Phase-sensitive optical low-coherence reflectometry technique applied to the characterization of photonic crystal fiber properties

Localized measurements of group-velocity dispersion and birefringence of photonic crystal fibers are achieved with a phase-sensitive optical low-coherence reflectometry technique. This technique is efficient for fiber samples no longer than 1 m. Theoretical simulations are in good agreement with experimental results. As a result, the stress-induced birefringence proves to be at most 1 order of magnitude below the geometrical-shape birefringence.     

Corrigendum

Corrigendum

Corrigendum     

Stereoselective access to the versatile 4-aminohex-5-ene-1,2,3-triol pattern

We developed a stereocontrolled route allowing potential access to the eight isomers of 4-benzylaminohex-5-ene-1,2,3-triol in two or four steps and ca. 50% yield from readily available chiral nonracemic cis- or trans-alpha,beta-epoxyimine precursors. A new (NH(4))(2)CO(3)-based carboxylation/intramolecular cyclization sequence allowed regio- and stereocontrolled C-3 epoxide opening while neat C-2 hydrolysis was ensured by simple aqueous acidic treatment.     

An efficient, stereoselective approach to syn-1,2-diols protected as cyclic carbonates

Enantioenriched 4-hydroxyalk-2-ynyl carbonates (or benzoates) have been prepared by stereoselective zinc-mediated addition of alkyl 2-propynyl carbonates (or their benzoate analogues) to aldehydes. Their partial reduction to Z-olefins followed by cyclization under mild Pd-catalyzed conditions allowed a straightforward access to enantioenriched syn-1,2-diols protected as cyclic carbonates.     

Isomerization of a peptidic fragment studied theoretically in vacuum and in explicit water solvent at finite temperature

The cis-trans isomerization of N-methylacetamide, a molecular model of the polypeptide chain, is examined via umbrella sampling Car-Parrinello MD and classical MD, in both gas and solution phases at 300 K. A new analysis of the C(O)-N bond interconversion and a full examination of the solvent shell structure are presented.     

Topological Dynamics and Local Product Structure

Topological properties of dynamical systems admitting a localproduct structure are studied. The results obtained are appliedto hyperbolic systems on covers. The main theorem characterizestransitivity on solvable covers in terms of Frobenius elementsof periodic orbits.     

Sticky flows on the circle and their noises

This paper gives a construction of sticky flows on the circle. Sticky flows give examples of stochastic flows of kernels that interpolates between Arratias coalescing flow and the deterministic diffusion flow. They are associated with systems of sticky independent Brownian particles on the circle, for some fixed parameter of stickyness. It is proved that the noise generated by Brownian sticky flows is black. A new proof of the fact that the noise of Arratias coalescing flow is black is given.