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Université de Fribourg

Winter weather affects asp viper Vipera aspis population dynamics through susceptible juveniles

Altwegg, Res ; Dummermuth, Stefan ; Anholt, Bradley R. ; Flatt, Thomas

In: Oikos, 2005, vol. 110 (1), p. 55

Detailed studies on mammals and birds have shown that the effects of climate variation on population dynamics often depend on population composition, because weather affects different subsets of a population differently. It is presently unknown whether this is also true for ectothermic animals such as reptiles. Here we show such an interaction between weather and demography for an ectothermic...

Université de Fribourg

Stabilizing factors interact in promoting host–parasite coexistence

Flatt, Thomas ; Scheuring, István

In: Journal of Theoretical Biology, 2004, vol. 228(2), p. 241

Understanding the mechanisms that promote coexistence among species is a fundamental problem in evolutionary ecology. Such mechanisms include environmental noise, spatial population structure, density dependence, and genetic variation. In natural populations such factors may exert combined effects on coexistence. Thus, to disentangle the contribution of several factors to coexistence, their...

Université de Fribourg

Assessing natural variation in genes affecting Drosophila lifespan

Flatt, Thomas

In: Mechanisms of Ageing and Development, 2004, vol. 125(3), p. 155

Université de Fribourg

Altitudinal differences in flower traits and reproductive allocation

Fabbro, Thomas ; Körner, Christian

In: Flora - Morphology, Distribution, Functional Ecology of Plants, 2004, vol. 99(1), p. 70

We tested whether alpine plants increase their effort to attract pollinators to compensate for assumed pollinator scarcity at high altitude. A three times larger fraction of the shoot was allocated to flowers in alpine plants (30 species, 2700m asl) compared to lowland plants (20 species, 600m asl), while leaf mass fraction did not differ between the altitudes. At high elevation, a three times...

Université de Fribourg

Accumulation of deleterious mutations in hybridogenetic organisms

Archetti, Marco

In: Journal of Theoretical Biology, 2005, vol. 234(2), p. 151

Université de Neuchâtel

Feasibility study of the geoelectric structure of the Araguainha impact, Brazil

Schnegg, Pierre-André ; Fontes, S. L.

In: Earth, Planets and Space, 2002, vol. 54, p. 597-606

We have re-examined the modelling of magnetotelluric and GDS soundings carried out on the Araguainha Dome, Brazil, published a few years ago, in the light of a new modelling method and with particular stress on the induction of the vertical component of the magnetic field, which had been neglected in the early publications. By careful selection of the period range of the measured data, we obtain...

Université de Neuchâtel

Sonde for Downhole Measurement of Water Turbidity and Dye Tracer Concentration

Schnegg, Pierre-André ; Bossy, F.

In: Articles of Geomagnetism Group at the University of Neuchâtel, Swets & Zeitlinger Lisse, 2001, p. 795-798

A new flow-through field fluorometer sonde has been designed for use in downhole tracer tests in 2’’ boreholes. The instrument is capable of determining the partial concentration of two dye tracers present simultaneously in the water. In addition, turbidity can be measured if the water is free of tracers. Although the sonde is aimed at boreholed hydrological investigations, it can also be...

Université de Neuchâtel

An inexpensive field fluorometer for hydrogeological tracer tests with three tracers and turbidity measurement

Schnegg, Pierre-André

In: Articles of the Geomagnetism Group at the University of Neuchâtel, Groundwater and Human Development, 2002, p. 1484-1488

The Geomagnetism Group of the University of Neuchâtel has recently designed a flow-through field fluorometer with added spectral capabilities for hydrological tracer tests. This instrument is equipped with four optical axes allowing water sample illumination with four independent light sources at different wavelenghs covering the full spectrum from UV to red. As many as three conveniently...

Université de Neuchâtel

Tracer Test Monitoring Using Wells with Long Screened Intervals : Benefits and Disadvantages

Schnegg, Pierre-André ; Flynn, Raymond Matthew ; Mallèn, German ; Perrochet, Pierre

In: Articles of the Centre d'Hydrogéologie at the University de Neuchâtel (CHYN), 2004, p. 1-4

Analytical and economic limitations often make fully-penetrating wells an attractive alternative for monitoring tracer test responses in aquifers. Modelling of breakthrough curves generated using long-screened (LS) wells in an unconfined gravel aquifer demonstrated that prolonged tailing could be reproduced with a series of partial breakthrough curves. The results suggested tracer arrived at...

Université de Neuchâtel

Fold interference patterns in the Late Palaeozoic Anti-Atlas belt of Morocco

Burkhard, Martin ; Caritg, Séverine ; Ducommun, Romain ; Helg, Urs ; Kopp, Lionel ; Sue, Christian

In: Terra Nova, 2004, vol. 16, p. 27-37

We document two phases of folding within the central part of the Late Palaeozoic Anti-Atlas chain of Morocco. A first generation of SW-NE folds involve a horizontal shortening of 10-20%, accommodated by polyharmonic buckle folding of contrasting wavelengths in Ordovician Jbel Bani quartzites and Devonian Jbel Rich carbonates. A second generation of folds with similar style and wavelengths in an...