• Advances in biomechanics and applications
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• 제1권2호
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• pp.77-83
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• 2014

Creep phenomenon at the scale of bone tissue (small specimens) is known to be present and demonstrated for low strains. Here creep is demonstrated on a pair of fresh-frozen human femurs at the organ level at high strains. Under a constant displacement applied on femur's head, surface strains at the upper neck location increase with time until fracture, that occurs within 7-13 seconds. The monotonic increase in strains provides evidence on damage accumulation in the interior (probably damage to the trabeculae) prior to final fracture, a fact that hints on probable damage of the trabecular bone that occurs prior to the catastrophic fracture of the cortical surface layer.

• Earthquakes and Structures
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• 제11권4호
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• pp.649-664
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• 2016

A seismic damaged bridge may be hit again by a strong aftershock or another earthquake in a short interval before the repair work has been done. However, discussions about the impact of the unrepaired damages on the residual earthquake resistance of a steel bridge are very scarce at present. In this paper, nonlinear time-history analysis of a steel arch bridge was performed using multi-scale hybrid model. Two strong historical records of main shock-aftershock sequences were taken as the input ground motions during the dynamic analysis. The strain response, local deformation and the accumulation of plasticity of the bridge with and without unrepaired seismic damage were compared. Moreover, the effect of earthquake sequence on crack initiation caused by low-cycle fatigue of the steel bridge was investigated. The results show that seismic damage has little impact on the overall structural displacement response during the aftershock. The residual local deformation, strain response and the cumulative equivalent plastic strain are affected to some extent by the unrepaired damage. Low-cycle fatigue of the steel arch bridge is not induced by the earthquake sequences. Damage indexes of low-cycle fatigue predicted based on different theories are not exactly the same.

• 대한조선학회논문집
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• 제45권5호
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• pp.538-546
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• 2008

In this paper, the constitutive equation is developed to analyze the characteristics of strain-induced plasticity in the range of low temperature of 316 stainless steel. The practical usefulness of the developed equations is evaluated by the comparison between experimental and numerical results. For 316 stainless steel, constitutive equations, which represent the characteristics of nonlinear material behavior under the cryogenic temperature environment, are developed using the Bodner's plasticity model. In order to predict the material behaviour such as damage accumulation, Bodner-Chan's damage model is implemented to the developed constitutive equations. Based on the developed constitutive equations, 3-D finite element analysis program is developed, and verified using experimental results.

• 산업기술연구
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• 제18권
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• pp.187-193
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• 1998

In this study, about the fatigue life of welded structure material under fluctuation loading, the prediction life which is produced by using the Histogram Recorder System was compared with the experimental life which is produced by the RMC model which is imported by conception of equivalent stress. In this result, this is represented few difference by comparing prediction life which is produced by damage analysis depended on Miner's rule, by using the Histogram Recorder System, with experimental life which is produced by the RMC load model which is imported by conception of equivalent of stress, therefore fatigue life is easily predicted by using Histogram Recorder System, and result of prediction has equivalent accuracy with other method which is more complex than the Histogram Recorder System. Besides the damage which is produced by stress which is high thirty percentage rank in the stress range of damage inducing, is nearly equal to the damage which is induced the rest of seventy percentage, there fore we can see that damage accumulation which is induced few time overload which is effected welded structure material is great.

• BMB Reports
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• 제56권3호
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• pp.166-171
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• 2023

Monocytes are peripheral leukocytes that function in innate immunity. Excessive triglyceride (TG) accumulation causes monocyte death and thus can compromise innate immunity. However, the mechanisms by which TG mediates monocyte death remain unclear to date. Thus, this study aimed to elucidate the mechanisms by which TG induces monocyte death. Results showed that TG induced monocyte death by activating caspase-3/7 and promoting poly (ADP-ribose) polymerase (PARP) cleavage. In addition, TG induced DNA damage and activated the ataxia telangiectasia mutated (ATM)/checkpoint kinase 2 and ATM-and Rad3-related (ATR)/checkpoint kinase 1 pathways, leading to the cell death. Furthermore, TG-induced DNA damage and monocyte death were mediated by caspase-2 and -8, and caspase-8 acted as an upstream molecule of caspase-2. Taken together, these results suggest that TG-induced monocyte death is mediated via the caspase-8/caspase-2/DNA damage/executioner caspase/PARP pathways.

