• Composites Research
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• v.33 no.1
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• pp.1-6
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• 2020

Dispersion and electrical resistance (ER) properties of polyurethane (PU) type topcoat were evaluated using carbon nanotube (CNT) with different CNT weight fraction. CNT was dispersed in PU type topcoat using ultra sonication dispersion method. CNT/PU topcoat was coated on carbon fiber reinforced epoxy composite (CFRC) surface using gravity feed spraying method. Static contact angles of CFRC and CNT/PU topcoat were performed using 4 types of solvents to calculate the work of adhesion between CNT/PU topcoat and CFRC surface. Surface resistance of CNT added PU topcoat was measured to determine CNT dispersion. Adhesion property between CNT/PU topcoat and CFRC was determined via cross hatch cutting test based on ASTM D3359. The optimized condition of CNT weight fraction was found.

• Microbiology and Biotechnology Letters
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• v.18 no.3
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• pp.268-272
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• 1990

The structural gene (zadhII) encoding an alcohol dehydrogenase II from Zyrnornonas mobilis was cloned into Escherichia coli in our laboratory (Yoon et al., 1989. Kor. J. Microbiol. Biotechnol.). From E. coli (pADS93) carrying the zadhII gene, the Z mobilis alcochol dehydrogenase II (ZADH-II) was purified by sonication, $(NH_4)_2SO_4$, fractionation, and chromatography. The ZADH-I1 enzyme produced by Z. mobilis cell was also purified to compare to the enzyme produced by E. coli (pADS93). The purified enzyme from cell extract of E. coli (pADS93) was identified to be a tetramer being composed of four identical subunits having molecular weight of 40, 000 dalton like that of Z. mobilis. The pH optimum for the reaction oxidizing ethanol to acetaldehyde was 10.0 while the optimum for the reverse reaction was 7.5-8.5. The apparent $K_m$ values for ethanol and NAD + were $1.2 \times 10^{-1}M$and $5.1\times 10^{-5}M$, respectively. In addition, it was found that the $K_m$ value for acetaldehyde was very lower than that for ethanol.

• Journal of Veterinary Clinics
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• v.7 no.1
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• pp.391-402
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• 1990

To examine the effects of vaccination against Babesia gibsoni infection in dogs, 15 normal mixed-breed dogs(5 month to 1 year old) divided into 3 groups with 5 dogs in a group. One of them was selected as control group(group A) and others were selected as experimental groups(group B and C). The group B was vaccinated with sonicated antigens and the group C was vaccinated with 0.2% of formalin treated antigens. The results obtained in the examination were summarized as follows : 1. In the western blot, the lane A revealed specific two bands on the regions of 54kd and 100kd, respectively. 2. After the first vaccination, the antibody titers of group B and C were higher 5 times(1 ： 200) than those of control group(1：40). After the second vaccination, the antibody titers of group B and C have not changed. When challenged with the protozoa(Babesia gibsoni), the antibody titers(1 : 5,000) were elevated in all groups. But these were not exceeded over 1 ： 5,000 for 4 weeks. 3. After challenge, the peak time of increased numbers of the protozoa was the 15th day (12-18 days) in all groups. During these days, the rate of parasitized erythrocytes in control group was 55.0${\pm}$5.4%. But those of group B and group C were 26.0${\pm}$6.4%, and 15.6${\pm}$7.8％, respectively. 4. After challenge, all of the values of PCV, Hb, RBC were shown to decrease in all of the control and experimental groups. 5. The total leukocytes counts are shown a tendency of reduction in all groups after challenge. 6. In all groups, there were increase in lymphocytes and monocytes after challenge.

• Analytical Science and Technology
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• v.13 no.5
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• pp.616-623
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• 2000

The most common phthalate acid esters (8 compounds) and adipate were determined from water and sediment simultaneously. After liquid-liquid extraction with n-hexane for water and sonication extraction with dichloromethane for sediment, these were determined by the GC/MS with SIM mode. There were good linearities (above $R^2=0.993$) on the range of the 0.1-20 ng/ml (water) and 10-500 ng/g (sediment), and the detection limits of method were below 0.1 ng/ml and 10 ng/g for water samples and sediment samples, respectively. The method shows a good precision and accuracy for measurement of phthalates and adipate.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.67-67
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• 2018

