• Journal of Microbiology and Biotechnology
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• v.9 no.1
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• pp.84-90
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• 1999

The growth of Bifidobacterium breve strain HP2 was completely inhibited by the addition of lactate higher than 4.0％ but not by the addition of acetate. Two kinds of lactate-tolerant mutants were isolated by the nitrosoguanidine treatment, enrichment on a liquid medium with 5％ lactate, and selection on agar plates with 5％ lactate. The mutants were not only able to grow in the presence of 5％ lactate but also improved in viable cell stability in the acidic pH range. In a pH-controlled fermentor, mutant N-1-5 grew at a rate slower than that of the wild type but its growth yield was higher. Notably, mutants were more halotolerant and more osmotolerant than the wild type and they were able to grow in the presence of 3％ NaCl or 25％ lactose at which the wild type entirely stopped the growth. The enzyme activities involved in the lactose metabolism in B. breve were measured to elucidate the biochemical basis for lactate tolerance. In the mutants, activities of several enzymes including phosphoglucomutase decreased compared to the wild-type, which may explain their lower growth rate. However, the activity of lactate dehydrogenase or its nature of inhibition by lactate was not altered.

• KSBB Journal
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• v.7 no.2
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• pp.112-117
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• 1992

An optimal composition of medium for hyaluronic acid production and some characteristics of its from Streptococcus zooepidemicus were investigated. The hyaluronic acid from S. zooepidemicus was reached maximum level in the BY-medium containing 0.1% beef extract, 0.1% yeast extract, 3.0% glucose, 2.0% peptone, 0.1% NaCl and $0.5%CaCO_3$ (pH 7.5) at $37^{\circ}C$ for 36 hours with shaking. Addition of $CaCO_3$ to the medium was necessary to neulralize the lowered pH which was resulted from hyaluronic acid production. Molecular weights of extracelluar and cellular hyaluronic acid produced by the strain were $1-1.4{\times }10^6$ and $5{\times}10^6$, respectively. The amount of extracellular hyaluronic acid was 91.9% of total hyaluronic acid produced and the vest was all intracellular.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.30-36
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• 2020

We demonstrated a successful fabrication of 4" Gallium Nitride (GaN)/Diamond High Electron Mobility Transistors (HEMTs) incorporated with Inner Slot Via Hole process. We made in manufacturing technology of 4" GaN/Diamond HEMT wafers in a compound semiconductor foundry since reported [1]. Wafer thickness uniformity and wafer flatness of starting GaN/Diamond wafers have improved greatly, which contributed to improved processing yield. By optimizing Laser drilling techniques, we successfully demonstrated a through-substrate-via process, which is last hurdle in GaN/Diamond manufacturing technology. To fully exploit Diamond's superior thermal property for GaN HEMT devices, we include Aluminum Nitride (AlN) barrier in epitaxial layer structure, in addition to conventional Aluminum Gallium Nitride (AlGaN) barrier layer. The current collapse revealed very stable up to Vds = 90 V. The trapping behaviors were measured Emission Microscope (EMMI). The traps are located in interface between Silicon Nitride (SiN) passivation layer and GaN cap layer.

• The Journal of Engineering Geology
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• v.30 no.3
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• pp.379-397
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• 2020

In this study, Long-term change of water quality in Donrae Hot Spring was characterized using water quality data from 1922 to 2019. According to Mann-Kendall analysis and Sen's slope using long-term water quality data of Dongnae Hot Spring from 1922 to 2019, temperature, Ca, SiO₂, and HCO₃ show an increasing trend whereas EC, Na, K, Mg, Cl, and SO₄ show a decreasing trend or negligible trend. In addition, the water type of Dongnae Hot Spring stably belongs to Na-Cl type over time. The spatial distributions of water temperature and chemical constituents in 2004, 2009, 2014, and 2019 show variable patterns with showing some difference depending on sampling locations in different years. These results indicate that despite the long-term pumping of the hot spring water, the water quality is quite stable during the entire study period.

• Korean Journal of Materials Research
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• v.4 no.1
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• pp.9-23
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• 1994

Epitaxial $CoSi_2$ layer has been grown on NaCl(100) substrate at low deposition temperature($200^{\circ}C$) by multitarget bias cosputter deposition(MBCD). The phase sequence and crystallinity of deposited silicide as a function of deposition temperature and substrate bias voltage were studied by X-ray diffraction(XRD) and transmission electron microscopy(TEM) analysis. Crystalline Si was grown at $200^{\circ}C$ by metal induced crystallization(M1C) and self bias effect. In addition to, the MIC was analyzed both theoretically and experimentally. The observed phase sequence was $Co_2Si \to CoSi \to Cosi_2$ and was in good agreement with that predicted by effective heat of formation rule. The phase sequence, the CoSi(l11) preferred orientation, and the crystallinity had stronger dependence on the substrate bias voltage than the deposition temperature due to the collisional cascade mixing, the in-situ cleaning, and the increase in the number of nucleation sites by ion bombardment of growing surface. Grain growth induced by ion bombardment was observed with increasing substrate bias voltage at $200^{\circ}C$ and was interpreted with ion bombardment dissociation model. The parameters of $E_{Ar}\;and \alpha(V_s)$ were chosen to properly quantify the ion bombardment effect on the variation in crystallinty at $200^{\circ}C$ with increasing substrate bias voltage using Langmuir probe.

