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The paper presents the results of a numerical simulation of the effects of N2 on the characteristics of Trichel pulses in SF6 at 0.4 MPa. The simulation was performed in a 2D axisymmetric geometry assuming a three species discharge model for the applied voltage on the discharge electrode to be −25 kV. Three drift-diffusion equations coupled with Poisson's equation are considered to determine the dynamic behavior of Trichel pulses and the temporal and spatial distributions of charged species. The reduced ionization coefficient, the reduced attachment coefficient, the electron mobility, and the electron diffusion coefficient of SF6/N2 mixtures are obtained by solving the two-term Boltzmann equations. The content of N2 varies from 20% to 80%. The distribution of three charged species and the reduced electric field at the discharge tip are presented at different instants of time to explain the formation mechanism of the Trichel pulses in SF6/N2 mixtures. The time-dependent current, the total number of electrons, the positive ions, and the negative ions as well as the reduced electric field at the discharge tip under different SF6/N2 mixtures are analyzed to investigate the sensitivities of these properties to the N2 content. [ABSTRACT FROM AUTHOR]

A new method for the interneedle-distance optimization of a multineedle-to-plane barrier discharge reactor is presented. As we know, there is gas breakdown when, in some regions between electrodes, the electric field is higher than the breakdown field; hence, the regionmay play a dominant role for the discharge, and the enhancement of its volume ratio in the reactor will allow an increase in discharge energy density. This can be achieved by structure optimization. With the finite-element method, the 3-D profiles of an electrostatic field in the reactor are acquired for a series of interneedle distances, thereby the one-to-one relationship between the volume ratio and interneedle distance is obtained. This allows the optimal interneedle distance for power input efficiency to be identified, as related to the maximal volume ratio. The optimal distance is between 7.2 and 8.4 mm in our simulation range, decreasing with the increase of operating voltages from 16 to 26 kV. The simulation results are experimentally validated by discharge energy measurement as well as the performance of SO2 removal from indoor air. This structure optimization method leads to a simple way to obtain the optimal interneedle distance for energy input efficiency and hence benefits commercial use. [ABSTRACT FROM AUTHOR]

The transportation of drugs through model tissues that are being treated by an argon plasma jet was investigated in this paper. Gelatin gel films were used to construct the model tissues and lidocaine was used as a representative drug. The argon plasma jet enhanced the penetration of lidocaine and the enhancement rate increased with the discharge voltage and the frequency. When the discharge power of the plasma jet was low, it was deduced that the enhancement effect was mainly attributed to the electric field of the plasma jet. The enhancement effect was holistic and was hindered by the macromolecules of gelatin in the model tissues. When the discharge power of the plasma jet increased beyond a threshold level, the surface streamers of the plasma jet produced a deformation effect in the model tissue, thereby resulting in a star-shaped pattern on the surface of the model tissue. In that case, the penetration enhancement of lidocaine was dominated by the deformation effect; however, it was mainly confined to the surface layer. For comparison, a helium plasma jet was also used to enhance the penetration of lidocaine. When the discharge power was low, the enhancement effect of the helium plasma jet was higher than that of the argon plasma jet because the He gas flow and the electric field of He plasma jet enhanced the penetration of lidocaine jointly; however, the enhancement effect of the Ar plasma jet was only attributed to the electric field. When the discharge power increased beyond a threshold level, the enhancement effects of the two plasma jets were almost the same. [ABSTRACT FROM AUTHOR]

Gelatin gels are used as surrogates of human tissues to study their barrier effects on incoming reactive oxygen and nitrogen species (RONS) generated by surface air discharge. The penetration depth of nitrite into gelatin gel is measured in real time during plasma treatment, and the permeabilities of nitrite, nitrate, O3 and H2O2 through gelatin gel films are quantified by measuring their concentrations in the water underneath such films after plasma treatment. It is found that the penetration speed of nitrite increases linearly with the mass fraction of water in the gelatin gels, and the permeabilities of nitrite and O3 are comparably smaller than that for H2O2 and nitrate due to differences in their chemistry in gelatin gels. These results provide a quantitative basis to estimate the penetration processes of RONS in human tissues, and they also confirm that the composition of RONS is strongly dependent on the tissue depth and the plasma treatment time. A small electric field of up to 20 V cm−1 can greatly reduce the barrier effects of the tissue model regardless of their directions, for which the underlying mechanism is unclear. However, the electric field force on the objective RONS should not be the dominant mechanism. [ABSTRACT FROM AUTHOR]