621 research outputs found
Detecting Heart Disease from Multi-View Ultrasound Images via Supervised Attention Multiple Instance Learning
Aortic stenosis (AS) is a degenerative valve condition that causes
substantial morbidity and mortality. This condition is under-diagnosed and
under-treated. In clinical practice, AS is diagnosed with expert review of
transthoracic echocardiography, which produces dozens of ultrasound images of
the heart. Only some of these views show the aortic valve. To automate
screening for AS, deep networks must learn to mimic a human expert's ability to
identify views of the aortic valve then aggregate across these relevant images
to produce a study-level diagnosis. We find previous approaches to AS detection
yield insufficient accuracy due to relying on inflexible averages across
images. We further find that off-the-shelf attention-based multiple instance
learning (MIL) performs poorly. We contribute a new end-to-end MIL approach
with two key methodological innovations. First, a supervised attention
technique guides the learned attention mechanism to favor relevant views.
Second, a novel self-supervised pretraining strategy applies contrastive
learning on the representation of the whole study instead of individual images
as commonly done in prior literature. Experiments on an open-access dataset and
an external validation set show that our approach yields higher accuracy while
reducing model size.Comment: multiple-instance learning; self-supervised learning; semi-supervised
learning; medical imagin
Observation of plaquette fluctuations in the spin-1/2 honeycomb lattice
Quantum spin liquids are materials that feature quantum entangled spin
correlations and avoid magnetic long-range order at T = 0 K. Particularly
interesting are two-dimensional honeycomb spin lattices where a plethora of
exotic quantum spin liquids have been predicted. Here, we experimentally study
an effective S=1/2 Heisenberg honeycomb lattice with competing nearest and
next-nearest neighbor interactions. We demonstrate that YbBr avoids order
down to at least T=100 mK and features a dynamic spin-spin correlation function
with broad continuum scattering typical of quantum spin liquids near a quantum
critical point. The continuum in the spin spectrum is consistent with plaquette
type fluctuations predicted by theory. Our study is the experimental
demonstration that strong quantum fluctuations can exist on the honeycomb
lattice even in the absence of Kitaev-type interactions, and opens a new
perspective on quantum spin liquids.Comment: 32 pages, 7 Figure
Observation of Wannier-Stark localization at the surface of BaTiO films by photoemission
Observation of Bloch oscillations and Wannier-Stark localization of charge
carriers is typically impossible in single-crystals, because an electric field
higher than the breakdown voltage is required. In BaTiO however, high
intrinsic electric fields are present due to its ferroelectric properties. With
angle-resolved photoemission we directly probe the Wannier-Stark localized
surface states of the BaTiO film-vacuum interface and show that this effect
extends to thin SrTiO overlayers. The electrons are found to be localized
along the in-plane polarization direction of the BaTiO film
How Combining Terrorism, Muslim, and Refugee Topics Drives Emotional Tone in Online News: A Six-Country Cross-Cultural Sentiment Analysis
This study looks into how the combination of Islam, refugees, and terrorism topics leads to text-internal changes in the emotional tone of news articles and how these vary across countries and media outlets. Using a multilingual human-validated sentiment analysis, we compare fear and pity in more than 560,000 articles from the most important online news sources in six countries (U.S., Australia, Germany, Switzerland, Turkey, and Lebanon). We observe that fear and pity work antagonistically—that is, the more articles in a particular topical category contain fear, the less pity they will feature. The coverage of refugees without mentioning terrorists and Muslims/Islam featured the lowest fear and highest pity levels of all topical categories studied here. However, when refugees were covered in combination with terrorism and/or Islam, fear increased and pity decreased in Christian-majority countries, whereas no such pattern appeared in Muslim-majority countries (Lebanon, Turkey). Variations in emotions are generally driven more by country-level differences than by the political alignment of individual outlets
Dipolar spin-waves and tunable band gap at the Dirac points in the 2D magnet ErBr3
Topological magnon insulators constitute a growing field of research for
their potential use as information carriers without heat dissipation. We report
an experimental and theoretical study of the magnetic ground-state and
excitations in the van der Waals two-dimensional honeycomb magnet ErBr3. We
show that the magnetic properties of this compound are entirely governed by the
dipolar interactions which generate a continuously degenerate non-collinear
ground-state on the honeycomb lattice with spins confined in the plane. We find
that the magnon dispersion exhibits Dirac-like cones when the magnetic moments
in the ground-state are related by time-reversal and inversion symmetries
associated with a Berry phase \pi as in single-layer graphene. A magnon band
