• Elastomers and Composites
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• 제34권1호
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• pp.11-19
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• 1999

카본블랙 첨가량, 촉진제에 대한 황 함량비에 따른 가황고무의 점탄성 특성을 반발탄성, 저장 및 손실 모듈러스, tan ${\delta}$를 통하여 고찰하였다. 반발탄성은 촉진제에 대한 황 함량비가 낮을수록, 배합고무중 카본-블랙의 체적분율이 낮을수록 높게 나타났다. 저장 모듈러스는 카본블랙 첨가량과 변형이 증가할수록 감소하였으나, 가황시스템과는 무관하게 나타났다. 특히 카본블랙 첨가량이 낮은 수준 ($40{\sim}50phr$)에서는 변형이 3% 이상에서, 첨가량이 높은 수준(60phr 이상)에서는 변형이 6% 이상에서 일정한 저장 모듈러스를 보이고 있어 입자간에 형성되는 망상구조는 6% 이상의 변형에서 파괴됨을 알 수 있다. 손실 모듈러스는 카본블랙 첨가량이 낮은 수준에서는 별다른 영향이 없으나, 높은 수준에서는 1% 변형에서 최대값을 보인 후 완만히 감소하였다. Tan ${\delta}$는 가황시스템에 대한 의존성은 약하나 카본블랙 첨가량 및 변형이 증가함에 따라 증가하였으나, 카본블랙 첨가량에 관계없이 2% 변형에서 최대값을 나타내었다.

• Communications for Statistical Applications and Methods
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• 제25권5호
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• pp.471-488
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• 2018

In this paper, we propose extending proportional hazards frailty models to allow a discrete distribution for the frailty variable. Having zero frailty can be interpreted as being immune or cured. Thus, we develop a new survival model induced by discrete frailty with zero-inflated power series distribution, which can account for overdispersion. This proposal also allows for a realistic description of non-risk individuals, since individuals cured due to intrinsic factors (immunes) are modeled by a deterministic fraction of zero-risk while those cured due to an intervention are modeled by a random fraction. We put the proposed model in a Bayesian framework and use a Markov chain Monte Carlo algorithm for the computation of posterior distribution. A simulation study is conducted to assess the proposed model and the computation algorithm. We also discuss model selection based on pseudo-Bayes factors as well as developing case influence diagnostics for the joint posterior distribution through ${\psi}-divergence$ measures. The motivating cutaneous melanoma data is analyzed for illustration purposes.

• Asian Pacific Journal of Cancer Prevention
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• 제15권22호
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• pp.9673-9678
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• 2014

Background: Breast cancer is a fatal disease and the most frequently diagnosed cancer in women with an increasing pattern worldwide. The burden is mostly attributed to metastatic cancers that occur in one-third of patients and the treatments are palliative. It is of great interest to determine factors affecting time from cancer diagnosis to secondary metastasis. Materials and Methods: Cure rate models assume a Poisson distribution for the number of unobservable metastatic-component cells that are completely deleted from the non-metastasis patient body but some may remain and result in metastasis. Time to metastasis is defined as a function of the number of these cells and the time for each cell to develop a detectable sign of metastasis. Covariates are introduced to the model via the rate of metastatic-component cells. We used non-mixture cure rate models with Weibull and log-logistic distributions in a Bayesian setting to assess the relationship between metastasis free survival and covariates. Results: The median of metastasis free survival was 76.9 months. Various models showed that from covariates in the study, lymph node involvement ratio and being progesterone receptor positive were significant, with an adverse and a beneficial effect on metastasis free survival, respectively. The estimated fraction of patients cured from metastasis was almost 48%. The Weibull model had a slightly better performance than log-logistic. Conclusions: Cure rate models are popular in survival studies and outperform other models under certain conditions. We explored the prognostic factors of metastatic breast cancer from a different viewpoint. In this study, metastasis sites were analyzed all together. Conducting similar studies in a larger sample of cancer patients as well as evaluating the prognostic value of covariates in metastasis to each site separately are recommended.

