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        검색결과 213

        21.
        2021.06 KCI 등재후보 구독 인증기관 무료, 개인회원 유료
        Aluminum (Al) is one of the most widely applied metals in various industries. Anthropogenic activities of industrial waste result in increased accumulation of Al in natural water resources and aqueous organisms, leading to increased heavy metal pollution in the environment. This will ultimately associate with health risks to all living beings including humans. The present study addresses the possible toxic effects of Al on the motility and regeneration of planarians, using Dugesia japonica as the experimental animal model. Planarians were exposed to varying concentrations of Al (50–1,200 mg/L) for 1 hr, and subsequently evaluated for their motility, seizure-like behaviors, regeneration and alterations of the cell-organelles in their body. Results of the study exhibit that increasing Al concentrations lead to decreased motility and increased seizure-like behaviors, especially the c-type and head bob behaviors in planarians (p<0.05). The regeneration ability in the tail segments was reduced by increased Al concentrations, and the eyespot and optic nerves were more clearly observed in the control groups than planarians exposed to Al. Organelle analysis revealed morphological abnormalities in the mitochondria, golgi apparatus, endoplasmic reticulum, and cilia in the head region of planarians, as compared to the control groups. Taken together, our results indicate that exposure to Al alters the behavior of planarians and delays the regeneration of amputated body parts. Therefore, we suggest that Al exposure adversely can affect the lives of aquatic organisms, and induce toxicity such as cell abnormalities in animals.
        4,000원
        22.
        2021.06 KCI 등재후보 구독 인증기관 무료, 개인회원 유료
        Lead (Pb) is a major heavy metal that augments environmental pollution and is a health risk to living organisms. This study was performed to investigate the effect of lead on characteristics of planarian, Dugesia japonica. Briefly, planarians were cultivated in water containing different concentrations (0–400 mg/L) of Pb, and incubated for varying durations (1, 3, and 5 hr). After termination of the incubation time, motility and seizure-like behaviors (c-like, head-bop, snake-like, and screw-like) of the planarians were counted in fresh water. Results showed that increasing Pb concentration and time resulted in decreased motility of the planarians (p<0.05). Increasing concentrations of Pb also resulted in significant increase in the seizure-like behavioral patterns, in particular the c-like and head-bop behaviors. In order to examine eye regeneration, the head region was cut, and rest of the body was incubated in water in the absence or presence of Pb, until emergence of the eye extrusion. Formation of eye spots was initiated in amputated fragments of the control group (without Pb) on day 4 after incubation, whereas appearance of the eye spots was delayed in planarian exposed to 200 mg/L Pb. Moreover, immunohistochemistry revealed that formation of the optic nerve was delayed in planarians exposed to Pb. Thus, our studies determined that planarians exposed to high concentrations of Pb resulted in decreasing motility and induction of seizure-like behaviors, as well as delayed eye regeneration. Results of the current study therefore validate that exposure to lead has a negative effect on the lifespan of aquatic organisms and can cause disturbance of the nervous system in animals, thereby implying the possibility of threatening health.
        4,000원
        26.
        2021.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In recent years, various methods of measuring body temperature have been developed using wireless biosensors to facilitate an early detection of pregnancy and parturition in cows. However, there are no studies on real-time monitoring of cattle body temperature throughout pregnancy. Therefore, we investigated the daily mean ruminal temperature in pregnant cows throughout pregnancy using a ruminal bio-capsule sensor and then evaluated the temperature variation between pregnant and non-pregnant cows. In pregnant cows, the mean and standard deviation of ruminal temperature was 38.86 ± 0.17℃. Ruminal temperature in pregnant cows slowly decreased until 180 to 190 days after artificial insemination and after that, the temperature increased dramatically until just before parturition. Furthermore, the means ruminal temperature was significantly different between pregnant and nonpregnant cows. The mean and standard deviation of ruminal temperature were as follows: 38.68 ± 0.01℃ from days 80 to 100, 38.78 ± 0.02℃ from days 145 to 165, 38.99 ± 0.45℃ from days 200 to 220, 39.14 ± 0.38℃ from days 250 to 270 before parturition. Therefore, our results could provide useful data for early detection of pregnancy and parturition in Korean cows.
        4,000원
        27.
        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
        28.
        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
        33.
