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        검색결과 166

        63.
        2016.10 구독 인증기관·개인회원 무료
        For useful research animal to study human’s disease and for xenotransplantation donor, pig was studied to improve the quality of in vitro production (IVP). But, still the developmental ability of in vitro porcine embryos is still lower than in vivo embryos. Using a antioxidant is one of the strategy to overcome the drawback of in vitro producted embryos by protecting the oocyte from free radicals during in vitro maturation (IVM). Resveratrol, one of the plant-derived polyphenol antioxidants, have been used as effective antioxidants. Therefore, resveratrol treatment during IVM of porcine oocytes is expected to improve efficiency of the IVP by reducing free radical accumulation. In this study, we designed control (no treated) and resveratrol treatment groups (0, 2 and 4uM), evaluated maturation rate, cleavage rate, blastocyst formation rate and total cell number. Additionally GSH and ROS accumulation levels were measured via staining oocytes. In the results, maturation rate had not shown significant difference among the groups. However, in further development, not only the results of cleavage rate (0uM : 84.64±2.65 vs 4uM : 93.67±2.36, p<0.05) and blastocyst formation rate (0uM : 6.39± 0.90, vs 4uM : 13.67±2.32, P<0.05) were significantly increased in 4uM resveratrol treated group, and result of total cell number (0uM : 22.47±0.76 vs 2, 4uM : 30.35±1.76, 27.65±1.23, P<0.05) also shown significant difference in 2, 4uM resveratrol groups with control. GSH accumulated levels of matured oocytes in resvetrol treated groups were significantly higher than control. Meanwhile ROS levels of treated groups were significantly reduced [GSH (0uM : 142±10.49 vs 2, 4uM : 163.2±3.29, 169.7±0.94, P<0.05), ROS (0uM : 170.2±7.76 vs 2, 4uM : 118.6±7.90, 130±7.07, P<0.05)]. From these results, we conclude the treatment of resveratol improved further development of porcine embryos by regulating intracellular GSH, ROS levels during porcine IVM. Therefore, exogenous antioxidants such as a resveratol can be supportive substances for obtaining the improved quality of IVP.
        64.
        2016.10 구독 인증기관·개인회원 무료
        Euzophera batangensis (Lepidotera: Pyralidae) is seriously damaging trunks or branches of persimmon tree (Diospyros sp.). We tested the attractiveness of (Z)-9-tetradecen-1-ol (Z9-14OH) and (Z9,E12)-tetradeca- 9,12-dien-1-ol (Z9,E12-14OH) with single or blended baits at southern parts of Korea in 2014 and 2015. The monoene was not attractive at all at three places during the two years. In 2014, diene was equally or more attractive than the mixture in Jinju and Suncheon, respectively. In 2015 too, the attractiveness of diene and mixture was not different in Jinju and Munsan. Monitoring of the seasonal occurrence of E. batangesis with the sex pheromone components revealed that it occurred three times a year; the first occurrence from early April to mid May, the second from early Jun to mid July, and the third from late August to late September.
        65.
        2016.07 구독 인증기관·개인회원 무료
        The purpose of this study is to present theoretical and experimental evidence for a niche strategy for small and medium online shopping malls to run business against large famous shopping malls prevailing the E-commerce market. For this, the present study demonstrates how chronic construal levels of consumers may affect their alternative choice for online shopping via various contexts (Experiment 1-3) and categories (Experiment 3-5). This series of experiments suggests that consumers with high construal level can be defined as a group that is relatively less susceptible to reputation of the shopping malls. Thus, strategically targeting this group of consumers will help small and medium-sized online malls lacking store reputation to mitigate their competitive disadvantage. Based on both existing literature and the experimental results as above, this research discusses possible methods for small and medium-sized online shopping malls to target high-construal segmentation.
        66.
        2016.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The squid Todarodes pacificus is a commercially important fishery species in East Asia. As East Asians consume raw or lightly cooked squids, there has been growing concern about parasitic infections associated with squid consumption. In the current study, five squids caught in the East Sea were sampled for parasitological research from the biggest fishery market in Seoul, Republic of Korea. They were dissected and examined for parasites using a light microscope. Proteocephalus sp. was isolated and identified using field emission scanning electron microscopy, PCR, and sequencing. Given that Proteocephalus spp. can be affected by water temperature and geographical characteristics, further research on Proteocephalus spp. with respect to changes in water temperature in the East Sea is important.
