• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.171-176
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• 2003

The sonolytic decomposition of NHCs, such as atrazine［6-chloro-N-ethyl-N＇ -(1-methylethyl)-1,3,5-triazine-2,4-diamine］, simazine( 6-chloro-N,N＇ -diethyl-l ,3,5-triazine-2,4-diamine), trietazine(6-chloro-N,N,N＇-triethyl-l,3,5-triazine-2,4-diamine), in water was investigated at a ultrasound frequency of 200kHz with an acoustic intensity of 200W under argon and air atmospheres. The concentration of NHCs decreased with irradiation, indicating pseudo-first-order kinetics. The rates were in the range 1.06∼2.07 (x10/sup -3/ min/sup -1/) under air and 1.30∼2.59(x10/sup -3/ min/sup -1/)under argon at a concentration of 200μM of NHCs. The rate of hydroxyl radicals(·OH) formation from water is 19.8μM min/sup -1/ under argon and 14.7 μM min/sup -1/ under air in the same sonolysis conditions. The sonolysis of NHCs is effectively inhibited, but not completely, by the addition of t-BuOH(2-methyl-2-propanol), which is known to be an efficient ·OH radical scavenger in aqueous sonolysis. This suggests that the main decomposition of NHCs proceeds via reaction with ·OH radical; a thermal reaction also occurs, although its contribution is small. The addition of appropriate amounts of Fenton's reagent ［Fe/sup 2＋/］ accelerates the decomposition. This is probably due to the regeneration of ·OH radicals from hydrogen peroxide, which would be formed from recombination of ·OH radicals and which may contribute a little to the decomposition.

• Journal of Ginseng Research
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• v.13 no.1
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• pp.92-97
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• 1989

This study investigated the effects of high light intensity (100 KLw) and high temperature (45 ℃, dark) on enzyme (glucose-6-phosphate dehydrogenase, acid phosphatase, catalase, peroxidase, and proteinase) activities and characteristics of Panax ginseng C.A. Meyer leaves. Enzyme activity and protein content decreased rapidly under treatment with high light intensity In P ginseng the thermal stabilities of catalase and peroxidase were high (above 70%), and the coagulation rates of soluble proteins were low (below 17%). Therefore, the decrease in enzyme activity and protein content was not caused by increase in leaf temperature due to the high light intensity, but by increase in proteolytic activities. The photochemical formation rate of superoxide radical (O-2) was higher in the P ginseng leaf extracts than in Solanum nigmm, and was accelerated by addition of crude saponin to the buffer extracts.

• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.561-567
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• 2004

The influence of ultrasound frequency, dissolved gases, and initial concentration on the decomposition of sodium dodecylbenzene sulfonate(DBS) aqueous solution was investigated using ultrasound generator with 200 W ultrasound power. The decomposition rates at three frequencies(50, 200, and 600 kHz) examined under argon atmosphere were highest at 200 kHz. The highest observed decomposition rate at 200 kHz occurred in the presence of oxygen followed by air and argon, helium, and nitrogen. The effect of initial concentration of DBS on the ultrasonic decomposition was decreased with increasing initial concentration and would depend upon the formation of micelle in aqueous solution. It appears that the ultrasound frequency, dissolved gases, and initial concentration play an important role on the sonolysis of DBS. Sonolysis of DBS mainly take place at the interfacial region of cavitation bubbles by both OH radical attack and pyrolysis to alkyl chain, aromatic ring, and headgroup.

• Polymer(Korea)
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• v.26 no.3
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• pp.353-359
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• 2002

High intensity ultrasound has been applied to a series of poly(ethylene oxide) (PEO)/water systems having different molecular weights of PEO. Major interest was focused on the effect of ultrasonic wane on the melt viscosity chemical structure and thermal properties of PEO. The expected role of ultrasound used in this study was to generate macroradicals of PEO chains by the formation and subsequent collapse of bubbles. It was found that the melt viscosity and chemical structure of PEO change significantly depending on the sonication time. For the prolonged sonication, PEO chains were significantly degraded and new end groups were formed by the interplay of various radical species. When the molecular weight of PEO was relatively higher, the crystallization rate was decreased and the intensity of the melting peak was reduced.

