Artificial gravity has been proposed as a method to counteract the physiological deconditioning of long-duration spaceflight; however, the effects of hypergravity on the central nervous system has had little study. The study aims to investigate whether there is a relationship between prefrontal cortex brain activity and prefrontal cortex oxygenation during exposure to hypergravity. Twelve healthy participants were selected to undergo hypergravity exposure aboard a short-arm human centrifuge. Participants were exposed to hypergravity in the +Gz axis, starting from 0.6 +Gz for women, and 0.8 +Gz for men, and gradually increasing by 0.1 +Gz until the participant showed signs of syncope. Brain cortical activity was measured using electroencephalography (EEG) and localized to the prefrontal cortex using standard low-resolution brain electromagnetic tomography (LORETA). Prefrontal cortex oxygenation was measured using near-infrared spectroscopy (NIRS). A significant increase in prefrontal cortex activity (P < 0.05) was observed during hypergravity exposure compared with baseline. Prefrontal cortex oxygenation was significantly decreased during hypergravity exposure, with a decrease in oxyhemoglobin levels (P < 0.05) compared with baseline and an increase in deoxyhemoglobin levels (P < 0.05) with increasing +Gz level. No significant correlation was found between prefrontal cortex activity and oxy-/deoxyhemoglobin. It is concluded that the increase in prefrontal cortex activity observed during hypergravity was most likely not the result of increased +Gz values resulting in a decreased oxygenation produced through hypergravity exposure. No significant relationship between prefrontal cortex activity and oxygenation measured by NIRS concludes that brain activity during exposure to hypergravity may be difficult to measure using NIRS. Instead, the increase in prefrontal cortex activity might be attributable to psychological stress, which could pose a problem for the use of a short-arm human centrifuge as a countermeasure.

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Plasma acid is an acidic solution simply produced from water and a carrier gas in an electrical discharge. These produced solutions are of high value for biological decontamination and industrial pollutant abatement applications. While several electrical discharges have been shown to produce plasma acid, the subject of this study is the gliding arc plasmatron, a rotating gliding arc discharge. Air and oxygen were used as gases to carry for distilled water through the discharge, and pH and conductivity of the resulting solution was measured. Consistent with other studies of plasma acid, solutions with a lower pH were obtained with air at the carrier gas than with oxygen, and the conductivity increased appropriately with the pH decrease. Other studies noted a transient change in plasma acid after treatment in an air carrier gas, whereas in this study, oxygen also was observed to temporally decrease the acidity over several days.