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This paper presents the results of detailed studies of the processes of droplet formation and its characteristics under conditions of artificially induction of a bag-breakup fragmentation event. A shadow imaging method was used in combination with the high-speed video filming of the side-view fragmentation process. Trajectories and ejection velocity characteristics of the formed droplets are determined by identifying particles in consecutive frames with combined use of Particle Imaging Velocimetry (PIV) and Particle Tracking Velocimetry (PTV). Based on the results of trajectory processing, the distributions of droplet velocities for the selected regions are obtained, and estimates of the ejection velocities at various heights are proposed.

In this study, a pressurized, water-filled impedance tube (WFIT) was developed to measure the reflection coefficients of sound-absorbing materials under various hydrostatic pressures. The developed WFIT was calibrated using a two-microphone, three-parameter calibration method (3PCM). The accuracy and repeatability of the measured reflection coefficients for the water–air interface in the WFIT were determined by comparing these coefficients with corresponding theoretical reflection coefficients. The WFIT was then used to measure the acoustic reflection coefficient of a porous rubber specimen on three dates, and the corresponding measurement results exhibited satisfactory repeatability. The aforementioned impedance tube was also used to measure the reflection coefficient of a porous rubber specimen under a hydrostatic pressure of 4 Patm three times on the same day, and one time each on three days, using the same experimental setup and measurement procedure. The results obtained in the aforementioned tests also exhibited satisfactory repeatability. Finally, the WFIT was used to measure the reflection coefficients of porous rubber specimens with various thicknesses under different hydrostatic pressures. The results of this study indicate that the developed WFIT calibrated with the 3PCM can achieve suitable repeatability in the measurement of the reflection coefficients of sound-absorbing materials under various hydrostatic pressures.

International audience; Plastic debris in the marine environment are the subject of an extensive literature. According to studies dedicated to the determination of plastic litter abundance and to the characterisation of degradation and fragmentation processes, models were used to estimate the global plastic debris abundance and to simulate their transfer and distribution. Despite these efforts, there is still missing plastic in the models used as areas exist where plastic abundance is less than that estimated. In parallel, microplastics presence in the atmosphere and in remote areas was confirmed suggesting long range atmospheric transport. Potentially addressing both these issues, recent literature suggests that microplastics (MPs) and nanoplastics (NPs) can be transferred from the marine environment to the atmosphere via the bursting of air bubbles at the sea surface. Nevertheless, to date there is no direct evidence of this transfer. In this study, we evaluate plastic particles transfer as a function of MPs/NPs characteristics and water composition by simulating the bubble bursting phenomenon in a laboratory reactor. Size distribution of transferred particles were recorded, and their plastic nature was confirmed using electron microscopy. Results show that under tested conditions, the transfer is possible but limited to particles smaller than 1 μm. The influence of the presence of proxies of components of the sea surface microlayer in the water was evaluated showing a higher particle transfer rate in the presence of a surfactant (sodium dodecyl sulfate) and no significant effect of polysaccharides (xanthan gum and dextran). The surface state of the particles can alter their behaviour in the aqueous phase and thus their transfer to the atmosphere. The effect of bubble size was also evaluated showing a higher transfer rate with the smaller bubble size. In addition, experiments performed with grounded polyethylene (PE) samples showed higher transfer for UV-aged PE than for pristine PE.

This paper investigates the physical processes involved in the water filling and air expelling process of a pipe with multiple air valves under water slow filling condition, and develops a fully coupledwater&ndash, air two-phase stratified numerical model for simulating the process. In this model, the Saint-Venant equations and the Vertical Average Navier&ndash, Stokes equations (VANS) are respectively applied to describe the water and air in pipe, and the air valve model is introduced into the VANS equations of air as the source term. The finite-volume method and implicit dual time-stepping method (IDTS) with two-order accuracy are simultaneously used to solve this numerical model to realize the full coupling between water and air movement. Then, the model is validated by using the experimental data of the pressure evolution in pipe and the air velocity evolution of air valves, which respectively characterize the water filling and air expelling process. The results show that the model performs well in capturing the physical processes, and a reasonable agreement is obtained between numerical and experimental results. This agreement demonstrates that the proposed model in this paper offers a practical method for simulating water filling and air expelling process in a pipe with multiple air valves under water slow filling condition.

