• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.10-16
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• 2007

In this study, we examined the preparation and hydrolysis property of immobilized urease membrane to decompose harmful urea in the body and remove ammonia which was produced by its decomposition. Urease immobilized membrane was prepared by introducing anion-exchange group DEA into porous hollow-fiber membrane by radiation graft polymerization method, and immobilization of urease. When urease was immobilized at membrane introduced with anion-exchange group, the more increasing grafting rate, the more increasing immobilization amount. The result originates from the fact that a greater amount of protein was immobilized by forming a multilayer on the longer grafted chain. Meanwhile, the addition of the cross-linker was possible not only to suppress separation phenomenon produced during a washing process of immobilized urease membrane but also to enable the recycling of membrane. Urease Immobilized membrane with no separation phenomenon was prepared by cross-linking reaction for 5 h, and the hydrolysis rate of prepared urease immobilized membrane was over 98% and 50%, respectively, in 1 mol and 4 mol urea solutions.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.44-48
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• 2013

In this work, we have prepared tungsten doped vanadium oxide ($W-VO_2$) particles with a low phase transition temperature. $W-VO_2$ particles were synthesized via thermolysis method using vanadyl (IV) sulfate and ammonium bicarbonate as precursors. The structure and thermochromic property of synthesized $W-VO_2$ particles were investigated by FE-SEM, EDS, XRD, XPS, and DSC analysis. The prepared $W-VO_2$ showed a nearly platy morphology, which indicates that the tungsten was successfully doped in the crystal lattices of $VO_2$. $W-VO_2$ nanoparticles with the size of 60 nm exhibited a monoclinic crystal structure and its chemical composition and surface state were also likely to be close to that of $VO_2$. In addition, the phase transition temperature of $W-VO_2$ was $38.5^{\circ}C$, which was approximately $29.2^{\circ}C$ lower than that of pure $VO_2$ ($67.7^{\circ}C$), indicating that the prepared sample had a good reversible thermochromic stability.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.6
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• pp.606-615
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• 2010

This study aims to identify the characteristics of soil in Mongolia, one of the major Asian dust sources that influence the Korean Peninsula. Soil particle size was analyzed and the result shows that sand (57.5~97.3%) was identified prominently in most regions, followed by silt (2.5~34.7%) and clay (0.0~7.8%). Soil pH of the covered regions were in the range 7.1~10.1, either weak alkaline or strong alkaline. Analysis of ion species in the soil samples exhibited that $Na^+$ ($91.9\;mg\;kg^{-1}$), $Cl^-$ ($65.9\;mg\;kg^{-1}$), and $Ca^{2+}$ ($53.5\;mg\;kg^{-1}$) were detected more in the soil than other species such as ${SO_4}^{2-}$ ($19.2\;mg\;kg^{-1}$), ${NO_3}^-$ ($46.6\;mg\;kg^{-1}$), ${NH_4}^+$ ($3.9\;mg\;kg^{-1}$), $K^+$ ($22.0\;mg\;kg^{-1}$), and $Mg^{2+}$ ($10.2\;mg\;kg^{-1}$). As for heavy metal content in the soil, concentrations of soil-borne metals including Fe, Al, Ca, Mg, and K tended to be high, while metals that come from manmade sources Pb, Cd, Cr, V, and Ni were remarkably low. The concentration of organic carbon (OC) was relatively high at $15.9\;{\mu}g\;mg^{-1}$, while elemental carbon (EC), directly released in the process of fossil fuel combustion, was not detected at all or found in very small amounts. The result indicates that pollution from manmade sources scarcely occurred. The analysis results from this study may contribute to improving modeling accuracy by providing input data for Asian dust prediction models, and be used as base data for determining the process of physiochemical transformation of Asian dust during long-range transport.

• Korean Journal of Food Science and Technology
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• v.33 no.3
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• pp.282-287
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• 2001