• 한국산학기술학회논문지
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• 제17권3호
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• pp.31-41
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• 2016

홍수 시 하천을 따라 이동하는 유송잡물로 인해 교량을 비롯한 구조물 피해가 급증하고 있다. 따라서 본 연구에서는 유송잡물 저감시설인 수직분리대, 우회말뚝, 스위퍼를 제작하여 실험수로에서 저감시설 유무에 대한 집적실험을 실시하였다. 수직분리대는 교량에 집적되는 유송잡물에 평행 흐름을 발생시켜 이를 통과시키는 저감시설로써 목재를 이용해 제작하였으며, 우회말뚝은 유송잡물의 방향을 우회시키는 방식으로 강파이프를 이용해 제작하였다. 스위퍼는 스크류 형태의 원통형 구조물이 흐름에 의한 자력 회전으로 유송잡물을 통과시키는 방법으로 아크릴을 이용하여 제작하였다. 실험은 유송잡물의 경도 및 투하 방법에 따른 집적 정도를 분석하여 저감시설의 집적률을 비교하는 방법으로 수행하였으며 5회 반복실험을 수행하였다. 실험결과 저감시설의 종류, 유송잡물 형태 등에 따라 차이가 있는 것으로 나타났으며 초기 유송잡물이 집적되는 형태에 따라 크게 좌우되는 경우가 많았다. 교량에 대한 직접적인 저감효과는 우회말뚝, 스위퍼, 수직분리대 순으로 나타났지만 우회말뚝의 경우 말뚝에 직접 집적되는 유송잡물로 인하여 흐름교란, 수위 및 하상변동, 말뚝의 유실 등으로 인한 피해가 발생할 수 있으므로 이를 고려한 설계가 필요하다.

• 생약학회지
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• 제42권2호
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• pp.175-181
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• 2011

Oxidative stress or accumulation of reactive oxygen species (ROS) leads neuronal cellular death and dysfunction, and it contributes to neuronal degenerative disease such as Alzheimer's disease, Parkinson's disease and stroke. Glutamate is one of the major excitatory neurotransmitter in the central nervous system (CNS). Glutamate contributes to fast synaptic transmission, neuronal plasticity, outgrowth and survival, behavior, learning and memory. In spite of these physiological functions, high concentration of glutamate causes neuronal cell damage, acute insults and chronic neuronal neurodegenerative diseases. Heme oxygenase-1 (HO-1) enzyme plays an important role of cellular antioxidant system against oxidant injury. NNMBS020, the water-insoluble fraction of the 70% EtOH extract of root barks of Dictamnus dasycarpus, showed dominant neuroprotective effects on glutamate-induced neurotoxicity in mouse hippocampal HT22 cells by induced the expression of HO-1 and increased HO activity. In mouse hippocampal HT22 cells, NNMBS020 makes the nuclear accumulation of Nrf2 and stimulates extracellular signal-regulated kinase (ERK) pathway. The ERK MAPK pathway inhibitor significantly reduced NNMBS020-induced HO-1 expression, whereas the JNK and p38 inhibitors did not. In conclusion, the water-insoluble fraction of the 70% EtOH extract of root barks of D. dasycarpus (NNMBS020) significantly protect glutamate-induced oxidative damage by induction of HO-1 via Nrf2 and ERK pathway in mouse hippocampal HT22 cells.

• 한국환경과학회지
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• 제14권12호
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• pp.1093-1102
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• 2005

