Heteroatom-doped carbon matrices have been attracting significant attention due to their superior electrochemical stability, light weight and low cost. Hence, in this study, various types of heteroatom, including single dopants of N, B and P and multiple dopants of B-N and P-N with a carbon matrix were synthesized by an innovative method named the solution plasma process. The heteroatom was doped into the carbon matrix during the discharge process by continuous dissociation and recombination of precursors. The chemical bonding structure, ORR activity and electrochemical performance were compared in detail for each single dopant and multiple dopants. According to the Raman spectra, the carbon structures were deformed by the doped heteroatoms in the carbon matrix. In comparison with N-doped structures (NCNS), the ORR potential of PN-doped structures (PNCNS) was positively shifted from -0.27 V to -0.24 V. It was observed that doping with N decreased the bonding between P and C in the matrix. The multiple doping induced additional active sites for ORR which further enhanced ORR activity and stability. Therefore, PNCNS is a promising metal-free catalyst for ORR at the cathode in a fuel cell.

In this study, the enhancement of ORR activity and durability by an N-doped carbon nanocomposite on tungsten carbide (WC) nanoparticles was reported. The nanocomposite of tungsten carbide on two different carbon matrices, pure carbon matrix (WC/C) and N-doped carbon matrix (WC/N-C), was at first prepared by a simple discharge process in the mixture of benzene/dodecane and pyrrole/dodecane. The nanoparticles of tungsten carbide were formed via the sputtering effect of tungsten electrodes during discharge. The results of TEM and XRD demonstrated that tungsten carbide nanoparticles with a mean size of 6 nm were evenly dispersed on both carbon matrices. The results of cyclic voltammetry measurements showed that both obtained metal/carbon matrices promoted a significant oxygen reduction reaction (ORR) in alkaline solution. The ORR potential of tungsten carbide/carbon matrix and nitrogen-doped carbon were À0.29 V and À0.36 V, respectively. The enhancement of ORR activity in WC/N-C was attributed to the combined catalytic effects of WC and N in the carbon matrix. Although the ORR activity of WC/N-C was still incomparable with commercial Pt/C, the durability of the catalyst was significant higher than that of Pt/C in a methanol environment. The catalyst did not exhibit an evident change of initial current after 4000 s. Therefore, the inexpensive N-doped WC/C nanocomposite might be a promising and highly durable catalytic material for cathodes in fuel cell applications.

Tibial tubercle avulsion fracture caused by knee extensor is very rare; furthermore, non-traumatic fractures during running or bilateral fractures have been reported. The purpose of this study was to evaluate any differences according to the mechanisms of injury in adolescents with tibial tubercle avulsion fracture. Thirty patients with tibial tubercle avulsion fractures were reviewed and the average age was 13 years 1 month. Seven patients (low-stress group) had a spontaneous fracture during running without definite trauma. Twenty-three patients (high-stress group) experienced pain during jumping and landing, or definite trauma. The mechanisms of injury, age, height, weight, body mass index (BMI), BMI percentile, fracture type, as well as any complication, such as limitation of motion and deformity related to the physeal arrest, were compared between groups. There was no definite difference in age, fracture type, and surgical outcomes between groups. There was no patient with significant early physeal arrest in both groups. The weight ( P = .02), BMI ( P = .03) and BMI percentile ( P = .01) in low-stress group were higher than those in high-stress group. In low-stress group, 6 patients’ BMIs were in the 97th percentile, and 1 patient's BMI was in the 5th percentile. Extreme BMI may be a risk factor for tibial tubercle avulsion fractures in adolescents during running without definite trauma. However, there was no difference in the final outcome according to injury mechanisms.

Daniel K. Inouye Solar Telescope (formerly known as Advanced Technology Solar Telescope) will be the largest optical solar telescope ever built to provide greatly improved image, spatial and spectral resolution and to collect sufficient light flux of Sun. To meet the requirements of the telescope the design adopted a 4m aperture off-axis parabolic primary mirror with challenging specifications of the surface quality including the surface figure, irregularity and BRDF. The mirror has been completed at the College of Optical Sciences in the University of Arizona and it meets every aspect of requirement with margin. In fact this mirror may be the smoothest large mirror ever made.This paper presents the detail fabrication process and metrology applied to the mirror from the grinding to finish, that include extremely stable hydraulic support, IR and Visible deflectometry, Interferometry and Computer Controlled fabrication process developed at the University of Arizona.

No abstract