• Polymer(Korea)
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• v.25 no.2
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• pp.186-198
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• 2001

pH/Thermal sensitive copolymers with the various acidic comonomer compositions composed of N-isopropylacrylamide (NIPAAm) with acrylic acid (AAc), 2-acrylamido glycolic acid (AAmGAc), and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were synthesized by free radial polymerization. In this study, to characterize the effect of different acidic comonomer composition and pH on the lower critical solution temperature (LCST) behaviors of their copolymers. phase transition experiments were performed with a thermo-optical analyzer (TOA). The phase transition temperature (T$^{p}$ ) of aqueous poly(NIPAAm-co-AAc) solution was lowered with increasing the ionization of the acid group in AAc, that is, the ionized state induced the electrostatic repulsion of ionized groups. In contrast, when AAmGAc was introduced into PNIPAAm, T$^{p}$ was little changed at pH 1-3, whereas climbed up significantly from pH 1 to pH 3. In the range of pH 6-10, Tp was lower than that of pH 3-5. This result was considered to be \"Ionic Screen Effect\" and this effect had been also observed in the case of poly(NIPAAm-co-AMPS).-co-AMPS).

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.265-269
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• 2006

This study was to investigate the effect of acidic leachate on the landfill liner system and healing of cracks by using industrial by-products; BFS(Blast Furnace Slag) and FA(Fly Ash). From the results of pH measurement, for OPC(Ordinary Portland Cement) and DM(Dredged Mud) mixtures immersed acidic leachate, the initial pH($4.5{\sim}5.5$) was heavily increased to approximately 10 after 60 days experiment due to the production of 2 mole $OH^-$ which was occurred by hydrolysis of CaO and MgO etc.. Meanwhile, the initial pH of acidic leachate immersed DM mixtures with BFS and FA respectively was lasted for longer period as compared to the comparison. The reason was that production of low Ca C-S-H hydrates which stabilized in acidic liquid. The physical properties(compressive strength, hydraulic conductivity) of DM mixtures added BFS and FA was improved. It was concluded that the dissolution of hydrates was disturbed by high alkalinity of BFS and FA.

• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.59-59
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• 2001

The purpose of this study was to investigate the molecular mechanism by which environmental pH alters the radiation-induced expression of p53, the key regulator of cellular responses to radiation. We have already reported that an acidic environment markedly prolongs the radiation-induced expression of p53 and also prolongs the radiation-induced G2/M arrest.(omitted)

• Tribology and Lubricants
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• v.19 no.4
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• pp.211-216
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• 2003

This paper was studied on the corrosion and corrosion-wear behavior of chromium (Cr) plating in the acidic environments. In the various pH of acidic solutions, the electrochemical polarization test and wear-corrosion test of Cr plating were carried out. And thus potential, corrosion current density and corrosion-wear loss behaviour of Cr plating are investigated.

• Korean journal of food and cookery science
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• v.6 no.3 s.12
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• pp.9-15
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• 1990

Peanut prptein isolate was tested for the purpose of finding out the effect of pH, Sodium Chloride concentration and heat treatment on the solubility, surface hydrophobicity, foam expansion and foam stability. The solubility of peanut protein isolate was affected by pH and showed the lowest value at pH 4.5. When the peanut protein isolate was heated, the solubility decreased at pH 3 and pH 7 but at pH 9 solubility increased. At all pH range, solubility decreased as NaCl was added. The surface hydrophobicity of peanut protein isolate showed the highest value at pH 1.5. Generally, at acidic pH range the surface hydrophobicity was high, but at alkaline region, the surface hydrophobicity increased as the temperature increased. And when NaCl was added, the surface hydrophobicity was also increased. Foam expansion of peanut protein isolate was no significant difference among the values about pH. When the peanut protein was heated and NaCl was added, foam expansion was increased at pH 7. Foam stability was significantly low at pH 4.5 and foam stability was increased at acidic pH region below pH 4.5. At pH 7 and pH 9, heat treatment above $60^{\circ}C$ increased foam stability. When NaCl was added, foam stability was significantly increased at pH 3 and pH 7.

