• Journal of the Korean Society for Heat Treatment
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• v.34 no.5
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• pp.218-225
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• 2021

In this study, damping capacities were comparatively investigated for Mg-9%Al alloy with as-cast (AC) and fully discontinuous precipitates (DPs) microstructures, respectively. The DPs microstructure was obtained by solution treatment at 678 K for 24 h, followed by furnace cooling to RT. The AC microstructure was typically characterized by partially divorced eutectic β(Mg₁₇Al₁₂) phase particles distributed along the α-(Mg) matrix cell boundaries. The DPs microstructure showed lamellar morphology consisting of α and β thin layers with various interlamellar spacings. The DPs microstructure had better damping capacity than the AC microstructure in the strain-amplitude independent region, while in the strain-amplitude dependent region, the damping behavior was reversed. In view of the microstructural features of AC and DPs, the lower concentration of Al in the α-(Mg) phase for the DPs microstructure and the lower β phase number density for the AC microstructure would be responsible for the higher damping capacities in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.81-87
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• 2019

PURPOSE. The purpose of this study was to evaluate the effects of various protocols and systems for finishing and polishing monolithic zirconia on surface topography, phase transformation, and bacterial adhesion. MATERIALS AND METHODS. Three hundred monolithic zirconia specimens were fabricated and then treated with three finishing and polishing systems (Jota [JO], Meisinger [ME], and Edenta [ED]) using four surface treatment protocols: coarse finishing alone (C); coarse finishing and medium polishing (CM); coarse finishing and fine polishing (CF); and coarse finishing, medium polishing, and fine polishing (CMF). Surface roughness, crystal phase transformation, and bacterial adhesion were evaluated using atomic force microscopy, X-ray diffraction, and streptococcal biofilm formation assay, respectively. One-way and two-way analysis of variance with Tukey post hoc tests were used to analyze the results (${\alpha}=.05$). RESULTS. In this study, the surface treatment protocols and systems had significant effects on the resulting roughness. The CMF protocol produced the lowest roughness values, followed by CM and CF. Use of the JO system produced the lowest roughness values and the smallest biofilm mass, while the ME system produced the smallest partial transformation ratio. The ED group exhibited the highest roughness values, biofilm mass, and partial transformation ratio. CONCLUSION. Stepwise surface treatment of monolithic zirconia, combined with careful polishing system selection, is essential to obtaining optimal microstructural and biological surface results.

• Clinical and Experimental Pediatrics
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• v.49 no.9
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• pp.987-990
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• 2006

Intravenous immunoglobulin (IVIG) infusion is an effective therapy for acute Kawasaki disease (KD). Nonetheless, approximately 10 percent to 20 percent of patients have persistent or recrudescent fever despite IVIG treatment, leading to a higher risk for coronary artery aneurysms (CAA). This unresponsiveness may pose a challenge to the clinicians. Tumor necrosis $factor-{\alpha}$ levels are elevated in the acute phase of the disease, especially in patients who develop CAA. We report a 10-month-old male with KD who failed to respond to multiple doses of IVIG and methylprednisolone and who then was treated with infliximab (5 mg/kg single dose). After infliximab treatment, he became afebrile with normalization of inflammatory markers and no further progression of CAA.

• Journal of the Korean Ceramic Society
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• v.28 no.9
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• pp.667-674
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• 1991

In this study, Kaolin was carbonized at 1300~175$0^{\circ}C$ and its constituent mineral change was investigated. Carbonized kaolin at 1$650^{\circ}C$ was mixed with metallic silicon, formed and nitrified at 135$0^{\circ}C$ in N2-NH3 atmosphere. Properties of this product such as porosity, bulk density, MOR, nitrization rate and oxidation resistence were measured, and its mineralogical changes were investigated by XRD. The results were as follows; 1) $\beta$-SiC was initially synthesized at 150$0^{\circ}C$, and its amount was continuously increased with reaction temperature to 1$700^{\circ}C$. 2) At 1$600^{\circ}C$, mullite was rapidly decomposed and the amounts of $\beta$-SiC and $\alpha$-Al2O3 were increased simultaneously. 3) By adding alkali to kaolin, the decomposition temperature of mullite was dropped approximately 10$0^{\circ}C$, but the amount of $\alpha$-SiC was increased. 4) The highest values of their nitrization rate and MOR were obtained at the specimen of 35 wt% metallic silicon in nitrization reaction. 5) It seems that increment of $\alpha$-Si3N4 and $\alpha$-Al2O3 phase during nitrization was due to the decomposition of Al4SiC4 existed in carbonized kaolin. 6) Si3N4 bonded SiC-Al2O3 composite were fabricated from kaolin at relatively low temperature (135$0^{\circ}C$).

• Journal of Korea Foundry Society
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• v.31 no.6
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• pp.362-365
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• 2011

In the present work, the corrosion properties of Mg-xSn (x = 1, 3, 5, 7 and 9 wt.%) alloys have been investigated. Potentiodynamic polarization and immersion tests were carried out in 3.5% NaCl solution of pH 7.2 at room temperature to measure the corrosion properties of Mg-xSn (x = 1, 3, 5, 7 and 9 wt.%) alloys. With increase of the Sn contents, the volume fraction of the $Mg_2Sn$ phase was increased. The corrosion rate of Mg-xSn alloys was increased up to 7 wt.%Sn and decreased above 9 wt.%Sn. Initiation of galvanic site during immersion mainly occurred at Mg/$Mg_2Sn$ interface and propagation went into ${\alpha}$-Mg. For this reason, corrosion properties of Mg-xSn (added from 1 wt.%Sn to 7 wt.%Sn alloys) alloys are decreased because the galvanic site was increased with increasing Sn addition. In Mg-9wt.%Sn alloy, however, the corrosion site were changed from Mg/$Mg_2Sn$ interface to ${\alpha}$-Mg/$M_2Sng$ interface in lamellar structure. Preferentially corrosion of ${\alpha}$-Mg/$M_2Sn$ interface in lamellar structure impeded corrosion propagation went into ${\alpha}$-Mg.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.5
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• pp.734-740
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• 2005

