• Membrane and Water Treatment
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• 제11권1호
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• pp.69-77
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• 2020

Former studies revealed that sepiolite thermally treated at high temperature have high adsorption capacity for phosphate. However, its micron size (75 ㎛) limits its application to water treatment. In this study, we synthesized sepiolite impregnated polysulfone (PSf) beads to separate it easily from an aqueous solution. PSf beads with different sepiolite ratios were synthesized and their efficiencies were compared. The PSf beads with 30% impregnated sepiolite (30SPL-PSf bead) possessed the optimum sepiolite ratio for phosphate removal. Kinetic, equilibrium, and thermodynamic adsorption experiments were performed using the 30SPL-PSf bead. Equilibrium adsorption was achieved in 24 h, and the pseudo-first-order model was suitable for describing the phosphate adsorption at different reaction times. The Langmuir model was appropriate for describing the phosphate adsorption onto the 30SPL-PSf bead, and the maximum adsorption capacity of the 30SPL-PSf bead obtained from the model was 24.48 mg-PO₄/g. Enthalpy and entropy increased during the phosphate adsorption onto the 30SPL-PSf bead, and Gibb's free energy at 35 ℃ was negative. An increase in the solution pH from 3 to 11 induced a decrease in the phosphate adsorption amount from 27.30 mg-PO₄/g to 21.54 mg-PO₄/g. The competitive anion influenced the phosphate adsorption onto the 30SPL-PSf bead was in the order of NO₃^- > SO₄^2- > HCO_3^-. The phosphate breakthrough from the column packed with the 30SPL-PSf bead began after ~2000 min, reaching the influent concentration after ~8000 min. The adsorption amounts per unit mass of 30SPL-PSf and removal efficiency were 0.775 mg-PO₄/g and 61.6%, respectively. This study demonstrates the adequate performance of 30SPL-PSf beads as a filter for phosphate removal from aqueous solutions.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.667-674
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• 2007

Phase behavior for the mixed aqueous surfactant systems of cationic octadecyl trimethyl ammonium chloride (OTAC)/anionic ammonium dodecyl sulfate (ADS)/water was examined. Below the total surfactant concentrations of 1.5 m molal, mixed micelles were formed. At the total surfactant concentrations higher than 1.5 m molal, there appeared a region where mixed micelles and vesicles coexist. As the surfactant concentration increased, the systems looked very turbid and much more vesicles were observed. The vesicles were spontaneously formed in this system and their existence was observed by negative-staining transmission electron microscopy (TEM), small-angle neutron scattering (SANS) and encapsulation efficiency of dye. The vesicle region was where the molar fraction α of ADS to the total mixed surfactant was from 0.1 to 0.7 and the total surfactant concentration was above 5 × 10-4 molality. The size and structure of the vesicles were determined from the TEM microphotographs and the SANS data. Their diameter ranged from 450 nm to 120μm and decreased with increasing total surfactant concentration. The lamellar thickness also decreased from 15 nm to 5 nm with increasing surfactant concentration and this may be responsible for the decrease in vesicle size with the surfactant concentration. The stability of vesicles was examined by UV spectroscopy and zeta potentiometry. The vesicles displayed long-term stability, as UV absorbance spectra remained unchanged over two months. The zeta potentials of the vesicles were large in magnitude (40-70 mV) and the observed longterm stability of the vesicles may be attributed to such high ζ potentials.

• 접착 및 계면
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• 제2권2호
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• pp.11-19
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• 2001

트리카프릴메틸 암모니움 클로라이드를 상이동촉매로 사용하여 $Na_2S_2O_8$의 수용액과 톨루엔의 이상계에서 질소분위기하에 $60^{\circ}C$에서 스티렌의 라디칼중합을 행하였다. 중합시의 초기 중합속도는 촉매와 $Na_2S_2O_8$의 초기공급 농도보다는 수용액 상에서의 4급 암모늄양이온과 퍼록시디슬페이트 음이온의 농도로 나타낼 수 있었다. 관찰된 초기중합속도를 사용하여 분균일 액-액계에서의 순환 상이동에 의한 개시과정을 포함한 중함메카니즘을 밝힐 수 있었다. 폴리스티렌의 점도평균분자량은 $Na_2S_2O_8$의 농도에 역비례하였는데, 라디칼 중합메카니즘에 의하여 $[Q^+]([S_2O{_8}^{2-}]{\alpha}_2)^{1/2}$로 나타내어졌다.

