• Applied Microscopy
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• v.27 no.1
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• pp.31-46
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• 1997

Ultrastructure of mouse thymus was evaluated, following the administration of potassium dichromate and mercuric chloride, the heavy metals of evironmental pollutants. Potassium dichromate (20 mg/kg) or mercuric chloride solutions (10 mg/kg) were subcutanously injected to the mice. Six hours, three days and two weeks after the injections, animals were sacrificed. Thymic tissues were fixed in 2.5% glutaraldehyde-1.5% paraformaldehyde solutions. The procedure was followed by the fixation in 1% osmium tetroxide solutions. Washed and dehydrated tissue-blocks were embedded in the araldite mixture. Ultra-thin sections were stained with uranyl acetate-lead citrate solutions. Results observed were as follows: 1. In electron microscopy, cortical population of thymocytes in the thymus of experimental groups were reduced. especially in the outer cortex. Subcapsular cortices of potassium dichromate treated mice were filled with many epithelial reticular cells, whereas the similar area of mercuric chloride-treated mice exhibited large intercellular spaces. 2. In the thymus of mercuric chloride treated group, large intercellular spaces were formed by shrinkage of epithelial reticular cells, and the space was invaded by numerous cytoplasmic projections of macrophages. Thymocytes nuded out from the shrunken cytoplasm of epithelial reticular cells, presented numerous microvilli. 3. In the thymus of potassium dicromate treated group, many activated macrophages and plasma cells migrated into thymic cortices. 4. In the perivascular spaces of thymic cortices of potassium dichromate- and mercuric chloride-treated mice, activated macrophages. plasma cells, collagen fibrils, and flocculent substance of exudated materials were exhibited. From the above findifgs, it was concluded that potassium dichromate or mercuric chloride could disturb the normal differentiation or 'education' of T cells in the thymic cortex. In turn, these heavy metals may hurt the immunological defense mechanism.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.605-611
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• 2014

$SrGd_{2-x}(MoO_4)_4:Er^{3+}/Yb^3$ phosphors with doping concentrations of $Er^{3+}$+ and $Yb^{3+}$ ($x=Er^{3+}+Yb^{3+}$, $Er^{3+}=0.05$, 0.1, 0.2, and $Yb^{3+}=0.2$, 0.45) were successfully synthesized by the cyclic microwave-modified sol-gel method, and their upconversion mechanism and spectroscopic properties have been investigated in detail. Well-crystallized particles showed a fine and homogeneous morphology with grain sizes of $2-5{\mu}m$. Under excitation at 980 nm, $SrGd_{1.7}(MoO_4)_4:Er_{0.1}Yb_{0.2}$ and $SrGd_{1.5}(MoO_4)_4:Er_{0.05}Yb_{0.45}$ particles exhibited a strong 525-nm emission band, a weak 550-nm emission band in the green region, and a very weak 655-nm emission band in the red region. The Raman spectra of the doped particles indicated the domination of strong peaks at higher frequencies of 1023, 1092, and $1325cm^{-1}$ and at lower frequencies of 223, 2932, 365, 428, 538, and $594cm^{-1}$ induced by the incorporation of the $Er^{3+}$+ and $Yb^{3+}$+ elements into the $Gd^{3+}$ site in the crystal lattice, which resulted in the unit cell shrinkage accompanying a new phase formation of the $[MoO_4]^{2-}$ groups.

• The Korean Journal of Physiology and Pharmacology
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• v.10 no.6
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• pp.329-335
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• 2006

This study was aimed to investigate the nitric oxide (NO)-induced cytotoxic mechanism in PC12 cells. Sodium nitroprusside (SNP), an NO donor, decreased the viability of PC12 cells in dose-and time-dependent manners. SNP enhanced the production of reactive oxygen species (ROS), and gave rise to apoptotic morphological changes including cell shrinkage, chromatin condensation, and DNA fragmentation. Expression of Bax was not affected, whereas Bcl-2 was downregulated in SNP-treated PC12 cells. SNP augmented the release of cytochrome c from mitochondria into cytosol and enhanced caspase -8, -9, and -3 activities. SNP upregulated both Fas and Fas-L, which are known to be components of death receptor assembly. These results suggest that NO induces apoptosis of PC12 cells through both mitochondria-and death receptor-mediated pathways mediated by ROS and Bcl-2 family.

• Steel and Composite Structures
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• v.50 no.6
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• pp.659-674
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• 2024

Casting Ultra High-Performance Concrete (UHPC) on an orthotropic steel deck and forming a composite action by connectors could improve the steel deck fatigue performance. This study presents the mechanical performance of a proposed post-combination connection between UHPC and steel, which had a low constraint effect on UHPC shrinkage. A total of 10 push-out tests were conducted for static and fatigue performance investigations. And the test results were compared with evaluation methods in codes to verify the latter's applicability. Meanwhile, nonlinear simulation and parametric works with material damage plasticity models were also conducted for the static and fatigue failure mechanism understanding. The static and fatigue test results both showed that fractures at stud roots and surrounding local UHPC crushes were the main failure appearances. Compared with normally arranged studs, group arrangement could result in reductions of static stud shear stiffness, strength, and fatigue lives, which were about 18%, 12%, and 27%, respectively. Compared with the test results, stud shear capacity and fatigue lives evaluations based on the codes of AASHTO, Eurocode 4, JSCE and JTG D64 could be applicable in general while the safety redundancies tended to be smaller or even insufficient for group studs. The analysis results showed that arranging studs in groups caused obviously uneven strain distributions. The severer stress concentration and larger strain ranges caused the static and fatigue performance degradations of group studs. The research outcome provides a very important basis for establishing a design method of connections in the novel post-combination steel-UHPC composite deck.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.103-111
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• 2012

