Institution
University of Fribourg
Education•Fribourg, 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.
Topics: Population, Glacier, Excited state, Hubbard model, Scattering
Papers published on a yearly basis
Papers
More filters
••
TL;DR: Barycentric interpolation is a variant of Lagrange polynomial interpolation that is fast and stable and deserves to be known as the standard method of polynometric interpolation.
Abstract: Barycentric interpolation is a variant of Lagrange polynomial interpolation that is fast and stable. It deserves to be known as the standard method of polynomial interpolation.
1,177 citations
••
TL;DR: The root-mean-square charge radius, rp, has been determined with an accuracy of 2 per cent by electron–proton scattering experiments, and the present most accurate value of rp (with an uncertainty of 1 per cent) is given by the CODATA compilation of physical constants.
Abstract: Considering that the proton is a basic subatomic component of all ordinary matter — as well as being ubiquitous in its solo role as the hydrogen ion H+ — there are some surprising gaps in our knowledge of its structure and behaviour. A collaborative project to determine the root-mean-square charge radius of the proton to better than the 1% accuracy of the current 'best' value suggests that those knowledge gaps may be greater than was thought. The new determination comes from a technically challenging spectroscopic experiment — the measurement of the Lamb shift (the energy difference between a specific pair of energy states) in 'muonic hydrogen', an exotic atom in which the electron is replaced by its heavier twin, the muon. The result is unexpected: a charge radius about 4% smaller than the previous value. The discrepancy remains unexplained. Possible implications are that the value of the most accurately determined fundamental constant, the Rydberg constant, will need to be revised — or that the validity of quantum electrodynamics theory is called into question. Here, a technically challenging spectroscopic experiment is described: the measurement of the muonic Lamb shift. The results lead to a new determination of the charge radius of the proton. The new value is 5.0 standard deviations smaller than the previous world average, a large discrepancy that remains unexplained. Possible implications of the new finding are that the value of the Rydberg constant will need to be revised, or that the validity of quantum electrodynamics theory is called into question. The proton is the primary building block of the visible Universe, but many of its properties—such as its charge radius and its anomalous magnetic moment—are not well understood. The root-mean-square charge radius, rp, has been determined with an accuracy of 2 per cent (at best) by electron–proton scattering experiments1,2. The present most accurate value of rp (with an uncertainty of 1 per cent) is given by the CODATA compilation of physical constants3. This value is based mainly on precision spectroscopy of atomic hydrogen4,5,6,7 and calculations of bound-state quantum electrodynamics (QED; refs 8, 9). The accuracy of rp as deduced from electron–proton scattering limits the testing of bound-state QED in atomic hydrogen as well as the determination of the Rydberg constant (currently the most accurately measured fundamental physical constant3). An attractive means to improve the accuracy in the measurement of rp is provided by muonic hydrogen (a proton orbited by a negative muon); its much smaller Bohr radius compared to ordinary atomic hydrogen causes enhancement of effects related to the finite size of the proton. In particular, the Lamb shift10 (the energy difference between the 2S1/2 and 2P1/2 states) is affected by as much as 2 per cent. Here we use pulsed laser spectroscopy to measure a muonic Lamb shift of 49,881.88(76) GHz. On the basis of present calculations11,12,13,14,15 of fine and hyperfine splittings and QED terms, we find rp = 0.84184(67) fm, which differs by 5.0 standard deviations from the CODATA value3 of 0.8768(69) fm. Our result implies that either the Rydberg constant has to be shifted by −110 kHz/c (4.9 standard deviations), or the calculations of the QED effects in atomic hydrogen or muonic hydrogen atoms are insufficient.
1,152 citations
••
TL;DR: Evidence is presented that wortmannin, a known inhibitor of respiratory-burst activity, acts on PtdIns 3-kinase, the enzyme producing PTDInsP3 from Ptd Ins(4,5)P2, which implies that PtdinsP3 production is not a primary event triggering elongation of actin filaments in neutrophils.
