• Applied Microscopy
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• v.29 no.2
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• pp.189-193
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• 1999

The response of ameloblast to long term (3 weeks) exposure to fluoride was examined in continuously erupting mandibular incisors of pregnancy rats as compared to control rats receiving a similar diet (Teklad L-356) but no sodium fluoride in there drinking water. Rats were started on water containing 0 ppm, 100 ppm, 200 ppm, and 300 ppm NaF at the beginning of pregnancy. To examine on the ultrastructural changes of the ameloblast, electron microscopy was used. The results indicated that rat incisors expressed two major changes in normal amelogenesis that could be attributed to chronic fluoride treatment. The fluoride produces marked alteration in the fine structure of ameloblast from teeth of young rats, such as large confluent distensions of the endoplasmic reticulum and swelling of isolated mitochondria, in particular on the morphology of the rough-surfaced endoplasmic reticulum. A graded series of alterations to these organelles were produced, and the severity of the changes would seem to be dependent on dose and time. This experimental data suggested that exposure prolonged of animal to high level of fluoride appears to induce morphological changes in the normal appositional growth and initial mineralization of enamel created during amelogenesis.

• Applied Microscopy
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• v.34 no.2
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• pp.145-157
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• 2004

The aim of the present study was to examine in detail, both at light and electron microscopical levels, the morphological variations in ameloblast of the fetal rat incisor enamel organ. Rats were started on distilled water at the beginning of pregnancy. The pups were sacrificed 11 days after delivery and animals were perfused intravascularly with glutaraldehyde and the incisors were removed. To examine on the ultrastructure of the ameloblast, the study employed primary light microscopy but electron microscopy was used to clarify some of the light microscopic finding. Longitudinal sections through the incisors of the rat show a continuous layer of ameloblasts on the labial surface of the tooth. This layer contains the entire sequence of developmental stages in enamel production. The ameloblast layer was divided into three main zones: 1) Presecretory zone, region of ameloblasts facing pulp. 2) Secretory zone, region of inner and outer enamel secretion. 3) Maturation zone, region of reduced ameloblasts. In particularly, the present study has shown that two distinctively different types of ameloblasts appear in the enamel organ during enamel maturation in the rat incisor. These two types have been designated ruffle-ended ameloblasts (rAB) and smooth-ended ameloblasts (sAB). The fluoride produces marked alteration in the fine structure of ameloblast from teeth of young rats, such as large confluent distensions of the endoplasmic reticulum and swelling of isolated mitochondria. This experimental data suggested that exposure prolonged of animal to high level of fluoride appears to induce a few dramatic changes in the normal appositional growth and initial mineralization of enamel created during amelogenesis.

• Science of Emotion and Sensibility
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• v.15 no.1
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• pp.37-46
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• 2012

We tested the effects of endogenous attention and reorienting on the performance of detection task. In the classic detection paradigm of Posner and Cohen (1980), performance on target detection is measured, where target appears either on the same or difference spatial location of cue stimulus after brief period of SOA (stimulus onset asynchrony). In this study, we induced exogenous attention by manipulating predictability of cue for target, and also induced reorientation by inserting additional (reorienting) cue between initial cue and target. Experiment 1 had three conditions of reorienting speed: Early, middle, and late. Facilitation and IOR (inhibition of return) occurred in different forms depending on SOA and reorienting speed, but we were not able to discover interpretable pattern in the results. However, reanalysis of early reorienting condition revealed that facilitation and IOR occurred in a crossed manner where short SOA found facilitation and long SOA did IOR, the typical results of simple detection task. Experiment 2 collected additional data to replicate the results in early reorienting condition of experiment 1. The results obtained that facilitation occurred with short SOA and IOR with long SOA. These results contrast with those of Wright and Richard (2000) where they reported elimination of IOR when cue had predictability of target locations. These results suggest that additional cue (here, orienting cue), which rapidly appears before extinction of IOR by prior cue, brings about double IOR. The present research demonstrates that even when attention is allocated to certain location via endogenous mechanism, rapidly repeating cues in certain location maximizes IOR that offsets the effects of endogenous attention to the same location.

