Plasma Generation Research Articles

A bispecific inhibitor of complement and coagulation blocks activation in complementopathy models via a novel mechanism

AbstractInhibitors of complement and coagulation are present in the saliva of a variety of blood-feeding arthropods that transmit parasitic and viral pathogens. Here, we describe the structure and mechanism of action of the sand fly salivary protein lufaxin, which inhibits the formation of the central alternative C3 convertase (C3bBb) and inhibits coagulation factor Xa (fXa). Surface plasmon resonance experiments show that lufaxin stabilizes the binding of serine protease factor B (FB) to C3b but does not detectably bind either C3b or FB alone. The crystal structure of the inhibitor reveals a novel all β-sheet fold containing 2 domains. A structure of the lufaxin-C3bB complex obtained via cryo–electron microscopy (EM) shows that lufaxin binds via its N-terminal domain at an interface containing elements of both C3b and FB. By occupying this spot, the inhibitor locks FB into a closed conformation in which proteolytic activation of FB by FD cannot occur. C3bB-bound lufaxin binds fXa at a separate site in its C-terminal domain. In the cryo-EM structure of a C3bB-lufaxin-fXa complex, the inhibitor binds to both targets simultaneously, and lufaxin inhibits fXa through substrate-like binding of a C-terminal peptide at the active site as well as other interactions in this region. Lufaxin inhibits complement activation in ex vivo models of atypical hemolytic uremic syndrome (aHUS) and paroxysmal nocturnal hemoglobinuria (PNH) as well as thrombin generation in plasma, providing a rationale for the development of a bispecific inhibitor to treat complement-related diseases in which thrombosis is a prominent manifestation.

Plasma Emission, Wave Speeds, and Temperatures of Laser-Supported Plasmas in Air

A study of the generation and subsequent expansion of plasmas using a single beam (532 nm) from the second harmonic generator of a Q-switched Nd:YAG laser is described. The plasmas in air are studied using an intensified charge-coupled device camera over periods of 1000 ns following the laser pulses. The plasma experimental results are interpreted in terms of wave speeds and plasma temperatures. Energy balance equations are considered to estimate the plasma temperatures and the laser-supported radiation (LSR) and the laser-supported detonation (LSD) wave speeds. Within 1000 ns observation time, the circular spectral images turn elliptical because of plasma expansion toward the laser beam. The plasma expansion increases with increasing laser irradiance. A laser irradiance range of yields LSR wave speeds between 45 and 170 km/s and LSD wave speeds of 90–130 km/s. The measured wave speeds are compared with the LSR and the LSR wave speed models. The plasma temperatures are between 90,000 and 120,000 K at 15 ns after the laser pulse based on measured emission spectra and are between 640,000 and 760,000 K at 3 ns based on the LSR model.

The partial electrical breakdown mechanism by high voltage electric pulses in multi-fractured granite

High-voltage electric pulse (HVEP) technology has currently become a new efficient rock breaking method. In order to reveal the influence of internal fracture characteristics of heterogeneous granite on electric pulse rock breaking, the two-dimensional numerical model of multi-physical field coupling electrical breakdown of fractured rock is established, which the high-voltage electric pulse plasma generation in multi-fractured heterogeneous granite is realized from the coupling of circuit field, current field, breakdown field, heat transfer field and solid mechanics. This paper analyzes the influence of fracture porosity, fracture types and granite heterogeneity on the electrical breakdown of rock (i.e. the formation of plasma channel inside the rock). At the same time, the two-dimensional numerical model of electrical breakdown parameters, which considers the circuit structure parameters of the pulsed tool, the initiation and development of the electrical breakdown, the dependence between electrical breakdown intensity and time, and rock heterogeneity, are analyzed. The simulation results indicate that with the heterogeneity H of granite changing, the plasma channel inside the rock samples are different, while the time required for breakdown t and rock breaking volume Vrock of rock samples with different heterogeneous H will show obvious fluctuations; among the rock samples with different heterogeneity H, existing a single crack requires a longer breakdown time and the extreme value of the internal conductivity is also significantly larger. And then, the formation of plasma channel is directional selective, extending towards fractures and the weak electrical breakdown intensity. With the dip angle of the fracture increasing, the required breakdown time increases accordingly, and conversely, the broken volume decreases accordingly. The larger porosity of fracture is, the larger broken volume and the shorter required break down time of the rock sample. Furthermore, with the continuous action of electric pulses, multi-fractured rock form interpenetrating plasma channels to improve the rock breaking efficiency. The research results can provide help and theoretical support for optimization of electric pulse rock breaking parameters and the development of electric pulse drilling technology.