This study was carried out to investigate the difference of ginsenoside compositions in crude ginseng saponins prepared by five different methods including three new methods. Two known methods are hot methanol(MeOH) extraction/n-butanol(n-BuOH) fractionation and hot MeOH extraction/Diaion HP-20 adsorption/MeOH elution. Three new methods are hot MeOH extraction/cation AG 50W $absorption/H_2O$ elution/n-BuOH extraction, cool MeOH extraction/Diaion HP-20 adsorption/MeOH elution and direct extraction with ethyl acetate(EtOAc)/n-BuOH. Analysis of ginsenoside composition in the crude saponins by conventional HPLC/RI(Refractive Index) did not show great difference between methods except EtOAc/n-BuOH method. However, HPLC/ELSD (evaporative light scattering detector) employing gradient mobile phase afforded fine resolution of ginsenoside Rf, $Rg_1$ and $Rh_1$, and great difference of ginsenoside compositions between methods. LC/MS revealed that large amount of prosapogenins were produced during the pass through the cation exchange (AG 50W) column being strongly acidic. Six major ginsenosides such as $Rb_1,w;Rb_2,$ Rc, Rd, Re and $Rg_1$, 5 prosapogenins and one chikusetsusaponin were identified by LC/MS. A newly established HPLC method employing ODS column and gradient mobile phase of $KH_2PO_4/CH_3CN$ revealed that malonyl ginsenosides were detected only in the crude saponin obtained from cool MeOH extraction.

• Atmosphere
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• v.26 no.2
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• pp.257-275
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• 2016

Asian dust is a seasonal meteorological phenomenon influencing most East Asia, irregularly occurring during spring. Unusual heavy Asian dust event in winter was observed in Seoul, Korea, with up to $1,044{\mu}g\;m^{-3}$ of hourly mean $PM_{10}$, in 22~23 February 2015. Causes of such infrequent event has been studied using both ground based and spaceborne observations, as well as numerical simulations including ECMWF ERA Interim reanalysis, NOAA HYSPLIT backward trajectory analysis, and ADAM2-Haze simulation. Analysis showed that southern Mongolia and northern China, one of the areas for dust origins, had been warm and dry condition, i.e. no snow depth, soil temperature of ${\sim}0^{\circ}C$, and cumulative rainfall of 1 mm in February, along with strong surface winds higher than critical wind speed of $6{\sim}7.5m\;s^{-1}$ during 20~21 February. While Jurihe, China, ($42^{\circ}23^{\prime}56^{{\prime}{\prime}}N$, $112^{\circ}53^{\prime}58^{{\prime}{\prime}}E$) experienced $9,308{\mu}g\;m^{-3}$ of hourly mean surface $PM_{10}$ during the period, the Asian dust had affected the Korean Peninsula within 24 hours traveling through strong north-westerly wind at ~2 km altitude. KMA issued Asian dust alert from 1100 KST on 22nd to 2200 KST on 23rd since above $400{\mu}g\;m^{-3}$ of hourly mean surface $PM_{10}$. It is also important to note that, previously to arrival of the Asian dust, the Korean Peninsula was affected by anthropogenic air pollutants ($NO_3^-$, $SO_4^{2-}$, and $NH_4^+$) originated from the megacities and large industrial areas in northeast China. In addition, this study suggests using various data sets from modeling and observations as well as improving predictability of the ADAM2-Haze model itself, in order to more accurately predict the occurrence and impacts of the Asian dust over the Korean peninsula.

• Korean Journal of Materials Research
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• v.20 no.10
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• pp.518-523
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• 2010

In this study, partially stabilized zirconia was synthesized using a chemical $Y_2O_3$ stabilizer and hydrothermal method. First, $YCl_3-6H_2O$ and $ZrCl_2O-8H_2O$ was dissolved in distilled water. Y-TZP (a $Y_2O_3$-doped toughened zirconia polycrystalline precursor) was also prepared by conventional co-precipitates in the presence of an excess amount of $NH_4OH$ solution under a fixed pH of 12. The Y-TZP precursors were filtered and repeatedly washed with distilled water to remove $Cl^-$ ions. $ZrO_2$-Xmol%$Y_2O_3$ powder was synthesized by a hydrothermal method using Teflon Vessels at $180^{\circ}C$ for 6 h of optimized condition. The powder added with the Xmol%- $Y_2O_3$ (X = 0,1,3,5 mol%) stabilizer of the $ZrO_2$ was synthesized. The crystal phase, particle size, and morphologies were analyzed. Rectangular specimens of $33mm{\times}8mm{\times}3$ mm for three-point bend tests were used in the mechanical properties evaluation. A teragonal phase was observed in the samples, which contains more than 3 mol% $Y_2O_3$. The $3Y-ZrO_2$ agglomerated particle size was measured at $7.01{\mu}m$. The agglomerated particle was clearly observed in the sample of 5 mol % $Y_2O_3-ZrO_2$, and and the agglomerated particle size was measured at 16.4 um. However, a 20 nm particle was specifically observed by FE-SEM in the sample of 3 mol% $Y_2O_3-ZrO_2$. The highest bending fracture strength was measured as 321.3 MPa in sample of 3 mol% $Y_2O_3-ZrO_2$.

