Conservation and management in the French sub-Antarctic islands and surrounding seas

Of the French islands in the Southern Indian Ocean, Archipel Crozet and Iles Kerguelen are considered sub-Antarctic, and Ile Amsterdam and Ile Saint-Paul temperate. All have endemic species amongst their biota. The Terres Australes et Antarctiques Franyaises (TAAF) is responsible for sovereignty of these islands, the French Polar Institute (IPEV) is the central agency for research, and the Committee for the Polar Environment (CEP) provides advice on environmental protection and management issues. In 2006 all of the islands gained the status of Nature Reserve, and a management plan is expected to be in place within three years, providing greater protection for the environment and biota

2D Axisymmetric Coupled Computational Fluid Dynamics–Kinetics Modeling of a Nonthermal Arc Plasma Torch for Diesel Fuel Reforming

International audienceThe present study is dedicated to the 2D axisymmetric coupled computational fluid dynamics–kinetics modeling of a plasma-assisted diesel fuel reformer developed for two different applications: (i) onboard H2 production for fuel-cell feeding and (ii) NOx trap regeneration. These cases correspond to very different reaction conditions. In the first case, diesel fuel reacts with air, while in the second case, it reacts with diesel engine exhaust gas. The plasma is modeled with a simple power source domain. n-Heptane has been chosen as a surrogate molecule for diesel fuel. A reduced kinetic mechanism is used for the study. Both cases have been studied under adiabatic and nonadiabatic postreactor conditions. We can distinguish four zones in the torch: a reactant heating zone, a plasma zone, a mixing zone, and a postdischarge zone. The main precursors of the reforming reactions are H, O, and OH radicals. The oxygen rate is a key point of the application. The thermal losses make the reforming reaction difficult to ignite and beget a lower syngas production and a lower postdischarge temperature. For the nonadiabatic reactor, the results have been compared to experimental data. The model predicts relevant gas fractions

3D MHD modelling of low current-high voltage dc plasma torch under restrike mode

International audienceWe present in this paper a magnetohydrodynamic (MHD) modelling of the gliding arc behaviour of a dc plasma torch operating with air under low current and high voltage conditions. The low current leads to instabilities and difficulties with simulating the process because the magnetic field is not sufficient to constrict the arc. The model is 3D, time dependent and the MHD equations are solved using CFD software Code_Saturne®. Although the arc is definitively non-local thermodynamic equilibrium (LTE), the LTE assumption is considered as a first approach. The injection of air is tangential. A hot gas channel reattachment model has been used to simulate the restriking process of the arc root. After the description of the model, the most appropriate electrical voltage breakdown parameter has been selected in comparing with experimental results. A typical operating point is then studied in detail and shows the helical shape of the arc discharge in the nozzle. Finally, the mass flow rate and the current have been varied in the range 0.16-0.5 g s−1 and 100-300 mA, respectively, corresponding to typical glidarc operating points of our experimental plasma torch. The model shows good consistency with experimental data in terms of global behaviour, arc length, mean voltage and glidarc frequency

Theoretical study of Diesel fuel reforming by a non-thermal arc discharge

International audienceNitrogen oxides are in the center of future EURO VI norm, the European anti-pollution norm namely for Diesel powered vehicles. NOx (NO, NO2,...) are very irritant pollutants for people and are considered as tropospherical ozone precursors. Their effect is observed when ozone peak pollution is noticed during rush hours. A promising post-treatment technology is to add a NOx trap in exhaust line to store NOx under nitrate form. An alternative to fuel-air ratio increase and catalytic tech-nologies purge is the use of non-thermal plasma. Plasma reforming of diesel fuel and exhaust gas mix-ture creates reducing chemical species like hydrogen and carbon monoxide, which are able to purge the NOx trap

Exhaust gas fuel reforming of Diesel fuel by non-thermal arc discharge for NOx trap regeneration application

