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Sökning: WFRF:(Hattori Takashi)

  • Resultat 1-4 av 4
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  • Izumi, Takuma, et al. (författare)
  • 2015
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 811:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 1 observations of the central kiloparsec region of the luminous type. 1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.'' 5x0.'' 4 = 165 x 132 pc) at submillimeter wavelengths. Utilizing the wide. bandwidth of ALMA, we simultaneously obtained HCN(4-3), HCO+(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860 mu m continuum. The region consists of the central similar to 1 '' component and the surrounding starburst ring with a radius of similar to 1.'' 5-2.'' 5. Several structures connect these components. Except for CO(3-2), these dense gas tracers are significantly concentrated toward the central similar to 1 '', suggesting their suitability to probe the nuclear regions of galaxies. Their spatial distribution resembles well those of centimeter and mid-infrared continuum emissions, but it is anticorrelated with the optical one, indicating the existence of dust-obscured star formation. The integrated intensity ratios of HCN(4-3)/HCO+(4-3) and HCN(4-3)/CS(7-6) are higher at the active galactic nucleus (AGN) position than at the starburst ring, which is consistent with our previous findings (submillimeter-HCN enhancement). However, the HCN(4-3)/HCO+(4-3) ratio at the AGN position of NGC 7469 (1.11 +/- 0.06) is almost half of the corresponding value of the low-luminosity type. 1 Seyfert galaxy NGC 1097 (2.0 +/- 0.2), despite the more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the ratio is comparable to that of the close vicinity of the AGN of NGC 1068 (similar to 1.5). Based on these results, we speculate that some heating mechanisms other than X-ray (e.g., mechanical heating due to an AGN jet) can contribute significantly for shaping the chemical composition in NGC 1097.
  • Kuncarayakti, Hanindyo, et al. (författare)
  • Direct Evidence of Two-component Ejecta in Supernova 2016gkg from Nebular Spectroscopy
  • 2020
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 902:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Spectral observations of the type-IIb supernova (SN) 2016gkg at 300-800 days are reported. The spectra show nebular characteristics, revealing emission from the progenitor star's metal-rich core and providing clues to the kinematics and physical conditions of the explosion. The nebular spectra are dominated by emission lines of [O i] lambda lambda 6300, 6364 and [Ca ii] lambda lambda 7292, 7324. Other notable, albeit weaker, emission lines include Mg I] lambda 4571, [Fe ii] lambda 7155, O I lambda 7774, Ca II triplet, and a broad, boxy feature at the location of H alpha. Unlike in other stripped-envelope SNe, the [O i] doublet is clearly resolved due to the presence of strong narrow components. The doublet shows an unprecedented emission line profile consisting of at least three components for each [O i]lambda 6300, 6364 line: a broad component (width similar to 2000 km s(-1)), and a pair of narrow blue and red components (width similar to 300 km s(-1)) mirrored against the rest velocity. The narrow component appears also in other lines, and is conspicuous in [O i]. This indicates the presence of multiple distinct kinematic components of material at low and high velocities. The low-velocity components are likely to be produced by a dense, slow-moving emitting region near the center, while the broad components are emitted over a larger volume. These observations suggest an asymmetric explosion, supporting the idea of two-component ejecta that influence the resulting late-time spectra and light curves. SN 2016gkg thus presents striking evidence for significant asymmetry in a standard-energy SN explosion. The presence of material at low velocity, which is not predicted in 1D simulations, emphasizes the importance of multidimensional explosion modeling of SNe.
  • Morokuma, Tomoki, et al. (författare)
  • Subaru FOCAS Spectroscopic Observations of High-Redshift Supernovae
  • 2010
  • Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - 0004-6264. ; 62:1, s. 19-37
  • Tidskriftsartikel (refereegranskat)abstract
    • We present spectra of high-redshift supernovae (SNe) that were taken with the Subaru low-resolution optical spectrograph, FOCAS. These SNe were found in SN surveys with Suprime-Cam on Subaru, the CFH12k camera on the Canada-France-Hawaii Telescope, and the Advanced Camera for Surveys on the Hubble Space Telescope. These SN surveys specifically targeted z > 1 Type la supernovae (SNe Ia). From the spectra of 39 candidates, we obtained redshifts for 32 candidates and spectroscopically identified 7 active candidates as probable SNe Ia, including one at z = 1.35, which is the most distant SN la to be spectroscopically confirmed with a ground-based telescope. An additional 4 candidates were identified as likely SNe la from the spectrophotometric properties of their host galaxies. Seven candidates are not SNe la, either being SNe of another type or active galactic nuclei. When SNe la were observed within one week of the maximum light, we found that we could spectroscopically identify most of them up to z = 1.1. Beyond this redshift, very few candidates were spectroscopically identified as SNe Ia. The current generation of super red-sensitive, fringe-free CCDs will push this redshift limit higher.
  • Okura, Takashi, et al. (författare)
  • Involvement of the pyrilamine transporter, a putative organic cation transporter, in blood-brain barrier transport of oxycodone.
  • 2008
  • Ingår i: Drug Metabolism And Disposition. - 0090-9556 .- 1521-009X. ; 36:10, s. 2005-2013
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of this study was to characterize blood-brain barrier (BBB) transport of oxycodone, a cationic opioid agonist, via the pyrilamine transporter, a putative organic cation transporter, using conditionally immortalized rat brain capillary endothelial cells (TR-BBB13). Oxycodone and [3H]pyrilamine were both transported into TR-BBB13 cells in a temperature- and concentration-dependent manner with Km values of 89 and 28 microM, respectively. The initial uptake of oxycodone was significantly enhanced by preloading with pyrilamine and vice versa. Furthermore, mutual uptake inhibition by oxycodone and pyrilamine suggests that a common mechanism is involved in their transport. Transport of both substrates was inhibited by type II cations (quinidine, verapamil, and amantadine), but not by classic organic cation transporter (OCT) substrates and/or inhibitors (tetraethylammonium, 1-methyl-4-phenylpyridinium, and corticosterone), substrates of OCTN1 (ergothioneine) and OCTN2 (L-carnitine), or organic anions. The transport was inhibited by metabolic inhibitors (rotenone and sodium azide) but was insensitive to extracellular sodium and membrane potential for both substrates. Furthermore, the transport of both substrates was increased at alkaline extracellular pH and decreased in the presence of a protonophore (carbonyl cyanide-p-trifluoromethoxyphenylhydrazone). Intracellular acidification induced with ammonium chloride enhanced the uptakes, suggesting that the transport is driven by an oppositely directed proton gradient. The brain uptake of oxycodone measured by in situ rat brain perfusion was increased in alkaline perfusate and was significantly inhibited by pyrilamine. These results suggest that blood-brain barrier transport of oxycodone is at least partly mediated by a common transporter with pyrilamine, and this transporter is an energy-dependent, proton-coupled antiporter.
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  • Resultat 1-4 av 4

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