• Fibers and Polymers
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• v.3 no.3
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• pp.109-112
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• 2002

Polybutadiene(PB) was epoxidized to various extents with m-chloroperbenzoic acid (MCPBA) in homogeneous solution. The thermal properties of the epoxidized PBs were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). As a result of epoxidation the glass transition temperature (Tg) of PB increased by approximately $0.8^{\circ}$ for each 1 mol% of epoxidation. The thermal decomposition of the epoxidised PBs occurred in two-step process, while that of PB exhibited apparent one-step degradation process.

• Bulletin of the Korean Chemical Society
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• v.15 no.5
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• pp.364-368
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• 1994

Growth inhibition potency of the anthraquinones, anthraquinone-1,5-disulfonic acid and carminic acid, for Sarcoma 180 and L1210 leukemia cells in vivo and in vitro, was induced by the divalent transition metal ion, $Cu^{2+}$. On the other hand spectroscopic titration data show that the anthraquinone drugs form $Cu2^+$ chelate complexes (carminic acid : $Cu^{2+}$ = 1 : 6; anthraquinone-1,5-disulfonic acid : $Cu^{2+}$ = 1 : 3). Furthermore the $Cu^{2+}$-drug complexes associate with DNA to form the $Cu^{2+}$-anthraquinone-DNA ternary complexes. The formation of the complexes was further supported by the $H_2O_2-dependent$ DNA degradation, which can be inhibited by ethidium bromide, caused by the $Cu^{2+}$-drug complexes. It is likely that the $Cu^{2+}$-mediated cytotoxicity of the anthraquinone drugs is related with the $Cu^{2+}-mediated$ binding of the anthraquinone drugs to DNA and DNA degradation.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.439-445
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• 2001

The destructive method is reliable and widely used lot the estimation of material degradation but, it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the estimation of degraded structural materials used at high temperature by nondestructive evaluation such as electric resistance method, replica method, Barkhausen noise method, electro-chemical method and ultrasonic method are strongly desired. Ultrasonic nondestructive evaluation technique has been reported good to attain efficiency of measurement, high sensitivity of measurement, and rapidity and reliability of result interpretation. In this study, it was verified experimentally the feasibility of the evaluation of degraded 2.25Cr-1Mo steel specimens which were prepared by the isothermal aging heat treatment at $630^{\circ}C$ by high frequency longitudinal wave method investigating the change of attenuation coefficient by FFT analysis and wavelet transform. Because of carbide precipitation increase and spheroidization near grain boundary of microstructure to aging degradation, attenuation coefficient had a tendency to increase as degradation proceeded. It was identified possibly to evaluate degradation using the characteristics of high-frequency ultrasonics. Frequency dependence of ultrasonic attenuation coefficient to aging degradation appeared large, which made sure that attenuation coefficient is an important parameter for evaluation of aging degradation.

• Journal of the Korean Wood Science and Technology
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• v.45 no.2
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• pp.168-181
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• 2017

Whole cell of Phanerochaete chrysosporium with reducing agent was applied to verify the degradation mechanism of aromatic compounds derived from lignin precisely. Unlike the free-reducing agent experiment, various degraded products of aromatic compounds were detected under the fungal treatment. Our results suggested that demethoxylation, $C_{\alpha}$ oxidation and ring cleavage of aromatic compounds occurred under the catabolic system of P. chrysosporium. After that, degraded products stimulated the primary metabolism of fungus, so succinic acid was ultimately main degradation product of lignin derived-aromatic compounds. Especially, hydroquinone was detected as final intermediate in the degradation of aromatics and production of succinic acid. In conclusions, P. chrysosporium has an unique catabolic metabolism related to the production of succinic acid from lignin derived-aromatic compounds, which was meaningful in terms of lignin valorization.

• Journal of The Geomorphological Association of Korea
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• v.19 no.2
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• pp.187-195
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• 2012

Daisetsuzan National Park in Hokkaido, Japan, has an extensive alpine region due to the topographic feature of lava plateau, and exhibits the surface geology largely composed of pyroclastic materials. In addition, the peak season of mountain climbing in the park coincides with a snow-melting period, resulting in severe soil erosion along hiking trails generated by human trampling, snow-melting water and pipkrake. Trail section has been particularly enlarged because the snow-melting water scours a trail surface and the pipkrake erodes sidewalls of a trapezoid-shaped trail. The scoured tread also forces hikers to walk out of a trail, and then frequently brings about path divergence as well as path widening. The soil particles, which are produced by erosional processes in a slope reach, flow downward, and cause the secondary trail degradation by covering a tread in a flat reach and nearby grassland.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.347-351
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• 2011

Hydroxyapatite (HAp) powders with different crystallinities were synthesized at various calcination temperatures through the co-precipitation of $Ca(OH)_2$ and $H_3PO_4$. The degradation behavior of these HAp powders with different crystallinities was assessed in a simulated body fluid solution (SBF) for 8 weeks. Below $800^{\circ}C$, the powders were nonstochiometric HAp, and the single HAp phase was successfully synthesized at $800^{\circ}C$. The degree of crystallinity of the HAp powders increased with an increasing calcination temperature and varied in a range from 39.6% to 92.5%. In the low crystallinity HAp powders, the Ca and P ion concentrations of the SBF solution increased with an increasing soaking time, which indicated that the low crystallinity HAp degraded in the SBF solution. The mass of the HAp powders linearly decreased with respect to the soaking time, and the mass loss was higher at lower crystallinities. The mass loss ranged from 0.8% to 13.2% after 8 weeks. The crystallinity of the HAp powders increased with an increasing soaking time up to 4 weeks and then decreased because of HAp degradation. The pH of the SBF solution did not change much throughout the course of these experiments. These results suggested that the crystallinity of HAp can be used to control the degradation.

