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Institution

University of Fribourg

EducationFribourg, Freiburg, Switzerland
About: University of Fribourg is a education organization based out in Fribourg, Freiburg, Switzerland. It is known for research contribution in the topics: Population & Glacier. The organization has 6040 authors who have published 14975 publications receiving 542500 citations. The organization is also known as: UNIFR & Universität Freiburg.


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Journal ArticleDOI
TL;DR: The data demonstrate that these usually poorly modulated neurons display context-dependent phasic activity in specific behavioral situations.
Abstract: The behavioral relationships of 396 striatum neurons with regular, tonically elevated discharge rates were studied. While monkeys performed a delayed gonogo task, neurons predominantly located in medial putamen responded with phasic depressions (n = 30) or activations (n = 5) to task-specific stimuli. Particularly effective was an instruction light preparing for movement or no-movement reactions, and an auditory signal associated with reward delivery. Stimuli triggering arm or mouth movements were less effective. The data demonstrate that these usually poorly modulated neurons display context-dependent phasic activity in specific behavioral situations.

172 citations

Journal ArticleDOI
TL;DR: This review focusses on the two most thoroughly studied holometabolous species, the fruitfly Drosophila melanogaster and the tobacco hornworm moth Manduca sexta, and emphasises the strength of the insect model system used in developmental studies, rendering it clearly the most important system for studies at the cellular level.

172 citations

Journal ArticleDOI
TL;DR: In this article, the axion-wind spin-precession frequencies of stored ultracold neutrons and 199Hg atoms were analyzed for axion induced oscillating electric dipole moment of the neutron and an axion wind spin precession effect.
Abstract: We report on a search for ultra-low-mass axion-like dark matter by analysing the ratio of the spinprecession frequencies of stored ultracold neutrons and 199Hg atoms for an axion-induced oscillating electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range 1024 eV ma 10 17 eV. Our null result sets the first laboratory constraints on the coupling of axion dark matter to gluons, which improve on astrophysical limits by up to 3 orders of magnitude, and also improves on previous laboratory constraints on the axion coupling to nucleons by up to a factor of 40.

172 citations

Journal ArticleDOI
TL;DR: It is concluded that sex-chromosome homomorphy in these tree frogs does not result from a recent turnover but is maintained over evolutionary timescales by occasional X-Y recombination, a result at odds with the view that sex chromosomes necessarily decay until they are replaced.
Abstract: Non-recombining sex chromosomes are expected to undergo evolutionary decay, ending up genetically degenerated, as has happened in birds and mammals. Why are then sex chromosomes so often homomorphic in cold-blooded vertebrates? One possible explanation is a high rate of turnover events, replacing master sex-determining genes by new ones on other chromosomes. An alternative is that X-Y similarity is maintained by occasional recombination events, occurring in sex-reversed XY females. Based on mitochondrial and nuclear gene sequences, we estimated the divergence times between European tree frogs (Hyla arborea, H. intermedia, and H. molleri) to the upper Miocene, about 5.4-7.1 million years ago. Sibship analyses of microsatellite polymorphisms revealed that all three species have the same pair of sex chromosomes, with complete absence of X-Y recombination in males. Despite this, sequences of sex-linked loci show no divergence between the X and Y chromosomes. In the phylogeny, the X and Y alleles cluster according to species, not in groups of gametologs. We conclude that sex-chromosome homomorphy in these tree frogs does not result from a recent turnover but is maintained over evolutionary timescales by occasional X-Y recombination. Seemingly young sex chromosomes may thus carry old-established sex-determining genes, a result at odds with the view that sex chromosomes necessarily decay until they are replaced. This raises intriguing perspectives regarding the evolutionary dynamics of sexually antagonistic genes and the mechanisms that control X-Y recombination.

172 citations

Journal ArticleDOI
TL;DR: In this article, the authors studied the behavior of snow in the Swiss Alps, in particular the duration of the seasonal snow-pack, on the basis of observational data from a number of Swiss climatological stations.
Abstract: ¶In many instances, snow cover and duration are a major controlling factor on a range of environmental systems in mountain regions. When assessing the impacts of climatic change on mountain ecosystems and river basins whose origin lie in the Alps, one of the key controls on such systems will reside in changes in snow amount and duration. At present, regional climate models or statistical downscaling techniques, which are the principal methods applied to the derivation of climatic variables in a future, changing climate, do not provide adequate information at the scales required for investigations in which snow is playing a major role. A study has thus been undertaken on the behavior of snow in the Swiss Alps, in particular the duration of the seasonal snow-pack, on the basis of observational data from a number of Swiss climatological stations. It is seen that there is a distinct link between snow-cover duration and height (i.e., temperature), and that this link has a specific “signature” according to the type of winter. Milder winters are associated with higher precipitation levels than colder winters, but with more solid precipitation at elevations exceeding 1,700–2,000 m above sea-level, and more liquid precipitation below. These results can be combined within a single diagram, linking winter minimum temperature, winter precipitation, and snow-cover duration. The resulting contour surfaces can then be used to assess the manner in which the length of the snow-season may change according to specified shifts in temperature and precipitation. While the technique is clearly empirical, it can be combined with regional climate model information to provide a useful estimate of the length of the snow season with snow cover, for various climate-impacts studies.

171 citations


Authors

Showing all 6204 results

NameH-indexPapersCitations
Jens Nielsen1491752104005
Sw. Banerjee1461906124364
Hans Peter Beck143113491858
Patrice Nordmann12779067031
Abraham Z. Snyder12532991997
Csaba Szabó12395861791
Robert Edwards12177574552
Laurent Poirel11762153680
Thomas Münzel116105557716
David G. Amaral11230249094
F. Blanc107151458418
Markus Stoffel10262050796
Vincenzo Balzani10147645722
Enrico Bertini9986538167
Sandeep Kumar94156338652
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202367
2022348
20211,110
20201,112
2019966
2018924