Daegu, South Korea
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Lee J.Y.,Kyungpook National University | Jee S.B.,Daegu Science High School | Park W.Y.,Daegu Science High School | Choi Y.J.,Daegu Science High School | And 3 more authors.
Journal of Microbiology and Biotechnology | Year: 2014

To examine the effect of tumor suppressor protein p53 on the antitumor activity of 2-methoxyestradiol (2-MeO-E2), 2-MeO-E2-induced cell cycle changes and apoptotic events were compared between the human colon carcinoma cell lines HCT116 (p53+/+) and HCT116 (p53-/-). When both cell types were exposed to 2-MeO-E2, a reduction in the cell viability and an enhancement in the proportions of G2/M cells and apoptotic sub-G1 cells commonly occurred dose-dependently. These 2-MeO-E2-induced cellular changes, except for G2/M arrest, appeared to be more apparent in the presence of p53. Immunofluorescence microscopic analysis using anti-α-tubulin and anti-lamin B2 antibodies revealed that after 2-MeO-E2treatment, impaired mitotic spindle network and prometaphase arrest occurred similarly in both cell types. Following 2-MeO-E2treatment, only HCT116 (p53+/+) cells exhibited an enhancement in the levels of p53, p-p53 (Ser-15), p21WAF1/CIP1, and Bax; however, the Bak level remained relatively constant in both cell types, and the Bcl-2 level decreased only in HCT116 (p53+/+) cells. Additionally, mitochondrial apoptotic events, including the activation of Bak and Bax, loss of Δψm, activation of caspase-9 and-3, and cleavage of lamin A/C, were more dominantly induced in the presence of p53. The Bak-specific and Bax-specific siRNA approaches confirmed the necessity of both Bak and Bax activations for the 2-MeO-E2-induced apoptosis in HCT116 cells. These results show that among 2-MeO-E2-induced apoptotic events, including prometaphase arrest, up-regulation of Bax level, down-regulation of Bcl-2 level, activation of both Bak and Bax, and mitochondria-dependent caspase activation, the modulation of Bax and Bcl-2 levels is the target of the pro-apoptotic action of p53. © 2014 by The Korean Society for Microbiology and Biotechnology.


Jeong K.H.,Kyungpook National University | Jeon M.-T.,Kyungpook National University | Kim H.D.,Kyungpook National University | Jung U.J.,Kyungpook National University | And 6 more authors.
Journal of Medicinal Food | Year: 2015

This study investigated the effect of nobiletin, a flavonoid found in citrus fruits, on the degeneration of dopaminergic (DA) neurons in a neurotoxin model of Parkinson's disease (PD). 1-Methyl-4-phenylpyridinium (MPP+) was unilaterally injected into the median forebrain bundle of rat brains (to generate a neurotoxin model of PD) with or without daily intraperitoneal injection of nobiletin. Our results showed that nobiletin treatment at 10 mg/kg bw, but not at 1 or 20 mg/kg bw, significantly protected DA neurons in the substantia nigra (SN) of MPP+-treated rats. In parallel to the neuroprotection, nobiletin treatment at 10 mg/kg inhibited microglial activation and preserved the expression of the glial cell line-derived neurotrophic factor, which is a therapeutic agent against PD, in the SN. These results suggest that the proper supplementation with nobiletin may protect against the neurodegeneration involved in PD. © 2015, Mary Ann Liebert, Inc. and Korean Society of Food Science and Nutrition.


