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International audience; A two dimensional model of bread baking was developed including , for the first time, the dependence of dough viscosityon both temperature and moisture content, the carbon dioxide dissolved from liquid water together with gas generati onfrom yeast at the beginning of baking and the shrinkage due to dough drying. Particular attention was paid to experi-mental validation of both overall and local variables such as local temperature, overall mass loss, and local moisturecontent, overall CO2released into the oven, and overall deformation and local expansion or shrinkage. Sensitivity stud-ies on generation of carbon dioxide, gravity, and shrinkage are presented to discuss their influences on bread geometry,porosity (reflecting the alveolar structure) and gas pressure.

The effects of the number of fat layers (4-162 layers) on expansion and loss of CO2 and water in Danish pastries (yeasted puff pastry) were studied at each processing step. Proving contributed to most of the expansion (200-300%) and no specific role of fat layers was evidenced at this stage; this was confirmed by measurements of CO2 released. Relative expansion during baking ranged from 20% to 65% for 4 to 32 fat layers and remained unchanged above 48 layers. Images cross sections of Danish pastry showed that bubbles were few for 4 fat layers, but very large (3-4 cm) and elongated in the direction of layering. For high numbers of fat layers, bubbles were numerous, smaller and round (2-7 mm). The loss of water vapor retention during baking in relation to fragmentation of fat layers during sheeting explained the leveling-off of expansion and the decreasing size of bubbles. © 2015 Published by Elsevier Ltd.

Black leaf streak disease (BLSD), caused by the fungal pathogen Mycosphaerella fijiensis, is considered as the most destructive foliar disease of banana. To advance our knowledge of the dynamics of the disease at plant scale as well as of the components of varietal resistance, we designed, calibrated and evaluated a mechanistic model to simulate the disease on a banana plant. The model runs in discrete time at plant scale and describes plant growth and pathogen dynamics under optimal epidemiological conditions. The model is divided into two modules: a deterministic plant sub-model that simulates the simplified architecture and growth of the banana, and a pathogen sub-model that simulates the detailed life cycle of the pathogen including infection, lesion growth, asexual and sexual sporulation, and the dispersal of spores on the plant. The three most influential epidemiological parameters identified by sensitivity analysis of the model (lesion growth rate, infection efficiency, and incubation period) were estimated in a Bayesian framework using Markov chain Monte Carlo methods and acquired data on the dynamics of leaf lesions under natural conditions. The posterior densities provided precise knowledge on pathogen life history traits. The evaluation of the model using an independent data set confirmed the good quality of the predictions. Simulations allowed us to evaluate the impact of host resistance components, auto-infection at plant scale, and of the leaf emergence rate, which is linked with cropping practices, on the severity of BLSD. This foliar disease simulation model will help design new methods of controlling BLSD. (Resume d'auteur)

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEE; International audience; The potentiality of MRI to quantify fat content in flesh and subcutaneous fat in fish cutlets was investigated. Low measurement time was aimed at in a view to handling large number of samples needed in selective breeding programs for example. Results on fresh and frozen-thawed cutlets were compared to assess this way of conservation. As MRI generates unwanted spatial variations of the signal, a correction method was developed enabling the measurement on several cutlets simultaneously in less than 3 min per sample. For subcutaneous fat, the results were compared with vision measurements. High correlations between both techniques were found (R2 = 0.77 and 0.87 for the ventral and dorsal part). Fat in flesh was validated vs NMR measurements. No statistical difference was found between fresh and frozen-thawed cutlets. RMSE was respectively 0.8% and 0.89%. These results confirmed the potentiality of MRI for fat measurement in fish particularly for a large number of samples.

International audience; Previous studies comparing Crassostrea gigas selected lines with different susceptibility to summer mortality concluded that the higher the reproductive effort the lower the survival. But they were acking individual follow up of this reproductive effort which would be of great interest to help us to understand the physiology of the oysters facing summer mortalities. The most frequently used method for assessing the volume of the gonad is to measure the area it occupies on histological sections. Gonad measurement by magnetic resonance imaging, in contrast, is non-destructive and therefore makes it possible to assess individual evolution as well as to compare individuals. The present study compared the values of gonad volume by this method with the values of gonad surface obtained by the histological method. The two methods were used successively to assess the volume of the gonads of the same individual oysters at different maturation stages. There is a very highly significant linear relation between the results of these two methods. The estimated uncertainty about the volume value is 29%. Causes of this uncertainty are considered and discussed.

[Notes_IRSTEA]Article number 023118 [Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEE; International audience; The long time dynamics of large particles trapped in two inhomogeneous turbulent shear flows is studied experimentally. Both flows present a common feature, a shear region that separates two colliding circulations, but with different spatial symmetries and temporal behaviors. Because large particles are less and less sensitive to flow fluctuations as their size increases, we observe the emergence of a slow dynamics corresponding to back-and-forth motions between two attractors, and a super-slow regime synchronized with flow reversals when they exist. Such dynamics is substantially reproduced by a one dimensional stochastic model of an over-damped particle trapped in a two-well potential, forced by a colored noise. An extended model is also proposed that reproduces observed dynamics and trapping without potential barrier: the key ingredient is the ratio between the time scales of the noise correlation and the particle dynamics. A total agreement with experiments requires the introduction of spatially inhomogeneous fluctuations and a suited confinement strength.

Procédé d'identification et de quantification des proportions relatives des différentes fractions cristallisées et liquide présentes dans un coulis d'hydrate, défini comme un solide en suspension dans un fluide porteur, caractérisé en ce qu'il est effectué au moyen d'un spectromètre de résonance magnétique nucléaire à bas champ et d'une sonde de radiofréquence permettant de détecter et de quantifier les protons par mesure directe sur ledit coulis d'hydrate. Le coulis d'hydrate est par exemple composé d'un clathrate hydrate d'alkyl-onium. Application à l'identification, la caractérisation et la quantification des différents polymorphes d'hydrates formés dans des fluides frigoporteurs diphasiques, en mode statique ou dynamique.

