Les Diptères comme outil d’évaluation de l’état du corridor rivulaire – premières expérimentations sur des cours d’eau du Massif central, et comparaison avec des cours d’eau de Bretagne et des Pyrénées

Riparian corridors are the most diverse and complex habitats in the world, the site of many processes essential to maintaining water quality and biodiversity. Diptera, the second largest group of insect species in the world, have ecological requirements that can express the complexity of riverine habitats and subsurface water exchanges. Moreover, they are the most abundant and diverse group in our river corridors. They therefore occupy a major role in the food webs of rivers and riparian terrestrial ecosystems. A rapid sampling method of riverine or aquatic Diptera imagos was applied on 11 stations, including 5 in the Massif central, while the quality of their river corridor was characterised using the IBCR index. The relationships between dipteran communities and riparian corridor characteristics were analyzed. For this, I used a traditional taxonomic approach and a functional approach based on the ecological traits of their larvae (feeding and water affinity). 252 dipteran taxa, including seven dipteran species cited for the first time in France, were identified. The climate, the state of conservation and the flow diversity of the streams in the Puy-de-Dôme seem to be particularly favourable for the communities of riverine Diptera. Our results indicate that an older, wider river corridor with river dynamics favoring a complex mosaic of habitats hosts a greater diversity of species and larval feeding modes and water affinities. In addition, the sampling of dipterans gives indications on the carrying capacity of marginal habitats, making it possible to better valorize hydromorphological restorations.Les corridors rivulaires sont les habitats les plus diversifiés et complexes du globe, sièges de nombreux processus indispensables au maintien de la qualité de l’eau et de la biodiversité. Les Diptères, second plus vaste groupe d’espèces d’insectes dans le monde, possèdent des exigences écologiques susceptibles d’exprimer la complexité des habitats rivulaires et des échanges hydriques de subsurface. De plus, il s’agit du groupe le plus abondant et le plus diversifié de nos corridors rivulaires. Ils occupent donc un rôle majeur dans les réseaux trophiques des cours d’eau et des écosystèmes terrestres riverains. Une méthode rapide d’échantillonnage des imagos de Diptères rivulaires ou aquatiques a été appliquée sur onze stations dont cinq du Massif central, tandis que la qualité de leur corridor rivulaire a été caractérisée à partir de l’indice IBCR. Les relations entre communautés de Diptères et caractéristiques du corridor rivulaire ont été analysées. Pour cela, une approche taxonomique traditionnelle et une approche fonctionnelle basée sur les traits bio-écologiques de leurs larves (alimentation et affinité à l’eau) ont été utilisées. 252 taxons de Diptères, dont sept espèces citées pour la première fois en France ont été identifiés. Le climat, l’état de conservation et la diversité des écoulements des cours d’eau du Puy-de-Dôme semblent particulièrement favorables aux communautés de Diptères rivulaires. Nos résultats indiquent qu’un corridor rivulaire plus ancien, plus large et disposant d’une dynamique fluviale favorisant une mosaïque complexe d’habitats accueille une plus grande diversité d’espèces et de modes alimentaires et d’affinités à l’eau des larves. De plus, l’échantillonnage des Diptères donne des indications sur la capacité d’accueil des habitats hygropétriques et intertidaux, permettant de mieux valoriser les travaux de restauration hydromorphologique

TCAD simulation capabilities towards gate leakage current analysis of advanced AlGaN/GaN HEMT devices

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Advantages of TCAD simulation towards inverstigation of reliability concerns in GaN HEMTs for RF power applications

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Anchoring groups for dyes in p-DSSC application: insights from DFT

We present hybrid, periodic, spin-polarized density functional theory calculations of antiferromagnetic NiO bulk, of its clean (100) surface and of the binding on this latter of four different organic ligands, relevant for p-type dye-sensitized solar cells (p-DSSC) applications. We find evidence for a strong chemisorption of all ligands to the NiO surface in the form of short interatomic distances between surface Ni atoms and ligand atoms, confirmed by high binding energies. Although the analysis of the impact of the ligand adsorption on the density of states of the NiO substrate reveals significant modifications, the overall picture obtained is in line with the operation principles of p-DSSC in all cases. However, some of the considered ligands significantly shift the density of states to lower energies, which, in p-DSSCs employing these ligands to anchor dyes to NiO, could force the use of dyes with deeper HOMO energies and alternative redox couples capable of accepting electrons from the dye (assuming dye bandgaps in the UV/visible range)

Conduction Mechanisms in Oxide–Carbonate Electrolytes for SOFC: Highlighting the Role of the Interface from First-Principles Modeling

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Phytoplankton biodiversity and NW Mediterranean Sea warming: changes in the dinoflagellate genus Ceratium in the 20th century