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Energy and Fuels copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/ef101674rInternational audienceThe present study is dedicated to the reforming of diesel fuel with diesel engine exhaust gas (i.e., air, CO2, and H2O mixture) using a nonthermal plasma torch for a NOx trap regeneration application. The plasma technology developed is based on a high voltage/low current nonthermal plasma torch. In the first part of the paper, experimental results on synthesis gas production from exhaust gas fuel reforming of diesel fuel are reported. In the second part of the paper, these experimental results are compared with a 1D multistage model using n-heptane as a surrogate molecule for diesel fuel. Two compositions of synthetic diesel engine exhaust gas, corresponding to high and low engine loads, have been studied. It has been demonstrated that the oxygen from CO2 and H2O hardly ever intervenes in the reforming reactions. In the most favorable condition corresponding to a higher O2 rate, a production of 7 × 10−3 mol*s−1 of syngas has been reached, corresponding to an energy efficiency and a conversion rate of 40% and 95%, respectively. The 1D multistage model shows fair trends with experimental results despite an important shift mainly due to thermal losses, which are not taken into account in the 1D model. From these results and considering a real NOx trap regeneration onboard application, it can be estimated for the most favorable case that, during the regeneration phase (approximately 12 s every 11 km), the power needed to run the plasma will be around 2.2% of the engine power

3D MHD unsteady state modeling of a high voltage - low current plasma torch operating with air

Available on: http://ispc20.plasmainstitute.org/my_ispc/papers/170.pdfInternational audienceA non-transferred high voltage - low current DC plasma torch operating with air has been simulated using Code_Saturne CFD software for current lower than 1 A. The 3D MHD model considers two injection configurations: axial and vortex. The current and the air flow rate have been tuned in the range 0.3 to 0.6 A and 0.16 to 0.5 g/s, respectively. The influence of these parameters on the arc behavior and the arc characteristics has been studied in terms of temperature, velocity, electrical potential and Joule heating

Experimental and theoretical study of exhaust gas fuel reforming of Diesel fuel by a non-thermal arc discharge for syngas production

Available on: http://ispc20.plasmainstitute.org/my_ispc/papers/105.pdfInternational audienceAn experimental set-up has been developed to study two typical operating points of Diesel powered vehicle, corresponding to high load and low load points. A sensibility study over O/C ratio, injected electric current and mass flow rate have been carried out. The plasma reformer performances have been evaluated in terms of energy efficiency and conversion rate. At low engine load, an energy efficiency of 40% and a conversion rate of 95% have been reached which correspond to a syngas dry molar fraction of 25%. For the most favorable case, only 12 s are needed to regenerate the NOx trap catalyst. The 1D multistage kinetic model developed has shown good trend correlation with experimental results. It has been demonstrated that the oxygen from CO2 and H2O almost does not intervene in the exhaust gas Diesel fuel reforming. At the contrary, CO2 and H2O decrease temperatures, the kinetic reaction speed and the energy efficiency compared to POx reaction. To higher the temperature, more oxygen is needed but local combustion can happen and promote H2O and CO2 production

Diagnostic value of minor salivary glands biopsy for the detection of Lewy pathology

The recent demonstration of the presence of Lewy pathology in the submandibular glands of Parkinson\u27s disease (PD) patients prompted us to evaluate the diagnostic performance of minor salivary gland biopsy for PD. Minor salivary glands were examined for Lewy pathology using phosphorylated alpha-synuclein antibody in 16 patients with clinically diagnosed PD and 11 control subjects with other neurological disorders. Abnormal accumulation of alpha-synuclein was found in 3 out of 16 PD patients. Two control subjects exhibited weak phosphorylated alpha-synuclein immunoreactivity. Our results do not support the use of minor salivary glands biopsy for the detection of Lewy pathology in living subjects

Food uptake, lipid transport and vitellogenesis in the sea anemone Nematostella vectensis