International audience; The aim of this study was to investigate the momentum transport occurring during bub- ble growth in a viscoelastic material. The mechanical behaviour was modelled with a 5- element Maxwell model, implemented with the finite elements method, and a sensitivity analysis of the model parameters was undertaken. Air was injected into the bubble and growth was monitored with pressure sensors and by the analysis of MRI image. The ex- periment was repeated three times. Each time mechanical parameters were characterised on the same material as that used for the experimental validation of the model. Simula- tions were conducted in geometric and boundary conditions as close as possible to those of the experiment, and yielded good agreement with the experimental results.

National audience; Cette présentation avait pour objectif de sensibiliser la communauté de la thermique Française sur les latitudes que peut offrir le pilotage de la pression externe en complément de l’apport d’énergie.

International audience; Transmission of active transcriptional states from mother to daughter cells has the potential to foster precision in the gene expression programs underlying development. Such transcriptional memory has been specifically proposed to promote rapid reactivation of complex gene expression profiles after successive mitoses in Drosophila development [1]. By monitoring transcription in living Drosophila embryos, we provide the first evidence for transcriptional memory in animal development. We specifically monitored the activities of stochastically expressed transgenes in order to distinguish active and inactive mother cells and the behaviors of their daughter nuclei after mitosis. Quantitative analyses reveal that there is a 4-fold higher probability for rapid reactivation after mitosis when the mother experienced transcription. Moreover, memory nuclei activate transcription twice as fast as neighboring inactive mothers, thus leading to augmented levels of gene expression. We propose that transcriptional memory is a mechanism of precision, which helps coordinate gene activity during embryogenesis.

International audience; Pulsed field gradient - nuclear magnetic resonance (PFG-NMR) was used to monitor the diffusion of caseins throughout the rennet coagulation of a highly concentrated casein suspension. Two types of casein species were distinguished according to their diffusing properties and attributed to the dissolved casein fraction, i.e. dissociated caseins and caseinomacropeptides (CMP), and casein particles, respectively. The NMR signal intensity coming from the dissolved casein fraction, which is related to the number of protons it contains, increased all along the experiment whereas the opposite tendency was observed for casein particles. This was explained by the increasing amount of CMP in the whey and the reciprocal loss of protons contained by casein particles, and used to quantitatively estimate the kinetics of the chymosin action. The diffusion of the dissolved casein fraction remained nearly constant during the coagulation process whereas, as revealed by rheometry measurements, the diffusion of casein particles was very sensitive to the structural reorganization of the sample. It decreased by about 35 % during the sol-gel transition and increased in similar proportions during the succeeding rise in gel porosity. Our results also provide different types of information on the respective behaviors of dissociated caseins and casein particles during the course of the process, the most remarkable one being that all the casein particles did not aggregate during the sol-gel transition of our sample. This strongly suggests that the rennet gelation of a concentrated dairy solution may be better visualized by the formation of a network backbone during the sol-gel transition which is thereafter reinforced upon further incorporation of casein particles.

This manuscript presents a synthesis of my research activities since I have been recruited at Irstea. It outlines fifteen years of work to catch the dynamics of turbulent flows by combining metrology, simulations and advanced signal processing methodologies. The first chapter presents, the research and the methodological developments to discriminate the most energetic structures from PIV and DNS fields into non-canonical turbulent flows that can be found in air conditioning. In a second chapter a hot-wire anemometry technique giving simultaneous velocity and temperature measurements is presented. The third chapter details how the optical flow paradigm can be exploited to fluid flow measurements instead of correlation techniques classically used in PIV. To estimate the motion vector fields from image sequences, the different classes of problems to be solved are explained. The last chapter exhibits the potentiel given by image data assimilation for the development of the future measurement and simulation techniques. To progressively reconstruct 3D realistic turbulent flows, two first applications are presented and perspectives are proposed., Ce mémoire présente une synthèse de mes travaux de recherche effectués depuis mon recrutements à Irstea. Il retrace quinze années de travaux visant à saisir la dynamique turbulente dans les fluides en combinant métrologies, simulations et méthodes de traitement du signal avancées. Un premier chapitre présente les actions de recherche et les développements méthodologiques visant à discriminer à partir de champs PIV et DNS les structures énergétiquement dominantes dans une série d'écoulements turbulents non-canoniques que l'on trouve dans les applications aérauliques. Le second chapitre présente le développement d'une technique d'anémothermométrie permettant la mesure simultanée de la vitesse et de la température. Le troisième chapitre détaille l'exploitation du paradigme du flot optique pour la mesure du mouvement fluide en lieu et place des techniques de corrélation classiquement utilisées en PIV. Les différentes classes de problèmes à résoudre pour déterminer le champ vectoriel de la vitesse d'un écoulement turbulent à partir de l'analyse d'une séquence d'images d'un scalaire sont explicitées. Enfin le quatrième chapitre, expose le potentiel offert par l'assimilation de données pour développer les futures techniques de mesures et de simulations. Deux premières applications sont présentées pour aller progressivement vers la reconstruction 3D réaliste des écoulements turbulents.

