• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.81-87
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• 2019

In this study, synthetic methods and physical properties for a new class of glycidyl azide polymer (GAP) were investigated for energetic thermoplastic elastomers (ETPE). Four kinds of GAP copolymer polyols were synthesized by introducing nucleophiles such as azide, alkoxide and alkyl amine into poly(epichlorohydrin) (PECH). The GAP copolymer synthetic reaction can be evaluated as an environmental benign and efficient synthetic method due to the simultaneous one-step reaction using two kinds of nucleophiles and the complete consumption of sodium azide. The relative stoichiometric substitution ratio analysis and the progress of reaction were checked and monitored by inverse gated decoupled $^{13}C$ NMR and Fourier transform infrared (FT-IR) spectroscopy. The glass transition temperature and molecular weight were measured by differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) analysis. The synthesized poly($GA_{0.8}-butoxide_{0.2}$), poly($GA_{0.7}-n-butylamine_{0.3}$), poly($GA_{0.7}-dipropylamine_{0.3}$) and poly($GA_{0.7}-morpholine_{0.3}$) had a glass transition temperature ranged from -39 to $-26^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.64 no.6
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• pp.360-370
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• 2020

This study explored the learning environment for promoting conceptual understanding, immersion, and situational interest in small group learning using augmented reality, according to the level of students' self-regulation. 95 ninth-grade students from a coed high school in Seoul participated in this study. Students were divided into a group of four and each group was randomly assigned to three learning environments that provide one marker and one smart device(1-1), two markers and two smart devices(2-2), and four markers and four smart devices(4-4) for a group. Small group learning using augmented reality was conducted for two class periods about the chemical bonding concept from the Integrated Science subject. Two-way ANOVA results revealed that students in the 4-4 learning environment scored significantly higher than those in the 1-1 or 2-2 learning environment in a conception test. Changes in the learning environment have affected students with a low level of self-regulation. In an immersion test, students in the 4-4 learning environment scored significantly higher than those in the 1-1 learning environment, and changes in the learning environment have affected students with a high level of self-regulation. As a result of situational interest test, students in the 4-4 and 2-2 learning environments scored significantly higher than those in the 1-1 learning environment, and changes in the learning environment have affected students with a low and a high level of self-regulation. Based on the results, the educational implications of the learning environment for promoting conceptual understanding, immersion, and situational interest in small group learning using augmented reality are discussed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.905-917
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• 2021

Atmospheric pollutant emissions, mainly exhaust gas emissions from vessels, and the resultant social costs of pollution in the Korean harbor cities of Incheon, Mokpo, Gwangyang, Busan and Ulsan, are examined in this study, and the need for an emissions reduction plan is highlighted. Busan had several vessels entering its port, while Mokpo had few vessels, yet the vessels emission contribution was high in both the cities. Ulsan had world-class heavy-chemical industries, Gwangyang had steel mills and Incheon had a manufacturing industry and more vessels entering its port than Mokpo, yet the emission contribution was low in these cities. By calculating exhaust gas emissions from the vessels, it was found that CO₂ was the highest, followed by NOx and SOx. By vessel type, Busan, Ulsan, and Incheon had more oil tank vessels, Gwangyang had more cargo vessels, and Mokpo had more ferries. As a result of social cost, Busan paid the highest, while the highest emission was PM. The use of low-sulfur oil can directly reduce PM and, SOx emissions and indirectly reduce NOx emissions. However, in order to reduce high CO₂ emissions, only low-sulfur oil will not help. Therefore, the study suggested the need for reduction plan that use of fossil fuels, by using alternative maritime power (AMP).

