• Journal of Microbiology and Biotechnology
• /
• v.31 no.5
• /
• pp.717-725
• /
• 2021

This study aimed to optimize medium composition and culture conditions for enhancing the biomass of Lactobacillus plantarum 200655 using statistical methods. The one-factor-at-a-time (OFAT) method was used to screen the six carbon sources (glucose, sucrose, maltose, fructose, lactose, and galactose) and six nitrogen sources (peptone, tryptone, soytone, yeast extract, beef extract, and malt extract). Based on the OFAT results, six factors were selected for the Plackett-Burman design (PBD) to evaluate whether the variables had significant effects on the biomass. Maltose, yeast extract, and soytone were assessed as critical factors and therefore applied to response surface methodology (RSM). The optimal medium composition by RSM was composed of 31.29 g/l maltose, 30.27 g/l yeast extract, 39.43 g/l soytone, 5 g/l sodium acetate, 2 g/l K₂HPO₄, 1 g/l Tween 80, 0.1 g/l MgSO₄·7H₂O, and 0.05 g/l MnSO₄·H₂O, and the maximum biomass was predicted to be 3.951 g/l. Under the optimized medium, the biomass of L. plantarum 200655 was 3.845 g/l, which was similar to the predicted value and 1.58-fold higher than that of the unoptimized medium (2.429 g/l). Furthermore, the biomass increased to 4.505 g/l under optimized cultivation conditions. For lab-scale bioreactor validation, batch fermentation was conducted with a 5-L bioreactor containing 3.5 L of optimized medium. As a result, the highest yield of biomass (5.866 g/l) was obtained after 18 h of incubation at 30℃, pH 6.5, and 200 rpm. In conclusion, mass production by L. plantarum 200655 could be enhanced to obtain higher yields than that in MRS medium

• Journal of Conservation Science
• /
• v.30 no.4
• /
• pp.335-343
• /
• 2014

This study classified the result of non-metallic inclusion analysis and result of microstructure investigation on the ironware excavated in the Baekje region into Han River, Geum River, and Yeongsan River to estimate the iron making temperature and study the characteristics of regional and temporal characteristics of the heat treatment technology and steel making technology. Regardless of era, bloom iron and sponge iron are judged to be the major method for making as a directreduction process in all three regions. The result of the reinterpretation of the non-metallic inclusion by the oxide ternary constitutional diagram suggest that the temperature inside of the furnace is estimated to be between $1,100{\sim}1,300^{\circ}C$ while making the steel. The magnetic iron ores are the major raw material of steel ore and irons with high $TiO_2$ are estimated to use iron sands. Ironware with $CaO/SiO_2$ rate higher than 0.4% are considered to have artificially added the flux of calcareous materials. It was found that the iron making method is the solid caburizing-steel which caburizes low-carbon steels by the CO gas and $CO_2$ gas created when heating the forging furnace with charcoal. Also, the ironware manufacturers in the Baekje during 3rd century recognized the heat treatment technology as they performed carburizing process and quenching to intentionally increase the strength of necessary parts.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.290-290
• /
• 2012

본 실험에서는 RF magnetron sputtering법과 evaporator법을 이용하여 다층박막 OMO구조를 $30{\times}30mm$ 유리기판 위에 제작하였다. Oxide층은 Sputter장비를 이용 IGZO막을 제작하였으며, Metal 층은 evaporator장비를 이용 Ag 막을 제작하였다. 변수로는 Oxide층의 시간에 따른 특성 변화를 연구하였다. 소결된 타겟으로는 In:Ga:ZnO를 각각 1:1:1 mol%의 조성비로 혼합하여 이용하였으며, Ag는 99.999%의 순도를 가진다. Oxide층의 RF sputter 공정 조건으로는 초기압력 $3.0{\times}10^{-6}$ Torr 이하로 하였으며, 증착 압력 $2.0{\times}10^{-2}$ Torr, Rf power 30 W, Ar gas 50 sccm으로 고정 시켰으며, 변수로는 5, 7, 9, 11분은 시간 차이를 두어 증착을 하였다. Metal층의 Evaporator 공정조건으로는 $5.0{\times}10^{-6}$ Torr이하, 전압은 0.3 V, Thickness moniter로 두께를 확인해가며 증착하였으며, $100{\AA}$으로 고정시켰다. 분석결과로는 XRD 측정 결과 35도 부근에서 Ag 피크가 관찰되었다. IGZO막 하나일때 90% 이상의 평균 투과율을 보였으며, 3층의 구조가 모두 증착됐을때의 투과도는 가시광영역에서 평균 80% 이상의 투과율을 보였으며, 500 nm부터 투과율이 떨어지기 시작해 800 nm부근에서는 평균 투과율이 30%까지 떨어져 Metal층인 Ag가 하나의 layer로 잘 증착이 된것을 보여주며, 플라즈몬효과를 보여줌을 알수있다. AFM측정 결과 평균 거칠기는 1.2 nm 정도의 거칠기를 확인했다. 홀 측정결과 전기적 특성은 발견되지 않았다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.317-317
• /
• 2012

