• Restorative Dentistry and Endodontics
• /
• v.21 no.1
• /
• pp.19-34
• /
• 1996

It has been demonstrated that intracoronal bleaching of pulpless teeth may result in cervical root resorption. Several authors postulated that bleaching agents such as hydrogen peroxide penetrated through the dentinal tubules to damage the surrounding tissues that cause cervical root resorption. The purpose of this study was to suggest on in vitro model for direct determination of hydrogen peroxide penetration through CEJ during nonvital bleaching. In addition, this model permit the quantification of the amount of hydrogen peroxide penetrated during the procedure. Freshly extracted intact premolars, removed for orthodontic reasons were used. Root canal treatment was performed in each tooth. And then the outer surface and crown portion of the teeth was sealed with wax leaving the CEJ. The prepared teeth mounted on the wax laminates were placed in plastic assay tubes containing 1.5ml bidistilled water with their entire root, including the CEJ, submerged in the solution. The teeth were dividied into four groups. Thermo group : thermocatalytic bleaching with superoxol Walk group: walking bleaching with sodium perborate & superoxol Combi group : combination of thermocatalytic & walking bleaching Dw group : walking bleaching with sodium perborate & water The bleaching procedure was performed three times. The bleaching intervals were at 3 days. The hydrogen peroxide present in the assay system was added to ferrous ammonium sulfate resulting in ferric ion release. Upon the addition of potassium thiocyanate a ferrithiocyanate complex results, which absorbs light at the wavelength of 467nm. The radicular penetration of hydrogen peroxide in the four groups was assessed directly using spectrophotometer. The amount of hydrogen peroxide in the samples tested is determined by comparing them with a standard curve generated by known amounts of hydrogen peroxide. The results were obtained as follows : 1. In all experimental groups except the Dw group showed lower penetration amount in day 4 than day 1, there was statistical importance in the difference (P<0.05). 2. After 3rd treatment, Thermo group showed slightly increased value and narrow distribution. Walk group showed much more penetration amount and widely dispersed value. Value of Combi group showed wide distribution without regard to treatment time, but value of Dw group evenly distributed. 3. Thermo group, Walk group and Dw group showed a tendency of increasing penetration amount with increasing treatment times(P<0.01), but Combi group revealed no statistically important differences. 4. Combi group showed the highest degree of penetration. Walk group showed lower penetration than Combi group. Thermo group & Dw group showed lower than Walk group. 5. Cervical root permeability to hydrogen peroxide varied from 0 to 35 %.

• Korean Journal of Environmental Biology
• /
• v.18 no.1
• /
• pp.163-198
• /
• 2000

This study aim was to propose plant taxa as an alternative proposal for the purpose of solving many kinds of difficulties occurred in the floral item of environmental impact assessment (EIA) used to date. Plant taxa presented here for environmental assessment can probably be useful in understanding the excellence of natural environment to specific regional space as well as in determining the order of priority as to species preservation. These taxa, selected by the floristic analysis with distributional range, can be classified into five degrees: the fifth degree, characterized by the discontinuous and/or isolated distribution, includes 83 taxa, 76 genera, 41 families; the fourth degree, occurred in only one subprovince as southern and northern plants, includes 314 taxa, 217 genera, 78 families; the third degree, two subprovinces as southern and northern plants, includes 307 taxa, 223 genera, 93 families; the second degree, generally distributed more than 1,000 meter in altitude, a whole subprovince, includes 109 taxa, 92 genera, 43 families; the first degree, at least three subprovinces, includes 258 taxa, 207 genera, 91 families. The taxa mentioned here environmental assessment, therefore, summed up to 1,071 taxa, 559 genera, 142 families from the Korean flora. It is suggested that the taxa belonging to the fifth degree might structually have by far extinctive possibility in respond to environmental damage comparing with other degrees, simply because these have narrow distributional ranges. [Floristics, Korean flora, Geographical distribution, Natural environment, Environmental assessment, Plant taxa].

