• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.381-381
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• 2010

$(ZrO_2)_{0.66}(HfO_2)_{0.34}$ thin films as gate dielectrics have been proposed to overcome the problems of tunneling current and degradation mobility inachieving a thin equivalent oxide thickness. An extremely thin $SiO_2$ layer is used in order to separate the carrier in MOSFET channel from the dielectric field fluctuation caused by phonons in the dielectric which decreases the carrier mobility. The electronic and optical properties influenced the device performance to a great extent. $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ dielectric films on p-Si (100) were grown by atomic layer deposition method, for which the conduction band offsets, valence band offsets and band gapswere obtained by using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap, valence and conduction band offset values for $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ dielectric thin film, grown on Si substrate were about 5.34, 2.35 and 1.87 eV respectively. This band alignment was similar to that of $ZrO_2$. In addition, The dielectric function (k, $\omega$), index of refraction n and the extinction coefficient k for the $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ thin films were obtained from a quantitative analysis of REELS data by comparison to detailed dielectric response model calculations using the QUEELS-$\varepsilon$(k, $\omega$)-REELS software package. These optical properties are similar with $ZrO_2$ dielectric thin films.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.2
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• pp.241-248
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• 2019

Objective: To isolate and identify new methanogens from the rumen of Holstein steers in Korea. Methods: Representative rumen contents were obtained from three ruminally cannulated Holstein steers ($793{\pm}8kg$). Pre-reduced media were used for the growth and isolation of methanogens. Optimum growth temperature, pH, and sodium chloride (NaCl) concentration as well as substrate utilization and antibiotic tolerance were investigated to determine the physiological characteristics of the isolated strain. Furthermore, the isolate was microscopically studied for its morphology. Polymerase chain reaction of 16S rRNA and mcrA gene-based amplicons was used for identification. Results: One strain designated as KOR-2 was isolated and found to be a non-motile irregular coccus with a diameter of 0.2 to $0.5{\mu}m$. KOR-2 utilized $H_2+CO_2$ and formate but was unable to metabolize acetate, methanol, trimethylamine, 2-propanol, and isobutanol for growth and methane production. The optimum temperature and pH for the growth of KOR-2 were $38^{\circ}C$ and 6.8 to 7.0, respectively, while the optimum NaCl concentration essential for KOR-2 growth was 1.0% (w/v). KOR-2 tolerated ampicillin, penicillin G, kanamycin, spectromycin, and tetracycline. In contrast, the cell growth was inhibited by chloramphenicol. Phylogenetic analysis of 16S rRNA and mcrA genes revealed the relatedness between KOR-2 and Methanoculleus bourgensis. Conclusion: Based on the physiological and phylogenetic characteristics, KOR-2 was thought to be a new strain within the genus Methanoculleus and named Methanoculleus bourgensis KOR-2.

• Korean Journal of Food Science and Technology
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• v.35 no.1
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• pp.103-110
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• 2003

Stable production of fermented kanjang containing 1.8% (v/v) ethanol was obtained within four days using traditional kanjang containing 4% added glucose in packed-bed bioreactor systems filled with immobilized Zygosaccharomyces rouxii and Candida versatilis on porous alumina ceramic bead carrier at $28{\pm}0.5^{\circ}C$ and aeration rate of 0.05 vvm. Specific rates of alcohol production for Z. rouxii and C. versatilis were 0.0033 and 0.0031/day, respectively, and those of glucose consumption were both -0.0087/day in the batch type of alcoholic fermentation. In semi-continuous alcoholic fermentation at a dilution rate of 0.25/day, specific rates of alcohol production for Z. rouxii and C. versatilis were 0.0045 and 0.0029/day, and those of glucose consumption were -0.01 and -0.008/day, respectively, using identical bioreactor system. Similar specific rates of alcohol production were observed both in the batch or semi-continuous process and in the continuous one at the dilution rate of 0.25/day. Sensory characteristics of all alcoholic-fermented kanjang by Z. rouxii, C. versatilis, and a mixture of both yeasts (2:1, w/w) were shown to be significantly superior to those of home-made kanjang as revealed through organoleptic evaluation tests (p<0.05).

