• Title/Summary/Keyword: 비극

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The Influence of Plasma Surface Modification on Frictional Property of Natural Rubber Vulcanizates

  • Nah, C.;Kim, D.H.;Mathew, G.;Jeon, D.J.;Jurkowski, B.;Jurkowska, B.
    • Elastomers and Composites
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    • v.39 no.1
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    • pp.12-22
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    • 2004
  • The plasma surface modification of natural rubber vulcanizate was carried out using chlorodifluoromethane in a radio-frequency (13.56 MHz) electrodeless bell type plasma reactor. The modification was qualitatively assessed by Fourier transform infrared spectroscopy. The frictional force of the plasma-treated surface was found to decrease with the time of plasma treatment. An increase in the surface polarity, as evidenced by the decrease in contact angle of a sessile drop of water and ethylene glycol on the natural rubber vulcanizate surface, was noted with the plasma modification. In the case of similar plasma treatment of glass surface, only a reduction in the polarity was observed. The use of geometric and harmonic mean methods was found to be useful to evaluate the London dispersive and specific components of surface free energy. Irrespective of the method used for evaluation, an increasing trend in the surface free energy was noted with increasing plasma treatment time. However, the harmonic mean method yielded comparatively higher values of surface free energy than the geometric mean method. The plasma surface modification was found to vary the frictional coefficient by influencing the interfacial, hysteresis and viscous components of friction in opposing dual manners.

Incentive Design Considerations for Free-riding Prevention in Cooperative Distributed Systems (협조적 분산시스템 환경에서 무임승차 방지를 위한 인센티브 디자인 고려사항 도출에 관한 연구)

  • Shin, Kyu-Yong;Yoo, Jin-Cheol;Lee, Jong-Deog;Park, Byoung-Chul
    • Journal of the Korea Society of Computer and Information
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    • v.16 no.7
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    • pp.137-148
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    • 2011
  • Different from the traditional client-server model, it is possible for participants in a cooperative distributed system to get quality services regardless of the number of participants in the system since they voluntarily pool or share their resources in order to achieve their common goal. However, some selfish participants try to avoid providing their resources while still enjoying the benefits offered by the system, which is termed free-riding. The results of free-riding in cooperative distributed systems lead to system collapse because the system capacity (per participant) decreases as the number of free-riders increases, widely known as the tragedy of commons. As a consequence, designing an efficient incentive mechanism to prevent free-riding is mandatory for a successful cooperative distributed system. Because of the importance of incentive mechanisms in cooperative distributed system, a myriad of incentives mechanisms have been proposed without a standard for performance evaluation. This paper draws general incentive design considerations which can be used as performance metrics through an extensive survey on this literature, providing future researchers with guidelines for the effective incentive design in cooperative distributed systems.

Determination of the Antioxidant Capacity of Korean Ginseng Using an ORAC Assay (ORAC Assay 에 의한 인삼의 항산화 활성 연구)

  • Kim, Sung-Hwan;Kim, Young-Mok
    • Journal of the East Asian Society of Dietary Life
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    • v.17 no.3
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    • pp.393-401
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    • 2007
  • This study was performed to investigate the antioxidant activity of Korean ginseng using an ORAC(Oxygen Radical Absorbance Capacity) assay. Four fractions each (80% ethanol, ethyl acetate, water saturated 1-butanol, and water) were obtained from different ginseng samples (White Ginseng: ; 6 yrs-., 5 yrs-., ; Cork Ginseng: ; 5 yrs-., 4 yrs-.). The saponin content of each fraction was quantified by LC/MS, and the antioxidant capacity of the ginseng was measured by the ORAC assay. The ORAC method, which was recently validated using automatic liquid handling systems, has been adapted for manual handling with the use of a conventional fluorescence microplate reader. Furthermore, the ORAC assay provides a direct measure of hydrophilic chain-breaking antioxidant capacity against peroxy radical, which is the exiting and emission of 2,2'-Azobis (2-methylpropionamidine)-dihychloride (AAPH). As a result of our experiments, ginsenosides Rg1 and Rb1 were the two major saponins found in the ginseng samples, and Rc, Rb2, Re, Rd, Rg3, and Rh1 were detected in a small quantities. For the antioxidant capacities of the fractions (80% ethanol, ethyl acetate, butanol, and water), we found that the organic solvent fraction had similar antioxidant capacities, and were higher than the capacity of the water fraction. When determining the similarities in each fraction, only the ethyl acetate fraction showed similarity compared to other fractions (p>0.05). The antioxidant capacity of ginseng may come from phenolic compounds and some nonpolar saponins. However, based on the results of this study, we hypothesize that some acidic polysaccharides and other biological components may contribute to its antioxidant capacity. Additional research is required to determine other possible biological response modifiers that contribute to the antioxidant capacity of ginseng.

