581 research outputs found
Scalable precision wide-field imaging in radio interferometry: II. AIRI validated on ASKAP data
Accompanying Part I, this sequel delineates a validation of the recently
proposed AI for Regularisation in radio-interferometric Imaging (AIRI)
algorithm on observations from the Australian Square Kilometre Array Pathfinder
(ASKAP). The monochromatic AIRI-ASKAP images showcased in this work are formed
using the same parallelised and automated imaging framework described in Part
I: ``uSARA validated on ASKAP data''. Using a Plug-and-Play approach, AIRI
differs from uSARA by substituting a trained denoising deep neural network
(DNN) for the proximal operator in the regularisation step of the
forward-backward algorithm during deconvolution. We build a trained shelf of
DNN denoisers which target the estimated image-dynamic-ranges of our selected
data. Furthermore, we quantify variations of AIRI reconstructions when
selecting the nearest DNN on the shelf versus using a universal DNN with the
highest dynamic range, opening the door to a more complete framework that not
only delivers image estimation but also quantifies epistemic model uncertainty.
We continue our comparative analysis of source structure, diffuse flux
measurements, and spectral index maps of selected target sources as imaged by
AIRI and the algorithms in Part I -- uSARA and WSClean. Overall we see an
improvement over uSARA and WSClean in the reconstruction of diffuse components
in AIRI images. The scientific potential delivered by AIRI is evident in
further imaging precision, more accurate spectral index maps, and a significant
acceleration in deconvolution time, whereby AIRI is four times faster than its
sub-iterative sparsity-based counterpart uSARA.Comment: Accepted for publication in MNRA
Exploratory Analysis of Functional Data via Clustering and Optimal Segmentation
We propose in this paper an exploratory analysis algorithm for functional
data. The method partitions a set of functions into clusters and represents
each cluster by a simple prototype (e.g., piecewise constant). The total number
of segments in the prototypes, , is chosen by the user and optimally
distributed among the clusters via two dynamic programming algorithms. The
practical relevance of the method is shown on two real world datasets
Prevalence and Associated Factors for Chlamydia trachomatis Infection Among Undocumented Immigrants in a Primary Care Facility in Geneva, Switzerland: A Cross-Sectional Study
Chlamydia trachomatis infection (CTI) is the most frequent sexually transmitted infection in western countries. Its prevalence in undocumented immigrants, a rapidly growing vulnerable population, remains unknown. We aimed to document the prevalence of CTI and associated factors at the primary health care level. This cross-sectional study included all undocumented immigrants attending a health care facility in Geneva, Switzerland. Participants completed a questionnaire and were tested for CTI by PCR assay. Three-hundred thirteen undocumented immigrants (68.4% female, mean age 32.4 (SD 8) years) agreed to participate. CTI prevalence was 5.8% (95% CI 3.3-8.4). Factors associated with higher prevalence were age ≤25 (OR 3.9, 95% CI 1.3-12.2) and having had two or more sexual partners during the precedent year (OR 4.5, 95% CI 1.5-13.7). Prevalence and associated factors for infection in this vulnerable population were comparable with other populations in Western countries. Our findings support the importance of facilitating access to existing screening opportunities in particular to individuals at higher ris
Equation of motion and subsonic-transonic transitions of rectilinear edge dislocations: A collective-variable approach
A theoretical framework is proposed to derive a dynamic equation motion for
rectilinear dislocations within isotropic continuum elastodynamics. The theory
relies on a recent dynamic extension of the Peierls-Nabarro equation, so as to
account for core-width generalized stacking-fault energy effects. The degrees
of freedom of the solution of the latter equation are reduced by means of the
collective-variable method, well known in soliton theory, which we reformulate
in a way suitable to the problem at hand. Through these means, two coupled
governing equations for the dislocation position and core width are obtained,
which are combined into one single complex-valued equation of motion, of
compact form. The latter equation embodies the history dependence of
dislocation inertia. It is employed to investigate the motion of an edge
dislocation under uniform time-dependent loading, with focus on the
subsonic/transonic transition. Except in the steady-state supersonic range of
velocities---which the equation does not address---our results are in good
agreement with atomistic simulations on tungsten. In particular, we provide an
explanation for the transition, showing that it is governed by a
loading-dependent dynamic critical stress. The transition has the character of
a delayed bifurcation. Moreover, various quantitative predictions are made,
that could be tested in atomistic simulations. Overall, this work demonstrates
the crucial role played by core-width variations in dynamic dislocation motion.Comment: v1: 11 pages, 4 figures. v2: title changed, extensive rewriting, and
new material added; 19 pages, 12 figures (content as published
Cost-effectiveness of Chagas disease screening in Latin American migrants at primary health-care centres in Europe: a Markov model analysis
Background Chagas disease is currently prevalent in European countries hosting large communities from Latin
America. Whether asymptomatic individuals at risk of Chagas disease living in Europe should be screened and
treated accordingly is unclear. We performed an economic evaluation of systematic Chagas disease screening of the
Latin American population attending primary care centres in Europe.
