Stoichiometry of lipid synthesizing calanoid copepods in Arctic and sub-Arctic marine regions Insights into limitation and elemental cycling from characterization of C:N:P ratios

Calanoid copepods, Calanus finmarchicus, C. glacialis and C. hyperboreus, are key species in Arctic and sub-Arctic marine ecosystems. They represent important prey for a number of species such as juvenile herring and cod because of their high but seasonally variable calorific value: they synthesize and store lipids as part of their survival strategy. Limitations in food quantity and quality can have strong impact on the copepods’ lipid synthesis and development, with implications for their predators and thus for the lipid-driven Arctic marine food web. Ecological stoichiometry, i.e. the study of the relative abundance of elements (most commonly carbon, nitrogen, and phosphorus) in biological entities, is a powerful tool to study potential limitation of aquatic organisms, particularly in primary producers and in omnivorous and herbivorous zooplankton grazers. However, studies that apply a stoichiometric approach to the high-latitude marine regions are extremely rare. The main aim of this thesis is to reveal the elemental requirements and potential limitation of high-latitude calanoid copepods by investigating their C:N:P composition in combination with information on other biochemical compounds. The impact of copepods on nutrient recycling and C:N:P export through fecal pellets is also investigated. The study was conducted in a sub-Arctic north-Norwegian fjord, and in the western part of the European Arctic Ocean, focusing on the period of intense primary production during spring. Somatic stoichiometric ratios in copepods were calculated by subtracting C in the lipid sac from the total body C. Due to the strong influence of lipid storage on total body stoichiometry, high-latitude calanoid copepods, and by implication lipid-synthesizing zooplankton in general, should be treated through a two-compartment stoichiometric approach, with lipid storage and somatic tissues separated. Both season and development stage influence the somatic elemental ratios. The somatic C:P ratios of high-latitude calanoid copepods are somewhat lower than those reported in marine copepods from other areas, suggesting that they have higher growth rates than temperate and tropical copepods. Seston C:N:P stoichiometry is used as a proxy for food quality in the calculation of copepod elemental limitation. The seston C:P and N:P ratios are among the first to be reported for the Arctic Ocean and indicate a higher relative proportion of nutrients (N and P) compared to published seston values from other marine regions. Seston C:N:P ratios varied according to bloom stage, which therefore also impacts the potential C, N or P limitation of copepods. Unless they have high assimilation efficiency for C, calanoid copepods are shown to be most likely subject to C limitation. However, variable requirements during ontogeny make specific stages, such as copepodite IV, and females more sensitive to nutrient limitation (N or P). This study is the first to present data on stoichiometric ratios including P for copepod fecal pellets in the Arctic, and shows their high potential not only to vertically export P at depth but also to provide a source of P in the upper layers during the productive season if degraded. The Arctic marine regions are experiencing the greatest climate change, and the potential future stoichiometric changes in the Arctic and how climate change affects copepod-seston interaction are discussed

Cycloadditions [2+2+2] catalysées par des complexes du cobalt (utilisation de nouveaux partenaires et développement de nouveaux systèmes catalytiques)

Cette thèse porte sur les cycloadditions [2+2+2] catalysées par les complexes du cobalt. La première partie de ce manuscrit traite de la cocyclisation d esters alcynylboroniques avec des alcènes. Nous avons obtenu différents cyclohexadiènes diborés qui ont pu être fonctionnalisés par couplage de Suzuki. Le développement de nouveaux systèmes catalytiques fait ensuite l objet d une seconde partie. Un système à base de diiodure de cobalt, de manganèse et d un carbène N-hétérocyclique s est révélé être très efficace pour la cyclisation d ènediynes. Enfin la réactivité d un nouveau complexe du cobalt, stable à l air, a été étudiée.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Export stoichiometry and contribution of copepod faecal pellets to vertical flux of particulate organic carbon, nitrogen and phosphorus

Peer reviewe

Le CO2 supercritique pour la régénération des masques FFP2

L' épidémie de Covid-19 (maladie à coronavirus), déclarée pandémie en mars 2020 par l’OMS, a mis en exergue la problématique mondiale de pénurie de protections faciales filtrantes, et tout particulièrement la disponibilité des masques respiratoires chirurgicaux et FFP2. Afin de faire face à la pénurie de masques et limiter la pollution liée à l’amoncellement de ces déchets usagés, plusieurs équipes de recherche, à l’échelle nationale, se sont organisées pour trouver dessolutions pérennes afin de décontaminer les protections faciales en vue de les réutiliser. Cette question se pose notamment pour la décontamination des FFP2 au service des soignants, les plus exposés au risque de contamination

Progression of adenomyosis magnetic resonance imaging features under ulipristal acetate for symptomatic fibroids

International audienceResearch question: What is the evolution of adenomyosis on magnetic resonance imaging (MRI) after a 3-month treatment course of daily 5 mg doses of ulipristal acetate (UPA) for symptomatic fibroids?Design: A monocentric prospective pilot study on patients who underwent a 3-month treatment course of UPA for symptomatic fibroids between January 2014 and December 2017. Patients underwent pelvic MRI shortly before (pre-MRI) and after treatment (post-MRI). The diagnosis of adenomyosis on MRI was defined by the observation of intramyometrial cysts and/or haemorrhagic foci within these cystic cavities and/or a thickening of the junctional zone >12 mm. The progression of adenomyosis was defined by the presence of at least one of the aforementioned criteria of adenomyosis on the pre-MRI and by at least one of the following on the post-MRI: (i) increased thickness of the junctional zone ≥20% and/or (ii) increased number of intramyometrial cysts. The appearance of adenomyosis was defined by the absence of the aforementioned criteria of adenomyosis on the pre-MRI and the presence of at least one of these criteria on the post-MRI.Results: Seventy-two patients were included. The MRI features of adenomyosis progressed for 12 of 15 patients (80.0%) for whom adenomyosis was identified on the pre-MRI. An appearance of adenomyosis was identified after treatment for 15 of 57 patients (26.3%) for whom adenomyosis was not identified on the pre-MRI.Conclusions: A 3-month treatment course of daily 5 mg doses of UPA could provoke a short-term progression or an emergence of typical adenomyosis intramyometrial cysts on MRI examinations

Vegetable Oil-based Hybrid Submicron Particles Loaded with JMV5038: A Promising Formulation against Melanoma

International audienc

3D Imaging of On-Chip Porous Medium Using X-ray Laminography: Application to Reactive Flow Dissolution at Small Scales

International audienceIn this study, X-ray laminography is used to monitor the evolution of a model 3D packed bed porous medium on a chip (micromodels) undergoing reactive flows. The obtained 3D images are used to compute the fluid flow patterns and develop insights into dissolution mechanisms. This study is a first proof of concept study, with controlled micromodels, and could later be extended towards deeper understanding of the dissolution and precipitation processes occurring in porous media at the microscale, mechanisms which are relevant to many industrial areas including catalysis, geochemistry, energy, and waste storage in deep geological formations, etc