• Journal of the Korean Applied Science and Technology
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• v.9 no.2
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• pp.175-179
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• 1992

In order to investigate the effect of tannic acid and ${\alpha}$-tocopherol on methyl linoleate autoxidation and on inhibition activity of lipoxygenase in phospholipid, the rate of formation of methyl linoleate hydroperoxide was measured by HPLC. The reaction mixture contained methyl linoleate 70mM, radical initiator AMVN 0.7mM, tannic acid and ${\alpha}$-tocopherol 0.7mM, each, in a mixture of hexane/isopropanol(1 : 1, v/v). Under this reaction condition, tannic acid was good enough antioxidant. The tannic acid and ${\alpha}$-tocopherol for the inhibition activivity of lipoxygenase were measured at the reaction conditions: phospholipid $1{\mu}M$. tannic acid and ${\alpha}$-tocopherol were reacted as an inhibitor of lipoxygenase in phospholipid, especialy in phosphatidy lcholine.

• Journal of the Korean institute of surface engineering
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• v.37 no.4
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• pp.220-225
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• 2004

A new ion beam extraction system is designed using a simple ion mass filter and a micro mass balance and a QMS based detecting system. A quadrupole Mass Filter is used for selective ion beam formation from inductively coupled high density plasma sources with appropriate electrostatic lens and final analyzing QMS. Also a quartz crystal microbalance is set between a QMF and a QMS to measure the etching and polymerization rate of the mass selected ion beam. An inductively coupled plasma was used as a ion/radical source which had an electron temperature of 4-8 eV and electron density of $4${\times}$10^{11}$＃/㎤. A computer interfaced system through 12bit AD-DA board can control the pass ion mass of the qmf by setting RF/DC voltage ratio applied to the quadrupoles so that time modulation of pass ion's mass is possible. So the direct measurements of ion - surface chemistry can be possible in a resolution of $1\AA$/sec based on the qcm's sensitivity. A full set of driving software and hardware setting is successfully carried out to get fundamental plasma information of the ICP source and analysed $Ar^{+}$ beam was detected at the $2^{nd}$ QMS.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.2
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• pp.187-196
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• 1991

Aging is the progressive accumulation of changes with time associated with responsible for the ever-increasing susceptibility to disease and death which accompanies advancing age. Lipid peroxides easily produced in the membrane system by the chain reaction of free radicals which occurred from various environmental factors. The amount of lipid peroxides produced in biological system increased with aging process, and lipid peroxidation damages involved in aging process and pathological disorders. Although lipid peroxides have such deleterious effects on the organisms, there are numerous substances and mechanisms which prevent the reaction of peroxide formation and protect the subject from its toxicity. This review provides an overview of how does lipid peroxidation of unsaturated lipids take place by free radical, and what is the intervention of lipid peroxides in pathogenesis of some human diseases, and also how does food restriction influences the aging process and various pathological disorders. The major focus of this paper is to review the evidence indicating that food restriction retards the aging process, and possible mechanisms of its actions. Therefore, it discussed the effects of age and food restriction on life-span, membrane yield, lipid peroxidation, fatty acid composition and peroxidizability, cholesterol and triglyceride levels, prostaglasndin and thromboxane synthesis, which may be concerned with blood flow, membrane fluidity, homeostasis and glomerular filtration rate in living body.