사파이어는 우수한 광학적, 물리적, 화학적 특성을 가지고 있는 물질 중의 하나이며, 청색 발광특성을 나타내는 GaN와 격자상수, 열팽창 계수가 가장 유사할 뿐만 아니라 가격도 상대적으로 저렴하여 GaN 성장을 위한 기판으로 사용된다. 실제로 사파이어는 프로젝터와 전자파장치, 군사용 장비 등 다양한 분야에 응용되고 있으며, 발광 다이오드(LED)를 위한 기판으로 활용됨으로써 그 수요가 급격히 증가하고 있다. 그러나 사파이어 결정의 성장 중에 생길 수 있는 전위(dislocation)와 적층결함(stacking fault) 등의 결정 결함들은 결정 내에 존재하여 역학적, 전기적 성질에 큰 영향을 미칠 수 있다. 특히 사파이어가 청색 발광소자의 기판으로 사용되는 경우, 사파이어 기판 내부의 결정 결함은 증착되는 박막 특성에 영향을 미치게 된다. 따라서 사파이어의 보다 나은 응용을 위해서는 결함의 형성 메커니즘과 결정 결함의 평가기술 등에 대한 이해가 필요하고, 특히 결함의 정량적 평가 기술의 개발은 사파이어의 상용화에 중요한 핵심요소 중 하나이다. 결정 내 결함이 위치하는 부분은 분자나 원자간의 결합이 약하거나 높은 에너지 상태이므로, 결정의 표면을 적절한 산이나 염기 등을 이용하여 에칭하면 에칭반응은 결정의 전위 위치에 해당하는 부분부터 일어나 결정의 표면에 에치핏을 형성한다. 따라서 결정 표면에 나타나는 에치핏의 개수를 관찰하면 결정의 전위 밀도 파악이 비교적 간단하고, 에칭반응의 이러한 특징은 전위의 정량적 평가에 이용이 가능하다. 본 연구는 4인치 사파이어 조각기판을 수산화칼륨(KOH)으로 습식에칭 후 표면에 나타나는 에치핏의 형성거동과 이의 시간 및 온도 의존성에 관한 연구를 진행하였다. 또한 단결정의 전위밀도를 예측하기 위해 사파이어 조각시편의 단위면적당 에치핏의 개수를 파악하여 에치핏밀도(EPD, etch pid density)를 계산하였고, 값의 불확도(uncertainty)를 계산하여 전위밀도의 신뢰도를 평가하였다. 그 결과, 사파이어 조각시편의 에치핏밀도는 단위면적($cm^2$)당 약 ${\sim}10^2$개로 확인되었고, 이 값은 약 2%의 상대불확도를 가지는 것으로 나타났다.

• Economic and Environmental Geology
• /
• v.46 no.5
• /
• pp.375-390
• /
• 2013

The Kenticha rare-element (Ta-Li-Nb-Be) mineralized zone is located in ophiolitic fold and thrust complex of southern Ethiopia and was firstly discovered by joint exploration program of Ethiopia-Soviet in 1980s. It includes Dermidama, Kilkele, Shuni Hill, Kenticha, and Bupo pegmatites from south to north. The Kenticha pegmatite intruded parallel to NS-striking serpentinite and talc-chlorite schist, and is exposed approximately 2 km length and 400-700 m width. The Kenticha pegmatite is internally zoned and subdivided into lower quartz-muscovite-albite granite, intermediate muscovite-quartz-albite-microcline pegmatite, and upper spodumene-quartz-albite pegmatite, based on their mineral assemblage. The major, trace elements (e.g., Rb, Li, Nb, Ta, and Ga), and element ratios (e.g., K/Rb, Nb/Ta, Mg/Li, and Al/Ga) suggest that the fractionation and solidification of pegmatite have progressed from the lower towards upper pegmatite. In contrast, unlike general magmatic fractionation, Mg/Li ratios of the Kenticha pegmatite tend to be increased towards the upper pegmatite. It may result from post-magmatic hydrothermal alteration and/or interaction with upper ultramafic rock. Rare-element mineralization in Kenticha pegmatite concentrates on the upper pegmatite, which contains up to 3.0 wt % $Li_2O$, 3,780 ppm Rb, 111 ppm Cs, 1,320 ppm Ta, and 332 ppm Nb. Ore minerals in Kenticha pegmatite mostly include tantalite, spodumene, and lepidolite, and tantalite has an association with coarser quartz-spodumene and relatively fine sacchroidal albite. The tantalite is classified into Mn-tantalite as a function of $Mn^*[Mn/(Mn+Fe)]$ and $Ta^*[Ta/(Ta+Nb)]$ values. Its compositions ($Mn^*$, $Ta^*$, and Nb/Ta) between coarse and fine tantalites are different and the former is strongly enriched in Ta and depleted in Nb compared to latter one. In conclusion, rare-element mineralization in the Kenticha pegmatite may has occurred in the latest stage of magmatic fractionation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.10
• /
• pp.2497-2502
• /
• 2014

