• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.335-335
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• 2008

눈에 안정한(1.53um) 인산염 레이저 유리를 제조하기 위한 기본 조성 (mole%)은 $55P_2O_5\cdot24BaO\cdot10K_2O\cdot4Al_2O_3\cdot6Yb_2O_3$로 하고, 활성 이온은 $Er^{+3}$로, sensitizer로는 $Cr^{+3}(Yb^{+3})$을 사용하였다. 혼합된 원료 조성은 대기와 원료로부터 혼입되는 OH group을 제거하기 위하여 open 시스템에서 가스 버블을 공급하였으며, 용융물에 공급된 시간 변화에 따라 분광학적 특성 변화를 조사하였다. OH oscillations linear 에 의해 quenching된 $Er^{+3}$ 형광방출 확률은 $3500cm^{-1}$ 에서 OH stretching vibration band의 흡수계수에 의존하고 있으며, 이때 $Er^{+3}$의 농도는 $1.6\times10^{19}$에서 $21.2\times10^{19}$ ion/$cm^2$ 범위에서 존재하였다.

• Journal of Pharmaceutical Investigation
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• 제23권3호spc1호
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• pp.41-50
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• 1993

The iontophoretic delivery across rat skin of quaternary ammonium salts (isopropamide: ISP, pyridostigmine: PS), which are positively charged over a wide pH range, was measured ill vitro. The study showed that: (a) iontophoresis significantly enhanced delivery of ISP and PS compared to respective passive transport; (b) delivery of ISP and PS was directly proportional to the applied continuous direct current density over the range of $0-0.69\;mA/cm^2;$ (c) delivery of ISP and PS was also proportional to the drug concentration in the donor compartment over the range of $0-2{\time}l0^{-2}M:$ (d) sodium ion in the donor compartment inhibited the drug transport possibly due to decreasing the electric transference number of the drug; (e) delivery of ISP and PS increased as the pH of the donor solution increased over the pH range 2-7 suggesting permselective nature of the epidermis, and inhibition of the transference number of the drugs by hydronium ion; (f) some organic anions such as taurodeoxycholate, salicylate and benzoate which form lipophilic ion-pair complexes with ISP inhibited the delivery of ISP. The degree of inhibition by the organic anions was linearly proportional to the extraction coefficient $(K_e)$ of ISP from the partition system with each counteranion between phosphate buffer (pH 7.4) and n-octanol. For PS, however, taurodeoxycholate, but not salicylate and benzoate inhibited the iontophoretic delivery. It suggests that not only sodium ion and hydronium ion but also the counteranions which form lipophilic ion-pairs with quaternary ammonium drugs are not favorable components in formulating the donor solution of the drugs to achieve an effective iontophoretic delivery.

• Applied Biological Chemistry
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• 제2권
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• pp.45-52
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• 1961

The decomposition of malathion in dust for mulations prepared from four Korean tales as carriers during storage period has been studied. Amberlite CG-120, a cation exchange resin . which has higher cation exchange capacity than tales, was also used as a carrier in hope of finding out the effect of nagative charge upon the decomposition of malathion. Besides the original talc powders obtained directly from the mines, the hydrogen ion saturated forms were also used as carriers for comparisonal study. The saturated ions for the resin were hydrogen, sodium and magnesium. As the physical properties of the tales, colloid content, water adsorption capacity, PH, specific surface, phosphate fixing capacity and exchangeable canons were determined, and these properties were correlated with the amount of the decomposition. Following results were obtained from the experiment. 1. The malathion in the talc in dust was found to decompose around 10-15% ofthe total withina month. About 50% of the decom position that took place after a month was found to occur within a week. 2. The resin which has higher cation exchange capacity than the tales was highly effective in the decomposition of malathion compared with the tales. 3. In every case the saturation of the exchange complexes with hydrogen ion greatly accelerated the decomposition of malathion. 4. The most highly correlated physical properties with the decomposition were colloid content and specific surface of the tales. 5. The water adsorption and phosphate fixing capacities of the tales were found not to correlate with the amount of malathion decomposed. From the experimental results it was concluded that the active negative spots on the colloidal tales or the resin attract the electropositive phosphorus atom in a malathion molecule thereby inducing the decomposition easier. The presence of hydrogen ion nearby might cause a catalytic effect in the decomposition of malathion.

