• BMB Reports
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• v.43 no.8
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• pp.554-560
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• 2010

Smad4 is involved in cancer progression and metastasis. Using a pair of human syngeneic epithelial ovarian cancer cells with low (HO-8910) and high (HO-8910PM) metastatic abilities, we aimed to reveal the role of Smad4 in ovarian cancer metastasis in vitro. Smad4 was down-regulated in HO-8910PM cell line relative to HO-8910 by implicating Smad4 was probably a potential tumor suppressor gene for ovarian cancer. Re-expression of Smad4 decreased the migration ability and inhibited the invasion capacity of HO-8910PM, while promoted the cell adhesion capacity for HO-8910PM. The stable expression of Smad4 increased the expression of E-cadherin, reduced the expression of plasminogen activator inhibitor-1 (PAI-1) and slightly down-regulated the expression of VEGF. Smad4 suppresses human ovarian cancer cell metastasis potential through its effect on the expressions of PAI-1, E-cadherin and VEGF. Results from current work implicate Smad4 might suppress the invasion and metastasis of human ovarian tumor cells through a TGF-$\beta$/Smad-mediated pathway.

• Journal of Ocean Engineering and Technology
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• v.21 no.3 s.76
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• pp.46-51
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• 2007

A multi-purpose environmental monitoring system has been developed as a commercially available standard using the technique of hetero-core spliced fiber optic sensors, for the purposes of monitoring large-scale structures and preserving natural environments. The monitoring system has been tested and evaluated in a possible outdoor condition, in view of the full-scale operation at actual sites to be monitored. Additionally, the developed system in this work conveniently provides us with various options of sensor modules intended for monitoring such physical quantities as displacement, distortion, pressure, binary states, and liquid adhesion. Two channels of optical fiber line were monitored in each channel, three displacement sensor modules were connected in series, in order to examine the performance to a pseudo-cracking experiment in the outdoor situation and to clarify temperature influences an the system, in terms of the coupling of optical connectors and the OTDR stability. The results from the pseudo-cracking experiment agreed with the actual cracks, by means of calculation, based an the detected displacement values and their geometrical arrangement of the used sensor modules. The temperature change, ranging from 10 to $20^{\circ}C$ resulting from the 10-days free running operation, was found to influence the system stability of ${\pm}10{\mu}m$, primarily due to the coupling instability of the used optical connectors. It was found that fusion splicing, rather than the use of connectors, reduced the fluctuation dawn to ${\pm}2{\mu}m$. The specification and performance of various option modules have been demonstrated to show the capability of inspecting various physical quantities by use of the single system, which would be suitable for multi-purpose environmental monitoring.

• Biomaterials Research
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• v.22 no.4
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• pp.279-289
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• 2018

Background: Cell behavior is the key to tissue regeneration. Given the fact that most of the cells used in tissue engineering are anchorage-dependent, their behavior including adhesion, growth, migration, matrix synthesis, and differentiation is related to the design of the scaffolds. Thus, characterization of the scaffolds is highly required. Micro-computed tomography (micro-CT) provides a powerful platform to analyze, visualize, and explore any portion of interest in the scaffold in a 3D fashion without cutting or destroying it with the benefit of almost no sample preparation need. Main body: This review highlights the relationship between the scaffold microstructure and cell behavior, and provides the basics of the micro-CT method. In this work, we also analyzed the original papers that were published in 2016 through a systematic search to address the need for specific improvements in the methods section of the papers including the amount of provided information from the obtained results. Conclusion: Micro-CT offers a unique microstructural analysis of biomaterials, notwithstanding the associated challenges and limitations. Future studies that will include micro-CT characterization of scaffolds should report the important details of the method, and the derived quantitative and qualitative information can be maximized.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.476-482
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• 2013

