Progrès récents de l'Imagerie par Résonance Magnétique (IRM) chez le nouveau-né. Recent advances in newborn MRI

International audienceAbstractThe accurate morphological exploration of the brain is a major challenge in neonatology that advances in magnetic resonance imaging (MRI) can now provide. MRI is the gold standard if an hypoxic ischemic pathology is suspected in a full term neonate. In prematures, the specific role of MRI remains to be defined, secondary to US in any case. We present a state of the art of hardware and software technical developments in MRI. The increase in magnetic field strength (3 tesla) and the emergence of new MRI sequences provide access to new information. They both have positive and negative consequences on the daily clinical data acquisition use. The semiology of brain imaging in full term newborns and prematures is more extensive and complex and thereby more difficult to interpret. The segmentation of different brain structures in the newborn, even very premature, is now available. It is now possible to dissociate the cortex and basal ganglia from the cerebral white matter, to calculate the volume of anatomical structures, which improves the morphometric quantification and the understanding of the normal and abnormal brain development. MRI is a powerful tool to analyze the neonatal brain. The relevance of the diagnostic contribution requires an adaptation of the parameters of the sequences to acquire and of the image processing methods.RésuméL’exploration morphologique fine du cerveau est un enjeu majeur en néonatalogie que les avancées de l’imagerie par résonance magnétique (IRM) permettent actuellement. L’IRM est l’examen de choix devant une suspicion de pathologie anoxo-ischémique à terme. Chez le prématuré, la place précise de l’IRM reste à définir, toujours en seconde intention après l’échographie transfontanellaire (ETF). Nous dressons un panorama des évolutions techniques récentes matérielles et logicielles, en IRM. L’augmentation de l’intensité des champs magnétiques (3 teslas) et l’apparition de nouvelles séquences donnent accès à de nouvelles informations. Elles ont des conséquences positives et négatives sur l’acquisition des données en utilisation clinique quotidienne. La sémiologie de l’imagerie cérébrale du nouveau-né et du prématuré est désormais plus riche, plus complexe et donc d’interprétation plus difficile. La segmentation des différentes structures cérébrales devient accessible chez le nouveau-né, même grand prématuré. Il est aujourd’hui possible de dissocier le cortex et les noyaux gris de la substance blanche cérébrale, de calculer des volumes de structures anatomiques, ce qui améliore la quantification morphométrique et la compréhension du développement cérébral normal et pathologique. L’IRM est un outil inégalable et puissant pour l’analyse du cerveau du nouveau-né, dont la pertinence de l’apport diagnostique requiert une adaptation des paramètres des séquences à acquérir et des méthodes de traitement d’images

Characterizing cell adhesion by using micropipette aspiration

International audienceWe have developed a technique to directly quantify cell-substrate adhesion force using micropipette aspiration. The micropipette is positioned perpendicular to the surface of an adherent cell and a constant-rate aspiration pressure is applied. Since the micropipette diameter and the aspiration pressure are our control parameters, we have direct knowledge of the aspiration force, whereas the cell behavior is monitored either in brightfield or interference reflection microscopy. This setup thus allows us to explore a range of geometric parameters, such as projected cell area, adhesion area, or pipette size, as well as dynamical parameters such as the loading rate. We find that cell detachment is a well-defined event occurring at a critical aspiration pressure, and that the detachment force scales with the cell adhesion area (for a given micropipette diameter and loading rate), which defines a critical stress. Taking into account the cell adhesion area, intrinsic parameters of the adhesion bonds, and the loading rate, a minimal model provides an expression for the critical stress that helps rationalize our experimental results

Améliorer la connaissance du patrimoine en France pour une gestion durable du patrimoine des réseaux d'eau potable

IWA World Water Congress & Exhibition, Tokyo, JPN, 16-/09/2018 - 21/09/2018International audienceWith the aim of improving the implementation and evaluation of public policy in France relating to sustainable drinking water asset management (regulation at national level and subsidies at watershed level) the French Ministry of Ecology asked Irstea, a state research body, to create an ongoing system to manage technical and financial knowledge relating to drinking water network assets. In this study we develop a statistical approach to model pipe length by category, based on the geographical characteristics of the territory in which they are installed. Multivariate models including road length have been found to be pertinent. This technical analysis is accompanied by a study of asset values and renewal costs, based on a typology of water suppliers and an examination of economic and financial ratios. A number of disparities between territories are highlighted

Leaf Eh and pH: A Novel Indicator of Plant Stress. Spatial, Temporal and Genotypic Variability in Rice (Oryza sativa L.)

