Multi-scale analysis of a viscoelastic liquid jet

WOS:000403628200001International audienceA multi-scale analyzing tool is now available to investigate the temporal evolution of two phase flows such as liquid systems experiencing an atomization process. Thanks to its multi-scale and global nature, it allows identifying all dynamics simultaneously involved in the process with no restriction of the liquid system shape. In the present work this multi-scale tool is applied on 2D visualizations of free falling jets of a low-viscosity viscoelastic solution. The jets are produced from a cylindrical discharge orifice and the liquid is a very dilute polymer solution containing 5 ppm of Poly(ethylene oxide). High spatial resolution images of the free falling jets are performed as a function of the velocity and at several distances from the discharge orifice. For every operating condition, the liquid jet remains cylindrical first, then shows the development of a sinusoidal perturbation and finally adopts a beads-on-a-string pattern before breakup occurs. The multi-scale analysis is performed on a high number of images and at several spatial positions in order to return statistical and temporal information, respectively. The results of this analysis show that during the sinusoidal perturbation stage, the large-scale region follows an exponential increase as predicted by the linear stability theory and during the beads-on-a-string stage, the small-scale region follows an exponential decrease similar to an elasto-capillary regime from which the relaxation time of the polymer solution can be extracted. This work positions the multi-scale approach as a promising and complementary tool to the currently used techniques in order to probe complex liquid rheology, especially in the case of mobile viscoelastic solutions

Enhance quality care performance: Determination of the variables for establishing a common database in French paediatric critical care units

Abstract Selected variables for the French Paediatric Intensive Care registry. Rationale, aims, and objectives Providing quality care requires follow-up in regard to clinical and economic activities. Over the past decade, medical databases and patient registries have expanded considerably, particularly in paediatric critical care medicine (eg, the Paediatric Intensive Care Audit Network (PICANet) in the UK, the Australian and New Zealand Paediatric Intensive Care (ANZPIC) Registry in Australia and New Zealand, and the Virtual Paediatric Intensive Care Unit Performance System (VPS) in the USA). Such a registry is not yet available in France. The aim of this study was to determine variables that ought to be included in a French paediatric critical care registry. Methods Variables, items, and subitems from 3 foreign registries and 2 French local databases were used. Items described each variable, and subitems described items. The Delphi method was used to evaluate and rate 65 variables, 90 items, and 17 subitems taking into account importance or relevance based on input from 28 French physicians affiliated with the French Paediatric Critical Care Group. Two ratings were used between January and May 2013. Results Fifteen files from 10 paediatric intensive care units were included. Out of 65 potential variables, 48 (74%) were considered to be indispensable, 16 (25%) were considered to be optional, and 1 (2%) was considered to be irrelevant. Out of 90 potential items, 62 (69%) were considered to be relevant, 23 (26%) were considered to be of little relevance, and 5 (6%) were considered to be irrelevant. Out of 17 potential subitems, 9 (53%) were considered to be relevant, 6 (35%) were considered to be of little relevance, and 2 (12%) were considered to be irrelevant. Conclusions The necessary variables that ought to be included in a French paediatric critical care registry were identified. The challenge now is to develop the French registry for paediatric intensive care units

Origine dynamique de la multifragmentation nucléaire

The study of the peripheral and semi-peripheral collisions in the reaction Xe+Sn at 50 A.MeV has lead to the identification of the role of out-of-equilibrium aspects in the production of intermediate mass fragments (IMF). First, it is shown that the experimental observations are incompatible with a model in which a very hot layer of matter is primarily responsible for the production of IMF at intermediate velocity. Next, the same data are compared with a calculation using the quantum molecular dynamics approach (QMD). the quality of agreement with the predictions of this model allows to draw conclusions concerning the production mechanism of fragments. The IMF originate from region that is intermediate between the projectile and the target. It is furthermore shown that this region is not in thermal equilibrium, that the fragments are pre-formed and that their velocity and composition strongly depend on the initial conditions of the reaction. The quasi-projectile and the quasi-target, on the other hand, are only mildly influenced by the collision and their excitation energies are estimated to be below the limit at which multifragmentation will take place. In parallel, an analysis is carried out which correlates he multiplicity of the IMF with the violence of the collision. This shows that a proper analysis of a process as complex as nuclear multifragmentation must simultaneously involve kinetic variables (velocity, energy,...) as well as static ones (multiplicity. charge distribution,...).L'étude des collisions périphériques et semi-périphériques dans la réaction Xe + Sn à 50 A.MeV nous a permis de mettre en évidence l'aspect hors équilibre du mécanisme de production de fragments de masse intermédiaire (IMF). Dans une première étape, nous avons montré que les données expérimentales sont incompatibles avec un modèle dans lequel un col de matière très excité serait responsable de la production d'IMF à vitesse intermédiaire. Dans un deuxième temps, la qualité des résultats obtenus avec un modèle microscopique de type dynamique moléculaire (QMD) nous autorise à étudier en détail le mécanisme de production des fragments. Les IMF sont produits dans une zone intermédiaire (zone participante) entre le projectile et la cible. Il a été démontré que cette zone n'est pas équilibrée thermiquement, les fragments sont préformés et gardent une forte mémoire de la voie d'entrée en ce qui concerne leur vitesse et leur composition. Le quasi-projectile et la quasi-cible sont quant à eux très peu perturbés par la collision et les énergies d'excitation atteintes sont estimées à une valeur inférieure au seuil de multifragmentation d'origine thermique. Parallèlement, une analyse basée sur l'étude de l'évolution de la multiplicité d'IMF en fonction de la violence de la collision montre que la caractérisation d'un processus aussi complexe que la production multiple de fragments ne peut être menée sans étudier conjointement les variables cinétiques (vitesse, énergie…) et les variables statiques (multiplicité, distribution en charge…)

