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        검색결과 1,065

        81.
        2021.03 KCI 등재후보 구독 인증기관 무료, 개인회원 유료
        This study was undertaken to evaluate the toxic effect of cadmium sulfate (Cds) on planarians (Dugesia japonica), and the suitability of planarians as an alternative animal model for toxicity studies. Planarians were exposed to varying concentrations of experimental solutions containing 0.1–25 mg/L Cds, and incubated for 1, 3, and 5 hrs. Motility, seizure-like behaviors (c-like, head-bop, snake-like, and screw-like) and regeneration ability of the amputated fragment were subsequently evaluated. Results showed decreased motility with increasing concentrations of Cds (p<0.05), with the lowest motility being observed at the highest concentration of 25 mg/L Cds. Results also indicate that seizure-like behavior patterns were significantly affected by increments in the Cds concentrations, especially the c-like and head-bop behaviors were notably increased. Compared to the control, the regeneration ability of the planarians was decreased in the experimental solutions containing Cds. Planarians exposed to Cds showed either delayed eye formation or no eye regeneration during incubation. Moreover, increased concentrations of Cds resulted in failure to regenerate and death of the planarians. In conclusion, this study confirm that the heavy metal Cds exerts a toxic effect on planarians. Furthermore, the performances of the planarians in the experimental period exhibit their suitability as an alternative animal model for toxicity studies.
        4,000원
        82.
        2021.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Abstract Activated carbon from the shell of the cashew of Para (SCP) was produced by chemical activation with ZnCl using the ratio of SCP: ZnCl2 1.0:1.5 at 700 °C. The prepared activated carbon (SCP700) was used for the removal of two emerging contaminants, 4-bromophenol (4-BrPhOH) and 4-chloroaniline (4-ClPhNH2) that are primarily employed in the industry. Different analytical techniques were used to characterize the activated carbon. From the N2 adsorption–desorption isotherms were obtained the specific surface area of 1520 m2 g− 1 and total pore volume of 0.492 cm3 g−1. The functional groups were identified by the FTIR technique and quantified by modified Boehm titration. The results revealed the bearing of several functional groups on the SCP700 surface, which may utterly influence the removal of the emerging contaminants. The equilibrium experiments showed that the maximum uptaken capacities (Qmax) achieved at 45 °C were 488.2 (4-BrPhOH) and 552.5 mg g−1 (4-ClPhNH2). The thermodynamic parameters demonstrated that the processes of 4-BrPhOH and 4-ClPhNH2 adsorption are exothermic, spontaneous, energetically suitable, and the magnitude of ΔH° is compatible with physisorption. The mechanism of the adsorption of the emerging contaminants onto the carbon surface is dominated by microporous filling, hydrogen bonds, π-stacking interactions, and other Van der Waals interactions. The use of activated carbon for the treatment of industrial synthetic wastewater with several inorganic and organic molecules commonly found in industrial effluents showed a very high percentage of uptaking (up to 98.64%).
        4,900원
        83.
        2020.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Nickel nanopowders are obtained by the spark discharge method, which is based on the evaporation of the electrode surface under the action of the discharge current, followed by vapor condensation and the formation of nanoparticles. Nickel electrodes with a purity of 99.99% are used to synthesize the nickel nanoparticles in the setup. Nitrogen is used as the carrier gas with a purity of 99.998%. XRD, TEM, and EDX analyses of the nanopowders are performed. Moreover, HRTEM images with measured interplanar spacings are obtained. In the nickel nanopowder samples, a phase of approximately 90 wt% with an expanded crystal lattice of 6.5% on average is found. The results indicate an unusual process of nickel nanoparticle formation when the spark discharge method is employed.
        3,000원
        84.
        2020.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        양배추는 짐바브웨 소규모 농가의 음식, 영양 및 소득원으로서 가장 중요한 엽채류 중의 한가지이다. 본 연구에서는 2종의 한국산 양배추 품종(K5 적보라색과 K8 녹색)이 짐바브웨의 열대성 기후에 적응이 가능한지 확인하고자 현지 생산 품종인 Fabiola과 생산성(yield), 조숙성(earliness) 및 연도 (tenderness) 등의 특성 비교 실험을 실시하였다. 본 실험은 2017년 짐바브웨 과학산업연구개발센터(SIRDC, Scientific Industrial Research and Development Center)의 시험포장에서 격리 상태로 5반복 실험으로 진행되었다. 1. 품종별 재배 기간은 현지 품종인 Fabiola가 85-90일, K5 품종이 120-140일 및 K8 품종이 100-120일 정도였다. 2. 양배추 두부 무게는 K8가 Fabiola와 K5 품종에 비하여 유의적으로 무거운 것으로 나타났다(P<0.05). 흥미로운 점은 K5 품종의 경우 타 품종에 비하여 무게가 2-3배 적었다. 3. K8은 35 ton/ha로서 K5의 18과 Fabiola의 25에 비하여 유의적으로 높은 판매 가능한 양배추 생산성이 있는 것으로 확인되었다(P<0.05). 이상의 결과를 종합해보면 K8과 K5 두 한국 양배추 품종 의 생산성, 재배기간 및 품질 특성 등을 현지 품종인 Fabiola 와 비교한 결과 열대성 기후인 짐바브웨에서도 재배가 가능하며 상품성 또한 가지고 있다고 사료된다.
