Publications by authors named "Chulwon Chung"

Analog synaptic devices have made significant advances based on various electronic materials that can realize the biological synapse properties of neuromorphic computing. Ferroelectric (FE) HfO-based materials with nonvolatile and low power consumption characteristics are being studied as promising materials for application to analog synaptic devices. The gradual reversal of FE multilevel polarization results in precise changes in the channel conductance and allows analogue synaptic weight updates.

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Neuromorphic computing has garnered significant attention because it can overcome the limitations of the current von-Neumann computing system. Analog synaptic devices are essential for realizing hardware-based artificial neuromorphic devices; however, only a few systematic studies in terms of both synaptic materials and device structures have been conducted so far, and thus, further research is required in this direction. In this study, we demonstrate the synaptic characteristics of a ferroelectric material-based thin-film transistor (FeTFT) that uses partial switching of ferroelectric polarization to implement analog conductance modulation.

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Zinc sulfide (ZnS) thin film was deposited on the flexible polyethylene-terephtalate (PET) polymer substrate by radio frequency (RF) magnetron sputtering system. ZnS film has a critical thickness range affecting crystal structure where it shows preferred orientation with intensity peak of X-ray diffractometer at 28.4 degrees for ZnS thinner than 200 nm while hexagonal wurtzite and cubic zinc-blend (101) are co-existed for film thicker than 200 nm.

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Cu2ZnSnS4 (CZTS) thin film applicable to an absorber material in compound thin film solar cells was deposited by a single quaternary sputtering target containing four components--Cu, Zn, Sn, and S-and its material properties were investigated. A single quaternary sputtering target was fabricated by sequential powder mixing/ball milling, pressure moulding, and a sintering process. An as-fabricated pellet or sputter target sintered at 500 degrees C-700 degrees C showed relevant peaks associated with CZTS phases.

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The integral interaction of signaling components in the regulation of visceral inflammation-induced central sensitization in the spinal cord has not been well studied. Here we report that phosphoinositide 3-kinase (PI3K)-dependent Akt activation and N-methyl-d-aspartic acid receptor (NMDAR) in lumbosacral spinal cord independently regulate the activation of cAMP response element-binding protein (CREB) in vivo in a rat visceral pain model of cystitis induced by intraperitoneal injection of cyclophosphamide (CYP). We demonstrate that suppression of endogenous PI3K/Akt activity with a potent PI3K inhibitor LY294002 reverses CYP-induced phosphorylation of CREB, however, it has no effect on CYP-induced phosphorylation of NR1 at Ser(897) and Ser(896); conversely, inhibition of NMDAR in vivo with MK801 fails to block CYP-induced Akt activation but significantly attenuates CYP-induced CREB phosphorylation in lumbosacral spinal cord.

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Type I collagen forms the main constituent of the extracellular matrix in visceral organs. We reported here that cyclophosphamide (CYP)-induced cystitis significantly increased the production of type I collagen in the inflamed bladder leading to increases in the bladder weight and the thickness of the bladder wall. The endogenous nerve growth factor (NGF) in the urinary bladder regulated type I collagen expression because the neutralizing NGF antibody attenuated cystitis-induced type I collagen up-regulation in the inflamed bladder.

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Severe chronic active Epstein-Barr virus (EBV) infection is a rare and life-threatening illness. Although the criteria for diagnosis include chronic or recurrent infectious mononucleosis-like symptoms lasting more than 6 months and high titers of anti-EBV antibodies, clinical and laboratory findings may be heterogeneous and flexible application of those criteria is necessary in cases showing typical clinical and pathologic findings. We report a case of severe chronic active EBV infection in a 62-yr-old female patient who showed classical clinical findings with infiltration of EBV-infected T lymphocytes in the bone marrow, spleen, and lymph nodes, and died four months after presentation.

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