Sludge from a slaughter-house wastewater plant, and mixtures of bulking agent (crushed wood pallet) and sludge were studied by Nuclear Magnetic Resonance (NMR). The NMR spin–spin relaxation ( T 2 ) and spin–lattice relaxation ( T 1 ) signals for sludge, wet crushed wood pallet and mixtures of sludge and bulking agent were decomposed into three relaxation time components. Each relaxation time component was explained by a non-homogeneous water distribution on a microscopic length scale and by the porosity of the material. For all samples, the T 2 relaxation time value of each component was directly related to the dry matter content. The addition of wet crushed wood to sludge induced a decrease in the relaxation time, explained by water transfer between the sludge and the wood. Magnetic Resonance Imaging (MRI) and respirometric measurements were performed on sludge and wood mixtures. MR images of the mixtures were successfully obtained at different biodegradation states. Based on specific NMR measurements in an identified area located in the MRI cells, the results showed that grey levels of MR images reflected dry matter content. This preliminary study showed that MRI would be a powerful tool to measure water distribution in sludge and bulking agent mixtures and highlights the potential of this technique to increase the understanding of sludge composting.

International audience; Fat crystal networks confer their physical properties on fat-containing products. They are characterized by the solid fat content (SFC) and the design of the crystals, that is, their polymorphism and their size. Different techniques such as NMR,differential scanning calorimetry, and X-ray diffraction (XRD) are used to determine these parameters. Low-fieldNMR, the reference method for evaluation of SFC, has been proven to allow the determination of polymorphism through spin-lattice relaxation time (T1) and second moment (M2) measurements. However, this technique could provide more information on the system. On the basis of the effects of supercooling on theNMRparameters, the first evidence of a possible relationship between the size of the crystals and T1 was demonstrated. The effects of a liquid phase on the fat crystal network were investigated with liquid tricaprin and solid tristearin. It was demonstrated that the two triacylglycerols can cocrystallize, and that the liquid phase modified the polymorphic behavior of tristearin. The evolution of T1 over time could be related to the Ostwald ripening phenomenon. In view of this evidence, it was concluded that there was a relationship between T1 and the size of the crystals in the fat crystal network.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Magnetic Resonance Imaging (MRI) was performed on tomato fruit during two 3-week periods of postharvest ripening. Different image types were acquired to study macroscopic and microscopic structural changes. Air spaces were identified close to seeds and their shrinkage during the ripening period was estimated from the spin echo images. The development of the bubbles in the outer pericarp during ripening was estimated from the ratio of the long- and short-echo time gradient echo MRI images and supported by the macrovision imaging. Variations in the transverse (T2) and longitudinal (T1) relaxation times were determined from quantitative MRI images. They depended on the tissue type and matched fairly well between fruit. In the core, placenta, radial and outer pericarp, T2 decreased by about 25% from the initial values and T1 by about 25-30% from the initial values during postharvest ripening. In the locular tissue the relaxation times had less marked trends than in other tissues: both T2 and T1 increased slightly until the eighth or ninth measurement day and after that it returned to its approximate initial value. Multi-component characteristics of T2 and T1 decay were investigated by Nuclear Magnetic Resonance (NMR) relaxometry. They provided information about all major sub-cellular compartments and showed there was water redistribution among compartments during ripening. In addition to the relaxometry measurements, water content, weight loss and concentration of neutral sugars and acids were measured on some of the tomato fruit. Cell size and organization were investigated by macrovision experiments. Although the overall dependence of the relaxation time on tissue type was to some extent explained by chemical composition and cell dimension, no relationships between trends in MR data and tissue properties were established.

International audience; A model of baking has been developed for one-dimension geometry. This model consists into coupled heat transport (conductivity, evapo-condensation-diffusion, convection), mass transport (diffusion, convection) and mechanical behaviour inside dough. It was validated with a set of experimental data gathering profiles in temperature, in water content, total water loss, total CO2 release, global and local expansion as measured continuously by MRI. Simulation makes it possible to study the relative influence of the parameters that favour expansion (kinetics of vaporisation and expansion of gases) and the restricting parameters: rupture of dough films according to a pressure differential and stiffening of the same films following heat modification of the macromolecules (starch and proteins). The latter are expressed in the model by the introduction of temperature ranges for rupturing of dough films (TKg) and for their stiffening (Tη). The effect of these temperatures of mechanical changes in dough films on the local and global expansion was studied. Additionally to these parameters related to the constitution of the dough, the effect of the external pressure was studied as an example of process parameters affecting expansion with a first experimental validation.

The aim of this study was to undertake a dynamic and quantitative evaluation of the local evolution of porosity in a section of bread using magnetic resonance imaging (MRI). A prototype of an oven compatible with continuous MRI acquisition had been previously developed and installed in the probe of the imager. Oil microcapsules, which provide a very different MRI signal to that obtained from the dough, were also incorporated in the dough before proving, and their position in the bread was monitored throughout baking. Microcapsules delimited dough layers of which initial thickness ranged from 7 to 20 mm. Monitoring of the expansion of these layers is presented and discussed. Local expansion of the lower part of the bread predominated, contributing to 82% of the overall expansion at an oven air temperature of 130 °C. This was related to a slight escape of gas in this region, favored by one-dimensional heat transport. When the crust was formed early, as for an oven air temperature of 182 °C, local expansion did not cease with the crust setting and occurred to the detriment of the other regions, which were compressed.

International audience; The self-diffusion coefficients of 620 and 96 750 g/mol poly(ethylene glycol) (PEG) were measured by pulsed field gradient (PFG)-NMR throughout the coagulation processes of a concentrated casein suspension induced by acidification alone and with the concomitant action of chymosin. The diffusion of water molecules was also investigated during the acidification process. In all experiments, the diffusion coefficient of the molecule studied was modified nonlinearly, and the precise moments at which its evolution changed corresponded to key stages of both coagulation processes. These variations were not directly related to sol-gel transitions as revealed by rheological measurements but were caused by other types of structural changes in the sample whatever its viscoelastic state (solution or gel). The diffusion of the large PEG was very sensitive to variations in the size of the casein particles and the casein aggregates constituting the network before and after gelation, respectively. In contrast, the diffusion of the small PEG and of water was sensitive to changes in the internal structure of the colloidal matter. The evolution of the sample microstructure could thus be monitored by diffusion measurements throughout the coagulation processes. In comparison, rheometry, stiffness measurements, and scanning electron microscopy revealed these modifications in the gel state only.

