled with clusters of hot small-scale loops commonly known as coronal bright points (CBPs). These ubiquitous structures stand out in the Sun by their strong X-ray and/or extreme-ultraviolet (EUV) emission for hours to days, which makes them a crucial piece when solving the solar coronal heating puzzle. In addition, they can be the source of coronal jets and small-scale filament eruptions. Here we present a novel 3D numerical model using the Bifrost code that explains the sustained CBP heating for several hours. We find that stochastic photospheric convective motions alone significantly stress the CBP magnetic field topology, leading to important Joule and viscous heating concentrated around the CBP’s inner spine at a few megameters above the solar surface. We also detect continuous upflows with faint EUV signals resembling observational dark coronal jets and small-scale eruptions when Hα fibrils interact with the reconnection site. We validate our model by comparing simultaneous CBP observations from the Solar Dynamics Observatory (SDO) and the Swedish 1‐m Solar Telescope (SST) with observable diagnostics calculated from the numerical results for EUV wavelengths as well as for the Hα line using the Multi3D synthesis code. Additionally, we provide synthetic observables to be compared with Hinode, Solar Orbiter, and the Interface Region Imaging Spectrograph (IRIS). Our results constitute a step forward in the understanding of the many different facets of the solar coronal heating problem.

Arrayed multiple atmospheric-pressure plasma jet sources for active stealth

Arrayed multiple atmospheric-pressure plasma jet sources for active stealth

Comparison of the Bacterial Inactivation Efficiency of Water Activated by a Plasma Jet Source and a Pin-to-Pin Electrode Configuration Source

In this comparative study, the bacterial inactivation efficiency of plasma-activated water (PAW) generated by two distinct plasma reactors, one utilizing a nitrogen plasma jet electrode and the other a hybrid argon plasma reactor, was explored. The present study involved the assessment of antimicrobial activity against suspensions of three Gram-positive and three Gram-negative bacterial strains in their planktonic cell state. Bacterial suspensions were introduced into PAW five days after generation. Subsequently, the viability of the bacteria was assessed at various time intervals, specifically at 0.5, 1, 3, 5, 10, and 24 h, in order to evaluate the effect of inactivation. Structural changes in bacteria after PAW treatment were assessed using a scanning electron microscope (SEM). The physicochemical properties of PAW, including pH, conductivity, and concentrations of H2O2, NO2−, and NO3− during aging were measured. The present study demonstrated the effective inactivation of the tested bacterial strains by PAW. Gram-positive bacteria displayed greater resistance compared to Gram-negative species, with the lowest reductions in bacterial counts observed for B. cereus, and the highest for Escherichia coli O157:H7. Morphological damage was evident across all bacterial species examined. Physicochemical measurements showed slow decay of the reactive species in the aging process. This study illustrated the potential utility of PAW as an alternative disinfectant.

Acceleration and Spectral Redistribution of Cosmic Rays in Radio-jet Shear Flows

A steady-state, semi-analytical model of energetic particle acceleration in radio-jet shear flows due to cosmic-ray viscosity obtained by Webb et al. is generalized to take into account more general cosmic-ray boundary spectra. This involves solving a mixed Dirichlet–Von Neumann boundary value problem at the edge of the jet. The energetic particle distribution function f 0(r, p) at cylindrical radius r from the jet axis (assumed to lie along the z-axis) is given by convolving the particle momentum spectrum with the Green’s function , which describes the monoenergetic spectrum solution in which as r → ∞ . Previous work by Webb et al. studied only the Green’s function solution for . In this paper, we explore for the first time, solutions for more general and realistic forms for . The flow velocity u = u(r) e z is along the axis of the jet (the z-axis). u is independent of z, and u(r) is a monotonic decreasing function of r. The scattering time in the shear flow region 0 < r < r 2, and , where s > 0 in the region r > r 2 is outside the jet. Other original aspects of the analysis are (i) the use of cosmic ray flow lines in (r, p) space to clarify the particle spatial transport and momentum changes and (ii) the determination of the probability distribution that particles observed at (r, p) originated from r → ∞ with momentum . The acceleration of ultrahigh-energy cosmic rays in active galactic nuclei jet sources is discussed. Leaky box models for electron acceleration are described.

