Search

To evaluate the effectiveness and safety of low-temperature plasma radiofrequency ablation (coblation) and Nd:YAG laser in treating recurrent nasolacrimal duct obstruction. A prospective study was performed on patients who agreed to be treated with coblation or Nd:YAG laser for recurrent nasolacrimal duct obstruction after failed lacrimal Nd:YAG laser combined with silicone intubation. The visual analogue scale (VAS) pain grade was assessed at baseline, immediately, and 3 and 7 days after surgery. The degree of watering, lacrimal passage irrigation, and complications were also evaluated 1 week and 1, 3, and 6 months after surgery. Ninety-five patients who met the criteria for recurrent nasolacrimal duct obstruction from February 2018 to February 2019 were included in this study, with 46 patients receiving coblation and 49 patients Nd:YAG laser. The intraoperative and postoperative (3 days after surgery) VAS pain grades of the patients who received coblation were significantly lower than those who received Nd:YAG laser (P < 0.001). The number of patients in the coblation group who achieved complete clinical relief (no epiphora symptoms with fluent lacrimal passage irrigation) was significantly larger than that in the lacrimal Nd:YAG laser group at 1, 3, and 6 months after surgery (P = 0.033, P = 0.006, P = 0.003, respectively). During the follow-up period, there were no unexpected complications in either group. Compared with Nd:YAG laser, coblation performed well in alleviating pain and maintaining sustained disease relief and may therefore be an alternative to conventional laser or dacryocystorhinostomy surgery in the management of recurrent nasolacrimal duct obstruction. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore the treatment effects of two surgical procedures, performed with nasal endoscopy, on treating adenoidal hypertrophy in children. A total of 100 children diagnosed with adenoidal hypertrophy were treated with curettage combined with microwave thermocoagulation and with low-temperature plasma radiofrequency ablation under nasal endoscopic guidance; 6 months after surgery, the effects on snoring, nasal congestion, hearing loss, and gland residue were retrospectively analyzed. Differences in snoring and hearing loss between the two groups were not statistically significant (P > 0.05), but the differences in nasal congestion and gland residue between the two groups were statistically significant (P < 0.05); the therapeutic effect was superior in the low-temperature plasma radiofrequency ablation group than in the curettage combined with microwave thermocoagulation group. Low-temperature plasma radiofrequency ablation with nasal endoscopy can achieve a better comprehensive effect on treating adenoidal hypertrophy in children than curettage combined with microwave thermocoagulation. [ABSTRACT FROM AUTHOR]

Highlights • Nonpolar InN films were grown by RF plasma-assisted evaporation technique. • The nonpolar InN films with uniform and smooth morphologies can be obtained. • New approach provides a low-cost route and have been rarely reported for the growth of InN films. Abstract Nonpolar InN nanocrystal films were grown by RF plasma-assisted evaporation technique on bare Si and quartz substrates, simultaneously. The as-grown InN films were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The synergistic cooperation among the evaporation temperature, chamber pressure and substrate temperature is critical for the formation of nonpolar InN films. The absence of the (0 0 2) peak in the X-ray diffraction patterns indicates that as-grown InN films grew preferentially along the nonpolar plane. In addition, the InN films grown on Si and quartz substrates exhibit different crystallinity, morphology and stress. The In-rich growth condition can be responsible for the formation of nonpolar InN films. [ABSTRACT FROM AUTHOR]

