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Choi, Younho,Shin, Hakdong,Lee, Ju-Hoon,Ryu, Sangryeol American Society for Microbiology 2013 Applied and environmental microbiology Vol.79 No.16
<P>A novel flagellatropic phage of <I>Salmonella enterica</I> serovar Typhimurium, called iEPS5, was isolated and characterized. iEPS5 has an icosahedral head and a long noncontractile tail with a tail fiber. Genome sequencing revealed a double-stranded DNA of 59,254 bp having 73 open reading frames (ORFs). To identify the receptor for iEPS5, Tn<I>5</I> transposon insertion mutants of <I>S</I>. Typhimurium SL1344 that were resistant to the phage were isolated. All of the phage-resistant mutants were found to have mutations in genes involved in flagellar formation, suggesting that the flagellum is the adsorption target of this phage. Analysis of phage infection using the Δ<I>motA</I> mutant, which is flagellated but nonmotile, demonstrated the requirement of flagellar rotation for iEPS5 infection. Further analysis of phage infection using the Δ<I>cheY</I> mutant revealed that iEPS5 could infect host bacteria only when the flagellum is rotating counterclockwise (CCW). These results suggested that the CCW-rotating flagellar filament is essential for phage adsorption and required for successful infection by iEPS5. In contrast to the well-studied flagellatropic phage Chi, iEPS5 cannot infect the Δ<I>fliK</I> mutant that makes a polyhook without a flagellar filament, suggesting that these two flagellatropic phages utilize different infection mechanisms. Here, we present evidence that iEPS5 injects its DNA into the flagellar filament for infection by assessing DNA transfer from SYBR gold-labeled iEPS5 to the host bacteria.</P>
Choi, Younho,Kim, Seongok,Hwang, Hyelyeon,Kim, Kwang-Pyo,Kang, Dong-Hyun,Ryu, Sangryeol American Society for Microbiology 2015 Infection and immunity Vol.83 No.1
<P>The aim of this study was to elucidate the function of the plasmid-borne <I>mcp</I> (methyl-accepting chemotaxis protein) gene, which plays pleiotropic roles in <I>Cronobacter sakazakii</I> ATCC 29544. By searching for virulence factors using a random transposon insertion mutant library, we identified and sequenced a new plasmid, pCSA2, in <I>C. sakazakii</I> ATCC 29544. An <I>in silico</I> analysis of pCSA2 revealed that it included six putative open reading frames, and one of them was <I>mcp</I>. The <I>mcp</I> mutant was defective for invasion into and adhesion to epithelial cells, and the virulence of the <I>mcp</I> mutant was attenuated in rat pups. In addition, we demonstrated that putative MCP regulates the motility of <I>C. sakazakii</I>, and the expression of the flagellar genes was enhanced in the absence of a functional <I>mcp</I> gene. Furthermore, a lack of the <I>mcp</I> gene also impaired the ability of <I>C. sakazakii</I> to form a biofilm. Our results demonstrate a regulatory role for MCP in diverse biological processes, including the virulence of <I>C. sakazakii</I> ATCC 29544. To the best of our knowledge, this study is the first to elucidate a potential function of a plasmid-encoded MCP homolog in the <I>C. sakazakii</I> sequence type 8 (ST8) lineage.</P>
Estimating Resident Registration Numbers of Individuals in Korea: Revisited
( Heeyoul Kim ),( Ki-woong Park ),( Daeseon Choi ),( Younho Lee ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.6
Choi et al's work [1] in 2015 demonstrated that the resident registration numbers (RRNs) of individuals could be conveniently estimated through their personal information that is ordinarily disclosed in social network services. As a follow-up to the study, we introduce the status of the RRN system in Korea in terms of its use in the online environment, particularly focusing on their secure use. We demonstrate that it is still vulnerable against a straightforward attack. We establish that we can determine the RRNs of the current president Moon Jae-In and the world-class singer PSY.
Private attribute inference from Facebook’s public text metadata: a case study of Korean users
Choi, Daeseon,Lee, Younho,Kim, Seokhyun,Kang, Pilsung Emerald Group Publishing Limited 2017 Industrial Management & Data Systems Vol. No.
<P>Originality/value - This paper investigates whether private attributes of SNS users can be inferred with a few pieces of publicly available information although users are not willing to disclose them. The experimental results showed that gender, age, marital status, and relationship status, can be inferred by machine-learning algorithms. Based on these results, an early warning system was designed to help both service providers and users to protect the users' privacy.</P>
배관부 부식 및 결함 평가를 위한 레이저 유도 초음파 적용 기술
최상우,이준현,조윤호 한국비파괴검사학회 2004 학술대회 논문집 Vol.- No.-
There are many tube and pipe-line in nuclear power plant under high temperature and high pressure. Erosion and corrosion defects were expected on these tube and pipe-line by environmental and mechanical factors. These erosion and corrosion defects can evaluated by ultrasonic technique. In these study, Scanning Laser Source(SLS) technique was applied to detect defect and construct image. This technique also makes detection possible on rough and curved surfaces such as tube and pipe-line by scanning. Conventional ultrasonic scanning technique requires immersion of specimen or water jet for transferring ultrasonic wave between transducer and specimen. However, this SLS technique does not need contacting and couplant to generate surface wave and to get flaw images. Therefore, this SLS technique has several advantages, for complicated production inspection, non-contact, remote from specimen, and high resolution. In this study, SLS images were obtained with various conditions of generation laser ultrasound and receiving in order to enhance detectability of flaws on the tube. Stress corrosion cracks were produced on tube and imgaes of stress corrosion cracks were constructed by using SLS technique.
원자로 스터드 볼트의 비파괴 평가를 위한 초음파 Phased Array 기법 적용
최상우,이준현,박문호,박민수,조윤호 한국비파괴검사학회 2004 학술대회 논문집 Vol.- No.-
The stud bolt is one of crucial parts for safety of reactor vessels in nuclear power plants. Cracks initiation and propagation were reported in stud bolts using closure of reactor vessel and head. Stud bolts are inspected by ultrasonic technique during overhaul periodically for the prevention of stud bolt failure and radioactive leakage from nuclear reactor. In conventional ultrasonic testing for inspection of stud bolts, crack was detected by using shadow effect. It take too much time to inspect stud bolt by using conventional ultrasonic technique. In addition, there were numerous spurious signal reflected from every thread. In this study, the advanced ultrasonic phased array technique was introduced for inspect stud bolts. The phased array technique provide fast inspection and high detectability of defects. There are sector scanning and linear scanning method in phased array technique, and these scanning methods were applied to inspect stud bolt and detectability was investigated.