Single-Step Synthesis of W₂C Nanoparticle-Dispersed Carbon Electrocatalysts for Hydrogen Evolution Reactions Utilizing Phosphate Groups on Carbon Edge Sites

A novel, one-step protocol for the selective synthesis of W₂C nanoparticles from phosphotungstic acid (H₃PW₁₂O₄₀), a low-cost and commercially available tungsten compound, was developed. The nanoparticles had diameters of 1–50 nm and were dispersed on a carbon substrate. The W₂C nanoparticles were prepared by a simple operation sequence, involving impregnation of carbon black with H₃PW₁₂O₄₀ followed by calcination at 1000 °C. X-ray diffraction study revealed the selective formation of the W₂C phase in the samples prepared, whereas the tungsten carbide (WC) phase was present in the control prepared from H₂WO₄. Stable W₂C nanoparticles were obtained using this method owing to the presence of phosphate at the interfaces between the W₂C nanoparticles and the carbon substrates, which inhibited the diffusion of carbon atoms from the carbon substrates to the W₂C nanoparticles, leading to the formation of WC. The W₂C nanoparticles prepared showed an excellent catalytic activity for the hydrogen evolution reaction (HER), with low Tafel slopes of ∼50 mV/decade. The HER catalytic activity was notably high, being comparable to that of MoS₂, which is a promising alternative to Pt. The present method can potentially be applied to produce highly effective, low-cost, Pt-free electrocatalysts for the HER

Comparative Study of Muscle Hardness during Water-Walking and Land-Walking Using Ultrasound Real-Time Tissue Elastography in Healthy Young People

Compared with land-walking, water-walking is considered to be beneficial as a whole-body exercise because of the characteristics of water (buoyancy, viscosity, hydrostatic pressure, and water temperature). However, there are few reports on the effects of exercise in water on muscles, and there is no standard qualitative assessment method for muscle flexibility. Therefore, we used ultrasound real-time tissue elastography (RTE) to compare muscle hardness after water-walking and land-walking. Participants were 15 healthy young adult males (24.8 ± 2.3 years). The method consisted of land-walking and water-walking for 20 min on separate days. The strain ratio of the rectus femoris (RF) and medial head of gastrocnemius (MHGM) muscles were measured before and immediately after walking using RTE to evaluate muscle hardness. In water-walking, the strain ratio significantly decreased immediately after water-walking, with p p < 0.05 for MHGM, indicating a significant decrease in muscle hardness after water-walking. On the other hand, land-walking did not produce significant differences in RF and MHGM. Muscle hardness after aerobic exercise, as assessed by RTE, was not changed by land walking but was significantly decreased by water walking. The decrease in muscle hardness induced by water-walking was thought to be caused by the edema reduction effect produced by buoyancy and hydrostatic pressure