• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.3
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• pp.209-215
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• 2024

Ishige foliacea belongs to class Phaeophyceae and family Ishigeaceae. This study investigated the physiological activities of the Korean marine algae I. foliacea. Its solvent extracts were prepared with 70% ethanol, 80% methanol, and distilled water. The ethanol and methanol extracts had higher α-glucosidase (half-maximal inhibitory concentration, IC₅₀: 0.67-0.73 mg/mL), xanthine oxidase (IC₅₀: 0.25-0.28 mg/mL), and angiotensin-converting enzyme (IC₅₀: 25.29-38.28 ㎍/mL) inhibitory activities than those of the water extract. The ethanol and methanol extracts possessed high acetylcholinesterase inhibitory activity (IC₅₀: 0.78c0.97 mg/mL). Conversely, the water extract exhibited the highest β-secretase inhibitory activity (IC₅₀: 0.48 mg/mL). These results indicate that I. foliacea may be useful as a functional substance in food and pharmaceuticals with anti-diabetic, anti-gout, anti-hypertension, and anti-dementia properties.

• Journal of the Korean Chemical Society
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• v.53 no.4
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• pp.432-444
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• 2009

In this study, we investigated the perceptions and the educational needs of pre-service primary and secondary teachers on cooperative learning in science. The survey was administered to 102 seniors at the department of science education in three universities of education and 64 seniors at the department of chemistry education in three colleges of education. The results revealed that the pre-service primary and secondary teachers learned the theories and experienced the practices on cooperative learning through various methods in the several subjects, and especially had many difficulties in appling cooperative learning to the demonstrations and/or the actual science classes. The degree of their understanding on cooperative learning was comparatively high, and the perceptions on the advantage/disadvantage of cooperative learning in science, the willingness practicing it, and the outside aids influencing on implementing it were relatively positive. They highly perceived on the necessities of diverse educations related on cooperative learning in science in pre-service teacher education processes. The willingness implementing cooperative learning in science class was significantly correlated with the necessities of diverse educations. These were also significantly correlated with the perceptions on the advantage/disadvantage of cooperative learning in science, the educational assessments on the advantage/disadvantage of it, and the educational assessments on the outside aids influencing on implementing it, respectively. Educational implications of these findings are discussed.

• Journal of the Korean Chemical Society
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• v.51 no.2
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• pp.186-192
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• 2007

In this study, the effects of concept mapping on the preservice elementary teachers' achievement, conceptual understanding, anxiety toward science, and science teaching efficacy belief were investigated in the undergraduate general chemistry course. The aptitude-treatment interaction (ATI) between preservice teachers' learning approach and concept mapping strategy was also investigated. Sixty-nine freshmen from a university of education were assigned to a control group and a treatment group. Tests regarding students' learning approach, anxiety toward science, and science teaching efficacy belief were administered as pretests. Treatment lasted for 9 weeks. In every class, students in the treatment group constructed concept maps, while those in the control group solved the problems of the textbook after the lecture. After the instructions, tests of achievement, conceptual understanding, anxiety toward science, and science teaching efficacy beliefs were administered. The results indicated that students in the treatment group significantly outperformed those of the control group in the achievement test. In the conceptual understanding and the science teaching efficacy beliefs, however, no statistically significant differences were found between two groups. Students of the treatment group showed significantly higher anxiety than their counterpart in the test of anxiety toward science. No aptitudetreatment interaction between students' learning approach and the concept mapping strategy was found.

• Journal of the Korean Wood Science and Technology
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• v.41 no.4
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• pp.337-345
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• 2013

Log grading rules are essential tools to ensure the quality of logs in distribution structure. The rules should reflect the long experience and accepted usage practice in the market. A gap between the rules and market should be improved based on analysis of log qualities that produced and market demand. In this study more than ten millions logs which were produced by 5 Regional Forest Services in 2010~2011 period, were analyzed in their qualities including diameters and lengths by species. A proposal was driven to improve the current log grading rules in terms of log diameter classes and length. The followings are the summary of this study. Most of domestic softwood logs are belong to small diameter class of 100~160 mm, which imply the diameter classes of current log grading rules are immoderate. Distributions of log diameter shows distinctive patterns by species, which indicate a necessity of differentiated diameter classes by species in an improved rules. Lengths of logs in productions do not corresponding to the demands and preferences in sawmills. Therefore it is highly recommended to include log length term in an improved log grading system. Based on these findings, 6 log grading systems for 3 species groups of softwood are newly proposed to improve current log grading rules. Limits of log diameter and log length are also proposed for each log grading system.

• Analytical Science and Technology
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• v.26 no.1
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• pp.19-26
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• 2013

Gibberllic acid ($GA_3$) is one of gibberellins (GAs) that are a class of plant growth hormones that exert profound and diverse effects on plant growth and development. $GA_3$ is essentially non-UV absorbing and is difficult to assay by UV-detector. For effective extraction of gibberellic acid from fruits by using liquid-liquid extraction, optimized pH and extraction solvent were established. The selective and sensitive derivative of $GA_3$ for HPLC/UV-vis was derivatized using phenacyl bromide, and the experimental factors, including reaction time, reaction temperature and amount of derivatizing reagent and base were investigated for the effective synthesis. The derivatized $GA_3$ with phenacyl bromide was effectively analyzed by HPLC/UV-vis. The structure of derivatized $GA_3$ was confirmed by HPLC/ESI-MS. For apple, LOD and LOQ were 0.008 mg/kg and 0.027 mg/kg, respectively. For pear, LOD and LOQ were 0.003 mg/kg, 0.012 mg/kg, respectively. The established method can be applied to more effective analysis of $GA_3$ from plant and food.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.617-625
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• 2020