• 분석과학
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• 제8권2호
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• pp.161-166
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• 1995

이온쌍 액체크로마토그래피(IP-HPLC)에 의해 마주송이풀 중 acteoside를 분리 정량하였다. 시료를 메탄올 40mL로서 4시간 추출하였다. 추출물에 대한 분리, 정제를 Sep-Pak $C_{18}$ catridge와 메탄올-물(메탄을 50%, 물 50%, 인산 완충용액 pH=8.0)을 사용하였다. HPLC 분리조건은 poly(styrene-divinylbezene) PRP-1 역상컬럼($15cm{\times}4.6mm$ i. d., $5.0{\mu}m$)과 이동상으로 $5.0{\times}10^{-3}M$ tetrabutylammonium bromide가 포함된 메탄올-물(메탄을 60%, 물 40%, 인산 완충용액 pH=8.2)을 사용하였다. 이와 같은 조건으로 강원도 평창군 일대에서 채집한 마주송이풀 중에 함유된 acteoside를 분리 정량한 결과 그 함량 범위가 0.062~0.076%였다.

• 한국분말재료학회지
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• 제30권6호
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• pp.516-520
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• 2023

Highly safe lithium-ion batteries (LIBs) are required for large-scale applications such as electrical vehicles and energy storage systems. A highly stable cathode is essential for the development of safe LIBs. LiFePO₄ is one of the most stable cathodes because of its stable structure and strong bonding between P and O. However, it has a lower energy density than lithium transition metal oxides. To investigate the high energy density of phosphate materials, vanadium phosphates were investigated. Vanadium enables multiple redox reactions as well as high redox potentials. LiVPO₄O has two redox reactions (V⁵⁺/V⁴⁺/V³⁺) but low electrochemical activity. In this study, LiVPO₄O is doped with fluorine to improve its electrochemical activity and increase its operational redox potential. With increasing fluorine content in LiVPO₄O_1-xF_x, the local vanadium structure changed as the vanadium oxidation state changed. In addition, the operating potential increased with increasing fluorine content. Thus, it was confirmed that fluorine doping leads to a strong inductive effect and high operating voltage, which helps improve the energy density of the cathode materials.

• 원예과학기술지
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• 제33권6호
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• pp.854-859
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• 2015

본 시험은 배양액 내 pH 변화에 따른 이온과 EC의 모형을 구명하고자 수행하였다. 배양액 내 $HPO_4{^{-2}}$와 $H_2PO_4{^-}$의 변량에 따른 pH가 변하는데, pH 4.0-5.0은 EC의 변량이 상승하고, pH 5.0-7.0은 EC의 변량이 완만하고, pH 7.0-8.0은 다시 상승하였다. 배양액 내 다량원소의 변량을 보면, pH가 상승할수록 K, Ca, N, P의 이온 농도도 증가하는데, 특히 K과 P의 변량이 크게 나타났다. 반면 Mg와 S의 변량은 일정하게 유지되었다. 배양액의 IBM(ion balance model)에 따른 분석에서, EC의 변량은 크게 변하지 않고, 이온의 균형점이 a분면에서 d분면으로 이동하면 pH가 상승하면서 음이온 보다 양이온이 증가하는 것으로 나타났다. 또한 pH 변량이 높을수록 EC 중앙선으로부터 멀어져 배양액의 이온 불균형이 증가되었다. $HPO_4{^{-2}}$와 $H_2PO_4{^-}$의 변량에 대한 K와 Ca의 당량비 보정은 pH가 증가할수록 K는 감소하지만 Ca는 증가하였고, EC 변량의 영향보다 큰 것으로 나타났다. K와 Ca의 당량비 보정에 따른 pH 변량은 0.97의 이차 다항식 상관모형을 나타냈다. 본 연구를 통해 인산염의 구배에 따른 pH, 이온, EC의 변량에 대하여 pH 변량 모형이 구명되었다.

