École normale supérieure de Cachan

About: École normale supérieure de Cachan is a education organization based out in Cachan, Île-de-France, France. It is known for research contribution in the topics: Decidability & Nonlinear system. The organization has 2717 authors who have published 5585 publications receiving 175925 citations.

Ultrabright Fluorescent Polymeric Nanoparticles Made from a New Family of BODIPY Monomers

Abstract: Four novel BODIPY derivatives (π-) functionalized by different polymerizable groups, styrene (S), phenyl acrylate (PhA), ethyl methacrylate (EtMA) and ethyl acrylate (EtA) have been synthesized. Following a formerly established one-pot RAFT miniemulsion polymerization process (GrazonMacromol. Rapid Commun. 2011, 32, 699−705), the fluorophores were copolymerized in a controlled way at 2.6 mol % with styrene in water. On the basis of the polymerization-induced self-assembly (PISA) principle, the copolymers assembled during their formation into fluorescent nanoparticles. The distribution of the fluorescent monomers along the polymer backbone was monitored by kinetic studies of the copolymerization reaction. Fluorescent stationary and time-resolved spectroscopy was then performed on both the monomers and the nanoparticles (NPs) and the observed differences are discussed in view of the distribution of the fluorescent monomers in the polymer chain. With two of the novel fluorescent monomers (πS and πPhA), the b...

A non-intrusive global/local approach applied to phase-field modeling of brittle fracture

Abstract: This paper aims at investigating the adoption of non-intrusive global/local approaches while modeling fracture by means of the phase-field framework. A successful extension of the non-intrusive global/local approach to this setting would pave the way for a wide adoption of phase-field modeling of fracture, already well established in the research community, within legacy codes for industrial applications. Due to the extreme difference in stiffness between the global counterpart of the zone to be analized locally and its actual response when undergoing extensive cracking, the main foreseen issues are robustness, accuracy and efficiency of the fixed point iterative algorithm which is at the core of the method. These issues are tackled in this paper. We investigate the convergence performance when using the native global/local algorithm and show that the obtained results are identical to the reference phase-field solution. We also equip the global/local solution update procedure with relaxation/acceleration techniques such as Aitken’s $$\Delta ^2$$ Δ 2 -method, the Symmetric Rank One and Broyden’s methods and show that the iterative convergence can be improved significantly. Results indicate that Aitken’s $$\Delta ^2$$ Δ 2 -method is probably the most convenient choice for the implementation of the approach within legacy codes, as this method needs only tools already available for the so-called sub-modeling approach, a strategy routinely used in industrial contexts.

Synthesizing Probabilistic Invariants via Doob’s Decomposition

Abstract: When analyzing probabilistic computations, a powerful approach is to first find a martingale—an expression on the program variables whose expectation remains invariant—and then apply the optional stopping theorem in order to infer properties at termination time. One of the main challenges, then, is to systematically find martingales.

Octupolar Plasmonic Meta-Molecules for Nonlinear Chiral Watermarking at Subwavelength Scale

Abstract: Nonlinear chiroptical effects of precisely designed chiral plasmonic nanomaterials can be much stronger than such effects observed in the linear regime. We take advantage of this property to demonstrate the use of circularly polarized second-harmonic generation microscopy toward the efficient read-out of a microscopic pattern encoded by an array of triangular gold nanoprisms forming arrangements of adequate chiral symmetry. Strong chiroptical effects are observed in the backscattered second-harmonic generation intensity, enabling clear distinction of the laterally arranged enantiomers, down to nearly 1 μm resolution, with an overall intensity contrast of about 40% (second-harmonic generation circular dichroism of 20%). Numerical simulations show a noticeable change in the spatial distribution of plasmonic hot spots within the individual nanostructures under excitation by circularly polarized light of different handedness. This leads to rather weak chiroptical effect in the linear backscattering (theoretic...

New Tetrazines Functionalized with Electrochemically and Optically Active Groups: Electrochemical and Photoluminescence Properties.

Abstract: Original new fluorescent and electroactive compounds have been prepared, where the fluorescent moiety is a chloroalkoxy-s-tetrazine. Besides the tetrazine, several of these compounds possess a second active group, electroactive or able to absorb light at a lower wavelength. The electrochemical properties and photophysical properties of these bichromophoric compounds have been investigated, especially focusing on the occurrence of energy or electron transfer to the tetrazine. In one case, where the primary absorber is a naphthalimide, a quasi-complete energy transfer, followed by the tetrazine fluorescence, is observed. This allows the preparation of remarkable transparent solutions displaying a yellow fluorescence.