Objective: To investigate the curative effect of plasma radiofrequency catheter ablation on adenoid hypertrophy in children and its effect on ventilatory function and inflammatory response. Methods: 100 cases of adenoid hypertrophy in our hospital from December 2016 to August 2017 were selected, 50 cases patienta treated with surgical treatment was in plasma group, and 50 patients treated with conservative treatment were in control group in the same period. The control group was given montelukast and Mumetasone furfurfurate nasal spray, and the plasma group was given low temperature plasma radiofrequency ablation. The symptom score, ventilation function and inflammatory cytokines levels in two groups before and after treatment were compared. Results: Before treatment, symptom score, apnea hypopnea index (АШ), longest apnea time (LAT), oxygen reduction index (ODI), minimum nocturnal oximetry Lowest nocturnal oxygen saturation (LSa02), percentage of time when oxygen saturation less than 90% (SLT 90%), and serum inflammatory mediators (TNF-a), interleukin-4 (IL-4) and eosinophil cationic protein (ECP) levels were not significantly different between the two groups (P>0.05). After treatment, the scores of snoring, nasal obstruction and mouth breathing were significantly decreased in both groups (P<0.05), and the scores of snoring, nasal obstruction and mouth breathing in plasma group were significantly lower than those in control group (P<0.05). After treatment, the levels of АШ, LAT, ODI and SLT90 % in both groups were significantly decreased (P<0.05), and the LSa02 level was significantly increased (P<0.05). After treatment, the levels of АШ, LAT, ODI, SLT90 % in the plasma group were significantly lower than those in the control group (P<0.05), and the LSa02 level was significantly higher than the control group (P<0.05). Conclusion: Low-temperature plasma radiofrequency ablation can significantly relieve the clinical symptoms of children, improve the body's ventilatory function and reduce the inflammatory response. [ABSTRACT FROM AUTHOR]

In order to meet the heating requirement of EAST tokamak, ion cyclotron range of frequency (ICRF) heating is utilized as one of the main auxiliary heating methods, which plays an important role in coupling radio frequency (RF) power into the plasma. As a member of plasma facing components, ICRF antenna suffers the plasma radiation as well which is one of the causes of the thermal load on the antenna. Plasma radiation and RF thermal load during the operation of ICRF and thermal load caused by HALO current during vertical displacement event will contribute together to a huge thermal load on the surface of the antenna and consequently the structural stability and reliability of ICRF antenna will be affected. Therefore, cooling channels is needed to remove heat on the ICRF antenna. In this paper, cooling channels for straps of ICRF antenna are designed based on the thermal load on the antenna, and thermal-structural analysis of straps with cooling channels is also carried out by the finite-element method. [ABSTRACT FROM AUTHOR]

Power supplies have played crucial role to improve and extend plasma applications. Several dc, pulsed, and radio frequency (RF) stabilized power supplies have been developed over a wide range of frequencies and voltage waveforms. However, the influence of voltage waveform on the plasma densification, mainly due to the secondary electrons emission from the electrodes, has not been quite explored. This paper proposes an asymmetric pulsed bipolar power supply, adjustable in frequency, amplitude, pulsewidth, and number of pulses for generation of cold plasmas. Short period positive pulses, between longer negative pulses, increase greatly the secondary electron emission from the electrodes and, consequently, the plasma ionization rate. Short pulses (ns) are obtained by the phase shift between each carrier, and the high-intensity pulses are obtained by cascading the cell submodules in a half-bridge cascade topology, using a modular half-bridge converter configuration. The intensity of the positive and negative pulses can be varied independently. There is no unintended dc voltage level between the electrodes, which appear in RF plasmas. The plasma generated in this way is free of electric arc and can be kept stable within a broader range of operating parameters, mainly the voltage and the working gas pressure. [ABSTRACT FROM AUTHOR]

This paper reports the levitation of micro-organisms in the sheath of radio-frequency (RF) plasma. Based on simple force-balance calculations, the required electric field for the levitation of micro-organisms has been estimated. It is predicted that micro-organisms could levitate at the periphery of the sheath. Experimental results demonstrate the levitation of two species of bacillus micro-organisms Escherichia coli (E. coli) and Klebsiella pneumoniae in an RF plasma. The almost monodiverse Klebsiella pneumoniae levitating in the RF plasma formed an ordered state similar to a 2-D Coulomb crystal. Diverse E. coli particles demonstrate the tendency that the levitating height of micro-organisms decreases as the radius of particles increases. Levitating micro-organisms in plasmas can be referred as dusty plasmas. [ABSTRACT FROM AUTHOR]

A new method of measuring the charge of a single dust particle, which is used in a stratified glow discharge of small currents and pressures, is proposed. In this method, the vibrational characteristics of the dust particle trapped in a standing striation arising under the modulation of the discharge current are used for dust particle charge determination. The measured value of the charge is compared with theoretical estimates and literature data for glow discharge conditions. [ABSTRACT FROM AUTHOR]

