• 한국환경농학회지
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• 제27권4호
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• pp.362-367
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• 2008

The legume-rhizobia symbiosis is an important source of plant growth and nitrogen fixation for many agricultural systems. This study was conducted to investigate the effects of salinity stress on nitrogen fixation and growth of pea (Pisum sativum L.), which has antimutagenic activities against chemical mutagen, inoculated with R. leguminosarum bv. viciae cultured with additional plant-to-rhizobia signal compounds, naringenin (NA,15 uM), methyl-jasmonate (MJ, 50 uM) or both, under greenhouse conditions. Three salinity levels (0.6, 3.0 and $6.0\;dS\;m^{-1}$) were imposed at 3 days after transplanting and maintained through daily irrigations. Addition of signal compounds under non-stress and stress conditions increased dry weight, nodule numbers, leaf area and leaf greenness. The inducers increased photosynthetic rate under non-stress and stress conditions, by approximately 5-20% when compared to that of the non-induced control treatment. Under stress conditions, proline content was less in plants treated with plant-to-bacteria signals than the control, but phenol content was significantly increased, compared to that of the control. The study suggested that pre-incubation of bacterial cells with plant-to-bacteria signals could enhance pea growth, photosynthesis, nitrogen fixation and biomass under salinity stress conditions.

• 한국산학기술학회논문지
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• 제21권1호
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• pp.530-537
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• 2020

이 연구의 목적은 예비보육교사들이 지각한 보육실습 스트레스와 보육실습 과정에서 느끼는 갈등이 보육실습 만족도에 영향을 미치는 요인은 무엇인지를 알아보고자 하였다. 자료처리는 SPSS 통계 패키지 프로그램을 활용하여 빈도분석, 평균과 표준편차를 구하였다. 또한 신뢰도 검증과 각 변인간의 관련성을 알아보기 위해 상관관계 분석 및 다면적 회귀분석 방법을 활용하였다. 연구결과에 대하여 첫째, 예비보육교사들의 보육실습 스트레스에서는 보육실습 스트레스 내용과 실습환경이, 보육실습 과정에서 느끼는 갈등은 유아와의 갈등과 자신과의 갈등이, 보육실습 만족도에서는 실습교과 및 실습지도와 실습환경이 높게 인식하는 것으로 나타났다. 둘째, 예비보육교사들의 보육실습 스트레스, 보육실습 과정에서 느끼는 갈등, 보육실습 만족도 인식에서 통계적으로 유의미한 부적 상관관계가 있는 것으로 나타났다. 셋째, 예비 보육교사들의 보육실습 스트레스와 보육실습 과정에서 느끼는 갈등의 하위요인이 보육실습 만족도의 하위요인 모두에 영향을 미치는 것으로 나타났다. 이러한 연구결과로 볼 때, 보육전공 학생들의 보육실습 스트레스와 보육실습 과정에서 느끼는 갈등을 덜 경험하도록 하는 철저한 실습전 교육 및 현장 직무중심 교육과정을 운영하여 보육실습 만족도가 향상되도록 효과적인 방안 모색 연구가 진행되어야 할 것으로 사료된다.

• 한국간호교육학회지
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• 제10권2호
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• pp.262-270
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• 2004

Purpose: The purpose of this study was to define cognition of the preceptors on the preceptor's role stress and competency pre-post preceptorship experience. Method: This study was designed as a one group pre-test and post-test study. The subjects of this study were 22 preceptors who had the preceptor preparation education and then worked as preceptor for four weeks at a university hospital. For data analyses, percentage, mean, paired t-test, Pearson's Correlation Coefficient were adopted with the use of SPSS WIN 10.0. Result: The results of this study showed that after the preceptorship experience, role stress of the preceptor decreased significantly compared to before the preceptorship experience. All of the score of sub domains was decreased. Especially, there was a significantly difference in education conducting and evaluation, personal relation and communication, professional development. Also, after the preceptorship experience, competency of the preceptor increased significantly compared to before the preceptorship experience. All of the score of sub domains was increased. Particularly, there was a significantly difference in socialization facilitator and educator except learning planning performance. There was a significant positive correlation between educational experience and the number of learner before preceptorship experience of general characteristics and competency, but was not correlation between general characteristics and role stress. Also there was not correlation between role stress and competency. Conclusion: The finding above indicated that the preceptorship was effective in decreasing preceptor's role and increasing preceptor's competency.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.439-443
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• 2008

