• Journal of Microbiology and Biotechnology
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• v.19 no.8
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• pp.765-773
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• 2009

Edwardsiella tarda is a pathogen with a broad host range that includes human and animals. The E. tarda hemolysin (Eth) system, which comprises EthA and EthB, is a noted virulence element that is widely distributed in pathogenic isolates of E. tarda. Previous study has shown that the expression of ethB is regulated by iron, which suggests the possibility that the ferric uptake regulator (Fur) is involved in the regulation of ethB. The work presented in this report supports the previous findings and demonstrates that ethB expression was decreased under conditions when the E. tarda Fur ($Fur_{Et}$) was overproduced, and enhanced when $Fur_{Et}$ was inactivated. We also identified a second ethB regulator, EthR, which is a transcription regulator of the GntR family. EthR represses ethB expression by direct interaction with the ethB promoter region. In addition to ethB, EthR also modulates, but positively, luxS expression and AI-2 production by binding to the luxS promoter region. The expression of ethR itself is subject to negative autoregulation; interference with this regulation by overexpressing ethR during the process of infection caused (i) drastic changes in ethB and luxS expressions, (ii) vitiation in the tissue dissemination and survival ability of the bacterium, and (iii) significant attenuation of the overall bacterial virulence. These results not only provide new insights into the regulation mechanisms of the Eth hemolysin and LuxS/AI-2 quorum sensing systems but also highlight the importance of these systems in bacterial virulence.

• Korean Journal of Environmental Agriculture
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• v.29 no.2
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• pp.165-175
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• 2010

A gas chromatographic (GC) method was developed to determine residues of captan, folpet, captafol, and chlorothalonil, known as broad-spectrum protective fungicides for the official purpose. All the fungicide residues were extracted with acetone containing 3% phosphoric acid from representative samples of five agricultural products which comprised rice, soybean, apple, pepper, and cabbage. The extract was diluted with saline, and dichloromethane partition was followed to recover the fungicides from the aqueous phase. Florisil column chromatography was additionally employed for final cleanup of the extracts. The analytes were then determined by gas chromatography using a DB-1 capillary column with electron capture detection. Reproducibility in quantitation was largely enhanced by minimization of adsorption or thermal degradation of analytes during GLC analysis. Mean recoveries generated from each crop sample fortified at two levels in triplicate ranged from 89.0~113.7%. Relative standard deviations (RSD) were all less than 10%, irrespective sample types and fortification levels. As no interference was found in any samples, limit of quantitation (LOQ) was estimated to be 0.008 mg/kg for the analytes except showing higher sensitivity of 0.002 mg/kg for chlorothalonil. GC/Mass spectrometric method using selected-ion monitoring technique was also provided to confirm the suspected residues. The proposed method was reproducible and sensitive enough to determine the residues of captan, folpet, captafol, and chlorothalonil in agricultural commodities for routine analysis.

• Asian Journal of Atmospheric Environment
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• v.11 no.1
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• pp.1-14
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• 2017

For the quantitative analysis of volatile organic compounds (VOC), the use of a proper solvent is crucial to reduce the chance of biased results or effect of interference either in direct analysis by a gas chromatograph (GC) or with thermal desorption analysis due to matrix effects, e.g., the existence of a broad solvent peak tailing that overlaps early eluters. In this work, the relative performance of different solvents has been evaluated using standards containing 19 VOCs in three different solvents (methanol, pentane, and hexane). Comparison of the response factor of the detected VOCs confirms their means for methanol and hexane higher than that of pentane by 84% and 27%, respectively. In light of the solvent vapor pressure at the initial GC column temperature ($35^{\circ}C$), the enhanced sensitivity in methanol suggests the potential role of solvent vapor expansion in the hot injector (split ON) which leads to solvent trapping on the column. In contrast, if the recurrent relationships between homologues were evaluated using an effective carbon number (ECN) additivity approach, the comparability assessed in terms of percent difference improved on the order of methanol (26.5%), hexane (6.73%), and pentane (5.24%). As such, the relative performance of GC can be affected considerably in the direct injection-based analysis of VOC due to the selection of solvent.

• Journal of the Korean Magnetics Society
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• v.16 no.3
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• pp.163-167
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• 2006

Ultrasonic irradiation in a solution during the chemical reaction may accelerate the rate of the reaction and the crystallization at low temperature. We have synthesized nanometer sized magnetite particles using coprecipitation method, sonochemical method without surfactant, and sonochemical method with surfactant, in order to investigate the effect of ultrasonic irradiation and surfactant on the coprecipitates of metal ions. The size of the magnetite nanoparticles prepared by coprecipitation method, and sonochemical method without surfactant showed broad distributions. But we got uniform nanoparticles using a sonochemical method with oleic acid. The average size of the particles can be controlled by the ratio $R=[H_2O]/[surfactant]$. The size of the magnetite nanoparticles prepared by this method showed narrow distributions. We have characterized the nanoparticles using an X-ray diffraction (XRD), a superconducting quantum interference device (SQUID), and atomic force microscope (AFM). The size and distribution of the magnetite nanoparticles were measured by dynamic light scattering (DLS) method.