Uniform plasma generation with filament assisted DC discharge in a linear plasma device

Uniform and quiescent (δ n/n < 0.5%) laboratory plasma has been produced in a linear plasma device with a simple filament-assisted DC source without using any magnetic field for plasma confinement. A filament-assisted DC plasma source has been designed, fabricated in-house, and operated successfully to achieve the desired plasma parameters. A stainless steel(ss)-grid is placed in-front of the filament assembly and biased appropriately using a DC-regulated power supply to accelerate thermionically emitted electrons from the heated filaments along the length of the main chamber and facilitate the production of uniform plasma. Heating of the filaments was done by passing a current of ∼3.8 − 4.2 A through it using another DC-regulated power supply. 2-dimensional spatial profiles of plasma density (n e ), electron temperature (T e ) and plasma potential (V P ) obtained from the Langmuir Probe measurements by inserting 4 number of Langmuir Probes inside the plasma from 4 co-linear radial ports of the plasma chamber and scanning them radially with the help of indigenously built probe drive setups reveal spatially uniform plasma generation with n e in the range ∼(1 − 2) × 1015 m−3 and T e ∼ (2.5 − 3.5) eV. Variations of plasma parameters and its spatial uniformity with neutral pressure are also investigated. It is observed that the spatial uniformity of the plasma produced at neutral pressures in the range of ∼(3 − 6) × 10−4 mbar is very good with δ n/n < 0.5%.

Microwave atmospheric pressure plasma jet generated from substrate integrated waveguide resonator

AbstractA microwave atmospheric pressure plasma jet (MW‐APPJ) generator based on a substrate‐integrated waveguide (SIW) resonator is proposed. A thin, straight plasma needle with a length of 9 cm could be obtained. Higher than 90% of microwave feeding efficiency is obtained under a wide range of gas flow rates without a microwave matching network. As the gas flow increased from 1 to 14 L/min, a transition from laminar to turbulent mode is observed in the plasma jet's morphology. Furthermore, a preliminary surface treatment was tested for the device. The polyimide film became super hydrophilic after a 5‐min treatment with the developed SIW‐based plasma generator. Generally, the SIW‐based MW‐APPJ is low‐cost, electrodeless, and low‐profile along the plasma jet length direction.

Mechanism of Fe removal by Sn addition in Al-7Si-1Fe alloy

Excess impurity Fe will form various intermetallic compounds in Al-based alloys, such as α-Al8Fe2Si and β-Al5FeSi, which greatly reduce the elongation of alloys. Therefore, Fe removal is a promising approach for high performance Al-based alloy. In this paper, we propose an effective method for the Fe removal from Al-7Si alloys by adding Sn. Based on the thermodynamic calculations, the element Sn was selected for Fe removal. The microstructure of Fe-rich compounds and Fe content in alloy were compared by optical microscope (OM), scanning electron microscopy (SEM) and inductively coupled plasma generation spectrometer (ICP). It was observed that the reduction of Fe content in Sn can reach 33.8%, comparable to the level of adding B. More Fe-rich compounds deposited at the bottom after addition of Sn. However, the phase type and morphology of Fe-rich compound were unchanged. The β-Sn attached to the β-Al9Fe2Si2 which was determined by transmission electron microscopy (TEM), and a coherent interface between β-Sn and β-Al9Fe2Si2 phase was observed with the orientation of (0 0 1)[1 1 0]β-Sn∥(2 2 0)[0 0 1]β-Al9Fe2Si2. It deduced that the attached β-Sn with larger density than alloy would lead to more deposition of β-Al9Fe2Si2. This study provides an insight into the preparation of high-performance Al-Si alloy by removing Fe from secondary Al alloy with Sn addition.

