704 research outputs found
Probing clustering features around Cl 0024+17
I present a spatial analysis of the galaxy distribution around the cluster Cl
0024+17. The basic aim is to find the scales where galaxies present a
significant deviation from an inhomogeneous Poisson statistical process. Using
the generalization of the Ripley, Besag, and the pair correlation functions for
non-stationary point patterns, I estimate these transition scales for a set of
1,000 Monte Carlo realizations of the Cl 0024+17 field, corrected for
completeness up to the outskirts. The results point out the presence of at
least two physical scales in this field at 31.4 and 112.9 arcseconds. The
second one is statistically consistent with the dark matter ring radius (about
75 arcseconds) previously identified by Jee et al. (2007). However, morphology
and anisotropy tests point out that a clump at about 120 arcseconds NW from the
cluster center could be the responsible for the second transition scale. These
results do not indicate the existence of a galaxy counterpart of the dark
matter ring, but the methodology developed to study the galaxy field as a
spatial point pattern provides a good statistical evaluation of the physical
scales around the cluster. I briefly discuss the usefulness of this approach to
probe features in galaxy distribution and N-body dark matter simulation data.Comment: Accepted for publication in New Astronomy. 14 pages. 8 figure
A Bayesian Approach to the Detection Problem in Gravitational Wave Astronomy
The analysis of data from gravitational wave detectors can be divided into
three phases: search, characterization, and evaluation. The evaluation of the
detection - determining whether a candidate event is astrophysical in origin or
some artifact created by instrument noise - is a crucial step in the analysis.
The on-going analyses of data from ground based detectors employ a frequentist
approach to the detection problem. A detection statistic is chosen, for which
background levels and detection efficiencies are estimated from Monte Carlo
studies. This approach frames the detection problem in terms of an infinite
collection of trials, with the actual measurement corresponding to some
realization of this hypothetical set. Here we explore an alternative, Bayesian
approach to the detection problem, that considers prior information and the
actual data in hand. Our particular focus is on the computational techniques
used to implement the Bayesian analysis. We find that the Parallel Tempered
Markov Chain Monte Carlo (PTMCMC) algorithm is able to address all three phases
of the anaylsis in a coherent framework. The signals are found by locating the
posterior modes, the model parameters are characterized by mapping out the
joint posterior distribution, and finally, the model evidence is computed by
thermodynamic integration. As a demonstration, we consider the detection
problem of selecting between models describing the data as instrument noise, or
instrument noise plus the signal from a single compact galactic binary. The
evidence ratios, or Bayes factors, computed by the PTMCMC algorithm are found
to be in close agreement with those computed using a Reversible Jump Markov
Chain Monte Carlo algorithm.Comment: 19 pages, 12 figures, revised to address referee's comment
Dark Matter in the Galaxy Cluster CL J1226+3332 at Z=0.89
We present a weak-lensing analysis of the galaxy cluster CL J1226+3332 at
z=0.89 using Hubble Space Telescope Advanced Camera for Surveys images. The
cluster is the hottest (>10 keV), most X-ray luminous system at z>0.6 known to
date. The relaxed X-ray morphology, as well as its high temperature, is unusual
at such a high redshift. Our mass reconstruction shows that on a large scale
the dark matter distribution is consistent with a relaxed system with no
significant substructures. However, on a small scale the cluster core is
resolved into two mass clumps highly correlated with the cluster galaxy
distribution. The dominant mass clump lies close to the brightest cluster
galaxy whereas the other less massive clump is located ~40" (~310 kpc) to the
southwest. Although this secondary mass clump does not show an excess in the
X-ray surface brightness, the gas temperature of the region is much higher
(12~18 keV) than those of the rest. We propose a scenario in which the less
massive system has already passed through the main cluster and the X-ray gas
has been stripped during this passage. The elongation of the X-ray peak toward
the southwestern mass clump is also supportive of this possibility. We measure
significant tangential shears out to the field boundary (~1.5 Mpc), which are
well described by an Navarro-Frenk-White profile with a concentration parameter
of c200=2.7+-0.3 and a scale length of rs=78"+-19" (~600 kpc) with
chi^2/d.o.f=1.11. Within the spherical volume r200=1.6 Mpc, the total mass of
the cluster becomes M(r<r200)=(1.4+-0.2) x 10^15 solar mass. Our weak-lensing
analysis confirms that CL1226+3332 is indeed the most massive cluster known to
date at z>0.6.Comment: Accepted for publication in Ap
Rapid detection of Galba truncatula in water sources on pasture-land using loop-mediated isothermal amplification for control of trematode infections
Solid-state microprocessor-controlled detector for doublet peak measurements in flow-injection analysis
Temporal dynamics of trematode intermediate snail host environmental DNA in small water body habitats
[Figure: see text
Sensory Electrical Stimulation Improves Foot Placement during Targeted Stepping Post-Stroke
Proper foot placement is vital for maintaining balance during walking, requiring the integration of multiple sensory signals with motor commands. Disruption of brain structures post-stroke likely alters the processing of sensory information by motor centers, interfering with precision control of foot placement and walking function for stroke survivors. In this study, we examined whether somatosensory stimulation, which improves functional movements of the paretic hand, could be used to improve foot placement of the paretic limb. Foot placement was evaluated before, during, and after application of somatosensory electrical stimulation to the paretic foot during a targeted stepping task. Starting from standing, twelve chronic stroke participants initiated movement with the non-paretic limb and stepped to one of five target locations projected onto the floor with distances normalized to the paretic stride length. Targeting error and lower extremity kinematics were used to assess changes in foot placement and limb control due to somatosensory stimulation. Significant reductions in placement error in the medial–lateral direction (p = 0.008) were observed during the stimulation and post-stimulation blocks. Seven participants, presenting with a hip circumduction walking pattern, had reductions (p = 0.008) in the magnitude and duration of hip abduction during swing with somatosensory stimulation. Reductions in circumduction correlated with both functional and clinical measures, with larger improvements observed in participants with greater impairment. The results of this study suggest that somatosensory stimulation of the paretic foot applied during movement can improve the precision control of foot placement
