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Université de Fribourg

Heterogenous human dynamics in intra- and inter-day time scales

Wang, Peng ; Lei, T. ; Yeung, Chi-Ho ; Wang, Bing-Hong

In: Europhysics Letters, 2011, vol. 94, no. 1, p. 18005

In this paper, we study two large data sets containing the information of two different human behaviors: blog-posting and wiki-revising. In both cases, the interevent time distributions decay as power laws at both individual and population level. Unlike previous studies, we put emphasis on time scales and obtain heterogeneous decay exponents in the intra- and inter-day range for the same dataset....

Université de Fribourg

Evidence of a Precursor Superconducting Phase at Temperatures as High as 180 K in RBa₂Cu₃O7-δ (R=Y,Gd,Eu) Superconducting Crystals from Infrared Spectroscopy

Dubroka, Adam ; Rössle, Matthias ; Kim, Kyung Wan ; Malik, Vivek Kumar ; Munzar, Dominik ; Basov, D. N. ; Schafgans, A. A. ; Moon, S. J. ; Lin, C. T. ; Haug, D. ; Hinkov, V. ; Keimer, B. ; Wolf, Th. ; Storey, J. G. ; Tallon, Jeffery L. ; Bernhard, Christian

In: Physical Review Letters, 2011, vol. 106, no. 4, p. 047006

We show that a multilayer analysis of the infrared c-axis response of RBa₂Cu₃O7-δ (R=Y,Gd,Eu) provides important new information about the anomalous normal-state properties of underdoped cuprate high temperature superconductors. In addition to competing correlations which give rise to a pseudogap that depletes the low-energy electronic states below...

Université de Fribourg

Double L₃M ionization of Pd induced by impact with medium-energy electrons

Cao, Wei ; Dousse, Jean-Claude ; Hoszowska, Joanna ; Kavčič, Matjaz ; Kayser, Yves ; Schenker, Jean-Luc ; Žitnik, M.

In: Physical Review A: atomic, molecular and optical physics, 2011, vol. 83, no. 2, p. 022708

The electron-induced L₃M two-step double ionization cross sections of metallic Pd were determined experimentally for incident electron beam energies ranging from the double ionization threshold up to 18 keV. The double L₃M ionization cross sections were derived from the intensity ratios (ILαM:ILα) of the resolved M satellites to the parent diagram lines. The sample was...

Université de Fribourg

High temperature magnetic order in zinc sulfide doped with copper

Owens, Frank J. ; Gladczuk, L. ; Szymczak, R. ; Dluzewski, P. ; Wisniewski, A. ; Szymczak, H. ; Golnik, A. ; Bernhard, Christian ; Niedermayer, Ch.

In: Journal of Physics and Chemistry of Solids, 2011, p. -

We report the first observation of magnetic order above room temperature in zinc sulfide doped with Cu²⁺ made by a simple sintering process and detected by ferromagnetic resonance (FMR), SQUID magnetometry and the μSR experiments. FMR study shows nonzero absorption above room temperature indicating a high value of Curie temperature. Field-cooled and zero-field-cooled magnetization data...

Université de Fribourg

High-resolution experiments and B-spline R-matrix calculations for elastic electron scattering from krypton

Zatsarinny, O. ; Bartschat, K. ; Allan, Michael

In: Physical Review A: Atomic, Molecular, and Optical Physics, 2011, vol. 83, no. 3, p. 032713

In a joint experimental and theoretical effort, we carried out a detailed study of elastic electron scattering from Kr atoms. Absolute angle-differential cross sections for elastic electron scattering were measured over the energy range 0.3-9.8 eV with an energy width of about 13 meV at scattering angles between 0° and 180°. Excellent agreement is obtained between our experimental data and...

Université de Fribourg

Valence band structure of the Si(331)-(12 × 1) surface reconstruction

Battaglia, Corsin ; Schwier, Eike Fabian ; Monney, Claude ; Didiot, Clément ; Mariotti, Nicolas ; Gaál-Nagy, Katalin ; Onida, Giovanni ; Garnier, Michael Gunnar ; Aebi, Philipp

In: Journal of Physics: Condensed Matter, 2011, vol. 23, no. 13, p. 135003

Using angle-resolved photoelectron spectroscopy we investigate the electronic valence band structure of the Si(331)-(12 × 1) surface reconstruction for which we recently proposed a structural model containing silicon pentamers as elementary structural building blocks. We find that this surface, reported to be metallic in a previous study, shows a clear band gap at the Fermi energy, indicating...

Université de Fribourg

Information filtering via weighted heat conduction algorithm

Liu, Jian-Guo ; Guo, Qiang ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2011, p. -

In this paper, by taking into account effects of the user and object correlations on a heat conduction (HC) algorithm, a weighted heat conduction (WHC) algorithm is presented. We argue that the edge weight of the user–object bipartite network should be embedded into the HC algorithm to measure the object similarity. The numerical results indicate that both the accuracy and diversity could be...