A wealth of knowledge has been published in the last decade on redox regulations in plants. However, these works remained largely at cellular and organelle levels. Simple indicators of oxidative stress at the plant level are still missing. We developed a method for direct measurement of leaf Eh and pH, which revealed spatial, temporal, and genotypic variations in rice. Eh (redox potential) and Eh@pH7 (redox potential corrected to pH 7) of the last fully expanded leaf decreased after sunrise. Leaf Eh was high in the youngest leaf and in the oldest leaves, and minimum for the last fully expanded leaf. Leaf pH decreased from youngest to oldest leaves. The same gradients in Eh-pH were measured for various varieties, hydric conditions, and cropping seasons. Rice varieties differed in Eh, pH, and/or Eh@pH7. Leaf Eh increases and leaf pH decreases with plant age. These patterns and dynamics in leaf Eh-pH are in accordance with the pattern and dynamics of disease infections. Leaf Eh-pH can bring new insight on redox processes at plant level and is proposed as a novel indicator of plant stress/health. It could be used by agronomists, breeders, and pathologists to accelerate the development of crop cultivation methods leading to agroecological crop protection

New insights (and new interrogations) in perinatal arterial ischemic stroke

With an incidence of 1/2800 to 1/5000 live-births, perinatal arterial ischemic stroke is the most frequent form of cerebral infarction in children. About 40% of the children do not have specific symptoms in the neonatal period, and are only recognized later with the emergence of motor impairment, developmental delay, specific cognitive deficiency or seizures. In the remaining 60%, children present with early symptoms, mostly recurrent focal seizures in the first 3 days of life. The diagnosis is easily confirmed by cranial ultrasounds and MRI. Early MRI has both a key role in the diagnosis, dating the injury, but also an important prognostic value to predict the motor outcome of the child. Indeed, although the infarct does not recur, the majority of children show subsequent sequels: cerebral palsy, epilepsy, cognitive or behavioural problems. Finding predictors of outcome regarding these latter concerns (and the way to prevent or alleviate them) is of major interest.The main etiological hypothesis for perinatal AIS is a cerebral embolus, originating from the placenta through the foramen ovale. Most of the established risk factors are indeed either determinants or biomarkers of vasculo-placental pathology. Injury to the cervico-cerebral arteries, giving rise to thrombus/embolus during the birthing process is also suggested. Both placento-embolic and traumatic theories are supported by a few, but well-analysed pathological or arteriographic reports. Nevertheless, their relative frequency, the implication of other mechanisms, and their repercussions to evidence-based preventive strategies remain to be determined. Moreover, the mechanism of stroke in the different groups of newborns with stroke (term vs. preterm; symptomatic neonates vs. those with a delayed presentation) is likely to be different, and there is a need for future studies to assess all populations as different entities. Neonatal supportive care remains important for all infants while there is no evidence for preventive anticoagulant use at present. In an effort to reduce neurological dysfunction, and in adjunction with ongoing physical therapy and pharmacological treatment, new rehabilitative interventions, such as constraint-induced movement therapy and mirror therapy, are increasingly being used

Place et rôle du riz pluvial dans les systèmes de production du lac Alaotra Les systèmes SCV (semis direct sur couverture végétale permanente) : une alternative viable pour une agriculture pluviale durable

