114 research outputs found
MOSS: End-to-End Dialog System Framework with Modular Supervision
A major bottleneck in training end-to-end task-oriented dialog system is the
lack of data. To utilize limited training data more efficiently, we propose
Modular Supervision Network (MOSS), an encoder-decoder training framework that
could incorporate supervision from various intermediate dialog system modules
including natural language understanding, dialog state tracking, dialog policy
learning, and natural language generation. With only 60% of the training data,
MOSS-all (i.e., MOSS with supervision from all four dialog modules) outperforms
state-of-the-art models on CamRest676. Moreover, introducing modular
supervision has even bigger benefits when the dialog task has a more complex
dialog state and action space. With only 40% of the training data, MOSS-all
outperforms the state-of-the-art model on a complex laptop network
troubleshooting dataset, LaptopNetwork, that we introduced. LaptopNetwork
consists of conversations between real customers and customer service agents in
Chinese. Moreover, MOSS framework can accommodate dialogs that have supervision
from different dialog modules at both the framework level and model level.
Therefore, MOSS is extremely flexible to update in a real-world deployment
Dynamical modulation of solar flare electron acceleration due to plasmoid-shock interactions in the looptop region
A fast-mode shock can form in the front of reconnection outflows and has been
suggested as a promising site for particle acceleration in solar flares. Recent
development of magnetic reconnection has shown that numerous plasmoids can be
produced in a large-scale current layer. Here we investigate the dynamical
modulation of electron acceleration in the looptop region when plasmoids
intermittently arrive at the shock by combining magnetohydrodynamics
simulations with a particle kinetic model. As plasmoids interact with the
shock, the looptop region exhibits various compressible structures that
modulate the production of energetic electrons. The energetic electron
population varies rapidly in both time and space. The number of 510 keV
electrons correlates well with the area with compression, while that of 50
keV electrons shows good correlation with strong compression area but only
moderate correlation with shock parameters. We further examine the impacts of
the first plasmoid, which marks the transition from a quasi-steady shock front
to a distorted and dynamical shock. The number of energetic electrons is
reduced by at 1525 keV and nearly 40\% for 2550 keV, while
the number of 510 keV electrons increases. In addition, the electron energy
spectrum above 10 keV evolves softer with time. We also find double or even
multiple distinct sources can develop in the looptop region when the plasmoids
move across the shock. Our simulations have strong implications to the
interpretation of nonthermal looptop sources, as well as the commonly observed
fast temporal variations in flare emissions, including the quasi-periodic
pulsations.Comment: accepted for publication in ApJ
SiteFinding-PCR: a simple and efficient PCR method for chromosome walking
In this paper, we present a novel PCR method, termed SiteFinding-PCR, for gene or chromosome walking. The PCR was primed by a SiteFinder at a low temperature, and then the target molecules were amplified exponentially with gene-specific and SiteFinder primers, and screened out by another gene-specific primer and a vector primer. However, non-target molecules could not be amplified exponentially owing to the suppression effect of stem–loop structure and could not be screened out. This simple method proved to be efficient, reliable, inexpensive and time-saving, and may be suitable for the molecules for which gene-specific primers are available. More importantly, large DNA fragments can be obtained easily using this method. To demonstrate the feasibility and efficiency of SiteFinding-PCR, we employed this method to do chromosome walking and obtained 16 positive results from 17 samples
The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap: An Explanation for Nonthermal Loop-top Sources during Solar Flares
Nonthermal loop-top sources in solar flares are the most prominent
observational signature that suggests energy release and particle acceleration
in the solar corona. Although several scenarios for particle acceleration have
been proposed, the origin of the loop-top sources remains unclear. Here we
present a model that combines a large-scale magnetohydrodynamic simulation of a
two-ribbon flare with a particle acceleration and transport model for
investigating electron acceleration by a fast-mode termination shock at the
looptop. Our model provides spatially resolved electron distribution that
evolves in response to the dynamic flare geometry. We find a concave-downward
magnetic structure located below the flare termination shock, induced by the
fast reconnection downflows. It acts as a magnetic trap to confine the
electrons at the looptop for an extended period of time. The electrons are
energized significantly as they cross the shock front, and eventually build up
a power-law energy spectrum extending to hundreds of keV. We suggest that this
