1,678 research outputs found
IMPACT OF PERSISTENT ENDOTRACHEAL TUBE BIOFILM ON VENTILATOR-ASSOCIATED PNEUMONIA CLINICAL AND MICROBIOLOGICAL RESPONSE
Fossil Groups Origins: I. RX J105453.3+552102 a very massive and relaxed system at z~0.5
The most accepted scenario for the origin of fossil groups (FGs) is that they
are galaxy associations in which the merging rate was fast and efficient. These
systems have assembled half of their mass at early epoch of the Universe,
subsequently growing by minor mergers. They could contain a fossil record of
the galaxy structure formation. We have started a project in order to
characterize a large sample of FGs. In this paper we present the analysis of
the fossil system RX J105453.3+552102. Optical deep images were used for
studying the properties of the brightest group galaxy and for computing the
photometric luminosity function of the group. We have also performed a detail
dynamical analysis of the system based on redshift data for 116 galaxies. This
galaxy system is located at z=0.47, and shows a quite large line-of-sight
velocity dispersion \sigma_{v}~1000 km/s. Assuming the dynamical equilibrium,
we estimated a virial mass of M ~ 10^{15} h_{70} M_{\odot}. No evidence of
substructure was found within 1.4 Mpc radius. We found a statistically
significant departure from Gaussianity of the group members velocities in the
most external regions of the group. This could indicate the presence of
galaxies in radial orbits in the external region of the group. We also found
that the photometrical luminosity function is bimodal, showing a lack of M_{r}
~ -19.5 galaxies. The brightest group galaxy shows low Sersic parameter (n~2)
and a small peculiar velocity. Indeed, our accurate photometry shows that the
difference between the brightest and the second brightest galaxies is 1.9 mag
in the r-band, while the classical definition of FGs is based on a magnitude
gap of 2. We conclude that this fossil system does not follow the empirical
definition of FGs. Nevertheless, it is a massive, old and undisturbed galaxy
system with little infall of L^{*} galaxies since its initial collapse.Comment: 17 pages, 14 figures, accepted for publication at A&
Multi-Wavelength Observations of the Blazar 1ES 1011+496 in Spring 2008
The BL Lac object 1ES 1011+496 was discovered at Very High Energy gamma-rays
by MAGIC in spring 2007. Before that the source was little studied in different
wavelengths. Therefore a multi-wavelength (MWL) campaign was organized in
spring 2008. Along MAGIC, the MWL campaign included the Metsahovi radio
observatory, Bell and KVA optical telescopes and the Swift and AGILE
satellites. MAGIC observations span from March to May, 2008 for a total of 27.9
hours, of which 19.4 hours remained after quality cuts. The light curve showed
no significant variability. The differential VHE spectrum could be described
with a power-law function. Both results were similar to those obtained during
the discovery. Swift XRT observations revealed an X-ray flare, characterized by
a harder when brighter trend, as is typical for high synchrotron peak BL Lac
objects (HBL). Strong optical variability was found during the campaign, but no
conclusion on the connection between the optical and VHE gamma-ray bands could
be drawn. The contemporaneous SED shows a synchrotron dominated source, unlike
concluded in previous work based on nonsimultaneous data, and is well described
by a standard one zone synchrotron self Compton model. We also performed a
study on the source classification. While the optical and X-ray data taken
during our campaign show typical characteristics of an HBL, we suggest, based
on archival data, that 1ES 1011+496 is actually a borderline case between
intermediate and high synchrotron peak frequency BL Lac objects.Comment: 13 pages, accepted for publication in MNRA
The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in
the Canary island of La Palma, Spain. During summer 2011 and 2012 it underwent
a series of upgrades, involving the exchange of the MAGIC-I camera and its
trigger system, as well as the upgrade of the readout system of both
telescopes. We use observations of the Crab Nebula taken at low and medium
zenith angles to assess the key performance parameters of the MAGIC stereo
system. For low zenith angle observations, the standard trigger threshold of
the MAGIC telescopes is ~50GeV. The integral sensitivity for point-like sources
