• 멤브레인
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• 제14권2호
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• pp.117-125
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• 2004

본 연구는 직접메탄을 연료전지(Direct Methanol Fuel Cell)에 적용가능한 양이온교환막 개발에 관한 것으로 PVA/PAM/ZrP 막을 제조하여 PAM, ZrP의 함량 및 농도 변화에 따른 막의 특성을 연구하였다. PVA/PAM/ZrP 막은 PVA에 가교제인 PAM의 함량을 7∼11 wt%로 증가시켜 제조하였으며 그 각각의 막에 8$0^{\circ}C$에서 zirconyl chloride와 Phosphoric acid solution에 침적시켜 제조하였다. ZrP의 농도를 1, 2 M로 변화시켜 메탄을 투과도, 이온전도도, 함수율 및 이온교환용량을 측정하였다. PVA/PAM/ZrP 막의 메탄올 투과도는 10/^{-8}∼l0^{-6}$ $\textrm{cm}^2$/sec, 이온전도도는 $10^{-3}~10^{-2}$ S/cm 정도 나타내었으며 함수율은 0.26∼l.17 g $H_2O$/g membrane, 이온교환용량은 2.59∼5.1 meq/g membrane의 결과를 보였는데 이는 PVA/PAM 막과 비교하여 메탄을 투과도, 이온전도도는 각각 18%, 23% 정도 증가한 것으로 관찰되었다.

• The Journal of Advanced Prosthodontics
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• 제9권4호
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• pp.257-264
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• 2017

PURPOSE. To evaluate the adhesion to CAD/CAM feldspathic blocks by failure analysis and shear bond strength test (SBSt) of different restorative systems and different surface treatments, for purpose of moderate chipping repair. MATERIALS AND METHODS. A self-adhering flowable composite (Vertise Flow, Kerr) containing bi-functional phosphate monomers and a conventional flowable resin composite (Premise Flow, Kerr) applied with and without adhesive system (Optibond Solo Plus, Kerr) were combined with three different surface treatments (Hydrofluoric Acid Etching, Sandblasting, combination of both) for repairing feldspathic ceramics. Two commercial systems for ceramic repairing were tested as controls (Porcelain Repair Kit, Ultradent, and CoJet System, 3M). SBSt was performed and failure mode was evaluated using a digital microscope. A One-Way ANOVA (Tukey test for post hoc) was applied to the SBSt data and the Fisher's Exact Test was applied to the failure analysis data. RESULTS. The use of resin systems containing bi-functional phosphate monomers combined with hydrofluoric acid etching of the ceramic surface gave the highest values in terms of bond strength and of more favorable failure modalities. CONCLUSION. The simplified repairing method based on self-adhering flowable resin combined with the use of hydrofluoric acid etching showed high bond strength values and a favorable failure mode. Repairing of ceramic chipping with a self-adhering flowable resin associated with hydrofluoric acid etching showed high bond strength with a less time consuming and technique-sensitive procedure compared to standard procedure.

• Restorative Dentistry and Endodontics
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• 제14권1호
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• pp.7-24
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• 1989

The purpose of the study was to evaluate the cytotoxic effects of polycarboxylate cements and zinc phosphate cements in vitro. Human fibroblasts were cultured in ${\alpha}$-MEM, and each cement was manually mixed and filled in glass ring cylinder (8${\times}$8mm in diameter, in height.) Cement filled cylinders were placed in the center of the dish (35mm in diameter) containing 3ml of ${\alpha}$-MEM. Millipore filters to simulate dentinal barrier were also placed between the cylinder and the dish, then stored in 5% $CO_2$ containing chamber for 1 and 2 weeks at the temperature of $36.6^{\circ}C$. The results of the experiments were analyzed by counting the cells in the period of one week and two weeks respectively, and were assessed by calculating the cell multiplication rate and the relative growth rate. The experimental groups and the control group were compared. The results of the study were summarized as follows. 1. Durelone brand of the polycarboxylate cements showed marked cytotoxicity after one week, but after two weeks the toxicity decreased remarkably. Poly-F brand exhibited moderate cytotoxicity after one week, but after two weeks the toxicity slightly decreased. HY-BOND brand was weakly cytotoxic after one week, but after two weeks the toxicity became significant. 2. The cytotoxicity of the zinc phosphate cements was negligible after one week, but after two weeks Lee Smith brand revealed considerable cytotoxicity. 3. In general, the zinc phosphate cements were less cytotoxic than the polycarboxylate cements.

