Remediation of soil heavily polluted with polychlorinated biphenyls using a low-temperature plasma technique

Polychlorinated biphenyls （PCBs） were removed by low-temperature plasma technique （dielectric barrier discharge） from heavily polluted soil and their intermediate products were analyzed. The removal rate ranged from 40.1 to 84.6% by different treatments, and they were also influenced significantly （P 〈 0.01） by soil particle-size, electric power, gas flow rate and reaction time. The optimal reaction conditions of PCB removal from the soil were obtained experimentally when soil particle-size, electrical power, flow rate and reaction time were 5-10mm, 21w, 120mL. rain and 90rain, respectively. However, decreasing electrical power, flow rate and reaction time to 18 w, 60 mL. min- and 60 min respectively were also acceptable in view of the cost of remediation. This technique was characterized by the additional advantage of thorough oxidation of PCBs in the soil, with no formation of intermediate products after reaction. The technique therefore shows some promise for application in the remediation of soils contaminated with persistent organic pollutants in brown field sites in urban areas.

Detailed analysis and simulation verification for reconstruction of plasma optical boundary with spectrometric technique on HL-2M tokamak

The plasma optical boundary reconstruction technique based on Hommen's theory is promising for future tokamaks with high parameters. In this work, we conduct detailed analysis and simulation verification to estimate the ‘logic loophole' of this technique. The finite-width effect and unpredictable errors reduce the technique's reliability, which leads to this loophole. Based on imaging theory, the photos of a virtual camera are simulated by integrating the assumed luminous intensity of plasma. Based on Hommen's theory, the plasma optical boundary is reconstructed from the photos. Comparing the reconstructed boundary with the one assumed, the logic loophole and its two effects are quantitatively estimated. The finite-width effect is related to the equivalent thickness of the luminous layer, which is generally about 2-4 cm but sometimes larger. The level of unpredictable errors is around 0.65 cm. The technique based on Hommen's theory is generally reliable, but finite-width effect and unpredictable errors have to be taken into consideration in some scenarios. The parameters of HL-2M are applied in this work.

Experimental Research of Inactivation Effect of Low-Temperature Plasma on Bacteria

The killing logarithms index in killing a vegetative form in an explosure of about 90s and a spore in an explosure of about 120s, by using a low-temperature plasma produced by dielectric barrier discharge （DBD）, reached 5. The speed in killing the strains tested, by using a low-temperature plasma, was the highest with E. Coli, then S. Aureus and B. Subtilis var niger spore. The results of the scanning electron microscope showed that the low-temperature plasma destroyed the outer structure of the bacteria and that the vegetative form was more susceptible to the inactivation effect of the low-temperature plasma than was the spore. This indicated that the effects of the high voltage and high velocity particle flow, in plasma, penetrating through the outer structure of the bacteria might play a dominant role during the inactivation of the bacteria.

Surface Modification of Polyvinylidene Fluoride (PVDF) Membranes by Low-Temperature Plasma with Grafting Styrene

In order to control the surface pore sizes of polyvinylidene fluoride membranes and their distribution, low temperature plasma-induced grafting modifications of PVDF were studied to prepare hydrophobe membranes. By argon （Ar） treating and subsequent grafting reaction, a hydrophobe monomer, styrene, was introduced into the PVDF membrane. Fourier transform infrared attenuated total reflection （FTIR-ATR） was utilized to characterize the chemical and physical changes in the Ar plasma modified membrane. The surface modifications of PVDF membranes were investigated by using scanning electron microscopy （SEM）, atomic force microscopy （AFM） and differential scanning calorimeter （DSC）. The water permeability and the solute rejection were measured by PVDF membrane modified in different graft conditions. Results demonstrated that the pores in the modified membranes get smaller and the distribution of pores gets narrowed with the increase in grafting reaction duration. Longer graft time caused the water flux of PVDF membrane to decrease from 578 kg/（m^2· h） to 23 kg/（m^2· h） and the solute rejection to increase from 73% to 92%.