The 5 wt.% Ga-doped zinc oxide (GZO) thin films were fabricated on PES substrates with various RF power 50~80 W by using RF magnetron sputtering in order to investigate the optical and electrical properties of GZO thin films. The XRD measurement showed that GZO thin films exhibit c-axis orientation. At a RF power of 70W, the GZO thin film showed the highest (002) diffraction peak with a Full-Width-Half-Maximum (FWHM) of $0.44^{\circ}$. AFM analysis showed that the lowest surface roughness (0.20 nm) was obtained for the GZO thin film fabricated at 70 W of RF power. The electrical property indicated that the minimum resistivity ($6.93{\times}10^{-4}{\Omega}{\cdot}cm$) and maximum carrier concentration ($7.04{\times}10^{20}cm^{-3}$) and hall mobility ($12.70cm^2/Vs$) were obtained in the GZO thin film fabricated at 70W of RF power. The optical transmittance in the visible region was higher than 80 %, regardless of RF power. The optical band-gap showed the slight blue-shift with increased in carrier concentration which can be explained by the Burstein-Moss effect.

• Preventive Nutrition and Food Science
• /
• v.22 no.3
• /
• pp.184-190
• /
• 2017

Matrix metalloproteinases (MMPs) are endopeptidases that take significant roles in extracellular matrix degradation and therefore linked to several complications such as metastasis of cancer progression, oxidative stress, and hepatic fibrosis. Hizikia fusiformis, a brown algae, was reported to possess bioactivities, including but not limited to, antiviral, antimicrobial, and anti-inflammatory partly due to bioactive polysaccharide contents. In this study, the potential of H. fusiformis against cancer cell invasion was evaluated through the MMP inhibitory effect in HT1080 fibrosarcoma cells in vitro. H. fusiformis crude extract was fractionated with organic solvents, $H_2O$, n-BuOH, 85% aqueous MeOH, and n-hexane (n-Hex). The non-toxicity of the fractions was confirmed by MTT assay. All fractions inhibited the enzymatic activities of MMP-2 and MMP-9 according to the gelatin zymography assay. Cell migration was also significantly inhibited by the n-Hex fraction. In addition, both gene and protein expressions of MMP-2 and -9, and tissue inhibitor of MMPs (TIMPs) were evaluated by reverse transcription-polymerase chain reaction and Western blotting, respectively. The fractions suppressed the mRNA and protein levels of MMP-2, MMP-9 while elevating the TIMP-1 and TIMP-2, with the $H_2O$ fraction being the least effective while n-Hex fraction the most. Collectively, the n-Hex fraction from brown algae H. fusiformis could be a potential inhibitor of MMPs, suggesting the presence of various derivatives of polysaccharides in high amounts.

• KSBB Journal
• /
• v.10 no.1
• /
• pp.23-29
• /
• 1995

Calli were induced from leaf base region of germinated rice(Oryza sativa L. cv. Nakdong) with high frequency of up to 65% on LS medium supplemented with $2.5mg/{\ell}2$, 4-D in the dark at $27^{\circ}C$. Embryogenic calli of pale yellow, globular type were selected and used for the initiation of cell suspension cultures in AA2 liquid medium with $2mg/\ell$ 2,4-D, 0.2mg/$\ell$ kinetin arid $0.1mg/\ell$ GA3. Protoplasts were isolated from the embryogenic cell suspensions after 4 months of culture and then were electroporated with 400V/cm for 1 msec. Electroporated protoplasts divided with plating efficiency of 1.1% on PCM liquid medium supplemented with $2.5mg/\ell$ 2, 4-D, $0.1mg/\ell$ kinetin and 10mM proline. The protoplasts-derived microcalli were cultured on $0.2{\mu}m$ membrane fitter placed onto LS2.5 solid medium containing fine suspension cells as a feeder cells, for 2 weeks in the dark at $27^{\circ}C$. After an additional 2 weeks of culture under fluorescent light of $30{\pm}/3{\mu}E$.m^{-2}S^{-1}, yellow calli of 2mm diameter were transferred to regeneration medium. Shoots were produced from the green spot of protoplasts-derived calli and plants were regenerated form protoplast-derived green calli with frequencies of 11∼33%.

