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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>
Yonghun Song,Kwangho Lee,Hyun Park,Soo Hyun Hwang,Hye Jin Baek,In Sung Park 대한신경외과학회 2024 Journal of Korean neurosurgical society Vol.67 No.5
Lateral spinal artery (LSA) aneurysms are extremely rare lesions that can rupture and cause subarachnoid hemorrhage (SAH) even though the spinal arteries communicate directly with the subarachnoid space. To date, six cases of LSA aneurysms have been reported in the literature. Herein, three such cases are reported. All patients presented to the emergency department with headaches. The patients in the first two cases were confirmed to have SAH and LSA aneurysms on a brain computed tomography (CT) angiography performed at the hospital. Two patients had prior instances of cerebral infarction and coronary disease, respectively, and were undergoing antiplatelet therapy. The antiplatelet medication was stopped for 2 weeks and 1 week, respectively, while conservative care was provided. Subsequently, a suboccipital craniectomy was performed, followed by aneurysm clipping. Following the surgery, both patients were discharged without any significant neurological deficits. Regarding the third patient, no aneurysm was found on brain CT angiography, and cerebral angiography was performed during the patient’s hospital stay. She was hospitalized, where she received medication and conservative care, and was discharged with an improvement in bleeding without neurological symptoms. Subsequently, a LSA aneurysm was identified on a brain CT angiography performed at an outpatient clinic; however, the patient was transferred because she wanted to be treated at another hospital. LSA aneurysms are difficult to visualize using CT angiography; therefore, careful angiographic studies are required. Surgical clipping is the treatment of choice if the aneurysm is inaccessible by the endovascular treatment.
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.
Wafer-Scale Integration of Highly Uniform and Scalable MoS<sub>2</sub> Transistors
Kim, Yonghun,Kim, Ah Ra,Zhao, Guoqing,Choi, Sun Young,Kang, Soo Cheol,Lim, Sung Kwan,Lee, Kang Eun,Park, Jucheol,Lee, Byoung Hun,Hahm, Myung Gwan,Kim, Dong-Ho,Yun, Jungheum,Lee, Kyu Hwan,Cho, Byungjin American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.42
<P>Molybdenum disulfide with atomic-scale flatness has application potential in high-speed and low-power logic devices owing to its scalability and intrinsic high mobility. However, to realize viable technologies based on two-dimensional materials, techniques that enable their large-area growth with high quality and uniformity on wafer cale is a prerequisite. Here, we provide a route toward highly uniform growth of a wafer-scale, four-layered MoS2 film on a 2 in. substrate via a sequential process consisting of the deposition of a molybdenum trioxide precursor film by sputtering followed by postsulfurization using a chemical vapor deposition process. Spatial spectroscopic analyses by Raman and PL mapping validated that the as-synthesized MoS2 thin films exhibit high uniformity on a 2 in. sapphire substrate. The highly uniform MoS2 layers allow a successful integration of devices based on 4200 MoS2 transistor arrays with a yield of 95% because of their extreme homogeneity on Si wafers. Moreover, a pulse electrical measurement technique enabled investigation of the inherent physical properties of the atomically thin MoS2 layers by minimizing the charge-trapping effect. Such a facile synthesis method can be possibly applied to other 2D transition metal dichalcogenides to ultimately realize the chip integration of device architectures with all 2D-layered building blocks.</P>