Enthalpy Probe Technique for Thermal Plasma Diagnostics

The measuring principle and experimental results of the enthalpy probe technique for thermal plasma diagnostics are presented. Its calibration and errors are discussed. Typical results are presented for the system operation in an Ar/H2(5 % H2) plasma arc jet under a reactor chamber pressure of 101.3 kPa. The plasma temperature and velocity profiles are measured. The center temperature and velocity are 6600 K and 850 m/s for plasma power 9 kW at axial location of 17 mm.

Low-temperature Plasma Promotes Fibroblast Proliferation in Wound Healing by ROS-activated NF-κB Signaling Pathway

Low-temperature plasma（LTP） has shown great promise in wound healing,although the underlying mechanism remains poorly understood.In the present study,an argon atmospheric pressure plasma jet was employed to treat L929 murine fibroblasts cultured in vitro and skin wounds in BALB/c mice.The in vitro analysis revealed that treatment of fibroblasts with LTP for 15 s resulted in a significant increase in cell proliferation,secretion of epidermal growth factor（EGF） and transforming growth factor-β1（TGF-β1）,production of intracellular reactive oxygen species（ROS）,and the percentage of cells in S phase,protein expression of phosphorylated p65（P-p65） and cyclin D1,but a noted decrease in the protein expression of inhibitor kappa B（IκB）.The in vivo experiments demonstrated that 30-s LTP treatment enhanced the number of fibroblasts and the ability of collagen synthesis,while 50-s treatment led to the opposite outcomes.These results suggested that LTP treatment promotes the fibroblast proliferation in wound healing by inducing the generation of ROS,upregulating the expression of P-p65,downregulating the expression of IκB,and activating the NF-κB signaling pathway and consequently altering cell cycle progression（increased DNA synthesis in S phage）.

Bacteria Adherence Properties of Nitrided Layer on Ti6Al4V by the Plasma Nitriding Technique

The nitrided layer on Ti6A14V substrate was prepared by the plasma nitriding technique. The sample was characterized by X-ray diffraction （XRD）, glow discharge optical emission spectroscopy （GDOES）, X-ray photoelectron spectroscopy （XPS）, and rough-meter. X- ray diffraction analysis reveals that TiN, Ti2N and Ti phase exist in the nitrided layer subsurface. GDOES analysis shows the thickness of the nitrided layer is about 3 ~tm. XPS analysis shows that there is higher N, lower A1 and lower V in the nitrided layer surface than in the Ti6A14V surface. Rough-meter analysis results show the roughness of the nitrided layer is greater than that of Ti6A14V alloy base. The bacteria adherence property of the nitrided layer on Ti6A14V substrate on the Streptococcus mutans was investigated and compared with that of Ti6A14V alloy by fluorescence microscope. It shows that the nitrided layer inhibits the bacteria adherence.

Sensitivity of two drug-resistant bacteria to low-temperature air plasma in catheterassociated urinary tract infections under different environments

The high incidence of catheter-associated urinary tract infections,which are dominated by drugresistant bacteria,has attracted an increasing number of researchers interested in solving this public health problem.The purpose of this study was to explore the killing effect of lowtemperature air plasma(LTAP)on extended-spectrum beta-lactamase-producing Escherichia coli and high level gentamycin resistance enterococci under two simulated environments in vitro.The results showed that the survival rate of these two kinds of bacteria decreased to less than20%after being treated by LTAP in different environments for 5 min.A comparison of the LTAP treatments showed that the killing efficacy of the two kinds of bacteria in the early stage(0-1 min)was up to 50%.Moreover,the results of transmission electron microscopy,reactive nitrogen species measurement,and a temperature test indicated that the bactericidal effect of the LTAP treatment on the two kinds of bacteria worked through the destruction of the ribosome and other organelles inside the bacteria,rather than the thermal effect,to achieve sterilization.

