Déformations d'interface engendrées par une excitation électromagnétique basse fréquence et mesure des transferts de masse associés

We study the parametric instabilities of a surface or interface generated by the application of a very low frequency electromagnetic field to a mercury tank. To this end, we have developed two new methods for measuring surface or interface deformations. A resistive measurement method using a carbon fiber probe and an electrochemical method for measuring interfacial mass transfer. The obtained results allow from one hand to check the relevance of earlier theoretical predictions on this subject (linear stability analysis of a metal surface under a low frequency electromagnetic field) and to the other to highlight new dynamic behaviors of the interface, including the electrochemical method for measuring interfacial mass transfer. The latter makes possible to obtain comprehensive information on the behavior of an interface opposite to the local character of the resistive type measurement. The results of transfers were related to the Davies' approach on this topic, consolidating the importance of capillary scale in the mechanisms governing mass transfer at free interfaces. The method for measuring interfacial mass transfer is especially suited to the study of hydrodynamic regimes dealing with large interface deformations where optical measurements are difficult to implement.Nous étudions les instabilités paramétriques de surface et d’interface provoquées par l’application d’un champ électromagnétique très basse fréquence sur une cuve de mercure. A cette fin, nous avons développé deux nouvelles méthodes de mesure des déformations de surface ou d’interface. Une méthode de mesure résistive utilisant une sonde en fibres de carbone et une méthode électrochimique de mesure des transferts de masse interfaciaux. Les résultats obtenus ont permis, d’une part de vérifier la pertinence des prévisions théoriques antérieures sur ce sujet (analyse linéaire de la stabilité d’une surface de métal soumise à un champ électromagnétique basse fréquence) et d’autre part de mettre en évidence de nouveaux comportements dynamiques de l’interface, notamment par la méthode de mesure électrochimiques des transferts de masse interfaciaux. Cette dernière permet en effet d’obtenir une information globale sur le comportement d’une interface en mouvement à l’opposé du caractère local de la mesure de type résistive. Les résultats de transferts ont été reliés à l’approche de Davies sur ce sujet, confortant l’importance de l’échelle capillaire dans les mécanismes qui gouvernent les transferts de masse aux interfaces. La méthode de mesure des transferts de masse interfaciaux s’avère particulièrement adaptée à l’étude des régimes hydrodynamiques engendrant de fortes déformations d’interface, domaine où les mesures optiques s’avèrent difficiles à mettre en œuvre

Experimental evidence of Alfv\'en wave propagation in a Gallium alloy

Experiments with a liquid metal alloy, galinstan, are reported and show clear evidence of Alfv\'en wave propagation as well as resonance of Alfv\'en modes. Galinstan is liquid at room temperature, and although its electrical conductivity is not as large as that of liquid sodium or NaK, it has still been possible to study Alfv\'en waves, thanks to the use of intense magnetic fi elds, up to 13 teslas. The maximal values of Lundquist number, around 60, are similar to that of the reference experimental study by Jameson [1]. The generation mechanism for Alfv\'en waves and their refl ection is studied carefully. Numerical simulations have been performed and have been able to reproduce the experimental results despite the fact that the simulated magnetic Prandtl number was much larger than that of galinstan. An originality of the present study is that a poloidal disturbance (magnetic and velocity fields) is generated, allowing us to track its propagation from outside the conducting domain, hence without interfering.Comment: 19 pages; Physics of Fluids (2011)

LES POLITIQUES ENVIRONNEMENTALES A L'EPREUVE DE L'INTERCOMMUNALITE : VERS DE NOUVEAUX TERRITOIRES D'ACTION ?

