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        검색결과 1,331

        91.
        2023.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        For practical applications of graphene sheets in a variety of fields, mass production of high-quality graphene sheets is necessary. Herein, we reported a cost-effective, green, and simple approach to synthesizing mass production exfoliated graphene (EG) flakes employing electrochemical exfoliation of pencil graphite in neutral aqueous electrolytes. Pencil graphite cores of different grades were applied as anode and cathode electrodes and exposed to the electrolyte solution at a different voltage. Several parameters were examined and optimized, including pencil grade (2,4,6,8 B), applied voltage (10, 15, 20, 30 V), different inorganic electrolytes ((NH4)2SO4, Na2SO4, NaNO3, NaCl, and CH3COONa), and the concentration of electrolytes. The optimal condition was chosen by considering the mass of produced graphene and the conductivity of the graphene solution. The optimal conditions were as follow: pencil grade: 6B; applied voltage: 10 V; electrolyte type: Na2SO4; electrolyte concentration: 0.1 M. Under these conditions, the production yield was > 95% within 3 h and 9 min. The EG was characterized by utilizing FT-IR, XRD, Raman spectroscopy, FE-SEM, Cyclic Voltammetry, and Electrochemical Impedance Spectroscopy (EIS). Characterization indicates that the synthesized EG had an XRD peak at 2θ = 26.6° and an ID/ IG ratio of 0.36. Furthermore, the EG showed good conductivity when tested by cyclic voltammetry and EIS whereas the R2 values were 985.8 and 76.3 Ω for bare GCE and EG/GCE, respectively. In addition, EG effectively removed cadmium (Cd(II)) with an adsorption level of 8.72 mg/g. The results from this study suggest that EG can be scaled up and commercialized in an environmentally friendly and low-cost manner, especially in low-income countries, and using it to rectify metal ions.
        4,200원
        92.
        2023.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study examined the subacute oral toxicity of Dendropanax morbiferus H.Lév leaves hot-water extracts (DMWE) using male and female Spargue-Dawley rats. Rats were orally administered the DMWE at dose levels of 0, 250, 500, 1,000, and 2,000 mg/kg body weight (BW) for four weeks. For experimental period, clinical signs and the number of deaths were examined, and feed intake and BW of all experimental animals were measured once a week for four weeks. At the end of the experiment, blood samples were collected from all rats, and all animals were euthanized and autopsies were performed to collect major organs. No dead animals were found during the experimental period. In addition, no differences were found between control and DMWE-treated groups in feed intakes, BW changes, organ weights, clinical signs, hematological parameters, and serum biochemical parameters. The results of this study provided evidence that oral administration of DMWE at the dose of 2,000 mg/kg BW is safe in rats and may not exert severe toxic effects.
        4,000원
        93.
        2023.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, the acute toxicity of Dendropanax morbiferus H.Lév leaf hot-water extracts (DMWE) was examined in male and female ICR mice. Mice were orally administered the DMWE at dose levels of 0, 250, 500, 1,000 and 2,000 mg/kg body weight (BW) for single-dose toxicity test. There were no significant differences in change of BW between control and all DMWE treated-groups. In hematological and blood biochemical analysis, none of the parameters were affected by the DMWE. Similarly, there were no significant effects on markers for liver and kidney functions in all DMWE treated-groups. Since there were no adverse effects of the DMWE in single oral toxicity tests, even at the highest doses, it was concluded that the lethal dose 50 (LD50) of DMWE is estimated at > 2,000 mg/kg BW.
        4,000원
        94.
        2023.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In additive manufacturing, the flowability of feedstock particles determines the quality of the parts that are affected by different parameters, including the chemistry and morphology of the powders and particle size distribution. In this study, the microstructures and flowabilities of gas-atomized heat-resistant alloys for additive manufacturing applications are investigated. A KHR45A alloy powder with a composition of Fe-30Cr-40Mn-1.8Nb (wt.%) is fabricated using gas atomization process. The microstructure and effect of powder chemistry and morphology on the flow behavior are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and revolution powder analysis. The results reveal the formation of spherical particles composed of single-phase FCC dendritic structures after gas atomization. SEM observations show variations in the microstructures of the powder particles with different size distributions. Elemental distribution maps, line scans, and high-resolution XPS results indicate the presence of a Si-rich oxide accompanied by Fe, Cr, and Nb metal oxides in the outer layer of the powders. The flowability behavior is found to be induced by the particle size distribution, which can be attributed to the interparticle interactions and friction of particles with different sizes.
        4,000원
        95.
        2022.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Bacterial phytopathogen Pectobacterium causes soft rot disease in several vegetable crops globally, resulting in heavy agricultural losses at both the pre and postharvest stages. The present work was carried out to screen Kimchi cabbage genetic resources conserved at the National Agrobiodiversity Center, Rural Development Administration, Korea, for resistance against the soft rot pathogen Pectobacterium carotovorum subsp. carotovorum KACC 21701 over a period of three years (from 2020 to 2022). Infection of the phytopathogen was carried out at four-leaf stage and for each accession, twenty-five plants per germplasm were infected with KACC 21701. Kimchi cabbage cultivars Wangmatbaechu, Seoulbaechu, and CR Kiyoshi were used as control. Seven-days post-infection, the Disease Index (DI) values were manually recorded from zero to four, zero matched perfectly heathy plants and four completely dead plants. The 682 accessions of Kimchi cabbage exhibited varying degrees of disease resistance to KACC 21701 and thirty accessions, exhibiting a DI≤2, were considered for replication studies. During the replication studies, four landrace germplasms (IT102883, IT120036, IT120044, and IT120048) and one cultivar (IT187919) were confirmed to be moderately susceptible to KACC 21701. Results of the preliminary screening as well as replication studies were documented for the all the 682 germplasms. Addition of such information to the passport data of stored germplasms might serve as potential bio-resource for future breeders and researchers to develop resistant varieties or study the mechanisms involved in resistance of plants to such phytopathogen.
