Four-wave interaction in gas and vacuum: definition of a third-order nonlinear effective susceptibility in vacuum: χvacuum(3)

International audienceSemiclassical methods are used to study the nonlinear interaction of light in vacuum in the context of four wave mixing. This study is motivated by a desire to investigate the possibility of using recently developed powerful ultrashort (femtosecond) laser pulses to demonstrate the existence of nonlinear effects in vacuum, predicted by quantum electrodynamics (QED). An approach, similar to classical nonlinear optics in a medium, is developed in this article. A third-order nonlinear effective susceptibility of vacuum is then introduced

Ultrasoft Finemet thin films for magneto-impedance microsensors

International audienceFeCuNbSiB thin films have been deposited using RF sputtering. Characterizations have shown that oxygen contamination and residual stress are mainly responsible for magnetic hardening. The sputtering and annealing conditions have been optimized and films with coercive field as low as 10 A m-1 (0.125 Oe) have been achieved. In addition, the influence of film thickness on the magnetic properties has been studied. Thus, magnetic field microsensors based on the magneto-impedance effect have been fabricated by stacking up Finemet/copper/Finemet films. The highest sensitivity (4000 V/T/A) is reached for 750 nm thick films. It is in the same range as cm-sized macroscopic devices realized using 20 μm thick ribbons

Films minces ultradoux pour la réalisation de microcapteurs GMI

National audienceLe procédé de dépôt de films minces de Finemet par pulvérisation RF a été étudié de manière à minimiser la coercivité des films. Ce matériau devient particulièrement intéressant pour la réalisation de microcapteurs à magnétoimpédance géante puisque la sensibilité et l'hystérésis de ces capteurs sont directement liés aux propriétés de la couche ferromagnétique qui les constitue. La coercivité du Finemet est particulièrement sensible à la contamination en oxygène. La vitesse de dépôt nécessairement rapide induit alors des contraintes importantes. La température de recuit a été optimisée de manière à relaxer les contraintes et amorcer la cristallisation. Les études ont montré que les conditions de recuit optimales correspondent à la température de cristallisation Tx. Après optimisation des conditions de dépôt et de recuit, la coercivité a été réduite à 10 A m-1 pour un film de 500 nm. L'intégration du Finemet dans des microcapteurs GMI a permis d'obtenir des sensibilités importantes, du même ordre de grandeur que celle de capteurs macroscopiques (autour de 4100 V/T/A pour un capteur de 4 mm x 200 µm x 2 µm)

River temperature analysis with a new way of using Independant Component Analysis

In the context of global warming, river management is essential to maintain favourable water temperature ranges for aquatic species. Therefore, understanding the main factors influencing the water temperature becomes a key part in the management process. In this paper, we used Independent Component Analysis (ICA) to identify these main factors and improve water temperature forecasting. The study is caried out on two rivers in Normandy (France) with quite different characteristics. Each river was equipped with several temperature sensors which series range from 2011 to 2021. The ICA analysis of the data series reveals that the thermal regime of these two rivers is mainly controlled by seasonal and daily climatic factors. The Sélune regime also turns out to be influenced by the presence of a dam, dismantled during the monitoring of the river. The temperature of the Odon appears to be clearly controlled by seasonal lightening conditions in connection with the presence of the riparian vegetation. Complementary, an innovative approach called “successive ICA” is used to reconstruct the natural thermal regime of the Sélune without the presence of the dam. Emphasis is therefore placed here on the interest of ICA in hydrology as en elementary method for extracting the main influencing factors and quantifying their importance on the thermal regime of a river. It also allows to remove the influence of a particular factor and reconstruct time series better suited for temperature forecasting. The method used here is not specific to temperature time series and can be applied to any region even with different hydrological characteristics

Inorganic pyrophosphate generation by transforming growth factor-beta-1 is mainly dependent on ANK induction by Ras/Raf-1/extracellular signal-regulated kinase pathways in chondrocytes