Cette recherche a questionné l'hypothèse généralement admise que l'intercommunalité permet une rationalisation de l'action publique qui engendre " une plus grande efficacité, une plus grande cohérence et une solidarité territoriale renforcée " et ce, dans le domaine des politiques environnementales. En effet, pour conduire une analyse approfondie des effets de l'intercommunalité sur le contenu substantiel des politiques, il était nécessaire de restreindre l'analyse à un champ d'action donné ; compte-tenu de l'importance de l'environnement dans l'action publique des intercommunalités et des compétences de l'équipe répondante tant dans le domaine des politiques environnementales (UMR CITERES) que dans celui de l'intercommunalité (EA LERAD), c'est ce champ qui a été investi. Il a ainsi été proposé, sur la base d'une analyse de politiques environnementales conduites par des intercommunalités sur deux territoires tests (le SCoT du Saumurois et le SCoT de l'Amboisie, du Blérois et du Castelrenaudais (ABC)), de vérifier les effets du développement de l'intercommunalité sur le contenu des politiques menées

Little Earth Experiment: An instrument to model planetary cores

In this paper, we present a new experimental facility, Little Earth Experiment, designed to study the hydrodynamics of liquid planetary cores. The main novelty of this apparatus is that a transparent electrically conducting electrolyte is subject to extremely high magnetic fields (up to 10 T) to produce electromagnetic effects comparable to those produced by moderate magnetic fields in planetary cores. This technique makes it possible to visualise for the first time the coupling between the principal forces in a convection-driven dynamo by means of Particle Image Velocimetry (PIV) in a geometry relevant to planets. We first present the technology that enables us to generate these forces and implement PIV in a high magnetic field environment. We then show that the magnetic field drastically changes the structure of convective plumes in a configuration relevant to the tangent cylinder region of the Earth's core. Published by AIP Publishing

(Post-)queer citizenship in contemporary republican France

1996 saw the publication of Frédéric Martel’s Le Rose et le noir, a comprehensive study of three decades of gay life in metropolitan France. The predominantly anti-communitarian stance adopted by Martel in the epilogue to the first edition of his work had evolved, by the time of the book’s publication en poche in 2000, into a more nuanced view of the interactions and intersections between queer and republican identities in contemporary France. This development was influenced, in large part, by concrete changes which took place over the second half of the 1990s, centring around the introduction of the PACS in 1999, and leading to an ever-broadening debate. This paper will begin by setting forth the ways in which Martel’s position changed and analysing the attitudinal, social, and legislative backdrop which paved the way for such a change to occur. It will then bring Martel’s work into a dialogue with the writings of Eric Fassin and Maxime Foerster, both of whom have, like Martel, offered crucial analyses of the place of queer citizens within the contemporary French republic. Particular attention will first be paid to the ways in which Fassin, in his writings, has underlined the salience of the ‘droit du sol/droit du sang’ debate, traditionally associated with questions of ethnic belonging, in light of public and political discussions revolving around questions of queer kinship raised by the introduction of the PACS. This will lead into an examination of Foerster’s assertion that gay citizens of the Republic, in the era of the PACS, find themselves in a role previously held by women, in other words, as elements that require integration within a republican model. Foerster argues that this requirement to integrate is indicative of the fact that the traditional republican claim that the citizen is a blank canvas is at best misguided, and, at worst, has been deliberately subverted. This paper will examine the manner in which Martel and Fassin’s observations can be used to further strengthen the points raised by Foerster, concluding with the latter that a true engagement with the issues raised by debates around queer citizenship over the past decade can, in fact, allow the contemporary republican citizen to ‘devenir ceux [qu’il] est’. In other words, the article will conclude that the potential impact of the PACS legislation and the broader discussions it has provoked could be a renegotiation of the relationship between queer citizens and the republic

POLG2 deficiency causes adult-onset syndromic sensory neuropathy, ataxia and parkinsonism

