Prunus sargentii of Rosaceae familiy, has been reported to have radical scavenging activity and anti-inflammatory effect. On these facts, this research was conducted to evaluate pharmaceutical activities of the bark extracts P. sargentii. Free radical scavenging activities of fraction (Fr) -510 isolated from P. sargentii was higher than 80% respectively at 10ppm. The superoxide dismutase (SOD)-like activity of Fr-5, 9 were about 97, 84%, respectively at 1,000 ppm. Xanthine oxidase inhibitory effect of Fr-9, 10 were about 75, 78%, respectively at 1,000 ppm. The tyrosinase inhibitory effect related to skin-whitening was 72, 68% in Fr-2, 9 isolated from Prunus sargentii R. at 1,000 ppm. Hyaluronidase inhibition activity related to the anti-inflammation effect was 98% for Fr-8 at 500 ppm. Isolation of the methanol soluble fraction from P. sargentii yielded two major phenol compounds, (-)-epicatechin and taxifolin. The structure of the compound was certainly determined by chemical analyses, as well as NMR and Mass spectroscopy. The present study was carried out in a search for new cosmetic material from the bark from P. sargentii. and, (-)-epicatechin and taxifolin were isolated as active principles. So P. sargentii R. methanolic extracts may be used for the cosmetic material.
NiFe-layered double hydroxide (LDH) is thought of as a promising bifunctional water-splitting catalyst, owing to its excellent performances for alkaline oxygen evolution reactions (OERs). However, it shows extremely poor activity toward hydrogen evolution reactions (HERs) due to the weak hydrogen adsorption. We demonstrated that the integration of Rh species and NiFe-LDH can dramatically improve its HER kinetics without sacrificing the OER performance. The Rh species were initially integrated into NiFe-LDH as oxidized dopants and metallic clusters (< 1 nm). In 1 M KOH electrolyte, an overpotential of 58 mV is needed to catalyze 10 mA cm–2 HER current density. Furthermore, this catalyst only requires 1.46 V to drive an electrolyzer at 10 mA cm–2. A strong interaction between metallic Rh clusters and NiFe hydroxide during the HER process is revealed. The theoretical calculation shows the Rh ions replace Fe ions as the major active sites that are responsible for OERs.
Abstract Electrochemical nitrogen reduction reaction (NRR) is a sustainable alternative to the Haber‒Bosch process for ammonia (NH 3 ) production. However, the significant uphill energy in the multistep NRR pathway is a bottleneck for favorable serial reactions. To overcome this challenge, we designed a vanadium oxide/nitride (V 2 O 3 /VN) hybrid electrocatalyst in which V 2 O 3 and VN coexist coherently at the heterogeneous interface. Since single‐phase V 2 O 3 and VN exhibit different surface catalytic kinetics for NRR, the V 2 O 3 /VN hybrid electrocatalyst can provide alternating reaction pathways, selecting a lower energy pathway for each material in the serial NRR pathway. As a result, the ammonia yield of the V 2 O 3 /VN hybrid electrocatalyst was 219.6 µg h −1 cm −2 , and the Faradaic efficiency was 18.9%, which is much higher than that of single‐phase VN, V 2 O 3 , and VN x O y solid solution catalysts without heterointerfaces. Density functional theory calculations confirmed that the composition of these hybrid electrocatalysts allows NRR to proceed from a multistep reduction reaction to a low‐energy reaction pathway through the migration and adsorption of intermediate species. Therefore, the design of metal oxide/nitride hybrids with coherent heterointerfaces provides a novel strategy for synthesizing highly efficient electrochemical catalysts that induce steps favorable for the efficient low‐energy progression of NRR.
Yellow Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce) nanophosphors are prepared through a coprecipitation method. The optimal one shows a single phase, with a particle size of less than 50 nm and the broad photoluminescence (PL) spectra with a maximum peak at 560 nm. Its best quantum efficiency of 65% is achieved, and its lumen maintenance at 200 °C approaches 76%, which is comparable with that of a commercial bulk phosphor. Its applications to white light‐emitting diode (LED) and photovoltaic cell as downconverter are demonstrated. The white LED with the nanophosphor shows higher color rendering index (79) than that of the bulk (74). The significant photovoltaic efficiency is enhanced from 17.2% to 19.1%.
Low-temperature dielectric and pyroelectric properties were investigated for filled and unfilled tungsten bronze (TB) crystals, i.e., (Sr0.61Ba0.39)5Nb10O30, (K0.5Na0.5)1.0(Sr0.75Ba0.25)4.5Nb10O30, K5.80Li3.82Nb10.12O30, and K5.20Li2.34Nb10.88O30 with the spontaneous polarizations along the c axis at room temperature except for the last one. In all samples, transverse dielectric constant along the a axis showed a universal dielectric dispersion in the low-temperature range resembling a diffuse phase transition. Characteristic relaxation times obtained from the dielectric loss peaks followed the Arrhenius law, signifying thermal activation processes. The distribution of relaxation times seems to be caused by the distribution of activation energy, which has been successfully obtained by scaling the temperature- and frequency-dependent dielectric losses. This broadening may be attributed to the intrinsic randomness due to the charge disorder and quenched random fields caused by the unfilled structure and the off-stoichiometry of the TB compounds. Observed low-temperature dynamics were isotropic in the ab plane, and were insensitive to the poling conditions, degree of disorder, and high-temperature phase transitions. Structural phase transition accompanying a polarization tilt from the c axis toward the [110] axis, which was suggested to be the origin of the low-temperature anomalies, was not confirmed in our study. Some dynamics which are still active in the ferroelectric phase, like the concerted rotations of the oxygen octahedra, have been suggested as one of the possible origins of the observed phenomena.
Post-annealing effects on microstructure and magnetic properties of Nd-Fe-B die-upset magnets were investigated using the commercial melt-spun flakes with a composition of Nd 13.6 Fe 73.6 Ga 0.6 Co 6.6 B 5.6 . The die-upset magnets from the melt-spun flakes were subjected to post-annealing at temperatures ranging from 400 °C to 800 °C for 1 h in vacuum and then again annealed at a constant temperature, 600 °C. The coercivity was largely enhanced about 2.4 kOe after the first post-annealing treatment at 600 °C. However, the coercivity decreased at temperatures except for 600 °C and 700 °C. In the case of high temperature, 800 °C, annealing caused the grain growth, resulting coercivity degradation. After the second post-annealing treatment at 600 °C, the coercivity of the magnets post-annealed at low temperatures below 500 °C increased, whereas the coercivity of the magnets post-annealed at above 700 °C decreased. The $\alpha $ and ${N} _{\mathrm {eff}}$ values obtained from the result of temperature dependence of coercivity increased after post-annealing at 600 °C. These results indicate that post-annealing at 600 °C was effective in improving the grain surface structure, but could induce the local stray field in the magnet.
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