Micro signaux de surface en anesthésie pédiatrique (possibilités offertes par le traitement des signaux électroencéphalographiques et électrocardiographiques pour la pratique clinique)

RENNES1-BU Santé (352382103) / SudocSudocFranceF

Evaluation de l'influence de l'âge sur le suivi des variations de concentration expirée en halothane lors d'anesthésie générales et monitorage de la profondeur d'anesthésie par le "BIS"

RENNES1-BU Santé (352382103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Influence de l'âge sur le bispectre et sur la valeur de l'index bispectral (BIS) chez l'enfant sous sévoflurane

RENNES1-BU Santé (352382103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Droit des obligations

hors coll.International audienc

Influence de l'âge sur les variations de l'index bispectral et du bispectre de l'EEG lors d'une anesthésie générale par propofol en mode AIVOC en pédiatrie

RENNES1-BU Santé (352382103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Variation of bispectral index under TIVA with propofol in a paediatric population.

International audienceBACKGROUND: In this prospective observational study, we aim to explore the relationship between age and bispectral index (BIS) values at different plasma concentrations of propofol. METHODS: Fifty children aged from 3 to 15 yr were included. Anaesthesia was induced using a target-controlled infusion of propofol with the Kataria pharmacokinetic model together with a bolus of remifentanil followed by a continuous infusion rate at 0.2 microg kg(-1) min(-1). Target plasma propofol concentration was initially stabilized to 6 microg ml(-1) and continued for 6 min. The target was then decreased and stabilized to 4 microg ml(-1) and then to 2 microg ml(-1). BIS values, plasma propofol concentration, and EEG were continuously recorded. In order to explore the relationship between variations in propofol concentration and the EEG bispectrum, we used a multiple correspondence analysis (MCA). Results are shown in median (range). RESULTS: We found no statistical difference between BIS values with propofol 6 microg ml(-1) [23 (12-40)] and 4 microg ml(-1) [28 (9-67)]. At 2 microg ml(-1), BIS was significantly different [52 (24-71)], but a significant correlation between the age of children and BIS values was found (r2=0.66; P<0.01). There was little change in children's position between 6 and 4 microg ml(-1) in the structure model of the MCA. From 4 to 2 microg ml(-1), the position of children moved only on axis 2. CONCLUSIONS: These results showed the difficulty to interpret BIS values because of the absence of significant change for higher plasma propofol concentration variation or because of the link with age for the lower plasma concentration

Extensional properties of mobile polymer solutions

International audienceA deep understanding of the influence of viscoelasticity on the dynamics of liquid flows remains a challenge in the non-Newtonian fluid mechanics field. Previous work has revealed that the addition of minute amount (2.5 part per million) of high molecular weight polymer to water, forming a viscoelastic solution with strong extensional properties, modifies the fission process during droplet snap off with spectacular effects: inhibition of the singularity observed in the reference Newtonian case and formation of a long-lived (milli-second) filament. The measurement of the extensional properties for such mobile polymer solutions is one of the most pressing problem. Here, a global measurement technique, based on the multi-scale analysis of the capillary instability of a free falling jet of a mobile polymer solution, is introduced. The method of analysis allows the characterisation of the jet breakup mechanism from which the relaxation time of the polymer solution can be extracted. One of the advantages of the technique is the simple experiment it requires