On bornologicalC $$\overline V $$ (X) spaces

Archiv der Mathematik -     

Synthesis of (+) dictyopterene a constituent of marine brown algae and (+) dictyopterene C′ by chirality transfer of optically active allylic benzoate with palladium (O) catalyst.

The first enantioselective syntheses of (+) dictyopterene A $\text{1}$ and (+)dictyopterene C′ were reported. The key reaction was based on palladium promoted cyclisation of chiral allylic benzoate $\text{5}$ with transfer of chirality (anti attack of the palladium with respect to the leaving group) to give optically active vinylcyclopropane $\text{7}$ with (R) configuration which contains proper functionality for further elaboration into $\text{1}$ and $\text{3}$     

Mechanism of sulfur extrusion from thiirane

The thermal decomposition of thiirane $\text{1}$ to olefin $\text{2}$ is not a first order reaction, and is therefore not a simple chelotropic process.     

Annihilation of quantized vortex lines in rotating<Superscript>3</Superscript>He-A

The maximum number of vortex lines at a given angular velocity Ω is obtained during deceleration when vortices annihilate at the wall of the container. The width of the vortex-free region in the decelerated state has been measured by cw NMR for vortex lines with singular and continuous core structures. It corresponds to the limit of stability of peripheral vortices for single and double quantization respectively.     

57Fe Mössbauer investigation of the ternary hydride Pd3FeHx

Ordered alloys of Pd₃Fe are shown to readily absorbe hydrogen through electrolytic loading. The resultant ternary hydride phase is observed to retain the fcc structure of Pd₃Fe with approximately the same lattice constant. The ⁵⁷Fe hyperfine field determined by Mössbauer spectroscopy is found to be 30% smaller in the hydride compared to Pd₃Fe. The reduction appears to be associated with a perturbation of the Pd moment by hydrogen. The results suggest the occupation of one type of interstitial site in the structure. The absence of the site in disordered Pd₃Fe would explain the much smaller hydrogen capacity observed for this alloy.     

Über die Verteilung der pythagoreischen Zahlentripel

Ohne Zusammenfassung     

Tunable far-infrared Raman generation

Tunable resonance enhanced far-infrared stimulated Raman scattering was observed in 60–160 μm range for the Q(J) transitions in hydrogen chloride. The tuning range was about 2.3 cm^-1 around each studied transition (J = 2 to 7) and the photon efficiency was measured to be of the order of 12% giving peak power around 80 kW.     

Cluster-molecule systems: Analysis and tuning of the interaction potential

The interaction (modelled by a LEPS potential) of a D₂ molecule with an icosahedral Ni₁₃ cluster is mapped and analyzed in the form of equipotential contour plots. The topological features of the map correlate with the energetic and dynamical characteristics of the dissociative adsorption of the molecule on the cluster, which were extracted from quasiclassical trajectory simulations. A modification of the LEPS potential used originally is introduced. It brings the calculated reactivity of the cluster into agreement with the experimental data.     

Effets comparés des impuretés de terres rares sur la résonance ferrimagnétique et la relaxation nucléaire dans le grenat de fer et d’yttrium

The anomalous properties of impure yttrium iron garnet are related to the susceptibilities of the rare earth ions which it contains. The susceptibilities are calculated assuming a slow relaxation. It is shown that the success of the theory of “slow relaxation” requires the existence of a coupling between the transverse magnetization of the iron lattice on the one hand, and components of the magnetic moments of the rare earth ions, with non zero diagonal matrix elements, on the other hand. The temperature variations of the ferrimagnetic linewidth and the nuclear relaxation time are compared.     

Spectrophotometric determination of calcium in soil extracts with calcichrome

A simple direct method is presented for the spectrophotometric determination of calcium in hydrochloric acid soil extracts. The chromugenic agent used is Calciehrome (self-coupled diazotized H-acid), and the method covers the range 4 to 175 μg of calcium. A comprehensive study of interferences has been carried out. and a cation-exchange procedure described for the preliminary separation of large amounts of phosphate.