Mise en place d’une nouvelle méthodologie pour la mesure in situ des vitesses verticales océaniques grâce aux données de la campagne FUMSECK 2019

Vertical velocities knowledge is essential to study fine-scale physical processes in the surface layers of the ocean and to understand biological production mechanisms. However, these vertical velocities are often neglected due to mainly two reasons: their order of magnitude (mm.s-1) lower than the one of the horizontal velocities (cm.s-1), and the challenge of this in situ measurement. The FUMSECK cruise, which took place in spring 2019, in the gulf of Genoa, collected in situ measurements of vertical velocities using various instruments, including Acoustic Doppler Current Profilers (ADCP). The analysis of these data, object of this report, required the elaboration of an original processing chain, first developed for the data of the 5th beam of a Sentinel V (ADCP next generation), then generalized to other types of acoustic recording of vertical velocities. We obtain vertical velocity estimates of the order of mm.s-1, as expected, and we show the accuracy of these measurements for all datasets. Finally, the complementary use of satellite data (sea surface temperature, chlorophyll concentration, altimetric currents), together with the continuous in situ physical and biological measurements, result in a three-dimensional view of fine-scale dynamics. Therefore, the promising results of this innovative study open up the possibility of generalizing in situ vertical velocity measurements in the ocean.La connaissance des vitesses verticales, point essentiel de l’étude des processus physiques de fine échelle dans les couches superficielles de l’océan, est indispensable aÌ la compréhension des processus de production biologique. Cependant, le défi que représente leur acquisition in situ, et l’ordre de grandeur de cette composante inférieur à celui des composantes horizontales, entraînent souvent la négligence de ces vitesses dans les études de terrain. La campagne FUMSECK, réalisée dans le golfe de Gênes du 30 avril au 07 mai 2019, a permis de récolter des mesures in situ de vitesses verticales aÌ l’aide d’instruments conventionnels mais utilisés de manière originale, notamment des profileurs de courant acoustiques à effet doppler (Acoustic Doppler Current Profilers, ADCP). L’analyse de ces données, objet de ce rapport, a nécessité la mise en place d’une chaine de traitement originale, développée dans un premier temps pour les données du 5ème faisceau d’un Sentinel V (ADCP nouvelle génération), puis généralisée à d’autres types d’enregistrement acoustique de vitesses verticales. Grâce à cette méthode, les mesures de vitesse verticales atteignent un ordre de grandeur correspondant au mm.s-1 attendu pour cette composante. La mise en parallèle de ces résultats in situ ponctuels à des mesures satellites de courantologie altimétrique, de température de surface et d’abondance chlorophyllienne, ainsi qu’aux mesures in situ continues de physique et de biologie, aboutit à une vision tridimensionnelle de la dynamique de fine échelle en place dans la zone d’étude. Les résultats prometteurs de cette étude innovante ouvrent donc la possibilité d’une généralisation de la mesure in situ des vitesses verticales océaniques

Near Inertial Oscillations and Vertical Velocities Modulating Phytoplankton After a Storm in the Mediterranean Sea

Understanding the impact of storms on phytoplankton dynamics is a complex and crucial issue, both on regional and global scales. Here we address this question by conducting a numerical modeling study to represent the physical forcing and phytoplankton response of an intense storm that occurred in the northwestern Mediterranean Sea in late spring 2019. This numerical study, employing the SYMPHONIE regional circulation model, covers and complements in situ observations gathered during the FUMSECK cruise. Our realistic numerical simulation unveils that the storm event triggered robust near-inertial oscillations (NIOs) in a two-layer system, spanning a 5000 km² area and persisting for a duration of 3-4 days. We demonstrate the oscillatory pattern of the NIOs vertical velocities. Notably, our modeled vertical velocities reach a maximum of 10-3 m s-1 and coincide with a substantial 1.3-fold increase in total chlorophyll concentration. These findings underline the significance of considering the vertical dynamics linked to NIOs induced by meteorological events that are projected to grow both in frequency and intensity in the context of ongoing climate change. The outcomes of this study contribute valuable insights into the intricate relationship between storms and phytoplankton, shedding light on the potential ecological consequences of future climate shifts, and emphasizing the need for more comprehensive investigations to address this complex issue effectively

