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Temperature-induced mobility in octacalcium phosphate impacts crystal symmetry: water dynamics studied by NMR crystallography
No full textInternational audienceOctacalcium phosphate (OCP, Ca8(PO4)4(HPO4)2$5H2O) is a notable calcium phosphate due to its biocompatibility, making it a widely studied material for bone substitution. It is known to be a precursor of bone mineral, but its role in biomineralisation remains unclear. While the structure of OCP has been the subject of thorough investigations (including using Rietveld refinements of X-ray diffraction data, and NMR crystallography studies), important questions regarding the symmetry and H-bonding network in the material remain. In this study, it is shown that OCP undergoes a lowering of symmetry below 200 K, evidenced by 1 H, 17O, 31P and 43Ca solid-state NMR experiments. Using ab initio molecular-dynamics (MD) simulations and gauge including projected augmented wave (GIPAW) DFT calculations of NMR parameters, the presence of rapid motions of the water molecules in the crystal cell at room temperature is proved. This information leads to an improved description of the OCP structure at both low and ambient temperatures, and helps explain long-standing issues of symmetry. Remaining challenges related to the understanding of the structure of OCP are then discussed
El Niño and droughts in Southeast Asia: A stochastic-chaotic modeling approach
No full textInternational audienceThe El Niño-Southern Oscillation (ENSO) significantly impacts global weather, with strong El Niño events often linked to prolonged dry conditions in Southeast Asia. While some high-impact El Niño events have coincided with prolonged dry conditions, leading to droughts, the underlying causal mechanisms remain complex and inconsistent. In this study, we develop a minimal, datadriven model to quantify the conditions under which ENSO events amplify prolonged dry conditions risk in Southeast Asia. Unlike correlation-based approaches, our model identifies thresholds in sea surface temperatures and atmospheric patterns that increase the probability of prolonged dry conditions, highlighting both seasonal timing and intensity as critical factors. Our results show that when ENSO-induced anomalies exceed specific temperature and atmospheric thresholds, prolonged dry conditions probability rises significantly, aligning with observed historical droughts. Additionally, the model reveals periods where this link weakens due to competing regional climate factors, suggesting that certain conditions mitigate the typical ENSO-prolonged dry conditions connection. These findings provide a more nuanced understanding of ENSO-driven prolonged dry conditions variability, offering a probabilistic predictive framework with potential applications in climate adaptation, agricultural planning, and regional resource management. I. INTRODUCTIONEl Niño-Southern Oscillation (ENSO) is a naturally occurring climate phenomenon that affects weather patterns and precipitation across the globe [1]. ENSO is characterized by the cyclic warming and cooling of the tropical Pacific Ocean, which can lead to a wide range of impacts on global climate. El Niño (i.e. the positive phase of ENSO) which occurs when the sea surface temperature in the central and eastern Pacific is warmer than normal, is one of the most documented phases of ENSO [2].</div
Twelve Years of LabEx PRIMES (2012-2024)
No full textInternational audienceAn overview of the research performed in the Auvergne Rhône Alpes Region within theLaboratoire d’Excellence Physics, Radiobiology, Medical Imaging, and Simulatio
First unambiguous detection of ammonia in the atmosphere of a planetary mass companion with JWST/MIRI coronagraphs
No full textInternational audienceContext. The newly accessible mid-infrared (MIR) window offered by the James Webb Space Telescope (JWST) for exoplanet imaging is expected to provide valuable information to characterize their atmospheres. In particular, coronagraphs on board the JWST Mid-InfraRed instrument (MIRI) are capable of imaging the coldest directly imaged giant planets at the wavelengths where they emit most of their flux. The MIRI coronagraphs have been specially designed to detect the NH3 absorption around 10.5 µm, which has been predicted by atmospheric models and should be detectable for planets colder than 1200 K.Aims. We aim to assess the presence of NH3 while refining the atmospheric parameters of one of the coldest companions detected by directly imaging GJ 504 b. Its mass is still a matter of debate and depending on the host star age estimate, the companion could either be placed in the brown dwarf regime of ∼20 MJup or in the young Jovian planet regime of ∼4 MJup.Methods. We present an analysis of new MIRI observations, using the coronagraphic filters F1065C, F1140C, and F1550C of the GJ 504 system. We took advantage of previous observations of reference stars to build a library of images and to perform a more efficient