Impact of N-Substituent and pKa of Azole Rings on Fuel Cell Performance and Phosphoric Acid Loss.

The influence of N-substituent and pKa of azole rings has been investigated for the performance of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Imidazole, benzimidazole, and triazole groups were functionalized on the side chains of poly(phenylene oxide), respectively. Each azole group is categorized by their N-substituent into two types: unsubstituted and methyl-substituted azoles. The membranes with methyl-substituted azoles showed higher phosphoric acid (PA) doping levels with an average increase of 20% compared to those with unsubstituted azoles in the full-doped states. However, unsubstituted azoles more effectively improved the proton conductivity and the membrane with unsubstituted imidazole (IMPPO-H) showed a high anhydrous proton conductivity of 153 mS/cm at 150 °C. In contrast, the membranes with methyl-substituted azoles showed a higher PA retention with an average increase of 81% compared to those with unsubstituted azoles. The higher PA retention of methyl-substituted azoles also led to the higher fuel cell performance with the maximum increase of 95% in the power density. It was also revealed that higher pKa of azoles enhanced the PA retention and the fuel cell performance. Based on the experimental results of PA retention and density functional theory calculations, the PA loss mechanism was also proposed.

N-methyl-D-aspartate antagonist inhibits NR-1 subunit phosphorylation of the spinal N-methyl-D-aspartate receptor induced by low frequency electroacupuncture.

We investigated whether the 2 Hz electroacupuncture (EA) analgesia is associated with phosphorylation of N-methyl-D-aspartate receptor (NMDAR) NR-1 subunits and NMDAR antagonism in the lumbar spinal cord of rats. EA stimulation produced an increase of serine phosphorylation of NMDAR NR-1 subunits in the spinal cord as compared with normal conditions. However, the intrathecal injection of NMDAR antagonist D-2-amino-5-phosphonopentanoic acid significantly prevented serine phosphorylation of NMDAR NR-1 subunits induced by EA stimulation in the dorsal horn of spinal cord. These results indicate that EA analgesia by stimulation of peripheral nerves may be involved in an increase of NR-1 serine phosphorylation in the dorsal horn of the spinal cord.