• Journal of Microbiology and Biotechnology
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• v.21 no.3
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• pp.236-242
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• 2011

A psychrotrophic bacterium, Arthrobacter sp. ON14, isolated from Antarctica, was shown to exhibit a high ${\beta}$-galactosidase activity at a low temperature. A genomic library of ON14 was constructed and screened for ${\beta}$-galactosidase genes on functional plates containing 5-bromo-4-chloro-3-indolyl-${\beta}$-D-galactopyranoside (X-gal) as the substrate. Two different ${\beta}$-galactosidase genes, named as galA, galB, were found in ON14. Computational analyses of the genes revealed that the encoded protein GalA belongs to family 2 of glycosyl hydrolysases and is a cold-active protein, whereas GalB belongs to family 42 of glycosyl hydrolysases and is a mesophilic protein. Reverse transcription analyses revealed that the expression of galA is highly induced at a low temperature ($4^{\circ}C$ ) and repressed at a high temperature ($28^{\circ}C$ ) when lactose is used as the sole carbon source. Conversely, the expression of galB is inhibited at a low temperature and induced at a high temperature. The purified GalA showed its peak activity at $15^{\circ}C$ and pH 8. The mineral ions $Na^+$, $K^+$, $Mg^{2+}$, and $Mn^{2+}$ were identified as enzyme activators, whereas $Ca^{2+}$ had no influence on the enzyme activity. An enzyme stability assay revealed that the activity of GalA is significantly decreased when it is incubated at $45^{\circ}C$ for 2 h, and all its activity is lost when it is incubated at $50^{\circ}C$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.29.1-29.1
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• 2011

The selective catalytic reduction (SCR) of $MnO_x$ with $NH_3$ is an effective method for the removal of $MnO_x$ from stationary system. The typical catalyst for this method is $V_2O_5-WO_3(MoO_3)/TiO_2$, caused by the high activity and stability. However, This catalyst is active within $300{\sim}400^{\circ}C$ and occurs the pore plugging from the deposition of ammonium sulfate salts on the catalysts surface. It needs to locate the SCR unit after the desulfurizer and electrostatic precipitator without reheating of the flue gas as well as deposition of dust on the catalyst. The manganese oxides supported on titania catalysts have attracted interest because of its high SCR activity at low temperature. The catalytic activity of $MnO_x/TiO_2$ SCR catalyst with different manganese precursors have investigated for low-temperature SCR in terms of structural, morphological, and physico-chemical analyses. The $MnO_x/TiO_2$ were prepared from three different precursors such as manganese nitrate, manganese acetate (II), and manganese acetate (III) by the sol-gel method and then it calcinated at $500^{\circ}C$ for 2 hr. The structural analysis was carried out to identify the phase transition and the change intensity of catalytic activity by various manganese precursors was analyzed by FT-IR and Raman spectroscopy. These different precursors also led to various surface Mn concentrations indicated by SEM. The Mn acetate (III) tends to be more suppressive the crystalline phase (rutile), and it has not only smaller particle size, but also better distributed than the others. It was confirmed that the catalytic activity of MA (III)-$MnO_x/TiO_2$ was the highest among them.

• Microbiology and Biotechnology Letters
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• v.28 no.6
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• pp.329-333
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• 2000

Alkaline bacterium producing a high pro-tease activity at low temperature was isolated by using enrichment culture from soil samples and identified as Bacil-lus sp. WRD-1 Cell growth was maximal at 10 hours and the optimal initial pH and culture time of culture condition for enzyme production was pH 7 and 10 hours, respectively. Temperature range of high enzyme activity were $10~40^{\circ}C$. The optimal pH and temperature for the enzyme activity were pH9 and $30^{\circ}C$.