        4,000원
        85.
        2020.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We report the discovery of a giant exoplanet in the microlensing event OGLE-2017-BLG-1049, with a planet―host star mass ratio of q = 9.53 ± 0.39 × 10-3 and a caustic crossing feature in Korea Microlensing Telescope Network (KMTNet) observations. The caustic crossing feature yields an angular Einstein radius of θE = 0.52 ± 0.11 mas. However, the microlens parallax is not measured because the time scale of the event, tE ≃ 29 days, is too short. Thus, we perform a Bayesian analysis to estimate physical quantities of the lens system. We fi nd that the lens system has a star with mass Mh = 0.55+0.36 -0.29 M⊙ hosting a giant planet with Mp = 5.53+3.62 -2.87 MJup, at a distance of DL = 5.67+1.11 -1.52 kpc. The projected star{planet separation is aㅗ = 3.92+1.10 -1.32 au. This means that the planet is located beyond the snow line of the host. The relative lens{source proper motion is μrel ~ 7 mas yr-1, thus the lens and source will be separated from each other within 10 years. After this, it will be possible to measure the flux of the host star with 30 meter class telescopes and to determine its mass.
        4,000원
        86.
        2020.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Gravitational lensing of point sources located inside the lens caustic is known to produce four images in a con guration closely related to the source position. We study this relation in the particular case of a sample of quadruply-imaged quasars observed by the Hubble Space Telescope. Strong correlations between the parameters de ning the image con guration are revealed. The relation between the image con guration and the source position is studied. Some simple features of the selected data sample are exposed and commented upon. In particular, evidence is found for the selected sample to be biased in favor of large magni cation systems. While having no direct impact on practical analyses of speci c systems, our results have pedagogical value and deepen our understanding of the mechanism of gravitational lensing.
        4,200원
        87.
        2020.12 KCI 등재후보 구독 인증기관 무료, 개인회원 유료
        Cyanobacteria (blue green algae) blooms formed in natural water resources due to the environmental pollution produce toxic compounds as secondary metabolites, causing health hazards to both humans and other living beings. Microcystin is a well-known toxin produced by cynobacteria. The present study was undertaken to evaluate varying concentrations and exposure times of two different forms of microcystin, viz., -LR (MCLR) and -LA (MCLA), on the motility and seizure-like behavior of planarian (Dugesia japonica). Compared to control, reduced motility was observed in both the MCLR or MCLA treated groups, but did not differ significantly with increasing concentrations of microcystin. However, the number of seizure-like behaviors were increased dose-dependently in planarian exposed to MLCR or MCLA. Exposure time to microcystine also affected the motility and seizure-like behaviors of planarians; 24 hrs incubation with MCLR, and 48 and 96 hrs exposure to MCLA, showed significantly (p<0.05) lower motility, as compared to the control. Assessing regeneration of the planarians revealed the simultaneous completion of eye formation at day 9 in planarians incubated in the absence or presence of MCLR or MCLA, thereby indicating that exposure to microcystin has no effect on the process. In conclusion, we determined that exposure to microcystins resulted in decrease in the number of motility, and induced abnormal behavior pattern in planarians. Further studies are required to identify the toxicity of microcystin that affects aquatic ecosystems.
        4,000원
        88.
        2020.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Differences between the littoral states regarding the status of the Malacca Strait result in disharmony and inconsistencies in handling spatial planning and preventing marine pollution in the strait. International cooperation with user countries carried out so far is also not optimal due to conflict of interests. Using a normative juridical approach and secondary data of the provisions of United Nations Convention on the Law of the Sea (UNCLOS) 1982 and the Declaration of the Three Strait States, the Malacca Strait is under the sovereignty of the littoral states and used for international navigation with transiting passage. Spatial planning in the Malacca Strait, which results in overlapping uses for cross-fishing vessels, conservation, and traditional fishing, cannot be performed because the problem of maritime boundary determination has not been resolved by the littoral states. Tripartite cooperation needs to continue to be built through agreements that not only bind the littoral states but also the user states.
        5,200원
        93.
