• Journal of The Korean Association For Science Education
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• v.18 no.2
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• pp.245-256
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• 1998

In this study, we discussed about the implications of the idealization, which take an important role in physics, to the physics education. First, understanding of the idealization help the physics learning itself. This is because that various types of idealizations are included in the physics terms and concepts, derivation processes of physics laws and formulas, and explanation of natural phenomena and problem solving activities. Second, understanding of the idealization can help the application of the physics world to the real world. That is, by understanding the extent and the limit of idealization used in physics world, physics students can understand the discrepancies between the real world and the physics world. And also, by modifying or eliminating the idealization, students can extend the extent of understanding about how predictions based on the idealization used in the physics world will change. To do this, we suggested the application of computer simulation program in physics laboratories. Third, idealization take an important role in the inquiry learning for students' originality. The activities of identifying or controlling the variables, as one of the principal factors of scientific inquiry, need the appropriate establishment of the ideal conditions. And to analyze the limiting case or practice the thought experiments for understanding the impossible situation in the real world, ideal conditions also are needed. This study discussed above three aspects with various concrete examples and, with Park et al.'s study (Park et al., 1998), present the theoretical basis for the study of students' and teachers' understanding the idealization.

• Journal of Life Science
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• v.23 no.10
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• pp.1223-1229
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• 2013

Ursolic acid (UA) a bio-active ingredient found in a variety of fruits and vegetables, and it has potent antioxidant activity. However, the role of UA in mouse embryonic stem (ES) cells is poorly understood. This study investigated the functional role of UA in regulating the development of mouse ES cells under hypoxia. Hypoxia did not exert a significant effect on the undifferentiated state of mouse ES cells. However, it induced reactive oxygen species (ROS) generation and increased the level of lactate dehydrogenase (LDH) production at 48 h of hypoxic exposure. Conversely, oxidative stress induced by hypoxia was significantly inhibited by UA ($30{\mu}M$) pretreatment. Hypoxia significantly decreased cell survival and the level of [$^3H$] thymidine incorporation, both of which recovered following pretreatment of UA. In addition, UA decreased the apoptotic effect of hypoxia by attenuating caspase-3 cleavage or by recovering cellular inhibition of the apoptotic protein (cIAP)-2 and Bcl-2 expression. We further found that UA decreased senescence-associated beta-galactosidase activity. We suggest that UA is a natural antioxidant and one of the functional modulators of hypoxia-induced survival, apoptosis, proliferation, and aging in mouse ES cells.

• Journal of Life Science
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• v.17 no.6 s.86
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• pp.831-835
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• 2007

This study was carried out to obtain information about the valuable combination and concentration to produce good plants of cut gerbera flowers of 19 domestically - bred gerbera cultivars. BA and kinetin combination is more effective than NAA and BA combination to produce good plants and mass propagation of domestically - bredgerbera cultivars. Normally almost of 19 cultivars, mass propagation was more effective on the medium containing 1.0 mg/L BA + 0.5, 1.0 mg/L kinetin. But some cultivars, 'Sunnyeo', 'Oksaem','Piny', and 'Pink Light', vitrified plants were induced on MS medium high level of BA concentration(BA 1.0 mg/L), in comparison with those on the medium with low level of BA(0.1 mg/L).Fresh and dry weight, more effective on the medium containing BA 0.5 mg/L . Kinetin 0.1, 0.5 mg/L. Anatomical investigation of vitrified leaf, stomata of vitrified leaves were circular and inflated, where-as those of normal leaves.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.6
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• pp.888-895
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• 2015

For effective utilization of butter clam shell as a natural calcium resource, the optimal conditions for preparation of calcium acetate (BCCA) with high solubility were determined using response surface methodology (RSM). The polynomial models developed by RSM for pH, solubility, and yield were highly effective in describing the relationships between factors (P<0.05). Increased molar ratio of calcined powder (BCCP) from butter clam shell led to reduction of solubility, yield, color values, and overall quality. Critical values of multiple response optimization to independent variables were 2.70 M and 1.05 M for acetic acid and BCCP, respectively. The actual values (pH 7.04, 93.0% for solubility and 267.5% for yield) under optimization conditions were similar to predicted values. White indices of BCCAs were in the range of 89.7~93.3. Therefore, color value was improved by calcination and organic acid treatment. Buffering capacity of BCCAs was strong at pH 4.88 to 4.92 upon addition of ~2 mL of 1 N HCl. Calcium content and solubility of BCCAs were 20.7~22.8 g/100 g and 97.2~99.6%, respectively. The patterns of fourier transform infrared spectrometer and X-ray diffractometer analyses from BCCA were identified as calcium acetate monohydrate, and microstructure by field emission scanning electron microscope showed an irregular form.

