• Carbon letters
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• v.11 no.4
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• pp.332-335
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• 2010

The photodegradation of the model compounds Quinol, an aromatic organic compound and Acid blue FFS, an acid dye of chemical class Triphenylmethane was studied by using illumination with UV lamp of light intensity 250W. $TiO_2$ and $TiO_2$ doped with Boron and Nitrogen was used as catalyst. The sol-gel method was followed with titanium isopropoxide as precursor and doping was done using Boron and Nitrogen. In photocatalytic degradation, $TiO_2$ and doped $TiO_2$ dosage, UV illumination time and initial concentration of the compounds were changed and examined in order to determine the optimal experimental conditions. Operational time was optimized for 360 min. The optimum dosage of $TiO_2$ and BN doped $TiO_2$ was obtained to be 2 $mgL^{-1}$ and 2.5 $mgL^{-1}$ respectively. Maximum degradation % for quinol and Blue FFS acid dye was 78 and 95 respectively, at the optimum dosage of BN-doped $TiO_2$ catalyst. It was 10 and 4% higher than when undoped $TiO_2$ catalyst was used.

• The Korean Journal of Food And Nutrition
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• v.34 no.5
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• pp.553-559
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• 2021

The aim of study to investigate the phytochemicals and biological activities the bark of Betula schmidtii. The studies consisted of the solvent extraction, followed by the isolation of phenolic components 1~3 from ethyl acetate-soluble fraction of Betula schmidtii Bark. Their chemical structures were identified as arbutin (1), ρ-coumaric acid (2) and ferulic acid (3) using Ultraviolet-Visible (UV-Vis) Spectrophotometer, Electrospray Ionization Mass Spectrometry (ESI-MS) (negative ion mode), ¹H-Nuclear Magnetic Resonance (NMR), ¹³C-NMR, ¹H-¹H Correlation Spectroscopy (COSY) and ¹H-¹³C Hetero Nuclear Multiple Quantum Correlation (HMQC) spectral data. Compounds 1~3 shows the anti-oxidant effect with IC₅₀ values of 29.74±1.52, 21.32±1.07 and 34.41±1.24 in 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, respectively. Also, compounds 1~3 exhibited mushroom tyrosinase inhibitory activity with IC₅₀ values of 31.14±1.07, 42.54±1.46 and 69.22±1.43 µM, respectively.

• Korean Journal of Materials Research
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• v.31 no.12
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• pp.672-676
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• 2021

In this paper, the effect of Ni (0, 0.5 and 1.0 wt%) additions on the microstructure, mechanical properties and electrical conductivity of cast and extruded Al-MM-Sb alloy is studied using field emission scanning electron microscopy, and a universal tensile testing machine. Molten aluminum alloy is maintained at 750 ℃ and then poured into a mold at 200 ℃. Aluminum alloys are hot-extruded into a rod that is 12 mm in diameter with a reduction ratio of 39:1 at 550 ℃. The addition of Ni results in the formation of Al₁₁RE₃, AlSb and Al3Ni intermetallic compounds; the area fraction of these intermetallic compounds increases with increasing Ni contents. As the amount of Ni increases, the average grain sizes of the extruded Al alloy decrease to 1359, 536, and 153 ㎛, and the high-angle grain boundary fractions increase to 8, 20, and 34 %. As the Ni content increases from 0 to 1.0 wt%, the electrical conductivity is not significantly different, with values from 57.4 to 57.1 % IACS.

• Tribology and Lubricants
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• v.37 no.2
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• pp.62-70
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• 2021

The problem with intermetallics coating using the heat of molten casting is that the heat generated during combustion synthesis dissolves the coating and the substrate metal. This study investigates whether pre-annealing before synthesis can control the reaction heat, with the aim of Ni₃Al coating on the casting surface. Therefore, the effects of the annealing temperature and time on the combustion synthesis behavior of the powder compact of Ni-25at%Al after annealing were investigated. As results, the reaction heat when synthesized decreased as the annealing temperature was high and the annealing time was longer. This was attributed to the fact that Al was diffused to Ni particles during low temperature annealing and intermediate Ni-Al compounds were formed during high temperature annealing. After combustion synthesis, however, it was found that their microstructures were almost identical except for the amount of intermediate intermetallics. Furthermore, an annealing temperature above 450℃, at which intermediate compounds begin to form, is needed to prevent the dissolving problem during synthesizing. The intermetallics synthesized after annealing at higher temperature and prolonger annealing time showed a good wear resistance. This might be because much intermediate intermetallics of high hardness were remained in the microstructure.

• Journal of the Korean Chemical Society
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• v.67 no.2
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• pp.137-144
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• 2023

In this study were evaluated the whitening and anti-oxidative activities from the extracts of Sorbus alnifolia branches, and identified the chemical structures of the active ingredients. In the whitening tests using α-MSH stimulated B16F10 melanoma cells, the 70% ethanol extract and n-butanol (n-BuOH) fractions concentration-dependently inhibited cellular melanogenesis and intracellular tyrosinase activities without causing cell toxicity. The total polyphenol content of n-BuOH and ethyl acetate (EtOAc) fractions were measured to be respectively 241.1 ± 1.1 and 222.9 ± 2.4 (mg/g GAE), and the total flavonoid content of EtOAc fraction was 75.3 ± 2.0 (mg/g QE). Upon anti-oxidant studies with DPPH and ABTS⁺ radicals, potent radical scavenging activities were observed in the EtOAc and n-BuOH fractions. Moreover, in the study of cell protection efficacy using HaCaT keratinocytes damaged by H₂O₂, the EtOAc and n-BuOH fractions showed a very positive results on prevention of oxidative stress. Phytochemical studies for this extract resulted in the isolation of four compounds; 2-oxopomolic acid (1), euscaphic acid (2), epi-catechin (3), prunasin (4). These results suggested that the extract of S. alnifolia branches containing compounds 1-4 as natural ingredients could be used as whitening and anti-oxidant ingredients in cosmetic formulations.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2023.04a
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• pp.18-18
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• 2023

