590 research outputs found
AKARI IRC 2.5-5 um Spectroscopy of Infrared Galaxies over a Wide Luminosity Range
We present the result of a systematic infrared 2.5-5 um spectroscopic study
of 22 nearby infrared galaxies over a wide infrared luminosity range (10 <
log(L_IR / Lsun) < 13) obtained from AKARI Infrared Camera (IRC). The unique
band of the AKARI IRC spectroscopy enables us to access both the 3.3 um
polycyclic aromatic hydrocarbon (PAH) emission feature from star forming
activity and the continuum of torus-dust emission heated by an active galactic
nucleus (AGN). Applying our AGN diagnostics to the AKARI spectra, we discover
14 buried AGNs. The large fraction of buried AGNs suggests that AGN activity
behind the dust is almost ubiquitous in ultra-/luminous infrared galaxies
(U/LIRGs). We also find that both the fraction and energy contribution of
buried AGNs increase with infrared luminosity from 10 < log(L_IR / Lsun) < 13,
including normal infrared galaxies with log (L_IR / Lsun) < 11. The energy
contribution from AGNs in the total infrared luminosity is only ~7% in LIRGs
and ~20% in ULIRGs, suggesting that the majority of the infrared luminosity
originates from starburst activity. Using the PAH emission, we investigate the
luminosity relation between star formation and AGN. We find that these infrared
galaxies exhibit higher star formation rates than optically selected Seyfert
galaxies with the same AGN luminosities, implying that infrared galaxies could
be an early evolutionary phase of AGN.Comment: 13 pages, 8 figures, accepted for publication in Ap
Turbulent Structures in Unsteady Open-Channel Flows
Turbulence measurements over a smooth wall in unsteady open-channel flows were conducted accurately by the simultaneous use of a two-component LDA system and water-wave gauges. The “ general ” log-law distributions, in which the von Karman constant is a universal one of χ=0.41 but the integration constant A is a function of main-flow conditions, were obeyed well in the wall region for both the rising and falling stages of flood. On the other hand, the log-wake law was reasonably applied to the outer region including the depth-varying zone. The Coles' wake parameter Π increased for the rising stage, whereas it decreased for the falling stage. The turbulence is stronger for the rising stage than for the falling stage, except for very near the free surface. These unsteady characteristics in open-channel flows with variation of the water surface are quite different from those in closed duct flows. Of particular significance is the findings counterclockwise loops of velocity and turbulence against the varying depth in unsteady open-channel flows
Loss of AtPDR8, a Plasma Membrane ABC Transporter of Arabidopsis thaliana, Causes Hypersensitive Cell Death Upon Pathogen Infection
Plants contain a large number of ATP-binding cassette (ABC) transporters belonging to different subclasses. AtPDR8 is the only member of the pleiotropic drug resistance (PDR) ABC transporter subclass in Arabidopsis that is constitutively highly expressed. In transgenic Arabidopsis plants harboring the AtPDR8 promoter fused to β-glucuronidase (GUS), reporter expression was shown to be strong in the stomata and hydathode. In the stomata, transcripts of AtPDR8 were particularly frequent in the cells surrounding air spaces. Subcellular fractionation and immunochemical analysis showed that AtPDR8 was localized in the plasma membrane. When a knockout mutant of AtPDR8 (atpdr8) was infected with bacterial and oomycete pathogens, the plants exhibited chlorotic lesions and a hypersensitive response (HR)-like cell death. Cell death was detected in the atpdr8 mutants within 10h of infection with the virulent bacterial pathogen, Pseudomonas syringae. As a result, the growth of P. syringae in the leaves of the atpdr8 mutant was reduced to 1% of that in the wild type. The defense response genes, PR-1, PR-2, PR-5, VPEγ, AtrbohD and AtrbohF were highly expressed when the mutant plants were grown under non-sterile conditions. The expression of the AtPDR8 gene was enhanced by infection of virulent and avirulent bacterial pathogens. Our results indicate that AtPDR8 is a key factor controlling the extent of cell death in the defense response and suggest that AtPDR8 transports some substance(s) which is closely related to the response of plants to pathogen
Infrared and hard X-ray diagnostics of AGN identification from the Swift/BAT and AKARI all-sky surveys
We combine data from two all-sky surveys in order to study the connection
between the infrared and hard X-ray (>10keV) properties for local active
galactic nuclei (AGN). The Swift/Burst Alert Telescope all-sky survey provides
an unbiased, flux-limited selection of hard X-ray detected AGN.
