About the Authors
- Jan Opfer
- Kay-Eberhard Gottschalk
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* E-mail: kay.gottschalk@uni-ulm.de
Affiliation Institut für Experimentelle Physik, Universität Ulm, Ulm, Germany
Competing Interests
The authors have declared that no competing interests exist.
Author Contributions
Conceived and designed the experiments: JO KEG. Performed the experiments: JO. Analyzed the data: JO KEG. Wrote the paper: JO KEG.