The blood samples were collected from dairy cows at the same milking stage. The single-strand conformation polymorphism (PCR-SSCP) method was used to analyze for polymorphism at the 5'flanking region of the hsp70 gene. The mRNA expression levels of HSP70, HSF1, Bcl-2 and Bax-$\alpha$ at different daily-mean-temperature were analyzed by relative quantitative RTPCR. The DNA content, cell phase and the ratio of apoptosis of lymphocytes in peripheral blood of dairy cattle at different daily-meantemperature were determined by FCM. The PCR-SSCP products of primer pair 1 showed polymorphisms and could be divided into four genotypes: aa, ab, ac, cc, with the cis-acting element (CCAAT box) included. Mutations in the hsp70 5'flanking region (468-752 bp) had different effects on mRNA expression of HSP70, HSF1, Bcl-2 and Bax-$\alpha$. The ac genotypic cows showed higher expressions of HSP70mRNA, HSF1mRNA and Bcl-2mRNA/Bax-$\alpha$mRNA and lower ratio of apoptosis. These mutation sites can be used as molecular genetic markers to assist selection for anti-heat stress cows.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.7
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• pp.3293-3297
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• 2014

Background: Pine needle oil from crude extract of pine needles has anti-tumor effects, but the effective component is not known. Methods: In the present study, compounds from a steam distillation extract of pine needles were isolated and characterized. Alpha-pinene was identified as an active anti-proliferative compound on hepatoma carcinoma BEL-7402 cells using the MTT assay. Results: Further experiments showed that ${\alpha}$-pinene inhibited BEL-7402 cells by arresting cell growth in the G2/M phase of the cell cycle, downregulating Cdc25C mRNA and protein expression, and reducing cycle dependence on kinase 1(CDK1) activity. Conclusion: Taken together, these findings indicate that ${\alpha}$-pinene may be useful as a potential anti-tumor drug.

• The Korean Journal of Food And Nutrition
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• v.20 no.2
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• pp.120-124
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• 2007

The thermal degradation kinetics of alpha-, gamma- and delta-tocopherols was studied during heating at 100, 150 200 and 250$^{\circ}C$ for 5, 15, 30 and 60 min in the absence of oxygen. The tocopherols were separated by HPLC using a reversed phase ${\mu}$-Bondapak C$_{18}$-column with two kinds of elution solvent system in a gradient mode. The kinetics for degradation of ${\alpha}$-, ${\gamma}$- and ${\delta}$-tocopherols was analyzed as a function of temperatures and times. The degradation of tocopherols was described by the first-order kinetics in the absence of oxygen. The rate of tocopherols degradation was dependent on heating temperatures. The degradation rate constants for ${\alpha}$-, ${\gamma}$ and ${\delta}$-tocopherols showed an increasing trend as the heating temperature increased. The magnitude order of the experimental activation energy was ${\delta}$->${\gamma}$->${\alpha}$-tocopherol.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.147-156
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• 1992

Supported lead oxide catalysts were prepared by using ${\alpha}-,{\beta}-{\gamma}$-alumina, and MgO as a support. Among the supported lead oxide catalysts, MgO-supported catalyst showed the highest $C_2^+$ hydrocarbon selectivity for the methane conversion into $C_2^+$ hydrocarbons, but ${\gamma}$-alumina-supported PbO catalyst gave the highest $CO_2$ selectivity. And ${\alpha}$-alumina-supported catlyst showed the midium activity, whereas ${\beta}$-alumina-supported catalyst gave little activity. These reaction characteristics seemed to be largely dependent on the acticity of lattice oxygens in supported catalysts, which would be influnto be largely dependent on the activity of lattice oxygens in supported catalysts, which would be influenced in the interaction between the supports and lead oxides and the properties of supports. Especially, much higher ration of (002)/(111) peak intensities for PbO phase on MgO support than on the other supports in X-ray diffraction analysis was considered to be ab evidence that methane oxidative coupling of methane might be so-called structure-sensitive reaction, and this seemed to be an example of surface oxide-support interaction (SOSI) in the oxidative coupling reaction.

• Korean Journal of Materials Research
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• v.27 no.4
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• pp.206-210
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• 2017

In this study, an ${\alpha}-Fe_2O_3$ (hematite) coated porcelain plate was sintered in a temperature range from $1100^{\circ}C$ to $1250^{\circ}C$ using ferrous sulfate. The specimens were investigated by X-ray diffractometer (XRD), scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), and UV-visible spectrophotometer. It was confirmed that ${\alpha}-Fe_2O_3$ (hematite) was densely fused to the surface at several tens of ${\mu}m$, the ${\alpha}-Fe_2O_3$ (hematite) was in the form of thin platelet and polyhedra, and no other compounds appeared in the sintering process. In the specimen coated with ${\alpha}-Fe_2O_3$ (hematite), the reflectance spectra show a red absorption band of 560-650 nm. The $L^*$ value decreased from 53.18 to 46.94 with the firing temperature. The values of $a^*$ and $b^*$ were at 19.03 and 15.25 at $1100^{\circ}C$ and gradually decreased with increasing temperature; these values decreased rapidly at $1250^{\circ}C$ to 11.54 and 7.98, respectively. It is considered that the new phases are formed by the phase transition of the porcelain plate (clay), and thus the $a^*$ and $b^*$ values are greatly influenced.