• The tire
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• s.65
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• pp.10-17
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• 1976

아민계열화방지제(이하 아민이라고 한다)를 첨가한 천연고무 순고무가유물에 대해서 고온으로 반복대신장피로를 주어서 응력변화, 피로수명에 주는 열화방지제의 영향을 조사하였다. 아민첨가시료에 대해서 고온으로 반복 신장피로를 가하면 무첨가시료와 동양, 화학응력 연화가 출현했다. 아민첨가시료의 화학응력연화의 임계온도는 NR-DPG로 110℃, NR-MBTS로 110℃, NR-TT로 130℃이며 가교구조의 내열성에 일치하며 무첨가시료의 임계온도보다도 10~30℃높아졌다. 아민첨가시료의 반복신장피로수명은 60℃로 극대화 되어 (NR-DCP만이 40℃이었으나) 무첨가시료의 피로수명은 40℃에서 극대화됐다. 전보에서 보고한 피로수명과 변형률과의 관계식(F=A(εb-ε)n)은 100℃에서 아민첨가시료에 대해서만이 성립하고 무첨가시료에 대해선 성립되지 않았다. 이들의 결과는 아민을 고무에 첨가함으로써 고무의 열산화반응이 억제되었음에 원인하고 있다고 생각된다.

• The Korean Journal of Pharmacology
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• v.21 no.2
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• pp.79-89
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• 1985

Mechanism of calcium transport inhibition of cardiac sarcoplasmic reticulum (SR) by oxygen free radicals was examined. Effects of oxygen free radicals generated by xanthine/xanthine oxidase (X/XO) system on isolated porcine ventricle SR were studied with respect to its calcium binding, lipid peroxidation, SH-group content and alteration of membrane protein components. The results are as follows. 1) Calcium binding of isolated SR was markedly inhibited by X/XO. 2) During the incubation of sarcoplasmic reticulum with xanthine/xanthine oxidase, there were marked inclose in lipid peroxidation and reduction of SH-group content. 3) An antioxidant, p-phenylenediamine effectively prevented the lipid peroxidation but partially prevented the calcium binding inhibition of X/XO treated SR. 4) The reduction of SH-group content of SR treated with X/XO was partially prevented by p-phenylendiamine. 5) When modifying SH-group of SR by treatment with DTNB, the inhibition of calcium binding activity was partially prevented. 6) On gel-permeation chromatography of X/XO-treated sarcoplasmic reticulum, there was an increase of small molecular weight products, probably protein degradation products. 7) Semicarbazide, which prevents the cross-linking reaction of protein components, did not affect the calcium binding inhibition of X/XO-treated SR. From these results, it is suggested that the inhibition of calcium binding of SR by oxygen free radicals results from the consequence of multiple changes of SR components, which are lipid peroxidation, SH-group oxidation and degradation of protein components.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.527-536
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• 2019

This study examines the degradation of PTT BCF and fading behavior of disperse dye by heat treatment and UV irradiation. The behavior in strength degradation of PTT BCF after treat treatment was examined by measuring the tensile strength of samples. The strength retention of PTT BCF rapidly decreased with increasing exposure time at 150℃. The K/S value decreased with increasing temperature and its trend accelerated with increasing exposure time on heat. The behavior on strength degradation of PTT BCF and the fading of disperse dye on it were studied under UV irradiation at various temperatures. The tensile strength of PTT BCF and the K/S value of the sample dyed with disperse dye after UV irradiation decreased with increasing temperature and exposure time. PTT BCF exposed under UV irradiation exhibited lower strength and K/S value compared with the sample after heat treatment. Additional study on the effects of additives used to improve the resistance to fading of disperse dye and degradation of PTT BCF revealed that antioxidant and UV absorbent in PTT BCF showed a small improvement in the strength degradation of PTT BCF and the fading of dye.

• Journal of Biomedical Engineering Research
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• v.23 no.2
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• pp.139-145
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• 2002

Bis-GMA, 2.2-bis[p(2-hydroxy-3-methacryloyloxypropokyl)phenyl]Propane, is an essential component as a multifunctional methacrylate prepolymer in the light-curable polymeric dental composite resins. Two hydroxyl groups of the Bis-GMA molecule are considered to induce water sorption of the photocured composite resin in a mouth, resulting in gradual long-term deterioration of aesthetics and mechanical properties of the composite resins. In this study, some additives such as light stabilizer and antioxidant were added to composite resins to promote durability and storage stability of the last product. First of all, color change increased as a light stabilizer. Tinuvin P, was added to the composed resins and color stability was improved as an antioxidant, Irganox 245, was added to ones. In addition, when Tinuvin P and Irganox 245 were added together to the composed resins. the color stability was enhanced and mechanical properties such as diametral tensile strength before and after acceleration tests were also not greatly decreased. Therefore, when 0.5 weight Percent of Tinuvin P and 0.1 weight percent of Irganox 245 were added together to dental composite resins. the durability and color stability were enhanced, and furthermore the storage stability was also improved for the composed resins.