• Economic and Environmental Geology
• /
• v.32 no.2
• /
• pp.129-139
• /
• 1999

Hydrothermal gold deposits of the Trabong district in Vietnam occur as single-stage quartz $\pm$ calcite veins (0.3-1.2 m thick) which fill fault fractures in graphite-bearing gneiss and schist of the Chulai Complex and Kham Duc Formation of the Proterozoic age. Ore grades are 1.3 to 92.4 g/ton Au. Ore mineralogy is very simple, consisting mainly of pyrite with minor amounts of base-metal sulfides and electrum. Gold grains occur in two assemblages as follows: (1) early, Fe-rich (7.2-10.4 mole % FeS) sphalerite + electrum (50.4-64.3 atom % Au) assemblage occurring as inclusions in pyrite; (2) late, Fe-poor «4.7 mole % FeS) sphalerite + galena + electrum (47.6-81.7 atom % Au) assemblage occurring along fractures of pyrites. Based on fluid inclusion data and thermochemical considerations of ore mineral assemblages, ore minerals were formed at high temperatures (about $230^{\circ}C$ to $420^{\circ}C$) from $H_{2}O-CO_{2}(-CH_{4})$-NaCI fluids with the sulfur fugacity of about $10^{-6}$ to $10^{-10}$ atm. Fluid inclusion data also indicate that ore mineralization occurred mainly as a result of fluid unmixing accompanying $CO_2$ effervescence. Calculated oxygen and measured hydrogen isotope compositions of mineralizing waters (${\delta}^{18}O_{V-SMOW}$ values = 5.3 to 8.6$\textperthousand$, ${\delta}D_{V-SMOW}$ values = - 60 to - 52$\textperthousand$), along with the sulfur isotope compositions of vein sulfides (${\delta}^{34}S_{CDR}$ values = - 1.2 to 2.8$\textperthousand$) and carbon isotope compositions of inclusion $CO_2$ (${\delta}^{13}C_{PDB}$ values = - 4.7 to - 2.0$\textperthousand$) indicate that the high temperature (mesohypothermal) gold mineralization formed from a magmatic fluid.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2010.05a
• /
• pp.54.1-54.1
• /
• 2010

산화물 기반의 TFT는 유리, 금속, 플라스틱 등 기판 종류에 상관없이 균일한 제작이 가능하며, 상온 및 저온에서 대면적으로 제작이 가능하고, 저렴한 비용으로 제작 가능하다는 장점 때문에 최근 많은 연구가 이루어지고 있다. 현재 TFT 물질로 많이 연구되고 있는 산화물은 ZnO (3.4 eV)나 InOx (3.6 eV), GaOx (4.9 eV), SnOx(3.7 eV)등의 물질과 각각의 조합으로 구성된 재료들이 주로 사용되고 있으며, 가장 많은 연구가 이루어진 ZnO 기반의 TFT는 mobility와 switching 속도에서 우수한 특성을 보이나, 트렌지스터의 안정성이 떨어지는 것으로 보고 되고 있다. 그러나 IGZO 물질의 경우 결정학적으로 비정질이며 상온 및 저온에서 대면적으로 제작이 가능하고, 높은 전자 이동도의 특성을 가지고 있는 장점 때문에 최근 차세대 산화물 트렌지스터로 각광받고 있다. IGZO TFT 소자의 경우 Ag, Au, In, Pt, Ti, ITO 등 다양한 전극 물질이 사용되고 있는데, 이들 중 active channel과 ohmic contact을 이루는 Al, Ti, Ag의 적용을 통해 향상된 성능을 얻을 수 있다. 하지만 이들 전극 재료는 TFT 소자 제작시 필수적인 열처리 공정에 노출되면서 active channel 과 전극 사이 계면에 문제점을 야기할 수 있다. 특히, Ti의 경우 산화가 잘되기 때문에 전극계면에 TiO2를 형성하여 contact resistance의 큰 영향을 미치는 것으로 보고 되고 있다. 본 연구에서는 ohmic 전극재료인 Ti 또는 Ti/Au를 적용하여 TFT 소자 제작 및 특성에 대한 평가를 진행했으며, 열처리에 따른 전극과 IGZO 계면 사이의 미세구조와 전기적인 특성간의 상관관계를 연구하였다. 이를 통해, 소자 제작 공정을 최적화하고 신뢰성 있는 소자 특성을 얻을 수 있었다.