• Journal of Science Education
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• v.35 no.2
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• pp.119-126
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• 2011

The purpose of this study was to examine the effects of experimental learning using the small-scale chemistry (SSC) on high school students' academic achievement, scientific attitude and science-related attitude in high school chemistry I. For this study, two high school 2nd grade classes were divided into an experimental group and a control group. Experimental learning using the SSC in the experimental group, traditional experimental learning presented in the textbook in the control group were performed. The results showed that experimental learning using the SSC compared to traditional experimental learning was effective in improving academic achievement. The experimental learning also was effective in improving voluntary, patience, cooperativity in the scientific attitudes and social implications of science, attitude for science curriculum, attitude toward science in the science-related attitudes. Therefore, experimental learning using the SSC is necessary to actively utilize in high school chemistry curriculum.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.3013-3016
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• 2013

Two new isoflavanones, (3R) 7,2',4'-trihydroxy-3'-methoxy-5-methoxycarbonyl-isoflavanone (1) and (3R) 7,2'-dihydroxy-3',4'-dimethoxy-5-methoxycarbonyl-isoflavanone (2), together with six known isoflavanones (3-8), were isolated from the stems of Cassia siamea. The structure of 1-8 was elucidated by spectroscopic methods including extensive 1D- and 2D-NMR techniques. Compounds 1, 2, 5-8 were evaluated for their anti-tobacco mosaic virus (Anti-TMV) activity. The results showed that compounds 1 and 6 showed potential anti-TMV activity with inhibition rates of 24.6% and 26.9%, respectively. Compounds 2, 5, 7, 8 also showed anti-TMV activity with inhibition rates in the range of 11.8-18.6%.

• Current Applied Physics
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• v.18 no.11
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• pp.1422-1425
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• 2018

$NaTa_{1-x}Fe_xO_3$ ($0{\leq}x{\leq}0.40$) nanocubes were synthesized by a relatively low temperature hydrothermal method, using $Ta_2O_5$, $FeCl_3$ and NaOH as the precursors. The UV-vis diffuse reflectance spectra showed that $NaTa_{1-x}Fe_xO_3$ had significant visible-light-absorbing capability, and the absorption edge of $NaTaO_3$ shifted to longer wavelength with the increase of Fe dopants. Moreover, $NaTa_{1-x}Fe_xO_3$ exhibited room-temperature ferromagnetism when $Fe^{3+}$ occupied $Ta^{5+}$ sites in $NaTaO_3$ crystal lattice. The ferromagnetism is mainly attributed to the superexchange interactions between doped $Fe^{3+}$, rather than the contribution of oxygen vacancies caused by Fe doping. Therefore, Fe doping can simultaneously regulate the optical and magnetic properties of $NaTaO_3$ semiconductor, which will enable its potential applications in multifunctional optical-electronics and opticalspintronics devices.

• Journal of the Korean Chemical Society
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• v.52 no.3
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• pp.303-314
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• 2008

The purpose of this study was to understand the experiment for measuring chemical reaction rate by precipitate formation and to develop experiments applying small-scale chemistry. For this study, the experimental method for measuring the effect of concentration and temperature on chemical reaction rates presented in the 10 high school science textbooks were classified by their experimental methods of confirming production. Subsequently, problems observed in carrying out the experiments for measuring chemical reaction rates by precipitate formation frequently presented in the 10 high school science textbooks were analyzed. Experiments applying small-scale chemistry were developed measuring chemical reaction rate by precipitate formation. According to the result of this study, there were some problems in the experimental method of precipitate formation for measuring chemical reaction rates presented in the high school science textbooks. Those problems in the science textbook experiments were insufficient specification of mixing methods of reaction solutions, obscurity of knowing when the character letter X disappeared, time delay in collecting the experimental data, formation of hazardous sulfur dioxide, uneasiness of fixing water bath container, controlling the reaction temperature, and low reproducibility. Those problems were solved by developing experiments applying smallscale chemistry. Presenting the procedure of mixing reaction solutions on the A4 reaction paper sheet made the experimental procedure clearly, using well plates and stem pipette shortened the reaction time and made it possible to continuously collect the experimental data. Furthermore, the quantity of hazardous sulfur dioxide was reduced 1/7 times and the time when the character letter X disappeared could be observed clearly. Since experiments for measuring the effect of concentration and temperature on chemical reaction rates could be performed in 30 minutes, the developing experiments applying SSC would help students understand the scientific concepts on the effect of concentration and temperature on chemical reaction rates with enough time for experimental data analysis and discussion.

• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.645-653
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• 2004

The purpose of this study was to compare and analyze the cognitive levels of 11th grade students and those required in high school chemistry I textbooks standardized by the 7th national education curriculum. For this study, the cognitive development stages of 456 11th grade students were surveyed using short-version GALT (group assessment of logical thinking). Furthermore, 15 basic concepts were extracted from the contents on water and air, 2 units in chemistry I order to analyze the cognitive levels necessary for understanding high school textbooks, using CAT (curriculum analysis taxonomy). The results showed that 52.5% of the surveyed 11th grade students reached the formal operational level, 28.3% transitional levels, and 19.5% concrete operational levels. 68.9% of the academic high school students and 6.6% of the technical high school students reached the formal operational levels, and the ratio of formation was very different in each logics. As a result of the analyzing the cognitive levels needed for understanding chemistry I textbook contents, in spite of a change in national education curriculum, there were no great change in cognitive levels required by scientific concept except some inquiry activities. The cognitive levels in high school chemistry I textbooks by the 7th national education curriculum appeared higher than the cognitive levels of 11th grade student, but cognitive levels of inquiry activities were similar to the cognitive levels of the students. Chemistry teachers thought of chemistry I textbooks by the 7th national education curriculum as desirable because scientific concepts were reduced and a lot of real life materials were adapted. However, they pointed out a problem of difference in contents levels compared with chemistry I textbooks because scientific concepts were greatly reduced in chemistry I textbooks. The cognitive levels required in chemistry I textbooks still appeared higher than those of the students. Consequently, various teaching and learning methods and materials will have to be developed to be suitable for the students' cognitive levels.

• Applied Biological Chemistry
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• v.27 no.1
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• pp.1-6
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• 1984

The lipoprotein-bound carotenoids occurred in the viscera of abalone (Haliotis discus hannai) were separated and characterized to be the mixture of fatty acid esters of lutein and free lutein. The main fatty acid components of the esters were lauric (68%) and myristic acid (17%), and indicated the characteristic pattern compared with that of triglycerides and cholesterol esters in abalone. Patterns of carotenoids from the lipoproteins were, simple and this suggested selected metabolisms of various feed-originated carotenoids found in the whole acetone extract of abalone.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1625-1632
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• 2014

A concise and efficient one-pot synthesis of chroman-2,4-dione-based HKA derivatives by three component reaction of HKAs, triethoxymethane and 4-hydroxycoumarin derivatives under solvent-free and catalyst-free conditions is described. This protocol has many advantages, in that the GAP (Group-Assistant-Purification) chemistry process is involved in this method. As a result, the experimenter can avoid cumbersome process steps such as traditional chromatography and recrystallization purifications. The desired products can be easily obtained by washing the crude products with 95% EtOH.

• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.694-695
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• 1992

• Bulletin of the Korean Chemical Society
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• v.14 no.3
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• pp.404-411
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• 1993

• Bulletin of the Korean Chemical Society
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• v.7 no.6
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• pp.483-484
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• 1986