2,287 research outputs found
Conditional Image-Text Embedding Networks
This paper presents an approach for grounding phrases in images which jointly
learns multiple text-conditioned embeddings in a single end-to-end model. In
order to differentiate text phrases into semantically distinct subspaces, we
propose a concept weight branch that automatically assigns phrases to
embeddings, whereas prior works predefine such assignments. Our proposed
solution simplifies the representation requirements for individual embeddings
and allows the underrepresented concepts to take advantage of the shared
representations before feeding them into concept-specific layers. Comprehensive
experiments verify the effectiveness of our approach across three phrase
grounding datasets, Flickr30K Entities, ReferIt Game, and Visual Genome, where
we obtain a (resp.) 4%, 3%, and 4% improvement in grounding performance over a
strong region-phrase embedding baseline.Comment: ECCV 2018 accepted pape
TB10: A Comparison of Arch-yarding and Ground-skidding of Pine Sawlogs in the University of Maine Forest
The decision whether to use a trailing-arch or operate by ground-skidding methods may face many sawlog producers. This case study attempted to determine statistically whether there existed significant differences between the two methods of operation by examining the various activities performed by a crawler-type tractor within the arch-yarding and ground-skidding phases of a harvesting system.https://digitalcommons.library.umaine.edu/aes_techbulletin/1192/thumbnail.jp
Magnons in Ferromagnetic Metallic Manganites
Ferromagnetic (FM) manganites, a group of likely half-metallic oxides, are of
special interest not only because they are a testing ground of the classical
doubleexchange interaction mechanism for the colossal magnetoresistance, but
also because they exhibit an extraordinary arena of emergent phenomena. These
emergent phenomena are related to the complexity associated with strong
interplay between charge, spin, orbital, and lattice. In this review, we focus
on the use of inelastic neutron scattering to study the spin dynamics, mainly
the magnon excitations in this class of FM metallic materials. In particular,
we discussed the unusual magnon softening and damping near the Brillouin zone
boundary in relatively narrow band compounds with strong Jahn-Teller lattice
distortion and charge/orbital correlations. The anomalous behaviors of magnons
in these compounds indicate the likelihood of cooperative excitations involving
spin, lattice, as well as orbital degrees of freedom.Comment: published in J. Phys.: Cond. Matt. 20 figure
Long-Term Evolution of Massive Black Hole Binaries. II. Binary Evolution in Low-Density Galaxies
We use direct-summation N-body integrations to follow the evolution of binary
black holes at the centers of galaxy models with large, constant-density cores.
Particle numbers as large as 400K are considered. The results are compared with
the predictions of loss-cone theory, under the assumption that the supply of
stars to the binary is limited by the rate at which they can be scattered into
the binary's influence sphere by gravitational encounters. The agreement
between theory and simulation is quite good; in particular, we are able to
quantitatively explain the observed dependence of binary hardening rate on N.
We do not verify the recent claim of Chatterjee, Hernquist & Loeb (2003) that
the hardening rate of the binary stabilizes when N exceeds a particular value,
or that Brownian wandering of the binary has a significant effect on its
evolution. When scaled to real galaxies, our results suggest that massive black
hole binaries in gas-poor nuclei would be unlikely to reach gravitational-wave
coalescence in a Hubble time.Comment: 13 pages, 8 figure
Fermions and bosons in nonsymmorphic PdSb2 with sixfold degeneracy
PdSb2 is a candidate for hosting 6-fold-degenerate exotic fermions (beyond
Dirac and Weyl fermions).The nontrivial band crossing protected by the
nonsymmorphic symmetry plays a crucial role in physical properties. We have
grown high-quality single crystals of PdSb2 and characterized their physical
properties under several stimuli (temperature, magnetic field, and pressure).
While it is a diamagnetic Fermi-liquid metal under ambient pressure, PdSb2
exhibits a large magnetoresistance with continuous increase up to 14 T, which
follows the Kohler's scaling law at all temperatures. This implies one-band
electrical transport, although multiple bands are predicted by first principles
calculations. By applying magnetic field along the [111] direction, de Haas-van
Alphen oscillations are observed with frequency of 102 T. The effective mass is
nearly zero (0.045m0) with the Berry phase close to {\pi}, confirming that the
band close to the R point has a nontrivial character. Under quasihydrostatic
pressure (p), evidence for superconductivity is observed in the resistivity
below the critical temperature Tc. The dome-shaped Tc versus p is obtained with
maximum Tc~2.9 K. We argue that the formation of Cooper pairs (bosons) is the
consequence of the redistribution of the 6-fold-degenerate fermions under
pressure
Pre-clinical evaluation of antiproteases as potential candidates for HIV-1 pre-exposure prophylaxis
Previous studies on highly HIV-1-exposed, yet persistently seronegative women from the Punwami Sex Worker cohort in Kenya, have shed light on putative protective mechanisms, suggesting that mucosal immunological factors, such as antiproteases, could be mediating resistance to HIV-1 transmission in the female reproductive tract. Nine protease inhibitors were selected for this study: serpin B4, serpin A1, serpin A3, serpin C1, cystatin A, cystatin B, serpin B13, serpin B1 and α-2-macroglobulin-like-protein 1. We assessed in a pilot study, the activity of these antiproteases with cellular assays and an ex vivo HIV-1 challenge model of human ecto-cervical tissue explants. Preliminary findings with both models, cellular and tissue explants, established an order of inhibitory potency for the mucosal proteins as candidates for pre-exposure prophylaxis when mimicking pre-coital use. Combination of all antiproteases considered in this study was more active than any of the individual mucosal proteins. Furthermore, the migration of cells out of ecto-cervical explants was blocked indicating potential prevention of viral dissemination following amplification of the founder population. These findings constitute the base for further development of these mucosal protease inhibitors for prevention strategies
