• The Korean Journal of Mycology
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• v.24 no.1 s.76
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• pp.8-16
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• 1996

The ${\alpha}-amylase$ of Alternaria alternata was purified through ammonium sulfate precipitation, dialysis and Sephadex G-100 column chromatography. One single band was obtained in SDS-polyacrylamide gel electrophoresis. The optimum pH for enzyme activity was 5.0 and the enzyme activity was maintained at $3.6{\sim}7.0$pH range. The optimum temperature for ${\alpha}-amylase$ activity was $40^{\circ}C$ and 71% of the activity was still maintained until 30 min after heating at $80^{\circ}C$. The ${\alpha}-amylase$ was slightly activated by $Mn^{2+},\;Zn^{2+}\;and\;Sn^{2+}$, but inhibited by $Ba^{2+},\;Pb^{2+},\;Co^{2+}\;and\;Ag^{1+}$. The $Hg^{2+}\;and\;Ag^{2+}$ slightly inhibited the activity of the enzyme at concentrations of $10^{-3}\;and\;10^{-4}M$. The Michaelis constant $(K_m)$ to soluble starch was $6.50{\times}10^{-2}M$ and inhibition constant $(K_i)$ by the 1mM EDTA was $8.0{\times}10^{-2}M$. The inhibition of this enzyme by EDTA was competitive one.

• The Korean Journal of Mycology
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• v.13 no.3
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• pp.149-156
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• 1985

The study was carried out to find effects of the saponins that were extracted from red ginseng on the growth of, aflatoxins production by, and protein patterns of Aspergillus flavus NRRL 3357. A. flavus with $10^6$ conidia as grown at $30^{\circ}C$ for seven days on the enriched medium. Mycelial growth and pH changes of medium which cultured the mold, were similar to those of the control group. However, aflatoxin which produced by the mold was less than that of the control in all concentration of the saponin. To be more specific, 0.3 % of the saponin inhibited production of aflatoxin $B_1$ and $G_1$ to the extent of 31.6 and 21% of the control. The protein peaks of A. flavus at the fourth day of the culture were shown high intensity near the level of 14,300 daltons. However, the mold which cultured in the medium containing the saponin showed low intensity of protein than that of the control group on all molecular weight.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.81.2-81.2
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• 2012

To fabricate a metal mold for injection molding, hot-embossing and imprinting process, mechanical machining, electro discharge machining (EDM), electrochemical machining (ECM), laser process and wet etching ($FeCl_3$ process) have been widely used. However it is hard to get precise structure with these processes. Electrochemical etching has been also employed to fabricate a micro structure in metal mold. A through mask electrochemical micro machining (TMEMM) is one of the electrochemical etching processes which can obtain finely precise structure. In this process, many parameters such as current density, process time, temperature of electrolyte and distance between electrodes should be controlled. Therefore, it is difficult to predict the result because it has low reliability and reproducibility. To improve it, we investigated this process numerically and experimentally. To search the relation between processing parameters and the results, we used finite element simulation and the commercial finite element method (FEM) software ANSYS was used to analyze the electric field. In this study, it was supposed that the anodic dissolution process is predicted depending on the current density which is one of major parameters with finite element method. In experiment, we used stainless steel (SS304) substrate with various sized square and circular array patterns as an anode and copper (Cu) plate as a cathode. A mixture of $H_2SO_4$, $H_3PO_4$ and DIW was used as an electrolyte. After electrochemical etching process, we compared the results of experiment and simulation. As a result, we got the current distribution in the electrolyte and line profile of current density of the patterns from simulation. And etching profile and surface morphologies were characterized by 3D-profiler(${\mu}$-surf, Nanofocus, Germany) and FE-SEM(S-4800, Hitachi, Japan) measurement. From comparison of these data, it was confirmed that current distribution and line profile of the patterns from simulation are similar to surface morphology and etching profile of the sample from the process, respectively. Then we concluded that current density is more concentrated at the edge of pattern and the depth of etched area is proportional to current density.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.78.2-78.2
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• 2012

