Radiation defects and spin-lattice relaxation studied with neutron-activated β emitters

A review is given of the principles of β-radiation detected nuclear magnetic resonance (β NMR) and of some recent applications to defect and relaxation phenomena. Advantages and disadvantages compared to conventional NMR on stable nuclei are discussed. Measurements of radiation defects in the silver halides, and of spin-lattice relaxation phenomena in liquid lithium alloys and in lithiumsilicate glass are reported in some detail.     

Free states of the canonical anticommutation relations

Each gauge invariant generalized free state _A of the anticommutation relation algebra over a complex Hilbert spaceK is characterized by an operatorA onK. It is shown that the cyclic representations induced by two gauge invariant generalized free states _A and _B are quasi-equivalent if and only if the operatorsA ^1/2–B ^1/2 and (I–A)^1/2–(I–B)^1/2 are of Hilbert-Schmidt class. The combination of this result with results from the theory of isomorphisms of von Neumann algebras yield necessary and sufficient conditions for the unitary equivalence of the cyclic representations induced by gauge invariant generalized free states.Work supported in part by US Atomic Energy Commission, under Contract AT (30-1)-2171 and by the National Science Foundation.     

Ein vollautomatisch arbeitendes Torsionspendel für den Temperaturbereich von −180°C bis + 250°C

Zusammenfassung Zur Ermittlung des komplexen SchubmodulsG ^* bei Kunststoffen wurde ein Torsionspendel an einen Prozeßrechner angeschlossen. Das Meßsystem gestattet es, Messungen in einem Temperaturbereich von –180°C bis +250°C bei einer konstanten Schwingungsfrequenz von 1 Hz ± 0,09 Hz vollautomatisch durchzuführen. Der Rechner hat die Aufgabe, das Experiment zu steuern, die Versuchsbedingungen zu kontrollieren, die Meßwerte zu erfassen und die Auswertung durchzuführen. Die Ergebnisse können in Form von Tabellen oder graphisch ausgegeben werden. Ferner ist es möglich, die Ergebnisse auf dem Massenspeicher des Rechners in einer Datei abzulegen.

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Summary A torsional pendulum has been connected to a minicomputer in order to measure the complex shear modulus (G ^*). This experimental set-up allows to take computer controlled measurements in the temperaturerange –180°C to +250°C at a constant oscillation frequency of 1 Hz ± 0,09 Hz. The setting and controlling of the experimental parameters, the take-up of the data and the calculations are performed by the computer. The results are obtained in tabulated form or in form of plotted diagrams. In addition it is possible to store the results on the disc of the computer.

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Mit 10 Abbildungen     

Molecular Dynamics Investigation of Bonded Twist Boundaries

Molecular dynamics simulations using empirical potentials have been performed to describe atomic interactions at interfaces created by macroscopic wafer bonding. Misalignment due to relative twist rotation of the wafers influences the bondability of larger areas. Depending on the twist angle the bond energy varies and different defect and atomic arrangements at the interfaces occur. In addition, if very thin wafers are being bonded the free surfaces are modified by the resulting interface relaxation.     

Die Dimensionen der Räume automorpher Formen zu Modulgruppen in Quaternionenschiefkörpern über reellquadratischen Zahlkörpern

Ohne Zusammenfassung