• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.735-740
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• 2002

In order to improve the anti-fogging property of polymer films, organic-inorganic hybrid coating solutions which have good hydrophilic property and transmission in the range of visible light were synthesized by the sol-gel method. The coating solutions were prepared by adding glycidoxypropyl trimethoxysilane(GPS) to a colloidal silica(15 nm) suspension(Ludox). GPS as silane coupling agent forms strong bonds to the colloidal silica and surrounding polymer matrix and links two different materials together. Solutions prepared by addition of GPS at the acidic condition resulted in coatings that were less prone to cracking, while those at the basic condition caused coatings with more cracking. These resulted in better hydrophilic property and transmission in the range of visible light for the solution prepared at the acidic condition(pH 2). Compared with coatings under acidic conditions, coatings prepared at basic conditions showed worse hydrophilic property and transmission in the range of visible light.

• Korean journal of food and cookery science
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• v.7 no.3
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• pp.53-59
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• 1991

This study was carried out in order to investigate the change of protein functionalities such as foaming and emulsifying properties by succinylation of protein isolates. Succinylated and unsuccinylated munghean protein isolates were tested for finding out the effects of pH, heat treatment and sodium chloride concentration on the solubility, emulsion capacity, emulsion stability, foaming capacity, and foam stability. The results are summarized as follows: 1. Succinylation enhanced the solubility of MPI except at pH 4.5. When heated, succinylation greatly increased the solubility of succinylated MPI above $60^{\circ}C$. With the addition of NaCl, succinylation increased the solubility of MPI at acidic condition. 2. Emulsion capacity of succinylated MPI showed the lowest value at pH 7 and higher values at acidic and alkaine condition. when succinylated MPI was heated, emulsion capacity showed the highest at $80^{\circ}C$. With NaCl was added, emulsion capacity of succinylated MPI lincreased at pH 7, 9 or 11 decreased at pH 3 except addition of 1.0M NaCl. 3. Emulsion stability of MPI and succinylated MPI showed the highest at pH 4.5. Succinylation enhanced the emulsion stability of MPI at acidic condition. 4. The foaming capacity of MPI was increased at pH 3, 7 or 9 by succinylation. 5. When heated, foam stability of MPI and succinylated MPI showed the highest at pH 4.5 and at pH 11, respectively. When heated, both proteins showed the highest stability at $100^{\circ}C$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.4
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• pp.736-740
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• 2004

Preparation of ginseng concentrate with high content of acidic polysaccharide from white tail ginseng marc that was obtained after preparation of white tail ginseng extract. As a result of extraction of white tail ginseng under various concentrations of ethanol (0∼90%), both amount of acidic polysaccharide and extraction yield decreased by increasing the ethanol concentration. However, acidic polysaccharide extracted by water from white tail ginseng marc was increased in accordance with the increase of ethanol concentration. The optimal condition for the extraction of acidic polysaccharide from the marc was treatment of $\alpha$-amylase in 390∼650 unit/g residue/15 mL of distilled water for 5 min at 4$0^{\circ}C$. The amount of acidic polysaccharide in water extract of the marc was increased from 8.3% to 10.5% by the treatment of $\alpha$-amylase. A new ginseng extract mixture was manufactured by mixing 50% ethanol extract of white tail ginseng and water extract of alcoholic residue in the ratio of 8:2 (w/w). Crude saponin content and acidic polysaccharide content were 10.5% and 17%, respectively. The mixture had a same crude saponin content and twice acidic polysaccharide content comparing to 50% ethanol extract of white tail ginseng. It suggests that preparation of new ginseng concentrate with high content of acidic polysaccharide from white tail ginseng marc has high potencies in the utilization of waste material.

• Polymer(Korea)
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• v.26 no.4
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• pp.492-500
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• 2002

Oxidized-polyacrylonitrile (oxy-PAN) was prepared by oxidation of PAN fiber at $240^{\circ}C$, followed by base catalyzed hydrolysis reaction. The chemical structure of PAN fiber in various pH conditions was characterized by $^{13}C-NMR$ spectroscopy. The characteristic contraction and expansion behavior of oxy -PAN fiber was observed in acidic and basic medium, respectively. In basic condition, water molecules might be absorbed into the fiber with the movement of charge balancing $Na^+$ ion, on the other hand, the water molecules seemed to be expelled in acidic condition to result in contraction. It was also observed that the facile chemical modification occurred due to free diffusion of aqueous reagent into the hydrophilic PAN fiber, and the morphology was affected by pH condition.

• Microbiology and Biotechnology Letters
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• v.23 no.4
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• pp.373-377
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• 1995

We investigated the survival, $\beta$-galactosidase activity and cellular permeability of lactic acid bacteria such as Lactobacillus acidophilus ATCC 4356, Lactobacillus casei subsp. casei IFO 3533, Streptococcus thermophilus KCTC 2185, Lactobacillus delbrueckii subsp. lactis ATCC 4797, and Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842 in anaerobic condition of pH 1.5-3.5 range. Numbers of all tested viable cells did not decrease at pH 3.5, but decreased rapidly at pH 1.5 and pH 2.5 during 2 hour incubation at modified EG medium. Immediately after 2 hour incubation, the decrease in population at pH 1.5 and pH 2.5 was about 6-8 and 5-7 log cycles/ml, respectively. Lactobacillus acidophilus ATCC 4356 showed the higest survival of all tested bacteria. The $\beta$-galactosidase activity from Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842 and Streptococcus thermophilus KCTC 2185 decreased rapidly at pH 1.5 and 2.5, but there was a little decrease at pH 3.5. The cellular permeability that was measured by the leakage of intracellular materials increased with decrease of pH. These results suggest that the ingested lactic acid bacteria may be destroyed in contact with low pH of gastric acid.