Kim B.-G.,Kyungpook National University | Dho J.,Kyungpook National University | Jeong S.,Daegu Science High School | Shin H.B.,Daegu Science High School | And 2 more authors.
New Physics: Sae Mulli | Year: 2016

Inverse spinel NiFe2O4 (NFO) films were prepared on (110) MgAl2O4 substrates by using pulsed laser deposition. The NFO films were deposited at a substrate temperature of 600 °C and an oxygen partial pressure of 1 mTorr, and their thicknesses were in the range of 20 nm - 240 nm. As the film's thickness increased, the positon of the (440) NFO peak moved to a higher angle, implying a relaxation of the lattice strain. For 240 nm, the lattice constant of the NFO film was about 8.39 Å, which corresponded to a lattice mismatch of about 0.6% with the lattice constant of the NFO bulk. The magnetic hysteresis measurement suggested an increasing tendency of the perpendicular magnetic anisotropy with increasing film thickness. For 160 nm, the ratio of the remanent magnetization to the saturation magnetization (Mrem./Msat.) was maximally ∼0.22. The magnetic domain structure was observed by using magnetic force microscopy. The image contrast was improved with increasing film thickness, and it was the best for a film with a thickness of 160 nm.


Jang S.-Y.,Kyungpook National University | Bae J.-S.,Daegu Science High School | Lee Y.H.,Daegu Science High School | Oh K.Y.,Gyeongsang National University | And 2 more authors.
Natural Product Research | Year: 2011

A methanol extract of Houttuynia cordata showed an inhibitory effect on mammalian DNA topoisomerase I. Two topoisomerase I inhibitory compounds were purified and identified as caffeic acid and quercitrin. Caffeic acid and quercitrin inhibited the activity of topoisomerase I with IC50 values of about 0.15 and 0.05 mM, respectively. A concentration of 45μ M caffeic acid caused 50% growth inhibition in human leukaemia U937 cells, but not on those of normal fibroblast NIH3T3 cells. However, quercitrin mysteriously stimulated proliferation of U937 and NIH3T3 cells. Caffeic acid-induced cell death was characterised with the cleavage of poly (ADP-ribose) polymerase and procaspase-3, indicating that this inhibitor triggered apoptosis. The apoptotic induction by caffeic acid was also confirmed using flow cytometry analysis. Because DNA topoisomerase I is an important target for tumour chemotherapy, the present study suggests that caffeic acid, but not quercitrin, may function by suppressing oncogenic disease through the inhibition of cellular topoisomerase I activity. © 2011 Taylor & Francis.


Kang D.,Ulsan National Institute of Science and Technology | Kwon J.Y.,Daegu Science High School | Cho H.,Daegu Science High School | Sim J.-H.,Daegu Science High School | And 5 more authors.
ACS Nano | Year: 2012

Protecting the surface of metals such as Fe and Cu from oxidizing is of great importance due to their widespread use. Here, oxidation resistance of Fe and Cu foils was achieved by coating them with reduced graphene oxide (rG-O) sheets. The rG-O-coated Fe and Cu foils were prepared by transferring rG-O multilayers from a SiO 2 substrate onto them. The oxidation resistance of these rG-O-coated metal foils was investigated by Raman spectroscopy, optical microscopy, and scanning electron microscopy after heat treatment at 200 °C in air for 2 h. The bare metal surfaces were severely oxidized, but the rG-O-coated metal surfaces were protected from oxidation. This simple solution process using rG-O is one advantage of the present study. © 2012 American Chemical Society.


Koh J.,Korea Advanced Institute of Science and Technology | Park S.H.,Korea Advanced Institute of Science and Technology | Kim H.W.,Daegu Science High School | Kim Y.,Daegu Science High School | And 3 more authors.
International Journal of Hydrogen Energy | Year: 2015

