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Physico-chemical and biological effects of atmospheric pressure plasmas (APPs) find numerous applications in biotechnology, medicine, and other fields. Recent studies revealed APPs’ potential for ischemic stroke treatment through the protection of neuronal cells from injuries. However, the mechanisms of the plasma neuroprotection effects still remain unknown. This study reveals the key mechanisms of APP plasma jet (APPJ) enabled reduction of neuronal cell death caused by oxygen and glucose deprivation (OGD) under stroke-relevant conditions. Plasma reduced OGD induced apoptosis of SH-SY5Y neuronal cells is based on reactive oxygen and nitrogen species production and on nitric oxide related activation of the cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase G (PKG) pathway, followed by the Bcl-2/Bax level modulation and caspase3/9 activity inhibition. In addition, the protective effect of APPJ treatment on OGD injured SH-SY5Y cells could be abolished by cGMP pathway inhibitor LY83583 pretreatment. Collectively, our findings highlight that the mechanism of the neuroprotection effects of the plasma treatment is closely related to the intracellular cGMP/PKG pathway, which provide experimental and theoretical references for future studies on plasma medicine.

Underwater shock waves generated by pulsed electrical discharges are an effective, economical, and environmentally friendly means of stimulating reservoirs, and this technology has received much attention and intensive research in the past few years. This paper reviews the main results of recent work on underwater electrical wire explosion (UEWE) for reservoir stimulation. A platform is developed for microsecond single-wire explosions in water, and diagnostics based on a voltage probe, current coil, pressure probe, photodiode, and spectrometer are used to characterize the UEWE process and accompanying shock waves. First, the UEWE characteristics under different discharge types are studied and general principles are clarified. Second, the shock-wave generation mechanism is investigated experimentally by interrupting the electrical energy injection into the wire at different stages of the wire-explosion process. It is found that the vaporization process is vital for the formation of shock waves, whereas the energy deposited after voltage collapse has only a limited effect. Furthermore, the relationships between the electrical-circuit and shock-wave parameters are investigated, and an empirical approach is developed for estimating the shock-wave parameters. Third, how the wire material and water state affect the wire-explosion process is studied. To adjust the shock-wave parameters, a promising method concerning energetic material load is proposed and tested. Finally, the fracturing effect of the pulsed-discharge shock waves is discussed, as briefly are some of the difficulties associated with UEWE-based reservoir stimulation.

In this paper, we report a nitrogen (N) doped zinc oxide (N:ZnO) film grown by the reactive high power impulse magnetron sputtering (HiPIMS) technique on glass substrates, where nitrogen gas (N2) is used as the N source. The proposal is to investigate the influence of process parameters on the alteration of the N:ZnO film from n- to p-type conductivity and the stability of the p-type behavior. It is obtained that the n- or p-type behavior of the as-deposited N:ZnO film is affected by the N2 flow rate, deposition temperature, and inductively coupled plasma (ICP) assistance, of which the ICP assistance had a great impact. It is noticed that, owing to the improved ionization rate of the N2 dopant by ICP, the N:ZnO film almost totally prefers to exhibit p-type behavior. Based on the measurement by temporal resolution optical emission spectroscopy, the components in plasma are obtained and the ion reaction in film growth is confirmed: a high concentration of active N+ in the ICP-assisted plasma reacts with sputtered Zn+ in vapor to form No defect in the p-type N:ZnO film. We then forecast that a stable p-type N:ZnO film can be grown using the HiPIMS technique.

This paper explores the predominant mechanisms for the deviation of micro-gap dc gas breakdown and the transition between different mechanisms as the electrode separation d changing under a pin-to-plate electrode configuration using 2d3v particle-in-cell simulation with Monte Carlo collisions. The deviated breakdown characteristic curves as a function of d or gas pressure p are investigated and both present a plateau region. Through researching the position of discharge path, it is found that a self-modulation effect manages to maintain the breakdown voltage at the minimum value defined by Paschen’s curve in a certain d or p range and forms the plateau. The ranges of d and p for the plateau are also established. Theoretical calculation on the secondary electron emission coefficient induced by ion-enhanced field and determined by a surface roughness factor confirms that the ion-enhanced field emission effect affects the breakdown voltage significantly when d is below a critical value. The smaller the surface roughness factor is, the smaller the critical d will be. Under this effect, the breakdown voltage is decreased with d decreasing (also referred to as an increasing left branch with d increasing). Conclusively, the deviation characters of micro-gap gas breakdown are controlled by different mechanisms at different d ranges. The predominant mechanism for the deviation is the self-modulation effect, serving as the main reason for the plateau region, at moderate d of several micrometers and will transit to the ion-enhanced field emission effect, which is responsible for the increasing left branch at smaller d.