1,228 research outputs found
Adapting Binary Information Retrieval Evaluation Metrics for Segment-based Retrieval Tasks
This report describes metrics for the evaluation of the effectiveness of
segment-based retrieval based on existing binary information retrieval metrics.
This metrics are described in the context of a task for the hyperlinking of
video segments. This evaluation approach re-uses existing evaluation measures
from the standard Cranfield evaluation paradigm. Our adaptation approach can in
principle be used with any kind of effectiveness measure that uses binary
relevance, and for other segment-baed retrieval tasks. In our video
hyperlinking setting, we use precision at a cut-off rank n and mean average
precision.Comment: Explanation of evaluation measures for the linking task of the
MediaEval Workshop 201
The Tip of the Red Giant Branch and Distance of the Magellanic Clouds: results from the DENIS survey
We present a precise determination of the apparent magnitude of the tip of
the red giant branch (TRGB) in the I (0.8 micron), J (1.25 micron), and K_S
(2.15 micron) bands from the luminosity function of a sample of data extracted
from the DENIS catalogue towards the Magellanic Clouds (Cioni et al. 2000).
From the J and Ks magnitudes we derive bolometric magnitudes m_bol. We
present a new algorithm for the determination of the TRGB magnitude, which we
describe in detail and test extensively using Monte-Carlo simulations. We note
that any method that searches for a peak in the first derivative (used by most
authors) or the second derivative (used by us) of the observed luminosity
function does not yield an unbiased estimate for the actual magnitude of the
TRGB discontinuity. We stress the importance of correcting for this bias, which
is not generally done. We combine the results of our algorithm with theoretical
predictions to derive the distance modulus of the Magellanic Clouds. We obtain
m-M = 18.55 (0.04 formal, 0.08 systematic) for the Large Magellanic Cloud
(LMC), and m-M = 18.99 (0.03 formal, 0.08 systematic) for the Small Magellanic
Cloud (SMC). These are among the most accurate determinations of these
quantities currently available, which is a direct consequence of the large size
of our sample and the insensitivity of near infrared observations to dust
extinction.Comment: 16 pages, 8 figures, revised version, accepted for publication in A&
Persuasive technologies: a systematic literature review and application to PISA
Persuasive Technologies is an expansive eld that covers various research areas including engineering and social sciences. This document summarizes current and historical models of information processing, persuasion and persuasive systems design in order to place other studies in the eld within context. The Persuasive Systems Design Model is then selected as the most recent and comprehensive model in the eld, afer which a series of sample context analyses are performed using this model. The case used for these context analyses is the PISA tool. Finally, we consider the limitations and possible future work of this literature review
The M31 Velocity Vector. III. Future Milky Way-M31-M33 Orbital Evolution, Merging, and Fate of the Sun
We study the future orbital evolution and merging of the MW-M31-M33 system,
using a combination of collisionless N-body simulations and semi-analytic orbit
integrations. Monte-Carlo simulations are used to explore the consequences of
varying the initial phase-space and mass parameters within their observational
uncertainties. The observed M31 transverse velocity implies that the MW and M31
will merge t = 5.86 (+1.61-0.72) Gyr from now, after a first pericenter at t =
3.87 (+0.42-0.32) Gyr. M31 may (probability p=41%) make a direct hit with the
MW (defined here as a first-pericenter distance less than 25 kpc). Most likely,
the MW and M31 will merge first, with M33 settling onto an orbit around them.
Alternatively, M33 may make a direct hit with the MW first (p=9%), or M33 may
get ejected from the Local Group (p=7%). The MW-M31 merger remnant will
resemble an elliptical galaxy. The Sun will most likely (p=85%) end up at
larger radius from the center of the MW-M31 merger remnant than its current
distance from the MW center, possibly further than 50 kpc (p=10%). The Sun may
(p=20%) at some time in the next 10 Gyr find itself moving through M33 (within
10 kpc), but while dynamically still bound to the MW-M31 merger remnant. The
arrival and possible collision of M31 (and possibly M33) with the MW is the
next major cosmic event affecting the environment of our Sun and solar system
that can be predicted with some certainty. (Abridged)Comment: 58 pages, 16 figures, to be published in ApJ. Version with high
resolution figures and N-body movies available at
http://www.stsci.edu/~marel/M31 . Press materials, graphics, and
visualizations available at
http://hubblesite.org/newscenter/archive/releases/2012/2
Gaia TGAS search for Large Magellanic Cloud runaway supergiant stars:Candidate hypervelocity star discovery, and the nature of R71
We search for runaway stars in the Large Magellanic Cloud (LMC) by computing
the space velocities of the visually brightest stars in the LMC that are
included in the Gaia TGAS proper motion catalog. We compare with predictions
from stellar dynamical models to obtain (peculiar) velocities relative to their
local stellar environment. Two of the 31 stars have unusually high proper
motions. Of the remaining 29 stars we find that most objects in this sample
have velocities in very good agreement with model predictions of a circularly
rotating disk model. Indeed the excellent fit to the model implies that the
TGAS uncertainty estimates are likely overestimated. The fastest outliers in
this subsample contain the LBV R71 and a few other well known emission line
objects though in no case do we derive velocities consistent with fast (~100
km/s) runaways. Our results imply that R 71 in particular has a moderate
