• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.33-42
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• 2000

Adsorption onto the surfaces of solid particles is a well known phenomenon that causes the retardation effect of heavy metals in soils. For adequate remediation of soil and groundwater contamination, it is important to investigate the mobility of heavy metals that largely depends on pH conditions in the soil water since adsorption of heavy metals is pH-dependent. In this study, we investigated the transport of Zn ion under various pH conditions in a sandy soil by conducting batch and column tests. The batch test was performed using the standard procedure of equilibrating fine fractions collected from the soil with eleven different initial $ZnCl_2$ concentrations, and analysis of Zn ion in the equilibrated solutions using ICP-AES. The column test consisted of monitoring the concentrations of soil solutions exiting the soil column with time known as a breakthrough curve (BTC). We injected respectively $ZnCl_2$ and KCl solutions with the concentration of 10 g/L as a tracer in a square pulse type under three different pH conditions (7.7, 5.8, 4.1) and monitored the flux concentration at the exit boundary using an EC meter and ICP-AES. The resident concentration was also monitored at the 10cm-depth by Time Domain Reflectometry (TDR). The results of batch test showed that ion exchange process between Zn and other cations (Ca, Mg) was predominant. The retardation coefficients obtained from adsorption isotherms (Linear, Freundlich, Langmuir) resulted in the various values ranging from 1.2 to 614.1. No retardation effect but ion exchange was found for the BTCs under all pH conditions. This can be explained by the absence of other cations to desorb Zn ion from soil exchange sites under the conditions of ETC experiment imposing blank water as leachate in steady-state flow. As pH decreased, the peak concentration of Zn increased due to the competition of Zn with hydrogen ions ($H^+$) and the concentrations of other cations decreased. The peak concentration of Zn was increased by 12.7 times as pH decreased from 7.7 to 4.1.

• Journal of the Korean Applied Science and Technology
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• v.8 no.1
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• pp.59-67
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• 1991

The reactions of semicarbazide hydrochloride with aliphatic and alicyclic ketones were studied kinetically at 15, 25, 35 and 45$^{\circ}C$ in 20% ethanol solution buffered at pH 2.9. The rate of cyclohexanone semicarbazone formation is 5.5 times as fast as that of cyclopentanone semicarbazone, while 3-pentanone semicarbazone is 4.7 times as slow as that of 2-pentanone, The activation energy of cyclohexanone, 2-pentanone, 2 hexanone, cyclopentanone, 4-methyl-2-pentanone and 3-pentanone semicarbazone formation are calculated 5.08, 7.52, 8.79, 9.59, 9.49, 11.59, respectively. It is concluded from the effect of ionic strength that the reaction is affected by not ion but neutral molecules being progressed hydrogen bond between oxygen atom of carbonyl group and hydrogen atom of acid-catalyst and concerted nucleophilic attack of free base on the carbonly compound. Dependence on pH of the rate of 2-pentanone semicarbozone formation is linear relationship below pH 4.60 and above pH 5.60. As a result of studing citric acid catalysis, second order constants increase linearly with citric acid concentration. As the catalyst concentration is varied from 0.025 to 0.10 mol/1 at pH 2.90, the rate constants increase 1.4 times, but slight increase is observed at pH 5.60. Conclusively, the rate-determining step is formation of tetrahedral interemediate below pH 4.65 and dehydration between pH 5.60 and pH 7.11. It is concluded that the formation reaction of cyclohexanone semicarbazone is faster than cyclopentanone semicarbazone due to the steric strain in the process of forming tetrahedral intermediate.

• Applied Biological Chemistry
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• v.25 no.3
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• pp.166-172
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• 1982

The changes of hydrogen ton concentration, viscosity and free sugars in the water-soluble mucilage of Ulmus Coreana, Nakai root upon storage at 10^{\circ}C were studied. Hydrogen ion concentration in the mucilage changed $pH7{\rightarrow}pH4{\rightarrow}pH6$ or 7. The viscosity of mucilage decreased very slowly. The mucilage contained glucose and galacturonic acid. The hydrolyzed products of mucilage consisted of rhamnose, mannose, galactose, arabinose, xylose, glucose and galacturonic acid.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.2
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• pp.133-138
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• 2001

In this study, an attempt was made to increase the survival rate of bifidobacteria entrapped in alginate in the gastrointestinal tract, and to investigate the potential industrial applications, for example lyophilized capsules and yogurt. First, the protective effect of various food additives on bifidobacterial survivability was determined after exposure to simulated gastric juices and bile salts. The additives used in this study were skim milk (SM), polydextrose (PD), soy fiber (SF), yeast extract (YE), chitosan (CS), $\kappa$-carageenan ($\kappa$-C) and whey, which were added at 0.6% concentration (w/v) to 3% alginate-bifidobacterial solution. In the simulated gastric juices and bile salts, the protective effect of 0.6% skim milk-3% alginate (SM-A) beads on the survival rate of bifidobacteria proved to be higher than the other additives. Second, the hydrogen ion permeation was detected through SM-A vessel without bifidobacterial cells at different SM concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%). There were no differences in terms of the pH decrease in SM-A vessels at 0.6%, 0.8%, and 1.0% (w/v) SM concentrations. The survival rate of bifidobacteria in SM-A beads would appear to be related to the SM buffering capacity against hydrogen ions and its tendency to reduce the pore size of bead. In this experiment, the survival rate of bifidobacteria entrapped in beads containing 0.6% SM showed the highest viability after exposure to simulated gastric juices for 3h, thereby indicating that 0.6% SM is the optimum concentration fir 3% alginate bead preparation. Third, the effect of SM-A beads on the freeze-drying and yogurt storage for 10 days was investigated. SM-A beads were found to be more efficient for freeze drying and yogurt storage than untrapped cells and the alginate bead. Consequently, the survival rate of bifidobacteria entrapped in SM-A beads was increased in simulated gastric juices, bile salts and probiotic products, such as lyophilized capsules and yogurt, SM-A beads can be expected to produce high value probiotic products.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.384-387
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• 2005