La région de l'Alaotra repose sur un plateau situé à 750 mètres d'altitude avec au cœur de la plaine le lac Alaotra. La surface cultivée en riziculture est estimée à 148 500 ha en 2000 (FAO/UPDR, 2000), dont 75-80 000 ha dans la cuvette du Lac et plus de 65-70 000 ha au sud et dans les zones en périphérie, qui constitue 10% de la surface rizicole nationale pour seulement 4% des riziculteurs malgaches. Cette région réalise 33% de la valeur ajoutée de l'ensemble de la filière nationale et 15% de la richesse générée par le secteur riz. Le climat irrégulier constitue une contrainte majeure pour tous les agriculteurs du lac Alaotra. Les relations agriculture-élevage sont au cœur de la problématique de développement et d'évolution des exploitations agricoles.Ainsi, avec la saturation des rizières irrigables ou à Mauvaise Maîtrise de l'Eau (RMME), la colonisation agricole des tanety anciennement dévolus aux pâturages extensifs depuis les années 1980 s'est accélérer, induisant la perturbation des activités d'élevage bovin traditionnel extensif à objectif de capitalisation qui évoluent aujourd'hui vers un élevage productif (embouche et production laitière) ou de trait. Le diagnostic réalisé en 2007 a mis en évidence 7 types d'exploitations agricoles différents. Les différents systèmes de riziculture pluviale se retrouvent sur les plateaux sommitaux et les pentes des collines (en rotation jachère culture sur les sols très pauvres), les bas de pente et les baiboho, en rotation avec d'autres cultures pluviales (maïs, manioc, pois de terre...) avec ou sans jachère, ou en système SCV depuis leur introduction au début des années 2000. L'introduction de variétés composites poly-aptitudes de type Sebota a pu lever une contrainte majeure des zones ni totalement irriguées ni totalement pluviales mais intermédiaires dans les RMME (riziculture pluviale partiellement irriguée, selon l'accès à l'eau et les caractéristiques climatiques de la saison), Les systèmes SCV mis au point sur baiboho avec des successions culturales de type riz de saison / haricot de contre saison - maïs de saison ou riz de saison puis vesce de contre saison associée ou non à des cultures maraîchères montrent également un niveau de production et de sécurité par rapport aux aléas climatiques très proche voire supérieurs à ceux obtenus en riziculture irriguée. La part du riz pluvial dans la formation du revenu et la sécurité alimentaire a été analysée pour chaque type d'exploitation et varie de 20 à 30 % du revenu riz total (avant autoconsommation), et se révèle croissante en fonction du rapport tanety / rizière dans l'exploitation. Ainsi, sur certaines zones, le riz pluvial semble avoir de beaux jours devant lui

CVM studies on the atomic ordering in complex perovskite alloys

The atomic ordering in complex perovskite alloys is investigated by the cluster variation method (CVM). For the 1/3\{111\}-type ordered structure, the order-disorder phase transition is the first order, and the order parameter of the 1:2 complex perovskite reaches its maximum near x=0.25. For the 1/2\{111\}-type ordered structure, the ordering transition is the second order. Phase diagrams for both ordered structures are obtained. The order-disorder line obeys the linear law.Comment: 10 pages, 6 figure

Charge transfer electrostatic model of compositional order in perovskite alloys

We introduce an electrostatic model including charge transfer, which is shown to account for the observed B-site ordering in Pb-based perovskite alloys. The model allows charge transfer between A-sites and is a generalization of Bellaiche and Vanderbilt's purely electrostatic model. The large covalency of Pb^{2+} compared to Ba^{2+} is modeled by an environment dependent effective A-site charge. Monte Carlo simulations of this model successfully reproduce the long range compositional order of both Pb-based and Ba-based complex A(BB^{'}B^{''})O_3 perovskite alloys. The models are also extended to study systems with A-site and B-site doping, such as (Na_{1/2}La_{1/2})(Mg_{1/3}Nb_{2/3})O_3, (Ba_{1-x}La_{x})(Mg_{(1+x)/3}Nb_{(2-x)/3})O_3 and (Pb_{1-x}La_{x})(Mg_{(1+x)/3}Ta_{(2-x)/3})O_3. General trends are reproduced by purely electrostatic interactions, and charge transfer effects indicate that local structural relaxations can tip the balance between different B-site orderings in Pb based materials.Comment: 15 pages, 6 figure

Electrostatic model of atomic ordering in complex perovskite alloys

We present a simple ionic model which successfully reproduces the various types of compositional long-range order observed in a large class of complex insulating perovskite alloys. The model assumes that the driving mechanism responsible for the ordering is simply the electrostatic interaction between the different ionic species. A possible new explanation for the anomalous long-range order observed in some Pb relaxor alloys, involving the proposed existence of a small amount of Pb^4+ on the B sublattice, is suggested by an analysis of the model.Comment: 4 pages, two-column style with 1 postscript figure embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/index.html#lb_orde