• Korean Journal of Agricultural Science
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• v.33 no.1
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• pp.35-41
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• 2006

This study was conducted to investigate the developmental ability of interspecies cloned embryos after nuclear transfer of goat fetal fibroblast cells into porcien oocytes. Recipient porcine and goat oocytes were obtained from slaughterhouse and matured in vitro according to established protocols. Enucleation was accomplished by aspirating the first polar body and cytoplasm and a single donor cell was individually microinjected into vitelline space of the enucleated oocyte. The reconstructed oocytes were electrically fused with 0.3M mannitol fusion medium. After electro-fusion, interspecies reconstituted embryos were cultured in PZM-3 for 7 days. In porcine interspecies nuclear transfer with goat fetal fibroblast cells, the cleavage rate of reconstituted embryos were 58.9% which was no significant different from that in porcine nuclear transfer embryos (67.4%). However, the developmental rate into blastocyst stage was 5.4% in interspecies nuclear transfer which was significantly lower than that in porcine intraspecies nuclear transfer (13.6%). When the developmental ability of porcine interspecies nuclear transfer with goat cells was compared with goat intraspecies nuclear transfer, the cleavage rate of embryos were 59.2% and the developmental rate into morular and blastocyst stage was 13.6% in interspecies nuclear transfer which were significantly lower than those in intraspecies nuclear transfer embryos. This result indicated that porcine interspecies nuclear transfer with goat fetal fibroblast cells showed the developmental potential in vitro with lower cleavage and developmental rate compared with intraspecies nuclear transfer.

• Clinical and Experimental Pediatrics
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• v.46 no.2
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• pp.143-153
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• 2003

Purpose : Infection with Shiga-like toxin (SLT)-producing Escherichia coli, an emerging human pathogen found particularly in young children under 5 years of age, causes a spectrum of illnesses with high morbidity and mortality, ranging from diarrhea to hemorrhagic colitis and hemolytic uremic syndrome. Host mediators play an important role in the pathogenesis of SLT-I toxicity. The experiments described here were designed to investigate the effect of SLT-I on TNF-${\alpha}$ production and to understand the effect of TNF-${\alpha}$ on GB3 expression. We also further examine the relationship between the Gb3 level and the differential susceptibility of cells to the cytotoxic action of SLT-I. Methods : The effect of purified SLT-1 from E. coli O157 : H7 (ATCC 43890) on tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) production in Raw264.7 cells was investigated. Many mediators regulate endothelial cell membrane expression of the glycolipid globotriaosyleramide (Gb3), which serves as the toxin receptor, suggesting that the host response to the toxin or other bacterial products may contribute to pathogenesis by regulating target cell sensitivity to the toxins. Therefore, the relationships between Gb3 expression and cytotoxicity against SLT-I on three types of cells were evaluated. Results : Detectable levels of TNF-${\alpha}$ were produced as early as six hours after induction and continued to increase during 48 hours by SLT-I. It was also found that Vero cells and dendritic cells (DC2.4 cells) expressed high levels of Gb3, 83% and 68%, respectively, and that Raw264.7 cells had a low level of Gb3 (29%) and appeared refractory to cytotoxicity against SLT-I. Vero cells and DC2.4 cells expressing high levels of Gb3 were highly susceptible to SLT-I. Furthermore, macrophages showed a resistance to SLT-I cytotoxicity, despite the fact that Gb3 expression was enhanced. Conclusion : These results strongly suggest that the expression of Gb3 is necessary but not sufficient to confer sensitivity of macrophages to SLT-I and further underpin the important role of SLT-I and its Gb3 receptors in the pathogenesis of E. coli O157 infection.

• Investigative Magnetic Resonance Imaging
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• v.5 no.1
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• pp.57-65
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• 2001