Wood-plastic composites (WPC) are widely used for many purposes due to their interesting properties, but they have poor surface adhesion due to the chemical inertness of the matrix. Thus, in this work, the effect of plasma treatment on the WPC was investigated regarding its influence in the aluminum oxide (Al2O3) nanoparticles attachment to the surface. WPC were prepared in a polypropylene (PP) matrix, plasma-treated at 100 W for 600 s, and then covered with Al2O3 nanoparticles dispersion. TheWPC/Al2O3 surfaces have been investigated by means of morphology, surface roughness, chemical structure, wettability, and nanohardness. Plasma treatment improved the attachment of Al2O3 onto WPC, which was confirmed by the higher presence of aluminum and oxygen-containing functional groups and the reduction of the intensity of peaks of methylene (CH2) and methyl (CH3) groups on the WPC surface. The higher surface reactivity of plasma-treated WPC resulted in a better distribution of the nanoparticles over the entire surface. In addition, plasma treatment avoided the formation of coffee-ring phenomenon but it was able to create cone-like structures on theWPC, increasing the surface roughness due to the etching effect and the attachment of Al2O3 nanoparticles. Plasma treatment followed by Al2O3 nanoparticles attachment increased the wettability, hardness, and elastic modulus of WPC at nanometric scale. [ABSTRACT FROM AUTHOR]

In this paper, using the optical emission spectroscopy technique, a comparative study is performed on the argon excitation and nitrogen vibrational temperatures in the plasma discharge medium of a manufactured RF plasma jet. The argon contribution in the Ar/N2 mixture is varied from 70% to 98% and the obtained optical emission spectra from argon and molecular nitrogen are analyzed. The highest emission intensities of neutral argon (Ar I) are recorded in the wavelength range of 790-850 nm. It is seen that, at the higher argon percentages in the mixture, the emission intensity from all the formed species in the plasma discharge medium of the RF plasma jet will increase. In addition, at the lower Ar contributions in the mixture, both the argon excitation and nitrogen vibrational temperatures are higher. Furthermore, it is shown that, at the higher Ar percentages in the mixture, both of the electronic temperatures are decreased. [ABSTRACT FROM AUTHOR]

The surface properties of poly-3-hydroxybutyrate (P3HB) membranes were modified using oxygen and an ammonia radio-frequency (RF, 13.56 MHz) plasma. The plasma treatment procedures used in the study only affected the surface properties, including surface topography, without inducing any significant changes in the crystalline structure of the polymer, with the exception being a power level of 250 W. The wettability of the modified P3HB surfaces was significantly increased after the plasma treatment, irrespective of the treatment procedure used. It was revealed that both surface chemistry and surface roughness changes caused by the plasma treatment affected surface wettability. A treatment-induced surface aging effect was observed and resulted in an increase in the water contact angle and a decrease in the surface free energy. However, the difference in the water contact angle between the polymers that had been treated for 4 weeks and the untreated polymer surfaces was still significant. A dependence between cell adhesion and proliferation and the polar component of the surface energy was revealed. The increase in the polar component after the ammonia plasma modification significantly increased cell adhesion and proliferation on biodegradable polymer surfaces compared to the untreated P3HB and the P3HB modified using an oxygen plasma. [ABSTRACT FROM AUTHOR]

Yttria stabilized zirconia thin films have been deposited by RF plasma enhanced MOCVD technique on silicon substrates at substrate temperature of 400 °C. Plasma of precursor vapors of (2,7,7-trimethyl-3,5-octanedionate) yttrium (known as Y(tod) 3 ), (2,7,7-trimethyl-3,5-octanedionate) zirconium (known as Zr(tod) 4 ), oxygen and argon gases is used for deposition. To the best of our knowledge, plasma assisted MOCVD of YSZ films using octanediaonate precursors have not been reported in the literature so far. The deposited films have been characterized by GIXRD, FTIR, XPS, FESEM, AFM, XANES, EXAFS, EDAX and spectroscopic ellipsometry. Thickness of the films has been measured by stylus profilometer while tribological property measurement has been done to study mechanical behavior of the coatings. Characterization by different techniques indicates that properties of the films are dependent on the yttria content as well as on the structure of the films. [ABSTRACT FROM AUTHOR]

