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Unconditional CNN denoisers contain sparse semantic representation of images
No full textGenerative diffusion models learn probability densities over diverse image datasets by estimating the score with a neural network trained to remove noise. Despite their remarkable success in generating high-quality images, the internal mechanisms of the underlying score networks are not well understood. Here, we examine the image representation that arises from score estimation in a {fully-convolutional unconditional UNet}. We show that the middle block of the UNet decomposes individual images into sparse subsets of active channels, and that the vector of spatial averages of these channels can provide a nonlinear representation of the underlying clean images. Euclidean distances in this representation space are semantically meaningful, even though no conditioning information is provided during training. We develop a novel algorithm for stochastic reconstruction of images conditioned on this representation: The synthesis using the unconditional model is "self-guided" by the representation extracted from that very same model. For a given representation, the common patterns in the set of reconstructed samples reveal the features captured in the middle block of the UNet. Together, these results show, for the first time, that a measure of semantic similarity emerges, unsupervised, solely from the denoising objective
New SOCOL:14C-Ex model reveals that the Late-Glacial radiocarbon spike in 12350 BC was caused by the record-strong extreme solar storm
No full textInternational audienceThe Sun rarely produced extreme solar particle events (ESPEs), orders of magnitude stronger than everything directly observed. Their enormous power can greatly distort the production of cosmogenic isotopes, e.g., radiocarbon 14C, in the terrestrial system, leaving clear signatures in natural terrestrial archives including dateable tree rings. Eight such events were known to occur during the past 12 millennia of the Holocene, with the strongest one being that of 775 AD. Recently, a new and the only ESPE candidate beyond the Holocene has been discovered as the largest known 14C peak dated to ca. 12350 BC, nearly twice as big as that of 775 AD. However, it could not be analysed earlier due to the lack of appropriate models applicable to glacial climate conditions. We have developed a brand-new state-of-the-art chemistry-climate model SOCOL:14C-Ex to study fast changes in 14C. It was tested on the well-studied event of 775 AD and applied to the ESPE of 12350 BC. We found that it was stronger by 18±11% than by 775 AD and likely occurred between January – April 12350 BC with the most probable date in early March. This makes the ESPE of 12350 BC the record strongest known event, pushing the bounds of the extreme solar-terrestrial events even further, forming the new worst-case scenario paradigm and providing the global tie point for dendrochronological dating before the Holocene. The newly developed model lifts the existing limitation to the Holocene and extends our ability to analyse radiocarbon data even for glacial climate conditions
Molecular gas stratification and disturbed kinematics in the Seyfert galaxy MCG-05-23-16 revealed by JWST and ALMA
No full textInternational audienceUnderstanding the processes that drive the morphology and kinematics of molecular gas in galaxies is crucial for comprehending star formation and, ultimately, galaxy evolution. Using data from the Galactic Activity, Torus and Outflow Survey (GATOS) obtained with the James Webb Space Telescope (JWST) and the archival data from the Atacama Large Millimeter/submillimeter Array (ALMA), we study the behavior of the warm molecular gas at temperatures of hundreds of Kelvin and the cold molecular gas at tens of Kelvin in the galaxy MCG−05−23−16, which hosts an active galactic nucleus (AGN). Hubble Space Telescope (HST) images of this spheroidal galaxy, classified in the optical as S0, show a dust lane resembling a nuclear spiral and a surrounding ring. These features are also detected in CO(2−1) and H 2 , and their morphologies and kinematics are consistent with rotation plus local inward gas motions along the kinematic minor axis in the presence of a nuclear bar. The H 2 transitions 0-0 S(3), 0-0 S(4), and 0-0 S(5), which trace warmer and more excited gas, show more disrupted kinematics than 0-0 S(1) and 0-0 S(2), including clumps of high velocity dispersion (of up to ∼160 km s −1 ), in regions devoid of CO(2−1). The kinematics of one of these clumps, located ∼350 pc westward of the nucleus, are consistent with outflowing gas, possibly driven by localized star formation traced by polycyclic aromatic hydrocarbon emission at 11.3 μm. Overall, we observe a stratification of the molecular gas, with the colder gas located in the nuclear spiral, ring, and connecting arms, and most of the warmer gas with a higher velocity dispersion filling the inter-arm space. The compact jet, approximately 200 pc in size, detected with Very Large Array (VLA) observations, does not appear to significantly affect the distribution and kinematics of the molecular gas, possibly due to its limited intersection with the molecular gas disk
Unveiling the bulge–disc structure, AGN feedback, and baryon landscape in a massive spiral galaxy with Mpc-scale radio jets
