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        검색결과 1,734

        811.
        2015.10 구독 인증기관·개인회원 무료
        We describe an early angiosperm and a leaf mine ichnofossil from the Lower Cretaceous Potomac Group of Virginia, USA. The descriptions are based on a fossil leaf that was first reported in 1895 but identified as a fragment of a fossil fern. Leaf architectural features and sedimentological context indicate that this leaf was produced by an herbaceous eudicot angiosperm, possibly associated with Ranunculales. The leaf mine is a full depth linear-blotch mine with frass, a trace of puparium inside the blotch mine section, and feeding/oviposition-related puncture marks. The features of the mine are most consistent with those produced by agromyzid flies. This fossil extends the record of agromyzid flies by about 40 million years ago. This fossil provides evidence that agromyzid flies or their ancestors were feeding on herbaceous basal eudicots similar to modern herbaceous ranunculids during the Early Cretaceous, prior to the appearance and diversification of asterids. Our finding contradicts the previous hypotheses on the dipteran radiations associated with the past environmental changes. Insect feeding damages remained in fossilized leaves are currently considered as an important source for climate change studies. We review progresses in the study of the insect feeding trace fossils and their usefulness for monitoring environmental changes.
        812.
        2015.10 구독 인증기관·개인회원 무료
        The small brown planthopper (SBPH), Laodelphax striatellus Fallén (Hemiptera: Delphacidae) is one of the major insect pest against rice, Oryza sativa L. in Korea. High density of SBPH could cause severe damage on rice plant by directly sucking and indirectly transmitting viral pathogens, Rice stripe virus and Rice streaked dwarf virus. As a preliminary study for de novo whole-genome sequencing of SBPH, we investigated 6 transcriptomes isolated from different developmental stages, sex, and tissue (egg, 1st ~ 3rd nymphs, 4th ~ 5th nymphs, female and male adults, salivary gland). Clean-sequence data of 19.3 Gb were obtained from total 47.8 Gb raw data after adaptor and quality trimming (Q30) and overlapped reads joining. As a suitable assembler, Bridger was selected based on the results of reference mapping (93.45%) and CEGMA completeness (95.97%). Finally, we obtained 158,207 reads (size range: 201 ~ 22,162 bp; Mean size: 1,048.04 bp; N50: 2,417 bp) after clustering the assembly results by CD-HIT-EST (similarity threshold: 99%). Based on these results, we are conducting further studies such as transcript expression pattern among different developmental stages and gene annotation.
        813.
        2015.10 구독 인증기관·개인회원 무료
        The family Scelionidae is distributed all around the world, which has approximately 3,000 species within 150 genera in the world. To date 39 species of 15 genera from 3 subfamilies in Scelionidae are recorded in South Korea. In this study, we report a new record of the genus Idiris with one species. There are many parasitory and predatory insects specializing on spider eggs. Among scelionids, some species (Baeus achaearneus, Comastichus zopheros, Idris sp.) parasitize spider eggs. However, there was no Korean record for scelionid wasps parasitizing in egg sacs of spider. Based on morphology, ecology, and DNA identification, we recognized this species, Idris sp., being new to Korea. All examined specimens and DNA samples are deposited in Kunsan National University.
        814.
        2015.10 구독 인증기관·개인회원 무료
        Leptotrombidium pallidum is the major vector mites for Orientia tsutsugamushi, the causative agent of scrub typhus. To understand the molecular mechanism of L. pallidum, we sequenced the whole genome using Illumina sequencing technology. Totally four genomic libraries with different insert sizes ranging from 280 bp to 8 kb were used to generate 45.1 Gb of genome in the combination of paired-end and mate-pairs sequencing reads. Quality filtering and correction of paired-end reads for very small and/or bad-quality sequences yielded 26.9 Gb of high-quality sequences, which are used to estimate the genome size as 175 Mbusing kmer methods and assembled into a 193.7 Mb genomic sequence scaffolds with N50 length of 92,945 bp. Furthermore, 94% of CEGMA completeness score were obtained from genome scaffold assembly. To facilitate gene annotation, we used a combination of de novo and homology based tools to predict gene models in the chigger mite genome. A combination of evidence-based and de novo approaches predicted 15,842 high-confidence protein-coding genes with an average transcript length of 1,511 bp and 2.4 exons per gene which corresponds to about 12.4% total gene length. Bacterial endosymbiosis are very common in mite species and can range from mutualistic to pathogenic associations. Henceforth, the endosymbionts in L. pallidum were predicted using the NCBI microbial draft genomes and mitochondrial genome. Besides, this L. pallidum draft genome can be used as a significant reference for comparative genomic studies across mite species.