A series of combinatorial optical screening analysis was operated, first for the selection of metal candidates for the ternary Ru-based catalyst and later for the selection of optimized compositions with high performance towards ORR. Among the binary Ru-based catalysts, combinations with Co and Se exhibited the highest performance towards ORR. To investigate a possible synergic effect from the selected metals, the ternary Ru-based combinatorial optical screening was preceded. Among the various combinations and compositions, the optimum composition towards ORR for ternary Ru-Se-Co based catalyst was chosen at 73:12:15=Ru:Se:Coat. % (named RSC-1). The RSC-1 catalyst measured a current density of -1.28mAcm-2 at 0.75V (vs. RHE), which was about 5 times higher than that of Ru/C (-0.26mAcm-2). The mass activity of RSC-1 (12.20mAmg-1) had an enhanced performance of about 6.8 times than that of Ru/C (1.78mAmg-1) at 0.75V (vs. RHE). It was deduced that a synergic effect between the repulsion of oxy-species on the Ru atoms by Se and the alternation of electron configuration by Co, the adequate amounts of Co and Se in the ternary Ru-Se-Co based catalyst could have induced the enhanced ORR performance of the RSC-1 catalyst. © 2015 Hydrogen Energy Publications, LLC.


Moon G.-H.,Daegu Science High School
Journal of Astronomy and Space Science | Year: 2012

Polar cap potential has long been considered as an indicator for the amount of energy flowing in the magnetosphere-ionosphere system. Thus, the estimation of polar cap potential is important to understand the physical process of the magnetosphere. To estimate the polar cap potential in the Northern Hemisphere, merging electric field by Kan & Lee (1979) is adopted. Relationships between the PC index and calculated merging electric field (E*) are examined during full-time and storm-time periods separately. For this purpose Dst, AL, and PC indices and solar wind data are utilized during the period from 1996-2003. From this linear relationship, polar cap potential (Φ*) is estimated using the formula by Doyle & Burke (1983). The values are represented as 58.1 ± 26.9 kV for the full-time period and 123.7 ± 84.1 kV for a storm-time period separately. Considering that the average value of polar cap potential of Doyle & Burke (1983) is about 47 kV during moderately quiet intervals with the S3-2 measurements, these results are similar to such. The monthly averaged variation of Dst, AL, and PC indices are then compared. The Dst and AL indices show distinct characteristics with peaks during equinoctial season whereas the average PC index according to the month shows higher values in autumn than in spring. The monthly variations of the linear correlation coefficients between solar wind parameters and geomagnetic indices are also examined. The PC-AL linear correlation coefficient is highest, being 0.82 with peaks during the equinoctial season. As with the AL index, the PC index may also prove useful for predicting the intensity of an auroral substorm. Generally, the linear correlation coefficients are shown low in summer due to conductance differences and other factors. To assess the role of the PC index during the recovery phase of a storm, the relation between the cumulative PC index and the duration is examined. Although the correlation coefficient lowers with the storm size, it is clear that the average correlation coefficient is high. There is a tendency that duration of the recovery phase is longer as the PC index increases. © The Korean Space Science Society.


Koh J.,Korea Advanced Institute of Science and Technology | Park S.H.,Korea Advanced Institute of Science and Technology | Kim H.W.,Daegu Science High School | Kim Y.,Daegu Science High School | And 3 more authors.
20th World Hydrogen Energy Conference, WHEC 2014 | Year: 2014

A series of combinatorial optical screening analysis was operated, first for the selection of metals adequate for the ternary Ru-based catalyst and later for the selection of the optimized compositions with high performance towards ORR. Among the binary Ru-based catalysts (Co, Cu, and etc), Co and Se exhibit higher performance towards ORR compared to other binary Ru-based combinations. To investigate a possible synergic effect from the selected metals, the ternary Ru-based combinatorial optical screening was preceded. The optimum composition towards ORR for ternary Ru-Se-Co based catalyst was chosen at 73: 12: 15 = Ru: Se: Co at. % (named RSC-1). The RSC-1 catalyst measured a current density of-1.28 mAcm-2 at 0.75 V (vs. RHE), which was about 5 times than that of Ru/C (-0.26 mAcm-2). The mass activity of RSC-1 (12.20 mAmg-1) had an enhanced performance of about 6.8 times than that of Ru/C (1.78 mAmg-1) at 0.75 V (vs. RHE). A synergic effect between the repulsion of oxy-species on the Ru atoms by Se and the electron modification by Co, at adequate amounts of Co and Se in the ternary Ru-Se-Co based catalyst, could have induced the enhanced ORR performance of the RSC-1 catalyst.


