• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1459-1474
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• 2006

The present study is focused on the development of the RIF (Representative Interactive Flamelet) model which can overcome the shortcomings of conventional approach based on the steady flamelet library. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the RIF model can effectively account for the detailed mechanisms of $NO_x$ formation including thermal NO path, prompt and nitrous $NO_x$ formation, and reburning process by hydrocarbon radical without any ad-hoc procedure. The flamelet time of RIFs within a stationary turbulent flame may be thought to be Lagrangian flight time. In context with the RIF approach, this study adopts the Eulerian Particle Flamelet Model (EPFM) with mutiple flamelets which can realistically account for the spatial inhomogeneity of scalar dissipation rate. In order to systematically evaluate the capability of Eulerian particle flamelet model to predict the precise flame structure and NO formation in the multi-dimensional elliptic flames, two methanol bluffbody flames with two different injection velocities are chosen as the validation cases. Numerical results suggest that the present EPFM model has the predicative capability to realistically capture the essential features of flame structure and $NO_x$ formation in the bluff-body stabilized flames.

• 한국식품영양과학회지
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• 제32권6호
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• pp.937-941
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• 2003

재래종 적갓(Brassica juncea czerniak et coss)을 주재료로 담금하여 발효시킨 적갓김치(red mustard leaf kimchi, RML kimchi)의 crude anthocyanin(CA) 및 refined anthocyanin(RA) 획분들에 대한 항산화성을 규명하였다. 발효된 적갓김치는 산도 0.72(%), pH 4.6 그리고 crude anthocyanin 함량(건조물기준)은 49.4 mg/g이었다. 동결건조 적갓김치로부터 얻어진 조색소용액 (crude pigment solution)을 계통 추출분획하여 증류수 획분, methanol 획분, TFA-methanol (CA) 획분을 얻었으며, CA 획분을 계속 분획하여 정제된 5개의 정제된 RA 획분(Fr.1, Fr.2, Fr.3, Fr,4, Fr.5)을 얻었다. 이들의 항산화 활성을 linoleic acid의 autoxidation system에서 peroxide formation 억제능과 DPPH($\alpha$, $\alpha$＇-diphenyl-$\beta$-picrylhydrazyl)의 free radical 소거능에 대하여 실험하였다. 그 결과 조색소용액 분획물 중 CA 획분이 항산화능이 높았고, CA 획분으로부터 얻어진 RA 획분 중 Fr.3이 가장 높은 항산화성을 보였다. 특히 Fr.3은 적갓김치의 대표적인 anthocyanin이었고 항산화 활성은 $\alpha$-tocopherel보다는 낮았으나 그것에 접근하는 유사한 특성을 보였다. 그리고 그 활성은 지질의 과산화 억제능과 수소공여성에서 다같이 비슷한 수준의 항산화성을 보였다.

• Journal of Gastric Cancer
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• 제21권1호
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• pp.16-29
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• 2021

Purpose: Incidence, risk factors, and clinical consequences of pancreatic fistula (POPF) after D1+/D2 radical gastrectomy have not been well investigated in Western patients, particularly those from Eastern Europe. Materials and Methods: A total of 358 D1+/D2 radical gastrectomies were performed by surgeons with high caseloads in a single surgical center from 2002 to 2017. A retrospective analysis of data that were prospectively gathered in an electronic database was performed. POPF was defined and graded according to the International Study Group for Pancreatic Surgery (ISGPS) criteria. Uni- and multivariate analyses were performed to identify potential predictors of POPF. Additionally, the impact of POPF on early complications and long-term outcomes were investigated. Results: POPF was observed in 20 patients (5.6%), according to the updated ISGPS grading system. Cardiovascular comorbidities emerged as the single independent predictor of POPF formation (risk ratio, 3.051; 95% confidence interval, 1.161-8.019; P=0.024). POPF occurrence was associated with statistically significant increased rates of postoperative hemorrhage requiring re-laparotomy (P=0.029), anastomotic leak (P=0.002), 90-day mortality (P=0.036), and prolonged hospital stay (P<0.001). The long-term survival of patients with gastric adenocarcinoma was not affected by POPF (P=0.661). Conclusions: In this large series of Eastern European patients, the clinically relevant rate of POPF after D1+/D2 radical gastrectomy was low. The presence of co-existing cardiovascular disease favored the occurrence of POPF and was associated with an increased risk of postoperative bleeding, anastomotic leak, 90-day mortality, and prolonged hospital stay. POPF was not found to affect the long-term survival of patients with gastric adenocarcinoma.