• Journal of Physiology & Pathology in Korean Medicine
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• v.16 no.1
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• pp.172-180
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• 2002

Polychlorinated biphenyls(PCBs) are large scale industrial chemicals which are using in diverse applications. The goal of this study was to determine if exposure to 2,2',5,5'-tetrachlorobiphenyl (PCB 52) leads to an increase in the production of active oxidants, and subsequently promotes apoptosis of neuronal SK-N-MC cells. Reactive oxygen species (ROS) formation was examined in SK-N-MC cells after treatment of PCB 52 by concentrations and incubation times, respectively. It showed that the rate of ROS production in the cells was increased in a does-dependent manner to 45 min, followed by a return towards control levels after 120 min treatment. We also examined the association of PCB-induced apoptosis with the modulation of biomakers of oxidative damage to lipids (malondialdehyde [MDA]) in SK-N-MC cells. Increased MDA was observed in a dose-dependent manner in groups treated with 10, 15, and 20 figJ me of PCB 52 for 24 h. After treatment of PCB 52, the cells did not show any significant change in the rate of Cu/Zn-superoxide dismutase (Cu/Zn-SOD) activity. Whereas, the cells had a two-fold greater rate of change in catalase activity at 20 ㎍/㎖ of PCB 52 for 24 h when compared to control group. Korean Ginseng is one of the most important crude drugs which has been used as a traditional Oriental medicine. We next investigated protective effect of extracts of ginseng on cytotoxicity induced by PCB 52 in SK-N-MC cells. Pretreatment of SK-N-MC cells with 25-200 μg/ml of ginseng were reduced cell death in a dose-dependent manner in PCB 52-treated cells. To examine the sensitivity of beta-catenin to ginseng, the protective effect of a range of ginseng concentrations was examined in SK-N-MC cells treated with PCB 52. The result demonstrated that ginseng efficiently blocked PCB 52 inducible beta-catenin proteolysis in a concentration dependent manner. The ROS formation was also measured in the presences of extract of ginseng and superoxide dismutase (inhibitor of oxygen free radical production). The both SOD (400 U/ml) and ginseng (200 μg/ml) significantly inhibited RDS generation in PCB 52-treated group.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.136.1-136.1
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• 2015

In the present study, UHF (320 MHz) in combination with RF (13.56 MHz) plasmas was used for the synthesis of hydrogenated silicon nitride (SiNx:H) films by PECVD process at low temperature. RF/UHF hybrid plasmas were maintained at a fixed pressure of 410 mTorr in the N2/SiH4 and N2/SiH4/NH3 atmospheres. To investigate the radical generation and plasma formation and their control for the growth of the film, plasma diagnostic tools like vacuum ultraviolet absorption spectroscopy (VUVAS), optical emission spectroscopy (OES), and RF compensated Langmuir probe (LP) were utilized. Utilization of RF/UHF hybrid plasmas enables very high plasma densities ~ 1011 cm-3 with low electron temperature. Measurements using VUVAS reveal the UHF source is quite effective in the dissociation of the N2 gas to generate more active atomic N. It results in the enhancement of the Si-N bond concentration in the film. Consequently, the deposition rate has been significantly improved up to 2nm/s for the high rate synthesis of highly transparent (up to 90 %) SiNx:H film. The films properties such as optical transmittance and chemical composition are investigated using different analysis tools.

• Nuclear Engineering and Technology
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• v.51 no.8
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• pp.1957-1963
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• 2019

A UVC photo-Fenton advanced oxidation process (AOP) was studied to develop a process for the decomposition of oxalic acid waste generated in the chemical decontamination of nuclear power plants. The oxalate decomposition behavior was investigated by using a UVC photo-Fenton reactor system with a recirculation tank. The effects of the three operational variables-UVC irradiation, H₂O₂ and Fenton reagent-on the oxalate decomposition behavior were experimentally studied, and the behavior of the decomposition product, CO₂, was observed. UVC irradiation of oxalate resulted in vigorous CO₂ bubbling, and the irradiation dose was thought to be a rate-determining variable. Based on the above results, the oxalate decomposition kinetics were investigated from the viewpoint of radical formation, propagation, and termination reactions. The proposed UVC irradiation density model, expressed by the first-order reaction of oxalate with the same amount of H₂O₂ consumption, satisfactorily predicted the oxalate decomposition behavior, irrespective of the circulate rate in the reactor system within the experimental range.