• Korean Journal of Plant Resources
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• v.28 no.6
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• pp.682-689
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• 2015

Abeliophyllum distichum Nakai (A. distichum) has been reported to exert the inhibitory effect on angiotensin converting enzyme and aldose reductase. Recently, our group found that branch extracts of A. distichum (EAFAD-B) induce apoptosis through ATF3 activation in human colon cancer cells. However, anti-cancer reagents exert their activity through the regulation of various molecular targets. Therefore, the elucidation of potential mechanisms of EAFAD-B for anti-cancer activity may be necessary. To elucidate the potential mechanism of EAFAD-B for anti-cancer activity, we evaluated the regulation of cyclin D1 in human colon cancer cells. EAFAD-B decreased cellular accumulation of cyclin D1 protein. However, cyclin D1 mRNA was not changed by EAFAD-B. Inhibition of proteasomal degradation by MG132 attenuated EAFAD-B-mediated cyclin D1 downregulation and the half-life of cyclin D1 was decreased in the cells treated with EAFAD-B. In addition, EAFAD-B induced cyclin D1 phosphorylation at threonine-286 and the point mutation of threonine-286 to alanine attenuated EAFAD-B-mediated cyclin D1 proteasomal degradation. Inhibitions of both ERK1/2 by PD98059 and NF-κB by a selective inhibitor, BAY 11-7082 suppressed cyclin D1 downregulation by EAFAD-B. From these results, we suggest that EAFAD-B-mediated cyclin D1 downregulation may result from proteasomal degradation through its threonine-286 phosphorylation via ERK1/2-dependent NF-κB activation. The current study provides new mechanistic link between EAFAD-B and anti-cancer activity in human colon cancer cells.

• Korean Journal of Environmental Agriculture
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• v.39 no.1
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• pp.58-64
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• 2020

BACKGROUND: Most of the researches on the dye removal using ozonation have been focused on the removal efficiency. However, the research on their removal characteristics and mechanism according to the reaction time has been still insufficient. METHODS AND RESULTS: In this study, the effects of initial pH and dye concentration with reaction time on the degradation characteristics of methyl orange (MO) and methylene blue (MB) by ozonation were evaluated. The degradation efficiency of MB by ozonation increased with increasing pH. On the other hand, the degradation efficiency of MO by ozonation did not show a significant difference with varing pH. The both MO and MB by ozonation were decomposed within 30 min irrespective of the dye concentration, but the decomposition rates of dyes were faster at lower initial dye concentration. The decomposition efficiency of total organic carbon (TOC) in each dye solution by ozonation was low, which was found to be effective for partial decomposition such as decolorization rather than complete degradation of the dye. CONCLUSION: Overall, ozonation was an effective method for removing nondegradable dyes. However, it is necessary to study the optimization of dye degradation under various environmental conditions for ozonation.

• Biomolecules & Therapeutics
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• v.27 no.6
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• pp.503-513
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• 2019

Osteoarthritis is a chronic degenerative articular disorder. Formation of bone spurs, synovial inflammation, loss of cartilage, and underlying bone restructuring have been reported to be the main pathologic characteristics of osteoarthritis symptoms. The onset and progression of osteoarthritis are attributed to various inflammatory cytokines in joint tissues and fluids that are produced by chondrocytes and/or interact with chondrocytes, as well as to low-grade inflammation in intra-articular tissues. Disruption of the equilibrium between the synthesis and degradation of the cartilage of the joint is the major cause of osteoarthritis. Hence, developing a promising pharmacological tool to restore the equilibrium between the synthesis and degradation of osteoarthritic joint cartilage can be a useful strategy for effectively managing osteoarthritis. In this review, we provide an overview of the research results pertaining to the search for a novel candidate agent for osteoarthritis management via restoration of the equilibrium between cartilage synthesis and degradation. We especially focused on investigations of medicinal plants and natural products derived from them to shed light on the potential pharmacotherapy of osteoarthritis.

• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.345-350
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• 2007

During PEMFC operation, OCV(open circuit voltage) and low humidity conditions accelerate the degradation of perfluorosulfonic acid membrane. There have been no studies that clearly explain why these conditions accelerate the membrane degradation. In this study, the hydrogen permeability through the membrane, I-V polarization of MEA, fluoride emission rate(FER) and $H_2O_2$ concentration in condensed water were measured during cell operation under OCV and low relative humidity(RH). The experimental results were evaluated with oxygen radical mechanism the most commonly known for membrane degradation. It seems that low RH of anode is a good condition for $H{\cdot}$ radical formation on the Pt catalyst and the OCV condition accelerate the $H{\cdot}$ to form $HO_2{\cdot}$ radical attacking the polymer membrane.