• Tribology and Lubricants
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• v.3 no.2
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• pp.15-22
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• 1987

윤활유는 일반적으로 윤활기유의 물성을 개량하기 위해 여러종류의 윤활유 첨가제를 포함하고 있는데 이 첨가제는 윤활기유가 가지고 있는 물성을 강화시키기 위해 첨가하는 것과 윤활기유에는 없는 물성을 얻기 위해 첨가하는 두가지로 나눌수 있다. 윤활기유의 산화분해, 열분해, 마찰이나 마모의 감소등을 위해 첨가흔 넉승 전자에 속하는 경우이고 기유 분해분의 침적을 막아주거나 부식을 방지하며 온도에 따른 점도변화를 극소화시키기 위한 첨가제는 후자에 해당한다. 즉 윤활유 첨가제는 윤활기유의 물리적, 화학적 성질을 보완 또는 강화시키므로서 윤활유로서의 소기의 목적을 달성하도록 첨가하는 화학물질을 말한다. 본 보에서는 위에서 열거한 여러종류의 첨가제 중 사용물량이 많아 수입대체 효과가 뚜렷한 6종의 첨가제의 국산화에 대한 연구결과를 간략하게 기술하였으며 앞으로 2회에 걸쳐 나누어 설명코자 한다.

• Development and Reproduction
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• v.2 no.1
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• pp.29-37
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• 1998

To investigate the role of oviductal environment in early mammalian development, we examined the effects of bovine oviductal fluid (bOF) on the development of mouse 2-cell embryos in vitro. All of the embryos cultured in medium containing 5% or more of bOF underwent degeneration after 48 hr, whereas only 5% of embryos cultured in the absence of bOF degenerated. When bOF was heated at 65 \circ C for 30 min and then added to the culture medium, the embryotoxic effect of bOF was not removed at all such that none of the embryos remained alive after 48 hr. However, when bOF heated at 90 \circ C for 30 min was added to the culture, nearly most (95%) of embryos was alive. Similarly, pretreatment of bOF with 0.1% chymotrypsin for 1 hr or overnight following heating at 65 \circ C resulted in the development of 95.5% of mouse 2-cell embryos to early blastula after 48 hr culture in the presence of treated bOF. Interestingly addition of an anti-oxidant removed the evbryotoxic effect of bOF so that 91.0% of 2-cell embryos developed to morulae or blastulae in the presence of both 5% bOF and 10 mM of glutathione (GSH) after 48 hr culture. Neither oxidized form of GSH (GSSG) nor other antioxidants, however, could support the embryonic development in the presence of bOF. From these results, it is suggested that bOF contains a protein-like factor(s) which becomes embryotoxic by exposing in vitro, probably via oxidation reaction.

• Korean Journal of Food Science and Technology
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• v.50 no.5
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• pp.535-542
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• 2018

The current study investigated the beneficial effects of 15 essential oils isolated from tree branches, leaves, and flowers. Among these oils, clove bud and Illicium anisatum oils showed the most potent anti-oxidant effects on 1,1-diphenyl-2-picrylhydrazyl and 2,2'azinbis-(3-ethyl-benzothiazoline-6-sulfonic acid) radical scavenging activities. Next, we evaluated the antibacterial effects of 15 essential oils on Staphylococcus aureus, Listeria monocytogenes, Escherichia coli O157:H7, Salmonella typhimurium, and Streptococcus mutans. Clove bud significantly decreased growth of 5 bacterial strains. In addition, clove bud, Magnolia kobus, Picea abies and Chamaecyparis obtuse significantly reduced growth of the fungi, Aspergillus fumigatus, Aspergillus ochraceus, Candida albicans and Trichophyton rubrum. Additionally, clove bud also remarkably reduced the expression of cyclooxygenase-2 and inducible NO synthase in lipopolysaccharide-activated RAW264.7 cells. These results indicate that essential oils isolated from trees, which exhibit antioxidant, antibacterial, antifungal and anti-inflammatory properties, may be potentially useful in the development of cosmetic ingredients.

