Alkaloids from Croton flavens L. and their affinities to GABA-receptors

Phytochemical investigation of several plants of Croton flavens L. from Barbados has led to the isolation of the tetrahydroprotoberberine alkaloids scoulerine and coreximine, as well as the morphinanedienones salutaridine and its racemic form salutarine, sebiferine, norsinoacutine and flavinantine. In a screening for 3H-GABA displacing activity coreximine showed the highest affinity to the GABA(A) receptor.     

Theoretical and experimental aspects of chaos control by time-delayed feedback

We review recent developments for the control of chaos by time-delayed feedback methods. While such methods are easily applied even in quite complex experimental context the theoretical analysis yields infinite-dimensional differential-difference systems which are hard to tackle. The essential ideas for a general theoretical approach are sketched and the results are compared to electronic circuits and to high power ferromagnetic resonance experiments. Our results show that the control performance can be understood on the basis of experimentally accessible quantities without resort to any model for the internal dynamics.     

The υ3 = 1 state of 37ClO2 studied by laser-microwave double resonance

Laser-microwave double-resonance experiments have been carried out which enable rotational and coupling constants of the υ₃ = 1 state of ³⁷ClO₂ to be determined. This work utilized an accidental coincidence between the 9R(24)C¹⁸O₂ laser line and hyperfine components of the ^QR_o(1) transition of the v₃ band of ³⁷ClO₂. A novel type of IR-MW-MW triple resonance is described.     

Projection operator approach to the thermodynamic formalism of dynamical systems

An analytical perturbative treatment of characteristic exponents describing the fluctuations of temporal coarse-grained quantities in the context of nonlinear dynamical systems is proposed. It is based on the analysis of the resolvent of the corresponding transfer operator by a projection operator method similar to those used in statistical mechanics. Two different approximation schemes are presented and tested for the case of an exactly solvable but nontrivial model system.     

A microscopic description of the (γ,pn)-reaction

The quasideuteron process has been investigated for photon energies 40 MeV<E _γ< 160 MeV on the basis of a shell model picture modified by short range nucleon-nucleon correlations. It turns out that the cross section for the (γ,pn)-reaction depends sensitively on the details of the correlation function, i.e. on the exchange of high momenta between otherwise independently moving nucleons. The final state interaction has been consistently taken care of by using optical model wave functions for the outgoing nucleons. The results of the calculations for¹⁶O indicate that precise measurements of the (γ,pn) cross section do contain information on the properties of the nuclear wave functions for small internucleonic distances.