Titanium nitrides have good tribo-mechanical and biomedical properties. They are employed to harden and protect cutting and sliding surfaces for industrial purpose and as a non-toxic outer-surface for bio-medical applications. In this study, pure titanium was nitrided using RF plasma technique. The microstructural, mechanical, tribological, electrochemical and biomedical properties of nitrided titanium were investigated. The X-ray diffraction demonstrates the formation of ε-Ti 2 N and the cubic δ-TiN phases after plasma nitriding. The microhardness of the nitride samples increases as the plasma-processing power increases up to 1300 HV 0.1 . That represents approximately 7-fold increment in the microhardness in comparison with the untreated titanium. High nitriding rate of 0.17 μm 2 /s was recorded for the sample that was treated at 650 W. The wear and corrosion resistance are improved after plasma nitriding. Moreover, the friction coefficient is reduced from nearly 0.75 for the untreated titanium to 0.25 for the nitride one. An enhancement in the biocompatibility of the nitrided titanium has been achieved. The number of grown mesenchymal stem cells was higher for nitrided substrates compared to that of the untreated titanium. The improved tribo-mechanical and electrochemical performance of the nitrided titanium can be attributed to the formation of super-hard titanium nitrided phases. [ABSTRACT FROM AUTHOR]

A set of discharges performed with the JET ITER-like wall is investigated with respect to control capabilities on tungsten sources and transport. In attached divertor regimes, increasing fueling by gas puff results in higher divertor recycling ion flux, lower divertor tungsten source, higher ELM frequency and lower core plasma radiation, dominated by tungsten ions. Both pedestal flushing by ELMs and divertor screening (including redeposition) are possibly responsible. For specific scenarios, kicks in plasma vertical position can be employed to increase the ELM frequency, which results in slightly lower core radiation. The application of ion cyclotron radio frequency heating at the very center of the plasma is efficient to increase the core electron temperature gradient and flatten electron density profile, resulting in a significantly lower central tungsten peaking. Beryllium evaporation in the main chamber did not reduce the local divertor tungsten source whereas core radiation was reduced by approximately 50%. [ABSTRACT FROM AUTHOR]

Poly( o-toluidine) (POT) polymer was synthesized by chemical methods and RF plasma polymerization at a radio frequency (RF) power input of 15 W on ultrasonically cleaned glass and silicon wafer substrates. These samples were characterized by DC conductivity measurements, UV-visible, XRD and FTIR techniques. The DC-conductivity was measured at 410 K, which was found to increase by two orders of magnitude for thin film as compared to pellet samples. It has been observed that the activation energy increases for RF plasma-polymerized POT. Transmission and reflectance spectra were studied for measuring optical constants like absorption coefficient ( α), extinction coefficient ( K), optical band gap ( E), Urbach energy ( E), and refractive index ( n). From XRD studies, one can infer that the samples grown by both the methods are amorphous in nature. The results indicate that the structures of plasma-polymerized POT are rather different from polymers synthesized by conventional chemical methods, due to a higher degree of cross-linking and branching reactions in plasma polymerization. This makes them suitable for various electroactive devices. A higher and more stable conductivity can be obtained with RF plasma-polymerized POT which is much smoother and more uniform. [ABSTRACT FROM AUTHOR]

Surface modification of polylactic acid (PLLA) by plasma of radio-frequency magnetron discharge with hydroxyapatite target sputtering was investigated. Increased biocompatibility was demonstrated using studies with bone marrow multipotent mesenchymal stromal cells. Atomic force microscopy demonstrates that the plasma treatment modifies the surface morphology of PLLA to produce rougher surface. Infrared spectroscopy and X-ray diffraction revealed that changes in the surface morphology are caused by the processes of PLLA crystallization. Fluorescent X-ray spectroscopy showed that the plasma treatment also changes the chemical composition of PLLA, enriching it with ions of the sputtered target: calcium, phosphorus and oxygen. It is hypothesized that these surface modifications increase biocompatibility of PLLA without increasing toxicity. [ABSTRACT FROM AUTHOR]

