Einige Bemerkungen zu verschiedenen Fragen der Rheologie

Zusammenfassung Es wird zu einigen Fragen der Rheologie, wie tensorielle Darstellung der Flie?gesetze, Viskosit?tsbegriff bei nicht-Newtonschen Flüssigkeiten, kritisch Stellung genommen und einige einschl?gige Ver?ffentlichungen diskutiert. Für die wertvollen Diskussionen m?ehte der Verfasser Herrn Dr. It. Giesekus (Leverkusen) und Herrn Dipl.-Physiker U. Rost (G?ttingen) aueh an dieser Stelle herzlich danken.     

Effects of Adsorbed Polyaniline on Redox Processes on As(2)O(3) Surfaces

Polyaniline deposited on As(2)O(3) surface resulted in a new material, which was characterized by infrared spectoscopy, thermogravimetry, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and cyclic voltammetry. The mass percentage of polymer deposited on oxide surface is approximately 13%. The scanning electron microscopy images as well as the X-ray diffraction patterns provided conclusive evidence that the oxide surface is coated by the polymer. The cyclic voltammograms of the polyaniline adsorbed on As(2)O(3) surface showed that the adsorbate exerts remarkable effects on redox processes on this oxide. The pure oxide exhibited two oxidation/reduction peaks at 0.25/-0.06 and 0.47/-0.25 V attributed tentatively to the processes As(2)O(3)(s)+6H(+)+6e(-)=2As(s)+3H(2)O and As(s)+3H(+)+3e(-)=AsH(3)(g), respectively. The polyaniline-coated sample exhibited a better-defined voltammogram in which the first oxidation peak of the oxide had its intensity increased about four times. Copyright 2000 Academic Press.     

Crystal and Molecular Structures of Barium cis(NO2)-trans(N)-Bis(glycinato)dinitrocobaltate(III) Hydrate [Ba(H2O)4][Co(Gly)2(NO2)2]2 · 1.43H2O

Crystals of [Ba(H₂O)₄][Co(Gly)₂(NO₂)₂]₂ · 1.43H₂O (a=8.1917(6) , b=8.4440(4) , c=19.444(1) , =98.189(9)°, Z=2, space group P2/n) contain infinite strips of alternating axially symmetric [Ba(H₂O)₄]²⁺ fragments and two dinitro-bis(glycinato)cobaltate(III) ions. In addition to four oxygen atoms of water molecules, the nearest environment of Ba includes six oxygen atoms of the carboxyl groups of four anions, two of which are also coordinated by the cobalt atoms (Ba-O, 2.77–3.01 ). The nitrite ions do not interact with the Ba²⁺ ions.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 5, 2005, pp. 329–332.Original Russian Text Copyright © 2005 by Zabel, Poznyak, Pawlowski.     

Materials for Optical Data Storage

The outstanding feature of materials research in the eighties has been the convergence of basic research and practical application, leading to ever shorter cycles of innovation. This is especially true of materials which form the basis of key technologies. The mass storage units of the next generations of computers will be based on optical processes having a storage density which exceeds that of all hitherto known storage techniques that are practicable from the technical standpoint. In view of the fact that since 1982 read-only memories in the form of compact discs (CD-ROM) have become very successful in the field of audio electronics, research and development are now concentrated on materials for write-once (WORM) and erasable (EDRAW) storage systems. Suitable materials for optical data storage are substances in which data markings can be recorded and deleted respectively using semiconductor lasers. Materials development is centered on the synthesis of infrared-absorbing dyes for WORM memories and the production of rare earth/transition metal alloys for magneto-optical data recording. An introduction to CD-ROM technology will be followed by an overview of the state of development of the most important storage materials which are currently available commercially, and then the properties of these materials will be discussed with reference to selected examples.     

Synthesis and solid state 13C-NMR studies of some cellulose derivatives

Several cellulose derivatives were synthesized and characterized by IR and ¹H-NMR spectroscopy. The positions of substitution in these derivatives were confirmed using solid state ¹³C-NMR spectroscopy techniques.