• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.194-200
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• 2006

Self-assembled InAs/InAl(Ga)As quantum dots (QDs) were grown on InP substrates by a molecular-beam epiaxy, and their structural and optical properties were investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), and room-temperature photoluminescence (PL). AFM images indicated that the InAs quantum structures showed various shapes such as quantum dashes, asymmetric and symmetric QDs mainly caused by the initial surface conditions of InAl(Ga)As with the intrinsic phase separation. For the buried InAs QDs in an InAlGaAs matrix, the average lateral size and height of QDs were 23 and 2 nm, respectively. By changing the growth conditions for the QD samples, the emission wavelength of $1.55{\mu}m$ was obtained, which is one of the wavelength windows for fiber optic communications.

• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.375-380
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• 2009

Polyepichlorohydrin rubber was treated with sodium azide (Na$N_3$) to replace its chlorine by azide ($N_3$). Then, the azidated polyepichlorohydrin rubber (Az-PECH) was blended with thermoplastic styrene-acrylonitrile copolymer with the rubber/plastic ratio of 80/20, 70/30 and 60/40 (wt/wt). The miscibility, mechanical and dynamic mechanical properties as well as elastic recovery properties of the blends were evaluated by DMA (Dynamic Mechanical Analyzer) and tensile tests. When azidation level in azidated PECH was upto 50%, the blends exhibited excellent miscibility, manifested by a single $T_g$, and fairly good elastic recovery. When azidation level was 75%, the blends showed phase separation. The miscible Az-PECH/SAN blends exhibited typical thermoplastic elastomer like properties, ie. melt processibility and high extensibility as well as good elastic recovery rate. It was also observed from combustion test that higher energy is released with the increase in the azidation level of the Az-PECH in the blends.

• Analytical Science and Technology
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• v.7 no.1
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• pp.33-39
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• 1994

The purpose on this study was to develop a new improved chromatographic method for determination of trace phenols from environmental waste water. The research was carried out with selected 8 phenols, and solid-phase extraction was employed as sample pretreatment method. The coupling of XAD-4 and Dowex $1{\times}8$ resin as preconcentration column increased the selectivities toward interferences coexisted in matrix. Automation was accomplished with on-line process of pretreatment and HPLC system. After elution of sample through XAD-4 column, phenols were adsorbed by dispersion force, then displaced from it by ACN basified, simultaneously and selectively readsorbed via anion exchange on Dowex $1{\times}8$. Dowex $1{\times}8$ column was washed by water. Phenols readsorbed were removed from Dowex $1{\times}8$ column by a minimum volumn of methanol containing HCl. Each pretreatment step was connected by switching valves and the eluate was directly on-line injected to obtain fast and reliable results into the HPLC. Recovery of phenols was greater than 90%. To examine utility of this method, analysis of phenols from laboratory waste water sample which was added some organic pollutants to find with phenols on environmental waste water were also accomplished without their interference effects.

• Journal of the Korean Vacuum Society
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• v.22 no.6
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• pp.321-326
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• 2013

The effect of rapid thermal annealing (RTA) on the optical properties of digital-alloy InGaAlAs multiple quantum well (MQW) structures have been investigated by using photoluminescence (PL) and time-resolved PL measurements as a function of RTA temperature. The MQW samples were annealed from $700^{\circ}C$ to $850^{\circ}C$ for 30 s in a nitrogen atmosphere. The MQW sample annealed at $750^{\circ}C$ exhibited the strongest PL intensity and the narrowest FWHM (Full width at half maximum), indicating the reduced nonradiative recombination centers and the improved interfaces between the wells and barriers. The MQW samples annealed at $800^{\circ}C$ and $850^{\circ}C$ showed the decreased PL intensities and blueshifted PL peaks compared to $750^{\circ}C$-annealed sample. The blueshift of PL peak with increasing RTA temperatures are ascribed to the increase of aluminum due to intermixing of gallium (Ga) and aluminum (Al) in the interfaces of InGaAs/InAlAs short-period superlattices. The decrease of PL intensity after annealing at $800^{\circ}C$ and $850^{\circ}C$ are attributed to the interface roughening and lateral composition modulation caused by the interdiffusion of Ga and Al and indium segregation, respectively. With increasing RTA temperature the PL decay becomes slower, indicating the decrease of nonradiative defect centers. The optical properties of digital-alloy InGaAlAs MQW structures can be improved significantly with optimum RTA conditions.

