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        검색결과 610

        21.
        2018.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        K.-H. Hwang, H.-W. Kim, D.-J. Kim, A. Gould, M. D. Albrow, S.-J. Chung, C. Han, Y. K. Jung, Y.-H. Ryu, I.-G. Shin, Y. Shvartzvald, J. C. Yee, W. Zang, W. Zhu, S.-M. Cha, S.-L. Kim, C.-U. Lee, D.-J. Lee, Y. Lee, B.-G. Park, R. W. Pogge
        We present the analysis of KMT-2016-BLG-0212, a low flux-variation (Iflux−var ∼ 20 mag) microlensing event, which is in a high-cadence (Γ = 4hr −1) field of the three-telescope Korea Microlensing Telescope Network (KMTNet) survey. The event shows a short anomaly that is incompletely covered due to the brief visibility intervals that characterize the early microlensing season when the anomaly occurred. We show that the data are consistent with two classes of solutions, characterized respectively by low-mass brown-dwarf (q = 0.037) and sub-Neptune (q < 10−4) companions. Future high-resolution imaging should easily distinguish between these solutions.
        4,000원
        22.
        2018.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Oyema E. Obasogie, Ambali S. Abdulkareem, Is’haq A. Mohammed, Mercy T. Bankole, Jimoh. O.Tijani, Oladiran K. Abubakre
        In this study, an empirical relationship between the energy band gap of multi-walled carbon nanotubes (MWCNTs) and synthesis parameters in a chemical vapor deposition (CVD) reactor using factorial design of experiment was established. A bimetallic (Fe-Ni) catalyst supported on CaCO3 was synthesized via wet impregnation technique and used for MWCNT growth. The effects of synthesis parameters such as temperature, time, acetylene flow rate, and argon carrier gas flow rate on the MWCNTs energy gap, yield, and aspect ratio were investigated. The as-prepared supported bimetallic catalyst and the MWCNTs were characterized for their morphologies, microstructures, elemental composition, thermal profiles and surface areas by high-resolution scanning electron microscope, high resolution transmission electron microscope, energy dispersive X-ray spectroscopy, thermal gravimetry analysis and Brunauer-Emmett-Teller. A regression model was developed to establish the relationship between band gap energy, MWCNTs yield and aspect ratio. The results revealed that the optimum conditions to obtain high yield and quality MWCNTs of 159.9% were: temperature (700ºC), time (55 min), argon flow rate (230.37 mL min–1) and acetylene flow rate (150 mL min–1) respectively. The developed regression models demonstrated that the estimated values for the three response variables; energy gap, yield and aspect ratio, were 0.246 eV, 557.64 and 0.82. The regression models showed that the energy band gap, yield, and aspect ratio of the MWCNTs were largely influenced by the synthesis parameters and can be controlled in a CVD reactor.
        4,000원
        23.
        2018.11 구독 인증기관·개인회원 무료
        K.S. Park, J.H. Lee, K.B. Ji, D.E. Kim, E.J. Lee, D.C.M. Kulatunga, K.Y. Kim, B.S. Kim, E.Y. Kim, M.K. Kim
        To preserve the superior genetic resources and restore the endangered species, Somatic cell nuclear transfer (SCNT) has been used widely. In Korea, the research of dog cloning has made outstanding achievements including the production of the world`s first cloned dog. Sapsaree (Sapsalgae), the representative dog of Gyeongsan-si was designated as a Korea natural monument (No. 368). This male dog used in this study has azoospermia due to unknown cause. In this study, the aim was to confirm the cause of infertility in the cell donor dog and to evaluate the reproduction potential of dog cloning using infertile male dog by SCNT. First, to confirm the infertility of the cell donor dog, the reproductive history and the testis were evaluated. The breeding histology was not recorded in individual document. In histopathology, the Sertoli cell tumor was confirmed in biopsy of the cell donor dog after death. But, these tumors are predominantly in older dogs. Second, we produced the cloned dogs with the somatic cells of the infertile dog and the appearance was similar with the cell donor dog. Also, microsatellite analysis confirmed the genetic relationship between the cell donor and clone dogs. Third, the potential breeding capacity of the cloned dog was confirmed. In T4 assay, the normal dog (same age with cloned dogs), cell donor dog, and cloned dogs was investigated. The cell donor dog with azoospermia had very low T4 level, and cloned dogs showed higher level of T4 than normal dogs. In CASA, There was no significant difference in sperm motor ability between normal dogs and cloned dogs. As a result, cloned dogs produced by SCNT had no problem regarding the reproductive function of the testis. In AI experiment, the semen of clone dogs was used to fertilize a natural female bitch and was diagnosed pregnancy by ultrasonography. In total, 7 puppies were born by normal delivery (male: 3, female: 4). In conclusion, this study confirmed that the reproduction problem of non-genetic infertility can generate a normal descendant by SCNT. Also, the first successful research to restore infertile dogs was completed. Furthermore, SCNT would be useful for the restoration of endangered species and application of superior traits.
