The influence of high-temperature H2 reduction treatment on Rh and Pd catalysts supported on Al2O3 was studied in relation to thermal aging in air. After air-aging at ≥900 °C, the Rh/Al2O3 catalyst was more strongly deactivated compared with the Pd/Al2O3 catalyst. As has been widely recognized, the solid-state reactions between Rh oxide and Al2O3 decreased the active surface area and stabilized inactive Rh3+ species. The activity was restored by the postreduction treatment with 20% H2/He at 200 °C, whereas a striking enhancement of activity was achieved by the reduction at 800–1100 °C, where substantial deactivation occurred for Pd/Al2O3. A mechanistic interpretation is proposed based on local structural characterization, which explains these contrasting thermal behaviors. The high-temperature reduction treatment produced active and thermostable Rh metal nanoparticles, which were highly dispersed on Al2O3. The observed dispersion (as high as ∼20% after reduction at 1000 °C) is among the highest for supported Rh catalysts reported in the literature. This is in complete contrast to the rapid sintering of Pd and other precious metals (Ru and Pt) into large metal agglomerates greater than 50 nm. Because the thermal behavior observed for Rh/ZrO2 under both oxidizing and reducing atmospheres was similar to that of Pd/Al2O3, the stability of metal nanoparticles depended not only on metal species but also on the interactions with support materials. An important implication of this study is that Al2O3 is a very efficient support for anchoring Rh metal nanoparticles via interfacial Rh–O–Al bonding under strong reducing conditions, in contrast to the well-known incompatibility with Rh oxide under oxidizing conditions.

Background: Choroidal circulation hemodynamics in eyes with ocular blunt trauma has not been quantitatively examined yet. We quantitatively examined changes in choroidal blood flow velocity and thickness at the lesion site using laser speckle flowgraphy (LSFG) and enhanced depth imaging optical coherence tomography (EDI-OCT) in a patient with chorioretinopathy associated with ocular blunt trauma. Case presentation: A 13-year-old boy developed a chorioretinal lesion with pigmentation extending from the optic disc to the superotemporal side in the right eye after ocular blunt trauma. The patient's best-corrected visual acuity (BCVA) was 0.2 in the right eye. Indocyanine green angiography showed hypofluorescence from the initial phase, with a decrease of mean blur rate (MBR) on LSFG color map, which corresponded to the chorioretinal lesion. The BCVA and foveal outer retinal morphologic abnormality spontaneously improved during follow-up. MBR and choroidal thickness increased by 23-31% and 13-17 μm at the lesion site and by 11-22% and 33-42 μm at the fovea, respectively, during the 6-month follow-up period after baseline measurements in the affected eye. In contrast, these parameters showed little or no changes at the normal retinal site in the affected eye and the fovea in the fellow eye. Conclusions: Current data revealed that both blood flow velocity and thickness in the choroid at the lesion site decreased in the acute stage and subsequently increased together with improvements in visual function and outer retinal morphology. These results suggest that LSFG and EDI-OCT may be useful indices that can noninvasively evaluate activity of choroidal involvement in ocular blunt trauma-associated chorioretinopathy.

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