• Journal of Pharmaceutical Investigation
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• v.41 no.4
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• pp.255-262
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• 2011

Method using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was developed and validated for the determination of pregabalin in plasma samples. Acquisition was performed by monitoring the transitions: m/z 160.1${\rightarrow}$142.2 for pregabalin and m/z 423.2${\rightarrow}$207.1 for losartan (as an internal standard). After cold acetonitrileinduced protein precipitation of the plasma samples, separation was performed with C18 column by isocratic mobile phase consisted of 10 mM ammonium acetate and acetonitrile (15:85, v/v). Results were linear over the concentration ranged from 0.1 to $10{\mu}g$/mL and the correlation coefficients (r) were $\geq0.99$. Intra- and inter-day precisions were $\leq6.02$ and $\leq11.04%$, respectively, and intra- and inter-day accuracies were 96.60-101.09 and 98.10-102.60%, respectively. This validated method was successfully applied to a bioequivalence study of two formulations of pregabalin, Daewoong pregabalin capsule (Daewoong Pharm. Co., Ltd.) and Lyrica$^{(R)}$ capsule (Pfizer Korea Ltd.) in twenty eight healthy Korean volunteers. The subjects received a single oral dose of each formulation (150 mg as pregabalin) in a randomized $2{\times}2$ crossover study and plasma samples were obtained from each subject at predetermined time intervals. Then, the pharmacokinetic parameters ($AUC_{0-t}$, $C_{max}$ and $T_{max}$) were calculated and statistically analyzed to assess the differences between two formulations. The 90% confidence intervals for the log-transformed data were acceptable range of log 0.8-log 1.25 (e.g., log 1.0048-log 1.0692 for AUC0-t, log 0.9142-log 1.0421 for $C_{max}$). Thus, $AUC_{0-t}$ and $C_{max}$ met the criteria of the Korea Food and Drug Administration (KFDA) for bioequivalence test indicating that Daewoong pregabalin capsule was bioequivalent to Lyrica$^{(R)}$ capsule.

• Herbal Formula Science
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• v.21 no.2
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• pp.133-143
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• 2013

Objectives : We carry out the simultaneous quantification for quality control of four components in Bangpungtongseong-san (BPTSS) sample. In addition, we assessed the antioxidant effects of BPTSS sample. Methods : The used column for separation and analysis of four compounds was Luna C18 column and column oven temperature was maintained at $40^{\circ}C$. The mobile phase for simultaneous determination consisted of two solvent systems, 1.0% acetic acid in water and 1.0% acetic acid in acetonitrile. High performance liquid chromatography-photodiode array (HPLC-PDA) method for analysis was performed at a flow rate of 1.0 mL/min with PDA detection at 254 and 280 nm. The injection volume was 10 ${\mu}L$. The antioxidant activities of BPTSS were evaluated by measuring free radical scavenging activities on 2,2'-Azinobis-3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) and 1-1-diphenyl-2-picrylhydrazyl (DPPH). The inhibitory effects on low-density lipoprotein (LDL) oxidation were evaluated by the formation of thiobarbituric acid relative substances (TBARS) and relative electrophoretic mobility (REM). Results : Calibration curves were acquired with $r^2{\geq}0.9999$. The values of limit of detection (LOD) and quantification (LOQ) were 0.06-0.29 ${\mu}g/mL$ and 0.20-0.98 ${\mu}g/mL$, respectively. The amounts of geniposide, liquiritin, baicalin, and glycyrrhizin in BPTSS were 5.06, 7.33, 27.56, and 7.81 mg/g, respectively. The BPTSS showed the radical scavenging activity in a dose-dependent manner. The concentration required for 50% reduction (RC50) against ABTS and DPPH radicals were 72.51 ${\mu}g/mL$ and 128.49 ${\mu}g/mL$. Furthermore, GMGHT reduced the oxidation properties of LDL induced by CuSO4. Conclusions : The established HPLC-PDA method will be helpful to improve quality control of BPTSS. In addition, BPTSS has potentials as therapeutic agent on anti-atherosclerosis.

• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.35-41
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• 2011

In this study, the interface soaking effect in InAs/GaAs strained-layer superlattice (SLS) on crystalline phase modulation has been analyzed by the x-ray diffraction (XRD) curve. The strain variation induced by As and/or Sb soaking was determined by the separation angle between the substrate peak and the 0th-order superlattice satellite peak in the XRD spectra. Contrated that the As/InAs soaking arises minor GaAs-like interfacial layer, the Sb/GaSb soaking induces InSb-like one. The Fourier-transformed curves of the Pendellosung interference oscillation shows that the optimum soaking times of As/InAs and Sb/GaSb are 2 sec and 12 sec, at which the highest crystallineity has, respectively. An anomalous twin-peak phenomenon that a satellite peak splits into two peaks was observed in the SLS structure co-soaked by As and Sb at InAs${\rightarrow}$GaSb interfaces. We suggest that it may be resulted from coexistence of two kinds crystalline phases of InAsSb and GaAsSb due to intermixing of In${\leftrightarrow}$Ga and Sb${\leftrightarrow}$As.

