Precise subnanometer control of the position of a macro object by light pressure

For the first time to the authors' knowledge, efficient control of the position of a macro object by coherent light was demonstrated. The minimal controllable mechanical displacement induced by the light pressure was 9 pm. No dependence of light pressure on wavelength in a broad wavelength range (405-1560 nm) was observed, as predicted by Maxwell's theory.     

Sedimentation of DNA supercoils and bacterial nucleoids

The sedimentation of DNA supercoils and bacterial nucleoids is discussed in terms of an asymptotic expression for the size of branched supercoils exhibiting an excluded-volume effect between superhelical segments. A Kirkwood–Riseman approximation is adopted for the sedimentation coefficient. The theory predicts the sedimentation of DNA supercoils fairly well despite their relatively small size in current simulations and experiments. We introduce a crosslinked supercoil model for bacterial nucleoids that are known to contain a variety of adsorbed proteins. Sedimentation experiments of the 1970s are discussed.     

A synthetic construction of the Figueroa planes

The constructions of the Figueroa planes by Figueroa, Hering-Schaeffer and Dempwolff make essential use of the collineation groups. Here we give a synthetic construction of these planes, which avoids coordinates and groups.Dedicated to Professor Hanfried Lenz on the occasion of his 70th birthday     

Ausbreitung von Stosswellen in einem Bodenmaterial mit linearem Zustandsdiagramm

Summary Going out from two earlier reports [1, 2] on one-dimensional shock waves in the ground, the special case of the shock wave propagation in a material with a linear pressure-deformation relation is discussed. The pressure distribution along the shock front as well as the velocity distribution on the surface can explicitly be given by means of an infinite sum, for which in the case of a strongly plastic ground an integral gives a good approximation. For completely elastic or plastic ground material the sum is explicitly evaluated. The theory is applied to a shock loading followed by a triangular pressure fall-off. Also the case of the exponentially decreasing shock loading is discussed.     

Some classes of line singularities

Supported by the Netherlands foundation for Mathematics SMC with financial aid from the Netherlands Organization for the Advancement of Pure Research ZWO.     

Can the observed structures in positron spectra be caused by internal conversion?

The energy distribution of positrons emitted in quasimolecular collisions of Uranium on Uranium and Uranium on Curium has been measured by several groups. Peak structures in the positron spectra were observed. We discuss the possibility that these structures originate from internal conversion processes following nuclear Coulomb excitation or transfer reactions. Consequences for the nuclear photon spectra and theδ-ray distribution are pointed out and experimental procedures for an unambiguous determination of the significance of conversion processes are discussed.