• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.57-63
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• 2015

In order to prepare a low-cost conductive filler material possessing improved anti-oxidation property, Ag-coated Cu flakes were fabricated and the effects of an applying method of ammonium-based pretreatment solution on the Cu flakes were analyzed. The pretreatment solution was used to remove the surface oxide layer on Cu flake. During a single-stage pretreatment process, hole-shaped defects were formed on the flake surface during the pretreatment after 2 min, and the number and size increased in proportion to the pretreatment time. In the case that Ag plating solution was injected in the pretreatment solution after the pretreatment for 2 min, the defects were also formed during Ag plating. In contrast, the defects tremendous decreased in the case that the pretreatment solution was removed after the first pretreatment for 2 min and the Ag plating proceeded after the second pretratment using a low concentration pretreatment solution. As the final result, the 15 wt% Ag-coated Cu flake sample which was fabricated using the single-stage pretreatment oxidized at $166^{\circ}C$, but the sample fabricated by the double-stage pretreatment oxidized at $224^{\circ}C$, indicating definitely improved anti-oxidation property.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.5
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• pp.420-431
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• 2009

Characteristics and advantages of the thermal desorption-comprehensive two dimensional gas chromatography-time of flight mass spectrometry (TD-GCxGC-TOFMS) were discussed and the organic compound's analysis result was shown for the ambient $PM_{2.5}$ sample collected in Seoul, Korea. Over 10,000 individual organic compounds were separated from about $70{\mu}g$ of aerosols in a single procedure with no sample pre-treatment. Among them, around 300 compounds were identified and classified based on the mass fragmentation patterns and GCxGC retention times. Several aliphatic compounds groups such as alkanes, alkenes, cycloalkanes, alkanoic acids, and alkan-2-ones were identified as well as 72 PAH compounds including alkyl substituted compounds and 8 hopanes. In Seoul aerosol, numerous oxidized aromatic compounds including major components of secondary organic aerosols were observed. The inventory of organic compounds in $PM_{2.5}$ of Seoul, Korea suggested that organic aerosol were constituted by the compounds of primary source emission as well as the formation of secondary organic aerosols.

• 보존과학연구
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• s.30
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• pp.203-215
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• 2009

In the conservation treatment of wood remains, polymers, treatment methods, and treatment period can be varied, depending on the percentage of moisture content and species of trees. Thus, in order to apply the appropriate conservation treatment, a lot of information from the wood remains are required. Despite the information from the wood remains, testing a part of the wood remains is necessary to get information about the polymers. When the wooden coffin made of camphor trees was excavated, it was cracked in the section of radiation, and there were hairlines cracks. Therefore, without any conservation treatment, it is impossible to restore it. This experiment is for the conservation treatment of the wooden coffin excavated from Songhyun-dong tombs No 7, Changnyeong. For this experiment, I used camphor trees from Jejudo. The purpose of this experiment is to asses the possibility of preliminary testing materials before the conservation treatment on the wooden coffin. After the camphor trees from Jejudo are artificially aged by Fenton's reagent, they are As a result of oxidation by Fenton, the degree of oxidation is high in proportion to the amount of peroxide and iron sulfate. Among several samples, the sample 'na' made the most similar result to the wooden coffin from Songhyun-dong. If I use this condition to make the sample in polymer tests, it is very helpful to find the most suitable polymer for the conservation treatment of wooden coffin. After the same species of trees are oxidized by Fenton and they become the similar condition, we are able to find suitable methods of conservation treatment. The suitable methods reduce the demage of the remains and make us to get more information. Thus, we are able to carry out conservation treatment more exactly.