• Elastomers and Composites
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• 제44권3호
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• pp.315-322
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• 2009

이피디엠/폴리프로필렌 열가소성 경화물을 오일의 배합 순서를 달리한 두 가지 방식(오일 블렌드 후 가교방식과 가교 후 오일 블렌드 방식)으로 제조하여 가교도(겔분율), 경도, 인장강도, 신율, 용융흐름지수 등을 조사, 오일의 블렌드 방식이 열가소성 경화물의 물성에 미치는 영향을 알아보았다. 오일의 블렌드 방식에 따른 두 경화물의 가교도와 기계적 물성의 차는 크지 않았으나, 가공성에 있어서는 가교 후 오일 블렌드 방식으로 제조한 경화물의 용융흐름지수가 현저히 증가한 결과를 보였다.

• 대한한방내과학회지
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• 제39권6호
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• pp.1225-1243
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• 2018

The berries of Schisandra chinensis (Schisandra fructus) are given the name Omiza in Korean (五味子), which translates as "five flavor fruit" because they possess all five basic flavors in Korean traditional herbal medicine: salty, sweet, sour, pungent (spicy), and bitter. It is used as a remedy for many ailments: to resist infections, increase skin health, and cure insomnia, coughing, and thirst. This study was designed to investigate the effects of Schisandra fructus butanol fraction (SFB) on serum lipid levels in hyperlipidemic mice. In this experiment, effects on total cholesterol, HDL-cholesterol, and triglyceride in serum were measured. In our results, SFB did not affect weight gain in hyperlipidemic mice. Oral administration of SFB lowered levels of total cholesterol and triglyceride, which were elevated by induction of hyperlipidemia. Finally, administration of SFB regulated changes in gene expression which were related to cell growth and differentiation.

• Communications for Statistical Applications and Methods
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• 제25권3호
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• pp.245-261
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• 2018

Attempts have been made to define new classes of distributions that provide more flexibility for modelling skewed data in practice. In this work we define a new extension of the generalized gamma distribution (Stacy, The Annals of Mathematical Statistics, 33, 1187-1192, 1962) for Marshall-Olkin generalized gamma (MOGG) distribution, based on the generator pioneered by Marshall and Olkin (Biometrika, 84, 641-652, 1997). This new lifetime model is very flexible including twenty one special models. The main advantage of the new family relies on the fact that practitioners will have a quite flexible distribution to fit real data from several fields, such as engineering, hydrology and survival analysis. Further, we also define a MOGG mixture model, a modification of the MOGG distribution for analyzing lifetime data in presence of cure fraction. This proposed model can be seen as a model of competing causes, where the parameter associated with the Marshall-Olkin distribution controls the activation mechanism of the latent risks (Cooner et al., Statistical Methods in Medical Research, 15, 307-324, 2006). The asymptotic properties of the maximum likelihood estimation approach of the parameters of the model are evaluated by means of simulation studies. The proposed distribution is fitted to two real data sets, one arising from measuring the strength of fibers and the other on melanoma data.

• BMB Reports
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• 제34권5호
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• pp.463-471
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• 2001

The bark of Ulmus darvidiana var. japonica Nakai (UDN) has been used for a long time to cure inflammation in oriental medicine. In the present study, two types of extracts, Ulmus water-eluted fraction (UWF) and Ulmus ethanol-eluted fraction (UEF), were prepared from the UDN stem bark, and employed to test the extracts to see if they had anti-oxidative properties against hydroxyl radicals that could alter immune reactivity in mouse immune cells. Deoxyribose assay, DNA nicking assay, and glucose/glucose oxidase assay showed that both fractions had scavenging activity against oxygen free radicals at 50 mg/ml. In addition, hydroxyl radical-mediated apoptosis in mouse thymocytes was not protected by UEF treatment, but the apoptosis was protected by UWF at the same concentration. DNA synthesis and cytokine production that were induced in splenocytes by mitogens (Concanavalin A and lipopolysaccharide) were reduced by the addition of both fractions. These results indicate that both extracts that were prepared from the UDN stem bark have anti-oxidative activities, anti-apoptotic effects, and inhibitory effects on DNA synthesis and cytokine production in mouse immune cell cultures.