Laminar Swirling Wall Jets

The problem of determining the characteristics of a laminar swirling wall jet of an incompressible fluid is considered. Numerical solutions of the Navier–Stokes equations are obtained in the stationary and non-statitonary formulations. It is shown that the jet characteristics obey a self-similar law at large distances from the jet source, as in the case of a three-dimensional laminar non-swirling jet, but in our case the jet propagates at a certain angle to the initial direction of jet blowing. With a large swirling of flow in the jet, regions of recirculation flow appear and the jet flow becomes unsteady.

The cylindrical jet base of M 87 within 100 μas of the central engine

A recent article on high-resolution 86 GHz observations with the Global Millimeter VLBI Array, the phased Atacama Large Millimeter/submillimeter Array, and the Greenland Telescope describes the detection of a limb-brightened cylindrical jet, 25 μas &lt; z &lt; 100 μas, where z is the axial displacement from the supermassive black hole in the sky plane. It was shown to be much wider and much more collimated than 2D simulations of electromagnetic (Blandford-Znajek) jets from the event horizon predicted. This was an unanticipated discovery. The claimed detection of a jet connected to the accretion flow provides a direct observational constraint on the geometry and physics of the jet launching region for the first time in any black hole jetted system. This landmark detection warrants further analysis. This Letter focuses on the most rudimentary properties, the shape and size of the source of the detected jet emission, the determination of which is not trivial due to line-of-sight effects. Simple thick-walled cylindrical shell models for the source were analyzed to constrain the thickness of the jet wall. The analysis indicates a tubular jet source with a radius R ≈ 144 μas ≈ 38M and that the tubular jet walls have a width W ≈ 36 μas ≈ 9.5M, where M is the geometrized mass of the black hole (a volume comparable to that of the interior cavity). The observed cylindrical jet connects continuously to the highly limb-brightened jet (previously described as a thick-walled tubular jet) that extends to z &gt; 0.65 mas, and the two are likely in fact the same outflow (i.e., from the same central engine).

On the Subparsec-scale Core Composition of FR 0 Radio Galaxies

Although Fanaroff–Riley type 0 (FR 0) radio galaxies are known to be the most numerous jet population in the local Universe, they are much less explored than the well-established class of FR type I (FR I) and FR type II galaxies due to their intrinsic weakness. Observationally, their nuclear radio, optical, and X-ray properties are comparable to the nuclear environment of FR Is. The recent detection of two FR 0s in the high-energy band suggests that, like in FR Is, charged particles are accelerated there to energies that enable gamma-ray production. Up to now, only the lack of extended radio emission from FR 0s distinguishes them from FR Is. By comparing the spectral energy distribution of FR 0s with that of FR Is and in particular with that of M87 as a well-studied reference source of the FR I population, we find the broadband spectrum of FR 0 s exceptionally close to M87's quiet core emission. Relying on that similarity, we apply a lepto-hadronic jet-accretion flow model to FR 0s. This model is able to explain the broadband spectral energy distribution, with parameters close to particle-field equipartition and matching all observational constraints. In this framework, FR 0s are multimessenger jet sources, with a nature and highly magnetized environment similar to those of the naked quiet core of FR Is.