Destruction of Gaseous Styrene with a Low-Temperature Plasma Induced by a Tubular Multilayer Dielectric Barrier Discharge

The destruction of gaseous styrene was studied using a low-temperature plasma induced by tubular multilayer dielectric barrier discharge（DBD）.The results indicate that the applied voltage,gas flow rate,inlet styrene concentration and reactor configuration play important roles in styrene removal efficiency （ηstyrene） and energy yield（EY）.Values of ηstyrene and EY reached 96%and 15567 mg/kWh when the applied voltage,gas flow rate,inlet styrene concentration and layers of quartz tubes were set at 10.8 kV,5.0 m/s,229 mg/m^3 and 5 layers,respectively.A qualitative analysis of the byproducts and a detailed discussion of the reaction mechanism are also presented.The results could facilitate industrial applications of the new DBD reactor for waste gas treatment.

Remove of Phenolic Compounds in Water by Low-Temperature Plasma: A Review of Current Research

Phenolic compounds have very strong toxicity, so it has been paid sharply attention to find an effective way of controlling the wastewater containing phenolic compounds. The work on this subject done by domestic and overseas scholars is studied in this paper, and the progress of researches on low-temperature plasma treatment is summarized through the electrical discharge types, mechanism, kinetics of phenolic compounds decomposition and combination of several methods with low-temperature plasma treatment. In addition, the crucial problem and the developing tendency on low-temperature plasma treatment for phenol-bearing wastewater are briefly discussed.

Anti-oxidation characteristics of Cr-coating on surface of Ti-45Al-8.5Nb alloy by plasma surface metallurgy technique

TiAl-based alloys have received extensive attention recently due to their excellent properties. However, the weak oxidation resistance at temperatures higher than 800℃ can limit their further high-temperature structural applications.To improve the oxidation resistance of a high-Nb-content γ-TiAl alloy(Ti-45 Al-8.5 Nb, in units of at.%), a chromium(Cr)coating is prepared by using the plasma surface alloying technique, separately, at 800℃ and 1000℃. The x-ray diffraction(XRD) patterns reveal that an oxide surface layer consisting of Cr2O3, Al2O3, and TiO2 is produced on the Cr-coated Nb containing γ-TiAl substrates during the initial oxidation. However, the Cr2O3 is dominated in the oxide surface layer after being isothermally oxidized for 300 h. The oxidation kinetic curves are composed of a parabolic law stage(≤ 90 h) and a biquadratic law stage(≥ 90 h), fit by weight–gain curves. Due to diffusion in the fabrication process and oxidation process,the Cr-coated specimens have an adhesion force after being isothermally oxidized, specifically 69 N for a specimen after oxidation for 300 h. These results demonstrate that the Cr coating enhances the oxidation resistance and adhesion of a Ti-45 Al-8.5 Nb alloy, which may provide a new feasible scheme for designing oxidation protection layers.

Evaluation of the intraoperative trauma degree and postoperative speech function of low-temperature plasma radiofrequency surgery treatment of children with OSAHS

Objective:To evaluate the intraoperative trauma degree and postoperative speech function of low-temperature plasma radiofrequency surgery treatment of children with obstructive sleep apnea hypopnea syndrome (OSAHS).Methods: A total of 118 children with OSAHS were divided into the control group (n=59) who received general surgery and the observation group (n=59) who received the low-temperature plasma radiofrequency surgery according to the random number table. Before operation and 24 h after operation, serum levels of stress hormones, acute phase proteins and inflammatory markers of two groups of children were determined, and the speech function parameter levels were assessed.Results:Before operation, differences in serum contents of stress hormones, acute phase proteins and inflammatory factors as well as speech function parameter levels were not statistically significant between two groups of patients. 24 h after operation, serum stress hormones adrenocorticotropic hormone (ACTH), angiotensin-2 (Ang-2), norepinephrine (NE), cortisol (Cor) contents of observation group were lower than those of control group, serum acute phase proteins haptoglobin (HP), ceruloplasmin (CER), and prealbumin (PA) contents were lower than those of control group, and serum inflammatory factors interleukin-1 (IL-1), interleukin-4 (IL-4), interleukin-27 (IL-27), tumor necrosis factorα(TNF-α) contents were lower than those of control group;speech function parameters NNE and NHR levels of observation group were higher than those of control group.Conclusion:Compared with routine surgery, low-temperature plasma radiofrequency surgery treatment of children with OSAHS causes less surgical trauma and more greatly improves the postoperative speech level.

