• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.94-99
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• 2003

For the assessment of combustion stability of a liquid rocket engine, a device called "Pulse Gun" should be developed first, which can induce artificial perturbations that may lead to excitations of pressure oscillations in a combustion chamber. A model chamber has been used for identifying design parameters of a pulse gun that defines its characteristics. Dynamic pressure measurements showed that shock waves generated from pulse guns are axisymmetric around the axis of a pulse gun barrel. Pressure waves perturbed by a pulse gun induce resonant acoustic frequencies of a model chamber. This fact indicates that successful pressure field perturbations of the KSR-III combustion chamber can be performed by a newly developed pulse gun device. A maximum value of dynamic pressure peaks measured at the opposite point against a pulse gun outlet becomes stronger as charge mass of pulse gun powder increases.

• Journal of Plant Biotechnology
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• v.37 no.4
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• pp.394-399
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• 2010

During the last three years (2007 to 2009), 1,212 articles of SCI journals, 451 articles of non-SCI journals, and 348 items of registered patents were reported by the research scientists involved in the BioGreen 21 Project, Rural Development Administration and Crop Functional Genomics Center (CFGC), The 21st century Frontier Program, in Korea. Out of these, the percentages of articles or patents directly related to the development of GM plants were 6.0% (SCI), 10.2% (non-SCI) and 12.6% (patents) from BioGreen 21 Project while 15.7% (SCI), 21.1% (non-SCI) and 81.6% (patents) from CFGC, respectively. It was observed that rice and pepper were major host crops for genetic modification mainly to provide the resistance or tolerance activities against to biotic as well as abiotic stresses. Very low cases were reported for the field test of GM plants regarding to the commercialization (less than 15 articles). These observations indicates that more research grants needs to be invested for the risk assessment of GM plants under early developmental stage to commercialize in Korea.

• Journal of Life Science
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• v.13 no.4
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• pp.400-411
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• 2003

This study was carried out to identify the phylogenetic relationship and to know the distribution of the entomopathogenic fungi by comparing the DNA sequences of internal transcribed spacer regions (ITS1 and ITS2) and 5.8S ribosomal DNA (rDNA) repeat unit. The entomopathogenic fungi had their specific sequences in ITS1 and 2 regions depending on species. The comparison of the ITS sequences of standard strains indicated that the sequences ITS1 were more variable than those of ITS2. It seems that Paecilomyces tenuipes, Isaria japonicus and P. japonicus are the same species but called as different names because of very similar sequences, and unidentified Paecilomyces sp. KACC 40220 and KACC 40656 showed identical sequences to P. tenuipes. Thirty six strains of the commercial products of entomopathogenic fungi used in this study were divided into four groups by the phylogenetic analysis based on 5.85 rDNA and ITS regions. We found twenty-three strains were P. tenuipes / japonica, eleven strains were C. militaris, and other two strains were Beauveria bassiana and C. multiaxialis, respectively.

• Journal of Food Hygiene and Safety
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• v.17 no.3
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• pp.146-151
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• 2002

The contents [average(minimum∼maximum), Unit:mg/kg] of hazardous heavy metals(Hg, Cd and Pb) were estimated from 951 fishery products in Seoul(468 fishes,373 shellfishes, 39 crustaceans and 71 others) from January to December in 2001 by Atomic Absorption Spectrometer. Hg contents showed in shellfishes [0.033(N.D.∼0.19)]>others(0.026(N.D.∼0.11)]>crustaceans[0.026(N.D.∼0.09)]>fishes[0.018(N.D.∼0.19)], Misgurnus mizolepis(0.19) and Tegillarca granosa(0.19) were the highest. Pb content were shellfishes [0.223(N.D.∼l.38)] >fishes[0.213(N.D.∼1.68)]>others[0.15(N.D.∼0.39)]>crustaceans[0.144(N.D.∼0.444)], and Misgurnus mizolepis (1.68)>Hypomesus olidus(1.44)>Tapes philippinarum(1.38)>Anguilla japonica(1.35). Also, Tegillarca granosa(1.85) was the most Cd contents among shellfishes[0.288(N.D.∼1.85)].

