• Korean Journal of Materials Research
• /
• v.15 no.3
• /
• pp.161-165
• /
• 2005

We investigated selective dry etching of GaAs over AlGaAs and InGaP in high density planar inductively coupled $BCl_3/SF_6$ plasmas. The process parameters were ICP source power (0-500 W), RE chuck power (0-30W) and gas composition $(60-100\%\;BCl_3\;in\;BCl_3/SF_6)$. The process results were characterized in terms of etch rate, selectivities of GaAs over AlGaAs and InGaP, surface morphology, surface roughness and residues after etching. $BCl_3/SF_6$ selective etching of GaAs showed quite good results in this study. Selectivities of GaAs $(GaAs:AlGaAs\~36:1,\;GaAs:InGaP\~45:1)$ were superior at $18BCl_3/2SF_6$, 20 W RF chuck power, 300 W ICP source power and 7.5 mTorr. Addition of $(5-15\%)SF_6\;to\;BCl_3$ produced relatively high selectivities of GaAs over AlGaAs and InGaP during etching due to decrease of etch rates of AlGaAs and InGaP (boiling points of etch products: $AlF_3\~1300^{\circ}C,\;InF_3>1200^{\circ}C$ at atmosphere) at the condition. SEM and AFM data showed slightly sloped sidewall and somewhat rough surface$(RMS\~9nm)$. XPS study on the surface of processed GaAs proved a very clean surface after dry etching. It shows that planar inductively coupled $BCl_3/SF_6$ plasmas could be a good candidate for selective dry etching of GaAs over AlGaAs and InGaP.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.11
• /
• pp.4555-4561
• /
• 2014

Background: Silencing due to methylation of suppressor of cytokine signaling-3 (SOCS-3), a negative regulator gene for the JAK/STAT signaling pathway has been reported to play important roles in leukemogenesis. Imatinib mesylate is a tyrosine kinase inhibitor that specifically targets the BCR-ABL protein and induces hematological remission in patients with chronic myeloid leukemia (CML). Unfortunately, the majority of CML patients treated with imatinib develop resistance under prolonged therapy. We here investigated the methylation profile of SOCS-3 gene and its downstream effects in a BCR-ABL positive CML cells resistant to imatinib. Materials and Methods: BCR-ABL positive CML cells resistant to imatinib (K562-R) were developed by overexposure of K562 cell lines to the drug. Cytotoxicity was determined by MTS assays and $IC_{50}$ values calculated. Apoptosis assays were performed using annexin V-FITC binding assays and analyzed by flow cytometry. Methylation profiles were investigated using methylation specific PCR and sequencing analysis of SOCS-1 and SOCS-3 genes. Gene expression was assessed by quantitative real-time PCR, and protein expression and phosphorylation of STAT1, 2 and 3 were examined by Western blotting. Results: The $IC_{50}$ for imatinib on K562 was 362nM compared to 3,952nM for K562-R (p=0.001). Percentage of apoptotic cells in K562 increased upto 50% by increasing the concentration of imatinib, in contrast to only 20% in K562-R (p<0.001). A change from non-methylation of the SOCS-3 gene in K562 to complete methylation in K562-R was observed. Gene expression revealed down-regulation of both SOCS-1 and SOCS-3 genes in resistant cells. STAT3 was phosphorylated in K562-R but not K562. Conclusions: Development of cells resistant to imatinib is feasible by overexposure of the drug to the cells. Activation of STAT3 protein leads to uncontrolled cell proliferation in imatinib resistant BCR-ABL due to DNA methylation of the SOCS-3 gene. Thus SOCS-3 provides a suitable candidate for mechanisms underlying the development of imatinib resistant in CML patients.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.11
• /
• pp.4671-4676
• /
• 2014

Background: MicroRNA-200a (miR-200a) has been reported to regulate tumour progression in several tumours but little is known about its role in neuroblastoma. Our aim was to investigate the potential role and mechanism of miR-200a in neuroblastomas. Materials and Methods: Expression levels of miR-200a in tissues were determined using RT-PCR. The effect of miR-200a and shAP-$2{\gamma}$ on cell viability was evaluated using MTS assays, and target protein expression was determined using Western blotting and RT-PCR. Luciferase reporter plasmids were constructed to confirm direct targeting. Results were reported as mean${\pm}$S.E.M and differences were tested for significance using the 2-tailed Students t-test. Results: We determined that miR-200a expression was significantly lower in neuroblastoma tumors than the adjacent non-cancer tissue. Over-expression of miR-200 are reduced cell viability in neuroblastoma cells and inhibited tumor growth in mouse xenografts. We identified AP-$2{\gamma}$ as a novel target for miR-200a in neuroblastoma cells. Thus miR-200a targets the 3'UTR of AP-$2{\gamma}$ and inhibits its mRNA and protein expression. Furthermore, our result showed that shRNA knockdown of AP-$2{\gamma}$ in neuroblastoma cells results in significant inhibit of cell proliferation and tumor growth in vitro, supporting an oncogenic role of AP-$2{\gamma}$ in neuroblastoma. Conclusions: Our study revealed that miR-200a is a candidate tumor suppressor in neuroblastoma, through direct targeting of AP-$2{\gamma}$. These findings re-enforce the proposal of AP-$2{\gamma}$ as a therapeutic target in neuroblastoma.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.251-251
• /
• 2016