• Journal of Life Science
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• v.27 no.4
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• pp.383-389
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• 2017

This study intends to analyze the contents of rutin, procyanidin B3, quercetin, kaempferol, known to have antioxidant, anti-inflammatory and anti-carcinogenic effects, among the polyphenol type contained in the grape pruning stem extracts (GPSE), utilizing grape stems being discarded after harvest, measure the effects on the skin moisture, inhibition of skin cell proliferation, anti-inflammatory on the damaged skin of a HR-1 mice induced with UVB, and verify the applicability as a material for functional food and functional cosmetics. The results of verifying the photoprotection effects through the skin proliferation control through of GPSE showed similar result to suncream was achieved at the GPSE concentration of 2,000 mg/kg on the epidermis (p<0.05). The results showed anti-inflammatory effects on all groups applied with GPSE as compared to the control group irradiated with UVB, but at the GPSE concentration of 1,000 mg/kg, a lower COX-2 protein expression at 8%, lower than the 22% of suncream, was observed to achieve an excellent anti-inflammatory effect (p<0.05). The results of this study confirmed the existence of active polyphenol type, such as rutin, kaempferol, querocetin and procyanidin B3, within the GPSE, and GPSE has improvement effects on moisturizing effects, skin proliferation control effect, inflammatory control effect and improvement effects on the skin barrier function through UV ray damage. GPSE is a functional ingredient with a potential for skin protection effects, and has high utilization as an ingredient for functional food and functional cosmetics.

• Journal of Korean Society of Forest Science
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• v.90 no.4
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• pp.476-487
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• 2001

In this study, three tree species (Populus euramericana, Kalopanax pictus and Quercus serrata) exhibiting different levels of shade tolerance were employed to investigate photosynthetic responses to the lower light condition on forest floors. Chlorophyll contents, spectral properties and photosynthetic characteristics were examined by using the tree species grown under high light intensity (PPFD $920{\mu}mol\;m^{-2}s^{-1}$) or low light intensity (PPFD $80{\mu}mol\;m^{-2}s^{-1}$). Plants grown under the low light intensity tended to have reduced leaf area, chlorophyll content per unit leaf area, light absorption and respiration in the shade intolerant tree species of P. euramericana. However, the shade tolerant species K. pictus and Q. serrata showed increased leaf area, chlorophyll content and net apparent quantum yield. Therefore, light absorption and light utilization efficiency were improved under the low light intensity. Also shade tolerant species maintained activities of photosystems and $CO_2$ fixation systems with little changes in low light intensity condition.

• Korean Journal of Food Science and Technology
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• v.14 no.3
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• pp.236-243
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• 1982

In order to remove the high content of malic acid (0.48%) in freshly fermented apple wine by applying malo-alcoholic fermentation(MAF) using malate-decomposing yeasts, Schizosaccharomyces japonicus var. japonicus or Schizosaccharomyces pombe, some factors which influenced malic acid decomposition in apple wine by malate-decomposing yeasts were investigated. By incubating the apple wine with these yeasts, 80% of initial malic acid was decomposed in 13 days at $20^{\circ}C$, whereas only 32% reduction in malic acid was observed in 40 days when MAF was not induced. For malic acid decomposition, Schizosaccharomyces pombe was superior to Schizosaccharomyces japonicus var. japonicus in natural medium such as apple wine, whereas Schizosaccharomyces japonicus var. japonicus was superior to Schizosaccharomyces pombe in synthetic medium. The optimum temperature for the MAF using these yeasts was between $20\;to\;30^{\circ}C$ and no adverse effect was detected by the addition of $SO_2$ up to 200ppm. Additions of $Mg^{2+}$ or certain amino acids such as alanine, aspartic acid to the wine could enhance the composition of malic acid.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.10
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• pp.1404-1410
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• 2011