New Evidence on the Origin of Solar Wind Microstreams/Switchbacks

Microstreams are fluctuations in the solar wind speed and density associated with polarity-reversing folds in the magnetic field (also denoted switchbacks). Despite their long heritage, the origin of these microstreams/switchbacks remains poorly understood. For the first time, we investigated periodicities in microstreams during Parker Solar Probe (PSP) Encounter 10 to understand their origin. Our analysis was focused on the inbound corotation interval on 2021 November 19–21, while the spacecraft dove toward a small area within a coronal hole (CH). Solar Dynamics Observatory remote-sensing observations provide rich context for understanding the PSP in situ data. Extreme ultraviolet images from the Atmospheric Imaging Assembly reveal numerous recurrent jets occurring within the region that was magnetically connected to PSP during intervals that contained microstreams. The periods derived from the fluctuating radial velocities in the microstreams (approximately 3, 5, 10, and 20 minutes) are consistent with the periods measured in the emission intensity of the jetlets at the base of the CH plumes, as well as in larger coronal jets and in the plume fine structures. Helioseismic and Magnetic Imager magnetograms reveal the presence of myriad embedded bipoles, which are known sources of reconnection-driven jets on all scales. Simultaneous enhancements in the PSP proton flux and ionic (3He, 4He, Fe, O) composition during the microstreams further support the connection with jetlets and jets. In keeping with prior observational and numerical studies of impulsive coronal activity, we conclude that quasiperiodic jets generated by interchange/breakout reconnection at CH bright points and plume bases are the most likely sources of the microstreams/switchbacks observed in the solar wind.

In situ measurement of dynamic surface charge on dielectrics interacted with plasma jet arrays

As a flexible tool to generate large-scale non-thermal plasma in ambient air, plasma jet arrays have attracted academic attention from multiple fields of biomedicine and material surface sciences. Optimization of plasma processing that heavily relies on trial-and-error experiments requires quantitative in situ diagnostics of plasma–surface interaction. This study focuses on the fundamental surface charge evolution in quartz dielectric deposited by plasma jet arrays. The thin quartz plate is attached to an electro-optic BSO crystal that is conductive and grounded in the back. These jet arrays are driven by a positive microsecond pulsed voltage with kHz frequency. Special attention is paid to the properties and mechanisms of the intriguing convergence of multiple adjacent surface charge patterns. The measured 1D and 2D jet arrays verify the trend of homopolar charge fusion at the plasma–surface interface, which was initially thought to be repulsive under electrostatic forces. The fusion of surface charges is considerably enhanced when more charges are transported onto targeted dielectrics, as well as at smaller separations. The simulation results reveal the mechanism of charge fusion that occurs when surface ionization waves (IWs) are in close proximity, and the high electric field between their heads provides a cluster of high-energy electrons that forces two IWs to merge until they connect. In the case of extremely small separations, the close-in IWs directly merge in bulk before touching the target. Quantitative in situ measurements of surface charges and the corresponding simulations provide fresh insight into the electrical interaction in large-scale atmospheric-pressure plasma jets. The properties of charge fusion can help with manufacturing and optimizing large-area uniform plasma jet sources for various dielectric materials.

An empirical model of noise sources in subsonic jets

Modelling the noise emitted by turbulent jets is made difficult by their acoustic inefficiency: only a tiny fraction of the near-field turbulent kinetic energy is propagated to the far field as acoustic waves. As a result, jet-noise models must accurately capture this small, acoustically efficient component hidden among comparatively inefficient fluctuations. In this paper, we identify this acoustically efficient near-field source from large-eddy simulation data and use it to inform a predictive model. Our approach uses the resolvent framework, in which the source takes the form of nonlinear fluctuation terms that act as a forcing on the linearised Navier–Stokes equations. First, we identify the forcing that, when acted on by the resolvent operator, produces the leading spectral proper orthogonal decomposition modes in the acoustic field for a Mach 0.4 jet. Second, the radiating components of this forcing are isolated by retaining only portions with a supersonic phase speed. This component makes up less than 0.05 % of the total forcing energy but generates most of the acoustic response, especially at peak (downstream) radiation angles. Finally, we propose an empirical model for the identified acoustically efficient forcing components. The model is tested at other Mach numbers and flight-stream conditions and predicts noise within 2 dB accuracy for a range of frequencies, downstream angles and flight conditions.