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Search Results: 1 - 10 of 25351 matches for " Changhyun Lee "
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A Brief Review: Stage-Convertible Power Amplifier Using Differential Line Inductor  [PDF]
Jonghoon Park, Changhyun Lee, Changkun Park
Wireless Engineering and Technology (WET) , 2012, DOI: 10.4236/wet.2012.34027
Abstract: In this review article, a stage-convertible RF power amplifier designed with a 0.18-μm RF CMOS process is described. A method to implement a low-power matching network is an essential technology for the stage-convertible power amplifier. Various low-power matching networks with distributed active transformers as an output power combiner are compared in terms of the amounts of undesired coupling, the chip size, and the amount of power loss. The feasibility of a differential line inductor for the stage-convertible power amplifier is assessed and explained. Finally, we show that the differential line inductor is a realistic means of reducing the overall chip size, enhancing the quality factor of the matching network, and minimizing the undesired coupling between the inter-stage matching network and any output matching network. Additionally, the operating mechanism of the stage-convertible power amplifier using the differential line inductor for a low-power matching network is described in detail.
SO/Sp Monopoles and Branes with Orientifold 3 Plane
Changhyun Ahn,Bum-Hoon Lee
Physics , 1998, DOI: 10.1103/PhysRevD.59.026001
Abstract: We study BPS monopoles in 4 dimensional N=4 SO(N) and $Sp(N)$ super Yang-Mills theories realized as the low energy effective theory of $N$ (physical and its mirror) parallel D3 branes and an {\it Orientifold 3 plane} with D1 branes stretched between them in type IIB string theory. Monopoles on D3 branes give the natural understanding by embedding in SU(N) through the constraints on both the asymptotic Higgs field (corresponding to the horizontal positions of D3 branes) and the magnetic charges (corresponding to the number of D1 branes) imposed by the O3 plane. The compatibility conditions of Nahm data for monopoles for these groups can be interpreted very naturally through the D1 branes in the presence of O3 plane.
Study of the Coil Structure for Wireless Chip-to-Chip Communication Applications
Changhyun Lee;Jonghoon Park;Jinho Yoo;Changkun Park
PIER Letters , 2013, DOI: 10.2528/PIERL13022002
Abstract: In this work, we propose a merged coil structure for wireless chip-to-chip communication technology. Using the proposed coil structure, the chip size can be reduced, and the transmitted power can be improved by approximately 5 dB compared to typical coil structure. To verify the feasibility of the coil, an electromagnetic simulation and a schematic simulation are performed. The coil was implemented using 50-nm digital CMOS technology. From the experimental results, the feasibility was proved.
Intense ultraviolet emission from needle-like WO3 nanostructures synthesized by noncatalytic thermal evaporation
Park Sunghoon,Kim Hyunsu,Jin Changhyun,Lee Chongmu
Nanoscale Research Letters , 2011,
Abstract: Photoluminescence measurements showed that needle-like tungsten oxide nanostructures synthesized at 590°C to 750°C by the thermal evaporation of WO3 nanopowders without the use of a catalyst had an intense near-ultraviolet (NUV) emission band that was different from that of the tungsten oxide nanostructures obtained in other temperature ranges. The intense NUV emission might be due to the localized states associated with oxygen vacancies and surface states.
