• The Korean Journal of Quaternary Research
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• v.23 no.1
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• pp.25-37
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• 2009

Geochemical composition and clay minerals of surface and core sediments around off the Jeju Island were analyzed for identification of sediment origins. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. Smectite is highly concentrated (>8%) in the northwest near the South Yellow Sea and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where fine-grained sediments are discharged from modern and ancient Huanghe River. The relatively high abundance of kaolinite are found in northeastern nearshore area and the southwest near Changjiang estuary. It seems to be supplied from Changjiang River and the southwestern Korea rivers. The sediment accumulation rates measured by $^{210}Pb$ geochronrom mowere 0.20 to 0.54cm/mr or 0.15 to $0.42g/cm^2{\cdot}mr^{-1}$ AOJI, with decreasing rates from the west part to the east part, resulting in the supply of fine-grained suspended sediments from the Changjiang and Huanghe Rivers system. The discrimination diagrams clearly show that the sediments around Jeju Island in the northern East China Sea are ultimately sourced from Chinese rivers, especially from the Huanghe River, whereas the sediment in the northeast part might come from Korean rivers and the Jeju Island.

• 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.

• Journal of Microbiology and Biotechnology
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• v.22 no.10
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• pp.1343-1349
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• 2012

Most of the Helicobacter pylori strains containing the cag pathogenicity island (PAI) have been associated with more severe gastric disease in infected humans. The cag PAI is composed of 27 proteins, and some of the components are required for CagA translocation into host cells as well as induction of proinflammatory cytokines, such as interleukin-8 (IL-8); however, the exact function of most of the components remains unknown or poorly characterized. In this study, we demonstrated that CagT (HP0532), which is an essential structural component of the cag PAI apparatus, plays an important role in the translocation of CagA into host epithelial cells. In addition to being located on the bacterial surface, CagT is also partially localized in the inner membrane, where it acts as a chaperone-like protein and promotes CagA translocation. However, CagT secretion was not detected by immunoprecipitation analysis of cell culture supernatants. Meanwhile, CagT was related to the introduction of IL-8 of the host cell. These results suggest that CagT is expressed on both the inner and outer bacterial membranes, where it serves as a unique type IV secretion system component that is involved in CagA secretion and cag PAI apparatus assembly.

• Analytical Science and Technology
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• v.18 no.6
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• pp.511-519
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• 2005

A method for determination of toluene diisocyanates (TDI) in toluene diisocynate (TDI)-based polyurethane (PUR) packing material was investigated, and also the migration of TDI to food was studied. TDI was extracted using food simulants such as n-haptane and 4% aqueous acetic acid. The determinations were performed using gas chromatography/mass spectrometry (GC/MS). One of major components for polyurethane, toluene diisocyanates, were detected in ten samples among twenty six food contact materials with the concentration range of $0.51{\sim}60.88{\mu}g/ml$. However the highest extracted amount was just 0.7% of $60.88{\mu}g/ml$ if the contact surface of food packing for extracting liquid was limited to the outer layer without exposure of the cutting edge of food packing multi-layers. The result of this study and the analysis method for TDI diisocyanate will be very useful for further study about food contact material, and the monitoring result could be used for evaluating the safety of food contact material before it is to be used for food, preservation.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.144-152
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• 2000

Intracoronal bleaching is currently disregarded by many clinicians because of the potential consequence of cervical resorption. To prevent this complication it is recommended that intra coronal barrier materials be placed over the root canal obturation and sodium perborate be used with water rather than with hydrogen peroxide. The purpose of this study was to evaluate the amount of the hydrogen peroxide penetration according to the difference in intracanal base materials and sodium perborate preparation. Fifty extracted intact premolars were instrumented, and filled with gutta-percha. And then the outer surface of the teeth was sealed with wax exposing the CEJ. The prepared teeth were placed in plastic tubes containing 1.5ml distilled water with their entire root submerged into the solution, The teeth were divided into the following five groups. In the first two groups gutta-percha was removed without placement of barrier, and then water or superoxole(30% $H_2O_2$) with sodium perborate were used respectively for bleaching. In the other three groups, after removal of gutta-percha, an intracanal isolating barrier(ZPC, IRM, Fuji II LC) was placed and then bleached with sodium perborate and superoxole. The bleaching procedure was performed 4 times with 1 week interval. The results were as follows : 1. All the groups showed a tendency of increasing penetration amount with increasing treatment times(P<0.05). 2. After the 1st and 2nd treatments, there was no significant difference in microleakage among the groups. 3. After the 3rd bleaching with superoxole and sodium perborate, there was no significant difference in microleakage between gutta-percha alone group and gutta-percha with ZPC, Fuji II LC barrier group. But significant difference was found between IRM barrier group and other groups(P<0.01). 4. After the 4th bleaching with superoxole and sodium perborate, there was no significant difference between gutta-percha alone group and gutta-percha with barrier groups. 5. After the 4th treatment, the group bleached with sodium perborate and water without barrier showed lower hydrogen peroxide penetration than that of other groups(P<0.01).