• Journal of Microbiology and Biotechnology
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• 제30권5호
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• pp.762-769
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• 2020

Vitamin K2 (menaquinone) is an essential vitamin existing in the daily diet, and menaquinone-7 (MK-7) is an important form of it. In a recent work, we engineered the synthesis modules of MK-7 in Bacillus subtilis, and the strain BS20 could produce 360 mg/l MK-7 in shake flasks, while the methylerythritol phosphate (MEP) pathway, which provides the precursor isopentenyl diphosphate for MK-7 synthesis, was not engineered. In this study, we overexpressed five genes of the MEP pathway in BS20 and finally obtained a strain (BS20DFHG) with MK-7 titer of 415 mg/l in shake flasks. Next, we optimized the fermentation process parameters (initial pH, temperature and aeration) in an 8-unit parallel bioreactor system consisting of 300-ml glass vessels. Based on this, we scaled up the MK-7 production by the strain BS20DFHG in a 50-l bioreactor, and the highest MK-7 titer reached 242 mg/l. Here, we show that the engineered strain BS20DFHG may be used for the industrial production of MK-7 in the future.

• 한국재료학회지
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• 제19권4호
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• pp.220-223
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• 2009

Lithium dihydrogen phosphate ($LiH_2PO_4$) powder was purchased from Aldrich Chemical Co. From the scanning electron microscope (SEM) observation, these polycrystals have dimensions in the range of $25-250{\mu}m$. The electrical conductivity was measured at a measuring frequency of 1 kHz on heating polycrystalline lithium dihydrogen phosphate ($LiH_2PO_4$) from room temperature to 493 K. Two anomalies appeared at 451 K ($T_{p1}$) and 469 K ($T_{p2}$). The electrical conductivity reached the magnitude of the superprotonic phases: $3{\times}10^{-2}{\Omega}^{-1}cm^{-1}$ at 451 K ($T_{p1}$) and $1.2{\times}10{\Omega}^{-1}cm^{-1}$ at 469 K ($T_{p2}$). It is uncertain whether the superprotonic phase transformations are due to polymorphic transitions in the bulk, surface transitions, or chemical reactions (thermal decomposition) at the surface. Considering several previous thermal studies (differential scanning calorimetry and thermogravimetry), our experimental results seem to be related to the last case: chemical reactions (thermal decomposition) at the surface with the progressive solid-state polymerization.

• 한국지하수토양환경학회지:지하수토양환경
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• 제23권6호
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• pp.46-53
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• 2018

Mobility reduction of 2,4,6-trinitrotoluene (TNT) was tested by amending monopotassium phosphate (MKP) and montmorillonite to a firing range soil contaminated with TNT. While addition of MKP enhanced sorption of TNT on soil matrix, and combined use of MKP with montmorillonite significantly decreased desorption of TNT as well as remarkably increased the TNT sorption. Montmorillonite amendment by 5% of soil mass resulted in TNT desorption of 0.12 mg/kg from soil loaded with 9.93 mg/kg-TNT. The decrease of TNT desorption was proportional to the amount of montmorillonite amended. At 10 and 15% amendment, only 0.79 and 1.23 mg/kg-TNT was desorbed from 29.33 and 48.80 mg/kg-TNT. In addition, the leaching of TNT with synthetic precipitation leaching procedure (SPLP) and hydroxypropyl-${\beta}$-cyclodextrin (HPCD) decreased, indicating that TNT in MKP/montmorillonite-treated soil became more stable and less leachable. The results demonstrate that addition of MKP and montmorillonite to TNT-contaminated soil reduces the mobility of TNT from soil not only by increasing TNT sorption, but also decreasing TNT desorption. It was found that MKP and montmorillonite amendments by 5 and 10% of soil mass, respectively, were optimal for reducing the mobility of soil TNT.

• Parasites, Hosts and Diseases
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• 제60권5호
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• pp.339-344
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• 2022

The development of drug resistance is one of the most severe concerns of malaria control because it increases the risk of malaria morbidity and death. A new candidate drug with antiplasmodial activity is urgently needed. This study evaluated the efficacy of different dosages of aqueous extract of Strychnos ligustrina combined with dihydroartemisinin and piperaquine phosphate (DHP) against murine Plasmodium berghei infection. The BALB/c mice aged 6-8 weeks were divided into 6 groups, each consisting of 10 mice. The growth inhibition of compounds against P. berghei was monitored by calculating the percentage of parasitemia. The results showed that the mice receiving aqueous extract and combination treatment showed growth inhibition of P. berghei in 74% and 94%, respectively. S. ligustrina extract, which consisted of brucine and strychnine, effectively inhibited the multiplication of P. berghei. The treated mice showed improved hematology profiles, body weight, and temperature, as compared to control mice. Co-treatment with S. ligustrina extract and DHP revealed significant antimalarial and antipyretic effects. Our results provide prospects for further discovery of antimalarial drugs that may show more successful chemotherapeutic treatment.