        2019.10 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        There is evidence that the luminosities of Type Ia supernova (SN Ia) depend on their environments. While the impact of this trend on estimating cosmological parameters is widely acknowledged, the origin of this correlation is still under debate. In order to explore this problem, we first construct the YONSEI (YOnsei Nearby Supernova Evolution Investigation) SN catalog. The catalog consists of 1231 spectroscopically confirmed SNe Ia over a wide redshift range (0.01 < z < 1.37) from various SN surveys and includes light-curve fit data from two independent light-curve fitters, SALT2 and MLCS2k2. For a sample of 674 host galaxies, we use the stellar mass and the star formation rate data in Kim et al. (2018). We find that SNe Ia in low-mass and star-forming host galaxies are 0.062 ± 0.009 mag and 0.057 ± 0.010 mag fainter than those in high-mass and passive hosts, after light-curve corrections with SALT2 and MLCS2k2, respectively. When only local environments of SNe Ia (e.g., locally star-forming and locally passive) are considered, this luminosity difference increases to 0.081 ± 0.018 mag for SALT2 and 0.072 ± 0.018 mag for MLCS2k2. Considering the significant difference in the mean stellar population age between the two environments, this result suggests that the luminosity evolution of SNe Ia with redshift is most likely the origin of the environmental dependence.
        6,300원
        34.
        2019.06 KCI 등재후보 구독 인증기관 무료, 개인회원 유료
        Nicotine is a component of tobacco products and is one of the most commonly abused substances that leads to addiction. Therefore, the present study was performed to investigate the behavioral pattern and toxicity by nicotine exposure in planarians. Basically, planarians were exposed to different concentration of nicotine for 5 min. To investigate detoxification effect, planarians were exposed to nicotine for 5 min, and treated glycyrrhizin for 5 min, then motility and seizure-like behavior were observed for 5 min. As a result, the motility of nicotine-exposed planarians decreased approximately more than 50% compared to freshwater control. However, the motility of glycyrrhizin-exposed planarians recovered than nicotineexposed planarians. In the assessment of seizure-like behavioral pattern, planarians exposed to nicotine showed head-bop or c-like type rather than screw-like or snake-like patterns. However, planarians exposed to glycyrrhizin showed no seizure-like behavior. To examine the oxidative stress response, planarians were cultured in fresh water containing 1 mM nicotine for 1 day. Planarians were homogenized and extracted to assay the contents of reactive oxygen species (ROS), lipid hydroperoxides (LH), glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD). The result showed that a significantly higher level of ROS, LH indicated in planarians exposed to nicotine, on the other hand, glycyrrhizin-exposed planarians were significantly decreased ROS, LH levels. In conclusion, the motility decreased when planarians were exposed to nicotine, in a dose-dependent manner, whereas seizurelike behavior increased. Nicotine induced behavioral disturbances and cell toxicity in planarians were recovered by glycyrrhizin, suggesting a candidate substance for nicotine addiction treatment.
        4,000원
        35.
        2018.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        자외선차단 화장품은 기능성 화장품 중의 하나로서, 유·무기 자외선차단물질이 함유되어 있다. 무기계 자외선차단제는 주로 산화아연, 이산화티탄 등이 있다. 무기계 자외선차단제는 입자의 지름이 60 ~ 100 nm로 자외선 A, B의 차단능이 좋은 것으로 알려져 있다. 또한 자외선을 포함한 태양광선에 대해 비활성이 크고 안전성이 우수하다. 그리고 유기계 자외선차단제처럼 피부에 흡수 또는 축적되지 않으므로 피부 자극이나 알레르기를 유발하지 않는다. 본 연구에서는 판상 무기안료인 마이카, 자외선차단 효과를 갖는 이산화티탄 나노입자, 소수성 실리카를 각각 계면활성제로 표면처리 하였고, 각 물질의 전하 차이에 따른 비화학적인 상호 인력 작용에 의해 마이카에 이산화티탄 나노입자, 실리카를 물리적으로 흡착시켰다. 이후, 소수성 표면처리제인 실란을 표면처리 하여 소수성을 갖는 자외선 차단 판상 마이카 복합체를 제조하였다. 자외선 차단 판상 마이카 복합체는 일반적인 나노입자 이산화티탄의 응집성을 개선하고 균일한 분산에 따른 자외선차단 효과가 증대되었으며, 소수성으로 표면처리를 하여 화장품 제형에서의 분산안정성을 크게 개선할 수 있었다. 안료의 표면전하는 제타전위로 평가하였으며, 제조된 자외선차단 마이카 복합체의 특성 평가는 FE-SEM, XRD, FT-IR, UV-VIS 등으로 확인하였다.
        4,000원
        36.
