Formation and reactivity of novel pyranosidic nicholas oxocarbenium ions: access to C-ketosides and branched-chain C-ketosides

[Structure: see text] Dicobalt hexacarbonyl propargyl complexes, prepared from alkynyl ketoses, display an unexpected reactivity when treated with Lewis acids in the presence of nucleophiles and furnish C-ketosides, branched-chain C-ketosides, or branched-chain C-glycals depending on the nucleophile and the carbohydrate starting material.     

Magnetically-Induced Buckling of a Whirling Conducting Rod with Applications to Electrodynamic Space Tethers

We study the effect of a magnetic field on the behaviour of a slender conducting elastic structure, motivated by stability problems of electrodynamic space tethers. Both static (buckling) and dynamic (whirling) instability are considered and we also compute post-buckling configurations. The equations used are the geometrically exact Kirchhoff equations. Magnetic buckling of a welded rod is found to be described by a surprisingly degenerate bifurcation, which is unfolded when both transverse anisotropy of the rod and angular velocity are considered. By solving the linearised equations about the (quasi-) stationary solutions, we find various secondary instabilities. Our results are relevant for current designs of electrodynamic space tethers and potentially for future applications in nano- and molecular wires.     

Diterpenes from teucrium capitatum L. X-ray crystal and molecular structure of capitatin

Two diterpenes, capitatin 4 and teucapitatin 5 have been isolated from Teucrium capitatum. The X-ray structure of 4, including absolute stereochemistry, is given. Diterpene 4 has been chemically related to picropolin 1 and picropolinone 2, thereby establishing the absolute stereochemistry of these two neoclerodane-type diterpenes.     

Study by in situ FTIR of the SCR of NO by propene on Cu ion-exchanged Ti-PILC

Adsorption on Cu ion-exchanged titanium pillared clay (Cu-Ti-PILC) was investigated by in situ infrared spectroscopy to provide insight into the reaction intermediates present in the selective catalytic reduction (SCR) of NO by propene in the presence of oxygen. The NO/O₂ adsorption produced different nitrate species due to the presence of terminal and bridged Cu²⁺–OH groups. These nitrates evolved into N₂ and N₂O in small amounts once the NO catalytic cycle was finished. It can be concluded that the Cu²⁺–OH groups reacted with the nitro group, thus forming nitrates. C₃H₆ adsorption was higher and stronger than NO adsorption on the active sites of the catalyst. C₃H₆ reacted in the active site producing hydrocarbon intermediates (an organic nitro compound and acetate), which were responsible for the NO reduction.     

Betrachtungen zur Kinetik und zum Mechanismus der Aufl?sung von Metalloxiden in sauren L?sungen

Ohne Zusammenfassung     

Topological Conjugations of Normal Forms in Bifurcations

One way to deal with bifurcations in the theory of dynamical systems is to find some normal forms of the system, that is, doing some changes of coordinates, the system can be led to a similar form to that given for the normal forms. But usually it is a complicated problem to elucidate if the truncated normal form of the system is (locally) topologically conjugated to the normal one. Here, we provide a way to avoid this problem when we study bifurcations, through the consideration of the surface of the fixed points which allows us to generalize the non-degenerated conditions of certain bifurcations to appear.