Balancing energy input and output is crucial for the survival of all organisms, and involves the coordination of many physiological processes such as food uptake, nutrient storage, reproduction and growth. The uptake of food particles through endocytic mechanisms (e.g. phagocytosis, receptor-mediated endocytosis) is broadly observed and likely the ancestral mode of feeding in metazoans. However, only little is known about the biology and evolution of endocytic cell types involved in animal nutrition. Similarly, the dynamics and molecular pathways underlying the transport of nutrients is poorly investigated in animals without a circulatory system. The lack of available studies, especially in non-bilaterian animals (e.g. cnidarians, sponges) leaves a number of key questions unresolved: how did endocytic cell types evolve? What are the ancestral modalities of nutrient transport in animals? In my thesis, I address these questions by investigating the cells and molecular pathways underlying food uptake and, as a specific example of lipid transport, vitellogenesis, in the sea anemone Nematostella vectensis. By characterizing the path of food particles and dietary lipids from their ingestion to their incorporation into yolk, I aim to fill in gaps in our understanding of nutrient uptake and transport in non-bilaterians and thereby shed light on the evolution of these processes in animals. In Nematostella, nutrient acquisition starts with the extracellular digestion of prey in the gastric cavity through secreted digestive enzymes. Using single-cell RNA sequencing (scRNA-seq), I characterized the cellular composition of the gastrodermal folds lining the gastric cavity (mesenteries) and found a high diversity of specialized gland cells expressing specific enzymatic repertoires. Extra-cellular digestion is followed by endocytosis and subsequent intracellular digestion of food particles. By using particle uptake assays, I revealed that phagocytosis and receptor-mediated endocytosis predominantly occur in specific regions of the mesenteries in Nematostella, highlighting a surprising regionalization of the anthozoan gastrodermis. These regions colocalize with the cellular expression of Nematostella orthologs of bilaterian genes typically involved in endocytosis (e.g. mannose receptor, clathrin). This strongly supports the digestive function of these cells and indicates a conserved nature of endocytic molecular pathways between cnidarians and bilaterians. These results were further validated by scRNA-seq, which revealed three distinct populations of trophic endocytes co-localizing within the endocytic region of the mesentery. In bilaterians, dietary nutrients are most often transported towards other tissues via the circulatory system in order to be stored or to support the metabolism of peripheral tissues. Cnidarians lack a circulatory system, and the gastro-vascular cavity is thought to distribute nutrients throughout the body. The extracellular matrix (mesoglea) was previously proposed to participate in nutrient transport, but its role in this process has so far been unclear. In the present work, I describe for the first time the dynamic trans-epithelial transport of lipids from the gastric cavity into maturing oocytes located in the mesoglea in a cnidarian. Consistent with their function in shuttling lipids between the gastric cavity and the oocyte, somatic cells of the gonad epithelium also produce the glycolipoprotein Vitellogenin, a conserved yolk precursor. Gene expression data shows that the uptake of Vitellogenin into growing oocytes likely occurs through receptor-mediated endocytosis using orthologs of the vldlr/apolipophorin receptor gene family. This supports the hypothesis that a specific Vitellogenin ligand/receptor pair is highly conserved in vitellogenesis between cnidarians and bilaterians. Finally, I characterized the expression and protein localization of ApoB, a Nematostella ortholog of the bilaterian systemic lipid transport proteins Apolipoprotein-B/Apolipophorins. ApoB protein was not detected in growing oocytes in Nematostella but surprisingly localized in spermaries, suggesting a role during spermatogenesis. Overall, these results demonstrate the mesogleal transport of lipids potentially using conserved lipoprotein-lipoprotein receptor pairs in the absence of a circulatory system, and raise the possibility of a rudimentary systemic lipid transport system in Nematostella. Altogether, my thesis revealed that nutrient uptake in Nematostella involves a remarkable diversity of specialized cell types that define functional domains in the mesenteries. The molecular machinery for food uptake, intracellular digestion and lipid transport seems to be highly conserved between Nematostella and bilaterians, providing an opportunity to elucidate the ancestral state of mechanisms underlying energy homeostasis in the last common ancestor to cnidarians and bilaterians.Doktorgradsavhandlin