with Crab Nebula-like spectrum above 220GeV is (0.66+/-0.03)% of Crab Nebula
flux in 50 h of observations. The angular resolution, defined as the sigma of a
2-dimensional Gaussian distribution, at those energies is < 0.07 degree, while
the energy resolution is 16%. We also re-evaluate the effect of the systematic
uncertainty on the data taken with the MAGIC telescopes after the upgrade. We
estimate that the systematic uncertainties can be divided in the following
components: < 15% in energy scale, 11-18% in flux normalization and +/-0.15 for
the energy spectrum power-law slope.Comment: 21 pages, 25 figures, accepted for publication in Astroparticle
Physic
Probing the very-high-energy gamma-ray spectral curvature in the blazar PG 1553+113 with the MAGIC telescopes
PG 1553+113 is a very-high-energy (VHE, ) -ray
emitter classified as a BL Lac object. Its redshift is constrained by
intergalactic absorption lines in the range . The MAGIC telescopes
have monitored the source's activity since 2005. In early 2012, PG 1553+113 was
found in a high-state, and later, in April of the same year, the source reached
its highest VHE flux state detected so far. Simultaneous observations carried
out in X-rays during 2012 April show similar flaring behaviour. In contrast,
the -ray flux at observed by Fermi-LAT is
compatible with steady emission. In this paper, a detailed study of the flaring
state is presented. The VHE spectrum shows clear curvature, being well fitted
either by a power law with an exponential cut-off or by a log-parabola. A
simple power-law fit hypothesis for the observed shape of the PG 1553+113 VHE
-ray spectrum is rejected with a high significance (fit probability
P=2.6 ). The observed curvature is compatible with the
extragalactic background light (EBL) imprint predicted by current generation
EBL models assuming a redshift . New constraints on the redshift are
derived from the VHE spectrum. These constraints are compatible with previous
limits and suggest that the source is most likely located around the optical
lower limit, , based on the detection of Ly absorption. Finally,
we find that the synchrotron self-Compton (SSC) model gives a satisfactory
description of the observed multi-wavelength spectral energy distribution
during the flare.Comment: 13 pages, 7 figures, accepted for publication in MNRA
Fossil groups origins II. Unveiling the formation of the brightest group galaxies through their scaling relations
(Abridged) Fossil systems are galaxy associations dominated by a relatively
isolated, bright elliptical galaxy, surrounded by a group of smaller galaxies
lacking L* objects. We analyzed the near-infrared photometric and structural
properties of a sample of 20 BGGs present in FGs in order to better understand
their formation mechanisms. Their surface-brightness distribution was fitted to
a Sersic profile using the GASP2D algorithm. Then, the standard scaling
relations were derived for the first time for these galaxies and compared with
those of normal ellipticals and brightest cluster galaxies in non-fossil
systems. The BGGs presented in this study represent a subset of the most
massive galaxies in the Universe. We found that their ellipticity profiles are
continuously increasing with the galactocentric radius. Our fossil BCGs follow
closely the fundamental plane described by normal ellipticals. However, they
depart from both the log \sigma_0 vs. log L_{K_{s}} and log r_{\rm e} vs. log
L_{K_{s}} relations described by intermediate mass ellipticals. This occurs in
the sense that our BGGs have larger effective radii and smaller velocity
dispersions than those predicted by these relations. We also found that more
elliptical galaxies systematically deviate from the previous relations while
more rounder object do not. No similar correlation was found with the Sersic
index. The derived scaling relations can be interpreted in terms of the
formation scenario of the BGGs. Because our BGGs follow the fundamental plane
tilt but they have larger effective radii than expected for intermediate mass
ellipticals, we suggest that they only went through dissipational mergers in a
early stage of their evolution and then assembled the bulk of their mass
through subsequent dry mergers, contrary to previous claims that BGGs in FGs
were formed mainly by the merging of gas-rich galaxies.Comment: 16 pages, 10 figures, accepted for publication at A&
Expression of AMPA and NMDA receptor subunits in the cervical spinal cord of wobbler mice