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.2
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• pp.171-181
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• 1999

A field experiments was carried out to investigate the physicochemical properties of soil and cucumber growth in vinyl house when irrigation point was made at 0.2, 1/3, 0.5 and 1.0 bar. The obtained results was summarized as follow: The taxonomic class of the soil used was loam and each content of the required water was 4.4, 7.3, 9.6 and 13.4 mm per each irrigation time at 0.2, 1/3, 0.5 and 1.0 bar treatments in spring culture, respectively. At 0.2 bar and 1.0 bar treatments, interval of irrigation was 2.3 and 14.8 day, the times of irrigation was 37 and 6, and total irrigation volume was 163.5 and 80.3 mm, respectively. After cucumber culture, pH, EC concentration and exchangeable K content of soil at 0.2 bar treatment was distributed near to the level of improvement target while EC, available $P_2O_5$ and exchangeable base content in other treatments were higher compared to improvement target. At 1.0 bar treatment, ratios of the solid and liquid phase were 44.9 and 27.1%, respectively, and bulk density was $1.26g\;cm^{-3}$ which was the highest among the treatments. At 0.2 bar treatment, the ratio of the solid and liquid phase was 41.7 and 22.8%, respectively, and bulk density was $1.09g\;cm^{-3}$ which was the lowest. The root length and radius at 0.2 bar treatment were best, while those at 1/3 bar were worst. At 0.2 bar treatment, the total yield was 7,269 kg and the weight of good products was 5,677 kg which was the highest among treatments. At 0.33 bar treatment, the yield was the lowest with the high ratio of deformity.

• Applied Biological Chemistry
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• v.23 no.2
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• pp.131-139
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• 1980

TOK (2,4-Dichlolo-4'-nitrodiphenyl ether) was applied to two Korean soils possessing different physico-chemical properties at a certain concentration and incubated for a certain time under flooded conditions. The metabolites and the soil microorganisms involved in the degradation of TOK are studied. Chong Ju and Chung Ju soils treated with TOK at a concentration of 500 ppm and incubated for two, four, and six months at $30^{\circ}C$ yielded 4-chloro-4'-amino diphenyl ether, 2, 4-dichloro-4'-amino diphenyl ether(amino-TOK), N-[4'-(4-chloro-phenoxy)] phenyl acetamide, and N-[4'-(4-chloro-phenoxy)] phenyl formamide as the major metabolites. TOK underwent the reduction of nitrogroup to amino group, dechlorination, acetylation, and formylation. No cleavage at the ether linkage was recognized. TOK was more readily degraded in Chung Ju soil which is characterized by the higher pH (PH 6.43), clay loam in textural class, and the higher cation exchange capacity. The toxicity of TOK as a possible environmental contaminant is expected to be considerably reduced as a result of the above degradation Twelve strains of soil bacteria were isolated from the TOK-treated Chong Ju and Chung Ju soils. As a result of the incubation of TOK in pure cultures of the isolates, T-1-1 strain isolated from Chong Ju soil had almost no degradability, whereas T-2-3 strain turned out to be the most potent. The degradation of TOK by the isolates constituted mostly the reduction of the nitro group to amino group. The citrate buffer extract of Chung Ju soil reduced TOK more readily to amino-TOK than that of Chong Ju soil.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.12
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• pp.1718-1734
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• 2009

The aim of this review is to address some characteristics that influence meat quality. Genetic groups, nutrition, finishing systems and gender are the major factors that change carcass characteristics, chemical composition and fatty acid profile. Genetic groups that have zebu genes in their composition show higher hot carcass dressing than genetic groups without zebu genes. Genetic groups that have European breeds in their composition have higher marbling scores. On the other hand, genetic groups that have zebu breeds show low marbling scores. Bulls finished in feedlots present higher final weight than steers, cull cows and heifers. Fat thickness is one of the principal parameters that are affected by different gender. Cull cows (4.72 mm) and heifers (4.00 mm) present higher values than bulls (1.75 mm) and steers (2.81 mm). The major effects observed by different systems of termination are fat thickness and marbling. Crude protein presents variation due to nutrition. Nutrition influences variation of fatty acid profile. Genetic groups also influence fatty acid profile. Genetic groups that have zebu genes in their composition show high percentage of PUFA. The major class of fatty acids that is changed with nutrition is PUFA. The better ratios of PUFA/SFA and n-6/n-3 are found in Longissimus muscle of animals finished in pasture systems.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.1
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• pp.255-260
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• 2012

