• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.401-406
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• 2010

For the lower-temperature preparation of calcium monoaluminate(CA, C:CaO, A:$Al_2O_3$) clinker which is hard to synthesize purely within its melting point, an equimolar hydrate was obtained and then used as a starting raw material of clinker burning. The hydrate was prepared from a mixture of waste oyster shell and industrial aluminium hydroxide by heating to $1200^{\circ}C$, grinding and mixing with water. The hydrate was composed of amorphous aluminium hydroxide and $C_3AH_6$(H:$H_2O$) formed by resolution-precipitation mechanism of the system C-A-H. By heating the hydrate, nearly pure and porous calcium monoaluminate clinker was formed at $1400^{\circ}C$ which is fairly lower temperature than that of its melting point. The formation of calcium monoaluminate was performed mainly by the reaction between amorphous alumina and $C_{12}A_7$ caused by the decomposition of $C_3AH_6$. The immediate and earlier formation of $C_{12}A_7$ seemed to be accelerated by not only high surface area and instability of the thermally decomposed hydrate but also the catalytic effect of water decomposed from the hydrate. The final calcium monoaluminate clinker was very porous because of the influence of highly porous shape of the thermally decomposed hydrate.

• Journal of Microbiology and Biotechnology
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• v.21 no.7
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• pp.719-727
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• 2011

Botulism is a neuroparalytic disease caused by Clostridium botulinum, which produces seven (A-G) antigenically diverse neurotoxins (BoNTs). BoNTs are the most poisonous substances known to humans, with a median lethal dose ($LD_{50}$) of approximately 1 ng/kg of body weight. Owing to their extreme potency and lethality, they have the potential to be used as a bioterrorism agent. The mouse bioassay is the gold standard for the detection of botulinum neurotoxins; however, it requires at least 3-4 days for completion. Attempts have been made to develop an ELISA-based detection system, which is potentially an easier and more rapid method of botulinum neurotoxin detection. The present study was designed using a synthetic gene approach. The synthetic gene encoding the catalytic domain of BoNT serotype B from amino acids 1-450 was constructed with PCR overlapping primers (BoNT/B LC), cloned in a pQE30 UA vector, and expressed in an E. coli M15 host system. Recombinant protein production was optimized at 0.5 mM IPTG final concentration, 4 h post induction, resulting in a maximum yield of recombinant proteins. The immunogenic nature of the recombinant BoNT/B LC protein was evaluated by ELISA. Antibodies were raised in BALB/c mice using various adjuvants. A significant rise in antibody titer (p<0.05) was observed in the Alum group, followed by the Titermax Classic group, Freund's adjuvant, and the Titermax Gold group. These developed high-titer antibodies may prove useful for the detection of botulinum neurotoxins in food and clinical samples.

• Journal of Microbiology and Biotechnology
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• v.23 no.1
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• pp.7-14
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• 2013

In the Bacillus amyloliquefaciens ${\alpha}$-amylase (BAA), the loop (residues 176-185; region I) that is the part of the calcium-binding site (CaI, II) has two more amino acid residues than the ${\alpha}$-amylase from Bacillus licheniformis (BLA). Arg176 in this region makes an ionic interaction with Glu126 from region II (residues 118-130), but this interaction is lost in BLA owing to substitution of R176Q and E126V. The goal of the present work was to quantitatively estimate the effect of ionic interaction on the overall stability of the enzyme. To clarify the functional and structural significance of the corresponding salt bridge, Glu126 was deleted (${\Delta}$E126) and converted to Val (E126V), Asp (E126D), and Lys (E126K) by site-directed mutagenesis. Kinetic constants, thermodynamic parameters, and structural changes were examined for the wild-type and mutated forms using UV-visible, atomic absoption, and fluorescence emission spectroscopy. Wild-type exhibited higher $k_{cat}$ and $K_m$ but lower catalytic efficiency than the mutant enzymes. A decreased thermostability and an increased flexibility were also found in all of the mutant enzymes when compared with the wild-type. Additionally, the calcium content of the wild-type was more than ${\Delta}E126$. Thus, it may be suggested that ionic interaction could decrease the mobility of the discussed region, prevent the diffusion of cations, and improve the thermostability of the whole enzyme. Based on these observations, the contribution of loop destabilization may be compensated by the formation of a salt bridge that has been used as an evolutionary mechanism or structural adaptation by the mesophilic enzyme.

