• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.4
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• pp.750-756
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• 2008

Supernumerary teeth are frequently found in the anterior portion of the maxilla and develop as a result of abnormal proliferation of the dental lamina during tooth germ formation, caused by genetic or environmental factors. They may result in various complications, such as eruption interference, displacement, rotation of adjacent teeth, diastema, eruption into the nasal cavity, and development of dentigerous cyst. The optimal time for surgical extraction of supernumerary teeth has been a controversial issue. Someone prefer early surgical extraction because supernumerary teeth can cause eruption interference and displacement of adjacent teeth, eventually altering occlusion. Others prefer to delay surgical extraction until $8{\sim}10$ years of age in consideration of root maturation of the adjacent teeth and also patient's behavior. When surgical extraction of supernumerary teeth is postponed, there is possibility that impacted supernumerary teeth in the inverted or horizontal position move toward the nasal cavity, hard palate, or premolar area. When such intraosseous tooth migration is combined with the vertical growth of the maxilla, surgical approach becomes even harder. Therefore, possibility of intraosseous tooth migration should be considered as an important factor when deciding appropriate time for surgical extraction. We are presenting cases of mesiodens which showed intraosseous migration during $6{\sim}7$ years of follow-up period since the first diagnosis had been made at the $2{\sim}3$ years of age.

• Tuberculosis and Respiratory Diseases
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• v.39 no.3
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• pp.228-235
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• 1992

Background: Although polymorphonuclear leukocytes (PMN) are important in protecting the airways and alveolar surfaces, there is evidence that they can also injure the lung while exercising their defensive role. However it has been unclear whether PMN-induced pneumocyte injury is mediated by their direct cytotoxic effect on target cells or by PMN-derived cytotoxic mediators. On the other hand histamine was known not only to act as an important chemical mediator participated in the pathogenesis of some atotic and allegic disorders, but also to have an inhibitory effect on normal PMN functions. Method: To study the mechanism by which PMN induce pneumocyte injury, we cocultured PMN from four healthy nonsmokers or their PMN-derived supernatants (PMN-SPN) with monolayers of $^{51}Cr$-labeled human A549 pneumocytes and compared PMN-and PMN-SPN-mediated pneumocyte injuries measured by $^{51}Cr$ release assay. We also compared the effects of histamine on each pneumocyte injury. Results: 1) PMN-SPN showed more injurious effect on A549 pneumocytes than that of PMN itself regardless histamine pretreatment of PMN. 2) Pneumocyte injury by PMN with histamine pretreatment was increased or decreased compared with that by PMN without histamine pretreatment, according to histamine concentrations, and PMN stimulating agents and their concentrations. 3) Pneumocyte injury by PMN-SPN with histamine pretreatment tended to be decreased compared with that by PMN-SPN without histamine pretreatment. Conclusion: Our results suggest that PMN-SPN may play more important role in mediating pneumocyte injury than PMN itself and that histamine may partially play a protective role on PMN-induced pneumocyte injury. Alternatively we conclude that the effects of histamine on PMN-induced pneumocyte injury may be affected by microenvironment in vivo.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.3
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• pp.218-228
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• 2010