• 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 the korean academy of Pediatric Dentistry
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• v.24 no.4
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• pp.719-726
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• 1997

The aim of this study was to evaluate the in vitro effects of exposure to acidic beverages on microhardness of enamel and dentin. Thirty enamel specimens and thirty dentin specimens were obtained from extracted bovine maxillay incisiors. Enamel and dentin specimens were divided into three groups and treated with acidic beverages as follows; Group 1 : cola(pH 2.52), Group 2 : plain soda water(pH 2.93) and Group 3 : orange juice(pH 3.75). Erosive treatment was performed by storing each specimens for 5 min in 50ml solution of cola, soda water and orange juice. Average microhardness values(VHN) were determined before and after erosive treatment. All beverages produced significant loss of microhardness of enamel and dentin. Microhardness of enamel was reduced in the following order: Group 1 : $42.71{\pm}4.36(%)$, Group 2 : $37.09{\pm}6.25(%)$, Group 3 : $35.46{\pm}4.98(%)$. Microhardness of dentin was reduced in the following order: Group 1 : $17.14{\pm}3.42(%)$, Group 2 : $13.89{\pm}3.18(%)$, Group 3 : $13.82{\pm}3.50(%)$. The differences between group 1 and group 2, 3 were statistically significant(p< 0.05).

• Journal of Microbiology and Biotechnology
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• v.24 no.6
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• pp.781-787
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• 2014

2-Ketogluconic acid production by Klebsiella pneumoniae is a pH-dependent process, strictly proceeding under acidic conditions. Unfortunately, cell growth is inhibited by acidic conditions, resulting in low productivity of 2-ketogluconic acid. To overcome this deficiency, a two-stage fermentation strategy was exploited in the current study. During the first stage, the culture was maintained at neutral pH, favoring cell growth. During the second stage, the culture pH was switched to acidic conditions favoring 2-ketogluconic acid accumulation. Culture parameters, including switching time, dissolved oxygen levels, pH, and temperature were optimized for the fed-batch fermentation. Characteristics of glucose dehydrogenase and gluconate dehydrogenase were revealed in vitro, and the optimal pHs of the two enzymes coincided with the optimum culture pH. Under optimum conditions, a total of 186 g/l 2-ketogluconic acid was produced at 26 h, and the conversion ratio was 0.98 mol/mol. This fermentation strategy has successfully overcome the mismatch between optimum parameters required for cell growth and 2-ketogluconic acid accumulation, and this result has the highest productivity and conversion ratio of 2-ketogluconic and produced by microorganism.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.3
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• pp.400-405
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• 2003

The surimi processing from jack mackerel and white croaker muscle using acidic and alkaline solubilization was evaluated. The optimum pH for solubilizing protein in acidic and alkaline range was around 2.5 and 10.5, respectively. The optimum pH value for recovery of protein was around 5. The protein solubility was decreased with increase of salt. The homogenized speed and time for maximum solubility were below 9,500 rpm and 30s, respectively The optimum ratio of water to minced muscle was 6 by evaluating breaking force, deformation and whiteness of cooked gel. The protein yield of alkaline processing is higher than that of conventional processing. In addition, the waste water of conventional processing had high solid, nitrogen content and chemical oxygen demand compare to those of acidic and alkaline processing.

• Microbiology and Biotechnology Letters
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• v.35 no.1
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• pp.26-29
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• 2007

Tautomycetin (TMC), which is produced by Streptomyces sp. CK4412, is a novel activated T cell-specific immunosuppressive compound with an ester bond linkage between a terminal cyclic anhydride moiety and a linear polyketide chain bearing an unusual terminal alkene. Antifungal activity against Aspergillus niger and TMC productivity assayed by HPLC using culture extracts from Streptomyces sp. CK4412 grown on solid medium adjusted at various pH were measured. The cells cultured at acidic pH (pH 4-5) medium exhibited much stronger antifungal activity as well as higher TMC productivity than those cultured at neutral pH medium, implying that the acidic pH-shock should be an efficient strategy to induce the productivity of secondary metabolites in Streptomyces culture.