Flow phenomena in floppy tubes

Collapsible tubes, which occur all over the body, have unique properties from the point of view of both physics and physiology. A brief review is attempted of first the basic observable properties, followed by simple theory to explain the steady-flow aspects and an overview of the somewhat more complex theories for unsteady flow, in particular the flow-induced oscillations. The experimental evidence from laboratory studies is reviewed with particular emphasis on the dynamical system aspects. A final section looks at the current position and prospects.     

Magnetism and superconductivity in ErNi2B2C

We have performed a series of neutron diffraction experiments from the magnetic order and the vortex lattice in single crystal ErNi₂B₂C. The incommensurate magnetic structure develops additional even harmonics below the ‘ferromagnetic’ ordering temperature, T _F of 2.3 K. This feature and the existence of rods of diffuse scattering suggest the development of ferromagnetic microdomain walls. The magnetic structure is very sensitive to the application of a magnetic field with changes in modulation vector and harmonic content. Studies of the vortex lattice show the presence of a 45° reorientation transition and a distorted hexagonal to square transition as a function of applied field. Further distortions of the vortex lattice occur at T _N, but no changes are seen at T _F.     

Datenvorbehandlung zur Erzeugung von Derivativspektren mit der Fourier-Transformation

Zusammenfassung Für die Ableitung und Glättung digitalisierter Spektren mittels der diskreten Fourier-Transformation wird die Punktspiegelung der Daten als ein neues Verfahren der Datenvorbehandlung vorgestellt. Im Gegensatz zum herkömmlichen Verfahren werden auch in kritischen Fällen keine Artefakte durch die Ableitungs- und Glättungsoperationen hervorgerufen. Durch Verwendung eines speziellen Algorithmus kommt das neue Verfahren mit derselben Anzahl von Speicherplätzen und einer nur geringfügig höheren Rechenzeit wie das herkömmliche Verfahren aus.

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Data preprocessing for generating derivative spectra with Fourier Transforms

Summary For smoothing and differentiation of digitized spectra using the Discrete Fourier Transform the inversion of data is presented as a new data preprocessing procedure. Contrary to the usual procedure, even in critical cases no artifacts are produced by smoothing and differentiation. Due to the utilization of a tailored algorithm, the computing performance does not seriously suffer. With regard to storage the new approach is equivalent and needs only slightly increased computing time compared to the previous method.

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Prof. Dr. Carl Mahr zum 85. Geburtstag in Dankbarkeit gewidmet