International audience; Quantitative Magnetic Resonance Imaging (MRI) is an appropriate non-destructive tool for studying plants. The transverse relaxation time (T2), which is related to the water status in samples (i.e. water content, water mobility and interaction between water and macromolecules), was revealed relevant for studying plant microstructure. Recent developments [1] allow accessing multi-exponential transverse relaxation of water protons, providing data about water repartition and status at subcellular level. Apparent microporosity in fruit tissues can also be estimated by MRI [2], providing additional information about gas distribution. The first aim of this study was to characterise the heterogeneity of apple fruit tissues according to cell water status and gas distribution. MRI and histological macrovision measurements were performed on fruits from three different cultivars; fruits of different sizes were selected for each cultivar to provide tissues with cells of different dimensions. This study highlighted the heterogeneity of apple tissues in terms of relaxation parameters, apparent microporosity and cell morphology. Variations in cell size partially explained the different T2 observed. The second aim of the study was to investigate the link between cell water characteristics, apparent tissue microporosity and biochemical analyses and mechanical properties reflecting fruit texture quality. Correlations between the measurements were studied for six apple cultivars with storage times varying from one to six months. A general behaviour patterns independent of cultivar and storage time were demonstrated, providing understanding of the parameters involved in mechanical properties.

International audience; The object of this study is to assess the relevance of MRI water/fat separation to quantify fat and water in fish in a view of high throughput measurements. The major issue for this purpose is the spatial inhomogeneities of the signal. They are inherent to MRI and they may induce a position dependent bias in the quantification. We have combined water/fat separation methods from the literature and extended them in order to estimate these inhomogeneities. Experimental results show the efficiency of our method and validate the possibility to use MRI for water and fat quantification at a rate higher than one minute per fish cutlet.

International audience; High temperatures during bread baking deteriorates the mould. Numerical tools are used to find new processes of baking to preserve mould and bread quality.

National audience; La Résonance Magnétique Nucléaire est un outil puissant qui donne accès à des informations à la fois à l'échelle microscopique et à l'échelle macroscopique et qui permet de caractériser et de suivre des phénomènes physiques et chimiques qui existent dans un vaste domaine d'échelle de longueur et de temps. Elle peut fournir des informations sur les structures et sur la dynamique des structures à l'échelle moléculaire ou micronique (fusion, cristallisation, coagulation, gélatinisation, localisation et interaction de l'eau avec les solutés et les macromolécules,...). L'imagerie IRM donne potentiellement accès aux hétérogénéités structurales des produits à l'échelle millimétrique (distribution des tissus, cristallisation de l'eau ou de la matière grasse,...) et aux profils de concentration, de vitesse ou de température.

International audience; Starch swelling and gelatinization are transition processes occurring upon hydration and heating of starch granules (Biliaderis 1992, Donald 2004) and, apart from textural changes, induce variations in water distribution, in starch structure and interactions between them in various food products. In such systems, the interpretation of NMR parameters such as longitudinal, T1, and transversal, T2, relaxation times parameters could help to understand these chemical and physical modifications, but the task can be very tedious by using conventional 1D NMR spectroscopy. In order to help in interpreting the T1 and T2 distributions measured in starch-water systems heated up to 90 °C, we performed 2D T1-T2 NMR spectroscopy as well as Differential Scanning calorimetry (DSC) experiments for samples containing 11%, 35% to 50% water content (wet basis). This multi-method approach aimed at helping to understand the effect of water content on the degree of wheat starch gelatinization but also to interpret water transfers in starchy products. The 2D NMR approach was based on a joint observation with respect to the two relaxation parameters and a data processing based on maximum entropy regularization and truncated Newton optimization (Chouzenoux, Moussaoui et al. 2010). We will show that 2D T1-T2 correlations permitted not only to confirm previously assigned proton populations using 1D NMR (Rondeau-Mouro, Cambert et al. 2015) but also to quantify water and starch changes induced by the thermal processing of starch.

International audience; Gas generation and dough mechanical resistance inside bread drive the bubble growth during bread making. The objective was to evaluate the impact of a lowering in external pressure on bread expansion during baking. It was evaluated by numerical vacuum baking simulations ans MRI experiments.

International audience; Bubbles in number and size are part of the sensory evaluation by the consumer at purchasing and eating Swiss-type cheese. To better understand the formation of eyes in cheese, comprehensive knowledge of the transport phenomena including mechanics and gas production is required. The aim of the present study was to investigate both the momentum transport occurring around a bubble and the way the production of carbon dioxide and its diffusion locally affects the bubble growth during cheese ripening. A model was developed and fed with parameters (gas production and mechanical parameters) that were measured on the same cheese loaf as the one used for experimental validation. The mechanics and gas transport phenomena included in the model were validated independently. For mechanical validation, bubble volume as well as deformation of the upper surface of the cylinder were dynamically assessed by MRI within the same experiment. Uncertainties on these measurements were estimated, and used as an additional criterion at the validation step of the model. A first sensitivity analysis was performed on the mechanical parameters using Sobol indices method to better understand the influence of mechanics on bubble growth. A sensitivity study of the bubble growth to mass transport parameters was performed and simulations were compared to the growth of bubbles as measured on industrial blocks. Simulated data were in good agreement with simulations, validating the adequacy of the mechanical model and the range of diffusivity applicable to well describe the actual bubble growth in cheese blocks. As expected, the bubble growth was mainly driven by the viscous part of the viscoelastic model and gas production and transport were found to control bubble growth in the Semi-hard cheese under study.

