• Korean Journal of Materials Research
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• v.18 no.1
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• pp.38-44
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• 2008

The micro-structural changes, strength characteristics, and micro-fractural behaviors at the joint interface between a Sn-4.0wt%Ag-0.5wt%Cu solder ball and UBM treated by isothermal aging are reported. From the reflow process for the joint interface, a small amount of intermetallic compound was formed. With an increase in the isothermal aging time, the type and amount of the intermetallic compound changed. The interface without an isothermal treatment showed a ductile fracture. However, with an increase in the aging time, a brittle fracture occurred on the interface due mainly to the increase in the size of the intermetallic compounds and voids. As a result, a drastic degradation in the shear strength was observed. From a microshear test by a scanning electron microscope, the generation of micro-cracks was initiated from the voids at the joint interface. They propagated along the same interface, resulting in coalescence with neighboring cracks into larger cracks. With an increase in the aging time, the generation of the micro-structural cracks was enhanced and the degree of propagation also accelerated.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.633-639
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• 2018

In anion exchange membrane fuel cells, Pd nanoparticles are extensively studied as promising non-Pt catalysts due to their electronic structure similar to Pt. In this study, to fabricate Pd nanoparticles well dispersed on carbon support materials, we propose a synthetic strategy using mixed organic ligands with different chemical structures and functions. Simultaneously to control the Pd particle size and dispersion, a ligand mixture composed of oleylamine(OA) and trioctylphosphine(TOP) is utilized during thermal decomposition of Pd precursors. In the ligand mixture, OA serves mainly as a reducing agent rather than a stabilizer since TOP, which has a bulky structure, more strongly interacts with the Pd metal surface as a stabilizer compared to OA. The specific roles of OA and TOP in the Pd nanoparticle synthesis are studied according to the mixture composition, and the oxygen reduction reaction(ORR) activity and durability of highly-dispersed Pd nanocatalysts with different particles sizes are investigated. The results of this study confirm that the Pd nanocatalyst with large particles has high durability compared to the nanocatalyst with small Pd nanoparticles during the accelerated degradation tests although they initially indicated similar ORR performance.

• Korean Journal of Veterinary Research
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• v.59 no.3
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• pp.133-139
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• 2019

Autophagy is a fundamental cellular process that maintains homeostasis and cell integrity, under stress conditions. Although the involvement of autophagy in various conditions has been elucidated, the role of autophagy in renal structure is not completely clarified. Our aim was to investigate the cytoprotective effect of autophagy against acute kidney injury (AKI) through cisplatin deteriorative pathway, which leads to AKI via renal cell degradation. For in vivo experiments, male Sprague Dawley rats were divided in to 2 groups (n = 6/group) as control, Cis-5D. Following a single intraperitoneal injection of cisplatin, rats were sacrificed after 5 days. Blood urea nitrogen (BUN), creatinine (Cr) and histological alterations were examined. Further, expression of key regulators of autophagy, light-clain 3 (LC3), p62, and Beclin1, was evaluated by immunohistochemistry (IHC). The rats exhibited severe renal dysfunction, indicated by elevated BUN, Cr. Hematoxylin and eosin staining revealed histological damages in cisplatin-treated rats. Furthermore, IHC analysis revealed increased expression of LC3, Beclin1 and decreased expression of p62. Furthermore, expression of aforementioned autophagy markers was restricted to proximal tubule. Taken together, our study demonstrated that cisplatin can cause nephrotoxicity and lead to AKI. This phenomenon accelerated autophagy in renal proximal tubules and guards against AKI.

• Journal of Industrial Convergence
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• v.18 no.6
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• pp.33-39
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• 2020

The multi-screen image system could make the audiences appreciate contents without special devices by expansively composing the images played on a single screen to many facets suitable for the use, which could provide the great immersiveness to the audiences. Based on the recent interest in realistic images, it is produced as films through the multi-projection technology such as Screen X or Escape, and it is developed into the media that could deliver stories and information. Also, the size of display tends to gradually get larger while the image quality is improved to high definition. Thus, the development is accelerated in the form of Digital Signage that could play the high definition image contents by solidly composing many HD or UHD display screens. Moreover, through the convergence of digital technologies, it is developed into the higher value-added industry that could have two-way communication. This study aims to understand the developmental history of multi-screen image from 1950 to the present, technical analysis, and the production method, and then to research how to minimize the image degradation when playing the contents, in various platforms using the multi-screen image.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.6-10
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• 2021