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.2
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• pp.244-250
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• 2019

We investigated the relationship between morphological characteristics and individual dry weight to develop a method for estimating the individual dry weight of sheet form macroalgae: Ulva australis, Ulva linza, Pachymeniopsis lanceolata, and Pyropia yezoensis. In Total, 319 thalli of various sizes were collected at six sites from February 2017 to December 2018. An interspecific allometric exponent of 0.28 was found for length-biomass allometry in four sheet form macroalgae, corresponding to a 1/4-power law for primary producers. The relationships between surface area and individual dry weight, as well as between individual fresh weight and individual dry weight, were found to fit significantly using linear regression equations. This explained 94-99 % of individual dry weight, indicating that surface area and individual fresh weight can be used to accurately estimate individual dry weight. We propose the use of this method when experimental processes do not allow individual dry weight to be measured directly, so researchers can save both time and expense.

• Korean Journal of Veterinary Service
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• v.42 no.2
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• pp.53-60
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• 2019

This study was performed to investigate antimicrobial resistance in bacterial isolates obtained from companion dogs in veterinary hospitals and an animal shelter in Incheon. Drug resistance was examined respectively with the isolates of Escherichia coli, Enterococcus faecalis, and Staphylococcus pseudintermedius. The prevalence of drug resistance was calculated for each bacterial species towards 163 E. coli isolates, 156 E. faecalis isolates, and 86 S. pseudintermedius isolates by using selected antimicrobials. E. coli isolates were highly resistant to ampicillin, ciprofloxacin and tetracycline (47.9%, 28.2% and 28.2%, respectively). E. faecalis isolates were highly resistant to quinupristin-dalfopristin, tetracycline, kanamycin, rifampicin (69.8%, 66.0%, 53.8% and 51.9%, respectively). Higher levels of resistance were detected for ampicillin, penicillin, tetracycline, erythromycin, trimethoprim/sulfamethoxazole, telithromycin in S. pseudintermedius isolates (83.7%~52.6%, respectively). Occurrence of methicillin-resistant S. pseudintermedius (MRSP) was confirmed by oxacillin disc diffusion method, resulted in 23.3% occurrence among the S. pseudintermedius isolates (20/86 strains). The occurrence ratio of multidrug-resistance in the isolates of E. coli, E. faecalis, and S. pseudintermedius was 34.5%, 56.9%, and 67.9%, respectively. In this study, higher levels of antimicrobial drug resistance were observed in bacterial isolates obtained from dogs in Incheon. A regular monitoring and surveillance program should be implemented to prevent the emergence and spread of the drug-resistant bacteria carried in companion dogs.

• Korean Journal of Veterinary Service
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• v.42 no.1
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• pp.17-24
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• 2019

The aim of this study was to investigate the prevalence and characterization of plasmid-mediated quinolone resistance (PMQR) gene in 79 Enterobacteriaceae isolated from dogs and cats. Of 79 isolates, PMQR genes were found in 10 (12.7%) isolates, including aac(6')-lb-cr, qnrB, qnrS and qnrA detected alone or in combination in 8 (10.1%), 4 (5.1%), 2 (2.5%) and 1 (1.3%) isolates, respectively. Interestingly, two qnrS genes were detected in nalidixic acid and ciprofloxacin susceptible isolates. Extended-spectrum ${\beta}$-lactamase (ESBL) was detected in 90% (9 isolates) of PMQR positives isolates. Among ESBL genes, CTX-M, TEM and SHV were detected in 9, 8 and 3 isolates, respectively. Almost all PMQR genes were detected in co-existence with ESBL genes. All PMQR positives isolates were multidrug resistance (i.e. resistant to five or more antibiotics). qepA, OXA and CMY-2 genes were not found. The six transconjugants were obtained by conjugation experiment. The aac(6')-lb-cr, qnrB and qnrS were co-transferred with CTX-M, TEM and/or SHV, whereas qnrA was not observed among transconugants. This is the first report of the presence of aac(6')-lb-cr and qnrA gene among Enterobacteriaceae isolates from dogs in Korea. The prudent use of antimicrobials and continuous monitoring for companion animals are required.

