3,546 research outputs found
Comparative genomic analysis and molecular examination of the diversity of enterotoxigenic Escherichia coli isolates from Chile
Enterotoxigenic Escherichia coli (ETEC) is one of the most common diarrheal pathogens in the low- and middle-income regions of the world, however a systematic examination of the genomic content of isolates from Chile has not yet been undertaken. Whole genome sequencing and comparative analysis of a collection of 125 ETEC isolates from three geographic locations in Chile, allowed the interrogation of phylogenomic groups, sequence types and genes specific to isolates from the different geographic locations. A total of 80.8% (101/125) of the ETEC isolates were identified in E. coli phylogroup A, 15.2% (19/125) in phylogroup B, and 4.0% (5/125) in phylogroup E. The over-representation of genomes in phylogroup A was significantly different from other global ETEC genomic studies. The Chilean ETEC isolates could be further subdivided into sub-clades similar to previously defined global ETEC reference lineages that had conserved multi-locus sequence types and toxin profiles. Comparison of the gene content of the Chilean ETEC identified genes that were unique based on geographic location within Chile, phylogenomic classifications or sequence type. Completion of a limited number of genomes provided insight into the ETEC plasmid content, which is conserved in some phylogenomic groups and not conserved in others. These findings suggest that the Chilean ETEC isolates contain unique virulence factor combinations and genomic content compared to global reference ETEC isolates
Evidence for mechanisms underlying the functional benefits of a myocardial matrix hydrogel for post-MI treatment
Background There is increasing need for better therapies to prevent the development of heart failure after myocardial infarction (MI). An injectable hydrogel derived from decellularized porcine ventricular myocardium has been shown to halt the post-infarction progression of negative left ventricular remodeling and decline in cardiac function in both small and large animal models. Objectives This study sought to elucidate the tissue-level mechanisms underlying the therapeutic benefits of myocardial matrix injection. Methods Myocardial matrix or saline was injected into infarcted myocardium 1 week after ischemia-reperfusion in Sprague-Dawley rats. Cardiac function was evaluated by magnetic resonance imaging and hemodynamic measurements at 5 weeks after injection. Whole transcriptome microarrays were performed on RNA isolated from the infarct at 3 days and 1 week after injection. Quantitative polymerase chain reaction and histologic quantification confirmed expression of key genes and their activation in altered pathways. Results Principal component analysis of the transcriptomes showed that samples collected from myocardial matrix-injected infarcts are distinct and cluster separately from saline-injected control subjects. Pathway analysis indicated that these differences are due to changes in several tissue processes that may contribute to improved cardiac healing after MI. Matrix-injected infarcted myocardium exhibits an altered inflammatory response, reduced cardiomyocyte apoptosis, enhanced infarct neovascularization, diminished cardiac hypertrophy and fibrosis, altered metabolic enzyme expression, increased cardiac transcription factor expression, and progenitor cell recruitment, along with improvements in global cardiac function and hemodynamics. Conclusions These results indicate that the myocardial matrix alters several key pathways after MI creating a pro-regenerative environment, further demonstrating its promise as a potential post-MI therapy
No evidence for an Eddington-ratio dependence of X-ray weakness in BALQSOs
Several works have studied the relation between X-ray, UV, and wind
properties in broad absorption line quasars (BALQSOs), generally concluding
that the formation of strong winds is tightly connected with the suppression of
the ionizing EUV/X-ray emission. The Eddington ratio (), which
measures the accretion rate, is also known to be related with outflow and
emission-line properties in the general quasar population. Moreover, models
describing quasar accretion depend on , which can thus possibly
affect the relative production of accelerating UV and ionizing EUV/X-ray
radiation. In this work, for the first time, we investigated whether BALQSO
X-ray properties are related with the Eddington ratio. We selected a sample of
30 BALQSOs with accurate measurements of black-hole mass and BAL properties
from the literature, and we complemented it with 4 additional BALQSOs we
observed with \xmm\, to populate the low and high Eddington-ratio regimes. We
did not find evidence for a strong relation between and X-ray
suppression, which however shows a significant correlation with the strength of
the UV absorption features. These findings are confirmed also by considering a
sample of mini-BALQSOs collected from the literature.Comment: 8 pages, 2 figures, Accepted 2018 June 29. Received 2018 June 29; in
original form 2018 April 2
Piercing Through Highly Obscured and Compton-thick AGNs in the Chandra Deep Fields: I. X-ray Spectral and Long-term Variability Analyses
We present a detailed X-ray spectral analysis of 1152 AGNs selected in the
Chandra Deep Fields (CDFs), in order to identify highly obscured AGNs (). By fitting spectra with physical models, 436 (38%)
sources with are confirmed to be highly
obscured, including 102 Compton-thick (CT) candidates. We propose a new
hardness-ratio measure of the obscuration level which can be used to select
highly obscured AGN candidates. The completeness and accuracy of applying this
method to our AGNs are 88% and 80%, respectively. The observed logN-logS
relation favors cosmic X-ray background models that predict moderate (i.e.,
between optimistic and pessimistic) CT number counts. 19% (6/31) of our highly
obscured AGNs that have optical classifications are labeled as broad-line AGNs,
suggesting that, at least for part of the AGN population, the heavy X-ray
obscuration is largely a line-of-sight effect, i.e., some high-column-density
clouds on various scales (but not necessarily a dust-enshrouded torus) along
our sightline may obscure the compact X-ray emitter. After correcting for
several observational biases, we obtain the intrinsic NH distribution and its
evolution. The CT-to-highly-obscured fraction is roughly 52% and is consistent
with no evident redshift evolution. We also perform long-term (~17 years in the
observed frame) variability analyses for 31 sources with the largest number of
counts available. Among them, 17 sources show flux variabilities: 31% (5/17)
are caused by the change of NH, 53% (9/17) are caused by the intrinsic
luminosity variability, 6% (1/17) are driven by both effects, and 2 are not
classified due to large spectral fitting errors.Comment: 32 pages, 21 figures, 9 tables, accepted for publication in Ap