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Enhanced size uniformity and dispersibility of BaTiO3 nanoparticles by hydrothermal synthesis (균일성과 분산성이 향산된 BaTiO3 나노입자의 수열합성)

  • Cho, Hoyeon;Park, Byoungnam
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.30 no.3
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    • pp.91-95
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    • 2020
  • In this study, we report a hydrothermal synthesis in which BaTiO3 nanoparticles (NPs) with enhanced size uniformity and dispersibility are synthesized by increased time and temperature, increasing nucleation and diffusion rates. The formation process of an uniform size of 20 nm BaTiO3 NPs, which has not been extensively researched, was optimized through hydrothermal synthesis at 180℃. Simultaneous increase in the nucleation rate of TiO2 and diffusion length of Ba2+ ions, resulting from a higher temperature, allowed for the synthesis of BaTiO3 NPs (20 nm) with significantly enhanced size-uniformity. The size and crystallinity of BaTiO3 NPs which exhibit excellent dispersibility in hexane solvent were investigated using transmission electron microscopy and X-ray diffraction. The results presented herein provide insights into improving the size uniformity and dispersibility of BaTiO3 NPs by hydrothermal synthesis for applications to variety of electronic devices.

A Photoreduction of Phenanthrenequinone by ESR and TRESR Spectroscopy(I)-Solvent Effect on Hyperfine-Splitting Constant of Radicals (ESR 및 TRESR 分光法에 의한 Phenanthrenequinone의 光環元反應(I). Radical의 超微細分離常數에 미치는 溶媒效果)

  • Daeil Hong;Chang Jin Kim
    • Journal of the Korean Chemical Society
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    • v.37 no.3
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    • pp.271-278
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    • 1993
  • The hyperfine splitting constants of phenanthrenequinone anion radical have been determined for the solution of triethylamine with 2-propanol, 2-pentanol or benzene by cwESR and time-resolved ESR methods. The radical anion was produced by photolysis using a pulsed excimer laser. The resulting hyperfine splitting constant A$_{H1}$ and A$_{H2}$ are 1.662, 0.378 in 2-propanol, 1.602, 0.361 in 2-pentanol and 1.518 in benzene respectively. The hyperfine coupling constants decrease with the decreasing of polarity of the mixed solvent. The tendency of the variation depends on the polarity of the solvents, thus, making it in impossible to observe the magnetic equivalent proton in a mixed solvent of nonpolar benzene. Particularly, time-resolved ESR spectrum of triethylamine radical (TEA${\cdot}$) has been observed in 0.15∼0.30 ${\mu}s$ from the solvent of 3 : 1 with 2-pentanol and triethylamine. Thus from the results of solvent effect, we can suggest that the identification of the unstable short-lived spin polarized phenanthrenequinone anion radical(*PQ${\cdot}^-$) proceed through photochemistry.