Methods We constructed a decision tree model that compared the test option (screening of asymptomatic individuals,
treatment, and follow-up of positive cases) with the no-test option (screening, treating, and follow-up of symptomatic
individuals). The decision tree included a Markov model with five states, related to the chronic stage of the disease:
indeterminate, cardiomyopathy, gastrointestinal, response to treatment, and death. The model started with a target
population of 100 000 individuals, of which 4·2% (95% CI 2·2–6·8) were estimated to be infected by Trypanosoma cruzi.
The primary outcome was the incremental cost-effectiveness ratio (ICER) between test and no-test options.
Deterministic and probabilistic analyses (Monte Carlo simulations) were performed.
Findings In the deterministic analysis, total costs referred to 100 000 individuals in the test and no-test option were
€30 903 406 and €6 597 403 respectively, with a difference of €24 306 003. The respective number of quality-adjusted
life-years (QALYs) gained in the test and no-test option were 61 820·82 and 57 354·42. The ICER was €5442. In the
probabilistic analysis, total costs for the test and no-test option were €32 163 649 (95% CI 31 263 705–33 063 593) and
€6 904 764 (6 703 258–7 106 270), respectively. The respective number of QALYs gained was 64 634·35 (95% CI
62 809·6–66 459·1) and 59 875·73 (58 191·18–61 560·28). The difference in QALYs gained between the test and no test
options was 4758·62 (95% CI 4618·42–4898·82). The incremental cost-effectiveness ratio (ICER) was €6840·75
(95% CI 2545–2759) per QALY gained for a treatment efficacy of 20% and €4243 per QALY gained for treatment
efficacy of 50%. Even with a reduction in Chagas disease prevalence to 0·05% and with large variations in all the
parameters, the test option would still be more cost-effective than the no-test option (less than €30000 per QALY).
Interpretation Screening for Chagas disease in asymptomatic Latin American adults living in Europe is a cost-effective
strategy. Findings of our model provide an important element to support the implementation of T cruzi screening
programmes at primary health centres in European countries hosting Latin American migrants
Edge pinch instability of liquid metal sheet in a transverse high-frequency AC magnetic field
We analyze the linear stability of the edge of a thin liquid metal layer
subject to a transverse high-frequency AC magnetic field. The layer is treated
as a perfectly conducting liquid sheet that allows us to solve the problem
analytically for both a semi-infinite geometry with a straight edge and a thin
disk of finite radius. It is shown that the long-wave perturbations of a
straight edge are monotonically unstable when the wave number exceeds some
critical value which is determined by the surface tension and the linear
density of the electromagnetic force acting on the edge. The higher the density
of electromagnetic force, the shorter the critical wavelength. The
perturbations with wavelength shorter than the critical are stabilized by the
surface tension, whereas the growth rate of long wave perturbations reduces as
for wave numbers . Thus, there is the fastest growing
perturbation with the wave number k_\max=2/3 k_c. By applying the general
approach developed for the semi-infinite sheet, we find that a circular disk
becomes linearly unstable with respect to exponentially growing perturbation
with the azimuthal wave number when the magnetic Bond number exceeds
. The instability characteristics agree well with the experimental
data.Comment: 11 pages, 11 figures, minor grammatical changes; to appear in Phys.
Rev.
The Economic Consequences of Social-Network Structure
We survey the literature on the economic consequences of the structure of social networks. We develop a taxonomy of "macro" and "micro" characteristics of social-interaction networks and discuss both the theoretical and empirical findings concerning the role of those characteristics in determining learning, diffusion, decisions, and resulting behaviors. We also discuss the challenges of accounting for the endogeneity of networks in assessing the relationship between the patterns of interactions and behaviors
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