We investigate the mechanical behavior of a pre-heat treated steel of ESW95, which is being used for automotive parts including tie-rods to save manufacturing cost and enhance product quality. SCM435 is also investigated to reveal the characteristics of the pre-heat treated steel tested. AFDEX/MAT is used to extract the true stress-strain curve over the large strain with higher accuracy. It has been found that ESW95 has very week strain-hardening behavior which can be negligible compared with SCM435 and that the initial yield strength is quite high and the toughness of ESW95 reaches nearly 75% of SCM435. ESW95 is characterized by the weak strain-hardening behavior and high yield strength that can be lead to minimization of post-processing including heat treatment and straightening. ESW95 and SCM435 are also compared by applying them to ball-stud forging by computer simulation. It is expected that a great deal of change may take place in production as well as in service if the pre-heated steels are adopted.

• Corrosion Science and Technology
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• 제20권2호
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• pp.69-76
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• 2021

In this work, we have performed a corrosion failure analysis of a leaking tube connected to an upper header of a condensate pre-heater in a heat recovery steam generator. It was revealed that the leakage position in the tube was the location where the materials were easily vulnerable due to tensile residual stresses induced by the material manufacturing process and welding process. In addition to an imbalance in the module induced by temperature difference during operation of the pre-heater, the weight of the modules and thermal fatigue provoked a type of stress of tensile-tensile fatigue on the tube. Thus, the leakage position of the pre-heater was exposed to the tensile stress on the inner surface of the tube facing the gas, which rendered the unstable oxide layer susceptible to corrosion and the formation of pits on the water side. The cracks propagated along with the degraded microstructure in a transgranular cracking mode under fatigue loading and finally resulted in water leakage.

• Journal of Ginseng Research
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• 제34권2호
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• pp.138-144
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• 2010

Ginseng (Panax ginseng C.A. Meyer) has been shown to have anti-stress effects in animal studies. However, most studies have only managed to detect altered levels of biomarkers or enzymes in blood or tissue, and the actual molecular mechanisms by which ginseng exerts these effects remain unknown. In this study, the anti-oxidative effect of Korean red ginseng (KRG) was examined in human SK-N-SH neuroblastoma cells. Incubation of SK-N-SH cells with the oxidative stressor hydrogen peroxide resulted in significant induction of cell death. In contrast, pre-treatment of cells with KRG decreased cell death significantly. To elucidate underlying mechanisms by which KRG inhibited cell death, the expression of apoptosis-related proteins was examined by Western blot analysis. KRG pre-treatment decreased the expression of the pro-apoptotic gene caspase-3, whereas it increased expression of the anti-apoptotic gene Bcl-2. Consistent with this, immunoblot analysis showed that pre-treatment of the SK-N-SH cells with KRG inhibited expression of the pro-inflammatory gene cyclooxygenase 2 (COX-2). RT-PCR analysis revealed that the repression of COX-2 expression by KRG pre-treatment occurred at the mRNA level. Taken together, our data indicate that KRG can protect against oxidative stress-induced neuronal cell death by repressing genes that mediate apoptosis and inflammation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.219-222
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• 2001

The objective of the present study is to evaluate the effects of the stenting shapes on flow velocity and wall shear stress in angulated coronary stenosis by computer simulation. Coronary angiogram and Doppler ultrasound measurement in the patients with angulated coronary stenosis were obtained. Inlet wave velocity distribution obtained from in vivo intracoronary Doppler data was used for the numerical simulation. Spatial pattern of blood flow velocity and recirculation area were drawn through out the selected segment of coronary models. Wall shear stresses in the intracoronary stent models were calculated from three-dimensional computer simulation. A negative shear stress region, which is consistent with re-circulation area on flow pattern, was noted on the inner wall of post-stenotic area of pre-stenting model. The negative shear stress was disappeared after stenting. Shear stress in the post-stenting model was markedly reduced up to about two orders of magnitude compared to that of the pre-stenting model.