Abstract: Phosphatidylinositol 3,4,5-trisphosphate (PtdInsP3) is rapidly produced upon exposure of neutrophils to the chemoattractant N-formylmethionyl-leucylphenylalanine (fMLP), and has been proposed to act as a second messenger mediating actin polymerization and respiratory-burst activity. Here we present evidence that wortmannin, a known inhibitor of respiratory-burst activity, acts on PtdIns 3-kinase, the enzyme producing PtdInsP3 from PtdIns(4,5)P2. Pretreatment of 32P-labelled human neutrophils with 100 nM wortmannin totally abolished fMLP-mediated PtdInsP3 production, raised PtdInsP2 levels, and did not affect cellular PtdInsP and PtdIns contents. The inhibitory effect on PtdInsP3 formation in intact cells was dose-dependent, with an IC50 of approximately 5 nM. Similar results were obtained with PtdIns 3-kinase immunoprecipitated by antibodies against the p85 regulatory subunit: wortmannin totally inhibited PtdIns3P production in immunoprecipitates at concentrations of 10-100 nM (IC50 approximately 1 nM). These results illustrate the direct and specific inhibition of PtdIns 3-kinase by wortmannin. Since agonist-mediated respiratory-burst activation is most sensitive to wortmannin (IC50 = 12 nM), this suggests that agonist-mediated PtdInsP3 formation is indispensable for this cell response. Neutrophils pretreated with wortmannin develop oscillatory changes in F-actin content, but actin polymerization in response to fMLP is not inhibited. This, and the absence of PtdInsP3 under these conditions, are in agreement with a modulatory role for PtdInsP3 in cytoskeletal rearrangements, but imply that PtdInsP3 production is not a primary event triggering elongation of actin filaments in neutrophils.
1,140 citations
••
TL;DR: Interestingly, LY294002 and the lead compound on which it was designed, quercetin, as well as the closely related flavonoid myricetin bind PI3K in remarkably different orientations that are related to each other by 180 degrees rotations.
1,140 citations
••
University of Bayreuth1, Institut national de la recherche agronomique2, Canterbury of New Zealand3, Lund University4, Academy of Sciences of the Czech Republic5, Charles University in Prague6, Helmholtz Centre for Environmental Research - UFZ7, University of Tartu8, University of Fribourg9, Hungarian Academy of Sciences10, ETH Zurich11, University of Leeds12, CABI13, University of Bern14, Saint Petersburg State University15, National Academy of Sciences of Belarus16, Polish Academy of Sciences17, Joseph Fourier University18, Spanish National Research Council19, Potsdam Institute for Climate Impact Research20
TL;DR: It is emphasised that global warming has enabled alien species to expand into regions in which they previously could not survive and reproduce and management practices regarding the occurrence of 'new' species could range from complete eradication to tolerance.
Abstract: Climate change and biological invasions are key processes affecting global biodiversity, yet their effects have usually been considered separately. Here, we emphasise that global warming has enabled alien species to expand into regions in which they previously could not survive and reproduce. Based on a review of climate-mediated biological invasions of plants, invertebrates, fishes and birds, we discuss the ways in which climate change influences biological invasions. We emphasise the role of alien species in a more dynamic context of shifting species' ranges and changing communities. Under these circumstances, management practices regarding the occurrence of 'new' species could range from complete eradication to tolerance and even consideration of the 'new' species as an enrichment of local biodiversity and key elements to maintain ecosystem services.
1,138 citations
Authors
Showing all 6204 results
Name | H-index | Papers | Citations |
---|---|---|---|
Jens Nielsen | 149 | 1752 | 104005 |
Sw. Banerjee | 146 | 1906 | 124364 |
Hans Peter Beck | 143 | 1134 | 91858 |
Patrice Nordmann | 127 | 790 | 67031 |
Abraham Z. Snyder | 125 | 329 | 91997 |
Csaba Szabó | 123 | 958 | 61791 |
Robert Edwards | 121 | 775 | 74552 |
Laurent Poirel | 117 | 621 | 53680 |
Thomas Münzel | 116 | 1055 | 57716 |
David G. Amaral | 112 | 302 | 49094 |
F. Blanc | 107 | 1514 | 58418 |
Markus Stoffel | 102 | 620 | 50796 |
Vincenzo Balzani | 101 | 476 | 45722 |
Enrico Bertini | 99 | 865 | 38167 |
Sandeep Kumar | 94 | 1563 | 38652 |