• Journal of Korean Society for Atmospheric Environment
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• v.34 no.4
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• pp.554-566
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• 2018

The rice husk contains nutrients which can be easily utilized by microorganisms, and also has a water retaining ability, which played a crucial part in enabling it to become a biofilter media. In this study, we evaluated the applicability of rice husk pellet bio-scrubber as a microbiological carrier. The pelletization experiment of rice husk as a biological media was performed using PVA and EVA binder. Also, the feasibility tests of rice husk as a biological media for odor removal were carried out in order to know whether rice-husk contains useful components as a media for microbiological growth or not. Lastly, a combined test for odor gas absorption and biological oxidation was conducted using a lab scale bio-filter set-up packed with rice-husk pellets as wet-scrubber. The major components of the rice husk were carbon, hydrogen, nitrogen, and oxygen, while carbon acted as the main ingredient which comprised up to 23.00%. The C : N : P ratio was calculated as 45 : 1 : 2. Oxygen uptake rate, yield and decay rate of the rice husk eluent was calculated to be $0.0049mgO_2/L/sec$, 0.24 mgSS/mgCOD and 0.004 respectively. The most stable form of rice husk pellets was produced when the weight of the rice husk, EVAc, PVAc, and distilled water was 10 : 2 : 0.2 : 10. The prepared rice husk pellets had an apparent density of 368 g/L and a porosity of 59.00% upon filling. Dry rice husks showed high adsorption capacity for ammonia gas but low adsorption capacity for hydrogen sulfide. The bio-filter odor removal column filled with rice husk pellets showed more than 99.50% removal efficiency for NH3 and H2S gas. Through the analysis of circulation water, the prime removal mechanism is assumed to be the dissolution by water, microbial nitrification, and sulfation. Finally, it was confirmed that the microorganisms could survive well on the rice husk pellets, which provided them a stable supply of nutrients for their activity in this long-term experiment. This adequate supply of nutrients from the rice husk enabled high removal efficiency by the microorganisms.

• Journal of Microbiology and Biotechnology
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• v.22 no.3
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• pp.292-300
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• 2012

We report the expression, purification, and characterization of L-asparaginase (AnsA) from Rhizobium etli. The enzyme was purified to homogeneity in a single-step procedure involving affinity chromatography, and the kinetic parameters $K_m$, $V_{max}$, and $k_{cat}$ for L-asparagine were determined. The enzymatic activity in the presence of a number of substrates and metal ions was investigated. The molecular mass of the enzyme was 47 kDa by SDS-PAGE. The enzyme showed a maximal activity at $50^{\circ}C$, but the optimal temperature of activity was $37^{\circ}C$. It also showed maximal and optimal activities at pH 9.0. The values of $K_m$, $V_{max}$, $k_{cat}$, and $k_{cat}/K_m$ were $8.9{\pm}0.967{\times}10^{-3}$ M, $128{\pm}2.8$ U/mg protein, $106{\pm}2s^{-1}$, and $1.2{\pm}0.105{\times}10^4M^{-1}s^{-1}$, respectively. The L-asparaginase activity was reduced in the presence of $Mn^{2+}$, $Zn^{2+}$, $Ca^{2+}$, and $Mg^{2+}$ metal ions for about 52% to 31%. In addition, we found that $NH_4{^+}$, L-Asp, D-Asn, and ${\beta}$-aspartyl-hydroxamate in the reaction buffer reduced the activity of the enzyme, whereas L-Gln did not modify its enzymatic activity. This is the first report on the expression and characterization of the L-asparaginase (AnsA) from R. etli. Phylogenetic analysis of asparaginases reveals an increasing group of known sequences of the Rhizobial-type asparaginase II family.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.3-27
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• 1996

