HAL-CEA
Not a member yet
145450 research outputs found
Sort by
Euclid: Star clusters in IC 342, NGC 2403, and Holmberg II
No full textInternational audienceWe examine the star cluster populations in the three nearby (3.20-3.45 Mpc) galaxies IC 342, NGC 2403, and Holmberg II, observed as part of the Euclid Early Release Observations programme. Our main focus in this paper is old globular clusters (GCs), for which the wide field of view and excellent image quality of Euclid offer substantial advantages over previous works. With respect to IC 342, in particular, this is the first study of stellar clusters that goes beyond its nuclear cluster. After a selection process based on size and magnitude criteria, followed by visual inspection, we identified 111 old ( 1 Gyr) GC candidates in IC 342, 49 in NGC 2403 (of which 15 were previously known), along with 7 in Holmberg II. In addition, a number of younger and/or intermediate-age candidates were identified. The colour distributions of GC candidates in the two larger galaxies show hints of bimodality, with peaks at (I E -H E ) 0 = 0.36 and 0.79 in both IC 342 and NGC 2403, corresponding to metallicities of [Fe/H] ≈ -1.5 and [Fe/H] ≈ -0.5. These results are similar to those reported for the metal-poor and metal-rich GC subpopulations in the Milky Way. The luminosity functions of our GC candidates exhibit an excess of relatively faint objects, relative to a canonical, approximately Gaussian GC luminosity function (GCLF). Although some contamination from background galaxies and younger clusters might be present in our GC samples, we argue that the excess could be at least partially real. In particular, we find this could be the case for IC 342, where the excess objects could be similar to those previously identified, for example, in M101 and NGC 6946. The specific frequency of old GCs in IC 342, as determined on the basis of the brighter half of the GCLF, appears to be unusually low with S N ≈ 0.2-0.3. The combined luminosity function of young and intermediate-age clusters in all three galaxies is consistent with a power-law distribution of dN/dL ∝ L -2.3±0.1 . The total numbers of young clusters brighter than M(I E ) = -8 in NGC 2403 and Holmberg II are comparable with those found in their Local Group counterparts, namely, M33 and the Small Magellanic Cloud, respectively.</div
Multifractality in critical neural field dynamics
No full textThe brain criticality hypothesis has largely only characterized brain dynamics in terms of their self-similarity, although experimental evidence suggests that the brain exhibits significant multifractality. To understand how multifractality may emerge in critical-like systems modeling neuronal activity, we used a neural field model exhibiting neural oscillations and a critical phase transition. We find that multifractality emerges near a synchronization phase transition, and that the pattern of variation of multifractality changes when placing the model at a different phase transition. These findings show that multifractality in temporal dynamics emerges near criticality in neural fields, providing a formal basis for interpreting multifractality in brain recordings
Status of ocean observations in the Indian Sector of the Southern Ocean
No full textInternational audienceOne of the largest sectors of the Southern Ocean is the Indian Sector, which plays an important role in regulating the Earth’s climate and supports a diverse ecosystem. To understand how climate change impacts the environment in this sector, ocean observations are collected via various platforms, including conventional ship-based technologies, autonomous instruments (e.g., animal-borne sensors, autonomous underwater vehicles, and profiling floats), satellites, and other remote sensing methods. However, the harsh environment, remoteness, and natural obstacles such as sea ice and clouds limit year-round ocean observations by vessel and satellite, respectively. This incomplete data coverage makes predicting future scenarios a challenge. Here, led by the Regional Working Group for the Indian Sector of the Southern Ocean in the Southern Ocean Observing System, we examined the status of multidisciplinary ocean observations in the Indian Sector. Our review covers oceanography, sea ice, biogeochemistry, air–sea flux, pelagic and benthic biology, and direct anthropogenic pressures. We also address seasonal and spatial gaps, along with platform biases. Furthermore, we explore the synergies between modelling and observations, highlighting how models can test hypotheses, address observational gaps, and, in turn, benefit from improved observational data. Finally, we provide recommendations for enhancing the observing system in the Indian Sector of the Southern Ocean to better understand its current state and anticipated future changes
Warm Equatorial Upper Ocean Thermal Structure During the Mid‐Pliocene Warm Period: A Data‐Model Comparison
No full textInternational audienceAbstract The tropical Pacific climate has an outsized impact on global climate, yet future projections are poorly constrained. Data‐model comparisons from the mid‐Pliocene warm period (3.3 million years ago) can help investigate warm climate dynamics and evaluate model behavior. Here we compare proxy records to PlioMIP2 models and a model with modified cloud albedo. Relative to modern, the mid‐Pliocene warm period records show subsurface warming across the tropical Pacific, strong eastern Pacific surface warming and weak western Pacific surface warming. Using clustering analyses to group model behavior relative to the proxy data, we find the model cluster with the best fit with the proxy data has enhanced warming in mid‐latitude thermocline source water regions which connect to the equator through the ventilated thermocline. Our study shows tropical ocean heat content during the mid‐Pliocene warm period was higher than today and has broad implications for the ocean's ability to absorb anthropogenic heat
Peripheral positioning of lysosomes supports melanoma aggressiveness