subtraction of the stellar diffraction pattern. We used an atmospheric grid from the Exo-REM model to refine the atmospheric parameters by combining archival near-infrared (NIR) photometry with the MIR photometry.Results. We detected the presence of NH3 at 12.5 σ and measured its volume mixing ratio of 10−5.3±0.07 in the atmosphere of GJ 504 b. These results are in line with atmospheric model expectations for a planetary-mass object and observed in brown dwarfs within a similar temperature range. The best-fit model with Exo-REM provides updated values of its atmospheric parameters, yielding a temperature of Teff = 512 ± 10 K and radius of R = 1.08−0.03+0.04 RJup.Conclusions. These observations demonstrate the capability of MIRI coronagraphs to detect NH3 and to provide the first MIR observations of one of the coldest directly imaged companions. Overall, NH3 is a key molecule for characterizing the atmospheres of cold planets, offering valuable insights into their surface gravity. These observations provide valuable information for future spectroscopic observations planned with JWST, in particular, with the MIRI medium-resolution spectrometer (MRS), which will allow us to characterize the atmosphere of GJ 504 b in depth
Identification of Gut Biomarkers of FPIES in a Longitudinal Comparative Pediatric Study
No full textInternational audienceFood protein-induced enterocolitis syndrome (FPIES) is a non-IgE-mediated allergy without known biomarkers. We aimed to compare fecal biomarkers related to gut inflammation and immunity in children with FPIES, with resolved FPIES (tolerant), and in matched controls. Methods: Stools were collected from FPIES children on elimination diet, before and after an oral food challenge (OFC) performed to assess their natural tolerance, at the end of a follow-up in tolerant FPIES children, and in matched controls (1:1 ratio). Concentrations of calprotectin, EDN (eosinophilic derived neurotoxin), and secretory IgA (sIgA) underwent comparative paired analysis. Results: Thirty-eight patients were included (age: 1.3 years old, interquartile range: IQR [0.9-2.0]), of which 22 became tolerant during follow-up. Upon inclusion, allergic patients and controls had similar concentrations of calprotectin (38 μg/g [8-85] vs. 27 μg/g [11-46], p = 0.15) and EDN (504 ng/g [275-1252] vs. 516 ng/g [215-844], p = 0.86). However, concentrations of these inflammatory biomarkers increased transiently after a failed OFC (p < 0.001 and p = 0.01 respectively), without correlating with the severity of an allergic reaction. sIgA were higher in allergic than in tolerant patients: 2224 μg/g [878-3529] vs. 794 μg/g [699-1767] (p < 0.01). Calprotectin, EDN, and sIgA were comparable in tolerant patients and controls. sIgA less than 2637 μg/g had a negative predictive value of 75.3% for the differentiation allergic patients from tolerant patients and controls (area under curve: 0.63, 95% CI: 0.52-0.74). Conclusion: A few days after an acute allergic reaction, there was no detectable chronic gut inflammation in FPIES. sIgA may be a useful tool for clinicians in timing OFC
Detecting slow magnetization relaxation via magnetotransport measurements based on the current-reversal method
No full textInternational audienceSlow magnetization relaxation processes are an important time-dependent property of many magnetic materials. We show that magnetotransport measurements based on a well-established current-reversal method can be utilized to implement a simple and robust screening scheme for such relaxation processes. We demonstrate our approach considering the anomalous Hall effect in a Pt/Co/AlOx trilayer model system, and then explore relaxation in τ -MnAl films. Compared to magnetotransport experiments based on ac lock-in techniques, we find that the dc current-reversal method is particulary sensitive to relaxation processes with relaxation time scales on the order of seconds, comparable to the current-reversal measurement time scales
Coupling genetic and demographic data to reveal dispersal processes in emperor penguins
No full textInternational audienceDispersal is an ubiquitous phenomenon that affects the dynamics of the population and the evolution of natural populations; however, it is challenging to measure in most species.Furthermore, the influence of informed dispersal behaviors, referring to the non-random selection of breeding habitats by individuals, on species' responses to rapid global change is substantial but difficult to comprehend.Here, we present a modeling framework to assess the dispersal characteristics and behaviors of a metapopulation, when observations provide information on its neutral genetic structure for a restricted sampling of locations. Our mechanistic-statistical model couples a deterministic model capturing the spatio-temporal dynamics of four genetic clusters across all breeding colonies by integrating demographic processes with genetic projections, with a probabilistic observation model describing the probability to sample an individual from a given genetic cluster.We apply this new framework to the emperor penguin, a species living in Antarctica and currently experiencing habitat loss. The model estimates the species' dispersal distance, rates of emigration, and behaviors associated with dispersal (informed or random). By incorporating these estimations with satellite censuses of breeding colonies, we can identify environmental and demographic factors that influence the { dispersal} of emperor penguins. Finally, we provide new global population forecasts for emperor penguins that can inform conservation actions in Antarctica