        815.
        2015.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The Kepler mission has shown that small planets are extremely common. It is likely that nearly every star in the sky hosts at least one rocky planet. We just need to look hard enough - but this requires vast amounts of telescope time. MINERVA (MINiature Exoplanet Radial Velocity Array) is a dedicated exoplanet observatory with the primary goal of discovering rocky, Earth-like planets orbiting in the habitable zone of bright, nearby stars. The MINERVA team is a collaboration among UNSW Australia, Harvard-Smithsonian Center for Astrophysics, Penn State University, University of Montana, and the California Institute of Technology. The four-telescope MINERVA array will be sited at the F.L. Whipple Observatory on Mt Hopkins in Arizona, USA. Full science operations will begin in mid-2015 with all four telescopes and a stabilised spectrograph capable of high-precision Doppler velocity measurements. We will observe ~100 of the nearest, brightest, Sun-like stars every night for at least five years. Detailed simulations of the target list and survey strategy lead us to expect 154 new low-mass planets.
        4,000원
        816.
        2015.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this paper we introduce the Plasma Physics of Active Galactic Nuclei project, which is an ongoing experiment with Korean VLBI Network (KVN) and KVN and VERA Array (KaVA) to study multi- frequency polarimetric properties on parsec scales of active galaxies. The goal of the project is to improve our understanding of fundamental jet physics, especially evolution of the relativistic out ow coupled with the large-scale magnetic field. We selected six radio-loud AGN as our targets. So far we (i) detected resolved emissions regions at 86 and 129 GHz on VLBI scales, (ii) constructed 2D spectral index maps of the out ows, and (iii) found polarizations at 22 and 43 GHz for a few targets. Here we present spectral index distributions of 3C 120 between 22 and 43 GHz and a linear polarization map of BL Lac at 43 GHz obtained with KVN.
        3,000원
        817.
        2015.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A 26-month-old male mixed-breed dog of Korean origin was subjected to necropsy following death after a history of decreased appetite and weight loss. Necropsy revealed generalized lymphadenopathy and splenomegaly. Histopathological examination of samples from the spleen, mandibular lymph nodes, liver, kidney, and large intestine showed granulomas with numerous macrophages containing intracytoplasmic Leishmania amastigotes. Transmission electron microscopy revealed Leishmania amastigotes in the macrophage cytoplasm. All tissues with granulomas were positive for Leishmania spp, which was confirmed to be Leishmania infantum by conventional polymerase chain reaction (PCR), real-time PCR, and in situ hybridization. To our knowledge, this is the second case of canine visceral leishmaniasis in Korea.
        3,000원
        818.
        2015.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Surface modified carbon felts were utilized as an electrode for the removal of inorganic ions from seawater. The surfaces of the carbon felts were chemically modified by alkaline and acidic solutions, respectively. The potassium hydroxide (KOH) modified carbon felt exhibited high Brunauer-Emmett-Teller (BET) surface areas and large pore volume, and oxygencontaining functional groups were increased during KOH chemical modification. However, the BET surface area significantly decreased by nitric acid (HNO3) chemical modification due to severe chemical dissolution of the pore structure. The capability of electrosorption by an electrical double-layer and the efficiency of capacitive deionization (CDI) thus showed the greatest enhancement by chemical KOH modification due to the appropriate increase of carboxyl and hydroxyl functional groups and the enlargement of the specific surface area.
        4,000원