Simulation of a pulse-modulated radio-frequency atmospheric pressure glow discharge

A one-dimensional fluid model is developed for describing the pulse-modulated radio-frequency glow discharges in atmospheric helium. The influences of the duty cycle of modulation pulses on the characteristics of discharge are studied. The numerical results show that there are two different regimes with reducing duty cycle, and that in each regime, the dependence is linear. The reason for it is the residual electrons in the electrode gap, which play an important role during the plasma ignition phase. It is consistent with the experimental study.     

Oxidation of nitric oxide in a two-stage chemical scrubber using dc corona discharge

The dc corona was studied as an alternative for NO oxidation in a two-stage chemical scrubber. The dc corona plasma reactor completely oxidized 150 ppm of NO to NO₂ in an air stream. The NO₂ was further oxidized at a higher voltage. For some cases, the NO₂ in the effluents of the plasma reactor was absorbed quantitatively by a caustic sodium sulfite aqueous solution in a 2 l bubble column gas absorber. The outlet concentrations of both NO and NO₂ from the plasma-scrubber combination system (corona-induced chemical scrubber) were below the detection limit of the chemiluminescent NO_x analyzer.     

直流电弧放电法合成In2O3纳米粒子

电弧放电法因能在瞬间产生高温使原料气化而成为一种高效的纳米材料制备方法。以金属In为原料,在无催化剂的条件下,采用直流电弧放电法直接合成了In2O3纳米粒子。XRD、SEM和TEM结果表明所制备的In2O3纳米粒子为立方结构,形貌为结晶良好的八面体,平均粒径为60～120nm。纳米粒子之间以点接触和面接触相连。     

Increased in vivo glucose recovery via nitric oxide release

The in vivo glucose recovery of subcutaneously implanted nitric oxide (NO)-releasing microdialysis probes was evaluated in a rat model using saturated NO solutions to steadily release NO. Such methodology resulted in a constant NO flux of 162 pmol cm(-2) s(-1) from the probe membrane over 8 h of perfusion daily. The in vivo effects of enhanced localized NO were evaluated by monitoring glucose recovery over a 14 day period, with histological analysis thereafter. A difference in glucose recovery was observed starting at 7 days for probes releasing NO relative to controls. Histological analysis at 14 days revealed lessened inflammatory cell density at the probe surface and decreased capsule thickness. Collectively, the results suggest that intermittent sustained NO release from implant surfaces may improve glucose diffusion for subcutaneously implanted sensors by mitigating the foreign body reaction.     

Characteristics of pulse-modulated radio-frequency atmospheric pressure glow discharge

In this letter, the electrical and optical characteristics of pulse-modulated radio-frequency atmospheric pressure glow discharge are presented. The 13.56 MHz glow discharge is modulated with pulses at repetition frequency of 100 kHz. It is shown that the discharge during power on has similar characteristics to that of discharge without pulsing, except during the discharge ignition and extinguishment phase. The spatio-temporal evolution of discharge in phases of ignition and extinguishment is studied by time-resolved imaging and optical emission spectrograph.     

Detection of nitric oxide and nitrogen dioxide with photoluminescent porous silicon

The visible photoluminescence of porous Si is quenched by nitric oxide and nitrogen dioxide to detection limits of 1.4 × 10(-)(3) and 5.3 × 10(-)(5) Torr, respectively (corresponding to 2 ppm and 70 ppb). At analyte partial pressures in the low milliTorr range, the photoluminescence quenching is partially reversible; recovery from nitrogen oxide exposure occurs on a time scale of minutes. For both NO and NO(2), the reversible photoluminescence quenching response fits a Stern-Volmer kinetic model. At higher partial pressures, quenching deviates from Stern-Volmer kinetics and some permanent loss of photoluminescence intensity occurs due to oxidation of the porous Si surface. Photoluminescence from porous Si is not quenched by nitrous oxide or carbon dioxide and only slightly quenched by carbon monoxide and oxygen.     

Rapid synthesis and characterization of magnesium oxide nanocubes via DC arc discharge

Direct current (DC) arc discharge method gives high temperature in a short time, which has been widely used to prepare carbon nanotubes. We use this simple approach to synthesize magnesium oxide (MgO) nanocubes without any catalyst. Structural characterizations indicate that the as-synthesized MgO nanocubes are all single crystalline, and enclosed by {100} facets. The edge lengths mainly range from 60 nm to 100 nm. Most nanocubes interlace with adjacent nanocubes as three types: point contacts, line contacts and face contacts. The blue band in PL spectrum is ascribed to various structural defects, the nanosize effect and surface states of MgO nanocubes.     

