Electrical Conductivity in TCNQ Salts of Bis(4-dimethylaminophenylimino) sulfur and its Structural Analogues

Four compounds, N,N,N',N'-tetramethyl-p-phenylene diamine, N,N,N',N'-tetramethyl-benzidine, 4,4'-bis(dimethylamino)azobenzene and bis(4-dimethylaminophenylimino)sulfur (BAPIS) were examined electrochemically and spectroscopically. Each was shown to be a fairly good donor forming in its first oxidation state a radical-cation. The latter two materials surprisingly exhibited only single one-electron oxidations. Conformational flexibility about the -NSN- unit was studied by NMR spectroscopy and ab initio molecular orbital theory. The experimental ΔG* for a cis-trans to trans-cis interconversion in BAPIS was found to be 11.9 kcal/mole.

The four donors all form 1:1 adducts with TCNQ. The compaction resistances of the complexes have been measured as a function of temperature. Of the four, (BAPIS)(TCNQ) appears to be a one-dimensional material. The other three complexes behave as typical mixed stack organic semiconductors.     

Wall roughness effects in laminar flows: an often ignored though significant issue

The effect of wall roughness, which is strong in turbulent flows often, is neglected in laminar flows, though without justification. With an experimental set-up which allows for changes in the relative roughness of a channel without requiring manipulation of the rough channel surface, it can be shown that there is a non-negligible influence of wall roughness even for laminar flows. Based on the consideration of entropy production in these flows, an increased dissipation rate in the vicinity of the roughness elements is identified as the physical mechanism that leads to an increased total head loss when the walls are no longer smooth.     

Mössbauer investigations of intermolecular interactions of Fe(CO)5 in frozen organic solutions

The Mössbauer spectra of Fe(CO)₅ dissolved in 39 organic solvents were investigated. An influence on the quadrupole split was found only for those solvents containing carbonylic CO, but not for solvents containing another polar group. The change of the quadrupole split means always a reduction and is independent of temperature. The concentration dependence of the additional split indicates that it is caused only by nearest neighbours.—These results give a hint for a specific weak interaction between the carbonylic CO group of Fe(CO)₅ and the solvents. This cannot be a general dipole-dipole interaction because of the missing influence of other polar solvents, so that a weak chemical bond is suggested.     

Röntgenkleinwinkeluntersuchungen der Eisen(III)-oxidhydrat-Micelle des Ferritins in Lösung

Ohne Zusammenfassung     

Three Power Series Techniques

The techniques and concepts we present are flags of regularschemes and their persistence under blow-up, the Gauss–Bruhatdecomposition of the group of formal automorphisms of affinespace, and coordinate-free initial ideals. All three are usedto construct and study invariants for resolution of singularities.2000 Mathematics Subject Classification 14B05, 14E15, 32S05,32S10, 32S45.