Disorder Averaging and Finite Size Scaling

We propose a new picture of the renormalization group (RG) approach in the presence of disorder, which considers the RG trajectories of each random sample (realization) separately instead of the usual renormalization of the averaged free energy. The main consequence of the theory is that the average over randomness has to be taken after finding the critical point of each realization. To demonstrate these concepts, we study the finite-size scaling properties of the two-dimensional random-bond Ising model. We find that most of the previously observed finite-size corrections are due to the sample-to-sample fluctuation of the critical temperature and scaling is more adequate in terms of the new scaling variables.Comment: 4 pages, 6 figures include

Prokaryotic and Eukaryotic Community Structure in Field and Cultured Microbialites from the Alkaline Lake Alchichica (Mexico)

The geomicrobiology of crater lake microbialites remains largely unknown despite their evolutionary interest due to their resemblance to some Archaean analogs in the dominance of in situ carbonate precipitation over accretion. Here, we studied the diversity of archaea, bacteria and protists in microbialites of the alkaline Lake Alchichica from both field samples collected along a depth gradient (0–14 m depth) and long-term-maintained laboratory aquaria. Using small subunit (SSU) rRNA gene libraries and fingerprinting methods, we detected a wide diversity of bacteria and protists contrasting with a minor fraction of archaea. Oxygenic photosynthesizers were dominated by cyanobacteria, green algae and diatoms. Cyanobacterial diversity varied with depth, Oscillatoriales dominating shallow and intermediate microbialites and Pleurocapsales the deepest samples. The early-branching Gloeobacterales represented significant proportions in aquaria microbialites. Anoxygenic photosynthesizers were also diverse, comprising members of Alphaproteobacteria and Chloroflexi. Although photosynthetic microorganisms dominated in biomass, heterotrophic lineages were more diverse. We detected members of up to 21 bacterial phyla or candidate divisions, including lineages possibly involved in microbialite formation, such as sulfate-reducing Deltaproteobacteria but also Firmicutes and very diverse taxa likely able to degrade complex polymeric substances, such as Planctomycetales, Bacteroidetes and Verrucomicrobia. Heterotrophic eukaryotes were dominated by Fungi (including members of the basal Rozellida or Cryptomycota), Choanoflagellida, Nucleariida, Amoebozoa, Alveolata and Stramenopiles. The diversity and relative abundance of many eukaryotic lineages suggest an unforeseen role for protists in microbialite ecology. Many lineages from lake microbialites were successfully maintained in aquaria. Interestingly, the diversity detected in aquarium microbialites was higher than in field samples, possibly due to more stable and favorable laboratory conditions. The maintenance of highly diverse natural microbialites in laboratory aquaria holds promise to study the role of different metabolisms in the formation of these structures under controlled conditions

Etude numérique de modèles désordonnés classiques et quantiques

En utilisant des simulations de Monte-Carlo, nous avons étudié des modèles désordonnés classiques et quantiques. Nous avons introduit une nouvelle manière de moyenner sur le désordre que nous avons testée sur un modèle classique, le modèle d Ising désordonné à deux dimensions. Elle nous a permis de déterminer précisément les exposants critiques associés à ce modèle. Ensuite, nous nous sommes intéressés aux phases du modèle d Hubbard bosonique au cœur dur apparaissant à température nulle. Pour le cas put et sans autre interaction que la contrainte de cœur dur, nous sommes parvenus à déterminer des expressions analytiques pour de nombreuses quantités physiques. L accord en ces résultats analytiques et des simulations de Monte Carlo est excellent à deux et trois dimensions. Enfin, en étudiant l effet du désordre sur ce modèle avec l interaction entre les plus proches voisins, nous avons vu notamment la création d une nouvelle phase isolante compressible qui remplace la phase solide en échiquier.We have studied classical and quantum disordered systems with Monte Carlo simulations. We have introduced a new way to average over disorder and tested it on a classical model, the two dimensional Ising model. It allows us to extract accurately the critical exponents of this model. Then, we were interested in the zero temperature properties of the bosonic Hubbard model. For the case with only the onsite hardcore repulsion, we have been able to establish analytic expressions for many physical quantities. The agreement between these analytic results and Monte Carlo simulations is excellent in two and three dimensions. Finally, we have studied the effect of disorder on this model, the disorder produces a new glassy phase which replaces the check board solid present at strong near neighbor interaction.NICE-BU Sciences (060882101) / SudocSudocFranceF

CoreBook et la Cyber-carothèque nationale : deux outils pour bancariser des métadonnées riches lors des opérations de carottage scientifique (continental, marin, glaciaires)

International audienc

New insights of the Northern Current in the Western Mediterranean Sea from Gliders data: Mean structure, Transport, and Seasonal Variability

