• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.10
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• pp.1278-1286
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• 2008

The effect of Tween 20 addition on changes in the stability of methylcellulose (MC) emulsions (1 wt% MC, 10 wt% n-tetradecane, 20 mM bis-tris buffer, pH 7) was investigated by creaming stability and orthokinetic stability measurements. In the case of MC emulsions containing varying amounts of oil (1$\sim$30 wt%) and no Tween 20 added, creaming stability, judged by mean migration velocity of fat globules ($V_m$), was found to depend on droplet size: the larger the droplet size, the worse the stability [$V_m$: 0.326 $\mu$m $min^{-1}$ ($d_{32}$: 0.32 $\mu$m) ${\rightarrow}V_m$: 0.551 $\mu$m $min^{-1}$ ($d_{32}$: 0.53 $\mu$m)]. With Tween 20, creaming stability was found to be worse than the one without Tween 20, except for MC emulsion containing 0.2 wt% Tween 20. In addition, cream stability was the lowest with the lowest concentration of Tween 20 and a tendency to recover with increasing Tween 20 concentration [$V_m$: 0.598 $\mu$m $min^{-1}$ (0.01 wt%)${\rightarrow}V_m$: 0.389 $\mu$m $min^{-1}$ (0.2 wt%)] was found. From viscosity measurement for aqueous bulk phase of MC emulsions, such a change in the creaming stability was found to coincide well with the results of viscosity measurement. Therefore, it was reasonable to say that creaming stability of MC emulsions containing Tween 20 depended on MC concentration in aqueous bulk phase, which was in turn varied by competitive adsorption between MC and Tween 20 at the oil droplet surface. In case of orthokinetic stability, judged by destabilization time ($t_d$), it was found that the addition of Tween 20 resulted in lowered stability with more pronounce tendency at higher concentrations [$t_d$: 160 min (0.03 wt%)${\rightarrow}t_d$: 100 min (0.2 wt%)]. Moreover, combined with previous results, the orthokinetic stability of MC emulsions containing Tween 20 was found to be exponentially proportional to MC load. In conclusion, competitive adsorption between MC and Tween 20 may affect the stability properties of MC emulsion to varying extents, depending on the concentration of Tween 20.

• Korean Journal of Food Science and Technology
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• v.33 no.2
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• pp.166-172
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• 2001

In order to increase ginsenoside content, to reduce chemical change, to shorten extracting procedure, new methods of extraction and fractionation of crude ginseng saponin were established and compared for their chemical composition. Those are hot MeOH extraction/n-BuOH fractionation (BuOH method) and hot MeOH extraction/Diaion HP-20 adsorption/MeOH elution (HP-20 method), which are already known methods, and additional three new methods: hot MeOH extraction/cation AG 50W $adsorption/H_2O$ elution/n-BuOH extraction (AG 50W method), cool MeOH extraction/Diaion HP-20 adsorption/MeOH elution (cool extraction method) and direct extraction with EtOAc/n-BuOH (direct extraction method). AG 50W method provided a crude saponin showing the highest content of ginsenosides of 61.5% and the lowest contents of protein and free amino acids of 0.93% and 0.19%, respectively. The protein content was the highest as 14.18% in the crude saponin by HP-20 method, while free sugar content was the highest as 13.5% by BuOH method, indicating that these are factors that lower the rate of ginsenoside in crude saponins by those methods. On the other hand, it was revealed that AG 50W method produced large amount of prosapogenins during the pass through the cation exchange resin (AG 50W) column being strongly acidic. Crude saponin from direct extraction method showed relatively higher composition of ginsenoside $Rg_1$ and Re. The results suggest that contents and composition of ginsenosides and other chemical components in crude ginseng saponin greatly depend on the condition of the extraction and fractionation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.5
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• pp.455-462
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• 2000

