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Provenance of lead ores used for water pipes production in the ancient Roman Gaul (Vienne, France)
No full textInternational audienceThe urban fabric of Roman cities developed through the installation of water supply networks, mainly made of lead (Pb). In Gaul, the city of Vienne (France) was central to the manufacturing of Pb artifacts, including large volumes of Pb water pipes. Although Pb artifacts were often labeled with Roman-period stamps indicating the location of manufacturing, our knowledge of the provenance of extracted Pb ore and the way they were imported remains limited. In this study, Roman-period artifacts were analyzed for Pb isotope signatures to document the source of Pb ore used in Vienne’s manufactories. Lead isotope signatures were then compared with new local Pb ores data and an updated Pb isotope database using a new algorithm to identify the provenance of Pb. Results indicate that Pb used for artifact manufacturing at Vienne originates mainly from a single source. Data treatment with the new algorithm identifies the Rhenish Massif and the Pennines mining regions as the primary and most probable source, but some artifacts exhibit a similar isotope composition to that of local Pb ores. The similarity of the Pb isotopic signatures of the artifacts produced in Vienne with those of Mainz pipes and lead ingots from the Rhenish massif, as well as the synchronicity of the mining periods in this region, support the Rhenish Massif as the most likely source of Pb for Vienne. Finally, we propose the Rhine and Saone Rivers as the most probable Pb ores conveyance routes to Vienne during the Roman Period
Torrential rainfall with severe flooding associated with a baroclinic disturbance on November 17, 2023, United Arab Emirates (UAE)
No full textInternational audienceThis work examines a severe weather event caused by a baroclinic disturbance with heavy rainfall and thunderstorms, which struck parts of the UAE and caused major flooding on November 17, 2023. A low-pressure trough extending from the Red Sea Trough (RST) towards the Eastern Mediterranean (EM) led to extreme flooding. The unique intensity of this heavy rainfall was correlated to midlatitude disturbance amplification even in the middle and upper tropospheric produced by RST. During the rain event, two intense moisture sources were injected into the region: one from the Indian Ocean, carried by southeasterly near-surface winds at 10m, and the other from the Red Sea and Equatorial Africa, transported at a mid-tropospheric level. A significant temperature gradient with ~8 °C difference in surface temperatures, particularly between the northern areas in contrast with the southern regions, and the wind shear formation over the northern parts of the study area initiated the baroclinicity structure in the borderlines of the cold front and thunderstorms. The findings also revealed an abnormal westerly jet stream intensification at 200 hPa, associated with a negative meridional wind anomaly, signaling the stretching of a Rossby wave over the study area during the heavy rainfall and flooding.</div
Optimal design of interpolation methods for time-delay interferometry
No full textInternational audienceTime-delay interferometry (TDI) suppresses laser frequency noise by forming linear combinations of time-shifted interferometric measurements. The time-shift operation is implemented by interpolating discretely sampled data. To enable in-band laser noise reduction by eight to nine orders of magnitude, interpolation has to be performed with high accuracy. Optimizing the design of those interpolation methods is the focus of this work. Previous research that studied constant time-shifts suggested Lagrange interpolation as the interpolation method for TDI. Its transfer function performs well at low frequency but requires a high number of coefficients. Furthermore, when applied in TDI we observed prominent time-domain features when a time-varying shift scanned over a pure integer sample shift. To limit this effect we identify an additional requirement for the interpolation kernel: when considering time-varying shifts the interpolation kernel must be sufficiently smooth to avoid unwanted time-domain transitions that produce glitch-like features in power spectral density estimates. The Lagrange interpolation kernel exhibits a discontinuous first derivative by construction, which is insufficient for the application to LISA or other space-based GW observatories. As a solution we propose a novel design method for interpolation kernels that respect a predefined requirement on in-band interpolation residuals and that possess continuous derivatives up to a prescribed order. Using this method we show that an interpolation kernel with 22 coefficients is sufficient to respect LISA's picometre-requirement and to allow for a continuous first derivative which suppresses the magnitude of the time-domain transition adequately. The reduction from 42 (Lagrange interpolation) to 22 coefficients enables us to save computational cost and increases robustness against artefacts in the data