• BMB Reports
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• 제34권1호
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• pp.21-27
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• 2001

The structural stability of brain pyrydoxine-5'-phosphate (PNP) oxidase and the catalytic properties of the monomeric species were investigated. The unfolding of brain pyridoxine-5'-phosphate (PNP) oxidase by guanidine hydrochloride (GuHCl) was monitored by means of fluorescence and circular dichroism spectroscopy Reversible dissociation of the dimeric enzyme into subunits was attained by the addition of 2 M GuHCl. The perturbation of the secondary structure under the denaturation condition resulted in the release of the cofactor FMN. Separation of the processes of refolding and reassociation of the monomeric species was achieved by the immobilization method. Dimeric PNP oxidase was immobilized by the covalent attachment to Affi-gel 15 without any significant lass of its catalytic activity. Matrix-bound monomeric species were obtained from the reversible refolding processes. The matrix bound-monomer was found to be catalytically active, possessing only a slightly decreased specific activity when compared to the refolded dimeric enzyme. In addition, limited chymotrypsin digestion of the oxidase yields two fragments of 12 and 161 kDa with a concomitant increase of catalytic activity The catalytically active fragment was isolated by ion exchange chromatography and analyzed for association of two subunits using the FPLC gel filtration analysis. The retention time indicated that the catalytic fragment of 16 kDa behaves as a compact monomer. Taken together, these results are consistent with the hypothesis that the native quaternary structure of PNP oxidase is not a prerequisite for catalytic function, but it could play a role in the regulation.

• Environmental Engineering Research
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• 제18권4호
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• pp.267-276
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• 2013

This study presents a comparison of different protocols for the synthesis of iron-loaded zeolites, and the results of their application, as well as that of zeolite-A (Z-A), to the removal of ammonium and phosphate from aqueous media. Zeolites prepared by three methods were evaluated: iron-incorporated zeolites (IIZ), iron-exchanged zeolites (IEZ), and iron-calcined zeolites (ICZ). The optimal iron content for preparing of IIZ, as determined via scanning electron microscopy and X-ray photoelectron spectroscopy analyses, expressed as molar ratio of $SiO_2:Al_2O_3:Fe$, was below 0.05. Ammonia removal revealed that the iron-loaded zeolites have a higher removal capacity than that of Z-A due, not only to ion-exchange phenomena, but also via adsorption. Greater phosphate removal was achieved with IEZ than with ICZ; additionally, no sludge production was observed in this heterogeneous reaction, even though the coagulation process is generally accompanied by the production of a large amount of undesired chemical sludge. This study demonstrates that the developed synthetic iron-loaded zeolites can be applied as a heterogeneous nutrient-removal materials with no sludge production.

• 대한금속재료학회지
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• 제47권3호
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• pp.188-194
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• 2009

Recently, new extraction technology for manganese nodule has been developed as alternative noble metallic resources. It is important to understand thermodynamic behaviors of phosphorus in low basic slag system from the viewpoint of the refining processing optimization. Thermodynamic behaviors of phosphorus in the $FeO-MnO-CaO-SiO_2-MgO_{satd.}$ slag system were investigated at 1723 K with various oxygen potential and slag composition of low basicity. The experimental results for dependence of phosphorus on oxygen potential and slag basicity indicated that the dissolution mechanism of phosphorus into slag of low basicity could be derived as follows; $[P]+5/4O_2+(O^{2-})=({PO_{3.5}}^{2-})$ Present experimental results implied that stability of phosphorus in slag would be depended on both of $O^{2-}$ (basicity) and content of $Ca^{2+}$ in molten slag. The thermodynamic effect of FeO, MnO and $Na_2O$ on low basicity on phosphate capacity was discussed.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.354-361
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• 2022

In a direct methanol fuel cell system (DMFC), one of the drawbacks is methanol crossover. Methanol from the anode passes through the membrane and enters the cathode, causing mixed potential in the cell. Only Pt-based catalysts are capable of operating as cathode for oxygen reduction reaction (ORR) in a harsh acidic condition of DMFC. However, it causes mixed potential due to high activity toward methanol oxidation reaction of Pt. To overcome this situation, developing Pt-based catalyst that has methanol tolerance is significant, by controlling reactant adsorption or reaction kinetics. Pt/C decorated with phosphate ion was prepared by modified polyol method as cathode catalyst in DMFC. Phosphate ions, bonded to the carbon of Pt/C, surround free Pt surface and block only methanol adsorption on Pt, not oxygen. It leads to the suppression of methanol oxidation in an oxygen atmosphere, resulting in high DMFC performance compared to pristine Pt/C.