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Cho, Kyoungah,Park, Sukhyung,Chung, Isaac,Kim, Sangsig American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.11
<P>We investigate the memory characteristics of ZnO(x(S(1-x) based resistive switching random access memory (ReRAM) devices with Al and Pt bottom electrodes (BEs). Both the ReRAM devices with Al and Pt BEs exhibit unipolar resistive switching behaviors, regardless of the materials of the BEs. The ratios of the high resistance state (HRS) to the low resistance state (LRS) of the Au/annealed ZnO(x)S(1-x)/Al and the Au/annealed ZnO(x)S(1-x)/Pt devices are more than 10(6) and 10(4), respectively. The HRS depends more significantly on the material of the BE than the LRS. The resistance in the HRS of the device with the Al BE is more stable in the endurance characteristics and higher in magnitude than that of the device with the Pt BE. For an anealed ZnO(x)S(1-x)/Al film, the oxygen signal in the auger depth profile shows the formation of an AIO(x) layer at the interface between the annealed ZnO(x)S(1-x) layer and the Al BE. The difference between the memory characteristics of the annealed ZnO(x)S(1-x) devices with the Al and Pt BEs is explained with the presence or absence of the oxidized layers formed in the interfaces between the annealed ZnO(x)S(1-x) films and the BEs.</P>
6-Hydroxydopamine로 유도된 In Vitro 파킨슨병 모델에서 토란추출물의 Brain Resilience에 미치는 영향
조혜영(Cho Hyeyoung),강경아(Kang Kyoungah) 한국기초간호학회 2020 Journal of korean biological nursing science Vol.22 No.4
Purpose: The purpose of this study was to investigate the effects of taro extract on brain resilience in in vitro Parkinson’s disease model induced by 6-hydroxydopamine (6-OHDA). Methods: To induce a neuroinflammatory reaction and the in vitro Parkinson’s disease model, SH-SY5Y cells were stimulated with lipopolysaccharide (LPS) and 6-OHDA, respectively. After that, cells were treated with at various concentrations (1, 5, and 10 mg/mL) of taro extract. Then nitric oxide (NO) production, inducible nitric oxide synthase (iNOS), interleukin (IL)-6, synaptophysin (SYP) and growth associated protein (GAP)-43 messenger ribonucleic acid (mRNA) expression level were measured. Results: Taro extract significantly suppressed LPS-induced NO production. Meanwhile, iNOS and IL-6 mRNA expression decreased in a dose-dependent manner. In addition, taro increased the mRNA expression of SYP and GAP-43 mRNA. Conclusion: These findings indicate that taro played an important role in brain resilience by inhibiting neuronal cell death and promoting neurite outgrowth, synaptogenesis, and neural plasticity. The results of this study suggest that taro may contribute to the prevention of neurodegenerative disease and become a new and safe therapeutic strategy for Parkinson’s disease.
Park, Sukhyung,Cho, Kyoungah,Kim, Sangsig The Korean Institute of Electrical and Electronic 2014 Transactions on Electrical and Electronic Material Vol.15 No.3
In this study, cholesterol sensors consisting of a mixture of cholesterol oxidase (ChOx) and zinc oxide (ZnO) nanoparticles (NPs) are constructed on plastic substrates and their sensing characteristics are examined in air. The current of the ChOx-ZnO NP film decreases in magnitude as cholesterol molecules are adsorbed on the film, due to the resulting increase in the number of electrons generated by the reaction between the cholesterol and the ChOx. The cholesterol sensor shows a high sensitivity of $1.08{\mu}A/mM$ and a wide detection range from 10 nM to 1 mM.