• Economic and Environmental Geology
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• v.30 no.6
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• pp.553-566
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• 1997

Origin, behavior and enrichment of environmental toxic elements from the Deokpyeong area were investigated on the basis of major, trace and rare earth element geochemistry. Coaly metapelites of the Deokpyeong area are subdivided into grey phyllite, dark grey phyllite, coaly slate and black slate, which are interbedded along the Ogcheon Supergroup. The coaly slate had been mined for coal, but mining is closed. The coaly and black slates are lower contents of $SiO_2$ and $Al_2O_3$, and higher contents of LOI, CaO, $Na_2O$ and BaO as compared with the phyllitic rocks. Rare earth elements are highly enriched in the coaly and black slate. Average compositions (ppm) of minor and/or environmental toxic elements in the coaly and black slate are revealed as As=127, Ba=30,163, Cd=18, Cr=740, Cu=84, Mo=378, Pb=43, Sb=12, Se=44, U=144, V=8,147 and Zn=292, which are extremely high concentrations than those in the NASC compositions. Major elements (average enrichment index; 5.34) in the coaly metapelites are mostly depleted, excepting $P_2O_5$ and BaO, normalized by NASC. Rare earth elements (average enrichment index; 1.48) are enriched in the coaly slate. On the basis of NASC, minor and/or environmental toxic elements in the coaly metapelites were strongly enriched of all the elements with the exception of Co, Cs, Ni and Sr. Average enrichment index of trace elements in coaly metapelite is 31.51 (coaly slate; 51.94 and black slate; 15.46). Especially, enrichment index of potentially toxic elements (As, Ba, Cr, Cu, Mo, Ni, Sb, Se, U, V and Zn) of the rock is 46.10 (grey phyllite; 7.15, dark grey phyllite; 4.77, coaly slate; 88.96 and black slate; 22.11). These coal formations were deposited in basin of boundary between terrestrial and marine environments deduced to carbon, sulfur (C/S=2.2 to 275.7), trace and rare earth elements characteristics. Irregular behavior and dispersion between major, minor and rare earth elements of those metapelites indicates a variable source materials, incomplete mixing of differential source and/or reequilibrium of diagenesis and metamorphism.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.1
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• pp.53-60
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• 2004

This work describes a l0b 150 MSample/s CMOS pipelined A/D converter (ADC) based on advanced bootsuapping techniques for higher input bandwidth than a sampling rate. The proposed ADC adopts a typical multi-step pipelined architecture, employs the merged-capacitor switching technique which improves sampling rate and resolution reducing by $50\%$ the number of unit capacitors used in the multiplying digital-to-analog converter. On-chip current and voltage references for high-speed driving capability of R & C loads and on-chip decimator circuits for high-speed testability are implemented with on-chip decoupling capacitors. The proposed AU is fabricated in a 0.18 um 1P6M CMOS technology. The measured differential and integral nonlinearities are within $-0.56{\~}+0.69$ LSB and $-1.50{\~}+0.68$ LSB, respectively. The prototype ADC shows the signal-to-noise-and-distortion ratio (SNDR) of 52 dB at 150 MSample/s. The active chip area is 2.2 mm2 (= 1.4 mm ${\times}$ 1.6 mm) and the chip consumes 123 mW at 150 MSample/s.