• Clean Technology
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• v.22 no.2
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• pp.89-95
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• 2016

The nanotoxicity of ZnO nanoparticles used in cosmetics and tire industry is one of emerged issues. Herein, the removal of ZnO nanoparticles dispersed in aqueous phase and its ecotoxicity were investigated. In the short-term exposure for fertilized eggs (O. latipes), the deformity was observed at 5 mg L⁻¹ of ZnO nanoparticles in some individuals and delayed hatching of eggs by retarded growth was observed at 10 mg L⁻¹ of ZnO nanoparticles. This result show that ZnO nanoparticles have cytotoxic effect to the organisms lived in water phase. Therefore, herein, the removal of ZnO nanoparticles in aqueous phase by chemical precipitation was investigated. After addition of Na₂S and Na₂HPO₄, the precipitated ZnO was transformed to ZnS and Zn₃(PO₄)₂ particles, respectively. The removal efficiency of ZnO was reached to almost 100% for two cases. In addition, the toxicity tests about ZnS and Zn₃(PO₄)₂ particles showed no acute toxicity for D. magna. This implies that transformation of ZnO to ZnS and Zn₃(PO₄)₂ particles with very low ionization constant might decrease effectively the toxicity of ZnO.

• The Korean Journal of Mycology
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• v.14 no.1
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• pp.79-84
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• 1986

A cellulose-degrading enzyme from Ganoderma lucidum was partially purified by ammonium sulfate precipitation and its enzymatic properties were studied. The enzyme had an optimum pH for activity at 4.0, and its stability range was pH $4.0{\sim}7.0$. The optimum temperature was $55^{circ}C$ and the enzyme retained 80% original activity after heated at $50^{\circ}C$ for 60 min. The activation energy of the enzyme for CMC degradation was caculated and found to be 6.2 Kcal/mole. The enzyme was activited by the addition of $Co^{++},\;Mn^{++}$, but slightly inactivated by $Hg^{++}$. Various enzyme inhibitors and chemical reagents did not affect the enzyme activity. The enzyme acted on native celluose as well as CMC. The Michaelis constant for CMC was calculated to be 2.4 mg glucose ep/ml.

• Nuclear Engineering and Technology
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• v.28 no.5
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• pp.458-466
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• 1996

The effects of dopants on the modification of microstructure of UO$_2$ and UO$_2$-4wt%CeO$_2$ sintered pellets have been studied in hydrogen and $CO_2$/CO mixture atmospheres by using $Ta_2O_5$, TiO$_2$ and $Nb_2O_5$ as sintering additives. The dopant were added as oxide powders and homogenized by attrition milling. The mixed powders were pressed, and then sintered in hydrogen at 1$700^{\circ}C$ , or in oxidizing atmosphere using Controlled $CO_2$/CO mixtures at 125$0^{\circ}C$. Both density and microstructure of UO$_2$ are modified by the addition of dopants in reducing atmosphere. The sintered density is increased with $Ta_2O_5$ addition up to 0.33wt% and subsequently decreased with higher content of the additive. The effect on the densification and the gain growth are apparent with the addition of 0.24wt% $Nb_2O_5$. With 0.lwt% titania and 0.6wt% $Ta_2O_5$, the sintered density is decreased, but the grain size is increased. In oxidizing atmosphere, the grain sizes for UO$_2$ doped with the above additives are smaller than that for pure UO$_2$. The grain size of Ta or Nb-doped UO$_2$ is decreased with increasing $CO_2$/CO ratio, but that of pure UO$_2$or T-doped UO$_2$ is increased. A large portion of second phases is observed in UO$_2$ doped with 0.lwt% TiO$_2$ sintered in hydrogen atmosphere, while, in $CO_2$/CO atmospheres, the second phases or dopant agglomerates are not observed. For UO$_2$-4wt%CeO$_2$ mixed oxide, the effect of additives on the gain growth is not so much as that for the pure UO$_2$. This is attributed to the formation of clusters by dopant cations and Ce ions, so that the additives contribute to a lesser exent to the grain growth for the mixed oxide.

• Journal of Electrochemical Science and Technology
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• v.12 no.4
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• pp.406-414
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• 2021

Electrochemical devices are constructed for continuous syngas (CO + H₂) production with controlled selectivity between CO₂ and proton reduction reactions. The ratio of CO to H₂, or the faradaic efficiency toward CO generation, was mechanically manipulated by adjusting the space volume between the cathode and the polymer gas separator in the device. In particular, the area added between the cathode and the ion-conducting polymer using 0.5 M KHCO₃ catholyte regulated the solution acidity and proton reduction kinetics in the flow cell. The faradaic efficiency of CO production was controlled as a function of the distance between the polymer separator and cathode in addition to that manipulated by the electrode potential. Further, the electrochemical CO₂ reduction device using Au NPs presented a stable operation for more than 23 h at different H₂:CO production levels, demonstrating the functional stability of the flow cell utilizing the mechanical variable as an important operational factor.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.3
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• pp.477-481
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• 1998

Sea mustard paste was prepared by treating wet and dried sea mustard with 0.1M Na2CO3, which mainly aimed to extract alginate from the cell wall of sea mustard. The pastes were added to beef, chicken and pork to manufacture the meat patties. The effects of adding the paste were investigated in terms of sensory properties, texture(hardness)and weight changes after cooking. The sensory attributes such as taste, color, texture and juiciness were generally enhanced by adding the paste. The hardness of cooked patties was significantly decreased, so the paste provided softer texture. The addition of paste also resulted in decreasing the weight loss of meat patties after cooking.