gap opens when the dipoles are rotated away from this state, entailing a finite
Berry curvature in the vicinity of the K and K' Dirac points. Our results
illustrate that the spin-wave dispersion of dipoles on the honeycomb lattice
can be reversibly controlled from a magnetic phase with Dirac cones to a
topological antiferromagnetic insulator with non-trivial valley Chern number
The Rice Miniature Inverted Repeat Transposable Element mPing Is an Effective Insertional Mutagen in Soybean
Insertional mutagenesis of legume genomes such as soybean (Glycine max) should aid in identifying genes responsible for key traits such as nitrogen fixation and seed quality. The relatively low throughput of soybean transformation necessitates the use of a transposon-tagging strategy where a single transformation event will produce many mutations over a number of generations. However, existing transposon-tagging tools being used in legumes are of limited utility because of restricted transposition (Ac/Ds: soybean) or the requirement for tissue culture activation (Tnt1: Medicago truncatula). A recently discovered transposable element from rice (Oryza sativa), mPing, and the genes required for its mobilization, were transferred to soybean to determine if it will be an improvement over the other available transposon-tagging tools. Stable transformation events in soybean were tested for mPing transposition. Analysis of mPing excision at early and late embryo developmental stages revealed increased excision during late development in most transgenic lines, suggesting that transposition is developmentally regulated. Transgenic lines that produced heritable mPing insertions were identified, with the plants from the highest activity line producing at least one new insertion per generation. Analysis of the mPing insertion sites in the soybean genome revealed that features displayed in rice were retained including transposition to unlinked sites and a preference for insertion within 2.5 kb of a gene. Taken together these findings indicate that mPing has the characteristics necessary for an effective transposon-tagging resource
Molecular Basis of the Waxy Endosperm Starch Phenotype in Broomcorn Millet (Panicum miliaceum L.)
Waxy varieties of the tetraploid cereal broomcorn millet (Panicum miliaceum L.) have endosperm starch granules lacking detectable amylose. This study investigated the basis of this phenotype using molecular and biochemical methods. Iodine staining of starch granules in 72 plants from 38 landrace accessions found 58 nonwaxy and 14 waxy phenotype plants. All waxy types were in plants from Chinese and Korean accessions, a distribution similar to that of the waxy phenotype in other cereals. Granule-bound starch synthase I (GBSSI) protein was present in the endosperm of both nonwaxy and waxy individuals, but waxy types had little or no granule-bound starch synthase activity compared with the wild types. Sequencing of the GBSSI (Waxy) gene showed that this gene is present in two different forms (L and S) in P. miliaceum, which probably represent homeologues derived from two distinct diploid ancestors. Protein products of both these forms are present in starch granules. We identified three polymorphisms in the exon sequence coding for mature GBSSI peptides. A 15-bp deletion has occurred in the S type GBSSI, resulting in the loss of five amino acids from glucosyl transferase domain 1 (GTD1). The second GBSSI type (L) shows two sequence polymorphisms. One is the insertion of an adenine residue that causes a reading frameshift, and the second causes a cysteine–tyrosine amino acid polymorphism. These mutations appear to have occurred in parallel from the ancestral allele, resulting in three GBSSI-L alleles in total. Five of the six possible genotype combinations of the S and L alleles were observed. The deletion in the GBSSI-S gene causes loss of protein activity, and there was 100% correspondence between this deletion and the waxy phenotype. The frameshift mutation in the L gene results in the loss of L-type protein from starch granules. The L isoform with the tyrosine residue is present in starch granules but is nonfunctional. This loss of function may result from the substitution of tyrosine for cysteine, although it could not be determined whether the cysteine isoform of L represents the functional type. This is the first characterization of mutations that occur in combination in a functionally polyploid species to give a fully waxy phenotype
Elastic Pion Scattering on the Deuteron in a Multiple Scattering Model
Pion elastic scattering on deuterium is studied in the KMT multiple
scattering approach developed in momentum space. Using a Paris wave function
and the same methods and approximations as commonly used in pion scattering on
heavier nuclei excellent agreement with differential cross section data is
obtained for a wide range of pion energies. Only for MeV and very
backward angles, discrepancies appear that are reminiscent of disagreements in
pion scattering on He, H, and He. At low energies the second order
corrections have been included. Polarization observables are studied in detail.
While tensor analyzing powers are well reproduced, vector analyzing powers
exhibit dramatic discrepancies.Comment: 25 pages LATEX and 9 postscript figures in a self-extracting uufile
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