• Archives of Plastic Surgery
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• v.38 no.5
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• pp.594-601
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• 2011

Purpose: The frontal sinuses are a pair of triangularly shaped, air-filled chambers lined by mucoperiosteum and located between the inner and outer tables of the frontal bone. Until recently, our understanding of gender variations in craniofacial anatomy has been chiefly built upon anthropometric studies, which typically employ facial surface measurements or plain film radiography. The aim of this study i to determine the sizes of the frontal sinus in both sexes in Koreans. Methods: 95 Korean subjects who underwent maxillofacial 3-Dimensional computed tomography (CT) between January 2009 and December 2009 were enrolled. Frontal sinus dimensions and forehead measurements were taken at midline and at 10, 20, and 30 mm to the left and right of midline using sagittal, coronal, and axial images. The data was analyzed for significant differences between measurements made at the selected points in the frontal sinus, for left to right variations, for gender variations, and for racial differences. Results: The mean thickness of the anterior table ranged from 2.31 to 3.23 mm. Mean anteroposterior depth of the frontal sinus ranged from 7.38 to 9.45 mm and did not vary significantly at any distance from midline. Frontal sinus height was greatest at midline (mean=29.24 mm) and progressively lessened at lateral distances. Mean total width at the level of the supraorbital ridge was 53.66 mm. For all measurements, no significant left to right variation was noted. Comparing the sexes, males were found to have greater dimensions in most frontal sinus measurements, though these differences were only found to be significant at or close to midline. The male forehead was marked by more acute nasofrontal angle ($133.3^{\circ}$ versus $141.6^{\circ}$) and a steeper posterior forehead inclination ($14.9^{\circ}$ versus $7.7^{\circ}$). Conclusion: Using CT imaging, forehead and frontal sinus dimensions have been described. Generally, males had larger overall frontal sinus dimensions. And Korean had similar sized frontal sinus to Caucasian in height and width. But in AP distance Korean had lesser measurement. The result of this study may be helpful in the comprehension of normal size of frontal sinus in Korean.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.108-115
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• 2008

The wear on engine valve and seat insert is one of the most important factors affecting engine performance. The engine valve and seat insert must be able to withstand the severe environment that is created by: high temperature exhaust gases generated while the engine is running, rapid movement of the valve spring, high pressure generated in the explosive process. In order to study such problems, a simulator has been developed to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focused on the test of various degrees of wear on four different exhaust valve materials such as HRV40, HRV40-FNV (face nitrided valve), STL #32, STL #6,. Throughout all tests performed in this study, the outer surface temperature of the seat insert was controlled at $350^{\circ}C$, the cycle number was $4.0{\times}10^6$, the test load was 6860 N, the fuel was LPG the test speed was 20 Hz (2400 RPM) and the seat insert material was HVS1-2. The mean (standard deviation) maximum roughness of the exhaust valve and seat insert was $25.44\;(3.16)\;{\mu}m$ and $27.53\;(3.60)\;{\mu}m$ at the HRV40, $21.58\;(2.38)\;{\mu}m$ and $25.94\;(3.07)\;{\mu}m$ at the HRV40-FNV, $36.73\;(8.98)\;{\mu}m$ and $61.38\;(7.84)\;{\mu}m$ at the STL #32, $73.64\;(23.80)\;{\mu}m$ and $60.80\;(13.49)\;{\mu}m$ at the STL #6, respectively. It was discovered that the maximum roughness of exhaust valve was lower as the high temperature hardness of the valve material was higher under the same test conditions such as temperature, test speed, cycle number, test load and seat insert material. The set of the HRV40-FNV exhaust valve and the HVS1-2 seat insert showed the best wear resistance.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2003.05a
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• pp.66-66
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• 2003