Effects of abscisic acid(ABA) and temperature on the anthocyanin accumulation and phenylalanine ammonia Iyase(PAL) activity were investigated in seedlings of Arabidopsis thaliana. In time course study, exogenous application of ABA $(50-1000\;{\mu}M)$ led to a noticeable increase in anthocyanin pigments which persisted over the following 5 days. Anthocyanins increased in concert with the chlorophyll loss. The activity of PAL, a key enzyme in the phenylpropanoid pathway, increased on exposure to ABA and reached maximum on the 4th day, This result shows that anthocyanin synthesis and PAL activity have a close physiological relationships. In the effects of temperatures ($10^{\circ}C,\;17^{\circ}C,\;25^{\circ}C$and $30^{\circ}C$) on anthocyanin accumulation and PAL activity in seedlings, a moderate-low temperatures ($17^{\circ}C$) enhanced both anthocyanin content and PAL activity, whereas elevated temperatures ($30^{\circ}C$) showed low levels of anthocyanin and PAL activity, suggesting a correlation between temperature-induced anthocyanin synthesis and the accumulation of PAL mRNA. Simultaneous application of ABA with temperatures Induced higher anthocyanin synthesis and PAL activity in seedlings than ABA or temperature stress alone. Moderate-low temperature with ABA exposure elicited the maximal induction of anthocyanin synthesis and PAL activity. Therefore, ABA treatment significantly increased thermotolerance in .A. thalinan seedlings. Ethephon and ABA showed similar mode of action in physiological effects on anthocyanin accumulation and PAL activity. Our data support that anthocyanins may be protective in preventing damage caused by environmental stresses and play an important role in the acquisition of freezing tolerance.

• Nutrition Research and Practice
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• 제10권1호
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• pp.19-25
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• 2016

BACKGROUND/OBJECTIVES: Cadmium is a toxic metal that is an occupational and environmental concern especially because of its human carcinogenicity; it induces serious adverse effects in various organs and tissues. Even low levels of exposure to cadmium could be harmful owing to its extremely long half-life in the body. Cadmium intoxication may be prevented by the consumption of dietary components that potentially reduce its accumulation in the body. Dietary chitosan is a polysaccharide derived from animal sources; it has been known for its ability to bind to divalent cations including cadmium, in addition to other beneficial effects including hypocholesterolemic and anticancer effects. Therefore, we aimed to investigate the role of dietary chitosan in reducing cadmium accumulation using an in vivo system. MATERIALS/METHODS: Cadmium was administered orally at 2 mg (three times per week) to three groups of Sprague-Dawley rats: control, low-dose, and high-dose (0, 3, and 5%, respectively) chitosan diet groups for eight weeks. Cadmium accumulation, as well as tissue functional and histological changes, was determined. RESULTS: Compared to the control group, rats fed the chitosan diet showed significantly lower levels of cadmium in blood and tissues including the kidneys, liver, and femur. Biochemical analysis of liver function including the determination of aspartate aminotransferase and total bilirubin levels showed that dietary chitosan reduced hepatic tissue damage caused by cadmium intoxication and prevented the associated bone disorder. CONCLUSIONS: These results suggest that dietary chitosan has the potential to reduce cadmium accumulation in the body as well as protect liver function and bone health against cadmium intoxication.

• Environmental Analysis Health and Toxicology
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• 제14권4호
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• pp.155-163
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• 1999

Heavy metal accumulation in living organisms through food-wed can give serious damage on physiological responses for vital activities. The initiation of heavy metal supposed to begin from the bio-accumulation of plants. To establish basic data fur heavy metal contents in plants at the area without artificial contamination, both woody and herb plants at Mt. Kwang-Duk were studied. The content of heavy metals in various organs of plants were analyzed by ICP. The range of heavy metals in plants for Al, As, Cd, Co, Cr, Cu, Fe. Mn, Pb, Se and Zn were 1.019∼257.200ppm, O∼2.929ppm, 0∼0.079ppm, 0∼0.054ppm, 0.023∼3.007ppm, 0∼1.997ppm, 2.031∼148.500ppm, 1.069∼51.320ppm, O∼126.900ppm, 0.708∼4.927ppm and 0.846∼4.949ppm, respectively. The amount of heavy metals in plants are much less than that of soil except some species. In woody plants, it was detected that the metal contents of leaves were higher than that of stems especially in case of Al and Fe with statistical significance. There were significant differences between shoots and roots of herb plants in metal content of Al, Co and Fe. Those metals have more accumulated in roots comparing with shoots. Some species of plants had shown the difference tendency of heavy metal accumulation. Generally, most species had not exceeded over twice of mean value each other, and had various difference according to the kinds of heavy metals.