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The preferential hydrogen bond (H-bond) structures of protonated methanol clusters, H(+)(MeOH)n, in the size range of n = 4-8, were studied by size-selective infrared (IR) spectroscopy in conjunction with density functional theory calculations. The IR spectra of bare clusters were compared with those with the inert gas tagging by Ar, Ne, and N2, and remarkable changes in the isomer distribution with the tagging were found for clusters with n≥ 5. The temperature dependence of the isomer distribution of the clusters was calculated by the quantum harmonic superposition approach. The observed spectral changes with the tagging were well interpreted by the fall of the cluster temperature with the tagging, which causes the transfer of the isomer distribution from the open and flexible H-bond network types to the closed and rigid ones. Anomalous isomer distribution with the tagging, which has been recently found for protonated water clusters, was also found for H(+)(MeOH)5. The origin of the anomaly was examined by the experiments on its carrier gas dependence.

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Changes in topography of the dentin surface induced by Er:YAG laser irradiation during laser scaling should be considered because alterations to the microstructure of the root surface may lead to post-operative pain, including dental hypersensitivity. The aim of this study was to examine the effects of Er:YAG laser irradiation on the dentin surface. We observed the dentin surface after irradiation by scanning electron microscope (SEM) and performed a morphometric analysis.The dentin slice discs from extracted human teeth were irradiated with the Er:YAG laser under three power conditions : 10 pps-30 mJ/pulse, 10 pps-40 mJ/pulse, or 10 pps-50 mJ/pulse. The chip was moved at 1 cm/s during irradiation. The discs were observed by SEM, and the length, width, and depth of cavities formed by one pulse of laser irradiation were measured. There was no significant difference in the surface shape of cavities (length and width) among the groups. The depth of cavities formed by 30 mJ/pulse, 40 mJ/pulse, or 50 mJ/pulse irradiation significantly increased with energy. Our study demonstrates