• Elastomers and Composites
• /
• v.39 no.4
• /
• pp.281-285
• /
• 2004

In this paper, the simple way to evaluate the value of the activation energy for the overall rate of free radical polymerization by using DSC thermograms was studied using free radical polymerization or butylacrylate as a model. Activation ehergies were determined at heating rates of 1, 2, 5, and $10^{\circ}C/min$ by applying the multiple scanning-rate methods of Kissinger, Osawa, and half-width methods as well as the single rate method of Barrett. The value of the overall activation energy measured was closely matched with the values calculated from individual data. This work also demonstrated that the use of the isoconversional method was a simple and effective way to estimate the activation energy for the overall free radical polymerization.

• Journal of the East Asian Society of Dietary Life
• /
• v.20 no.1
• /
• pp.54-59
• /
• 2010

Basil is known to contain six types of polyphenols that engage in physiological activation; protocateuic acid, caffeic acid, chlorogenic acid, courmaric acid, rosmarinic acid and quercetin. In this study, the antioxidants in eight types of basil were evaluated. Specifically, the antioxidative activation of basil was evaluated based on the relationship between active oxygen scavenging (DPPH radical-scavenging), which was used as an index showing the content and functionality of the polyphenol compounds in basil, and $Fe^{2+}$/ascorbate (FTC) and 2-thiobarbituric acid (TBA). The total polyphenol content of the different types basil occurred in the following order: Dark-opal> Lettuce> Bush> Greek> Lemon> Sweet> Geno> Holy. The highest content Dark-opal was 173.3 mg, which was about three times greater than the lowest content Holy, which was 49.85 mg. In addition, DPPH radical-scavenging by Dark-opal 51%, which was the highest scavenging activity occurred in the folling order: Dark-opal> Lettuce> Bush> Greek> Lemon> Sweet> Geno> Holy. The antioxidative activation values measured using the FTC and TBA were the same as the value obtained using the DPPH method. Finally, the level of antioxidative activation measured using FTC, TBA and DPPH methods showed that the higher the content of polyphenol substance was, the stronger the antioxidative activation became.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.63-63
• /
• 1999

The stability of hydrogenated amorphous silicon (a-Si:H) films under the light soaking are very important since the applications of a-Si:H films are solar cells, color sensors, photosensors, and thin film transistors(TFTs). We found the changes of the electric conductivity and the conductivity activation energy (Ea) of a-Si:H films by argon radical annealing. The deposition rate of a-Si:H films depends on the argon radical annealing time. The optical band gap and the hydrogen contents in the a-Si:H films are changes along the argon radical annealing time. We will discuss the microscopic processes of argon radical annealing in a-si:H films.

• Macromolecular Research
• /
• v.14 no.5
• /
• pp.539-544
• /
• 2006

2-Furancarboxaldehyde-2-pyridinylhydrazone (FPH) and 5-methyl-2-furancarboxaldehyde-2-pyridinylhydrazone (MFPH) were synthesized and used as tridentate ligands of copper (I) bromide for the atom transfer radical polymerization of methyl methacrylate (MMA) and styrene. The polymerization of methyl methacrylate achieved high conversion and yielded polymers with a good control of molecular weight and low polydispersity (PDI=1.33). Higher PDI were observed in the polymerization of styrene. Using 1-phenyl ethylbromide (PEBr) and ethyl 2-bromoisobutyrate (EBiB) as model compounds for the polymeric chain ends, the activation rate constants of the new catalytic systems were measured. These results were correlated with the polymerization results and compared with another catalytic system previously reported.

• Preventive Nutrition and Food Science
• /
• v.18 no.1
• /
• pp.80-84
• /
• 2013

This study was conducted to evaluate the increase of DPPH radical scavenging activity of meat substitute by heating. The meat substitute showed higher DPPH radical scavenging activity than those of other foods rich in protein such as beef, pork, chicken, and soybean curd. The DPPH radical scavenging activity of meat substitute was dependent upon concentration, heating temperature and heating time of meat substitute. The DPPH radical scavenging activity of meat substitute was enhanced with increasing heating temperature and time. The increase of DPPH radical scavenging activity was only applied to meat substitute without showing any activation in other foods rich in protein such as beef, pork, chicken, and soybean curd.

• Environmental Engineering Research
• /
• v.20 no.3
• /
• pp.205-211
• /
• 2015

Reduced forms of iron, such as zero-valent ion (ZVI) and ferrous ion (Fe[II]), can activate dissolved oxygen in water into reactive oxidants capable of oxidative water treatment. The corrosion of ZVI (or the oxidation of (Fe[II]) forms a hydrogen peroxide ($H_2O_2$) intermediate and the subsequent Fenton reaction generates reactive oxidants such as hydroxyl radical ($^{\bullet}OH$) and ferryl ion (Fe[IV]). However, the production of reactive oxidants is limited by multiple factors that restrict the electron transfer from iron to oxygen or that lead the reaction of $H_2O_2$ to undesired pathways. Several efforts have been made to enhance the production of reactive oxidants by iron-induced oxygen activation, such as the use of iron-chelating agents, electron-shuttles, and surface modification on ZVI. This article reviews the chemistry of oxygen activation by ZVI and Fe(II) and its application in oxidative degradation of organic contaminants. Also discussed are the issues which require further investigation to better understand the chemistry and develop practical environmental technologies.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.715-719
• /
• 2000

