• 한국분말재료학회지
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• 제8권1호
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• pp.13-19
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• 2001

Ni and NiO particles were made by a combustion synthesis process. The characteristics of synthesized powders were investigated with various kinds and amounts of fuels such as urea, citric acid and glycine. Ni phase particles without NiO phase were obtained through combustion synthesis process in air atmosphere with-out further calcinations process, when the content of glycine was 2.44 times of the stoichiometric ratio in the precursor solution. Primary particle sizes of synthesized Ni and NiO particles were about 20∼30 nm.

• 한국입자에어로졸학회지
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• 제8권2호
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• pp.89-95
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• 2012

Spherical mesoporous silica particles, of which main pore diameter was 3.8 nm, were successfully prepared by spray pyrolysis from aqueous silicic acid. The effect of precursor concentration, reaction temperature, and the addition of urea and PEG on the particle diameter and pore properties such as pore diameter, total pore volume, and specific surface area were investigated by using FE-SEM, particle size analyzer, and nitrogen absorption-desorption analysis. With an increase of the precursor concentration from 0.2 M to 0.7 M, the average particle diameter, total pore volume, and specific surface area of the porous silica particles increased from 0.56 to $0.96\;{\mu}m$, 0.434 to $0.486\;cm^3/g$, 467.8 to $610.4\;m^2/g$, respectively. Within the temperature range $(600\;^{\circ}C{\sim}800\;^{\circ}C)$, there was no significant difference in the pore diameter, total pore volume, and specific surface area. In addition, the addition of urea as an expansion aid led to slight increases in particle diameter, pore diameter, and specific surface area. However, when the polyethylene glycol (PEG) as an organic template was used, the total pore volume of porous particles increased dramatically.

• 한국입자에어로졸학회지
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• 제12권3호
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• pp.65-72
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• 2016

Nanoporous $SiO_2$ particles containing different pore volume and size were prepared from silicic acid by a spray pyrolysis. The pore size, pore volume and particle size could be controlled with varying the precursor concentration, reaction temperature, and amount of organic templates such as Urea and poly ethylene glycol (PEG). The pore size distribution, pore volume and specific surface area of as-prepared particles were analyzed by BET and BJH methods, and the average particle sizes were measured by a laser diffraction method. The nanoporous $SiO_2$ particles ranged $0.6-0.9{\mu}m$ in diameter were successfully synthesized and the average particle size increased as the silicic acid concentration increased. The morphology of nanoporous $SiO_2$ particles was spherical and pores ranged 1 - 40 nm in diameter were measured in the particles. In case of Urea added into silicic acid, it showed no much difference in the morphology, pore size and pore volume at different Urea concentration. On the other hand, when PEG was added, it was clearly observed that pore diameter and pore volume of the particles surface increased with respect to PEG concentration.

• 유기물자원화
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• 제29권4호
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• pp.5-13
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• 2021

가축분뇨의 요소에서 유래하는 암모니아는 미세먼지(PM2.5) 생성의 주요 전구체로 작용하여 대기질을 저하시키고 공중 보건에 유해한 영향을 미치는 것으로 알려져 있다. 본 연구의 목적은 Acetohydroxamic acid(AHA)의 주입에 따른 요소로부터 암모니아 전환의 억제에 대한 효과를 평가하는 것이었다. 실험은 다양한 요소 농도(500-4,000 mg Urea-N/L), AHA 농도(0-4,000 mg AHA/L), pH(pH 6-10) 및 온도(10-35℃)범위에서 수행되었다. 그 결과 AHA 농도가 높을수록 Urease 억제 효율이 증가함을 보여주었다. 그러나 특정 Urease 억제 활성은 pH가 높을수록 감소하여 pH 6에서 867.1±6.7 Unit/g AHA, pH 10에서 1,167.9±17.4 Unit/g AHA를 나타냈다. AHA와 대조군 모두에서 높은 온도에서 요소분해효소 억제 효율이 감소됨을 확인하였다. 본 연구결과를 통해 AHA가 가축분뇨 관리에서 암모니아 배출을 줄이기 위한 요소분해효소 억제제로 사용될 수 있음을 확인하였다.

