• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.187-192
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• 2013

Fatigue crack was detected from a temperature change around surface crack using the thermographic technique. Thermal gradient across the crack decreased very much due to thermal resistance of contact surface in the crack. Heat diffusion flow passing through the discontinuity was visualized in temperature by infrared camera to find and locate the crack. A fatigue crack specimen(SM-45C), which was prepared according to KS specification and notched in its center to initiate fatigue crack from the notch tip, was heated by halogen lamp at the end of one side to generate a heat diffusion flow in lateral direction. A abrupt jump in temperature across the fatigue crack was observed in thermographic image, by which the crack could be located and sized from temperature distribution.

• International Journal of Oral Biology
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• v.30 no.3
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• pp.91-98
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• 2005

Gamma-aminobutyric acid (GABA) is known as an inhibitory neurotransmitter in the neurons of the central nervous system. However, its detailed action mechanisms in the rostral gustatory zone of the nucleus tractus solitarius (rNTS) have not been established. The present study was aimed to investigate the distribution, role and action mechanisms of GABA in rNTS. Membrane potentials were recorded by whole cell recordings in isolated brain slices of the rat medulla. Superfusion of GABA resulted in a concentration-dependent reduction in input resistance in the neurons in rNTS. The change in input resistance ws accompanied by response to a depolarizing pulse were diminished by GABA. Superfusion of the slices with either $GABA_A$ agonist, muscimol, $GABA_B$ agonist, baclofen or $GABA_C$ agonist, TACA, decreased input resistance and reduced the nerve activity in association with membrane hyperpolarization. It is suggested that inhibitory signals playa role in sensory processing by the rNTS, in that GABA actions occur through activation of $GABA_A,\;GABA_B\;and\;GABA_C$ receptor. These results suggest that GABA has an inhibitory effect on the rNTS through an activation of $GABA_A,\;GABA_B\;and\;GABA_C$ receptors and that the GABAergic inhibition probably plays an important role in sensory processing by the rNTS.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.310-315
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• 2008

Herein, we synthesized silica-coated chrome yellow particles having improved chemical resistance. The intermediate with a good dispersion stability was prepared and the chemical resistance of the final product was investigated. The effects of pH and temperature, as the main parameters influencing the formation of particles, the reduced particle size by homogenizer on the silica coating were investigated. The change in the particle morphology by temperature and pH was also studied. As the results, small and monodisperse particles were achieved at low pH and high temperature. Good silica coating was obtained when used reduced size of the particles by homogenizer. Furthermore, the sufficient silica coating by microencapsulation was obtained at 9~10 pH and the temperature above $90^{\circ}C$.

• Annals of Surgical Treatment and Research
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• v.95 no.5
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• pp.240-248
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• 2018

Purpose: This study aimed to validate the synergistic effect of ABT-737 on docetaxel using MDA-MB-231, a triple negative breast cancer (TNBC) cell line overexpressing B-cell lymphoma-2 (Bcl-2). Methods: Western blot analysis was performed to assess expression levels of Bcl-2 family proteins and caspase-related molecules. Cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell cycle distribution was determined by flow cytometry analysis. Benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (z-VAD-fmk) was used for pretreatment to assess the role of caspases. Results: Cell viability of MDA-MB-231 after combination treatment with ABT-737 and docetaxel was significantly lower than that after docetaxel or ABT-737 monotherapy based on MTT assay (both P < 0.001), with a combination index of 0.41. The proportion of sub-G1 population after combination treatment was significantly higher than that after docetaxel or ABT-737 monotherapy (P = 0.001, P = 0.003, respectively). Pretreatment with z-VAD-fmk completely restored cell viability of MDA-MB-231 from apoptotic cell death induced by combination therapy (P = 0.001). Although pro-caspase-8 or Bid did not show significant change in expression level, pro-casepase-9 showed significantly decreased expression after combination treatment. Cleaved caspase-3 showed increased expression while poly (ADP-ribose) polymerase cleavage was induced after combination treatment. However, hypoxia-inducible factor 1-alpha and aldehyde dehydrogenase 1 totally lost their expression after combination treatment. Conclusion: Combination of ABT-737 with docetaxel elicits synergistic therapeutic effect on MDA-MB-231, a TNBC cell line overexpressing Bcl-2, mainly by activating the intrinsic pathway of apoptosis. Therefore, adjunct of ABT-737 to docetaxel might be a new therapeutic option to overcome docetaxel resistance of TNBCs overexpressing Bcl-2.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.101-120
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• 2023