Objective: Mitochondrial dysfunction plays a key role in the pathophysiology of neurodegenerative disorders such as ataxia and Parkinson's disease. We describe an extended Belgian pedigree where seven individuals presented with adult-onset cerebellar ataxia, axonal peripheral ataxic neuropathy, and tremor, in variable combination with parkinsonism, seizures, cognitive decline, and ophthalmoplegia. We sought to identify the underlying molecular etiology and characterize the mitochondrial pathophysiology of this neurological syndrome. Methods: Clinical, neurophysiological, and neuroradiological evaluations were conducted. Patient muscle and cultured fibroblasts underwent extensive analyses to assess mitochondrial function. Genetic studies including genome-wide sequencing were conducted. Results: Hallmarks of mitochondrial dysfunction were present in patients' tissues including ultrastructural anomalies of mitochondria, mosaic cytochrome c oxidase deficiency, and multiple mtDNA deletions. We identified a splice acceptor variant in POLG2, c.970-1G>C, segregating with disease in this family and associated with a concomitant decrease in levels of POLG2 protein in patient cells. Interpretation: This work extends the clinical spectrum of POLG2 deficiency to include an overwhelming, adult-onset neurological syndrome that includes cerebellar syndrome, peripheral neuropathy, tremor, and parkinsonism. We therefore suggest to include POLG2 sequencing in the evaluation of ataxia and sensory neuropathy in adults, especially when it is accompanied by tremor or parkinsonism with white matter disease. The demonstration that deletions of mtDNA resulting from autosomal-dominant POLG2 variant lead to a monogenic neurodegenerative multicomponent syndrome provides further evidence for a major role of mitochondrial dysfunction in the pathomechanism of nonsyndromic forms of the component neurodegenerative disorders

Schizencephaly associated with a severe prothrombotic syndrome caused by antithombin III deficiency

peer reviewedaudience: professional, studen

Kidney and vascular function in adult patients with hereditary fructose intolerance

Objective: Previous studies have shown that patients with hereditary fructose intolerance (HFI) are characterized by a greater intrahepatic triglyceride content, despite a fructose-restricted diet. The present study aimed to examine the long-term consequences of HFI on other aldolase-B-expressing organs, i.e. the kidney and vascular endothelium. Methods: Fifteen adult HFI patients were compared to healthy control individuals matched for age, sex and body mass index. Aortic stiffness was assessed by carotid-femoral pulse wave velocity (cf-PWV) and endothelial function by peripheral arterial tonometry, skin laser doppler flowmetry and the endothelial function biomarkers soluble E-selectin [sE-selectin] and von Willebrand factor. Serum creatinine and cystatin C were measured to estimate the glomerular filtration rate (eGFR). Urinary glucose and amino acid excretion and the ratio of tubular maximum reabsorption of phosphate to GFR (TmP/GFR) were determined as measures of proximal tubular function. Results: Median systolic blood pressure was significantly higher in HFI patients (127 versus 122 mmHg, p = .045). Pulse pressure and cf-PWV did not differ between the groups (p = .37 and p = .49, respectively). Of all endothelial function markers, only sE-selectin was significantly higher in HFI patients (p = .004). eGFR was significantly higher in HFI patients than healthy controls (119 versus 104 ml/min/1.73m2, p = .001, respectively). All measurements of proximal tubular function did not differ significantly between the groups. Conclusions: Adult HFI patients treated with a fructose-restricted diet are characterized by a higher sE-selectin level and slightly higher systolic blood pressure, which in time could contribute to a greater cardiovascular risk. The exact cause and, hence, clinical consequences of the higher eGFR in HFI patients, deserves further study.</p

Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy.

peer reviewedBranched-chain amino acids (BCAA) are essential amino acids playing crucial roles in protein synthesis and brain neurotransmission. Branched-chain ketoacid dehydrogenase (BCKDH), the flux-generating step of BCAA catabolism, is tightly regulated by reversible phosphorylation of its E1α-subunit. BCKDK is the kinase responsible for the phosphorylation-mediated inactivation of BCKDH. In three siblings with severe developmental delays, microcephaly, autism spectrum disorder and epileptic encephalopathy, we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK. Plasma and cerebrospinal fluid concentrations of BCAA were markedly reduced. Hyperactivity of BCKDH and over-consumption of BCAA were demonstrated by functional tests in cells transfected with the mutant BCKDK. Treatment with pharmacological doses of BCAA allowed the restoring of BCAA concentrations and greatly improved seizure control. Behavioral and developmental skills of the patients improved to a lesser extent. Importantly, a retrospective review of the newborn screening results allowed the identification of a strong decrease in BCAA concentrations on dried blood spots, suggesting that BCKDK is a new treatable metabolic disorder probably amenable to newborn screening programs