• Polymer(Korea)
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• v.35 no.3
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• pp.244-248
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• 2011

Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was synthesized by oxidative polymerization using various Cu(I)-amine catalyst system. The effects of catalyst/monomer ratio, different amine ligand, and the content of 2,4,6-trimethylphenol (TMP) additive on the polymer yield and molecular weight were investigated by using gel permeation chromatography. The catalytic activity of various Cu-amine systems on the 2,S-dimethylphenol (DMP) polymerization was monitored and compared each other through oxygen-uptake experiment. In addition, the effect of catalyst removal using aqueous EDTA on the thermal stability of the prepared polymer was elucidated by thermogravimetric analysis.

• Fire Science and Engineering
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• v.26 no.4
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• pp.42-47
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• 2012

In the study, fire extinguishing concentration of $K_2CO_3$-Zeolite composite was measured. Zeolite composite is a porous adsorbent which has small particle size, low density and anti-catalytic effect. Scanning Electron Microscopy, X-Ray diffraction and thermal analysis were also conducted to investigate the structural properties of composite. The result showed that despite of weight ratio, the extinguishing concentration of the composite was lower than pure $K_2CO_3$. The extinguishing concentration of $K_2CO_3$-Zeolite composite which has weight ratio of 7 : 3 was 5.72 times lower than that of pure $K_2CO_3$ and 1.1 times lower than that of ABC powder. The SEM and XRD patterns showed that $K_2CO_3$ was adsorbed on the Zeolite properly, and through the thermal analysis, it was founded that the composite is more effective extinguishing agent than pure $K_2CO_3$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4250-4256
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• 2011

Mn catalyst promoted with Cu were prepared and tested for selective catalytic reduction of $NO_x$ with $NH_3$. Performance of each catalyst was investigated for $NO_x$ activity while changing temperature, space velocity, water content and $O_2$ concentration. Hydrogen conversion efficiency of catalyst was also measured in the $H_2$-TPR system. The inhibition effect of water on catalyst was investigated with the on-off control of water supply. High activity of Mn-Cu catalyst was observed for $160{\sim}260^{\circ}C$. It is found that increase of oxygen concentration acts as a promotor to the increase of catalyst activity but water content acts as a inhibitor.

• Advances in nano research
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• v.5 no.2
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• pp.127-140
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• 2017

Metal nanoparticles have been intensively studied within the past decade. Nano-sized materials have been an important subject in basic and applied sciences. Zinc oxide nanoparticles have received considerable attention due to their unique antibacterial, antifungal, and UV filtering properties, high catalytic and photochemical activity. In this study, microbiological aspects of scale formation in PVC pipelines bacteria and fungi were isolated. In the emerging issue of increased multi-resistant properties in water borne pathogens, zinc oxide (ZnO) nanoparticle are being used increasingly as antimicrobial agents. Thus, the minimum bactericidal concentration (MBC) and minimum fungal concentration of ZnO nanoparticles towards pathogens microbe were examined in this study. The results obtained suggested that ZnO nanoparticles exhibit a good anti fungal activity than bactericidal effect towards all pathogens tested in in-vitro disc diffusion method (170 ppm, 100 ppm and 30 ppm). ZnO nanoparticles can be a potential antimicrobial agent due to its low cost of production and high effectiveness in antimicrobial properties, which may find wide applications in various industries to address safety issues. Stable ZnO nanoparticles were prepared and their shape and size distribution characterized by Dynamic light scattering (35.7 nm) and transmission electron microscopic TEM study for morphology identification (20 nm), UV-visible spectroscopy (230 nm), X-ray diffraction (FWHM of more intense peak corresponding to 101 planes located at $36.33^{\circ}$ using Scherrer's formula), FT-IR (Amines, Alcohols, Carbonyl and Nitrate ions), Zeta potential (-28.8). The antimicrobial activity of ZnO nanoparticles was investigated against Bacteria and Fungi present in drinking water PVC pipelines biofilm. In these tests, Muller Hinton agar plates were used and ZnO nanoparticles of various concentrations were supplemented in solid medium.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.802-807
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• 1996