Electrical resistivity survey have been widely conducted at diverse scales, from a few centimeters for laboratory tests to kilometers for field tests. It measures electrical resistance through relationship of electric potential difference and current between two electrodes penetrated on the surface of medium, and eventually quantifies electrical resistivity known as inherent properties of the medium. In field or full-scale test, it assumes the electrodes as equivalent half-sphere electrodes that have a same surface area with different electrodes for ease of calculation because the contact area between electrode and medium is small and sufficient distance between two electrodes. However, small-scale laboratory test is significantly affected by the electrode geometries (penetrated depth, height, radius of electrode and distance between electrodes), which change the equipotential surface and electric current flow. Indeed, the electrode geometries may eventually cause a difference of electrical resistivity value. This study reviews the theoretical electrical resistance derived with various electrode geometries (half-sphere, cylinder, cylindrical with half-spherical tip, cylindrical with conical tip) and verifies the developed numerical module by comparing results with the theoretical electrical resistance. The distributions of electrical resistance around electrodes and among electrodes are analyzed. In addition, it is discussed how the electrical characteristic of cylindrical electrode with conical tip widely used in field test has effect on the electric current flow.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.919-930
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• 2014

In this study, the load capacities and behaviors of a shotcrete member with steel supports, as composite member, are investigated numerically by using a fiber section element. The cross section of a shotcrete lining with steel support is divided into a bundle of fibers, which are allocated nonlinear stress-strain relations and used for determining internal forces. To verify the used approach of the finite element method for shotcrete with steel supports, the load-displacement relations of shotcrete lining obtained by numerical analysis are compared with existing experimental results and are analyzed with the stress distribution of the shotcrete and steel support obtained numerically. As a result, it is shown that the proposed approach can predict the load capacities of each material and the overall nonlinear behavior of shotcrete lining with steel supports. The change of location of the neutral axis and the flexural resistance ratio of each material are also derived from the stress distribution of the cross section of the shotcrete lining with steel supports. From the results, it is concluded that the flexural resistance performance of steel support should be considered in shotcrete lining design.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.172-177
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• 2014

We present on a threshold switching device based on AsGeTeSi material which is significantly improved by two $N_2$ processes: reactive $N_2$ during deposition, and $N_2$ plasma hardening. The introduction of N2 in the two-step processing enables a stackable and thermally stable device structure, is allowing integration of switch and memory devices for application in nano scale array circuits. Despite of its good threshold switching characteristics, AsTeGeSi-based switches have had key issues with reliability at a high temperature to apply resistive memory. This is usually due to a change in a Te concentration. However, our chalconitride switches(AsTeGeSiN) show high temperature stability as well as high current density over $1.1{\times}10^7A/cm^2$ at $30{\times}30(nm^2)$ celll. A cycling performance of the switch was over $10^8$ times. In addition, we demonstrated a memory cell consisted of 1 switch-1 resistor (1S-1R) stack structure using a TaOx resistance memory with the AsTeGeSiN select device.

