142 research outputs found
Two phase residence time distribution in a modified twin screw extruder
Biomass fractionation is performed with a modified Clextral twin-screw extruder used as a thermo-mechano-chemical reactor. This new process is firstly analyzed. Visual observations, residence time distributions, and global mass balances are used to obtain information about the process phenomena and their coupling. Residence time distributions (RTD) classical models are adopted to represent the experimental plots. The influence of continuous and discrete process parameters upon the RTD of the solid and liquid phases is analyzed
SPHERE: the exoplanet imager for the Very Large Telescope
Observations of circumstellar environments to look for the direct signal of
exoplanets and the scattered light from disks has significant instrumental
implications. In the past 15 years, major developments in adaptive optics,
coronagraphy, optical manufacturing, wavefront sensing and data processing,
together with a consistent global system analysis have enabled a new generation
of high-contrast imagers and spectrographs on large ground-based telescopes
with much better performance. One of the most productive is the
Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE)
designed and built for the ESO Very Large Telescope (VLT) in Chile. SPHERE
includes an extreme adaptive optics system, a highly stable common path
interface, several types of coronagraphs and three science instruments. Two of
them, the Integral Field Spectrograph (IFS) and the Infra-Red Dual-band Imager
and Spectrograph (IRDIS), are designed to efficiently cover the near-infrared
(NIR) range in a single observation for efficient young planet search. The
third one, ZIMPOL, is designed for visible (VIR) polarimetric observation to
look for the reflected light of exoplanets and the light scattered by debris
disks. This suite of three science instruments enables to study circumstellar
environments at unprecedented angular resolution both in the visible and the
near-infrared. In this work, we present the complete instrument and its on-sky
performance after 4 years of operations at the VLT.Comment: Final version accepted for publication in A&
X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope
X-shooter is the first 2nd generation instrument of the ESO Very Large
Telescope(VLT). It is a very efficient, single-target, intermediate-resolution
spectrograph that was installed at the Cassegrain focus of UT2 in 2009. The
instrument covers, in a single exposure, the spectral range from 300 to 2500
nm. It is designed to maximize the sensitivity in this spectral range through
dichroic splitting in three arms with optimized optics, coatings, dispersive
elements and detectors. It operates at intermediate spectral resolution
(R~4,000 - 17,000, depending on wavelength and slit width) with fixed echelle
spectral format (prism cross-dispersers) in the three arms. It includes a
1.8"x4" Integral Field Unit as an alternative to the 11" long slits. A
dedicated data reduction package delivers fully calibrated two-dimensional and
extracted spectra over the full wavelength range. We describe the main
characteristics of the instrument and present its performance as measured
during commissioning, science verification and the first months of science
operations.Comment: accepted for publication in A&
Use of Arthropod Rarity for Area Prioritisation: Insights from the Azorean Islands
We investigated the conservation concern of Azorean forest fragments and the entire Terceira Island surface using arthropod species vulnerability as defined by the Kattan index, which is based on species rarity. Species rarity was evaluated according to geographical distribution (endemic vs. non endemic species), habitat specialization (distribution across biotopes) and population size (individuals collected in standardized samples). Geographical rarity was considered at ‘global’ scale (species endemic to the Azorean islands) and ‘regional’ scale (single island endemics)
Discovery of a brown dwarf companion to the star HIP 64892
We report the discovery of a bright, brown dwarf companion to the star HIP
64892, imaged with VLT/SPHERE during the SHINE exoplanet survey. The host is a
B9.5V member of the Lower-Centaurus-Crux subgroup of the Scorpius Centaurus OB
association. The measured angular separation of the companion
(") corresponds to a projected distance of AU. We
observed the target with the dual-band imaging and long-slit spectroscopy modes
of the IRDIS imager to obtain its SED and astrometry. In addition, we
reprocessed archival NACO L-band data, from which we also recover the
companion. Its SED is consistent with a young (<30 Myr), low surface gravity
object with a spectral type of M9. From comparison with the
BT-Settl atmospheric models we estimate an effective temperature of
K, and comparison of the companion photometry
to the COND evolutionary models yields a mass of M at
the estimated age of Myr for the system. HIP 64892 is a rare
example of an extreme-mass ratio system () and will be useful for
testing models relating to the formation and evolution of such low-mass
objects.Comment: 12 pages, 11 figures, accepted for publication in A&
The SPHERE infrared survey for exoplanets (SHINE). III. The demographics of young giant exoplanets below 300 au with SPHERE
The SHINE project is a 500-star survey performed with SPHERE on the VLT for
the purpose of directly detecting new substellar companions and understanding
their formation and early evolution. Here we present an initial statistical
analysis for a subsample of 150 stars that are representative of the full SHINE
sample. Our goal is to constrain the frequency of substellar companions with
masses between 1 and 75 MJup and semimajor axes between 5 and 300 au. We adopt
detection limits as a function of angular separation from the survey data for
all stars converted into mass and projected orbital separation using the
BEX-COND-hot evolutionary tracks and known distance to each system. Based on
the results obtained for each star and on the 13 detections in the sample, we
use a MCMC tool to compare our observations to two different types of models.
The first is a parametric model based on observational constraints, and the
second type are numerical models that combine advanced core accretion and
gravitational instability planet population synthesis. Using the parametric
model, we show that the frequencies of systems with at least one substellar
companion are , , and
for BA, FGK, and M stars, respectively. We also
demonstrate that a planet-like formation pathway probably dominates the mass
range from 1-75 MJup for companions around BA stars, while for M dwarfs, brown
dwarf binaries dominate detections. In contrast, a combination of binary
star-like and planet-like formation is required to best fit the observations
for FGK stars. Using our population model and restricting our sample to FGK
stars, we derive a frequency of , consistent with
predictions from the parametric model. More generally, the frequency values
that we derive are in excellent agreement with values obtained in previous
studies.Comment: 24 pages, 14 figures, 3 tables. Accepted for publication in A&
Global Island Monitoring Scheme (GIMS) : a proposal for the long-term coordinated survey and monitoring of native island forest biota
Islands harbour evolutionary and ecologically unique biota, which are currently disproportionately threatened by a multitude of anthropogenic factors, including habitat loss, invasive species and climate change. Native forests on oceanic islands are important refugia for endemic species, many of which are rare and highly threatened. Long-term monitoring schemes for those biota and ecosystems are urgently needed: (i) to provide quantitative baselines for detecting changes within island ecosystems, (ii) to evaluate the effectiveness of conservation and management actions, and (iii) to identify general ecological patterns and processes using multiple island systems as repeated 'natural experiments'. In this contribution, we call for a Global Island Monitoring Scheme (GIMS) for monitoring the remaining native island forests, using bryophytes, vascular plants, selected groups of arthropods and vertebrates as model taxa. As a basis for the GIMS, we also present new, optimized monitoring protocols for bryophytes and arthropods that were developed based on former standardized inventory protocols. Effective inventorying and monitoring of native island forests will require: (i) permanent plots covering diverse ecological gradients (e.g. elevation, age of terrain, anthropogenic disturbance); (ii) a multiple-taxa approach that is based on standardized and replicable protocols; (iii) a common set of indicator taxa and community properties that are indicative of native island forests' welfare, building on, and harmonized with existing sampling and monitoring efforts; (iv) capacity building and training of local researchers, collaboration and continuous dialogue with local stakeholders; and (v) long-term commitment by funding agencies to maintain a global network of native island forest monitoring plots.Peer reviewe
A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)
Meeting abstrac
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