For several decades, industrial processes consume a huge amount of raw water for various objects that consequently results in the generation of large amounts of wastewater. Wastewaters are consisting of complex mixture of different inorganic and organic compounds and some of them can be toxic, hazardous and hard to degrade. These effluents are mainly treated by conventional technologies such are aerobic and anaerobic treatment and chemical coagulation. But, these processes are not suitable for eliminating all hazardous chemical compounds form wastewater and generate a large amount of toxic sludge. Therefore, other processes have been studied and applied together with these techniques to enhance purification results. These include photocatalysis, absorption, advanced oxidation processes, and ozonation, but also have their own drawbacks. In recent years, electrochemical techniques have received attention as wastewater treatment process that could be show higher purification results. Among them, boron doped diamond (BDD) attract attention as electrochemical electrode due to good chemical and electrochemical stability, long lifetime and wide potential window that necessary properties for anode electrode. So, there are many researches about high quality BDD on Nb, Ta, W and Si substrates, but, their application in effluents treatment is not suitable due to high cost of metal and low conductivity of Si. To solve these problems, Ti has been candidate as substrate in consideration of cost and property. But there are adhesion issues that must be overcome to apply Ti as BDD substrate. Al, Cu, Ti and Nb thin films were deposited on Ti substrate to improve adhesion between substrate and BDD thin film. In this paper, BDD films were deposited by hot filament chemical vapor deposition (HF-CVD) method. Prior to deposition, cleaning processes were conducted in acetone, ethanol, and isopropyl alcohol (IPA) using sonification machine for 7 min, respectively. And metal layer with the thickness of 200 nm were deposited by DC magnetron sputtering (DCMS). To analyze microstructure X-ray diffraction (XRD, Bruker gads) and field emission scanning electron microscopy (FE-SEM, Hitachi) were used. It is confirmed that metal layer was effective to adhesion property and improved electrode property. Electrochemical measurements were carried out in a three electrode electrochemical cell containing a 0.5 % H2SO4 in deionized water. As a result, it is confirmed that metal inter layer heavily effect on BDD property by improving adhesion property due to suppressing formation of titanium carbide.

• Journal of the Korean Chemical Society
• /
• v.46 no.1
• /
• pp.57-63
• /
• 2002

The hydropurification reaction of CTA (crude terephthalic acid) was carried out with hydrogen over PdRu/CCM (carbon-carbonaceous composite material) catalyst in a batch reactor at high temperature. The first order kinetics of hydropurification is confirmed with the linear dependence of ln(4-CBA; 4-carboxybenzaldehyde) with reaction time. The reaction condition studied is thought to represent the hydropurification well because of the linear dependence of catalytic activity on the catalyst weight. The p-toluic acid (p-tol) in solid and liquid increases with the conversion of reaction or the decrease of 4-CBA. However, the benzoic acid (BA) concentration does not depend much on the conversion. The AT (alkali transmittance) does not depend on the 4-CBA when the concentration is higher than about 0.2% which shows the 4-CBA, in itself, does not cause the coloring effect. The AT of PTA depends inversely with the concentration of 4-CBA when the 4-CBA is less than about 0.15%. This may show the coloring materials are removed in parallel with the hydrogenation of 4-CBA. The (0.3%Pd-0.2%Ru)/CCM shows larger residual catalytic activity than a commercial catalyst, 0.5%Pd/C, after using in a commercial reactor even though the former has smaller fresh activity than the latter. The palladium and ruthenium in PdRu/CCM show the synergetic effect in activity when the ruthenium concentration is about $0.2{\sim}0.35$ wt%. It may be supposed that the PdRu/CCM catalyst can be a promising candidate to replace the commercial Pd/C catalyst.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.22 no.4
• /
• pp.183-189
• /
• 2012

Surface treatments and their effects on high temperature properties for the Hastelloy X, which is a promising candidate alloy for high temperature heat-transport system, have been evaluated. For TiAlN and $Al_2O_3$ overlay coatings, the two different PVD (physical vapor deposition) methods using an arc discharge and a sputtering, were applied, respectively. In addition, a different surface treatment method of the diffusion coating by a pack cementation of Al (aluminiding) was also adopted in this study. To achieve enhanced thermal oxidation resistance at $1000^{\circ}C$ by suppressing the inhomogeneous formation of thick $Cr_2O_3$ crust at the surface region, a study for the surface modification methods on the morphological and structural properties of Hastelloy X substrates has been conducted. The structural and compositional properties of each sample were characterized before and after heat-treatment at $1000^{\circ}C$ under air and He environment. The results showed that the Al diffusion coating showed the more enhanced high temperature properties than the overlay coatings such as the suppressed thick $Cr_2O_3$ crust formation and lower wear loss.