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.11 no.1
• /
• pp.100-106
• /
• 2018

Since the concept of virtual currency called Bitcoin was announced in 2008, the blockchain technology, which is the basis of Bitcoin, is attracting attention as an important platform technology in the era of the 4th industrial revolution that can change our society in the future. Although Existing electronic financial transactions store and manage all transaction history at a reliable central organization such as government and bank, blockchain-based electronic financial transactions are composed of a distributed structure in which all participants participating in the transaction store and manage the transaction history, it is possible to secure transaction transparency while reducing system construction and operation costs. Besides the virtual currency that started with bit coins, the technology of these blockchains has been extended in various fields such as smart contracts and document management. The key technology area of this blockchain is security based on proven cryptographic technology to make it difficult to forge and hack, but there are security risks such as security vulnerabilities in the virtual currency trading service, We will discuss security risks in using virtual currency and discuss countermeasures. Especially security accidents of virtual currency exchanges are occurring frequently recently, the damage of users who trade the virtual currency is also increasing, we propose security threats and security countermeasures against virtual currency exchanges.

• Korean Journal of Remote Sensing
• /
• v.36 no.5_1
• /
• pp.835-846
• /
• 2020

Recent severe climate changes and extreme weather events have caused the uncommon types of forest ecosystem disturbances such as hails and gypsy moths. This paper describes the analysis of the forest ecosystem disturbances using ISODATA (Iterative Self-organizing Data Analysis Technique Algorithm) with the RapidEye and Sentinel-2 images, regarding the cases of the hail damages in Hwasun in 2017 and the gypsy moth damages in the Chiak Mountain in 2020. In the case of hail damages, the comparison of the June image of this study and the July field survey of the previous study showed that the damage severity increased from June to July as the drought overlapped after the trees were injured by the hails. In the case of gypsy moths, significant leaf damages were found from the image of June, and the damages were mainly distributed at the low-altitude slope near Wonju City. We made sure that satellite remote sensing is a very effective method to detect various and unusual forest ecosystem disturbances caused by climate change. Also, it is expected that the Korean Medium Satellite for Agriculture and Forestry scheduled to launch in 2024 can be actively utilized to monitor such forest ecosystem disturbances.

• Radiation Oncology Journal
• /
• v.12 no.2
• /
• pp.129-141
• /
• 1994

Intracellular ions which have a major role in cellular function have been reported to affect repair of radiation damage. Recently it has been reported that ouabain sensitizes A549 tumor cellls but not CCL-120 normal cells to radiation. Ouabain inhibits the $Na^+-K^+$-pump rapidly thus it increases intracellular Na concentration, Vanadate which is distributed extensively in almost all living organisms is known to be a $Na^+-K^+$-ATPase inhibitors, This study was performed to see any change in radiosensitivity of tumor cell by vanadate and any role of $Na^+-K^+$ATPase in radiosensitization. Experiments have been carried out by pretreatment with vanadate in human cell line(A549, JMG) and mouse cell line(L1210, spleen). For the cell survival MTT assay was performed for A549 and JMC cells and frypan blue dye exclusion test for L120, and spleen cells. Measurements of $Na^+-K^+$-ATPase activity in control, vanadate treated cell, radiation treated cell (9 Gy for A549 and JMG, 2 Gy for L1201, spleen), and combined $10^{-6}M$ vanadate and radiation treated cells were done. The results were summerized as fellows. 1. L1210 cell was most radiosensitive, and spleen cell and JMG cell were intermediate, and A549 cell was least radiosensitive. 2. Mininum or no cytotoxicity was seen with vanadate below concentration of $10^{-6}M$. 3. In A549 cells there was a little change in radiosensitivity with treatment of vanadate. However radiation sensitization was shown in low dose level of radiation i. e. 2- Gy. In JMG cells no change in radiosensitivity was noted. Both L1210 and spleen cell had radiosensitization but change was greater in tumor cell. 4. $Na^+-K^+$-ATPase activity was inhibited significantly in tumor cell by treatment of vanadate. 5. Radiaiton itself inhibited $Na^+-K^+$-ATPase activity of tumor cell with high $Na^+-K^+$-ATPase concention. Increase in radiosensitivity by vanadate was closely associated with orginal $Na^+-K^+$-ATPase contents. From the above results vanadate had little cytotoxicity and it sensitized tumor cells to radiation. Inhibitory effect of vanadate on $Na^+-K^+$-ATPase activity might be one of the contributing factors for radiosensitization to tumor cells which has greater enzyme activity than that of normal cell. It was suggested vanadate could be used as a potential radiosensitizer for tumor cells.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.19 no.6
• /
• pp.87-100
• /
• 2016