Components of dental resin-based restorative materials are reported to leach from the filling materials even after polymerization. Hydroquinone (HQ) is one of the major monomers used in the dental resin and is known as a carcinogen. Thus, carcinogenic risk of HQ leaching from the dental resin becomes a public health concern. The present study attempted to examine the carcinogenic potentials of HQ on the human epithelial cell, which is the target cell origin of the most of oral cancers. Cytotoxicity of HQ was observed above 50${\mu}M$ as measured by LDH assay, indicating a relatively low toxicity of this substance in human epithelial cells. The parameters of neoplastic cellular transformation such as cell saturation density, soft agar colony formation and cell aggregation were analyzed to examine the carcinogenic potential of HQ. The study showed that 2-week exposure of HQ showed the tendency of increase in the saturation density and the significant enhancement of soft agar colony formation at the highest dose, 50 ${\mu}M$ only. It is suggested that HQ has a weak potential of carcinogenicity. When cells were treated with HQ and TPA, a well-known tumor promoter, the parameters of neoplastic cellular transformation was significantly increased. This result indicates that the potential risk of carcinogenicity from HQ is largely dependent upon the presence of promoter. Exposure of 50 ${\mu}M$ HQ increased the time-dependent apoptosis as measured by the ELISA kit. This concentration coincides with a dose of neoplastic transformation, indicating a possible link between apoptosis and HQ-induced cellular transformation. Hydroquinone generated Reactive Oxygen Species (ROS) which was evidenced by the treatment of antioxidants such as trolox and N-acetyl cysteine and the GSH depleting agent, BSO. Antioxidants blocked the generation of ROS and the GSH depleting agent, BSO dramatically increased the ROS production. Since HQ is known to increase ROS production thru activation of transcriptional factor such as c-Myb and Pim-1, it is speculated that ROS generation by HQ plays a role in the activation of oncogene, which may lead to neoplastic transformation. In addition, ROS is involved in the alteration of signal transduction, which regulates the apoptosis in many cellular systems. Thus, ROS-mediated apoptosis may be involved in the HQ-induced carcinogenic processes. Protein kinase C (PKC) is known to play pivotal roles in neoplastic transformation of cells and its high expression is often found in a variety of types of tumors including oral cancer. PKC translocation of PKC-${\alpha}$ was observed following HQ exposure. Altered signaling system may also play a role in the transformation process. Taken together, HQ leached from the dental resin does not pose a significant threat as a cancer causing agent, but its carcinogenic potential can be significantly elevated in the presence of promoter. The mechanism of HQ-induced carcinogenesis involved ROS generation, apoptosis and altered signaling pathway. The present study will provide a valuable data to estimate the potential risk of HQ as a carcinogen and understand mechanism of HQ-induced carcinogenesis in human epithelial cells.

• Journal of The Korean Association For Science Education
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• v.38 no.4
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• pp.541-553
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• 2018

The purpose of this study is to explore the relationship between epistemic goals, epistemic considerations and complexity of reasoning of science high school students in an open inquiry and to explore the context on how open inquiry compares with the characteristics of an authentic scientific inquiry. Two teams were selected as focus groups and a case study was conducted. The findings are as follows: First, the contexts, such as 'sharing the value for the phenomenon understanding, reflection on the value of the research, task characteristics that require collaboration and consensus, and sufficient communication opportunities,' promote epistemic goals and considerations. On the other hand, contexts such as 'lack of opportunity for critical review of related literature and environmental constraints' lowered epistemic sides. Second, epistemic goals and considerations influenced the reasoning complexity. The goal of 'scientific sense making' led to reasoning that pose testable hypotheses based on students' own questions. The high justification considerations led to purposely focusing attention to the control designs and developing creative experimental know-how. The high audience considerations led to defending their findings through argumentation and suggesting future research. On the other hand, the goal of 'doing the lesson' and the low justification considerations led to reasoning that did not interpret the meaning of the data and did not control the limit of experiment. The low audience considerations led to reasoning that did not actively defend their findings and not suggest future research. The results of this study suggest that guidance should provide communication and critical review opportunities.

• Journal of Korean Society of Forest Science
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• v.84 no.2
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• pp.226-238
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• 1995

This research was conducted to investigate the influential factors of the runoff of water and hillslope erosion caused by the large-scale harvesting operation. It was carried out on harvested sites (13ha) and non-harvested sites(13ha) in Seoul National University Research Forest [(Mt.) Paekunsan], from 1993 to 1994. 1. The amount of runoff of water was increased as the unit of rainfall increases, and the amount of runoff on harvested sites was larger than that of non-harvested sites by 28% in the first year and 24.5% in the second year after harvesting. According to the multiple regression equation for surface runoff, unit and number of rainfall, amount of hillslope erosion and soil bulk density showed statistically significance($R^2$=0.91). 2. The amount of hillslope erosion on harvested sites was larger than that of non-harvested sites by 7 times during the first year of harvesting and 2 times during the second year. 3. The multiple regression equations for hillslope erosion showed that soil bulk density, surface runoff of water and unit of rainfall(these factors were not controllable) had statistically significance($R^2$=0.74). 4. Soil runoff in harvested and non harvested sites were maximum 6.7% and 1% of the amount of hillslope erosion, respectively during the first year of harvesting. And the second year of harvesting soil runoff in harvested and non harvested cites were maximum 5.7% and 1.9%of the amount of hillslope erosion. From the above results, when in planning for timber harvesting, the buffer strip-woods zone must be remained to diminish soil and water runoff and to preserve water quality.