• Journal of Photoscience
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• v.9 no.2
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• pp.252-254
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• 2002

Djungarian hamsters show distinct seasonal rhythms in several physiological parameters. One of them is daily torpor that occurs in winter with decreased body temperature (about 1O-20$^{\circ}$C) during daytime. Daily torpor is induced by short-day photoperiod, food restriction and castration. But the mechanism to induce daily torpor has not been clarified. In the present study, we tried to clarify the process of daily torpor induction in detail. Adult male hamsters were kept in long photoperiod and high temperature (LP-HT) before the experiment and, thereafter, the animals were transferred to short photoperiod and low temperature (SP-LT), and they were kept in this condition for about six months. The daily rhythms of locomotor activity and body temperature were recorded every three-minutes by using the Minimitter telemetry system. Locomotor activity and body temperature showed very closely synchronized rhythms. All animals under LP-HT showed daily rhythms with higher locomotor activity and body temperature in nighttime than in daytime. Under SP-LT, there were two types of animals with and without showing daily torpor. Thus, they have individual differences in the response to SP -LT.

• Journal of Environmental Science International
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• v.22 no.1
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• pp.1-6
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• 2013

A fixed biofilm reactor system composed of anaerobic, anoxic(1), anoxic(2), aerobic(1) and aerobic(2) reactor was packed with synthetic activated ceramic (SAC) media and adopted to reduce the inhibition effect of low temperature on nitrification activities. The changes of nitrification activity at different wastewater temperature were investigated through the evaluation of temperature coefficient, volatile attached solid (VAS), specific nitrification rate and alkalinity consumption. Operating temperature was varied from 20 to $5^{\circ}C$. In this biofilm system, the specific nitrification rates of $15^{\circ}C$, $10^{\circ}C$ and $5^{\circ}C$ were 0.972, 0.859 and 0.613 when the specific nitrification rate of $20^{\circ}C$ was assumed to 1.00. Moreover the nitrification activity was also observed at $5^{\circ}C$ which is lower temperature than the critical temperature condition for the microorganism of activated sludge system. The specific amount of volatile attached solid (VAS) on media was maintained the range of 13.6-12.5 mg VAS/g media at $20{\sim}10^{\circ}C$. As the temperature was downed to $5^{\circ}C$, VAS was rapidly decreased to 10.9 mg VAS/g media and effluent suspended solids was increased from 3.2 mg/L to 12.0 mg/L due to the detachment of microorganism from SAC media. And alkalinity consumption was lower than theoretical value with 5.23 mg as $CaCO_3$/mg ${NH_4}^+$-N removal at $20^{\circ}C$. Temperature coefficient (${\Theta}$) of nitrification rate ($20^{\circ}C{\sim}5^{\circ}C$) was 1.033. Therefore, this fixed film nitrogen removal process showed superior stability for low temperature condition than conventional suspended growth process.

• Journal of Ecology and Environment
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• v.31 no.4
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• pp.317-325
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• 2008

P. glehnii, an evergreen conifer found in northern areas, is known as a cold-resistant species. In this experiment, we measured the water content, PSⅡ efficiency, chlorophyll fluorescence, pigments of the xanthophyll-cycle and activity of enzymes of the ascorbate-glutathione cycle during cold acclimation and at subsequent low-temperature conditions to examine the importance of acclimation to cold tolerance. P. glehnii showed a decrease in PSⅡ efficiency (especially in Fv) during cold acclimation and at subsequent low temperatures. However, cold-acclimated needles showed higher PSⅡ efficiency at low temperatures than nonacclimated needles. In addition, 0-YON (first-year needles) showed an increase in $\beta$-carotene and lutein, while 1-YON (one-year-old needles) immediately developed an antioxidant mechanism in the ascorbate-gluthathione cycle as soon as they were exposed to low temperature and both 0-YON and 1-YON showed increased zeaxanthin and de-epoxidation ratios at continuous low temperature. Based on our results, we suggest that P. glehnii maintain PSⅡ efficiency at low temperature by effectively protecting the photosynthetic apparatus from photo-damage by rapid induction of an antioxidant mechanism in 1-YON and dissipation of excess energy by $\beta$-carotene and lutein in 0-YON.

