944 research outputs found
The dynamical state of RXCJ1230.7+3439: a multi-substructured merging galaxy cluster
We analyse the kinematical and dynamical state of the galaxy cluster
RXCJ1230.7+3439, at z=0.332, using 93 new spectroscopic redshifts of galaxies
acquired at the 3.6m TNG telescope and from SDSS DR16 public data. We find that
RXCJ1230 appears as a clearly isolated peak in the redshift space, with a
global line-of-sight velocity dispersion of km s,
and showing a very complex structure with the presence of three subclusters.
Our analyses confirm that the three substructures detected are in a pre-merger
phase, where the main interaction takes place with the south-west subclump. We
compute a velocity dispersion of and
km s for the main cluster and the
south-west substructure, respectively. The central main body and south-west
substructure differ by km s in the LOS velocity. From these
data, we estimate a dynamical mass of
M and M for the RXCJ1230 main
body and south-west clump, respectively, which reveals that the cluster will
suffer a merging characterized by a 2:1 mass ratio impact. We solve a two-body
problem for this interaction and find that the most likely solution suggests
that the merging axis lies almost contained in the plane of the sky and the
subcluster will fully interact in Gyr. The comparison between the
dynamical masses and those derived from X-ray data reveals a good agreement
within errors (differences \%), which suggests that the innermost
regions () of the galaxy clumps are almost in hydrostatical
equilibrium. To summarize, RXCJ1230 is a young but also massive cluster in a
pre-merging phase accreeting other galaxy systems from its environment.Comment: To be published in A&
RXCJ1111.6+4050 galaxy cluster: the observational evidence of a transitional fossil group
We present a detailed kinematical and dynamical study of the galaxy cluster
RXCJ1111.6+4050 (RXCJ1111), at z = 0.0756 using 104 new spectroscopic redshifts
of galaxies observed at the TNG 3.5m telescope and SDSS DR16 public archive.
Our analysis is performed in a multiwavelength context in order to study and
compare mainly optical and X-ray properties using XMM-Newton data. We find that
RXCJ1111 is a galaxy cluster showing a velocity distribution with clear
deviations from Gaussianity, that we are able to explain by the presence of a
substructure within the cluster. The two cluster components show velocity
dispersions of km/s and km/s, which yield dynamical
masses of M= M and M for the main system and substructure, respectively.
RXCJ1111 presents an elongation in the North-South direction and a gradient of
250-350 km/s/Mpc in the velocity field, suggest that the merger axis between
the main system and substructure is slightly tilted with respect to the
line-of-sight. The substructure is characterized by a magnitude gap , so it fits the "fossil-like" definition of a galaxy group.
Mass estimates derived from X-ray and optical are in good agreement when two
galaxy components are considered separately. We propose a 3D merging model and
find that the fossil group is in an early phase of collision with the RXCJ1111
main cluster and almost aligned with the line-of-sight. This merging model
would explain the slight increase found in the T with respect to what we
would expect for relaxed clusters. Due to the presence of several brightest
galaxies, after this collision, the substructure would presumably lose its
fossil condition. Therefore, RXCJ1111 represents the observational evidence
that the fossil stage of a system can be temporary and transitional.Comment: 16 pages, 11 figures, 3 tables and 1 appendi
Lensed CMB power spectra from all-sky correlation functions
Weak lensing of the CMB changes the unlensed temperature anisotropy and
polarization power spectra. Accounting for the lensing effect will be crucial
to obtain accurate parameter constraints from sensitive CMB observations.
Methods for computing the lensed power spectra using a low-order perturbative
expansion are not good enough for percent-level accuracy. Non-perturbative
flat-sky methods are more accurate, but curvature effects change the spectra at
the 0.3-1% level. We describe a new, accurate and fast, full-sky
correlation-function method for computing the lensing effect on CMB power
spectra to better than 0.1% at l<2500 (within the approximation that the
lensing potential is linear and Gaussian). We also discuss the effect of
non-linear evolution of the gravitational potential on the lensed power
spectra. Our fast numerical code is publicly available.Comment: 16 pages, 4 figures. Changes to match PRD version including new
section on non-linear corrections. CAMB code available at http://camb.info
Accounting for variability in ion current recordings using a mathematical model of artefacts in voltage-clamp experiments
Mathematical models of ion channels, which constitute indispensable components of action potential models, are commonly constructed by fitting to whole-cell patch-clamp data. In a previous study, we fitted cell-specific models to hERG1a (Kv11.1) recordings simultaneously measured using an automated high-throughput system, and studied cell-cell variability by inspecting the resulting model parameters. However, the origin of the observed variability was not identified. Here, we study the source of variability by constructing a model that describes not just ion current dynamics, but the entire voltage-clamp experiment. The experimental artefact components of the model include: series resistance, membrane and pipette capacitance, voltage offsets, imperfect compensations made by the amplifier for these phenomena, and leak current. In this model, variability in the observations can be explained by either cell properties, measurement artefacts, or both. Remarkably, by assuming that variability arises exclusively from measurement artefacts, it is possible to explain a larger amount of the observed variability than when assuming cell-specific ion current kinetics. This assumption also leads to a smaller number of model parameters. This result suggests that most of the observed variability in patch-clamp data measured under the same conditions is caused by experimental artefacts, and hence can be compensated for in post-processing by using our model for the patch-clamp experiment. This study has implications for the question of the extent to which cell-cell variability in ion channel kinetics exists, and opens up routes for better correction of artefacts in patch-clamp data. This article is part of the theme issue 'Uncertainty quantification in cardiac and cardiovascular modelling and simulation'