최근 PRAM의 집적도 향상 및 3차원 적층에 의한 메모리 용량 향상을 위해 셀 선택 스위치로서 박막형 Ovonic Threshold Switching (OTS) 소자를 적용한 Cross bar 구조의 PRAM이 제안된 바 있다. OTS 소자는 비정질 칼코지나이드를 핵심층으로 하는 2단자 소자로서 고저항의 Off 상태에 특정 값 (문턱스위칭 전압) 이상의 전압을 가해주면 저저항의 On 상태로 바뀌고 다시 특정 값 (유지전압) 이하로 전압을 감소시킴에 따라 고저항의 Off 상태로 복원하는 특성을 갖는다. 셀 선택용 스위치로 적용되기 위해서는 핵심적으로 On-Off 상태간의 가역적인 변화 중에도 재료가 비정질 구조를 안정하게 유지해야 하며 전기적으로는 Off 상탱의 저항이 크고 또한 전류값의 점멸비가 커야 한다. GeSe는 이원계 재료로서 단수한 구성에도 불구하고 OTS 소자가 갖추어야할 기본적인 특성을 가지는 것으로 알려져 있다. 본 연구에서는 GeSe로 구성된 OTS 재료에 경원소인 질소를 첨가하여 비정질 상태의 안정성과 소자특성의 개선 효과를 조사하였다. RF-puttering 시 Ar과 $N_2$의 혼합 Gas를 사용하여 조성이 $Ge_{62}Se_{38}$ ($N_2$ : 3%)인 박막을 제작하여 DSC를 통해 결정화온도(Tx)를 확인하였고, $N_2$ gas의 함유량이 각각 1 %, 2 %, 3 %인 $Ge_{62}Se_{38}$인 박막을 전극의 접촉 부 면적이 $10{\times}10\;{\mu}m^2$인 cross-bar 구조의 소자로 제작하여 Threshold switching voltage ($V_{th}$), Delay time ($t_d$), $I_{on}/I_{off}$ 그리고 Endurance 특성을 평가하였다. DSC 분석 결과 $N_2$ 가 3 % 첨가된 GeSe 박막은 Tx가 $371^{\circ}C$에서 $399^{\circ}C$로 증가되었다. $N_2$가 1% 첨가된 GeSe 소자를 측정한 결과 $V_{th}$의 변화 없는 가운데 $I_{on}/I_{off}$이 약 $2{\times}10^3$에서 $5{\times}10^4$로 향상되었다. Endurance 특성 역시 $10^4$에서 $10^5$번으로 향상되었다. $t_d$의 경우 비정질 상태의 저항 증가로 인해 약 50% 증가되었다. 이러한 $N_2$의 첨가로 인한 비정질 GeSe 박막의 변화 원인에 대한 분석 결과를 소개할 예정이다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.12 no.3
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• pp.197-206
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• 2010

To provide baseline information essential for assessing environmental impacts of monsoon rainfalls in a mountainous watershed under mixed land use, we investigated spatiotemporal variations in water quality using a combined approach of seasonal water quality survey and intensive storm samplings. Biannual water sampling at nine locations encompassing major land use types showed generally lower electrical conductivity and Cl- concentrations during the typical wet period compared to the dry period, indicating rainfall-induced dilution of dissolved ions. Total metal concentrations, however, were significantly higher during the monsoon period, probably associated with rainfall-induced increases in suspended sediments. Intensive storm sampling during a small monsoon rainfall event (18 mm) and an extreme event (452 mm) showed rapid changes in both suspended sediments and dissolved solutes in an agricultural stream draining the Haean Basin where arable lands have expanded rapidly over the recent decades. By contrast, a nearby forest stream derived from North Korea showed little responses to the small event compared to larges changes during the extreme event. In the agricultural stream total Pb concentrations showed significant positive relationships with suspended sediments. Although limited sampling frequency and locations require a cautious interpretation, the overall results suggest that expansion of agricultural fields in steep mountainous watersheds can increase the susceptibility of soil erosion and its off-site environmental impacts under increasing rainfall variability and extremes.

• Korean Journal of Animal Reproduction
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• v.24 no.1
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• pp.59-67
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• 2000

This study was investigated the developmental potential of bovine embryos following nuclear transfer with bovine fetal fibroblasts (BFF). BFF were isolated from a male 45-day-old-fetus. Non-starved BFF labeled with MitoTracker were transferred into perivitelline space of enucleated oocytes. BFF-oocyte units were fused by electric pulse, and then fused oocytes were activated with calcium ionophore A23187 and subsequently 6-dimethylaminopurine (6-DMAP). The resulting zygotes were placed into CRlaa bovine embryo culture medium. Transfer of the nucleus into enucleated oocyte led to premature chromosome condensation, swelling and pronucleus formation. Remodeled oocytes were developed to the mitotic and 2-cell stage at 18 to 26 h after nuclear transfer. The incidence of in vitro development to the blastocyst stages was 21% of fused oocytes. Mitochondria of BFF eliminated rapidly and were not detected at 8 h after fusion. These results suggest that BFF can be successfully reprogrammed in enucleated bovine oocytes, and that reconstructed embryos can develop to the blastocyst stage.