• 대한화장품학회지
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• 제40권1호
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• pp.11-20
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• 2014

본 연구에서는 떡쑥 추출물의 항산화 활성 및 활성 성분을 확인하였다. 모든 실험은 떡쑥 추출물의 70% 에탄올 추출물, 에틸아세테이트 분획, 아글리콘 분획을 이용하여 진행하였다. DPPH (1,1-diphenyl-2-picrylhydrazyl)법을 이용한 free radical 소거활성(FSC50)은 에틸아세테이트 분획($6.15{\mu}g/mL$)이 비교물질인(+)-${\alpha}$-tocopherol ($8.89{\mu}g/mL$)보다 높게 나타났다. 루미놀 발광법을 이용한 $Fe^{3+}$-EDTA/$H_2O_2$계에서 생성된 활성산소종(reactive oxygen species, ROS)에 대한 떡쑥 추출물의 총 항산화능($OSC_{50}$)은 70% 에탄올 추출물의 경우 $1.60{\mu}g/mL$, 에틸아세테이트 분획의 경우 $0.075{\mu}g/mL$, 아글리콘 분획의 경우 $2.28{\mu}g/mL$로 비교물질인 L-ascorbic acid ($6.88{\mu}g/mL$)보다 큰 활성을 나타내었다. 사람 적혈구의 $^1O_2$로 유도된 세포손상에 대한 보호효과 실험에서 70% 에탄올 추출물과 아글리콘 분획의 ${\tau}50$은 $10{\mu}g/mL$에서 각각 52.0, 60.6 min으로 지용성 항산화제로 알려진 (+)-${\alpha}$-tocopherol (38.0 min)보다 더 큰 세포 보호 효과를 나타내었다. TLC와 HPLC를 이용한 아글리콘 분획의 성분분석 결과 luteolin, apigenin 등이 존재함을 확인하였다. 이상의 결과들로부터 떡쑥 추출물은 라디칼을 포함한 활성산소종을 소거하는 항산화제로서 응용될 수 있음을 시사한다.

• 생약학회지
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• 제11권2호
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• pp.69-74
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• 1980

The rhizome of Polygonatum robustum Nakai (Liliaceae) has been used as a crude drug for the purpose of tonic and thirst cure in Korea. The dried rhizomes were extracted with hot ether, then the residue was extracted with hot alcohol. 1) The three kinds of chemical constituents, substance, I, II and III were isolated by silicagel column chromatography from ether and alcohol extracts of the rhizomes. Substance I was confirmed as ${\beta}-sitosterol$, $C_{29}H_{50}O$ by mass and IR spectroscopy. Substance II was identified as stigmasterol by GLC. 2) Substance III was obtained by crystallization from the column chromatography of alcohol fraction. It was suggested as diosgenin based on chemical and spectral discussions. 3) The concentration of blood sugar was significantly decreased in the group administered the ether extract with 20% dextrose and adrenaline in comparison to that of 20% dextrose and adrenaline along.

• 한국산학기술학회논문지
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• 제17권2호
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• pp.528-535
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• 2016

Ethyl acrylate(EA) 혹은 lauryl acrylate(LA)와 hydroxy ethyl acrylate(HEA)를 용액중합법에 의해 공중합하여 2종의 친유성 아크릴 전구중합체를 얻은 다음, 여기에 가교제로서 hexamethylene diisocyanate(HDI)를 첨가 배합하여, 폴리프로필렌 velvet 편직물에 통상의 pad-dry-cure방법으로 수지가공을 실시하여 유흡착재를 제조하였다. 가교 아크릴 수지(EA-HEA-HDI)의 겔화도는 전체 acrylate에 대한 HEA의 사용량과 가교제인 HDI의 농도가 증가할수록 증가하였다. 얻어진 유흡착재의 수지 부착율에 따른 흡유능과 유보유율은 시험유로서 n-decane, toluene, 대두유, 윤활유, 벙커C유를 사용하여 평가 하였고 대두유를 제외하고 사용된 모든 오일에 걸쳐 흡유능에 미치는 최적의 부착율은 약 6%로 나타났다. 한편 유보유율은 부착율의 증가에 따라 증가하였고 더욱이 고비중, 고점도 오일의 경우에서 전반적으로 보다 증가된 값을 나타내었다. 또한 흡유능은 LA-HEA-HDI로 처리된 유흡착재가 EA-HEA-HDI의 그것에 비하여 높았으며, 아크릴 수지의 측쇄 알킬기의 길이가 증가할수록 보다 높은 흡유능을 나타내었다.