Ueber die Darstellung von Traubenzucker

Ohne Zusammenfassung     

On the application of slip boundary condition on curved boundaries

Hydrodynamic simulations of sloshing phenomena often involve the application of slip boundary condition at the wetted surfaces. If these surfaces are curved, the ambiguous nature of the normal vector in the discretized problem can interfere with the application of such a boundary condition. Even the use of consistent normal vectors, preferred from the point of view of conservation, does not assure good approximation of the continuum slip condition in the discrete problem, and non‐physical recirculating flow fields may be observed. As a remedy, we consider the Navier slip condition, and more successfully, the so‐called BC‐free boundary condition. Copyright © 2004 John Wiley & Sons, Ltd.     

Study of the peak effect phenomenon in single crystals of 2H-NbSe2

The weakly pinned single crystals of the hexagonal 2H-NbSe₂ compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of the peak effect phenomenon in three crystals of 2H-NbSe₂, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability effects and pinning.     

Fourier transform IR product study of the reaction of CFO radicals with O2 at 298 K

Experimental results are presented of a Fourier transform IR product study at 298 K of the reaction system CFO+O₂ at oxygen pressures between 3 and 250 mbar. Pulsed photolysis of oxalyl fluoride (CFO)₂ or formyl fluoride (CHFO) at 193 nm was used to produce CFO. As stable products we detected bis-fluoroformyl peroxide, carbonyl fluoride and carbon dioxide. The yields of the peroxide and of CF₂O were measured as a function of [O₂]/[precursor] and are discussed qualitatively.     

Synthesis and hybridization properties of oligonucleotides containing polyamines at the C-2 position of purines: a pre-synthetic approach for the incorporation of spermine into oligodeoxynucleotides containing 2-(4,9,13-triazatridecyl)-2'-deoxyguanosine

We have developed a synthesis of spermine-containing oligonucleotides (ODN-sper) which allows incorporation of multiple polyamine residues. This approach was based on the pertrifluoroacetylated 5'DMT-dGsper phosphoramidite synthon. Its coupling yield with resin-bound ODN decreased dramatically when close to the 3'-end. Optimization of the coupling conditions allowed 22-mer ODNs containing up to six spermine residues to be synthesized. Several ODNs of different sequences with 1-4 pendent spermines could be purified and their hybridization properties were evaluated. Duplex melting temperatures increased linearly with the number of polyamine residues (deltaTm/sper = 3.0 +/- 0.2 degrees C in 100mM NaCl). This compares very favorably with values reported for duplexes of similar initial stability containing other cation-substituted bases. Moreover, the stability increase was neither sequence nor position-dependent, and even contiguous spermine residues did not cross-talk. Extrapolation based on these findings leads to the conclusion that a duplex formed with a 22-mer oligonucleotide containing seven spermine residues would be as stable as genomic DNA, which highlights its potential for DNA strand invasion.     

Shaping Solid-State Supramolecular Cavities: Chemically Induced Accordionlike Movement of gamma-Zirconium Phosphate Containing Polyethylenoxide Pillars

The hydrophilic oxygen atoms of polyethylenoxide chains inserted as pillars in gamma-zirconium phosphate form hydrogen bonds with the acid groups of the host. As a result the pillars are almost perpendicular to the gamma layers. Upon changing the pH level of the supernatant solution the hydrogen bonds are broken and the pillars become almost perpendicular to the layers (shown schematically). Thus there is a reversible enlargement-shortening of the interlayer space.