Detonation studies with nitric oxide, nitrous oxide, nitrogen tetroxide, carbon monoxide, and ethylene

This paper presents the results of detonation studies conducted by the Bureau of Mines on nitric oxide, nitrous oxide, nitrogen tetroxide, carbon monoxide, and ethylene to evaluate the potential hazards of these materials to explosive shock initiation. Charge arrangements, construction details, and interpretation of results are given.Nitric oxide was observed to be the simplest known molecule capable of detonation-detonating in all three phases. Nitrous oxide, as a solid, nonboiling liquid, and nitrogen tetroxide and carbon monoxide, as nonboiling liquids, could not be initiated to detonation. Ethylene, as a gas at elevated pressure, gave evidence of a mild reaction but did not detonate; as a nonboiling liquid, it could not be initiated to detonation.     

Sputter-deposition of Ag films in a nitrogen discharge

In general, the presence of a reactive gas in the sputtering atmosphere must be avoided to prevent the formation of any other phases during the preparation of metal films. However, we hypothesized that films of metals, which do not form a nitride phase, could be prepared even in 100% nitrogen. Ag films were sputter-deposited in nitrogen and characterized. We found that it is feasible to obtain pure Ag films by rf sputtering in a nitrogen discharge. No other phase but Ag was detected by X-ray diffraction (XRD) analysis and nitrogen was not detected in the film by Auger electron spectroscopy. Electrical resistivity was also as low as 2.8 μΩ cm. Moreover, we found that Ag films thus deposited at a substrate temperature of 100 °C exhibited preferential orientation of (100), though that of (111) is generally observed in films sputtered in Ar. At other substrate temperatures, the degree of (100) orientation decreased. Consequently, we have found that sputter-deposition by the present method is useful for preparing pure Ag films with texture controlled by selecting the appropriate conditions.     

Making oxides of nitrogen in a vortex glow discharge

Parameter measurements are reported for a vortex glow discharge and the way they affect the synthesis of oxides of nitrogen from air.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 5, pp. 820–824, May, 1990.     

Correlative analyses of nitric oxide generation rates and nitric oxide synthase levels in individual cells using a modular cell-retaining device

Nitric oxide (NO) is recognized as one of the major immune system agents involved in the pathogenesis and control of various diseases that may benefit from novel drug development, by exploiting NO signaling pathways and targets. This calls for detection of both intracellular levels of NO and expression of its synthesizing enzymes (NOS) in individual, intact, living cells. Such measurements are challenging, however, due to short half-life, low and fluctuating concentrations of NO, cellular heterogeneity, and inability to trace the same cells over time. The current study presents a device and methodology for correlative analysis of NO generation rates and NOS levels in the same individual cells, utilizing fluorescent imaging followed by immunohistochemistry (IHC). U937 promonocyte cell populations demonstrated significant heterogeneity in their baseline levels, in NO-generation kinetics, and in their response rates to stimuli. Individual cell analysis exposed cell subgroups which showed enhanced NO production upon stimulation, concomitantly with significant up-regulation of inducible NOS (iNOS) levels. Exogenous NO modulated the expression of iNOS in nondifferentiated cells within 1 h, in a dose-dependent manner, while treatment with lysophosphatidylcholine (LPC) enhanced the expression of iNOS, demonstrating a nondependence on NO production.     

Comparative process analysis of fullerene production by the arc and the radio-frequency discharge methods

In this work, comparative analysis of processes in carbon arc and radio frequency (RF) plasma during fullerene synthesis has been presented. The kinetic model of fullerene formation developed earlier has been verified in both types of plasma reactors. The fullerene yield depended on carbon concentration, velocity of plasma flame and rotational temperature of C2 radicals predominantly. When mean rotational temperature of C2 radicals was 3000 K, the fullerene yield was the highest regardless of the type of used reactor. The zone of fullerene formation is larger significantly in RF plasma reactor compared to arc reactor.     

Two-photon nitric oxide laser-induced fluorescence measurements in a diesel engine

A two-photon nitric oxide (NO) laser-induced fluorescence (LIF) technique was developed and applied to study in-cylinder diesel combustion. The technique prevents many problems associated with in-cylinder, single-photon NO planar-laser-induced fluorescence measurements, including fluorescence interference from the Schumann-Runge bands of hot O2, absorption of a UV excitation beam by in-cylinder gases, and difficulty in rejecting scattered laser light while simultaneously attempting to maximize fluorescence signal collection. Verification that the signal resulted from NO was provided by tuning of the laser to a vibrational off-resonance wavelength that showed near-zero signal levels, which resulted from either fluorescence or interference at in-cylinder pressures of as much as 20 bar. The two-photon NO LIF signal showed good qualitative agreement with NO exhaust-gas measurements obtained over a wide range of engine loads.     