Non-Cartesian non-Fourier fmri imaging for high-resolution retinotopic mapping at 7 Tesla

International audienceFunctional MRI (fMRI) is an invaluable tool for neuroscience, but it necessitates a trade-off between spatial and temporal resolution to maintain a reasonable temporal signal-to-noise ratio (tSNR). Non-Cartesian acquisition schemes are more efficient sampling strategies as compared to Cartesian ones and were proposed as a way to push the limits of spatiotemporal resolution further. 3D-SPARKLING is a novel non-Cartesian scheme recently evaluated for fMRI applications. However, 3D-SPARKLING is highly sensitive to B0 field imperfections. Such imperfections are detrimental to fMRI applications, especially at ultra-high magnetic fields. In this work, we collect measurements of the static and dynamic B0 field perturbations concurrently with 3D-SPARKLING fMRI data acquisition and retrospectively correct these perturbations during image reconstruction. The advantages of this image reconstruction strategy are assessed on the statistical sensitivity to the BOLD contrast during a retinotopic mapping fMRI experiment. Importantly, a gain of 44% (resp., 159%) additionally activated voxels was quantified when adopting this brain activity-enhanced image reconstruction technique at a type-I statistical control level of 0.001 without multiple comparisons correction (resp., 0.05 with false discovery rate correction). Additionally, significantly improved retinotopic maps were retrieved on the cortical surface

Non-Cartesian non-Fourier fmri imaging for high-resolution retinotopic mapping at 7 Tesla

International audienceFunctional MRI (fMRI) is an invaluable tool for neuroscience, but it necessitates a trade-off between spatial and temporal resolution to maintain a reasonable temporal signal-to-noise ratio (tSNR). Non-Cartesian acquisition schemes are more efficient sampling strategies as compared to Cartesian ones and were proposed as a way to push the limits of spatiotemporal resolution further. 3D-SPARKLING is a novel non-Cartesian scheme recently evaluated for fMRI applications. However, 3D-SPARKLING is highly sensitive to B0 field imperfections. Such imperfections are detrimental to fMRI applications, especially at ultra-high magnetic fields. In this work, we collect measurements of the static and dynamic B0 field perturbations concurrently with 3D-SPARKLING fMRI data acquisition and retrospectively correct these perturbations during image reconstruction. The advantages of this image reconstruction strategy are assessed on the statistical sensitivity to the BOLD contrast during a retinotopic mapping fMRI experiment. Importantly, a gain of 44% (resp., 159%) additionally activated voxels was quantified when adopting this brain activity-enhanced image reconstruction technique at a type-I statistical control level of 0.001 without multiple comparisons correction (resp., 0.05 with false discovery rate correction). Additionally, significantly improved retinotopic maps were retrieved on the cortical surface

Lanthanide Bimetallic Helicates for in Vitro Imaging and Sensing

As the need for targeting luminescent biolabels increases, for mapping selected analytes, imaging of cells and organs, and tracking in cellulo processes, lanthanide bimetallic helicates are emerging as versatile bioprobes. The wrapping of three ligand strands around two metallic centers by selfassembly affords robust molecular edifices with tunable chemical and photophysical properties. In addition, heterometallic helical chelates can be assembled leading to bioprobes with inherent chiral properties. In this paper, we review the literature demonstrating that neutral [Ln2(LCX)3] (x=1–3) helicates represent a viable alternative to existing chelating agents for bio-analyses,while featuring specific enhanced properties. These bimetallic chelates self-assemble inwater, and at physiological pH the 2:3 (Ln:LCX) complex is by far the dominant species, conditional stability constants logβ23 being in the range 23–30. The metal ions are 9-coordinate and lie in sites with slightly distorted D3 symmetry. Efficient protection fromwater interaction by the tightly wrapped ligand strands results in sizeable photophysical properties, with quantum yields up to 24% for EuIII and 11% for TbIII,while the luminescence of several other visible and/or near-infrared emitting LnIII ions is also sensitized. Noncytotoxicity for all the helicates is established for several living cell lines including HeLa, HaCat, MCF-7, 5D10, and Jurkat.We present new data pertaining to the live cell imaging ability of [Eu2(LC1)3] and compare the three systems with x=1–3 with respect to thermodynamic stability, photophysics, cell-permeation ability, and targeting capability for sensing in cellulo processes. Prospects of derivatization for characterizing specific biological interactions are discussed