        27.
        2017.10 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        K.-S. Cho, S.-C. Bong, S. Choi, H. Yang, J. Kim, J.-H. Baek, J. Park, E.-K. Lim, R.-S. Kim, S. Kim, Y.-H. Kim, Y.-D. Park, S.W. Clarke, J.M. Davila, N. Gopalswamy, V.M. Nakariakov, B. Li, R.F. Pinto
        The Korea Astronomy and Space Science Institute plans to develop a coronagraph in collaboration with National Aeronautics and Space Administration (NASA) and to install it on the International Space Station (ISS). The coronagraph is an externally occulted one-stage coronagraph with a field of view from 3 to 15 solar radii. The observation wavelength is approximately 400~nm, where strong Fraunhofer absorption lines from the photosphere experience thermal broadening and Doppler shift through scattering by coronal electrons. Photometric filter observations around this band enable the estimation of 2D electron temperature and electron velocity distribution in the corona. Together with a high time cadence ($<$12~min) of corona images used to determine the geometric and kinematic parameters of coronal mass ejections, the coronagraph will yield the spatial distribution of electron density by measuring the polarized brightness. For the purpose of technical demonstration, we intend to observe the total solar eclipse in August 2017 with the filter system and to perform a stratospheric balloon experiment in 2019 with the engineering model of the coronagraph. The coronagraph is planned to be installed on the ISS in 2021 for addressing a number of questions (e.g., coronal heating and solar wind acceleration) that are both fundamental and practically important in the physics of the solar corona and of the heliosphere.
        4,200원
        28.
        2017.10 구독 인증기관·개인회원 무료
        Ho Seong Hwang, M. J. Geller, Changbom Park, D. G. Fabricant, M. J. Kurtz, K. J. Rines, Juhan Kim, A. Diaferio, H. J. Zahid, P. Berlind, M. Calkins, S. Tokarz, S. Moran
        32.
        2017.09 구독 인증기관·개인회원 무료
        Befekadu Chemere, M. J. Kim, Peng JingLun, S. C. Kim, B. H. Lee, J. Y. Kim, M. H. Jo, J. Ghassemi Nejad, B. W. Kim, K. I. Sung
        33.
        2017.05 구독 인증기관·개인회원 무료
        Baek S. Y, Kim D. W, Min Y. J, Cho E. S, Choi T. J, Soh H. C, Kim Y. M, Kang S. J, Kim B. K, Cho K. H, Cho K. H1
        The purpose of this study was to investigate the effect of estrus synchronization to altrenogest regumate (progesterone), PMSG/hCG, and artificial insemination (AI) on galectin-3, FGF-9 gene and protein expression. The morpho-metrical parameters of the endometrium and the number of corpora lutea (CL) were recorded. RNA was isolated from endometrial, oviduct and ovary tissues of non-synchronized (Control; n = 7) and AI synchronized (regumate, PMSG/hCG; n = 7) sows. The total number of CL was higher (P<0.05) in pigs treated with regumate/PMSG/hCG. The content of gelactin-3 and FGF-9 mRNA in pre-embryonic development stages increased on particular days, in control and studied in regumate/PMSG/hCG administered pigs. Gelactin-3 and FGF-9 were affected by regumate/PMSG/hCG treatment in the both pre-embryonic development stages (P<0.001, P<0.05) and encdometrial tissue (P<0.001, P<0.01). The regumate/PMSG/hCG treatment resulted in elevated expression of gelactin-3 (P<0.001) and FGF-9 (P<0.005) in oviduct and ovary tissues in comparison to control sows. Moreover, oviduct amount of gelectin-3 mRNA was higher in regumate/PMSG/hCG sows in comparison to the control group (P<0.05), whereas, expression characteristics of gelactin-3 and FGF-9 were investigated by hematoxylin and eosin stained and immunohistochemical staining. The results showed that galectin-3 and FGF-9 were significantly shown in the endometrium, oviduct and ovary tissues of the regumate/PMSG/ hCG. Presented data show that exogenous hormones administration can affect gene and protein expression in the sow reproductive tract.