Development of ultra-light pixelated ladders for an ILC vertex detector
The development of ultra-light pixelated ladders is motivated by the
requirements of the ILD vertex detector at ILC. This paper summarizes three
projects related to system integration. The PLUME project tackles the issue of
assembling double-sided ladders. The SERWIETE project deals with a more
innovative concept and consists in making single-sided unsupported ladders
embedded in an extra thin plastic enveloppe. AIDA, the last project, aims at
building a framework reproducing the experimental running conditions where sets
of ladders could be tested
A Comparison of Algorithms for the Construction of SZ Cluster Catalogues
We evaluate the construction methodology of an all-sky catalogue of galaxy
clusters detected through the Sunyaev-Zel'dovich (SZ) effect. We perform an
extensive comparison of twelve algorithms applied to the same detailed
simulations of the millimeter and submillimeter sky based on a Planck-like
case. We present the results of this "SZ Challenge" in terms of catalogue
completeness, purity, astrometric and photometric reconstruction. Our results
provide a comparison of a representative sample of SZ detection algorithms and
highlight important issues in their application. In our study case, we show
that the exact expected number of clusters remains uncertain (about a thousand
cluster candidates at |b|> 20 deg with 90% purity) and that it depends on the
SZ model and on the detailed sky simulations, and on algorithmic implementation
of the detection methods. We also estimate the astrometric precision of the
cluster candidates which is found of the order of ~2 arcmins on average, and
the photometric uncertainty of order ~30%, depending on flux.Comment: Accepted for publication in A&A: 14 pages, 7 figures. Detailed
figures added in Appendi
A nonlinear and time-dependent leak current in the presence of calcium fluoride patch-clamp seal enhancer [version 1; peer review: 2 approved with reservations]
Automated patch-clamp platforms are widely used and vital tools in both academia and industry to enable high-throughput studies such as drug screening. A leak current to ground occurs whenever the seal between a pipette and cell (or internal solution and cell in high-throughput machines) is not perfectly insulated from the bath (extracellular) solution. Over 1 GΩ seal resistance between pipette and bath solutions is commonly used as a quality standard for manual patch work. With automated platforms it can be difficult to obtain such a high seal resistance between the intra- and extra-cellular solutions. One suggested method to alleviate this problem is using an Fâ containing internal solution together with a Ca2+ containing external solution â so that a CaF2 crystal forms when the two solutions meet which âplugs the holesâ to enhance the seal resistance. However, we observed an unexpected nonlinear-in-voltage and time-dependent current using these solutions on an automated patch-clamp platform. We performed manual patch-clamp experiments with the automated patch-clamp solutions, but no biological cell, and observed the same nonlinear time-dependent leak current. The current could be completely removed by washing out Fâ ions to leave a conventional leak current that was linear and not time-dependent. We therefore conclude fluoride ions interacting with the CaF2 crystal are the origin of the nonlinear time-dependent leak current. The consequences of such a nonlinear and time-dependent leak current polluting measurements should be considered carefully if it cannot be isolated and subtracted
The OPERA experiment Target Tracker
The main task of the Target Tracker detector of the long baseline neutrino
oscillation OPERA experiment is to locate in which of the target elementary
constituents, the lead/emulsion bricks, the neutrino interactions have occurred
and also to give calorimetric information about each event. The technology used
consists in walls of two planes of plastic scintillator strips, one per
transverse direction. Wavelength shifting fibres collect the light signal
emitted by the scintillator strips and guide it to both ends where it is read
by multi-anode photomultiplier tubes. All the elements used in the construction
of this detector and its main characteristics are described.Comment: 25 pages, submitted to Nuclear Instrument and Method
Rhythmic dynamics and synchronization via dimensionality reduction : application to human gait
Reliable characterization of locomotor dynamics of human walking is vital to understanding the neuromuscular control of human locomotion and disease diagnosis. However, the inherent oscillation and ubiquity of noise in such non-strictly periodic signals pose great challenges to current methodologies. To this end, we exploit the state-of-the-art technology in pattern recognition and, specifically, dimensionality reduction techniques, and propose to reconstruct and characterize the dynamics accurately on the cycle scale of the signal. This is achieved by deriving a low-dimensional representation of the cycles through global optimization, which effectively preserves the topology of the cycles that are embedded in a high-dimensional Euclidian space. Our approach demonstrates a clear advantage in capturing the intrinsic dynamics and probing the subtle synchronization patterns from uni/bivariate oscillatory signals over traditional methods. Application to human gait data for healthy subjects and diabetics reveals a significant difference in the dynamics of ankle movements and ankle-knee coordination, but not in knee movements. These results indicate that the impaired sensory feedback from the feet due to diabetes does not influence the knee movement in general, and that normal human walking is not critically dependent on the feedback from the peripheral nervous system
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