Plasma polymerization of aniline is carried out by means of continuous RF and pulsed DC glow discharge plasma in a common reactor at different applied powers. The discharge control variables are optimized for good quality film growth and the role of fragmentation of the molecular structure on the structural, optical, morphological and optophysical properties of the deposited plasma polymerized aniline (PPAni) layers is investigated. Retention of the conjugated structure is found to be prominent at optimum applied power to the plasma in both the continuous RF and pulsed DC polymerization techniques. Improvement in conjugated structure and chain length have been observed in both the continuous RF and pulse DC PPAni thin films with the increase in applied power to the plasma up to a certain limit of applied power when working pressure is fixed at 0.15 mbar. A decrease in optical bandgap with the increase in applied power to the plasma is observed in both the pulsed DC and RF PPAni thin films, but it is more significant in case of RF PPAni films. The plasma polymerized aniline thin films are found to emit photoluminescence due to band to band transition and defects generated in the structure. [ABSTRACT FROM AUTHOR]

In the present RF-driven plasma with a lot of high-energy electrons, there may be anisotropic plasma pressure, which makes the usual equilibrium analysis difficult, but the Cauchy condition surface method can reconstruct the plasma shape precisely regardless of the anisotropy. In addition, the plasma current effect in the open magnetic surfaces outside of the closed magnetic surfaces is considered in the RF-driven divertor plasma. In the reconstruction process, singular value (SV) decomposition is used and optimal criterion function for generalized cross validation is estimated concerning truncation or reduction of the small-SV components. [ABSTRACT FROM PUBLISHER]

The beam power produced by the negative ion source for the production of ion of deuterium extracted from RF plasma is mainly absorbed by the beam dump component which has been designed also for measuring the temperatures on the dumping panels for beam diagnostics. A finite element code has been developed to characterize, by thermo-hydraulic analysis, the sensitivity of the beam dump to the different beam parameters. The results prove the capability of diagnosing the beam divergence and the horizontal misalignment, while the entity of the halo fraction appears hardly detectable without considering the other foreseen diagnostics like tomography and beam emission spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: We report the robust technique allowing manufacturing of superhydrophobic and oleophobic (omniphobic) surfaces with industrial grade low density polyethylene. The reported process includes two stages: (1) hot embossing of polyethylene with micro-scaled steel gauzes; (2) treatment of embossed surfaces with cold radiofrequency plasma of tetrafluoromethane. The reported surfaces demonstrate not only pronounced superhydrophobicity but also superoleophobicity. Superoleophobicity results from the hierarchical nano-scaled topography of fluorinated polyethylene surface. The observed superoleophobicity is strengthened by the hydrophobic recovery. The stability of the Cassie wetting regime was studied. [Copyright &y& Elsevier]

A triode magnetron injection gun (MIG) is designed for a 1-MW 170-GHz gyrotron, which will be used in an electron cyclotron resonance heating system for the International Thermonuclear Experimental Reactor. The initial design of MIG is performed by using the in-house code MIGSYN. For the electron-beam emission and propagation, the 2-D code EGUN is implemented. The transverse-to-axial velocity ratio α is 1.37, and the transverse velocity spread less than 4% is realized. The results are also validated against two other 2-D and 3-D codes, i.e., TRAK and CST-Particle Studio, respectively, which are in close agreement. From the fabrication and operation point of view, the parametric analysis and misalignment study of electron beam are also performed. [ABSTRACT FROM PUBLISHER]

The annealed low alloy 4140 steel samples have been nitrided for different treatment periods (1-6 h) in an RF inductive plasma discharge with very low bias voltage (≈400 V). The resulting nitrided layer has been observed by means of an optical microscope whereas the nitride phases have been characterised by X-ray analysis. The corrosion response, assessed by the potentiodynamic tests in the 3.5% NaCl solution, presents both higher noble potential values and lower corrosion rates when compared with the untreated sample. The Vickers microhardness tests values show an appreciable increment compared to that of the untreated sample. The process is characterized by a high overall e  ciency because similar average Vickers tests values were obtained, no matter for how long the treatment was extended. Likewise, the scanning electron micrographs confirmed no appreciable size evolution of the compound layer microstructure at different times of treatment. [ABSTRACT FROM AUTHOR]