Design and characteristics investigation of a miniature low-temperature plasma spark discharge device

Atmospheric pressure low-temperature plasma is a promising tool in biomedicine applications including blood coagulation,bacterial inactivation,sterilization,and cancer treatment,due to its high chemical activity and limited thermal damage.It is of great importance to develop portable plasma sources that are safe to human touch and suitable for outdoor and household operation.In this work,a portable and rechargeable low-temperature plasma spark discharge device(130 mm×80 mm×35 mm,300 g)was designed.The discharge frequency and plume length were optimized by the selection of resistance,capacitance,electrode gap,and ground electrode aperture.Results show that the spark plasma plume is generated with a length of 12 mm and a frequency of 10 Hz at a capacitance of 0.33μF.resistance of 1 MΩ,electrode gap of 2 mm,and ground electrode aperture of 1.5 mm.Biological tests indicate that the plasma produced by this device contains abundant reactive species,which can be applied in plasma biomedicine,including daily sterilization and wound healing.

Continuous Emission Spectrum Measurement for Electron Temperature Determination in Low-Temperature Collisional Plasmas

Continuous emission spectrum measurement is applied for the inconvenient diagnos- tics of low-temperature collisional plasmas. According to the physical mechanism of continuous emission, a simplified model is presented to analyze the spectrum in low temperature plasma. The validity of this model is discussed in a wide range of discharge parameters, including electron tem- perature and ionization degree. Through the simplified model, the continuous emission spectrum in a collisional argon internal inductively coupled plasma is experimentally measured to determine the electron temperature distribution for different gas pressures and radio-frequency powers. The inverse Abel transform is also applied for a better spatially resoluted results. Meanwhile, the result of the continuous emission spectrum measurement is compared to that of the electrostatic double probes, which indicates the effectiveness of this method.

Ti Coating on Magnesium Alloy by Arc-Added Glow Discharge Plasma Penetrating Technique

Arc-added glow discharge plasma penetrating technique is a new surface coating method. With the help of vacuum arc discharge, a cold cathode arc source continually emits ion beams of coating elements with high currency density and high ionizing ratio. As the ion bombard and diffusion working on, the surface of the parts form deposited layer, penetrated layer and hybrid layer. Under lab condition, a commercial magnesium alloy Az91 had been coated with Ti film layer with the aim of improving its’ anti-corrosion performance. This paper mainly summarized our studies on the testing and analyzing of the coating layer. The composition and microstructure of the coating layer had been analyzed by means of X-ray diffraction (XRD) and glow discharge spectrum (GDS), and the surface appearance had been surveyed by scanning electronic microscope (SEM). The adhesion strength between film and matrix had been evaluated by experiments of sticking-tearing. The results indicated that the coated layer on magnesium alloy were homogeneous, dense and robustly adhered.