Hydrophobins (HPs) are small secreted fungal proteins possibly involved in several processes such as formation of fungal aerial structures, attachment to hydrophobic surfaces, interaction with the environment and protection against the host defense system. The genome of the necrotrophic plant pathogen Fusarium graminearum contains five genes encoding for HPs (FgHyd1-5). Single and triple FgHyd mutants were produced and characterized. A reduced growth was observed when the ΔFghyd2 and the three triple mutants including the deletion of FgHyd2 were grown in complete or minimal medium. Surprisingly, the growth of these mutants was similar to wild-type when grown under ionic, osmotic or oxidative stress conditions. All the mutant strains confirmed the ability to develop conidia and perithecia, suggesting that the FgHyds are not involved in normal development of asexual and sexual structures. A reduction in the ability of hyphae to penetrate through the water-air interface was observed for the single mutants ΔFghyd2 and ΔFghyd3 as well as for the triple mutants including the deletion of FgHyd2 and FgHyd3. Besides, ΔFghyd3 and the triple mutant ΔFghyd234 were also affected in the attachment to hydrophobic surface. Indeed, wheat infection experiments showed a reduction of symptomatic spikelets for ΔFghyd2 and ΔFghyd3 and the triple mutants only when spray inoculation was performed. This result could be ascribed to the affected ability of mutants deleted of FgHyd2 and FgHyd3 to penetrate through the water-air interface and to attach to hydrophobic surfaces such as the spike tissue. This hypothesis is strengthened by a histological analysis, performed by fluorescence microscopy, showing no defects in the morphology of infection structures produced by mutant strains. Interestingly, triple hydrophobin mutants were significantly more inhibited than wild-type by the treatment with a systemic triazole fungicide, while no defects at the cell wall level were observed.

Hydrophobins (HPs) are small secreted fungal proteins possibly involved in several processes such as formation of fungal aerial structures, attachment to hydrophobic surfaces, interaction with the environment and protection against the host defense system. The genome of the necrotrophic plant pathogen Fusarium graminearum contains five genes encoding for HPs (FgHyd1-5). Single and triple FgHyd mutants were produced and characterized. A reduced growth was observed when the ΔFghyd2 and the three triple mutants including the deletion of FgHyd2 were grown in complete or minimal medium. Surprisingly, the growth of these mutants was similar to wild-type when grown under ionic, osmotic or oxidative stress conditions. All the mutant strains confirmed the ability to develop conidia and perithecia, suggesting that the FgHyds are not involved in normal development of asexual and sexual structures. A reduction in the ability of hyphae to penetrate through the water-air interface was observed for the single mutants ΔFghyd2 and ΔFghyd3 as well as for the triple mutants including the deletion of FgHyd2 and FgHyd3. Besides, ΔFghyd3 and the triple mutant ΔFghyd234 were also affected in the attachment to hydrophobic surface. Indeed, wheat infection experiments showed a reduction of symptomatic spikelets for ΔFghyd2 and ΔFghyd3 and the triple mutants only when spray inoculation was performed. This result could be ascribed to the affected ability of mutants deleted of FgHyd2 and FgHyd3 to penetrate through the water-air interface and to attach to hydrophobic surfaces such as the spike tissue. This hypothesis is strengthened by a histological analysis, performed by fluorescence microscopy, showing no defects in the morphology of infection structures produced by mutant strains. Interestingly, triple hydrophobin mutants were significantly more inhibited than wild-type by the treatment with a systemic triazole fungicide, while no defects at the cell wall level were observed.

