27,998 research outputs found
Identifying Anticyclonic Vortex Features Produced by the Rossby Wave Instability in Protoplanetary Disks
Several nearby protoplanetary disks have been observed to display large scale
crescents in the (sub)millimeter dust continuum emission. One interpretation is
that these structures correspond to anticyclonic vortices generated by the
Rossby wave instability within the gaseous disk. Such vortices have local gas
over-densities and are expected to concentrate dust particles with Stokes
number around unity. This process might catalyze the formation of
planetesimals. Whereas recent observations showed that dust crescent are indeed
regions where millimeter-size particles have abnormally high concentration
relative to the gas and smaller grains, no observations have yet shown that the
gas within the crescent region counter-rotates with respect to the
protoplanetary disk. Here we investigate the detectability of anticyclonic
features through measurement of the line-of-sight component of the gas velocity
obtained with ALMA. We carry out 2D hydrodynamic simulations and 3D radiative
transfer calculation of a protoplanetary disk characterized by a vortex created
by the tidal interaction with a massive planet. As a case study, the disk
parameters are chosen to mimic the IRS 48 system, which has the most prominent
crescent observed to date. We generate synthetic ALMA observations of both the
dust continuum and 12CO emission around the frequency of 345 GHz. We find that
the anticyclonic features of vortex are weak but can be detected if both the
source and the observational setup are properly chosen. We provide a recipe for
maximizing the probability to detect such vortex features and present an
analysis procedure to infer their kinematic properties.Comment: 14 pages, 8 figures, Accepted for publication in Astrophysical
Journa
Neural Collaborative Subspace Clustering
We introduce the Neural Collaborative Subspace Clustering, a neural model
that discovers clusters of data points drawn from a union of low-dimensional
subspaces. In contrast to previous attempts, our model runs without the aid of
spectral clustering. This makes our algorithm one of the kinds that can
gracefully scale to large datasets. At its heart, our neural model benefits
from a classifier which determines whether a pair of points lies on the same
subspace or not. Essential to our model is the construction of two affinity
matrices, one from the classifier and the other from a notion of subspace
self-expressiveness, to supervise training in a collaborative scheme. We
thoroughly assess and contrast the performance of our model against various
state-of-the-art clustering algorithms including deep subspace-based ones.Comment: Accepted to ICML 201
Biochar-amended potting medium reduces the susceptibility of rice to root-knot nematode infections
Background: Biochar is a solid coproduct of biomass pyrolysis, and soil amended with biochar has been shown to enhance the productivity of various crops and induce systemic plant resistance to fungal pathogens. The aim of this study was to explore the ability of wood biochar to induce resistance to the root-knot nematode (RKN) Meloidogyne graminicola in rice (Oryza sativa cv. Nipponbare) and examine its histochemical and molecular impact on plant defense mechanisms.
Results: A 1.2 % concentration of biochar added to the potting medium of rice was found to be the most effective at reducing nematode development in rice roots, whereas direct toxic effects of biochar exudates on nematode viability, infectivity or development were not observed. The increased plant resistance was associated with biochar-primed H2O2 accumulation as well as with the transcriptional enhancement of genes involved in the ethylene (ET) signaling pathway. The increased susceptibility of the Ein2b-RNAi line, which is deficient in ET signaling, further confirmed that biochar-induced priming acts at least partly through ET signaling.
Conclusion: These results suggest that biochar amendments protect rice plants challenged by nematodes. This priming effect partially depends on the ET signaling pathway and enhanced H2O2 accumulation
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