4,920 research outputs found
Experimental determination of pressure drop and flow characteristics of dilute gas-solid suspensions
Loading ratio, glass particle size, and air Reynolds number effects on pressure drop and flow characteristics of air-solid suspension in turbulent pipe flo
The structure of Abell 1351: a bimodal galaxy cluster with peculiar diffuse radio emission
We aim to review the internal structure and dynamics of the Abell 1351
cluster, shown to host a radio halo with a quite irregular shape. Our analysis
is based on radial velocity data for 135 galaxies obtained at the Telescopio
Nazionale Galileo. We combine galaxy velocities and positions to select 95
cluster galaxy members and analyse the internal dynamics of the whole cluster.
We also examine X-ray data retrieved from Chandra and XMM archives. We measure
the cluster redshift, =0.325, the line-of-sight (LOS) velocity dispersion,
\sigma_v~1500 km/s, and the X-ray temperature, kT~9 keV. From both X-ray and
optical data independently, we estimate a large cluster mass, in the 1--4
M range. We attribute the extremely high value of \sigma_v to
the bimodality in the velocity distribution. We find evidence of a significant
velocity gradient and optical 3D substructure. The X-ray analysis also shows
many features in favour of a complex cluster structure, probably supporting an
ongoing merger of substructures in Abell 1351. The observational scenario
agrees with the presence of two main subclusters in the northern region, each
with its brightest galaxy (BCG1 and BCG2), detected as the two most important
X-ray substructures with a rest-frame LOS velocity difference of \Delta v~2500
km/s (in the rest frame) and probably being in large part aligned with the LOS.
We conclude that Abell 1351 is a massive merging cluster. The details of the
cluster structure allow us to interpret the quite asymmetric radio halo as a
`normal' halo plus a southern relic, strongly supporting a previous suggestion
based only on inspection of radio and preliminary X-ray data.Comment: 13 pages, 13 figures, 1 tabl
An agent-based approach to assess drivers’ interaction with pre-trip information systems.
This article reports on the practical use of a multi-agent microsimulation framework to address the issue of assessing drivers’
responses to pretrip information systems. The population of drivers is represented as a community of autonomous agents,
and travel demand results from the decision-making deliberation performed by each individual of the population as regards
route and departure time. A simple simulation scenario was devised, where pretrip information was made available to users
on an individual basis so that its effects at the aggregate level could be observed. The simulation results show that the
overall performance of the system is very likely affected by exogenous information, and these results are ascribed to demand
formation and network topology. The expressiveness offered by cognitive approaches based on predicate logics, such as the
one used in this research, appears to be a promising approximation to fostering more complex behavior modelling, allowing
us to represent many of the mental aspects involved in the deliberation process
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Improving Visual Field Examination of the Macula Using Structural Information
Purpose: To investigate a novel approach for structure-function modeling in glaucoma to improve visual field testing in the macula.
Methods: We acquired data from the macular region in 20 healthy eyes and 31 with central glaucomatous damage. Optical coherence tomography (OCT) scans were used to estimate the local macular ganglion cell density. Perimetry was performed with a fundus-tracking device using a 10-2 grid. OCT scans were matched to the retinal image from the fundus perimeter to accurately map the tested locations onto the structural damage. Binary responses from the subjects to all presented stimuli were used to calculate the structure-function model used to generate prior distributions for a ZEST (Zippy Estimation by Sequential Testing) Bayesian strategy. We used simulations based on structural and functional data acquired from an independent dataset of 20 glaucoma patients to compare the performance of this new strategy, structural macular ZEST (MacS-ZEST), with a standard ZEST.
Results: Compared to the standard ZEST, MacS-ZEST reduced the number of presentations by 13% in reliable simulated subjects and 14% with higher rates (≥20%) of false positive or false negative errors. Reduction in mean absolute error was not present for reliable subjects but was gradually more important with unreliable responses (≥10% at 30% error rate).
Conclusions: Binary responses can be modeled to incorporate detailed structural information from macular OCT into visual field testing, improving overall speed and accuracy in poor responders.
Translational Relevance: Structural information can improve speed and reliability for macular testing in glaucoma practice
Medida de molhabilidade e da energia superficial de filmes biopoliméricos de interesse a confecção de embalagens.
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