211 research outputs found
Mode competition in superradiant scattering of matter waves
Superradiant Rayleigh scattering in a Bose gas released from an optical
lattice is analyzed with incident light pumping at the Bragg angle for resonant
light diffraction. We show competition between superradiance scattering into
the Bragg mode and into end-fire modes clearly leads to suppression of the
latter at even relatively low lattice depths. A quantum light-matter
interaction model is proposed for qualitatively explaining this result.Comment: 6 pages, 6 figures, accepted by PR
Cooperative scattering measurement of coherence in a spatially modulated Bose gas
Correlations of a Bose gas released from an optical lattice are measured
using superradiant scattering. Conditions are chosen so that after initial
incident light pumping at the Bragg angle for diffraction, due to matter wave
amplification and mode competition, superradiant scattering into the Bragg
diffracted mode is preponderant. A temporal analysis of the superradiant
scattering gain reveals periodical oscillations and damping due to the initial
lack of coherence between lattice sites. Such damping is used for
characterizing first order spatial correlations in our system with a precision
of one lattice period.Comment: 4pages, 3figures, to appear in Phys. Rev.
Experimentally well-constrained masses of 27P and 27S: implications for studies of explosive binary systems
The mass of 27P is expected to impact the X-ray burst (XRB) model predictions of burst light curves and the composition of the burst ashes, but large uncertainties and inconsistencies still exist in the reported 27P masses. We have used the Ăź-decay spectroscopy of 27S to determine the most precise mass excess of 27P to date to be keV, which is 63 keV (2.3s) higher and a factor of 3 more precise than the value recommended in the 2016 Atomic Mass Evaluation. Based on the new 27P mass, the P reaction rate and its uncertainty were recalculated using Monte Carlo techniques. We also estimated the previously unknown mass excess of 27S to be 17678(77) keV, based on the measured Ăź-delayed two-proton energy and the Coulomb displacement energy relations. The impact of these well-constrained masses and reaction rates on the modeling of the explosive astrophysical scenarios has been investigated by post-processing XRB and hydrodynamic nova models. Compared to the model calculations based on the masses and rates from databases, the abundance of in the burst ashes is increased by a factor of 2.4, while no substantial change was found in the XRB energy generation rate or the light curve. Our calculation also suggests that 27S is not a significant waiting point in the rapid proton capture process, and the change of the P reaction rate is not sufficiently large to affect the conclusion previously drawn on the nova contribution to the synthesis of galactic 26Al.Postprint (published version
Detecting Sockpuppets in Deceptive Opinion Spam
This paper explores the problem of sockpuppet detection in deceptive opinion
spam using authorship attribution and verification approaches. Two methods are
explored. The first is a feature subsampling scheme that uses the KL-Divergence
on stylistic language models of an author to find discriminative features. The
second is a transduction scheme, spy induction that leverages the diversity of
authors in the unlabeled test set by sending a set of spies (positive samples)
from the training set to retrieve hidden samples in the unlabeled test set
using nearest and farthest neighbors. Experiments using ground truth sockpuppet
data show the effectiveness of the proposed schemes.Comment: 18 pages, Accepted at CICLing 2017, 18th International Conference on
Intelligent Text Processing and Computational Linguistic
Leveraging Anatomical Constraints with Uncertainty for Pneumothorax Segmentation
Pneumothorax is a medical emergency caused by abnormal accumulation of air in
the pleural space - the potential space between the lungs and chest wall. On 2D
chest radiographs, pneumothorax occurs within the thoracic cavity and outside
of the mediastinum and we refer to this area as "lung+ space". While deep
learning (DL) has increasingly been utilized to segment pneumothorax lesions in
chest radiographs, many existing DL models employ an end-to-end approach. These
models directly map chest radiographs to clinician-annotated lesion areas,
often neglecting the vital domain knowledge that pneumothorax is inherently
location-sensitive.
We propose a novel approach that incorporates the lung+ space as a constraint
during DL model training for pneumothorax segmentation on 2D chest radiographs.
To circumvent the need for additional annotations and to prevent potential
label leakage on the target task, our method utilizes external datasets and an
auxiliary task of lung segmentation. This approach generates a specific
constraint of lung+ space for each chest radiograph. Furthermore, we have
incorporated a discriminator to eliminate unreliable constraints caused by the
domain shift between the auxiliary and target datasets.
Our results demonstrated significant improvements, with average performance
gains of 4.6%, 3.6%, and 3.3% regarding Intersection over Union (IoU), Dice
Similarity Coefficient (DSC), and Hausdorff Distance (HD). Our research
underscores the significance of incorporating medical domain knowledge about
the location-specific nature of pneumothorax to enhance DL-based lesion
segmentation
- …