• Journal of the Korean earth science society
• /
• v.28 no.4
• /
• pp.393-404
• /
• 2007

The purpose of this study was to identity scientific models included in the Earth domain of the $10^{th}$ grade science textbooks. Three earth science-related chapters in each of 11 trade books were analyzed. A framework was developed and used to classify a scientific model from three different perspectives: medium of representation, method of representation, and mobility of a model. Results showed that the science textbooks utilized domain-specific models in which the nature of sub-areas of earth science was embedded. That is, the unit of 'Change of the Earth' included many iconic models that represented the inaccessible inner structure of the earth and the movement of the tectonic plates. These were also two-dimensional pictorial and static models. In the chapter of 'Atmosphere and Oceans', symbolic and diagrammatic models were dominant in use, which included weather maps and contour line graphs of sea surface temperature and salinity. The unit of 'Solar System and Galaxies' showed the highly frequent use of iconic and analogical models for the large-scale celestial objects and their movements. Implications for earth science education and relevant research were discussed.

• The korean journal of orthodontics
• /
• v.36 no.4
• /
• pp.251-262
• /
• 2006

Objective: The purpose of this study was to compare the bacterial flora at the peri-implant sulcus of the orthodontic mini-implant placed in the alveolar mucosa with the bacterial flora at the adjacent healthy gingival sulcus. Methods: Two plaque samples from 7 patients were collected by inserting paper points into the sulcus between the mini-implant and ligature wire connected to the mini-implant head and inflamed alveolar mucosa, and from the gingival sulcus of a healthy tooth adjacent to the mini-implant. Results: Using 16S rDNA clone library, the 24 kinds of bacteria including Haemophilus aphrophilus, Sphingomonas species, Capnocytophaga species, Prevotella melaninogenica, Lachnospiraceae species, Porphyromonas species, Neisseria flava were identified only from the sulcus around the mini-implant. These bacteria constituted only 9.2% of total clones, and the bacteria identified from both the sulcus around mini-implants and the gingival sulcus constituted 80.4% of total clones. Of these bacteria, clones of Prevotella species, Atopobium rimae, Veillonella species, Streptococcus intermedius/constellatus, Streptococcus salivarius were more frequently isolated from the peri-implant sulcus. Conclusion: This study suggests that a broad epidemiological study is needed to find causative bacteria which induce inflammation from the peri-implant sulcus.

• Korean Journal of Soil Science and Fertilizer
• /
• v.14 no.3
• /
• pp.117-129
• /
• 1981

An experiment with the tobacco plant was conducted in the pots. A sandy humic soil was used with 2 levels of pH, 3.5 and 5.8 with 2 kinds of anions, Cl as $NH_4Cl$ and $SO_4$ as $(NH_4)_2SO_4$, and with 4 levels of pF, 1.5, 2.0, 2.5, and 3.5. The pH-treatment created different N-forms; $NH_4$ at low pH(3.5) and $NO_3$ at high pH (5.8). The results are summarized as follows: 1. At low pH (3.5) with high concentration of $NH_4$ given as $NH_4Cl$, the high content of $NH_4$ and Cl in tobacco resulted in plants suffering from $NH_4$ and Cl toxicity as well as Mn toxicity. As a result of these toxicity, an extremly abnormal growth of tobacco was clearly appeared. In the tobacco grown at low pH with $NH_4$ given as $(NH_4)_2SO_4$, a large amount of the $NH_4$ uptake developed Mg and Ca deficiencies. $NH_4-N$, which had been applied to the soil of high pH (5.8), was almost completely transformed into $NO_3-N$ by nitrification and, on this low acidic soil, the plants were all healthy regardless of Cl or $SO_4$ added together with $NH_4-N$. However, dry matter production was higher and maturity faster when $SO_4$ was used as anion than when Cl was used. 2. High moisture content in soil, to some extent, is necessary for a good development and growth of the tobacco plant. Phosphate uptake seemed to be limited at higher moisture stress. The dry matter yield of tops and roots of tobacco were in the order of pF 1.8 > 2.1 > 2.6 > 3.6, respectively. 3. Data of chemical analysis and dry matter yields of tops and roots showed that the tobacco plant followed the normal (C-A) concept. In the normal growth of plants, the carboxylate content of tops was quite comparable to the estimated (C-A) values. If $NH_4$ content of plants remains in quite high quantities, it must be analysed and taken into consideration for the (C-A) calculation. Al is not transported toward tops in toxic amounts due to its high immobility, it mostly stay in or on the roots, probably due to precipitation as a aolt. When Al is present in high quantities, it has to be considered into the (C-A) calculation.