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        검색결과 612

        46.
        2023.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, graphene oxide (GO) was synthesized by the improved Hummers’ method. The degree of oxidation from graphite (Gi) to GO was determined through interlayer spacing calculated from X–ray diffraction. Besides, the effect of KMnO4: Gi ratios (X1), H2SO4 volume (X2), oxidation temperature (X3), oxidation time of stage 1 (X4), and oxidation time of stage 2 (X5) was screened by the Plackett–Burman model. The simultaneous impact of three factors that influenced the degree of oxidation (X1, X2, and X3) was studied by the Box–Behnken experimental model of response surface methodology to achieve suitable conditions for the GO synthesis process. The characterization of GO product was investigated via the modern analytical methods: X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Inaddition, the study was also carried out on a pilot scale for orientation in industrial application with the yield of 14 g/batch.
        4,300원
        47.
        2023.01 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We present the deep homogeneous 𝑈𝐵𝑉𝑅𝐼 photometric data of 135,071 stars down to 𝑉 ∼ 23 mag and 𝐼 ∼ 22 mag toward the Carina Nebula. These stars are cross-matched with those from the previous surveys in the X-ray, near-infrared, and mid-infrared wavelengths as well as the Gaia Early Data Release 3 (EDR3). This master catalog allows us to select reliable members and determine the fundamental parameters distance, size, stellar density of stellar clusters in this star-forming region. We revisit the reddening toward the nebula using the optical and the near-infrared colors of early-type stars. The foreground reddening [𝐸(𝐵 −𝑉) 𝑓 𝑔] is determined to be 0.35 ± 0.02, and it seems to follow the standard reddening law. On the other hand, the total-toselective extinction ratio of the intracluster medium (𝑅𝑉,𝑐𝑙) decreases from the central region (Trumpler 14 and 16, 𝑅𝑉,𝑐𝑙 ∼ 4.5) to the northern region (Trumpler 15, 𝑅𝑉,𝑐𝑙 ∼ 3.4). It implies that the central region is more dusty than the northern region. We find that the distance modulus of the Carina Nebula to be 11.9 ± 0.3 mag (𝑑 = 2.4 ± 0.35 kpc) using a zero-age main-sequence fitting method, which is in good agreement with that derived from the Gaia EDR3 parallaxes. We also present the catalog of 3,331 pre-main-sequence (PMS) members and 14,974 PMS candidates down to 𝑉 ∼ 22 mag based on spectrophotometric properties of young stars at infrared, optical, and X-ray wavelengths. From the spatial distribution of PMS members and PMS candidates, we confirm that the member selection is very reliable down to faint stars. Our data will have a legacy value for follow-up studies with different scientific purposes.
        5,400원
        48.
        2022.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study evaluated the effect of lactic acid bacteria (LAB, a mixture of Enterococcus faecium and Lactobacillus plantarum) supplementation, the storage temperature, and storage period on the fermentation characteristics and in vitro ruminal digestibility of a total mixed ration (TMR). The TMR was prepared into two groups, namely, CON (control TMR without the LAB) and ML (supplementing a mixture of E. faecium and L. plantarum in the ratio of 1% and 2% (v/w), respectively). Both groups were divided and stored at 4°C or 25°C for 3, 7, and 14 d fermentation periods. Supplementing LAB to the TMR did not affect the chemical composition of TMR except for the lactate and acetate concentration. Storage temperatures affected (p<0.05) the chemical composition of the TMR, including pH, lactate, and acetate contents. The chemical composition of TMR was also affected (p<0.05) by the storage period. During in vitro rumen fermentation study, the ML treatment showed lower (p<0.05) dry matter digestibility at 24 h incubation with a higher pH compared to the CON. There was no difference in the in vitro dry matter digestibility (IVDMD) of TMR between the CON and ML treatment however, at 24 h, ML treatment showed lower (p<0.05) IVDMD with a higher pH compared to the CON. The effects of storage temperature and period on IVDMD were not apparent at 24 h incubation. In an in vivo study using Holstein steers, supplementing LAB to the basal TMR for 60 d did not differ in the final body weight and average daily gain. Likewise, the fecal microbiota did not differ between CON and ML. However, the TMR used for the present study did include a commercial yeast in CON, whereas ML did not; therefore, results were, to some extent, compromised in examining the effect of LAB. In conclusion, storage temperature and period significantly affected the TMR quality, increasing acetate and lactate concentration. However, the actual effects of LAB supplementation were equivocal.
        4,000원
        58.
        2022.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The leaves of Allium victorialis (AV) are known an edible perennial herb, which has been used in Korean traditional medicine. However, the beneficial pharmacological effects of AV extracts (AVE) on the antioxidant activity and atopic dermatitis (AD) have not been thoroughly examined. Therefore, the present study aims to investigate both antioxidant activity and anti-inflammatory effect of AVE on AD in vitro and in vivo. Antioxidant activity was evaluated by total polyphenol content and ferric reducing ability. AVE showed a level of polyphenol content and reducing power activity. The five-week-old BALB/c mice were used as an AD-like mouse model by treating them with 1-chloro-2, 4-dinitrobenzene (DNCB). Topical administration of AVE for 3 weeks to DNCB-treated mice significantly alleviated clinical skin lesion dermatitis severity and epidermal thickness. Histopathological analysis also demonstrated that AVE decreased eosinophil and mast cell infiltration into skin and ear tissue. These results suggest that topical application of AVE inhibits the development of AD-like skin lesion in mice by their antioxidant activity. Thus, AVE may be a potential therapeutic agent for AD.
        4,000원
        59.
        2022.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Swine atrophic rhinitis is a respiratory disease that causes nasal turbinate loss and septal deformation due to Bordetella bronchiseptica and Pasteurella multocida. Turbinate loss facilitates pathogens to infect lungs, which leads to various respiratory diseases and productivity reduction. In this study, descriptive analysis was implemented for atrophic rhinitis and pneumonia. From 6 pig farms shipped to slaughterhouses in Chungbuk province, 20 heads and 20 lungs were collected by each farm from March 2020 to September 2020. Their atrophic rhinitis lesions and lung lesions were scored and blood samples were also collected to test the seroprevalence of several respiratory diseases. Pasteurella multocida from nasal swab was cultured and antibiotic resistance tests were performed. Correlation between atrophic rhinitis scores and lung lesion scores was not found. Abdominal nasal lesions were more severe than dorsal lesions. Differences in lung lesion scores were relatively small between lobes. The score of pneumonia was higher in castrated pigs than in female pigs. There was no relationship between lesion score and seroprevalence of respiratory diseases. Antibiotic resistance levels for Pasteurella multocida differed by farm, and several antibiotics were not effective. The results of this study imply that antimicrobial susceptibility tests are highly recommended before administration.
        4,000원
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