• Journal of the Korean Chemical Society
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• v.28 no.6
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• pp.403-411
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• 1984

Amberlite XAD-7 and XAD-4 resins impregnated with DXHQ (5,7-dihalo-8-hydroxyquinoline) were prepared for the adsorption, separation and recovery of heavy metal ions from aqueous solutions. The characteristics of the impregnated resins, DXHQ (X : Cl, Br, I)-XAD were studied to find out the proper pairs of resin and DXHQ for the adsorption of metal ions. The increasing order of the impregnated amount of DXHQ onto XAD-7 resin was as follows: DCHQ < DBHQ < DIHQ. It was observed from the plot of log $K_d$ vs. pH that the optimum pH range for the adsorption of DIHQ onto XAD-4 resin was from 3.0 to 7.0. The stabilities of the DXHQ-XAD resins were investigated by measuring the amount of DXHQ remained on the XAD resin after shaking the DXHQ-XAD resins in various solutions of pH ranging from 2 to 12 and hydrochloric acid solutions. The impregnated resins were considerably stable in both acidic and neutral solutions. The amount of DIHQ leached from DIHQ-XAD-4 resin by eluting with various HCl solutions (1 ∼ 5M) was negligible, but in the case of XAD-7 resin it increases as the concentration of HCl solution increases. The optimum pH ranges, absorption mole ratio (M : DXHQ) and adsorption capacities (mmol metal per gram of resin) for the adsorption of metal ions onto the DXHQ-XAD resins were determined respectively. The stability of metal ion absorbed by the DXHQ-XAD resins was observed as the following order: M-DCHQ-XAD-7 < M-DBHQ-XAD-7 < M-DIHQ-XAD-7. The adsorbed metal ions were quantitatively recovered by eluting with HCl (0.5 ∼ 5M) and DXHQ-XAD resins could be reused over 5 times without re-impregnation of DXHQ.

• Korean Journal of Materials Research
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• v.25 no.8
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• pp.423-428
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• 2015

Impedancemetric $NO_x$ (NO and $NO_2$) gas sensors were designed with a stacked-layer structure and fabricated using $LaCr_xCo_{1-x}O_3$ (x = 0, 0.2, 0.5, 0.8 and 1) as the receptor material and $Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ plates as the solid-electrolyte transducer material. The $LaCr_xCo_{1-x}O_3$ layers were prepared with a polymeric precursor method that used ethylene glycol as the solvent, acetyl acetone as the chelating agent, and polyvinylpyrrolidone as the polymer additive. The effects of the Co concentration on the structural, morphological, and $NO_x$ sensing properties of the $LaCr_xCo_{1-x}O_3$ powders were investigated with powder X-ray diffraction, field emission scanning electron microscopy, and its response to 20~250 ppm of $NO_x$ at $400^{\circ}C$ (for 1 kHz and 0.5 V), respectively. When the as-prepared precursors were calcined at $700^{\circ}C$, only a single phase was detected, which corresponded to a perovskite-type structure. The XRD results showed that as the Co concentration of the $LaCr_xCo_{1-x}O_3$powders increased, the crystal structure was transformed from an orthorhombic phase to a rhombohedral phase. Moreover, the $LaCr_xCo_{1-x}O_3$ powders with $0{\leq}x<0.8$ had a rhombohedral symmetry. The size of the particles in the $LaCr_xCo_{1-x}O_3$powders increased from 0.1 to $0.5{\mu}m$ as the Co concentration increased. The sensing performance of the stack-structured $LaCr_xCo_{1-x}O_3/Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ sensors was found to divide the impedance component between the resistance and capacitance. The response of these sensors to NO gas was more sensitive than that to $NO_2$ gas. Compared to other impedancemetric sensors, the $LaCr_{0.8}Co_{0.2}O_3/Li_{1.3}Al_{0.3}Ti_{1.7}(PO_4)_3$ sensor exhibited good reversibility and reliable sensingresponse properties for $NO_x$ gases.

