Ref HAL: hal-01927223_v1
DOI: 10.1109/cleoe-eqec.2017.8087591
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Open channels are peculiar incidents modes of the optical field that are transmitted by a highly diffusing medium with high efficiency (100 % in the ideal case). The existence of these modes has been predicted by Dorokhov et al. [1] more than 25 years ago. Although many experiments were made to prepare these modes [2,3], the maxima of transmission obtained in experiments, are ever much lower than 100 %. To test the theory, we have considered here another Dorokhov's prediction: the average transmission of the modes that sustain the transmitted field must be TT=66%, where TT is defined by N2 TT= N1 T (where T is the averaged transmission of energy, and N1 and N2 the number of incident and transmitted modes i.e. the size of the incident and transmitted mode basis). Fig.1 (a) Holographic experimental setup. (b) Residual correlation of the transmitted field. The horizonal axis is SQ'. The sample transverse size is L=70 µm red, 50 µm green, 35 µm blue.... The horizontal grey line is the residual correlation expected for N1=N2. To verify this prediction, we have measured N2 on a slab sample of ZNO powder (transverse size L<=70 µm, thickness 20 µm) [4], by assuming that N1 is given by the sample geometry. The experimental setup is seen in Fig. 1(a). The incident fields are random (there are scrambled by a diffusing liquid DL) and digital holography is used to measure the complex transmitted field E(x,y) for the two polarisations. N2 is measured by analysing the residual correlations of the transmitted field measured for uncorrelated incident fields. Since the average transmission is T=1/25, we expect N2=N1/16. To get this optimal result, the transverse size of sample L must be infinite and the defocusing SQ' of the microscope objective MO2 must be zero (where S is the sample outgoing surface and Q' the plane imaged by MO2). Figure 1 (b) shows the residual correlation (which is proportional to 1/N2) as a function these two parameters. We get N2=N1/12 without extrapolation, and N2=N1/16 with extrapolation to L infinite. Here, the open channel effect is huge (factor 16) and the aggreement with the Dorokhov's prediction is excellent. We acknowledge Labex Numev (convention ANR-10-LABX-20) for funding. References 1. O.N. Dorokhov. On the coexistence of localized and extended electronic states in the metallic phase. Solid state communications, 51(6): 381-384, (1984).

Ref HAL: hal-01427072_v1
Ref Arxiv: 1604.02360
DOI: 10.1103/PhysRevFluids.1.083302
WoS: 000390345900001
Ref. & Cit.: NASA ADS
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8 Citations
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We investigate the dynamics of freely expanding liquid sheets prepared with fluids with different rheological properties, (i) viscous fluids with a zero-shear viscosity $\eta_0$ in the range $(1-1000) \, \mathrm{mPa.s}$ and (ii) viscoelastic Maxwell fluids whose elastic modulus, $G_0$, characteristic relaxation time, $\tau$, and zero-shear viscosity, $\eta_0=G_0 \tau$, can be tuned over several orders of magnitude. The sheets are produced by impacting a drop of fluid on a small cylindrical solid target. For viscoelastic fluids, we show that, when $\tau$ is shorter than the typical lifetime of the sheet ($\sim 10$ ms), the dynamics of the sheet is similar to that of Newtonian viscous liquids with equal zero-shear viscosity. In that case, for little viscous samples ($\eta_0 <\sim 30$ mPa.s), the maximal expansion of the sheet, $d_{\rm{max}}$, is independent of $\eta_0$, whereas for more viscous samples, $d_{\rm{max}}$ decreases as $\eta_0$ increases. We provide a simple model to account for the dependence of the maximal expansion of the sheet with the viscosity that is based on an energy balance between inertia, surface tension and viscous shear dissipation on the solid target, and which accounts well for our experimental data. By contrast, when $\tau$ is longer than the typical lifetime of the sheet, the behavior drastically differs. The sheet expansion is strongly enhanced as compared to that of viscous samples with comparable zero-shear viscosity, but is heterogeneous with the occurrence of cracks, revealing the elastic nature of the viscoelastic fluid.

Ref HAL: hal-02070663_v1
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Biophysical approach of the mucociliary function: Mucus rheology and beating coordination

Ref HAL: hal-02070646_v1
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The Continuous Droplet Interface Crossing Encapsulation (cDICE) is an easy and robust method for producing, at high yield, monodisperse lipid vesicles with a controlled content as well as capsules with a designed shell. It consists in forcing a droplet through an interface between two imiscible fluids, using an external force such as centrifugation. At high inertia, the droplet entrain fluid that will constitute the shell of the capsule. At low inertia, the presence of amphiphile and the deformable interface interactions lead to monolayers zipping and formation of an amphiphile bilayer around the droplet. We will discuss the physical mechanisms involved in the production of both cDICE vesicles (low droplets inertia) and capsules (at high inertia), and the potential applications of this method. This method founds indeed many applications in biomimetics as it allows to encapsulate various biological solutions (biopolymers, hemoglobin, colloids, polymeric gels, cells. . . ) in membranes that can be composite and/or assymetric, or polymeric, and in the field of microencapsulation.

Ref HAL: hal-02070634_v1
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The Continuous Droplet Interface Crossing Encapsulation (cDICE) is an easy and robust method for producing, at high yield, monodisperse lipid vesicles with a controlled content as well as capsules with a designed shell. It consists in forcing a droplet through an interface between two imiscible fluids, using an external force such as centrifugation. At high inertia, the droplet entrain fluid that will constitute the shell of the capsule. At low inertia, the presence of amphiphile and the deformable interface interactions lead to monolayers zipping and formation of an amphiphile bilayer around the droplet. We will discuss the physical mechanisms involved in the production of both cDICE vesicles (low droplets inertia) and capsules (at high inertia), and the potential applications of this method. This method founds indeed many applications in biomimetics as it allows to encapsulate various biological solutions (biopolymers, hemoglobin, colloids, polymeric gels, cells. . . ) in membranes that can be composite and/or assymetric, or polymeric, and in the field of microencapsulation.

Ref HAL: hal-02070620_v1
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The Continuous Droplet Interface Crossing Encapsulation (cDICE) is an easy and robust method for producing, at high yield, monodisperse lipid vesicles with a controlled content as well as capsules with a designed shell. It consists in forcing a droplet through an interface between two imiscible fluids, using an external force such as centrifugation. At high inertia, the droplet entrain fluid that will constitute the shell of the capsule. At low inertia, the presence of amphiphile and the deformable interface interactions lead to monolayers zipping and formation of an amphiphile bilayer around the droplet. We will discuss the physical mechanisms involved in the production of both cDICE vesicles (low droplets inertia) and capsules (at high inertia), and the potential applications of this method. This method founds indeed many applications in biomimetics as it allows to encapsulate various biological solutions (biopolymers, hemoglobin, colloids, polymeric gels, cells. . . ) in membranes that can be composite and/or assymetric, or polymeric, and in the field of microencapsulation.

Ref HAL: hal-02060930_v1
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