• Korean Journal of Veterinary Service
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• v.44 no.1
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• pp.27-33
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• 2021

Q fever is a worldwide zoonotic disease caused by Coxiella burnetii. Domestic ruminants are considered to be major source of human infection. The aim of this survey was to investigate seroprevalence of C. burnetii in ruminants in Gwangju area. A total of 1,000 samples (serum and lactoserum) were collected from 987 Korean native cattle, 5 Korean native goats, 2 beef cattle, 6 bulk-tank milk from each dairy farm in Gwangju area from January to October 2020 and analyzed by ELISA. The seroprevalence of C. burnetii in bulk-tank milk from each dairy farms was 50.0%. Korean black goat and beef cattle had negative antibody test results for C. burnetii. The seroprevalence of C. burnetii in Korean native cattle in Gwangju area was 7.1% and was higher in female (7.8%) than in male (3.4%) (P=0.024). The seroprevalence of C. burnetii in Korean native cattle appeared to increase with age (3.8% in 1 year-old, 7.1% in 3 year-old, and 10.7% in more than 5 year-old) (P<0.001). The seroprevalence of C. burnetii of Korean native cattle increased in spring and May was the highest in particular (P<0.001). As the distribution and density of tick-habitat are expected to increase due to climate crisis, this survey highlights the need for monitoring C. burnetii in domestic ruminants, including surveillance of C. burnetii infection in people working for livestock industry.

• Korean Journal of Veterinary Service
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• v.44 no.4
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• pp.209-216
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• 2021

This study was aimed to investigate occurrence and the antimicrobial resistance of Escherichia coli isolates obtained from the feces of wild birds in Daegu. In total, 98 E. coli isolates (17.9%) were obtained from 547 fecal samples of wild birds. The E. coli carried by the birds showed a relatively high rate of antimicrobial resistance to tetracycline (27.6%) and ampicillin (21.4%). Drug resistance of the isolates to the others (penicillins, cephems, carbapenems, aminoglycosides, quinolones, sulfonamides and phenicols) resulted in the rates less than 20%, and all isolates were susceptible to imipenem, ciprofloxacin, cefotetan, and amikacin. Approximately, 45% E. coli among the isolates were resistant to one or more drugs tested. The higher rate of tetracycline resistance led us to determine the prevalence of the tet genes (tetA, tetB, tetC, tetD and tetE) in the tetracycline-resistant E. coli isolates by using PCR. All isolates of the tetracycline-resistant E. coli contained at least one or more of these tet genes examined. The most prevalent one was tetA (59.3%), and followed by tetB (7.4%) when tested with the selected 5 tet genes. Except tetA and tetB, however, the remaining tet genes (tetC, tetD, and tetE) tested were not found in this study. Nine isolates among the tetracycline-resistant E. coli contained the two (tetA and tetB) determinants of tetracycline resistance, simultaneously.

• Journal of Environmental Science International
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• v.32 no.5
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• pp.315-328
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• 2023

Cyanobacteria have been used as pollution indicator species in freshwater ecosystems, and identifying their fluctuations can be an important part about management of surface waters globally. Cyanotoxins produced by cyanobacteria are directly or indirectly a threat to human and environmental health. In order to confirm the potential risk of these cyanotoxins, the fluctuations of phytoplankton and phylogenetic analysis of cyanotoxin synthetase genes were conducted at each point in the Yeongsan River water system in Gwangju from November 2021 to October 2022. Diatoms which grow well in winter were dominant at 99.4 ~ 99.5%, and diatoms and green algae were dominant from the spring to autumn when the water temperature rises. Stephanodiscus spp. were dominant at 92.7 to 97.5 % at all sites in the winter, and Aulacoseira spp., which grow in warm water temperatures, were dominant in summer and autumn. Microcystis aeruginosa was dominant at 25.2% in summer only at site 5. mcyB and anaC have been detected as cyanotoxin synthetase genes. The phylogenetic tree of anaC could be divided into two groups (Group 1 & Group 2). Group 1 contained Aphanizomenon sp. and Cuspidothrix issatschenkoi. It is combined with Aphanizomenon sp. and Cuspidothrix issatschenkoi, which are known to produce cyanotoxins.