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Extraction Conditions and Green Index of Green Pigments from Discolored Garlic (녹변된 마늘의 색소 추출 조건과 Green Index)

  • Hwang, Jin-Bong;Ha, Jae-Ho;Shin, Dong-Bin;Park, Wan-Soo;Nahmgung, Bae;Lee, Young-Chun
    • Korean Journal of Food Science and Technology
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    • v.37 no.4
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    • pp.678-684
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    • 2005
  • Extraction conditions, spectrometric, and sensory properties of pigment extracts from green discolored garlic (GDG) were studied for development of green index to evaluate degree of green discoloration of garlic. GDG pigments were extracted using polar solvents, such as methanol, ethanol, and water. Methanol with 1% HCl resulted in highest extraction of green pigments. Extraction of pigments was affected by temperature, and extracted pigments were partially destroyed at high temperatures. Optimum conditions for extraction of green pigments were $20^{\circ}C$ for 30 min. Because green pigments are unstable at room temperature, and no method has been reported to evaluate degree of green discoloration of garlic, color chart was designed by mixing varying amounts of control and GDG. High correlation was observed between sensory scores and "a" value of color chart samples (y=-3.465x - 11.676) with $R^2$ of 0.993. Green index (GI) was developed based on linear regression equation between sensory scores and "a" values. Sensory panel recognized green discoloration of garlic at $GI{\geq}3.0$. GI developed in this study could be utilized to evaluate degree of green discoloration of garlic during cold storage and distribution of garlic.

Physicochemical Characteristics of Yellowtail Myosin and Whelk Paramyosin (방어 Myosin과 갈색띠 매물고둥 Paramyosin의 물리화학적 성질)

  • Pyeun, Jae-Hyeung;Choi, Yeung-Joon
    • Korean Journal of Food Science and Technology
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    • v.19 no.1
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    • pp.29-37
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    • 1987
  • The native myosin and paramyosin extracted from the ordinary muscle of yellowtail (Seriola quinqueradita) and the adductor muscle of whelk (Neptunea arthritica cumingi) were studied for their physico-chemical characteristics. Molecular weight, molar extinction coefficient at 278 nm and intrinsic viscosity were accounted for $4.6{\times}10^5$dalton, 5.44 in $E^{1cm}_{1%}$ and 1.60 dl/g in yellowtail myosin, and $2.0{\times}10^5$ dalton, 3.04 in $E^{1cm}_{1%}$ and 2.60 dl/g in whelk paramyosin, respectively. Yellowtail myosin showed a $0.342\;{\mu}mole-Pi/min/mg-protein$ of ${Ca}^{2+}-ATPase$ activity and contained 40 group-SH/mole-myosin. The ratio of polar amino acids to non-polar amino acids and that of acidic amino acids to basic amino acids were 0.54 and 1.64 in yellowtail moysin, and were 0.47 and 2.42 in whelk paramyosin, respectively.

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Black Sesame Ethanolic Extract Promotes Melanin Synthesis (Melanin 합성을 촉진하는 흑임자 에탄올추출물의 효능)

  • Jeon, Sojeong;Kim, Moon-Moo
    • Journal of Life Science
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    • v.27 no.12
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    • pp.1452-1461
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    • 2017
  • Melanin production by melanocytes in human hair follicles decreases with time and leads to the graying process, which is a phenotype of human aging and an index of aging. The reduction in melanin production is the result of decreased tyrosinase activity in hair follicles and an accumulation of active oxygen species, such as hydrogen peroxide. This study investigated antioxidant effects and melanin-promoting effects in B16F1 cells treated with black sesame ethanolic nonpolar-soluble extract (SBEEO) and black sesame ethanolic polar-soluble extract (SBEEP). In antioxidation experiments, both SBEEP and SBEEO did not eliminate 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical, but SBEEO at $64{\mu}g/ml$ showed low reducing power. SBEEP exerted cytotoxic effects at concentrations greater than $8{\mu}g/ml$, whereas SBEEO showed cytotoxic effects at concentrations greater than $4{\mu}g/ml$. SBEEP and SBEEO induced melanin synthesis, tyrosinase activity, and DOPA oxidase activity in vitro. In live cells, melanin synthesis was greater in the SBEEP treatment group as compared with that in the SBEEO treatment group. SBEEP stimulated melanin synthesis by modulating the expression of tyrosinase-related protein-2 (TRP-2), which is an important enzyme in melanin synthesis. These results imply that SBEEP obtained from black sesame ethanolic extract may have the potential to improve melanin synthesis.