Blob transport properties in the plasma edge in the presence and absence of radio-frequency (RF) convective cells are compared. For the first time, the interactions between RF convective cells and intermittent plasma blobs in the scrape-off layer (SOL) are observed with gas puff imaging in the ASDEX Upgrade tokamak. It is found that the RF convective cells induce a sheared flow in the far SOL, which is able to stretch, distort and even split the blobs poloidally. The observed phenomena indicate that an externally generated sheared flow in the SOL can be considered as a method to modify blob transport in a favorable way. [ABSTRACT FROM AUTHOR]

Abstract: Inductively coupled RF plasmas (ICP) in oxygen at low pressure have been intensively studied as a molecular and electronegative model system in the last funding period of the Collaborative Research Centre 24 “Fundamentals of Complex Plasmas”. The ICP configuration consists of a planar coil inside a quartz cylinder as dielectric barrier which is immersed in a large stainless steel vacuum chamber. In particular, the E-H mode transition has been investigated, combining experimental results from comprehensive plasma diagnostics as input for analytical rate equation calculation of a volume averaged global model. The averaged density was determined for electrons, negative ions O−, molecular oxygen ground state O2(X3Σg−) and singlet metastable state O2(a1∆g) from line-integrated measurements using 160 GHz Gaussian beam microwave interferometry coupled with laser photodetachment experiment and VUV absorption spectroscopy, respectively. Taking into account the relevant elementary processes and rate coefficients from literature together with the measured temperatures and averaged density of electrons, O2(X3Σg−) and O2(a1∆g) the steady state density was calculated for O(3P), O2(b1Σg+), O(1D), O(1S), O3, O−, O2−, and O3−, respectively. The averaged density of negative ions O− from the rate equation calculation is compared with the measured one. The normalized source and loss rates are discussed for O(3P), O2(b1Σg+) and O−. Graphical abstract: [ABSTRACT FROM AUTHOR]

We report an experimental observation of the coupling of the transverse vertical and longitudinal in-plane dust-lattice wave modes in a two-dimensional complex plasma crystal in the absence of mode crossing. A new large-diameter rf plasma chamber was used to suspend the plasma crystal. The observations are confirmed with molecular dynamics simulations. The coupling manifests itself in traces of the transverse vertical mode appearing in the measured longitudinal spectra and vice versa. We calculate the expected ratio of the trace to the principal mode with a theoretical analysis of the modes in a crystal with finite temperature and find good agreement with the experiment and simulations. [ABSTRACT FROM AUTHOR]

In Ar and He radio-frequency (RF) plasmas with admixtures of C2H2 and CH4 the hydrocarbon chemistry has been studied in relation to dust particle formation by means of infrared tunable diode laser absorption spectroscopy (TDLAS) combined with Fourier transform infrared (FTIR) spectroscopy. The experiments were performed in a RF capacitively coupled parallel plate reactor at a frequency of f = 13.56 MHz, a pressure of p = 0.1 mbar and a flow rate of Φ = 8 sccm of Ar or He with admixtures of 0.5 sccm C2H2 or 1 sccm CH4. The power was P = 15 W. Using TDLAS, the temporal evolution of the concentrations of the methyl radical and of four stable molecules, C2H2, CH4, C2H4 and CO, was monitored in the plasma. Simultaneously, the growth process of the dust particles was analysed by FTIR spectroscopy. The degree of dissociation of the acetylene precursor was found to be nearly constant in the range of 96% under stabilized conditions for both the Ar and He plasmas. In contrast, the degree of dissociation of the methane precursor varied between 45% and 90% depending (i) on the appearance of dust particles in the reactor volume and (ii) on the Ar or He plasma conditions. The methyl radical concentration was found to be in the range of 1011 molecules cm−3. The concentrations of all hydrocarbon species were strongly correlated with the dynamic of the dust formation. Fragmentation efficiencies of acetylene (RF (C2 H2) = 3.2 × 1016 molecules J−1) and of methane (RF (CH4) = (0.16–2.5) × 1016 molecules J−1) and conversion efficiencies to the produced hydrocarbons (RC = (0.23–8.5) × 1014 molecules J−1) could be estimated in dependence on the discharge conditions in the RF plasma. [ABSTRACT FROM AUTHOR]