19,537 research outputs found
Multiple Disk Gaps and Rings Generated by a Single Super-Earth: II. Spacings, Depths, and Number of Gaps, with Application to Real Systems
ALMA has found multiple dust gaps and rings in a number of protoplanetary
disks in continuum emission at millimeter wavelengths. The origin of such
structures is in debate. Recently, we documented how one super-Earth planet can
open multiple (up to five) dust gaps in a disk with low viscosity
(). In this paper, we examine how the positions, depths,
and total number of gaps opened by one planet depend on input parameters, and
apply our results to real systems. Gap locations (equivalently, spacings) are
the easiest metric to use when making comparisons between theory and
observations, as positions can be robustly measured. We fit the locations of
gaps empirically as functions of planet mass and disk aspect ratio. We find
that the locations of the double gaps in HL Tau and TW Hya, and of all three
gaps in HD 163296, are consistent with being opened by a sub-Saturn mass
planet. This scenario predicts the locations of other gaps in HL Tau and TW
Hya, some of which appear consistent with current observations. We also show
how the Rossby wave instability may develop at the edges of several gaps and
result in multiple dusty vortices, all caused by one planet. A planet as low in
mass as Mars may produce multiple dust gaps in the terrestrial planet forming
region.Comment: 16 pages; ApJ accepte
Distinct roles of NMB and GRP in itch transmission
A key question in our understanding of itch coding mechanisms is whether itch is relayed by dedicated molecular and neuronal pathways. Previous studies suggested that gastrin-releasing peptide (GRP) is an itch-specific neurotransmitter. Neuromedin B (NMB) is a mammalian member of the bombesin family of peptides closely related to GRP, but its role in itch is unclear. Here, we show that itch deficits in mice lacking NMB or GRP are non-redundant and Nmb/Grp double KO (DKO) mice displayed additive deficits. Furthermore, both Nmb/Grp and Nmbr/Grpr DKO mice responded normally to a wide array of noxious stimuli. Ablation of NMBR neurons partially attenuated peripherally induced itch without compromising nociceptive processing. Importantly, electrophysiological studies suggested that GRPR neurons receive glutamatergic input from NMBR neurons. Thus, we propose that NMB and GRP may transmit discrete itch information and NMBR neurons are an integral part of neural circuits for itch in the spinal cord
Shadows and photon spheres with spherical accretions in the four-dimensional Gauss-Bonnet black hole
We investigate the shadows and photon spheres of the four-dimensional
Gauss-Bonnet black hole with the static and infalling spherical accretions. We
show that for both cases, the shadow and photon sphere are always present. The
radii of the shadow and photon sphere are independent of the profiles of
accretion for a fixed Gauss-Bonnet constant, implying that the shadow is a
signature of the spacetime geometry and it is hardly influenced by accretion in
this case. Because of the Doppler effect, the shadow of the infalling accretion
is found to be darker than that of the static one. We also investigate the
effect of the Gauss-Bonnet constant on the shadow and photon sphere, and find
that the larger the Gauss-Bonnet constant is, the smaller the radii of the
shadow and photon sphere will be. In particular, the observed specific
intensity increases with the increasing of the Gauss-Bonnet constant.Comment: published versio
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