• Korean Journal of Microbiology
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• v.53 no.4
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• pp.251-256
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• 2017

Some rhizobacteria were isolated, that have copper resistance and can confer copper resistance to plants allowing growth under copper stress. Isolated strains Pseudomonas veronii MS1 and P. migulae MS2 produced 0.13 and 0.26 mmol/ml of siderophore, that is a metal-chelating agent, and also showed 64.6 and 77.9% of biosorption ability for Cu in 20 mg/L Cu solution, respectively. Copper can catalyze a formation of harmful free radicals, which may cause oxidative stress in organisms. Removal activity of 1,1-diphenyl-2-picryl hydrazyl radical and antioxidant capacity of strains MS1 and MS2 increased up to 82.6 and 78.1%, respectively compared to those of control at 24 h of incubation. They exhibited 7.10 and $6.42{\mu}mol$ ${\alpha}$-ketobutyrate mg/h of 1-aminocyclopropane-1-carboxylic acid deaminase activity, respectively, which reduced levels of stress hormone, ethylene in plants, and also produced indole-3-acetic acid and salicyclic acid that can help plant growth under abiotic stress. All these results indicated that these copper-resistant rhizobacteria could confer copper resistance and growth promotion to plants.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.861-867
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• 2019

$Li_4Ti_5O_{12}$ is a promising next-generation anode material for lithium-ion batteries due to excellent cycle life, low irreversible capacity, and little volume expansion during charge-discharge process. However, it has poor charge capacity at high current density due to its low electrical conductivity. To improve this weakness, porous $Li_4Ti_5O_{12}$ was synthesized by sol-gel method with P123 as chelating agent. The physical characteristics of as-prepared sample was investigated by XRD, SEM, and BET analysis, and electrochemical properties were characterized by cycle performance test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS). $Li_4Ti_5O_{12}$ synthesized by 0.01mol ratio of P123/Ti showed most unified particle size, high specific surface area, and relatively high porosity. EIS analysis showed that depressed semicircle size was remarkably reduced, which suggested resistance value in electrode was decreased. Capacity in rate performance showed 178 mAh/g at 0.2C, 170 mAh/g at 0.5C, 110 mA/h at 5C, and 90 mAh/g at 10C. Capacity retention also showed 99% after rate performance.

• Journal of Life Science
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• v.31 no.5
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• pp.520-526
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• 2021

Microbial protein is one of the sources of protein in the rumen and can also be the source of glutamate production. Glutamic acid is used as fuel in the metabolic reaction in the body and the synthesis of all proteins for muscle and other cell components, and it is essential for proper immune function. Moreover, it is used as a surfactant, buffer, chelating agent, flavor enhancer, and culture medium, as well as in agriculture for such things as growth supplements. Glutamic acid is a substrate in the bioproduction of gamma-aminobutyric acid (GABA). This review provides insights into the role of glutamic acid and glutamic acid-producing microorganisms that contain the glutamate decarboxylase gene. These glutamic acid-producing microorganisms could be used in producing GABA, which has been known to regulate body temperature, increase DM intake and milk production, and improve milk composition. Most of these glutamic acid and GABA-producing microorganisms are lactic acid-producing bacteria (LAB), such as the Lactococcus, Lactobacillus, Enterococcus, and Streptococcus species. Through GABA synthesis, succinate can be produced. With the help of succinate dehydrogenase, propionate, and other metabolites can be produced from succinate. Furthermore, clostridia, such as Clostridium tetanomorphum and anaerobic micrococci, ferment glutamate and form acetate and butyrate during fermentation. Propionate and other metabolites can provide energy through conversion to blood glucose in the liver that is needed for the mammary system to produce lactose and live weight gain. Hence, health status and growth rates in ruminants can be improved through the use of these glutamic acid and/or GABA-producing microorganisms.

• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.577-586
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• 2002

