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Octahedral Pt alloy nanocrystals (NCs) have shown excellent activities as electrocatalysts toward oxygen reduction reaction (ORR). As the activity and stability of NCs are highly dependent on their structure and the elemental distribution, it is of great importance to understand the formation mechanism of octahedral NCs and to rationally synthesize shape-controlled alloy catalysts with optimized ORR activity and stability. However, the factors controlling the structural and compositional evolution during the synthesis have not been well understood yet. Here, we systematically investigated the structure and composition evolution pathways of Pt-Ni octahedra synthesized with the assistance of W(CO) and revealed a unique core-shell structure consisting of a Pt core and a Pt-Ni alloy shell. Below 140 °C, sphere-like pure Pt NCs with the diameter of 3-4 nm first nucleated, followed by the isotropic growth of Pt-Ni alloy on the seeds at temperatures between 170 and 230 °C forming Pt@Pt-Ni core-shell octahedra with {111} facets. Owing to its unique structure, the Pt@Pt-Ni octahedra show an unparalleled stability during potential cycling, that is, no activity drop after 10 000 cycles between 0.6 and 1.0 V. This work proposes the Pt@Pt-Ni octahedra as a high profile electrocatalyst for ORR and reveals the structural and composition evolution pathways of Pt-based bimetallic NCs.

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The free energy of H adsorption (ΔG H ) on a metallic catalyst has been taken as a descriptor to predict the hydrogen evolution reaction (HER) kinetics but has not been well applied in alkaline media. To assess this, we prepare Pd@Pt and PdH@Pt core−shell octahedra enclosed by Pt(111) facets as model catalysts for controlling the ΔG H affected by the ligand, the strain, and their ensemble effects. The Pt shell thickness is adjusted from 1 to 5 atomic layers by varying the amount of Pt precursor added during synthesis. In an alkaline electrolyte, the HER activity of core−shell models is improved either by the construction of core−shell structures or by the increased number of Pt shells. These experimental results are in good agreement with the ΔG H values calculated by the first-principles density functional theory with a complex surface strained core−shell slab model. However, enhanced HER activities of Pd@Pt and PdH@Pt core−shell nanocrystals over the Pt catalyst are inconsistent with the thermodynamic ΔG H scaling relationship only but can be explained by the work function and apparent ΔG H models that predict the interfacial electric field for the HER.

Background: The blood-brain barrier (BBB) maintains homeostasis of the brain environment by tightly regulating the entry of substances from systemic circulation. A breach in the BBB results in increased permeability to potentially toxic substances and is an important contributor to amplification of ischemic brain damage. The precise molecular pathways that result in impairment of BBB integrity remain to be elucidated. Autophagy is a degradation pathway that clears damaged or unnecessary proteins from cells. However, excessive autophagy can lead to cellular dysfunction and death under pathological conditions. Methods:In this study, we investigated whether autophagy is involved in BBB disruption in ischemia, using in vitro cells and in vivo rat models. We used brain endothelial bEnd.3 cells and oxygen glucose deprivation (OGD) to simulate ischemia in culture, along with a rat ischemic stroke model to evaluate the role of autophagy in BBB disruption during cerebral ischemia.Results: OGD 18 h induced cellular dysfunction, and increased permeability with degradation of occludin and activation of autophagy pathways in brain endothelial cells. Immunostaining revealed that occludin degradation is co-localized with ischemic autophagosomes. OGD-induced occludin degradation and permeability changes were significantly decreased by inhibition of autophagy using 3-methyladenine (3-MA). Enhanced autophagic activity and loss of occludin were also observed in brain capillaries isolated from rats with middle cerebral artery occlusion (MCAO). Intravenous administration of 3-MA inhibited these molecular changes in brain capillaries, and recovered the increased permeability as determined using Evans blue. Conclusions:Our findings provide evidence that autophagy plays an important role in ischemia-induced occludin degradation and loss of BBB integrity.

Atopic dermatitis is a common skin disease in adolescents, which may have a negative effect on the mental and emotional health. We investigated the relationship between atopic dermatitis and suicidal behaviors in Korean adolescents. Participants included 74,186 adolescents (38,221 boys and 35,965 girls) in middle and high school who completed the Eighth Korea Youth Risk Behavior Web-Based Survey. There were significant associations between atopic dermatitis and suicidal behaviors for girls. The overestimation of weight perception might have an additive impact on suicidal risk among girls. However, there were no significant associations between atopic dermatitis and suicidal behaviors in boys.

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