        2018.10 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The DEEP-South (the Deep Ecliptic Patrol of the Southern Sky) photometric census of small Solar System bodies produces massive time-series data of variable, transient or moving objects as a by- product. To fully investigate unexplored variable phenomena, we present an application of multi-aperture photometry and FastBit indexing techniques for faster access to a portion of the DEEP-South year-one data. Our new pipeline is designed to perform automated point source detection, robust high-precision photometry and calibration of non-crowded fields which have overlap with previously surveyed areas. In this paper, we show some examples of catalog-based variability searches to find new variable stars and to recover targeted asteroids. We discover 21 new periodic variables with period ranging between 0.1 and 31 days, including four eclipsing binary systems (detached, over-contact, and ellipsoidal variables), one white dwarf/M dwarf pair candidate, and rotating variable stars. We also recover astrometry (< ±1–2 arcsec level accuracy) and photometry of two targeted near-earth asteroids, 2006 DZ169 and 1996 SK, along with the small- (0.12 mag) and relatively large-amplitude (0.5 mag) variations of their dominant rotational signals in R-band.
        4,600원
        37.
        2018.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Samples were collected from planktonic habitats of the fresh and brackish waters in Korea from August 2016 to May 2018. As a result, three genera and nine species were newly recorded in Korea. The unrecorded indigenous genera were Anathece, Chondrocystis and Geminocystis, and nine species were Anabaenopsis arnoldii, Anathece smithii, Chondrocystis dermochroa, Coelosphaerium aerugineum, Eucapsis microscopica, Geminocystis herdmanii, Microcystis panniformis, Synechococcus nidulans and Woronichinia karelica. Anathece smithii, Coelosphaerium aerugineum, Eucapsis microscopica, Microcystis panniformis and Synechococcus nidulans had been reported to inhabit freshwater, but these were found in brackish water in this study. Microcystis panniformis, which is a potential genus for causing green-tide, is taxonomically valuable in Korea.
        4,000원
        38.
        2018.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Samples were collected from benthic and subaerophytic habitats of fresh and brackish water in Korea from April 2017 to April 2018. Accordingly, three genera and seven species were newly recorded in Korea. Three unrecorded genera were Cephalothrix, Cyanophanon and Toxifilum, and seven species were Anagnostidinema pseudacutissimum, Calothrix elenkinii, Cephalothrix komarekiana, Cyanophanon mirabile, Cyanosarcina chroococcoides, Leptolyngbya ectocarpi and Toxifilum mysidocida. Anagnostidinema pseudacutissimum and Cephalothrix komarekiana had been previously reported to inhabit freshwater, but these were found to be present in brackish water during the period of the present study. Also, Cyanosarcina chroococcoides previously reported to inhabit moorland waters and swamps, were found to be present in subaerophytic habitat.
        4,000원
        39.
        2018.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Phytoplanktons were collected from various environments including small marshes, small ponds, reservoirs and brackish water from March 2017 to November 2017. In this study, five species of family Scenedesmaceae were newly recorded in Korea. The genus Desmodesmus was newly reported in Korea. The newly recorded species are Scenedesmus nanus, S. praetervisus, Desmodesmus costato-granulatus, D. lunatus and D. spinulatus. S. nanus and S. praetervisus are known to occur in freshwater, but they were found in the brackish water in this study.
        4,000원
        40.
        2018.07 구독 인증기관·개인회원 무료
        Brand equity (BE) previously focused on consumers’ perceptions under brand marketing stimuli, they often used financial performance indicators for evaluating brand value (Aaker,1996;Keller,1993). However the primary stakeholders of a service brand are employees (Brexendorf & Kernstock,2007).Thus, the enhancement of employee- based BE could be an important topic for in-depth investigation in the fields of brand and internal marketing. Morhart (2009) was the first to introduce the concepts of brand-specific transformational leadership (TFL) and brand-specific transactional leadership (TRL) based on employees’ brand-building behavior. Theory asserts that leaders should endeavor to influence employees through the internalization of brand values and a brand-based role (Morehart,2001) . In the process of brand internalization, leaders with brand experience and brand knowledge should also uphold and constantly reaffirm brand values because they're more capable than ordinary leaders to clearly convey brand values (Hoffman,1999). For this reason, brand-specific leadership based on employee brand-building behaviors is the focus of this study. This study adopts hierarchical linear modeling for individual and organizational-level analyses. This research to investigate (1)whether TFL and TRL have directly affect employee-based individual-level BE.(2)whether TFL and TRL have indirectly affect employee-based BE as an individual-level mediator.(3)how managers use brand-specific leadership to elicit employees’ perceived brand value congruence for improved employee-based BE.
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