• Bulletin of the Korean Chemical Society
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• 제12권5호
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• pp.474-477
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• 1991

The preferential transport phenomena of neutral cation-anion moieties in neutral macrocycle-facilitated emulsion liquid membrane were described in this study. Emulsion membrane systems consisting of (1) aqueous source phase containing 0.001 M M($NO_3$)$_2(M=Mn^{2+},\;Co^{2+},\;Ni^{2+},\;Cu^{2+},\;Zn^{2+},\;Sr^{2+},\;Cd^{2+},\;and\;Pb^{2+})$ (2) a toluene membrane containing 0.01 M ligand $(DBN_3O_2$, DA18C6, DT18C6, TT18C6, HT18C6) and the surfactant span 80 (sorbitan monooleate) (3% v/v) and (3) an aqueous receiving phase containing $Na_2S_2O_3$ or $NaNO_3$ were studied with respect to the disappearence of transition metal ions from the source phase as a function of time. Cation transports for various two component or three component equimolar mixture of transition metal and $Cu^{2+}$ in a emulsion membrane system incorporating macrocyclic ligand (HT18C6) as carrier were determinded. $Cu^{2+}$ was transported higher rates than the other $M^{2+}$ in the mixture solution. Equilibrium constants for cation-source phase co-anion, cation macrocycle and cation-receiving phase reagent interaction are examined as parameters for the prediction of cation transport selectivities.

• 대한본초학회지
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• 제28권6호
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• pp.59-70
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• 2013

Objectives : Hyangsayangyi-tang (香砂養胃湯) is a polyherbal formula, has been used as one of the representative So-eumin (少陰人) prescriptions in Sasang-medicine (四象醫學), a famous Korean medicinal theory. The aqueous extract of Hyangsayangyi-tang (HSYYT) was evaluated for its possible ameliorative effect in the regulation of hypothyroidism related reproductive organ damages in propylthiouracil (PTU)-induced rat model. Methods : HSYYT aqueous extracts were administered, once day for 42 days from 2 weeks before start of PTU treatment as an oral dose of 500, 250 and 125 mg/kg (bodyweight), and hypothyroidism was induced by daily subcutaneous treatment of PTU 10 mg/kg for 28days. Results : PTU induced hypothyroidism and related male reproductive organ (testis, epididymis and prostate) damages were favorably and dose-dependently inhibited by treatment of HSYYT 500 and 250 mg/kg, and they also effectively regulated the PTU-induced abnormal antioxidant defense system changes in the testis. No effective or any harmful changes on the PTU induced hypothyroidism and related male reproductive organ damages were observed in HSYYT 125 mg/kg treated rats as compared with PTU control in this experiment. Conclusions : The results obtained in this study suggest that oral administration of 500 and 250 mg/kg of HSYYT showed favorable effects on the hypothyroidism and related reproductive organ damages through augmentation of antioxidant defense system in the testis, and it is considered that HSYYT may be help to ameliorate the hypothyroidism and related organ damages in clinics.

• Journal of Electrochemical Science and Technology
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• 제14권1호
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• pp.75-84
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• 2023

The accumulation of spent carbide (YG8), not only pollutes the environment but also causes waste of tungsten, cobalt and other rare metal resources. To better address this issue, we proposed a combined electrochemical separation process of low-temperature aqueous solution and high-temperature molten salt for tungsten and cobalt. H₂WO₄ was obtained from spent carbide in an aqueous solution, and we calcined it to obtain WO₃, which was used as a raw material to obtain tungsten by using molten salt electrodeposition. The influence of the current efficiency and the electrochemical behavior of the discharge precipitation of W(VI) were also studied. The calcination results showed that the morphology of WO₃ was regular and there were no other impurities. The maximum current efficiency of 82.91% was achieved in a series of electrodeposition experiments. According to XRD and SEM analysis, the recovered product was high purity tungsten, which belongs to the simple cubic crystal system. In the W(VI) reduction mechanism experiments, the electrochemical process of W(VI) in NaCl-Na₂WO₄-WO₃ molten salt was investigated using linear scanning voltammetry (LSV) and chronoamperometry in a three-electrode system. The LSV showed that W(VI) was reduced at the cathode in two steps and the electrode reaction was controlled by diffusion. The fitting results of chronoamperometry showed that the nucleation mechanism of W(VI) was an instantaneous nucleation mode, and the diffusion coefficient was 7.379×10^-10 cm²·s^-1.