King George island, Antarctica, is mostly covered by ice sheet and glaciers, but the land area is focally exposed for several thousand years after deglaciation. For a mineralogical study of chemical weathering in the polar environment, glacial debris was sampled at the well-developed patterned ground which was formed by long periglaclal process. As fresh equivalents, recently exposed tills were sampled at the base of ice cliff of outlet glaciers and at the melting margin of ice cap together with fresh bedrock samples. Fresh tills are mostly composed of quartz, plagioclase, chlorite, and illite, but those derived from hydrothermal alteration zone contain smectite and illite-smectite. In bedrocks, chlorite was the major clay minerals in most samples with minor illite near hydrothermal alteration zone and interstratified chlorite-smectite in some samples. Smectite closely associated with eolian volcanic glass was assigned to alteration in their source region. Blocks with rough surface due to chemical disintegration showed weathering rinds of several millimeter thick. Comparision between inner fresh and outer altered zones did not show notable change in clay mineralogy except dissolution of calcite and some plagioclase. Most significant weathering was observed in the biotite flakes, eolian volcanic glass, sulfides, and carbonates in the debris. Biotite flakes derived from granodiorite were altered to hydrobiotite and vermiculite of yellow brown color. Minor epitactic kaolinite and gibbsite were formed in the cleaved flakes of weathered biotite. Pyrite was replaced by iron oxides. Calcite was congruently dissolved. Volcanic glass of basaltic andesite composition showed alteration rim of several micrometer thick or completely dissolved leaving mesh of plagioclase laths. In the alteration rim, Si, Na, Mg, and Ca were depleted, whereas Al, Ti, and Fe were relatively enriched. Mineralization of lichen and moss debris is of much interest. They are rich of A3 and Si roughly in the ratio of 2:1 to 3:1 typical of allophane. In some case, Fe and Ti are enriched in addition to Al and Si. Transmission electron microscopy of the samples rich of volcanic glass showed abundant amorphous aluminosilicates, which are interpreted as allophane. Chemical weathering in the King George Island is dominated by the leaching of primary phyllosilicates, carbonates, eolian volcanic glass, and minor sulfides. Authigenesls of clay minerals is less active. Absence of a positive evidence of significant authigenic smectite formation suggests that its contribution to the clay mineralogy of marine sediments are doubtful even near the maritime Antarctica undergoing a more rapid and intenser chemical weathering under more humid and milder climate.

• Tunnel and Underground Space
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• v.18 no.2
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• pp.98-106
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• 2008

When a tunnel is excavated in a rock mass of poor condition, the adjacent zone of excavation surface may be reinforced by adopting the appropriate methods such as grouting and rock bolting. The reinforced effect can be evaluated by use of various numerical approaches, where the reinforcing elements may be expressed as distinct discretizations or smeared into the equivalent material properties. In this study, a simple numerical method, which can be classified as the latter approach, was developed for the elasto-plastic analysis of a circular tunnel. If a circular tunnel in a Mohr-Coulomb rock mass is reinforced to a finite thickness, the reinforced annulus may have different material properties from the in-situ rock mass. In the proposed elasto-plastic method for assessing the reinforcing effect, Lee & Pietruszczak (2007)'s method is applied to both the reinforced annulus and the outer insitu rock mass of the fictitious tunnel, and then two results are combined by enforcing the compatibility condition. The method were verified through comparing the results with the proposed method and the commercial finite difference code FLAC. When taking the variation of deformation modulus and strength parameters in the reinforced zone into account, the distributions of stress and radial displacement were much different from those obtained with the assumption of homogeneous rock mass.

• Parasites, Hosts and Diseases
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• v.31 no.4
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• pp.301-314
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• 1993

An electron microscopic study was performed to observe the ultrastructure of the tegument of U seoulensis. The outer surface of the tegument was covered with a tnlaminated plasma membrane. The electron-dense cytoplasmic layer was $2.5{\;}\mu\textrm{m}$ wide In the anterior portion and contained numerous vacuoles, mitochondriae and granular materials in its matrix. The basement layer was 330 nm wade or so, and Its numerous extensions protruded into the cytoplasmic layer. The sensory organ was composed of a small vesicle of $1.7{\;}{\times}{\;}1.1{\;}\mu\textrm{m}$ in dimensions, which possessed a cilium of $1.2{\;}{\times}{\;}0.19{\;}\mu\textrm{m}$ in size. The pharynx was composed of the epithelial layer of about $0.5{\;}\mu\textrm{m}$ wide, well developed muscle layer and basement layer. The tegument of the oral sucker was composed of a cytoplasmic layer of $0.4-0.5{\;}\mu\textrm{m}$ width, a narrow basement layer, a well developed muscle layer and tegumental cells. Some kinds of secretory granules that seemed to be originated from the cells of the oral sucker were observed In the parenchymal portions of the adjacent cells. The tribocytic organ consisted of numerous microvilli. The microvilli were 5 nm wide and heptalaminated. Two types of secretory granules originated from the gland cells of tribocytic organ were observed In the tegument and parenchyme. The tegumental cells were irregular in shape, and of which nuclei were multifarious.