        4,000원
        96.
        2022.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Subunit vaccines are being developed as a potential therapy for preventing microbial pathogen infection. In this study, the immunogenicity of recombinant Brucella (B.) abortus Fe/Mn superoxide dismutase (rFe/Mn SOD) protein as a subunit vaccine against B. abortus was investigated in BALB/c mice model. Brucella Fe/Mn SOD gene was cloned into a pcold-TF DNA vector. The bacterial recombinant protein was expressed using the Escherichia coli DH5α strain with a size of 82.50 kDa. The western blotting assay showed that rFe/Mn SOD reacted with Brucella-positive serum, indicating the potential immunoreactivity of this recombinant protein. After the second and third vaccinations, the peripheral CD4+ T cell population was increased significantly in the rFe/Mn SOD-immunized mice group compared to the PBS control group. Moreover, immunization of this recombinant protein increased the CD4+ T cell population from the first vaccination to the third vaccination. Meanwhile, the CD8+ T cells were slightly enhanced after the second vaccination compared to the first vaccination and compared to control groups. Fourteen days after the bacterial infection, the splenomegaly and the number of bacteria in the spleen were evaluated. The result showed that both rFe/Mn SOD and positive control RB51 decreased the bacterial replication in the spleen and the splenomegaly compared to control groups. Altogether, these results suggested that rFe/Mn SOD could induce host immunity against B. abortus infection.
        4,000원
        97.
        2022.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The ambiguity of complex regional pain syndrome (CRPS) posed a challenge to many medical researchers in the early days after its discovery and continues to do so till date. The establishment of the Budapest Criteria of the International Association for the Study of Pain resolved certain queries on CRPS. Many aspects of CRPS, such as pathophysiology and etiology, remain unknown. Therefore, of these aspects, we focused on the genetic basis of CRPS. In this qualitative review, we summarized the recent findings on the genetic association of CRPS and analyzed the roles of genes identified in each study and limitations of the studies. In particular, we confirmed the reliability of each study by comparing the following research, which used the following control groups or the same candidate genes. Notably, specific phenotypes of CRPS with dystonia indicate a significant association with human leukocyte antigen (HLA)-DQ8. Further, HLA-DQ8, which is associated with aberrant CD4+ T-cell reaction, could be associated with CRPS etiology since an increased CD4+ T-cell population was reported in CRPS patients. In addition, matrix metalloproteinase (MMP)-9 found in genome-wide expression profiling is noteworthy since MMP-9 is associated with neuro-inflammatory reactions. Despite these suggestions on the genetic aspects of CRPS, the pathophysiology and etiology of CRPS may be polygenic and multifactorial, influenced by multiple genes and other factors. Further, some studies have suggested that CRPS phenotypes have different etiologies. Thus, further studies with the precise classification of CRPS on a unified basis and with a significant number of case groups are required
        4,000원
        99.
        2022.10 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We complete the survey for finite-source/point-lens (FSPL) giant-source events in 2016–2019 KMTNet microlensing data. The 30 FSPL events show a clear gap in Einstein radius, 9 μas < θE < 26 μas, which is consistent with the gap in Einstein timescales near tE ∼ 0.5 days found by Mr´oz et al. (2017) in an independent sample of point-source/point-lens (PSPL) events. We demonstrate that the two surveys are consistent. We estimate that the 4 events below this gap are due to a power-law distribution of freefloating planet candidates (FFPs) dNFFP/d logM = (0.4 ± 0.2) (M/38 M⊕)−p/star, with 0.9 ≲ p ≲ 1.2. There are substantially more FFPs than known bound planets, implying that the bound planet power-law index γ = 0.6 is likely shaped by the ejection process at least as much as by formation. The mass density per decade of FFPs in the Solar neighborhood is of the same order as that of ‘Oumuamua-like objects. In particular, if we assume that ‘Oumuamua is part of the same process that ejected the FFPs to very wide or unbound orbits, the power-law index is p = 0.89 ± 0.06. If the Solar System’s endowment of Neptune-mass objects in Neptune-like orbits is typical, which is consistent with the results of Poleski et al. (2021), then these could account for a substantial fraction of the FFPs in the Neptune-mass range.
        5,800원
        100.
        2022.10 구독 인증기관·개인회원 무료
        Dose-rate monitoring instruments are indispensable to protect workers from the potential risk of radiation exposure, and are commonly calibrated in terms of the ambient dose equivalent (H*(10)), an operational quantity that is widely used for area monitoring. Plastic scintillation detectors are ideal equipment for dosimetry because of their advantages of low cost and tissue equivalence. However, these detectors are rarely used owing to the characteristics caused by low-atomic-number elements, such as low interaction coefficients and poor gamma-ray spectroscopy. In this study, we calculated the G(E) function to utilize a plastic scintillation detector in spectroscopic dosimetry applications. Numerous spectra with arbitrary energies of gamma rays and their H*(10) were calculated using Monte Carlo simulations and were used to obtain the G(E) function. We acquired three different types of G(E) functions using the least-square and first-order methods. The performances of the G(E) functions were compared with one another, including the conventional total counting method. The performance was evaluated using 133Ba, 137Cs, 152Eu, and 60Co radioisotopes in terms of the mean absolute percentage error between the predicted and true H*(10) values. In addition, we confirmed that the dose-rate prediction errors were within acceptable uncertainty ranges and that the energy responses to 137Cs of the G(E) function satisfied the criteria recommended by the International Commission.
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