• The Korean Journal of Pharmacology
• /
• v.26 no.1
• /
• pp.55-66
• /
• 1990

In both resting and opsonized zymosan activated neutrophils, ATP stimulated superoxide generation, whereas adenosine inhibited it slightly. The superoxide generation in activated neutrophils to ATP was greater than that of resting neutrophils. In $Ca^{++}$ free medium, inhibitory effect of adenosine on superoxide generation was detectable, whereas ATP did not have any effect. The stimulatory effect of ATP on superoxide generation was inhibited by adenosine in a dose dependent manner. Neither ATP nor adenosine had any effect on NADPH oxidase acitivity. Effects of ATP or adenosine on superoxide generation were more prominent than that by other triphosphate nucleotides or nucleosides. ATP and ADP further stimulated $Ca^{++}$ uptake and increased cytosolic free $Ca^{++}$ level in neutrophils activated by opsonized zymosan, but adenosine inhibited a $Ca^{++}$ mobilization. Verapamil effectively and tetrodotoxin slightly inhibited an increase of cytosolic free $Ca^{++}$ level induced by ATP. Inhibitory effect of either verapamil or tetrodotoxin on superoxide generation in the ATP plus opsonized zymosan-activated neutrophils was greater than in the cells activated by opsonized zymosan alone. Tetraethylammonium chloride had no apparent effect on superoxide generation. CCCP, 2,4-dinitrophenol, diphenylhydantoin and procaine all inhibited superoxide generation in neutrophils activated by opsonized zymosan. Among these, CCCP only inhibited a stimulatory effect of ATP. ATP further stimulated a loss of sulfhydryl groups in activated neutrophils, whereas adenosine had no effect on it. These results suggest that functional responses of neutrophils may be regulated at least partly by purines. ATP and adenosine may further after functional responses of activated neutrophils through their effect on $Ca^{++}$ uptake, membrane phosphorylation and oxidation of soluble sulfhydryl groups.

• 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.

• Korean Chemical Engineering Research
• /
• v.47 no.4
• /
• pp.441-445
• /
• 2009

Effect of temperature on membrane degradation in PEMFCs was studied. After cell operation at different temperatures($60{\sim}90^{\circ}C$) under accelerating degradation conditions(OCV, anode dry, cathode RH 65%) for 144 h, cell performance decreased from 12 to 35%. The results of FER in effluent water showed that this decrease in cell performance was caused by membrane degradation by the attack of $H_2O_2$ or oxygen radicals(${\cdot}OH$, $HO_2{\cdot}$) and that resulted in increase in gas crossover for radical formation. Radical formation on the electrode was confirmed by ESR. Activation energy of 66.2 kJ/mol was obtained by Arrhenius plot used to analyze the effect of temperature on membrane degradation. Increase of cell temperature enhanced gas crossover rate, radical formation rate and membrane degradation rate.

• Journal of the Korean Chemical Society
• /
• v.65 no.1
• /
• pp.9-14
• /
• 2021

In this study, the DFT calculation was performed using the B3LYP/6-31G(d,p) basis sets for the reaction process in which phenanthrene decomposes due to the chain reaction of two OH radicals on phenanthrene in the gaseous state of 298 K at 1 atm. As a result of the calculation, even when two OH radicals act on phenanthrene in a chain, the reaction for producing phenanthren-9-ol is predicted to be more advantageous than the reaction for producing phenanthren-1-ol. On the other hand, it was predicted that the OH addition process at room temperature would be advantageous for the priority of the OH addition and H abstraction process.

• Journal of the Korean Chemical Society
• /
• v.34 no.2
• /
• pp.136-142
• /
• 1990

PMO (Pertubation Molecular Orbital) energies, ${\delta}E$, have been calculated from NBMO (Nonbonding Molecular Orbital) coefficient for some hydrocarbons by PMO method. It was found that the stabilization energies are correlated with activation energies, bond dissociation energies, and G-values observed from vapor phase radiolysis in the free radical reactions.

• 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.

• Korean Journal of Food Science and Technology
• /
• v.50 no.2
• /
• pp.209-215
• /
• 2018

To evaluate the radical scavenging activity of phenolic-rich fractions of Gardenia jasminoides, we first measured the levels of total polyphenols in hexane, ethyl acetate, and butanol fractions from the extract of G. jasminoides. The ethyl acetate fraction of G. jasminoides extract (GJ-EA) showed high level of phenolics, potent reducing power, and 2,2-diphenyl-1-picrylhydrazyl/2,2'-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid radical scavenging effect. In addition, GJ-EA inhibited the overproduction of nitric oxide in lipopolysaccharide-activated BV-2 microglia. Furthermore, we found that GJ-EA suppressed $H_2O_2$-induced PANC-1 pancreatic cancer cell proliferation in a concentration-dependent manner and also reduced their migratory ability. These results suggest that GJ-EA may be a good source for functional foods with antioxidant and chemo-preventive activities.

• Korean Journal of Food Science and Technology
• /
• v.53 no.3
• /
• pp.296-303
• /
• 2021

The antioxidant and anti-neuroinflammatory activities of water, 30, 70, and 100% ethanol extracts of leaves of three different species of bamboo (Phyllostachys nigra, P. bambusoides, and Sasa borealis) were investigated. The levels of total polyphenol and flavonoid were measured, and antioxidant activity was evaluated using various antioxidant assays (DPPH, ABTS, and FRAP). Lipopolysaccharide (LPS)-induced BV2 microglial cell activation was used to evaluate the anti-neuroinflammatory properties of the bamboo leaf extracts. Treatment with both aqueous and ethanolic extracts showed no cytotoxicity in BV-2 microglial cells. Pre-treatment of BV-2 cells with bamboo leaf extracts significantly inhibited LPS-induced excessive production of nitric oxide in a dose-dependent manner. Moreover, phytochemical analysis based on the extraction solvent showed that caffeic acid, p-coumaric acid, and tricin are the principal constituents of all three bamboo leaf extracts. Therefore, our findings suggest that bamboo leaf extract contains potent antioxidants and anti-neuroinflammatory compounds that can be used as potential therapeutic agents for the treat neuroinflammatory diseases.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.4
• /
• pp.547-554
• /
• 2002

We are facing the serious environmental pollution difficulties such as acid rain, green house effects, etc. The gaseous matter 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 emissions strictly, especially the exhaust emissions from a Diesel engine without an aftertreatment device. The objective of this study is to find out soot and NO removal characteristics focused on the emissions of a Diesel engine by using nonthermal plasma for each engine speeds and loads. Electrostatic precipitator(wire-to-plate type reactor) is used for soot removal. Radicals generated from outer air and put into a mixing chamber in the end of exhaust line are used for NO removal. Concentration of exhaust emissions is analyzed from the gas analyzer(KaneMay) and FTIR to estimate by-products.

• Journal of the Korean Applied Science and Technology
• /
• v.37 no.5
• /
• pp.1100-1105
• /
• 2020

We investigated the driving force and the required charges for spontaneous reduction of metal nanoparticles (NPs) on a scotch tape induced by mechanochemical activation. The charges were analyzed based on anodic stripping voltammetry (ASV) of silver, which is proportional to the number of charge identities on the tape. The results supported that the driving force is mechanochemical radicals rather than ions in the light of the high charge density on the tape.