분체의 입자 배열이 불규칙한 경우뿐만 아니라 입자 크기가 극미세하여 X선회절분석이 불가능한 경우에도 비정질물질이라 한다. 수용액 속에서 이런 비정질 물질을 합성하기 위해서는 합성용액의 과포화도를 높여 계속 유지시킴에 따라 극미세 1차핵 생성의 지속적인 유도에 따른 입자 성장을 최대한 억제시켜야만 한다. 본 연구에서는 흡습제, 칼슘제 및 식품 첨가제 등으로 이용되는 비정질 탄산칼슘을 계에서 합성하고, 이때 생성된 비정질 상태의 겔을 수용액 환경을 변화시켜가면서 따라 결정화를 유도하고 탄산칼슘의 동질이상을 관찰하였다. CO2의 유속을 11/min, 교반속도를 600rpm으로 고정시키고, Ca(OH)2의 양을 10g에서 50g까지 변화시켜가면서 겔 상태의 비정질 탄산칼슘을 합성하였다. 이때 전기전도도는 CO2의 용해와 더불어 Ca(OH)2의 용해도가 증가함에 따라 변화하였으며, 반응종반부에는 겔화가 시작될 때까지 거의 일정하였다. 따라서, 이러한 사실들로부터 현탁액 내에서의 전기전도도의 변화는 Ca이온의 영향을 받는 것으로 사료된다. 비정질 탄산칼슘은 수용액에서 불안정하여 CO2 가스를 방출하면서 급격히 결정화되는데, 본 연구에서는 Ca(OH)2의 양을 20g으로 하여 위의 방법에 의해 얻어진 겔을 수용액의 종류와 농도 및 결정화 온도, 교반속도를 달리하면서 결정화시켰다. 교반속도를 100rpm으로 하여 물의 온도변화에 다라 결정화시킨 경우 전 온도범위에서 칼사이트상이었으며, 물의 온도가 5$^{\circ}C$일 경우에는 미세한 입자들이 응집된 형태였으나, 그 외의 온도변화조건에서는 모두 평균입경 0.4$\mu\textrm{m}$정도의 비교적 균일하 능면체 형태였다. 또한 교반속도를 500rpm으로 증가시켰을 경우에는 8$0^{\circ}C$에서 침상의 아라코나이트가 소량생성되었음을 SEM사진으로 관찰할 수 있었으며, 소량의 바테라이트도 혼재되어 결정화되었음을 XRD결과로 알 수 있었다. 교반속도를 100rpm으로 한 NH4Cl 0.5mol/l 수용액에서는 입자의 형태와 크기가 불규칙한 칼사이트로 결정화되었으며, MgCl2 0.05mol/l 수용액의 경우에는 순수한 H2O의 경우에서와는 달리 2$0^{\circ}C$에서는 모서리가 무딘 매우 균일한 크기의 칼사이트 입자가 관찰되었으며, 6$0^{\circ}C$부터는 아라고나이트가 생성됨을 관찰할 수 있었다. 따라서, 고온(8$0^{\circ}C$)의 농도 MgCl2 수용액(0.1, 0.2 mol/l)에서 교반속도를 높여(800rpm) 겔을 결정화시킨 결과 아라고나이트의 생성수율이 증가되는 것을 확인할 수 있었다.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.25 no.3
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• pp.1-12
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• 2012

Objectives : Fagopyrum esculentum(FE) has been used for removal of inflammation of internal organs and treatment of sore and ulcer by heat toxin in Korean herbal medicines. In this study, To investigated the protective effect of FE on allergic response, we determined whether FE inhibits allergic response. Methods : The effect of FE was analyzed by ELISA, RT-PCR and Western blot in RBL-2H3 cells. We investigated cell viability, ${\beta}$-hexosaminidase, as a marker of degranulation, cytokne, and intracellular ROS and MAPK and NF-${\kappa}B$ signaling. Results : We found that FE suppressed ${\beta}$-hexosaminidase release, the production of IL-4 and TNF-${\alpha}$ and intracellular ROS level in RBL-2H3 by the anti-DNP IgE plus DNP-HSA stimulation. FE also significantly inhibited cytokine mRNA expressions, such as IL-$1{\beta}$, IL-2, IL-3, IL-4, IL-5, IL-6, IL-13, TNF-${\alpha}$ and GM-CSF in RBL-2H3. In addition, PF suppressed the phospholyation of ERK1/2, JNK1/2, p38 and $I{\kappa}B{\alpha}$ and NF-${\kappa}B$ signal transduction pathway. Conclusions : Our results indicate that FE protects against allergic response and exerts an anti-inflammatory effect through the inhibition of degranulation and production of cytokines and ROS via the suppression MAPK and NF-${\kappa}B$ of signal transduction. Abbrevations : FE, Fagopyrum esculentum; RBL-2H3, rat basophilic leukemia cell line; ROS, reactive oxygen species; MAPK, Mitogen-activated protein kinase; $NF{\kappa}B$, nuclear factor ${\kappa}B$; $TNF{\alpha}$, Tumor necrosis factor alpha; GM-CSF, Granulocyte macrophage colony-stimulating factor; ERK, extracellular-signal-regulated kinase; JNK, c-Jun NH2-terminal kinase; p38, p38 MAP kinase; $I{\kappa}B{\alpha}$, inhibitory-kappa B alpha.