• Food Science and Biotechnology
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• v.18 no.3
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• pp.610-617
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• 2009

The stability of corn oil-in-water emulsions coated by milk proteins, sodium caseinate (CAS), or whey protein concentrate (WPC), was compared under the environmental stress of pH change. Emulsions were prepared at 0.1 of protein:oil because the majority of droplets were relatively small ($d_{32}=0.34$ and $0.35\;{\mu}m$, $d_{43}=0.65$ and $0.37\;{\mu}m$ for CAS- and WPC-emulsions, respectively) and there was no evidence of depletion flocculation. As the pH of the emulsions was gradually dropped from 7 to 3, there was no significant difference in the electrical charges of the emulsion droplets between the 2 types of emulsions. However, laser diffraction measurements, microscopy measurements, and creaming stability test indicated that WPC-emulsions were more stable to droplet aggregation than CAS-emulsions under the same circumstance of pH change. It implies that factors other than electrostatic repulsion should contribute to the different magnitude of response to pH change.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.33.1-33.1
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• 2018

pH is expressed mathematically as $pH=-{\log}[H^+]$, is a measure of the hydrogen ion concentration, [$H^+$] to specify the acidity or basicity of an aqueous solution. The pH scale usually ranges from 0 to 14. Every aqueous solution can be measured to determine its pH value. The pH values below 7.0 express the acidity, above 7.0 are alkalinity and pH 7.0 is a neutral solution. The solution pH can be determined by indicator or by measurement using pH sensor, which measuring the voltage generated between a glass electrode and a reference electrode according to the Nernst Equation. The pH value of solutions depends on the temperature and the activity of contained ions. In nickel electroless plating process, the controlled pH value in some limited ranges are extremely important to achieve optimal deposition rate, phosphorus content as well as solution stability. Basically, nickel electroless plating solution contains of $Ni^{2+}ions$, reducing agent, buffer and complexing agents. The plating processes are normally carried out at $82-92^{\circ}C$. However, the change of its pH values with temperatures does not follow any rule. Thus, the purpose of study is to understand the relationship between pH and temperature of some based solutions and electroless nickel plating solutions. The change of pH with changing temperatures is explained by view of the thermal dynamic and the practical measurements.

• Microbiology and Biotechnology Letters
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• v.25 no.3
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• pp.240-247
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• 1997

Bacillary is the most common form of H. pylori observed during human infection. However, it is known that the morphology change of H. pylori from bacillary to coccoid can be occurred with a response to the environmental stresses such as the nutrient depletion, accumulation of toxic metabolites, pH alteration, and exposure to antimicrobial agents. The coccoid form of H. pylori, which is viable but non-culturable in vitro, seems to be the major cause of antibiotic resistancy and high reinfectability of H. pylori. In this regard, we studied the environmental factors that can induce the morphological change in vitro of H. pylori, and the change of fatty acid composition of plasma membrane. The morphological change from bacillary to coccoid could be observed with the depletion of nutrients, pH variation and reactive oxygen species added in the culture media. This morphologic conversion was paralleled by a dramatic decrease in unsaturated fatty acids and an increase in saturated fattv acids of plasma membrane. The change in composition of membrane fatty acid seems to be a kind of protection mechanism of H. pylori against these environmental stresses.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.404-408
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• 2003

In this study, we examined the influences of pH and total concentration on the speciation of heavy metals (Cd, Cu, Zn) in acid mine drainage. Their labile concentrations were analyzed by Anodic Stripping Voltammetry (ASV) at both natural pH and adjusted pHs (from 2 to 8). We obtained regression equations for predicting labile concentrations as a function of the water pH and contamination level (total dissolved metal concentration). Our data show that labile Cu depends on both the total concentration and pH, while labile Cd and Zn concentrations are controlled mainly by their total concentration rather than pH. Therefore, the pH variation of AMD may significantly change the toxicity and bioavailability especially of Cu, owing to its speciation change.