The 5xxx series aluminum alloys are recently used in not only marine system but also automotive area because of a low density material, good mechanical properties and better resistance to corrosion. However, Aluminum alloys are less resistant than the purest aluminum such as 1xxx aluminum alloy. Electrochemical anodization technique has attracted in the area of surface treatment because of a simple procedure, a low-cost efficiency than other techniques such as lithography and a large volume of productivity, and so on. Here, The relationship between the corrosion behavior and the thickness of aluminum anodic oxide have been studied. Prior to anodization, The 5052 aluminum sheets ($30{\times}20{\times}1mm$) were degreased by ultra-sonication in acetone and ethanol for 10 minutes and eletropolished in a mixture of perchloric acid and ethanol (1:4, volume ratio) under an applied potential of 20V for 60 seconds to obtain a regular surface. During anodization process, Aluminum alloy was used as a working electrode and a platinum was used as a counter electrode. The two electrodes were separated at a distance of 5cm. The applied voltage of anodization is conducted at 40V in a 0.3M oxalic acid solution at $0^{\circ}C$ with appropriate magnetic stirring. The surface morphology and the thickness of AAO films was observed with a Scanning Electron Microscopy (SEM). The corrosion behavior of all samples was evaluated by an open-circuit potential and potentio-dynamic polarization test in 3.5wt% NaCl solution. Thus, The corrosion resistance of 5052 aluminum alloy is improved by the formation of an anodized oxide film as function of increase anodization time which artificially develops on the metal surface. The detailed electrochemical behavior of aluminum 5052 alloy will be discussed in view of the surface structures modified by anodization conditions such as applied voltages, concentration of electrolyte, and temperature of electrolyte.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.35-38
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• 2014

Herein, we report on the preparation of red fluorescent Si nanoparticles stabilized with styrene. Nano-sized Si particles emit fluorescence under UV excitation, which could be used to open up new applications in the fields of optics and semi-conductor research. Unfortunately, conventional methods for the preparation of red fluorescent Si nanoparticles suffer from the lack of a fully-established standard synthesis protocol. A common initial approach during the preparation of semi-conductors is the etching of crystalline Si wafers in a HF/ethanol/$H_2O$ bath, which provides a uniformly-etched surface of nanopores amenable for further nano-sized modifications via tuning of various parameters. Subsequent sonication of the etched surface crumbles the pores on the wafer, resulting in the dispersion of particles into the solution. In this study, we use styrene to occupy these platforms to stabilize the surface. We determine that the liberated silicon particles in ethanol solution interact with styrene, resulting in the substitution of Si-H bonds with those of Si-C as determined via UV photo-catalysis. The synthesized styrene-coated Si nanoparticles exhibit a stable, bright, red fluorescence under excitation with a 365 nm UV light, and yield approximately 100 mg per wafer with a synthesis time of 2 h. We believe this protocol could be further expanded as a cost-effective and high-throughput standard method in the preparation of red fluorescent Si nanoparticles.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.693-701
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• 1997

In 1992, Prevotella intermedia was shown to be comprised of another spoecies now known as Prevotella nigrescens. Strain ATCC 33563 is now designated the type strain of P. nigrescens while strain ATCC 25611 is remains the type strain of P. intermedia. The purpose of this study was to find the differences in protein profiles of P. intermedia and P. nigrescens, using sodium dodecyl sulfate polyacrylamide gel electrophoresis, which can be used for differentiation of those two species. A partial amino acid sequence of the 18.6 kDa protein band, which was specific in P. nigrescens, was also determined. The cellular proteins were extracted from the cell pellets of pure cultures of P. intermedia. and P. nigrescens by either sonication or being shaken continuously for 20 min at $21^{\circ}C$ with 1 % SDS or being boiled for 3 min with 1 % SDS. SDS-PAGE was performed according to the method of laemmli using either 12% (w/v) gels or 18% (w/v) gels. Results were as follows ; 1. The similar electrophoretic protein profiles were shown by 3 cellular protein extraction methods for each strain. (Fig. 1 and 2) 2. the 18.6 kDa band which was specific only in P. nigrescens could be used for the differentiation of P. intermedia. and P. nigrescens. (Fig. 1 and 2, Table 1) 3. A total of 4 different tryptic fragments from the 18.6 kDa protein were sequenced. the resulting amino acid sequences were fragment 1.GNPVNIGGEW, 2.FNVVR, 3.NYLT-VAPY, and 4.GGDNVTTYQVLPEIGYN. By comparison to the sequences of known proteins in the Swiss-Prot database and PIR database. 90 % matching between fragment 1 and serine hydroxymethyl transferase(P24060) in the Swiss-Prot, and 90% matching between fragment 1 and glycine hydroxymethyl transferase(S15203) in the PIR were shown, but the identity and function of the 18.6 kDa protein remains unknown.