• 대한치과보철학회지
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• 제40권3호
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• pp.262-268
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• 2002

Statement of problem. In-Ceram system is one of the all-ceramic crowns that can be used in anterior 3 unit fixed partial dentures and posterior single crowns. The alumina core used in In-Ceram system is manufactured using slip-casting technique. The slip-casting technique is difficult and technique sensitive. To improve this problem, tape-casting method was introduced into dentistry. There were no studies to examine the effect of margin design on the margin fitness of all-ceramic crowns fabricated from alumina tape. Purpose. The purpose of this study was to compare the marginal fitness of glass infiltrated alumina core fabricated from aqueous-based alumina tape according to different margin types ($90^{\circ},\;110^{\circ},\;135^{\circ}$ shoulder margin). Material and method. Three upper central resin incisors were prepared with $90^{\circ},\;110^{\circ}$, and $135^{\circ}$ shoulder margins for all-ceramic crowns, respectively. The resin teeth were duplicated and master die and special plaster die were made as usual. After alumina cores were fabricated from aqueous-based alumina tape, cores were cemented to each 15 epoxy dies replicated from three resin teeth with resin cement. These cemented cores were embedded in epoxy resin. Specimens were cut mesiodistally and buccolingually. Marginal gap and discrepancy were measured under microscope. Results. The marginal gap and discrepancy of $90^{\circ}$ marginal angle was $75.1{\mu}m,\;86.6{\mu}m,\;110^{\circ}$ marginal angle was $41.5{\mu}m,\;50.7{\mu}m$ and $135^{\circ}$ marginal angle was $51.7{\mu}m,\;54.2{\mu}m$, respectively. The smallest value was seen in 110 (angle, which was statistically significant compared to that of $90^{\circ}$ angle (p<0.05). Conclusion. Marginal fitness of alumina cores made of alumina tape with $110^{\circ}$ shoulder margin was best and others were clinically acceptable.

• 한국응용과학기술학회지
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• 제31권4호
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• pp.642-652
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• 2014

The synthesis of octenyl succinyl ${\beta}$-gucan (OSA-${\beta}$-glucan) was carried out and its interfacial properties at the oil-water interface and in emulsion systems were investigated. An aqueous ethanol system as a reaction media was used to facilitate the synthesis process; 10% (w/w) ethanol found to be the best as it showed a maximum degree of substitution (DS: 0.0132). FT-IR showed a characteristic absorption spectrum at $1736cm^{-1}$, indicating the esterification of octenyl succinyl groups to ${\beta}$-glucan backbone. As for interfacial tension measurements, it was decreased with increasing concentration of OSA-${\beta}$-glucan in the aqueous phase and when NaCl was added to aqueous OSA-${\beta}$-glucan solution in the range of 0.01 M to 0.1 M and also when pH was raised (pH 3 ~ pH 9). In systems of emulsion stabilized with OSA-${\beta}$-glucan, fat globule size found to decrease with increasing concentration of OSA-${\beta}$-glucan, showing a critical value of about $0.32{\mu}m$ at 0.5 wt%. When the OSA-${\beta}$-glucan emulsions were stored, it was found that fat globule size was increased with storage time and particularly pronounced increase was observed in emulsion with 1% OSA-${\beta}$-glucan, possibly due to depletion flocculation. Results of creaming stability evaluated by light scattering technique showed that it was more stable in emulsions containing smaller fat globule size. Surface load of OSA-${\beta}$-glucan in emulsions increased with increasing concentration of OSA-${\beta}$-glucan, suggesting a multilayer adsorption.

