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Search Results: 1 - 10 of 144461 matches for " F. Dalnoki-Veress "
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Theta 13 Determination with Nuclear Reactors
F. Dalnoki-Veress
Physics , 2004,
Abstract: Recently there has been a lot of interest around the world in the use of nuclear reactors to measure theta 13, the last undetermined angle in the 3-neutrino mixing scenario. In this paper the motivations for theta 13 measurement using short baseline nuclear reactor experiments are discussed. The features of such an experiment are described in the context of Double Chooz, which is a new project planned to start data-taking in 2008, and to reach a sensitivity of sinsq(2 theta 13) < 0.03.
Snap-off production of monodisperse droplets
Solomon Barkley,Eric R. Weeks,Kari Dalnoki-Veress
Physics , 2015,
Abstract: We introduce a novel technique to produce monodisperse droplets through the snap-off mechanism. The methodology is simple, versatile, and requires no specialized or expensive components. The droplets produced have polydispersity <1% and can be as small as 2.5 $\mu$m radius. A convenient feature is that the droplet size is constant over a 100-fold change in flow rate, while at higher flows the droplet size can be continuously adjusted.
A Scintillator Purification System for the Borexino Solar Neutrino Detector
J. Benziger,L. Cadonati,F. Calaprice,M. Chen,A. Corsi,F. Dalnoki-Veress,R. Fernholz,R. Ford,C. Galbiati,A. Goretti,E. Harding,Aldo Ianni,Andrea Ianni,S. Kidner,M. Leung,F. Loeser,K. McCarty,D. McKinsey,A. Nelson,A. Pocar,C. Salvo,D. Schimizzi,T. Shutt,A. Sonnenschein
Physics , 2007, DOI: 10.1016/j.nima.2007.12.043
Abstract: Purification of the 278 tons of liquid scintillator and 889 tons of buffer shielding for the Borexino solar neutrino detector was performed with a system that combined distillation, water extraction, gas stripping and filtration. The purification of the scintillator achieved unprecedented low backgrounds for the large scale liquid scintillation detector. This paper describes the principles of operation, design, construction and commissioning of the purification system, and reviews the requirements and methods to achieve system cleanliness and leak-tightness.
Capillary levelling of a cylindrical hole in a viscous film
Matilda Backholm,Michael Benzaquen,Thomas Salez,Elie Rapha?l,Kari Dalnoki-Veress
Physics , 2014,
Abstract: The capillary levelling of cylindrical holes in viscous polystyrene films was studied using atomic force microscopy as well as quantitative analytical scaling arguments based on thin film theory and self-similarity. The relaxation of the holes was shown to consist of two different time regimes: an early regime where opposing sides of the hole do not interact, and a late regime where the hole is filling up. For the latter, the self-similar asymptotic profile was derived analytically and shown to be in excellent agreement with experimental data. Finally, a binary system of two holes in close proximity was investigated where the individual holes fill up at early times and coalesce at longer times.
Cooperative Strings and Glassy Interfaces
Thomas Salez,Justin Salez,Kari Dalnoki-Veress,Elie Rapha?l,James A. Forrest
Physics , 2015,
Abstract: We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length $\xi$ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to $\xi$. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows to quantify the temperature-dependent thickness $h_{\textrm{m}}$ of the interfacial mobile layer.
Approach to universal self-similar attractor for the levelling of thin liquid films
Michael Benzaquen,Paul Fowler,Laetitia Jubin,Thomas Salez,Kari Dalnoki-Veress,Elie Rapha?l
Physics , 2014,
Abstract: We compare the capillary levelling of a random surface perturbation on a thin polystyrene film with a theoretical study on the two-dimensional capillary-driven thin film equation. Using atomic force microscopy, we follow the time evolution of samples prepared with different initial perturbations of the free surface. In particular, we show that the surface profiles present long term self-similarity, and furthermore, that they converge to a universal self-similar attractor that only depends on the volume of the perturbation, consistent with the theory. Finally, we look at the convergence time for the different samples and find very good agreement with the analytical predictions.
