Toward highly efficient bifunctional electrocatalysts for zinc-air batteries: from theoretical prediction to a ternary FeCoNi design.

3d Transition-metal nitrogen-carbon nanocomposites (T-N-C, T = Fe, Co, Ni, etc.) with highly active M-Nx sites have received much attention in the field of rechargeable zinc-air battery research. However, how to rationally dope metallic elements to decorate T-N-C catalysts and enhance their electrocatalytic performances remains unclear. Herein, we demonstrated that cobalt-doped Fe-rich catalysts are effective in improving ORR performances by density functional theory (DFT) calculations. On this basis, we reported a kind of novel bifunctional electrocatalyst of hollow nitrogen-doped carbon tubes with coexisting M-N-C single atoms and alloy nanoparticles (denoted FexCoyNiz@hNCTs). Benefiting from the synergistic effect between different components, the as-prepared Fe4Co1Ni2@hNCT catalyst exhibited a small overpotential difference of 0.75 V between an OER potential at 10 mA cm-2 and an ORR half-wave potential, as well as an excellent zinc-air battery performance, when serving as the air cathode. This work provided a scalable design concept for multi-metal doping toward high-performance T-N-C electrocatalysts.

Thermal Stability, Mechanical Properties and Ceramization Mechanism of Epoxy Resin/Kaolin/Quartz Fiber Ceramifiable Composites.

The application of epoxy resins in high temperature and thermal protection fields is limited due to their low decomposition temperature and low carbon residual rate. In this paper, epoxy resin (EP)/quartz fiber (QF) ceramifiable composites were prepared using a prepreg-molding process. The thermal stability, phase change and mechanical properties after high-temperature static ablation and ceramization mechanism of EP/QF ceramifiable composites were investigated. The addition of glass frits and kaolinite ceramic filler dramatically increases the thermal stability of the composites, according to thermogravimetric (TG) studies. The composite has a maximum residual weight of 61.08%. The X-ray diffraction (XRD) results show that the mullite ceramic phase is generated, and a strong quartz diffraction peak appears at 1000 °C. The scanning electron microscope (SEM) and element distribution analyses reveal that the ceramic phase generated inside the material, when the temperature reaches 1000 °C, effectively fills the voids in composites. The composites have a bending strength of 175.37 MPa at room temperature and retain a maximum bending strength of 12.89 MPa after 1000 °C treatment.

A review of prophylactic antibiotics use in plastic surgery in China and a systematic review.

The purpose of this study was to investigate the use of antibiotic prophylaxis for plastic surgical procedures at our hospital, and to perform a systematic literature review of randomized controlled trials evaluating the use of prophylactic antibiotics in plastic surgery. The records of patients who received plastic surgical procedures with Class I surgical incisions between 2009 and 2010 were retrospectively reviewed. A systematic literature review was conducted for studies examining the use of prophylactic antibiotics for Class I surgical wounds. A total of 13,997 cases with Class I surgical incisions were included. Prophylactic antibiotics were given in 13,865 cases (99.1%). The antibiotics used were primarily cefuroxime, clindamycin, metronidazole, cefoxitin sodium, and gentamicin. The average duration of administration was 4.84 ± 3.07 (range, 1-51) days. Antibiotics were administered postoperatively in >99% of cases while preoperative antibiotic administration was only given in 32 cases (0.23%). Wound infections occurred in 21 cases for an overall infection rate of 0.15%. Fourteen studies met the inclusion criteria of the systematic review. There was marked variation in the timing of antibiotic administration with antibiotics given pre-, peri-, and postoperatively. Of studies that compared the use of prophylactic antibiotics with placebo, a reduction in wound infections was noted in 4 trials and no difference was noted in 6 trials. No significant difference in infection rates was shown between the prophylactic and postoperative arms. In conclusion, prophylactic antibiotics are overused in plastic surgical procedures. Evidence-based guidelines for the use of prophylactic antibiotics in plastic surgical procedures are needed.

Effect of electrode materials on AlN-based bipolar and complementary resistive switching.

We report the complementary resistive switching (CRS) behaviors in aluminum nitride (AlN)-based memory devices as the promising new material system for large-scale integration of passive crossbar arrays. By utilizing different electrodes (Cu, Pt, and TiN), CRS characteristics are demonstrated in both TiN/AlN/Cu/AlN/TiN electrochemical metallization cells and Pt/AlN/TiN/AlN/Pt ionic resistive switching systems. The instability of Pt/AlN/Cu/AlN/Pt based CRS is explained by the relatively small reset voltage caused by the thermal effects enhanced reset process in the corresponding bipolar resistive switching element. It is concluded that the prerequisite for reliable and stable CRS is that the reset voltage of the bipolar resistive switching element must be much larger than half of the set voltage.