416 research outputs found
Axisymmetric solitary waves on the surface of a ferrofluid
We report the first observation of axisymmetric solitary waves on the surface
of a cylindrical magnetic fluid layer surrounding a current-carrying metallic
tube. According to the ratio between the magnetic and capillary forces, both
elevation and depression solitary waves are observed with profiles in good
agreement with theoretical predictions based on the magnetic analogue of the
Korteweg-deVries equation. We also report the first measurements of the
velocity and the dispersion relation of axisymmetric linear waves propagating
on the cylindrical ferrofluid layer that are found in good agreement with
theoretical predictions.Comment: to be published in Phys. Rev. Let
The distant galaxy cluster CL0016+16: X-ray analysis up to
To study the mass distribution of galaxy clusters up to their Virial radius,
CL0016+16 seems to be a good candidate,since it is a bright massive cluster,
previously considered as being dynamically relaxed. Using XMM-Newton
observations of CL0016+16, we performed a careful X-ray background analysis,
and we detected convincingly its X-ray emission up to . We then
studied its dynamical state with a detailed 2D temperature and surface
brightness analysis of the inner part of the cluster. Using the assumption of
both spherical symmetry and hydrostatic equilibrium (HE) we can determine the
main cluster parameters: total mass, temperature profile, surface brightness
profile and -parameter. We also build a temperature map which clearly
exhibits departure from spherical symmetry in the centre. To estimate the
influence of these perturbations onto our total mass estimate, we also compute
the total mass in the framework of the HE approach, but this time with various
temperature profiles obtained in different directions. These various total mass
estimates are consistent with each other. The temperature perturbations are
clear signatures of ongoing merger activity. We also find significant residuals
after subtracting the emissivity map by a 2D -model fit. We conclude
that, although CL0016+16 shows clear signs of merger activity and departure
from spherical symmetry in the centre, its X-ray emissivity can be detected up
to and the corresponding mass can be computed directly. It
is therefore a good candidate to study cosmological scaling laws as predicted
by the theory.Comment: 11 pages, 17 figures, Accepted for publication in A&
Phase-field models for brittle and cohesive fracture
In this paper we first recapitulate some basic notions of brittle and cohesive fracture models, as well as the phase-field approximation to fracture. Next, a critical assessment is made of the sensitivity of the phase-field approach to brittle fracture, in particular the degradation function, and the use of monolithic versus partitioned solution schemes. The last part of the paper makes extensions to a recently developed phase-field model for cohesive fracture, in particular for propagating cracks. Using some simple examples the current state of the cohesive phase-field model is shown
Time-Fractional Optimal Control of Initial Value Problems on Time Scales
We investigate Optimal Control Problems (OCP) for fractional systems
involving fractional-time derivatives on time scales. The fractional-time
derivatives and integrals are considered, on time scales, in the
Riemann--Liouville sense. By using the Banach fixed point theorem, sufficient
conditions for existence and uniqueness of solution to initial value problems
described by fractional order differential equations on time scales are known.
Here we consider a fractional OCP with a performance index given as a
delta-integral function of both state and control variables, with time evolving
on an arbitrarily given time scale. Interpreting the Euler--Lagrange first
order optimality condition with an adjoint problem, defined by means of right
Riemann--Liouville fractional delta derivatives, we obtain an optimality system
for the considered fractional OCP. For that, we first prove new fractional
integration by parts formulas on time scales.Comment: This is a preprint of a paper accepted for publication as a book
chapter with Springer International Publishing AG. Submitted 23/Jan/2019;
revised 27-March-2019; accepted 12-April-2019. arXiv admin note: substantial
text overlap with arXiv:1508.0075
Direct and Inverse Variational Problems on Time Scales: A Survey
We deal with direct and inverse problems of the calculus of variations on
arbitrary time scales. Firstly, using the Euler-Lagrange equation and the
strengthened Legendre condition, we give a general form for a variational
functional to attain a local minimum at a given point of the vector space.
Furthermore, we provide a necessary condition for a dynamic
integro-differential equation to be an Euler-Lagrange equation (Helmholtz's
problem of the calculus of variations on time scales). New and interesting
results for the discrete and quantum settings are obtained as particular cases.
