검색결과

검색조건
좁혀보기
검색필터
결과 내 재검색

간행물

    분야

      발행연도

      -

        검색결과 557

        81.
        2015.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We describe a survey of nearby core-collapse supernova (SN) explosion sites using integral field spec- troscopy (IFS) techniques, which is an extension of the work described in Kuncarayakti et al. (2013). The project aims to constrain SN progenitor properties based on the study of the immediate environment of the SN. The stellar populations present at the SN explosion sites are studied by means of integral field spectroscopy, which enables the acquisition of both spatial and spectral information of the object simultaneously. The spectrum of the SN parent stellar population gives an estimate of its age and metal- licity. With this information, the initial mass and metallicity of the once coeval SN progenitor star are derived. While the survey is mostly done in optical, the additional utilization of near-infrared integral field spectroscopy assisted with adaptive optics (AO) enables us to examine the explosion sites in high spatial detail, down to a few parsecs. This work is being carried out using multiple 2-8 m class telescopes equipped with integral field spectrographs in Chile and Hawaii.
        4,000원
        82.
        2015.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The major limiting factor of the reproductive performance on many farms is the failure to detect estrus in a timely and accurate manner. The estrus detection for Hanwoo cows (Bos taurus coreanea) is generally performed by the visual observation which is estimated at about 40% detection rate only. This recurring problem among farmers has motivated the development of various estrus detection aids. The mounting event duration threshold, standing heat event frequency threshold, estrus detection algorithm and so on, are necessarily needed in order to detect the estrus of Hanwoo cows accurately when using some automatic devices. However, they are not yet investigated for Hanwoo cows. Therefore, the objective of this study was to establish a mounting event duration threshold and standing heat event frequency threshold more specifically for Hanwoo breed by discriminating the duration of standing heat mounting from shorter duration spurious mountings which routinely occur in cattle herds. One hundred and fifty Hanwoo cows with an age between 2 to 5 years were used in this study. Cows that were expected to come into estrus within 3days were randomly assigned to each compartment for the estrus group (EG). The heated cows were video recorded for about 24 hours until after post estrus. The results showed that Hanwoo cows can be considered on estrus when it stand immobile during mounted by any other cow in more than or equal to 3.15s and 3.22s in chest-tail head mount (CTM) and head-above back mount (HBM) and that occurs consecutively at least three times within 876.4s interval. The algorithm was also developed using the thresholds of the mount duration, mount interval and consecutive occurrence number.
        4,000원
        87.
        2014.07 구독 인증기관·개인회원 무료
        Prior research has investigated the consumer effects of cash and card payments in service settings, but the growing trend of innovative payment with a mobile device hasn’t been considered in the literature so fare. This article represents one of the first studies that considers the adoption of mobile as a new payment method and investigate how the ‘checkout’ phase affect the shoppers’ overall price image of retail stores (OSPI). Results from our studies show that the ‘checkout’ phase is the ‘moment of truth’ for shoppers judging OSPI. We investigate the effects of cash, card, and mobile payments and show that the less transparent a payment method, the lower OSPI judgments of shoppers. In particular, favorable comparisons of basket prices to shoppers’ mental budgets trigger lower store price perceptions. Subsequently, these results have major implications for retailers aiming to lower their OSPI in customers’ minds.
        89.
        2013.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Fe-TiC composite was fabricated from Fe and TiC powders by high-energy milling and subsequent spark- plasma sintering. The microstructure, particle size and phase of Fe-TiC composite powders were investigated by field emission scanning electron microscopy and X-ray diffraction to evaluate the effect of milling conditions on the size and distribution of TiC particles in Fe matrix. TiC particle size decreased with milling time. The average TiC particle size of 38 nm was obtained after 60 minutes of milling at 1000 rpm. Prepared Fe-TiC powder mixture was densified by spark- plasma sintering. Sintered Fe-TiC compacts showed a relative density of 91.7~96.2%. The average TiC particle size of 150 nm was observed from the FE-SEM image. The microstructure, densification behavior, Vickers hardness, and frac- ture toughness of Fe-TiC sintered compact were investigated.
        4,000원
        90.
        2013.10 구독 인증기관·개인회원 무료