Mass Cytometry Defines Virus-Specific CD4 + T Cells in Influenza Vaccination
The antiviral response to influenza virus is complex and multifaceted, involving many immune cell subsets. There is an urgent need to understand the role of CD4+ T cells, which orchestrate an effective antiviral response, to improve vaccine design strategies. In this study, we analyzed PBMCs from human participants immunized with influenza vaccine, using high-dimensional single-cell proteomic immune profiling by mass cytometry. Data were analyzed using a novel clustering algorithm, denoised ragged pruning, to define possible influenza virus-specific clusters of CD4+ T cells. Denoised ragged pruning identified six clusters of cells. Among these, one cluster (Cluster 3) was found to increase in abundance following stimulation with influenza virus peptide ex vivo. A separate cluster (Cluster 4) was found to expand in abundance between days 0 and 7 postvaccination, indicating that it is vaccine responsive. We examined the expression profiles of all six clusters to characterize their lineage, functionality, and possible role in the response to influenza vaccine. Clusters 3 and 4 consisted of effector memory cells, with high CD154 expression. Cluster 3 expressed cytokines like IL-2, IFN-γ, and TNF-α, whereas Cluster 4 expressed IL-17. Interestingly, some participants had low abundance of Clusters 3 and 4, whereas others had higher abundance of one of these clusters compared with the other. Taken together, we present an approach for identifying novel influenza virus-reactive CD4+ T cell subsets, a method that could help advance understanding of the immune response to influenza, predict responsiveness to vaccines, and aid in better vaccine design
Case Series of a Knowledge Translation Intervention to Increase Upper Limb Exercise in Stroke Rehabilitation
Background and Purpose. Current approaches to upper limb rehabilitation are not sufficient to drive neural reorganization and maximize recovery after stroke. To address this evidence-practice gap, a knowledge translation intervention using the Behaviour Change Wheel was developed. The intervention involves collaboratively working with stroke therapy teams to change their practice and increase therapy intensity by therapists prescribing supplementary self-directed arm exercise. The purposes of this case series are: (1) to provide an illustrative example of how a research-informed process changed clinical practice and (2) to report on staff members’ and patients’ perceptions of the utility of the developed intervention.
Case Descriptions. A participatory action research approach was used in 3 stroke rehabilitation units in the United Kingdom. The intervention aimed to change 4 therapist-level behaviors: (1) screening patients for suitability for supplementary self-directed arm exercise, (2) provision of exercises, (3) involving family and caregivers in assisting with exercises, and (4) monitoring and progressing exercises. Data on changes in practice were collected by therapy teams using a bespoke audit tool. Utility of the intervention was explored in qualitative interviews with patients and staff.
Outcomes. Components of the intervention were successfully embedded in 2 of the 3 stroke units. At these sites, almost all admitted patients were screened for suitability for supplementary self-directed exercise. Exercises were provided to 77%, 70%, and 88% of suitable patients across the 3 sites. Involving family and care givers and monitoring and progressing exercises were not performed consistently.
Conclusions. This case report is an example of how a rigorous research-informed knowledge translation process resulted in practice change. Research is needed to demonstrate that these changes can translate into increased intensity of upper limb exercise and affect patient outcome
Mock galaxy redshift catalogues from simulations: implications for Pan-STARRS1
We describe a method for constructing mock galaxy catalogues which are well
suited for use in conjunction with large photometric surveys. We use the
semi-analytic galaxy formation model of Bower et al. implemented in the
Millennium simulation. We apply our method to the specific case of the surveys
soon to commence with PS1, the first of 4 telescopes planned for the Pan-STARRS
system. PS1 has 5 photometric bands (grizy), and will carry out an all-sky 3pi
survey and a medium deep survey (MDS) over 84 sq.deg. We calculate the expected
magnitude limits for extended sources in the two surveys. We find that, after 3
years, the 3pi survey will have detected over 10^8 galaxies in all 5 bands, 10
million of which will lie at redshift z>0.9, while the MDS will have detected
over 10^7 galaxies with 0.5 million lying at z>2. These numbers at least double
if detection in the shallowest band, y is not required. We then evaluate the
accuracy of photometric redshifts estimated using an off-the-shelf photo-z
code. With the grizy bands alone it is possible to achieve an accuracy in the
3pi survey of Delta z/(1+z)~0.06 for 0.25<z<0.8, which could be reduced by
about 15% using near infrared photometry from the UKIDDS survey, but would
increase by about 25% for the deeper sample without the y band photometry. For
the MDS an accuracy of Delta z/(1+z)~0.05 is achievable for 0.02<z<1.5 using
grizy. A dramatic improvement in accuracy is possible by selecting only red
galaxies. In this case, Delta z/(1+z)~0.02-0.04 is achievable for ~100 million
galaxies at 0.4<z<1.1 in the 3pi survey and for 30 million galaxies in the MDS
at 0.4<z<2. We investigate the effect of using photo-z in the estimate of the
baryonic acoustic oscillation scale. We find that PS1 will achieve a similar
accuracy in this estimate as a spectroscopic survey of 20 million galaxies.Comment: 23 pages, 18 figures, accepted by MNRA
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