• Radiation Oncology Journal
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• v.35 no.2
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• pp.144-152
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• 2017

Purpose: The role of radiotherapy (RT) was largely deserted after the introduction of platinum-based chemotherapy, but still survival rates are disappointingly low. This study focuses on assessing the clinical efficacy of RT in relation to chemotherapy resistance. Materials and Methods: From October 2002 to January 2015, 44 patients were diagnosed with epithelial ovarian cancer (EOC) and treated with palliative RT for persistent or recurrent EOC. All patients received initial treatment with optimal debulking surgery and adjuvant platinum-based chemotherapy. The biologically effective dose (BED) was calculated with ${\alpha}/{\beta}$ set at 10. Ninety-four sites were treated with RT with a median BED of 50.7 Gy (range 28.0 to 79.2 Gy). The primary end-point was the in-field local control (LC) interval, defined as the time interval from the date RT was completed to the date any progressive or newly recurring disease within the RT field was detected on radiographic imaging. Results: The median follow-up duration was 52.3 months (range 7.7 to 179.0 months). The 1-year and 2-year in-field LC rates were 66.0% and 55.0%, respectively. Comparisons of percent change of in-field tumor response showed similar distribution of responses among chemoresistant and chemosensitive tumors. On multivariate analysis of predictive factors for in-field LC analyzed by sites treated, $BED{\geq}50Gy$ (hazard ratio, 0.4; confidence interval, 0.2-0.9; p = 0.025) showed better outcomes. Conclusion: Regardless of resistance to platinum-based chemotherapy, RT can be a feasible treatment modality for patients with persistent of recurrent EOC. The specific role of RT using updated approaches needs to be reassessed.

• Journal of Pharmaceutical Investigation
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• v.36 no.1
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• pp.1-9
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• 2006

Human solid tumors exhibit a multicellular resistance (MCR) resulting from limited drug penetration and decreased sensitivity of tumor cells when interacting with their microenvironments. Multicellular cultures represent solid tumor condition in vivo and provide clinically relevant data. There is little data on antitumor effect of paclitaxel (PTX) in multicellular cultures although its MCR has been demonstrated. In the present study, we evaluated antiproliferative effects of PTX in multicellular layers (MCL) of DLD-1 human colorectal carcinoma cells. BrdU labeling index (LI), thickness of MCL, cell cycle distribution and cellular uptake of calcein were measured before and after exposure to PTX at 0.1 to 50 ${\mu}M$ for 24, 48 and 72 hrs. BrdU LI and thickness of MCL showed a concentration- and time-dependent decrease and the changes in both parameters were similar, i.e., 34.2% and 40.6% decrease in BrdU LI and thickness, respectively, when exposed to $50\;{\mu}M$ for 72 hr. The DLD-1 cells grown in MCL showed increase in $%G_{0}/G_{1}$ and resistance to cell cycle arrest and apoptosis compared to monolayers. Calcein uptake in MCL did not change upon PTX exposure, indicating technical problems in multicellular system. Overall, these data indicate that antitumor activity of PTX may be limited in human solid tumors (a multicellular system) and MCL may be an appropriate model to study further pharmacodynamics of PTX.

• International Journal of Korean Welding Society
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• v.1 no.1
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• pp.58-62
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• 2001

The surface of AC8A Ah alloy was modified by adding the Cu powder using a Plasma Transferred Arc (PTA) welding process. Under the optimum fabricating conditions, the modified surface of AC8A Ah alloy was observed to possess the sound microstructure with a minimum porosity. Hardness and wear resistance properties of the as-fabricated alloy were compared with those of the 76 heat-treated one. In case of the as-fabricated alloy, the hardness of the modified layer was twice that of the matrix region. Although significant increase in the hardness of the matrix region was observed after T6 heat treatment, the hardness of the modified layer was not observed to change. The wear resistance of the modified layer was significantly increased compared to that of the matrix region. The microstructure of a weld zone and the matrix region were investigated using the optical microscope, scanning electron microscope (SEM), electron probe microanalysis (EPMA), and transmission electron microscope (TEM). The primary and eutectic silicon in the weld zone were finer and more curved than in the matrix region, while some precipitates has had been found therein. According to the TEM observation, the predominant precipitate present in the weld zone was the $\theta$'phase, which is precipitated during cooling by rapid solidification in PTA welding process. Improvement of hardness and wear properties in the weld zone in the as-fabricated condition can be explained based on the presence of $\theta$’precipitates and fine primary and eutectic silicon distribution.