The Sagnac effect in Coupled-Resonator Slow-Light Waveguide Structures

We study the effect of rotation on the propagation of electromagnetic waves in slow-light waveguide structures consisting of coupled micro-ring resonators. We show that such configurations exhibit new a type of the Sagnac effect which can be used for the realization of highly-compact integrated rotation sensors and gyroscopes

Preparation of double emulsions using hybrid polymer/silica particles: New pickering emulsifiers with adjustable surface wettability

A facile route for the preparation of water-in-oil-in-water (w/o/w) double emulsions is described for three model oils, namely, n-dodecane, isopropyl myristate, and isononyl isononanoate, using fumed silica particles coated with poly(ethylene imine) (PEI). The surface wettability of such hybrid PEI/silica particles can be systematically adjusted by (i) increasing the adsorbed amount of PEI and (ii) addition of 1-undecanal to the oil phase prior to homogenization. In the absence of this long-chain aldehyde, PEI/silica hybrid particles (PEI/silica mass ratio = 0.50) produce o/w Pickering emulsions in all cases. In the presence of 1-undecanal, this reagent reacts with the primary and secondary amine groups on the PEI chains via Schiff base chemistry, which can render the PEI/silica hybrid particles sufficiently hydrophobic to stabilize w/o Pickering emulsions at 20 °C. Gas chromatography, 1H NMR and X-ray photoelectron spectroscopy provide compelling experimental evidence for this in situ surface reaction, while a significant increase in the water contact angle indicates markedly greater hydrophobic character for the PEI/silica hybrid particles. However, when PEI/silica hybrid particles are prepared using a relatively low adsorbed amount of PEI (PEI/silica mass ratio = 0.075) only o/w Pickering emulsions are obtained, since the extent of surface modification achieved using this Schiff base chemistry is insufficient. Fluorescence microscopy and laser diffraction studies confirm that highly stable w/o/w double emulsions can be achieved for all three model oils. This is achieved by first homogenizing the relatively hydrophobic PEI/silica hybrid particles (PEI/silica mass ratio = 0.50) with an oil containing 3% 1-undecanal to form an initial w/o emulsion, followed by further homogenization using an aqueous dispersion of relatively hydrophilic PEI/silica particles (PEI/silica mass ratio = 0.075). Dye release from the internal aqueous cores into the aqueous continuous phase was monitored by visible absorption spectroscopy. These studies indicate immediate loss of 12-18% dye during the high speed homogenization that is required for double emulsion formation, but no further dye release is observed at 20 °C for at least 15 days thereafter

Interfacial properties in solid-stabilized emulsions

We prepared concentrated monodisperse oil-in-water emulsions stabilized by solid particles. The osmotic resistance, Π, of the emulsions was measured for different oil volume fractions above the random close packing ( $\phi ^*\approx 64{\%}$ ). The dimensionless osmotic resistance, Π/(γ/R) (γ being the interfacial tension and R being the undeformed drop radius), was always substantially higher than the corresponding values obtained for surfactant-stabilized emulsions. It can be concluded that droplet deformation in solid-stabilized emulsions is not controlled by the capillary pressure, γ/R, of the non-deformed droplets but rather by σ0/R, σ0 being a parameter characterizing the rigidity of the droplets surfaces. The data can be interpreted considering that the interfacial layers are elastic at small deformations and exhibit plasticity at intermediate deformations. σ0 corresponds to the surface yield stress, i.e. the transition between elastic and plastic regimes. We discuss the origin of the surface behavior considering the strong lateral interactions that exist between the adsorbed solid particles. We propose an independent measurement of σ0 based on the critical bulk stress that produces droplet fragmentation in dilute emulsions submitted to shear. Finally, the bulk shear elastic modulus was measured as a function of φ and confirms many of the features revealed by the osmotic resistance. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005