International audienceIn the last 5 years, an unprecedented effort in the sampling of the Northern Current (NC) has been carried out using gliders which collected more than 50 000 profiles down to 1000m maximum along a few repeated sections perpendicular to the French coast. Based on this dataset, this study presents a very first quantitative picture of the NC on 0-1000m depth. We show its mean structure of temperature and salinity characterized by the different Water Masses of the basin (Atlantic Water, Winter Intermediate Water, Levantine Intermediate Water and Western Mediterranean Deep Water) for each season and at different location. Geostrophic currents are derived from the integration of the thermal-wind balance using the mean glider-estimate of the current during each dive as a reference. Estimates of the heat, salt, and volume transport are then computed in order to draw an heat and salt budget of the NC. The results show a strong seasonal variability due to the intense surface buoyancy loss in winter resulting in a vertical mixing offshore that makes the mixed layer depth reaching several hundreds of meters in the whole basin and in a very particular area down to the bottom of the sea-floor (deep convection area). The horizontal density gradient intensifies in winter leading to geostrophic currents that are more intense and more confined to the continental slope, and thus to the enhancement of the mesoscale activity (meandering, formation of eddies through baroclinic instability...). The mean transport estimates of the NC is found to be about 2-3Sv greater than previous spurious estimates. The heat budget of the NC also provides an estimate of the mean across shore heat/salt flux directly impacting the region in the Gulf of Lion where deep ocean convection, a key process in the thermohaline circulation of the Mediterranean Sea, can occur in Winter

Survey of submesoscale structures at the margin of the Northern Current in the North Western Mediterranean Sea using Gliders: observations and diagnostics

International audienceFrom 2008 on, repeated sections crossing the Northern Current (NC) were operated by gliders as part of a global observing system (MOOSE project) of the North Western Mediterranean Sea. This work is dedicated to the analysis of the submesoscale thermohaline variability at the margin of this current observed by gliders. The mean circulation of the basin is characterized by a cyclonic gyre (whose Northern part is the so-called NC) associated with a doming of the isopycnals preconditionning the whole interior basin to great vertical mixing. The thermal and haline differences between the Atlantic Water (AW) transported by the NC and older and modified AW off the coast leads to a frontal structure. Especially in winter, when the mixed layer depth used to reach several hundreds of meters offshore, isopycnal outcropping and the role of frontal processes are enhanced leading to intense variability at scales smaller than the deformation radius. Based on diagnostics using the Potential Vorticity (PV) computed from the glider data assuming quasi-geostrophic conditions and no variation in the alongshore direction, we discuss the dynamical processes at work, with a focus on 2 typical examples: (1) the first example takes place in winter during a strong vertical mixing event. While the glider crossed the frontal region, the temperature and salinity fields exhibit vertical motions at depths about 0-400m. Frontogenesis might be at play through mesoscale strain since the glider shows an intense mesoscale activity but a weak stratification and enhanced horizontal buoyancy gradient actually make the Ertel PV reach negative values and symmetric instability is likely to be a prominent mechanism explaining the observed variability. (2) the second example takes place in spring. We identify an episode of down-front wind blowing during the glider deployment which could have extracted PV from the surface layer. However, the geostrophic turbulence is in that case likely to play a key role in the formation of the observed variability of the temperature and salinity since it is organized along slopes characterized by an aspect ratio of an order of f/N

Characteristics of Geostrophic Eddies in the North Western Mediterranean as observed by Gliders and simulated by a high-resolution Model: formation, behaviour and dissipation

International audienceSince 2008, gliders repeated transects crossing the basin of the North Western Mediterranean Sea and regularly sampled mesoscale structures with an high horizontal resolution of about 2-3 km between each profile required in that region of small internal deformation radius (<10km). By analysing more than 50 000 profiles collected by these gliders in the last 5 years, we were able to identify several types of eddies regarding the water mass composing their cores: Winter Intermediate Water (WIW), Levantine Intermediate Water (LIW), Western Mediterranean Deep Water (WMDW). Most of them are anticyclonic structures with Rossby Number greater than 0.1 and tend to be characterized by a core in the inner ocean. Some of them whose formation has been dated several months back in time can be qualified as long lived features. Of particular interest to assess the role of mesoscale eddies in the ocean circulation, a Submesoscale Coherent Vortex (SCV) composed of newly WMDW was observed nine months after its formation. We also used a 1 year run of a high resolution (1km, 40 vertical levels) numerical model of the region (SYMPHONIE) which is able to reproduce similar eddies. In this study we discuss their formation process (instability of the boundary current, or diapycnal mixing followed by geostrophic adjustment) based on comparisons between these observations and the model outputs, and try to estimate their impact on the general circulation of this basin

HF radar in French Mediterranean Sea: an element of MOOSE Mediterranean Ocean Observing System on Environment

