151,579 research outputs found
Structural ambiguity of the Chinese version of the hospital anxiety and depression scale in patients with coronary heart disease
Background
The Hospital Anxiety and Depression Scale (HADS) is a widely used screening tool designed as a case detector for clinically relevant anxiety and depression. Recent studies of the HADS in coronary heart disease (CHD) patients in European countries suggest it comprises three, rather than two, underlying sub-scale dimensions. The factor structure of the Chinese version of the HADS was evaluated in patients with CHD in mainland China.
Methods
Confirmatory factor analysis (CFA) was conducted on self-report HADS forms from 154 Chinese CHD patients.
Results
Little difference was observed in model fit between best performing three-factor and two-factor models.
Conclusion
The current observations are inconsistent with recent studies highlighting a dominant underlying tri-dimensional structure to the HADS in CHD patients. The Chinese version of the HADS may perform differently to European language versions of the instrument in patients with CHD
Jastrow-Correlated Wavefunctions for Flat-Band Lattices
The electronic band structure of many compounds, e.g., carbon-based
structures, can exhibit essentially no dispersion. Models of electrons in
flat-band lattices define non-perturbative strongly correlated problems by
default. We construct a set of Jastrow-correlated ansatz wavefunctions to
capture the low energy physics of interacting particles in flat bands. We test
the ansatz in a simple Coulomb model of spinless electrons in a honeycomb
ribbon. We find that the wavefunction accurately captures the ground state in a
transition from a crystal to a uniform quantum liquid.Comment: 5 pages, 4 figures, update context, references and publication
informatio
Theory of doped Mott insulators: duality between pairing and magnetism
By bosonizing the electronic t-J model exactly on any two-dimensional (2D)
lattices, and integrating out the gauge fluctuations combined to slave
particles beyond mean fields, we get a theory in terms of physical Cooper pair
and spin condensates. In the sense of mutual Berry phase they turns out to be
dual to each other. The mutual-duality is the missing key in the
resonant-valance-bond idea\cite{rvb} to work as a paradigm of doped 2D Mott
insulators. We argue that essential aspects of high- phenomenology find
natural solutions in the theory. We also provide interesting predictions for
systems on hexagonal lattices.Comment: 4 pages, no figures, Submitted to Phys. Rev. Let
Challenges to smartphone applications for melanoma detection
This commentary addresses the emerging market for health-related smartphone applications. Specific to dermatology, there has been a significant increase not only in applications that promote skin cancer awareness and education but also in those meant for detection. With evidence showing that 365 dermatology-related applications were available in 2014--up from 230 in 2012--and that 1 in 5 patients under the age of 50 have used a smartphone to help diagnose a skin problem, there is clearly a large subset of patients participating in this growing trend. Therefore, we are obligated to take a closer look into this phenomenon. Studies have shown that applications are inferior to in-person consultations with one study showing that 3 out of 4 applications incorrectly classified 30% or more melanomas as low-risk lesions. Although the FDA gained regulatory oversight over mobile health applications in 2012 and recently released their statement in 2015, their reach only extends to cover a selected portion of these applications, leaving many unregulated as they continue to be marketed toward our patients. Dermatologists should be updated on our current situation in order to properly counsel patients on the risks and benefits of these applications and whether they are acceptable for use. © 2016 by the article author(s)
Joint Reconstruction of Absorbed Optical Energy Density and Sound Speed Distribution in Photoacoustic Computed Tomography: A numerical Investigation
Photoacoustic computed tomography (PACT) is a rapidly emerging bioimaging
modality that seeks to reconstruct an estimate of the absorbed optical energy
density within an object. Conventional PACT image reconstruction methods assume
a constant speed-of-sound (SOS), which can result in image artifacts when
acoustic aberrations are significant. It has been demonstrated that
incorporating knowledge of an object's SOS distribution into a PACT image
reconstruction method can improve image quality. However, in many cases, the
SOS distribution cannot be accurately and/or conveniently estimated prior to
the PACT experiment. Because variations in the SOS distribution induce
aberrations in the measured photoacoustic wavefields, certain information
regarding an object's SOS distribution is encoded in the PACT measurement data.
Based on this observation, a joint reconstruction (JR) problem has been
proposed in which the SOS distribution is concurrently estimated along with the
sought-after absorbed optical energy density from the photoacoustic measurement
data. A broad understanding of the extent to which the JR problem can be
accurately and reliably solved has not been reported. In this work, a series of
numerical experiments is described that elucidate some important properties of
the JR problem that pertain to its practical feasibility. To accomplish this,
an optimization-based formulation of the JR problem is developed that yields a
non-linear iterative algorithm that alternatingly updates the two image
estimates. Heuristic analytic insights into the reconstruction problem are also
provided. These results confirm the ill-conditioned nature of the joint
reconstruction problem that will present significant challenges for practical
applications.Comment: 13 pages, submitted to IEEE Transactions on Computational Imagin
Quasinormal modes and late-time tails in the background of Schwarzschild black hole pierced by a cosmic string: scalar, electromagnetic and gravitational perturbations
We have studied the quasinormal modes and the late-time tail behaviors of
scalar, electromagnetic and gravitational perturbations in the Schwarzschild
black hole pierced by a cosmic string. Although the metric is locally identical
to that of the Schwarzschild black hole so that the presence of the string will
not imprint in the motion of test particles, we found that quasinormal modes
and the late-time tails can reflect physical signatures of the cosmic string.
Compared with the scalar and electromagnetic fields, the gravitational
perturbation decays slower, which could be more interesting to disclose the
string effect in this background.Comment: 17 pages; 7 figure
Role of Interlayer Coupling on the Evolution of Band Edges in Few-Layer Phosphorene
Using first-principles calculations, we have investigated the evolution of
band-edges in few-layer phosphorene as a function of the number of P layers.
Our results predict that monolayer phosphorene is an indirect band gap
semiconductor and its valence band edge is extremely sensitive to strain. Its
band gap could undergo an indirect-to-direct transition under a lattice
expansion as small as 1% along zigzag direction. A semi-empirical interlayer
coupling model is proposed, which can well reproduce the evolution of valence
band-edges obtained by first-principles calculations. We conclude that the
interlayer coupling plays a dominated role in the evolution of the band-edges
via decreasing both band gap and carrier effective masses with the increase of
phosphorene thickness. A scrutiny of the orbital-decomposed band structure
provides a better understanding of the upward shift of valence band maximum
surpassing that of conduction band minimum.Comment: 25 pages, 9 figure
- …