Dynamics and quenching of non-premixed edge-flames in oscillatory counterflows

The dynamics of non-premixed edge-flames, including the generation of cellular structures, in an unsteady, symmetric counterflow are examined for positive rates of strain. A one-step reaction is assumed, νYF+νXO→νpP, in which the oxidizer Lewis number is 1. For a variety of Damköhler numbers, we examine the edge-flame evolution for two values of the fuel Lewis number LeY, 0.3 and 1, and two values of the initial mixture fraction γ, 0.36 and 1, representing fuel lean and stoichiometric supply conditions. For LeY=0.3 and γ=0.36, unsteady forcing can convert non-cellular edge-flames into ones containing various characteristics of near- or sub-limit cellular structures, including drifting, splitting and stationary flame strings. The transition regimes between the different edge-flame structures are examined as a function of the amplitude and frequency of the strain rate variations in the unsteady counterflow and also as a function of the instantaneous and equivalent strain rate functions. For LeY=0.3 and γ=1, while no cellular edge-flames can be generated for steady counterflows, we show that cellular structures can be observed in the presence of unsteady forcing. For LeY=1 and γ=1, it is shown that unsteady forcing can significantly modify the mean propagation speeds of both ignition and failure waves. Finally, the quenching boundaries of two-dimensional edge-flames induced by the unsteady counterflow are examined for LeY=0.3, γ=0.36 and LeY=1, γ=1.     

Struktur und Design von Cyclopeptiden zur Regulation des Immunsystems

Structure and Design of Cyclic Peptides for the Regulation of the Immune System The immune system of higher animals is regulated and can be influenced by a number of peptides and small proteins. Enhanced activity, selectivity and metabolic stability can be achieved by cyclization of bioactive parts of these peptides, provided the bioactive conformation is matched correctly. Several cyclic peptidic antibiotica are found which stimulate or suppress immune response. It is demonstrated how modern NMR spectroscopy in combination with molecular dynamics calculations can be used to determine the conformation of these compounds in solution. This article emphasizes the work of the author in this field.