22,863 research outputs found
Torsional nodeless vibrations of quaking neutron star restored by combined forces of shear elastic and magnetic field stresses
Within the framework of Newtonian magneto-solid-mechanics, relying on
equations appropriate for a perfectly conducting elastic continuous medium
threaded by a uniform magnetic field, the asteroseismic model of a neutron star
undergoing axisymmetric global torsional nodeless vibrations under the combined
action of Hooke's elastic and Lorentz magnetic forces is considered with
emphasis on a toroidal Alfv\'en mode of differentially rotational vibrations
about the dipole magnetic moment axis of the star. The obtained spectral
equation for frequency is applied to -pole identification of
quasi-periodic oscillations (QPOs) of X-ray flux during the giant flares of SGR
1806-20 and SGR 1900+14. Our calculations suggest that detected QPOs can be
consistently interpreted, within the framework of this model, as produced by
global torsional nodeless vibrations of quaking magnetar if they are considered
to be restored by the joint action of bulk forces of shear elastic and magnetic
field stresses.Comment: 18 pages, 5 figures; accepted in Ap
Bayesian analysis of multiple direct detection experiments
Bayesian methods offer a coherent and efficient framework for implementing
uncertainties into induction problems. In this article, we review how this
approach applies to the analysis of dark matter direct detection experiments.
In particular we discuss the exclusion limit of XENON100 and the debated hints
of detection under the hypothesis of a WIMP signal. Within parameter inference,
marginalizing consistently over uncertainties to extract robust posterior
probability distributions, we find that the claimed tension between XENON100
and the other experiments can be partially alleviated in isospin violating
scenario, while elastic scattering model appears to be compatible with the
frequentist statistical approach. We then move to model comparison, for which
Bayesian methods are particularly well suited. Firstly, we investigate the
annual modulation seen in CoGeNT data, finding that there is weak evidence for
a modulation. Modulation models due to other physics compare unfavorably with
the WIMP models, paying the price for their excessive complexity. Secondly, we
confront several coherent scattering models to determine the current best
physical scenario compatible with the experimental hints. We find that
exothermic and inelastic dark matter are moderatly disfavored against the
elastic scenario, while the isospin violating model has a similar evidence.
Lastly the Bayes' factor gives inconclusive evidence for an incompatibility
between the data sets of XENON100 and the hints of detection. The same question
assessed with goodness of fit would indicate a 2 sigma discrepancy. This
suggests that more data are therefore needed to settle this question.Comment: 29 pages, 8 figures; invited review for the special issue of the
journal Physics of the Dark Universe; matches the published versio
Machine Learning and Integrative Analysis of Biomedical Big Data.
Recent developments in high-throughput technologies have accelerated the accumulation of massive amounts of omics data from multiple sources: genome, epigenome, transcriptome, proteome, metabolome, etc. Traditionally, data from each source (e.g., genome) is analyzed in isolation using statistical and machine learning (ML) methods. Integrative analysis of multi-omics and clinical data is key to new biomedical discoveries and advancements in precision medicine. However, data integration poses new computational challenges as well as exacerbates the ones associated with single-omics studies. Specialized computational approaches are required to effectively and efficiently perform integrative analysis of biomedical data acquired from diverse modalities. In this review, we discuss state-of-the-art ML-based approaches for tackling five specific computational challenges associated with integrative analysis: curse of dimensionality, data heterogeneity, missing data, class imbalance and scalability issues
Perceptual telerobotics
A sensory world modeling system, congruent with a human expert's perception, is proposed. The Experiential Knowledge Base (EKB) system can provide a highly intelligible communication interface for telemonitoring and telecontrol of a real time robotic system operating in space. Paradigmatic acquisition of empirical perceptual knowledge, and real time experiential pattern recognition and knowledge integration are reviewed. The cellular architecture and operation of the EKB system are also examined
Anomalous coupling between topological defects and curvature
We investigate a counterintuitive geometric interaction between defects and
curvature in thin layers of superfluids, superconductors and liquid crystals
deposited on curved surfaces. Each defect feels a geometric potential whose
functional form is determined only by the shape of the surface, but whose sign
and strength depend on the transformation properties of the order parameter.
For superfluids and superconductors, the strength of this interaction is
proportional to the square of the charge and causes all defects to be repelled
(attracted) by regions of positive (negative) Gaussian curvature. For liquid
crystals in the one elastic constant approximation, charges between 0 and
are attracted by regions of positive curvature while all other charges
are repelled.Comment: 5 pages, 4 figures, minor changes, accepted for publication in Phys.
Rev. Let
From Common to Special: When Multi-Attribute Learning Meets Personalized Opinions
Visual attributes, which refer to human-labeled semantic annotations, have
gained increasing popularity in a wide range of real world applications.
Generally, the existing attribute learning methods fall into two categories:
one focuses on learning user-specific labels separately for different
attributes, while the other one focuses on learning crowd-sourced global labels
jointly for multiple attributes. However, both categories ignore the joint
effect of the two mentioned factors: the personal diversity with respect to the
global consensus; and the intrinsic correlation among multiple attributes. To
overcome this challenge, we propose a novel model to learn user-specific
predictors across multiple attributes. In our proposed model, the diversity of
personalized opinions and the intrinsic relationship among multiple attributes
are unified in a common-to-special manner. To this end, we adopt a
three-component decomposition. Specifically, our model integrates a common
cognition factor, an attribute-specific bias factor and a user-specific bias
factor. Meanwhile Lasso and group Lasso penalties are adopted to leverage
efficient feature selection. Furthermore, theoretical analysis is conducted to
show that our proposed method could reach reasonable performance. Eventually,
the empirical study carried out in this paper demonstrates the effectiveness of
our proposed method
Role of the Pauli principle in collective-model coupled-channels calculations
A multi-channel algebraic scattering theory, to find solutions of
coupled-channel scattering problems with interactions determined by collective
models, has been structured to ensure that the Pauli principle is not violated.
By tracking the results in the zero coupling limit, a correct interpretation of
the sub-threshold and resonant spectra of the compound system can be made. As
an example, the neutron-12C system is studied defining properties of 13C to 10
MeV excitation. Accounting for the Pauli principle in collective
coupled-channels models is crucial to the outcome.Comment: 4 pages, 1 figure, version appearing in Phys. Rev. Let
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