• Journal of Technologic Dentistry
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• v.25 no.1
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• pp.9-20
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• 2003

Using a nickel-chrome casting alloy called 'Rexillium V' which is also available as base metal alloy for dental ceramic crown, 4 types of mixtures(A, B, C, D) with old and new metal were prepared for cyclic casting. The results of cyclic casting can be outlined as follows: 1. For Vickers hardness after casting, specimen A and D tended to have lower hardness in the course of cyclic casting, while specimen B and C tended to higher hardness. 2. The results of X-ray diffraction analysis showed that major crystal phase contained nickelchrome compounds and carbide. 3. The observation results of SEM photographs after cyclic casting show that there was a significant tendency to have similar structures among experimental groups. 4. The results of EDX analysis after cyclic casting showed that there were little differences in chemical composition between parent metal and base metal alloy. Although industrial nickel-chrome cast alloy did not show any significant change in material properties even through cyclic casting over several times, it is recommended that more there be more in-depth studies on how to detect any potential corrosion, discoloration and toxication of dental ceramic crown implanted in patient's oral cavity.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.2
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• pp.63-68
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• 2003

The DC and RF characteristics of $In_{0.5}Ga_{0.5}P/In_{0.22}Ga_{0.78}As/GaAs$ p-HEMTs with a gate oxide layer of various thicknesses ($50{\;}{\AA},{\;}300{\;}{\AA}$) were investigated and compared with those of a Schottky-gate p-HEMT without the gate oxide layer. A prominent improvement in the breakdown voltage characteristics were observed for a p-HEMT having a gate oxide layer, which was implemented by using a liquid phase oxidation technique. The on-state breakdown voltage of the p-HEMT having the oxide layer of $50{\;}{\AA}$was ~2.3 times greater than that of a Schottky-gate p-HEMT. However, the p-HEMT having the gate oxide layer of $300{\;}{\AA}$ suffered from a poor gate-control capability due to the drain induced barrier lowering (DIBL) resulting from the thick gate oxide inspite of the lower gate leakage current and the higher on-state breakdown voltage. The results for a primitive p-HEMT having the gate oxide layer without any optimization of the structure and the process indicate the potential of p-HEMT having the gate oxide layer for high-power applications.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.22-28
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• 2003

This paper describes the frequency dependence of the grounding impedance. In order to propose the evaluation method of the transient response of powered grounding systems, the grounding impedances were measured with varying the frequency of incoming currents by way of the variable frequency inverter and band pass filter. The magnitude and phase of the grounding impedance were analyzed in the frequency range of 20 [Hz]∼2.1[kHz]. The grounding impedance were increased with increasing the frequency of the test current. The grounding impedance at the frequency of 2[kHz] in the actual 22.9[kV] substation grounding system was approximately 3 times as large as the 60[Hz] grounding impedance. It was found that the frequency dependence of the grounding impedance is mainly subject to the inductive reactance of the grounding conductors. As a result, it is critical to determine the shape and size of grounding grid reducing the resultant inductance in grounding systems for lightning surge protection.

• Advances in materials Research
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• v.2 no.3
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• pp.141-153
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• 2013

Nanocrystalline Barium niobate ($BaNbO_3$) has been synthesized by a novel auto-igniting combustion technique. The X-Ray diffraction studies reveals that $BaNbO_3$ posses a cubic structure with lattice constant $a=4.071{\AA}$. Phase purity and structure of the nano powder are further examined using Fourier-Transform Infrared and Raman spectroscopy. The average particle size of the as prepared nano particles from the Transmission Electron Microscopy is 20 nm. The UV-Vis absorption spectra of the samples are recorded and the calculated average optical band gap is 3.74eV. The sample is sintered at an optimized temperature of $1425^{\circ}C$ for 2h and attained nearly 98% of the theoretical density. The morphology of the sintered pellet is studied with Scanning Electron Microscopy. The dielectric constant and loss factor of a well-sintered $BaNbO_3$ at 5MHz sample is found to be 32.92 and $8.09{\times}10^{-4}$ respectively, at room temperature. The temperature coefficient of dielectric constant was $-179pp/^{\circ}C$. The high dielectric constant, low loss and negative temperature coefficient of dielectric constant makes it a potential candidate for temperature sensitive dielectric applications.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.1
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• pp.315-321
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• 2016