• 한국세라믹학회지
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• 제35권5호
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• pp.451-457
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• 1998

$Li_2$$ZrO_3$ powder which is one of the candidates of breeding materials for the fusion reactor was syn-thesized by a precipitation-combustion process. Although precipitates from the reaction between zirconium nitrate and citric acid were existed in a precursor solution. $Li_2$$ZrO_3$ could easily be obtained by using the mixed fuel of urea and citric acid in stoichiometric composition. The phases of as-synthesized powder con-sisted of $Li_2$$ZrO_3$ and small amounts of $Li_6$$Zr_2O_3$ and $Li_2$$ZrO_3$ The latter phases disappeared after the cal-cination at $1100^{\circ}C$ for 2 h. The primary particle size and the specific surface area of as-synthesized powders were smaller than 20nm and 10-14 $M^2$/g, respectively. The primary particle size of the precipitation-combustion synthesized powders was affected by the size of precipitates present in a precursor solution.

• Bulletin of the Korean Chemical Society
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• 제35권10호
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• pp.2917-2921
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• 2014

Cerium-activated yttrium aluminate ($Y_3Al_5O_{12}:Ce^{3+}$) exhibiting a garnet structure has been widely utilized in the production of light emitting diodes (LEDs) as a yellow emitting phosphor. The commercialized yttrium aluminum garnet (YAG) phosphor is typically synthesized by a solid-state reaction, which produces irregular shape particles with a size of several tens of micrometers by using the top-down method. To control the shape and size of particles, which had been the primary disadvantage of top-down synthetic methods, we synthesized YAG:Ce nanoparticles with a diameter of 500 nm using a coprecipitation method under the atmospheric pressure without the use of template or special equipment. The precursor particles were formed by refluxing an aqueous solution of the nitrate salts of Y, Al, and Ce, urea, and polyvinylpyrrolidone (55 K) at $100^{\circ}C$ for 12 h. YAG:Ce nanoparticles were formed by the calcination of precursor particles at $1100^{\circ}C$ for 10 h under atmospheric conditions. The phase identification, microstructure, and photoluminescent properties of the products were evaluated by X-ray powder diffraction, scanning electron microscopy, absorption spectrum and photoluminescence analyses.

• Korean Chemical Engineering Research
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• 제59권3호
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• pp.435-442
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• 2021

요소를 이용한 균일용액침전법으로 망간이 첨가된 바륨 헥사알루미네이트를 제조하였다. 합성 후 수세 여부와 건조온도에 따른 영향을 열중량분석, X선 회절분석과 장방출 주사현미경으로 분석하였다. 수세하지 않은 여과단계만 거친 소성촉매가 수세단계를 거친 소성촉매보다 순수한 헥사알루미네이트 상을 얻을 수 있었다. 건조과정 동안 합성 후 잔존한 요소가 전구체에 탈수과정을 도와 주요 금속종인 깁사이트를 순수한 헥사알루미네이트로 변환되기 쉬운 보에마이트로 상변이에 영향을 주었다. 제조된 촉매의 메탄 연소성능 평가는 WO200이 가장 우수하였으며, 모든 촉매연소반응에서 NOx가 배출되지 않았다. 헥사알루미네이트는 최고 CO 배출량을 감소시키는데 영향을 주는 것으로 확인되었다.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 1988년도 학술대회지
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• pp.1-10
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• 1988

