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Jaekyung Choi,Young Joon Yoon,Youn-Suk Choi,Hyo Tae Kim,김지훈,이종흔,Jong-hee Kim 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.2
A novel microfabrication process for the creation of a magnetohydrodynamic (MHD) mixer is presented using a photoimageable low temperature co-fired ceramic (LTCC). A monolithic structure was formed by UV photolithographic patterning and screen printing. The structure consists of a microfluidic channel and silver electrodes on a LTCC layer. The fluids in the microfluidic channel were controlled by a Lorentz force. A maximum mixing efficiency of 85.4% was achieved with AC peak-to-peak voltages of 8 V at 1 Hz. A photolithographic technique for patterning the microfluidic channel in the LTCC process is promising in order to realize a complex heterogeneous structure and it serves as an enabling tool in extending the applicability of ceramic-based microfluidic devices.
Structure of the Tripartite Multidrug Efflux Pump AcrAB-TolC Suggests an Alternative Assembly Mode
Kim, Jin-Sik,Jeong, Hyeongseop,Song, Saemee,Kim, Hye-Yeon,Lee, Kangseok,Hyun, Jaekyung,Ha, Nam-Chul Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.2
Escherichia coli AcrAB-TolC is a multidrug efflux pump that expels a wide range of toxic substrates. The dynamic nature of the binding or low affinity between the components has impeded elucidation of how the three components assemble in the functional state. Here, we created fusion proteins composed of AcrB, a transmembrane linker, and two copies of AcrA. The fusion protein exhibited acridine pumping activity, suggesting that the protein reflects the functional structure in vivo. To discern the assembling mode with TolC, the AcrBA fusion protein was incubated with TolC or a chimeric protein containing the TolC aperture tip region. Three-dimensional structures of the complex proteins were determined through transmission electron microscopy. The overall structure exemplifies the adaptor bridging model, wherein the funnel-like AcrA hexamer forms an intermeshing cogwheel interaction with the ${\alpha}$-barrel tip region of TolC, and a direct interaction between AcrB and TolC is not allowed. These observations provide a structural blueprint for understanding multidrug resistance in pathogenic Gram-negative bacteria.
A subpopulation of cancer stem cells identifies radiographic characteristics in glioblastoma
Kim, Ja Eun,Kim, Sung Kwon,Shin, Jaekyung,Se, Young-Bem,Choi, Seung Hong,Park, Sung-Hye,Choi, Seung Ah,Lee, Ji Yeoun,Phi, Ji Hoon,Wang, Kyu-Chang,Park, Chul-Kee,Kim, Seung-Ki D.A. Spandidos 2017 Oncology letters Vol.13 No.3
<P>Cancer stem cells (CSCs), defined by CD133 expression, harbor heterogeneous subpopulations of cells, including endothelial progenitor cells (EPCs). This study aimed to investigate whether a subpopulation of CSCs could affect the radiographic characteristics of glioblastoma. Tissue samples from 10 patients newly diagnosed with glioblastoma were selected according to the radiographic characteristics of their tumors. The patients were divided into two groups based on preoperative magnetic resonance imaging demonstrating contrast enhancement, necrosis and infiltrative patterns: the enhancement/necrosis group (E/N, n=5) and the non-enhancement/infiltration group (NE/I, n=5). Flow cytometry was used to assess the CSCs while immunohistochemistry was used to study microvessel density and the proliferation index. The EPC (CD34<SUP>+</SUP>/CD133<SUP>+</SUP>) fraction in CSCs (CD133<SUP>+</SUP>) was larger in the NE/I group. However, there was little difference in the angiogenic activity assessed using microvessel density between the two groups. The proliferation index (assessed using the antibody Ki-67) was higher in the E/N group and was negatively correlated with the EPC fraction. The non-EPC (CD34<SUP>−</SUP>/CD133<SUP>+</SUP>) fraction is a major factor responsible for radiographic characteristics of contrast enhancement, thus establishing an association between a subpopulation fraction of CSCs and radiographic characteristics in glioblastoma. Therefore, the simple non-invasive assessment of studying contrast enhancement lesions in glioblastomas may be used to estimate CSC subpopulations.</P>
Variation in the <i>c</i>-axis conductivity of multi-layer graphene due to H<sub>2</sub> exposure
Kim, Jaekyung,Kwak, Cheol Hwan,Jung, Woochan,Huh, Yun Suk,Kim, Byung Hoon The Royal Society of Chemistry 2016 Physical chemistry chemical physics Vol.18 No.23