• Macromolecular Research
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• v.8 no.6
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• pp.276-284
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• 2000

A wettability chemogradient on poly(L-lactide-co-glycolide) (PLGA) films was prepared by treating the films in air with corona from a knife-type electrode whose power increases gradually along the sample length. The PLGA surfaces oxidized gradually with the increasing corona power, and the wettability chemogradient was created on the surfaces as evidenced by the measurement of water contact angles and electron spectroscopy for chemical analysis. The wettability chemogradient PLGA surfaces were used to investigate the interaction of four different types of cells such as hepatoma (Hep G2), osteoblast (MG 63), bovine aortic endothelial (CPAE), and fibroblast (NIH/3T3) cells in terms of the surface hydrophilicity/hydrophobicity of PLGA. The cells adhered and grown on the chemogradient surface along the sample length were counted and observed by scanning electron microscopy. It was observed that the cells were adhered, spread, and grown more onto the positions with moderate hydrophilicity of the wettability chemogradient PLGA surface than the more hydrophobic or hydrophillic positions, regardless of the cell types used. The maximum adhesion and growth of the cells appeared at around water contact angles of 53～55°. This result seems closely related with the serum protein adsorption on the surface; the serum proteins were also adsorbed more onto the positions with moderate hydrophilicity of the wettability chemogradient surface. It seems that the wettability plays important roles for cell adhesion, spreading and growth on the PLGA surface. The surface modification technique used in this study may be applicable tothe area of tissue engineering for the improvement of tissue compatibility of films- or scaffold-type substrates.

• The Journal of Advanced Prosthodontics
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• v.1 no.2
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• pp.91-96
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• 2009

STATEMENT OF PROBLEM. The aim of this study was to study the effects of various surface treatments to a titanium surface on the expression of Runx2 in vitro. MATERIAL AND METHODS. Human Osteosarcoma TE-85 cells were cultured on machined, sandblasted, or anodic oxidized cpTi discs. At various times of incubation, the cells were collected and then processed for the analysis of mRNA expression of Runx2 using reverse transcription-PCR. RESULTS. The expression pattern of Runx2 mRNA was differed according to the types of surface treatment. When the cells were cultured on the untreated control culture plates, the gene expression of Runx2 was not increased during the experiments. In the case of that the cells were cultured on the machined cpTI discs, the expression level was intermediate at the first day, but increased constitutively to day 5. In cells on sandblasted cpTi discs, the expression level was highest in the first day sample and the level was maintained to 5 days. In cells on anodized cpTi discs, the expression level increased rapidly to 3 days, but decreased slightly in the 5-th day sample. CONCLUSION. Different surface treatments may contribute to the regulation of osteoblast function by influencing the level of gene expression of key osteogenic factors.

• Journal of the Korean Chemical Society
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• v.5 no.1
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• pp.42-47
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• 1961

A titration of a small amount of iron with standard potassium ferrocyanide using potassium thiocyanate as indicator has been studied. A sample solution containing $0.1{\sim}1.0$ mg. $Fe^{3+}$ in 60 ml. is pipeted into 100 ml. Erlenmyer flask and the pH of the solution is adjusted to $1.5{\sim}3.0$ with 0.1 N or 1 N $HNO_3$ and $NH_4OH.$ To this solution one ml. of 1 M KCNS solution as indicator is added. The solution colored by iron thiocyanate complex is titrated with 1/200 M or 1/400 M standard solution of potassium ferrocyanide from a 5 ml. micro-buret. Near the end point, when the color of sample changes from deep red to green, about 20 ml. of ether is added and shake the flask vigorously. The red color is extracted to the ether layer. To settle the ether layer a few drops of ethanol is added and then standard solution is added dropwise and shake vigorously. The end point is reached when the color of the ether layer disappears owing to the quantitative formation of $Fe_4[Fe(CN)_6]_3.$ In this titration, 0.lmg. of $Fe^{3+}$ can be determined within 1.0% of titration error, provided the following optimum conditions, i.e., pH $1.5{\sim}3.0$, final concentration of KCNS indicator; $0.01{\sim}0.02M$, at room temperature. The titration found to be interfered by the presence of slightly soluble salts, stable complex forming ions and the ions which would be reduced by ferrocyanide or oxidized by ferric ion.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.25-31
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• 1994