BACKGROUND: The localisation of AMPA and NMDA receptor subunits was studied in a model of degeneration of cervical spinal motoneurons, the wobbler mouse. Cervical regions from early or late symptomatic wobbler mice (4 or 12 weeks of age) were compared to lumbar tracts (unaffected) and to those of healthy mice. RESULTS: No differences were found in the distribution of AMPA and NMDA receptor subunits at both ages. Western blots analysis showed a trend of reduction in AMPA and NMDA receptor subunits, mainly GluR1 and NR2A, exclusively in the cervical region of late symptomatic mice in the triton-insoluble post-synaptic fraction but not whole homogenates. Colocalisation experiments evidenced the expression of GluR1 and NR2A receptors in activated astrocytes from the cervical spinal cord of wobbler mice, GluR2 did not colocalise with GFAP positive cells. No differences were found in the expression of AMPA and NMDA receptor subunits in the lumbar tract of wobbler mice, where neither motoneuron loss nor reactive gliosis occurs. CONCLUSION: In late symptomatic wobbler mice altered levels of GluR1 and NR2A receptor subunits may be a consequence of motoneuron loss rather than an early feature of motoneuron vulnerability
Effective Rheology of Bubbles Moving in a Capillary Tube
We calculate the average volumetric flux versus pressure drop of bubbles
moving in a single capillary tube with varying diameter, finding a square-root
relation from mapping the flow equations onto that of a driven overdamped
pendulum. The calculation is based on a derivation of the equation of motion of
a bubble train from considering the capillary forces and the entropy production
associated with the viscous flow. We also calculate the configurational
probability of the positions of the bubbles.Comment: 4 pages, 1 figur
Tumour compartment transcriptomics demonstrates the activation of inflammatory and odontogenic programmes in human adamantinomatous craniopharyngioma and identifies the MAPK/ERK pathway as a novel therapeutic target
Adamantinomatous craniopharyngiomas (ACPs) are clinically challenging tumours, the majority of which have activating mutations in CTNNB1. They are histologically complex, showing cystic and solid components, the latter comprised of different morphological cell types (e.g. β-catenin-accumulating cluster cells and palisading epithelium), surrounded by a florid glial reaction with immune cells. Here, we have carried out RNA sequencing on 18 ACP samples and integrated these data with an existing ACP transcriptomic dataset. No studies so far have examined the patterns of gene expression within the different cellular compartments of the tumour. To achieve this goal, we have combined laser capture microdissection with computational analyses to reveal groups of genes that are associated with either epithelial tumour cells (clusters and palisading epithelium), glial tissue or immune infiltrate. We use these human ACP molecular signatures and RNA-Seq data from two ACP mouse models to reveal that cell clusters are molecularly analogous to the enamel knot, a critical signalling centre controlling normal tooth morphogenesis. Supporting this finding, we show that human cluster cells express high levels of several members of the FGF, TGFB and BMP families of secreted factors, which signal to neighbouring cells as evidenced by immunostaining against the phosphorylated proteins pERK1/2, pSMAD3 and pSMAD1/5/9 in both human and mouse ACP. We reveal that inhibiting the MAPK/ERK pathway with trametinib, a clinically approved MEK inhibitor, results in reduced proliferation and increased apoptosis in explant cultures of human and mouse ACP. Finally, we analyse a prominent molecular signature in the glial reactive tissue to characterise the inflammatory microenvironment and uncover the activation of inflammasomes in human ACP. We validate these results by immunostaining against immune cell markers, cytokine ELISA and proteome analysis in both solid tumour and cystic fluid from ACP patients. Our data support a new molecular paradigm for understanding ACP tumorigenesis as an aberrant mimic of natural tooth development and opens new therapeutic opportunities by revealing the activation of the MAPK/ERK and inflammasome pathways in human ACP.
KEYWORDS:
Craniopharyngioma; IL1-β; Inflammasome; MAPK/ERK pathway; Odontogenesis; Paracrine signalling; Trametini
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