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Increasing evidence indicates the occurrence of cognitive impairment in astronauts under spaceflight compound conditions, but the underlying mechanisms and countermeasures need to be explored. In this study, we found that learning and memory abilities were significantly reduced in rats under a simulated long-duration spaceflight environment (SLSE), which includes microgravity, isolation confinement, noises, and altered circadian rhythms. Dammarane sapogenins (DS), alkaline hydrolyzed products of ginsenosides, can enhance cognition function by regulating brain neurotransmitter levels and inhibiting SLSE-induced neuronal injury. Bioinformatics combined with experimental verification identified that the PI3K-Akt-mTOR pathway was inhibited and the MAPK pathway was activated during SLSE-induced cognition dysfunction, whereas DS substantially ameliorated the changes in brain. These findings defined the characteristics of SLSE-induced cognitive decline and the mechanisms by which DS improves it. The results provide an effective candidate for improving cognitive function in spaceflight missions.

In this paper, β-Ga 2 O 3 thin films were grown on a p-Si substrate using the sol-gel method. Structural characterization of the films was performed using X-ray diffraction. Electrical parameters such as breakdown field, interface traps density (D it ), and series resistance (R s ) were investigated at room temperature. The interface trap density was found to be 10 12 eV −1 cm −2 using the Hill-Coleman method. This result is valuable for MOS capacitor applications. Dielectric parameters were investigated in the wide frequency range (20 kHz-1 MHz) at room temperature. We observed that these parameters have a strong dependence on frequency and voltage. Index Terms-β-Ga 2 O 3 dielectric film, dielectric properties, electrical properties.

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PurposeThe objective was to investigate autonomic control in groups of European and Chinese astronauts and to identify similarities and differences.MethodsBeat-to-beat heart rate and finger blood pressure, brachial blood pressure, and respiratory frequency were measured from 10 astronauts (five European taking part in three different space missions and five Chinese astronauts taking part in two different space missions). Data recording was performed in the supine and standing positions at least 10 days before launch, and 1, 3, and 10 days after return. Cross-correlation analysis of heart rate and systolic pressure was used to assess cardiac baroreflex modulation. A fixed breathing protocol was performed to measure respiratory sinus arrhythmia and low-frequency power of systolic blood pressure variability.ResultsAlthough baseline cardiovascular parameters before spaceflight were similar in all astronauts in the supine position, a significant increase in sympathetic activity and a decrease in vagal modulation occurred in the European astronauts when standing; spaceflight resulted in a remarkable vagal decrease in European astronauts only. Similar baseline supine and standing values for heart rate, mean arterial pressure, and respiratory frequency were shown in both groups. Standing autonomic control was based on a balance of higher vagal and sympathetic modulation in European astronauts.ConclusionPost-spaceflight orthostatic tachycardia was observed in all European astronauts, whereas post-spaceflight orthostatic tachycardia was significantly reduced in Chinese astronauts. The basis for orthostatic intolerance is not apparent; however, many possibilities can be considered and need to be further investigated, such as genetic diversities between races, astronaut selection, training, and nutrition, etc.

β-Ga 2 O 3 thin films were grown on n-type GaN substrates using the sol-gel method. The forward-biased temperature dependent current-voltage (I-V-T) characteristics of Ni/β-Ga 2 O 3 /GaN structure have been investigated in the temperature range of 298-473 K. The apparent barrier height (ap) increased while the ideality factor (n) decreased with the increase in temperature. Such a temperature dependent behavior of ap and n was explained by the inhomogeneity of ap , which obeyed Gaussian distribution with zero-bias mean barrier height (̄B 0) of 1.02 ± 0.02 eV and standard deviation (s0) of 153 ± 0.04 mV. Subsequently, ̄B 0 and Richardson constant A * were obtained from the slope and intercept of the modified Richardson plot as 0.99 ± 0.01 e V and 67.2 A cm −2 K −2 , respectively. The ̄B 0 obtained from the modified Richardson plot was in good agreement with the theoretical value calculated from the work function of Ni and electron affinity of β-Ga 2 O 3. The I-V-T characteristics of Ni/β-Ga 2 O 3 /GaN MOS structures can be successfully explained by the thermionic emission theory with a single Gaussian distribution of the barrier height.

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