Koh J.,Korea Advanced Institute of Science and Technology | Park S.H.,Korea Advanced Institute of Science and Technology | Kim H.W.,Daegu Science High School | Kim Y.,Daegu Science High School | And 3 more authors.
International Journal of Hydrogen Energy | Year: 2015

A series of combinatorial optical screening analysis was operated, first for the selection of metal candidates for the ternary Ru-based catalyst and later for the selection of optimized compositions with high performance towards ORR. Among the binary Ru-based catalysts, combinations with Co and Se exhibited the highest performance towards ORR. To investigate a possible synergic effect from the selected metals, the ternary Ru-based combinatorial optical screening was preceded. Among the various combinations and compositions, the optimum composition towards ORR for ternary Ru-Se-Co based catalyst was chosen at 73:12:15 = Ru:Se:Co at. % (named RSC-1). The RSC-1 catalyst measured a current density of -1.28 mAcm-2 at 0.75 V (vs. RHE), which was about 5 times higher than that of Ru/C (-0.26 mA cm-2). The mass activity of RSC-1 (12.20 mA mg-1) had an enhanced performance of about 6.8 times than that of Ru/C (1.78 mA mg-1) at 0.75 V (vs. RHE). It was deduced that a synergic effect between the repulsion of oxy-species on the Ru atoms by Se and the alternation of electron configuration by Co, the adequate amounts of Co and Se in the ternary Ru-Se-Co based catalyst could have induced the enhanced ORR performance of the RSC-1 catalyst. Copyright © 2015 Hydrogen Energy Publications, LLC.


Moon G.-H.,Daegu Science High School
Journal of Astronomy and Space Science | Year: 2011

It is generally believed that the occurrence of a magnetic storm depends upon the solar wind conditions, particularly the southward interplanetary magnetic field (IMF) component. To understand the relationship between solar wind parameters and magnetic storms, variations in magnetic field polarity and solar wind parameters during magnetic storms are examined. A total of 156 storms during the period of 1997~2003 are used. According to the interplanetary driver, magnetic storms are divided into three types, which are coronal mass ejection (CME)-driven storms, co-rotating interaction region (CIR)-driven storms, and complicated type storms. Complicated types were not included in this study. For this purpose, the manner in which the direction change of IMF B y and B z components (in geocentric solar magnetospheric coordinate system coordinate) during the main phase is related with the development of the storm is examined. The time-integrated solar wind parameters are compared with the time-integrated disturbance storm time (Dst) index during the main phase of each magnetic storm. The time lag with the storm size is also investigated. Some results are worth noting: CME-driven storms, under steady conditions of B z < 0, represent more than half of the storms in number. That is, it is found that the average number of storms for negative sign of IMF B z (T1~T4) is high, at 56.4%, 53.0%, and 63.7% in each storm category, respectively. However, for the CIR-driven storms, the percentage of moderate storms is only 29.2%, while the number of intense storms is more than half (60.0%) under the B z < 0 condition. It is found that the correlation is highest between the time-integrated IMF B z and the time-integrated Dst index for the CME-driven storms. On the other hand, for the CIR-driven storms, a high correlation is found, with the correlation coefficient being 0.93, between time-integrated Dst index and time-integrated solar wind speed, while a low correlation, 0.51, is found between timeintegrated B z and time-integrated Dst index. The relationship between storm size and time lag in terms of hours from B z minimum to Dst minimum values is investigated. For the CME-driven storms, time lag of 26% of moderate storms is one hour, whereas time lag of 33% of moderate storms is two hours for the CIR-driven storms. The average values of solar wind parameters for the CME and CIR-driven storms are also examined. The average values of |Dst min| and |B zmin| for the CME-driven storms are higher than those of CIR-driven storms, while the average value of temperature is lower. © The Korean Space Science Society.

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