Fuel cell has been well known as a clean alternative power for vehicles. Recently, an experimental technique has been developed measurement of species and distributions by using gas chromatograph. In this study, cathode channel oxygen distributions as various conditions were investigated using gas chromatograph and cell visualization. And discussed relation between flooding and oxygen concentrations. As a result of experiment, oxygen consumpt ion is affected wi th flooding. Flooding is observed in channel near hydrogen inlet, and oxygen consumption is low at that region.

• Journal of the Korean Chemical Society
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• v.4 no.1
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• pp.62-66
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• 1957

With the intention of preparing cation exchangers from the domestic coals, and using these for softening hard water and some other purposes, seven kinds of raw coal were tested and the results are as follows. 1) The following conditions of preparation were given the good results. Reaction time 5 hours Reaction temperature $95^{\circ}$ Concentration of sulfuric acid 98% Amount of sulfuric acid 10 times to the sample (as weight) 2) The raw coals which is rich in fixed carbon and have the fuel ratio 0.8 to 1.0 were suitable, and Kampo lignite has shown the best results. 3) The cation exchangers from coals were able to exchange the cation, both hydrogen and sodium type dynamically and statically, like the synthetic ion exchange resin. The exchange capacities were as follows. Total capacity 1.60 meq/g. Breakthrough capacity 1.30 meq/g. Usable breakthrough capacity 1.20 meq/g National Central Research laboratory

• Journal of dental hygiene science
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• v.14 no.2
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• pp.87-93
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• 2014

Dental plaque resides passively at a site and makes an active contribution to the maintenance of health. The bacterial composition of plaque remains relatively stable despite regular exposure to minor environmental stress. This stability, homeostasis is due to a dynamic balance of microbial interactions. However, the homeostasis can break down, leading to shifts in the balance of the microflora. This change can be a sign of initial dental caries. It is proposed that disease can be prevented or treated not only by targeting the putative pathogens but also by interfering with the processes that drive the breakdown in homeostasis. It is essential to understand the plaque as a mixed species biofilm. In this essay I reviewed an extension of the caries ecological hypothesis to explain the relation between dynamic changes in the phenotypic/genotypic properties of plaque bacteria and the demineralization and remineralization balance of the dental caries process. We will have the strategies to impact significantly on clinical practice as understanding dental biofilm.

• Journal of Biosystems Engineering
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• v.30 no.4 s.111
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• pp.249-253
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• 2005

This study was carried out to develop enzyme biosensor for lactic acid bacteria. Lactic acids produced by lactic acid bacteria (LAB) was measured and good correlation $R^2=0.98$ between LAB count and lactic acids concentration was found. Hydrogen ion produced by L-lactate dehydrogenase (L-LDH) was measured by a potentiometer. Glutamic-pyruvic transminase (GPT) was used for eliminating inhibitor in the reaction. Polyacrylamide gel was used for immobilizing matrix of the sensor. The biosensor was tested and showed good feasibility with $R^2=0.99$ on validation.

• Journal of the Korean Chemical Society
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• v.7 no.2
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• pp.186-188
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• 1963

An attempt to improve the method of volumetric determination of tungsten developed by Luke has been made successfully. Using amalgam coated lead instead of pure metallic lead in the reduction procedure. W(VI)-W(III) reduction has been found to be quantitative in rather concentrated hydrochloric acid. Since there was no excessive dissolution of lead via reduction of hydrogen ion, lead surface was totally accessible for the reduction of tungsten and no trouble was caused by dereposition of $PbCl_2$ crystals at the nozzle of Jones reductor. Furthermore, it has been confirmed that almost 100 mg. of $WO_3$ can be handled easily if the chloride concentration of the HCl is increased by adding solid $NH_4Cl$.

• The Journal of the Korean dental association
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• v.9 no.12
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• pp.841-845
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• 1971

Author has made the studies on the pH of pus in the 53 suppurative disesed patients who had admitted to department of ora surgery, Infirmary of Schoo of Dentistry, Seoul National University. The results were obtained as follows; 1. The average pH of pus in the patients with suppurative oral diseases was 6.46 and the pH of pus was ranging 5.0 to 7.2. 2. The pH value of pus was not significant between the males(pH: 6.58) and females (pH: 6.40). 3. The pH vaule of pus in patients treated by antibiotics trend to slightly alkaline than that of untreated patients. 4.The pH vaule of pus in the pericoronitis, periodontal abscess and other localized oral infections were slightly alkaline than buccal abscess and osteomyelitis, and acute suppurative diseases of jaws was more acid than chronic diseases. In general, it was seemed the early stages of inflammation was alkaline, and the later stages was acid.