Purpose : $T_2$-weighted half courier Echo Planar Imaging (T2HEPI) method is proposed to reduce measurement time of existing EPI by a factor of 2. In addition, high $T_2$ contrast is obtained for clinical applications. High resolution single-shot EPI images with $T_2$ contrast are obtained with $128{\times}128$ matrix size by the proposed method. Materials and methods : In order to reduce measurement time in EPI, half courier space is measured, and rest of half courier data is obtained by conjugate symmetric filling. Thus high resolution single shot EPI image with $128{\times}128$ matrix size is obtained with 64 echoes. By the arrangement of phase encoding gradients, high $T_2$ weighted images are obtained. The acquired data in k-space are shifted if there exists residual gradient field due to eddy current along phase encoding gradient, which results in a serious problem in the reconstructed image. The residual field is estimated by the correlation coefficient between the echo signal for dc and the corresponding reference data acquired during the pre-scan. Once the residual gradient field is properly estimated, it can be removed by the adjustment of initial phase encoding gradient field between $70^{\circ}$ and $180^{\circ}$ rf pulses. Results : The suggested T2EPl is implemented in a 1.0 Tela whole body MRI system. Experiments are done with the effective echo times of 72ms and 96ms with single shot acquisitions. High resolution($128{\times}128$) volunteer head images with high $T_2$ contrast are obtained in a single scan by the proposed method. Conclusion : Using the half courier technique, higher resolution EPI images are obtained with matrix size of $128{\times}128$ in a single scan. Furthermore $T_2$ contrast is controlled by the effective echo time. Since the suggested method can be implemented by software alone (pulse sequence and corresponding tuning and reconstruction algorithms) without addition of special hardware, it can be widely used in existing MRI systems.

• Journal of Embryo Transfer
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• v.16 no.3
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• pp.213-221
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• 2001

This study was conducted to examine in vitro developmental ability of porcine embryos after somatic cell nuclear transfer. The porcine ear fell was cultured in vitro for confluency in serum-starvation condition(TCM-199 + 0.5% FBS) far 3~6 days of cell confluency. The zona pellucida of IVM oocytes were partially drilled using laser system. Single somatic cell was individually transferred into enucleated oocytes. And the reconstructed embryos were electrically fused(single DC 1.9kv/cm, 30$\mu$ sec) with 0.3M mannitol. After electrofusion, embryos were activated(single AC 5v/mm, 5sec) and cultured in HCSU-23 medium containing 10% FBS at 39$^{\circ}C$, 5% $CO_2$ in air for 6 to 8 days. The fusion rate of donor cells was 45.6, 36.8 and 46.1% in 3~4, 5~6 days of serum starvation and non serum starvation(N-S), and were 52.7. 53.0 and 51.7% in 1~2. 5~6 and 13~14 passages of donor cell culture, respectively. No significant difference was found in the fusion rate of donor cells by the duration of serum starvation treatment or the number of donor cell passages. By the size of donor cells, however, the fusion rate was significantly higher(P<0.05) for reconstructed embryos derived from 25r $\mu$m $\geq$ site of donor cells (65.3%) than that of 25~30$\mu$ m(42.5%) or 30$\mu$ m(45.5%)$\leq$ cells. The cleavage rate was significantly (P<0.05) higher in 3~4 darts of serum starvation treatment(67.1%) than that in N-S (50.7%) or 5~6 days of starvation(57.1%). The activation rate by the size of donor cells in fused oocytes was 56.5, 68.8 and 58.5%, respectively, and was not significant.

• Journal of the Korean Vacuum Society
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• v.6 no.4
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• pp.348-353
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• 1997

Hydrogenated amorphous carbon(a-C:H) films were deposited on p-type Si(100) by DC saddle-field plasma enhanced CVD to investigate the effect of substrate bias on optical properties and structural changes. They were deposited using pure methane gas at a wide range of substrate bias at room temperature and 90 mtorr. The substrate bias voltage ($V_s$) was employed from $V_s=0 V$ to $V_s=400 V$. The information of optical properties was investigated by photoluminescence and transmitance. Chemical bondings of a-C:H have been explored from FT-IR and Raman spectroscopy. The thickness and relative hydrogen content of the films were measured by Rutherford backscattering spectroscopy (RBS) and elastic recoil detection (ERD) technigue. The growth rate of a-C:H film was decreased with the increase of $V_s$, but the hydrogen content of the film was increased with the increase of $V_s$. The a-C:H films deposited at the lowest $V_s$ contain the smallest amount of hydrogen with most of C-H bonds in the of $CH_2$ configuration, whereas the films produced at higher $V_s$ reveal dominant the $CH_3$ bonding structure. The emission of white photoluminescence from the films were observed even with naked eyes at room temperature and the PL intensity of the film has the maximum value at $V_s$=200 V. With $V_s$ lower than 200 V, the PL intensity of the film increased with V, but for V, higher than 200 V, the PL intensity decreased with the increase of $V_s$. The peak energy of the PL spectra slightly shifted to the higher energy with the increase of $V_s$. The optical bandgap of the film, determined by optical transmittance, was increased from 1.5 eV at $V_s$=0V to 2.3 eV at $V_s$=400 V. But there were no obvious relations between the PL peak and the optical gap which were measured by Tauc process.