National audience; Dans une perspective d’agriculture moderne et durable, l’un des chantiers majeurs réside dans la compréhension des relations entre le génotype et le phénotype. Dans ce contexte de phénotypage, la composante Agro-Scans de la plateforme PRISM à Irstea développe des méthodes de caractérisation non-destructive par IRM ayant la potentialité d’être réalisées à haut débit.

International audience; Experimental and numerical approaches are facing strong limitations for the study of complex scenarios. The former, based on particle image velocimetry (PIV), are subject to measurements uncertainties, to limited spatiotemporal resolution, and can be affected by regions of the images where no information on the flow are available. The latter need accurate simulations that may strongly depend on complex unknown boundary conditions, and on a fine and often ad hoc tuning of turbulence model parameters. It follows that complex flows cannot be accurately analysed on the single basis of one of those two kinds of approaches. Here we present our recent research on data assimilation to combine numerical model and experimental observations. Two distinct flow configurations and data assimilation approaches are proposed: (1), a EnWKF assimilation scheme to reconstruct free surface flows form Kinect depth sensor images; (2), a 4DVar assimilation technique, integrating PIV data and DNS, to reconstruct turbulent flows.

Les acides organiques sont utilisés en agro-alimentaire afin de neutraliser certaines bactéries. Différentes études ont montré que des bactéries pouvaient rester actives dans certains milieux type émulsion huile dans eau mais l’ajout d’acides organiques en très faibles concentrations peuvent les désactiver. Le mécanisme proposé est en lien avec les formes H+ qui seraient en mesure de diffuser dans les cellules bactériennes. A travers la mesure des différences de mobilités d'un acide dans des mélanges Huile/Eau, il s’agit de vérifier où se localise préférentiellement l'acide pour différents pH: à l'interface des gouttelettes d’huile, ou dans les phases continue ou dispersée. La localisation de l'acide dans l'émulsion est étudiée via des mesures d’auto- diffusion par RMN.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEE; International audience; We investigate the combined use of a kinect depth sensor and of a stochastic data assimilation (DA) method to recover free-surface flows. More specifically, we use a weighted ensemble Kalman filter method to reconstruct the complete state of free-surface flows from a sequence of depth images only. This particle filter accounts for model and observations errors. This DAscheme is enhanced with the use of two observations instead of one classically. We evaluate the developed approach on two numerical test cases: a collapse of a water column as a toy-example and a flow in an suddenly expanding flume as a more realistic flow. The robustness of the method to depth data errors and also to initial and inflow conditions is considered. We illustrate the interest of using two observations instead of one observation into the correction step, especially for unknown inflow boundary conditions. Then, the performance of the Kinect sensor in capturing the temporal sequences of depth observations is investigated. Finally, the efficiency of the algorithm is qualified for a wave in a real rectangular flat bottomed tank. It is shown that for basic initial conditions, the particle filter rapidly and remarkably reconstructs the velocity and height of the free surface flow based on noisy measurements of the elevation alone.

International audience; NMR relaxation parameters as spin-spin (T2) and spin-lattice (T1) relaxation times have been shown to be very relevant to study the microstructure of plant tissues. Magnetic Resonance Imaging (MRI) has also been used to study plant tissues. This non-destructive and non-invasive technique allows the recording of images. Many MRI studies have focused on the quality and defects of fruits. The combination of NMR and MRI technics is an efficient way to monitor agricultural practices and industrial processes like ripening, cooking or freezing. Indeed the association of these two methods enables a study at different scales of the structure and the tissue integrity and seems to be convenient for the study of juice extraction processes. The aim of this study was to understand the determinants that contribute to the extraction yield optimization. TD-NMR relaxometry and quantitative MRI were performed to characterize the impact of the grinding and pressing processes on apple tissues. The authors demonstrated here that TD-NMR and MRI are reliable tools providing information about the heterogeneous structure of apple parenchyma tissue as well as the subcellular water distribution at the origin of the multi-exponential T2 signal measured. The results also indicated that complementary investigations should be necessary using biochemical quantitative analyses and mechanical tests to understand the water distributions in pressed materials.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEE; International audience; In order to describe the phenomenon of intermittency in wall turbulence and, more particularly, the behaviour of moments p r δV and pr ε and intermittency exponents ζP with the order p and distance to the wall, we developed a new geometrical framework called “entropic-skins geometry” based on the notion of scale-entropy which is here applied to an experimental database of boundary layer flows. Each moment has its own spatial multi-scale support Ωp (“skin”). The model assumes the existence of a hierarchy of multi-scale sets Ωp ranged from the “bulk” to the “crest”. The crest noted characterizes the geometrical support where the most intermittent (the highest) fluctuations in energy dissipation occur; the bulk is the geometrical support for the whole range of fluctuations. The model assumes then the existence of a dynamical flux through the hierarchy of skins. The specific case where skins display a fractal structure is Investigated. Bulk fractal dimension Δ f and crest dimension Δ∞ are linked by a scale-entropy flux defining a reversibility efficiency ( )/( ) f γ d = Δ −Δ −Δ ∞ ∞ (d is the embedding dimension). The model, initially developed for homogeneous and isotropic turbulent flows, is applied here to wall bounded turbulence where intermittency exponents are measured by extended self-similarity. We obtained for intermittency exponents the analytical expression [ ] /3 ( (1 ) 3 2) / 3 (3 )(1 ) pp ζ γγ γ p = Δ − + − + −Δ − ∞ ∞ with γ ≈ 0.36 in agreement withexperimental results.

L'invention concerne un dispositif de protection d'une zone d'opération, notamment pour la manipulation de produits. Ledit dispositif comprenant un plateau, appelé plateau de diffusion, présentant deux faces opposées, l'une dite face supérieure, orientée vers la zone d'opération, et l'autre, dite face inférieure. Ledit plateau de diffusion comprend un étage de redressement, un étage d'orientation et un écran de diffusion, lesdits étages présentant chacun des ouvertures de passage d'un flux de fluide, et chaque ouverture de l'écran de diffusion débouchant sur la face supérieure du plateau et présentant une section de passage dont la surface est plus petite que celle de chacune desdites ouvertures de l'étage d'orientation. L'invention concerne également un procédé de manipulation correspondant.

