5,641 research outputs found
Preen Gland-Secreted Alkanols Enhance Male Attractiveness in Parrots
The skin glands are widely used in pheromone production throughout the vertebrate worlds. Growing evidences show that birds also have chemical communication, but the uropygial (also called preen or oil) glands, serving as only specialized skin glands of birds, have no sex pheromones characterized. Here, by combining GC-MS analysis and bioassay, we show with the budgerigar, Melopsittacus undulatus, that birds can used the preen gland-secreted volatiles (a blend of octadecanol, nonadecanol and eicosanol for male budgerigars) spread over body plumage when preening to convey sex information. Here, we first report the avian pheromones derived from the uropyginal gland and suggests that the gland has broader implications than previously known (e.g. plumage waterproofing and reflectance in sexual behaviour of birds
CUR Algorithm for Partially Observed Matrices
CUR matrix decomposition computes the low rank approximation of a given
matrix by using the actual rows and columns of the matrix. It has been a very
useful tool for handling large matrices. One limitation with the existing
algorithms for CUR matrix decomposition is that they need an access to the {\it
full} matrix, a requirement that can be difficult to fulfill in many real world
applications. In this work, we alleviate this limitation by developing a CUR
decomposition algorithm for partially observed matrices. In particular, the
proposed algorithm computes the low rank approximation of the target matrix
based on (i) the randomly sampled rows and columns, and (ii) a subset of
observed entries that are randomly sampled from the matrix. Our analysis shows
the relative error bound, measured by spectral norm, for the proposed algorithm
when the target matrix is of full rank. We also show that only
observed entries are needed by the proposed algorithm to perfectly recover a
rank matrix of size , which improves the sample complexity of
the existing algorithms for matrix completion. Empirical studies on both
synthetic and real-world datasets verify our theoretical claims and demonstrate
the effectiveness of the proposed algorithm
Half Metallic Bilayer Graphene
Charge neutral bilayer graphene has a gapped ground state as transport
experiments demonstrate. One of the plausible such ground states is layered
antiferromagnetic spin density wave (LAF) state, where the spins in top and
bottom layers have same magnitude with opposite directions. We propose that
lightly charged bilayer graphene in an electric field perpendicular to the
graphene plane may be a half metal as a consequence of the inversion and
particle-hole symmetry broken in the LAF state. We show this explicitly by
using a mean field theory on a 2-layer Hubbard model for the bilayer graphene.Comment: 4+ pages, 4 figure
Localized States and Quantum Spin Hall Effect in Si-Doped InAs/GaSb Quantum Wells
We study localized in-gap states and quantum spin Hall effect in Si-doped
InAs/GaSb quantum wells. We propose a model describing donor and/or acceptor
impurities to describe Si dopants. This model shows in-gap bound states and
wide conductance plateau with the quantized value in light dopant
concentration, consistent with recent experiments by Du et al. We predict a
conductance dip structure due to backward scattering in the region where the
localization length is comparable with the sample width but much
smaller than the sample length .Comment: 4+pages main text including 4 figures, supplementary materials with 3
figures are include
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Explore the Spatial Relationship between Airbnb Rental and Crime
Sharing lodging business like Airbnb thrives in recent years, meanwhile crimes and safety issues are along with the development of this burgeoning market. By using geographical weighted regression and mapping techniques revealed significant positive correlations between Airbnb clusters and crime indices. This relationship was not only significant by crime type and listing type, but also varied by spatial distribution. For the relationships altered by crime type, positive correlations were found in property crime, while negative correlations exist in violent crime. Robbery and motor vehicle theft had positive correlations, while negative correlations were recognized in murder/rape. For the crime opportunity varies by room type, shared room shows positive correlations with crimes, particularly in less touristy area, while private room and entire home carry negative correlations. Finally, spatially varying relationships were found across the studied area. The study provides security suggestions for sharing lodging guests/hosts, local government and the overall lodging industry
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