662 research outputs found
How agency models inspire large scale participatory planning and its evaluation
International audienceWe describe how three models, for sustainable change, human agency in collective resource management, and socio-environmental systems, have been used to design a protocol and the tools for a large scale (1500 participants, 35 villages) multi-level participatory process held in Africa for Integrated Natural Resource Management, through the European Project Afromaison. The process especially combines a common action model to support proposals by stakeholders, an integration matrix to build coherent plans, a role playing game design process, and a method to combine planning and playing to engage into the plans. It has also inspired the design of the attached monitoring and evaluation process. We describe the process in two countries, Ethiopia and Uganda, present the theoretical bases of the evaluation framework using the ENCORE paradigm and the implemented methodology transferred to local evaluators. We introduce some results and propose comments on potential learning back to the modelling community
Identification of target-specific bioisosteric fragments from ligand-protein crystallographic data
Bioisosteres are functional groups or atoms that are structurally different but that can form similar intermolecular interactions. Potential bioisosteres were identified here from analysing the X-ray crystallographic structures for sets of different ligands complexed with a fixed protein. The protein was used to align the ligands with each other, and then pairs of ligands compared to identify substructural features with high volume overlap that occurred in approximately the same region of geometric space. The resulting pairs of substructural features can suggest potential bioisosteric replacements for use in lead-optimisation studies. Experiments with 12 sets of ligand-protein complexes from the Protein Data Bank demonstrate the effectiveness of the procedure
The role of angiography in the congruence of cardiovascular measurements between autopsy and postmortem imaging.
Postmortem CT angiography is the method of choice for the postmortem imaging investigations of the cardiovascular (CV) system. However, autopsy still remains the gold standard for CV measurement. Nevertheless, there are not any studies on CV measurements on the multi-phase postmortem angiography (MPMCTA) which includes comparisons with autopsy. Therefore, the aim of this study is to compare CV measurements between the native CT scan and the three phases of the MPMCTA to find out which of these modalities correlate the best with autopsy measurements.
For this study, we selected retrospectively 50 postmortem cases that underwent both MPMCTA and autopsy. A comparison was carried out between the CV measurements obtained with imaging (aorta; heart cavities and cardiac wall thicknesses; maximum cardiac diameter and cardiothoracic ratio) and at the autopsy (aorta; cardiac valves, ventricular thicknesses, and weight).
Our results show that the dynamic phase displays an advantage for the measurement of the aortas. However, the MPMCTA is not accurate to measure the cardiac wall thicknesses. The measurements of the heart cavities show no correlation with the heart valves. The cardiothoracic ratio measured by the MPMCTA shows no correlation with the heart weight. Nevertheless, the maximum cardiac diameter exhibits a correlation with the latter on the venous and dynamic phase.
These results show that only few CV parameters measured with imaging correlate with measurement obtained at the autopsy. These results indicate that in order to better estimate values obtained at the autopsy, we need to define new reference values for the CV measurement on MPMCTA
Fancine 2003, n. 08
Abstract not availabl
No thick carbon dioxide atmosphere on the rocky exoplanet TRAPPIST-1 c
Seven rocky planets orbit the nearby dwarf star TRAPPIST-1, providing a
unique opportunity to search for atmospheres on small planets outside the Solar
System (Gillon et al., 2017). Thanks to the recent launch of JWST, possible
atmospheric constituents such as carbon dioxide (CO2) are now detectable
(Morley et al., 2017, Lincowski et al., 2018}. Recent JWST observations of the
innermost planet TRAPPIST-1 b showed that it is most probably a bare rock
without any CO2 in its atmosphere (Greene et al., 2023). Here we report the
detection of thermal emission from the dayside of TRAPPIST-1 c with the
Mid-Infrared Instrument (MIRI) on JWST at 15 micron. We measure a
planet-to-star flux ratio of fp/fs = 421 +/- 94 parts per million (ppm) which
corresponds to an inferred dayside brightness temperature of 380 +/- 31 K. This
high dayside temperature disfavours a thick, CO2-rich atmosphere on the planet.