International audience; The ingress of water in starchy products is of interest because it has relevance to the storage, drying, enzymatic activities and processing of starch-based materials, but also for the formulation of controlled release materials [1-3]. Among the various methods of approach of the hydration and release properties of starch, the technique of NMR has the advantage of measuring in a noninvasive way of the dynamic phenomena at various scales [4]. NMR imaging is widely used in medical diagnosis, but since several years it has been developped to investigate the solvent penetration in cross-linked polymers and pharmaceutical excipients [5-7]. We have used this technic to study the kinetic of the water uptake of extruded potato starch with a resolution better than 100 µm. Another method, called NMR-MOUSE, is based on a portable open NMR sensor equipped with a permanent low-field magnet and a surface RF coil. This scanner produces one-dimensional profiles of the sample structure with a resolution close to 10µm and can be used to follow the water uptake or drying into few millimeters thick concrete samples as wheat flour-based products (bread...).

International audience; Water status and distribution at subcellular level in whole apple fruit were evaluated by Magnetic Resonance Imaging (MRI) measurement of the multi-exponential transverse (T2) relaxation of water protons. Apparent microporosity, also estimated by MRI, provided mapping of gas distribution in fruit tissues. Measuring for the first time the multi-exponential relaxation of water and apparent tissue microporosity in whole fruit and combining these with histological measurements provided a more reliable interpretation of the origins of variations in the transverse relaxation time (T2) and better characterization of the fruit tissue. Measurements were performed on 54 fruits from 3 different cultivars. Fruits of different sizes were selected for each cultivar to provide tissues with cells of different dimensions. Macrovision measurements were carried out on parenchymal tissue from all fruits to investigate the impact of cell size on T2 value. The results showed that the MRI transverse relaxation signal is well fitted by a tri-exponential decay curve that reflects cell compartmentalization. Variations in cell size partially explained the different T2 observed. This study highlighted the heterogeneity of apple tissues in terms of relaxation parameters, apparent microporosity and cell morphology and in relation to specific variations between fruit of different cultivars.

National audience; At ambient temperature, hydration of starch leads to the heterogeneous distribution of water due to the semi-crystalline structure of granules. When starch is heated in the presence of water, it undergoes a series of changes known as reversible swelling and gelatinization [1,2] that induce variations in water distribution, in starch structure and interactions between them. In order to help in interpreting the T1 and T2 distributions measured by NMR in starch-water systems heated up to 90 °C, we performed 2D T1 -T2 NMR spectroscopy as well as DSC measurements for samples containing 35% to 50% water content (wet basis).

L'objectif de ce stage est la mise au point d'une méthode de quantification de transfert de matière par estimation du flot optique. Le travail s'est basé sur l'utilisation d'une fonction de calcul de flot optique déjà existante. Une validation expérimentale a été menée sur une base d'images réelles déjà acquises. Nous avons évalué en particulier la sensibilité de la méthode aux différents paramètres de réglage.

A travers la mesure des différences de mobilités d'un acide dans des mélanges Huile/Eau, il s’agit de vérifier où se localise préférentiellement l'acide pour différents pH: à l'interface des gouttelettes d’huile, ou dans les phases continue ou dispersée. La localisation de l'acide dans l'émulsion est étudiée via des mesures d’auto- diffusion par RMN. Des émulsions huile/eau 50/50 ou 35/65 ont été préparées en utilisant de l’héxadécane et de l’eau avec des gouttelettes dont la taille est inférieure au micron ou de l’ordre de 2.5µm (émulsion 50/50 ici).

Les acides organiques sont utilisés en agro-alimentaire afin de neutraliser certaines bactéries. Différentes études ont montré que des bactéries pouvaient rester actives dans certains milieux type émulsion huile dans eau mais l’ajout d’acides organiques en très faibles concentrations peuvent les désactiver. Le mécanisme proposé est en lien avec les formes H+ qui seraient en mesure de diffuser dans les cellules bactériennes. A travers la mesure des différences de mobilités d'un acide dans des mélanges Huile/Eau, il s’agit de vérifier où se localise préférentiellement l'acide pour différents pH: à l'interface des gouttelettes d’huile, ou dans les phases continue ou dispersée. La localisation de l'acide dans l'émulsion est étudiée via des mesures d’auto-diffusion par RMN.

The signals in MRI are multi-exponential decreases and the relaxation time constants provide many information on the tissues. The cartographies of those constants allow one to spatially analyze the aliments. The Levenberg-Marquardt algorithm is usually used to nd the values of the constants. The maximum entropy method present several advantage compare to the Levenberg-Marquardt algorithm. The number of exponential components is not set and the algorithm is not initialized. The goal is to establish a cartography only from the MRI images. However, the method is more complex to use, partly due to the noise in MRI. This internship is a rst try on the application of the maximum entropy method to establish the cartographies of the relaxation times.; Les signaux en IRM sont des décroissances multi-exponentielles et les constantes de temps de relaxation donnent beaucoup d'informations sur les tissus analysés. Faire une cartographie de ces constantes permet d'analyser spatialement les aliments. L'algorithme de Levenberg-Marquardt est généralement utilisé pour retrouver les valeurs des constantes. La méthode de maximisation d'entropie possède plusieurs avantages par rapport à l'algorithme de Levenberg-Marquardt. Il n'y a pas besoin d'avoir une connaissance à priori du nombre de composantes exponentielles et l'algorithme n'a pas besoin d'être initialisé. Le but est d'établir automatiquement une cartographie uniquement à partir des images IRM. Mais cette méthode est plus complexe à appliquer, notamment à cause du bruit présent en IRM. Ce stage est un premier essai pour l'application de la méthode de maximisation d'entropie pour établir des cartographies des temps de relaxation.

