• 한국연소학회:학술대회논문집
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• 1997.06a
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• pp.1-11
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• 1997

The soot and OH radical distributions have been experimentally studied in ethylene and propane laminar diffusion flames. The integrated soot volume fraction was measured along the centerline of a flame using a laser light extinction method. Planar laser light scattering and PLIF techniques are employed for the soot and OH radical distribution measurements utilizing Nd:YAG laser and OPO, FDO system. The concentration of OH radical is rapidly decreased at the edge of sooting region, which implies the importance of OH radical species on the soot oxidation process. For ethylene flames, the addition of air in fuel moves the OH radical distribution towards the center line of a flame at the soot oxidation region, while the concentration of OH radical remains relatively high at the soot formation region. The interaction between soot particles and OH radicals becomes more active with fuel-air at the soot oxidation region. For propane flames, however, any indication of the increased interaction between soot particles and OH radicals with fuel-air was not noticed.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.54-59
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• 2001

OH radical concentration have been measured in a methane-air partially premixed flames using PLIF. Excitation lines were selected $Q_{1}(6)$ branch, (1,0) band. The system is consisted of Nd:YAG laser, dye laser and frequency doubler to make pump beam for OH radical. On the direct photographs, flame height increases as fuel flow rate and equivalence ratio increase. And on the PLIF images, OH radical is distributed from premixed flame front to nonpremixed flame front through the flame structure with all equivalence ratio. OH overall concentrations increase with equivalence ratio. At the stoichiometric equivalence ratio, the peak of OH radical concentration exists strongly near the inner cone. As equivalence ratio is changed to richer, OH radical distribution goes thinly and the peak is increased as longitudinal direction. As the flow goes to the downstream, OH radical concentration decreases and broadens, because OH radical reacts with another species after OH formation at the initial oxidization. This phenomenon resembles radial distribution. At the l00cc fuel flowrate, the radial peak of OH radical exists from x/R=l.0 to 1.5.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1907-1910
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• 2004

Generation of hydroxyl radical, one of their major active species in ozonation of water was directly observed with spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-pyrrolidine-1-oxyl (DMPO) as a spin-trapping reagent. Hydroxyl radical was trapped with DMPO as a stable radical, DMPO-OH. 80 mM of ozone produced $1.08{\times}10^{-6}$M of DMPO-OH, indicating that 1.4% of ${\cdot}$OH is trapped with DMPO if ${\cdot}$OH is produced stoichiometrically from ozone. Humic acid suppressed DMPO-OH generation in a dose-dependent manner. Generation rate of DMPO-OH was determined with ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance·OH generation during ozonation of water.

• The Korean Journal of Food And Nutrition
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• v.10 no.1
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• pp.6-13
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• 1997

Reactivity and reaction mechanism for the photosensitized generation of hydroxyl radical by various coumarin derivatives are investigated by means of ESR and laser flash photolysis methods. The nine kinds of coumarin derivatives show to be proceeded through the OH·radical generation mechanism, however 1-ethyl-3-nitro-1-nitrosoguanidine decomposes and produces the carbene intermediate before OH·radical generation reaction occurs. The nine coumarin derivatives show the signals, which are corresponded to DMPO-OH spin adducts. NaN3, EtOH and HCOONa act as a strong photosensitizer to quench OH·radical. The decay rate constants of the hydrated electrons in the case of added N2O show higher than added K3Fe(CN)6.

• Korean Journal of Agricultural Science
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• v.39 no.4
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• pp.511-514
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• 2012

In this study, the comparison of antioxidative effect of the methanol (MeOH) extracts from grains were investigated in vitro radical scavenging system. Ten grains (black rice, rice, barley, wheat, millet, sorghum, glutinous millet, buckwheat, phellines linteus rice and brown rice) were extracted with MeOH. Among the MeOH extracts of grains, sorghum and black rice showed effective scavenging activities of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The $IC_{50}$ values of sorghum and black rice were $47.4{\mu}g/mL$ and $50.6{\mu}g/mL$, respectively. In addition, black rice also exerted the strongest activities on hydroxyl radical (${\cdot}OH$) scavenging activity. Furthermore, the MeOH extracts of black rice showed effective and dose dependant scavenging activities of DPPH radical and ${\cdot}OH$. These results indicated that black rice showed strong free radical scavenging activity. It suggested that black rice could be a promising natural antioxidant against free radical-induced oxidative damage.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.184.2-184.2
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• 2013