• 유기물자원화
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• 제30권1호
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• pp.33-39
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• 2022

혐기성 소화 슬러지 탈리여액을 대상으로 마그네슘 공급원이 인산암모늄마그네슘(MAP) 결정화에 의한 인산염 회수에 어떠한 영향을 미치는지 알아보기 위해 회분식 실험을 실시하였다. 마그네슘 공급원으로 염화마그네슘, 수산화마그네슘 그리고 산화마그네슘을 사용하여 다양한 pH (7.5, 8.0 및 8.5) 조건 및 Mg/P 몰 비율(1.0, 1.5, 2.0 및 2.5)에서 인산염 회수를 실시하였다. 그 결과, 마그네슘 공급원과 관계없이 pH 조건과 Mg/P 몰 비율이 높을수록 인산염 회수율이 증가하였다. pH가 가장 낮은 7.5의 조건에서는 Mg/P 몰 비율이 증가할수록 인산염 회수율이 증가하였는데 산화마그네슘, 수산화마그네슘, 염화마그네슘의 순으로 높았다. 그러나 pH가 가장 높은 8.5의 조건에서는 Mg/P 몰 비율과 관계없이 모든 마그네슘 공급원에서 90% 이상의 높은 인 회수율을 얻을 수 있었다. 따라서 낮은 pH 조건에서도 높은 인산염 회수율을 얻을 수 있었던 수산화마그네슘과 산화마그네슘이 경제적인 측면뿐만 아니라 효율적인 측면에서도 염화마그네슘을 대체할 수 있을 것으로 기대된다.

• BMB Reports
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• 제29권4호
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• pp.277-285
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• 1996

In Pseudomonas fluorescens grown on malonate as sole carbon source, acetyl-CoA synthetase was induced, suggesting that malonate is metabolized through acetate and then acetyl-CoA. Acetyl-CoA synthetase was purified 18.6-fold in 4 steps to apparent homogeneity. The native molecular mass of the enzyme estimated by a native acrylamide gel electrophoresis was 130 kDa. The enzyme was composed of two identical subunits with a molecular mass of 67 kDa. Optimum pH was 70. The acetyl-CoA synthetase showed typical Michaelis-Menten kinetics for the substrates, acetate, ATP and CoA, whose $K_m$ values were calculated to be 33.4, 74.8, and 40.7 mM respectively. Propionate. butyrate and pentanoate were also used as substrates by the enzyme, but the rate of the formation of the CoA derivatives was decreased in the order of the increase in carbon number. The enzyme was inhibited by the group-specific reagents diethylpyro-carbonate, 2,3-butanedione, pyridoxal-5'-phosphate and N-bromosuccinimide. In the presence of substrates the inactivation rate of the enzyme, by all of the group-specific reagents mentioned above decreased, indicating the presence of catalytically essential histidine, arginine, lysine and tryptophan residues at or near the active site. Preincubation of the enzyme with ATP, $Mg^{2+}$ resulted in the increase of its susceptibility to diethylpyrocarbonate, suggesting that ATP, $Mg^{2+}$ may induce a conformational change in the active site exposing the essential histidine residue to diethylpyrocarbonate. The enzyme was acetylated in the presence of acetyl-CoA, indicating that this is one of acyl-enzyme.

• 공업화학
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• 제26권3호
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• pp.270-274
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• 2015

본 연구에서는 고농도 무전해 니켈도금 폐액을 처리하기 위한 고도산화공정 기술을 개발하였다. 추출, 농축 공정을 이용한 니켈 금속 회수보다는 폐수를 방류수 수준으로 처리할 수 있는 기술 개발을 위하여 차아인산염과 아인산염을 침전이 용이한 인산염으로 효과적으로 전환시킬 수 있는 공정 개발에 초점을 맞추었다. 광화학적 방법인 $UV/H_2O_2$ 방식을 채택하여 COD, $PO_4-P$ 변화 효율 및 과산화수소의 소모량을 분석함으로써 고농도 무전해 니켈도금 폐액의 고도산화처리 특성을 평가하였다. 특히, $UV/H_2O_2/O_3$ 방식으로 오존산화법을 추가함으로써 과산화수소 사용량을 30% 가량 절감하고 처리시간을 약 6 h 단축시킬 수 있었다.