• Korean Journal of Veterinary Service
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• v.31 no.3
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• pp.385-395
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• 2008

This study was carried out to investigate the residue level of fluoroquinolones in hen's general eggs and specific eggs by microbiological assay method and high performance liquid chromatography (HPLC) method. HPLC separation was carried out by reversed phase chromatography on a Symmetry $C_{18}$ (250${\times}$4.6 mm, $5{\mu}m$ particle size) with a phase composed of distilled water (containing 0.4% triethylamine and phosphoric acid) : Methanol (780 : 220, v/v), pumped isocratically at a flow rate of 1.0ml/min. A fluorescence detector was utilized with an excitation wavelength of 278nm and an emission wavelength of 456nm. The calibration curves were linear $({\gamma}^2{\geq}0.999)$ over a concentration range of $0.025{\sim}0.4{\mu}g/ml$. Average recoveries of the five fluoroquinolones in whole eggs at fortified levels of $0.05{\sim}0.2{\mu}g/g$ were ranged mean $78.1{\sim}91.7%$ and low coefficient of variation was less than 10% for all analysed samples. The limits of detection and limits of quantification for whole eggs were $1.2{\sim}6.0ng/g$ and $2.3{\sim}9.1ng/g$, respectively. Only one hen's general eggfrom chicken farm in Incheon was detected with the residual fluoroquinolones (Microbiological assay method; 1 of 47 general eggs) ; the range of residual concentration enrofloxacin was 0.12ppm. Those in food stores were detected with the residual fluoroquinolones (Microbiological assay method; 4 of 88 general eggs) ; the ranges of residual concentration enrofloxacin were $0.15{\sim}2.2 ppm$, ciprofloxacin $0.01{\sim}0.06ppm$, and hen's specific eggs (40) in food stores were not detected. For the microbiological assay method of fluoroquinolones in hen's eggs, as the results of comparative analysis, the disc diffusion method with E coli may be a little highly detected for the residual fluoroquinolones.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.9
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• pp.1205-1209
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• 2000

The present study was undertaken to investigate the effect of stimulation of follicular development with eCG on the peripheral levels of inhibin and FSH in Murrah buffaloes. Estrus was synchronized in five normally cycling females by insertion of Crestar (Intervet, Boxmeer, Holland) implants for nine days. Estradiol valerate was administered i.m. on the day of implant insertion. On the 10th day of the induced estrous cycle a single dose of 3000 IU eCG (Folligon, Intervet, Boxmeer, Holland) was given, followed by treatment with 25 mg of $PGF_2$ alpha (Lutalyse, Upjohn, Belgium) 48 h later. Blood samples were obtained during the induced estrus, on cycle day 10 (luteal phase), at the superovulatory estrus (43 h after PGF) and during the periovulatory period (64 h after PGF). Ultrasonography was done daily to monitor follicular development. Plasma concentrations of inhibin and FSH were determined by specific radioimmunoassays. Differences between $mean{\pm}SEM$ values of different phases of the cycle were compared by ANOVA. The mean number of small (2-5 mm), medium (6-9 mm) and large (>10 mm) follicles observed two days after eCG treatment and on the day of superovulatory estrus was $2.8{\pm}0.31$, $5.2{\pm}0.30$ and $1.4{\pm}0.09$ and $1.9{\pm}0.21$, $2.8{\pm}0.40$ and $5.0{\pm}0.83$, respectively. The mean number of ovulations was $3.6{\pm}0.37$ and the mean number of unovulated follicles was $6.1{\pm}0.47$. Most of the follicles >10 mm in diameter had ovulated (72%). The mean ${\pm}SEM $ of plasma inhibin concentration $(2584.15{\pm}17.92pg/ml)$ during the superovulatory estrus was significantly higher $(p{\leq}0.05)$ than during the induced estrus $(749.87{\pm}17.29pg/ml)$, the luteal phase $(1099.54{\pm}24.98pg/ml)$ and periovulatory period $(1682.71{\pm}29.88pg/ml)$, respectively. $Mean{\pm}SEM$ plasma FSH concentration during the induced estrus $(10.35{\pm}0.41ng/ml)$ was not different from that during the superovulatory estrus $(8.52{\pm}0.39ng/ml)$, but was significantly higher $(p{\leq}0.05)$ than during the luteal phase $(2.81{\pm}0.42ng/ml)$ and periovulatory period $(5.7{\pm}0.28ng/ml)$. These data indicate that treatment with eCG in buffaloes for inducing superovulation results in a significant elevation in plasma inhibin levels and a decrease in plasma FSH levels during the superovulatory estrus. Thus, we suggest that the elevated plasma inhibin coming from fully developed follicles continued for a long time which results in inhibition of FSH leading to poor ovulation in the remaining follicles, which may be the cause of suboptimal superovulatory response.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.53.2-53.2
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• 2010