        Since Montreal protocol in1989 designated MB(methyl bromide) as ozone depleting chemicals, IPPC(International Plant Protection Convention) has adopted replacing the MB with alternative chemical and reducing the rate of MB use in plant quarantine in 2008. Pineapples are one of the most frequently fumigated imported fruit with MB in Korea. However, there was no technically available replacement. Therefore, we evaluated phosphine(PH3) fumigation as alternative to MB in applying pineapples. In the preliminary test, PH3 gas in 12L desicators to calculate ranged to 0.1 from 2g/m3 was tested at 2 and 24hr exposure to target pest, citrus mealy bug(CMB, Planococcus citri). All different of stage of CMB was shown 100% mortality when 2g/m3 of PH3 applied for 24hrs at 8℃. To confirm studies designed in 0.5m3 fumigation chamber, all egg, nymph and adult stages of CMB was killed completely and there wasn’t any phytotoxic and quality damages on pineapples for 2 weeks post-fumigation periods at 8℃. In terms of commercial use, further commercial research will need to be carry out in cooperation with importers and fumigators.
        92.
        2013.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We present a multi-dimensional reduction method of the surveyed cube database obtained using a single- dish radio telescope in Taeduk Radio Astronomy Observatory (TRAO). The multibeam receiver system installed at the 14 m telescope in TRAO was not optimized at the initial stage, though it became more stabilized in the following season. We conducted a Galactic Plane survey using the multibeam receiver system. We show that the noise level of the first part of the survey was higher than expected, and a special reduction process seemed to be definitely required. Along with a brief review of classical methods, a multi-dimensional method of reduction is introduced; It is found that the ‘background’ task within IRAF (Image Reduction and Analysis Facility) can be applied to all three directions of the cube database. Various statistics of reduction results is tested using several IRAF tasks. The rms value of raw survey data is 0.241 K, and after primitive baseline subtraction and elimination of bad channel sections, the rms value turned out to be 0.210 K. After the one-dimensional reduction using ‘background’ task, the rms value is estimated to be 0.176 K. The average rms of the final reduced image is 0.137 K. Thus, the image quality is found to be improved about 43% using the new reduction method.
        4,000원
        94.
        2012.10 구독 인증기관·개인회원 무료
        Understanding how researchers are tackling globally important issues, such as climate change, is crucial to identify whether current research is comprehensive enough to make substantive predictions about general responses to climate change. We assessed the type of studies being conducted by researchers to understand the impacts of climate change on insects, published. Most published research is generated from Europe and North America and being dedicated to core data analysis, with reviews being highly produced. Temperature – only is the main climate change factor being analysed, with most researchers are assessing changes in abundance or distribution/range shifts. Of most concern is the number of studies which do not specifically identify a climate change factor (ie just arm wave), the lack of studies on Hemimetabolous insects and the need for more studies to assess specific mechanistic responses to climate change.
        95.
        2012.09 KCI 등재 구독 인증기관·개인회원 무료
        We investigate the relation between star formation activity and PAH 3.3 μm emission. Our targets are mid-infrared-excess galaxies selected from the AKARI all-sky survey point source catalog. We performed AKARI near-infrared spectroscopy for them. As a result, we obtained 2.5 − 5 μm spectra of 79 galaxies, and selected 35 star-forming galaxies out of them. Comparing the PAH 3.3 μm luminosities with the infrared luminosities, we find a linear correlation between them. However, by adding the results from literatures for luminous infrared galaxies and ultra-luminous infrared galaxies that are more luminous than our sample, the ratio of the PAH to the infrared luminosity is found to decrease towards the luminous end.
        96.
        2012.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We utilize AKARI's slitless spectroscopic capability to detect the 3.3 μm polycyclic aromatic hydrocarbons (PAHs) emission and measure star formation (SF) activity for various AKARI programs. First, we obtain 2∼5μm spectra of 20 flux-limited galaxies with mixed SED classes in order to calibrate the 3.3 μm PAH luminosity (LPAH 3.3) as a star formation rate (SFR) indicator. We find that LPAH3.3 correlates with LIR as well as with the 6.2 μm PAH luminosity ( LPAH 6.2). The correlations does not depend on SED classes. We find that ULIRGs deviate from the correlation between PAH luminosities and LIR, while they do not for the correlation between PAH luminosities. We suggest possible effects to cause this deviation. On the other hand, how AGN activity is linked to SB activity is one of the most intriguing questions. While it is suggested that AGN luminosity of quasars correlates with starburst (SB) luminosity, it is still unclear how AGN activity is connected to SF activity based on host galaxy properties. We are measuring SFRs for the LQSONG sample consisting of reverberation mapped AGNs and PG-QSOs. This is an extension of the ASCSG program by which we investigated the connection between SB and AGN activities for Seyferts type 1s at z ~ 0.36. While we found no strong correlation between LPAH3.3 and AGN luminosity for these Seyferts 1s, LPAH3.3 measured from the central part of galaxies correlates with AGN luminosity, implying that SB and AGN activities are directly connected in the nuclear region.
        3,000원
        97.
        2012.09 KCI 등재 구독 인증기관·개인회원 무료