Assessment of the Contribution of Polarimetric Persistent Scatterer Interferometry on Sentinel-1 Data
Time series of Sentinel-1 data are widely used for monitoring displacements of the Earth surface using persistent scatterer interferometry. By default over land, Sentinel-1 images include two polarimetric channels: VV and VH. However, most works in this application exploit only the VV channel, whereas the VH channel is discarded for its lower amplitude. Thanks to the development of polarimetric persistent scatterer interferometry methods, one can integrate multi-polarisation channels into a single optimal one. Previous studies proved that the number and spatial density of measurement points is increased. In this work, we explore the reason why the VH channel increases the number of measurement points when using the amplitude dispersion ( DA ) as selection criterion. Results obtained over three geographical locations show that the VH channel helps in two ways. In first place, the mean amplitude is increased for targets which have higher amplitude in VH channel, usually associated with rotated elements in the scene. In second place, and more importantly, the amplitude dispersion is decreased over many areas for which the VV channel exhibits fluctuations and peaks. Thanks to the insensitivity of the VH channel to these scene changes, it provides additional measurement points which are reliable despite their low amplitude. The increment of measurement points not only extends the spatial density and enables the detection of active deformation areas not found in the VV results, but also provides more accurate results than only using the VV channel, thanks to the increased density of points, which helps the deformation estimation.This work was supported by the Spanish Ministry of Science and Innovation (State Agency of Research, AEI) and the European Funds for Regional Development (EFRD) under Projects PID2020-117303GB-C21 and PID2020-117303GB-C22. The research was carried out partially in the framework of the ESA-MOST China DRAGON-5 project with ref. 59339
Nonlinear dynamics of asymmetric bistable energy harvesters
The paper investigates asymmetries effects over a nonlinear vibration energy
harvester dynamics. The asymmetric system performance is compared with
symmetric ones. Different asymmetry levels on restoring force and gravity
action are investigated from a system-sloping angle variation. Bifurcation
diagrams and basins of attraction are used to examine the local and global
characteristics underlying dynamical systems under different excitation energy.
The results show the adverse effects of asymmetries on system dynamics. They
also reveal ways to overcome them by canceling asymmetric influence from
optimal sloping angle values and improving asymmetric system performance over
symmetrical ones. This comprehensive numerical study provides novel valuable
insights into asymmetrical energy harvester dynamics, a wide and still less
explored topic
A Systemic Assessment of the European Offshore Wind Innovation: Insights from the Netherlands, Denmark, Germany and the United Kingdom
The development and diffusion of offshore wind energy technology is important for European energy policy. However, the large potential does not automatically lead to a large share in future energy systems; neither does an emergent stage of technological development automatically lead to success for companies and the related economic growth and growth in employment. Recent insights in innovation studies suggest that the success chances of technological innovations are, to a large extent, determined by how the surrounding system (the innovation system) is built up and how it functions. Many innovation systems are characterized by flaws that hamper the development and diffusion of innovations. These flaws are often labelled as system problems or system challenges. Intelligent innovation policy therefore evaluates how innovation systems are functioning, tries to create insight into the systems’ challenges and develops policies accordingly. This report assesses the European offshore wind innovation system based on insights from four countries: Denmark, the UK, the Netherlands and Germany. We use the Technological Innovation System (TIS) approach to analyse the state and functioning of the system at the end of 2011. Based on the analysis we identify four types of systemic challenges: (i) actor-related such as deficiency of engineers; (ii) institutional, e.g. non-aligned national regulatory frameworks; (iii) interaction-related like poor transferability of scientific knowledge to specific contexts of application and; (iv) infrastructural such as poor grid infrastructure. We suggest the challenges require a systemic, coordinated policy effort at a European level if the system is expected to contribute to the goals of climate change reduction and stimulation of green growth.JRC.F.6-Energy systems evaluatio
Formas de energia mínima na representação de sistemas lineares como grafos
International audienc
The X-ray properties of quasars: no evident evolution of accretion physics in the first Gyr of the Universe
X-ray emission from QSOs has been used to assess SMBH accretion properties up
to ~6. However, at only ~15 QSOs are covered by sensitive X-ray
observations, preventing a statistically significant investigation of the X-ray
properties of QSOs in the first Gyr of the Universe. We present new Chandra
observations of 10 QSOs, selected to have virial black-hole mass
estimates from Mg II line spectroscopy. Adding archival X-ray data for an
additional 15 QSOs, we investigate the X-ray properties of the QSO
population in the first Gyr of the Universe, focusing in particular on the
relation, which is traced by the parameter, and
the shape of their X-ray spectra. We performed photometric analyses to derive
estimates of the X-ray luminosities, and thus the values and
bolometric corrections (). We compared the resulting
and distributions with the results found for QSO
samples at lower redshift. Finally, we performed a basic X-ray spectral
analysis of the brightest QSOs to derive their individual photon indices,
and joint spectral analysis of the whole sample to estimate the average photon
index. We confirm a lack of significant evolution of with
redshift, extending the results from previous works up to , and the trend
of an increasing bolometric correction with increasing luminosity found for
QSOs at lower redshifts. The average power-law photon index of our sample
( and for sources
with net counts, respectively) is slightly steeper than, but
still consistent with, typical QSOs at . All these results point toward
a lack of substantial evolution of the inner accretion-disk/hot-corona
structure in QSOs from low redshift to . Our data hint at generally high
Eddington ratios at .Comment: 15 pages. 10 figures. 7 tables. Accepted for publication in A&
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