Background: Herbal medicine has becoming a potential source of treatment for different types of cancer including breast cancer. It has been shown that plants from the family Rhamnaceae possess anticancer activity. Objective: In this study, we determined the antiproliferative influence of Ziziphus spina christi- a species from this family- on the MCF-7 (human breast adenocarcinoma) cell line. Materials and Methods: The cytotoxicity of the total extract, ethanol, ethanol-aqueous (1:1) as well as aqueous fractions of Ziziphus spina christi leaves was evaluated through MTT assay against MCF-7 cell line. Cell cycle inhibition and apoptosis induction were assessed by flowcytometry cycle RNase/PI analysis and Annexin V-FLUOS, respectively. Apoptosis was also analyzed by immunoblotting assay. Results: Our results indicated that the ethanolic fraction had the lowest $IC_{50}$ value (0.02 mg/ml), induced cell cycle arrest at the G1/S phase as well as apoptosis after a 48h of treatment. Conclusions: This is the first report on anticancer effect of Ziziphus spina christi ethanolic fraction on breast cancer cells, providing a scientific basis for its utility in traditional medicine. However, further in-depth studies are needed to confirm the precise mechanisms.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.13
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• pp.5265-5271
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• 2015

Background: The effects of plant products on cancer cells has become a field of major importance. Many substancesmay induce apoptosis in anti-cancer treatment. Pectins, a family of complex polysaccharides, and their degradation products may for exasmple exert apoptotic effects in cancer cells. Apples and citrus fruits are the main sources of pectin which can be applied for anti-cancer research. The present study concerned an intact form of pectic-oligoshaccharide named pectic acid (poly galactronic acid). Materials and Methods: Inhibition of cell proliferation assays (MTT), light microscopy, fluorescence microscopy (acridin orange/ethidium bromide), DNA fragmentation tests, cell cycle analysis, annexin PI and Western blotting methods were applied to evaluate apoptosis. Results: The results indicated that pectic acid inhibited cell growth and reduced cell attachment after 24h incubation. This did not appear to be due to necrosis, since morphological features of apoptosis were detected with AO/EB staining and cell cycling was blocked in the sub-G1 phase. Annexin/PI and DNA fragmentation findings indicated that apoptosis frequency increased after 24h incubation with pectic acid. In addition, the data showed pectic acid induced caspase-dependent apoptosis. Conclusions: These data indicate that apple pectic acid without any modification could trigger apoptosis in MDA-MB-231 human breast cancer cells and has potential to improve cancer treatment as a natural product.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.20
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• pp.8829-8836
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• 2014

Background: Cyclooxygenase-2 (COX-2), considered to have tumor-promoting potential, is highly expressed in a variety of tumors, including breast cancer. Since the functions and action mechanisms of COX-2 in breast cancer have not been fully elucidated, in the present study, the effects of target inhibiting COX-2 with recombinant adenovirus Ad-COX-2-shRNA on malignant biological behavior were investigated in representative cell lines. Materials and Methods: Breast cancer MDA-MB-231 and MCF-7 cells were transfected with Ad-COX-2-shRNA and COX-2 expression was tested by RT-PCR and Western blotting. Changes in proliferation, apoptosis and invasion of breast cancer cells were detected with various assays including MTT, colony forming, flowcytometry and Transwell invasion tests. The expression of related proteins involved in the cell cycle, apoptosis, invasion and signaling pathways was assessed by Western blotting. Results: COX-2 expression was significantly reduced in both breast cancer cell lines infected with Ad-COX-2-shRNA, with obvious inhibition of proliferation, colony forming rate, G2/M phase passage and invasion, as well as induction of apoptosis, in MDA-MB-231 and MCF-7 cells, respectively. At the same time, proteins related to the cell cycle, anti-apoptosis and invasion were significantly downregulated. In addition, c-myc expression and phosphorylation activation of Wnt/${\beta}$-catenin and p38MAPK pathways were reduced by the Ad-COX-2-shRNA. Conclusions: COX-2 expression is associated with proliferation, apoptosis and invasion of breast cancer cells, and its mechanisms of action involve regulating expression of c-myc through the p38MAPK and Wnt/${\beta}$-catenin pathways.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.7
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• pp.3293-3297
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• 2014

