6,590 research outputs found
Adaptation to the Edge of Chaos in the Self-Adjusting Logistic Map
Self-adjusting, or adaptive systems have gathered much recent interest. We
present a model for self-adjusting systems which treats the control parameters
of the system as slowly varying, rather than constant. The dynamics of these
parameters is governed by a low-pass filtered feedback from the dynamical
variables of the system. We apply this model to the logistic map and examine
the behavior of the control parameter. We find that the parameter leaves the
chaotic regime. We observe a high probability of finding the parameter at the
boundary between periodicity and chaos. We therefore find that this system
exhibits adaptation to the edge of chaos.Comment: 3 figure
Correction: Patients affected with Fabry disease have an increased incidence of progressive hearing loss and sudden deafness: an investigation of twenty-two hemizygous male patients
Image restoration using sparse approximations of spatially varying blur operators in the wavelet domain
6 pagesInternational audienceRestoration of images degraded by spatially varying blurs is an issue of increasing importance in the context of photography, satellite or microscopy imaging. One of the main difficulty to solve this problem comes from the huge dimensions of the blur matrix. It prevents the use of naive approaches for performing matrix-vector multiplications. In this paper, we propose to approximate the blur operator by a matrix sparse in the wavelet domain. We justify this approach from a mathematical point of view and investigate the approximation quality numerically. We finish by showing that the sparsity pattern of the matrix can be pre-defined, which is central in tasks such as blind deconvolution
The XXL Survey V: Detection of the Sunyaev-Zel'dovich effect of the Redshift 1.9 Galaxy Cluster XLSSU J021744.1-034536 with CARMA
We report the detection of the Sunyaev-Zel'dovich (SZ) effect of galaxy
cluster XLSSU J021744.1-034536, using 30 GHz CARMA data. This cluster was
discovered via its extended X-ray emission in the XMM-Newton Large Scale
Structure survey, the precursor to the XXL survey. It has a photometrically
determined redshift , making it among the most distant
clusters known, and nominally the most distant for which the SZ effect has been
measured. The spherically integrated Comptonization is
, a measurement which is relatively
insensitive to assumptions regarding the size and redshift of the cluster, as
well as the background cosmology. Using a variety of locally calibrated cluster
scaling relations extrapolated to z~2, we estimate a mass - from the X-ray flux and SZ signal. The measured
properties of this cluster are in good agreement with the extrapolation of an
X-ray luminosity-SZ effect scaling relation calibrated from clusters discovered
by the South Pole Telescope at higher masses and lower redshifts. The full
XXL-CARMA sample will provide a more complete, multi-wavelength census of
distant clusters in order to robustly extend the calibration of cluster scaling
relations to these high redshifts.Comment: ApJ, in press. 9 pages, 4 figures, 4 table
Baseline corticosterone does not reflect iridescent plumage traits in female tree swallows
The production of high quality secondary sexual traits can be constrained by trade-offs in the allocation of energy and nutrients with other metabolic activities, and is mediated by physiological processes. In birds, the factors influencing male plumage quality have been well studied; however, factors affecting female plumage quality are poorly understood. Furthermore, it remains uncertain which physiological traits mediate the relationship between body condition and ornaments. In this three-year study of after-second-year female tree swallows (Tachycineta bicolor), we investigated (1) the relationship between baseline corticosterone near the end of the brood-rearing period (CORTBR) and feather colour characteristics (hue, saturation, brightness) the following year, and (2) the relationship between baseline corticosterone measured during incubation (CORTI) and brood rearing (CORTBR), and feather colour in the same year. To control for reproductive effort, we included reproductive parameters as covariates in all analyses. In this first study between CORT and the plumage colour characteristics of a species bearing iridescent feathers, we did not find any relationship between CORTBR and the colour of subsequently-produced feathers, nor did we find any relationship between CORT and the colour of feathers displayed during that breeding season. If CORT levels at the end of breeding carry over to influence the immediately subsequent moult period as we expect, our results generally indicate that structural plumage quality may not be as sensitive to circulating CORT levels compared to carotenoid-based colouration. Future studies, particularly those employing experimental manipulations of CORT during moult in species with iridescent traits, are necessary to fully determine the role glucocorticoids play in mediating the quality of secondary sexual characteristics
On the bounded cohomology of semi-simple groups, S-arithmetic groups and products
We prove vanishing results for Lie groups and algebraic groups (over any
local field) in bounded cohomology. The main result is a vanishing below twice
the rank for semi-simple groups. Related rigidity results are established for
S-arithmetic groups and groups over global fields. We also establish vanishing
and cohomological rigidity results for products of general locally compact
groups and their lattices
Measurement of low-energy cosmic-ray electron and positron spectra at 1 AU with the AESOP-Lite spectrometer
We report on a new measurement of the cosmic ray (CR) electron and positron
spectra in the energy range of 20 MeV -- 1 GeV. The data were taken during the
first flight of the balloon-borne spectrometer AESOP-Lite (Anti Electron Sub
Orbital Payload), which was flown from Esrange, Sweden, to Ellesmere Island,
Canada, in May 2018. The instrument accumulated over 130 hours of exposure at
an average altitude of 3 g.cm of residual atmosphere. The experiment
uses a gas Cherenkov detector and a magnetic spectrometer, consisting of a
permanent dipole magnet and silicon strip detectors (SSDs), to identify
particle type and measure the rigidity. Electrons and positrons were detected
against a background of protons and atmospheric secondary particles. The
primary cosmic ray spectra of electrons and positrons, as well as the
re-entrant albedo fluxes, were extracted between 20 MeV -- 1 GeV during a
positive solar magnetic polarity epoch. The positron fraction below 100 MeV
appears flat, suggesting diffusion dominated solar modulation at low rigidity.
The all-electron spectrum is presented and compared with models from a
heliospheric numerical transport code.Comment: 21 pages, 13 figure
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