• 품질경영학회지
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• 제48권3호
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• pp.493-510
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• 2020

Purpose: As of July 31, there were 14,336 confirmed cases of COVID-19 in South Korea, including 301 deaths. Since the daily confirmed number of cases hit 909 on February 29, the spread of the disease had gradually decreased due to the active implementation of preventive control interventions, and the daily confirmed number had finally recorded a single digit on April 19. Since May, however, the disease has re-emerged and retaining after June. In order to eradicate the disease, it is necessary to suggest suitable forward preventive strategies by predicting future infectivity of the disease based on the cases so far. Therefore, in this study, we aim to evaluate the transmission potential of the disease in early phases by estimating basic reproduction number and assess the preventive control measures through effective reproduction number. Methods: We used publicly available cases and deaths data regarding COVID-19 in South Korea as of July 31. Using ensemble model integrated stochastic linear birth model and deterministic linear growth model, the basic reproduction number and the effective reproduction number were estimated. Results: Estimated basic reproduction number is 3.1 (95% CI: 3.0-3.2). Effective reproduction number was the highest with 7 on February 15, decreased as of April 20. Since then, the value is gradually increased to more than unity. Conclusion: Preventive policy such as wearing a mask and physical distancing campaigns in the early phase of the outbreak was fairly implemented. However, the infection potential increased due to weakening government policy on May 6. Our results suggest that it seems necessary to implement a stronger policy than the current level.

• Journal of Preventive Medicine and Public Health
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• 제53권6호
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• pp.405-408
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• 2020

In epidemiology, the basic reproduction number (R₀) is a term that describes the expected number of infections generated by 1 case in a susceptible population. At the beginning of the coronavirus disease 2019 (COVID-19) pandemic, R₀ was frequently referenced by the public health community and the wider public. However, this metric is often misused or misinterpreted. Moreover, the complexity of the process of estimating R₀ has caused difficulties for a substantial number of researchers. In this article, in order to increase the accessibility of this concept, we address several misconceptions related to the threshold characteristics of R₀ and the effective reproduction number (R_t). Moreover, the appropriate interpretation of the metrics is discussed. R₀ should be considered as a population-averaged value that pools the contact structure according to a stochastic transmission process. Furthermore, it is necessary to understand the unavoidable time lag for R_t due to the incubation period of the disease.

• 한국가축번식학회지
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• 제21권1호
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• pp.9-18
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• 1997

These studies were carried out to establish an effective and practical system for commercialization of embryo production techniques by analyzing several factors influencing in vivo embryo production in Korean native cattle. In vivo embryos were flushed 226 times from 128 donors. The results obtained in studies on the factors influencing in vivo embryo production were as follows : 1. There were no significant differences in the number of total recovered, fertilized, transferable and freezable embryos among the hormone doses(FSH-P, 28∼34mg; SUPER-OV, 75IU) used for superovulation. However, over 30mg doses of FSH-P showed a slightly higher effect than others. 2. There were slight decrease in the number of fertilized, transferable and freezable embryos in 3 times repeated superovulation. But there were no significant differences among 1, 2 and 3 times repeated superovulations. 3. Age of donors did not affect the number of transferable and freezable embryos, but the number of fertilzed embryos were highest in 2∼3 years old donors and were lowest in 8∼9 years old donors(P<0.05). 4. Season had a significant effect on the production of embryos(P<0.05). the embryo production, and the number of fertilized, transferable and freezable embryos were most effective in summer and follow by spring, autumn and winter. 5. The number of transferable and freezable embryos was highest in donors flushed at 7∼8 days after estrus(P<0.05).

• Asian-Australasian Journal of Animal Sciences
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• 제18권8호
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• pp.1066-1070
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• 2005

To estimate the cumulative power of discrimination (CPD) existing within Haimen chicken populations in China, we isolated a total of 252 genomic DNAs from four chicken populations (Rugao, Jiangchun, Wan-Nan and Cshiqishi) through a saturated salt procedure. All the genomic DNAs were used in a polymerase chain reaction (PCR) with ten microsatellite markers. Amplified PCR-products with the selected markers were separated on a 12% polyacrylamide gel with pBR322DNA/MspI used as internal standard marker. Genetic diversity indices including mean allele number among loci, unbiased heterozygosity ($h_i$) within locus, effective number of alleles ($N_e$) and polymorphism information content (PIC) as well as the unbiased average heterozygosity (H) among loci in the populations were calculated using the generated allele frequencies by each marker. The mean allele number for all loci ranged between 4.00${\pm}$0.33 (Rugao) to 4.90${\pm}$0.48 (Cshiqishi) and across populations for all loci was 4.60${\pm}$0.20, while (H) ranged from 0.65${\pm}$0.03 (Rugao) to 0.69${\pm}$0.03 (Jiangchun) among loci and across populations, (H) was 0.67${\pm}$0.01. The generated unbiased average heterozygosity among loci in each population was integrated to the global formula of CPD and the result demonstrated that the CPD within the four Haimen chicken populations was 98.75%.

