村上 朝之

Abstract A biochemical reaction model clarifies for the first time how cold atmospheric plasmas (CAPs) affect mitochondrial redox homeostasis and energy metabolism. Fundamental mitochondrial functions in pyruvic acid oxidation, the tricarboxylic acid (TCA) cycle and oxidative phosphorylation involving the respiratory chain (RC), adenosine triphosphate/adenosine diphosphate (ATP/ADP) synthesis machinery and reactive oxygen species/reactive nitrogen species (ROS/RNS)-mediated mechanisms are numerically simulated. The effects of CAP irradiation are modelled as 1) the influx of hydrogen peroxide (H${}_{2}$O${}_{2}$) to an ROS regulation system and 2) the change in mitochondrial transmembrane potential induced by RNS on membrane permeability. The CAP-induced stress modifies the dynamics of intramitochondrial H${}_{2}$O${}_{2}$ and superoxide anions, i.e., the rhythm and shape of ROS oscillation are disturbed by H${}_{2}$O${}_{2}$ infusion. Furthermore, CAPs control the ROS oscillatory behaviour, nicotinamide adenine dinucleotide redox state and ATP/ADP conversion through the reaction mixture over the RC, the TCA cycle and ROS regulation system. CAPs even induce a homeostatic or irreversible state transition in cell metabolism. The present computational model demonstrates that CAPs crucially affect essential mitochondrial functions, which in turn affect redox signalling, metabolic cooporation and cell fate decision of survival or death.

We describe a magnetohydrodynamic (MHD) electrical power generator equipped with a convexly divergent channel, as determined through shock-tunnel-based experiments and quasi-three-dimensional numerical calculations based on large eddy simulation. In the experiments, the quality of MHD power-generating plasma and the energy conversion efficiency in the convexly divergent channel are compared with those from a linearly divergent channel. Despite the present approach is simple and requires a relatively minor modification of the MHD channel profile, the plasma quality and the generator performance of the convexly divergent channel are improved. The slight enhancement in a MHD channel divergence upstream provides boundary layer relief in a MHD flow decelerated by a retarding Lorentz force an excessive increase in static pressure is suppressed and a Hall field is enhanced, whereby notably high isentropic efficiency is achieved. In the calculation, the MHD channel profile is finely tuned in four types of geometry, that is, a concavely divergent channel, the linearly divergent channel, the convexly divergent channel and a highly convexed channel. The calculation suggests that the convexly divergent channel exhibits the highest energy conversion performance, which is followed by the highly convexed, linearly and concavely divergent channels in order. For scaling the effect of the wall geometry modification on the MHD plasma-fluid and generator performance, a convexity parameter (dH/dr{pipe}inlet), defined as dH/dr at the channel inlet, is used. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.