Cross-correlating the 22-month hard X-ray survey with the AKARI all-sky survey,
we studied 158 AGN detected by the AKARI instruments. We find a strong
correlation for most AGN between the infrared (9, 18, and 90 micron) and hard
X-ray (14-195 keV) luminosities, and quantify the correlation for various
subsamples of AGN. Partial correlation analysis confirms the intrinsic
correlation after removing the redshift contribution. The correlation for radio
galaxies has a slope and normalization identical to that for Seyfert 1s,
implying similar hard X-ray/infrared emission processes in both. In contrast,
Compton-thick sources show a large deficit in the hard X-ray band, because high
gas column densities diminish even their hard X-ray luminosities. We propose
two photometric diagnostics for source classification: one is an X-ray
luminosity vs. infrared color diagram, in which type 1 radio-loud AGN are well
isolated from the others in the sample. The other uses the X-ray vs. infrared
color as a useful redshift-independent indicator for identifying Compton-thick
AGN. Importantly, Compton-thick AGN and starburst galaxies in composite systems
can also be differentiated in this plane based upon their hard X-ray fluxes and
dust temperatures. This diagram may be useful as a new indicator to classify
objects in new and upcoming surveys such as WISE and NuSTAR.Comment: 17 pages, 5 figures, 5 tables. Accepted for publication in the
Astrophysical Journa
Superconductivity protected by spin-valley locking in ion-gated MoS2
Symmetry-breaking has been known to play a key role in noncentrosymmetric
superconductors with strong spin-orbit-interaction (SOI). The studies, however,
have been so far mainly focused on a particular type of SOI, known as Rashba
SOI, whereby the electron spin is locked to its momentum at a right-angle,
thereby leading to an in-planar helical spin texture. Here we discuss
electric-field-induced superconductivity in molybdenum disulphide (MoS2), which
exhibits a fundamentally different type of intrinsic SOI manifested by an
out-of-plane Zeeman-type spin polarization of energy valleys. We find an upper
critical field of approximately 52 T at 1.5 K, which indicates an enhancement
of the Pauli limit by a factor of four as compared to that in centrosymmetric
conventional superconductors. Using realistic tight-binding calculations, we
reveal that this unusual behaviour is due to an inter-valley pairing that is
symmetrically protected by Zeeman-type spin-valley locking against external
magnetic fields. Our study sheds a new light on the interplay of inversion
asymmetry with SOI in confined geometries, and its unprecedented role in
superconductivity.Comment: 37 pages, 11 figures,
http://meetings.aps.org/Meeting/MAR15/Session/G11.1
Association Between SLFN11 and Antitumor Activity of Trabectedin
Background/Aim: Trabectedin is a DNA-damaging agent and has been approved for the treatment of patients with advanced soft tissue sarcoma. Schlafen 11 (SLFN11) was identified as a dominant determinant of the response to DNA-damaging agents. The aim of the study was to clarify the association between SLFN11 expression and the antitumor activity of trabectedin. Materials and Methods: The antitumor activity of trabectedin was evaluated under different expression levels of SLFN11 regulated by RNA interference and CRISPR-Cas9 systems, and the combined antitumor activity of ataxia telangiectasia and Rad3-related protein kinase (ATR) inhibitor and trabectedin in sarcoma cell lines using in vitro a cell viability assay and in vivo xenograft models. Results: SLFN11-knockdown cell lines had a lower sensitivity to trabectedin, compared to parental cells. ATR inhibitor enhanced the antitumor activity of trabectedin in SLFN11-knockdown cells and in a SLFN11-knockout xenograft model. Conclusion: SLFN11 expression might be a key factor in the antitumor activity of trabectedin
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