The objective of this study was to examine the physicochemical characteristics of coagulation reaction between loess and red tide organisms (RTO) and its feasibility, in developing a technology for the removal of RTO bloom in coastal sea. The physicochemical characteristics of loess were examined for a particle size distribution, surface characteristics by scanning electron microscope, zeta potential, and alkalinity and pH variations in sea water. Two kinds of RTO that were used in this study, Cylindrothen closterium and Skeietonema costatum, were sampled in Masan bay and were cultured in laboratory. Coagulation experiments were conducted using various concentrations of loess, RTO, and a jar tester. The supernatant and RTO culture solution were analyzed for pH, alkalinity, RTO cell number. A negative zeta potential of loess increased with increasing pH at $10^(-3)M$ NaCl solution and had -71.3 mV at pH 9.36. Loess had a positive zeta potential of +1,8 mV at pH 1.98, which resulted in a characteristic of material having an amphoteric surface charge. In NaCl and $CaCl_2$, solutions, loess had a decreasing negative zeta potential with increasing $Na^+\;and\;Ca^(+2)$ ion concentration and then didn't result in a charge reversal due to not occurring specific adsorption for $Na^+$ ion while resulted in a charge reversal due to occurring specific adsorption for $Ca^(+2)$ ion. In sea water, loess and RTO showed the similar zeta potential values of -112,1 and -9.2 mV, respectively and sea sand powder showed the highest zeta potential value of -25.7 mV in the clays. EDLs (electrical double-layers) of loess and RTO were extremely compressed due to high concentration of salts included in sea water, As a result, there didn't almost exist EDL repulsive force between loess and RTO approaching each other and then LVDW (London-yan der Waals) attractive force was always larger than EDL repulsive force to easily form a floe. Removal rates of RTO exponentially increased with increasing a loess concentration. The removal rates steeply increased until $800 mg/l$ of loess, and reached $100{\%}$ at 6,400 mg/l of loess. Removal rates of RTO exponentially increased with increasing a G-value. This indicated that mixing (i.e., collision among particles) was very important for a coagulation reaction. Loess showed the highest RTO removal rates in the clays.

• Advances in environmental research
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• v.2 no.3
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• pp.167-177
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• 2013

We investigated that removal of aqueous U(VI) by nano-sized Zero Valent Iron (nZVI) and Fe(II) bearing minerals (controls) in this study. Iron particles showed different U(VI) removal efficiencies (Mackinawite: 99%, green rust: 95%, nZVI: 91%, magnetite: 87%, pyrite: 59%) due to their different PZC (Point of Zero Charge) values and surface areas. In addition, noticeable amount of surface Fe(II) (181 ${\mu}M$) was released from nZVI suspension in 6 h and it increased to 384 ${\mu}M$ in the presence of U(VI) due to ion-exchange of U(VI) with Fe(II) on nZVI surface. Analysis of Laser-Induced Breakdown Detection (LIBD) showed that breakdown probabilities in both filtrates by 20 and 200 nm sizes was almost 24% in nZVI suspension with U(VI), while 1% of the probabilities were observed in nZVI suspension without U(VI). It indicated that Fe(II) colloids in the range under 20 nm were generated during the interaction of U(VI) and nZVI. Our results suggest that Fe(II) colloids generated via ion-exchange process should be carefully concerned during long-term remediation site contaminated by U(VI) because U could be transported to remote area through the adsorption on Fe(II) colloids.

• Korean Journal of Veterinary Research
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• v.21 no.2
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• pp.117-121
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• 1981

In order to estimate the efficiency of feed added urea-mixed zeolite the experiment was carried on in vitro. The results obtained were as follows: 1. The pH of all media added urea were inclined toward alkali, except 1% urea (included 99% zeolite) medium. 2. The concentration of ammonia in all media added urea-mixed zeolite was inversely proportional to added volume of zeolite; 1,349, 1,298, 1,255, 1,164 and $786{\mu}g/ml$ in 40%, 20%, 10%, 5% and 1% urea media respectively for 30 minutes incubation, and the concentration of ammonia in all media was increased steadily as incubation time proceeded until 9 hours. 3. The efficiency of adsorption of ammonia to zeolite of the feed added 40% urea mixture (dealing in the feed store) was hardly recognized. Accordingly, it is efficient to utilize the feed added 1~5% urea mixture, but it is of no use practica11y because they need much amount of zeolite.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.230-230
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• 2012

Graphene have showed promising performance as electrodes of organic devices such as organic transistors, light-emitting diodes, and photovoltaic solar cells. In particular, among various organic materials of graphene-based organic devices, pentacene has been regarded as one of the promising organic material because of its high mobility, chemical stability. In the bottom-contact device configuration generally used as graphene based pentacene devices, the morphology of the organic semiconductors at the interface between a channel and electrode is crucial to efficient charge transport from the electrode to the channel. For the high quality morphology, understanding of initial stages of pentacene growth is essential. In this study, we investigate self-assembly of pentacene molecules on graphene formed on a 6H-SiC (0001) substrate by scanning tunneling microscopy. At sub-monolayer coverage, adsorption of pentacene molecules on epitaxial graphene is affected by $6{\times}6$ pattern originates from the underlying buffer layer. And the orientation of pentacene in the ordered structure is aligned with the zigzag direction of the edge structure of single layer graphene. As coverage increased, intermolecular interactions become stronger than molecule-substrate interaction. As a result, herringbone structures the consequence of higher intermolecular interaction are observed.