• Asian Journal of Turfgrass Science
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• v.25 no.2
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• pp.223-228
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• 2011

This research was performed to investigate change of green speed according to growth of grass, for this, the method of effective green management for improvement of green speed was searched by investigating green density, soil moisture, surface hardness, and mowing height every day for 6 months. As the result of the study, reliability between, green density, soil moisture, surface hardness, mowing height and green speed were measured to be respectively 0.4742, 0.5690, 0.4632, 0.2806, i.e. soil moisture is considered as the factor which affects green speed the most. Therefore, it will be an advantageous environment to maintain soil moisture a little bit low to improve green speed within the range that does not disrupt the growth of green. In case of green density, it is considered to be effective to get a fast green speed when obtaining enough density during May~June, the most vigorous growth period and at the same time green up period. Surface hardness was confirmed that management work as rolling is a considerably effective method to increase hardness. However, rolling gives high stress to the green, combining another management work as regular hilling could be a good alternative. Reliability of green preview and green speed was 0.2806, lower than soil moisture or surface hardness. Through the results, it was confirmed that management of mowing height to be low less than 3.00 mm is helpful to improve green speed, timely, and it is advantageous to manage green speed when adjusting mowing height during the vigorous growth period of bent grass. However, considering the range of mowing height was not various, being 2.9~3.4 mm, henceforth research on investigation of green speed at more various mowing heights would be necessary. Consequently, except mowing height, other three factors, i.e. green density, soil moisture and surface hardness were investigated to have considerable level of reliability on green speed, and it is considered that each factor affects green speed respectively according to green condition and time. Accordingly, in order for the manager to maintain high speed all year round, intensive care for each factor per time unit considering green growth condition is considered to be necessary.

• Korean Journal of Ecology and Environment
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• v.49 no.3
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• pp.153-175
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• 2016

Daecheong Reservoir has suffered eutrophication and water-blooms by blue-green algae from initial impoundment, and algae alert system (AAS) was introduced in 1997. The purpose of this study was to investigate the effect of rainfall and hydrological factors in increase or decrease variability of green-tide and prolonged AAS, studied and analyzed the current situation of AAS has been operating for 19 years (1997~2015) in Daecheong Reservoir. The total issued number of AAS was 46 times, the most frequent period in August and September were 22 times (752 days) and 16 times (431 days), respectively, it accounted for 82.6%. Many number and frequency during this period were significantly associated with rainfall, various discharge and water level. Rainfall and hydrological events are associated with the rainy season of monsoon-Changma and the typhoon, it was concentrated in June~September, total rainfall in this period accounted for 69.9% of the annual rainfall. An increase in inflows was dependent on the intensity, frequency and the amount of rainfall. Accounted for 68.4% of the total annual inflow, it was a time when the most rapidly changing hydrological variability in the reservoir. The total outflow was closely related to rainfall, and compared the distinctive characteristics of hydropower generation and watergate-spillway discharge. In addition, the upreservoir zone of Daecheong Reservoir could be vulnerable to green-tide by regulating discharge of the upstream dam. The issue of AAS was strongly related to the with and without of watergate-spillway discharge. The watergate-spillway discharge had a total of 25 times, it was maximum 17 days from July to September in the year. And the opening times and each duration of the watergate were 1~4 times and the range of 3~37 days, respectively. When the watergate opened, the issue of AAS was maintained to 13 years and the movement of water bodies and green-tide was great about five times than that of non-open, had a profound effect on prolonged AAS within reservoir. In Daecheong Reservoir, Chusori (CHU) area of the So-ok Stream was still showing serious symptoms green-tide levels in the summer, but Janggye (JAN) waters of the main reservoir was pointed out that more important. AAS will be operated by an absolutely consider the rainfall and hydrological effects around the watergate-spillway discharge. The measures of green-tide will be included in the limnological studies more suited to the characteristics of the watershed and reservoir of the our country. Finally, from now on, we will prepare the systematic management and guidelines for vulnerable zone water-blooms that are the source within the reservoir before the monsoon rather than waiting for the arrival of green-tide on the operating stations of AAS.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.87-94
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• 2012