• Korean journal of food and cookery science
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• v.10 no.4
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• pp.357-362
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• 1994

Beef loaves(5${\times}5{\times}$5cm) were cooked by conventional moist-heat and by various levels of microwaves. The mean internal temperature of the meats cooked by low power microwaves for 5~15 min were not significantly different from the conventionally boiled meats for 30 min. When cooking was made by microwaves at low level for 5~10 min, or at high level for 2 min and additional heating at low power level for 5min, the percent cooking loss were comparable with the samples cooked conventionally for 20~40 min. General proteolytic activity determined with azocoll indicated that enzyme activity decreased as internal temperature increased(r=-0.5779, p<0.05), and maximum activity occured at meats conventionally moist-heated for 10 min and by low power microwave for 5 min. Sensory scores for tenderness were high at conventional moist-heat for 30 min, for 20 min, microwave cooked at thatwing power for 10 min and at low power level for 10 min, in descending order. There were no significant differences in the thiamin content of meats after various treatments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.395-395
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• 2008

Water-assisted synthesis of carbon nanotubes (CNTs) has been intensively studied in recent years, reporting that water vapor enhances the activity and lifetime of metal catalyst for the CNT growth. While most of these studies has been focused on the supergrowth of CNTs at high temperature, rarely has the similar approach been made for the CNT synthesis at low temperature. Since the metal catalyst are much less active at lower temperature, we expect that the addition of water vapor may increase the activity of catalyst more largely at lower temperature. We synthesized multi-walled CNTs at temperature as low as $360^{\circ}C$ by introducing water vapor during growth. The water addition caused CNTs to grow ~3 times faster. Moreover, the water-assisted growth prolonged the termination of CNT growth, implying the enhancement of catalyst lifetime. In general, a thinner catalyst layer is likely to produce smaller-diameter, longer CNTs. In a similar manner, the water vapor had a greater effect on the growth of CNTs for a smaller thickness of catalyst in this study. To figure out the role of process gases, CNTs were grown in the first stage and then exposed to each of process gases in the second stage. It was shown that water vapor and hydrogen did not etch CNTs while acetylene led to the additional growth of CNTs even faster in the second stage. As-grown CNTs were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and Raman spectroscopy.

• Korean Journal of Pharmacognosy
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• v.40 no.3
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• pp.178-183
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• 2009

In DPPH radical and nitric oxide scavenging ability, the extract of lowest temperature condition(40-15H ; 15 hours at $40^{\circ}C$ for drying) exhibited highest activity. The total phenolic and flavonoid contents of each extracts were found to be $120.4{\sim}193.3\;mg$/g and $86.91{\sim}94.55\;mg$/g respectively. It is shown that 40-15H was the highest content in each compound. In antimicrobial activity, a lower drying temperature conditions were found to be more strong activities in disc diffusion assay and each extracts showed MIC of identical level against every tested microbial strains. However 100-2H(2 hours at $100^{\circ}C$ for drying) was exhibited MIC of slightly low level against some strains. And every extract showed fine cell viabilities($101.7{\sim}122.9%$) against RAW 264.7 cell. In anti-proliferation activity against AGS, each extract showed a similar inhibition activity. However in anti-proliferation activity against HeLa, a lower drying temperature conditions showed more strong activities.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.153-156
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• 2009

Low temperature methane steam reforming to produce $H_2$ for fuel cells has been calculated thermodynamically considering both heat loss of the reformer and unreacted $H_2$ in fuel cell stack. According to the thermodynamic equilibrium analysis, it is possible to operate methane steam reforming at low temperatures. A scheme for the low temperature methane steam reforming to produce $H_2$ for fuel cells by burning both unconverted $CH_4$ and $H_2$ to supply the heat for steam methane reforming has been proposed. The calculated value of the heat balance temperature is strongly dependent upon the amount of unreacted $H_2$ and heat loss of the reformer. If unreacted $H_2$ increases, less methane is required because unreacted $H_2$ can be burned to supply the heat. As a consequence, it is suitable to increase the reaction temperature for getting higher $CH_4$ conversion and more $H_2$ for fuel cell stack. If heat loss increases from the reformer, it is necessary to supply more heat for the endothermic methane steam reforming reaction from burning unconverted $CH_4$, resulting in decreasing the reforming temperature. Experimentally, it has been confirmed that low temperature methane steam reforming is possible with stable activity.