ANK is a multipass transmembrane protein transporter thought to play a role in the export of intracellular inorganic pyrophosphate and so to contribute to the pathophysiology of chondrocalcinosis. As transforming growth factor-beta-1 (TGF-β1) was shown to favor calcium pyrophosphate dihydrate deposition, we investigated the contribution of ANK to the production of extracellular inorganic pyrophosphate (ePPi) by chondrocytes and the signaling pathways involved in the regulation of Ank expression by TGF-β1. Chondrocytes were exposed to 10 ng/mL of TGF-β1, and Ank expression was measured by quantitative polymerase chain reaction and Western blot. ePPi was quantified in cell supernatants. RNA silencing was used to define the respective roles of Ank and PC-1 in TGF-β1-induced ePPi generation. Finally, selective kinase inhibitors and dominant-negative/overexpression plasmid strategies were used to explore the contribution of several signaling pathways to Ank induction by TGF-β1. TGF-β1 strongly increased Ank expression at the mRNA and protein levels, as well as ePPi production. Using small interfering RNA technology, we showed that Ank contributed approximately 60% and PC-1 nearly 20% to TGF-β1-induced ePPi generation. Induction of Ank by TGF-β1 required activation of the extracellular signal-regulated kinase (ERK) pathway but not of p38-mitogen-activated protein kinase or of protein kinase A. In line with the general protein kinase C (PKC) inhibitor calphostin C, Gö6976 (a Ca2+-dependent PKC inhibitor) diminished TGF-β1-induced Ank expression by 60%, whereas a 10% inhibition was observed with rottlerin (a PKCδ inhibitor). These data suggest a regulatory role for calcium in TGF-β1-induced Ank expression. Finally, we demonstrated that the stimulatory effect of TGF-β1 on Ank expression was inhibited by the suppression of the Ras/Raf-1 pathway, while being enhanced by their constitutive activation. Transient overexpression of Smad 7, an inhibitory Smad, failed to affect the inducing effect of TGF-β1 on Ank mRNA level. These data show that TGF-β1 increases ePPi levels, mainly by the induction of the Ank gene, which requires activation of Ras, Raf-1, ERK, and Ca2+-dependent PKC pathways in chondrocytes

Structure of a Bathtub Vortex : Importance of the Bottom Boundary Layer

A bathtub vortex in a cylindrical tank rotating at a constant angular velocity [omega] is studied by meansof a laboratory experiment, a numerical experiment and a boundary layer theory. The laboratory and numerical experiments show that two regimes of vortices in the steady-state can occur depending on [omega] and the volume flux Q through the drain hole: when Q is large and [omega] is small, a potential vortex is formed in which angular momentum outside the vortex core is constant in the non-rotating frame. However, when Q is small or [omega] is large, a vortex is generated in which the angular momentum decreases with decreasing radius. Boundary layertheory shows that the vortex regimes strongly depend on the theoretical radial volume flux through the bottomboundary layer under a potential vortex : when the ratio of Q to the theoretical boundary-layer radial volume flux Qb (scaled by 2π R2([omega] ν)12 ) at the outer rim of the vortex core is larger than a critical value (of order 1), the radial flow in the interior exists at all radiiand Regime I is realized, where R is the inner radius of the tank and ν the kinematicviscosity.When the ratio is less than the critical value, the radial flow in the interior nearlyvanishes inside a critical radius and almost all of the radial volume flux occurs only in the boundary layer,resulting in Regime II in which the angular momentum is not constant with radius. This criterion is found to explain the results of the laboratory and numerical experiments very well

Beyond equilibrium: Re-evaluating physical modelling of fluvial systems to represent climate changes