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Quantifying the contributions to stratospheric ozone changes from ozone depleting substances and greenhouse gases
A state-of-the-art chemistry climate model coupled to a three-dimensional ocean model is used to produce three experiments, all seamlessly covering the period 1950–2100, forced by different combinations of long-lived Greenhouse Gases (GHGs) and Ozone Depleting Substances (ODSs). The experiments are designed to quantify the separate effects of GHGs and ODSs on the evolution of ozone, as well as the extent to which these effects are independent of each other, by alternately holding one set of these two forcings constant in combination with a third experiment where both ODSs and GHGs vary. We estimate that up to the year 2000 the net decrease in the column amount of ozone above 20 hPa is approximately 75% of the decrease that can be attributed to ODSs due to the offsetting effects of cooling by increased CO2. Over the 21st century, as ODSs decrease, continued cooling from CO2 is projected to account for more than 50% of the projected increase in ozone above 20 hPa. Changes in ozone below 20 hPa show a redistribution of ozone from tropical to extra-tropical latitudes with an increase in the Brewer-Dobson circulation. In addition to a latitudinal redistribution of ozone, we find that the globally averaged column amount of ozone below 20 hPa decreases over the 21st century, which significantly mitigates the effect of upper stratospheric cooling on total column ozone. Analysis by linear regression shows that the recovery of ozone from the effects of ODSs generally follows the decline in reactive chlorine and bromine levels, with the exception of the lower polar stratosphere where recovery of ozone in the second half of the 21st century is slower than would be indicated by the decline in reactive chlorine and bromine concentrations. These results also reveal the degree to which GHGrelated effects mute the chemical effects of N2O on ozone in the standard future scenario used for the WMO Ozone Assessment. Increases in the residual circulation of the atmosphere and chemical effects from CO2 cooling more than halve the increase in reactive nitrogen in the mid to upper stratosphere that results from the specified increase in N2O between 1950 and 2100
Stable manifolds and homoclinic points near resonances in the restricted three-body problem
The restricted three-body problem describes the motion of a massless particle
under the influence of two primaries of masses and that circle
each other with period equal to . For small , a resonant periodic
motion of the massless particle in the rotating frame can be described by
relatively prime integers and , if its period around the heavier primary
is approximately , and by its approximate eccentricity . We give a
method for the formal development of the stable and unstable manifolds
associated with these resonant motions. We prove the validity of this formal
development and the existence of homoclinic points in the resonant region.
In the study of the Kirkwood gaps in the asteroid belt, the separatrices of
the averaged equations of the restricted three-body problem are commonly used
to derive analytical approximations to the boundaries of the resonances. We use
the unaveraged equations to find values of asteroid eccentricity below which
these approximations will not hold for the Kirkwood gaps with equal to
2/1, 7/3, 5/2, 3/1, and 4/1.
Another application is to the existence of asymmetric librations in the
exterior resonances. We give values of asteroid eccentricity below which
asymmetric librations will not exist for the 1/7, 1/6, 1/5, 1/4, 1/3, and 1/2
resonances for any however small. But if the eccentricity exceeds these
thresholds, asymmetric librations will exist for small enough in the
unaveraged restricted three-body problem
Improved photometry of SDSS crowded field images: Structure and dark matter content in the dwarf spheroidal galaxy Leo I
We explore how well crowded field point-source photometry can be accomplished
with SDSS data: We present a photometric pipeline based on DoPhot, and tuned
for analyzing crowded-field images from the SDSS. Using Monte Carlo simulations
we show that the completeness of source extraction is above 80% to i < 21 (AB)
and a stellar surface density of about 200 sq.amin. Hence, a specialized data
pipeline can efficiently be used for e.g. nearby resolved galaxies in SDSS
images, where the standard SDSS photometric package Photo, when applied in
normal survey mode, gives poor results. We apply our pipeline to an area of
about 3.55sq.deg. around the dwarf spheroidal galaxy (dSph) Leo I, and
construct a high S/N star-count map of Leo I via an optimized filter in
color-magnitude space (g,r,i). Although the radial surface-density profile of
the dwarf deviates from the best fit empirical King model towards outer radii,
we find no evidence for tidal debris out to a stellar surface-density of
4*10^(-3) of the central value. We determine the total luminosity of Leo I, and
model its mass using the spherical and isotropic Jeans equation. Assuming that
'mass follows light' we constrain a lower limit of the total mass of the dSph
to be (1.7+/-0.2)*10^7 Msol. Contrary, if the mass in Leo I is dominated by a
constant density dark-matter (DM) halo, then the mass within the central 12' is
(2+/-0.6)*10^8 Msol. This leads to a mass-to-light ratio of >>6 (Ic_sol), and
possibly >75 if the DM halo dominates the mass and extends further out than
12'. In summary, our results show that Leo I is a symmetric, relaxed and bound
system; this supports the idea that Leo I is a dark-matter dominated system.Comment: 13 pages, 11 figures; accepted for publication in A
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