Towards Catalysts Prepared by Cold Plasma

Cold (non-equilibrium) plasma techniques have long been used as plasma deposition methods to create new materials, often with unique properties, which cannot be produced any other way, as well as plasma treatment methods for the sophisticated modification of conventional materials [...]

A nanosecond pulsed discharge circuit model for engine applications

Non-equilibrium plasma discharges in spark gaps have been an increasingly studied method for alleviating cycle to cycle variation in lean and dilute combustion environments. However, ignition models that account for streamer propagation, cathode fall, and transmission line amplification over nanosecond time scales have so far not been developed. The present study develops such a model, with emphasis on the energy delivered from circuit to cylinder. Key pieces of the relevant physics and chemistry are summarized, simplified, and systematically coupled to one another. The set of parameters is limited to a handful of key observables and modeled using Modelica. Results show non-trivial behavior in the energy delivery characteristics of such discharges with important implications for ignition.

Characteristics of pulsed nanosecond discharge excited by compact solid-state pulse forming line at atmospheric pressure air

Non-equilibrium plasma is a promising technology for the generation of ozone and removal of exhausted fuel gases. However, applications of non-equilibrium plasma are restricted by energy utilization efficiency in many industry fields. Discharge excited by nanosecond pulsed power is regarded as one of the most efficient methods. In this study, a compact 5 stages stacked blumlein pulse forming line and photoconductive semiconductor switches-based power source was introduced to generate pulsed plasma. This compact source could achieve over 50 kV with 10.1 ns pulse width and 4.8 ns pulse rising time. Coaxial cylindrical reactor was employed to generate a pulsed streamer discharge driven by the nanosecond pulsed source in atmospheric pressure air. Electrical parameters of the streamer discharge have been obtained in this study, the instantaneous power dissipation exceeds 8 MW and the average energy consumption of each pulse exceeds 56 mJ. Experiments of high speed photography have been conducted to observe the evolution process. It can be found that streamer heads start from the central wire electrode and then head to the grounded cylinder electrode in all radial direction of the coaxial electrode. Triple wire-to-cylinder electrodes discharge shows that all the three coaxial discharges develop synchronously and symmetrically, which shows that is capable of generating large volume non-equilibrium diffusive streamer discharge plasma.

The proton motive force determines Escherichia coli's robustness to extracellular pH

Maintaining intracellular homeostases is a hallmark of life, and key physiological variables, such as cytoplasmic pH, osmotic pressure, and proton motive force (PMF), are typically interdependent. Developing a mathematical model focused on these links, we predict that Escherichia coli uses proton-ion antiporters to generate an out-of-equilibrium plasma membrane potential and so maintain the PMF at the constant levels observed. The strength of the PMF consequently determines the range of extracellular pH over which the cell is able to preserve its near neutral cytoplasmic pH. In support, we concurrently measure the PMF and cytoplasmic pH in single cells and demonstrate both that decreasing the PMF's strength impairs E. coli's ability to maintain its pH and that artificially collapsing the PMF destroys the out-of-equilibrium plasma membrane potential. We further predict the observed ranges of extracellular pH for which three of E. coli's antiporters are expressed, through defining their cost by the rate at which they divert imported protons from generating ATP. Taken together, our results suggest a new perspective on bacterial electrophysiology, where cells regulate the plasma membrane potential by changing the activities of antiporters to maintain both the PMF and cytoplasmic pH.

CFD Modeling of Low Temperature Ignition Processes From a Nanosecond Pulsed Discharge at Quiescent Conditions

Recent interest in non-equilibrium plasma discharges as sources of ignition for the automotive industry has not yet been accompanied by the availability of dedicated models to perform this task in computational fluid dynamics (CFD) engine simulations. The need for a low-temperature plasma (LTP) ignition model has motivated much work in simulating these discharges from first principles. Most ignition models assume that an equilibrium plasma comprises the bulk of discharge kernels. LTP discharges, however, exhibit highly non-equilibrium behavior. In this work, a method to determine a consistent initialization of LTP discharge kernels for use in engine CFD codes like CONVERGE is proposed. The method utilizes first principles discharge simulations. Such an LTP kernel is introduced in a flammable mixture of air and fuel, and the subsequent plasma expansion and ignition simulation is carried out using a reacting flow solver with detailed chemistry. The proposed numerical approach is shown to produce results that agree with experimental observations regarding the ignitability of methane-air and ethylene-air mixtures by LTP discharges.

DETERMINATION OF THE OPTIMAL OZONATION MODE FOR WINTER GARLIC PLANTING MATERIAL

The study was carried out at the Institute of Vegetable and Melon Farming of the National Academy of Agrarian Sciences of Ukraine and the Department of Low-Temperature Non-equilibrium Plasma Chemistry of the NSC "Kharkov Institute of Physics and Technology" of the National Academy of Sciences of Ukraine using the varieties of winter garlic, such as Duchess and Merefyanskiy white. Pre-plant treatment with four-time repeatability was carried out 3-5 days before planting using an OzW Stream Ozone TM ozone generator. Laboratory studies of fungal diseases Fusarium and Penicillium progress on the treated material were carried out with four-time repeatability in wet chambers. The effect of ozone concentration of 10, 50, and 100 PPM and exposure time of 10, 60, and 180 min on infestation of garlic with black and green mold was studied.