8,289 research outputs found
A Simple and Effective Self-Supervised Contrastive Learning Framework for Aspect Detection
Unsupervised aspect detection (UAD) aims at automatically extracting
interpretable aspects and identifying aspect-specific segments (such as
sentences) from online reviews. However, recent deep learning-based topic
models, specifically aspect-based autoencoder, suffer from several problems,
such as extracting noisy aspects and poorly mapping aspects discovered by
models to the aspects of interest. To tackle these challenges, in this paper,
we first propose a self-supervised contrastive learning framework and an
attention-based model equipped with a novel smooth self-attention (SSA) module
for the UAD task in order to learn better representations for aspects and
review segments. Secondly, we introduce a high-resolution selective mapping
(HRSMap) method to efficiently assign aspects discovered by the model to
aspects of interest. We also propose using a knowledge distilling technique to
further improve the aspect detection performance. Our methods outperform
several recent unsupervised and weakly supervised approaches on publicly
available benchmark user review datasets. Aspect interpretation results show
that extracted aspects are meaningful, have good coverage, and can be easily
mapped to aspects of interest. Ablation studies and attention weight
visualization also demonstrate the effectiveness of SSA and the knowledge
distilling method
Loschmidt Echo and Berry phase of the quantum system coupled to the XY spin chain: Proximity to quantum phase transition
We study the Loschmidt echo (LE) of a coupled system consisting of a central
spin and its surrounding environment described by a general XY spin-chain
model. The quantum dynamics of the LE is shown to be remarkably influenced by
the quantum criticality of the spin chain. In particular, the decaying behavior
of the LE is found to be controlled by the anisotropy parameter of the spin
chain. Furthermore, we show that due to the coupling to the spin chain, the
ground-state Berry phase for the central spin becomes nonanalytical and its
derivative with respect to the magnetic parameter in spin chain
diverges along the critical line , which suggests an alternative
measurement of the quantum criticality of the spin chain.Comment: 15 pages, 5 figure
Characterization of a broad-based mosquito yeast interfering RNA larvicide with a conserved target site in mosquito semaphorin-1a genes
BACKGROUND:
RNA interference (RNAi), which has facilitated functional characterization of mosquito neural development genes such as the axon guidance regulator semaphorin-1a (sema1a), could one day be applied as a new means of vector control. Saccharomyces cerevisiae (baker's yeast) may represent an effective interfering RNA expression system that could be used directly for delivery of RNA pesticides to mosquito larvae. Here we describe characterization of a yeast larvicide developed through bioengineering of S. cerevisiae to express a short hairpin RNA (shRNA) targeting a conserved site in mosquito sema1a genes.
RESULTS:
Experiments conducted on Aedes aegypti larvae demonstrated that the yeast larvicide effectively silences sema1a expression, generates severe neural defects, and induces high levels of larval mortality in laboratory, simulated-field, and semi-field experiments. The larvicide was also found to induce high levels of Aedes albopictus, Anopheles gambiae and Culex quinquefasciatus mortality.
CONCLUSIONS:
The results of these studies indicate that use of yeast interfering RNA larvicides targeting mosquito sema1a genes may represent a new biorational tool for mosquito control
Effect of Pulse Shaping on Subharmonic Aided Pressure Estimation In Vitro and In Vivo.
OBJECTIVES: Subharmonic imaging (SHI) is a technique that uses the nonlinear oscillations of microbubbles when exposed to ultrasound at high pressures transmitting at the fundamental frequency ie, f
METHODS: Eight waveforms with different envelopes were optimized with respect to acoustic power at which the SHAPE study is most sensitive. The study was run with four input transmit cycles, first in vitro and then in vivo in three canines to select the waveform that achieved the best sensitivity for detecting changes in portal pressures using SHAPE. A Logiq 9 scanner with a 4C curvi-linear array was used to acquire 2.5 MHz radio-frequency data. Scanning was performed in dual imaging mode with B-mode imaging at 4 MHz and a SHI contrast mode transmitting at 2.5 MHz and receiving at 1.25 MHz. Sonazoid, which is a lipid stabilized gas filled bubble of perfluorobutane, was used as the contrast agent in this study.
RESULTS: A linear decrease in subharmonic amplitude with increased pressure was observed for all waveforms (r from -0.77 to -0.93; P \u3c .001) in vitro. There was a significantly higher correlation of the SHAPE gradient with changing pressures for the broadband pulses as compared to the narrowband pulses in both in vitro and in vivo results. The highest correlation was achieved with a Gaussian windowed binomial filtered square wave with an r-value of -0.95. One of the three canines was eliminated for technical reasons, while the other two produced very similar results to those obtained in vitro (r from -0.72 to -0.98; P
CONCLUSIONS: Using this waveform is an improvement to the existing SHAPE technique (where a square wave was used) and should make SHAPE more sensitive for noninvasively determining portal hypertension
Rotation of hydrogen molecules during the dissociative adsorption on the Mg(0001) surface: A first-principles study
Using first-principles calculations, we systematically study the potential
energy surfaces and dissociation processes of the hydrogen molecule on the
Mg(0001) surface. It is found that during the dissociative adsorption process
with the minimum energy barrier, the hydrogen molecule firstly orients
perpendicular, and then rotates to be parallel to the surface. It is also found
that the orientation of the hydrogen molecule at the transition state is
neither perpendicular nor parallel to the surface. Most importantly, we find
that the rotation causes a reduction of the calculated dissociation energy
barrier for the hydrogen molecule. The underlying electronic reasons for the
rotation of the hydrogen molecule is also discussed in our paper.Comment: 14 pages, 4 figure
- …