• Asian Journal of Atmospheric Environment
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• v.5 no.3
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• pp.146-151
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• 2011

1-Nitropyrene (1-NP), 2-NP and 2-nitrofluoranthene (2-NFR) are useful markers for studying the atmospheric behaviors of polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs). However, present methods for measuring trace levels of these compounds are lesssensitive and laborious. Here we describe several improvements to a previously reported high-performance liquid chromatography-chemiluminescence detection system that allows it to determine trace levels of 1-, 2-NPs and 2-NFR. The proposed system was equipped with a reducer column packed with Pt/Rh instead of zinc whose life-time was limited. The combination of Cosmosil MS-II (monomeric ODS) and AR-II (polymeric ODS) columns was used instead of polymeric ODS columns as the separator column to improve the separation. An ethanol mixture with acetate buffer (pH 5.5) was used in place of an acetonitrile mixture with the same buffer to activate the reducer column. The same ethanol mixture was used as the mobile phase for the clean-up column. The switching time of the column switching valve was optimized to concentrate the amino-derivatives of above NPAHs quantitatively on the concentrator column. The concentrations of bis(2,4,6-trichlorophenly) oxalate and hydrogen peroxide in the chemiluminescence reagent solution were optimized to 0.4 mM and 30 mM, respectively, to increase the sensitivity. Under the above conditions, the detection limits (S/N=3) of 1-, 2-NPs and 2-NFR were 1 fmol (0.25 pg), 10 fmol (2.5 pg) and 4 fmol (1 pg), respectively. The proposed system was effectively used to determine trace levels of 1-, 2-NPs and 2-NFR in airborne particulates collected at Noto Peninsula. The atmospheric concentrations of 1-, 2-NPs and 2-NFR were not more than sub pg $m^{-3}$ levels. They were higher in winter (January) than in summer (July). In both seasons, the concentrations were in decreasing order, [2-NFR]>[1-NP]>[2-NP].

• Journal of Pharmaceutical Investigation
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• v.27 no.4
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• pp.287-293
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• 1997

To make a stable o/w emulsion, the effects of egg lecithin as an emulsifier and polyvinylpyrrolidone (PVP) as an auxiliary emulsifier on the physical stability of emulsion were investigated. The oil-in-water emulsion system was manufactured by microfluidizer and evaluated the physical stability. Average particle size and size distribution of emulsion was measured by dynamic light scattering analyzer and interfacial tension was measured. From the interfacial tension tested, critical micelle concentration of the egg lecithin was 0.1 %w/v and optimal concentration for the preparation of emulsion was 1.0 %w/v. The mean particle size was about $0.2\;{\mu}m$ which was suitable for injections. The short-term accelerated stability studies were conducted by centrifugation, freeze-thaw method and shaking of the emulsion samples. The addition of PVP was caused the reduction in the particle size and improved the physical stability of emulsion. These results suggested that a mixed interfacial film comprising the egg lecithin and PVP was formed at the o/w interface and it was effective in preventing phase separation under thermic or mechanical stress. We used antineoplaston A10 (A10) as a model drug which is peptide and amino acid derivative having a action to the living organism against the development of neoplastic growth by a nonimmunological progress. It has a poor solubility in water and there may be a difficulty in formulation of A10. Emulsion formulation study about A10 was performed. Solubility of A10 in emulsion was about five times as high as that in water. From the results of solubility and partition coefficient, almost A10 molecules in o/w emulsion exist in the interface between oil and water.

• Journal of Pharmaceutical Investigation
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• v.39 no.1
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• pp.73-78
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• 2009

A simple LC-MS/MS method of rabeprazole in human plasma was developed and validated. Rabeprazole and Internal standard (I.S), omeprazole, were extracted from human plasma by liquid liquid extraction, chromatographic separation of rabaprazole in plasma was achieved at $45^{\circ}C$ with a Shiseido UG120 $C_{18}$ column and methanol-10 mM ammonium acetate buffer (pH 9.42 with ammonium water), as mobile phase. Rabeprazole produced a protonated precursor ion [$(M+H)^+$] at m/z 360.10 and corresponding product ion at m/z 242.21. Internal standard produced a protonated precursor ion [$(M+H)^+$] at 346.09 and corresponding product ion at m/z 198.09. This method showed linear response over the concentration range of $1{\sim}500\;ng/mL$ with correalation coefficient greater than 0.99. The lower limit of quantitation (LLOQ) using 0.2 mL plasma was 1 ng/mL, which was sensitive enough for pharmacokinetics studies. The method was specific and validated with a limit of quantitation of 1 ng/mL. The intra-day and inter-day precision and accuracy were acceptable for all samples including the LLOQ. The applicability of the method was demonstrated by analysis of plasma after administration of a single 10 mg dose to 36 healthy subject. From the plasma rabeprazole concentration versus time curves, the mean $AUC_t$ (The area under the plasma concentration-time curve from time 0 to 12 hr ) was $691.36{\pm}321.88\;ng{\cdot}hr/mL$, $C_{max}$ (maximum plasma drug concentration) of $353.21{\pm}131.52\;ng/mL$ reached $3.4{\pm}1.1\;hr$ after adiministration. The mean biological half-life of rabeprazole was $1.37{\pm}0.75\;hr$. Based on the results, this simple method could readily be used in pharmacokinetics studies.