Finally, we consider very general problems of the calculus of variations given
by the composition of a certain scalar function with delta and nabla integrals
of a vector valued field.Comment: This is a preprint of a paper whose final and definite form will be
published in the Springer Volume 'Modeling, Dynamics, Optimization and
Bioeconomics II', Edited by A. A. Pinto and D. Zilberman (Eds.), Springer
Proceedings in Mathematics & Statistics. Submitted 03/Sept/2014; Accepted,
after a revision, 19/Jan/201
Discovery of large-scale diffuse radio emission and of a new galaxy cluster in the surroundings of MACS J0520.7-1328
We report the discovery of large-scale diffuse radio emission south-east of the galaxy cluster MACS J0520.7-1328, detected through high-sensitivity Giant Metrewave Radio Telescope 323 MHz observations. This emission is dominated by an elongated diffuse radio source and surrounded by other features of lower surface brightness. Patches of these faint sources are marginally detected in a 1.4 GHz image obtained through a re-analysis of archival NVSS data. Interestingly, the elongated radio source coincides with a previously unclassified extended X-ray source. We perform a multi-wavelength analysis based on archival infrared, optical, and X-ray Chandra data. We find that this source is a low-temperature (~3.6 keV) cluster of galaxies, with indications of a disturbed dynamical state, located at a redshift that is consistent with the one of the main galaxy cluster MACSJ0520.7-132 (z = 0.336). We suggest that the diffuse radio emission is associated to non-thermal components in the intracluster and intergalactic medium in and around the newly detected cluster. We are planning deeper multi-wavelength and multi-frequency radio observations to accurately investigate the dynamical scenario of the two clusters and to address the nature of the complex radio emission more precisely. © 2014 ESO
Planck Intermediate Results II: Comparison of Sunyaev-Zeldovich measurements from Planck and from the Arcminute Microkelvin Imager for 11 galaxy clusters
A comparison is presented of Sunyaev-Zeldovich measurements for 11 galaxy
clusters as obtained by Planck and by the ground-based interferometer, the
Arcminute Microkelvin Imager. Assuming a universal spherically-symmetric
Generalised Navarro, Frenk & White (GNFW) model for the cluster gas pressure
profile, we jointly constrain the integrated Compton-Y parameter (Y_500) and
the scale radius (theta_500) of each cluster. Our resulting constraints in the
Y_500-theta_500 2D parameter space derived from the two instruments overlap
significantly for eight of the clusters, although, overall, there is a tendency
for AMI to find the Sunyaev-Zeldovich signal to be smaller in angular size and
fainter than Planck. Significant discrepancies exist for the three remaining
clusters in the sample, namely A1413, A1914, and the newly-discovered Planck
cluster PLCKESZ G139.59+24.18. The robustness of the analysis of both the
Planck and AMI data is demonstrated through the use of detailed simulations,
which also discount confusion from residual point (radio) sources and from
diffuse astrophysical foregrounds as possible explanations for the
discrepancies found. For a subset of our cluster sample, we have investigated
the dependence of our results on the assumed pressure profile by repeating the
analysis adopting the best-fitting GNFW profile shape which best matches X-ray
observations. Adopting the best-fitting profile shape from the X-ray data does
not, in general, resolve the discrepancies found in this subset of five
clusters. Though based on a small sample, our results suggest that the adopted
GNFW model may not be sufficiently flexible to describe clusters universally.Comment: update to metadata author list onl
Planck intermediate results. III. The relation between galaxy cluster mass and Sunyaev-Zeldovich signal
We examine the relation between the galaxy cluster mass M and
Sunyaev-Zeldovich (SZ) effect signal D_A^2 Y for a sample of 19 objects for
which weak lensing (WL) mass measurements obtained from Subaru Telescope data
are available in the literature. Hydrostatic X-ray masses are derived from
XMM-Newton archive data and the SZ effect signal is measured from Planck
all-sky survey data. We find an M_WL-D_A^2 Y relation that is consistent in
slope and normalisation with previous determinations using weak lensing masses;
however, there is a normalisation offset with respect to previous measures
based on hydrostatic X-ray mass-proxy relations. We verify that our SZ effect
measurements are in excellent agreement with previous determinations from
Planck data. For the present sample, the hydrostatic X-ray masses at R_500 are
on average ~ 20 per cent larger than the corresponding weak lensing masses, at
odds with expectations. We show that the mass discrepancy is driven by a
difference in mass concentration as measured by the two methods, and, for the
present sample, the mass discrepancy and difference in mass concentration is
especially large for disturbed systems. The mass discrepancy is also linked to
the offset in centres used by the X-ray and weak lensing analyses, which again
is most important in disturbed systems. We outline several approaches that are