        3,000원
        67.
        2016.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Graphene was grown on molybdenum (Mo) foil by a chemical vapor deposition method at different growth temperatures (1000°C, 1100°C, and 1200°C). The properties of graphene were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and Raman spectroscopy. The results showed that the quality of the deposited graphene layer was affected by the growth temperature. XRD results showed the presence of a carbide phase on the Mo surface; the presence of carbide was more intense at 1200°C. Additionally, a higher I2D/IG ratio (0.418) was observed at 1200°C, which implies that there are fewer graphene layers at this temperature. The lowest ID/IG ratio (0.908) for the graphene layers was obtained at 1200°C, suggesting that graphene had fewer defects at this temperature. The size of the graphene domains was also calculated. We found that by increasing the growth temperature, the graphene domain size also increased.
        4,000원
        68.
        2016.04 구독 인증기관·개인회원 무료
        Oxalic acid has a nematicidal activity against the root-knot nematode Meloidogyne incognita. High producer of oxalic acid was isolated, and then named as Aspergillus niger F22. Oxalic acid production was investigated under various temperatures from 20 – 33oC and rotational speeds in 5 L jar fermenters. Yield of oxalic acid increased with decreasing temperature. The highest yield was obtained at 23oC, showing the yield of oxalic acid of 8.7 g/L, whereas oxalic acid production was least at 33oC. At 20oC, the yield was lower than that of 23oC. At a rotational speed of 300 rpm, serious oxygen depletion was present from 48 - 72 h, resulting in low productivity of 26.2 mg /L·h. When a rotational speed was set at 600 rpm, dissolved oxygen tension was over 40% and oxalic acid production increased up to approximately 55%. Viscosity during the culture differed with temperatures. Viscosity increased with the increment of temperatures. When A. niger F22 was cultured at 23oC, viscosity was 810 cP, which was favorable for oxalic acid production.
        71.
        2015.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The sintering mechanisms of nanoscale copper powders have been investigated. A molecular dynamics (MD) simulation with the embedded-atom method (EAM) was employed for these simulations. The dimensional changes for initial-stage sintering such as characteristic lengths, neck growth, and neck angle were calculated to understand the densification behavior of copper nano-powders. Factors affecting sintering such as the temperature, powder size, and crystalline misalignment between adjacent powders have also been studied. These results could provide information of setting the processing cycles and material designs applicable to nano-powders. In addition, it is expected that MD simulation will be a foundation for the multi-scale modeling in sintering process.
        4,000원
        72.
        2015.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Powder injection molding is an important manufacturing technology to mass produce superalloy components with complex shape. Injection molding step is particularly important for realizing a desired shape, which requires much time and efforts finding the optimum process condition. Therefore computer aided engineering can be very useful to find proper injection molding conditions. In this study, we have conducted a finite element method based simulation for the spiral mold test of superalloy feedstock and compared the results with experimental ones. Sensitivity analysis with both of simulation and experiment reveals that the melt temperature of superalloy feedstock is the most important factor for the full filling of mold cavity. The FEM based simulation matches well the experimental results. This study contributes to the optimization of superalloy powder injection molding process.
        4,000원
        73.
        2014.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        To compensate for the critical shortage of human organs for allotransplantation, xenotransplantation studies using genetically modified pigs are being performed in Korea. Two types of pigs that are used are α1,3-galactosyltransferase gene knockout (GalT KO) pigs and GalT KO+hCD46 (human complement regulatory protein) pigs. The present study measured the gestation time, birth weight, daily growth rate, and heart weight of both kinds of transgenic minipigs. The gestation period for both types of pigs was 117∼119 days. There was no difference in the body weight of GalT KO (—/+) and GalT KO (—/—) piglets, but GalT KO+hCD46 (—hCD46+/+) pigs were significantly heavier at birth than were GalT KO+hCD46 (—hCD46+/—hCD46+) pigs. During the first 10 weeks of life, the daily weight gain of GalT KO+hCD46 (—hCD46+/—CD46+) piglets, which are considered the optimal type for xenotransplantation, was 0.19 kg. The weight of hearts from GalT KO piglets up to two months of age was affected more by body weight than by age. Transgenic pigs showed no differences in gestation period or reproductive ability compared with normal pigs. These results comprise basic data that may be used in xenotransplantation studies and transgenic animal production in Korea.
