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High dimensionally structured niobium oxide (HDS-NbO) containing fluoride (F–) was prepared by a hydrothermal synthesis. F– could be introduced into HDS-NbO by replacing lattice oxygen up to a solid F–/Nb ratio of 0.55. The introduction of an appropriate amount of F– promoted the crystal growth of HDS-NbO, while niobium oxyfluoride having the hexagonal tungsten bronze structure (HTB-Nb­(F,O) x ) was concomitantly formed by excess F– addition. HAADF-STEM analysis suggested that the number of micropores (hexagonal and heptagonal channels) in HDS-NbO was increased by the introduction of an appropriate amount of F–. The catalytic activity for Brønsted acid reactions was evaluated by Friedel–Crafts alkylation. The catalytic activity was significantly increased by the introduction of F–, while excess introduction of F– significantly decreased the activity. Catalytic activity for the Lewis acid reaction in the presence of water was evaluated by the transformation of pyruvaldehyde into lactic acid. The catalytic activity was changed by the introduction of F– in a manner similar to that observed in the Friedel–Crafts alkylation. On the basis of the results obtained, we propose that the local catalyst structure around the micropores of HDS-NbO is crucial for the acid reactions.

Context. Methanimine (CH 2 NH) is a simple molecule composed of methylene and imine. The molecule has been detected toward the Galactic center, star-forming regions, circumstellar envelopes, and other galaxies since 1973. In previous studies, the rest frequency of methanimine has been measured for normal species up to the 650-GHz region, but its 13 CH 2 NH, CH 2 15 NH, and CH 2 ND isotopologs were limited to the 100-GHz region. Aims. If a rotational temperature of 100 K is assumed for methanimine, the highest intensity falls at approximately 1.5 THz. In addition to normal methanimine, the 13 CH 2 NH, CH 2 15 NH, and CH 2 ND isotopologs in their ground-vibrational states were observed in the frequency range of 120-1600 GHz to provide accurate rest frequency information. Based on this study, the calculated rest frequencies below 2 THz should be sufficiently precise and support observations using all ALMA and Herschel/HIFI observational bands. Methods. Methanimine was generated by pyrolysis of diaminoethane (DAE) vapor at 850 • C. 13 CH 2 NH and CH 2 15 NH isotopologs were measured with their natural abundance, and deuterization of DAE was performed by mixing normal DAE with deuterated water, D 2 O, and then pyrolyzed. This gives the deuterated isotopolog of methanimine, CH 2 ND. Spectral measurements were performed by using the 23 kHz source-frequency modulated terahertz spectrometer at Toho University. Results. Both a-and b-type transitions up to 1.6 THz for the three isotopologs and the normal species were measured. Rotational and centrifugal distortion constants for the three isotopologs were accurately determined. For normal species (CH 2 NH), both electric quadrupole and nuclear spin-rotation coupling constants for nitrogen nucleus were determined, while for the 13 CH 2 NH and CH 2 ND species, only electric quadrupole-coupling constants for nitrogen nucleus were determined. Conclusions. Our spectral line frequencies are suitable for a future astronomical search for these isotopologs of methanimine. The 1σ frequency accuracy up to 2 THz is lower than 100 kHz.

Magnetic refrigeration technology is expected to be a highly efficient process at a temperature of around 20 K, which is the hydrogen liquefaction temperature. In magnetic refrigeration, a magnetic field change is applied to a magnetocaloric material (MCM) to obtain a magnetocaloric effect. In addition, since the greater the magnetic field change, the better the cooling characteristics, the magnetic field strength of permanent magnets is insufficient, and the use of superconducting coils that can generate strong magnetic fields with low power consumption is essential. We are researching and developing a static magnetic refrigeration system (SMRS) that does not have moving parts to obtain magnetic field changes, and generates them by altering the energizing current to the coil. The key to devising this system is an AC loss of the superconducting coil. In this study, we measured the AC loss under energization conditions of multiple palm-sized REBCO coils at liquid nitrogen temperature, and calculated the efficiency of the SMRS by improving the accuracy of the analysis method for evaluating the AC loss, based on the results. We report the results and discuss the technical feasibility of SMRS.

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