The shorting resistance (SR) of the PEMFC(Proton Exchange Membrane Fuel Cell) polymer membrane is an important indicator of the durability of the membrane. When SR decreases, shorting current (SC) increases, reducing durability and performance. When SR becomes less than about 0.1 kΩ·㎠, shorting occurs, the temperature rises rapidly, and MEA(Membrane Electrode Assembly) is burned to end stack operation. In order to prevent shorting, we need to control the SR, so the conditions affecting the SR were studied. There were differences in the SR measurement methods, and the SR measurement method, which improved the DOE(Department of Energy) and NEDO(New Energy and Industrial Technology Development Organization) method, was presented. It was confirmed that the SR decreases as the relative humidity, temperature and cell compression pressure increase. In the final stage of the accelerated durability evaluation process of the polymer membrane, SR rapidly decreased to less than 0.1 kΩ·㎠, and the hydrogen permeability became higher than 15 mA/㎠. After dismantling the MEA, SEM(Scanning Electron Microscope) analysis showed that a lot of platinum was distributed inside the membrane.

• Composites Research
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• v.22 no.3
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• pp.18-28
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• 2009

Blends of poly(lactic acid) (PLA) and poly(butylene terephthalate) (PBT) were prepared by reaction extrusion with para-phenylene diisocyanate (PPDI). The crystallization behavior and biodegradability were investigated by using a differential scanning calorimeter (DSC), a wide angle X-ray diffractometer (WAXD), a contact angle goniometer, and a buffer solution containing esterase. The addition of PBT into PLA polymer matrix induced the cold crystallization of PLA phase, and the crystallization rate of PLA phase was significantly accelerated when both PBT and PPDI participated in the reaction with PLA simultaneously. But the chain extension caused by PPDI decreased the crystallinity and hydrophilicity of PLA and PBT phases. The crystallinity and hydrophilicity did not affect the biodegradability of PLA/PBT blends. However, phase separation between PLA and PBT in PLA/PBT blends increased the interfacial area exposed to the hydrolysis of enzyme, resulting in the improved degradability rate of PLA phase. In contrast, the improved interfacial adhesion between PLA and PBT matrices by the reaction with PPDI reduced the area exposed to the enzyme to decrease the degradation rate of PLA phase.

• The Korean Journal of Physiology and Pharmacology
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• v.27 no.4
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• pp.407-416
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• 2023

The regeneration of myocardium following acute circulatory events remains a challenge, despite numerous efforts. Mesenchymal stem cells (MSCs) present a promising cell therapy option, but their differentiation into cardiomyocytes is a time-consuming process. Although it has been demonstrated that PSME4 degrades acetyl-YAP1, the role of PSME4 in the cardiac commitment of MSCs has not been fully elucidated. Here we reported the novel role of PSME4 in MSCs cardiac commitment. It was found that overnight treatment with apicidin in primary-cultured mouse MSCs led to rapid cardiac commitment, while MSCs from PSME4 knock-out mice did not undergo this process. Cardiac commitment was also observed using lentivirus-mediated PSME4 knockdown in immortalized human MSCs. Immunofluorescence and Western blot experiments revealed that YAP1 persisted in the nucleus of PSME4 knockdown cells even after apicidin treatment. To investigate the importance of YAP1 removal, MSCs were treated with shYAP1 and apicidin simultaneously. This combined treatment resulted in rapid YAP1 elimination and accelerated cardiac commitment. However, overexpression of acetylation-resistant YAP1 in apicidin-treated MSCs impeded cardiac commitment. In addition to apicidin, the universal effect of histone deacetylase (HDAC) inhibition on cardiac commitment was confirmed using tubastatin A and HDAC6 siRNA. Collectively, this study demonstrates that PSME4 is crucial for promoting the cardiac commitment of MSCs. HDAC inhibition acetylates YAP1 and facilitates its translocation to the nucleus, where it is removed by PSME4, promoting cardiac commitment. The failure of YAP1 to translocate or be eliminated from the nucleus results in the MSCs' inability to undergo cardiac commitment.