Biological compounds (caffeic acid, rosemarinic acid, and chlorogenic acid) from mulberry leaf extracts were administered to mice in order to confirm their stability. All male and female mice survived upon a 4,000 mg/g dose in an acute toxicity test, and they also survived after injection of 2,000 mg/kg for 13 weeks repeatedly. Therefore, the level of toxicity was not high. In a comparison of the control and test groups, there were no significant differences upon naked eye inspection, and the weights of stomachs infected by Helicobacter pylori were not significantly different. Regarding the effects on immune cells, NO of macrophages decreased more than that of control when medicine was administered. The spleens of the female mice group proliferated slightly in LPS and Con A within 48 hr, whereas the other test group showed a similar level and the cell toxicity of natural killing cells decreased. Therefore, we concluded that caffeic acid, rosemarinic acid, and chlorogenic acid from mulberry leaf extracts are not harmful for the treatment of infected patients the development as a healthy functional food.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.44.3-45
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• 2017

To date, luminous quasars at z ~ 6 have been found to be in maximal accretion with the Eddington ratios, ${\lambda}Edd$ ~ 1, suggesting enhanced nuclear activities in the early universe. However, this may not be the whole picture of supermassive black hole (SMBH) growth since previous studies have not reached on faint quasars that are more likely to harbor SMBHs with low ${\lambda}Edd$. To understand the accretion activities in quasars at high redshift, we obtained the deep near-infrared (NIR) spectrum of a quasar, IMS J2204+0112, one of the few faintest quasars that have been identified at z ~ 6. From the NIR spectrum, we find that IMS J2204+0112 harbors a SMBH with about a billion solar mass, with ${\log}({\lambda}Edd)=-0.91$. This is the lowest accretion rate found so far for quasars at z ~ 6, but a common value among quasars at z ~ 2. The inclusion of this object in the ${\lambda}Edd$ analysis gives the intrinsic ${\lambda}Edd$ distribution of z ~ 6 quasars, which is lower than previous results that are based on bright quasars, but it is still higher than ${\lambda}Edd$ of z ~ 2 quasars. Although the number statistics needs to be improved in future, the low peak ${\lambda}Edd$ value is consistent with the SMBH growth from a massive black hole seed (~ 105 Msun) or from a stellar mass black hole through short-duration super-Eddington accretion events (${\lambda}Edd$ > 10).

• Journal of Life Science
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• v.20 no.11
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• pp.1640-1647
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• 2010

Seaweeds have been recognized as a health food, having anti-obesity, anti-constipation and anticoagulation activities, and the use of seaweeds in the food, medicine, and cosmetic industries have recently significantly increased. In this study, methanol extracts were prepared from 35 different seaweeds (17 phaeophyta, 11 rhodophyta and 7 chlorophyta), and thrombin time (TT), prothrombin time (PT) and activated partial thromboplastin time (aPTT) were determined in order to develop safe and novel anticoagulation agents from natural products. In TT experiments, Ecklonia cava, Ecklonia stolonifera, Eisenia bicyclis (Kjellman) Setchell, Ishige foliacea, I. okamurai, Sargassum confusum and S. yamade showed strong thrombin inhibition activity among the 35 different seaweeds. In PT experiments, the inhibitions of prothrombin were identified in the selected seaweeds from TT experiment, with the exception of S. yamade. In aPTT experiments, the seaweeds with blood coagulation inhibition factors were E. cava, E. stolonifera, E. bicyclis (Kjellman) Setchell, I. foliacea, I. okamurai, S. confusum and Hixikia fusiforme Okamura. Further anticoagulation assay with the selected 8 seaweeds suggested that S. confusum is most effective in antithrombosis, and E. stolonifera, E. bicyclis (Kjellman) Setchell, and I. foliacea have high potential as antithrombosis agents. Based on components-activity correlation analysis, flavonoids are considered as active anticoagulation components of seaweeds These results suggest that edible seaweeds, especially S. confusum, have potential as safe and novel anticoagulants, and S. yamade and H. fusiforme Okamura could be used as a thrombin-specific and coagulation factor-specific inhibitors.