Deposition of low-resistivity gallium-doped zinc oxide films by low-temperature radio-frequency magnetron sputtering

The transparent and conductive gallium-doped zinc oxide (GZO) film was deposited on 1737F Corning glass using the radio-frequency (RF) magnetron sputtering system with a GZO ceramic target. (The Ga₂O₃ contents are approximately 5 wt. %). In this study, the effect of the sputtering pressure on the structural, optical and electrical properties of GZO films upon the glass or polyester film (PET) substrate was investigated and discussed in detail. The GZO film was grown under a steady RF power of 400 W and a lower substrate temperature from room temperature up to 200 °C. The crystal structure and orientation of GZO thin films were examined by X-ray diffraction. All of the GZO films under various sputtering pressures had strong c-axis (002)-preferred orientation. Optical transparency was high (> 80%) over a wide spectral range from 380 nm to 900 nm. According to the experimental data, the resistivity of a single-layered GZO film was optimized at  8.3 × 10^− 4 Ω cm and significantly influenced by the sputtering pressure. In further research, the sandwich structure of the GZO film/Au metal/GZO film was demonstrated to improve the electrical properties of the single-layered GZO film. The resistivity of the sandwich-structured GZO film was around 2.8 × 10^− 4 Ω cm.     

Sol-gel derived amperometric nitric oxide microsensor

An amperometric sol-gel derived nitric oxide microsensor is described. Several silicon-based xerogel membranes are evaluated to identify the optimum composition for maximizing NO permeability while providing sufficient selectivity for NO in the presence of common interfering species. Xerogel permeability and selectivity are further manipulated as a function of reaction/processing conditions. In addition, the effects of incorporating Nafion into the xerogel matrix on sensor performance and the stability of the ensuing xerogel/Nafion hybrid film are evaluated. The optimal permselective membrane is achieved by catalyzing polycondensation of the xerogel composed of methyltrimethoxysilane and (aminoethylaminomethyl)phenethyltrimethoxysilane and Nafion with NO gas. The resulting NO microsensor exhibits a sensitivity of 0.17 +/-0.02 pA/nM (from 25 to 800 nM, r = 0.9991), detection limit of 25 nM (S/N = 3), response time of 9 s (t(95%), a NO concentration change from 400 to 500 nM), selectivity (log K(NOj) amp) of -5.8, <-6, <-6, and <-6 for j = nitrite, ascorbic acid, uric acid, and acetaminophen, and a lifetime of 8 d (82% of initial sensitivity without serious deterioration in selectivity).     

Discharge characteristics of a radio-frequency capacitively coupled Ar/O2 glow discharge at atmospheric pressure

In this study, the discharge characteristics of the developed atmospheric pressure homogeneous and cold plasma source in Ar/O₂ glow discharge driven by radio-frequency (13.56 MHz) are investigated experimentally by means of electric measurements. The electron density is estimated to be in the order of 10¹¹ cm^− 3 in the abnormal discharge regime and is reduced by half in amount when the oxygen is mixed into argon plasma at oxygen-to-argon ratio of 0.3 and 0.6 vol.% at the same input power. The estimated electron temperature assumes the value of 1.4 eV in the abnormal discharge regime and the addition of oxygen to the argon plasma at the oxygen-to-argon ratio smaller than 1.0 vol.% does not alter the electron temperature appreciably.     

Mesoporous indium oxide synthesized via a nanocasting route

The synthesis of crystalline mesoporous indium oxide by using a mesoporous carbon (CMK-3) as hard template is described. Transmission electron microscopy (TEM) exhibits the presence of mesoporous structure in our sample and the corresponding wide-angle X-ray diffraction (XRD) pattern confirmed the crystalline wall of sample. N₂ adsorption measurement exhibits the synthesized crystalline mesoporous indium oxide possesses a specific surface area of 39 m²/g and the total pore volume of 0.17 cm³/g, and the corresponding pore size distribution curve reveals the presence of a mesopore of 7.0 nm in maximum. Our work demonstrates that the maintenance of the ordered structure of carbon template is very significant for obtaining high quality replicas via the nanocasting route.     

Integration of zinc oxide nanoparticles into transparent poly(butanediolmonoacrylate) via photopolymerisation

A new method for the preparation of transparent ZnO/PBDMA nanocomposites (PBDMA = poly(butanediolmonoacrylate)) is reported. Zinc oxide nanocrystals (4-10 nm) were synthesized in ethanol and then transferred into butanediolmonoacrylate (BDMA) to obtain a transparent and stable colloidal suspension. No further growth or aggregation of the particles could be observed, after dispersing the particles in the monomer. Effective size control in the range of 6-10 nm and concentrations up to 10 wt% zinc oxide were demonstrated for these systems. The particles and suspensions were characterized by transmission electron microscopy, X-ray diffraction, UV-VIS spectroscopy and dynamic light scattering. The addition of trimethylolpropane triacrylate (TMPTA) and a photoinitiator to the ZnO/BDMA suspension lead to a UV-curable liquid. Photoinduced polymerization was used to produce transparent nanocomposites containing the nanoparticles. The material exhibits a strong UV absorption below 360 nm, a high transmission (90%) in the visible spectral range and a green photoluminescence.