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Université de Fribourg

Decrypting silicic magma/plug fragmentation at Azufral crater lake, Northern Andes: insights from fine to extremely fine ash morpho-chemistry

Pardo, Natalia ; Avellaneda, Jose D. ; Rausch, Juanita ; Jaramillo-Vogel, David ; Gutiérrez, Mariana ; Foubert, Anneleen

In: Bulletin of Volcanology, 2020, vol. 82, no. 12, p. 79

Azufral (SW Colombia) is a dangerous silicic volcano hosting a crater lake, which serves as an excellent example of an incipient plug disruption through phreatomagmatism. We studied the youngest succession of dilute pyroclastic density currents (PDCs) onlapping the north-eastern crater rim. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy was used to carry out an...

Université de Fribourg

Bacterial oxidases of the cytochrome bd family: redox enzymes of unique structure, function, and utility as drug targets

Borisov, Vitaliy B. ; Siletsky, Sergey A. ; Paiardini, Alessandro ; Hoogewijs, David ; Forte, Elena ; Giuffrè, Alessandro ; Poole, Robert K.

In: Antioxidants & Redox Signaling, 2020, p. ars.2020.8039

Significance: Cytochrome bd is a ubiquinol:oxygen oxidoreductase of many prokaryotic respiratory chains with a unique structure and functional characteristics. Its primary role is to couple the reduction of molecular oxygen, even at submicromolar concentrations, to water with the generation of a proton motive force used for adenosine triphosphate production. Cytochrome bd is found in many...

Université de Fribourg

Optical signatures of multifold fermions in the chiral topological semimetal CoSi

Xu, Bing ; Fang, Zhenyao ; Sánchez-Martínez, Miguel-Angel ; Venderbos, Jorn W. F. ; Ni, Zhuoliang ; Qiu, Tian ; Manna, Kaustuv ; Wang, Kefeng ; Paglione, Johnpierre ; Bernhard, Christian ; Felser, Claudia ; Mele, Eugene J. ; Grushin, Adolfo G. ; Rappe, Andrew M. ; Wu, Liang

In: Proceedings of the National Academy of Sciences, 2020, vol. 117, no. 44, p. 27104–27110

We report the optical conductivity in high-quality crystals of the chiral topological semimetal CoSi, which hosts exotic quasiparticles known as multifold fermions. We find that the optical response is separated into several distinct regions as a function of frequency, each dominated by different types of quasiparticles. The low-frequency intraband response is captured by a narrow Drude peak...

Université de Fribourg

NESSi: The Non-Equilibrium Systems Simulation package

Schüler, Michael ; Golež, Denis ; Murakami, Yuta ; Bittner, Nikolaj ; Herrmann, Andreas ; U.R.Strand, Hugo ; Werner, Philipp ; Eckstein, Martin

In: Computer Physics Communications, 2020, vol. 257, no. 2020, p. 107484

The nonequilibrium dynamics of correlated many-particle systems is of interest in connection with pump–probe experiments on molecular systems and solids, as well as theoretical investigations of transport properties and relaxation processes. Nonequilibrium Green’s functions are a powerful tool to study interaction effects in quantum many-particle systems out of equilibrium, and to extract...

Université de Fribourg

Entropy and electronic orders of the three-orbital Hubbard model with antiferromagnetic Hund coupling

Yue, Changming ; Hoshino, Shintaro ; Werner, Philipp

In: Physical Review B, 2020, vol. 102, no. 19, p. 195103

An antiferromagnetic Hund coupling in multiorbital Hubbard systems induces orbital freezing and an associated superconducting instability, as well as unique composite orders in the case of an odd number of orbitals. While the rich phase diagram of the half-filled three-orbital model has recently been explored in detail, the properties of the doped system remain to be clarified. Here, we...

Université de Fribourg

Geochemical fingerprinting of key lithologies and depositional processes across the upper boundary of the Opalinus Clay (Aalenian, Middle Jurassic, northern Switzerland)

Lauper, Bruno ; Deplazes, Gaudenz ; Vogel, Hendrik ; Jaeggi, David ; Wohlwend, Stephan ; Ariztegui, Daniel ; Foubert, Anneleen

In: The Depositional Record, 2020, p. dep2.126

The Opalinus Clay is an argillaceous to silty mudstone formation, notable in Switzerland as the selected host rock for deep geological disposal of radioactive waste. Its upper bounding unit (Passwang Formation and eastern equivalents) is composed of successions of mudstone, sandy bioclastic marl and limestone separated by ooidal ironstone beds. The lithostratigraphic transition is diachronous...

Université de Fribourg

Correlations in multithermostat Brownian systems with Lorentz force

Abdoli, Iman ; Kalz, Erik ; Vuijk, Hidde D. ; Wittmann, René ; Sommer, Jens-Uwe ; Brader, Joseph M. ; Sharma, Abhinav

In: New Journal of Physics, 2020, vol. 22, no. 9, p. 093057

We study the motion of a Brownian particle subjected to Lorentz force due to an external magnetic field. Each spatial degree of freedom of the particle is coupled to a different thermostat. We show that the magnetic field results in correlation between different velocity components in the stationary state. Integrating the velocity autocorrelation matrix, we obtain the diffusion matrix that...

Université de Fribourg

Ultrafast coupled charge and spin dynamics in strongly correlated NiO

Gillmeister, Konrad ; Golež, Denis ; Chiang, Cheng-Tien ; Bittner, Nikolaj ; Pavlyukh, Yaroslav ; Berakdar, Jamal ; Werner, Philipp ; Widdra, Wolf

In: Nature Communications, 2020, vol. 11, no. 1, p. 4095

Charge excitations across an electronic band gap play an important role in opto- electronics and light harvesting. In contrast to conventional semiconductors, studies of above-band-gap photoexcitations in strongly correlated materials are still in their infancy. Here we reveal the ultrafast dynamics controlled by Hund’s physics in strongly correlated photoexcited NiO. By combining...

Université de Fribourg

High-harmonic generation in spin-orbit coupled systems

Lysne, Markus ; Murakami, Yuta ; Schüler, Michael ; Werner, Philipp

In: Physical Review B, 2020, vol. 102, no. 8, p. 081121

We study high-harmonic generation in two-dimensional electron systems with Rashba and Dresselhaus spin-orbit coupling and derive harmonic generation selection rules with the help of group theory. Based on the band structures of these minimal models and explicit simulations we reveal how the spin-orbit parameters control the cutoff energy in the high-harmonic spectrum. We also show that the...

Université de Fribourg

Rapid and sensitive quantification of cell-associated multi-walled carbon nanotubes

Steinmetz, Lukas ; Bourquin, Joel ; Barosova, Hana ; Haeni, Laetitia ; Caldwell, Jessica ; Milosevic, Ana ; Geers, Christoph ; Bonmarin, Mathias ; Taladriz-Blanco, Patricia ; Rothen-Rutishauser, Barbara ; Petri-Fink, Alke

In: Nanoscale, 2020, vol. 12, no. 33, p. 17362–17372

Evaluating nanomaterial uptake and association by cells is relevant for in vitro studies related to safe-by-design approaches, nanomedicine or applications in photothermal therapy. However, standard analytical techniques are time-consuming, involve complex sample preparation or include labelling of the investigated sample system with e.g. fluorescent dyes. Here, we explore lock-in...