804 research outputs found
Quantum Spin Liquid with Even Ising Gauge Field Structure on Kagome Lattice
Employing large-scale quantum Monte Carlo simulations, we study the extended
model on the kagome lattice. A quantum spin liquid phase
with effective even Ising gauge field structure emerges from the delicate
balance among three symmetry-breaking phases including stripe solid, staggered
solid and ferromagnet. This spin liquid is stabilized by an
extended interaction related to the Rokhsar-Kivelson potential in the quantum
dimer model limit. The phase transitions from the staggered solid to a spin
liquid or ferromagnet are found to be first order and so is the transition
between the stripe solid and ferromagnet. However, the transition between a
spin liquid and ferromagnet is found to be continuous and belongs to the 3D
universality class associated with the condensation of spinons. The
transition between a spin liquid and stripe solid appears to be continuous and
associated with the condensation of visons.Comment: 7 pages, 8 figure
A double neutron star merger origin for the cosmological relativistic fading source PTF11agg?
The Palomar Transient Factory (PTF) team recently reported the discovery of a
rapidly fading optical transient source, PTF11agg. A long-lived scintillating
radio counterpart was identified, but the search for a high energy counterpart
showed negative results. The PTF team speculated that PTF11agg may represent a
new class of relativistic outbursts. Here we suggest that a neutron star
(NS)-NS merger system with a supra-massive magnetar central engine could be a
possible source to power such a transient, if our line of sight is not on the
jet axis direction of the system. These systems are also top candidates for
gravitational wave sources to be detected in the advanced LIGO/Virgo era. We
find that the PTF11agg data could be explained well with such a model,
suggesting that at least some gravitational wave bursts due to NS-NS mergers
may be associated with such a bright electromagnetic counterpart without a
\gamma-ray trigger.Comment: Accepted for publication in ApJ Letter
Heterogeneous Graph Attention Network for Multi-hop Machine Reading Comprehension
Multi-hop machine reading comprehension is a challenging task in natural
language processing, which requires more reasoning ability and explainability.
Spectral models based on graph convolutional networks grant the inferring
abilities and lead to competitive results, however, part of them still face the
challenge of analyzing the reasoning in a human-understandable way. Inspired by
the concept of the Grandmother Cells in cognitive neuroscience, a spatial graph
attention framework named crname, imitating the procedure was proposed. This
model is designed to assemble the semantic features in multi-angle
representations and automatically concentrate or alleviate the information for
reasoning. The name "crname" is a metaphor for the pattern of the model: regard
the subjects of queries as the start points of clues, take the reasoning
entities as bridge points, and consider the latent candidate entities as the
grandmother cells, and the clues end up in candidate entities. The proposed
model allows us to visualize the reasoning graph and analyze the importance of
edges connecting two entities and the selectivity in the mention and candidate
nodes, which can be easier to be comprehended empirically. The official
evaluations in open-domain multi-hop reading dataset WikiHop and Drug-drug
Interactions dataset MedHop prove the validity of our approach and show the
probability of the application of the model in the molecular biology domain
Comparison of three magnetization transfer ratio parameters for assessment of intestinal fibrosis in patients with Crohn’s disease
Dehyrogenation catalysts of higher normal paraffins on a nanocrystalline -Al 2 O 3 support: Different impregnation sequences
In this paper, high surface area nanocrystalline gamma alumina was synthesized by the sol-gel method using cationic surfactant. The Pt-based dehydrogenation catalysts consisting of promoters and support modifiers (Sn, In, Li and Fe) were prepared using the synthesized gamma alumina and employed in the dehydrogenation reaction of n-dodecane. The effects of different successive impregnation methods for Pt, Sn and In elements were investigated in dehydrogenation of normal dodecane. The prepared samples were characterized by X-ray diffraction (XRD), N 2 adsorption (BET), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Temperature programmed reduction (TPR) techniques. The catalytic performances of the prepared samples showed the best catalytic results for the catalyst which was prepared by the co-impregnation of In, Sn and Fe in the first step followed by Pt and Li impregnation in the second and third step, respectively. The synthesized support also performed well as an efficient carrier for the dehydrogenation catalyst of higher normal paraffins
The Origin of the Prompt Emission for Short GRB 170817A: Photosphere Emission or Synchrotron Emission?
The first gravitational-wave event from the merger of a binary neutron star system (GW170817) was detected recently. The associated short gamma-ray burst (GRB 170817A) has a low isotropic luminosity (~1047 erg s−1) and a peak energy E p ~ 145 keV during the initial main emission between −0.3 and 0.4 s. The origin of this short GRB is still under debate, but a plausible interpretation is that it is due to the off-axis emission from a structured jet. We consider two possibilities. First, since the best-fit spectral model for the main pulse of GRB 170817A is a cutoff power law with a hard low-energy photon index (), we consider an off-axis photosphere model. We develop a theory of photosphere emission in a structured jet and find that such a model can reproduce a low-energy photon index that is softer than a blackbody through enhancing high-latitude emission. The model can naturally account for the observed spectrum. The best-fit Lorentz factor along the line of sight is ~20, which demands that there is a significant delay between the merger and jet launching. Alternatively, we consider that the emission is produced via synchrotron radiation in an optically thin region in an expanding jet with decreasing magnetic fields. This model does not require a delay of jet launching but demands a larger bulk Lorentz factor along the line of sight. We perform Markov Chain Monte Carlo fitting to the data within the framework of both models and obtain good fitting results in both cases
2-(2-Methoxyphenyl)butanedinitrile
In the title compound, C11H10N2O, the butanedinitrile unit adopts a synclinal conformation. The crystal packing is stabilized by weak intermolecular C—H⋯N hydrogen bonding
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