The magnetic properties of aluminum anodized film in which Co-Fe alloy electrodeposited are investigated with regard to the alloy composition of magnetic films. The electrodeposited Co-Fe particles are confirmed to be single phase Co-Fe alloys by X-ray diffractions. At 34 at% Co, the sample with small pore diameter(particle diameter $150\;{\AA}$) has a large magnetic energy product($B_{max}$) of about 1.44 MGOe due to the large saturation magnetization, the high coercive force and good squareness of the M-H curve. However, for the samples with particle diameter larger than $450\;{\AA}$, the bottom of each particle forms abnormal particle claaed branch-shaped unlike the sample of the particle diameter $150\;{\AA}$. In this case, the magnetic anisotropy energy was about zero at the compositions of 45 and 75 at% Co. Moreover, at the compositions from 50 to 70 at% Co, the anisotropy became negative value. This means that an easy axis of magnetization of the film is in plane in plane in spite of the perpendicular shape anisotropy of the particle. It was found that the bottom extremity of the particle contains FeC from the X-ray diffraction. Thus the effect of the bottom extremity, that is, an unusal magnetic property was removed by electrodepositing Cu at the bottom extremity of the particle. Itis clear that the magnetic properties of the ilms are influenced by he branch-shaped bottom extremity filled with FeC.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.330-335
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• 2009

We investigated the effects of the re-oxidation temperature and time on the positive temperature coefficient (PTC) of resistivity characteristics of Sm-doped $BaTiO_3$ sintered at $1200{\sim}1260^{\circ}C$ for 2 h in a reducing atmosphere (3% $H_2/N_2$), followed by re-oxidization processes in air, in which re-oxidization temperature and time were $600{\sim}1000^{\circ}C$ and $1{\sim}10$h, respectively. The result reveals that Smdoped (Ba,Ca)$TiO_3$ ceramics fired in a reducing atmosphere exhibit low PTC characteristics, whereas the sample re-oxidized at $800^{\circ}C$ for 1 h in air exhibit pronounced PTC characteristics. The room-temperature resistivity and jumping characteristics of resistivity (${\rho}_{max}/{\rho}25^{\circ}C$) decrease with Sm contents. The PTC characteristics with reoxidization time at $800^{\circ}C$ have improved about $2{\sim}3$ orders of magnitude whereas differed according to the sintering temperature. The 0.7 at% Sm-doped (Ba,Ca)$TiO_3$ samples reveal the best PTC characteristics in the present range of formula and processes.

• Journal of Powder Materials
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• v.22 no.1
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• pp.21-26
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• 2015

In this study, the control of microstructure for increasing surface roughness of Al with an electro-chemical reaction and a post treatment is systematically investigated. The Al specimen is electro-chemically treated in an electrolyte. In condition of the post treatment at $100^{\circ}C$ for 10 min, a change of the surface microstructure occur at 50V (5 min), and a oxidized layer is at 400V, to which lead a decreasing surface roughness. The minimum temperature of the post treatment for a change of microstructure is $80^{\circ}C$. Moreover, in the condition of 300V (5 min), the electro-chemical reaction is followed by the post treatment at $100^{\circ}C$, the critical enduring time for the change of microstructure is 3 min. The longer post treatment time leads to the rougher surface. The treated Al specimen demonstrate better heat release ability owing to the higher surface roughness than the non-treated Al.

• Toxicological Research
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• v.11 no.1
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• pp.23-29
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• 1995

Microsomes from human liver sample HL 110 oxidized aflatoxin $B_1$ $(AFB_1)$ to $AFB_1$ exo-8, 9-epoxide which was detected as a glutathione (GSH) conjugate with excess GSH S-transferase and to aflatoxin $Q_1$ ($AFB_1$; 3$\alpha$-hydroxyafiatoxin $B_1$), and testosterone to 6$\beta$-hydroxytestosterone. Anti-P450 3A4 nearly completely inhibited all of the reactions. Some fiavonoids inhibited all of the reactions. While other fiayonolds stimulated 8, 9-epoxidation and inhibited 3$\alpha$-hydroxylation. Gestodene inhibited all of the reactions when gestodene was metabolized by human liver microsomal P450 3A4 prior to adding substrate. But, ges-todene was added in the enzyme mixtures in the presence of $AFB_1$, it could not inhibit 8, 9-epoxidation of $AFB_1$. Nifedipine and troleandomycin inhibited both of the reactions of $AFB_1$ but only 3$\alpha$-hydroxylation was inhibited by the oxidation product of nifedipine. Although, troleandomycin was known as a mechanism-based inhibitor, the chemical did not show any detectable inhibitory effect on 6$\beta$-hydroxylation of testosterone. The results suggest that there are several different substrate-binding sites on P450 3A4.