The purpose of this in vitro study was to compare the effects of root canal cleanness following two Ni-Ti rotary instruments with different rake angle. Thirty-six sound, extracted human premolars with single root were randomly divided into three groups. The used rotary instruments were HEROShaper (Group 1, Micro-Mega, Besancon, France, n=12) and ProFile (Group 2, Maillefer, Ballaigues, Switzerland, n=12). Control group (n=12) was only extirpated with barbed broach (Mani, Matsutani Seisakusho Co., Japan) Group 1 & 2 teeth were prepared to a #40/.04 taper at the apex followed by 1 mm using crown-down technique. After canal preparation and frequent irrigation with 5.25% sodium hypochlorite, the roots split longitudinally into a bucco-lingual direction. Root halves were cross-sectioned in apical third portion again. All root specimens were processed for SEM investigation and photographed. Separate evaluations by one endodontist were undertaken for smear layer on prepared walls with a five score-index for each using reference photograph in root halves. The penetration depth of smear layer into dentinal tubules was also estimated in the other halves. Following results were obtained: 1. Smear layer was observed on all the prepared walls with two experimental groups except control group. 2. Smear layer characteristics in two experimental groups; 1) HEROShaper group showed snowy, dusty appearance and were shown open dentinal tubuli on the prepared walls of almost specimens, and the thickness of smear layer covering onto dentinal surfaces was within 1-2 ${\mu}m$ in a few specimens. 2) ProFile group showed shiny, burnished appearance and complete root canal wall covered by a homogenous smear layer with no open dentinal tubuli in all specimens. The penetration of smear layer into dentinal tubules was found in all specimens and the thickness was at 2-4 ${\mu}m$ in all specimens. These results demonstrated that a completely clean root canal could not be achieved regardless of positive or negative rake angle, which is in accordance with the majority of previous studies on root canal cleanliness In conclusion, through irrigation with antibacterial solutions or chelating agents is recommended to remove the smear layer on prepared canal wall in spite of Ni-Ti instrumentation.

• Journal of Periodontal and Implant Science
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• v.29 no.3
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• pp.561-578
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• 1999

The goal of periodontal therapy is the periodontal regeneration by the removal of microorganisms and their toxic products from the periodontally diseased root surface. To achieve periodontal regeneration, root conditioning as an adjunct to root planing has been done. There are low pH etchants such as citric acid, tetracycline-HCl, and EDTA solution which is a neutral chelating agent. The purpose of present study was to examine the effect of root conditioning by citric acid, tetracycline HCl, and EDTA. Total 35 root specimens(6${\times}$3${\times}$2mm) were prepared from the periodontally diseased teeth, scaled and root planed. The specimens were treated with normal saline for 1 minute, saturated citric acid(pH 1) for 3 minutes, 50mg/ml tetracycline-HCl(pH 2) for 5 minutes, 15% EDTA(pH 7) for 5 minutes using rubbing technique. The specimens were examined under scanning electron microscopy at 1000, and 3000 magnification. On the microphotographs taken at 1000 magnification, the numbers of opened and patent dentinal tubules per unit area(10,640${\mu}m^2$) were counted. And the diameters of opened dentinal tubules per unit are (10,640${\mu}m^2$) were measured. The differences of number and diameter among all groups were statistically analyzed by Kruskal Wallis Test. The results were as follows; 1. In the specimens applied with normal saline(control group), the root surface was finely cracked, and was covered by irregular smear layer. Neither exposed dentinal tubules nor any patent dentinal tubules could be seen. 2. In the specimens applied with saturated citric acid(experimental 1 group), the globular collagen fibers were exposed around the peritubular space, and many dentinal tubules were revealed. 3. In the specimens applied with tetracycline-HCl(experimental 2 group), the process-like collagen fibers were exposed around the peritubular space, and some dentinal tubules were revealed. 4. In the specimens applied with 15% EDTA(experimental 3 group), the root surface was covered by the collagenous fibrillar network, and many dentinal tubules were revealed. 5. The numbers of opened and patent dentinal tubules were significantly more in exp. 1 group and exp. 3 group than in exp. 2 group(P<0.05). But there was no significant difference between exp. 1 group and exp. 3 group. In control group, the number of opened and patent dentinal tubules could not be counted because any dentinal tubules couldn't be seen. 6 . The diameter of opened dentinal tubules was significantly smaller in exp. 1 group and exp. 3 group than in exp. 2 group(P<0.05). But there was no significant difference between exp. 1 group and exp. 3 group. In control group, the diameter of opened dentinal tubules could not be measured because any dentinal tubules couldn't be seen. The results demonstrate that root conditioning with citric acid, tetracycline- HCl, and EDTA is more effective in periodontal healing than only root planing, and 15% EDTA solution can replace low pH etching agents such as citric acid, tetracycline-HCl for root conditioning.