• Journal of the Korean Vacuum Society
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• v.16 no.6
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• pp.483-488
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• 2007

Current feeder system (CFS) for Korea superconducting tokamak advanced research(KSTAR) project plays a role to interconnect magnet power supply (MPS) and superconducting (SC) magnets through the normal bus-bar at the room temperature(300 K) environment and the SC bus-line at the low temperature (4.5 K) environment. It is divided by two systems, i.e., toroidal field system which operates at 35 kA DC currents and poloidal field system wherein 20$\sim$26 kA pulsed currents are applied during 350 s transient time. Aside from the vacuum system of main cryostat, an independent vacuum system was constructed for the CFS in which a roughing system is consisted by a rotary and a mechanical booster pump and a high vacuum system is developed by four cryo-pumps with one dry pump as a backing pump. A self interlock and its control system, and a supervisory interlock and its control system are also established for the operational reliability as well. The entire CFS was completely tested including the reliability of local/supervisory control/interlock, helium gas leakage, vacuum pressure, and so on.

• Applied Biological Chemistry
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• v.33 no.1
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• pp.93-100
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• 1990

The optimum conditions of electric stimulation for electrofusion of protoplasts of petunia, carrot and soybean, and the effects of calcium, magnesium, protease, trypsin, triton X-100, concanavalin A, dimethyl sulfoxide(DMSO), glycerol monooleate and spermine on fusion frequency and/or viability of petunia protoplast were investigated. The optimum frequencies(Hz)-amplitudes(V/cm) of AC Pulse for protoplast pearl-chain formation were 10 kHz-20 V/cm and 1 MHz-60 V/cm for petunia, 100 kHz-40 V/cm and $1\;MHz-40{\sim}60\;V/cm$ for carrot, and $1\;MHz-40{\sim}80\;V/cm$ for soybean, respectively. The optimum condition of DC pulse treatment at the 1 MHz-60 V/cm-15sec treatment of AC for electrofusion of petunia protoplasts was 2.5 kV/cm-40 sec, and under this condition the fusion frequency and viability of protoplasts were 45 % and 10 %, respectively, Both of the protoplasts of carrot and soybean were not fused under the AC and DC conditions tested in this experiment. The electrofusion of petunia protoplasts was stimulated by calcium, and the fusion frequency and the viability of the protoplasts were 43 % and 11 % , respectively at the calcium concentration of 140 mM. Although fusion frequency was not affected by magnesium only, magnesium stimulated fusion frequency in the presence of calcium, and the viability and fusion frequency of petunia protoplasts were 45 % and 13 %, respectively, at 140 mM of magnesium-140 mM of calcium. The relative fusion frequencies of petunia protoplasts to the controls were increased by 2.4, 2.1, 1.6, 1.4, 1.8, 1.5 and 2.2 folds, respectively, by the treatments of protease, trypsin, triton X-100, concanavalin A, DMSO, glycerol monooleate, and spermine. The viabilities of petunia protoplasts were decreased by these substances.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.122-130
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• 2013

This work proposes a 12b 100MS/s 45nm CMOS four-step pipeline ADC for high-speed digital communication systems requiring high resolution, low power, and small size. The input SHA employs a gate-bootstrapping circuit to sample wide-band input signals with an accuracy of 12 bits or more. The input SHA and MDACs adopt two-stage op-amps with a gain-boosting technique to achieve the required DC gain and high signal swing range. In addition, cascode and Miller frequency-compensation techniques are selectively used for wide bandwidth and stable signal settling. The cascode current mirror minimizes current mismatch by channel length modulation and supply variation. The finger width of current mirrors and amplifiers is laid out in the same size to reduce device mismatch. The proposed supply- and temperature-insensitive current and voltage references are implemented on chip with optional off-chip reference voltages for various system applications. The prototype ADC in a 45nm CMOS demonstrates the measured DNL and INL within 0.88LSB and 1.46LSB, respectively. The ADC shows a maximum SNDR of 61.0dB and a maximum SFDR of 74.9dB at 100MS/s, respectively. The ADC with an active die area of $0.43mm^2$ consumes 29.8mW at 100MS/s and a 1.1V supply.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.15 no.1
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• pp.71-81
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• 2005