The assessment of the atmospheric air breakdown voltage generated by the interaction between microwaves and metallic wires

The aim of this research is to understand the plasma initiation process generated by metallic wires when interacting with high energy density microwaves. Lead (Pb) and molybdenum (Mo) wires of 0.5 mm diameter were investigated in this experiment. The tip of the metallic wire was placed into the nodal point of a waveguide cavity attached to a microwave generator, where it was exposed to the high energy density of the microwave field. Following the interaction between microwaves and the metallic wire, a plasma was initiated having as effect the wire vaporization. The experiments were conducted in atmospheric air at ∼1 bar pressure. From optical emission spectroscopy investigations it was observed that electronic excitation of the plasma has high values and it is in a local thermal equilibrium. The theoretical calculation of the voltages induced in the metallic wires when exposed to high energy density microwave field are similar to those measured in air breakdown experiments. The scanning electron microscopy analysis of the tips of the metallic wires showed that the field emission process is responsible for the ignition of the metallic wires and plasma generation.

Monitoring prothrombin activation in plasma through loss of Förster resonance energy transfer

BackgroundCurrent assays that monitor thrombin generation in plasma rely on fluorogenic substrates to follow the kinetics of zymogen activation, which may be complicated by substrate cleavage from other proteases. In addition, these assays depend on activation following cleavage at the prothrombin R320 site and fail to report the cleavage at the alternative R271 site, leading to the shedding of the auxiliary Gla and kringle domains of prothrombin. ObjectivesTo develop a plasma assay that directly monitors prothrombin activation independent of fluorogenic substrate hydrolysis. MethodsCleavage at the R271 site of prothrombin is monitored through loss of Förster resonance energy transfer in plasma coagulated along the extrinsic or intrinsic pathway. ResultsThe availability of factor (F)V in plasma strongly influences the rate of prothrombin activation. The rate of thrombin formation is equally perturbed in FV or prothrombin-depleted plasma, implicating that the thrombin-catalyzed feedback reactions that amplify the coagulation response play an important role in generating sufficient amounts of FVa required for the assembly of prothrombinase. Congenital deficiencies in FVIII and FIX significantly slow down cleavage at R271 in plasma coagulated along the extrinsic and intrinsic pathways. Prothrombin activation in FXI-deficient plasma is only perturbed when coagulation is triggered along the intrinsic pathway. ConclusionThe Förster resonance energy transfer assay enables direct monitoring of prothrombin activation through cleavage at R271 without the need for fluorogenic substrates. The assay is sensitive enough to assess how deficiencies in coagulation factors affect thrombin formation.

Cross‐impact of beam local wavenumbers on the efficiency of self‐adaptive artificial boundary conditions for two‐dimensional nonlinear Schrödinger equation

In this paper, we propose self‐adaptive artificial boundary conditions (ABCs) for the two‐dimensional (2D) time‐dependent nonlinear Schrödinger equation and studied their efficiency. This equation describes the laser pulse interaction with a semiconductor layer under laser‐induced plasma generation. Because of its nonlinearity, the interaction process is very sensitive to the appearance of the optical beam spurious reflection; therefore, highly transparent ABCs are urgently required to avoid disturbing the interaction process by an unphysical reflected wave. This can be achieved by using time‐ and spatial‐dependent local wavenumbers computed near the artificial boundaries. We claim that it is necessary to account for both wavenumbers in each of the adaptive ABCs stated on both spatial coordinates. Based on computer simulation, we demonstrate an increase in the efficiency of the adaptive ABC stated on the coordinate along which the optical pulse propagates by involving both local wavenumbers. The accuracy of the developed approach is verified using a well‐known analytical solution of the linear Schrödinger equation as well as the reference problem solution, obtained by solving the problem with zero‐value boundary conditions on the extended spatial domain. For computer modeling, the finite‐difference scheme, possessing asymptotic stability, is applied together with a two‐stage iterative process for its realization. The algorithm and peculiarities of the local wavenumber computation are discussed in detail. The applicability of the developed approach is also demonstrated via the solution of both linear and nonlinear problems. The proposed method has widespread application for solving various laser physics problems governed by the Schrödinger equation.