• Korean Journal of Community Nutrition
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• v.2 no.5
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• pp.687-694
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• 1997

This study investigated the effects of vitamin C supplementation on the nutritional iron status of 31 adolescent girls, aged 12-15 years, with low hemoglobin levels. They were randomly divided into four groups, and for two groups daily150mg or 900mg of L-ascorbic acid(AsA) was given in three equal doses at three meals during 9 weeks. To another group daily 60mg iron as ferrous sulfate was given in the same way as AsA. The control group was given sugar placebo. Body iron status was monitored through the determination of Hb, Hct, MCHC, and serum ferritin concentrations. Dietary AsA and iron intakes were measured from food consumption surveys performed by 3-day 24-hour recalls. The amount of absorbed iron was estimated from the model of Monsen et al. The average amounts of food iron for four groups were 12.3- 15.0mg and 11.1 - 18.9mg at initial and at final period of the supplementation trial, respectively. The tentatively estimated amount of absorbed iron was significantly increased in the 900mg AsA and iron supplementing groups, but not in the 150mg AsA and placebo groups. Both Hb and MCHC were improved to above normal levels in all groups except the placebo group. Hct was elevated only in the AsA 900mg group whose Hct was relatively lower than the other groups. Serum ferritin concentrations of the four groups, which were as low as 8.50 - 14.39ng/mL on average at the intial periods, augmented significantly to 20.18ng/mL and 26.63ng/mL in the 900mg AsA and iron groups, respectively. Serum ferritin was not elevated in either the AsA 300mg group or the placebo group. The above data indicated that the daily supplementaion of 150mg AsA to the meals containing 12-15mg iron per day promoted Hb levels of adolescent girls with low Hb, and the 900mg AsA supplementing improved not only Hb level but also body iron store. A supplementation of 60mg iron per day appeared to be slightly more effective in improving the iron status in comparison to the 900mg AsA supplement. (Korean J Community Nutrition 2(5) : 687-694, 1997)

• KOREAN JOURNAL OF CROP SCIENCE
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• v.62 no.4
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• pp.325-332
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• 2017

This research was conducted to evaluate methods of enhancing the waterlogging resistance of soybean plant. Thus, we applied seven types of plant growth regulators (PGRs) to soybean plants and exposed them to waterlogged conditions for a total of 14 days. To evaluate stress resistance, we monitored plant growth characteristics data such as height, chlorophyll content, and chlorophyll fluorescence for 28 days after the initial waterlogging (14 days under waterlogging conditions and 14 days after waterlogging). According to the results, plant height was significantly increased by gibberellin A4 ($GA_4$) treatment compared to the control treatment and waterlogging-only treatment. However, we could not detect plant height owing to plant death when we applied abscisic acid (ABA). Except for $GA_4$ and ABA treatments, plant heights slightly decreased in all treatments compared to the waterlogging-only treatment. The chlorophyll content and chlorophyll fluorescence showed a similar tendency among PGR treatments. The chlorophyll content and chlorophyll fluorescence were significantly increased by ethephon and kinetin treatments 28 days after waterlogging compared to the waterlogging-only treatment. Consequently, kinetin and ethephon treatments induced more resistant phenotypes in soybean plants during or after exposure to waterlogging conditions.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.131-136
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• 2013

The aim of this study was to investigate the removal of fluoride using thermally treated pyrophyllite as adsorbent. Sorption experiments were conducted under batch conditions to examine the effects of adsorbent dose, reaction time, initial fluoride concentration and solution pH on fluoride removal. In the experiments, the pyrophyllite thermally treated at different temperatures [untreated (P-U), $400^{\circ}C$ (P-400), $600^{\circ}C$ (P-600)] were used. Results showed that the adsorption capacity was in the order of P-400 > P-U > P-600. The XRD analysis indicated that both P-U and P-400 were composed of quartz, dickite and pyrophyllite while P-600 was quartz. The BET analysis showed that the specific surface area was in the order of P-600 > P-400 > P-U. Kinetic data showed that fluoride sorption to P-400 arrived at equilibrium around 24 h. Equilibrium test demonstrated that the maximum sorption capacity of P-400 was 0.957 mg/g. In addition, fluoride removal by P-400 was not sensitive to solution pH between 4 and 10. However, fluoride removal decreased considerably at highly acidic (pH < 4) and alkaline (pH > 10) conditions. This study demonstrates that pyrophyllite could be used as a low-cost adsorbent for fluoride removal from aqueous solution.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.139-147
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• 2008

