On the Floquet Theory of Delay Differential Equations

We present an analytical approach to deal with nonlinear delay differential equations close to instabilities of time periodic reference states. To this end we start with approximately determining such reference states by extending the Poincar'e Lindstedt and the Shohat expansions which were originally developed for ordinary differential equations. Then we systematically elaborate a linear stability analysis around a time periodic reference state. This allows to approximately calculate the Floquet eigenvalues and their corresponding eigensolutions by using matrix valued continued fractions

Winner-take-all selection in a neural system with delayed feedback

We consider the effects of temporal delay in a neural feedback system with excitation and inhibition. The topology of our model system reflects the anatomy of the avian isthmic circuitry, a feedback structure found in all classes of vertebrates. We show that the system is capable of performing a `winner-take-all' selection rule for certain combinations of excitatory and inhibitory feedback. In particular, we show that when the time delays are sufficiently large a system with local inhibition and global excitation can function as a `winner-take-all' network and exhibit oscillatory dynamics. We demonstrate how the origin of the oscillations can be attributed to the finite delays through a linear stability analysis.Comment: 8 pages, 6 figure

AuCu/CeO2 bimetallic catalysts for the selective oxidation of fatty alcohol ethoxylates to alkyl ether carboxylic acids

International audienc

Pivotal role of H2 in the isomerisation of isosorbide over a Ru/C catalyst

International audienceIsosorbide isomerisation is a known reaction that can proceed over Ru and Ni-based heterogeneous catalysts. As a rule, an exogenous H2 pressure (40–100 bar) is required, even though H2 does not participate stoichiometrically in the reaction. By marrying experiments with DFT computations, we ascribe the role of H2 in isosorbide isomerisation to a coverage effect on the catalyst surface. We demonstrate the possibility of conducting the reaction at a low H2 pressure either in the presence of an inert gas to increase H2 solubility in an underlying solvent or using 2-propanol as a hydrogen donor. This might benefit the economy and safety of a potential industrial process

On the Visibility of Al Surface Sites of γ-Alumina: A Combined Computational and Experimental Point of View

International audienc