International audienceIn the framework of the French MOOSE project (Mediterranean Ocean Observing System on Environment), the Mediterranean Institute of Oceanography is operating HF radars on the North Western Mediterranean coast. The surface circulation in this region is characterized by a large-scale flow (Northern Current) and by a broad range of other scales of variability induced by meteorological and tidal forcing. The ability of HF radars is to provide synoptic observation as sea surface current map every hour and over long distances. One site is already operational nearby Toulon for more than two years and a second one is in deployment around Nice. This paper gives an overview of the radars network, of the surface current mapping facility offered by the system, and of recent observation results and applications

How to turn kilos of mud into megabytes of data? 10 years of efforts in curating lake sediment cores and their associated results

International audienceHere we present a series of connected efforts aiming at curating sediment cores and their related data. Far to be isolated, these efforts were conducted within national structured projects and led to the development of digital solutions and good practices in-line with international standards and practices.Our efforts aimed at ensuring FAIR-compatible practices (Plomp, 2020; Wilkinson et al., 2016) throughout the life cycle of sediment cores, from fieldwork to published data. We adopted a step-by-step, bottom-up strategy to formalize a dataflow, mirroring our workflow. We hence created a fieldwork mobile application (CoreBook) to gather information during coring operations and inject them toward the French national virtual core repository “Cyber-Carothèque Nationale” (CCN). At this stage, the allocation of an international persistent unique identifier was crucial and we naturally chose the IGSN.Beyond the traceability of samples, the curation of analysis data remains challenging. Most international repository (e.g. NOAA palaeo-data, PANGAEA) have taken the problem from the top by offering facilities to display published dataset with persistant unique identifier (DOI). Yet, those data are only a fraction of the gross amount of acquired data. Moreover, those repositories have very low requirements when it comes to the preservation and display of metadata, in particular analytical parameters, but also fieldwork data which are essential for data reusability. Finally, these repositories do not permit to get a synoptic view on the several strata of analyses that have been conducted on the same core through different research programs and publications. A partial solution is proposed by the eLTER metadata standard DEIMS, which offers a discovery interface of rich metadata. In order to bridge the gap between generalist data repositories and samples display systems (such as CCN, but also IMLGS, to cite an international system), we developed a data repository and visualizer dedicated to the re-use of lake sediment cores, samples and sampling locations (ROZA Retro-Observatory of the Zone Atelier). This system is still a prototype but opens yet interesting perspectives.Finally, the digital evolution of science allows the worldwide diffusion of data processing freewares. In that framework, we developed “Serac” an open-source R package to establish radionuclide-based age models following the most common sedimentation hypotheses (serac,). By implementing within this R package the input of a rich metadata file that gathers links to IGSN and other quality metadata, we are linking fieldwork metadata, the physical storage of the core and the analytical metadata. Indeed, Serac also stores data processing procedure in a standardized way.. We hence think that the development of such softwares could help in the spreading of good practices in data curation and favour the use of unique identifiers.By tackling all aspects of data creation and curation throughout a lake sediment core life cycle, we are now able to propose a theoretical model of data curation for this particular type of sample that could serve as the sole for further developments of integrated data curation systems.https://doi.org/10.5194/egusphere-egu21-1503

From the field to the database: a user-oriented approach to promote cyber-curating of scientific continental drilling cores

International audienceManaging scientific data is probably one the most challenging issues in modern science. In plaeosciences the question is made even more sensitive with the need of preserving and managing high value fragile geological samples: cores. Large international scientific programs, such as IODP or ICDP led intense effort to solve this problem and proposed detailed high standard work- and dataflows thorough core handling and curating. However many paleoscience results derived from small-scale research programs in which data and sample management is too often managed only locally – when it is… In this paper we present a national effort leads in France to develop an integrated system to curate ice and sediment cores. Under the umbrella of the national excellence equipment program CLIMCOR, we launched a reflexion about core curating and the management of associated fieldwork data. Our aim was then to conserve all data from fieldwork in an integrated cyber-environment which will evolve toward laboratory-acquired data storage in a near future. To do so, our demarche was conducted through an intimate relationship with field operators as well laboratory core curators in order to propose user-oriented solutions. The national core curating initiative proposes a single web portal in which all teams can store their fieldwork data. This portal is used as a national hub to attribute IGSNs. For legacy samples, this requires the establishment of a dedicated core list with associated metadata. However, for forthcoming core data, we developed a mobile application to capture technical and scientific data directly on the field. This application is linked with a unique coring-tools library and is adapted to most coring devices (gravity, drilling, percussion etc.) including multiple sections and holes coring operations. Those field data can be uploaded automatically to the national portal, but also referenced through international standards (IGSN and INSPIRE) and displayed in international portals (currently, NOAA’s IMLGS). In this paper, we present the architecture of the integrated system, future perspectives and the approach we adopted to reach our goals. We will also present our mobile application through didactic examples