• Journal of Life Science
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• v.18 no.8
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• pp.1159-1163
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• 2008

The purpose of this study was to establish a high-throughput assay method capable of estimating specific lipase activity at oil-water interface. The method is based on the fact that fluorescence intensity of fluorescein is affected by pH. The pH-dependence might be used to monitor pH change caused by the release of fatty acid through the action of lipase. Assay was performed by incubating a reaction mixture containing oil emulsion, fluorescein and enzyme and by monitoring fluorescence intensity periodically. Fluorescence intensity decreased linearly with a rate proportional to the enzyme amount. Linear relationship was observed between enzyme amount and reaction rate which was calculated from a graph of fluorescence change against time. The assay was possible at different pH conditions in the range of pH 6.0-8.0.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2415-2418
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• 2008

Polydiacetylenes (PDAs) are very attractive chemical substances which have distinctive features of color change and fluorescence emission by thermal or chemical stress. Especially, when PDAs contact with solutions of a particular pH, such as a strong alkaline sodium hydroxide (NaOH) solution or a strong acidic hydrogen chloride (HCl) solution, PDAs change their color from non-fluorescent blue to fluorescent red. In this study, we propose a novel method to detect alkaline pH using PDAs and NaOH solutions by hydrodynamic focusing on a microfluidic chip. Preliminary results indicate that the fluorescent intensity of PDAs increases in respond to the NaOH solution concentrations. Also, the fluorescence is quenched back when the PDAs are in contact with a HCl solution. These results are useful in a microfluidic PDA sensor chip design for pH detection.

• Bulletin of the Korean Chemical Society
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• v.6 no.5
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• pp.280-284
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• 1985

Kinetic measurements of the 5-nitrofurfural-hydrazine reaction in various pH ranges of aquous solution were carried out by ultraviolet spectrophotometry at $25^{\circ},\;35^{\circ}\;and\;45^{\circ}C$. The observed rate of the reaction varies with the change in pH, which gives characteristic "bell-type" rate acidity profile. The maximum rate is shown in the vicinity of pH 4. This reaction procceds with rate-determining attack of hydrazine on the 5-nitrofurfural at low pH and undergoes a change in rate-determining step to dehydration of the addition intermediate as pH increases. The reaction has a "reactant-like transition state" which precedes intermediate in low pH and "product-like transition state" which follows it in neutral pH. The geometry of 5-nitrofurfural-hydrazine intermediate was estimated with PCILO method associated with CNDO/2 scheme.

• Food Science and Preservation
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• v.5 no.3
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• pp.211-216
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• 1998

This study was carried out to how the effects of storage temperature of garlic bulbs, pH and temperature of garlic puree on its color change. Color change was severely appeared in puree made of garlics stored at pH 4.0, 2$^{\circ}C$ and pH 4.0, 25$^{\circ}C$. The color of garlic puree was changed from green to blue during storage. The yellowing occured by the oxidation at high temperature of puree. Garlic puree absorbed the wavelengths of 486nm. 580nm, and 656nm. The precursors of pigments produced by enzymatic reaction were seemed to be the reasons of color change because there was no my change of color in puree when the enzymes including alliinase were inactivated. However, the color changes of puree at low storage temperature should be studied further in the future.

• Journal of Korea Foresty Energy
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• v.25 no.1
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• pp.18-23
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• 2006

pH dependent K/S values, Hue, Value, and Chroma change of the hot-water and alkali extract of Boehmeria tricuspis have investigated as a part of the studies on natural dye resources. Maximum optical absorption of the dyed cotton, Korean paper, and silk with the extract were observed at 400 nm. According to the result of pH dependent K/S values change, it tended to increase as pH decreased except for the silk and there was no change near pH 7. For Hue, the materials dyed with hot-water and alkali extract indicated YR and R color, respectively. The change in Value of the dyed materials tended to increase, whereas Chroma of them decreased as the pH moved to alkali conditions although there were no significant changes near pH 7. As a result, it is considered that the optimum pH would be 7 when the mentioned materials are dyed with Boehmeria tricuspis extract.

• Clinical and Experimental Reproductive Medicine
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• v.20 no.1
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• pp.65-70
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• 1993

To maintain a good sperm motility is one of the key factors for the successful artificial insemination in retrograde ejaculation, and the sperm motility has been shown to be affected by various environmental factors, including change in pH and osmolarity. Herein we have analyzed the effect of change in pH and osmolarity in urine and normal saline on sperm motility by Sperm Quality Analyzer and Makler counting chamber. Semen, which sampled by masturbation from a 28 year old male and showed normal finding on semen analysis, was used for this study. The results were as follows: 1. When osmolarity was fixed to 300mOsm, pH did not show a definite effect on the sperm moility. However, the motility was generally a bit better in alkaline urine and saline than in acid, particularly than in pH 5.0. 2. When pH was fixed to 7.5, sperm motility was best in urine and saline of 300mOsm. Hyperosmolarity had more adverse.effect on the motility than hypoosmolarity. 3. The sperm motility was worse in the urine than in saline under the same pH and osmolarity. In conclusion, osmolarity has a definite effect on sperm motility, where as pH has relatively little effect. And certain components of urine other than pH and osmolarity might affect the sperm motility.