Second-order rate constants have been measured spectrophotometrically for the reactions of aryl benzoates (X-C6H4CO2C6H4-Y) with EtO-, Z-C6H4O- and Z-C6H4C(Me)=NO- in absolute ethanol at 25.0 ℃. All the reactions have been performed in the presence of excess 18-crown-6 ether in order to eliminate the catalytic effect shown by alkali metal ion. A good Hammett correlation has been obtained with a large ρ- value (-1.96) when σ- (Z) constant was used for the reaction of p-nitrophenyl benzoate (PNPB) with Z-C6H4O-. Surprisingly, the one for the reaction of PNPB with Z-C6H4C(Me)=NO- gives a small but definitely positive ρ- value (＋0.09). However, for reactions of C6H5CO2C6H4-Y with EtO-, correlation of log k with σ- (Y) constant gives very poor Hammett correlation. A significantly improved linearity has been obtained when σ0 (Y) constant was used, indicating that the leaving group departure is little advanced at the TS of the RDS. For reactions of X-C6H4CO2C6H4-4-NO2 with EtO-, C6H5O- and C6H5C(Me)=NO-, correlations of log k with σ (X) constants for all the three nucleophile systems give good linearity with large positive ρ values, e.g. 2.95, 2.81 and 3.06 for EtO-, C6H5O- and C6H5C(Me)=NO-, respectively. The large ρ values clearly suggest that the present reaction proceeds via a stepwise mechanism in which the formation of the addition intermediate is the RDS.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.1
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• pp.23-28
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• 2019

The Titanium oxide ($TiO_2$) is an attractive ceramic material which shows non-toxic, high refractive index, catalytic activity and biocompatibility, and can be fabricated at a low cost due to its high chemical stability and large anisotropy. $TiO_2$ nanoparticles have been prepared by sol-gel method. The pH of solution can affect the $TiO_2$ crystallinity during the formation of nanoparticles. The prepared nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy in order to investigate their structural and photoluminescence properties. Through these analysis, the size of $TiO_2$ nanoparticles were found to be smaller than 5 nm. As the crystallinity of the nanoparticles increased, the emission of PL in the 550 nm region increased. Therefore, luminescence characteristics can be improved by controlling the crystallinity of the $TiO_2$ nanoparticles.

• Journal of the Korean Wood Science and Technology
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• v.47 no.3
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• pp.344-359
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• 2019

Effects of various types of zeolite on the catalytic performance of hydrodeoxygenation (HDO) of bio-oil obtained from waste larch wood pyrolysis were investigated herein. Bifunctional catalysts were prepared via wet impregnation. The catalysts were characterized through XRD, BET, and SEM. Experimental results demonstrated that HDO enhanced the fuel properties of waste wood bio-oil, such as higher heating values (HHV) (20.4-28.3 MJ/kg) than bio-oil (13.7 MJ/kg). Water content (from 19.3 in bio-oil to 3.1-16.6 wt% in heavy oils), the total acid number (from 150 in bio-oil to 28-77 mg KOH/g oil in heavy oils), and viscosity (from 103 in bio-oil to $40-69mm^2/s$ in heavy oils) also improved post HDO. In our experiments, depending on the zeolite support, NiFe/HBeta exhibited a high Si/Al ratio of 38 with a high specific surface area ($545.1m^2/g$), and, based on the yield of heavy oil (18.3-18.9 wt%) and HHV (22.4-25.2 MJ/kg), its performance was not significantly affected by temperature and solvent concentration variations. In contrast, NiFe/zeolite Y, which had a low Si/Al ratio of 5.2, exhibited the highest improved quality for heavy oil at high temperature, with an HHV of 28.3 MJ/kg at $350^{\circ}C$ with 25 wt% of solvent.