IVIg treatment increases thrombin activation of platelets and thrombin generation in paediatric patients with immune thrombocytopenia.

Clinical manifestations and laboratory parameters of haemostasis were investigated in 23 children with newly diagnosed immune thrombocytopenia (ITP) before and after intravenous immunoglobulin (IVIg) treatment. ITP patients with platelet counts of less than 20 × 109 /L and mild bleeding symptoms, graded by a standardized bleeding score (BS), were compared with healthy children with normal platelet counts and children with chemotherapy-related thrombocytopenia. Markers of platelet activation and platelet apoptosis in the absence and presence of platelet activators were analysed by flow cytometry; thrombin generation in plasma was determined. ITP patients at diagnosis presented with increased proportions of platelets expressing CD62P and CD63 and activated caspases, and with decreased thrombin generation. Thrombin-induced activation of platelets was reduced in ITP compared with controls, while increased proportions of platelets with activated caspases were observed. Children with a higher BS had lower proportions of CD62P-expressing platelets compared with those with a lower BS. IVIg treatment increased the number of reticulated platelets, the platelet count to more than 20 × 109 /L and improved bleeding in all patients. Decreased thrombin-induced platelet activation, as well as thrombin generation, were ameliorated. Our results indicate that IVIg treatment helps to counteract diminished platelet function and coagulation in children with newly diagnosed ITP.

Numerical characterization of dual radio frequency micro-discharges

Micro-discharges have many excellent characteristics, such as generation of high-density and non-equilibrium plasmas at atmospheric pressure. In this paper, we used an implicit particle-in-cell/Monte Carlo collision method for three-dimensional velocities in a one-dimensional space combined with the secondary electron emission model to study the characteristics of micro-discharges driven by dual radio frequency (RF) power. The effect on plasma parameters was observed by varying the voltage of the RF power, the frequency, and the gas pressure of the discharge. Since the electrode spacing is very small in micro-discharges, the voltage change will affect the characteristics of micro-discharges. In addition, the plasma density increases with the frequency and the discharge mode changes at different frequencies. Finally, the influence of gas pressure on the characteristics of micro-discharges cannot be ignored. When the air pressure decreases, the ion flux reaching the electrodes is significantly increased, and the energy distribution of ions increases in the high-energy portion.

Plasma and Terahertz-Wave Propagation Characteristics in Atmospheric-Pressure Plasma Jet Under Different Operating Conditions

High-density plasma source device is of great significance for ground experiment verification of vehicle reentry communication. atmospheric-pressure plasma jet (APPJ), as a high-density plasma source, has received little attention in ground experiments on vehicle communications. In this article, terahertz (THz) wave propagation characteristics in APPJ are investigated by joint simulation of APPJ discharge and THz transport model and related experimental measurements. THz interferometer (THz-IF) system is used to diagnose the electron density and THz transmission characteristics of APPJ for the first time, and the measured results are in good agreement with the simulation results of a joint simulation model in this article and the measured results of THz time-domain spectroscopy (THz-TDS) system of other researchers. Sheath thickness and electron density produced by self-designed APPJ are highly matched with the plasma sheath environment of the HIFIRE-5b vehicle. Further analysis of the influence of different voltages and needle electrode radius on the THz transmission characteristics shows that the absorption effect plays a major role in THz-wave attenuation in APPJ, and the contribution of the collision effect almost disappears, which is completely consistent with the phenomenon observed in HIFIRE-5b vehicle. The joint simulation model and THZ-IF method developed in this article are of great significance for the ground test verification of reentry communication schemes.

Infl uence of self-discharge generator radiation on the growth of spirulina biomass

The article discusses the possibility of using the electromagnetic fi eld of a high-frequency plasma generator based on self-discharge to activate the processes of spirulina growth and metabolism during cultivation in deep culture. It is shown that the eff ect of this EMF on the spirulina biomass leads to the activation of metabolic processes, as a result of which an increase in the growth rate of the culture and the duration of its storage is observed. There is also an increase in the activity of synthesis of chlorophyll and a complex of biologically active substances with antioxidant activity.