In this work, the effects of electrochemical oxidation of carbon fiber surfaces on mechanical interfacial properties of carbon fibers-reinforced polarized-polypropylene matrix composites were studied with various current densities during the treatments. Surface properties of the fibers before and after treatments were observed by SEM, AFM, XPS, and contact angle measurements. Mechanical interfacial properties of the composites were measured in terms of critical stress intensity factor ($K_{IC}$). From the results it was found that $O_{1s}$ peaks of the fiber surfaces were strengthened after electrochemical oxidation which led to the enhancement of surface free energy of the fiber, resulting in good mechanical performance of the composites. It can be concluded that electrochemical oxidation of the carbon fiber surfaces can control the interfacial adhesion between the carbon fibers and polarized-polypropylene in this composites system.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.335-346
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• 2021

Since epoxy resin coating shows excellent properties in formability, adhesion, and corrosion resistance, they have been extensively used in many industries. However, various types of damages in the epoxy coated tube within a relative short time have been reported due to cavitation erosion, liquid impingement, variation of temperature and pressure. Nevertheless, there has been little research on the effect of temperature on the cavitation degradation of epoxy coatings. Therefore, this work used an ultrasonic cavitation tester to focus on the effect of solution temperature on the cavitation properties of 3 kinds of epoxy coatings in 3.5% NaCl. The cavitation properties were discussed basis on the material properties and environmental aspects. As the solution temperature increased, even though with large fluctuation, the cavitation degradation rates of A and B coatings were reduced rapidly, but the rate of C coating was decreased gradually. In addition to the cushioning effect, the reason that the cavitation degradation rate reduced with solution temperature was partly related to the brittle fracture and water absorptivity of the epoxy coatings, and the water density, but was little related to the shape and composition of the compound in the coatings or the phase transition of the epoxy coating.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.105-105
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• 2016

Recently, high power impulse magnetron sputtering (HIPIMS) has attracted considerable attentions due to its high potential for industrial applications. By pulsing the sputtering target with high power density and short duration pulses, a high plasma density and high ionization of the sputtered species can be obtained. HIPIMS has exhibited several merits such as increased coating density, good adhesion, microparticle-free and smooth surface, which make the HIPIMS technique desirable for synthesizing hard coatings. However, hard coatings present intrinsic defects (columnar structures, pinholes, pores, discontinuities) which can affect the corrosion behavior, especially when substrates are active alloys like steel or in a wear-corrosion process. Atomic layer deposition (ALD), a CVD derived method with a broad spectrum of applications, has shown great potential for corrosion protection of high-precision metallic parts or systems. In ALD deposition, the growth proceeds through cyclic repetition of self-limiting surface reactions, which leads to the thin films possess high quality, low defect density, uniformity, low-temperature processing and exquisite thickness control. These merits make ALD an ideal candidate for the fabrication of excellent oxide barrier layer which can block the pinhole and other defects left in the coating structure to improve the corrosion protection of hard coatings. In this work, CrN/Al2O3/CrN multilayered coatings were synthesized by a hybrid process of HIPIMS and ALD techniques, aiming to improve the CrN hard coating properties. The influence of the Al2O3 interlayer addition, the thickness and intercalation position of the Al2O3 layer in the coatings on the microstructure, surface roughness, mechanical properties and corrosion behaviors were investigated. The results indicated that the dense Al2O3 interlayer addition by ALD lead to a significant decrease of the average grain size and surface roughness and greatly improved the mechanical properties and corrosion resistance of the CrN coatings. The thickness increase of the Al2O3 layer and intercalation position change to near the coating surface resulted in improved mechanical properties and corrosion resistance. The mechanism can be explained by that the dense Al2O3 interlayer acted as an excellent barrier for dislocation motion and diffusion of the corrosive substance.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.393-393
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• 2010

The biocompatibility of materials used for biomedical applications depends on chemical composition, mechanical stiffness, surface energy, and roughness. The plasma treatment and etching process is a very important technology in the biomedical fields due to possibility of controlling the surface chemistry and properties of materials. In this work, $N_2/H_2$ plasma were treated on single-walled carbon nanotubes (SWCNTs) paper and characterization of treated SWCNTs paper was carried out. Also we investigated neurite outgrowth from SH-SY5Y on treated SWCNTs paper. The results indicated that $N_2/H_2$ plasma-modified SWCNTs paper enhanced neuronal cell adhesion, viability, neurite outgrowth and branching in vitro and exerted a positive role on the health of neural cells.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.426.2-426.2
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• 2016