Han, Yong,Cho, Kyoungah,Kim, Sangsig American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7
<P>In this study, Cu/ZnO0.4S0.6Al devices are fabricated on plastic substrates using the sputtering method at room temperature. The ratio of O/S in the zinc oxysulfide thin film is confirmed to be 0.4/0.6 from the Auger depth profiling. The Cu/ZnO0.4S0.6/Al devices show unipolar resistive switching behaviors and the ratio of the measured resistance in the low-resistance state (LRS) to that in the high-resistance state (HRS) is above 10(4). The conduction mechanism of the LRS is governed by Ohm's law. On the other hand, in the HRS, the conduction mechanism at low voltages is controlled by Ohm's law, but that at high voltages results from the Poole-Frenkel emission mechanism. The Ohmic and Poole-Frenkel conduction mechanisms observed in the LRS and HRS support the filament model of unipolar resistive switching. The memory characteristics of the Cu/ZnO0.4S0.6/Al devices are retained for 10(4) sec without any change.</P>
Kwak, Kiyeol,Cho, Kyoungah,Kim, Sangsig American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7
<P>In this study, we synthesize mercury sulfide (HgS) nanoparticles (NPs) by the colloidal method and investigate the optoelectronic characteristics of the resulting HgS NPs-thin films on plastic substrates in air at room temperature. The HgS NPs with a size of about 6-nm show quantum confinement effects in the absorption and photoluminescence spectra of the HgS NPs-thin film. The flexible optoelectronic device is constructed with the HgS NPs-thin film on finger-pattered Au electrodes. When 325-nm wavelength light is irradiated on the HgS NPs-thin film, charge carriers are photogenerated and transported by the hopping mechanism, thereby giving birth to a photocurrent in the film. The photocurrent efficiency at a bias voltage of 5 V is estimated to be 1.6 mu A/W . cm(2) and the photocurrent efficiency in the 1000 cycles-bending test changes by less than one order of magnitude compared to its initial value before bending.</P>
Thermal conductivity of silicon nanowires embedded on thermoelectric platforms
Choi, JinYong,Cho, Kyoungah,Yoon, Dae Sung,Kim, Sangsig IOP Pub 2016 Measurement science & technology Vol.27 No.10
<P>In this study, we propose a simple method for obtaining the thermal conductivity of silicon nanowires (SiNWs) embedded on a thermoelectric platform. The approximation of the heat flux in SiNWs with temperature differences enables the determination of thermal conductivity. Using this method, the thermal conductivities of our <I>n-</I> and <I>p-</I>type SiNWs are found to be 18.06 ± 0.12 and 20.29 ± 0.77 W m<SUP>−1</SUP> · K<SUP>−1</SUP>, respectively. The atomic weight of arsenic ions in the <I>n-</I>type SiNWs is responsible for a lower thermal conductivity than that of boron ions in the <I>p-</I>type SiNWs. Our results demonstrate that this simple method is capable of measuring the thermal conductivity of thermoelectric nanomaterials embedded on thermoelectric devices.</P>
Park, Byoungjun,Cho, Kyoungah,Kim, Hyunsuk,Kim, Sangsig Institute of Physics 2006 Semiconductor science and technology Vol.21 No.7
<P>In this work, the capacitance characteristics of gold nanoparticle-embedded metal–oxide-semiconductor (MOS) capacitors with Al<SUB>2</SUB>O<SUB>3</SUB> control oxide layers are investigated. The capacitance versus voltage (<I>C</I>–<I>V</I>) curves obtained for a representative MOS capacitor embedded with gold nanoparticles synthesized by the colloidal method exhibit large flat-band voltage shifts, which indicate the presence of charge storages in the gold nanoparticles. Their hysteresis characteristics are dependent on the voltage sweep range. The clockwise hysteresis and rightward shift of the flat band voltages observed from the <I>C</I>–<I>V</I> curves imply that electrons are trapped in a floating gate layer consisting of the gold nanoparticles present between SiO<SUB>2</SUB> and Al<SUB>2</SUB>O<SUB>3</SUB> layers in the MOS capacitor, and that these trapped electrons originate from the top electrode. In addition, the characteristics of the capacitance versus time curves for the gold nanoparticle-embedded MOS capacitor are discussed in this paper.</P>