• Journal of Life Science
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• v.18 no.10
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• pp.1447-1454
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• 2008

Effect of heat processing on thermal stability of kudzu root isoflavone was investigated for future use such as various processed foods and functional foods. Kudzu root extracts were heated at 80, 100, 121, 140, 165, and $180^{\circ}C$ for up to 90 minutes before and after concentration, respectively. Changes in the amount of isoflavones were monitored using HPLC and thermal stability was investigated using Arrhenius equation. The amount of both daidzin and genistin decreased slightly during heating at 80, 100 and $121^{\circ}C$ but decreased significantly above $140^{\circ}C$. This indicated that daidzin and genistin are stable at temperatures near the boiling point of water. The degradation of both daidzin and genistin occurred in two steps and each step showed typical first order kinetic. The degradation rates were faster in the first step than the second step in both daidzin and genistin. Additionally, the degradation was accelerated when they heated after concentration compared to the sample heated before concentration. These results suggested that degradation of kudzu root isoflavone was highly dependent on both their concentration and heating temperature. This study provides the basic information on thermal stability of kudzu root isoflavones, which can be used for future processing of functional foods.

• Journal of Food Hygiene and Safety
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• v.15 no.2
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• pp.144-150
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• 2000

The present study was peformed to determine the hydrolysis rate constants and degradation products of phosphamidon and proffnofos by the OECD method. Hydrolysis rate constants of phosphamidon in pH 4, pH 7, and pH 9 buffer solutions at 25 and 40$^{\circ}$C were 0.0020, 0.0022, 0.0049 and 0.0040, 0.0050, 0.0150, respectively. Hydrolysis rate of phosphamidon was accelerated by temprerature change under same pH conditions, and half-life of phosphamidon in pH 9 at 40。C was 3 times faster than that at 25。C. Hydrolysis rate of phosphamidon in alkaline solution(pH 9) was 2~4 times faster than that in acidic solution(pH 4) and neutral solution(pH 7) under same temperature. Hydrolysis rate constants of profenofos in pH 4, pH 7, and pH 9 buffer solutions at 25 and 40。C were 0.0022, 0.0047, 0.0860 and 0.0035, 0.0086, 0.1245, respectively. Hydrolysis rate of profenofos was accelerated by temprerature change under same pH conditions. Hydrolysis rate of profenofos in alkaline solution(pH 9) was 15~40 times faster than in acidic solution(pH 4) and neutral solution(pH 7) under same temperature condition, and half-life of profenofos was very fast within 8 hours. The hydrolysis rate of profenofos was faster than that of phosphamidon. In order to identify hydrolysis products, the extracts of degradation products were analyzed by GC/MS. The mass spectra of hydrolysis products of phosphamidon were at m/z 153 and 149, those of the profenofos were at m/z 208 and 240, respectively. The hydrolysis products of phosphamidon were O, O-dimethyl phosphate(DMP) and N, N-diethylchloroacetamide, and those of profenofos were 4-bromo-2-chlorophenol and O-ethyl-S-propyl phosphate.

• Korean Journal of Food Science and Technology
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• v.29 no.2
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• pp.211-217
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• 1997

The physical and chemical stability of anthocyanins from a Korean pigmented rice variety was investigated at various conditions of pH, temperature, metal ion, sugar, organic acid and light. The anthocyanin pigments were relatively stable with half-lives of 36 days (pH 2.0) and 17 days (pH 3.0), while they were decomposed in a day at neutral and basic pH of 7.0 and 9.0 at $25^{\circ}C$. The anthocyanins also showed high thermal stability at pH 3.0; the half-lives were 7.4 hr, 23.6 hr and 96.3 hr at $95^{\circ}C,\;75^{\circ}C\;and\;50^{\circ}$, respectively. Addition of di- and tri-valent metal ions at pH 3.0 resulted in the increase of color intensity and stability throughout 21 days of storage periods at $25^{\circ}C$. Most sugars added accelerated the degradation of anthocyanin pigments, so that fructose showed the greatest degradation effect on the pigments. Addition of citric acid at pH 3.0 increased stability of anthocyanins, while tartaric acid decreased stability. The anthocyanins were very sensitive on light irradiation with a degradation half-life of 14 hr under 20,000 lux-light dosage at pH 3.0.