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Université de Fribourg

Pleistocene sea-floor fibrous crusts and spherulites in the Danakil Depression (Afar, Ethiopia)

Jaramillo‐Vogel, David ; Foubert, Anneleen ; Braga, Juan Carlos ; Schaegis, Jean‐Charles ; Atnafu, Balemwal ; Grobéty, Bernard ; Kidane, Tesfaye

In: Sedimentology, 2019, vol. 66, no. 2, p. 480–512

Pleistocene fibrous aragonite fabrics, including crusts and spherules, occur in the Danakil Depression (Afar, Ethiopia) following the deposition of two distinctive Middle and Late Pleistocene coralgal reef units and pre‐dating the precipitation of evaporites. Crusts on top of the oldest reef unit (Marine Isotope Stage 7) cover and fill cavities within a red algal framework. The younger...

Université de Fribourg

A model based two-stage classifier for airborne particles analyzed with Computer Controlled Scanning Electron Microscopy

Meier, Mario Federico ; Mildenberger, Thoralf ; Locher, René ; Rausch, Juanita ; Zünd, Thomas ; Neururer, Christoph ; Ruckstuhl, Andreas ; Grobéty, Bernard

In: Journal of Aerosol Science, 2018, vol. 123, p. 1–16

Computer controlled scanning electron microscopy (CCSEM) is a widely-used method for single airborne particle analysis. It produces extensive chemical and morphological data sets, whose processing and interpretation can be very time consuming. We propose an automated two-stage particle classification procedure based on elemental compositions of individual particles. A rule-based classifier is...

Université de Fribourg

Nanoparticle shapes of LiMnPO4, Li+ diffusion orientation and diffusion coefficients for high volumetric energy Li+ ion cathodes

Kwon, Nam Hee ; Yin, , Hui ; Vavrova, Tatiana ; Lim, Jonathan H-W. ; Steiner, Ullrich ; Grobéty, Bernard ; Fromm, Katharina M.

In: Journal of Power Sources, 2017, vol. 342, p. 231–240

Nanoparticles of LiMnPO₄ were fabricated in rod, elongated as well as cubic shapes. The 1D Li⁺ preferred diffusion direction for each shape was determined via electron diffraction spot patterns. The shape of nano-LiMnPO₄ varied the diffusion coefficient of Li⁺ because the Li⁺ diffusion direction and the path length were different. The particles with the shortest dimension along the...

Université de Fribourg

Manufacturing of tubular dead-end membranes by continuous thermoplastic extrusion

Salehi, Mehdi ; Pfaff, Ewald M. ; Kaletsch, Anke ; Graule, Thomas ; Clemens, Frank ; Grobéty, Bernard

In: International Journal of Applied Ceramic Technology, 2015, vol. 12, p. E13–E18

Dense and gastight dead-end tubular Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) membranes were fabricated by thermoplastic extrusion. Optimal feedstocks for the extrusion of dead-end tubular structures were obtained for a feedstock consisting of 89.83 wt% BSCF powder, 5.63 wt% ethylene vinyl acetate (EVA), 3.56 wt% paraffin wax (PW), and 0.98 wt%...

Université de Fribourg

High-resolution 3D analyses of the shape and internal constituents of small volcanic ash particles: The contribution of SEM micro-computed tomography (SEM micro-CT)

Vonlanthen, Pierre ; Rausch, Juanita ; Ketcham, Richard A. ; Putlitz, Benita ; Baumgartner, Lukas P. ; Grobéty, Bernard

In: Journal of Volcanology and Geothermal Research, 2015, vol. 293, p. 1–12

The morphology of small volcanic ash particles is fundamental to our understanding of magma fragmentation, and in transport modeling of volcanic plumes and clouds. Until recently, the analysis of 3D features in small objects (< 250 μm) was either restricted to extrapolations from 2D approaches, partial stereo-imaging, or CT methods having limited spatial resolution and/or accessibility. In...

Université de Fribourg

Eifel maars: Quantitative shape characterization of juvenile ash particles (Eifel Volcanic Field, Germany)

Rausch, Juanita ; Grobéty, Bernard ; Vonlanthen, Pierre

In: Journal of Volcanology and Geothermal Research, 2015, vol. 291, p. 86–100

The Eifel region in western central Germany is the type locality for maar volcanism, which is classically interpreted to be the result of explosive eruptions due to shallow interaction between magma and external water (i.e. phreatomagmatic eruptions). Sedimentary structures, deposit features and particle morphology found in many maar deposits of the West Eifel Volcanic Field (WEVF), in contrast...

Université de Fribourg

Electron transfer in peptides: on the formation of silver nanoparticles

Kracht, Sonja ; Messerer, Matthias ; Lang, Matthieu ; Eckhardt, Sonja ; Lauz, Miriam ; Grobéty, Bernard ; Fromm, Katharina M. ; Giese, Bernd

In: Angewandte Chemie International Edition, 2015, vol. 54, no. 10, p. 2912–2916

Some microorganisms perform anaerobic mineral respiration by reducing metal ions to metal nanoparticles, using peptide aggregates as medium for electron transfer (ET). Such a reaction type is investigated here with model peptides and silver as the metal. Surprisingly, Ag⁺ ions bound by peptides with histidine as the Ag⁺-binding amino acid and tyrosine as photoinducible electron donor cannot...