        34.
        2017.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        K.-S. Cho, K. Marubashi, R.-S. Kim, S.-H. Park, E.-K. Lim, S.-J. Kim, P. Kumar, V. Yurchyshyn, Y.-J. Moon, J.-O. Lee
        We investigate two abnormal CME-Storm pairs that occurred on 2014 September 10 - 12 and 2015 March 15 - 17, respectively. The first one was a moderate geomagnetic storm (Dstmin  -75 nT) driven by the X1.6 high speed flare-associated CME (1267 km s−1) in AR 12158 (N14E02) near solar disk center. The other was a very intense geomagnetic storm (Dstmin  -223 nT) caused by a CME with moderate speed (719 km s−1) and associated with a filament eruption accompanied by a weak flare (C9.1) in AR 12297 (S17W38). Both CMEs have large direction parameters facing the Earth and southward magnetic field orientation in their solar source region. In this study, we inspect the structure of Interplanetary Flux Ropes (IFRs) at the Earth estimated by using the torus fitting technique assuming self-similar expansion. As results, we find that the moderate storm on 2014 September 12 was caused by small-scale southward magnetic fields in the sheath region ahead of the IFR. The Earth traversed the portion of the IFR where only the northward fields are observed. Meanwhile, in case of the 2015 March 17 storm, our IFR analysis revealed that the Earth passed the very portion where only the southward magnetic fields are observed throughout the passage. The resultant southward magnetic field with long- duration is the main cause of the intense storm. We suggest that 3D magnetic field geometry of an IFR at the IFR-Earth encounter is important and the strength of a geomagnetic storm is strongly affected by the relative location of the Earth with respect to the IFR structure.
        4,200원
        35.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Glenn J. White, Laia Barrufet de Soto, Chris Pearson, Stephen Serjeant, Tanya Lim, Hideo Matsuhara, S.K.Sirothia, S.Pal, Marios Karouzos, AKARI-NEP Team
        We have imaged the AKARI Deep Field with the GMRT radio telescope at 610 MHz, detecting 1224 radio components, which are optically identified with 455 optical galaxies having a mean r0 magnitude brighter of 22.5 (to a completeness limit of 25.4 mag), and an average redshift ~ 0.8.
        3,000원
        36.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        H. Matsuhara, T. Wada, N. Oi, T. Takagi, T. Nakagawa, K. Murata, T. Goto, S. Oyabu, T. Takeuchi, K. Ma lek, A. Solarz, Y. Ohyama, T. Miyaji, M. Krumpe, H. M. Lee, M. Im, S. Serjeant, C. P. Pearson, G. J. White, M. A. Malkan, H. Hanami, T. Ishigaki, D. Burgarella, V. Buat, A. Pollo
        The recent updates of the North Ecliptic Pole deep (0.5 deg2, NEP-Deep) multi-wavelength survey covering from X-ray to radio-wave is presented. The NEP-Deep provides us with several thousands of 15 μm or 18 μm selected galaxies, which is the largest sample ever made at these wavelengths. A continuous filter coverage in the mid-infrared wavelength (7, 9, 11, 15, 18, and 24 μm) is unique and vital to diagnose the contributions from starbursts and AGNs in the galaxies out to z=2. The new goal of the project is to resolve the nature of the cosmic star formation history at the violent epoch (e.g. z=1{2), and to find a clue to understand its decline from z=1 to present universe by utilizing the unique power of the multiwavelength survey. The progress in this context is brie y mentioned.
        4,000원
        39.
        2016.08 구독 인증기관 무료, 개인회원 유료
        K. S. Baek, I. C. Cho, N. Y. Kim, J. H. Woo, H. S. Chae, W. S. Lee, N. G. Park, S. S. Jang, Y. K. Oh
        3,000원
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