The Feasibility of Applying AC Driven Low-Temperature Plasma for Multi-Cycle Detonation Initiation

Ignition is a key system in pulse detonation engines （PDE）. As advanced ignition methods, nanosecond pulse discharge low-temperature plasma ignition is used in some combustion systems, and continuous alternating current （AC） driven low-temperature plasma using dielectric barrier discharge （DBD） is used for the combustion assistant. However, continuous AC driven plasmas cannot be used for ignition in pulse detonation engines. In this paper, experimental and numerical studies of pneumatic valve PDE using an AC driven low-temperature plasma igniter were described. The pneumatic valve was jointly designed with the low-temperature plasma igniter, and the numerical simulation of the cold-state flow field in the pneumatic valve showed that a complex flow in the discharge area, along with low speed, was beneficial for successful ignition. In the experiments ethylene was used as the fuel and air as oxidizing agent, ignition by an AC driven low-temperature plasma achieved multi-cycle intermittent detonation combustion on a PDE, the working frequency of the PDE reached 15 Hz and the peak pressure of the detonation wave was approximately 2.0 MPa. The experimental verifications of the feasibility in PDE ignition expanded the application field of AC driven low-temperature plasma.

Interaction of supersonic molecular beam with low-temperature plasma

The interaction between the supersonic molecular beam(SMB)and the low-temperature plasma is a critical issue for the diagnosis and fueling in the Tokamak device.In this work,the interaction process between the argon SMB and the argon plasma is studied by a high-speed camera based on the Linear Experimental Advanced Device(LEAD)in Southwestern Institute of Physics,China.It is found that the high-density SMB can extinct the plasma temporarily and change the distribution of the plasma density significantly,while the low-density SMB can hardly affect the distribution of plasma density.This can be used as an effective diagnostic technique to study the evolution of plasma density in the interaction between the SMB and plasma.Moreover,the related simulation based on this experiment is carried out to better understand the evolution of electron density and ion density in the interaction.The simulation results can be used to analyze and explain the experimental results well.

Plasma-assisted surface treatment for low-temperature annealed ohmic contact on AlGaN/GaN heterostructure field-effect transistors

In this study, a low-temperature annealed ohmic contact process was proposed on AlGaN/GaN heterostructure field effect transistors （HFETs） with the assistance of inductively coupled plasma （ICP） surface treatment. The effect of ICP treatment process on the 2DEG channel as well as the formation mechanism of the low annealing temperature ohmic contact was investigated. An appropriate residual AlGaN thickness and a plasma-induced damage are considered to contribute to the low-temperature annealed ohmic contact. By using a single Al layer to replace the conventional Ti/Al stacks, ohmic contact with a contact resistance of 0.35 Ω.mm was obtained when annealed at 575 ℃ for 3 min. Good ohmic contact was also obtained by annealing at 500 ℃ for 20 rain.

Application of persulfate in low-temperature atmospheric-pressure plasma jet for enhanced treatment of onychomycosis

Fungal infection of human nails,or onychomycosis,affects 10%of the world's adult population,but current therapies have various drawbacks.In this work,we employed a self-made low-temperature plasma(LTP)device,namely,an atmospheric-pressure plasma jet(APPJ)device to treat the nails infected with Trichophyton rubrum(T.rubrum)with the aid of persulfate solution.We found that persulfate solution had a promoting effect on plasma treatment of onychomycosis.With addition of sodium persulfate,the APPJ therapy could cure onychomycosis after several times of treatment.As such,this work has demonstrated a novel and effective approach which makes good use of LTP technique in the treatment of onychomycosis.

Progress of International Low-Temperature Plasma Research──Overview of the 15th International Symposium on Plasma Chemistry

International Symposium on Plasma Chemistry (ISPC) is the most influencial in- ternational symposium on science and technology research of low-temperature plasma, especially in the fields related to materials processing. People can be rightly informed of the current devel- oping trend of this field from the contents of these symposia. This paper will introduce briefly a general overview of the 15th ISPC. As viewed from the number of papers and their contents, there is still abundant research on thermal plasma, and the needs fOr micro-electronic technology and high performance films have driven forward continuous and intensive development of the research on low-pressure, non-equilibrium plasmas, while the research on normal pressure, non-equilibrium plasma has become a new highlight in this field.