• Korean Journal of Microbiology
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• v.27 no.1
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• pp.48-55
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• 1989

The purpose of the present investigation was to improve several procedures being used in the adherence assay of Streptococcus sanguis cells to hydroxyapatite (HA) beads and to study the effect of the beads on the counting of radioactivity. The standard adhere assay involved the adherence of radiolabeled bacteria to 40mg of HA beads. The beads were mixed with ['H]thymidine-labeled bacterial cells and incubated for 60 minutes at room temperature. Unadsorbed cells were removed, the beads with adsorbed cells were dried, and the radioactivity was monitered in a scintillation spectrometer. The 30 seconds sonication of cells in a form of long chains appeared to be adequate for obtaining mostly singlet or doublet cells. Unlike the counting of S. sanguis cell suspension, bacterial cells adhered to HA or saliva-coated HA(SHA) required smaller volume (2.5ml) of scintillaton fluid for better counting. Eighteen percent quenching of counts could be attributed to the beads. Among 3 procedures commonly used to equilibrate the beads for adherence assay, no differences were found in their effectiveness. The HA beads on which the bacteria remained attached in scintillant during the counting were found to be the source of sample self-absorption representing 34.5% of the total radioactivity counts resulting from the beads dissolved in HCl solution.

• Preventive Nutrition and Food Science
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• v.8 no.4
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• pp.301-305
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• 2003

This study was conducted to develop an HPLC method for determining vitamin B$_{12}$ in fortified foods which has typically been determined by microbiological assays according to AOAC and Korean Food Code approved methods. Vitamin B$_{12}$ (cyanocobalamin) was determined by reversed-phase HPLC with a triple column and UV/VIS dectector (550 nm) using the column switching technique after extraction with 5 mM potassium phosphate solution by sonication without a clean-up procedure. The recovery of spiked samples and limit of detection (LOD) by HPLC were 78.6 ∼107.5 % and 2 ppb ($\mu\textrm{g}$/kg), respectively. The LOD of the microbiological assay (MBA) was much lower than that of HPLC. The concentrations of vitamin B$_{12}$ analyzed in all tested samples (n=12) confirmed compliance with declared label claims. The range of recovery ratio by the HPLC method when compared to the microbiological assay was 76.2 ∼140.0 %. There was not significant difference between the HPLC and MBA methods (p < 0.01) with r=0.9791 and linear regression y=0.9923x-0.04. The HPLC method for determining vitamin B$_{12}$ using the column-switching technique appears to be suitable for determining vitamin B$_{12}$ concentrations above 1 $\mu\textrm{g}$/100 g in fortified foods.ied foods.

• Journal of Ginseng Research
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• v.34 no.3
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• pp.198-204
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• 2010

Korean ginseng (Panax ginseng C.A. Meyer) preserved in syrup, known as ginseng Jung Kwa (GJK), is a popular traditional snack in Korea. We investigated the effects of heat processing time on total phenolic content and antioxidant capacity of GJK. Water extract was prepared from GJK with different heat processing times, 3 hours (GJK-3), 6 hours (GJK-6), or 12 hours (GJK-12), with sonication for 2 hours. The GJK extract contained total phenolic content in the following order: GJK-12 (2.28%)>GJK-6 (1.57%)>GJK-3 (1.29%). Both the peroxy and hydroxyl radical-scavenging activity and cellular antioxidant capacity of GJK extract was significantly enhanced with increasing heat processing time. The hydroxyl radical-scavenging activity of GJK-12 extract was greater than that of the GJK-3 and GJK-6 extracts, consistent with metal chelating capacity and reducing capacity. In a cellular model, the GJK extract effectively reduced 2,2'-azobis(2-amidinopropane) dihydrochloride, $Cu^{2+}$-, and $H_2O_2$-induced oxidative stress, with GJK-12 and GJK-6 extracts demonstrating greater cellular antioxidant capacity than the GJK-3 extract. These results suggest that heat processing time can contribute to the antioxidant capacity of GJK and that GJK extract may have the potential to be used as an effective dietary antioxidant to prevent oxidative stress-related diseases.