particle acceleration and transport scenario driven by a flare termination
shock is a viable interpretation for the observed nonthermal loop-top sources.Comment: submitted to ApJ
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Numerical Investigations of Catastrophe in Coronal Magnetic Configuration Triggered by Newly Emerging Flux
We performed 2D magnetohydrodynamical numerical experiments to study the response of the coronal magnetic configuration to the newly emerging magnetic flux. The configuration includes an electric-current-carrying flux rope modeling the prominence floating in the corona and the background magnetic field produced by two separated magnetic dipoles embedded in the photosphere. Parameters for one dipole are fixed in space and time to model the quiet background, and those for another one are time dependent to model the new flux. These numerical experiments duplicate important results of the analytic solution but also reveal new results. Unlike previous works, the configuration here possesses no symmetry, and the flux rope could move in any direction. The non-force-free environment causes the deviation of the flux rope equilibrium in the experiments from that determined in the analytic solution. As the flux rope radius decreases, the equilibrium could be found, and it evolves quasi-statically until the flux rope reaches the critical location at which the catastrophe occurs. As the radius increases, no equilibrium exists at all. During the catastrophe, two current sheets form in different ways. One forms as the surrounding closed magnetic field is stretched by the catastrophe, and another one forms as the flux rope squeezes the magnetic field nearby. Although reconnection happens in both the current sheets, it erases the first one quickly and enhances the second simultaneously. These results indicate the occurrence of the catastrophe in asymmetric and non-force-free environment, and the non-radial motion of the flux rope following the catastrophe
Mutations of genes in synthesis of the carotenoid precursors of ABA lead to pre-harvest sprouting and photo-oxidation in rice
Pre-harvest sprouting (PHS) or vivipary in cereals is an important agronomic trait that results in significant economic loss. A considerable number of mutations that cause PHS have been identified in several species. However, relatively few viviparous mutants in rice (Oryza sativa L.) have been reported. To explore the mechanism of PHS in rice, we carried out an extensive genetic screening and identified 12 PHS mutants (phs). Based on their phenotypes, these phs mutants were classified into three groups. Here we characterize in detail one of these groups, which contains mutations in genes encoding major enzymes of the carotenoid biosynthesis pathway, including phytoene desaturase (OsPDS), ζ-carotene desaturase (OsZDS), carotenoid isomerase (OsCRTISO) and lycopene β-cyclase (β-OsLCY), which are essential for the biosynthesis of carotenoid precursors of ABA. As expected, the amount of ABA was reduced in all four phs mutants compared with that in the wild type. Chlorophyll fluorescence analysis revealed the occurrence of photoinhibition in the photosystem and decreased capacity for eliminating excess energy by thermal dissipation. The greatly increased activities of reactive oxygen species (ROS) scavenging enzymes, and reduced photosystem (PS) II core proteins CP43, CP47 and D1 in leaves of the Oscrtiso/phs3-1 mutant and OsLCY RNAi transgenic rice indicated that photo-oxidative damage occurred in PS II, consistent with the accumulation of ROS in these plants. These results suggest that the impairment of carotenoid biosynthesis causes photo-oxidation and ABA-deficiency phenotypes, of which the latter is a major factor controlling the PHS trait in rice
Current evidence, clinical applications, and future directions of transcranial magnetic stimulation as a treatment for ischemic stroke
Transcranial magnetic stimulation (TMS) is a non-invasive brain neurostimulation technique that can be used as one of the adjunctive treatment techniques for neurological recovery after stroke. Animal studies have shown that TMS treatment of rats with middle cerebral artery occlusion (MCAO) model reduced cerebral infarct volume and improved neurological dysfunction in model rats. In addition, clinical case reports have also shown that TMS treatment has positive neuroprotective effects in stroke patients, improving a variety of post-stroke neurological deficits such as motor function, swallowing, cognitive function, speech function, central post-stroke pain, spasticity, and other post-stroke sequelae. However, even though numerous studies have shown a neuroprotective effect of TMS in stroke patients, its possible neuroprotective mechanism is not clear. Therefore, in this review, we describe the potential mechanisms of TMS to improve neurological function in terms of neurogenesis, angiogenesis, anti-inflammation, antioxidant, and anti-apoptosis, and provide insight into the current clinical application of TMS in multiple neurological dysfunctions in stroke. Finally, some of the current challenges faced by TMS are summarized and some suggestions for its future research directions are made
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