In: Science, 2005, vol. 299, no. 5614, p. 1898 - 1902
Uncertainty is critical in the measure of information and in assessing the accuracy of predictions. It is determined by probability P, being maximal at P = 0.5 and decreasing at higher and lower probabilities. Using distinct stimuli to indicate the probability of reward, we found that the phasic activation of dopamine neurons varied monotonically across the full range of...
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In: Science, 2001, vol. 307, no. 5715, p. 1642-1645
It is important for animals to estimate the value of rewards as accurately as possible. Because the number of potential reward values is very large, it is necessary that the brain's limited resources be allocated so as to discriminate better among more likely reward outcomes at the expense of less likely outcomes. We found that midbrain dopamine neurons rapidly adapted to the information provided...
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In: Nature, 2001, vol. 414, p. 204-208
In Drosophila and mice, olfactory receptor neurons (ORNs) expressing the same receptors have convergent axonal projections to specific glomerular targets in the antennal lobe/olfactory bulb, creating an odour map in this first olfactory structure of the central nervous system1, 2, ³. Projection neurons of the Drosophila antennal lobe send dendrites into...
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In: Nature, 2003, vol. 426, p. 620
The group of enzymes known as TOR (for 'target of rapamycin') kinases regulates cell growth and proliferation in response to nutrients and hormone-dependent mitogenic signals1, 2. Here we show that TOR deficiency in the nematode Caenorhabditis elegans more than doubles its natural lifespan. This new function for TOR signalling in ageing control may represent a link between...
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In: Science 295(5554): 485 - 488, 2002, 2002, vol. 295, no. 5554, p. 485-488
Immigrants to habitats occupied by conspecific organisms are usually expected to be competitively inferior, because residents may be locally adapted. If residents are inbred, however, mating between immigrants and residents results in offspring that may enjoy a fitness advantage from hybrid vigor. We demonstrate this effect experimentally in a natural Daphnia metapopulation in which...
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Thèse de doctorat : Université de Fribourg, 2005.
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In: Physical Review B, 2006, vol. 74, p. 045126
The thermodynamical stabilities for the series of metal borohydrides M(BH₄)n (M=Li, Na, K, Cu, Mg, Zn, Sc, Zr, and Hf; n=1–4) have been systematically investigated by first-principles calculations. The results indicated that an ionic bonding between Mⁿ⁺ cations and [BH₄]⁻ anions exists in M(BH₄)n, and the charge...
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In: Journal of Physics: Condensed Matter, 2006, vol. 18, p. L339–L346
We investigate phase separation and structural evolution in a complex food colloid (casein micelles) and biopolymer (xanthan) mixture using small-angle light scattering. We demonstrate that phase separation is induced by a depletion mechanism, and that the resulting coexistence curve can be described by osmotic equilibrium theory for mixtures of colloids and polymer chains in a background...
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In: Journal of Physics: Condensed Matter, 2006, vol. 18, p. L363-L369
The static structure factor S(q) is measured for a set of deionized latex dispersions with different numbers of ionizable surface groups per particle and similar diameters. For a given volume fraction, the height of the main peak of S(q), which is a direct measure of the spatial ordering of latex particles, does not increase monotonically with the number of ionizable...
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In: Physical Review Letters, 2006, vol. 95, p. 267201
The compound TlCuCl₃ represents a model system of dimerized quantum spins with strong interdimer interactions. We investigate the triplet dispersion as a function of temperature by inelastic neutron scattering experiments on single crystals. By comparison with a number of theoretical approaches we demonstrate that the description of Troyer, Tsunetsugu, and Würtz [Phys. Rev. B 50, 13 515...
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