Porous media approaches to bread baking involving energy, mass transport and continuous mechanics have now been widely explored and can be implemented with commercial software. The challenges now are thorough experimental verification, and understanding of the physicochemical phenomena both on the small scale and the way they are taken into account in continuous macroscopic models. A new evaporation–condensation–diffusion formulation that idealizes the distribution of bubbles in dough as periodic cubes is presented here. The effects it elicited on water flux, total water loss and variations in local water content were investigated. Additionally, a continuous approach involving four components (dough, CO2, air and water), mass, energy transport and dough deformation was developed. Experimental validation was performed both on usual variables such as temperature, total height and water loss, and on CO2 release, and profiles of local gas fraction and water content. The mechanisms of expansion and compression in the expanding dough during baking are discussed for the first time, with the help of both a non-invasive technique (MRI) and numerical simulations. Only two parameters related to the mechanical properties of dough (viscosity and rupture leading to the opening of pores) were tuned; both CO2 release (onset), and local gas fractions (position of the squeezed region) were revealed to be highly sensitive to these parameters. A single set of physically-consistent values was found to reproduce satisfactorily the experimental findings related to the transport and expansion of the gaseous phase.

International audience; Semiclatrate hydrate crystals of tetra-n-butyl ammonium bromide (TBAB) form at atmospheric pressure and a positive temperature. In suspension in water, they can be used as a heat transport medium or for gas separation. In terms of thermal energy storage and secondary refrigeration applications, TBAB hydrate slurries may be characterized by their flow properties under specific thermophysical conditions. The study presented here investigated one of these important properties, i.e. the crystal content, also called the solid fraction, that is usually estimated using the TBAB:H2O phase diagram. Our investigations revealed that Time-Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry was remarkably sensitive to the solid content of TBAB:H2O hydrate slurries. Non-invasive and non-destructive measurements performed in real time demonstrated the power of NMR relaxometry to identify and quantify TBAB hydrates. Most importantly, NMR both measured and quantified type A and B hydrates, which no other technique can achieve without destroying the crystals or can only perform theoretically on the basis of a phase diagram, and thus without considering the possible conversion of type A to type B hydrates.

Les acides organiques sont utilisés en agro-alimentaire afin de neutraliser certaines bactéries. Différentes études ont montré que des bactéries pouvaient rester actives dans certains milieux type émulsion huile dans eau mais l’ajout d’acides organiques en très faibles concentrations peuvent les désactiver. Le mécanisme proposé est en lien avec les formes H+ qui seraient en mesure de diffuser dans les cellules bactériennes. A travers la mesure des différences de mobilités d'un acide dans des mélanges Huile/Eau, il s’agit de vérifier où se localise préférentiellement l'acide pour différents pH: à l'interface des gouttelettes d’huile, ou dans les phases continue ou dispersée. La localisation de l'acide dans l'émulsion est étudiée via des mesures d’auto- diffusion par RMN.

International audience; Mechanical properties of fruit depend on many parameters, including microporosity, cell characteristics and cell wall composition/structure. Recent developments in quantitative MRI provide the possibility of studying fruit through local measurements of multi-exponential T2 reflecting water status and distribution at the subcellular level, and apparent microporosity. In the present study, dynamic mechanical analysis provided Young's modulus and the damping factor, reflecting elastic and viscous properties of apple tissue, respectively. These measurements were compared to quantitative MRI measurements, biochemical analysis (water, free sugar and alcohol-insoluble solid contents, cell wall composition) and histological measurements, all performed on apple parenchyma tissue. The aim was to investigate the respective contributions of microporosity, intracellular water status and distribution, and chemical composition to mechanical properties characterizing fruit texture quality. Correlations between the measurements were studied for six apple cultivars with storage times varying from one to six months. A general behavior pattern independent of cultivar and storage time provided greater understanding of the parameters involved in mechanical properties. Cell wall arabinose composition and water status associated with the vacuole were correlated with Young's modulus, the xylose and hemicellulose compositions were correlated with the damping factor and the relative amount of water attributed to the cytoplasm and the apparent microporosity of the samples were correlated with both the damping factor and Young's modulus. Modification of the water pool attributed to the extracellular water/cell wall was shown to be involved in softening of the tissue. Comparison of the different measurements showed that variations in relaxation times were not explained by the water content, indicating that other phenomena such as membrane permeability, vacuole size and/or solute composition were predominant in the relaxation mechanism. A correlation between water pools attributed to the vacuole and cytoplasm evidenced water exchange occurring between the two compartments. © 2015 Elsevier B.V.

Pulsed field gradient NMR spectroscopy was used to determine the poly(ethylene glycol) (PEG) self-diffusion coefficient (DPEG) as a function of NaCl concentration (CNaCl) and denaturation time (tD) in whey protein solutions and gels. DPEG in the gel decreased with increasing CNaCl concentrations and increased with increasing tD; the increase ceased for all PEGs when the gel was fixed. This increase was more pronounced for the 82250 g/mol PEG than the 1080 g/mol PEG. Moreover, the diffusion coefficient of nonaggregated whey protein was measured and an increase for longer tD was also observed. Scanning electron microscopy images and 1H spectra demonstrated that DPEG were related to the structure changes and to the percentage of β-lactoglobulin denaturation. Keywords: Whey proteins; denaturation time; NMR; diffusion; ionic strength; SEM; gels

International audience; The changes in water proton transverse relaxation behavior induced by aggregation of whey proteins are explained in terms of the simple molecular processes of diffusion and chemical exchange. The water self-diffusion coefficient was measured in whey protein solutions and gels by the pulsed field gradient NMR method. As expected, water self-diffusion was reduced with increased protein concentrations. Whatever the concentration, the water molecules were free to diffuse over distances varying from 15 to 47 ím. Water diffusion was constant over these distances, demonstrating that no restrictions were found to explain the water hindrance. The modification in protein structure by gelation induced a decrease in water diffusion. The effects of protein concentration on water diffusion are discussed and modeled. Two approaches were compared, the obstruction effect induced by a spherical particle and the cell model, which considered two water compartments with specific self-diffusion coefficients.