The data rule out cloud-free O2/CO2 mixtures with surface pressures ranging
from 10 bar (with 10 ppm CO2) to 0.1 bar (pure CO2). A Venus-analogue
atmosphere with sulfuric acid clouds is also disfavoured at 2.6 sigma
confidence. Thinner atmospheres or bare-rock surfaces are consistent with our
measured planet-to-star flux ratio. The absence of a thick, CO2-rich atmosphere
on TRAPPIST-1 c suggests a relatively volatile-poor formation history, with
less than 9.5 +7.5 -2.3 Earth oceans of water. If all planets in the system
formed in the same way, this would indicate a limited reservoir of volatiles
for the potentially habitable planets in the system.Comment: Published in Nature on June 19th. 2023, 10 figures, 4 table
An eclipsing substellar binary in a young triple system discovered by SPECULOOS
Mass, radius, and age are three of the most fundamental parameters for
celestial objects, enabling studies of the evolution and internal physics of
stars, brown dwarfs, and planets. Brown dwarfs are hydrogen-rich objects that
are unable to sustain core fusion reactions but are supported from collapse by
electron degeneracy pressure. As they age, brown dwarfs cool, reducing their
radius and luminosity. Young exoplanets follow a similar behaviour. Brown dwarf
evolutionary models are relied upon to infer the masses, radii and ages of
these objects. Similar models are used to infer the mass and radius of directly
imaged exoplanets. Unfortunately, only sparse empirical mass, radius and age
measurements are currently available, and the models remain mostly unvalidated.
Double-line eclipsing binaries provide the most direct route for the absolute
determination of the masses and radii of stars. Here, we report the SPECULOOS
discovery of 2M1510A, a nearby, eclipsing, double-line brown dwarf binary, with
a widely-separated tertiary brown dwarf companion. We also find that the system
is a member of the Myr-old moving group, Argus. The system's age
matches those of currently known directly-imaged exoplanets. 2M1510A provides
an opportunity to benchmark evolutionary models of brown dwarfs and young
planets. We find that widely-used evolutionary models do reproduce the mass,
radius and age of the binary components remarkably well, but overestimate the
luminosity by up to 0.65 magnitudes, which could result in underestimated
photometric masses for directly-imaged exoplanets and young field brown dwarfs
by 20 to 35%
Ruelle–Takens–Newhouse scenario in reaction-diffusion-convection system
Direct numerical simulations of the transition process from periodic to chaotic dynamics are presented for two variable Oregonator-diffusion model coupled with convection. Numerical solutions to the corresponding reaction-diffusion-convection system of equations show that natural convection can change in a qualitative way, the evolution of concentration distribution, as compared with convectionless conditions. The numerical experiments reveal distinct bifurcations as the Grashof number is increased. A transition to chaos similar to Ruelle-Takens-Newhouse scenario is observed. Numerical results are in agreement with the experiments
SPECULOOS: a network of robotic telescopes to hunt for terrestrial planets around the nearest ultracool dwarfs
We present here SPECULOOS, a new exoplanet transit search based on a network
of 1m-class robotic telescopes targeting the 1200 ultracool (spectral
type M7 and later) dwarfs bright enough in the infrared (-mag )
to possibly enable the atmospheric characterization of temperate terrestrial
planets with next-generation facilities like the . The ultimate goals of the project are to reveal the frequency of
temperate terrestrial planets around the lowest-mass stars and brown dwarfs, to
probe the diversity of their bulk compositions, atmospheres and surface
conditions, and to assess their potential habitability.Comment: 21 pages, 13 figures, 1 table. Proceedings of SPI
Development of the SPECULOOS exoplanet search project
SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) aims to
perform a transit search on the nearest (pc) ultracool (K) dwarf
stars. The project's main motivation is to discover potentially habitable
planets well-suited for detailed atmospheric characterisation with upcoming
giant telescopes, like the James Webb Space Telescope (JWST) and European Large
Telescope (ELT). The project is based on a network of 1m robotic telescopes,
namely the four ones of the SPECULOOS-Southern Observatory (SSO) in Cerro
Paranal, Chile, one telescope of the SPECULOOS-Northern Observatory (SNO) in
Tenerife, and the SAINT-Ex telescope in San Pedro M\'artir, Mexico. The
prototype survey of the SPECULOOS project on the 60~cm TRAPPIST telescope
(Chile) discovered the TRAPPIST-1 system, composed of seven temperate
Earth-sized planets orbiting a nearby (12~pc) Jupiter-sized star. In this
paper, we review the current status of SPECULOOS, its first results, the plans
for its development, and its connection to the Transiting Exoplanet Survey
Satellite (TESS) and JWST
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