• Korea-Australia Rheology Journal
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• v.11 no.4
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• pp.321-328
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• 1999

This paper discusses the rheology of complex interfaces comprised of amphiphilic materials that are susceptible to flow-induced orientation and deformation. The consequence of the coupling of the film micro-structure to flow leads to nonlinear rheology and surface fluid dynamics. Experimental methods designed to determine the mechanical rheological material functions of fluid-fluid interfaces as well as local, molecular and morphological responses are presented. These include a newly developed interfacial stress rheometer, flow ultraviolet dichroism, and Brewster-angle microscopy. These techniques are applied to a number of complex interfaces ranging from low molecular weight amphiphiles to polymer monolayers. Nonlinear flow phenomena ranging from two-dimensional nematic responses to highly elastic surface flows that manifest surface normal stress differences and elongational viscosities are described.

• Corrosion Science and Technology
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• v.4 no.1
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• pp.33-38
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• 2005

Some feasibility studies are conducted to produce an advanced ceramic coating, which reveals superior chemical and mechanical strength, on metal base structure used in chemical plant. This advanced coating on metallic frame can replace ceramic delivery pipe and reaction chamber used in chemical plant, which are operated in hi-temperature and corrosive/erosive environment. An dual spraying is adopted to reduce the residual stress in order to increase the coating thickness and the residual stress is estimated by in-situ manner. Then new methodology is tried to form special coating of yttrium aluminum garnet(YAG), which reveals hi-strength and low-creep rates at hi-temperature, superior anti-corrosion property, hi-stability against Alkali-Vapor corrosion, and so on, on iron base structure. To verify the formation of YAG during thermal spraying, XRD(X ray diffraction) technique was used.

• Journal of Microbiology and Biotechnology
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• v.20 no.12
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• pp.1677-1680
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• 2010

The harmful effects of succinic acid and oxidative stress on cell growth were determined during batch fermentation with Mannheimia succiniciproducens LPK7, a powerful succinic acid-producing strain, and conditions were optimized to minimize these effects. In terms of toxicity, the cell concentration decreased as the concentration of succinic acid increased. By changing the pH from 6.5 to 7 during fermentation, the cell concentration increased by about 10%, and the level of succinic acid production was 6% higher than that of the control. In addition, by introducing protectants, the cell concentration increased by about 10%, and the level of succinic acid produced was increased by 3%.

• Elastomers and Composites
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• v.47 no.4
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• pp.336-340
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• 2012

Residual stress in the injection molded part is originated from thermal shrinkage and shear stress during injection molding process. There are many measurement methods of residual stress in the plastic part. Residual stress in opaque products can be measured by chemical cracking test. This method enables the solvent and specimen to react and to cause cracks. Cracks developed according to the level of residual stress. Thus the stresses in plastic part can be quantitatively measured by counting the number of cracks or measuring the size of cracks. Relationship between stress and number of cracks in a plastic specimen has been investigated in this study. Bergen jig was used to give a strain in the specimens those were molded using PC/PBT and PC/ABS. Solvent for the chemical cracking test was prepared using tetrahydrofuran and methyl alcol with the ratio of 1 to 3. Stresses in the specimen can be calculated by strains those were imposed by Bergen jig. Cracks were developed for stress higher than certain level. The number of cracks increased by second order function for stress.

• Proceedings of the Korean Society of Rheology Conference
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• 2001.09a
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• pp.165.5-165
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• 2001

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.701-706
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• 1999

The effect of siloxane oligomer content on thermal stability and internal stress of DGEBA epoxy resin was investigated. Siloxane-epoxy polymers having terminal epoxy group were prepared by reaction of siloxane-DDM prepolymer with DGEBA epoxy resin. Thermal stability was studied in terms of the initial decomposition temperature(IDT), temperature of maximum rate of weight loss($T_{max}$), integral procedural decomposition temperature(IPDT), and decomposition activation energy($E_t$) using TGA data. The thermal stability increased with increasing the siloxane oligomer content and showed a maximum value in the case of 5 wt% siloxane oligomer content in the blend system. While, the coefficient of thermal expansion(${\alpha}_r$) and the flexural modulus($E_r$) allowed us to study internal stress of the blend system. As the content of siloxane oligomer increases, the internal stress systematically decreases as decreasing both ${\alpha}_r$ and $E_r$.