Accelerating lensed quasars discovery and modeling with physics-informed variational autoencoders
No full textInternational audienceStrongly lensed quasars provide valuable insights into the rate of cosmic expansion, the distribution of dark matter in foreground deflectors, and the characteristics of quasar hosts. However, detecting them in astronomical images is difficult due to the prevalence of non-lensing objects. To address this challenge, we developed a generative deep learning model called VariLens, built upon a physics-informed variational autoencoder. This model seamlessly integrates three essential modules: image reconstruction, object classification, and lens modeling, offering a fast and comprehensive approach to strong lens analysis. VariLens is capable of rapidly determining both (1) the probability that an object is a lens system and (2) key parameters of a singular isothermal ellipsoid (SIE) mass model -- including the Einstein radius (), lens center, and ellipticity -- in just milliseconds using a single CPU. A direct comparison of VariLens estimates with traditional lens modeling for 20 known lensed quasars within the Subaru Hyper Suprime-Cam (HSC) footprint shows good agreement, with both results consistent within for systems with \theta_\mathrm{E}<3 arcsecs. To identify new lensed quasar candidates, we begin with an initial sample of approximately 80 million sources, combining HSC data with multiwavelength information from various surveys. After applying a photometric preselection aimed at locating z>1.5 sources, the number of candidates is reduced to 710,966. Subsequently, VariLens highlights 13,831 sources, each showing a high likelihood of being a lens. A visual assessment of these objects results in 42 promising candidates that await spectroscopic confirmation. These results underscore the potential of automated deep learning pipelines to efficiently detect and model strong lenses in large datasets
Complementaridade de múltiplas técnicas in-situ para a avaliação espaço-temporal das trocas entre águas subterrâneas e águas superficiais
No full textInternational audienceSite-specific heterogeneity in geological materials plays a crucial role in groundwater (GW) and surface water (SW) interaction, especially in ecosystems sensitive to groundwater influx; for example, salmonid habitats are influenced by localized GW input to streams. While numerous methods have emerged to better understand mechanisms governing GW-SW interaction, few studies compare these methods directly. Therefore, the objective of this study is to evaluate the strengths and limitations of an innovative active heat tracing method to quantify the role of riverbed heterogeneity on GW-SW exchanges. This method was compared with several established techniques such as seepage meters, piezometers, and passive heat tracing at a field site on the Sainte-Marguerite River in Quebec, Canada. The measured spatial variation of the exchange rates due to the presence of a sandbar with coarse materials was shown to be statistically significant. Additionally, temporal analysis helped to identify variations of GW flux even during the cold season when GW flux was expected to be limited due to frozen ground and low infiltration from the snow-covered ground surface. Seepage meters and active heat tracing allowed for spatial analysis of GW-SW interaction, while piezometers with water level loggers and passive heat tracing with installed temperature sensors in the riverbed were convenient for identifying temporal variation of GW-SW exchange rates. The combination of temperature sensors and a heating cable was used for the first time as a tool for active heat tracing and showed good potential to evaluate riverbed thermal properties and GW seepage rates in the river
Zooplankton in Kone Lagoon (New Caledonia): Natural variability versus mining effects
No full textInternational audienceThe objective of this study is to assess the potential impact of nickel mining activity on zooplankton communities in a coral reef channel lagoon (Voh Koné, New Caledonia). During a multidisciplinary campaign in February 2018, we analyzed the variation in zooplankton abundance, biomass and taxonomic diversity, as a function of the distance from the metallurgical plant site and of hydrodynamic conditions and environmental variables. We also compared these results with those obtained in an earlier study conducted in 2009 prior the mining. The results show the high variability of planktonic variables between stations and periods, mainly related to natural factors (hydrodynamics, climatic events). However, lagoon zooplankton also appears to be affected by mining development, and in particular by the increase in sediment inputs and consequent turbidity. Zooplankton taxonomic richness and diversity were negatively correlated with non-algal particle concentrations (C NAP considered as an indicator of turbidity) with 10 more sensitive taxa completely absent at the highest concentrations. We interpret these negative relationships as the result of the degradation of food quality by mixing with inedible and less assimilable non-algal particles. The effect of metal toxicity cannot be excluded, even though the metal concentrations recorded in the lagoon are far from known toxic concentrations, but this hypothesis should be further developed. Overall, our results highlight the good resilience of lagoon zooplankton probably partly related to the high renewal rate of the lagoon water
