• International Journal of Stem Cells
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• 제16권1호
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• pp.93-107
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• 2023

Background and Objectives: Chronic periodontitis can lead to alveolar bone resorption and eventually tooth loss. Stem cells from exfoliated deciduous teeth (SHED) are appropriate bone regeneration seed cells. To track the survival, migration, and differentiation of the transplanted SHED, we used super paramagnetic iron oxide particles (SPIO) Molday ION Rhodamine-B (MIRB) to label and monitor the transplanted cells while repairing periodontal bone defects. Methods and Results: We determined an appropriate dose of MIRB for labeling SHED by examining the growth and osteogenic differentiation of labeled SHED. Finally, SHED was labeled with 25 ㎍ Fe/ml MIRB before being transplanted into rats. Magnetic resonance imaging was used to track SHED survival and migration in vivo due to a low-intensity signal artifact caused by MIRB. HE and immunohistochemical analyses revealed that both MIRB-labeled and unlabeled SHED could promote periodontal bone regeneration. The colocalization of hNUC and MIRB demonstrated that SHED transplanted into rats could survive in vivo. Furthermore, some MIRB-positive cells expressed the osteoblast and osteocyte markers OCN and DMP1, respectively. Enzyme-linked immunosorbent assay revealed that SHED could secrete protein factors, such as IGF-1, OCN, ALP, IL-4, VEGF, and bFGF, which promote bone regeneration. Immunofluorescence staining revealed that the transplanted SHED was surrounded by a large number of host-derived Runx2- and Col II-positive cells that played important roles in the bone healing process. Conclusions: SHED could promote periodontal bone regeneration in rats, and the survival of SHED could be tracked in vivo by labeling them with MIRB. SHED are likely to promote bone healing through both direct differentiation and paracrine mechanisms.

• Nuclear Engineering and Technology
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• 제26권4호
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• pp.461-470
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• 1994

방사성 코발트, 스트론 , 세슘의 사암에 대한 수착특성평가 실험을 수행하였다. 수착반응속도론적 평가와 더불어 수착유형 및 가역성 등을파악하였다. 수착반응은 크게 두 단계로 나눌 수 있는데, 초기 10시간 이내에 사암외부표면에 대부분의 수착이 일어나고, 이후에는 사암입자내 미세공극을 통한 내부수착 표면으로의 확산이 수착속도 결정단계로 작용하는 과정이다. 방사성핵종이 지하매질에 수착하는 주된 수착유형을 정량적으로 평가하기 위한 방법으로서 순차적화학추출법을 도입하여 방사성핵종이 수착되어 있는 사암에 대해 탈착 실험을 수행하였다. 특히 이온교환되어 있는 세슘을 탈착시키기 위해 염화칼륨 용액으로 추출하는 공정을 도입하였다. 본 연구에서 고려한 수착유형은 지하수조건에서 가역적 수착, 이온 교환, 철망간산화 /산수소화물과의 결합, 비가역적 고착등이다. 스트론튬은 사암표면에 상대적으로 반응이 빠르고 가역적인 이온교환반응을 하였다. 코발트와 세슘은 복합적인 수착반응 양상을 보였다. 코발트의 경우, 주된 수착유형은 철망간산화 /산수소화물과의 결합이고, 비가역적인 고착도 상당비율 일어났다. 세슘의 경우, 비가역적 고착이 주된 수착유형이였으며, 이온교환도 상당비율 일어났다. 그러므로, 수착반응의 가역성 및 이동성은 스트론튬 ＞ 코발트 ＞ 세슘 순이였다.

• Geomechanics and Engineering
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• 제37권6호
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• pp.599-614
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• 2024

