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Université de Fribourg

Hybrid ligand-field theory/quantum chemical calculation of the fine structure and ZFS in lanthanide(III) complexes

Borel, Alain ; Helm, Lothar ; Daul, Claude A.

In: Chemical Physics Letters, 2004, vol. 383 (5-6), p. 584-591

Ligand field effects in lanthanide ions compounds have consequences for optical and magnetic spectroscopy. In the analysis of electron paramagnetic resonance spectra of Gd³⁺ complexes, a major role is played by the zero field splitting (ZFS), which is a high order consequence of the ligand field and the spin–orbit coupling. We present a general parameterized method and a computer program for...

Université de Fribourg

Application of the density functional theory derived orbital-free embedding potential to calculate the splitting energies of lanthanide cations in chloroelpasolite crystals

Zbiri, Mohamed ; Atanasov, Mihail ; Daul, Claude A. ; Garcia-Lastra, Juan Maria ; Wesolowski, Tomasz A.

In: Chemical Physics Letters, 2004, vol. 397(4-6), p. 441-446

Ligand field splitting energies of lanthanides Ln³⁺ (Ln = from Ce to Yb) in octahedral environment are calculated using the Hohenberg–Kohn theorems based orbital-free embedding formalism. The lanthanide cation is described at orbital level whereas its environment is represented by means of an additional term in the Kohn–Sham-like one-electron equations expressed as an explicit functional...

Université de Fribourg

The calculation of ESR parameters by density functional theory: the g- and A-tensors of Co(acacen)

Atanasov, Mihail ; Baerends, Evert Jan ; Baettig, Pio ; Bruyndonckx, Raf ; Daul, Claude A. ; Rauzy, Cédrick ; Zbiri, Mohamed

In: Chemical Physics Letters, 2004, vol. 399(4-6), p. 433-439

The new DFT based ligand field (LF) model is proposed to calculate the g- and A-tensors of [Co(acacen)] that is known to be a difficult case. The results obtained are compared with the ZORA approach implemented in ADF as well as with the experimental values. The calculations are in good agreement with the experimental data and demonstrate the ability of the method to reproduce the large...

Université de Fribourg

Hydrogen bond stabilization in Diels–Alder transition states: The cycloaddition of hydroxy-ortho-quinodimethane with fumaric acid and dimethylfumarate

Tamilmani, Venkatachalam ; Daul, Claude A. ; Lage Robles, Jaime ; Bochet, Christian G. ; Venuvanalingam, P.

In: Chemical Physics Letters, 2005, vol. 406 (4-6), p. 355-359

DFT investigations on the mechanism of Diels–Alder reactions of a hydroxy-ortho-quinodimethane with fumaric acid derivatives were performed to understand the origin of the syn or anti configuration of the adducts. The diene hydroxyl group and the dieneophile carboxyl group show hydrogen bonding in the transition state, significantly favouring the syn product. This reaction is poorly...

Université de Fribourg

Chromatic Orthogonality in Organic Synthesis

Bochet, Christian G.

In: Synlett, 2004, p. 2268-2274

A major challenge in organic synthesis is the selective reaction of a functional group in the presence of others. This can be achieved by using an appropriate reagent, tuned to react exclusively at the desired center. An alternate approach would be to use a single reagent, and to transmit from the outside the information as to where it should react. This account describes the use of light as a...

Université de Fribourg

Electron collisions with NO: Elastic scattering, vibrational excitation, and ²Πi1/2 ⇌ ²Π3/2 transitions

Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2005, vol. 38, p. 603

Absolute differential elastic and vibrational excitation cross sections have been measured for NO at 135° with resolution of the ²Π1/2 and ²Π3/2 spin-orbit components of the ground electronic term. The electronic fine structure excitation is dominated by the ³Σ⁻ and the ¹Δ resonances of NO⁻, the nonresonant contribution is very small. The cross section is very large, it has about the...

Université de Fribourg

Transitions between the ²Π₁͵₂ and ²Π₁͵₃ spin-orbit components of NO induced by impact of slow electrons

Allan, Michael

In: Physical Review Letters, 2004, vol. 93, p. 063201-63204

The electron impact cross section for the transition between the ²Π₁͵₂ and ²Π₁͵₃ spin-orbit components of the ground electronic term of nitric oxide, separated by 15 meV, has been measured as a function of electron energy at a scattering angle of Θ= 135°. It is dominated by the ³Σ⁻ and the ¹Δ resonances. Its magnitude is very large, at peak about equal to that of the elastic...

Université de Fribourg

Excitation of the four fundamental vibrations of CH₄ by electron impact near threshold

Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2005, vol. 38, p. 1679

Absolute differential elastic and vibrational excitation cross sections have been measured for CH₄ at 90° and from 0.1 to 1.5 eV, with the resolution of all four vibrational modes. Threshold peaks were observed in the excitation of the ν1, ν3 and ν4 modes, but not in the ν2 mode. These results are in good agreement with the recent calculation of Nishimura and Gianturco (2002 J. Phys. B:...

Université de Fribourg

The direct effect of leptin on skeletal muscle thermogenesis is mediated by substrate cycling between de novo lipogenesis and lipid oxidation

Solinas, Giovanni ; Summermatter, Serge ; Mainieri, Davide ; Gubler, Marcel ; Pirola, Luciano ; Wymann, Matthias P. ; Rusconi, Sandro ; Montani, Jean-Pierre ; Seydoux, Josiane

In: FEBS Letters, 2004, vol. 577 (3), p. 539-544

We report here studies that integrate data of respiration rate from mouse skeletal muscle in response to leptin and pharmacological interference with intermediary metabolism, together with assays for phosphatidylinositol 3-kinase (PI3K) and AMP-activated protein kinase (AMPK). Our results suggest that the direct effect of leptin in stimulating thermogenesis in skeletal muscle is mediated by...

Université de Fribourg

Substrate cycling between de novo lipogenesis and lipid oxidation: a thermogenic mechanism against skeletal muscle lipotoxicity and glucolipotoxicity

Dulloo, Abdul G. ; Gubler, Marcel ; Montani, Jean-Pierre ; Seydoux, Josiane ; Solinas, Giovanni

In: International Journal of Obesity, 2004, vol. 28 (Suppl. 4), p. S29-S37

Life is a combustion, but how the major fuel substrates that sustain human life compete and interact with each other for combustion has been at the epicenter of research into the pathogenesis of insulin resistance ever since Randle proposed a 'glucose-fatty acid cycle' in 1963. Since then, several features of a mutual interaction that is characterized by both reciprocality and dependency between...