• Journal of the Korea Society of Computer and Information
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• v.15 no.8
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• pp.41-49
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• 2010

Digital broadcasting system has various affecting factors unlike analog broadcasting system, and has possibility of no signal reception in case of errors due to characteristics of digital system. And, digital broadcasting system has monitoring system for error occurrences handling various factors. ATSC mobile DTV system uses legacy frequency and provides mobile broadcasting services, and also requires monitoring systems for monitoring online broadcasting services and reporting to administrator about interference or influence with legacy systems, and error situations. In this paper, we propose efficient monitoring system which monitors online broadcasting status of ATSC mobile DTV, reports on poor signal reception, video streaming failures to administrator, and maintains reliable digital broad ca sting system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.51-62
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• 2003

This paper presents a novel survivor memeory management and decoding techniques with sequential backward state transition control in the trace back Viterbi decoder. The Viterbi algorithm is an maximum likelihood decoding scheme to estimate the likelihood of encoder state for channel error detection and correction. This scheme is applied to a broad range of digital communication such as intersymbol interference removing and channel equalization. In order to achieve the area-efficiency VLSI chip design with high throughput in the Viterbi decoder in which recursive operation is implied, more research is required to obtain a simple systematic parallel ACS architecture and surviver memory management. As a method of solution to the problem, this paper addresses a progressive decoding algorithm with sequential backward state transition control in the trace back Viterbi decoder. Compared to the conventional trace back decoding techniques, the required total memory can be greatly reduced in the proposed method. Furthermore, the proposed method can be implemented with a simple pipelined structure with systolic array type architecture. The implementation of the peripheral logic circuit for the control of memory access is not required, and memory access bandwidth can be reduced Therefore, the proposed method has characteristics of high area-efficiency and low power consumption with high throughput. Finally, the examples of decoding results for the received data with channel noise and application result are provided to evaluate the efficiency of the proposed method.

• Journal of The Geomorphological Association of Korea
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• v.19 no.2
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• pp.173-185
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• 2012

Authors performed pollen analysis in deposits at a coastal plain at Yeongjong-do Island located in Incheon, South Korea. Sampling site (7.2 m a.s.l.) belongs to the cool temperate deciduous broad-leaf forest. Environmental changes since 8,900 yrs B.P. reconstructed from pollen analysis are as follows; JS-I stage (c.a. 8,900~8,500 yrs B.P. ) was cool temperate northern mixed-forest which is comparable to the early PostGlacial pollen stage RI in Japan, in which Pinus and Quercus were dominant and Abies and Picea were also found. At that time, climate was relatively cooler and dryer than today. JS-II stage (sometime between 8,500~4,000 yrs B.P.) was Pinus-dominant coniferous forest, which is comparable to the mid-Post-Glacial pollen stage RII. Mixed forest of Pinus, Quercus and Carpinus was dominant in JS-III stage (c.a. 4,000 yrs B.P). We assumed that JS-II and JS-III stage were relatively warmer and more humid than JS-I stage, and were more like present conditions. JS-IV stage (sometime between 4,000~900 yrs B.P.) was Pinus-dominant coniferous forest which is comparable to the late Post-Glacial pollen stage RIII. JS-V stage (c.a. 900 yrs B.P. ~present) was second growth Pinus-dominant coniferous forest stage. During the last stage, non-arboreal pollen was more common than arboreal pollen and Fagopyrum appeared among the herbaceous plant, which indicates that it is comparable to the RIIIb stage which was the age of human interference. From the JS-V stage, humans in the study site started agricultural activities.

• Korean Journal of Environment and Ecology
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• v.32 no.6
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• pp.618-638
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• 2018

This study examined the vegetation structure in the ridge of the Hannamgeumbuk-Jeongmaek and Geumbuk-Jeongmaek by selecting 7 sites(2 sites at Hannamgeumbuk-Jeongmaek and 5 sites at Geumbuk-Jeongmaek) in consideration of the environmental conditions and artificial influences and conducting the vegetation survey in the selected sites. The community classification based on TWINSPAN categorized the vegetation at Hannamgeumbuk-Jeongmaek into 8 groups: Quercus variabilis-Q. acutissima community, Pinus densiflora-Q. mongolica community, Pinus densiflora community, P. densiflora-Q. mongolica-Q. variabilis community, P. densiflora-Deciduous oaks community, P. koraiensis community, Q. mongolica-Q. variabilis community, and Larix kaempferi-P. koraiensis community. It also categorized the vegetation at Geumbuk-Jeongmaek into 9 groups: Quercus variabilis community, Deciduous broad-leaved community, Q. mongolica community, Pinus densiflora-Q. mongolica-Q. variabilis community, Q. acutissima community, P. densiflora-Q. acutissima-Q. variabilis community, P. densiflora-Q. mongolica-P. rigida community, P. densiflora-P. thunbergii-Deciduous oaks community, and P. koraiensis community. Two species, Quercus mongolica and Pinus densiflora, which are widely distributed in the ridges of the Jeongmaeks and Baekdudaegan in South Korea, were dominant in many of the surveyed sites. The appearance of planted Castanea crenata in some plots, although not in high population, suggests human intervention in most regions of the Hannamgeumbuk-Jeongmaek and Geumbuk-Jeongmaek in the past. The Gayasan area, which is part of the Geumbuk-Jeongmaek and where the maritime climate and continental climate overlap, showed Pinus thunbergii, reflecting the local climate characteristics.