To evaluate the safety status of deteriorated segments in a submarine shield tunnel during its service life, a seepage model was established based on a cross-sea shield tunnel project. This model was used to study the migration patterns of erosive ions within the shield segments. Based on these laws, the degree of deterioration of the segments was determined. Using the derived analytical solution, the internal forces within the segments were calculated. Lastly, by applying the formula for calculating safety factors, the variation trends in the safety factors of segments with different degrees of deterioration were obtained. The findings demonstrate that corrosive seawater presents the evolution characteristics of continuous seepage from the outside to the inside of the tunnel. The nearby seepage field shows locally concentrated characteristics when there is leakage at the joint, which causes the seepage field's depth and scope to significantly increase. The chlorine ion content decreases gradually with the increase of the distance from the outer surface of the tunnel. The penetration of erosion ions in the segment is facilitated by the presence of water pressure. The ion content of the entire ring segment lining structure is related in the following order: vault < haunch < springing. The difference in the segment's rate of increase in chlorine ion content decreases as service time increases. Based on the analytical solution calculation, the segment's safety factor drops more when the joint leaks than when its intact, and the change rate between the two states exhibits a general downward trend. The safety factor shows a similar change rule at different water depths and continuously decreases at the same segment position as the water depth increases. The three phases of "sudden drop-rise-stability" are represented by a "spoon-shaped" change rule on the safety factor's change curve. The issue of the poor applicability of indicators in earlier studies is resolved by the analytical solution, which only requires determining the loss degree of the segment lining's effective bearing thickness to calculate the safety factor of any cross-section of the shield tunnel. The analytical solution's computation results, however, have some safety margins and are cautious. The process of establishing the evaluation model indicates that the secondary lining made of molded concrete can also have its safety status assessed using the analytical solution. It is very important for the safe operation of the tunnel and the safety of people's property and has a wide range of applications.

• Membrane and Water Treatment
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• 제6권5호
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• pp.393-409
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• 2015

Zinc and lead pollution are public environmental issues that have attracted lots of attention for a long time. Landfill leachate contains heavy metals, such as Zn(II) and Pb(II), which are usually related to the pollution of groundwater, especially in developing countries. Bentonite has been proven to be effective in enhancing the membrane property of clay, by which landfill liners can have better barrier performance towards the migration of contaminants. In this study, 5% sodium bentonite amended with locally available Fukakusa clay was utilized to evaluate the membrane behavior towards the heavy metals zinc and lead. The chemico-osmotic efficiency coefficient, ${\omega}$, was obtained through Zn(II) and Pb(II) solutions with different concentrations of 0.5, 1, 5, 10, and 50 mM. According to the results, ${\omega}$ continually decreased as the Zn(II) and Pb(II) concentrations increased, which is consistent with the Gouy-Chapman theory. Compared to normal inorganic ions, the membrane behavior towards heavy metal ions was lower. The migration of heavy metal ions was not observed based on experimental results, which can be attributed to the adsorption or ion exchange reaction. The mechanisms of the membrane performance change were discussed with the assistance of XRD patterns, free swelling results, XRF results, and SEM images.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1992년도 폐기물 매립지의 공학적 특성과 개량기술
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• pp.33-66
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• 1992

Recently, waste landfills built on seashores have been increased because of the easy availability of broad area near the urban communities. To evaluate the performance of the marine clay landfill liner numerical contaminant transport analyses are performed by selecting the typical section of a waste landfill built on seashores and using hydraulic conductivity data obtained from the site. Also, the laboratory electrical resistivity test and the in-situ corrosion test are performed in order to analyze the influence of the soil and leachates composing the landfills on the construct ion materials. From the results of contaminant transport analyses, it is shown that the leachates can be migrated faster through narrow pervious channels than the wide homogeneous pervious tedium and the importance of good quality barriers to prevent the contaminant migration is recognized. In the laboratory electrical resistivity test all the earth materials except the cover soils saturated with distilled water have small resistivities, which shows a high potential of corrosivity of soils composing landfills. However, the degree of corrosion of specimens buried in the landfills was not so severe except the zinc and carbon steel specimens. This apparently conflict results present the necessity of the investigation of other major factors and the long term in-situ corrosion test.

• 한국지반환경공학회 논문집
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• 제6권4호
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• pp.13-26
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• 2005

본 연구에서는 여러 연구자들에 의해 제안된 단일 점토 및 혼합 차수재를 통한 유기 및 무기 오염물질 이동에 관한 연구결과를 정리하여 보았고, 이러한 연구결과를 바탕으로 오염물질 유출 기준을 만족하는 차수재의 두께를 산정할 수 있는 차수재 설계 프로그램을 개발하였다. 본 프로그램을 이용하여 점토 차수재를 통한 $Cl^-$이온의 이동성에 바탕을 둔 매립지 두께를 산정해본 결과 비교적 합리적인 결과를 얻을 수 있었다. 따라서 본 연구에서 개발된 프로그램을 이용할 경우에는 비교적 간편한 방법으로 매립지 차수재의 예비설계를 수행할 수 있을 것으로 사료된다.