Background: Pine needle oil from crude extract of pine needles has anti-tumor effects, but the effective component is not known. Methods: In the present study, compounds from a steam distillation extract of pine needles were isolated and characterized. Alpha-pinene was identified as an active anti-proliferative compound on hepatoma carcinoma BEL-7402 cells using the MTT assay. Results: Further experiments showed that ${\alpha}$-pinene inhibited BEL-7402 cells by arresting cell growth in the G2/M phase of the cell cycle, downregulating Cdc25C mRNA and protein expression, and reducing cycle dependence on kinase 1(CDK1) activity. Conclusion: Taken together, these findings indicate that ${\alpha}$-pinene may be useful as a potential anti-tumor drug.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.13
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• pp.5253-5257
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• 2014

Formaldehyde (FA) is an economically important chemical, and has been found to cause various types of toxic damage to the body. Formaldehyde-induced toxic damage involves reactive oxygen species (ROS) that trigger subsequent toxic effects and inflammatory responses, which may increase risk of cancer. Therefore, in the present study, we aimed to investigate the possible toxic mechanism in bone marrow caused by formaldehyde. In accordance with the principle of randomization, the mice were divided into four groups of 6 mice per group. One group was exposed to ambient air and the other three groups were exposed to different concentrations of formaldehyde (20, 40, $80mg/m^3$) for 15 days in the respective inhalation chambers, 2h a day. At the end of the 15-day experimental period, all mice were killed. Bone marrow cells were obtained. Some of those were used for the determination of blood cell numbers, bone marrow karyote numbers, CFU-F, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content; others were used for the determination of mitochondrial membrane potential (MMP), cell cycle and Bcl-2, Bax, CytC protein expression. WBC and PLT numbers in median and high dose groups were obvious reduced, but there was no change on RBC numbers. There was also reduced numbers of bone marrow karyotes and CFU-F in the high dose group. SOD activity was decreased, but MDA content was increased. MMP and Bcl-2 expression were decreased with increasing formaldehyde concentration, while expression of Bax and Cyt C was increased. We also observed change in cell cycling, and found that there was S phase arrest in the high dose group. Our study suggested that a certain concentration of formaldehyde could have toxic effects on the hematopoietic system, with oxidative stress as a critical effect.

• BMB Reports
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• v.29 no.5
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• pp.429-435
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• 1996

To investigate the structure-antagonistic relationship of the cyclohexapeptide L-659,877, a selective NK-2 tachykinin receptor antagonist, seven analogues were chemically synthesized by a solid phase method. The agonistic and antagonistic activities of the analogues were evaluated by contraction assay using the smooth muscle of guinea pig trachea (GPT) containing the NK-2 receptor. It was shown that the aromatic ring of Phe at position 3 and the sulfur group of Met at position 6 in L-659,877 were essential for binding to the NK-2 receptor. Decrease in antagonistic activity of L-659,877 caused by substituting Leu for Nle at position 5 indicates that the ${\gamma}$ methyl group and side chain length of Leu plays an important role in its antagonistic action. Although the activity was slightly lower than L-659,877, cyclo $[{\beta}Ala^{8}]NKA(4-10)$ (analogue 1) showed potential antagonistic activity for the NK-2 receptor. It was confirmed that the expansion of the ring in L-659,877 by substitution of ${\beta}Ala$ for Gly at position 4 stabilized its conformation monitored by CD spectra. The results suggest that analogue 1 can be used as a new leader compound to design a more powerful, selective, and stable NK-2 receptor antagonist.