Some general features of limited coalescence in solid-stabilized emulsions

We produce direct and inverse emulsions stabilized by solid mineral particles. If the total amount of particles is initially insufficient to fully cover the oil-water interfaces, the emulsion droplets coalesce such that the total interfacial area between oil and water is progressively reduced. Since it is likely that the particles are irreversibly adsorbed, the degree of surface coverage by them increases until coalescence is halted. We follow the rate of droplet coalescence from the initial fragmented state to the saturated situation. Unlike surfactant-stabilized emulsions, the coalescence frequency depends on time and particle concentration. Both the transient and final droplet size distributions are relatively narrow and we obtain a linear relation between the inverse average droplet diameter and the total amount of solid particles, with a slope that depends on the mixing intensity. The phenomenology is independent of the mixing type and of the droplet volume fraction allowing the fabrication of both direct and inverse emulsion with average droplet sizes ranging from micron to millimetre

Some general features of limited coalescence in solid-stabilized emulsions

We produce direct and inverse emulsions stabilized by solid mineral particles. If the total amount of particles is initially insufficient to fully cover the oil-water interfaces, the emulsion droplets coalesce such that the total interfacial area between oil and water is progressively reduced. Since it is likely that the particles are irreversibly adsorbed, the degree of surface coverage by them increases until coalescence is halted. We follow the rate of droplet coalescence from the initial fragmented state to the saturated situation. Unlike surfactant-stabilized emulsions, the coalescence frequency depends on time and particle concentration. Both the transient and final droplet size distributions are relatively narrow and we obtain a linear relation between the inverse average droplet diameter and the total amount of solid particles, with a slope that depends on the mixing intensity. The phenomenology is independent of the mixing type and of the droplet volume fraction allowing the fabrication of both direct and inverse emulsion with average droplet sizes ranging from micron to millimetre

Œdème aigu hémorragique du nourrisson associé à une infection à Coxsackie virus

International audienceAcute hemorrhagic edema of infancy is a rare but benign vasculitis occurring in infants aged from 4 to 24 months. Skin lesions can take various forms, including extensive hemorrhagic purpura, and can therefore be mistaken for purpura fulminans if associated with fever, which leads to initiating broad-spectrum antibiotic treatment. In the present case, we describe a 7-month-old boy with acute hemorrhagic edema of infancy and rapidly extensive purpura lesions that led to intravenous cefotaxime and amikacin treatment. Diagnosis was made on the next day by a dermatologist, based on the typical aspect of skin lesions, hemodynamic stability, and negative bacteriological samples. Coxsackie virus B5, a pathogenic enterovirus, was found by specific PCR in cerebrospinal fluid. The outcome was spontaneously favorable after discontinuation of antibiotics on day 2. We discuss the imputability of the enterovirus in triggering this case of acute hemorrhagic edema of infancy.L’œdème aigu hémorragique du nourrisson (OAHN) est une vascularite rare et bénigne survenant chez des nourrissons de 4 à 24 mois. Les lésions cutanées, prenant parfois l’aspect d’un purpura ecchymotique ou en nappe, peuvent faire évoquer le diagnostic de purpura fulminans lorsqu’une fièvre y est associée et entraîner alors la mise en route d’une antibiothérapie. Nous rapportons le cas d’un nourrisson de 7 mois dont la présentation clinique initiale d’OAHN a fait suspecter un purpura fulminans. L’évolution rapide des lésions a fait instaurer une antibiothérapie par céfotaxime et amikacine. Le diagnostic d’OAHN a été porté le lendemain devant l’aspect des lésions cutanées, la stabilité hémodynamique de l’enfant et la négativité du bilan bactériologique. Un entérovirus (Coxsackie virus B5) a été mis en évidence secondairement par réaction de polymérisation en chaîne spécifique (PCR) dans le liquide céphalorachidien. Après arrêt de l’antibiothérapie, l’évolution a été spontanément favorable. L’imputabilité de l’entérovirus dans le déclenchement de cet OAHN est discutée