Hirosaki University

This work aims to develop multifunctional electrocatalysts capable of efficiently facilitating the concurrent oxygen evolution reaction (OER), urea oxidation reaction (UOR), and hydrogen evolution reaction (HER) at high current densities, representing a key step toward a dual-purpose technology for clean hydrogen production and urea-rich wastewater treatment. To achieve this goal, a flower-like Fe₃N-MoN heterostructure electrocatalyst composed of nanorods was synthesized on nickel foam (NF) using a hydrothermal-nitridation approach. This electrocatalyst exhibited exceptional multifunctional activities for OER (overpotential: η_10,1000 = 206, 374 mV), UOR (potential: E_10,500 = 1.35, 1.49 V), and HER (η₁₀₀₀ = 445 mV), while maintaining remarkable stability for over 48 h at 500 mA cm^-2. When employed in a two-electrode system (Fe₃N-MoN/NF (+) || Fe₃N-MoN/NF (-)), the catalyst demonstrated low operating potentials for overall water electrolysis (E_10,500 = 1.54, 1.78 V). Notably, the urea-assisted electrolysis system required a significantly lower voltage, achieving E₁₀ = 1.33 V. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicate that the enhanced catalytic ability should be stemmed from electronic structure optimization and surface reconstruction of Fe₃N-MoN heterostructure. This work demonstrates a rational design method for high-efficiency multifunctional electrocatalysts that couple low-energy hydrogen production with electrolytic purification of urea-rich wastewater.

In the case of complete wetting, the mechanism by which surfactant solutions can spread over solid substrates much faster than pure liquids is still not understood, despite numerous studies. Spreading should be strongly influenced by the adsorption of surfactant on the substrate depending on the specific substrate chemistry and heterogeneity, but this has been barely addressed in the literature. Moreover, it is not clear which substrate characteristics are of importance. We hypothesise that substrate energy components are of importance, whereas the contact angle of water (CAW) is not always suitable for prediction of the spreading kinetics of surfactant solutions.

The spreading of aqueous surfactant solutions was studied on 7 different polymeric substrates characterised by surface roughness 1.6-480 nm, surface energy 38.5-61.6 mJ/m² and CAW 43-81°.

CAW does not provide a complete substrate characterisation for spreading of surfactant solutions: the same solution demonstrated different spreading kinetics on different substrates with the same CAW. Spreading kinetics was characterised by the dependence of spread area, A, with time, t, being A∝t^α. For complete wetting, all surfactant solutions on all substrates began the spreading process with a spreading exponent α ≤ 0.5, but two of them later went into superspreading mode with α ≥ 1. On substrates with the highest and lowest surface energy, superspreading solutions begin spreading with α ∼ 0.2, similar to pure liquids. On some substrates only spreading with α ∼ 0.2 was observed.

Reduced social interactions negatively impact adolescents. However, underlying mechanisms of social isolation (SI) stress and interventions remain unclear. Therefore, we investigated the effects of an exercise intervention on SI stress-induced behavioral abnormalities and the underlying mechanisms. We used male mice: Ctrl (N = 32), SI (N = 33), SI + voluntary wheel running (VWR) (N = 14), and SI + lurasidone (N = 7), and assessed emotion, anxiety, depression, social interactions, and cognitive functions using behavioral tests. In addition, we measured plasma corticosterone and performed immunohistochemical staining for ΔFosB, a marker of repeatedly activated neurons, to assess the stress response and identify brain regions associated with SI stress. Interventions lasted for 3 weeks, and behavioral assessments were initiated 2 weeks after the intervention initiation. The SI mice exhibited significant hyperactivity, reduced self-care and motivation, impaired recognition, excessive sniffing toward strangers and aggressive but avoidant social behaviors. We observed significant improvements in recognition impairments and excessive sniffing behavior after VWR. In addition, there was a trend toward reduced flight behavior. However, VWR did not induce a significant change in the number of attacks and the ΔFosB expression in the ventral tegmental area (VTA). Lurasidone administration significantly reduced sniffing and aggressive behavior and increased ΔFosB-positive cells in VTA. Our results suggest that, while VWR and lurasidone both mitigate some aspects of SI-induced behavioral deficits, they likely act independent or only partially overlapping neurobiological pathways. Thus, VWR may act through broader neuroadaptive processes, potentially involving serotonergic modulation, neurotrophic factors, or stress regulatory circuits.