340 research outputs found
Resolution-Independent Meshes of Superpixels
The over-segmentation into superpixels is an important preprocessing step to
smartly compress the input size and speed up higher level tasks. A superpixel
was traditionally considered as a small cluster of square-based pixels that
have similar color intensities and are closely located to each other. In this
discrete model the boundaries of superpixels often have irregular zigzags
consisting of horizontal or vertical edges from a given pixel grid. However
digital images represent a continuous world, hence the following continuous
model in the resolution-independent formulation can be more suitable for the
reconstruction problem.
Instead of uniting squares in a grid, a resolution-independent superpixel is
defined as a polygon that has straight edges with any possible slope at
subpixel resolution. The harder continuous version of the over-segmentation
problem is to split an image into polygons and find a best (say, constant)
color of each polygon so that the resulting colored mesh well approximates the
given image. Such a mesh of polygons can be rendered at any higher resolution
with all edges kept straight.
We propose a fast conversion of any traditional superpixels into polygons and
guarantees that their straight edges do not intersect. The meshes based on the
superpixels SEEDS (Superpixels Extracted via Energy-Driven Sampling) and SLIC
(Simple Linear Iterative Clustering) are compared with past meshes based on the
Line Segment Detector. The experiments on the Berkeley Segmentation Database
confirm that the new superpixels have more compact shapes than pixel-based
superpixels
Decreased PARP and procaspase-2 protein levels are associated with cellular drug resistance in childhood acute lymphoblastic leukemia
Drug resistance in childhood acute lymphoblastic leukemia (ALL) and acute
myeloid leukemia (AML) is associated with impaired ability to induce
apoptosis. To elucidate causes of apoptotic defects, we studied the
protein expression of Apaf-1, procaspases-2, -3, -6, -7, -8, -10, and
poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) in cells from
children with acute lymphoblastic leukemia (ALL; n = 43) and acute myeloid
leukemia (AML; n = 10). PARP expression was present in all B-lineage
samples, but absent in 4 of 15 T-lineage ALL samples and 3 of 10 AML
cases, which was not caused by genomic deletions. PARP expression was a
median 7-fold lower in T-lineage ALL (P < .001) and 10-fold lower in AML
(P < .001) compared with B-lineage ALL. PARP expression was 4-fold lower
in prednisolone, vincristine and L-asparaginase (PVA)-resistant compared
with PVA-sensitive ALL patients (P < .001). Procaspase-2 expression was
3-fold lower in T-lineage ALL (P = .022) and AML (P = .014) compared with
B-lineage ALL. In addition, procaspase-2 expression was 2-fold lower in
PVA-resistant compared to PVA-sensitive ALL patients (P = .042). No
relation between apoptotic protease-activating factor 1 (Apaf-1),
procaspases-3, -6, -7, -8, -10, and drug resistance was found. In
conclusion, low baseline expression of PARP and procaspase-2 is related to
cellular drug resistance in childhood acute lymphoblastic leukemia
Prenatal stress exposure is associated with increased dyspnea perception in adulthood
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Dyspnoea is the aversive cardinal symptom in various prevalent conditions such as respiratory, cardiovascular and neuromuscular diseases and is associated with great individual and socioeconomic burden [1]. Over the past years, several physiological and also psychological factors have been demonstrated to affect the perception of dyspnoea [1, 2]. For example, high levels of anxiety in adulthood were associated with increased dyspnoea perception in patients with asthma or chronic obstructive pulmonary disease (COPD), but also in healthy controls [2]. Moreover, adverse, separation-related experiences in childhood were linked to the subsequent development of increased anxiety and dyspnoea [3]. However, the effects of adverse experiences in early, prenatal life on dyspnoea perception remain widely unknown, although prenatal exposure to maternal stress and anxiety has convincingly been related to the development of other health and behavioural problems later in life, including impairments of the respiratory control system and high anxiety levels [4–9]. Therefore, this study investigated the relationship between prenatal exposure to maternal stress and the perception of dyspnoea in adulthood 28 years later
XMM-Newton X-ray and optical observations of the globular clusters M 55 and NGC 3201
We have observed two low concentration Galactic globular clusters with the
X-ray observatory XMM-Newton. We detect 47 faint X-ray sources in the direction
of M 55 and 62 in the field of view of NGC 3201. Using the statistical Log
N-Log S relationship of extragalactic sources derived from XMM-Newton Lockman