To compare monthly variations of phytoplankton biomass and community composition between in seawater and sediment of the Gomso Bay (tidal flat: approximately 75%), the photosynthetic pigments were analyzed by HPLC every month in 1999 and every two months in 2000. Ambient physical and chemical parameters (temperature, salinity, nutrients, dissolved oxygen, and chemical oxygen demand) were also examined to find the environmental factors controlling structure of phytoplankton community. The temporal and spatial variations of chlorophyll a concentration in seawater were correlated well with the magnitude of freshwater discharge from land. The biomass of microphytobenthos at the surface sediments was lower than that in other regions of the world and 2-3 times lower than phytoplankton biomass integrated in the seawater column. Based on the results of HPLC pigment analysis, fucoxanthin, a marker pigment of diatoms, was the most prominent pigment and highly correlated with chlorophyll a in seawater and sediment of the Gomso Bay. These results suggest that diatoms are the predominant phytoplankton in seawater and sediment of the Gomso Bay. However, the monthly variation of chlorophyll a concentration in seawater at the subtidal zone was not a good correlation with that in sediment of the Gomso Bay. Although pelagic plankton was identified in seawater by microscopic examination, benthic algal species were not found in the seawater. These results suggest that contribution from the suspended microphytobenthos in the tidal flat to the subtidal zone of the Gomso Bay may be low as a food source to the primary consumer in the upper water column of the subtidal zone. Further study needs to elucidate the vertical and horizontal transport magnitude of the suspended microphytobenthos in the tidal flat to the subtidal zone.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.4
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• pp.228-234
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• 2004

In organic farming, nutrients for the crop production are mostly supplied by compost containing various organic materials. The long-term organic cultivation would result in continuous changes of soil chemical properties and fertility. The aim of this study was to investigate the contribution of long-term organic cultivation to the soil fertility in Korea focusing on the chemical properties of soil. Soil samples were collected from organic farms that had been cultivated for 8-10 years after certification of organic product through the conversion periods of 2-3 years. Thereby each organic farm had acquired optimal cultivating techniques and soil condition. We separated organic farms into three groups by cultivating crops, i.e. leaf vegetables, fruit vegetables and fruit trees. In each group, five representative farms were chosen in order to investigate the relationships between application rate of compost and nutrient contents in soil. The application rate of compost was approximately $10-15Mg\;10a^{-1}$ for the first 2-3 years at the beginning of organic farming and then reduced to a rate of $3-4Mg\;10a^{-1}$ after stabilization of organic matter content in soil with $30-50g\;10a^{-1}$. However, the continuous organic farming for 8-10 years resulted in accumulation of nutrients, especially of P, in soil probably due to the excessive amounts of compost applied. In conclusion, we suggest that the application rate and organic sources of compost should be decided on the basis of P content in soil by soil testing and thereafter the lack of soil N content for crop cultivation should be compensated by crop rotation with such as legumes. This might be an approach to the original meaning of organic farming as an environmental friendly agriculture.

• Journal of agricultural medicine and community health
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• v.37 no.3
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• pp.167-180
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• 2012

Objective: This study was conducted to evaluate an education program for cardiocerebrovascular high-risk patients. Methods: This program was developed according to Tyler's model for curriculum development. To evaluate the effects of this program, we measured clinical outcome change (weight, waist circumference, systolic blood pressure, diastolic blood pressure) and behavior change stages (checking blood pressure, blood sugar levels, doing physical activity, consistent maintenance of food intake, eating low amounts of salt, abstention from tobacco and alcohol) before and 4 weeks after participation in the education program. The group of subjects consisted of High-risk group patients who attended basic program(32 patients), and staged program(37 patients) during KHyDDI meetings from Oct. 2009 to May 2010. Results: The staged educational program was developed three aspects(disease, nutrition and exercise)and three stages(basic, in-depth and individual education). In the staged education program, the evaluations were made by measuring clinical outcome and stage of behavior before and after education. Significant differences were found in waist circumference, systolic blood pressure, diastolic blood pressure, consistent maintenance of food intake(p<0.05), and eating low salt(p<0.001)and their self efficacy. Conclusion: In the practice-oriented staged education program, significant differences were found in the clinical outcomes and stage of behavior before and after education. Possible limitations of the study include the small number of participating subjects and the short follow-up management period, but the results indicate that continued application of this program could contribute to the prevention of cardiocerebrovascular diseases for the elderly patients with long periods of chronic diseases.