No full textInternational audienceWe study the bulge–disc components and stellar mass distribution in the fast-rotating, highly massive spiral galaxy 2MASX J23453268−0449256, which is distinguished by extraordinary radio jets extending to Mpc scales. Using high-resolution multiwavelength Hubble Space Telescope (HST) observations and multiparameter panchromatic spectral energy distribution (SED) fitting, we derive estimates of key properties, such as the star formation rate, total baryonic mass in stars, and the characteristics of warm dust. Our findings, validated at a spatial resolution of approximately 100 pc, reveal a pseudo-bulge rather than a classical bulge, as well as a small nuclear bar and resonant ring, challenging traditional models of galaxy formation. Furthermore, the absence of tidal debris and the highly symmetric spiral arms within a rotationally supported stellar disc suggest a peaceful co-evolution of the galactic disc and its central supermassive black hole (SMBH). Notably, the galaxy exhibits suppressed star formation in its central region, which may be influenced by feedback from the central accreting SMBH, producing powerful radio jets. Detailed multiwavelength studies of potential star-forming gas show that while hot X-ray gas cools in the galaxy’s halo, new stars do not form in the centre, likely due to this feedback. This study raises important questions about the efficient fuelling and sustained collimated jet activity in J2345−0449, highlighting the need for a better understanding of the central black hole’s properties. The exceptional rarity of galaxies like 2MASX J23453268−0449256 presents intriguing challenges in uncovering the physical processes behind their unique characteristics
(Anti)-de Sitter with leaky boundaries and corners
No full textInternational audienceWe construct charges for four-dimensional spacetimes with a non-vanishing cosmological constant, including charges that are not conserved because of a leaky boundary and charges associated with corner terms in the symplectic current. The construction leads to manifestly finite charges for any choice of boundary conditions, and reveals new charges in partial Bondi gauge for an enlarged class of field configurations which are not fully on-shell, including a Weyl charge for conformal boundary conditions. In addition, we generalize the variational principle for AdS gravity with Dirichlet boundary conditions to a wedge of spacetime where the conformal boundary includes a corner. The boundary data is completely general, with no conditions restricting time dependence or the determinant of the metric. The Ward identities associated with boundary diffeomorphisms are shown to reproduce the evolution equations for the mass and angular momentum of fully on-shell field configurations
Prevalence and associated factors of obesity, hypertension, and diabetes in French Polynesia: results from a nationwide cross-sectional study
No full textInternational audienceBackgroundNon-communicable diseases (NCDs) represent a major global health challenge, particularly in the Pacific. This study assessed the prevalence and associated factors of obesity, hypertension, and diabetes among adults in French Polynesia.MethodsA cross-sectional survey (2019–2021) was conducted on a nationally representative sample of adults across all five archipelagos (Tuamotu, Gambier, Marquesas, Austral, and Society including the Leeward and Windward Islands). Data included anthropometrics, blood pressure, biochemical markers (lipids, renal function), sociodemographic, lifestyle, and health history. NCDs were defined as hypertension (systolic BP >140 mmHg, diastolic BP >90 mmHg, and/or self-report of anti-hypertension medication use), diabetes (HbA1c >6·5%, and/or self-report of previous medical diagnosis), and obesity (using either BMI ≥30 kg/m2 or a revised definition incorporating ethnicity-specific thresholds and additional anthropometric criteria).FindingsA total of 1893 adults were included (987 women; 906 men). Among them, 669 (weighted prevalence: 35·5%, 95% CI: 33–38) had hypertension, 214 (weighted prevalence: 12·2%, 95% CI: 10–14) had diabetes (including 53 undiagnosed, weighted prevalence: 3·1%, 95% CI: 2–4), and 1022 (weighted prevalence: 51·1%, 95% CI: 48–54) or 847 (weighted prevalence: 42·7%, 95% CI: 40–46) were classified as obese, using BMI-based or revised definitions, respectively. Among those with revised obesity, 439 (weighted prevalence: 52·2%, 95% CI: 48–57) presented metabolic abnormalities typically associated with the condition, while 408 (weighted prevalence: 47·8%, 95% CI: 43–52) were metabolically healthy, a phenotype that declined with age.Women were less likely than men to have hypertension (OR = 0·59, 95% CI: 0·45–0·78), but more likely to present BMI-based obesity (OR = 1·61, 95% CI: 1·23–2·11). Hypertension odds were higher in Leeward versus Windward Islands (OR = 1·61, 95% CI: 1·24–2·09). Revised obesity was associated with low fruit/vegetable intake (OR = 1·53, 95% CI: 1·13–2·09), high meat consumption (OR = 1·52, 95% CI: 1·10–2·10), high fish consumption (OR = 1·54, 95% CI: 1·10–2·16), and low physical activity (OR = 1·58, 95% CI: 1·15–2·15). Obesity increased the odds of diabetes (OR = 2·99, 95% CI: 1·97–4·53) and hypertension (OR = 2·38, 95% CI: 1·80–3·14). Lower odds of obesity were observed in self-declared Polynesians of mixed ancestry (OR = 0·64, 95% CI: 0·42–0·96) and European immigrants (OR = 0·21, 95% CI: 0·07–0·61), as well as lower odds of diabetes in European immigrants (OR = 0·04, 95% CI: 0·01–0·19) compared to self-identified Polynesians.InterpretationThe high prevalence of obesity, a key driver of hypertension and diabetes, highlights the need for both population-wide prevention and targeted interventions across all archipelagos. Using standard indicators alongside locally revised definitions allows a more accurate mapping of NCDs, while the analysis of associated factors supports behavioural changes to reduce risk