• Journal of Plant Biology
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• v.30 no.3
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• pp.181-187
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• 1987

Copper inhibited PSII-mediated O2 evolution (H2OlongrightarrowDCIP, H2OlongrightarrowSiMo) but not PSImediated O2 uptake(DCIP. Asc.longrightarrowMV) in isolated Chinese cabbage chloroplasts. Copper toxicity on PSII-mediated O2 evolution was higher at alkaline condition than at acidic condition and was inhanced by light illumination after copper treatment. The increased toxicity by light illumination was not recovered by subsequent dark treatment. The inhibitory effect of copper on H2OlongrightarrowDCIP reaction was higher than that on H2OlongrightarrowSiMo reaction. This result suggests that there may be another inhibitory site of copper on PSII other than water oxidizing side of PSII.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.184-188
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• 2008

This study presented simple and efficient fabrication of chemical sensors for the detection of acidic gas using 1,3-bisdicyanovinylindane as an indicator because it can be promising materials having property of the rapid color change according to the variation of pH. The dissociation of proton and dye in acidic condition as changing of ion pairs give rise to dramatically change the absorbance intensity of 1,3-bisdicyanovinylindane, which can be easily applied to the development of chemical sensors. In addition, indicator dyes having negatively charge in aqueous phase can be easily fabricated using layer-by-layer (LBL) methods by way of electrostatic interaction. For the proof of concept, we demonstrated the abrupt presentation of skeleton symbol on the chemical sensor, which could be resulted from the reaction of 1,3-bisdicyanovinylindane as background color with acidic gas. Thus, the rapid appearance of symbol will induce user's caution under the emergency condition. The presented chemical gas sensor using 1,3-bisdicyanovinylindane have strong advantages. First, the fabrication process of gas sensor was very simple and low-cost. Secondly, sensors reacted by acidic gas could be reused for several times. Finally, the chemical gas sensor would be environmentally friend, which can be a basic tool for the realization of eco-organic sensor device.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.154-165
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• 2016

This paper presents experimental results to investigate the affects of acidic solution under loading condition on rock properties. In the experiment, the variations of various rock properties including effective porosity, thermal conductivity, and etc were investigated with different pHs of solution and magnitudes of loading. The results show that the rock property change was increased with low pH under loading. It was predicted that chemical reaction rate would be increased in low pH. Below the crack initiation stress of the rock specimen, the variation of rock property change was reduced with increased loading. It could be explained with the reduced chemical reaction area by the compressional loading if there is no crack generation.

• Journal of Electrochemical Science and Technology
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• v.13 no.2
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• pp.213-226
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• 2022

In the present study, the corrosion behavior of aluminum Al-7075 tempered (T-6 condition) alloy was evaluated by immersion testing and electrochemical testing in 1.75% and 3.5% NaCl environment at acidic, neutral and basic pH. The data obtained by both immersion tests and electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy tests) present that the corrosion rate of the alloy specimens is minimum for the pH=7 condition of the solution due to the formation of dense and well adherent thin protective oxide layer. Whereas the solutions with acidic and alkaline pH cause shift in the corrosion behavior of aluminum alloy to more active domains aggravated by the constant flux of acidic and alkaline ions (Cl^- and OH^-) in the media which anodically dissolve the Al matrix in comparison to precipitated intermetallic phases (cathodic in nature) formed due to T6 treatment. Consequently, the pitting behavior of the alloy, as observed by cyclic polarization tests, shifts to more active regions when pH of the solutions changes from neutral to alkaline environment due to localized dissolution of the matrix in alkaline environment that ingress by diffusion through the pores in the oxide film. Microscopic analysis also strengthens the results obtained by immersion corrosion testing and electrochemical corrosion testing as the study examines the corrosion behavior of this alloy under a systematic evaluation in marine environment.

• Toxicological Research
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• v.19 no.3
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• pp.173-180
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• 2003

The present study was conducted to investigate the single and 2-week repeated dose toxicity of red ginseng acidic polysaccharide (RGAP) in Sprague-Dawley rats. The test article was administered orally to rats at dose levels of 0, and 2000 mg/kg/day for single dose toxicity study and at dose levels of 0, 250, 500, and 1000 mg/kg/day for repeated dose toxicity study. In both studies, there were no treatment-related effects on mortality, clinical signs, food and water consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, necropsy findings and organ weights of all animals treated RGAP. Based on these results, it was concluded that the 2-week repeated oral dose of RGAP may have no toxic effect in rats at a dose level of 1000 mg/kg/day. In the condition of this study, the no-observed-adverse-effect level (NOAEL) was considered to be 1000 mg/kg/day for both sexes.