<P>The variation of the c-axis conductivity of a multilayer graphene (MLG) as a function of H-2 pressure from vacuum to 20 bar has been investigated. MLG was connected to the electrodes vertically using a wet transfer process. After exposure to H-2 gas pressure up to 20 bar, the chemisorption of dissociated atomic hydrogen on MLG affects its electrical and structural properties. The formation of C-H bonds causes a decoupling of graphene layers, and then interferes with charge transfer through the out of plane. As a result, the c-axis conductivity decreases. Furthermore, the electron doping effect and the decoupling of the layers were confirmed using Raman spectroscopy. Hydrogenated carbons induce a defect structure of MLG which results in the expansion of layers. We observed a 43.54% increase in the thickness of the MLG after H-2 exposure using atomic force microscopy.</P>
Analysis of Fabrication Process on Direct Edge Sealing with Microwave for Vacuum Glazing
Jaekyung Kim,Young Shin Kim,Euy Sik Jeon 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.2
According to a recent comprehensive study on window systems, windows account for approximately 60% of a building’s total energy loss. In this regard, much research is being conducted to reduce energy loss through windows, among them, vacuum glazing maximizes the insulation performance by sealing between two sheets of glass with a vacuum. In this study, proposes a novel strategy for fabricating vacuum glazing using microwave heating in vacuum pressure and direct glass edge sealing. By applying a process using microwaves, the energy used in the vacuum glazing fabrication process is minimized, and the structural strength of the vacuum glazing is improved by directly sealing the glass. In order to prevent arc discharge that can occur when microwaves are applied in vacuum pressure, microwave power was set as a variable, and heating experiments were conducted accordingly. The experiment enabled the analysis of the relationship between temperature and pressure change according to the power, and accordingly, a vacuum glass sample with direct sealing was fabricated. The fabricated vacuum glazing was tested for thermal transmittance (U-value) in single and double layers and confirmed to be 3.5 W/m2 K and 1.6 W/m2 K, respectively.
Effects of Hormone Replacement Therapy on Bone Mineral Density in Korean Adults With Turner Syndrome
Kim SunYoung,Kim Heeyon,Lee Inha,Choi Euna,Baek JinKyung,Lee Jaekyung,Kim Hae-Rim,Yun Bo Hyon,Choi Young Sik,Seo Seok Kyo 대한의학회 2024 Journal of Korean medical science Vol.39 No.1
Background: Turner syndrome (TS) is a common chromosomal abnormality, which is caused by loss of all or part of one X chromosome. Hormone replacement therapy in TS is important in terms of puberty, growth and prevention of osteoporosis however, such a study has never been conducted in Korea. Therefore, the purpose of our study was to determine relationship between the starting age, duration of estrogen replacement therapy (ERT) in TS and develop a hormone replacement protocol suitable for the situation in Korea. Methods: This is retrospective study analyzed the medical records in TS patients treated at the Severance hospital, Yonsei University College of Medicine, Seoul, Korea from 1997 to 2019. Total of 188 subjects who had received a bone density test at least once were included in the study. Korean National Health and Nutrition Examination Survey (KNHANES) was used for achieving bone mineral density (BMD) of normal control group. Student’s t-test, MannWhitney U test, ANOVA and correlation analysis were performed using SPSS 18.0. Results: Each BMD measurement was significantly lower in women with TS than in healthy Korean women. Early start and longer duration of ERT is associated with higher lumbar spine BMD but not femur neck BMD. Femur neck BMD, but not lumbar spine BMD was significantly higher in women with mosaicism than 45XO group. Conclusion: Early onset and appropriate duration of hormone replacement therapy is important for increasing bone mineral density in patients with Turner syndrome. Also, ERT affects differently to TS patients according to mosaicism.
An Open Source Based Assistive Clinical Application Development for Movement Disorder
하재경(Jaekyung Ha),황보효정(Hyojeong Hwangbo),권효정(Hyojeong Gwon),장지현(Jihyun Jang),배수한(Suhan Bae),윤다은(Daeun Yun),김연수(Yeonsu Kim),윤현진(Hyunjin Yun),이예인(Yein Lee),김영구(Young Goo Kim),안민규(Minkyu Ahn) Korean Institute of Information Scientists and Eng 2021 정보과학회논문지 Vol.48 No.5