• Analytical Science and Technology
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• v.12 no.3
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• pp.235-242
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• 1999

It is impossible to measure the fraction of the precipitates which are neither plenty nor distiguishable on micrographs, using point counting method or image analyzer. In this study, phase fraction of sigma, carbide and boride which are important to mechanical properties of Ni base superalloy Udimet 720 has been measured using a quantitative X-ray diffraction technique combined with electrochemical extraction. The alloys had been exposed at $800^{\circ}C$ for various times up to 3000 hours to have a variation of the amount of the minor precipitates. The amount of sigma had increased exponentially with increasing exposure time up to 3000 hours before saturation. It can be argued that the finishing point of precipitation is around 5000 hours and maximum amount of sigma to be produced is about 5% in weight. The amounts of $M_{23}C_6$ and $M_3B_2$ were maintained constant at the level of 0.1~0.5% in weight, regardless of exposure time.

• Analytical Science and Technology
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• v.13 no.5
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• pp.630-635
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• 2000

The concentration of neurotransmitters in rat brain was determined by HPLC-ECD (electrochemical detection) method and the effects of methanol extracts of some crude drugs, such as Polygala Radix, Myristicae Semen, Zizyphi Semen, Acori graminei Rhizoma, Visci Herba, Liriopsis Tuber, Myrrha on the concentration of neurotransmitters in the ethanol-treated rat brain were investigated. By the administration of ethanol, dopamine (DA), 3, 4-dihydroxyphenyl acetic acid (DOPAC) and serotonin (5-HT) levels in frontal cortex and 5-HT level in hippocampus were significantly increased compared with the neurotransmitter levels in the brain of saline-treated rats. The ${\gamma}$-aminobutyric acid (GABA) level in frontal cortex was decreased by the same treatment. There was a tendency that the DA level in frontal cortex and striatum of ethanol-treated rats were increased by the administration of crude drug extracts. Especially, Myrrha and Visci Herba significantly increased the DA level of frontal cortex in ethanol-treated rats, while they significantly decreased the 5-HT level in the same region of the brain. GABA level in striatum of ethanol-treated rats was significantly decreased by Myristicae Semen, Visci Herba and Myrrha. These results suggest that the tested crude drug extracts have selective interaction with neurotransmitters in specified region of central nervous system.

• Analytical Science and Technology
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• v.12 no.4
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• pp.306-311
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• 1999

Changes of silk protein compositions of average molecular weight (Mw) and free amino acid composition to different solubility conditions were studied by SDS-polyacrylamide electropholesis, gel permeation chromatography (GPC), and free amino acid analysis method. We can not detected average molecular weight distribution of different hydrochloric acid (HCl) conditions as SDS-polyacrylamide method, but as using GPC method, molecular weight distribution of 2N-HCl, 1N-HCl and 0.5N-HCl (3 hrs at $110^{\circ}C$ treated) are confirmed Mw 800, 1,500 and 3,700, respectively. The average molecular weight of calcium chroride and calcium chloride-enzyme treated samples are shown Mw 46,800 and 12,500, respectively. The degree of hydrolysis and the composition of the free amino acid in the fibroin hydrolysates effected significantly composition of free amino acids of the fibroin powder. The increase of the degree of hydrolysis and ratio of free amino acids and oligopeptides were found to be directly related to the concentration of hydrochloric acid and treatment of enzyme, resulting in the increase of water solubility.

• Analytical Science and Technology
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• v.25 no.5
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• pp.273-283
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• 2012

Phthalate plasticizers are regulated by RoHS, REACH and CPSC as hazardous substances. Responding to these international environmental restrictions, we developed ABS certified reference material (CRM) for determination of phthalate plasticizers such as DMP, DEP, DBP, BBP, DEHP and DnOP. The candidate material has been made with ABS resin widely used in electric and electronic products and 6 kinds of phthalate plasticizers. The making of the material involved a series of processes like extruding, cooling, pelletizing, and drying using twin screw extruder. Then it has been certified according to ISO Guide 35. Using isotope dilution-gas chromatography/mass spectrometry (ID-GC/MS), homogeneity, short-term stability, and long-term stability were evaluated. The certified values were determined by using primary reference material (PRM) of KRISS for traceability. From now on, we will provide ABS CRM to national and international companies and research institutes after certification as certified reference material and registering on COMAR (code of reference material).