Numerous of researches are being conducted to improve the efficiency of $Cu_2ZnSnSe_4$ (CZTSe)-based photovoltaic devices, which is one of the most promising candidates for low cost and environment-friendly solar cells. In this work, we concentrate on the back contact of the devices. A proper thickness of $MoSe_2$ in back contact structure is believed to enhance adhesion and ohmic contact between Mo back contact and absorber layer. Nevertheless, too thick $MoSe_2$ layers that are grown during high-temperature selenization process can impede the current collection, thus resulting in low cell performance. By applying molybdenum nitride as a barrier in back contact structure, we were able to control the thickness of $MoSe_2$ layer, which resulted in lower series resistance and higher fill factor of CZTSe devices. The phase transformation of Mo-N binary system was systematically studied by changing $N_2$ concentration during the sputtering process. With a proper phase of Mo-N fabricated by using an adequate partial pressure of $N_2$, the efficiency of CZTSe solar cells as high as 8.31% was achieved while the average efficiency was improved by about 2% with respect to that of the referent cells where no barrier layer was employed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.490.1-490.1
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• 2014

The ZnO nanowire (NW)-based nanogenerators (NGs) can have rectifying current and potential generated by the coupled piezoelectric and semiconducting properties of ZnO by variety of external stimulation such as pushing, bending and stretching. So, ZnO NGs needed to enhance durability for stable properties of NGs. The durability of the metal electrodes used in the typical ZnO nanogenerators(NGs) is unstable for both electrical and mechanical stability. Indium tin oxide (ITO) is used as transparent flexible electrode but because of high cost and limited supply of indium, the fragility and lack of flexibility of ITO layers, alternatives are being sought. It is expected that carbon nanotube and Ag nanowire conductive coatings could be a prospective replacement. In this work, we demonstrated transparent flexible ZnO NGs by using CNT/Ag nanowire hybrid electrode, in which electrical and mechanical stability of top electrode has been improved. We grew vertical type ZnO NW by hydrothermal method and ZnO NW was coated with hybrid silicone coating solution as capping layer to enhance adhesion and durability of ZNW. We coated the CNT/Ag nanowire hybrid electrode by using bar coating system on a capping layer. Power generation of the ZnO NG is measured by using a picoammeter, a oscilloscope and confirmed surface condition with FE-SEM. As a results, the NGs using the CNT/Ag NW hybrid electrode show 75% transparency at wavelength 550 nm and small change of the resistance of the electrode after bending test. It will be discussed the effect of the improved flexibility of top electrode on power generation enhancement of ZnO NGs.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.182-185
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• 2004

In this work, the effect of chemical treatments on surface properties of SiC was investigated in mechanical interfacial properties of carbon fibers-reinforced composites. The surface properties of the SiC were determined by acid/base values and contact angles. The thermal stabilities of carbon fibers-reinforced composites were investigated by thermogravimetric analysis (TGA). Also, the mechanical interfacial properties of the composites were studied in interlaminar shear strength (ILSS) and critical strain energy release rate mode II $(G_{IIC})$ measurements. As a result, tile acidically treated SiC (A-SiC) had higher acid value than that of untreated SiC (V-SiC) or basically treated SiC (B-SiC). According to the contact angle measurements, it was observed that chemical treatments led to an increase of surface free energy of the SiC surfaces, mainly due to the increase of the specific (polar) component. The mechanical interfacial properties of the composites, including ILSS and $(G_{IIC})$, had been improved in the specimens treated by chemical solutions. These results were explained that good wetting played an important role in improving the degree of adhesion at interfaces between SiC and epoxy resin matrix.