Analysis of the efficiency of MHD cycle supported by nanosecond pulsed discharge pre-ionization

A numerical analysis of plasma generation by a nanosecond pulsed discharge in a strong magnetic field was performed. A 2D model of the plasma formation and decay in magnetohydrodynamic (MHD) channel has been elaborated. A comparison with experimental results demonstrates good agreement between calculated and measured plasma distribution in the channel. Preliminary analysis of the efficiency of the MHD-generator based on the nanosecond dielectric barrier discharge flow pre-ionization shows that the ratio of the power required to maintain ionization in the flow to the power extracted from the flow in MHD process is ∼3% for an ideal Faraday MHD generator with segmented electrodes with BY ∼ 5 T and supersonic flow speed uZ ∼ 1600 m s−1. Such a high energy efficiency of the generator allows us to consider this concept of the generator as promising for energy generation and flow control.

Electrical equivalent model of a long dielectric barrier discharge plasma jet for endoscopy

Cold atmospheric plasmas are a known source of reactive species enabling various treatments, from the healing of chronic wounds to the treatment of surface cancers. Therapeutic endoscopic procedures require developing specific flexible tools that can be used through or alongside endoscopes. Plasma devices for endoscopy have aroused significant research interest over the past few decades, but their electrical behaviour is not yet fully understood and predictable. There is thus a clear need for a robust model that provides a way to understand and optimize future devices. In this work, for the first time, an electrical equivalent model of a long plasma source (comprising plasma generation, transport and target interaction) was designed, implemented, and validated. System parameters were estimated based on the system geometry and independent measurements. The model reliably reproduces the double ignition (in the quartz chamber and at the treatment site) observed experimentally. Simulations globally agree with measurements taken for various gas gap distances and input voltages. Internal parameters that are difficult to measure, such as the electrical charge at the gas gaps, were inferred. The model can predict leakage current in the body and current at the target site. This work provides a new understanding of endoscopic plasma systems that could be used in the future to ensure patient and operator safety.

Study on the plasma characteristics in a needle-plate dielectric barrier discharge with a rotating dielectric plate

The enhancement of plasma generation in atmospheric pressure dielectric barrier discharge (DBD) is gaining increasing interest for various plasma applications. In this paper, the effect of surface charges moving with the rotating dielectric plate on improving the generation of streamer channels is investigated by a statistical analysis of electrical measurements, optical diagnostics, and numerical simulation in a needle-plate DBD device with a rotating dielectric plate. Results suggest that rotating the dielectric plate can improve the spatiotemporal distribution of streamer channels by inducing a bending of the streamer channels and an increase in the number of discharges. Statistical results show that the number of current pulse and discharge energy are increased by 20% and 47%, respectively, at the rotating speed of 160 rps (revolution per second). Based on the interaction between the applied electric field and the electric field induced by surface charges, a formula is proposed to govern the effect of rotating the dielectric plate on the discharge energy and streamer bending. To further understand the mechanism of the influence of rotating the dielectric plate on plasma properties, a 2D fluid model is implemented, and the reduced electric field and streamer propagation are analyzed. Results show that the effective transfer and reuse of surface charges play an important role in the enhancement of plasma generation.

Beneficial Effects of Dinitrosyl Iron Complexes on Wound Healing Compared to Commercial Nitric Oxide Plasma Generator.

Nitric oxide (NO) is a gaseous molecule which plays a key role in wound healing. Previously, we identified the optimal conditions for wound healing strategies using NO donors and an air plasma generator. The aim of this study was to compare the wound healing effects of binuclear dinitrosyl iron complexes with glutathione (B-DNIC-GSH) and NO-containing gas flow (NO-CGF) at their optimal NO doses (0.04 mmol for B-DNIC-GSH and 1.0 mmol for NO-CGF per 1 cm2) in a rat full-thickness wound model over a 3-week period. Excised wound tissues were studied by light and transmission electron microscopy and immunohistochemical, morphometrical and statistical methods. Both treatments had an identical stimulating impact on wound healing, which indicated a higher dosage effectiveness of B-DNIC-GSH compared to the NO-CGF. B-DNIC-GSH spray application reduced inflammation and promoted fibroblast proliferation, angiogenesis and the growth of granulation tissue during the first 4 days after injury. However, prolonged NO spray effects were mild compared to NO-CGF. Future studies should determine the optimal B-DNIC-GSH solution course for a more effective wound healing stimulation.