National audience; Interactions des protéines dans l’eau et aux interfaces hydrophobes Des protéines, de l’eau, de l’air.... Première réunion plénière du GDR SLAMM (Solliciter LA Matière Molle)

A storage tunnel system is the critical infrastructure of urban drainage systems, in which the rapid filling of water and release of trapped air can lead to the &ldquo, geyser&rdquo, phenomenon. This may cause serious damage, threatening both system operation and personal safety. In this paper, a detailed experimental study was carried out based on synchronous recorded video images and digital image processing technology. According to experimental observations, gas-flow geysers and surge-type geysers were analyzed deeply. The former is caused by high-speed gas flow and is accompanied by a pressure drop, the latter is caused by surge pressure and is accompanied by a pressure increase. The free surface velocity of the gas-flow geyser is mainly affected by the external pressure, the air volume, the diameter of the shaft, and the height of the water column, and the geyser phenomenon cannot occur when the air column is mainly dominated by buoyancy. Based on dimensional analysis and data fitting, this paper presents the empirical formula for the free surface velocity and the interface net velocity and puts forward the critical occurrence conditions for the gas-flow geyser.

We report a novel multi-step method for the preparation of ordered mesoporous titania scaffolds and show an illustrative example of their application to solar cells. The method is based on (monolayer) colloidal nanosphere lithography that makes use of polystyrene nanoparticles organised at a water–air interface and subsequently transferred onto a solid substrate. A titania precursor solution (titanium(IV) isopropoxide in ethanol) is then drop-cast onto the monolayer and left to “incubate” overnight. Surprisingly, instead of the expected inverse monolayer-structure, a subsequent calcination step of the precursor yields an ordered monolayer of hollow titania nanospheres with a wall thickness of ∼30–50 nm, and a slightly larger diameter than that of the starting spheres. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterization of such scaffolds confirm that they consist of nanocrystalline anatase titania, and that any polystyrene/carbon residues in the scaffolds are below the XPS detection level. As an illustrative application we prepared perovskite solar cells incorporating the templated-nanoparticle scaffolds displaying a respectable power conversion efficiency of ∼9%, twice as large as that of our unoptimized “reference” cells (i.e. incorporating conventional mesoporous or compact titania scaffolds), thereby also demonstrating that the process is relatively robust with respect to optimization of the process parameters.

A triazole appended benzaldehydic lower rim derivative of calix[4]arene (L) has been synthesized and was thoroughly characterized. In CH3CN solution, the L showed greater sensitivity for Fe3+ by a 5-fold increase in the absorbance and 37% quenching in the fluorescence intensity, by forming a 1:1 complex. The Fe3+ induces aggregation in L as studied by microscopy. The Langmuir film formed at the air-water interface was characterized by pressure-area isotherm and Brewster angle micrographs, both in the presence and absence of metal ions. The Langmuir films of pure L, {L+Al3+} and {L+Zn2+} were transferred onto H-terminated Si-wafer and characterized using Atomic Force Microscopy, contact angle, Grazing Incidence Fourier Transform Infrared Spectrscopy and X-ray Photoelectron Spectroscopy. The study resulted selective binding of Al3+ to the Langmuir film of L among the nine metal ions studied. Thus, the calix[4]arene-conjugate L is sensitive and selective to Fe3+ in acetonitrile solution whereas to Al3+ in Langmuir film and hence acts as an ion switch depending upon the physical state of L.