• 대한화장품학회지
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• 제31권1호
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• pp.43-49
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• 2005

최근, 민감성 피부가 증가함에 따라 화장품의 안전성이 매우 중요시되고 있으며, 특히 방부제는 화장품 사용에 따른 부작용을 일으킬 수 있는 주요 자극원의 하나로 알려져 있다. 하지만, 방부제의 세포 독성 피부 투과, 유/수 분배, 항균력 비교 및 이를 통한 피부 자극과의 상관성 분석에 관한 연구는 전무한 실정이다. 본 연구의 목적은 상기의 여러 factor를 고려하여 화장품에서 빈번히 사용되고 있는 방부제의 하나인 phenoxyethanol을 이용한 저자극 방부시스템 개발에 관한 것이다. MTT assay를 통하여 human norm기 fibroblast cell에 대한 독성을 평가해 본 결과, 세포 독성은 propylparaben>butylparaben>ethylparaben>methylparaben>triciosan>phenoxyethanol 순으로 확인되어 phenoxyethanol이 다른 방부제에 비해 낮은 세포 독성을 나타낸 반면, 피부 일차자극을 알아보기 위하여 수행한 인체 첩포시험에서는 triclosan, methylparaben에 비해 높은 피부 자극을 나타내었다. 5 ${\~}$ 8 주령의 웅성 무모생쥐의 피부를 적출하여 in vitro Franz diffusion cell system을 이용한 방부제의 피부 투과도를 측정하여 본 결과, 피부 투과도는 phenoxyethanol > methylparaben > ethylparaben > propylparaben > butylparaben > triclosan 순으로 확인되어 세포 독성이 낮은 phenoxyethanol의 높은 피부 자극이 높은 피부 투과도와 연관성이 큰 것을 확인하였다. 따라서, 본 연구에서는 비교적 독성이 낮은 phenoxyethanol의 피부 투과도를 감소시킬 수 있는 방법을 찾고자 하였으며, 연구 결과, 제형내 polarity가 낮은 oil을 사용할 경우 phenoxyethanol의 피부 투과가 현격히 감소하며, 피부 자극도 감소함을 알 수 있었다. Oil polarity에 따른 Phenoxyethanol의 유/수 분배 측정 결과, Polarity가 낮은 oil에서는 $70\%$ 이상의 Phenoxyethanol이 수상에 존재한 반면, polarity가 높은 oil에서는 약 $70 {\~} 90\%$의 phenoxyethanol이 유상에 존재하였다. 또한, 미생물에 대한 항균력도 phenoxyethanol이 수상에 많이 존재할수록 증가하는 경향을 나타내었다. 따라서, 제형 내 oil tomposition을 변화시킴으로써 phenoxyethanol의 사용량을 줄일 수 있을 뿐만 아니라, 피부 투과를 감소시켜 보다 피부 자극이 적은 저자극 방부시스템 개발이 가능하리라 보여 진다.

• 공업화학
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• 제7권4호
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• pp.743-749
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• 1996

본 연구에서는 고밀집 섬유 다발체 내에 수용상과 유기상을 동시에 주입시켜 나타나는 모세관 현상을 이용하여 최소 공간에서 최대한의 물질 전달 면적을 갖게 한 정적 액-액 접촉 장치가 개발되었다. 이 장치의 특성과 안정성을 평가하기 위해 TBP와 우라닐 이온을 함유한 질산계의 연속 추출 실험이 수행되었으며, 추출 성능은 동일 상비 조건에서 수행된 회분식 성능과 동일하였다. 초기 수용액에 대한 추출 수율을 증가 시키기 위해서는 일정한 수용액 유속에서 유기상의 유속 증가가 필요하였고, 같은 상비 조건의 회분식의 추출수율을 갖기 위해서는 수용액이 장치 내에서 일정한 체류 시간을 유지해야함을 알 수 있었고 본 추출계에서는 약 1.9분이 필요함을 알 수 있었다. 본 연구에서 개발된 고 밀집 섬유체 접촉기는 안정성과 재현성이 뛰어 났으며, 일반 물질 분리용 뿐만 아니라, 액-액계면 넓고 안정되어 있어 용매 추출 속도론 해석에도 사용될 수 있음을 확인할 수 있었다.