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.

Storing Light with Subradiant Correlations in Arrays of Atoms

Abstract: We show how strong light-mediated resonant dipole-dipole interactions between atoms can be utilized in a control and storage of light. The method is based on a high-fidelity preparation of a collective atomic excitation in a single correlated subradiant eigenmode in a lattice. We demonstrate how a simple phenomenological model captures the qualitative features of the dynamics and sharp transmission resonances that may find applications in sensing

Deciding security of protocols against off-line guessing attacks

Abstract: We provide an effective procedure for deciding the existence of off-line guessing attacks on security protocols, for a bounded number of sessions.The procedure consists of a constraint solving algorithm for determining satisfiability and equivalence of a class of second-order E-unification problems, where the equational theory E is presented by a convergent subterm rewriting system.To the best of our knowledge, this is the first decidability result to use the generic definition of off-line guessing attacks due to Corin et al. based on static equivalence in the applied pi calculus.

Ribonucleotide reductase and the regulation of DNA replication: an old story and an ancient heritage.

Abstract: All organisms that synthesize their own DNA have evolved mechanisms for maintaining a constant DNA/cell mass ratio independent of growth rate. The DNA/cell mass ratio is a central parameter in the processes controlling the cell cycle. The co-ordination of DNA replication with cell growth involves multiple levels of regulation. DNA synthesis is initiated at specific sites on the chromosome termed origins of replication, and proceeds bidirectionally to elongate and duplicate the chromosome. These two processes, initiation and elongation, therefore determine the total rate of DNA synthesis in the cell. In Escherichia coli, initiation depends on the DnaA protein while elongation depends on a multiprotein replication factory that incorporates deoxyribonucleotides (dNTPs) into the growing DNA chain. The enzyme ribonucleotide reductase (RNR) is universally responsible for synthesizing the necessary dNTPs. In this review we examine the role RNR plays in regulating the total rate of DNA synthesis in E. coli and, hence, in maintaining constant DNA/cell mass ratios during normal growth and under conditions of DNA stress.

Resonant light scattering spectroscopy of gold, silver and gold–silver alloy nanoparticles and optical detection in microfluidic channels

Abstract: Dark field resonant light scattering by gold and silver nanoparticles enables the detection and spectroscopy of such particles with high sensitivity, down to the single-particle level, and can be used to implement miniaturised optical detection schemes for chemical and biological analysis. Here, we present a straightforward optical spectroscopic methodology for the quantitative spectrometric study of resonant light scattering (RLS) by nanoparticles. RLS spectroscopy is complementary to UV-visible absorbance measurements, and we apply it to the characterisation and comparison of different types of gold, silver and gold-silver alloy nanoparticles. The potential of gold and silver particles as alternatives for fluorescent probes in certain applications is discussed. RLS spectroscopy is shown to be useful for studying analyte-induced gold nanoparticle assembly and nanoparticle chemistry, which can induce radical changes in the plasmonic resonances responsible for the strong light scattering. Furthermore, the feasibility of dark field RLS detection and quantitation of metal nanoparticles in microfluidic volumes is demonstrated, opening interesting possibilities for the further development of microfluidic detection schemes.