Polarized light and X-ray precession study of the ferroelastic domains of YBa2Cu3O7-δ

The ferroelastic domains of the orthorhombic phase of YBa₂Cu₃O_7- have been observed in polarized light on ceramics and single crystals. By combining polarized light microscopy with the X-ray precession technique, the correlation of the orientation of the orthorhombica- andb-axes with that of thea-b-plane bireflectance, reflection dichroism, transmission dichroism (at a thickness of about 1m), reflection tints generated with compensators and upon uncrossing of polars, as well as the orientation of etch pits has been realized on ferroelastic single domains, bi-domains and more complicated domain patterns. Four ferroelastic orthorhombic domain states have been identified, at variance with former group theoretical considerations, predicting only two states. Ensembles of lamellar domains beyond optical resolution generate strong bireflectance with principal axes rotated by 45° relative to the truea, b-directions.     

Off-shell behaviour of theN-N interaction in a six-quark resonating group model of the deuteron

Two different 6-quark resonating group models of the deuteron are investigated to study the off-shell property of theN-N interaction. In the first model the quarks interact by a central one-gluon-exchange potential plus confinement potential. The meson-exchange contribution to then-p potential is simulated by a central GaussianN-N potential. In the second model the quarks interact by one-gluon-and one-pion-exchange potentials (central and noncentral) plus confinement potential. A small additional -exchange potential between neutron and proton binds the deuteron at the correct energy.Several off-shell variants of the two resonating group models are compared with each other by analyzing their elastic electron scattering cross sections. It is found that the standard renormalized version of the resonating group model yields potentials and wave functions that may be considered physical within the limitations of the model. Unitary off-shell transformations, which modify potentials and wave functions in any sizeable way, lead to a disagreement between the charge distribution predicted by the model via analysis of electron scattering and the charge distribution following from the microscopic quark distribution.Both of the 6-quark models support a soft repulsive core of the tripletn-p potential with a core height of around 900 MeV.     

Der Reaktionsmechanismus der allgemeinen Säure—Basen-Katalyse der Mutarotation der Glucose, 8. Mitt.: Die Aktivierungsenergie der heterogenen Kupfer-Katalyse der Glucose-Mutarotation (Kurze Mitteilung)

Ohne Zusammenfassung7. Mitt.:Hermann Schmid undG. Bauer, Mh. Chem.96, 1508 (1965); dort ältere Mitt. dieser Reihe zitiert.     

Kinetik und stereochemischer Verlauf der thermischen Umlagerung der vier stereoisomeren Propenyl-(but-2′-enyl)-äther

The gas-phase rearrangement of (1Z, 2′E)-, (1Z, 2′Z)-, (1E, 2′E)-, and (1E, 2′Z)- propenyl but-2′-enyl ether (Z, E)-, (Z, Z)-, (E, E)-, and (E, Z)-1) into erythro- and threo-2, 3-dimethyl-pent-4-en-al (erythro- and threo-2) was investigated over a temperature range from 142,5° to 190,0° at 20–35 Torr (for kinetic data and activation parameters see table 2). All four stereoisomeric ethers 1 rearrange preferentially via a chair-like transition state C into the aldehydes 2 (ΔΔG^≠ (160°) = 2,5–2,7 kcal/mol for B – C (B = boat-like transition state). The relative rates (k_rel) for (Z, Z)-1, (Z, E)-1, (E,Z)-1, and (E,E)-1 at 160° are 1,0, 2,9, 4,3 and 9,0 respectively (see table 5). Taking into account the relative enthalpies of the ethers 1 and the steric interaction in the C transition state of the ethers 1 (see table 6), k_rel values can be estimated. They are in good agreement with those observed (see table 5).     

Herstellung und Charakterisierung von Komplexen des Uran(IV) mit Di-n-butylphosphorsäure in Kontakt mit Perchlor-, Schwefel- und Salpetersäurelösungen

Zusammenfassung Die Herstellung von festen Komplexen des Uran(IV) mit Di-n-butylphosphorsäure in Kontakt mit Perchlor-, Schwefel-und Salpetersäure wird beschrieben. Es ergab sich für die beiden ersten Fälle eine Zusammensetzung U(DBP)₄ und für den letzten U(NO₃)(DBP)₃, wobeiDBP für das Anion der Di-n-butylphosphorsäure steht. Auf Grund der Infrarotspektren im Bereich von 4000 bis 700 cm^–1 wurde versucht, Anhaltspunkte über die Bindungsverhältnisse in den Komplexen zu erhalten. Die Absorptionsbanden des U(NO₃)(DBP)₃-Komplexes bei 1520 und 1275 cm^–1 weisen darauf hin, daß das Nitrat im wesentlichen kovalent an das Uran(IV) gebunden ist.

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The preparation and characterization of solid complexes of uranium(IV) with di-n-butyl phosphoric acid in contact with perchloric, sulfuric and nitric acid solutions

The preparation of solid complexes of uranium(IV) with di-n-butyl phosphoric acid in contact with aqueous perchloric, sulfuric and nitric acid solutions is described. The formula was found to be U(DBP)₄ for the complexes prepared in contact with the two first mentioned acids, and U(NO₃)(DBP)₃ for the complex prepared in contact with HNO₃ (DBP stands for the anion of the di-n-butyl phosphoric acid). Absorption spectra were registered in the infrared region from 4000–700 cm^–1. Due to the absorption bands at 1520 and 1275 cm^–1 it seems, that the nitrato group is bound mainly covalent in the U(NO₃)(DBP) complex.

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Mit 1 Abbildung

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Herrn Prof. Dr.O. Kratky zum 70. Geburtstag gewidmet.