Gachon UniversityGyeonggi do

South Korea

Gachon UniversityGyeonggi do

South Korea
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Chung S.Y.,Korea Advanced Institute of Science and Technology | Lee H.-J.,Korea Advanced Institute of Science and Technology | Lee T.I.,Gachon UniversityGyeonggi do | Kim Y.S.,Korea Advanced Institute of Science and Technology | Kim Y.S.,Advanced Institute of Convergence Technology
RSC Advances | Year: 2017

For simultaneous detection of bending curvature and speed, a wearable bending motion sensor was developed by measuring the output voltage signals. A discrepancy in the piezoelectric output voltages was effectively sensed as a function of bending curvature and speed for recognition of bending motions of the piezoelectric element. This simultaneously bending curvature and speed detectable flexible bending motion sensor is superior compared to other piezoelectric sensors which demonstrated a difference in piezoelectric output signals as a function of only bending curvature. For the wearable platform of the device, elastic ZnO NR-PDMS and Ag NW-SWCNT were utilized as active and electrode materials. This wearable and flexible piezoelectric bending motion sensor is expected to be applied toward the realization of artificial skin motion detectors. © The Royal Society of Chemistry.

Lee H.-J.,Korea Advanced Institute of Science and Technology | Chung S.Y.,Korea Advanced Institute of Science and Technology | Kim Y.S.,Korea Advanced Institute of Science and Technology | Kim Y.S.,Advanced Institute of Convergence Technology | Lee T.I.,Gachon UniversityGyeonggi do
Nano Energy | Year: 2017

A non-linear piezoelectric dual sensor consisting of one-directionally and randomly aligned bi-axially grown zinc oxide nanorods was introduced for simultaneous detection of the bending radius and angle of bending deformation. The tendency of the voltage peak according to the bending radius and angle was experimentally measured and theoretically calculated using COMSOL Multiphysics®. For the sensing measurements, the bending radius was set as the independent variable, and both the average voltage peak and the rate of change of the voltage peak value with respect to the bending angle were set as dependent variables. Based on these variables, an algorithm was designed to simultaneously recognize the bending radius and angle. Finally, a two-channel nonlinear piezoelectric dual sensor was fabricated and the bending radius and angle were successfully identified through the proposed algorithm with various bending deformations. © 2017 Elsevier Ltd

Oh E.,Hanseo UniversityChungcheongnam do | Kwon Y.,Samsung | Son S.-Y.,Gachon UniversityGyeonggi do
Energy and Buildings | Year: 2017

A demand response (DR) program for buildings is widely considered an effective way to improve energy efficiency using various potential resources, such as heating, ventilation, and air conditioning (HVAC) systems and distributed generators. This study presents a method for a cost-effective DR strategy for apartment-type factory buildings composed of individually owned cells. An apartment-type factory building has high energy density but there is limited control over the energy usage of each cell. To design the DR strategy, an energy response factor is defined, taking into account the energy consumption changes of each cell in relation to the outdoor temperature. Based on that, an optimization problem for the DR program participation is formulated by minimizing the total costs and an optimal DR strategy is proposed. The proposed DR strategy is based on the selection of the cells for the DR participants and their capacity. A case study using three apartment-type buildings in Korea shows that the proposed DR strategy can achieve the cost reduction of up to 67.4% on average compared to a conventional DR approach. © 2017 Elsevier B.V.

Baek N.,NanoEnTek Inc. | Seo O.W.,NanoEnTek Inc. | Lee J.,NanoEnTek Inc. | Hulme J.,Gachon UniversityGyeonggi do | An S.S.A.,Gachon UniversityGyeonggi do
Drug Design, Development and Therapy | Year: 2016

