• Journal of Korean Society of Water and Wastewater
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• v.31 no.6
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• pp.577-586
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• 2017

One of the major sources causing eutrophication and algal blooms of lakes or streams is phosphorus which comes from point and nonpoint pollution sources. HAP (hydroxyapatite) crystallization using granular alkaline materials can achieve the decrease of phosphorus load from wastewater treatment plants and nonpoint pollution control facilities. In order to induce HAP crystal formation, continuous supply of calcium and hydroxyl ions is required. In this research, considering HAP crystallization, several types of lime-based granular alkaline materials were prepared, and the elution characteristics of calcium and hydroxyl ions of each were analyzed. Also, column tests were performed to verify phosphorus removal efficiencies of granular alkaline materials. Material_1 (gypsum+cement mixed material) achieved the highest pH values in the column tests consistently, also, Material_2 (gypsum+slag mixed material) and Material_3 (calcined limestone material) achieved over pH 9.0 for 240 hours (10 days) and proved the efficiencies of long-term ion supplier for HAP crystallization. In the column tests using Material_3, considerable pH increase and phosphorus removal were carried out according to each linear velocity and filtration depth. T-P removal efficiencies were 87.0, 84.0, 68.0% and those of PO4-P 100.0, 97.0, 80.0% for linear velocity of 1.0, 2.5, 5.0 m/hr respectively. Based on the column test results, the applicability of phosphorus removal processes for small-scale wastewater treatment plants and nonpoint pollution control facilities was found out.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.35 no.1
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• pp.13-17
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• 2013

Purpose: This study evaluated the capability of bone formation of silk fibroin particles coated with hydroxyapatites (HA/SF), as bone graft material when put into the calvarial defect of rats. Methods: Twenty Sprague Dawley rats were used for this study and round shaped defects were formed in the center of parietal bones (diameter: 8.0 mm). The defect was filled with (1) HA/SF (experimental group), or (2) left as a vacant space (control group). The animals were sacrificed at 4 or 8 weeks, postoperatively. The specimens were decalcified and stained with Masson's trichrome for histomorphometric analysis. Results: The average of new bone formation was $33.18{\pm}3.10%$ in the experimental group and $20.49{\pm}5.79%$ in the control group at 4 weeks postoperatively. That was $42.52{\pm}7.74%$ in the experimental group and $25.50{\pm}7.31%$ in the control group at 8 weeks postoperatively. The difference between the groups was significantly higher at both 4 weeks and 8 weeks postoperatively (P<0.05). Conclusion: The rat calvarial defect was successfully repaired by HA/SF graft. The HA/SF graft showed more new bone formation compared with the unfilled control.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.52-61
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• 2009

In this study, TAPEH (t-amyl peroxy 2-ethyl hexanoate) was selected for the reaction initiator which is a core factor for developing acrylic polyol binder. Tone M100 (caprolactone acrylate), 4HBA (4-hydroxy butyl acrylate), and 2HEMA (2-hydroxy ethyl methacrylate) were used for hydroxy-monomers. To check the applicability of raw materials mentioned above into the binders of 2 components acrylic polyurethane paint and reduce the VOC, the reactivity and film performance by different kinds of aliphatic polyisocyanate hardeners which are already generalized were reviewed. As the Tin-based catalyst has been regulated, the comparison test of reactivity and performance between the conventional catalyst and non-toxic metal catalyst recommended as the alternative was conducted as well. As a result, we were able to obtain the basic data which are necessary for applying 2 components high solid polyurethane paint and also reached a conclusion that it can be applied for developing new paints in terms of high performance, workability and environmental care.

• Korean Journal of Materials Research
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• v.8 no.9
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• pp.865-870
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• 1998

The surfaces of titanium specimens were modified by immersion in calcium phosphate buffered solutions (pH 5.8, 7.0, 8.0) for 10 days and simulated body fluid(SBF) for 30 days by turns. The modified surfaces were characterized using scanning electron microscopy(SEM), X-ray diffractometery(XRD) and Fourier transform infrared spectrophotometer(FT-IR), and compared with specimen immersed in only SBF. The results indicated that the immersion in calcium phosphate buffered solutions accelerated the formation of the surface films. The formed layer showed granular shaped microstructure, and recognized as calcium phosphate such as a hydroxyapatite(HA) or a $\beta$-tri-calcium phosphate($\beta$-TCP). The thickness of the layer increased of the buffered solutions in order of pH 8.0, 7.0 and 5.8 and the density increased in order of pH 7.0, 8.0 and 5.8.

• KSBB Journal
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• v.29 no.4
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• pp.244-249
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• 2014

Biosynthesis pathway of medium-chain-length (MCL) polyhydroxyalkanoates (PHA) from fatty acid ${\beta}$-oxidation pathway was constructed in recombinant Escherichia coli by introducing the Pseudomonas sp. 61-3 PHA synthase gene (phaC2) and the maoC genes from Pseudomonas putida, Sinorhizobium meliloti, and Ralstonia eutropha. The metabolic link between fatty acid ${\beta}$-oxidation pathway and PHA biosynthesis pathway was constructed by MaoC, which is homologous to P. aeruginosa (R)-specific enoyl-CoA hydratase (PhaJ1). When the E. coli W3110 strains expressing the phaC2 gene and one of the maoC genes from P. putida, Sinorhizobium meliloti, and Ralstonia eutropha were cultured in LB medium containing 2 g/L of sodium decanoate as a carbon source, MCL-PHA that mainly consists of 3-hydroxyhexanoate (3HHx), 3-hydroxyoctanoate (3HO) and 3-hydroxydecanoate (3HD), was produced. The monomer composition of PHA and PHA contents varied depending on MaoC employed for the production of PHA. The highest PHA content of 18.7 wt% was achieved in recombinant E. coli W3110 expressing the phaC2 gene and the P. putida maoC gene. These results suggest that MCL-PHA biosynthesis pathway can be constructed in recombinant E. coli strains from the b-oxidation pathway by employing MaoC able to supply (R)-3-hydroxyacyl-CoA, the substrate of PHA synthase.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.685-691
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• 2009

