• Biomolecules & Therapeutics
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• v.9 no.2
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• pp.112-118
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• 2001

The effects of Malloti Cortex Water Extract (MCWE), bergenin (isolated as an active component from MCWE), and acetylbergenin (synthesized from acetylation of bergenin) on the liver fibrosis induced by bile duct ligation (BDL) in rats. We studied hydroxypro1ine (HYP) as a marker of collagen accumulation in the liver, alanine aminotransferase (s-ALT), aspartate aminotransferase (s-AST), and alkaline phosphatase (s-ALP) as serum markers of liver cell damage induced by BDL, MCWE, bergenin, and acetylbergenin decreased towards normal the accumulated levels of HYP in the liver and the elevated serum levels of s-ALT, s-AST and 5-ALP. The results indicate that MCWE, bergenin, and acetylbergenin ameliorated the liver damage induced by BDL in rats.

• Biomolecules & Therapeutics
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• v.27 no.2
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• pp.145-151
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• 2019

Methamphetamine (METH) acts strongly on the nervous system and damages neurons and is known to cause neurodegenerative diseases such as Alzheimer's and Parkinson's. Flavonoids, polyphenolic compounds present in green tea, red wine and several fruits exhibit antioxidant properties that protect neurons from oxidative damage and promote neuronal survival. Especially, epicatechin (EC) is a powerful flavonoid with antibacterial, antiviral, antitumor and antimutagenic effects as well as antioxidant effects. We therefore investigated whether EC could prevent METH-induced neurotoxicity using HT22 hippocampal neuronal cells. EC reduced METH-induced cell death of HT22 cells. In addition, we observed that EC abrogated the activation of ERK, p38 and inhibited the expression of CHOP and DR4. EC also reduced METH-induced ROS accumulation and MMP. These results suggest that EC may protect HT22 hippocampal neurons against METH-induced cell death by reducing ER stress and mitochondrial damage.

• Animal cells and systems
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• v.6 no.3
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• pp.263-269
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• 2002

The p53 tumor suppressor gene is among the most frequently mutated and studied genes in human cancer, but the mechanisms by which it sur presses tumor formation remain unclear. DNA damage regulates both the protein levels of p53 and its affinity for specific DNA sequences. Stabilization of p53 in response to DNA damage is caused by its dissociation from Mdm2, a downstream target gene of p53 and a protein that targets p53 for degradation in the proteosome. Recent studies have suggested that phosphorylation of human p53 at Ser20 is important for stabilizing p53 in response to DNA damage through disruption of the interaction between Mdm2 and p53. We generated mice with an allele encoding changes at Ser20, known to be essential for p53 accumulation following DNA damage, to enable analyses of p53 stabilization in vivo. Our data showed that the mutant p53 was clearly defective for full stabilization of p53 in response to DNA damage. We concluded that Ser20 phosphorylation is critical for modulating the negative regulation of p53 by Mdm2, probably through phosphorylation-dependent inhibition of p53-Mdm2 interaction in the physiological context.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.2
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• pp.140-149
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• 1985

Fully reversed push-pull low cycle fatigue tests under strain control of trapezoid cyclic mode have been conducted in air at temperature of 550.deg. C and with frequency of 0.5 cpm on the domestic stainless steel STS 316 after solution treatment for 1 hour at 1100.deg. C. As an experimental equipment for high temperature fatigue tests, an electric servo-hydraulic fatigue machine(Instron model 1350) was used. This paper presents the effects of creep hold time and plastic strain range on push-pull high temperature low cycle fatigue life and fracture behavior. The fracture surfaces were observed by means of the scanning electron microscope. The results are as follows. (1) The fatigue life decreases with increase of the plastic strain range equal hold time and also decreases as the hold time is getting longer. (2) The frequency modified damage function can predict fatigue life by incorporating a variation of Coffin's frequency modified approach into damage function. (3) The ratios of creep damage and fatigue damage can be calculated by using he linear accumulation damage concept and the ratio of creep damage increases as the hold time is getting longer. (4) At the creep hold time of 5 minutes and the strain range of 2.0%, the fracture mode was intergranular fracture and striations were hardly observed. In this case, the intergranular cracking was originated in void type('.gamma.' type) cracking.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.425-433
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• 2001

A correlation between fatigue damage and acousto-ultrasonic (AU) parameters has been obtained from signals acquired during fatigue loading of the single-lap joints of a carbon-fiber reinforced plastic (CFRP) laminates and A16061 plate. The correlation showed an analogy to those representing the stiffness reduction $(E/E_0)$ of polymer matrix composites by the accumulation of fatigue damage. This has been attributed to the transmission characteristics of acoustic wave energy through bonded joints with delamination-type defects and their influence on the change of spectral content of AU signals. Another correlation between fatigue cycles and the spectral magnitude of acoustic emission (AE) signals has also been found during the final stage of fatigue loading. Both AU and AE can be applied almost in real-time to monitor the evolution of damage during fatigue loading.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.511-523
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• 2023