A highly sensitive and selective viral protein detection method based on RNA oligonucleotide nanoparticle
Changhyun Roh, Ho-Young Lee, Sang-Eun Kim, et al
International Journal of Nanomedicine , 2010, DOI: http://dx.doi.org/10.2147/IJN.S10134
Abstract: highly sensitive and selective viral protein detection method based on RNA oligonucleotide nanoparticle Original Research (4471) Total Article Views Authors: Changhyun Roh, Ho-Young Lee, Sang-Eun Kim, et al Published Date April 2010 Volume 2010:5 Pages 323 - 329 DOI: http://dx.doi.org/10.2147/IJN.S10134 Changhyun Roh1, Ho-Young Lee2, Sang-Eun Kim2, Sung-Kee Jo1 1Radiation Research Division for Biotechnology, Advanced Radiation Technology Institute (ARTI), Korea Atomic Energy Research Institute (KAERI), Sinjeong-dong, Jeongeup, Jeonbuk, South Korea; 2Department of Nuclear Medicine, College of Medicine, Seoul National University, South Korea Abstract: Globally, approximately 170 million people (representing approximately 3% of the population worldwide), are infected with hepatitis C virus (HCV) and at risk of serious liver disease, including chronic hepatitis. We propose a new quantum dots (QDs)-supported RNA oligonucleotide approach for the specific and sensitive detection of viral protein using a biochip. This method was developed by immobilizing a HCV nonstructural protein 5B (NS5B) on the surface of a glass chip via the formation of a covalent bond between an amine protein group and a ProLinkerTM glass chip. The QDs-supported RNA oligonucleotide was conjugated via an amide formation reaction from coupling of a 5′-end-amine-modified RNA oligonucleotide on the surface of QDs displaying carboxyl groups via standard EDC coupling. The QDs-conjugated RNA oligonucleotide was interacted to immobilized viral protein NS5B on the biochip. The detection is based on the variation of signal of QDs-supported RNA oligonucleotide bound on an immobilized biochip. It was demonstrated that the value of the signal has a linear relationship with concentrations of the HCV NS5B viral protein in the 1 μg mL-1 to 1 ng mL-1 range with a detection limit of 1 ng mL-1. The major advantages of this RNA-oligonucleotide nanoparticle assay are its good specificity, ease of performance, and ability to perform one-spot monitoring. The proposed method could be used as a general method of HCV detection and is expected to be applicable to other types of diseases as well.
A highly sensitive and selective viral protein detection method based on RNA oligonucleotide nanoparticle
Changhyun Roh,Ho-Young Lee,Sang-Eun Kim,et al
International Journal of Nanomedicine , 2010,
Abstract: Changhyun Roh1, Ho-Young Lee2, Sang-Eun Kim2, Sung-Kee Jo11Radiation Research Division for Biotechnology, Advanced Radiation Technology Institute (ARTI), Korea Atomic Energy Research Institute (KAERI), Sinjeong-dong, Jeongeup, Jeonbuk, South Korea; 2Department of Nuclear Medicine, College of Medicine, Seoul National University, South KoreaAbstract: Globally, approximately 170 million people (representing approximately 3% of the population worldwide), are infected with hepatitis C virus (HCV) and at risk of serious liver disease, including chronic hepatitis. We propose a new quantum dots (QDs)-supported RNA oligonucleotide approach for the specific and sensitive detection of viral protein using a biochip. This method was developed by immobilizing a HCV nonstructural protein 5B (NS5B) on the surface of a glass chip via the formation of a covalent bond between an amine protein group and a ProLinkerTM glass chip. The QDs-supported RNA oligonucleotide was conjugated via an amide formation reaction from coupling of a 5′-end-amine-modified RNA oligonucleotide on the surface of QDs displaying carboxyl groups via standard EDC coupling. The QDs-conjugated RNA oligonucleotide was interacted to immobilized viral protein NS5B on the biochip. The detection is based on the variation of signal of QDs-supported RNA oligonucleotide bound on an immobilized biochip. It was demonstrated that the value of the signal has a linear relationship with concentrations of the HCV NS5B viral protein in the 1 μg mL-1 to 1 ng mL-1 range with a detection limit of 1 ng mL-1. The major advantages of this RNA-oligonucleotide nanoparticle assay are its good specificity, ease of performance, and ability to perform one-spot monitoring. The proposed method could be used as a general method of HCV detection and is expected to be applicable to other types of diseases as well.Keywords: hepatitis C virus, viral protein, RNA oligonucleotide, quantum dots, biochip
N=8 SCFT and M Theory on AdS_4 x RP^7
Changhyun Ahn,Hoil Kim,Bum-Hoon Lee,Hyun Seok Yang
Physics , 1998, DOI: 10.1103/PhysRevD.61.066002
Abstract: We study M theory on $AdS_4 \times \RP^7$ corresponding to 3 dimensional ${\cal N}=8$ superconformal field theory which is the strong coupling limit of 3 dimensional super Yang-Mills theory. For SU(N) theory, a wrapped M5 brane on $\RP^5$ can be interpreted as baryon vertex. For $SO(N)/Sp(2N)$ theory, by using the property of (co-)homology of $\RP^7$, we classify various wrapping branes and consider domain walls and the baryon vertex.