• Corrosion Science and Technology
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• v.18 no.6
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• pp.243-252
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• 2019

The pitting corrosion and inhibition studies of AZ31B magnesium alloy were investigated in the alkaline solution (pH12) with chloride and inhibitors. The corrosion behavior of passive film with/without Cl^- in the alkaline electrolyte were conducted by polarization curve and immersion tests in the presence of various additives (inhibitors) to clarify the inhibition efficiency of pitting corrosion at higher potential region. Critical concentration of pitting corrosion for Mg alloy was evaluated with 0.005 M NaCl in 0.01 M NaOH on the anodic polarization behavior. Critical pitting of AZ31B Mg alloy in 0.01 M NaOH is a function of chlorides; E_pit = - 1.36 - 0.2 log [Cl^-]. When the Sodium Benzoate (SB) was only used as an inhibitor, a few metastable pits developed on the Mg surface by an immersion test despite no pitting corrosion on the polarization curve meaning that adsorption of SB on the surface is insufficient protection from pitting corrosion in the presence of chloride. The role of SB and Sodium Dodecylbenzenesulfonate (SDBS) inhibitors for the Mg alloy surface in the presence of chloride was suppressed from pitting corrosion to co-adsorb on the Mg alloy surface with strong formation of passive film preventing pitting corrosion.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.143.2-143.2
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• 2016

The influence of electric field on CO adsorbed on Pt(111) was investigated with reflection-absorption infrared spectroscopy (RAIRS) in ultrahigh vacuum system. The ice film capacitor method was used to apply electric field to the amorphous ice film with CO on Pt(111). Two systems were compared by measuring the change of the CO stretching vibrational mode under applied electric field; one is CO on Pt(111), and the other is CO buried inside an ice film on Pt(111). By comparing them, we were able to calculate the additional effect of adsorption of CO on Pt(111) on peak shift. The CO adsorbed on Pt(111) has shown larger peak shift than CO adsorbed with H2O when we applied stronger electric field. Additionally, the differences were observable when the applied electric field exceeds $1{\times}10V/m^8$.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.113-113
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• 2016

반도체 산업이 발전하고 기술이 향상됨에 따라 미세화되고 복잡한 구조의 소자가 개발되고 있으며, 2차원 소재 등 다양하고 새로운 소재들이 발견 및 연구되고 있다. 새로운 소재 또는 기술을 이용한 고품질 소자를 개발하기 위해서는 우수한 특성(높은 순도, 우수한 분해 및 반응 특성)을 지닌 증착소재의 개발 및 평가가 선행되어야 한다. 기존의 증착소재의 기본 물성을 측정하는 방법인 단순 기상 Fourier transform infrared spectroscopy(FT-IR) 분석법은 실제 공정에서의 증착경향을 대변하기 어렵다는 단점이 있다. 이러한 단점을 보완하기 위해 개조된 attenuated total reflection (ATR) 액세서리를 이용하여 실제 공정에서의 증착경향을 대변하고자 하였다. 본 연구에서는 반도체 증착소재의 분해 및 표면 흡착 특성을 분석하기 위해 ATR-FTIR 분석법을 이용하여 수행하였으며, 분산안정도에 따른 nanoparticle을 ATR의 크리스탈 표면에 분포시켜 hexamethyldisilazane(HMDS) source의 흡착 효율을 향상시키는 연구를 수행하였다. Nanoparticle의 분산안정도를 높이기 위하여 suspension 상태에서 pH, sonication, 분산제를 이용하였으며, nanoparticle을 ATR crystal 표면에 분포하여 분석한 결과, 분산안정도에 따라 HMDS의 흡착효율이 달라짐을 확인하였다.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.768-774
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• 2017

Horseradish peroxidase (HRP) catalyzes the oxidation of aromatic compounds by hydrogen peroxide via insoluble polymer formation, which can be precipitated from the wastewater. For HRP immobilization, poly(lactic-co-glycolic acid) (PLGA) fine carrier supports were produced by using the Nano Spray Dryer B-90. Immobilized HRP was used to remove the persistent 2,4-dichlorophenol from model wastewater. Both extracted (9-16 U/g) and purified HRP (11-25 U/g) retained their activity to a high extent after crosslinking to the PLGA particles. The immobilized enzyme activity was substantially higher in both the acidic and the alkaline pH regions compared with the free enzyme. Optimally, 98% of the 2,4-dichlorophenol could be eliminated using immobilized HRP due to catalytic removal and partly to adsorption on the carrier supports. Immobilized enzyme kinetics for 2,4-dichlorophenol elimination was studied for the first time, and it could be concluded that competitive product inhibition took place.