Pore-scale simulation and tomography have been used in a combination over the past decade to study some fundamental physical and biogeochemical processes in soil that are difficult or impossible to measure, one of which is water flow in unsaturated soil. Considering that an important application of pore-scale simulation in soil is to elucidate how convective water flow distributes soluble nutrients through the heterogeneous pore space when water flow is in steady state, we propose an alternative model in this paper to simulate unsaturated water flow at pore scale. The model is quasi-static, consisting of two steps. The first one is to determine water distribution in the pore geometry using a morphological model; once the water distribution is known under a pressure, the water-air interface is fixed in space. The second step is to simulate water flow numerically by solving the Stokes equations in which the water-air interface is treated as a boundary. We test the water flow model against analytical solution of thin water film flow over a non-slip solid wall, and then combine it with the morphological model to simulate water flow in 3D soil structures acquired using X-ray tomography at resolution of 10 A mu m. As a validation, we compare the permeability calculated by the model under different saturations with those estimated by the van Genuchten formula using the saturated permeability and water retention parameters obtained from the morphological model. We also discuss the pros and cons of the model and its implications in unsaturated soil modelling.

International audience; Les biopolymères sont des composants essentiels des aliments et des boissons, ainsi que des composants clés d'autres types de produits non alimentaires. Le défi est de comprendre l'organisation à l'échelle macroscopique de ces architectures naturelles et élaborées, en relation avec les propriétés des composants de base et leurs interactions à une échelle mésoscopique.Dans un contexte de transition alimentaire mondiale, de nouvelles sources de protéines alternatives sont recherchées. Par conséquent, la connaissance approfondie de ces molécules ainsi que la caractérisation des interactions et des structures à plusieurs échelles dans les matrices alimentaires permettront l'utilisation optimale des biopolymères. Cette connaissance pluridisciplinaire aura un impact positif sur le contrôle de la structure finale, de la formulation de produits alimentaires, de la qualité sensorielle, de l'encapsulation de molécules saines, du comportement au cours de la digestion et de nombreuses autres caractéristiques essentielles.

International audience; We provide a detailed description of the structure of water at the interface with the air (liquid-vapor LV interface) from state-of-the-art DFT-based molecular dynamics simulations. For the first time, a two-dimensional (2D) H-bond extended network has been identified and fully characterized, demonstrating that interfacial water is organized into a 2D sheet with H-bonds oriented parallel to the instantaneous surface and following its spatial and temporal oscillations. By analyzing the nonlinear vSFG (vibrational sum frequency generation) spectrum of the LV interface in terms of layer-by-layer signal, we demonstrate that the 2D water sheet is solely responsible for the spectral signatures, hence providing the interfacial 3.5 Å thickness effectively probed in nonlinear interfacial spectroscopy. The 2D H-bond network unraveled here is the essential key to rationalize macroscopic properties of water-air interfaces, as demonstrated here for spectroscopy and the surface potential.

De la macromolécule au dessert: Comportement des protéines aux interfaces hydrophobes. Journée Scientifique ScanMAT 2017

Expression à l'interface eau-air de potentialités d'assemblage des protéines, et interactions aux concentrations élevées. Matière molle pour la science des aliments : Compréhension et Structuration

Interactions dans des films d'adsorption de protéines globulaires à l'interface eau-air: comportements différenciés et effets d'ions. Journées du Groupement de Recherche GDR 2980 Approches Multi-physiques pour les Colloïdes Concentrés (AMC2)

International audience; From their amphiphilic nature, proteins in solution adsorb spontaneously at hydrophobic interfaces. Proteins are thus able to change their conformation, which modifies their surface properties. In the confined space near the interface, these modifications favor the formation of many interactions of weak energy (hydrophobic interactions, hydrogen bonds, Van der Waals interactions), and thus the creation, in the interface plane, of a network of intermolecular interactions. Adsorbed proteins can thus, in favorable conditions, constitute at the interface a continuous film with visco-elastic properties. These mechanical properties contribute to the stabilization of the interface created in multiphasic systems such as foams. Our work focuses on the behavior at the air-water interface and, if needed the foam properties, of some model globular proteins: ovalbumin, lysozyme, ovotransferrin, β-lactoglobulin… The aim of our work is to understand, using these models, how protein properties (structure, biochemistry, physico-chemistry), potentially adjusted by the physico-chemical environment, chemical changes or thermo-mechanical treatments, take part in the interfacial behavior, film characteristics and macroscopic proprieties of foams (overrun, stability, texture). Besides, in systems where several proteins with different properties (size, hydrophobicity, charge, conformation flexibility,…) coexist, we look to understand how the interactions between proteins enhance behaviors that cannot be considered as the sum of the single behaviors. The issue over time is to control technological parameters to improve texture properties in relation to foaming capacity.