It is reported that we are facing the serious environment pollution difficulties such as acid rain, green house effects, etc. The gaseous matter CO, NOx, SOx, VOCs which are regarded as main factors for these current pollutions are mainly emitted from power plants and vehicles. Therefore several leading countries are regulating the related laws strictly, especially exhaust emissions from a Diesel engine without an after treatment device. The Objective of this study is to find out NOx removal characteristics focused on emissions of a Diesel engine using radical at each engine speed and load. It is generated from outer air and put into a mixing chamber in the end of exhaust line. In addition, the optimum temperature condition to activate reaction by radical is experimentally carried out. Concentration of exhaust emissions is analyzed from the gas anlayzer(KaneMay) and FTIR to estimate by-products.

• Macromolecular Research
• /
• v.15 no.1
• /
• pp.31-38
• /
• 2007

Pentamethylcyclopentadienyltitanium trichloride, bis(cyclopentadienyl)titanium dichloride ($Cp_2TiCl_2$), and bis(pentamethylcyclopentadienyl)titanium dichloride were used in the polymerization of styrene without the aid of Group I-III cocatalysts. The properties of the resulting polymer indicated that polymerization was more controlled than in thermal polymerization. The kinetic studies indicated that a lower level of termination is present and that the polymer chain can be extended by adding an additional monomer. To elucidate the mechanism of polymerization, a series of experiments was performed. All results supported the involvement of a radical mechanism in the polymerization using $Cp_2TiCl_2$. The possibility of atom transfer radical polymerization (ATRP) mechanism was investigated by isolating the intermediate species. We could confirm the activation step from the reaction of 1-PEC1 with $Cp_2TiCl$ by detecting the coupling product of the generated active radicals. However, the reversible deactivation reaction competes with other side reactions, and it detection was difficult with our model system.

• Preventive Nutrition and Food Science
• /
• v.18 no.3
• /
• pp.196-202
• /
• 2013

Citron seed extracts (CSEs) were made using distilled water (CSEW), ethanol (CSEE), and n-hexane (CSEH), to measure the total polyphenol contents, DPPH and ABTS radical scavenging activities, and anti-complementary activity. The total polyphenol content was observed the highest in CSEE (188.71 ${\mu}g/mL$), and occurred in the following order: CSEE>CSEW (141.11 ${\mu}g/mL$)>CSEH (26.19 ${\mu}g/mL$) at 10 mg/mL. CSEE (63.56%) and CSEW (56.61%) showed significantly higher DPPH radical scavenging activities when compared with CSEH (28.57%). ABTS radical scavenging activities of CSEE (45.53%) and CSEW (40.02%) were also observed to be higher, whereas CSEH did not show ABTS radical scavenging activity. Anti-complementary activity of CSEE (26.85%) showed a greater activity than that of CSEW (7.84%) at 1,000 ${\mu}g/mL$. Limonin and nomilin contents had the highest values (1.882% and 2.089%) in CSEE, and with 0.327% and 0.139% in CSEW; however, CSEH showed relatively very low values at 0.061% and 0.026%, respectively. Among the CSEs tested, CSEE as a by-product from citron may provide an important source of dietary antioxidant compounds with rich polyphenol and limonoid contents, and immunopotentiating activity, including the complement activation factor.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.23 no.6
• /
• pp.1320-1331
• /
• 2009

Oxidative stress and inflammation are important events in the development of chronic inflammatory diseases including arthritis, atherosclerosis, diabetes, hypertension. Cynomorium songaricum (CS) has been used as a traditional Korean herbal medicine, and it is currently used in traditional clinics to treat frequent urination, spermatorrhea, weakness of the sinews and constipation in the folk medicine. The aim of this study was to determine whether fractionated extracts of CS inhibit free radical generation such as DPPH radical, superoxide radical, nitric oxide and peroxynitrite, production of nitrite an index of NO, $PGE_2$, iNOS, COX-2 and pro-inflammatory cytokines in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages. Cytotoxic activity of extracts on RAW 264.7 cells was measured using 5-(3-caroboxymeth-oxyphenyl)-2H-tetra-zolium inner salt (MTS) assay. Our results indicated that the most superior extract which scavenged DPPH radical, reactive oxygen species (ROS) and RNS was CS ethyl acetate extract (CSEA). Moreover, CSEA significantly inhibited the LPS-induced NO, $PGE_2$ production and iNOS, COX-2 expression accompanied by an attenuation of TNF-$\alpha$, IL-$1{\beta}$ and IL-6 formation in macrophages. Furthermore, CSEA treatment also blocked LPS-induced intracellular ROS production and the activation of NF-${\kappa}B$. These findings indicate that CSEA inhibits the production of pro-inflammatory mediators and cytokines via the suppression of ROS production and NF-${\kappa}B$ activation. Take together, these results indicate that CSEA has the potential for use as an natural anti-oxidant and an agent of anti-chronic inflammatory diseases.