One of the basic physical properties of the hardened cement paste, the rigidity, is deteriorated during concrete matrix forming, depending on the replacement rate of the crushed stone powder, and due to drying shrinkage. Therefore, the concrete containing crushed stone powder has been limitedly used as non-structural construction material. To improve these disadvantages, a hydrothermal reaction employing method can be considered. High-temperature and high-pressure water is involved in the hydrothermal reaction in the mixing with specific materials. The rigidity improving mechanism is related to the synthesis of calcium silicate. The calcium silicate is produced through reaction between calcium compounds and the silicic acid. Various kinds of calcium silicate can be produced depending on the CaO/$SiO_2$ mole ratio, the temperature of the hydrothermal synthesis, the pressure, and the reaction time. The product of the synthesis mechanism, tobermorite crystal, plays a pivotal role for the rigidity reinforcement. The crushed stone powder, analyzed in this study, contains 50 to 60% of $SiO_2$ and 10 to 20% $Al_2O_3$. The composite rate is appropriate to create the tobermorite crystal through formation of hardened cement matrix under the hydrothermal synthetic conditions and with the CaO in the cement. Moreover, further reinforcement was promoted using the property of material under the identical density through promoting the formation of tobermorite crystal.

• Parasites, Hosts and Diseases
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• v.36 no.1
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• pp.7-14
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• 1998

In order to understand the action mechanism of polyhexamethylene biguanide (PHMB) to the cyst of Accnthcnloebc on the morphological basis, the cysts of four corneal isolates of Acanthanoebc were treated with minimal cysticidal concentration (MCC) of PHMB and their ultrastructural changes were examined by transmission electron microscopy. The most striking change of cysts treated with PHMB compared with normal cysts was the shrinkage of intracystic amoebae, which resulted in the separation of the plasma membrane of intracystic amoeba from endocystic wall. Subplasmalemmal lipid droplets became irregularly shaped . In severely damaged cysts, cytoplasm was aggregated and organelles were severely deformed. Cytoplasmic materials were leaked out through the damaged plasma membrane. Most cysts showed aggregation of nuclear chromatin material. Number of mitochondrial cristae was also reduced. Ecto- and endo-cystic walls were relatively well tolerated. Findings in the present study revealed that PHMB affected mainly on plasma membrane, but lesser on organellar membrane of intracystic amoeba. It seemed likely that PHMB might kill cystic forms of Accnthamoebc by similar mechanism in which this environmental biocide can damage the cell wall of Escherichia coli by binding with acidic phospholipids.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.93-93
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• 2016

Large scale integrated circuits (LSIs) has been improved by the shrinkage of the circuit dimensions. The smaller chip sizes and increase in circuit density require the miniaturization of the line-width and space between metal interconnections. Therefore, an extreme precise control of the critical dimension and pattern profile is necessary to fabricate next generation nano-electronics devices. The pattern profile control of plasma etching with an accuracy of sub-nanometer must be achieved. To realize the etching process which achieves the problem, understanding of the etching mechanism and precise control of the process based on the real-time monitoring of internal plasma parameters such as etching species density, surface temperature of substrate, etc. are very important. For instance, it is known that the etched profiles of organic low dielectric (low-k) films are sensitive to the substrate temperature and density ratio of H and N atoms in the H2/N2 plasma [1]. In this study, we introduced a feedback control of actual substrate temperature and radical density ratio monitored in real time. And then the dependence of etch rates and profiles of organic films have been evaluated based on the substrate temperatures. In this study, organic low-k films were etched by a dual frequency capacitively coupled plasma employing the mixture of H2/N2 gases. A 100-MHz power was supplied to an upper electrode for plasma generation. The Si substrate was electrostatically chucked to a lower electrode biased by supplying a 2-MHz power. To investigate the effects of H and N radical on the etching profile of organic low-k films, absolute H and N atom densities were measured by vacuum ultraviolet absorption spectroscopy [2]. Moreover, using the optical fiber-type low-coherence interferometer [3], substrate temperature has been measured in real time during etching process. From the measurement results, the temperature raised rapidly just after plasma ignition and was gradually saturated. The temporal change of substrate temperature is a crucial issue to control of surface reactions of reactive species. Therefore, by the intervals of on-off of the plasma discharge, the substrate temperature was maintained within ${\pm}1.5^{\circ}C$ from the set value. As a result, the temperatures were kept within $3^{\circ}C$ during the etching process. Then, we etched organic films with line-and-space pattern using this system. The cross-sections of the organic films etched for 50 s with the substrate temperatures at $20^{\circ}C$ and $100^{\circ}C$ were observed by SEM. From the results, they were different in the sidewall profile. It suggests that the reactions on the sidewalls changed according to the substrate temperature. The precise substrate temperature control method with real-time temperature monitoring and intermittent plasma generation was suggested to contribute on realization of fine pattern etching.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.3 s.32
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• pp.37-45
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• 2004