Three-dimensional (3D) cell cultivation is a powerful technique for monitoring and understanding diverse cellular mechanisms in developmental cancer and neuronal biology, tissue engineering, and drug development. 3D systems could relate better to in vivo models than two-dimensional (2D) cultures. Several factors, such as cell type, survival rate, proliferation rate, and gene and protein expression patterns, determine whether a particular cell line can be adapted to a 3D system. The 3D system may overcome some of the limitations of 2D cultures in terms of cell-cell communication and cell networks, which are essential for understanding differentiation, structural organization, shape, and extended connections with other cells or organs. Here, the effect of the anticancer drug cisplatin, also known as cis-diamminedichloroplatinum (II) or CDDP, on adenosine triphosphate (ATP) generation was investigated using 3D spheroid-forming cells and real-time monitoring for 7 days. First, 12 cell lines were screened for their ability to form 3D spheroids: prostate (DU145), testis (F9), embryonic fibroblast (NIH-3T3), muscle (C2C12), embryonic kidney (293T), neuroblastoma (SH-SY5Y), adenocarcinomic alveolar basal epithelial cell (A549), cervical cancer (HeLa), HeLa contaminant (HEp2), pituitary epithelial-like cell (GH3), embryonic cell (PA317), and osteosarcoma (U-2OS) cells. Of these, eight cell lines were selected: NIH-3T3, C2C12, 293T, SH-SY5Y, A549, HeLa, PA317, and U-2OS; and five underwent real-time monitoring of CDDP cytotoxicity: HeLa, A549, 293T, SH-SY5Y, and U-2OS. ATP generation was blocked 1 day after addition of 50 µM CDDP, but cytotoxicity in HeLa, A549, SH-SY5Y, and U-2OS cells could be visualized only 4 days after treatment. In 293T cells, CDDP failed to kill entirely the culture and ATP generation was only partially blocked after 1 day. This suggests potential CDDP resistance of 293T cells or metabolic clearance of the drug. Real-time monitoring and ATP measurements directly confirmed the cytotoxicity of CDDP, indicating that CDDP may interfere with mitochondrial activity. © 2016 Baek et al.

Zhong L.,Gachon UniversityGyeonggi do | Yun K.,Gachon UniversityGyeonggi do
International Journal of Nanomedicine | Year: 2015

Nanosized ZnO particles with diameters of 15 nm were prepared with a solution precipitation method at low cost and high yield. The synthesis of the particles was functionalized by the organic solvent dimethylformamide, and the particles were covalently bonded to the surface of graphene oxide. The morphology of the graphene oxide sheets and ZnO particles was confirmed with field emission scanning electron microscopy and biological atomic force microscopy. Fourier transform infrared spectroscopy and X-ray diffraction were used to analyze the physical and chemical properties of the ZnO/graphene oxide composites that differed from those of the individual components. Enhanced electrochemical properties were detected with cyclic voltammetry, with a redox peak of the composites at 0.025 mV. Excellent antibacterial activity of ZnO/graphene oxide composites was observed with a microdilution method in which minimum inhibitory concentrations of 6.25 µg/mL for Escherichia coli and Salmonella typhimurium, 12.5 µg/mL for Bacillus subtilis, and 25 µg/mL for Enterococcus faecalis. After further study of the antibacterial mechanism, we concluded that a vast number of reactive oxygen species formed on the surface of composites, improving antibacterial properties. © 2015, Zhong and Yun.

Jeong H.R.,Gachon UniversityGyeonggi do | An S.S.A.,Gachon UniversityGyeonggi do
Clinical Interventions in Aging | Year: 2015

Human islet amyloid polypeptide (h-IAPP) is a peptide hormone that is synthesized and cosecreted with insulin from insulin-secreting pancreatic β-cells. Recently, h-IAPP was proposed to be the main component responsible for the cytotoxic pancreatic amyloid deposits in patients with type 2 diabetes mellitus (T2DM). Since the causative factors of IAPP (or amylin) oligomer aggregation are not fully understood, this review will discuss the various forms of h-IAPP aggregation. Not all forms of IAPP aggregates trigger the destruction of β-cell function and loss of β-cell mass; however, toxic oligomers do trigger these events. Once these toxic oligomers form under abnormal metabolic conditions in T2DM, they can lead to cell disruption by inducing cell membrane destabilization. In this review, the various factors that have been shown to induce toxic IAPP oligomer formation will be presented, as well as the potential mechanism of oligomer and fibril formation from pro-IAPPs. Initially, pro-IAPPs undergo enzymatic reactions to produce the IAPP monomers, which can then develop into oligomers and fibrils. By this mechanism, toxic oligomers could be generated by diverse pathway components. Thus, the interconnections between factors that influence amyloid aggregation (eg, absence of PC2 enzyme, deamidation, reduction of disulfide bonds, environmental factors in the cell, genetic mutations, copper metal ions, and heparin) will be presented. Hence, this review will aid in understanding the fundamental causative factors contributing to IAPP oligomer formation and support studies for investigating novel T2DM therapeutic approaches, such as the development of inhibitory agents for preventing oligomerization at the early stages of diabetic pathology. © 2015 Jeong and An.