α-Glucosidase Inhibitory Effect of Vicine and α-Eleostearic Acid from the Seeds of Momordica charantia (여주씨에서 분리한 Vicine과 α-Eleostearic Acid의 α-glucosidase 저해효과)

  • Yuk, Heung Joo;Noh, Geon Min;Choe, Jeong Sook;Kwon, Oh Kyung;Hong, Su Young;Kang, Sang Soo;Cho, Kye Man;Park, Dong Sik
    • Korean Journal of Environmental Agriculture
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    • v.34 no.1
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    • pp.57-63
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    • 2015
  • BACKGROUND: Momordica charantia (MC) have been used in various parts of the world to treat diabetes. Despite the highest effects of phytochemicals than any other part of the plant, the main components of seed of MC grown in Korea and their properties have not been studied extensively. METHODS AND RESULTS: The seeds of MC were extracted into five different polarity solvents: 30%, 50%, 70%, 95% ethanol and distilled water. The 95% ethanol extract showed the most potent inhibition ($IC_{50}=88.7{\mu}g/mL$) against ${\alpha}$-glucosidase. To investigate the compounds responsible for this effect, activity guided fractionation of MC seeds by chromatography yielded two phytochemicals which were confirmed as vicine (1) and ${\alpha}$-eleostearic acid (2) based on their NMR and ESI-MS spectroscopic data. Among them, ${\alpha}$-eleostearic acid (2) possessed potent ${\alpha}$-glucosidase inhibitory activities with $IC_{50}$ values from $32.4{\mu}g/mL$. CONCLUSION: Collectively, the results from this present study strongly suggest that both extract and ${\alpha}$-eleostearic acid (2) have potent ${\alpha}$-glucosidase inhibitory activity. Furthermore, ${\alpha}$-eleostearic acid (2) as the most active ${\alpha}$-glucosidase inhibitor was proven to be present in high quantities in the MC seeds by a HPLC chromatogram.

Synergistic Solvent Extraction of Manganese(II) by using Cupferron and Tetrabutylammonium ion (Cupferron과 Tetrabutylammonium ion을 이용한 Mn(II)의 상승용매 추출에 관한 연구)

  • In, Gyo;So, Jin-Hwan;Choi, Jong-Moon;Kim, Young-Sang
    • Analytical Science and Technology
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    • v.17 no.1
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    • pp.1-7
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    • 2004
  • The synergistic solvent extraction of Mn(II) by N-nitroso-N-phenylhydroxylamineammonium salt (cupferron) and tetrabutylammonium ion ($TBA^+$) has been studied. In the presence of $TBA^+$, over 95% Mn(II) was extracted from an aqueous solution into chloroform by the cupferron in the pH range of 4 to 10. But a part of Mn(II) was extracted with only cupferron. The ternary complex of Mn(II) was more efficiently extracted into $CH_2Cl_2$ and $CHCl_3$ than other nonpolar solvents. The extracted Mn(II) was determined in the back-extracted $HNO_3$ solution by GF-AAS. This fixed procedure was applied to the determination of trace Mn(II) in tap water samples of pH 5.0. The detection limit equivalent to 3 times standard deviation of the background absorption was 0.37 ng/mL and Mn(II) was determined with the range of 0.4 to 1.01 ng/mL in our laboratory's tap water. And the recovery was 94 to 107% in samples in which 2.0 ng/mL Mn(II) was spiked. The interferences of common concomitant elements such as Cu(II), Ca(II), Fe(III) and so on were not shown up to $10{\sim}20{\mu}g/mL$. From these results, this procedure could be concluded to be applied for the determination of trace Mn(II) in other environmental water samples.