• Polymer(Korea)
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• v.24 no.2
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• pp.237-244
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• 2000

Phenolic resin used as a precursor of carbonized matrix for carbon-carbon composites was modified by addition of molybdenum disilicide (MoSi$_2$) in various concentrations of 0, 4, 12 and 20% by weight to improve the anti-oxidation properties of the composites. The green body was manufactured by a prepreg method and was submitted to carbonization up to 110$0^{\circ}C$. In this work, the oxidation behavior of carbon-carbon composites with MoSi$_2$ as an oxidation inhibitor was investigated at the temperature range of 600-100$0^{\circ}C$ in an air environment. The carbon-carbon composites with MoSi$_2$ showed a significantly improved oxidation resistance due to both the reduction of the porosity formation and the formation of mobile diffusion barrier for oxygen when compared to those without MoSi$_2$. Carbon active sites should be blocked, decreasing the oxidation rate of carbon. This is probably due to the effect of the inherent MoSi$_2$ properties, resulted from a formation of the protective layer against oxygen attack in the composites studied.

• Journal of Periodontal and Implant Science
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• v.36 no.1
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• pp.97-112
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• 2006

유리 라디칼과 활성 산소종, 산화방지제 간의 불균형이 염증성 구강내 질환의 발생과 진행에 있어 중요한 역할을 한다는 주장이 제기되었고 최근에는 만성 염증성 치주질환에서도 산화에 의한 소실이 관찰되었다. 다양한 내적인 항산화 방어 기전 중 superoxide dismutase 가 $O_2$를 $H_2O_2$로 효과적으로 전환시킴으로써 활성산소종에 대한 일차적인 방어를 맡고 있다. 현재까지 인간에서 발견된 superoxide dismutase 는 cytoplasmic copper-zinc SOD와 mitochondrial manganase SOD, extracellular SOD의 3가지 아형이다. 이번 연구는 만성 치주질환을 가전 환자의 치주조직에서 효소 항산화제인 SOD의 발현정도를 알아봄으로써 질환조직 내의 산화자극 정도를 평가해 보고자하였다. 전남대학교 치주과에 내원한 33명의 만성 치주질환자와 20명 의 임상적으로 건강한 대상으로부터 조직을 얻어 Cu/Zn-SOD와 Mn-SOD, EC-SOD를 이용한 면역조직화학 염색을 시행하였다. 임상적 소견과 조직학적 소견이 일치하지 않아 조직학적 소견을 기준으로 건강한 조직, 경도, 중등도, 중도 치주질환 조직으로 그룹을 나누고 완전한 상피와 결합조직을 가진 27개의 표본에 대한 분석을 시행하였다. 치주질환 조직에서 건강한 조직에 비해 Cu/Zn-SOD가 상피의 기저층과 상피에 근접한 결합조직에서 발현되고 Mn-SOD는 염증이 증가함에 따라 크게 상피의 과립증과 각화층, 그리고 상피에 근접한 결합조직에서 발현됨으로써 활성산소종이 치주조직 파괴에 관여한다는 것을 알 수 있었다. 세 아형 모두 혈관주위에서 발현되었고 특히 EC-SOD는 작은 모세혈관주위에서만 발현되었으나 염증에 의해 혈관벽이 두꺼워지고 혈관 수가 증가한 곳에서 뚜렷하게 염색되었다. 이번 연구는 염증성 치주조직내 증가된 SOD의 활성이 치주질환자의 산화자극 정도와 관련되어 있음을 시사하였다.

• The tire
• /
• s.65
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• pp.3-9
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• 1976

가유 고무에 대변형의 반복왜를 외부자극으로서 부여하면 초기에는 대폭의 응력의 변화현상이 보여져 서서히 일정응력치에 접근하여 파단에 이른다. 이 응력의 변화현상과 피로수명(파단하기까지의 회수)이 여하한 기계적 화학적 인자의 영향을 받는가를 천연고무의 순고무 가유물로 검토했다. 그 결과 실온으로 고무에 반복신장피로를 부여하면 가교구조, 망목밀도 및 신장률이 응력변화의 대소, 피로수명의 증감에 영향을 주었다. 고온으로 고무에 반복신장피로를 주면 열산화에 의하여 어느 온도로부터 현저한 응력연화(화학응력연화) 현상이 보였다. 연이나 고무에 열화방지제를 첨가하면 고온에 있어서의 산화반응이 억제되기 때문에 무첨가의 경우와 달라서 파단이나 현저한 응력연화가 일어나지 않았다. 피로수명(F)와 파괴신장(εb),반복신장률(ε)사이에 F=A(εb-ε)n 의 관계가 성립함이 인정되었다. An은 고유의 파라메에터어이며 천연고무의 순고무가유물로서 n은 4.0~4.5의 거의 일정치를 표시했다.