This research was performed for the purpose of providing useful and base data and preservation strategy of growth characteristics of Rhododendron micranthum. From the result of research, wild growth area of Rhododendron micranthum was discovered near steep forest road on 695~901m in altitude above sea level of Baekdu-daegan National Arboretum. Vegetation colony structure of Site I was resulted in Pinus densiflora(tree stratum M.I.P.=45.3%) is dominants, Betula schmidtii(arborescent M.I.P.=9.8%) is second dominant, and Site III resulted in Pinus densiflora(tree stratum M.I.P.=30.5%) is dominants, Betula schmidtii(arborescent M.I.P.=10.3%) is second dominant. Site II resulted in Betula schmidtii(arborescent M.I.P.=30.4%) is dominants and Pinus densiflora tree(tree stratum M.I.P.=8.3%) is second dominants. For herbs, it was researched that the rate of one year herb of chrysanthemum family(10), rice family(3), sedge(2) was higher than near forest area. Among Species diversity index, that of Shannon was in range of 0.7348~1.1090. After comparing this with similar area, this value was relatively low. Dominance analysis result was analyzed that various groups are evenly distributed. Monthly highest average temperature is $23.9^{\circ}$ in Site A and Site B, and monthly lowest average temperature is $-4.5^{\circ}C$ in Site I and $-4.7^{\circ}C$ in Site II. Monthly maximum average humidity is 85.6% in Site I and 83.2% in Site II. Monthly minimum average humidity is 60.9% in Site I and 60.8% in Site II and it showed that these 2 area are located far away but have similar temperature and humidity characteristic and climate environment is similar. It was analyzed that humidity is high with the result of annual average humidity is over 60%. In growth characteristic, it showed that doubt damage of Stephanitis pyrioides, exposure of roots, peeled bark was discovered and supplement on this is urgent.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.5
• /
• pp.611-617
• /
• 2018

The application of health monitoring, including a fault detection technique, is needed to secure the structural safety of large structures. A 2-step crack identification method for detecting the crack location and size of the beam structure is presented. First, a crack occurrence region was estimated using the modified Laplacian operator for the strain mode shape obtained from the distributed local strain data. The crack location and size were then identified based on the natural frequencies obtained from the acceleration data and the neural network technique for the pre-estimated crack occurrence region. The natural frequencies of a cracked beam were calculated based on an equivalent bending stiffness induced by the energy method, and used to generate the training patterns of the neural network. An experimental study was carried out on an aluminum cantilever beam to verify the present method for crack identification. Cracks were produced on the beam, and free vibration tests were performed. A crack occurrence region was estimated using the modified Laplacian operator for the strain mode shape, and the crack location and size were assessed using the natural frequencies and neural network technique. The identified crack occurrence region agrees well with the exact one, and the accuracy of the estimation results for the crack location and size could be enhanced considerably for 3 damage cases. The presented method could be applied effectively to the structural health monitoring of large structures.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.14 no.3
• /
• pp.165-170
• /
• 1981