Probing the heating of the neutral atomic interstellar medium in the Dwarf Galaxy Survey through infrared cooling lines
No full textInternational audienceContext. Star formation in galaxies is regulated by dynamical and thermal processes. In the Milky Way and star-forming galaxies with similar metallicity, the photoelectric effect on small dust grains usually dominates the heating of the neutral atomic gas, which constitutes the main star-forming gas reservoir. In more metal-poor galaxies, the lower dust-to-gas mass ratio together with the higher occurrence and luminosity of X-ray sources suggest that other heating mechanisms may be at play.Aims. We aim to determine the contribution of the photoelectric effect, photoionization by UV and X-ray photons, and ionization by cosmic rays to the total heating of the neutral gas in a sample of 37 low-metallicity galaxies. In particular, we wish to assess whether X-ray sources can be a significant source of heating. We also attempt to recover the intrinsic X-ray fluxes and compare them with observations when available.Methods. We used the statistical code MULTIGRIS together with a photoionization grid of Cloudy models propagating radiation from stellar clusters and potential X-ray sources to the ionized and neutral gas. This grid includes physical parameters such as metallicity, gas density, ionization parameter, and radiative source properties. We describe a galaxy as a combination of many 1D components linked by a few physical hyperparameters. We used infrared cooling lines as constraints to evaluate the most likely combinations and parameters.Results. We constrained the heating fractions for the main mechanisms for the first time in a low-metallicity galaxy sample. We show that for the higher metallicity galaxies, the photoelectric effect dominates the neutral gas heating. At metallicities below 1 /8 the Milky Way value, cosmic rays and photoionization can become predominant. We computed an observational proxy for the photoelectric effect heating efficiency on polycyclic aromatic hydrocarbons (PAHs) using the total cooling traced by [CII] 158 µm + [OI] 63 µm. We show that this proxy can match theoretical expectations when accounting for the fraction of the heating due to the photoelectric effect according to our models. Finally, we show that it is possible to predict the X-ray fluxes reasonably well in the 0.3–8 keV band from the gas cooling lines for most of the galaxies observed in this band. With the current grid and assumptions, determining the exact heating fraction due to cosmic rays remains difficult, but we speculate that heating from X-ray sources is more important.Conclusions. As expected from the low abundance of dust and PAHs in metal-poor galaxies, heating mechanisms other than the photoelectric effect heating must be accounted for. Bright X-ray sources may deposit their energy on large scales in such transparent, dust-poor interstellar medium, and thus they represent promising avenues to understand the physical properties of the main star-forming gas reservoir in galaxies. The modeling strategy adopted here makes it possible to recover the global intrinsic radiation field properties when X-ray observations are unavailable, such as in early universe galaxies
Interstellar Formamide (NH 2 CHO), a Key Prebiotic Precursor
No full textInternational audienceFormamide (NH2CHO) has been identified as a potential precursor of a wide variety of organic compounds essential to life, and many biochemical studies propose it likely played a crucial role in the context of the origin of life on our planet. The detection of formamide in comets, which are believed to have—at least partially— inherited their current chemical composition during the birth of the Solar System, raises the question whether a non-negligible amount of formamide may have been exogenously delivered onto a very young Earth about four billion years ago. A crucial part of the effort to answer this question involves searching for formamide in regions where stars and planets are forming today in our Galaxy, as this can shed light on its formation, survival, and chemical reprocessing along the different evolutionary phases leading to a star and planetary system such as our own. The present review primarily addresses the chemistry of formamide in the interstellar medium, from the point of view of (i) astronomical observations, (ii) experiments, and (iii) theoretical calculations. While focusing on just one molecule, this review also more generally reflects the importance of joining efforts across multiple scientific disciplines in order to make progress in the highly interdisciplinary science of astrochemistry