Dispersions of fumed silica are made in 6 kinds of mono-solvents and mixed solvents which have hydroxyl group, non hydroxyl group, different polarity, and different molecular size. The viscosity and rheology behaviors of the each dispersion are investigated according to the viewpoint of solvent characteristic. The silica dispersion in polar solvent with hydroxyl group is stable and low viscous sol. The silica dispersion in non-polar solvent with non-hydroxyl group is high viscous gel. When the solvent with hydroxyl group is added to the silica dispersions with non-polar solvents, they show the reduction of viscosity with solvent content. They have minimum critical content which shows no viscosity change. The minimum critical solvent content is decreased according to the polarity of solvents with no hydroxyl group. The solvation layer which is formed on the silica surface through hydrogen bonding between hydroxyl-containing solvent and the silanol group of silica surface is the reason of stable and low viscous sol. In case of non-polar solvent, silanol on adjacent silica particles interacted directly by hydrogen bonding show high viscous and flocculated gel.

• Korean Journal of Materials Research
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• v.16 no.4
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• pp.218-224
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• 2006

RF sputtering process was applied to produce thin hydroxyapatite(HAp) films on Ti-6Al-4V alloy substrates. The effects of different heat treatment conditions on the hardness between HAp thin films and Ti-6Al-4V alloy substrates were studied. Before deposition, the Ti-6Al-4V alloy substrates were heat treated for 1h at $850^{\circ}C\;under\;3.0{\times}10^{-3}torr$, and after deposition, the HAp thin films were heat treated for 1h at $400^{\circ}C,\;600^{\circ}C\;and\;800^{\circ}C$ under the atmosphere, and analyzed FESEM-EDX, FTIR, XRD, nano-indentor, micro-vickers hardness, respectively. Experimental results represented that the surface defects of thin films decreased by relaxation of internal stress and control of substrate structure followed by heat treatment of substrates before the deposition, and the HAp thin films on the heat-treated substrates had higher hardness than none heattreated substrates before the deposition, and the hardness properties of HAp thin films and Ti-6Al-4V alloy substrates appeared independent behavior, and the hardness of HAp thin films decreased by formation of $VTiO_3(OH),\;{\theta}-Al_{0.32}V_2O_5,\;Al_{0.33}V_2O_5$.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.625-629
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• 2007

Recently, there is a growing interest about unsaturated lecithin having excellent characteristics of skin affinity and absorbency. Accordingly, this study intended to develop a natural sulfuration material in order to enhance the stability of oxidation of unsaturated lecithin and substitute existing sulfuration materials which indicate variability and toxicity. As sulfuration components, plenol acid family, 3,5-dihydroxybenzoic acid, and flavanone were analyzed. Total polyphenol content was higher in the root extracts (133.85 mg/g) than in the fruit extracts (53.5 mg/g). Above 100 ppm polyphenol content, the free radical removal efficiency and lipid oxidation prevention of the root extracts were 20.1 and 19.2% superior compared with BHT respectively. Also, the extracts indicated high survival rate of more than 95% below 1250 ppm, showing the stability. For the stability of liposome made from an unsaturated lecithin, the root extracts were superior to the fruit extracts. Especially, 15.1 and 13.9% of sulfuration effect and zeta potential were improved with 9.3% reduced particle size compared with BHT as the control group, respectively.

• Journal of the Korean institute of surface engineering
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• v.51 no.3
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• pp.164-171
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• 2018

In this study, we have fabricated pure titanium (Ti)/hydroxyapatite (HA) double layer coating on medical grade PEEK from magnetron sputtering system, an investigation was performed whether the surface can be had more improve bio-active for orthopedi/dental applications than that of non-coated one. Pure Ti and HA coating layer were obtained by a radio-frequency and direct current power magnetron sputtering system. The microstructures surface, mechanical properties and wettability of the pure Ti/HA double layer deposited on the PEEK were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), nano-indentation, and contact angle test. According to the EDS and XRD results, the composition and crystal structure of pure Ti and HA coated surface were verified. The elastic modulus and hardness value were increased by pure Ti and HA coating, and the pure Ti/HA double layer coating surface has the highest value. The contact angle showed higher value for pure Ti/HA double layered coating specimens than that of non-coated (PEEK) surface.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.490-494
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• 2016

This paper describes the very efficient and highly enantioselective ring opening of terminal epoxides with alkyl and arene sulfonic acid. The dinuclear chiral (salen) Co complexes bearing Lewis acids of Al, Ga and In catalyze the reaction enantioselectively in the presence of tetrabutylammonium chloride using tert-butyl methyl ether as a solvent. The variation of the anion of the tetra butyl ammonium salt has significant impact on the reactivity and selectivity of the asymmetric ring opening of phenyl glycidyl ether with p-toluenesulfonic acid. The order of reactivity and selectivity was found to be $Cl^-$ > $l^-$ > $Br^-$ > $OH^-$. Strong synergistic effects of the different Lewis acid centers of Co-Al, Co-Ga and Co-In complexes were observed in the catalytic process. The dinuclear chiral salen catalyst containing $AlCl_3$ was found to be most active and highly enantioselective (91% ee).