More precise estimation of the bed change, primary cause of flood damage, has been recognized significant for designs of levees and other river facilities. In this study, the long-term bed change was examined as the application of the relatively new Surface-water Modeling System (SMS) Model because there has not been broad verification of the model empirically on river of South Korea. This 2-dimensional model was used to examine the bed change of Pochon Stream Basin, a tributary of Imjin River, where heavy rain damages annually occur. First, in order to verify the model, the simulating period was set from 1986 to 1998 because of the existence of the field measurements. Cross sectional field measurements of 1986 were used for the initial condition and output were compared and analyzed with the observed cross sectional data in 1998. As the results of the verification, the comparison in lateral and streamwise bed level between results from the model and the field measurements showed a reasonable agreement except for the some cases of local scours. However, in terms of the quantitative comparison, the change of the bed elevations for each cross section for 1998 was rather underestimated than that of the field measurements.

• Journal of Biomedical Engineering Research
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• v.21 no.4
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• pp.391-401
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• 2000

Flow through compliant tubes with linear taper in wall thickness is numerically simulated by finite element analysis. For verification of the numerical method, flow through a compliant stenotic vessel is simulated and the results are compared to the existing experimental data. Steady two-dimensional flow in a collapsible channel with initial tension is also simulated and the results are compared with numerical solutions from the literature. Computational results show that as cross-sectional area decreases with the reduction in downstream pressure, flow rate increases and reaches the maximum when the speed index (mean velocity divided by wave speed) is near the unity at the point of minimum cross-section area, indicating the flow limitation or choking (flow speed equals wave speed) in one-dimensional studies. for further reductions in downstream pressure, flow rate decreases. The flow limitation or choking consist of the main reasons of waterfall effect which occurs in the airways, capillaries of lung, and other veins. Cross-sectional narrowing is significant but localized. When the ratio of downstream-to-upstream wall thickness is 2, the area throat is located near the downstream end. As this ratio is increased to 3, the constriction moves to the upstream end of the tube.

• Restorative Dentistry and Endodontics
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• v.35 no.5
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• pp.374-379
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• 2010

Objectives: Nickel-titanium (Ni-Ti) rotary instruments have some unexpected disadvantages including the tendency to screw-in to the canal. The purpose of this study was to evaluate the influence of root canal curvatures on the screw-in effect of Ni-Ti rotary files. Materials and Methods: A total of 80 simulated root canals in clear resin blocks were used in the study. Canals with curvature of 0, 10, 20 and 30 degrees were instrumented with ProTaper instruments SX, S1, S2 and a ProFile of #25/0.06 to 1.0-2.0 mm beyond the initial point of root curvature. The screw-in force was measured with a specially designed device while canal was instrumented with a ProFile of #30/0.06 at a constant speed of 300 rpm. The data were subjected to one-way ANOVA and Scheffe multiple range test for post-hoc test. Results: Larger degree of canal curvature generated significantly lesser screw-in forces in all groups (p < 0.001). Conclusions: More attention needs to be paid when using rotary instruments in canals with less curvature than canals with more curvatures to prevent or reduce any accidental overinstrumentation.

• Applied Biological Chemistry
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• v.39 no.5
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• pp.398-402
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• 1996

This study was carried out to compare the fermentation rates of Dongchimi as affected by fermentation temperature and salt concentration of brining solution. The Dongchimi was prepared by fermentation of the radish in salt solutions of 2.0, 3.2 and 5.1% NaCl respectively with addition of garlic, green onion, ginger at $4^{\circ}C,\;10^{\circ}C,\;20^{\circ}C$. The fermentation was classified into 3 steps of initial, intermediate and final stages according to pH changes and the rates of fermentation and color change were calculated from intermediate stage. The time reached equilibrium in hardness of radish and salt concentration and their equilibrated values were also compared. Fermentation rate became more rapid as fermentation temperature and salt concentration increased. The rates of Hunter color change of Dongchimi liquid were increased as the temperature increased. The 'L' values decreased slowly, and 'a' and 'b' values increased rapidly to maximum at the intermediate stage. The time required to reach equilibrium was reduced for both salt concentration and hardness of radish as the fermentation temperature increased. The equilibrated values of salt concentration were increased while those of hardness of radish were decreased as the temperature and salt concentration increased. The data obtained can be used for prediction of some of the major characteristics of Dongchimi during fermentation.