Methane and volatile organic compounds and their influence on air quality in Boulder, Colorado
No full textInternational audienceThe Northern Colorado Front Range (NCFR) has a long history of air pollution problems, which include summertime ozone levels regularly exceeding the ozone National Ambient Air Quality Standard (NAAQS). The NCFR has been designated as a nonattainment area for the ozone NAAQS since 2007. Contributing factors to the elevated pollution buildup include meteorological conditions such as the mountain-valley thermal forcing that recirculates air enriched in volatile organic compound (VOC) emissions from oil and natural gas (O&NG) production and other sources such as vehicle traffic. This study examines data collected from continuous monitoring of methane and VOCs between 2017 and 2021 at the Boulder Reservoir (BRZ) to pinpoint the sources contributing to this pollution; 19,335 VOC samples of alkanes, alkenes, and aromatic hydrocarbons were collected during this period, with measurements taken every 1-2 h. BRZ is located on the outskirts of the Denver metropolitan area and lies between the oil and gas fields that are predominantly located in Weld County (starting about 15 km to the east) and the Rocky Mountain foothills (5 km to the west). The VOC composition is dominated by light alkanes with a "wet" (i.e., >15% weight of total VOCs in relation to methane) natural gas signature. VOCs are highly variable, with concentrations spanning %2 orders of magnitude. Plumes that carry elevated (>10 times the background) O&NG VOCs were observed on the order of >100 times per year. These events were mostly associated with winds from the north to southeast sector, which is the direction that aligns with the densest O&NG development. Averaged over a full year, O&NG and total VOC mole fractions were higher than in most U.S. cities, including those with much higher total population than that of Boulder County. A correlation and scaling analysis yielded total (excluding ethane) NCFR O&NG VOC emissions of 183.6 ± 12.6 Gg yr À1 for 2015, and 81.3 ± 16.1 Gg yr À1 for 2021, respectively, which is %2-2.5 times higher than the State's reported inventory flux. A preliminary data evaluation indicates no changes in methane emissions in the Denver-Julesburg Basin (DJB) that are outside of the measurement uncertainty. O&NG tracer VOCs (e.g., ethane, propane) show signs of possibly declining emissions. The identified discrepancies between the inferred emissions from air monitoring data and the emissions stated in the inventory reemphasize the importance of considering field observations in directing the State's air quality policy, rather than solely relying on inventory data
Transdimensional joint inversion of flow and well log data using a cascaded Metropolis sampler on a layer-cake model
No full textInternational audienceHistory matching is a type of inverse problem for subsurface georesource evaluation that adjusts the geological and petrophysical properties of a reservoir from dynamic data. Here, we aim to infer the geological structures and the associated permeability values of a model in a joint inversion using observed production data (pressure and fluid saturation) and permeability log data. To determine the appropriate level of complexity in the unknown model, we introduce a transdimensional Monte Carlo method applied to a one-dimensional layered reservoir model. In contrast to classical Bayesian modeling in which permeability values are predicted in a fixed reservoir geometry, the number of layers is treated as an unknown variable in the inversion. Layers remain horizontal for simplicity and are characterized only by their number, thickness, interface depth, and constant isotropic permeability values. Our method employs a cascaded Metropolis sampler based on a two-step sequential acceptance criterion in the Markov chain to reduce computational costs. The likelihood probability of well log data is first quickly computed as in a standard regression problem, and flow simulations are performed only on candidate models accepted by this first regression step to further reduce the uncertainty. Numerical flow simulations are solved on a mesh conformal to horizons, which is locally updated at each iteration. Synthetic tests on a simple reference model highlight the capability of the transdimensional cascaded Metropolis algorithm, which jointly uses flow and well log data, to recover a parsimonious representation of the subsurface. Results show that the proposed approach is able to successfully locate major geological discontinuities, quantify uncertainty, and spatially capture the level of information brought by different datasets in the joint inversion process. This suggests potential applicability to real data, more complex reservoir geometries, and other physics