deviation from the local stellar velocity field (40 km/s) lending support to
the proposition that this object cannot have evolved as a normal single star
since it lies too far from massive star forming complexes to have arrived at
its current position during its lifetime. Our findings therefore strengthen the
case for this LBV being the result of binary evolution. Of the two stars with
unusually high proper motions we find that one, the isolated B1.5 Ia+
supergiant Sk-67 2 (HIP 22237), is a candidate hypervelocity star, the TGAS
proper motion implying a very large peculiar transverse velocity (~360 km/s)
directed radially away from the LMC centre. If confirmed, for example by Gaia
Data Release 2, it would imply that this massive supergiant, on the periphery
of the LMC, is leaving the galaxy where it will explode as a supernova.Comment: 7 pages, 5 figures, revised versio
Three-dimensional finite element analysis of anterior two-unit cantilever resin-bonded fixed dental prostheses
The aim of this study was to evaluate the influence of different framework materials on biomechanical behaviour of anterior two-unit cantilever resin-bonded fixed dental prostheses (RBFDPs). A three-dimensional finite element model of a two-unit cantilever RBFDP replacing amaxillary lateral incisorwas created. Five frameworkmaterialswere evaluated: direct fibre-reinforced composite (FRC-Z250), indirect fibre-reinforced composite (FRC-ES), gold alloy (M), glass ceramic (GC), and zirconia (ZI). Finite element analysis was performed and stress distribution was evaluated. A similar stress pattern, with stress concentrations in the connector area, was observed in RBFDPs for all materials.Maximal principal stress showed a decreasing order: ZI >M>GC> FRC-ES > FRCZ250. The maximum displacement of RBFDPs was higher for FRC-Z250 and FRC-ES than for M, GC, and ZI. FE analysis depicted differences in location of the maximum stress at the luting cement interface between materials. For FRC-Z250 and FRC-ES, the maximum stress was located in the upper part of the proximal area of the retainer, whereas, for M, GC, and ZI, the maximum stress was located at the cervical outline of the retainer. The present study revealed differences in biomechanical behaviour between all RBFDPs.The general observation was that a RBFDP made of FRC provided a more favourable stress distribution
Mechanical cell-matrix feedback explains pairwise and collective endothelial cell behavior in vitro
In vitro cultures of endothelial cells are a widely used model system of the
collective behavior of endothelial cells during vasculogenesis and
angiogenesis. When seeded in an extracellular matrix, endothelial cells can
form blood vessel-like structures, including vascular networks and sprouts.
Endothelial morphogenesis depends on a large number of chemical and mechanical
factors, including the compliancy of the extracellular matrix, the available
growth factors, the adhesion of cells to the extracellular matrix, cell-cell
signaling, etc. Although various computational models have been proposed to
explain the role of each of these biochemical and biomechanical effects, the
understanding of the mechanisms underlying in vitro angiogenesis is still
incomplete. Most explanations focus on predicting the whole vascular network or
sprout from the underlying cell behavior, and do not check if the same model
also correctly captures the intermediate scale: the pairwise cell-cell
interactions or single cell responses to ECM mechanics. Here we show, using a
hybrid cellular Potts and finite element computational model, that a single set
of biologically plausible rules describing (a) the contractile forces that
endothelial cells exert on the ECM, (b) the resulting strains in the
extracellular matrix, and (c) the cellular response to the strains, suffices
for reproducing the behavior of individual endothelial cells and the
interactions of endothelial cell pairs in compliant matrices. With the same set
of rules, the model also reproduces network formation from scattered cells, and
sprouting from endothelial spheroids. Combining the present mechanical model
with aspects of previously proposed mechanical and chemical models may lead to
a more complete understanding of in vitro angiogenesis.Comment: 25 pages, 6 figures, accepted for publication in PLoS Computational
Biolog
Abundance of coral-associated fauna in relation to depth and eutrophication along the leeward side of Curaçao, southern Caribbean
Coral-associated invertebrates contribute much to the biodiversity of Caribbean coral reefs. Although the nature of their symbiotic relation is usually not fully understood, they can cause damage to their hosts, especially when they occur in high densities. The abundance of seven groups of coral-associated invertebrates was investigated on reefs along the leeward side of Curaçao, southern Caribbean. In particular, coral barnacles (Pyrgomatidae), boring mussels (Mytilidae: Leiosolenus spp.), gall crabs (Cryptochiridae), and Christmas tree worms (Serpulidae: Spirobranchus spp.) were recorded together with their host corals by means of a photo survey at four depths (5, 10, 15, 20 m) and across seven sites with high and five sites with low eutrophication values (based on δ15N isotope data). Feather duster worms (Sabellidae: Anamobaea), coral blennies (Chaenopsidae: Acanthemblemaria), and worm snails (Vermetidae: Petaloconchus) were insufficiently abundant for thorough quantitative analyses. The results show a decrease in the number of barnacles and Christmas tree worms per host over depth, which could be related to the availability of their host corals. Sites with high δ15N values show a higher abundance of barnacles and Christmas tree worms per host than sites with low values. This indicates that eutrophication could be favourable for these filter feeding organisms but when their densities become too high, they tend to overgrow their hosts and may become a threat to them
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