The behavior at the interface between the Pt catalyst and the ionomer, which functions as a reaction field determining the oxygen reduction reaction (ORR) activity in the cathode of polymer electrolyte fuel cells (PEFCs), was elucidated by combining the synthesis of new ionomers with precisely controlled model experiments. Four ionomers with different backbone rigidities and side-chain lengths were employed, and the effects of their molecular structural characteristics on the adsorptivity of sulfonate anions in the ionomer and on the ORR activity on the Pt surface were analyzed using a Pt(111) single-crystal electrode. As a result, it was revealed that the adsorptivity of sulfonate anions increases with increasing backbone flexibility and side-chain length. Furthermore, for ionomers with long side chains, the adsorption process was found to be governed by the kinetics of side-chain motion, whereas for those with short side chains, it was governed by the thermodynamics of backbone deformation — mechanisms that were clearly identified for ionomers with rigid backbones. For the ionomer with a flexible backbone and long side chains, the ORR activity decreased to 23% of that of the bare Pt(111) surface due to the adsorption of sulfonate anions. In contrast, by increasing the backbone rigidity and shortening the side chains, the activity was improved to 59% of that of the bare surface. The effect of backbone rigidity was particularly pronounced, providing a guideline for designing ionomer molecular structures with high ORR performance.
Tunnel junctions were applied to anode contacts in high-voltage GaN p–n diodes with sloped mesa terminations. The devices were composed of bottom p–n junctions with low doping concentrations to ensure a high blocking voltage, along with top n++/p++ tunnel junctions with doping concentrations greater than 3 × 1020 cm−3. The formation of fine square-shaped grooves through the tunnel junctions enabled dehydrogenation from the buried p-type layers, resulting in a reduction of the series resistance in the forward current–voltage curves. Repeatable reverse bias sweeps up to avalanche voltages were demonstrated for devices with and without grooves. The differential resistance in the voltage range of avalanche multiplication was reduced by the formation of grooves and by the reduction of the gaps, which corresponded to an increase in acceptor concentrations in the buried p-type layers, as indicated by capacitance–voltage curves. Because holes generated by avalanche events pass through the neutral region in the buried p-type layer, the resistance of this layer needs to be reduced by sufficient dehydrogenation to minimize Joule heating. In addition, GaN p–n diodes with tunnel junction anode contacts having fine square grooves passed a 1 h hold test at a constant current of 1 mA at the avalanche voltage. When the high-voltage p–n junction was in reverse bias, the tunnel junction was in forward bias; holes, therefore, passed through the tunnel junction. The results suggest that tunnel junctions enable the removal of holes generated by avalanche in high-voltage GaN transistors.
The asymmetric unit of the title compound, {[Cu 2 (C 8 Cl 4 O 4 ) 2 (C 4 H 4 N 2 ) 2 (H 2 O) 2 ]·H 2 O} n or {[Cu 2 (Cl 4 bdc) 2 (pyz) 2 (H 2 O) 2 ]·H 2 O} n comprises of a Cu II ion, one tetrachlorobenzenedicarboxylate ion (Cl 4 bdc 2− ), one pyrazine ligand (pyz), and one and a half water molecules. The Cu II ion exhibits a five-coordinated square-pyramidal geometry with a CuN 2 O 3 coordination environment comprising two oxygen atoms of the Cl 4 bdc 2− ligands, one oxygen atom of a water molecule, and two nitrogen atoms of the pyz ligands. The carboxylate group is almost perpendicular to the benzene ring and shows monodentate coordination to the Cu II ion. The Cu II ions of these units are bridged by both the Cl 4 bdc 2− and pyz ligands to form two-dimensional (2D) layers, which are linked by alternating hydrogen-bonding and C—Cl...π interactions to yield a three-dimensional network.
Introduction and Objective: Imeglimin is an oral antidiabetic agent with beneficial effects on mitochondrial function. Studies have shown that imeglimin reduces gluconeogenesis and stimulates muscle glucose uptake, thereby improving insulin resistance. Additionally, it promotes insulin secretion by increasing NAD+ levels in pancreatic β-cells. Studies have also demonstrated that imeglimin reduces mitochondrial oxidative stress and the activity of mitochondrial complex I in hepatic mitochondria of mice fed high-fat or high-sucrose diets. However, the effects of imeglimin on diabetic neuropathy remain unclear. Therefore, we investigated the effects of imeglimin on diabetic neuropathy in streptozotocin (STZ)-induced diabetic rats. Methods: Male Wistar rats were injected intraperitoneally with vehicle or STZ to induce diabetes. Four weeks after STZ injection, rats were orally gavaged with vehicle or imeglimin (200 mg/kg) twice daily for four weeks. Subsequently, assessments of mortor nerve conduction velocity (MNCV), sciatic nerve conduction velocity (SNCV), sciatic nerve blood flow (SNBF) were performed. Results: Imeglimin did not significantly affect body weight or blood glucose levels. Compared to controls, diabetic rats exhibited a trend toward decreased MNCV, which was attenuated by imeglimin. Diabetic rats also showed significant reductions in SNCV, and SNBF compared to controls. Imeglimin treatment significantly ameliorated the reduction in SNCV and SNBF. Conclusion: These findings from STZ-induced diabetic rats indicate the therapeutic potential of imeglimin for diabetic neuropathy. W. Nihei: None. A. Kato: None. T. Sato: None. T. Himeno: None. N. Nakamura: None. K. Sango: None. K. Naruse: None. J. Nakamura: Speaker's Bureau; Daiichi Sankyo, Novo Nordisk. H. Kamiya: Research Support; Sumitomo Dainippon Pharma Co., Ltd. Speaker's Bureau; Sumitomo Dainippon Pharma Co., Ltd. K. Kato: Speaker's Bureau; Daiichi Sankyo. JSPS KAKENHI (24K09971)