Ramasamy S.,Gachon UniversityGyeonggi Do | Bennet D.,Gachon UniversityGyeonggi Do | Kim S.,Gachon UniversityGyeonggi Do | Kim S.,Graduate Gachon Medical Research Institute
International Journal of Nanomedicine | Year: 2014

This review will present a brief discussion on the recent advancements of bioelectrical impedance cell-based biosensors, especially the electric cell-substrate impedance sensing (ECIS) system for screening of various bioactive molecules. The different technical integrations of various chip types, working principles, measurement systems, and applications for drug targeting of molecules in cells are highlighted in this paper. Screening of bioactive molecules based on electric cell-substrate impedance sensing is a trial-and-error process toward the development of therapeutically active agents for drug discovery and therapeutics. In general, bioactive molecule screening can be used to identify active molecular targets for various diseases and toxicity at the cellular level with nanoscale resolution. In the innovation and screening of new drugs or bioactive molecules, the activeness, the efficacy of the compound, and safety in biological systems are the main concerns on which determination of drug candidates is based. Further, drug discovery and screening of compounds are often performed in cell-based test systems in order to reduce costs and save time. Moreover, this system can provide more relevant results in in vivo studies, as well as high-throughput drug screening for various diseases during the early stages of drug discovery. Recently, MEMS technologies and integration with image detection techniques have been employed successfully. These new technologies and their possible ongoing transformations are addressed. Select reports are outlined, and not all the work that has been performed in the field of drug screening and development is covered. © 2014 Ramasamy et al.

Govindaraju S.,Gachon UniversityGyeonggi do | Samal M.,Gachon UniversityGyeonggi do | Yun K.,Gachon UniversityGyeonggi do
Materials Science and Engineering C | Year: 2016

A complete bacterialysis analysis of glucosamine-gold nanoparticle-graphene oxide (GlcN-AuNP-GO) and UV-irradiated GlcN-AuNP-GO was conducted. Analytical characterization of GlcN-AuNPs, GO and GlcN-AuNP-GO revealed UV-Vis absorbance peak at around 230 and 500 nm. Microscopic characterization of prepared nanomaterials was performed by scanning electron microscope, atomic force microscopy, and high-resolution transmission microscopy. The results confirmed that the GlcN-AuNPs were uniformly decorated on the surface and edges of graphene sheets. In addition, potent antibacterial activity of GlcN-AuNP-GO that was UV irradiated for 10 min and normal GlcN-AuNP-GO was detected, compared to the standard drug kanamycin, against both Gram-negative and positive bacteria. The minimum inhibitory concentration (MIC) and fluorescence intensity spectra results for Escherichia coli and Enterococcus faecalis showed that the UV-irradiated GlcN-AuNP-GO has better antibacterial activity than normal GlcN-AuNP-GO and kanamycin. Morphological changes were detected by AFM after treatment. These results confirmed that GlcN-AuNP-GO is a potent antibacterial agent with good potential for use in manufacturing medical instruments, pharmaceutical industries and in waste water treatment. © 2016

Choi W.-C.,Gachon UniversityGyeonggi do | Picornell M.,North Carolina A&T State University | Hamoush S.,North Carolina A&T State University
Construction and Building Materials | Year: 2016

Surface and subsurface defects, such as the scaling of a concrete surface, corrosion of the reinforcement, carbonation of concrete, cracks in concrete, etc., are often observed in historical structures. In order to assess the performance of the aged concrete in a historical structure, a combination of impact echo and ultrasonic surface wave techniques as well as ground penetrating radar (GPR) are believed to be the most effective approaches to determine not only the overall quality of the concrete in the structural components, but also the extent of any internal deterioration that may be present in the structure. In this study, the field evaluation of the old concrete in a historical reinforced concrete structure (a stadium) has been conducted using destructive and nondestructive methods. The extent of the damage and unseen patterns of concrete deterioration were determined successfully based on the results obtained using GPR and a seismic property analyzer. In addition, the material properties of the old concrete were compared to laboratory test results. © 2016 Published by Elsevier Ltd.

Yang J.,Gachon UniversityGyeonggi do | Lee Y.,Gachon UniversityGyeonggi do | Kang U.-G.,Gachon UniversityGyeonggi do
International Journal of Multimedia and Ubiquitous Engineering | Year: 2015

Globally, coronary heart diseases are one of the most common diseases and regarded as a cause of deaths. Prediction and management of such diseases with high mortality as well as occurrence rate (e.g., coronary heart diseases) are particularly critical. Often, coronary heart disease patients accompany depression symptoms hence, further accurate prediction and continuing management are warranted. Improper therapeutic treatments and failure of early detection of depression patients with coronary heart diseases may result serious clinical outcomes. Data mining, utilizing database, has been shown to aid for finding effective therapeutic patterns thereby pursuing qualitative improvement of medical treatments through diagnosis based on the dataset. In the current study therefore, we compared prediction models of coronary heart disease utilizing data-mining of depression patients data in order to develop the prediction model for coronary heart diseases of depression patients. In results, we demonstrated that the neural networks model predicted most accurately thus results herein may provide a basis of prediction model for coronary heart diseases in depression patients and be effective for the establishment of effective therapeutic treatments and management plans. © 2015 SERSC.

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