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Université de Fribourg

Phase Responses to Light Pulses in Mice Lacking Functional per or cry Genes

Spoelstra, Kamiel ; Albrecht, Urs ; Horst, Gijsbertus T. J. van der ; Brauer, Verena ; Daan, Serge

In: Journal of Biological Rhythms, 2004, vol. 19 (6), p. 518-529

The phase-resetting properties of the circadian system in mice with a functional deletion in mCry1, mCry2, mPer1, or mPer2 were studied in 2 experiments. In experiment 1, mCry1-/- and mCry2-/- mice as well as mPer1Brdm1 and mPer2Brdm1 mutant mice were exposed to 15-min light pulses during the 1st cycle following entrainment, either early (external time [ExT] 20) or late (ExT 4) in the subjective...

Université de Fribourg

Circadian expression of the clock gene Per2 is altered in the ruin lizard (Podarcis sicula) when temperature changes

Magnone, Maria Chiara ; Jacobmeier, Birgit ; Bertolucci, Cristiano ; Foà, Augusto ; Albrecht, Urs

In: Molecular Brain Research, 2005, vol. 133, p. 281-286

When exposed to the cold, the body temperature of the ruin lizard (Podarcis sicula), an ectothermic vertebrate, comes into equilibrium with that low environmental temperature. During this time, the behavioral output of the circadian clock, locomotor activity, disappears. We tested the activity of the circadian clockwork at low temperature (6 °C) by following the expression of one of its...

Université de Fribourg

The clock gene Per2 influences the glutamatergic system and modulates alcohol consumption

Spanagel, Rainer ; Pendyala, Gurudutt ; Abarca, Carolina ; Zghoul, Tarek ; Sanchis-Segura, Carles ; Magnone, Maria Chiara ; Lascorz, Jesús ; Depner, Martin ; Holzberg, David ; Soyka, Michael ; Schreiber, Stefan ; Matsuda, Fumihiko ; Lathrop, Mark ; Schumann, Gunter ; Albrecht, Urs

In: Nature Medicine, 2004, vol. 11, p. 35-42

Period (Per) genes are involved in regulation of the circadian clock and are thought to modulate several brain functions. We demonstrate that Per2Brdm1 mutant mice, which have a deletion in the PAS domain of the Per2 protein, show alterations in the glutamatergic system. Lowered expression of the glutamate transporter Eaat1 is observed in these animals, leading to reduced uptake of glutamate by...

Université de Fribourg

Discovery of dumbbell-shaped CsHe(n) exciplexes in solid ⁴He

Nettels, Daniel ; Hofer, Adrian ; Moroshkin, Peter ; Müller-Siebert, Reinhard ; Ulzega, Simone ; Weis, Antoine

In: Physical Review Letters, 2005, vol. 94, p. 063001

We have observed several new spectral features in the fluorescence of cesium atoms implanted in the hcp phase of solid helium following laser excitation to the 6²P states. Based on calculations of the emission spectra using semi empirical Cs-He pair potentials the newly discovered lines can be assigned to the decay of specific Cs*He(n) exciplexes: an apple-shaped Cs(AП(3/2))He₂ and a...

Université de Fribourg

Optimization and performance of an optical cardiomagnetometer

Bison, Georg ; Wynands, Robert ; Weis, Antoine

In: Journal of the Optical Society of America: B, 2005, vol. 22 No. 1, p. 77-87

Cardiomagnetometry is a growing field of noninvasive medical diagnostics that has triggered a need for affordable high-sensitivity magnetometers. Optical pumping magnetometers (OPMs) are promising candidates for satisfying that need since it has been demonstrated that they can be used to map the magnetic field of the beating human heart. We discuss the principle of a phase-detecting OPM and...

Université de Fribourg

Towards a new information theory

Zhang, Yi-Cheng

In: International Journal of Modern Physics B, 2004, vol. 18, p. 2361-2365

Université de Fribourg

Ecology of active and passive players and their impact on information selection

Bianconi, Ginestra ; Laureti, Paolo ; Yu, Yi-Kou ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2004, vol. 332, p. 519-532

Is visitors’ attendance a fair indicator of a web site's quality? Internet sub-domains are usually characterized by power-law distributions of visits, thus suggesting a rich-get-richer process. If this is the case, the number of visits is not a relevant measure of quality. If, on the other hand, there are active players, i.e., visitors who can tell the value of the information available, better...

Université de Fribourg

Selection by pairwise comparisons with limited resources

Laureti, Paolo ; Mathiesen, Joachim ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2004, vol. 338, p. 596-604

We analyze different methods of sorting and selecting a set of objects by their intrinsic value, via pairwise comparisons whose outcome is uncertain. After discussing the limits of repeated Round Robins, two new methods are presented: The ran-fil requires no previous knowledge on the set under consideration, yet displaying good performances even in the least favorable case. The min-ent method...

Université de Fribourg

Aggregating partial, local evaluations to achieve global ranking

Laureti, Paolo ; Moret, Lionel ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2005, vol. 345, 3-4, p. 705-712

We analyze some voting models mimicking online evaluation systems intended to reduce the information overload. The minimum number of operations needed for a system to be effective is analytically estimated. When herding effects are present, linear preferential attachment marks a transition between trustful and biased reputations.

Université de Fribourg

Supply and demand law under limited information

Zhang, Yi-Cheng

We present a model for the supply-demand law with quality and limited information capability. We postulate that imperfect information permeates in almost all economic transactions to varying degrees. Through a simple model we outline a research agenda that re-examines many standard issues in economics. Our analysis shows that whereas imperfect information can be improved, it leads to new...