• 공업화학
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• 제3권2호
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• pp.256-265
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• 1992

NaCl(30wt%)/ZnO(60wt%)/${\alpha}-Al_2O_3$ 촉매상에서 메탄의 oxidative coupling 반응의 속도식을 연구하여 활성 산소종에 관하여 고찰하였다. 반응온도 $650^{\circ}C$에서 $750^{\circ}C$까지 메탄의 전화율 10%미만의 범위에서 메탄과 산소의 분압을 변화시켜 가면서 메탄의 전환속도를 측정하여 속도식을 검증하였다. 제안된 메틸라디칼의 생성반응은 Langmuir-Hinshelwood형 반응기구를 따른다. 촉매표면의 서로 다른 활성점에 흡착된 메탄분자와 산소분자가 반응하여 메틸라디칼이 생성되는 반응이 속도결정단계이며, 이때 활성화 에너지는 약 39kcal/mol이었다. 메탄의 C-H 결합의 해리에 관여하는 산소종은 표면상의 이원자 산소인 $O{_2}{^{2-}}$나 $O_2{^-}$로 제시할 수 있었다.

• 한국연소학회지
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• 제8권1호
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• pp.9-16
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• 2003

Carbon soot emission from combustion processes, especially from diesel engines, is a subject of growing concern since soot is known to seriously affect human health. Efforts have been made to oxidize soot particles utilizing Non-Thermal Plasma(NTP) techniques. When oxygen is carried into a plasma device, electrons generated by the plasma dissociate the oxygen, resulting in the formation of oxygen atoms. These highly activated atoms, called O radicals, are known as strong oxidizing agent. This paper presents concentration variations of CO and $CO_2$ at the exit of the plasma device, resulting from the soot oxidation by O radicals, with variations of inlet oxygen concentration, gas temperature, and gas flow rate. Based on the data, Arrehenious rate constants of reactions between C(s)+O and C(s)+O+O were proposed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.73-73
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• 2008

In this work, the study on the $SiO_2$ film non-uniformity by PECVD (Plasma Enhanced Chemical Vapor Deposition) was performed. Plasma diagnostics was analyzed by a DLP(Double Langmuir Probe) and a probe-type QMS(Quadrupole Mass Spectrometer) in order to investigate the spatial distribution of the plasma species in the chamber. The relationship between the plasma species and the depositing rate of the films was examined. On the basis of this work, it was confirmed that O radical density mainly contributed to the increase in the depositing rate of the $SiO_2$ films and the electron temperature in the plasma had a main effect on the formation of the oxygen radicals.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.449-452
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• 2007

The present study numerically investigate the effects of the Syngas chemical kinetics on the basic flame properties and the structure of the Syngas diffusion flames. In order to realistically represent the turbulence-chemistry interact ion and the spatial inhomogeneity of scalar dissipation rate. the Eulerian Particle Flamelet Model(EPFM) with multiple flamelets has been applied to simulate the combustion processes and NOx formation in the syngas turbulent nonpremixed flames. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the EPFM model can effectively account for the detailed mechanisms of NOx format ion including thermal NO path, prompt and nitrous NOx format ion, and reburning process by hydrocarbon radical without any ad-hoc procedure. validation cases include the Syngas turbulent nonpremixed jet and swirling flames. Based on numerical results, the detailed discussion has been made for the sensitivity of the Syngas chemical kinetics as well as the precise structure and NOx formation characteristics of the turbulent Syngas nonpremixed flames.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2873-2876
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• 2010

