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Université de Fribourg

A Koebe distortion theorem for quasiconformal mappings in the Heisenberg group

Adamowicz, Tomasz ; Fässler, Katrin ; Warhurst, Ben

In: Annali di Matematica Pura ed Applicata (1923 -), 2020, vol. 199, no. 1, p. 147–186

We prove a Koebe distortion theorem for the average derivative of a quasiconformal mapping between domains in the sub-Riemannian Heisenberg group H1. Several auxiliary properties of quasiconformal mappings between subdomains of H1 are proven, including BMO estimates for the logarithm of the Jacobian. Applications of the Koebe theorem include diameter bounds for images of curves, comparison of...

Université de Fribourg

Novel reference-free methods for the determination of the instrumental response of Laue-type bent crystal spectrometers

Szlachetko, Monika ; Hoszowska, Joanna ; Szlachetko, Jakub ; Dousse, Jean-Claude

In: Journal of Analytical Atomic Spectrometry, 2019, vol. 34, no. 11, p. 2325–2332

We report on novel reference-free methods to determine the instrumental resolution of transmission-type bent crystal spectrometers. The novel methods are based on the measurements of a selected X-ray line in several orders of diffraction. It is shown that the angular broadening of the spectrometer and the natural linewidth of the selected transition can be obtained directly from the novel...

Université de Fribourg

A DuMond-type crystal spectrometer for synchrotron-based X-ray emission studies in the energy range of 15–26 keV

Jagodziński, Paweł ; Szlachetko, Jakub ; Dousse, Jean-Claude ; Hoszowska, Joanna ; Szlachetko, Monika ; Vogelsang, U. ; Banaś, Dariusz ; Pakendorf, T. ; Meents, A. ; Bokhoven, Jeroen A. van ; Kubala-Kukuś, Aldona ; Pajek, Marek ; Nachtegaal, Maarten

In: Review of Scientific Instruments, 2019, vol. 90, no. 6, p. 063106

The design and performance of a high-resolution transmission-type X-ray spectrometer for use in the 15–26 keV energy range at synchrotron light sources is reported. Monte Carlo X-ray-tracing simulations were performed to optimize the performance of the transmission-type spectrometer, based on the DuMond geometry, for use at the Super X-ray absorption beamline of the Swiss Light Source at...

Université de Fribourg

Distance dependence of single-molecule energy transfer to graphene measured with DNA origami nanopositioners

Kaminska, I. ; Bohlen, J. ; Rocchetti, S. ; Selbach, F. ; Acuna, Guillermo P. ; Tinnefeld, P.

In: Nano Letters, 2019, vol. 19, no. 7, p. 4257–4262

Despite the thorough investigation of graphene since 2004, altering its surface chemistry and reproducible functionalization remain challenging. This hinders fabrication of more complex hybrid materials with controlled architectures, and as a consequence the development of sensitive and reliable sensors and biological assays. In this contribution, we introduce DNA origami structures as...

Consortium of Swiss Academic Libraries

Conformational constraints on side chains in protein residues increase their information content

Bojarski, A. ; Nowak, M. ; Testa, B.

In: Cellular and Molecular Life Sciences CMLS, 2003, vol. 60, no. 11, p. 2526-2531