MRI thermometry methods are usually based on the temperature dependence of the proton resonance frequency. Unfortunately, these methods are very sensitive to the phase drift induced by the instability of the scanner which prevents any temperature mapping over long periods of time. A general method based on 3D spatial modelling of the phase drift as a function of time is presented. The MRI temperature measurements were validated on gel samples with uniform and constant temperature and with a linear temperature gradient. In the case of uniform temperature conditions, correction of the phase drift proved to be essential when long periods of acquisition were required, as bias could reach values of up to 200 degrees C in its absence. The temperature uncertainty measured by MRI was 1.2 degrees C in average over 290 min. This accuracy is coherent with the requirements for food applications especially when thermocouples are useless.

International audience; The water self-diffusion coefficients in casein matrixes were measured using a pulsed field gradient spin-echo nuclear magnetic resonance technique (PFG-SE NMR). The dependence of the water self-diffusion coefficient on the casein concentration and the aqueous phase composition is reported in both a rehydrated native phosphocaseinate dispersion and a concentrated casein retentate. A model has been proposed to explain the different behavior of the water self-diffusion coefficient in the two casein systems. This model demonstrates that the water self-diffusion cannot be simply explained by the water content only. So, taking into account the specific effect of each constituent of the aqueous dispersing phase, the water self-diffusion reduction induced by the casein micelle can be modeled. The effect of fat on the water self-diffusion coefficients was investigated. Anhydrous milk fat-reconstituted retentate samples were used in order to estimate the obstruction effect of fat globules in the modeling process. The dependence of the self-diffusion coefficient of water on the fat and casein content is reported. A general model included the effect of the aqueous phase composition, and the obstruction effects of casein micelles and fat globules were proposed. This model was validated for water self-diffusion coefficients in industrial fatty retentates.

Texture analysis methods quantify the spatial variations in gray level values within an image and thus can provide useful information on the structures observed. However, they are sensitive to acquisition conditions due to the use of different protocols and to intra- and interscanner variations in the case of MRI. The influence was studied of two protocols and four different conditions of normalization of gray levels on the discrimination power of texture analysis methods applied to soft cheeses. Thirty-two samples of soft cheese were chosen at two different ripening periods (16 young and 16 old samples) in order to obtain two different microscopic structures of the protein gel. Proton density and T2-weighted MR images were acquired using a spin echo sequence on a 0.2 T scanner. Gray levels were normalized according to four methods: original gray levels, same maximum for all images, same mean for all images, and dynamics limited to ± 3 . Regions of interest were automatically defined, and texture descriptors were then computed for the co-occurrence matrix, run length matrix, gradient matrix, autoregressive model, and wavelet transform. The features with the lowest probability of error and average correlation coefficient were selected and used for classification with 1-nearest neighbor ( ) classifier. The best results were obtained when using the limitation of dynamics to ± 3 , which enhanced the differences between the two classes. The results demonstrated the influence of the normalization method and of the acquisition protocol on the effectiveness of the classification and also on the parameters selected for classification. These results indicate the need to evaluate sensitivity to MR acquisition protocols and to gray level normalization methods when texture analysis is required.; Les methodes d`analyse de texture quantifient les variations spatiales des niveaux de gris dans les images et peuvent fournir ainsi des informations pertinentes sur les structures observées. Cependant elles sont sensibles aux conditions d`acquisition liées aux différents protocoles et aux variations intra et inter scanner dans le cas de l`imagerie par résonance magnétique nucléaire. L`influence de deux protocoles et de quatre types de normalisation des niveaux de gris sur l`analyse de texture de différents types de fromages à pâte molle a été étudiée en particulier sur ses capacités de discrimination . Trente deux échantillons de fromages à pâte molle ont été choisis à deux stades d`affinage différents (16 jeunes et 16 vieux) afin d`obtenir deux gels de structures différentes. Des images pondérées en densité de proton et en T2 ont été acquises avec une séquence écho de spin sur un IRM 0.2 T. Les niveaux de gris ont été normalisés suivant quatre méthodes : aucune normalisation, même moyenne pour toutes les images, même maximum pour toutes les images et une dynamique limitée à ± 3 . Des zones d`intérêts ont été automatiquement définies et les descripteurs de textures ont été calculés en utilisant la matrice de cooccurence, la matrice des longueurs de plage, la matrice des gradients, un modèle autorégressif et la transformée en ondelette. Les paramètres les plus discriminants étaient sélectionnés et utilises pour la classification avec l`algorithme du plus proche voisin. Les meilleurs résultats furent obtenus avec la normalisation des niveaux de gris utilisant la dynamique ± 3 qui augmentait la différence entre les deux classes. Les résultats ont mis en évidence l`influence de la méthode de normalisation des niveaux de gris et du protocole d`acquisition sur les performances de la classification ainsi que sur les paramètres les plus discriminants. Ces résultats indiquent la nécessité d`évaluer la sensibilité au protocole et à la normalisation des niveaux de gris quand l`analyse de texture est utilisée.

National audience; Dans le cadre de l'invitation de Yves Gossuin à l'Institut de Chimie de Rennes, les différentes équipes de Rennes spécialisées en RMN/IRM ont présenté leurs travaux.