needed to help achieve convergence in cluster mass measurement with X-ray and
weak lensing observations.Comment: 19 pages, 9 figures, matches accepted versio
InforMing the PAthway of COPD Treatment (IMPACT Trial) Single-Inhaler Triple Therapy (Fluticasone Furoate/Umeclidinium/Vilanterol) Versus Fluticasone Furoate/Vilanterol and Umeclidinium/Vilanterol in Patients With COPD: Analysis o the Western Europe and North America Regions
Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by airflow limitation and progressive respiratory symptoms.1 Global public health trends estimate that the COPD burden will continue to rise, with COPD deaths estimated to increase to 4.4% of all deaths in Europe and 6.3% in the World Health Organization-defined region of the Americas by 2060.2 There are differences in the COPD burden in different regions reflecting variations in etiology,3,4 disease severity,5 symptoms,6 medication use,7 and health care systems and utilization.7 These differences may help inform therapeutic strategies to optimize therapeutic approaches to reducing symptoms and exacerbation risk.1
In the global InforMing the PAthway of COPD Treatment (IMPACT) trial, single-inhaler triple therapy fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI) reduced moderate/severe exacerbation rates and improved lung function and health-related quality of life versus FF/VI or UMEC/VI dual therapy in patients ≥40 years of age with symptomatic COPD and a history of exacerbations.8 Within trial populations, regional differences such as patient characteristics, treatment patterns, access to care and cultural/socioeconomic factors may dictate treatment choices and influence disease severity and progression in particular geographical locations. For example, a meta-analysis conducted in 2015 comprising 123 studies between 1990 and 2010 found that the overall prevalence of COPD as well as the rate of increase was higher in the Americas (including both North and South America) compared with Europe.9 Furthermore, a cross-sectional study assessing the burden of COPD symptoms in the United States and Europe found variations between patients across countries who had experienced at least 1 symptom of COPD.10 In Europe, patients with more frequent symptoms were more likely to experience worsening of symptoms and unexpected hospitalization. Whereas in the United States, patients with more frequent symptoms were not only more likely to experience worsening of symptoms but also longer lasting symptoms and a longer length of exacerbations.10 A further difference was that treatment adherence was higher in the United States than Europe, however, adherence was consistent across patients in Europe when assessed by modified Global initiative for chronic Obstructive Lung Disease (GOLD) 2014 groups11 but varied in the United States with adherence highest in the GOLD Group C and lowest in Group A.10 Therefore, it is important to evaluate how overall population results pertain to patients treated in particular regions. As IMPACT is one of the largest trials conducted in patients with COPD to date, we have the unique opportunity to analyze study outcomes in patients enrolled in Western Europe and North America, the 2 main regions from an enrollment perspective
CHEX-MATE: A non-parametric deep learning technique to deproject and deconvolve galaxy cluster X-ray temperature profiles
Temperature profiles of the hot galaxy cluster intracluster medium (ICM) have a complex non-linear structure that traditional parametric modelling may fail to fully approximate. For this study, we made use of neural networks, for the first time, to construct a data-driven non-parametric model of ICM temperature profiles. A new deconvolution algorithm was then introduced to uncover the true (3D) temperature profiles from the observed projected (2D) temperature profiles. An auto-encoder-inspired neural network was first trained by learning a non-linear interpolatory scheme to build the underlying model of 3D temperature profiles in the radial range of [0.02- 2] R500, using a sparse set of hydrodynamical simulations from the THREE HUNDRED PROJECT. A deconvolution algorithm using a learning-based regularisation scheme was then developed. The model was tested using high and low resolution input temperature profiles, such as those expected from simulations and observations, respectively. We find that the proposed deconvolution and deprojection algorithm is robust with respect to the quality of the data, the morphology of the cluster, and the deprojection scheme used. The algorithm can recover unbiased 3D radial temperature profiles with a precision of around 5% over most of the fitting range. We apply the method to the first sample of temperature profiles obtained with XMM-Newton for the CHEX-MATE project and compared it to parametric deprojection and deconvolution techniques. Our work sets the stage for future studies that focus on the deconvolution of the thermal profiles (temperature, density, pressure) of the ICM and the dark matter profiles in galaxy clusters, using deep learning techniques in conjunction with X-ray, Sunyaev Zel'Dovich (SZ) and optical datasets
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