A Facile Inhibitor Screening of Hepatitis C Virus NS3 Protein Using Nanoparticle-Based RNA
Changhyun Roh
Biosensors , 2012, DOI: 10.3390/bios2040427
Abstract: Globally, over hundreds of million people are infected with the hepatitis C virus: the global rate of death as a direct result of the hepatitis C virus has increased remarkably. For this reason, the development of efficient drug treatments for the biological effects of the hepatitis C virus is highly necessary. We have previously shown that quantum dots (QDs)-conjugated RNA oligonucleotide can recognize the hepatitis C virus NS3 protein specifically and sensitively. In this study, we elucidated that this biochip can analyze inhibitors to the hepatitis C virus NS3 protein using a nanoparticle-based RNA oligonucleotide. Among the polyphenolic compounds examined, 7,8,4 '-trihydroxyisoflavone and 6,7,4 '-trihydroxyisoflavone demonstrated a remarkable inhibition activity on the hepatitis C virus NS3 protein. Both 7,8,4 '-trihydroxyisoflavone and 6,7,4 '-trihydroxyisoflavone attenuated the binding affinity in a concentrated manner as evidenced by QDs conjugated RNA oligonucleotide. At a concentration of 0.01 μg·mL ?1, 7,8,4 '-trihydroxyisoflavone and 6,7,4 '-trihydroxyisoflavone showed more than a 30% inhibition activity of a nanoparticle-based RNA oligonucleotide biochip system.
Biotransformation of Isoflavone Using Enzymatic Reactions
Changhyun Roh
Molecules , 2013, DOI: 10.3390/molecules18033028
Abstract: The roles of cytochrome P450 monooxygenases (CYPs) from Streptomyces spp. which are called the “treasure islands” for natural products for medicine and antibiotics are not well understood. Substrate specificity studies on CYPs may give a solution for elucidation of their roles. Based on homology sequence information, the CYP105D7 of a soluble cytochrome P450 known as heme protein from Streptomyces avermitilis MA4680 was expressed using the T7 promoter of the bacterial expression vector pET24ma, over-expressed in Escherichia coli system and characterized. An engineered whole cell system for daidzein hydroxylation was constructed using an exogenous electron transport system from ferredoxin reductase (PdR) and ferredoxin (Pdx). Also, an in vitro reaction study showed the purified CYP105D7 enzyme, using NADH-dependent-reducing equivalents of a redox partner from Pseudomonas putida, hydroxylated daidzein at the 3' position of the B ring to produce 7,3,'4' trihydroxyisoflavone. The hydroxylated position was confirmed by GC-MS analysis. The turnover number of the enzyme was 0.69 μmol 7,3,'4'-trihydroxyisoflavone produced per μmol P450 per min. This enzyme CYP105D7 represents a novel type of 3'-hydroxylase for daidzein hydroxylation. A P450 inhibitor such as coumarin significantly (ca.98%) inhibited the daidzein hydroxylation activity.
Free Superfield Realization of N=2 Quantum Super W_{3} Algebra
Changhyun Ahn
Physics , 1993, DOI: 10.1142/S0217732394000289
Abstract: We rewrite $ N=2$ quantum super $W_{3}$ algebra, a nonlinear extended $N=2$ super Virasoro algebra, containing one additional primary superfield of dimension $2$ which has no $U(1)$ charge, besides the super stress energy tensor of dimension $1$ in $N=2$ superspace. The free superfield realization of this algebra is obtained by two $N=2$ chiral fermionic superfields of dimension $1/2$ satisfying $N=2$ complex $ U(1)$ Kac-Moody algebras.
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