• 한국식물병리학회지
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• 제14권4호
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• pp.299-302
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• 1998

V8 juice agar (V8A) has been the most popular and commonly used medium for growth and reproduction of Phytophthora. However, frequently V8 vegetable juice is not available or difficult to obtain in Korea. We therefore developed widely accessible medium to substitute for V8A using domestically available five juices; two carrot (KCJA), two tomato (KTJA) and a vegetable-mix (KVMA). To prepare 10% juice medium, each vegetable juice 100 ml, DW 900 ml, agar 17 g and Ca CO3 0.5∼1.0g were supplemented to adjust pH ca. 6.0 Mycelial growth of P. cactorum and P. capsici on KTJA and KVMA was equally effective as V8A for the growth of P. cactorum, P. capsici, P. drechsleri and P. nicotianae under light. Sporangial production of P cactorum, P. capsici and P. nicotianae on KTJA and KVMA was as good as V8A and slightly better than CKJA, but the difference was insignificant by P. cactorum and P. nicotianae. The four fungi successfully formed oospores on all the media although the numbers were varied among species and media. While KTJA was the best for P. cactorum and P. capsici, V8A was the best for P. capsici and P. drechsleri. However, KCJA stimulated highest number of oopspores of P. nicotianae. Overall results showed that domestically available vegetable juices were highly effective on growth and reproduction of Phytophthora and comparable to V8 juice. Therefore, the domestic juice medium can be successfully replaced V8A in Phytophthora study.

• 대한치과보철학회지
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• 제40권2호
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• pp.140-155
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• 2002

Void-free impression taking is important for the fabrication of accurate dental restorations. One of the essential properties of an impression material used for indirect fabrication of precision castings is the reproduction of the fine detail. The objective in this study was to determine the influence of mixing methods on the number of voids and surface detail reproduction. The number of voids and surface detail reproduction were evaluated with the steteomicroscope $SZ-PT^{(R)}$ and photographed. The results were as follows ; 1. In comparison of the void formation according to mixing methods of all impression materials, mechanical mixing was better than hand mixing and there was significant difference(p<0.05) 2. In comparison of the void formation according to hand mixing of alginate impression materials($TOKUSO\;A-1{\alpha}^{(R)},\;CAVEX\;IMPRESSIONAL^{(R)},\;AROMA \;FINE\;DF\;III^{(R)}$), there was no significant difference among alginate groups. But the number of void was increased in the order of $Panasil^{(R)}\;contact,\;TOKUSO\;A-1{\alpha}^{(R)},\;Permlastic^{(R)}$ light bodied and there was significant difference (p<0.05). 3. In comparison of the void formation according to mechanical mixing of alginate impression materials($TOKUSO\;A-1{\alpha}^{(R)},\;CAVEX\;IMPRESSIONAL^{(R)},\;AROMA FINE\;DF\;III^{(R)}$), there was no significant different among alginate groups. But the number of void was decreased in order of $TOKUSO\;A-1{\alpha}^{(R)},\;Permlastic^{(R)}light\;bodied,\;Panasil^{(R)}$ contact and there was significant difference (p<0.05). 4. In comparison of the surface detail reproduction according to mixing methods of 3 types of impression materials($TOKUSO\;A-1{\alpha}^{(R)},\;Permlastic^{(R)}\;light\;bodied,\;Panasil^{(R)}\;contact$), there was no significant difference between hand mixing and mechanical mixing method 5. The surface detail reproduction was only influenced by impression materials, and produced better in order of $TOKUSO\;A-1{\alpha}^{(R)},\;Panasil^{(R)}\;contact,\;Permlastic^{(R)}$ light bodied. There was significat difference among 3 type of impression materials(p<0.05). From the above results, void formation is influenced by mixing methods and surface detail reproduction is influenced by impression materials than mixing methods. Therefore, to fabricate accurate restorations, proper impression material and mechanical mixing method are more effective and available clinically.

• 한국산학기술학회논문지
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• 제20권10호
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• pp.62-67
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• 2019