Excess free iron generates oxidative stress that may contribute to the pathogenesis of various causes of neurodegenerative diseases. Previous studies have shown that one of the primary causes of increased brain iron may be the release of excess iron from intracellular iron storage molecules. In this study, we attempted to characterize the oxidative damage of DNA induced by the reaction of ferritin with $H_2O_2$. When DNA was incubated with ferritin and $H_2O_2$, DNA strand breakage increased in a time-dependent manner. Hydroxyl radical scavengers strongly inhibited the ferritin/$H_2O_2$ system-induced DNA cleavage. We investigated the generation of hydroxyl radical in the reaction of ferritin with $H_2O_2$ using a chromogen, 2,2'-azinobis-(2-ethylbenzthiazoline-6-sulfonate) (ABTS), which reacted with ${\cdot}OH$ to form $ABTS^{+\cdot}$. The initial rate of $ABTS^{+\cdot}$ formation increased as a function of incubation time. These results suggest that DNA strand breakage is mediated in the reaction of ferritin with $H_2O_2$ via the generation of hydroxyl radicals. The iron-specific chelator, deferoxamine, also inhibited DNA cleavage. Spectrophotometric study using a color reagent showed that the release of iron from $H_2O_2$-treated ferritin increased in a time-dependent manner. Ferritin enhanced mutation of the lacZ' gene in the presence of $H_2O_2$ when measured as a loss of $\alpha$-complementation. These results indicate that ferritin/$H_2O_2$ system-mediated DNA cleavage and mutation may be attributable to hydroxyl radical generation via a Fenton-like reaction of free iron ions released from oxidatively damaged ferritin.

• Korean Chemical Engineering Research
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• 제45권4호
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• pp.345-350
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• 2007

고분자전해질 연료전지를 OCV(open circuit voltage)나 저가습 조건하에서 운전하면 고분자전해질 막의 열화 (degradation)가 가속화된다. 그런데 왜 이러한 조건에서 막 열화가 심하게 되는지 명확히 규명한 연구결과들이 없다. 본 연구에서는 OCV/저가습 조건에서 운전 중 막의 수소 투과도, I-V 분극곡선 변화를 측정하고 응축수 내 불소이온 방출 속도(FER)와 셀 내 생성된 과산화수소 농도를 측정하였다. 그리고 기존의 과산화수소와 라디칼에 의한 고분자막 열화 메카니즘이 실험결과를 설명할 수 있는지 비교 검토하였다. OCV/저가습 조건에서 고분자 막 열화가 잘 되는 것은 건조한 anode의 Pt 촉매 상에서 Pt와 수소원자가 결합된 상태 즉 [PtH]로의 반응이 잘 일어나고 이 [PtH]가 OCV 조건에서는 $HO_2{\cdot}$를 형성할 수 있는 조건을 만족하기 때문으로 보인다.

• 약학회지
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• 제36권2호
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• pp.180-187
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• 1992

This study investigated the hypothesis that carcinogen-induced elevation of oxyradical during the hepatocarcinogenesis in rat. The hepatic preneoplastic lesions in the Spraque-Dawley rats were induced by the carcinogen treatment such as diethylnitrosamine(DEN) and acetylaminofluorene(AAF) in combination with partial hepatectomy(PH). The liver sample was taken at 2, 6, 10 and 16 months after carcinogen treatments followed by PH. Carcinogen treatments initially increased the indices of oxidative damage(activities of xanthine oxidase and production rates of superoxide anion, microsomal hydrogen peroxide, hydroxyl radical) in the liver compared to PH groups. However, cytosolic hydrogen peroxide did not change significantly throughout the full time period. Of hydrogen peroxide scavenger, the catalase was remained lower than PH groups, whereas the peroxidase was increased after carcinogen treatments. Morphologically, the immunohistochemical analysis with glutathione-S-transferase of a placenta form(GSTP) antibody was used to detect the induction of preneoplastic nodules. During the hepatocarcinogenesis, both production rate of hydroxyl radical and activity of glutathione-S-transferase(GST) markedly increased with the appearance of the preneoplastic nodule. These results indicated that the hydroxyl radical of reactive oxygen species seemed to have a major influence on the hepatocarcinogenesis and the effect of time after removal of the carcinogen also appeared to be highly critical in the hepatocarcinogenesis.