© 2018 Elsevier B.V. The interactions between water, sediment and biology in fluvial systems are complex and driven by multiple forcing mechanisms across a range of spatial and temporal scales. In a changing climate, some meteorological drivers are expected to become more extreme with, for example, more prolonged droughts or more frequent flooding. Such environmental changes will potentially have significant consequences for the human populations and ecosystems that are dependent on riverscapes, but our understanding of fluvial system response to external drivers remains incomplete. As a consequence, many of the predictions of the effects of climate change have a large uncertainty that hampers effective management of fluvial environments. Amongst the array of methodological approaches available to scientists and engineers charged with improving that understanding, is physical modelling. Here, we review the role of physical modelling for understanding both biotic and abiotic processes and their interactions in fluvial systems. The approaches currently employed for scaling and representing fluvial processes in physical models are explored, from 1:1 experiments that reproduce processes at real-time or time scales of 10 −1 -10 0 years, to analogue models that compress spatial scales to simulate processes over time scales exceeding 10 2 –10 3 years. An important gap in existing capabilities identified in this study is the representation of fluvial systems over time scales relevant for managing the immediate impacts of global climatic change; 10 1 – 10 2 years, the representation of variable forcing (e.g. storms), and the representation of biological processes. Research to fill this knowledge gap is proposed, including examples of how the time scale of study in directly scaled models could be extended and the time scale of landscape models could be compressed in the future, through the use of lightweight sediments, and innovative approaches for representing vegetation and biostabilisation in fluvial environments at condensed time scales, such as small-scale vegetation, plastic plants and polymers. It is argued that by improving physical modelling capabilities and coupling physical and numerical models, it should be possible to improve understanding of the complex interactions and processes induced by variable forcing within fluvial systems over a broader range of time scales. This will enable policymakers and environmental managers to help reduce and mitigate the risks associated with the impacts of climate change in rivers

Biomarkers of browning of white adipose tissue and their regulation during exercise- and diet-induced weight loss

Background: A hypothesis exists whereby an exercise- or dietary-induced negative energy balance reduces human subcutaneous white adipose tissue (scWAT) mass through the formation of brown-like adipocyte (brite) cells. However, the validity of biomarkers of brite formation has not been robustly evaluated in humans, and clinical data that link brite formation and weight loss are sparse. Objectives: We used rosiglitazone and primary adipocytes to stringently evaluate a set of biomarkers for brite formation and determined whether the expression of biomarker genes in scWAT could explain the change in body composition in response to exercise training combined with calorie restriction in obese and overweight women (n = 79). Design: Gene expression was derived from exon DNA microarrays and preadipocytes from obesity-resistant and -sensitive mice treated with rosiglitazone to generate candidate brite biomarkers from a microarray. These biomarkers were evaluated against data derived from scWAT RNA from obese and overweight women before and after supervised exercise 5 d/wk for 16 wk combined with modest calorie restriction (∼0.84 MJ/d). Results: Forty percent of commonly used brite gene biomarkers exhibited an exon or strain-specific regulation. No biomarkers were positively related to weight loss in human scWAT. Greater weight loss was significantly associated with less uncoupling protein 1 expression (P = 0.006, R(2) = 0.09). In a follow-up global analysis, there were 161 genes that covaried with weight loss that were linked to greater CCAAT/enhancer binding protein α activity (z = 2.0, P = 6.6 × 10(−7)), liver X receptor α/β agonism (z = 2.1, P = 2.8 × 10(−7)), and inhibition of leptin-like signaling (z = −2.6, P = 3.9 × 10(−5)). Conclusion: We identify a subset of robust RNA biomarkers for brite formation and show that calorie-restriction–mediated weight loss in women dynamically remodels scWAT to take on a more-white rather than a more-brown adipocyte phenotype

Physical modelling of water, fauna and flora: knowledge gaps, avenues for future research and infrastructural needs

peer reviewedPhysical modelling is a key tool for generating understanding of the complex interactions between aquatic organisms and hydraulics, which is important for management of aquatic environments under environmental change and our ability to exploit ecosystem services. Many aspects of this field remain poorly understood and the use of physical models within eco-hydraulics requires advancement in methodological application and substantive understanding. This paper presents a review of the emergent themes from a workshop tasked with identifying the future infrastructure requirements of the next generation of eco-hydraulics researchers. The identified themes are: abiotic factors, adaptation, complexity and feedback, variation, and scale and scaling. The paper examines these themes and identifies how progress on each of them is key to existing and future eðorts to progress our knowledge of eco-hydraulic interactions. Examples are drawn from studies on biofilms, plants, and sessile and mobile fauna in shallow water fluvial and marine environments. Examples of research gaps and directions for educational, infrastructural and technological advance are also presented.PISCES work package of HYDRALAB FP