University of Konstanz

About: University of Konstanz is a education organization based out in Konstanz, Baden-Württemberg, Germany. It is known for research contribution in the topics: Population & Membrane. The organization has 12115 authors who have published 27401 publications receiving 951162 citations. The organization is also known as: University of Constance & Universität Konstanz.

Elastic effects of structural relaxation in glasses at low temperatures

Abstract: A complete theoretical description of the effect of the relaxation of two-state structural defects on the elastic properties of glasses at low temperatures is given. New experimental data on the ultrasonic attenuation in vitreous silica and borosilicate glass in the temperature range between 0.3 and 4 K and at frequencies between 30 and about 500 MHz are presented and explained by this theory. We propose that over the entire temperature range from our lowest temperature of 0.3 to about 100 K the attenuation is due to the relaxation of defects with similar atomic structure.

Measurement of the Wigner function of an ensemble of helium atoms

Abstract: Beams of atoms can exhibit interference and diffraction phenomena just like waves of light. For a coherent beam of helium atoms in a double-slit experiment, measurements of the quantum-mechanical analogue of the classical phase-space distribution function show that the motion of atoms behaves in a strongly non-classical manner.

The cytochrome b gene as a phylogenetic marker: the limits of resolution for analyzing relationships among cichlid fishes.

Abstract: The mitochondrial cytochrome b (cyt-b) gene is widely used in systematic studies to resolve divergences at many taxonomic levels. The present study focuses mainly on the utility of cyt-b as a molecular marker for inferring phylogenetic relationship at various levels within the fish family Cichlidae. A total of 78 taxa were used in the present analysis, representing all the major groups in the family Cichlidae (72 taxa) and other families from the suborders Labroidei and Percoidei. Gene trees obtained from cyt-b are compared to a published total evidence tree derived from previous studies. Minimum evolution trees based on cyt-b data resulted in topologies congruent with all previous analyses. Parsimony analyses downweighting transitions relative to transversions (ts1:tv4) or excluding transitions at third codon positions resulted in more robust bootstrap support for recognized clades than unweighted parsimony. Relative rate tests detected significantly long branches for some taxa (LB taxa) which were composed mainly by dwarf Neotropical cichlids. An improvement of the phylogenetic signal, as shown by the four-cluster likelihood mapping analysis, and higher bootstrap values were obtained by excluding LB taxa. Despite some limitations of cyt-b as a phylogenetic marker, this gene either alone or in combination with other data sets yields a tree that is in agreement with the well-established phylogeny of cichlid fish.