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Université de Fribourg

Mass transport properties of the tetrahydronaphthalene/n-dodecane mixture measured by investigating non-equilibrium fluctuations

Croccolo, Fabrizio ; Scheffold, Frank ; Bataller, Henri

In: Comptes Rendus Mécanique, 2013, vol. 341, no. 4–5, p. 378–385

We present preliminary near-field light scattering (NFS) data concerning the analysis of the static power spectrum and of the relaxation time constant as a function of the wave vector for non-equilibrium fluctuations (NEFs). The goal of these measurements is to obtain information about the Soret and the mass diffusion coefficients of a binary mixture undergoing thermodiffusion. In particular, we...

Université de Fribourg

Potential theory for directed networks

Zhang, Qian-Ming ; Lü, Linyuan ; Wang, Wen-Qiang ; Zhu, Yu-Xiao ; Zhou, Tao

In: PLoS ONE, 2013, vol. 8, no. 2, p. e55437

Uncovering factors underlying the network formation is a long-standing challenge for data mining and network analysis. In particular, the microscopic organizing principles of directed networks are less understood than those of undirected networks. This article proposes a hypothesis named potential theory, which assumes that every directed link corresponds to a decrease of a unit potential and...

Université de Fribourg

Does Bilateral Trust Affect International Movement of Goods and Labor?

Spring, Eva ; Grossmann, Volker

(Working Papers SES ; 442)

Trust in the citizens of a potential partner country may affect the decision to trade with or to migrate to a foreign country. This paper employs panel data to examine the causal impact of such bilateral trust on international trade and migration patterns. We apply instrumental variables (IV) approaches that capture the exogenous variance of bilateral trust separately with eight indicators of...

Université de Fribourg

The influence of constrictivity on the effective transport properties of porous layers in electrolysis and fuel cells

Holzer, L. ; Wiedenmann, Daniel ; Münch, B. ; Keller, L. ; Prestat, M. ; Gasser, Ph. ; Robertson, I. ; Grobéty, Bernard

In: Journal of Materials Science, 2013, vol. 48, no. 7, p. 2934-2952

The aim of the present investigation is to define microstructure parameters, which control the effective transport properties in porous materials for energy technology. Recent improvements in 3D-imaging (FIB-nanotomography, synchrotron X-ray tomography) and image analysis (skeletonization and graph analysis, transport simulations) open new possibilities for the study of microstructure effects. In...

Université de Fribourg

Thermodiffusion of the tetrahydronaphthalene and dodecane mixture under high pressure and in porous medium

Giraudet, Cédric ; Croccolo, Fabrizio ; Galliero, Guillaume ; Pijaudier-Cabot, Gilles ; Vaerenbergh, Stefan Van ; Saghir, M. Ziad ; Montel, François ; Bataller, Henri

In: Comptes Rendus Mécanique, 2013, vol. 341, no. 4-5, p. 340-347

A thermodiffusion cell is used in order to perform Soret experiments on binary mixtures at high pressure and in the presence of a porous medium. The cell is validated at atmospheric pressure with toluene/hexane and the tetrahydronaphthalene/dodecane mixtures. The mass separation follows a diffusive behaviour when the cell is filled with a porous medium. At least three times the relaxation time is...

Université de Fribourg

Prediction accuracy and sloppiness of log-periodic functions

Brée, David S. ; Challet, Damien ; Peirano, Pier Paolo

In: Quantitative Finance, 2013, vol. 13, no. 2, p. 275-280

We show that log-periodic power-law (LPPL) functions are intrinsically very hard to fit to time series. This comes from their sloppiness, the squared residuals depending very much on some combinations of parameters and very little on other ones. The time of singularity that is supposed to give an estimate of the day of the crash belongs to the latter category. We discuss in detail why and how the...

Université de Fribourg

Electric-Field-Induced Polar Order and Localization of the Confined Electrons in LaAlO₃/SrTiO₃ Heterostructures

Rössle, Matthias ; Kim, Kyung Wan ; Dubroka, Adam ; Maršík, Premysl ; Wang, Chen Nan ; Jany, R. ; Richter, C. ; Mannhart, J. ; Schneider, C. W. ; Frano, A. ; Wochner, P. ; Lu, Y. ; Keimer, B. ; Shukla, D. K. ; Strempfer, J. ; Bernhard, Christian

In: Physical Review Letters, 2013, vol. 110, no. 13, p. 136805

With ellipsometry, x-ray diffraction, and resistance measurements we investigated the electric-field effect on the confined electrons at the LaAlO₃/SrTiO₃ interface. We obtained evidence that the localization of the electrons at negative gate voltage is induced, or at least enhanced, by a polar phase transition in SrTiO₃ which strongly reduces the lattice polarizability and the subsequent...

Université de Fribourg

Depth profile of the ferromagnetic order in a YBa₂Cu₃O₇/La2/3Ca1/3MnO₃ superlattice on a LSAT substrate: A polarized neutron reflectometry study

Uribe-Laverde, Miguel Angel ; Satapathy, Dillip Kumar ; Marozau, Ivan ; Malik, Vivek Kumar ; Das, Saikat ; Sen, Kaushik ; Stahn, J. ; Rühm, A. ; Kim, Joo Young ; Keller, T. ; Devishvili, A. ; Toperverg, B. P. ; Bernhard, Christian

In: Physical Review B - Condensed Matter and Materials Physics, 2013, vol. 87, no. 11, p. 115105

Using polarized neutron reflectometry (PNR) we have investigated a [YBa₂Cu₃O₇(10 nm)/La2/3Ca1/3MnO₃(9 nm)]₁₀ (YBCO/LCMO) superlattice grown by pulsed laser deposition on a La0.3Sr0.7Al0.65Ta0.35O₃ (LSAT) substrate. Due to the high structural quality of the superlattice and the substrate, the specular reflectivity...

Université de Fribourg

Endothelial NF-κB : the remote controller of the backyard fire in the vascular wall?

Yang, Zhihong

In: Cardiovascular Research, 2013, vol. 97, no. 1, p. 8-9

It has been established in the past few decades that the vascular endothelium, the monolayer of cells covering the inner surface of the vessel wall, functions as a master regulator to maintain the physiological integrity of vascular function and structure by actively releasing numerous vasoactive hormones that control smooth muscle cell contraction and proliferation and inflammatory cell adhesion...