대기압 플라즈마와 생체용액과의 상호작용은 Bio-medical 분야에서 주목 받고 있다. 대기압 플라즈마는 전자온도가 고온 플라즈마 보다 상대적으로 낮기 때문에 생체에 적용하기가 적합하다. 따라서 플라즈마가 세포에 미치는 영향을 관측하기 위해서 대기압 플라즈마를 이용하여 생체용액과의 반응을 살펴보고자 한다. Ar gas를 이용하여 플라즈마를 발생시켜 생체용액 표면을 처리하고 OES (Optical Emission Spectroscopy)을 이용해 방출 선을 조사했다. Ar 기체를 이용한 대기압 플라즈마를 사용하여 다른종류의 용액내의 OH Radical Density를 측정하였다. 용액으로는 DI (deionized) water 와 PBS (1x phosphate buffered saline)를 사용하였다. Ar gas를 200 sccm ($cm^3/min$) 으로 흐르게 하였을 때, DI water의 OH Radical Density 는 $4.33{\times}10^{16}cm^{-3}$ 으로 측정되었으며, 자외선 흡수분광법으로 측정한 완충용액인 PBS의 OH Radical Density 측정값은 $1.87{\times}10^{16}cm^{-3}$ 이다. 이런 특성을 기반으로, PBS 용액내의 H460 (Lung Cancer Cell) 와 L132 (Lung Normal Cell)을 깊이와 시간에 따라 대기압 플라즈마로 처리하여 cell의 변화를 보았다. 실험 각각의 조건은 깊이를 2 mm, 4 mm, 6 mm이며 시간은 10 sec, 30 sec, 60 sec 로 설정하였다. 표면으로부터의 깊이가 2 mm, 4 mm, 6 mm 일때 의 OH Radical Density는 각각 $1.87{\times}10^{16}cm^{-3}$, $0.5{\times}10^{16}cm^{-3}$, 0으로써 용액이 깊어질수록 OH Radical Density가 감소함을 볼 수 있다. OH radical density가 높은 2 mm 에서, 처리한 시간이 길어질수록 Cell 은 영향을 많이 받음을 관찰 할 수 있었다. H460 이 L132 보다 플라즈마에 영향을 많이 받음을 확인하였다. 특성변화를 알아보기 위하여 raman spectroscopy, flow cytometry, electron spin resonance로 측정한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.710-719
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• 1996

Laser applied combustion diagnostic techniques-laser induced fluorescence (LIF) and coherent anti-Stokes Ramann spectroscopy (CARS)-are demonstrated. The profiles of hydroxyl radical (OH) and temperature in the counterflow burner are measured and compared with the numerical results. OH radical is excited on the Q$_1$(6) line of the $A^2$$\sum^+$$\leftarrow$$X^2{\prod}$(1, 0) band transition (281.1 nm) and LIF signal is measured at the the bands of (0, 0) and (1, 1) transition (306~326 nm). Absolute OH radical is obtained by using the laser absorption technique. The quenching effects are considered. Temperature is measured using broadband CARS system. Two dimensional OH radical profile is also obtained. The profiles of OH radical and temperature are found to agree well with those of numerical calculation.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.503-511
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• 2023

The aim of this study was to investigate in vitro antioxidant activities of defatted Camellia japonica L. seeds (DCJS). The DCJS were extracted using ethanol and then fractionated with butanol (BuOH), ethyl acetate (EtOAc), chloroform, and hexane. To evaluate antioxidant activity of extract and fractions from DCJS, we investigated free radical scavenging activities such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺), hydroxyl radical (^•OH), and superoxide anion (O₂^-) radicals. The five extract and fractions of DCJS dose-dependently increased DPPH, ABTS⁺ and O₂^- radical scavenging activities. The BuOH fraction of DCJS showed the highest free radical scavenging activities among other extract and fractions. The contents of total polyphenol and flavonoid in BuOH fraction of DCJS were 23.26 mg GAE/g and 32.39 mg QE/g, respectively. The polyphenol and flavonoids contents of BuOH fraction has highest than other extract and fractions. In addition, BuOH and EtOAc fraction of DCJS contained 102.37 and 165.05 ㎍/g of camelliaside B, respectively. Therefore, DCJS has higher antioxidant activity and may be useful as a natural antioxidant material.

• Korean Journal of Plant Resources
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• v.21 no.4
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• pp.254-259
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• 2008

The radical scavenging activities of 9 medicinal plants on peroxynitrite ($ONOO^-$) and hydroxyl (${\cdot}OH$) radical were investigated using in vitro system. The water extracts of 9 medicinal plants showed the protective effect against $ONOO^-$ and ${\cdot}OH$ radical. In particular, Akebia quinata, Aster scaber, Cudrania tricuspidata, Diospyros kaki, Eriobotrya japonica, Lycium chinense, Parthenocissus tricuspidata and Polygonum aviculare exhibited $ONOO^-$-scavenging activity by about 50% at the concentration of $10{\mu}g/ml$. Although those $ONOO^-$-scavenging activities were lower than that of penicillamine (94.08${\pm}$3.04%) as a positive control, Eriobotrya japonica (89.87${\pm}$4.57%) was the most potent scavenger of $ONOO^-$ at the concentration of $10{\mu}g/ml$. Also, Diospyros kaki and Urtica angustifolia showed the strong${\cdot}$OH-scavenging activity than thiourea, positive control, at the concentration of lmg/ml. Our results indicate that 9medicinal plants may act as free radical scavengers and reduce damages caused by oxidative stress associated with $ONOO^-$ and${\cdot}$OH radical.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.558-566
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• 2017

In this study, we developed an electron-emission OH radical generator for waste water treatment. The stability of the circuitry was ensured by implementing stable pulse waves with a MOSFET and reducing the momentary current rise. The OH radical generator uses a high-voltage and low-current discharger. The performance of the device was evaluated experimentally, which showed that it is possible to produce a stable and uniform pulse waveform for the drain current of the power MOSFET, which is connected to the input side of an AC multiplying converter through negative feedback circuitry with CR-snubber architecture. It was also possible to reduce the excitation current of the converter and improve the stability of the oscillation circuit. In addition, the generator can generate hydroxyl radicals stably. The bactericidal activities were also evaluated, and the germicidal power for E. coli, S. aureus, and S. flexneriwas improved by 99.9% or more after 60 minutes.