Research on the integration of unmanned aerial vehicles and deep learning for reinforced concrete damage detection is actively underway. Convolutional neural networks have a high impact on the performance of image classification, detection, and segmentation as backbones. The MobileNet, a pre-trained convolutional neural network, is efficient as a backbone for an unmanned aerial vehicle-based damage detection model because it can achieve sufficient accuracy with low computational complexity. Analyzing vanilla convolutional neural networks and MobileNet under various conditions, MobileNet was evaluated to have a verification accuracy 6.0~9.0% higher than vanilla convolutional neural networks with 15.9~22.9% lower computational complexity. MobileNetV2, MobileNetV3Large and MobileNetV3Small showed almost identical maximum verification accuracy, and the optimal conditions for MobileNet's reinforced concrete damage image feature extraction were analyzed to be the optimizer RMSprop, no dropout, and average pooling. The maximum validation accuracy of 75.49% for 7 types of damage detection based on MobilenetV2 derived in this study can be improved by image accumulation and continuous learning.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1122-1126
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• 2009

The exogenously added cadaverine is effective in protecting Vibrio vulnificus from methyl viologen (MV)-induced superoxide stress at pH 8.5. Such a protective effect by cadaverine was not observed at pH 7.5. Consistently, the accumulated level of intracellular cadaverine at pH 8.5 is approximately four times as much as that of the control cell at pH 7.5. Cadaverine accumulation is not affected by MV. The protection of V. vulnificus by cadaverine from superoxide stress was abolished when cadB coding for the lysine-cadaverine antiporter was interrupted. However, the cadaverine-mediated protection was complemented with cadB DNA. Therefore, CadB of V. vulnificus not only acts as a lysine-cadaverine antiporter at acid pH to neutralize the external medium, but also mediates cadaverine uptake at alkaline pH to result in cell protection from superoxide stress.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1097-1104
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• 1994

The external loads applied to a real structure may cause a severe damage and may eventually lead to total failure. It is thus the requirement that the structure must be designed to fulfil its safe function under any anticipated loads and must have the desired level of safety. The purpose of the present study is to propose a method of damage accumulation under seismic loadings to utilize it in the safety assessment of a reinforced concrete structure. To this end, the nonlinear hysteretic behavior of reinforced concrete structures is first modeled and the equivalent linearization technique is employed to solve numerically the probabilistic characteristics of response under random seismic loadings.

• Advances in concrete construction
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• v.9 no.5
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• pp.469-478
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• 2020

This study aims to establish a new methodological framework for the evaluation of the evolution of the reliability of plain concrete for pavement vs number of cycles under flexural fatigue loading. According to the framework, a new method calculating the reliability was proposed through probability simulation in order to describe a random accumulation of fatigue damage, which combines reliability theory, one-to-one probability density functions transformation technique, cumulative fatigue damage theory and Weibull distribution theory. Then the statistical analysis of flexural fatigue performance of cement concrete tested was carried out utilizing Weibull distribution. Ultimately, the reliability for the tested cement concrete was obtained by the proposed method. Results indicate that the stochastic evolution behavior of concrete materials under fatigue loading can be captured by the established framework. The flexural fatigue life data of concrete at different stress levels is well described utilizing the two-parameter Weibull distribution. The evolution of reliability for concrete materials tested in this study develops by three stages and may corresponds to develop stages of cracking. The proposed method may also be available for the analysis of degradation behaviors under non-fatigue conditions.

• Wind and Structures
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• v.31 no.3
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• pp.217-227
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• 2020

Based on translation models, both Gaussian and non-Gaussian wind fields are generated using spectral representation method for investigating the influence of non-Gaussian characteristics and directivity effect of wind load on fatigue damage of wind turbine. Using the blade aerodynamic model and multi-body dynamics, dynamic responses are calculated. Using linear damage accumulation theory and linear crack propagation theory, crack initiation life and crack propagation life are discussed with consideration of the joint probability density distribution of the wind direction and mean wind speed in detail. The result shows that non-Gaussian characteristics of wind load have less influence on fatigue life of wind turbine in the area with smaller annual mean wind speeds. Whereas, the influence becomes significant with the increase of the annual mean wind speed. When the annual mean wind speeds are 7 m/s and 9 m/s at hub height of 90 m, the crack initiation lives under softening non-Gaussian wind decrease by 10% compared with Gaussian wind fields or at higher hub height. The study indicates that the consideration of the influence of softening non-Gaussian characteristics of wind inflows can significantly decrease the fatigue life, and, if neglected, it can result in non-conservative fatigue life estimates for the areas with higher annual mean wind speeds.