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Université de Fribourg

Long-range orders and spin/orbital freezing in the two-band Hubbard model

Steiner, Karim ; Hoshino, Shintaro ; Nomura, Yusuke ; Werner, Philipp

In: Physical Review B, 2016, vol. 94, no. 7, p. 075107

We solve the orbitally degenerate two-band Hubbard model within dynamical mean field theory and map out the instabilities to various symmetry-broken phases based on an analysis of the corresponding lattice susceptibilities. Phase diagrams as a function of the Hund coupling parameter J are obtained both for the model with rotationally invariant interaction and for the model with Ising-type...

Université de Fribourg

Double-expansion impurity solver for multiorbital models with dynamically screened $U$ and $J$

Steiner, Karim ; Nomura, Yusuke ; Werner, Philipp

In: Physical Review B, 2015, vol. 92, no. 11, p. 115123

We present a continuous-time Monte Carlo impurity solver for multiorbital impurity models which combines a strong-coupling hybridization expansion and a weak-coupling expansion in the Hund's coupling parameter J. This double-expansion approach allows to treat the dominant density-density interactions U within the efficient segment representation. We test the approach for a two-orbital model with...

Université de Fribourg

Biodiversity effects on grape quality depend on variety and management intensity

Steiner, Magdalena ; Grace, James B. ; Bacher, Sven

In: Journal of Applied Ecology, 2021, p. 1-13

1. Interactions between plants can be beneficial, detrimental or neutral. In agricultural systems, competition between crop and spontaneous vegetation is a major concern. We evaluated the relative support for three non-exclusive ecological hypotheses about interactions between crop and spontaneous plants based on competition, complementarity or facilitation. 2. The study was conducted in...

Université de Fribourg

Restoration of semi-natural grasslands, a success for phytophagous beetles (Curculionidae)

Steiner, Magdalena ; Öckinger, Erik ; Karrer, Gerhard ; Winsa, Marie ; Jonsell, Mats

In: Biodiversity and Conservation, 2016, vol. 25, no. 14, p. 3005–3022

Semi-natural pastures have rich plant and animal communities of high conservation value which depend on extensive management. As the area of such land decreases, abandoned semi-natural grasslands have been restored to re-establish biodiversity. Restoration schemes, which include thinning of woody plants and reintroduction of grazing, are mainly designed according to the responses of...

Université de Fribourg

Effects of an iron-based fuel-borne catalyst and a diesel particle filter on exhaust toxicity in lung cells in vitro

Steiner, Sandro ; Czerwinski, Jan ; Comte, Pierre ; Heeb, Norbert V. ; Mayer, Andreas ; Petri-Fink, Alke ; Rothen-Rutishauser, Barbara

In: Analytical and Bioanalytical Chemistry, 2015, vol. 407, no. 20, p. 5977–5986

Metal-containing fuel additives catalyzing soot combustion in diesel particle filters are used in a widespread manner, and with the growing popularity of diesel vehicles, their application is expected to increase in the near future. Detailed investigation into how such additives affect exhaust toxicity is therefore necessary and has to be performed before epidemiological evidence points towards...

Université de Fribourg

Diesel exhaust: current knowledge of adverse effects and underlying cellular mechanisms

Steiner, Sandro ; Bisig, Christoph ; Petri-Fink, Alke ; Rothen-Rutishauser, Barbara

In: Archives of Toxicology, 2016, p. 1–13

Diesel engine emissions are among the most prevalent anthropogenic pollutants worldwide, and with the growing popularity of diesel-fueled engines in the private transportation sector, they are becoming increasingly widespread in densely populated urban regions. However, a large number of toxicological studies clearly show that diesel engine emissions profoundly affect human health. Thus the...

Université de Fribourg

Test-methods on the test-bench: a comparison of complete exhaust and exhaust particle extracts for genotoxicity/mutagenicity assessment

Steiner, Sandro ; Heeb, Norbert V. ; Czerwinski, Jan ; Comte, Pierre ; Mayer, Andreas ; Petri-Fink, Alke ; Rothen-Rutishauser, Barbara

In: Environmental Science & Technology, 2014, vol. 48, no. 9, p. 5237–5244

With the growing number of new exhaust after-treatment systems, fuels and fuel additives for internal combustion engines, efficient and reliable methods for detecting exhaust genotoxicity and mutagenicity are needed to avoid the widespread application of technologies with undesirable effects toward public health. In a commonly used approach, organic extracts of particulates rather than complete...

Université de Fribourg

Reduction in (pro-)inflammatory responses of lung cells exposed in vitro to diesel exhaust treated with a non-catalyzed diesel particle filter

Steiner, Sandro ; Czerwinski, Jan ; Comte, Pierre ; Müller, Loretta L. ; Heeb, Norbert V. ; Mayer, Andreas ; Petri-Fink, Alke ; Rothen-Rutishauser, Barbara

In: Atmospheric Environment, 2013, vol. 81, p. 117–124

Increasingly stringent regulation of particulate matter emissions from diesel vehicles has led to the widespread use of diesel particle filters (DPFs), the effect of which on exhaust toxicity is so far poorly understood. We exposed a cellular model of the human respiratory epithelium at the air-liquid interface to non-catalyzed wall-flow DPF-filtered diesel exhaust and compared the resulting...

Université de Fribourg

Comparison of the toxicity of diesel exhaust produced by bio- and fossil diesel combustion in human lung cells in vitro

Steiner, Sandro ; Czerwinski, Jan ; Comte, Pierre ; Popovicheva, Olga ; Kireeva, Elena ; Müller, Loretta ; Heeb, Norbert ; Mayer, Andreas ; Fink, Alke ; Rothen-Rutishauser, Barbara

In: Atmospheric Environment, 2013, vol. 81, p. 380–388

Alternative fuels are increasingly combusted in diesel- and gasoline engines and the contribution of such exhausts to the overall air pollution is on the rise. Recent findings on the possible adverse effects of biodiesel exhaust are contradictive, at least partly resulting from the various fuel qualities, engine types and different operation conditions that were tested. However, most of the...