Capillary leveling of stepped films with inhomogeneous molecular mobility
Joshua D. McGraw,Thomas Salez,Oliver B?umchen,Elie Rapha?l,Kari Dalnoki-Veress
Physics , 2013,
Abstract: A homogeneous thin polymer film with a stepped height profile levels due to the presence of Laplace pressure gradients. Here we report on studies of polymeric samples with precisely controlled, spatially inhomogeneous molecular weight distributions. The viscosity of a polymer melt strongly depends on the chain length distribution; thus, we learn about thin-film hydrodynamics with viscosity gradients. These gradients are achieved by stacking two films with different molecular weights atop one another. After a sufficient time these samples can be well described as having one dimensional viscosity gradients in the plane of the film, with a uniform viscosity normal to the film. We develop a hydrodynamic model that accurately predicts the shape of the experimentally observed self-similar profiles. The model allows for the extraction of a capillary velocity, the ratio of the surface tension and the viscosity, in the system. The results are in excellent agreement with capillary velocity measurements of uniform mono- and bi-disperse stepped films and are consistent with bulk polymer rheology.
Self-Similarity and Energy Dissipation in Stepped Polymer Films
Joshua D. McGraw,Thomas Salez,Oliver B?umchen,Elie Rapha?l,Kari Dalnoki-Veress
Physics , 2012, DOI: 10.1103/PhysRevLett.109.128303
Abstract: The surface of a thin liquid film with nonconstant curvature is unstable, as the Laplace pressure drives a flow mediated by viscosity. We present the results of experiments on one of the simplest variable curvature surfaces: a stepped polymer film. Height profiles are measured as a function of time for a variety of molecular weights. The evolution of the profiles is shown to be self-similar. This self-similarity offers a precise measurement of the capillary velocity by comparison with numerical solutions of the thin film equation. We also derive a master expression for the time dependence of the excess free energy as a function of the material properties and film geometry. The experiment and theory are in excellent agreement and indicate the effectiveness of stepped polymer films to elucidate nanoscale rheological properties.
Beyond Tanner's Law: Crossover between Spreading Regimes of a Viscous Droplet on an Identical Film
Sara L. Cormier,Joshua D. McGraw,Thomas Salez,Elie Raphael,Kari Dalnoki-Veress
Physics , 2012, DOI: 10.1103/PhysRevLett.109.154501
Abstract: We present results on the leveling of polymer microdroplets on thin films prepared from the same material. In particular, we explore the crossover from a droplet spreading on an infinitesimally thin film (Tanner's law regime) to that of a droplet leveling on a film thicker than the droplet itself. In both regimes, the droplet's excess surface area decreases towards the equilibrium configuration of a flat liquid film, but with a different power law in time. Additionally, the characteristic leveling time depends on molecular properties, the size of the droplet, and the thickness of the underlying film. Flow within the film makes this system fundamentally different from a droplet spreading on a solid surface. We thus develop a theoretical model based on thin film hydrodynamics that quantitatively describes the observed crossover between the two leveling regimes.
Capillary-driven flow induced by a stepped perturbation atop a viscous film
Thomas Salez,Joshua D. McGraw,Oliver B?umchen,Kari Dalnoki-Veress,élie Rapha?l
Physics , 2012, DOI: 10.1063/1.4763569
Abstract: Thin viscous liquid films driven by capillarity are well described in the lubrication theory through the thin film equation. In this article, we present an analytical solution of this equation for a particular initial profile: a stepped perturbation. This initial condition allows a linearization of the problem making it amenable to Fourier analysis. The solution is obtained and characterized. As for a temperature step in the heat equation, self-similarity of the first kind of the full evolution is demonstrated and a long-term expression for the excess free energy is derived. In addition, hydrodynamical fields are described. The solution is then compared to experimental profiles from a model system: a polystyrene nanostep above the glass transition temperature which flows due to capillarity. The excellent agreement enables a precise measurement of the capillary velocity for this polymeric liquid, without involving any numerical simulation. More generally, as these results hold for any viscous system driven by capillarity, the present solution may provide a useful tool in hydrodynamics of thin viscous films.
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