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Suppresion of Cathepsin A reduces pluripotency and differentiation in mESCs
Yonghun Sung,Song Park,Seong-Kyoon Choi 한국실험동물학회 2021 한국실험동물학회 학술발표대회 논문집 Vol.2021 No.7
Mouse embryonic stem cells (mESCs) are pluripotent cells that possess the ability to differentiate into three germ layers and self-renewal. Because of these characteristics, mESCs play a leading role for stem cell research and are being used in many clinical applications. Cathepsins are lysosomal proteolytic enzymes known to degrade many intracellular or extracellular substrates. Cathepsins have an effect on various tissue diseases, brain disorder, cancer, and immune disease, etc. Among the many Cathepsins, Cathepsin A (Ctsa), a serine protease, affects the function and properties of stem cells. However, this mechanism and phenotype are unknown. Here, we observed a significant increase in Ctsa expression during mESC differentiation at protein levels. Furthermore, we performed to produce establishment of Ctsa knockdown mESCs. We analyzed mESCs pluripotency, which Ctsa knockdown led to Erk1/2 phosphorylation and inhibited the pluripotency of mESCs. Ctsa knockdown mESCs also induced abnormal differentiation and aberrant expression of differentiation markers, ectoderm and endoderm. In addition, we observed that restrain of Ctsa inhibited teratoma formation in nude mice. Our results suggested that Ctsa affects mESC pluripotency, and differentiation, and highlighted the potential of Ctsa to act as a core factor that can regulate various mESC properties. In conclusion, Ctsa keeps the pluripotency and differentiates from ESCs to the three germ layers, which must occur at specific stimuli in the differentiation process. Further, the role of Ctsa in differentiation to cells, such as neuronal cells, is currently under investigation. We believe that our study will assist in identifying the mechanisms via which Ctsa regulates differentiation.
Hot-Carrier Instability of nMOSFETs Under Pseudorandom Bit Sequence Stress
Yonghun Kim,Soo Cheol Kang,Sang Kyung Lee,Ukjin Jung,Seung Mo Kim,Byoung Hun Lee IEEE 2016 IEEE electron device letters Vol.37 No.4
<P>Hot-carrier instability under stress conditions emulating a random logic operation (random ON and OFF) has been investigated using pseudorandom bit sequence (PRBS) stress patterns. Furthermore, the impacts of PRBS stress on circuit-level operation have been compared with the conventional dc (static) and ac (periodic) stress conditions using hot-carrier-induced random timing jitter. It was observed that the recovery achieved by charge trapping and detrapping under dynamic stress conditions significantly affects the degree of hot-carrier degradation.</P>
Kim, Yonghun,Kim, Ah Ra,Yang, Jin Ho,Chang, Kyoung Eun,Kwon, Jung-Dae,Choi, Sun Young,Park, Jucheol,Lee, Kang Eun,Kim, Dong-Ho,Choi, Sung Mook,Lee, Kyu Hwan,Lee, Byoung Hun,Hahm, Myung Gwan,Cho, Byung American Chemical Society 2016 NANO LETTERS Vol.16 No.9
<P>The long-term stability and superior device reliability through the use of delicately designed metal contacts with two-dimensional (2D) atomic-scale semiconductors are considered one of the critical issues related to practical 2D-based electronic components. Here, we investigate the origin of the improved contact properties of alloyed 2D metal semiconductor heterojunctions. 2D WSe2-based transistors with mixed transition layers containing van der Waals (M-vdW, NbSe2/WxNb1-xSe2/WSe2) junctions realize atomically sharp, interfaces, exhibiting long hot-carrier. :lifetimes of approximately 75,296 s (78 times longer than that of metal semiconductor, Pd/WSe2 junctions). Such dramatic lifetime enhancement in M-vdW-junctioned devices is attributed to the synergistic effects arising from the significant reduction in the number of defects and the Schottky barrier lowering at the interface. Formation of a controllable mixed-composition alloyed layer on the 2D active channel would be a breakthrough approach to maximize the electrical reliability of 2D nanomaterial-based electronic applications.</P>
Kim, Yonghun,Park, Woojin,Yang, Jin Ho,Cho, Chunhum,Lee, Sang Kyung,Lee, Byoung Hun Wiley - VCH Verlag GmbH & Co. KGaA 2016 Physica Status Solidi. Rapid Research Letters Vol.10 No.8
<P>Two‐dimensional transition metal dichalcogenides (TMDCs) are potential candidate materials for future thin‐film field effect transistors (FETs). However, many aspects of this device must be optimized for practical applications. In addition, low‐frequency noise that limits the design window of electronic devices, in general, must be minimized for TMD‐based FETs. In this study, the low‐frequency noise characteristics of multilayer molybdenum disulphide (MoS<SUB>2</SUB>) FETs were investigated in detail, with two different contact structures: titanium (Ti) metal–MoS<SUB>2</SUB> channel and Ti metal–TiO<SUB>2</SUB> interlayer–MoS<SUB>2</SUB> channel. The results showed that the noise level of the device with a TiO<SUB>2</SUB> interlayer reduced by one order of magnitude compared with the device without the TiO<SUB>2</SUB> interlayer. This substantial improvement in the noise characteristics could be explained using the carrier number of fluctuation model. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)</P>
Jeong, Sang Hwa,Kim, Sang Suk,Oh, Yonghun 대한기계학회 1996 International Sessions in Celebration of the 50th Vol.1 No.1
The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If tile tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surfice. However, as the accuracy requirement gets tight and desired surface contours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tap motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function to result in the estimated depth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in addition to position feedback control. In this work, the design methodology on the admittance model-based control with conventional a controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using the precision dynamometer. Based on the parameter estimation of cutting dynamics and the admittance model-based nanodynamic control scheme, simulation results are shown.
Lee, Yonghun,Kim, Dong-Min,Li, Zhenglin,Kim, Dong-Eun,Kim, Sung-Jin The Royal Society of Chemistry 2018 Lab on a chip Vol.18 No.6
<P>We demonstrate a microfiltration chip that separates blood plasma by using water-head-driven pulsatile pressures rather than any external equipment and use it for on-chip amplification of nucleic acids. The chip generates pulsatile pressures to significantly reduce filter clogging without hemolysis, and consists of an oscillator, a plasma-extraction pump, and filter units. The oscillator autonomously converts constant water-head pressure to pulsatile pressure, and the pump uses the pulsatile pressure to extract plasma through the filter. Because the pulsatile pressure can periodically clear blood cells from the filter surface, filter clogging can be effectively reduced. In this way, we achieve plasma extraction with 100% purity and 90% plasma recovery at 15% hematocrit. During a 10 min period, the volume of plasma extracted was 43 μL out of a 243 μL extraction volume at 15% hematocrit. We also studied the influence of the pore size and diameter of the filter, blood loading volume, oscillation period, and hematocrit level on the filtration performance. To demonstrate the utility of our chip for point-of-care testing (POCT) applications, we successfully implemented on-chip amplification of a nucleic acid (miDNA21) in plasma filtered from blood. We expect our chip to be useful not only for POCT applications but also for other bench-top analysis tools using blood plasma.</P>