Expression at the air{water interface of protein assembly potentiality, and interactions at high concentration. OMM Anual meeting

Here multiple angle of incidence ellipsometry was successfully applied to in situ assess the contact angle and surface coverage of gold nanoparticles as small as 18 nm, coated with stimuli-responsive polymers, at water–oil and water–air interfaces in the presence of NaCl and NaOH, respectively. The interfacial adsorption of the nanoparticles was found to be very slow and took days to reach a fairly low surface coverage. For water–oil interfaces, in situ nanoparticle contact angles agree with the macroscopic equilibrium contact angles of planar gold surfaces with the same polymer coatings, whilst for water–air interfaces, significant differences have been observed. Refereed/Peer-reviewed

Determinations of the adsorption at both solid-liquid and water-air interfaces of 1-alkyl-4-methylpyridinium salts have been performed. At the water-air interface, measurements of the surface tension as a function of the bulk concentration of 1-dodecyl-4-methylpyridinium chloride were performed. Mathematical treatment of the resulting isotherm allowed the size of the adsorbed molecule and the CMC to be obtained. The solid adsorbent was a titanium dioxide sample prepared in the laborato Adsorption isotherms of 1-dodecyl-4-methylpyridinium chloride and 1-butyl-4-methylpyridinium chloride were obtained at the same pH and ionic strength. For the shorter-chain surfactant, a second isotherm at a higher base electrolyte concentration was obtained. The experimental isotherms are discussed in the light of literature results and analyzed on the basis of the Frumkin-Fowler-Guggenheim adsorption equation. X-ray photoelectron spectroscopic analyses were performed both on the bare adsorbent and in the presence of the adsorbates. The binding energy of the surfactant elements (both nitrogen and carbon) was observed to undergo significant modifications when the compound was in the adsorbed state. The features of the adsorption of the two organic ions are discussed in light of the different experimental results.

Phosvitin is an egg yolk protein constituted by 50% of serines which are all phosphorylated. Because of this peculiarity, phosvitin has a high charge density and is known to be one of the most natural cation-binding proteins. In addition, phosvitin naturally forms aggregates through phosphocalcic bridges in egg yolk. This high charge density, doubled by this capacity to aggregate, limits the adsorption of the protein at oil–water or air–water interfaces. In this work, we investigated the impact of both the charge, by sodium chloride (NaCl) addition, and the aggregation, by calcium chloride addition, on the interfacial properties of phosvitin. The air–water interfacial activity of the phosvitin was studied with a Wilhelmy-type film balance and a Brewster angle microscope. In the presence of increasing NaCl concentrations, phosvitin presents improved interfacial properties and the film formed was more dense. The better adsorption of the phosvitin is attributed to the charge screening due to NaCl which could permit a higher spreading of the protein at the interface. Concerning the aggregation effect, calcium–phosvitin aggregates favour the contact between the protein and the interface and act on the interfacial film morphology inducing the formation of a thicker and a more rigid interfacial phosvitin film.

We experimentally and theoretically investigate the shapes of contact lines on the surfaces of micrometer-sized polystyrene ellipsoids at the water-air interface. By combining interferometry and optical trapping, we directly observe quadrupolar symmetry of the interface deformations around such particles. We then develop numerical solutions of the partial wetting problem for ellipsoids, and use these solutions to deduce the shapes of the corresponding contact lines and the values of the contact angles, theta(c)(k), as a function of the ellipsoid aspect ratio k. Surprisingly, theta(c) is found to decrease for increasing k suggesting that ellipsoid microscopic surface properties depend on ellipsoid aspect ratio.