No full textInternational audienceEmerging evidence suggests that the function and position of organelles are pivotal for tumor cell dissemination. Among them, lysosomes stand out as they integrate metabolic sensing with gene regulation and secretion of proteases. Yet, how their function is linked to their position and how this controls metastasis remains elusive. Here, we analyze lysosome subcellular distribution in patient-derived melanoma cells and patient biopsies and show that lysosome spreading scales with melanoma aggressiveness. Peripheral lysosomes promote matrix degradation and cell invasion which is directly linked to the lysosomal and cell transcriptional programs. Using chemo-genetical control of lysosome positioning, we demonstrate that perinuclear clustering impairs lysosome secretion, matrix degradation and invasion. Impairing lysosome spreading significantly reduces invasive outgrowth in two in vivo models, mouse and zebrafish. Our study provides a direct demonstration that lysosome positioning controls cell invasion, illustrating the importance of organelle adaptation in carcinogenesis and suggesting its potential utility for diagnosis of metastatic melanoma.Metastases are responsible for the majority of cancer-related deaths 1 . Melanoma shows strong negative correlation between cancer stage and 5-year patient survival, making it an ideal model to study phenotypic changes leading to cancer cell invasion, adaptation and survival. Melanoma progression consists of multiple sequential events and its early detection is key for patient survival. First, melanocytes are transformed and grow in the epidermis during radial growth phase (RGP), forming a lesion with low potential to develop metastasis. Changes in their transcription program lead to expression of matrixdegrading enzymes and to invasion through the dermis during vertical growth phase (VGP) followed by cancer dissemination through vascular and lymphatic routes, progressing into metastatic stages 2
Optimization of the VSV-G backbone for amino terminal fusion with nanobodies allowing its specific retargeting to HER2 receptors
No full textInternational audienceVesicular stomatitis virus (VSV) is a promising oncolytic virus.Additionally, its glycoprotein G (VSV-G) is the most commonly used envelope glycoprotein to pseudotype lentiviral vectors for gene therapy. However, VSV receptors (low-density lipoprotein receptor [LDL-R] family members) are ubiquitous and expressed at the surface of non-target cells, precluding in vivo gene therapy. Recently, we identified VSV-G mutants that no longer bind to LDL-R but retain their fusion activity. This created the opportunity to specifically retarget the glycoprotein to the desired receptors. Here, we engineered chimeric glycoproteins by fusing nanobodies to the amino terminus of VSV-G. Using experimental evolution, we identified two mutations in VSV-G improving the folding and functionality of chimeric glycoproteins, regardless of the nanobody inserted at the amino terminus. We then generated chimeric glycoproteins using several nanobodies targeting HER2 receptor, and into these chimeras, we introduced additional mutations that abolish recognition of LDL-R. VSV and lentiviruses pseudotyped with these glycoproteins specifically infect cells expressing HER2. We have, therefore, identified VSV-G mutations that optimize its backbone to tolerate amino-terminal insertion of a nanobody and establish proof of concept that this approach can be used to confer a new tropism on VSV-G. This paves the way for the development of targeted in vivo therapies.</p
Development of a phase-contrast SPRi biosensor for single-particle detection of pathogens
No full textInternational audienc
Development of Biomimetic Optoelectronic Nose for Analysis of Odors
No full textInternational audienc
Bond-dependent interactions and ill-ordered state in the honeycomb cobaltate BaCo(AsO)
No full textInternational audienceThe ground state and Hamiltonian of the honeycomb lattice material BaCo(AsO) hosting magnetic Co, have been debated for decades. The recent proposal for anisotropic bond-dependent interactions in such honeycomb cobaltates has raised the prospect of revisiting its Hamiltonian in the context of Kitaev physics. To test this hypothesis, we have combined magnetization, ac-susceptibility and neutron scattering measurements on a BaCo(AsO) single-crystal, together with advanced modeling. Our experimental results highlight a collinear magnetic ground state with intrinsic disorder associated to an average incommensurate propagation vector. Monte Carlo simulations and linear spin wave calculations were performed to obtain a spin model compatible with this unusual ground state, the dispersion of magnetic excitations and a magnetization plateau under magnetic field. We thus show that bond-dependent anisotropic interactions, including Kitaev-like interactions, are necessary to account for the puzzling properties of this long-explored material, and are hence a general ingredient in the cobaltates
Hydrophilic interaction liquid chromatography (HILIC) coupled to elemental and molecular mass spectrometry to evaluate the interaction of biomimetic peptides for actinides
No full textInternational audienceThe coupling of HILIC to electrospray ionization mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS) is powerful for the online and simultaneous structural, multi-elemental and isotopic characterization of the chemical species previously separated. We applied this approach to screen the interaction properties of multi-phosphorylated biomimetic peptides towards UO₂²⁺ and Th4+ at physiological pH. An affinity scale of the different peptides was determined for UO22+ as well as the effect of their structure on UO22+ affinity. The selectivity of the highest affinity peptides was determined when UO22+ was in presence of competitors such as biological endogenous cations (Ca2+, Cu2+, Zn2+) or non essential Th4+. This approach has been extended to study the interaction of lanthanides (Sm3+, Nd3+) at acidic pH (~2), with chelating molecules of interest for recycling in nuclear sector. Then, the HILIC separations were downscaled to capillary and nano-flow formats, leading to the reduction of effluent volumes and in the consumption of material