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Bayesian Mixed Effect Atlas Estimation with a Diffeomorphic Deformation Model
No full textInternational audienceIn this paper we introduce a diffeomorphic constraint on the deformations considered in the deformable Bayesian mixed effect template model. Our approach is built on a generic group of diffeo-morphisms, which is parameterized by an arbitrary set of control point positions and momentum vectors. This enables us to estimate the optimal positions of control points together with a template image and parameters of the deformation distribution which compose the atlas. We propose to use a stochastic version of the expectation-maximization algorithm where the simulation is performed using the anisotropic Metropolis adjusted Langevin algorithm. We propose also an extension of the model including a sparsity constraint to select an optimal number of control points with relevant positions. Experiments are carried out on the United States Postal Service database, on mandibles of mice, and on three-dimensional murine dendrite spine images
Flow distribution in parallel microfluidic networks and its effect on concentration gradient
No full textInternational audienceThe architecture of microfluidic networks can significantly impact the flow distribution within its different branches and thereby influence tracer transport within the network. In this paper, we study the flow rate distribution within a network of parallel microfluidic channels with a single input and single output, using a combination of theoretical modeling and microfluidic experiments. Within the ladder network, the flow rate distribution follows a U-shaped profile, with the highest flow rate occurring in the initial and final branches. The contrast with the central branches is controlled by a single dimensionless parameter, namely, the ratio of hydrodynamic resistance between the distribution channel and the side branches. This contrast in flow rates decreases when the resistance of the side branches increases relative to the resistance of the distribution channel. When the inlet flow is composed of two parallel streams, one of which transporting a diffusing species, a concentration variation is produced within the side branches of the network. The shape of this concentration gradient is fully determined by two dimensionless parameters: the ratio of resistances, which determines the flow rate distribution, and the Peclet number, which characterizes the relative speed of diffusion and advection. Depending on the values of these two control parameters, different distribution profiles can be obtained ranging from a flat profile to a step distribution of solute, with well-distributed gradients between these two limits. Our experimental results are in agreement with our numerical model predictions, based on a simplified 2D advection-diffusion problem. Finally, two possible applications of this work are presented: the first one combines the present design with self-digitization principle to encapsulate the controlled concentration in nanoliter chambers, while the second one extends the present design to create a continuous concentration gradient within an open flow chamber. (C) 2015 AIP Publishing LLC
Radical Solution to the Alkylation of the Highly Base-Sensitive 1,1-Dichloroacetone.: Application to the Synthesis of Z-Alkenoates and E,E-Dienoates
No full textInternational audienceA simple radical-based route to gem-alpha-dichloroketones, relying on the degenerative addition transfer of (S)-[3,3dichloro-2-oxopropyl]-O-ethyl dithiocarbonate (xanthate), is described. The adducts can then be converted into Z-enoates by exposure to Et3N in methanol. In the case of certain substrates, it was possible to form shipped dienoic acid and methyl E,E-dienoates
Spatial quality improvement of a Ti:Sapphire laser beam by modal filtering
No full textInternational audienceWe present a study on the improvement of the spatial quality of a laser beam, called modal filtering,suitable to high-energy lasers. The method is theoretically compared with the classical pinhole filtering technique in the case of an astigmatic Gaussian beam, illustrating, in this particular case, its efficiency for filtering low spatial frequencies. Experimental study of the modal filtering of a temporally chirped beam from a Ti:Sapphire chirped-pulseamplification system is presented. Beam profile, wavefront and pulse duration after compression were measured, showing a dramatic improvement of beam quality and no modifications of the temporal distribution. High-order harmonic generation in a rare gas, a highly nonlinear process which is phase-matching dependent, was used to test the effect of the filter and showed a clear enhancement of the generation
Sub-quadratic Decoding of One-point Hermitian Codes
No full textInternational audienceWe present the first two sub-quadratic complexity decoding algorithms for one-point Hermitian codes. The first is based on a fast realisation of the Guruswami–Sudan algorithm by using state-of-the-art algorithms from computer algebra for polynomial-ring matrix minimisation. The second is a Power decoding algorithm: an extension of classical key equation decoding which gives a probabilistic decoding algorithm up to the Sudan radius. We show how the resulting key equations can be solved by the matrix minimisation algorithms from computer algebra, yielding similar asymptotic complexities
Proof nets and the call-by-value λ-calculus
No full textInternational audienceThis paper gives a detailed account of the relationship between (a variant of) the call-by-value lambda calculus and linear logic proof nets. The presentation is carefully tuned in order to realize an isomorphism between the two systems: every single rewriting step on the calculus maps to a single step on proof nets, and viceversa. In this way, we obtain an algebraic reformulation of proof nets. Moreover, we provide a simple correctness criterion for our proof nets, which employ boxes in an unusual way, and identify a subcalculus that is shown to be as expressive as the full calculus
Optimal Production Channel for Private Labels: Too Much or Too Little Innovation?
No full textInternational audienceWe analyze the impact of the private label production channel on innovation. A retailer may either choose to integrate backward with a small firm (insourcing) or rely on a national brand manufacturer (outsourcing) to produce its private label. The trade-off between insourcing and outsourcing strategies is a choice between too much or too little innovation (i.e., quality investment) on the private label. When insourcing, an outside-option effect leads the retailer to overinvest to increase its buyer power. When outsourcing, a hold-up effect leads to underinvestment. In addition, selecting the national brand manufacturer may create economies of scale that spur innovation
Modélisation du string mismatch dans les installations PV équipées de réflecteurs
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Experimental and Numerical Study of the Influence of String Mismatch on the Yield of PV Modules Augmented By Static Planar Reflectors
No full textInternational audiencePhotovoltaic (PV) modules are generally installed by the application of empirical rules aimed at reducing shadows during the periods of high solar irradiation. A traditional installation on a horizontal surface results in largely spaced rows of modules with a relatively low tilt angle. The addition of inter-row reflectors permits to transmit more direct and diffuse flux to cells. The “Aleph” (Amélioration de l'Efficacité Photovoltaïque) project aims to define clear rules for optimal settings of systems of PV rows with fixed inter-row planar reflectors in a given location and under a given climate. Two PV technologies are tested for performance with this type of system: amorphous silicon (a-Si) and polycrystalline silicon (p-Si). This work combines experiments on panel behavior in an outdoor environment on the SIRTA (Site Instrumental de Recherche par Télédétection Atmosphérique) meteorology platform and a multiphysics numerical model used to couple all the important physical phenomena and accurately describe the system behavior. The model includes a ray tracing radiation/optics module based on the Monte-Carlo method, as well as an electrical module simulated in SPICE. This work presents the influence of the string mismatch losses, present at periods of heterogeneous illumination, on the yield of PV modules augmented by static planar reflectors
Termination of dependently typed rewrite rules
No full textInternational audienceOur interest is in automated termination proofs of higher-order rewrite rules in presence of dependent types modulo a theory T on base types. We first describe an original transformation to a type discipline without type dependencies which preserves non-termination. Since the user must reason on expressions of the transformed language, we then introduce an extension of the computability path ordering CPO for comparing dependently typed expressions named DCPO. Using the previous result, we show that DCPO is a well-founded order, behaving well in practice