Electroless Ni(P) has been widely used for under bump metallization (UBM) of flip chip and surface finish layer in microelectronic packaging because of its excellent solderability, corrosion resistance, uniformity, selective deposition without photo-lithography, and also good diffusion barrier. However, the brittle fracture at solder joints and the spatting of intermetallic compound (IMC) associated with electroless Ni(P) are critical issues for its successful applications. In the present study, the mechanism of IMC spatting and microstructure change of the Ni(P) film were investigated with varying P content in the Ni(P) film (4.6,9, and $13 wt.\%$P). A reaction between Sn penetrated through the channels among $Ni_3Sn_4$ IMCs and the P-rich layer ($Ni_3P$) of the Ni(P) film formed a $Ni_3SnP$ layer. Thickening of the $Ni_3SnP$ layer led to $Ni_3Sn_4$ spatting. After $Ni_3Sn_4$ spatting, the Ni(P) film directly contacted the molten solder and the $Ni_3P$ phase further transformed into a $Ni_2P$ phase. During the crystallization process, some cracks formed in the Ni(P) film to release tensile stress accumulated from volume shrinkage of the film.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.449-456
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• 1999

The concrete wall is the most useful of retaining structure which can obtain the engineering stability, but has problems that is not friendly with nature environment in a fine view, such as poor rear drainage, and shrinkage crack by temperature difference, etc. Because of this problems, the research for a segmental crib retaining wall has been performed. A segmental crib retaining wall is quickly and easily erected because is possible to be erected as the individual members, and is not sensitive to differential settlement and earthquakes. Also, it shows effective drainage and has a friendly advantage with nature environment because of being able to be planted with vines and shrubs in retaining walls The design of crib retaining walls has traditionally been based on classical soil mechanics theories. These theories, originally derived by Rankine(1857) and Coulomb(1776), assume that the wall acts as a rigid body. This assumption results in failure being predicted by either monolithic overturning or base sliding mechanisms. However, the wall consists of individual members which have been created a three dimensional grid. This grid confines an fill mass which becomes part of the wall. The filled wall resists the earth pressure with the same mechanism of classical gravity walls. Because of the flexibility of the individual segment, it allows relative movement between the individual members within the wall. The three dimensional flexible grid leads to stress redistribution when the wall is subjected to external or fill loads. Due to the flexibility and the stress redistribution, the failure of segmental crib wall consists of not only overturing and base sliding but the local deformation and the failure between the segmental members. It has been researched in the field that due to this flexibility and load redistribution, serviceability failure of segmental crib walls is unlikely to be due to overturning or base sliding. Therefore, in this study, the relative displacement appearance of retaining wall due to variation of inclination is measured to examine this behavior characteristics. Also, the behavior characteristics of retaining walls by surcharge load, and location of acting point of retaining wall rear, and the displacement characteristics and deflections are estimated about the existence and nonexistence of Rear Stretcher performing an role in transmitting earth pressure of Header and Stretcher organizing retaining walls. This research focuses on the characteristics due to the behavior of retaining walls. This research focuses on the characteristics due to the behavior of retaining walls.

• Tuberculosis and Respiratory Diseases
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• v.56 no.5
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• pp.514-522
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• 2004

Background : Non-steroidal anti-inflammatory drugs (NSAID) are useful in chemoprevention of colorectal cancers. Continuous NSAID administation causes 40% to 50% reduction in relative risk for colorectal cancer. Sulindac possesses an antiproliferative effect and induces apoptosis and tumor regression on colon cancer and other types of cancers. We intended to analyze the effects of sulindac in three non-small cell lung cancer cell lines. Materials and Methods : The human lung cancer cell lines, A549, NCI-H157 and NCI-H460 were used for this study. Viability was tested by MTT assay, and cell death rate was measured by lactate dehydrogenase(LDH) release. Apoptosis was estimated by flow cytometric analysis and nuclear staining. Results: Sulindac was able to decrease the viability of non-small cell lung cancer cells in a dose- and time- dependent manner. In a parallel effect of sulindac on cell death rate, LDH release was increased in sulindac-treated lung cancer cells. Sulindac significantly increased apoptosis characterized by an increase of $sub-G_0/G_1$ fraction and morphological change of nuclei. The rate of apoptotic cells after sulindac treatment in lung cancer cells increased in a time- and dose- dependent manner in flow cytometric analysis. Apoptotic cells were defined as nuclear shrinkage, chromatin condensation and nuclear fragmentation of cells. Conclusion : Sulindac decreases viability and induces the apoptosis of lung cancer cells. Further studies will be needed to elucidate the potential mechanism of sulindac-induced apoptosis in lung cancer cells.