        2020.11 구독 인증기관 무료, 개인회원 유료
        Marketers and retailers are increasingly interested in grabbing the opportunity to reach the consumer at the right time and place with a smart phone. Depending on Location Based Advertising (LBA) and associated sensors with the IBeacon technology, marketers can determined the consumer’s favorite products through his search history and previous purchase activities furthermore his location in-store. So, marketers and retailers pay more attention to in-store mobile LBA. In this work, the modified LBA in-store framework are constructed. This model proposed that the temporal time, type of information and the variety of receiver of mobile in-store LBA affect the Purchase intention in retail stores.
        4,000원
        94.
        2020.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Predicting the quality of materials after they are subjected to plasma sintering is a challenging task because of the non-linear relationships between the process variables and mechanical properties. Furthermore, the variables governing the sintering process affect the microstructure and the mechanical properties of the final product. Therefore, an artificial neural network modeling was carried out to correlate the parameters of the spark plasma sintering process with the densification and hardness values of Ti-6Al-4V alloys dispersed with nano-sized TiN particles. The relative density (%), effective density (g/cm3), and hardness (HV) were estimated as functions of sintering temperature (oC), time (min), and composition (change in % TiN). A total of 20 datasets were collected from the open literature to develop the model. The high-level accuracy in model predictions (>80%) discloses the complex relationships among the sintering process variables, product quality, and mechanical performance. Further, the effect of sintering temperature, time, and TiN percentage on the density and hardness values were quantitatively estimated with the help of the developed model.
        4,000원
        95.
        2020.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This work reports the syntheses of an inexpensive and efficient asphalt-derived mesoporous carbon (AdMC) as an adsorbent. The adsorbent was activated with potassium hydroxide to increase its surface area and then characterized by SEM–EDS, FT-IR, and BET. The adsorption properties of AdMC were evaluated for the adsorptive removal of eleven Poly Aromatic Hydrocarbons (PAHs) and diesel from water samples. The prepared AdMC showed very high surface areas and high micropore volumes equal to 2316 m2/g and 1.2 cm3/g, respectively. Various experimental conditions influencing the adsorption capacity of eleven PAHs and diesel were investigated. At high concentrations, PAHs and diesel solubility in water is very low. Hence, samples were emulsified with a surfactant, and then maximum adsorption capacity was investigated. Adsorption profile of individual PAHs was examined using gas chromatography/mass spectrometry analysis followed by liquid–liquid extraction. Total hydrocarbon removal was studied using a total organic analyzer. Asphalt-derived mesoporous sorbent showed an extreme ability to remove PAHs and diesel (average adsorption capacity of 166 mg/g for individual PAHs and diesel (maximum capacity of 1600 mg/g). The experimental results fitted the Langmuir model with a correlation efficiency of 0.9853. The results obtained for both adsorbents also matched to pseudo-second-order kinetics, suggesting that the adsorption of PAHs and diesel is chemical, monolayer, and homogeneous process.
        4,500원
        99.
        2020.09 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Digital media play an undeniably influential role in contemporary communication, facilitating new kinds of multimodal forms of representation. However, ELT pedagogy does not always take these multimodal aspects of communication into account in a systematic way. One pedagogical approach that has been developed for this purpose is ‘multimodal composing’ or ‘digital multimodal composing’. This approach caters to the needs of English language learners in the digital age by engaging with multimodal forms of communication in digital media which are ‘embedded’ alongside the reading and writing tasks that make up the core of traditional approaches to ELT. In this article, I provide an overview of scholarly work that has been done in developing this approach. Drawing on a case study of English language learners in Hong Kong, I demonstrate what the approach looks like in practice and suggest how it might be implemented in other contexts, balancing multimodal forms of communication with the traditional demands of the English language curriculum.
        4,600원
        100.
        2020.09 KCI 등재후보 구독 인증기관 무료, 개인회원 유료
        Melia azedarach is commonly used in traditional and folk medicine in Korea and China to treat a variety of diseases including diarrheal, diabetic, rheumatic, and hypertensive disease. The aim of this study was to determine the potential prophylactic and therapeutic effects of Melia azedarach against a broad spectrum of viruses in in vitro cell culture model and the protective effect against different influenza A subtypes in BALB/c mice model. An effective dose of pre-treatment, co-treatment, and post-treatment of Melia azedarach significantly reduced the replication of coxsackievirus, herpes simplex virus, influenza A virus, enterovirus, and bovine rhinovirus in both epithelial and macrophage cell lines. Melia azedarach treatment remarkably promoted the phosphorylation of the key molecules associated with the type-1 interferon and NF-κB signaling pathways. Furthermore, it induced the secretion of type-1 interferon and pro-inflammatory cytokines and the subsequent stimulation of the antiviral state in both epithelial and macrophage cells. Interestingly, oral inoculation of an effective dose of herb extract significantly improved viral clearance in the lungs of BALB/c mice, thus exhibiting protection against several subtypes of influenza A virus. Together with our results indicate that an extracts of Melia azedarach and its components could exhibit a potential natural source of an antiviral drug candidate for a broad spectrum of viruses in animal and humans.
        4,300원
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