High-resolution ALMA observations of H<sub>2</sub>S in LIRGs
No full textInternational audienceContext. Molecular gas plays a critical role in regulating star formation and nuclear activity in galaxies. Sulphur-bearing molecules, such as H 2 S, are sensitive to the physical and chemical environments in which they reside and are potential tracers of shocked, dense gas in galactic outflows and active galactic nuclei (AGNs). Aims. We aim to investigate the origin of H 2 S emission and its relation to dense gas and outflow activity in the central regions of nearby infrared-luminous galaxies. Methods. We present Atacama Large Millimeter/submillimeter Array (ALMA) Band 5 observations of the ortho-H 2 S 1 1,0 -1 0,1 transition in three nearby galaxies: NGC 1377, NGC 4418, and NGC 1266. We performed radiative transfer modelling using RADEX to constrain the physical conditions of the H 2 S-emitting gas and compare the results to ancillary CO and continuum data. Results. We detect compact H 2 S emission in all three galaxies, arising from regions smaller than ∼150 pc. The H 2 S spectral profiles exhibit broad line wings, suggesting an association with outflowing or shocked gas. In NGC 4418, H 2 S also appears to be tracing gas that is counter-rotating. A peculiar redshifted emission feature may be inflowing gas, or possibly a slanted outflow. RADEX modelling indicates that the H 2 S-emitting gas has high densities (n H 2 10 7 cm -3 ) and moderately warm temperatures (40-200 K). The derived densities exceed those inferred from CO observations, implying that H 2 S traces denser regions of the ISM
Microwave‐Assisted Rapid Hydrothermal Synthesis of Vanadium‐Based Cathode: Unravelling Charge Storage Mechanisms in Aqueous Zinc‐Ion Batteries
No full textInternational audienceThis contribution uses a rapid microwave‐assisted hydrothermal synthesis method to produce a vanadium‐based K 1.92 Mn 0.54 V 2 O 5 ⋅ H 2 O cathode material (quoted as KMnVOH). The electrochemical performance of KMnVOH is tested in an aqueous electrolyte, which exhibits a remarkable specific capacity of 260 mAh g −1 at 5 C and retains 94 % of its capacity over 2000 cycles. In contrast to the aqueous electrolyte, the KMnVOH electrode tested in the organic electrolyte provides a modest discharge capacity of 60 mAh g −1 at C/10, and the electrogravimetric analysis indicates that the charge storage mechanism is solely due to non‐solvated Zn 2+ intercalation. In aqueous electrolyte tests, Zn species insertion, interfacial pH increase, and subsequent formation of Zn x (OH) y (CF 3 SO 3 ) 2x‐y ⋅ nH 2 O (ZHT) are supported by in‐situ EQCM. Ex‐situ XRD measurements also confirm the ZHT formation and its characteristic plate‐like structure is observed by SEM. The ion diffusion coefficient values in aqueous and non‐aqueous electrolytes are very similar according to the GITT analysis, while it is expected to be higher in aqueous electrolytes. These results may further emphasize the complex redox dynamics in the aqueous electrolyte, namely the difficulty of intercalation of bare Zn 2+ , strong Zn 2+ solvation in the bulk electrolyte, solvent or proton intercalation, and ZHT formation
Unsupervised detection and fitness estimation of emerging SARS-CoV-2 variants. Application to wastewater samples (ANRS0160)
No full textInternational audienceRepeated waves of emerging variants during the SARS-CoV-2 pandemics have highlighted the urge of collecting longitudinal genomic data and developing statistical methods based on time series analyses for detecting new threatening lineages and estimating their fitness early in time. Most models study the evolution of the prevalence of particular lineages over time and require a prior classification of sequences into lineages which is prone to induce delays and biases. More recently, several authors studied the evolution of the prevalence of mutations over time with alternative clustering approaches, avoiding specific lineage classification. Most existing methods are either non parametric or unsuited to pooled data characterizing, for instance, wastewater samples. The analysis of wastewater samples has recently been pointed out as a valuable complementary approach to clinical sample analysis, however the pooled nature of the data involves specific statistical challenges. In this context, we propose an alternative unsupervised method for clustering mutations according to their frequency trajectory over time and estimating group fitness from time series of pooled mutation prevalence data. Our model is a mixture of observed count data and latent group assignment and we use the expectation-maximization algorithm for model selection and parameter estimation. The application of our method to time series of SARS-CoV-2 sequencing data collected from wastewater treatment plants in France from October 2020 to April 2021 shows its ability to agnostically group mutations in a consistent way with lineages B.1.160, Alpha, B.1.177, Beta, and with selection coefficient estimates per group in coherence with the viral dynamics in France reported by Nextstrain. Moreover, our method detected the Alpha variant as threatening as early as supervised methods (which track specific mutations over time) with the noticeable difference that, since unsupervised, it does not require any prior information on the set of mutations