Two new phenanthrenes, namely, (1R,2R)-1,7-hydroxy-2,8-methoxy-2,3-dihydrophenanthrene-4(1H)-one (1) and 2,7-dihydroxyphenanthrene-1,4-dione (2), were isolated from the ethyl acetate-soluble fraction of Dendrobii Herba, together with the eleven known compounds, densiflorol B (3), 6,7-dimethoxyphenanthrene2,5-diol (4), dehydroorchinol (5), 1,5,7-trimethoxy-2-phenanthrenol (6), denthyrsinin (7), ephemerantol A (8), lusianthridin (9), moscatilin (10), gigantol (11), 3-[(1E)-2-(3-hydroxyphenyl)ethenyl]-5-methoxyphenol (12) and (-)-syringaresinol (13). Structures of 1 and 2 were elucidated by analyzing 1D and 2D NMR as well as HR-ESI-MS data. The absolute configuration of compound 1 was confirmed by ECD spectroscopic method. In cytotoxicity evaluation using FaDu human hypopharyngeal squamous carcinoma cell line, compounds 3-6, 8, 10 and 12 showed activities, with IC₅₀ values ranging from 2.55 to 17.70 μM. Among them, compound 10 exhibited remarkable cytotoxic activity with IC₅₀ value of 2.55 μM. This is the first report on the anticancer mechanistic study of compound 10 in HNSCC including FaDu cells.

• Korean Journal of Materials Research
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• v.12 no.2
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• pp.153-159
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• 2002

The co-deposited behavior was investigated under varied bath compositions and current densities from Watt Ni plating bath containing Al and A1$_2$O$_3$powders. For single-particle bath, Al and A1$_2$O$_3$particles were agglomerated. The area percentage of A1$_2$O$_3$on plating surface decreased with increasing the current density, while that of Al on plating surface increased. On the other hand, in case of double-particle bath with 1.25g/$\ell$ of Al and 5.0g/$\ell$ of A1$_2$O$_3$5g, the area percentage of Ni-Al-A1$_2$O$_3$increased with increasing current density and the surface morphology was fine without agglomeration. Intermetallic compounds such as $\gamma$'and $\gamma$+$\gamma$' phases appeared when the co-deposited film was annealed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.4
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• pp.162-166
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• 2017

Thermoelectric compounds of $Zn_{1-x}Ag_xSb$ with x = 0~0.2 were prepared by vacuum melting and quenching process and their crystal phases and thermoelectric properties were examined. It was found that free metallic Sb phases were formed in the compound with x = 0.05, leading to increasing the electrical conductivities. The power factors were significantly affected by the electrical conductivity rather than Seebeck coefficient. When x > 0.05, the peak intensities of $Ag_3Sb$ phases in XRD patterns were increased and those of free Sb phases were weakened. These changes of second phases resulted in decreasing the electrical conductivities and the power factors and became more obvious in the compound with x = 0.2.

• Natural Product Sciences
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• v.25 no.4
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• pp.317-325
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• 2019

Here, we designed to examine the anti-inflammatory effects on RAW264.7 cells and the immunosuppressive effects by evaluating interleukin-2 (IL-2) production in Jurkat T cells using a MeOH extract of Panax notoginseng roots. The results showed that the MeOH extract inhibited the synthesis of nitric oxide (NO) in a dose-dependent manner (IC₅₀ value of 7.08 ㎍/mL) and displayed effects on T cell activation at a concentration of 400 ㎍/mL. In efforts to identify the potent compounds, bioactivity-guided fractionation of the MeOH extract and chemical investigation of its active CH₂Cl₂-, EtOAc-, and butanol-soluble fractions led to the successful isolation and identification of eleven compounds, including two polyacetylenes (1, 2), a steroid saponin (3), seven dammarane-type ginsenosides (4 - 10), and an oleanane-type ginsenoside (11). Among them, compound 11 was isolated from this plant for the first time. Compound 2 exhibited potent inhibitory effects on NO synthesis and an immunosuppressive effect with IC₅₀ values of 2.28 and 65.57 μM, respectively.

• Korean Journal of Materials Research
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• v.23 no.2
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• pp.104-111
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• 2013

In this study, GaN powders were synthesized from gallium oxide-hydroxide (GaOOH) through an ammonification process in an $NH_3$ flow with the variation of $B_2O_3$ additives within a temperature range of $300-1050^{\circ}C$. The additive effect of $B_2O_3$ on the hexagonal phase GaN powder synthesis route was examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transformation infrared transmission (FTIR) spectroscopy. With increasing the mol% of $B_2O_3$ additive in the GaOOH precursor powder, the transition temperature and the activation energy for GaN powder formation increased while the GaN synthesis limit-time ($t_c$) shortened. The XPS results showed that Boron compounds of $B_2O_3$ and BN coexisted in the synthesized GaN powders. From the FTIR spectra, we were able to confirm that the GaN powder consisted of an amorphous or cubic phase $B_2O_3$ due to bond formation between B and O and the amorphous phase BN due to B-N bonds. The GaN powder synthesized from GaOOH and $B_2O_3$ mixed powder by an ammonification route through ${\beta}-Ga_2O_3$ intermediate state. During the ammonification process, boron compounds of $B_2O_3$ and BN coated ${\beta}-Ga_2O_3$ and GaN particles limited further nitridation processes.