• 가정과삶의질연구
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• 제30권3호
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• pp.135-149
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• 2012

The aim of this study is to examine how perceived family-friendliness of community influences parents' efficacy and stress. This study asks three research questions: 1) what is the geographical boundary of community perceived by parents with pre-school children, 2) how the components of family-friendly community affect parents' perception on family-friendliness of their communities, 3) how the perceived family-friendliness of their community affects parenting efficacy and stress. Drawing on a sample of 628 parents(318 males, 310 females) who had at least one pre-school child, we analyze the data by frequencies, means and hierarchical regressions. The major findings are as follows. While the responses on the geographical boundary of community varies the most frequent response is 'Gu'. Both knowledge on family service infra and community social capital, which consist of family-friendly community, affect the perception of family-friendliness of community. The perceived family-friendliness of community is positively associated with parenting efficacy and negatively associated with parenting stress. The effect of the perceived family-friendliness of community on parenting efficacy disappears when social capital is included in the model. There is no such pattern in the association between the perceived family-friendliness of community and parenting stress.

• 한국치위생학회지
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• 제13권1호
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• pp.21-29
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• 2013

Objectives : The purpose of this study was to examine the participation attitude of students toward pre-clinical practicums, their satisfaction with the practicums and related stress, and to investigate the influential factors for their participation attitude to practicums. Methods : The subjects in this study were three different groups of students who took pre-clinical practicums at different times. One group of students who entered college in 2008 took a practicum in December, 2009, and another group of students who entered college in 2009 took a practicum in June, 2010. The third group of students who entered college in 2010 took a practicum in June, 2011. Results : 1. As for participation attitude, the students who completed a practicum before they underwent field training in the second semester of their sophomore year got a higher mark of 3.44(p<0.05). 2 Concerning the operation of practicum, they felt a lot of stress when they took a practicum before they underwent field training in the first semester of their sophomore year and when they had no dental experience(p<0.001). 3. Regarding satisfaction with practicum, they scored higher when they took a practicum before they underwent field training in the second semester of their sophomore year(p<0.05). And the students who were more gratified with dental experience expressed better satisfaction(p<0.001). 4. As to the influential factors for the participation attitude of the students, those who were more satisfied with the content of practicum, the operation of practicum and evaluation took a more positive participation attitude(p<0.001). More stress about the operation of practicum and more stress about evaluation exerted a greater negative influence on participation attitude(p<0.05). Conclusions : Given the findings of the study, a pre-clinical practicum should be offered before field training is provided in the second semester of the sophomore year in order to ensure the efficiency of education, and a wide variety of information should be offered so that students could gain dental experience before they take a practicum.

• 대한본초학회지
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• 제31권1호
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• pp.33-40
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• 2016

Objectives : Liver is one of the largest organs in the human, and has a function of detoxification and energy sensing to prevent severe disease. Paeoniae radix has been used to treat a variety of liver diseases such as hepatitis and chronic hepatic failure. Although P. radix has been used as an medicinal herb for a long time, the effects of P. radix on severe oxidative stress and its action mechanism on the liver was not clearly verified.Methods : This study investigated the protective effects of P. radix extract (PRE), and the underlying mechanism of its action in the liver. tert-butyl hydroperoxide (t-BHP) and carbon tetrachlroride (CCl₄) were used to induce oxidative stress in the HepG2 hepatocyte cell line and Sprague-Dawley rats, respectively.Results : t-BHP significantly induced cell death and ROS production in HepG2 cell, as indicated by MTT and FACS analysis. However, pretreatment of PRE inhibited a decrease in cell viability and H₂O₂ production in the HepG2 cells. PRE also blocked the ability of t-BHP to damage in mitochondrial membrane transition. More importantly, PRE induced Nrf2 activation and antioxidant Phase II enzyme, which may have a role in the effects of PRE. In mice, PRE inhibited the liver damage induced by CCl₄.Conclusions : PRE inhibited oxidative stress and hepatic damages as mediated with Nrf2 activation. This study unveil, in part, the effect and mechanism of old medicinal herb, P. radix.