The purposes of this study was to collect, analyze, and describe the MF exposure levels from subways in Korea and to measure and evaluate the MF levels generated from electric appliances used at general homes. The target subway lines were Seoul Metropolitan Line 1 to Line 8, Bundang Line, Incheon Line, Daegu Line, Gwangju Line, and Busan Line 1 and Line 2. We measured at each station in those subway lines and, all the train types (pantograph-equipped, motor-equipped, and common), and platform types(facing and isolating) were investigated by the distance(80, 200, 400 cm) from the train on 19 targeted subway lines using 3 magnetic field measuring devices (EMDEXII, Enertech Co.) during the survey from January till October, 2004. On the other hand, the levels of the 60Hz magnetic fields generated from 14 items of home electric appliances such as electric blankets, hair dryers, electric razors, etc. were measured at 10 general homes using 5 EMDEXII meters with a sampling interval of 1.5 second by the distance(surface, 30, 50, 100, 300cm ) from the target electric appliances. The survey results in the whole subway lines examined in this study were as follows; Seoul Metropolitan Line 4 using AC(alternating current) power source showed the highest mean value of $2.85{\mu}T$, followed by Seoul Metropolitan Line 1 running between Seoul and Incheon using AC($2.78{\mu}T$), Seoul Metropolitan Line 1 between Seoul and Uijongbu using AC($2.73{\mu}T$), Bundang Line using AC($1.79{\mu}T$), Seoul Metropolitan Line 1 connected from Yongsan using AC($1.67{\mu}T$), Seoul Metropolitan Line 1 between Seoul and Suwon using AC($0.79{\mu}T$), and so on. In general, the intensity of the magnetic field in the subway systems in Korea was significantly higher when using AC($2.14{\pm}0.91{\mu}T$) than when using DC($0.29{\pm}0.44{\mu}T$) power source. Among the home electric appliances examined, microwave ovens showed the highest mean value of $7.69{\mu}T$, followed by hair dryers($6.47{\mu}T$), vacuum cleaners($5.27{\mu}T$), televisions ($2.26{\mu}T$), electric blankets($1.38{\mu}T$), personal computers ($0.81{\mu}T$), and so on. Two items of electric appliances showed the excess value of $0.2{\mu}T$ at the distance of 30cm in the MF exposure level; electric razors $1.58{\pm}2.13{\mu}T$ and vacuum cleaners $0.48{\pm}0.44{\mu}T$. As a whole, this study showed a tendency that the shift of the MF levels according to the increase of distance from the electric appliances was lower than those of the results surveyed in UK and USA. As a result, this study is expected to suggest meaningful data for the future study in exposure assessment of magnetic fields and for the establishment of guidelines for subways and electric appliances in Korea. More detailed and large scaled exposure assessment studies should be performed continuously to get the various and useful information on health risk assessment of MFs in Korea.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.11 s.353
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• pp.58-68
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• 2006

This work proposes a 10b 250MS/s $1.8mm^2$ 85mW 0.13um CMOS A/D Converter (ADC) for high-performance integrated systems such as next-generation DTV and WLAN simultaneously requiring low voltage, low power, and small area at high speed. The proposed 3-stage pipeline ADC minimizes chip area and power dissipation at the target resolution and sampling rate. The input SHA maintains 10b resolution with either gate-bootstrapped sampling switches or nominal CMOS sampling switches. The SHA and two MDACs based on a conventional 2-stage amplifier employ optimized trans-conductance ratios of two amplifier stages to achieve the required DC gain, bandwidth, and phase margin. The proposed signal insensitive 3-D fully symmetric capacitor layout reduces the device mismatch of two MDACs. The low-noise on-chip current and voltage references can choose optional off-chip voltage references. The prototype ADC is implemented in a 0.13um 1P8M CMOS process. The measured DNL and INL are within 0.24LSB and 0.35LSB while the ADC shows a maximum SNDR of 54dB and 48dB and a maximum SFDR of 67dB and 61dB at 200MS/s and 250MS/s, respectively. The ADC with an active die area of $1.8mm^2$ consumes 85mW at 250MS/s at a 1.2V supply.