        Polycyclic aromatic hydrocarbons (PAHs) in Galactic planetary nebulae (PNe) are investigated by means of the unidentified infrared (UIR) bands. Continuous near- to mid-infrared spectra of PNe are obtained with the AKARI/IRC and the Spitzer/IRS. All 19 PNe in the present study show prominent dust emissions and we investigate the variation in the intensity ratios among the UIR bands. The ionization fraction and the size distribution of PAHs in PNe are derived using the UIR band ratios. We find that the ionization fraction of PAHs in PNe is around 0.0-0.6 and that small PAHs are scarce. The present result indicates a systematic trend of the 3.4 μm aliphatic feature to become weak as the PAH ionization fraction increases.
        99.
        2012.06 구독 인증기관·개인회원 무료
        The reactive oxygen species (ROS) generated during the somatic cell transfer nuclear (SCNT) procedures may cause the mitochondrial dysfunction and DNA damage, which may result in restricts the reprogramming of SCNT embryos and play a key direct role in apoptosis. The present study was conducted to investigate the effect of antioxidant treatment during the SCNT procedures on the inhibition of mitochondria and DNA damages in bovine SCNT embryos. The reconstituted oocytes were treated with antioxidants of 25 μM β-mercaptoethanol (β-ME) or 50 μM vitamin C (Vit. C) during the SCNT procedures. In vitro fertilization (IVF) was performed for controls. Mitochondrial morphology and membrane potential (ΔΨ) were evaluated by staining the embryos with MitoTracker Red or JC-1. Apoptosis was analyzed by Caspase-3 activity assay and TUNEL assay, and DNA fragmentation was measured by comet assay at the zygote stage. Mitochondrial morphology of non-treated SCNT embryos was diffused within cytoplasm without forming clumps, while the IVF embryos and antioxidant treated SCNT embryos were formed clumps. The ΔΨ of β-ME (1.3±0.1, red/green) and Vit. C-treated (1.4±0.2, red/green) SCNT embryos were significantly higher (p<0.05) than that of non-treated SCNT embryos (0.9±0.1, red/ green), which similar to that of IVF embryos (1.3±0.1, red/green). Caspase-3 activity was not difference among the groups. TUNEL assay also revealed that little apoptosis was occurred in SCNT embryos as well as IVF embryos regardless of antioxidant treatment. Comet tail lengths of β-ME and Vit. C-treated SCNT embryos (337.8±23.5 μm and 318.7 ±27.0 μm, respectively) were shorter than that of non-treated SCNT embryos (397.4± 21.4 μm) and similar to IVF embryos (323.3±10.6 μm). These results suggest that antioxidant treatment during SCNT procedures can inhibit the mitochondrial and DNA damages of bovine SCNT embryos.
        100.
        2012.06 구독 인증기관·개인회원 무료
        Cryopreservation of canine spermatozoa affords potential exchange of genetic material, and thus may lead to improvement in the breeding management. However, canine spermatozoa undergo many damages such as, cold shock, ice crystal formation, oxidative stress during cryopreservation. In this study used the CASA for investigating the effect of various trehalose concentrations and thawing temperatures on the sperm viability. In addition, the efficacy of the most optimal of the tested cryopreservation protocols in this study was verified by AI as the in vivo test. Also, this study evaluates the variation of frozen- thawed canine spermatozoa during different incubation condition. The addition of trehalose 25 mM was optimal concentration and frozen-thawed semen quality was significantly higher better than control (Glucose) and other concentration groups. In effect of thawing temperature on frozen-thawed sperm movement and intact acrosome evaluations, which result enhance the sperm motility and movement value depending on increase temperature condition at 36, 54 and 72℃. Also, in the effect of different incubation condition on frozen-thawed sperm after thawing at 36℃ for 60 sec, that the results trehalose 25 mM was significantly better (p<0.05) than glucose in general as well as, the post-thawed sperm motility and intact acrosome was reduced depending on increase the incubation time. Especially, incubation at 4 to 8 hour was rapidly depreciation of movement value and the rate of intact acrosome was dropped similar tendency. Thus, incubation 17℃ was better than other incubation groups on sperm motility and acrosome integrity. For the in vivo evaluate of spermatozoa survival and is the most definitive test of sperm function, we performed artificial insemination in estrous bitch. The semen was prepared for intrauterine insemination using the 25 mM trehalose freezing extender and thawing at 36℃, and 2 bitches were inseminated with 1×106 motile spermatozoa by surgical method. The results of AI, the pregnancy rates, mean litter size and oocyte fertilization rate were 16.6% (1/6), and 50% (2/4), respectively. In conclusion, based on the results of these experiments, the effect of addition of trehalose on extender improves the movement and intact acrosome of frozen-thawed semen. In particular, trehalose 25 mM groups was higher than other different concentration group on movement value and acrosome integrity of frozen-thawed sperm. Also, through incubation condition, this study identify the optimal incubation temperature after thawing was 17℃. Furthermore, the information will be contributed to develop the canine ART including AI, IVF and canine ICSI. * This research was supported by iPET (Grants 110056-3), Ministry for Food, Agriculture, Forestry and Fisheries, Republic of Korea.
        1 2 3 4 5