The purpose of this study was to elucidate the safety consciousness of high school students in chemistry-related departments in terms of disaster safety education, degree of safety education knowledge, and the relationship between safety consciousness and safety education knowledge. The subjects were 469 students attending technical high schools in Gyeonggi and Chungcheongnam-do. For the results, students responded that their level of safety consciousness (3.44) was better than that of others (2.85). In addition, safety regulations were considered in relation to others. Safety education at school was cited as necessary, but respondents were not interested in the education contents. Students had been receiving safety education at school, but they cited that the use of protective equipment in class was not performed well. Disaster awareness was positively (+) correlated, and safety and fire safety awareness were found to be significant. The results of this study can be used as basic data for safety education to improve disaster safety education. It is necessary to develop an education program to raise safety awareness and to develop an education manual. Based on this study, future studies should be conducted.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.159-164
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• 2009

Monomers of oxetane high explosives were theoretically examined in terms of reactivity, reaction mechanism and process of polymerization substituted by azido $(-CH_2N_3)$, nitrato $(-CH_2ONO_2)$ and hydrazino $(-CH_2N_2H_3)$ which belong to the 5th class hazardous materials and have explosiveness under acid catalyst using MINDO/3, MNDO, and AMI methods for formal charge, heat of formation, and energy level. Nucleophilicity and base of oxetane high explosives could be explained by negative charge size of oxetane oxygen atom and reactivity of oxetane in the growth stage of polymerization under acid catalyzer could be expected to be governed by positive charge size of axial carbon atom and low LUMO energy of electrophile. It could be estimated that carbenium ion was more beneficial in the conversion process of oxetane high explosives than that of stabilization energy (13.90~31.02 kcal/mole) of oxonium ion. In addition, concentration of oxonium ion and carbenium ion in equilibrium state influenced mechanism and it was also estimated that $S_N1$ mechanism reacts faster than that of $S_N2$ in prepolymer growth stage considering quick equilibrium based on form and calculation of polymerization under acid catalyzer.

• Journal of the Korean Chemical Society
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• v.60 no.1
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• pp.48-58
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• 2016

This study was to investigate the types of middle school students’ conceptual change on electrolyte and ion. Data were collected by pre- and post- exams of 9th grade students’ conceptions of electrolyte and ion, and by semi-structured interviews with nine students served as case representatives who participated in the study. All interviews were transcribed, analyzed and classified by conceptual change according to the responses of the students. The results are as follows: First, students’ ion conceptual change was classified into four types; simple conception to sophisticated conception, incomplete conception to scientific conception, misconception to confused conception, and misconception to misconception. Most students had difficulty in understanding of the concepts of ion in pre- and post-class, and they failed to distinguish between atom and subatomic particles precisely. Second, students’ conceptual change of electrolyte was also classified into the following four types; partially scientific conception to sophisticated conception, misconception to partial misconception, incomplete conception to incomplete conception and misconception to misconception. The study found that students had difficulty distinguishing the difference between electrolytes and nonelectrolytes. Third, students also had difficulty understanding the concepts on particles because they learned the ‘electrolyte and ion’ unit so quickly in the second semester of 9th grade in order to fill in the academic reports for applying high schools. Furthermore, some suggestions were made based on the results for understanding scientific concepts on particles.

• Journal of the Korean Chemical Society
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• v.66 no.2
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• pp.107-123
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• 2022

The purpose of this study is to investigate the effects of learning using computer-based science inquiry program. To this end, the three lessons computer-based science inquiry were developed in domain of material's properties. The developed program was put into K middle school located in Seoul and the effects were verified. For the experimental group, the three lessons computer-based science inquiry related to the separation of mixture were introduced, and for the comparison group, the contents presented in the textbook were introduced as a teacher-centered teaching method. To verify the effects of the program, 2-way ANCOVA was performed on positive experiences about science and science core competency, and 2-way ANOVA was performed on academic achievement. As a result of the study, there were significant differences between the two groups in positive experiernces about science and scientific core competencies and academic achievement (p<.05), and group^*gender interaction effect was only significant in academic achievement (p<.05). From the results of this study, we could see the possibility of using a computer-based science inquiry program as a chemistry teaching method that enables sustainable scientific inquiry.

• Journal of The Korean Association For Science Education
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• v.42 no.4
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• pp.383-396
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• 2022

In this study, pre-service chemistry teachers' questions in their teaching practices were analyzed considering the context of discourse. Five pre-service teachers participated in the study. Their questions were analyzed by considering various data including class videos, interviews, and teaching-learning materials. Their questions were classified into relevant question, affective question, dead-end question, rhetorical question, and structuring question. Each question was also classified into appropriate question and convenient question by the aspect of proper responses of students. The analyses of the results indicate the differences in the frequencies of several types of questions depending on the content of the lessons. After using convenient questions, pre-service teachers proceeded to prepared classes as they rather than prompted students' responses. The affective questions were rarely used. The dead-end questions were found to be used for promoting interaction with students. The rhetorical questions were used for various purposes such as arousing students' attention or promoting their thinking. Practical implications were discussed based on the results.