본 연구는 rotifer Brachionus rotundiformis의 유성생식을 유도하기 위해 효과적인 매개물질로 몇 가지 성 steroid hormone (serotonin, progesterone 및 ${\beta}$-estradiol)을 선정하여 농도별(Low, 30 mg/L 및 High, 300 mg/L)로 내구란 생산효과를 6일 동안 배양하면서 조사하였다. 배양 3일째 ${\beta}$-estradiol ($E_2$) 처리구가 다른 실험구에 비해 유성생식률이 20.6%로 가장 높게 나타났다. 배양 6일째 내구란 생산수(106 개)도 동일한 결과를 보였으며 다음으로는 serotonin이 높게 나타났다. 더하여, 위 스테로이드 호르몬이 몇 가지 유성생식관련 유전자의 발현에 미치는 영향에 대해 조사한 결과, NrbP, SRY, Cyclin 및 MrpmB 유전자가 처리한 모든 hormone에 대해 up-regulation되는 경향을 보였다. 결과를 종합해보면, B. rotundiformis의 내구란 생산에 가장 효과적인 steroid hormone은 ${\beta}$-estradiol인 것으로 판단되며 유성생식 관련 유전자로 NrbP, SRY, MrpmrB 및 Cyclin을 제안할 수 있다. 차후 효과적인 내구란 생산을 위한 $E_2$의 최적 처리농도규명에 관한 추가 연구가 필요할 것으로 판단된다.

• 한국동물생명공학회지
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• 제38권1호
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• pp.10-16
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• 2023

Intermuscular fat is essential for enhancing the flavor and texture of cultured meat. Mesenchymal stem cells derived from intermuscular adipose tissues are a source of intermuscular fat. Therefore, as a step towards developing a platform to derive intermuscular fat from mesenchymal stem cells (MSCs) for insertion between myofibrils in cultured beef, an advanced protocol of intermuscular adipose tissue dissociation effective to the isolation of MSCs from intermuscular adipose tissues was developed in cattle. To accomplish this, physical steps were added to the enzymatic dissociation of intermuscular adipose tissues, and the MSCs were established from primary cells dissociated with physical step-free and step-added enzymatic dissociation protocols. The application of a physical step (intensive shaking up) at 5 minutes intervals during enzymatic dissociation resulted in the greatest number of primary cells derived from intermuscular adipose tissues, showed effective formation of colony forming units-fibroblasts (CFU-Fs) from the retrieved primary cells, and generated MSCs with no increase in doubling time. Thus, this protocol will contribute to the stable supply of good quality adipose-derived mesenchymal stem cells (ADMSCs) as a fat source for the production of marbled cultured beef.

• Asian-Australasian Journal of Animal Sciences
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• 제23권4호
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• pp.456-464
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• 2010

RNA interference (RNAi) is an acknowledged useful and effective tool to study gene function in various cells. Here, we suppressed the Connexin 43 (Cx 43) gene expression during in vitro development of ovine pre-implantation embryos using the RNAi method. The 353 bp Cx 43 double-stranded RNA was microinjected into in vitro fertilized ovine zygotes, and the levels of target mRNA and protein were investigated. Control groups included uninjected zygotes or those injected with RNase-free water. The dsRNA injection resulted in the specific reduction of Cx 43 transcripts as analyzed by quantitative real-time RT-PCR and decreased protein levels as shown by Western blot analysis at the blastocyst stage. Microinjection of Cx 43 dsRNA led to 20.3%, 21.7% and 34.5% blastocyst rates and 19.2%, 37.5% and 41.3% hatched blastocyst rates in Cx 43 dsRNA-injected, water-injected and uninjected groups, respectively. Then the RNAi could not significantly affect cell number and cell death rates of blastocysts. Therefore, suppression of Cx 43 dsRNA and proteins did not apparently affect the development potential of ovine pre-implantation embryos but may play a role in embryo quality. RNAi technology is a promising approach to study gene function in early ovine embryogenesis.

• Asian-Australasian Journal of Animal Sciences
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• 제24권10호
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• pp.1365-1371
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• 2011

The intensity and duration of sexual behavior in Bos indicus was assessed through the continuous observation of sexual receptivity. Two groups of cows were formed: only synchronized (n = 50) and other group further superovulated (n = 20). An intravaginal implant that released progesterone over 9 d was used. After removing the implant, 25 mg of $PGF_{2{\alpha}}$ was administered. In the superovulated group, the administration of 280 mg (Follicle stimulant hormone) FSH-P1 per cow with a decreasing dosage over 4 d was utilized. In both groups, behavioral observations began at the moment of implant removal. Sexual behavior was analyzed using a Kruskal-Wallis test to compare the mean of hours in estrus, effective mountings and number of mounts/hour during estrus. A nonparametric survival analysis was performed using the time in two ways: i) when an event happened it was placed in a 24 h timeframe and, ii) the time of observation in continuous form (96 h) assessing the difference between curves by the log rank test Chi-square. The only significant difference was the number of mounts/h during receptivity (p<0.05). In the superovulated group three periods of sexual activity during the day were identified, with these events being of greater frequency and duration than the synchronized group (p = 0.02); besides, the superovulated group began estrus before the synchronized group (p = 0.0035) when using the total period. In a simulation study, when the number of observations went from two (06:00-18:00) to three periods (06:00, 12:00 and 18:00) cows detected accurately (<6 h after the onset) increased more than 20%. The results show that superovulated cows presented greater intensity and duration of sexual activity in contrast with only synchronized animals.