The electronic structure of the practical red phosphor SrTiO3;Pr3+,Al is studied by X-ray absorption and emission spectroscopy under ultraviolet (UV) irradiation. In contrast to the invariance of the oxygen Kα emission spectra, the titanium K-edge absorption spectra show two characteristic changes depending on UV energy, one of which is proportional to the photoluminescence excitation spectrum while the other is insensitive to it. With these results, a schematic energy diagram is proposed where the titanium 4p band pulled down by oxygen valence holes overlaps Pf 4f radiative centers situated just below the conduction band. The photoluminescence properties are briefly discussed in relation to the ferroelectric phase transition from an electronic viewpoint.
The ultraviolet-induced one-dimensional vibration of Ti ions in the red phosphor Sr(Ti0.939,Al0.061)O3:Pr3+ was successfully visualized using high-resolution X-ray diffraction, which was already predicted by X-ray absorption spectroscopy. The vibration of Ti 3d-eg states becomes clear with decreasing temperature, accompanied by the addition of blue-green luminescence intrinsic to SrTiO3 at low temperatures. These results clearly indicate that a weak coupling between photoexcited electrons and the T
1u phonon mode induces an anharmonic vibration of Ti ions.
BackgroundBoth polypharmacy and frailty are critical issues faced by the elderly. The decrease in gait speed is an index of frailty, and it is generally associated with falls and fractures, which are risk factors requiring the need for support or long-term patient care. In this study, we assess the risk factors responsible for the decrease in gait speed in older outpatients with polypharmacy.MethodsThirty-one persons (13 men, 18 women) aged 65 years or above and regularly taking 5 or more internal medications participated in this study.ResultsPropensity score-adjusted multivariate logistic analysis showed that only number of medications was associated with the risk of decreasing gait speed (odds ratio: 16.00, 95% confidence interval:1.72–149.00, p value = 0.0149). A negative correlation was found between the number of medications and gait speed. In addition, the gait speed of the calcium channel blocker medication group was significantly slower than that of the non-medication group.ConclusionThese results suggest that not only the number of medications but also the prescription contents is a risk factor for decrease in gait speed and may serve as indexes to identify patients at high risk of requiring support or long-term care.
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