Interior metric and ray-tracing map in the firework black-to-white hole transition

The possibility that a black hole could tunnel into a white hole has recently received attention. Here we present a metric that improves the 'firework' metric: it describes the entire process and solves the Einstein equations everywhere except on a small transition surface that corresponds to the quantum tunnelling. We compute the corresponding ray-tracing map from past infinity to future infinity explicitly.Comment: 5 pages, 10 figure

Evaporating black-to-white hole

We construct and discuss the form of the (effective) spacetime geometry inside a black hole undergoing a quantum transition to a white hole, taking into account the back-reaction of the component of the Hawking radiation falling into the hole

Fluorescence visualization of a convective instability which modulates the spreading of volatile surface films

The spontaneous spreading of a thin liquid film along the surface of a deep liquid layer of higher surface tension is a ubiquitous process which provides rapid and efficient surface transport of organic or biological material. For a source of constant concentration, the leading edge of a nonvolatile, immiscible film driven to spread by gradients in surface tension is known to advance as t^3/4 in time. Recent experiments using laser shadowgraphy to detect the advancing front of spreading films indicate, however, that immiscible but volatile sources of constant concentration spread with a reduced exponent according to t^1/2. Using a novel technique whereby fluorescent lines are inscribed in water, we have detected the evolution of a thermal instability beneath the leading edge of volatile films which strongly resembles a Rayleigh-Bénard roll. We propose that the increased dissipation from this rotational flow structure is likely responsible for the reduction in spreading exponent. This observation suggests a conceptual framework for coupling the effects of evaporation to the dynamics of spreading

Spreading characteristics of an insoluble surfactant film on a thin liquid layer: comparison between theory and experiment

We describe measurements of the surface slope and reconstruction of the interface shape during the spreading of an oleic acid film on the surface of a thin aqueous glycerol mixture. This experimental system closely mimics the behaviour of an insoluble surfactant film driven to spread on a thin viscous layer under the action of a tangential (Marangoni) surface stress. Refracted image Moiré topography is used to monitor the evolution of the surface slope over macroscopic distances, from which the time variant interface shape and advancing speed of the surfactant film are inferred. The interfacial profile exhibits a strong surface depression ahead of the surfactant source capped by an elevated rim at the surfactant leading edge. The surface slope and shape as well as the propagation characteristics of the advancing rim can be compared directly with theoretical predictions. The agreement is quite strong when the model allows for a small level of pre-existing surface contamination of the initial liquid layer. Comparison between theoretical and experimental profiles reveals the importance of the initial shear stress in determining the evolution in the film thickness and surfactant distribution. This initial stress appears to thin the underlying liquid support so drastically that the surfactant droplet behaves as a finite and not an infinite source, even though there is always an excess of surfactant present at the origin

Late stage kinetics for various wicking and spreading problems

The kinetics of spreading of a liquid drop in a wedge or V-shaped groove, in a network of such grooves, and on a hydrophilic strip, is re-examined. The length of a droplet of volume Omega spreading in a wedge after a time t is predicted to scale as Omega^(1/5) * t^(2/5), and the height profile is predicted to be a parabola in the distance along the wedge. If the droplet is spreading radially in a sparse network of V-shaped grooves on a surface, the radius is predicted to scale as Omega^(1/6) * t^(1/3), provided the liquid is completely contained within the grooves. A number of other results are also obtained.Comment: 5 pages, 2 figures, RevTeX

An experiment to test the discreteness of time

Time at the Planck scale ($\sim 10^{-44}~\mathrm{s}$) is an unexplored physical regime. It is widely believed that probing Planck time will remain for long an impossible task. Yet, we propose an experiment to test the discreteness of time at the Planck scale and show that it is not far removed from current technological capabilities.Comment: 11 pages, 5 figures, 1 tabl

New core-shell microgel offers creative texture and water-fresh sensory qualities to skin care products.

Sensorial attributes such as texture are essential to designing skin care products that satisfy growing consumer trends. Momentive’s patented, silicone-grafted polyacrylate microgel is an innovative, multifunctional structuring/texturing agent that can deliver a wide range of new, creative textures with a water-fresh feel. The swelling and emulsification properties of this multifunctional hydrophilic/hydrophobic particle demonstrate the microgel’s versatility and array of achievable textures. Core-shell microgel can emulsify a large volume of oil and provide excellent dispersion power for solid particles, and an enhanced, lightweight feel to sunscreen formulations. Silicone copolymer grafting can allow the development of skin care formulations that achieve more with less—more functionality, fewer ingredients

Reconstruction algébrique en tomographie à rayons X en 3D

Imagerie par tomographie à rayons X -- État de l'art -- Physique de la tomographie à rayons X -- État de l'art sur les méthodes de reconstruction analytiques -- État de l'art sur les méthodes algébriques -- Diverses détériorations d'image en tomographie à rayons X -- Modélisation du problème direct -- Modèle de formation des données -- Modélisation de l'épaisseur du faisceau -- Paramétrisation géométrique du problème -- Structure de données adaptée pour la mise en oeuvre