• Journal of Soil and Groundwater Environment
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• v.10 no.2
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• pp.35-43
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• 2005

Bioslurping combines the three remedial approaches of bioventing, vacuum-enhanced free-product recovery, and soil vapor extraction. Bioslurping is less effective in tight (low-permeability) soils. The greatest limitation to air permeability is excessive soil moisture. Optimum soil moisture is very soil-specific. Too much moisture can reduce air permeability of the soil and decrease its oxygen transfer capability. Too little moisture will inhibit microbial activity. So Modified Fenton reaction as chemical treatment which can overcome the weakness of Bioslurping was experimented for simultaneous treatment. Although the diesel removal efficiency of SVE process increased in proportion to applied vacuum pressure, SVE process was difficulty to remediation quickly semi- or non-volatile compounds absorbed soil strongly. And SVE process had variation of efficiency with distance from the extraction well and depth a air flow form of hemisphere centering around the well. Below 0.1 % hydrogen peroxide shows the potential of using hydrogen peroxide as oxygen source but the co-oxidation of chemical and biological treatment was impossible because of the low efficiency of Modified Fenton reaction at 0.1 % (wt) hydrogen peroxide. NTA was more efficiency than EDTA as chelating agent and diesel removal efficiency of Modified Fenton reaction increased in proportion to hydrogen peroxide concentration. Hexadecane as typical aliphatic compound was removed less than Toluene as aromatic compound because of its structural stability in Modified Fenton reaction. What minimum 10% hydrogen peroxide concentration has good remediation efficiency of diesel contaminated groundwater may show the potential use of Modified Fenton reaction after bioslurping treatment.

• Tuberculosis and Respiratory Diseases
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• v.62 no.2
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• pp.113-118
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• 2007

Background: Paraquat is known to induce oxidant injury that results in multiorgan failure and lung fibrosis. Iron has been considered to play a key role in paraquat-induced oxidant lung injury. This study examined the effect of deferoxamine, an iron-chelating agent, in the treatment of paraquat poisoning. Methods: From September, 2001 to April, 2005, 28 patients with paraquat poisoning who were admitted at a medical intensive care unit of a University-affiliated hospital, were enrolled in this study. Sixteen patients were treated according to the paraquat poisoning treatment guidelines and 12 received an intravenous infusion of deferoxamine in addition to the treatment guidelines. Results: There were no differences between the two groups in terms of age, gender, severity of paraquat poisoning, and the time elapsed from ingestion to presentation at hospital. There was no difference in overall mortality between the two groups but the incidence of respiratory failure in the deferoxamine group was higher than in the conventional group(4/7 versus 0/9, p=0.019). Conclusion: Deferoxamine seems to have no clinical benefit compared with the conventional treatment.

• Journal of Yeungnam Medical Science
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• v.12 no.1
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• pp.124-134
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• 1995

It is the most important to select optimal culture conditions to promote safe embryo growth in the technique of human in vitro fertilization and embryo transfer. It has been shown that the addition of biologic fluids, such as blood serum, of various origins, improved fertilization and early cleavage rates in numerous species. The purpose of this study is to attempt to measure developmental potential of mouse eggs fertilized and cleaved in Ham's F10 culture medium containing a chelating agent, EDTA and fetal cord serum. In this study, we selected 40 female mice and 20 male mice, and investigated optimal serum concentrations for mouse embryo growth. Two cell stage mouse embryos were cultured in Ham's F-10 medium, Ham's F-10 medium with various concentrations of EDTA, or Ham's F-10 medium with EDTA and 10% human cord serum. Developmental ratios to morula in Ham's F-10 medium containing various concentrations of EDTA and/or 10% fetal cord serum were significantly higher than in unsupplemented Ham's F-10 medium (p<0.05). Developmental ratios to blastocyst in Ham's F-10 containing 10% fetal cord serum and $50{\mu}M$ or $100{\mu}M$ EDTA were significanltly higher than in unsupplemented Ham's F-10 medium (p<0.05). Developmental ratios to morula in Ham's F-10 containing 10% fetal cord serum and $100{\mu}M$ EDTA were significanltly higher than in Ham's F-10 with 10% fetal cord serum used commonly in many human IVF centers(p<0.05). Developmental ratio to blastocyst in Ham's F-10 containing 10% fetal cord serum and $100{\mu}M$ EDTA was significanlty higher than in Ham's F-10 with $200{\mu}M$ EDTA(P<0.05). In summary, embryo development to morula and blastocyst was significanlty higher in the presence of human cord serum or EDTA than in the unsupplemented medium. The most significanly development to morula and blastocyst was obtained at Ham's F-10 medium with $100{\mu}M$ concentration of EDTA and 10% fetal cord serum. These results suggest that Ham's F-10 medium containing 10% fetal cord serum and optimal concentrations of EDTA significantly promoted early cleavage of mouse zygotes, and these will be useful as basic data for the selection of culture medium in human in vitro fertilization.