Plasma Expansion Characterization of a Vacuum Arc Thruster with Stereo Imaging

In order to support increasingly detailed simulation models in the field of plasma generation and expansion, more experimental data are needed to prove and verify these models. In addition to existing invasive probe methods and spectroscopy, optical diagnostics methods can be employed for this purpose. These can be used to obtain information about the transient behavior of the plasma plume itself. For this purpose, a pseudo stereo imaging system was assembled, which consisted of a biprism and one camera. The presented setup was used to observe the plasma plume expansion of a vacuum arc thruster and to detect how a magnetic nozzle changes the plume expansion behavior of the used thruster. For this, areas were calculated by means of contour detection from both view directions, and a 3D model was reconstructed by computing cross-sectional images. The results show that the magnetic nozzle provides a more uniform formation of the plasma plume, which can be seen by comparing the calculated areas from both directions of observation and is confirmed by the reconstructed 3D models. Thus, the used setup is suitable as an additional diagnostic tool in the future. Despite its simple design, it provides information about the spatial development of a plasma plume. It can serve as a fast and simple verification tool for simulation results, where otherwise complex tomographic setups and reconstructions would be necessary to obtain spatial information. Further measurements are recommended to improve and validate the recording and evaluation process.

Plasma Generated in Hydrodynamic Cavitation Bubbles for the Preparation of Plasma Activated Water

Objective: In recent years, the medical applications of plasma activated water (PAW) have attracted growing interest. PAW can be prepared using plasma generated by hydrodynamic cavitation bubbles (HCB). To facilitate this application, the current study was performed to investigate the efficiency of plasma generation in HCB. Methods: Based on the plasma generated in HCB, an experimental system has been constructed. We measured the characteristics of the cavitating flow, including pressure, temperature, and water flow rate, and estimated the system and cavitation power consumptions. High-speed images of cavitating flow were obtained to examine the evolution of the cavitation zone. Images of discharge emission at various velocities were captured to identify the location of electrodes. In addition, optical emission spectra were examined to determine the type of reactive species. H2O2 concentration and energy efficiency were measured and analyzed. Results: In this experiment, the system power consumption was 1.2W. The highest cavitation power consumption was 50.4W and increased with the elevation of throat velocities. The processing findings of high-speed images revealed that the cavitation characteristic length was essential for plasma generation and was necessary for establishing the location of electrodes. In addition, the UV-Vis emission spectra of the plasma discharge demonstrated that the hydroxyl radical ·OH was formed in situ and that cavitation increased the yield of ·OH. H2O2 was the principal active component of PAW. Plasma generated in HCB produced H2O2 with a high energy efficiency of 77.0mol/kWh. Conclusion: Plasma generated in HCB may provide a viable and cost-effective alternative method for PAW preparation.

Analysis of Plasma Reactor Interaction with the Power Grid Depending on the Power Supply Design

In this paper, the collaboration of a GlidArc-type plasma reactor with four dedicated power supplies was analysed. Each power supply is characterised by a different design solution. Plasma generation by electrical discharge requires a careful analysis of the power supply design, its operating characteristics, currents, voltages and frequencies. Although the power supplies tested have similar abilities and provide similar power supply parameters, different plasma reactor performance characteristics are obtained for each of them. The results indicate that some power supply parameters were overestimated or underestimated at the design stage. Some of the power supplies tested under plasma reactor load also show poor interaction with the mains. The interaction of the power supplies with the plasma reactor and the mains supply is strongly influenced by the type of plasma gas. Analyses indicate that an optimally designed power supply should combine the solutions contained in each of the power supplies tested.