Genäherte Berechnung von Wärmespannungen mit Hilfe der Variationsprinzipien der Elastostatik

Zusammenfassung Mit Hilfe von einfachen Näherungsansätzen, die in die, einem jeweiligen Problem zugehörigen Variationsintegrale eingeführt werden, kommt man im allgemeinen zu ausgezeichneten Approximationen. Neben der dem Ritzschen Verfahren entsprechenden Methode, Näherungsansätze bis auf willkürliche Konstanten vorzugeben, die dann aus Extremalbedingungen berechnet werden können, scheint vor allem das im letzten Abschnitt geschilderte Verfahren, das auf einfach lösbare Differentialgleichungen für die Näherungsfunktionen führt, eine besondere Bedeutung auch für andere Probleme der Elastizitätstheorie zu haben.Gekürzte Fassung einer von der Technischen Universität Berlin, Fakultät für Bauingenieurwesen, genehmigten Habilitationsarbeit. Der Verfasser spricht hiermit den Berichtern, Herrn Prof. I. Szabó und Herrn Prof. A. Teichmann seinen Dank aus.     

Hyperfine structure measurements in metastable states of165Ho

The hyperfine structure constants and the electronic g _J factor of the state 4f ¹¹ 6s ^{2 4} I _11/2 belonging to the holmium ground multiplet have been measured using the atomic beam magnetic resonance technique combined with a state-selective laser-induced detection of the resonant atoms. By the same method the g _J factor of the level 4f ¹¹6s ²⁴ I _9/2 was determined, while the hyperfine structures of this metastable state and of two high-lying even parity states have been investigated by high resolution laser spectroscopy. The results for the experimentalA andB factors of all four members of the ground multiplet allow a least-squares evaluation of the three magnetic dipole and the three electric quadrupole effective radial parameters for the configuration 4f ¹¹ 6s ² of holmium, yielding an accurate value for the spectroscopic nuclear electric quadrupole moment:Q _hfs(¹⁶⁵Ho)=2.716(9)b (uncorrected for quadrupole shielding). From a comparison to the quadrupole moments measured in mesic holmium atoms the shielding factor could be estimated.     

Lifetimes of O VI,O VII and O VIII states by the beam-foil technique

Radiative lifetimes of oxygen ions accelerated to 15 MeV and excited by a thin carbon foil have been measured using a grazing-incidence spectrometer. Where theoretical values are available, the measured lifetimes agree well with theory.     

Preparation dependent superconductivity in TlCaBa2Cu3O7.5±d above 100 K

Different heat treatment procedures were applied during sample preparation, which resulted in different superconducting properties in samples of the same nominal composition, TlCaBa₂Cu₃O_7.5±d . This manifests itself in different critical temperatures: 104 K, 107 K and 93 K. The highestT _c belongs to the best-crystallized samples in which the tetragonal Tl₂Ca₁Ba₂Cu₂O_8±d phase is responsible for the superconductivity. The effect of heat treatments is reflected in the structural and magnetic properties as well.     

On the charge distribution of calcium nuclei

The mean square charge radii and the quadrupole moments of Ca nuclei are discussed in the light of theoretical predictions. The very peculiar dependence of the charge radii on the mass number between double magic⁴⁰Ca and double magic⁴⁸Ca can be ascribed to changes of the nuclear deformation, whereas the volume of the nuclear charge remains constant for all the Ca isotopes. Furthermore, correlations between nuclear charge radii and binding energies are discussed.     

Light-cone expansion of matrix elements of current commutators

On the basis of general quantum field theory the existence of the light-cone expansion is shown for matrix elements of the current commutator. Mathematically, the problem consists of proving the expansion of entire functions in four complex variables in terms of harmonic polynomials.