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Yu J.H.,Yonsei University | Yu J.H.,New Drug Development Research Center Inc. | Cho S.O.,Yonsei University | Cho S.O.,Korea Institute of Patent Information | And 3 more authors.
International Journal of Biochemistry and Cell Biology | Year: 2015

Ataxia telangiectasia (AT) is caused by mutational inactivation of the ataxia telangiectasia mutated (Atm) gene, which is involved in DNA repair. Increased oxidative stress has been shown in human AT cells and neuronal tissues of Atm-deficient mice. Heme oxygenase-1 (HO-1) is an inducible antioxidant enzyme and protects cells against oxidative stress. The purpose of this study is to determine whether ATM induces antioxidant enzyme HO-1 and protects cells from oxidative stress-mediated apoptosis by driving the activation of PKC-δ and NF-κB, by increasing cell viability, and by downregulating DNA fragmentation and apoptotic indicators (apoptosis-inducing factor and cleaved caspase-3). AT fibroblasts stably transfected with human full-length ATM cDNA (YZ5 cells) or the empty vector (MOCK cells) were treated with H2O2 as a source of reactive oxygen species (ROS). As a result, transfection with ATM inhibited ROS-induced cell death and DNA fragmentation in MOCK cells. Transfection with ATM induced expression of HO-1 which was mediated by PKC-δ and NF-κB in H2O2-treated MOCK cells. ZnPP, an HO-1 inhibitor, and transfection with HO-1 siRNA increased ROS levels and apoptosis, whereas hemin, an HO-1 activator, reduced ROS levels and apoptosis in H2O2-treated YZ5 cells. Rottlerin, a PKC-δ inhibitor, inhibited NF-κB activation and HO-1 expression in H2O2-treated YZ5 cells. MOCK cells showed increased cell death, DNA fragmentation, and apoptotic indicators compared to YZ5 cells exposed to H2O2. In addition, transfection with p65 siRNA increased ROS levels and DNA fragmentation, but decreased HO-1 protein levels in H2O2-treated YZ5 cells. In conclusion, ATM induces HO-1 expression via activation of PKC-δ and NF-κB and inhibits oxidative stress-induced apoptosis. A loss of HO-1 induction may explain why AT patients are vulnerable to oxidative stress. © 2015 Elsevier Ltd. All rights reserved. Source


Roh B.-H.,Ajou University | Kim J.W.,Ajou University | Ryu K.-Y.,Ajou University | Ryu J.-T.,Korea Institute of Patent Information
Computers and Security | Year: 2013

Since SIP uses a text-based message format and is open to the public Internet, it is exposed to a number of potential threats of denial of service (DoS) by flooding attacks. Although several approaches have been proposed to detect and counteract SIP flooding attacks, most of these do not provide effective countervailing schemes to protect normal messages from abnormal ones after attacks have been detected. In addition, these approaches have some limitations in large user environments for SIP-based multimedia services. In this paper, a whitelist-based countermeasure scheme is proposed, to protect both normal SIP users and servers from malicious flooding attacks. To construct the whitelist, a Bloom filter approach is used, to reduce memory requirements and computational complexity. We use the non-membership ratio as a measure for the attack detection, instead of using the message rate usually used in conventional schemes. It is shown that the proposed method can provide more robust detection performances. © 2013 Elsevier Ltd. All rights reserved. Source


Bok K.-S.,Chungbuk National University | Kwak D.-W.,Korea Institute of Patent Information | Yoo J.-S.,Chungbuk National University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

In this paper, we propose a resource discovery scheme of mobile P2P with data dissemination that considers the interests and mobility of the peer. The proposed scheme manages a local information table, a resource index table, and a routing table in local database to enhance the accuracy and cost of the resource discovery. Each peer is recognized through a signal function and then the cost of data dissemination is reduced by timestamp messages. The transmitted resource is stored in the resource index table by ranking function. Our ranking function considers the distance, direction and peer's interest item in order to improve the performance of a resource discovery. © 2011 Springer-Verlag. Source


Lee K.,Hanyang University | Ko K.-Y.,Korea Institute of Patent Information | Ahn J.,Hanyang University
Thin Solid Films | Year: 2013

This paper reports a simple process to enhance the extraction efficiency of photoluminescence from Eu-doped yttrium oxide (Y2O3: Eu3 +) thin-film phosphor. The two-dimensional (2D) SiO2 photonic crystal layer was fabricated by vacuum nano-imprint method using a conventional spin-on dielectric solution as a nano-imprint resin and a 2D patterned Si stamp. The applied pressure and temperature of the patterning and annealing process facilitates the conversion of the spin-on dielectric solution into a SiO2 hemisphere structure resulting in high definition transfer of the 2D reverse pattern of the Si mold. The light extraction efficiency of the Y2O3: Eu3 + thin-film phosphor assisted by 2D SiO2 photonic crystal layer was approximately 1.72 times higher than that of the conventional Y2O3: Eu3 + thin-film phosphor. © 2013 Elsevier B.V. Source


Kim K.-S.,Korea Institute of Patent Information | Jin G.-W.,Woosong University
Communications in Computer and Information Science | Year: 2012

To find a balance point of quality required and network lifetime is a significant topic in wireless sensor network. In this paper, a duty-cycle type sleep/wakeup scheme with the barriers coverage is addressed to balance prolonged network lifetime and object detection quality. Proposed algorithm builds intruder detecting groups of sensor nodes and calculates the optimal duty-cycle ratio. The simulation results show network lifetime is prolonged with objective detection quality met. © 2012 Springer-Verlag. Source

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