Recently an unknown microbial desease and some parasitic crustaceans are prevailing in the sea-weed farms of Uudaria pinnatifida along the south-eastern coast of Korea.(1) Green spots probably caused by the microbial pathogens were found on the fronds of Undaira Pinnatifide. Particularly they were densely distributed on the distal half of the fronds. The tissues of the green spot area rot off, and small holes with green colored margin are formed. The holes at the distal part of the fronds are enlarged and they finally coalesced each other. Then this process accelerates decaying of the distal ends of the fronds.. The fronds growing in the central part of the farms are usually severely damaged, whereas in the marginal area of the farm toward the open sea side the damage is less serious. An examination revealed that the deseased fronds bore a number of viable bacteria, $6.8\times10^5\;to\;1.2\times10^6$ per gram at $15^{\circ}C$, whereas the healthy fronds $1.1\times10^4$. Twenty-six kinds of colonies, 247 strains of bacteria, were isolated from deseased fronds, belonging to Moraxella, Achromobacter, Vibrio, Flavobacterium, Acinetobacter, Pseudomonas, etc. (2) Pinholes occurred in one series on the frond. They were probably caused by a harpacticoid copepod, Thalestris sp. Seven years ago when the disease was first found to occur the copepod was observed on the fronds from March of the year. Recently, however, they have been found as early as December of the previous year. (3) A gammarid amphipod, Ceinina iaponica, invades the pith of the midrib through holdfast of thalli. This rarely causes the longitudinal seperation of the entire frond through the midrib as they bore a tunnel in the pith. Sometimes holdfasts of tile heavy damaged thalli make the frond departed from the substrate.

• Korean Journal of Veterinary Service
• /
• v.40 no.1
• /
• pp.61-66
• /
• 2017

Calf diarrhea is a disease experienced by almost all of calves after birth and is one of the representative causes of damage to farmers due to mass mortality and of economic losses to them by inhibiting normal growth. In this study, we conducted quick detection of etiologic agents of diarrhea by using a rapid diagnostic kit to multiply diagnose antigens of five etiologic agents of calf diarrhea (rotavirus, coronavirus, Escherichia coli, Cryptosporidium, Giardia) in Hanwoo (Korean native cattle) calves. When the positive antigen proportion of the calf diarrheal feces for each farm was analyzed, rotavirus, coronavirus, Escherichia coli, Cryptosporidium, and Giardia showed antigen positive rates of 0~67%, 0~20%, 0~60%, 0~20%, and 0~67%, respectively. With regard to the antigen positive rate by age in days after birth, 1-week-old calves showed the antigen positive rate of 20% in rotavirus and 20% in Giardia, and 2-week-old calves showed that of 50% in rotavirus. In addition, 4-week-old calves showed the antigen positive rate of 10% in rotavirus, 10% in coronavirus, 10% in Escherichia coli, and 30% in Giardia, and 8-week-old calves showed the antigen positive rate of 17% in coronavirus, 50% in Escherichia coli, 17% in Cryptosporidium, and 33% in Giardia. Based on the results of this study, the etiologic agents of diarrhea in Hanwoo calves for each farm are widely distributed. Although younger than 2-week-old calves were strongly positive for rotavirus, older than 4-week-old calves were highly positive for Giardia and Escherichia coli. In conclusion, we considered that a rapid diagnostic kit is an effective method for quick detection of etiologic agents and would be helpful for cattle farmers and veterinarians to select appropriate therapeutic method.

• Korean journal of applied entomology
• /
• v.58 no.4
• /
• pp.291-297
• /
• 2019

Since Metcalfa pruinosa was first reported in Koera, it has continually caused damage to sweet persimmon orchard in southern part of Korea. Metcafa pruinosa exist not only in farmland but also in forest areas, and are difficult to control due to the influx of individuals from near forest. M. pruinosa has been occurred in orchard and its surroundings because of various host range. Thus, it has been difficult to decide spatial range and control time for efficient management. In this study, occurrence and dispersal pattern of M. pruinosa in persimmon orchard were surveyed using clear sticky traps, and spatial patterns were analyzed with SADIE(Spatial Analysis by Distance IndicEs), based on location information at sticky traps. Spatial association between survey time was also analyzed to identify when the spatial pattern changed. In sweet persimmon orchard, M. pruinosa mainly dispersed in mid to late May, when the first instar hatches, and in August, emerging season of adult. The first instar nymphs hatched in mid-May were randomly distributed in orchard, but distribution was changed to aggregative pattern after dispersed surroundings of orchard. Adults showed random distribution pattern after immigration to orchard again. These tendency was also observed in density change at orchard and its surroundings, and matched to actual density of M. pruinosa in sweet persimmon trees.