306 research outputs found
solar building systems for the mediterranean region research outputs between italy and france
This paper comes from previous investigations carried out by the authors, in France and Italy, and from a cross border cooperation projects based on the joint collaboration between the University of Corsica Pascal Paoli and the University of Genoa. The authors focus on the enhancement of passive solar systems and thermal solar systems, with particular attention to their operation/efficiency and their architectural integration. The exchange between Italian and French experiences, especially between regions with similar climate, can enhance solar building strategies, in accordance with the new European energy standards as well as the Mediterranean climate, the traditional construction technologies and users' needs
Constraining atmospheric parameters and surface magnetic fields with : an application to SPIRou spectra
We report first results on a method aimed at simultaneously characterising
atmospheric parameters and magnetic properties of M dwarfs from high-resolution
nIR spectra recorded with SPIRou in the framework of the SPIRou Legacy Survey.
Our analysis relies on fitting synthetic spectra computed from MARCS model
atmospheres to selected spectral lines, both sensitive and insensitive to
magnetic fields. We introduce a new code, , obtained by
including the Zeeman effect and polarised radiative transfer capabilities to
. We compute a grid of synthetic spectra with
for different magnetic field strengths and develop a
process to simultaneously constrain , , [M/H],
[/Fe] and the average surface magnetic flux. In this paper, we present
our approach and assess its performance using simulations, before applying it
to six targets observed in the context of the SPIRou Legacy Survey (SLS),
namely AU Mic, EV Lac, AD Leo, CN Leo, PM J18482+0741, and DS Leo. Our method
allows us to retrieve atmospheric parameters in good agreement with the
literature, and simultaneously yields surface magnetic fluxes in the range 2-4
kG with a typical precision of 0.05 kG, in agreement with literature estimates,
and consistent with the saturated dynamo regime in which most of these stars
are.Comment: 17 pages plus supplementary material. Accepted for publication in
MNRA
A single zinc finger optimizes the DNA interactions of the nucleocapsid protein of the yeast retrotransposon Ty3
Reverse transcription in retroviruses and retrotransposons requires nucleic acid chaperones, which drive the rearrangement of nucleic acid conformation. The nucleic acid chaperone properties of the human immunodeficiency virus type-1 (HIV-1) nucleocapsid (NC) protein have been extensively studied, and nucleic acid aggregation, duplex destabilization and rapid binding kinetics have been identified as major components of its activity. However, the properties of other nucleic acid chaperone proteins, such as retrotransposon Ty3 NC, a likely ancestor of HIV-1 NC, are not well understood. In addition, it is unclear whether a single zinc finger is sufficient to optimize the properties characteristic of HIV-1 NC. We used single-molecule DNA stretching as a method for detailed characterization of Ty3 NC chaperone activity. We found that wild type Ty3 NC aggregates single- and double-stranded DNA, weakly stabilizes dsDNA, and exhibits rapid binding kinetics. Single-molecule studies in the presence of Ty3 NC mutants show that the N-terminal basic residues and the unique zinc finger at the C-terminus are required for optimum chaperone activity in this system. While the single zinc finger is capable of optimizing Ty3 NC's DNA interaction kinetics, two zinc fingers may be necessary in order to facilitate the DNA destabilization exhibited by HIV-1 NC
Unexpected population fragmentation in an endangered seabird: the case of the Peruvian diving-petrel
In less than one century, the once-abundant Peruvian diving petrel has become the first endangered seabird of the Humboldt Current System (HCS). This small endemic petrel of the South American Pacific coast is now an important indicator of ongoing habitat loss and of the success of local conservation policies in the HCS - an ecoregion designated as a priority for the conservation of global biodiversity. Yet so far, poorly understood life history traits such as philopatry or dispersal ability may strongly influence the species' response to ecosystem changes, but also our capacity to assess and interpret this response. To address this question, we explore the range-wide population structure of the Peruvian diving petrel, and show that this small seabird exhibits extreme philopatric behavior at the island level. Mitochondrial DNA sequences and genome-wide SNP data reveal significant isolation and low migration at very short distances, and provide strong evidence for questioning the alleged recovery in the Peruvian and Chilean populations of this species. Importantly, the full demographic independence between colonies makes local population rescue through migration unlikely. As a consequence, the Peruvian diving petrel appears to be particularly vulnerable to ongoing anthropogenic pressure. By excluding immigration as a major factor of demographic recovery, our results highlight the unambiguously positive impact of local conservation measures on breeding populations; yet at the same time they also cast doubt on alleged range-wide positive population trends. Overall, the protection of independent breeding colonies, and not only of the species as a whole, remains a major element in the conservation strategy for endemic seabirds. Finally, we underline the importance of considering the philopatric behavior and demographic independence of breeding populations, even at very fine spatial scales, in spatial planning for marine coastal areas
: a data-driven approach to correct for systematics in RV data -- Application to SPIRou data of the planet-hosting M dwarf GJ 251
Context: Recent advances in the development of precise radial velocity (RV)
instruments in the near-infrared (nIR) domain, such as SPIRou, have facilitated
the study of M-type stars to more effectively characterize planetary systems.
However, the nIR presents unique challenges in exoplanet detection due to
various sources of planet-independent signals which can result in systematic
errors in the RV data.
Aims: In order to address the challenges posed by the detection of
exoplanetary systems around M-type stars using nIR observations, we introduce a
new data-driven approach for correcting systematic errors in RV data. The
effectiveness of this method is demonstrated through its application to the
star GJ 251.
Methods: Our proposed method, referred to as (Weighted
principAl comPonent analysIs reconsTructIon), uses a dataset of per-line RV
time-series generated by the line-by-line (LBL) algorithm and employs a
weighted principal component analysis (wPCA) to reconstruct the original RV
time-series. A multi-step process is employed to determine the appropriate
number of components, with the ultimate goal of subtracting the wPCA
reconstruction of the per-line RV time-series from the original data in order
to correct systematic errors.