        4,000원
        74.
        2013.09 구독 인증기관 무료, 개인회원 유료
        Spermatogenesis is initiated from spermatogonial stem cells (SSCs) that has an ability of self-renewal and unipotency to generate differentiating germ cells. The objective of this study is to develop the simple method for derivation of SSCs using non-sorting of both spermatogonia and feeder cells. Simply uncapsulated mouse testes were treated with enzymes followed by surgical mincing, and single cells were cultured in stempro-34TM cell culture media at 37℃. After 5 days of culture, aciniform of SSC colony was observed, and showed a strong alkaline phosphatase activity. Molecular characterization of mouse SSCs showed that most of the mouse SSC markers such as integrin α6 and β1, CD9 and Stra8. In addition, pluripotency embryonic stem cell (ESC) marker Oct4 were expressed, however Sox2 expression was lowered. Interestingly, expression of SSC markers such as Vasa, Dazl and PLZF were stronger than mouse ESC (mESC). This data suggest that generated mouse SSCs (mSSCs) in this study has at least similar biomarkers expression to mESC and mSSCs derived from other study. Immunocytochemistry using whole mSSC colony also confirmed that mSSCs generated from this study expressed SSC specific biomarkers such as c-kit, Thy1, Vasa and Dazl. In conclusion, mSSCs from 5 days old mouse testes were successfully established without sorting of spermatogonia, and this cells expressed both mESC and SSC specific biomarkers. This simple derivation method for mSSCs may facilitate the study of spermatogenesis.
        4,000원
        78.
        2012.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The current standard solutions for somatic cells used for calibration of electronic somatic cell counts as reference material in raw milk are preserved with bronopol, boric acid, sodium azide, or potassium dichromate, and have a shelf-life of only up to 6 days at 4 ± 2℃. In the present study, a set of somatic cell standard solutions (SCSS) with a stability of 5 months for calibration of electronic instruments was developed. Somatic cells collected from cow’s milk and stored in a bulk tank at a dairy plant were treated with 10% formaldehyde in order to improve stability, and then separated by centrifugation. The resulting somatic cell suspension was preserved with glycerin, thimerosal, and dimethyl sulfoxide, and diluted in 3% processed skim milk solution ranging from 200,000~250,000 (low level), 350,000~ 450,000 (medium level), and 550,000~650,000 (high level) cells/㎖. Each SCSS was verified by direct microscope somatic cell counting (DMSCC), C-reader, and commercial standard samples. The average somatic cell count determined by DMSCC was 248, 214, 226 × 103 cells/㎖, 436, 382, 420 × 103 cells/㎖, and 612, 595, 609 × 103 cells/㎖. The coefficient of variation representing the repeatability of DMSCC decreased as the number of cells increased, and was <10.0% in almost all SCSS samples (range 4.6~7.1%). No statistically significant difference in somatic cell concentration was observed after storage at refrigeration temperature (2~6℃) over a period of 22 weeks (5 months). The stabilized SCSS may be useful as a reference material for determination of somatic cell count and quality control in testing of bovine raw milk.
        4,000원
        79.
        2011.12 구독 인증기관 무료, 개인회원 유료
        Pneumatosis cystoides intestinalis (PCI) is a rare condition characterized by multiple intramural pockets of gas filled cysts in the intestinal wall. PCI is usually found incidentally on an imaging study. Many different causes of PCI have been suggested, including mechanical, pulmonary, and bacterial causes. Treatment is usually conservative, including oxygen and antibiotic therapy. We report on two cases of PCI, without symptoms, in a 62-year-old male and a 72-year-old male. Computed tomography showed numerous, small, round, and air densities on the sigmoid colon. Colonoscopy showed numerous, variable-sized, sessile polypoid, balloon-like distended, and protruding subepithelial masses covered with normal colonic mucosa on the sigmoid colon. We observed that when the cyst was stuck with a needle, the size of the cyst was reduced and showed a flat termination. Therefore, we made a diagnosis of PCI and report on the case with references.
        4,000원
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