Epigenetic control of T-DNA during transgenesis and pathogenesis
No full textInternational audienceMobile elements known as T-DNAs are transferred from pathogenic Agrobacterium to plants and reprogram the host cell to form hairy roots or tumors. Disarmed non-oncogenic T-DNAs are extensively used to deliver transgenes in plant genetic engineering. Such T-DNAs were the first known targets of RNA silencing mechanisms, which detect foreign RNA in plant cells and produce small RNAs that induce transcript degradation. These T-DNAs can also be transcriptionally silenced by the deposition of epigenetic marks such as DNA methylation and the dimethylation of lysine 9 (H3K9me2) in plants. Here, we review the targeting and the roles of RNA silencing and DNA methylation on T-DNAs in transgenic plants as well as during pathogenesis. In addition, we discuss the crosstalk between T-DNAs and genome-wide changes in DNA methylation during pathogenesis. We also cover recently discovered regulatory phenomena, such as T-DNA suppression and RNA silencing-independent and epigenetic-independent mechanisms that can silence T-DNAs. Finally, we discuss the implications of findings on T-DNA silencing for the improvement of plant genetic engineering
General Circulation Models evaluation at different time scales over tropical region using ESA-CCI satellite data records: a case study of water vapour and cloud cover
No full textInternational audienceWater vapour and cloud cover are two essential components of the earth's atmosphere. General circulation models (GCM) are used to study the long term evolution of the Earth's climate over past and future periods. The present work consists of assessing the representation of total column water vapor (TCWV) and total cloud cover (TCC) in the Atmospheric Model Intercomparison Project Phase 6 (AMIP6), the ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF), and satellite data records from the European Space Agency Climate Change Initiative (ESA-CCI). ESA-CCI is used as the reference for the common observation period with AMIP6, spanning from July 2003 to December 2014, to calibrate the framework. For the period prior to the observational period, from January 1981 to June 2003, ERA5 serves as the reference. This study is carried out over the tropical region which has been splitted in two sub-regions: the tropical oceans and tropical lands. The assessment of TCWV and TCC at different time-frequency is performed using a mathematical tool called "multi-resolution analysis" (MRA). By applying the MRA decomposition, we found that the AMIP6 models produce consistent evolution of TCWV and TCC at seasonal to interannual scales (from 2 months to 5.6 years) in the tropical region, even if the representation of the amplitude of TCC remains sometimes challenging. The evaluation of ESA-CCI TCWV and TCC variability in AMIP6 models reveals that the models do not perform well at daily and subseasonal scales. At seasonal to interannual scales, the models reproduce more accurate variability of TCWV and TCC with respect to ESA-CCI. However, AMIP6 models do not capture the trend in the evolution of ESA-CCI TCWV and TCC. The co-variations between TCWV and TCC were analyzed in the Nino3.4 region, revealing a significant positive correlation at the subseasonal scale, with a value of 0.7 for ESA-CCI and 0.3 for AMIP6. At seasonal to annual scales, we found a strong positive correlation between TCWV and TCC, with the exception of the CanESM5 and IPSL models, which showed a negative but significant correlation around -0.5
Nuclear data measurements with a Solid COunter for NEutrons (SCONE)
No full textInternational audienceA new large volume neutron and γ-ray detector is presented. It has been developed for nuclear data measurements, and allows the study of reactions as complex as neutron-induced fission. It is capable of measuring, at the same time, the prompt neutron multiplicity probability densities, the average γ-ray multiplicity and total energy. Its performance is determined through simulations and measurements on 252Cf spontaneous fission (for neutron and γ-ray multiplicities), as well as on 238U neutron-induced fission for the γ-ray calorimetry. •Neutron counters can also perform calorimetry measurements.•When segmented those counters can be used to obtain γ-ray multiplicities.•This lead to correlated measurements of neutron and γ-ray multiplicities and total γ-ray energy