Results: The application of to GJ 251 successfully
eliminates spurious signals from the RV time-series and enables the first
detection in the nIR of GJ 251b, a known temperate super-Earth with an orbital
period of 14.2 days. This demonstrates that, even when systematics in SPIRou
data are unidentified, it is still possible to effectively address them and
fully realize the instrument's capability for exoplanet detection.
Additionally, in contrast to the use of optical RVs, this detection did not
require to filter out stellar activity, highlighting a key advantage of nIR RV
measurements.Comment: Submitted to A&A. For the publicly available Wapiti code, see
https://github.com/HkmMerwan/wapit
Magnetic fields & rotation periods of M dwarfs from SPIRou spectra
We present near-infrared spectropolarimetric observations of a sample of 43
weakly- to moderately-active M dwarfs, carried with SPIRou at the
Canada-France-Hawaii Telescope in the framework of the SPIRou Legacy Survey
from early 2019 to mid 2022. We use the 6700 circularly polarised spectra
collected for this sample to investigate the longitudinal magnetic field and
its temporal variations for all sample stars, from which we diagnose, through
quasi-periodic Gaussian process regression, the periodic modulation and
longer-term fluctuations of the longitudinal field. We detect the large-scale
field for 40 of our 43 sample stars, and infer a reliable or tentative rotation
period for 38 of them, using a Bayesian framework to diagnose the confidence
level at which each rotation period is detected. We find rotation periods
ranging from 14 to over 60d for the early-M dwarfs, and from 70 to 200d for
most mid- and late-M dwarfs (potentially up to 430d for one of them). We also
find that the strength of the detected large-scale fields does not decrease
with increasing period or Rossby number for the slowly rotating dwarfs of our
sample as it does for higher-mass, more active stars, suggesting that these
magnetic fields may be generated through a different dynamo regime than those
of more rapidly rotating stars. We also show that the large-scale fields of
most sample stars evolve on long timescales, with some of them globally
switching sign as stars progress on their putative magnetic cycles.Comment: MNRAS, in press (25 pages, 15 figures, 3 tables
Accurate spectra for high energy ions by advanced time-of-flight diamond-detector schemes in experiments with high energy and intensity lasers
Time-Of-Flight (TOF) methods are very effective to detect particles
accelerated in laser-plasma interactions, but they shows significant
limitations when used in experiments with high energy and intensity lasers,
where both high-energy ions and remarkable levels of ElectroMagnetic Pulses
(EMPs) in the radiofrequency-microwave range are generated. Here we describe a
novel advanced diagnostic method for the characterization of protons
accelerated by intense matter interactions with high-energy and high-intensity
ultra-short laser pulses up to the femtosecond and even future attosecond
range. The method employs a stacked diamond detector structure and the TOF
technique, featuring high sensitivity, high resolution, high radiation hardness
and high signal-to-noise ratio in environments heavily affected by remarkable
EMP fields. A detailed study on the use, the optimization and the properties of
a single module of the stack is here also described for an experiment where a
fast diamond detector is employed in an highly EMP-polluted environment.
Accurate calibrated spectra of accelerated protons are presented from an
experiment with the femtosecond Flame laser (beyond 100 TW power and ~
W/cm intensity) interacting with thin foil targets. The results that can be
readily applied to the case of complex stack configurations and to more general
experimental conditions.Comment: 19 pages, 8 figure
Accurate spectra for high energy ions by advanced time-of-flight diamond-detector schemes in experiments with high energy and intensity lasers
Time-Of-Flight (TOF) methods are very effective to detect particles accelerated in laser-plasma interactions, but they show significant limitations when used in experiments with high energy and intensity lasers, where both high-energy ions and remarkable levels of ElectroMagnetic Pulses (EMPs) in the radiofrequency-microwave range are generated. Here we describe a novel advanced diagnostic method for the characterization of protons accelerated by intense matter interactions with high-energy and high-intensity ultra-short laser pulses up to the femtosecond and even future attosecond range. The method employs a stacked diamond detector structure and the TOF technique, featuring high sensitivity, high resolution, high radiation hardness and high signal-to-noise ratio in environments heavily affected by remarkable EMP fields. A detailed study on the use, the optimization and the properties of a single module of the stack is here described for an experiment where a fast diamond detector is employed in an highly EMP-polluted environment. Accurate calibrated spectra of accelerated protons are presented from an experiment with the femtosecond Flame laser (beyond 100 TW power and ~ 1019 W/cm2 intensity) interacting with thin foil targets. The results can be readily applied to the case of complex stack configurations and to more general experimental conditions
Time-of-flight methodologies with large-area diamond detectors for ion characterization in laser-driven experiments
The time-of-flight technique coupled with semiconductor detectors is a powerful instrument to provide real-time characterization of ions accelerated because of laser-matter interactions. Nevertheless, the presence of strong electromagnetic pulses (EMPs) generated during the interactions can severely hinder its employment. For this reason, the diagnostic system must be designed to have high EMP shielding. Here we present a new advanced prototype of detector, developed at ENEA-Centro Ricerche Frascati (Italy), with a large-area (15 mm × 15 mm) polycrystalline diamond sensor having 150 μm thickness. The tailored detector design and testing ensure high sensitivity and, thanks to the fast temporal response, high-energy resolution of the reconstructed ion spectrum. The detector was offline calibrated and then successfully tested during an experimental campaign carried out at the PHELIX laser facility (100 J, fs, W/cm2) at GSI (Germany). The high rejection to EMP fields was demonstrated and suitable calibrated spectra of the accelerated protons were obtained
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