Hole observations, to estimate the background source population, we estimate
that very few of the sources (1.5+/-1.0) in the field of view of M 55 actually
belong to the cluster. These sources are located in the centre of the cluster
as we expect if the cluster has undergone mass segregation. NGC 3201 has
approximately 15 related sources, which are centrally located but are not
constrained to lie within the half mass radius. The sources belonging to this
cluster can lie up to 5 core radii from the centre of the cluster which could
imply that this cluster has been perturbed. Using X-ray (and optical, in the
case of M 55) colours, spectral and timing analysis (where possible) and
comparing these observations to previous X-ray observations, we find evidence
for sources in each cluster that could be cataclysmic variables, active
binaries, millisecond pulsars and possible evidence for a quiescent low mass
X-ray binary with a neutron star primary, even though we do not expect any such
objects in either of the clusters, due to their low central concentrations. The
majority of the other sources are background sources, such as AGN.Comment: 12 pages, 7 figures, accepted to be published in A&
Globular cluster systems in fossil groups: NGC6482, NGC1132 and ESO306-017
We study the globular cluster (GC) systems in three representative fossil
group galaxies: the nearest (NGC6482), the prototype (NGC1132) and the most
massive known to date (ESO306-017). This is the first systematic study of GC
systems in fossil groups. Using data obtained with the Hubble Space Telescope
Advanced Camera for Surveys in the F475W and F850LP filters, we determine the
GC color and magnitude distributions, surface number density profiles, and
specific frequencies. In all three systems, the GC color distribution is
bimodal, the GCs are spatially more extended than the starlight, and the red
population is more concentrated than the blue. The specific frequencies seem to
scale with the optical luminosities of the central galaxy and span a range
similar to that of the normal bright elliptical galaxies in rich environments.
We also analyze the galaxy surface brightness distributions to look for
deviations from the best-fit S\'ersic profiles; we find evidence of recent
dynamical interaction in all three fossil group galaxies. Using X-ray data from
the literature, we find that luminosity and metallicity appear to correlate
with the number of GCs and their mean color, respectively. Interestingly,
although NGC6482 has the lowest mass and luminosity in our sample, its GC
system has the reddest mean color, and the surrounding X-ray gas has the
highest metallicity.Comment: 16 pages, 13 figures. Accepted for publication in A&
The Physical Origins of The Morphology-Density Relation: Evidence for Gas Stripping from the SDSS
We provide a physical interpretation and explanation of the
morphology-density relation for galaxies, drawing on stellar masses, star
formation rates, axis ratios and group halo masses from the Sloan Digital Sky
Survey. We first re-cast the classical morphology-density relation in more
quantitative terms, using low star formation rate (quiescence) as a proxy for
early-type morphology and dark matter halo mass from a group catalog as a proxy
for environmental density: for galaxies of a given stellar mass the quiescent
fraction is found to increase with increasing dark matter halo mass. Our novel
result is that - at a given stellar mass - quiescent galaxies are significantly
flatter in dense environments, implying a higher fraction of disk galaxies.
Supposing that the denser environments differ simply by a higher incidence of
quiescent disk galaxies that are structurally similar to star-forming disk
galaxies of similar mass, explains simultaneously and quantitatively these
quiescence -nvironment and shape-environment relations. Our findings add
considerable weight to the slow removal of gas as the main physical driver of
the morphology-density relation, at the expense of other explanations.Comment: published in ApJ: http://adsabs.harvard.edu/abs/2010ApJ...714.1779
"Safe" Coulomb Excitation of 30Mg
We report on the first radioactive beam experiment performed at the recently
commissioned REX-ISOLDE facility at CERN in conjunction with the highly
efficient gamma spectrometer MINIBALL. Using 30Mg ions accelerated to an energy
of 2.25 MeV/u together with a thin nat-Ni target, Coulomb excitation of the
first excited 2+ states of the projectile and target nuclei well below the
Coulomb barrier was observed. From the measured relative de-excitation gamma
ray yields the B(E2; 0+ -> 2+) value of 30Mg was determined to be 241(31)
e2fm4. Our result is lower than values obtained at projectile fragmentation
facilities using the intermediate-energy Coulomb excitation method, and
confirms the theoretical conjecture that the neutron-rich magnesium isotope
30Mg lies still outside the ``island of inversion''
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