• Korean Journal of Organic Agriculture
• /
• v.23 no.2
• /
• pp.347-357
• /
• 2015

This experiment was conducted to test the efficiency of environmentally friendly materials for controlling garlic leaf blight by Stemphylium botryosum. Fifty five kinds of environmental friendly control agents are obtained from commercial market and are tested for spore germination using 96 well plate and among them, five agents (copper-, sulfur-, medinal herb extract-, sulfur+sodium bicarbonate- and oligo chitosan based compound) are selected for field test from 2012 and 2013 year. With reference of 2012 year test result, copper and oligo chitosan based compounds are chosen as 2013 year test. When the first symptoms were appeared early May season and environmental friendly control agents are applied as prompt as possible, the control value of copper and oligo chitosan based agents are 54% and 90% respectively as compared to the occasion of chemical agent Antracol WP (propineb 70%) and yield of bulbs are increased by 16% and 34% against untreated control and marketable garlic bulb yield were 79% and 95% against Antracol WP treatment, respectively. From this result, oligo chitosan based compound can be a good organic control agent candidate for garlic leaf blight disease in organic garlic cultivation.

• Korean Journal of Pharmacognosy
• /
• v.42 no.4
• /
• pp.309-316
• /
• 2011

Fatty liver disease refers to a range of disorders associated with fatty liver, which occur in excessive eating, evident infection or significant consumption of alcohol. This study was to investigate the effects of water and ethanol extracts of Triticum aestivum young leaf on lipid metabolism and accumulation in liver of mice fed with high-fat diet. Male C57BL/6 mice were divided into normal diet group, high fat diet (HFD) group, high fat diet group administrated with 200 mg/kg/day of T. aestivum water extract (HFD-TAWE) and high-fat group administrated with 200 mg/kg/day of T. aestivum ethanol extract (HFD-TAEE). TAWE and TAEE were administrated orally for 5 weeks once at the same time point. Both TAWE and TAEE significantly reduced body weight, food intake and liver tissue weight, which were augmented in high fat-fed mice. The serum levels of triglyceride, total and LDL-cholesterol also were significantly attenuated in both HFD-TAWE and HFD-TAEE groups compared to the HFD group. Moreover, administration of HFD-TAWE or HFD-TAEE reduced the lipid accumulation in liver tissue of mice fed with high fat diet. Levels of total lipids and triglyceride in liver tissues also was significantly reduced in HFDTAWE and HFD-TAEE groups compared to HFD group. The activities of serum ALT and AST revealed in HFD group were remarkedly decreased in HFD-TAEE groups. These results indicate that both water and ethanol extract of T. aestivum may improve the lipid accumulation in liver as well as lipid metabolism in serum, and that in particular, the ethanol extract of T. aestivum may has the potent anti-hyperlipidemic effect, suggesting that it may be a useful candidate for the therapy preventing fatty liver diseases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.7
• /
• pp.563-567
• /
• 2011

The most widely used piezoelectric ceramics are lead oxide based ferroelectrics (PZT). However, the toxicity of lead oxide and its high vapor pressure during processing have led to a demand for alternative lead-free piezoelectric materials. We synthesized Lead-free piezoelectric ceramics of $0.96(K_{0.5}Na_{0.5})NbO_3-0.04SrZrO_3+x$ mol% $ZrO_2$ [KNN-SZ+$xZrO_2$; x= 0~0.10] doped with 0.1 wt% $MnO_2$ by a conventional solid state method. We investigated the piezoelectric properties and microstructures of these disk samples sintered in reduced atmosphere in order to evaluate the possibility of the multilayered piezoelectric ceramics having the base metal such as Ni as a internal electrode. All of these KNN-SZ samples sintered in 3%$H_2-97%N_2$ atmosphere at $1,140^{\circ}C$ exhibit pure perovskite structure irrespective of the content of $ZrO_2$. Meanwhile, the sintering denisty and piezoelectric properties such as $K_p$, $Q_m$ and $d_{33}$ of KNN-SZ samples as a function of $ZrO_2$ content show the maxima ($k_p$=28.07%, $Q_m$= 101.34, $d_{33}$= 156 pC/N) at x= 0.04 and it is likely that there is some morphotropic phase boundary(MPB) in this KNN-SZ+$xZrO_2$ composition system. These results indicate that the ceramic composition is a promising candidate material for applications in lead free multilayer piezoelectric ceramics.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.3
• /
• pp.251-257
• /
• 2011

This paper deals with the statistical properties of parameters B and q in the creep crack growth rate (CCGR) law, da/dt=B$(C^*)^q$, in Mod. 9Cr-1Mo (ASME Gr.91) steel which is considered a candidate materials for fabricating next generation nuclear reactors. The CCGR data were obtained by creep crack growth (CCG) tests performed on 1/2-inch compact tension (CT) specimens under an applied load of 5000N at a temperature of $600^{\circ}C$. The CCG behavior was analyzed statistically using the empirical equation between CCGR, da/dt and the creep fracture mechanics parameter, $C^*$. The B and q values were determined for each specimen by the least-squares fitting method. The probability distribution functions for B and q were investigated using normal, log-normal, and Weibull distributions. As far as this study is considered, it can be appeared that B and q followed the log-normal and Weibull distributions. Moreover, a strong positive linear correlation was found between B and q.