조사포닌을 복강내 투여하면 1) 핵내의 RNA polymerase의 활성도, 2) 핵내의 RNA합성, 3) 세포질의 RNA합성,4) 세포질내의 폴리리보좀 함량, 5) in vitro 상태에서의 쥐간의 polysome과 micro-some으로의 아미노산 유입율, 6) 방사능 표지된 아미노산의 혈청 단백질로의 유입율이 증가하였음을 과거에 보고 한 바 있으며 또한 4주간 조사포닌을 투여한 쥐에서 적출한 간세포를 전자 현미경으로 조사한 결과, 조면 소포체가 상당히 증가하였으며 초원심분리기로서 막에 결합한 ribosome에서의 polysome함량의 증가를 확인하였다. 최근 streptozotocin으로 유도한 단백질 결핍성 당뇨병 쥐에 $Rb_2$를 계속적으로 주사한 결과 blood urea nitrogen과 간내의 urea 농도가 현저히 감소하였으며 혈청내의 총단백질과 알부민의 농도가 대조군의 수치에 비하여 증가한 반면 간내의 RNA와 총 ribosome, 막에 결합된 ribosome의 함량이 증가하였다. 또한 $Rb_2$투여로 혈청내의 총단백질로의 방사능 표지 전구물질의 유입량이 증가하였으며 당뇨쥐에서의 질소균형을 개선시켰다. 이러한 실험적 결과에 근거하여 인삼 사포닌은 대사를 촉진시키고 RNA, 단백질 합성 등을 촉진하는 것으로 생각된다.

• 농약과학회지
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• 제4권2호
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• pp.63-68
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• 2000

담배거세미나방(Spodoptera litura)에서 [$^{14}C$] 표지된 N-acetyl glucosamine, UDP-N-acetylglucosamine을 이용하여 신규살충제 DBI-1015와 DBI-3204의 살충 mechanism을 조사하였다. 담배거세미나방의 표피에 incorporation 되어진 방사논의 양은 신규살충제의 농도에 따라 함수관계를 나타내었다 In vivo실험에서 [$^{14}C$] N-ncetylslucosamine에 대한 DBI-1015, DBI-3204와 diflubenzuron의 $I_{50}$ (ppm)값은 각각 0.57, 0.89, 0.26 ppm을 나타내었으며, [$^{14}C$] UDP-N-acetylglucosamine의 $I_{50}$ (ppm)값은 각각 0.99, 0.53, 0.45 ppm을 나타내었다. 표피절편을 이용한 in vitro 실험에서 표피에 incorporation된 [$^{14}C$] N-acetylglucosamine과 [$^{14}C$] UDP-N-acetylglucosamine의 양은 적었지만, $2{\mu}M$ 농도에서 무처리구에 비해 $40{\sim}60%$ 억제되었다.

• 대한유전성대사질환학회지
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• 제2권1호
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• pp.77-79
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• 2002

The urea cycle, consisting of a series of six enzymatic reactions, plays key roles to prevent the accumulation of toxic nitrogenous compound and synthesize arginine de novo. Five well characterized diseases have been described, resulting from an enzymatic defect in the biosynthesis of one of the normally expressed enzyme. This presentation will focus on two representative diseases; ornithine transcarbamylase(OTC) deficiency and citrullinemia(argininosuccinate synthetase deficiency). OTC deficiency is one of the most common inborn error of urea cycle, which is inherited in X-linked manner. We identified 17 different mutations in 20 unrelated Korean patients with OTC deficiency; L9X, R26P, R26X, T44I, R92X, G100R, R141Q, G195R, M205T, H214Y, D249G, R277W, F281S, 853 del C, R320X, V323M and 10 bp del at nt. 796-805. These mutations occur at well conserved nucleotide sequences across species or CpG hot spot. The L9X and R26X lead to the disruption of leader sequences, required for directing mitochondrial localization of the OTC precursor. Their phenotypes are severe, and neonatal onset. The G100R, R277W and V323M mutations were uniquely identified in patients with late onset OTC deficiency. The other genotypes are associated with neonatal onset. Out of 20 patients with OTC deficiency, only 6 patients are alive; two were liver transplanted, and normal in growth and development at 2, 4 years after transplantation respectively. Citrullinemia is an autosomal recessive disease, caused by the mutations in the argininosuccinate synthetase(ASS) gene. We identified in 3 major mutations in 11 unrelated Korean patients with citrullinemia; G324S, $IVS6^{-2}$ A to G, and 67 bp ins at nt 1125-1126. Among these, the 67 base pair insertion mutation is novel. The allele frequency of each mutation is; G324S(45%), IVS6-2 A to G(32%), and 67 base pair insertion(14%). All patients are diagnosed at neonatal or infantile age. Interestingly, two patients presented with stroke like episode. Out of 11 patients, 5 patients died. Among 6 patients alive, one patient was successfully liver transplanted.