• Elastomers and Composites
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• v.42 no.4
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• pp.201-208
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• 2007

In this study, the thermal shrinkage and expansion stresses of filled NR and SBR vulcanizates were measured to investigate the dimensional stability at an elevated temperature. When a rubber sample was held at constant pre-strain, a thermal stress developed upon heating due to the entropic consideration. The peak shrinkage stress of carbon black or silica filled NR decreased with increasing filler content. In SBR compounds, however, the peak shrinkage stress of SBR with 30 phr filler content was higher than that of unfilled compounds. The expansion stress of carbon black filled NR was changed little, but that of filled SBR increased with increasing the filler content. The peak expansion stress of silica filled NR and SBR vulcanizates increased with increasing silica content.

• International Journal of Oral Biology
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• v.45 no.4
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• pp.190-196
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• 2020

Several factors, including genetic and environmental insults, impede protein folding and secretion in the endoplasmic reticulum (ER). Accumulation of unfolded or mis-folded protein in the ER manifests as ER stress. To cope with this morbid condition of the ER, recent data has suggested that the intracellular event of an unfolded protein response plays a critical role in managing the secretory load and maintaining proteostasis in the ER. Tauroursodeoxycholic acid (TUDCA) is a chemical chaperone and hydrophilic bile acid that is known to inhibit apoptosis by attenuating ER stress. Numerous studies have revealed that TUDCA affects hepatic diseases, obesity, and inflammatory illnesses. Recently, molecular regulation of ER stress in tooth development, especially during the secretory stage, has been studied. Therefore, in this study, we examined the developmental role of ER stress regulation in tooth morphogenesis using in vitro organ cultivation methods with a chemical chaperone treatment, TUDCA. Altered cellular events including proliferation, apoptosis, and dentinogenesis were examined using immunostaining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. In addition, altered localization patterns of the formation of hard tissue matrices related to molecules, including amelogenin and nestin, were examined to assess their morphological changes. Based on our findings, modulating the role of the chemical chaperone TUDCA in tooth morphogenesis, especially through the modulation of cellular proliferation and apoptosis, could be applied as a supporting data for tooth regeneration for future studies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.533-533
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• 2007

The stress effect of SiGe p-type metal oxide semiconductors field effect transistors(MOSFETs) has been investigated to compare device properties using Si bulk and partially depleted silicon on insulator(PD SOI). The electrical properties in SiGe PD SOI presented enhancements in subthreshold slope and drain induced barrier lowering in comparison to SiGe bulk. The reliability of gate oxides on bulk Si and PD SOI has been evaluated using constant voltage stressing to investigate their breakdown (~ 8.5 V) characteristics. Gate leakage was monitored as a function of voltage stressing time to understand the breakdown phenomena for both structures. Stress induced leakage currents are obtained from I-V measurements at specified stress intervals. The 1/f noise was observed to follow the typical $1/f^{\gamma}$ (${\gamma}\;=\;1$) in SiGe bulk devices, but the abnormal behavior ${\gamma}\;=\;2$ in SiGe PD SOI. The difference of noise frequency exponent is mainly attributed to traps at silicon oxide interfaces. We will discuss stress induced instability in conjunction with the 1/f noise characteristics in detail.

• Toxicological Research
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• v.28 no.4
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• pp.269-277
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• 2012

The purpose of this study was to understand the mechanism of cardiovascular disease (CVD) caused by exposure to hazardous chemicals. We investigated changes in the symptoms of metabolic syndrome, which is strongly related to CVD, and in levels of other CVD risk factors, with a special emphasis on the roles of catecholamines and oxidative stress. The results revealed that neither body mass index (BMI) nor waist and hip circumferences were associated with exposure to hazardous chemicals. Among metabolic syndrome criteria, only HDL-cholesterol level increased on exposure to hazardous chemicals. Levels of epinephrine (EP) and norepinephrine (NEP) were not influenced by exposure to hazardous chemicals; however, the total antioxidative capacity (TAC) reduced because of increased oxidative stress. Both hazardous chemical exposure level and metabolite excretion were related to EP, NEP, and the oxidative stress index (OSI). Logistic regression analysis with these factors as independent variables and metabolic syndrome criteria as dependent variables revealed that EP was associated with blood pressure, and NEP with metabolic syndrome in the chemical-exposed group. In conclusion, the results suggest that reactive oxygen species generated and oxidative stress due to exposure to hazardous chemicals act as mediators and cause changes in the physiological levels of EP and NEP to increase blood pressure. This ultimately leads to the development of CVD through increase in cholesterol, triglyceride, and blood glucose levels by lipid peroxidation.