지금까지 능동 구동 디스플레이의 TFT backplane에 사용하고 있는 채널 물질로는 수소화된 비정질 실리콘(a-Si:H)과 저온 폴리실리콘(low temperature poly-Si)이 대표적이다. 수소화된 비정질 실리콘은 TFT-LCD 제조에 주로 사용되는 물질로 제조 공정이 비교적 간단하고 안정적이며, 생산 비용이 낮고, 소자 간 특성이 균일하여 대면적 디스플레이 제조에 유리하다. 그러나 a-Si:H TFT의 이동도(mobility)가 1 cm2/Vs이하로 낮아 Full HD 이상의 대화면, 고해상도, 고속 동작을 요구하는 UD(ultra definition)급 디스플레이를 개발하는데 있어 한계 상황에 다다르고 있다. 또한 광 누설 전류(photo leakage current)의 발생을 억제하기 위해서 화소의 개구율(aperture ratio)을 감소시켜야하므로 패널의 투과율이 저하되고, 게이트 전극에 지속적으로 바이어스를 인가 시 TFT의 문턱전압(threshold voltage)이 열화되는 문제점을 가지고 있다. 문제점을 극복하기 위한 대안으로 근래 투명 산화물 반도체(transparent oxide semiconductor)가 많은 관심을 얻고 있다. 투명 산화물 반도체는 3 eV 이상의 높은 밴드갭(band-gap)을 가지고 있어 광 흡수도가 낮아 투명하고, 광 누설 전류의 영향이 작아 화소 설계시 유리하다. 최근 다양한 조성의 산화물 반도체들이 TFT 채널 층으로의 적용을 목적으로 활발하게 연구되고 있으며 ZnO, SnO2, In2O3, IGO(indium-gallium oxide), a-ZTO(amorphous zinc-tin-oxide), a-IZO (amorphous indium-zinc oxide), a-IGZO(amorphous indium-galliumzinc oxide) 등이 그 예이다. 이들은 상온 또는 $200^{\circ}C$ 이하의 낮은 온도에서 PLD(pulsed laser deposition)나 스퍼터링(sputtering)과 같은 물리적 기상 증착법(physical vapor deposition)으로 손쉽게 증착이 가능하다. 특히 이중에서도 a-IGZO는 비정질임에도 불구하고 이동도가 $10\;cm2/V{\cdot}s$ 정도로 a-Si:H에 비해 월등히 높은 이동도를 나타낸다. 이와 같이 a-IGZO는 비정질이 가지는 균일한 특성과 양호한 이동도로 인하여 대화면, 고속, 고화질의 평판 디스플레이용 TFT 제작에 적합하고, 뿐만 아니라 공정 온도가 낮은 장점으로 인해 플렉시블 디스플레이(flexible display)의 backplane 소재로서도 연구되고 있다. 본 실험에서는 rf sputtering을 이용하여 증착한 a-IGZO 박막에 대하여 열처리 조건 변화에 따른 a-IGZO 박막들의 광학적, 전기적 특성변화를 살펴보았고, 이와 더불어 a-IGZO 박막을 TFT에 적용하여 소자의 특성을 분석함으로써, 열처리에 따른 Transfer Curve에서의 우리가 요구하는 Threshold Voltage(Vth)의 변화를 관찰하였다.