• 한국재료학회지
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• 제12권5호
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• pp.347-352
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• 2002

A transparent dielectric of the $PbO-B_2O_3-SiO_2-A1_2O_3$ system which was a low melting glass has been used for PDP (Plasma Display Panel), but it has a problem which is a reaction to be occurred between a transparent dielectric layer and electrodes (Ag, ITO) after firing. This research was conducted for ion migration of $Ag^+\$ and $Sn^ {2+}$ during firing three different frits of low melting glass. The result showed that yellowing phenomena occurred through a chemical reaction between $Ag^+\$and $Sn^ {2+}$ at 550~58$0^{\circ}C$ for 20~60 min. In addition, it was confirmed that the migration of $Sn^{2+}$ from ITO electrode made a strong effect on the yellowing phenomena.

• 한국재료학회지
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• 제34권5호
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• pp.242-246
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• 2024

La modified lead zirconate titanate ceramics (Pb_0.92La_0.08)(Zr_0.95Ti_0.05)O₃ = PLZT-8/95/5 were prepared using the conventional solid state reaction method in order to investigate the complex impedance characteristics of the PLZT-8/95/5 ceramic according to temperature. The complex impedance in the PLZT-8/95/5 ceramic was measured over a temperature range of 30~550 ℃ at several frequencies. The complex dielectric constant anomaly of the phase transition was observed near T_U1 = 179 ℃ and T_U2 = 230 ℃. A remarkable diffuse dielectric constant anomalous behaviour of the complex dielectric constant was found between 100 ℃ and 550 ℃. The complex impedance spectra below and above T_U1 and T_U2 were fitted by the superposition of two Cole-Cole types of impedance relaxations. The fast component in the higher frequency region may be due to ion migration in the bulk, and the slow component in the lower frequency region is interpreted to be the formation and migration of ions at the grain boundary or electrode/crystal interfacial polarization.

• 한국재료학회지
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• 제18권12호
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• pp.673-677
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• 2008

Calcia (CaO) stabilized cubic-$HfO_2$ is studied by density functional theory (DFT) with generalized gradient approximation (GGA). When a Ca atom is substituted for a Hf atom, an oxygen vacancy is produced to satisfy the charge neutrality. The lattice parameter of a $2{\times}2{\times}2$ cubic $HfO_2$ supercell then increases by $0.02\;{\AA}$. The oxygen atoms closest to the oxygen vacancy are attracted to the vacancy as the vacancy is positive compared to the oxygen ion. When the oxygen vacancy is located at the site closest to the Ca atom, the total energy of $HfO_2$ reaches its minimum. The energy barriers for the migration of the oxygen vacancy were calculated. The energy barriers between the first and the second nearest sites, the second and the third nearest sites, and the third and fourth nearest sites are 0.2, 0.5, and 0.24 eV, respectively. The oxygen vacancies at the third and fourth nearest sites relative to the Ca atom represent the oxygen vacancies in undoped $HfO_2$. Therefore, the energy barrier for oxygen migration in the $HfO_2$ gate dielectric is 0.24 eV, which can explain the origin of gate dielectric leakage.

• 한국산학기술학회논문지
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• 제15권2호
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• pp.1188-1194
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• 2014

본 연구의 목적은 플라이 애시, 고로슬래그 미분말, 실리카흄을 사용하여 4성분계 콘크리트의 염해 저항성능을 평가하기 위한 것이다. 본 연구에서는 압축강도, 탄성계수, 염수침지 시험, 염화물 확산계수 및 침투계수를 실시하였다. 4성분계 콘크리트의 염화물 확산계수와 침투계수는 재령 17주에 $0.032{\times}10^{-12}m^2/sec$와 650 coulomb으로 측정되었다. 또한 침지시험 결과 염화물 이온 침투깊이와 염화물량은 3.7 mm and $10.211kg/m^3$로 측정 되었다. 이러한 결과로부터 플라이 애시, 고로슬래그 미분말, 실리카흄을 사용하여 제조한 4성분계 콘크리트는 염해 저항성능과 역학적 특성이 매우 높을 것을 알 수 있었다.