Microwaves (MWs) are often used to enhance various heterogeneous catalytic reactions. Here, we demonstrate real-time monitoring of a catalyst's oxidation state in a microwave catalytic reaction using a resonance frequency. The changes in the catalyst's oxidation state during the reaction induced changes in the resonance frequency in the cavity resonator. The resonance frequency was not affected by 2-propanol adsorption, while the frequency decreased with the reduction of WO 3 → WO 3−x . That is, the redox state of the WO 3 catalyst could be detected using the resonance frequency. The oxidation state of the WO 3 catalyst was then directly observed by the resonance frequency during the dehydration reaction of 2-propanol by microwaves as a model reaction. Resonance frequency monitoring revealed that the enhanced dehydration of 2-propanol by microwaves was attributable to the reduction of the WO 3 catalyst. Moreover, the temporal changes in the oxidation state of the WO 3 catalyst detected by the resonance frequency coincided with that observed by operando Raman spectroscopy. Therefore, real-time resonance frequency monitoring allowed facile detection of the bulk catalyst oxidation state under microwaves without using any spectroscopic apparatus.

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Comprehensive conformational analyses of 1-alkyl-3-methylimidazolium cations ([Cnmim]+ where n = 2–6) were performed by DFT calculations with dispersion correction in the gas phase. The energy difference (ΔE) of each conformer from the non-planar and all-trans (t) form was calculated. The planar forms have 2–3 kJ mol−1 higher energy than the corresponding non-planar form. A significant difference between these two forms is that unlike the non-planar form, the planar form cannot take gauche (g) or gauche′ (g′) in the second dihedral angle of the alkyl group. The conformational behavior for the alkyl group somewhat resembles that of alkane while interactions between the alkyl group and the imidazolium ring play an important role for [Cnmim]+ in both attractive and repulsive ways. For example, when the conformers contain g/g′ in the inner dihedral position, they tend to provide low ΔE due to the attractive interaction. Meanwhile, the strong repulsive interactions coming from steric hindrance do not allow some non-planar forms to stably exist. Instead, such a conformer takes the planar form that experiences less steric hindrance. The calculated results were compared with those from the Cambridge Structural Database, and Raman bands of the calculated cations were displayed and discussed.

Abstract. Recently, electromagnetic phenomena associated with earthquakes have gotten a lot of attention. So, we have been observed VHF band propagation for long time and analyzed statistical relation between anomalous line-of-sight propagation in the VHF band and occurrences of earthquakes using quantitative evaluation. Now, we need to detect the anomalous propagation from received data. Therefore, we used a statistical analysis to judge anomalous propagation in a previous study. In this paper, we judged the anomalous propagation by continuous wavelet transform and evaluated the relationship with earthquakes. Furthermore, we introduced hit rate and alarm rate to simplify the relationship between anomalous propagation and earthquakes. As a result, relation between anomalous propagation and earthquakes became clear.