Patients with non-small cell lung cancer (NSCLC) who have activating epidermal growth factor receptor (EGFR) mutations derive clinical benefit from treatment with EGFR-tyrosine kinase inhibitors ((EGFR-TKIs)-namely gefitinib and erlotinib. However, these patients eventually develop resistance to EGFR-TKIs. Despite the fact that this acquired resistance may be the result of a secondary mutation in the EGFR gene, such as T790M or amplification of the MET proto-oncogene, there are other mechanisms which need to be explored. MicroRNAs (miRs) are a class of small non-coding RNAs that play pivotal roles in tumorigenesis, tumor progression and chemo-resistance. In this study, we firstly successfully established a gefitinib resistant cell line-HCC827/GR, by exposing normal HCC827 cells (an NSCLC cell line with a 746E-750A in-frame deletion of EGFR gene) to increasing concentrations of gefitinib. Then, we found that miR-214 was significantly up-regulated in HCC827/GR. We also showed that miR-214 and PTEN were inversely expressed in HCC827/GR. Knockdown of miR-214 altered the expression of PTEN and p-AKT and re-sensitized HCC827/GR to gefitinib. Taken together, miR-214 may regulate the acquired resistance to gefitinib in HCC827 via PTEN/AKT signaling pathway. Suppression of miR-214 may thus reverse the acquired resistance to EGFR-TKIs therapy.

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.2083-2086
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• 2009

Human vascular endothelial growth factor receptor 2 (hVEGFR2) is an important signaling protein involved in angiogenesis and attractive drug target in cancer therapy. It has been reported that flavonols, a class of flavonoids, have anti-angiogenic activity in various cancer cell lines. We performed receptor-oriented pharmacophore based in silico screening for identification of hVEGFR2 inhibitors from flavonol database. By comparing with three X-ray complex structures of hVEGFR2 and its inhibitors, we evaluated the specific interactions between inhibitors and receptors and determined a single pharmacophore map. This map consisted of four features, a hydrogen bonding acceptor (HBA) on Cys917, two hydrogen bonding donors on Glu917 (HBD1) and Glu883 (HBD2), and one hydrophobic interaction (Lipo) with Val846, Ala864, Val897, Val914 and Phe1045 of hVEGFR2. Using this map, we searched a flavonol database including 9 typical flavonols and proposed that five flavonols, kaempferol, quercetin, fisetin, morin, and rhamnetin can be potent inhibitors of hVEGFR2. 3-OH of C-ring and 4’-OH of B-ring of flavonols are the essential features for hVEGFR2 inhibition. This study will be helpful for understanding the mechanism of inhibition of hVEGFR2 by natural products.

• Journal of The Korean Association For Science Education
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• v.23 no.3
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• pp.246-253
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• 2003

This study investigated the influences of role-playing analogy upon students' scientific conceptual understandings, application abilities, retentions of conception and application, and learning motivation. Four classes of 7th grade at a middle school in Seoul were assigned to control and treatment groups, and taught about 'motion of molecules' for 4 class hours. For the Treatment group, role-playing analogy instruction was used. The traditional instruction was used for the control group. Data analysis indicated that the scores of the treatment group were significantly higher than those of the control group in the tests on the conception, the retention of application, and the confidence. In the tests of the application, attention, and relevance, there were significant interactions between instruction and student' gender. Both female and male students in the treatment group scored significantly higher than those in the control group in the application test. In the case of attention and relevance tests, male students in the treatment group scored significantly higher than those in the control group. Educational implications are discussed.

• Analytical Science and Technology
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• v.24 no.6
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• pp.435-442
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• 2011

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants (BFRs) which have taken much interest recently due to their potential hazardous effects to human body and ecosystem. Many countries and European community prohibits the usage of certain BFRs in electronics and electronic devices (e.g. RoHS). In this perspectives, Korea Research Institute of Standards and Science (KRISS) has designed and practiced proficiency testing programs based on the ISO/IEC 17043 in order to assist laboratory accreditation activities. The programs for interlaboratory comparisons include congeners of PBDE (PBDE-154, 183, 206, 209) in high impact polystyrene (HIPS). A sample bottle that contains 10 g granular HIPS was distributed to 35 participating laboratories and the test results were calculated by the statistical procedure using z-scores to evaluate performance of each laboratory. The results and the laboratory's performance were discussed.