Enhanced optical output power of InGaN/GaN light-emitting diodes grown on a silicon (111) substrate with a nanoporous GaN layer.

We report the growth of InGaN/GaN multiple quantum wells blue light-emitting diodes (LEDs) on a silicon (111) substrate with an embedded nanoporous (NP) GaN layer. The NP GaN layer is fabricated by electrochemical etching of n-type GaN on the silicon substrate. The crystalline quality of crack-free GaN grown on the NP GaN layer is remarkably improved and the residual tensile stress is also decreased. The optical output power is increased by 120% at an injection current of 20 mA compared with that of conventional LEDs without a NP GaN layer. The large enhancement of optical output power is attributed to the reduction of threading dislocation, effective scattering of light in the LED, and the suppression of light propagation into the silicon substrate by the NP GaN layer.

Plasmonic wavelength splitter based on a large-area dielectric grating and white light illumination.

An optical process by which transmission wavelengths can be divided selectively by changing a resonance condition of surface plasmons (SPs) is demonstrated. When white light is incident to an SP resonance substrate with a dielectric grating, SP waves are excited at resonance and transmitted into the air via diffraction by a large-area grating pattern fabricated by nanoimprint lithography. While only a limited range of certain wavelengths is allowed to transmit, the peak transmission wavelength can be tuned continuously in the visible band. We also show that multiple wavelengths are transmitted into different directions simultaneously by using a wedge-shaped white light.

Effect of antioxidant activity in kimchi during a short-term and over-ripening fermentation period.

This study evaluated the antioxidant activities of kimchi at different fermentation times: short-term fermented kimchi (SK; less than 7days) and over-ripened kimchi (OK; greater than 2 years). In conclusion, antioxidant activity of the OK was significantly higher than the SK. The results of this study suggested that there was an increase in the antioxidant activity of fermented kimchi during the fermentation and ripening processes.

Determination of plasma topiramate concentration using LC-MS/MS for pharmacokinetic and bioequivalence studies in healthy Korean volunteers.

A rapid, simple and validated liquid chromatography coupled to tandem mass spectrometric method (LC-MS/MS) for topiramate analysis in human plasma has been applied to pharmacokinetic and bioequivalence studies in 24 healthy male Korean volunteers. The procedure involves a simple liquid extraction of topiramate and prednisone (internal standard) with acetonitrile and separation by HPLC equipped with a Capcell Pak C18 column using acetonitrile-0.1% triethylamine (80:20, v/v) as a mobile phase. Detection was carried out on an API 2000 MS system by multiple reactions monitoring mode. The ionization was optimized using ESI(-) and selectivity was achieved by MS/MS analysis, m/z 338.0 --> 77.5 and m/z 357.1 --> 327.2 for topiramate and prednisone, respectively. The method had a total run time of 2.5 min and showed good linearity over a working range of 20-5000 ng/mL in human plasma with a lower limit of quantification of 20 ng/mL. No metabolic compounds were found to interfere with the analysis. The inter-day and intra-day accuracy were in the ranges of 99.24-116.63 and 93.45-108.68%, respectively, and inter-day and intra-day precisions were below 6.24 and 5.25%, respectively. This method was successfully applied for pharmacokinetic and bioequivalence studies by analysis of blood samples taken up to 96 h after an oral administration of 100 mg of topiramate in 24 healthy Korean volunteers.

Antifatigue and antistress effect of the hot-water fraction from mycelia of Cordyceps sinensis.

This study was conducted to investigate the chemical component of the hot water (HW) fraction of mycelia of Cordyceps sinensis and its antifatigue and antistress effect against a stimulus in vivo using rats and mice. The growth of mycelia reached a maximum level of 31.6 g/l after 120 h of incubation. The main chemical composition of the HW fraction of mycelia of C. sinensis was found to be carbohydrate (78.9%) with 5% moisture. The swimming endurance capacity of mice orally administered with the HW fraction (150 and 300 mg/kg/d, respectively) was significantly prolonged from 75 to 90 min with a lessening of fatigue. When the HW fraction (150 mg/kg/d) was given to rats for 8 d including a 48 h stress period, the weight changes of the adrenal gland, spleen, thymus, and thyroid, which is an index of stress, were suppressed. The HW fraction also significantly inhibited the increase in total cholesterol and the decrease in alkaline phosphatase levels as biochemical parameters of immobilization stress in rats.