Université de Fribourg

High-resolution monitoring of water temperature and oxygen concentration in Lake Murten (Switzerland)

Kateb, Akram El ; Rüggeberg, Andres ; Stalder, Claudio ; Neururer, Christoph ; Spezzaferri, Silvia

In: Swiss Journal of Geosciences, 2018, vol. 111, no. 3, p. 501–510

Lake Murten is located in the Lake District in western Switzerland and so far, it has been poorly investigated. The Environmental Service of Fribourg (SEn) has monitored this lake once a month for several years by water profiles (water temperature, pH, dissolved oxygen, conductivity) at its deepest part. The SEn identified the stratification of water masses as one of the main causes for...

Université de Fribourg

Distribution of benthic foraminiferal assemblages in the transitional environment of the Djerba lagoon (Tunisia)

Kateb, Akram El ; Stalder, Claudio ; Neururer, Christoph ; Fentimen, Robin ; Spangenberg, Jorge E. ; Spezzaferri, Silvia

In: Swiss Journal of Geosciences, 2018, vol. 111, no. 3, p. 589–606

The eastern edge of the Djerba Island represents an important tourist pole. However, studies describing the environmental processes affecting this Island are scarce. Although never studied before, the peculiar Djerba lagoon is well known by the local population and by tourists. In July 2014, surface sediment and seawater samples were collected in this lagoon to measure grain size, organic...

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

Impact of industrial phosphate waste discharge on the marine environment in the Gulf of Gabes (Tunisia)

Kateb, Akram El ; Stalder, Claudio ; Rüggeberg, Andres ; Neururer, Christoph ; Spangenberg, Jorge E. ; Spezzaferri, Silvia

In: PLOS ONE, 2018, vol. 13, no. 5, p. e0197731

The marine environment in the Gulf of Gabes (southern Tunisia) is severely impacted by phosphate industries. Nowadays, three localities, Sfax, Skhira and Gabes produce phosphoric acid along the coasts of this Gulf and generate a large amount of phosphogypsum as a waste product. The Gabes phosphate industry is the major cause of pollution in the Gulf because most of the waste is directly...

Université de Fribourg

Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) feedstock development and optimization for thermoplastic forming of thin planar and tubular oxygen separation membranes

Salehi, Mehdi ; Clemens, Frank ; Pfaff, Ewald M. ; Junior, Roberto M. ; Bergmann, Carlos P. ; Diethelm, Stefan ; Neururer, Christoph ; Graule, Thomas ; Grobéty, Bernard

In: Journal of Membrane Science, 2013, p. -

This paper presents the processing steps for producing thin planar and tubular oxygen separation membranes by thermoplastic forming of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) with polystyrene (PS) and stearic acid (SA) as binder. The influence of powder content on the shape stability of thin membranes (tubular and planar structures)...

Université de Fribourg

Temperature evolution inside a pot during experimental surface (bonfire) firing

Maggetti, Marino ; Neururer, Christoph ; Ramseyer, Denis

In: Applied Clay Science, 2010///doi: 10.1016/j.clay.2010.09.013

Time–temperature evolutions of different parts inside a pot were recorded during three experimental surface (bonfire) firings. The experimental vessels were shaped from a calcareous clay, tempered with 30% vol. of oolithic limestone. The temperature–time recording showed: (1) Tmax. was reached after 12–22 min and differed between the firings as well as inside individual...

Université de Fribourg

Nanowire formation by gold nano-fragment coalescence on quantized vortices in He II

Moroshkin, Peter ; Lebedev, Victor ; Grobéty, Bernard ; Neururer, Christoph ; Gordon, E. B. ; Weis, Antoine

In: Europhysics Letters, 2010, vol. 90, no. 3, p. 34002

We demonstrate that laser ablation of a gold target immersed in superfluid and normal fluid helium leads to the formation of elongated gold nano-fragments. In the superfluid phase these nano-fragments aggregate into filaments with extremely large aspect ratios displaying metallic electric conductivity. We attribute this unusual structure to the coalescence of gold particles trapped on quantized...

Université de Fribourg

Antimonate opaque glaze colours from the faience manufacture of Le Bois d'Épense (19th century, Northeastern France)*

Maggetti, Marino ; Neururer, Christoph ; Rosen, J.

In: Archaeometry, 2009, vol. 51, no. 5, p. 791-807

Three types of antimony-based, opaque ceramic colours were used in the faience workshop of Le Bois d'Épense during the first decades of the 19th century; that is, yellow, tawny and green. Yellow is generated by lead antimonate crystals (Naples Yellow), which are incorporated into an uncoloured glass matrix. According to SEM–EDS measurements, these pigments contain iron. The tawny colour is the...

Université de Fribourg

Scanning electron microscope images of uncoated microfossils: applications, perspectives and limitations

Spezzaferri, Silvia ; Neururer, Christoph ; Pirkenseer, Claudius ; Grobéty, Bernard

In: The Journal of Foraminiferal Research, 2007, vol. 37, no. 3, p. 270-276

We present a recently developed method using a field emission scanning electron microscope (FEG) to view and photograph microfossil specimens that are not coated by conductive material. The FEG microscope provides high electron flux and offers the option to capture images at low beam voltage. Balancing incident energy with absorbed energy from the detector leads to charge-free images of...