Estimating ocean vertical velocities using an autonomous multipurpose profiler

International audienceA low-cost multipurpose oceanographic vertical profiler is described. Its application to the measurement of vertical currents, inspired by ocean glider flight-model methods, is presented. Preliminary results of the BioSWOT-Med campaign, carried out in April-May 2023, illustrate the instrument's ability to capture weak signals, potentially linked to sub-mesoscale oceanic structures

A Versatile Ditopic Ligand System for Sensitizing the Luminescence of Bimetallic Lanthanide Bio-Imaging Probes

The homoditopic ligand 6,6’- [methylenebis(1-methyl-1H-benzimid- azole-5,2-diyl)]bis(4-{2-[2-(2-methoxy- ethoxy)ethoxy]ethoxy}pyridine-2-carboxylic acid) (H2LC2) has been tailored to self-assemble with lanthanide ions (LnIII), which results in the formation of neutral bimetallic helicates with the overall composition [Ln2(LC2)3] and also provides a versatile platform for further derivatization. The grafting of poly(oxyethylene) groups onto the pyridine units ensures water solubility, while maintaining sizeable thermodynamic stability and adequate antenna effects for the excitation of both visible- and NIR-emitting LnIII ions. The conditional stability constants (logb23) are close to 25 at physiological pH and under stoichiometric conditions. The ligand triplet state features adequate energy (0-phonon transition at ~21 900 cm-1) to sensitize the luminescence of EuIII (Q=21%) and TbIII (11%) in aerated water at pH 7.4. The emission of several other VIS- and NIR-emitting ions, such as SmIII (Q=0.38%) or YbIII (0.15%), for which in cellulo luminescence is evidenced for the first time, is also sensitized. The EuIII emission spectrum arises from a main species with pseudo-D3 symmetry and without coordinated water. The cell viability of several cancerous cell lines (MCF-7, HeLa, Jurkat and 5D10) is unaffected if incubated with up to 500 mm [Eu2(LC2)3] during 24 h. Bright EuIII emission is seen for incubation concentrations above 10 mm and after a 15-minute loading time; similar images are obtained with TbIII and SmIII. The helicates probably permeate into the cytoplasm of HeLa cells by endocytosis. The described luminescent helical stains are robust chemical species which remain undissociated in the cell medium and in presence of other complexing agents, such as edta, dtpa, citrate or l-ascorbate. Their derivatization, which would open the way to the sensing of targeted in cellulo phenomena, is currently under investigation

Measuring vertical velocities with ADCPs in low-energy ocean

International audienceAbstract Vertical velocities knowledge is essential to study fine-scale dynamics in the surface layers of the ocean and to understand their impact on biological production mechanisms. However, these vertical velocities have long been neglected, simply parameterized, or considered as not measurable, due mainly to their order of magnitude (< mm s −1 up to cm s −1 ), generally much lower than the one of the horizontal velocities (cm s −1 to dm s −1 ), hence the challenge of their in situ measurement. In this paper, we present an upgraded method for direct in situ measurement of vertical velocities using data from different Acoustic Doppler Current Profilers (ADCPs) associated with CTD probes, and we perform a comparative analysis of the results obtained by this method. The analyzed data were collected during the FUMSECK cruise, from three ADCPs: two Workhorse (conventional ADCPs), one lowered on a carousel and the other deployed in free-fall mode, and one Sentinel V (a new generation ADCP with four classical beams and a fifth vertical beam), also lowered on a carousel. Our analyses provide profiles of vertical velocities on the order of mm s −1 , as expected, with standard deviations of a few mm s −1 . While the fifth beam of the Sentinel V exhibits a better accuracy than conventional ADCPs, the free-fall technique provides a more accurate measurement compared to the carousel technique. Finally, this innovative study opens up the possibility to perform simple and direct in situ measurements of vertical velocities, coupling the free-fall technique with a five-beam ADCP