7,626 research outputs found
A sub-kpc-scale binary AGN with double narrow-line regions
We present the kinematic properties of a type-2 QSO, SDSS J132323.33-015941.9
at z~0.35, based on the analysis of Very Large Telescope integral field
spectroscopy and Hubble Space Telescope (HST) imaging, which suggest that the
target is a binary active galactic nucleus (AGN) with double narrow-line
regions. The QSO features double-peaked emission lines ([OIII] and Hb) which
can be decomposed into two kinematic components. The flux-weighted centroids of
the blue and red components are separated by ~0.2" (0.8 kpc in projection) and
coincide with the location of the two stellar cores detected in the HST
broad-band images, implying that both stellar cores host an active black hole.
The line-of-sight velocity of the blue component is comparable to the
luminosity-weighted velocity of stars in the host galaxy while the red
component is redshifted by ~240 km/s, consistent with typical velocity offsets
of two cores in a late stage of a galaxy merger. If confirmed, the target is
one of the rare cases of sub-kpc scale binary AGNs, providing a test-bed for
understanding the binary AGN population.Comment: 5 pages, 3 figure
Assisted freeze-out
We explore a class of dark matter models with two dark matter candidates,
only one interacts with the standard model sector. One of the dark matter is
thermalized with the assistance of the other stable particle. While both stable
particles contribute to the total relic density only one can elastically
scatter with nuclei, thus effectively reducing the direct detection rate.Comment: 16 pages, 13 figures, minor corrections, the final version published
in JCA
Consistent Earnings Growth and the Credibility of Management Forecasts
This paper examines the relation between a series of past earnings increases and the credibility of voluntary management earnings forecasts. We demonstrate that both analyst forecast revisions and stock price reactions around management earnings forecasts that contain good news are more pronounced when the firm has posted a string of recent earnings increases. These results are consistent with our primary hypothesis that voluntary management earnings forecasts are more believable when they are made by firms with a history of consistent growth in earnings. This effect is more pronounced when firms are not widely followed by analysts. Additional analysis suggests that management forecasts are more accurate relative to ex post realized earnings when made by a firm with consistent growth in prior earnings. The effect of prior earnings growth on the credibility of management earnings forecasts is reduced when the level of net assets suggests a history of prior earnings management
Jamming transition in a highly dense granular system under vertical vibration
The dynamics of the jamming transition in a three-dimensional granular system
under vertical vibration is studied using diffusing-wave spectroscopy. When the
maximum acceleration of the external vibration is large, the granular system
behaves like a fluid, with the dynamic correlation function G(t) relaxing
rapidly. As the acceleration of vibration approaches the gravitational
acceleration g, the relaxation of G(t) slows down dramatically, and eventually
stops. Thus the system undergoes a phase transition and behaves like a solid.
Near the transition point, we find that the structural relaxation shows a
stretched exponential behavior. This behavior is analogous to the behavior of
supercooled liquids close to the glass transition.Comment: 5 pages, 5 figures, accepted by Phys. Rev.
Mesoporous TiO\u3csub\u3e2\u3c/sub\u3e Bragg Stack Templated by Graft Copolymer for Dye-Sensitized Solar Cells
Organized mesoporous TiO2 Bragg stacks (om-TiO2 BS) consisting of alternating high and low refractive index organized mesoporous TiO2(om-TiO2) films were prepared to enhance dye loading, light harvesting, electron transport, and electrolyte pore-infiltration in dye-sensitized solar cells (DSSCs). The om-TiO2 films were synthesized via a sol-gel reaction using amphiphilic graft copolymers consisting of poly(vinyl chloride) backbones and poly(oxyethylene methacrylate) side chains, i.e., PVC-g-POEM as templates. To generate high and low index films, the refractive index of om-TiO2 film was tuned by controlling the grafting ratio of PVC-g-POEM via atomic transfer radical polymerization (ATRP). A polymerized ionic liquid (PIL)-based DSSC fabricated with a 1.2-μm-thick om-TiO2 BS-based photoanode exhibited an efficiency of 4.3%, which is much higher than that of conventional DSSCs with a nanocrystalline TiO2 layer (nc-TiO2 layer) (1.7%). A PIL-based DSSC with a heterostructured photoanode consisting of 400-nm-thick organized mesoporous TiO2 interfacial (om-TiO2 IF) layer, 7-μm-thick nc-TiO2, and 1.2-μm-thick om-TiO2 BS as the bottom, middle and top layers, respectively, exhibited an excellent efficiency of 7.5%, which is much higher than that of nanocrystaline TiO2 photoanode (3.5%
Coulomb oscillations based on band-to-band tunneling in a degenerately doped silicon metal-oxide-semiconductor field-effect transistor
The Coulomb oscillations based on band-to-band tunneling through a valence band in silicon metal-oxide-semiconductor field-effect-transistors were discussed. It was found that the formation of tunnel barries and a quantum dot in a single-electron transistor structure originated from two p+ - p+ tunnel junctions and a p+ -doped channel with mesoscopic dimension, respectively. At liquid nitrogen temperature, the Coulomb-blockade oscillations with multiple peaks were also observed. Analysis shows that the single-electron charging effect based on band-to-band tunneling was confirmed using the electrical and thermal characterization of the quantum dots.open2
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