• Journal of Pharmaceutical Investigation
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• v.38 no.6
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• pp.373-380
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• 2008

In order to develop optimal formulation and iontophoresis condition for the transdermal delivery of levodopa, we have evaluated the effect of two permeation enhancers, ethanol and oleic acid in microemulsion, on transdermal delivery of levodopa. In vitro flux studies were performed at $33^{\circ}C$, using side-by-side diffusion cell and full thickness hairless mouse skin. Current density applied was $0.4\;mA/cm^2$ and current was off after 6 hours application. Levodopa was analysed by HPLC at 280 nm. The o/w microemulsions of oleic acid in buffer solution (pH 2.5 & 4.5) were prepared using oleic acid, Tween 80 and ethanol. The existence of microemulsion regions were investigated in pseudo-ternary phase diagrams. Contrary to our expectation, cumulative amount of levodopa transported from microemulsion (pH 2.5) for 10 hours was similar to that from aqueous solution in all delivery methods (passive, anodal and cathodal). When pH of the micro-emulsion was pH 4.5, cumulative amount of levodopa transported for 10 hours increased about 40% (anodal) to 50% (cathodal), when compared to that from aqueous solution. Flux from pH 4.5 microemulsion showed higher value than that from pH 2.5 in all delivery methods. These results seem to indicate that electroosmosis plays more dominant role than electrorepulsion in the flux of levodopa at pH 2.5. The effect of ethanol on iontophoretic flux was studied using pH 2.5 phosphate buffer solution containing 3% or 5% (v/v) ethanol. Flux enhancement was observed in passive and anodal delivery as the concentration of the ethanol increased. Without ethanol, cathodal delivery showed higher flux than anodal delivery. Anodal delivery increased the cumulative amount of levodopa transported 1.6 fold by 5% ethanol after 10 hours. However, in cathodal delivery, no flux enhancement of levodopa was observed during current application and only marginal increase in cumulative amount transported after 10 hours was observed by 5% ethanol. These results seem to be related to the decrease in dielectric constant of the medium and the lipid extraction of the ethanol, which decrease the electroosmotic flow, and thus decrease the flux. Overall, the results provide important insights into the role of electroosmosis and electrorepulsion in the transport of levodopa through skin, and provide some useful informations for optimal formulation for levodopa.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.3
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• pp.297-305
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• 1998

This study used in vivo intracellular recording in rat hippocampus to evaluate the effect of lidocaine and MK-801 on the membrane properties and the synaptic responses of individual neurons to electrical stimulation of the commissural pathway. Cells in control group typically fired in a tonic discharge mode with an average firing frequency of $2.4{\pm}0.9$ Hz. Neuron in MK-801 treated group (0.2 mg/kg, i.p.) had an average input resistance of $3.28{\pm}5.7\;M{\Omega}$ and a membrane time constant of $7.4{\pm}1.8$ ms. These neurons exhibited $2.4{\pm}0.2$ ms spike durations, which were similar to the average spike duration recorded in the neurons of the control group. Slightly less than half of these neurons were firing spontaneously with an average discharge rate of $2.4{\pm}1.1$ Hz. The average peak amplitude of the AHP following the spikes in these groups was $7.4{\pm}0.6$ mV with respect to the resting membrane potential. Cells in MK-801 and lidocaine treated group (5 mg/kg, i.c.v.) had an average input resistance of $3.45{\pm}6.0\;M{\Omega}$ and an average time constant of $8.0{\pm}1.4$ ms. The cells were firing spontaneously at an average discharge rate of $0.6{\pm}0.4$ Hz. Upon depolarization of the membrane by 0.8 nA for 400 ms, all of the tested cells exhibited accommodation of spike discharge. The most common synaptic response contained an EPSP followed by early-IPSP and late-IPSP. Analysis of the voltage dependence revealed that the early-IPSP and late-IPSP were putative $Cl^--and\;K^+-dependent$, respectively. Systemic injection of the NMDA receptor blocker, MK-801, did not block synaptic responses to the stimulation of the commissural pathway. No significant modifications of EPSP, early-IPSP, or late-IPSP components were detected in the MK-801 and/or lidocaine treated group. These results suggest that MK-801 and lidocaine manifest their CNS effects through firing pattern of hippocampal pyramidal cells and neural network pattern by changing the synaptic efficacy and cellular membrane properties.