International audienceOur knowledge of the response of phytoplankton to climate change is restricted by the lack of phytoplankton long-term studies, especially those reporting species data. To circumvent this problem, we combined recent data from sampling at monitoring sites with old bibliographic data. The study was conducted on the genus Ceratium (planktonic dinoflagellates) in the NW Mediterranean, as numerous studies have been conducted in the area since the beginning of the 20th century. In addition, species of this highly diverse genus are known to be particularly sensitive to water temperature, and should thus be responsive to global warming. The temporal distribution of Ceratium species over the last century showed a progressive disappearance from the surface layer of likely stenothermic species, which may have moved to deeper layers in response to water warming, along with a decrease of species richness during the annual cycle. Seasonal and phenological aspects of Ceratium assemblages were also affected, as illustrated by the earlier timing in the minimum of richness. A change in the overall species assemblage also occurred from past to present in the Ligurian Sea, suggesting a warming in this area consistent with the development in surface water temperatures. Our results suggest that Ceratium species may constitute good biological indicators of warming in the NW Mediterranean Sea. In addition, the present study showed the importance of time-series data and the value of historical literature as the basis for ecological studies of long-term trends needed to substantiate our current understanding of the impact of global change on marine biodiversity

Modelling diatom life forms and ecological guilds for river biomonitoring

Biomonitoring is central to the European Union's Water Framework Directive (WFD) and to the French water and aquatic environmental law, but most diatom indices do not separate different anthropogenic impacts. To address this gap, the effect of water chemistry on diatom ecological guilds and life forms was assessed in order to indicate stream perturbations. Generalised additive models (GAMs) were built on a large-scale data set of 1571 samples from the French monitoring network. The relationships between diatom ecological guild and life form metrics were investigated by Principal components analysis and the results predicted by GAMs. The models characterised eight chemical parameters that modified adaptive strategies (ecological guilds) and growth morphology (life forms). Total phosphorus, conductivity, nitrate and pH are the main influencing factors, followed by temperature, dissolved oxygen and organic matter. The findings confirm three groups of diatoms with different adaptive strategies: 1 - fast moving species, 2 - species growing close to the substrate and 3 - species extending to the surface layers of the biofilm. Thirteen diatom metrics displayed a variety of responses to different ranges of the eight chemical parameters. These metrics could be used to help to identify and quantify which chemical alterations are caused by polluted effluents in rivers

Role of smooth muscle cell mineralocorticoid receptor in vascular tone

International audienceIdentification of the mineralocorticoid receptor (MR) in the vasculature (i.e., endothelial and smooth muscle cells) raised the question of its role in vascular function and blood pressure control. Using a mouse model with conditional inactivation of MR in vascular smooth muscle cell (VSMC) (MR(SMKO)), we have recently shown that the VSMC MR is crucial for aldosterone-salt-induced carotid stiffening. In the present study, we have investigated the specific contribution of the VSMC MR in the regulation of vascular tone in large vessels. In MR(SMKO) mice, contractions induced by potassium chloride and calcium (Ca(2+)) are decreased in the aorta, whereas contraction is normal in response to phenylephrine and caffeine. The difference in response to Ca(2+) suggests that the VSMC-specific deficiency of the MR modifies VSM Ca(2+) signaling but without altering the intracellular Ca(2+) store handling. The relaxation induced by acetylcholine is not affected by the absence of MR. However, the relaxation induced by Ach in the presence of indomethacin and the relaxation induced by sodium nitroprussiate are significantly reduced in MR(SMKO) mice compared to controls. Since endothelial nitric oxide synthase (eNOS) activity is increased in mutant mice, their altered relaxation reflects impairment of the nitric oxide (NO) signaling pathway. In addition to altered NO and Ca(2+) signaling, the activity of myosin light chain and its regulators, myosin light chain kinase (MLCK) and myosin phosphatase (MLCP), is reduced. In conclusion, MR expressed in VSMC is required for NO and Ca(2+) signaling pathways and contractile protein activity leading to an altered contraction/relaxation coupling

Smooth Muscle Cell Mineralocorticoid Receptors Are Mandatory for Aldosterone\textendashSalt to Induce Vascular Stiffness

International audienceArterial stiffness is recognized as a risk factor for many cardiovascular diseases. Aldosterone via its binding to and activation of the mineralocorticoid receptors (MRs) is a main regulator of blood pressure by controlling renal sodium reabsorption. Although both clinical and experimental data indicate that MR activation by aldosterone is involved in arterial stiffening, the molecular mechanism is not known. In addition to the kidney, MR is expressed in both endothelial and vascular smooth muscle cells (VSMCs), but the specific contribution of the VSMC MR to aldosterone-induced vascular stiffness remains to be explored. To address this question, we generated a mouse model with conditional inactivation of the MR in VSMC (MRSMKO). MRSMKO mice show no alteration in renal sodium handling or vascular structure, but they have decreased blood pressure when compared with control littermate mice. In vivo at baseline, large vessels of mutant mice presented with normal elastic properties, whereas carotids displayed a smaller diameter when compared with those of the control group. As expected after aldosterone/salt challenge, the arterial stiffness increased in control mice; however, it remained unchanged in MRSMKO mice, without significant modification in vascular collagen/elastin ratio. Instead, we found that the fibronectin/α5-subunit integrin ratio is profoundly altered in MRSMKO mice because the induction of α5 expression by aldosterone/salt challenge is prevented in mice lacking VSMC MR. Altogether, our data reveal in the aldosterone/salt hypertension model that MR activation specifically in VSMC leads to the arterial stiffening by modulation of cell-matrix attachment proteins independent of major vascular structural changes

Large Mode Area Solid-Core Photonic Bandgap Yb-doped Fiber with Hetero-Structured Cladding for Compact High-Power Laser Systems

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