Affiner les résultats

Langue

Université de Fribourg

Novel iron tweezers complexes for hydrogenation and polymerization of olefins

Mafua, Roger ; Jenny, Titus A. (Dir.)

Thèse de doctorat : Université de Fribourg, 2006 ; no. 1503.

L’utilisation des complexes organométalliques comme catalyseurs est devenu un domaine très important de la chimie des matériaux. Cependant et malgré ce développement, les catalyseurs à base de fer(II) sont peu employés dans la polymérisation d’oléfines. Un de rares catalyseur utilisé dans ce contexte est le complexe tridenté diimine pyridine développé par Gibson et Brookhart....

Université de Fribourg

Truncating the memory time in nonequilibrium dynamical mean field theory calculations

Schüler, Michael ; Eckstein, Martin ; Werner, Philipp

In: Physical Review B, 2018, vol. 97, no. 24, p. 245129

The nonequilibrium Green's functions (NEGF) approach is a versatile theoretical tool, which allows to describe the electronic structure, spectroscopy, and dynamics of strongly correlated systems. The applicability of this method is, however, limited by its considerable computational cost. Due to the treatment of the full two-time dependence of the NEGF, the underlying equations of motion...

Université de Fribourg

Randomizing growing networks with a time-respecting null model

Ren, Zhuo-Ming ; Mariani, Manuel Sebastian ; Zhang, Yi-Cheng ; Medo, Matú?

In: Physical Review E, 2018, vol. 97, no. 5, p. 052311

Complex networks are often used to represent systems that are not static but grow with time: People make new friendships, new papers are published and refer to the existing ones, and so forth. To assess the statistical significance of measurements made on such networks, we propose a randomization methodology—a time- respecting null model—that preserves both the network's degree sequence...

Université de Fribourg

Revealing in-block nestedness: Detection and benchmarking

Solé-Ribalta, Albert ; Tessone, Claudio J. ; Mariani, Manuel S. ; Borge-Holthoefer, Javier

In: Physical Review E, 2018, vol. 97, no. 6, p. 062302

As new instances of nested organization—beyond ecological networks—are discovered, scholars are debating the coexistence of two apparently incompatible macroscale architectures: nestedness and modularity. The discussion is far from being solved, mainly for two reasons. First, nestedness and modularity appear to emerge from two contradictory dynamics, cooperation and competition. Second, ...

Université de Fribourg

Power enhancement via an ion-channel in a Raman free-electron laser

Huang, Xiaoli ; Zhang, Shi-Chang

In: Laser Physics, 2018, vol. 28, no. 9, p. 095002

As a high-power and high-efficiency coherent radiation source, the free-electron laser extends to two unique spectra: the region in the ultra-violet, x- and -rays, and the range in the millimeter- and terahertz-waves. Based on credible simulations, it is shown that the nonlinear power of a Raman free-electron laser in a millimeter wave range goes up and gets an increase of at least 9% when an...

Université de Fribourg

Colloidal fibers as structurant for worm-like micellar solutions

Zanchetta, Giuliano ; Mirzaagha, Shadi ; Guida, Vincenzo ; Zonfrilli, Fabio ; Caggioni, Marco ; Grizzuti, Nino ; Pasquino, Rossana ; Trappe, Veronique

In: Colloid and Polymer Science, 2018, vol. 296, no. 8, p. 1379–1385

We investigate the rheological properties of a simplified version of a liquid detergent composed of an aqueous solution of the linear alkylbenzene sulphonate (LAS) surfactant, in which a small amount of fibers made of hydrogenated castor oil (HCO) is dispersed. At the concentration typically used in detergents, LAS is in a worm-like micellar phase exhibiting a Maxwellian behavior. The...

Université de Fribourg

Metallic contact between MoS2 and Ni via Au nanoglue

Shi, Xinying ; Posysaev, Sergei ; Huttula, Marko ; Pankratov, Vladimir ; Hoszowska, Joanna ; Dousse, Jean?Claude ; Zeeshan, Faisal ; Niu, Yuran ; Zakharov, Alexei ; Li, Taohai ; Miroshnichenko, Olga ; Zhang, Meng ; Wang, Xiao ; Huang, Zhongjia ; Saukko, Sami ; González, Diego López ; Dijken, Sebastiaan van ; Alatalo, Matti ; Cao, Wei

In: Small, 2018, vol. 14, no. 22, p. 1704526

A critical factor for electronics based on inorganic layered crystals stems from the electrical contact mode between the semiconducting crystals and the metal counterparts in the electric circuit. Here, a materials tailoring strategy via nanocomposite decoration is carried out to reach metallic contact between MoS2 matrix and transition metal nanoparticles. Nickel nanoparticles (NiNPs) are ...

Université de Fribourg

Hypersatellite x-ray decay of $3d$ hollow-$K$-shell atoms produced by heavy-ion impact

Maillard, Yves-Patrick ; Dousse, Jean-Claude ; Hoszowska, Joanna ; Berset, Michel ; Mauron, Olivier ; Raboud, Pierre-Alexandre ; Kavčič, Matjaz ; Rzadkiewicz, J. ; Banaś, Dariusz ; Tökési, K.

In: Physical Review A, 2018, vol. 98, no. 1, p. 012705

We report on the radiative decay of double K-shell vacancy states produced in solid Ca, V, Fe, and Cu targets by impact with about 10 MeV/amu C and Ne ions. The resulting K hypersatellite x-ray emission spectra were measured by means of high- energy-resolution spectroscopy using a von Hamos bent crystal spectrometer. The experiment was carried out at the Philips variable energy cyclotron of...

Université de Fribourg

Linear response approach to active Brownian particles in time-varying activity fields

Merlitz, Holger ; Vuijk, Hidde D. ; Brader, Joseph M. ; Sharma, Abhinav ; Sommer, Jens-Uwe

In: The Journal of Chemical Physics, 2018, vol. 148, no. 19, p. 194116

In a theoretical and simulation study, active Brownian particles (ABPs) in three- dimensional bulk systems are exposed to time-varying sinusoidal activity waves that are running through the system. A linear response (Green-Kubo) formalism is applied to derive fully analytical expressions for the torque-free polarization profiles of non- interacting particles. The activity waves induce fluxes...