University of Fribourg

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

Alien plant species with a wider global distribution are better able to capitalize on increased resource availability

Abstract: • A high ability of alien plant species to capitalize on increases in resource availability has been suggested as an explanation for being globally successful. Here, we tested this hypothesis meta-analytically using existing data from experiments manipulating plant resources (light, water and nutrients). • From these studies we extracted the response to resource increase of biomass, as an indicator of plant performance, and the responses of two traits related to resource capture: root : shoot ratio and specific leaf area (SLA). For 211 species recorded in the Global Compendium of Weeds, we assessed the relationship between effect sizes from such studies and the number of global regions where a species was established. • We found that globally widespread species exhibited greater biomass responses to increases in resources overall, compared to less widespread species. Root : shoot ratio and SLA responses to increased resource availability were not related to species global distribution. • In general, globally widespread alien plant species were better able to capitalize on increased availability of resources, through achieving increased growth and biomass accumulation, while greater plasticity of key resource-capture traits per se did not appear to be related to greater success.

AgO investigated by photoelectron spectroscopy: Evidence for mixed valence

Abstract: We present photoelectron spectroscopy investigations of in-situ prepared AgO. The sample was prepared by room temperature oxidation of Ag in an electron cyclotron resonance ${\mathrm{O}}_{2}$ plasma. In contrast to other measurements based on ex situ prepared AgO powder samples, our investigations show a distinct double peak structure of the O $1s$ signal with a remarkable chemical shift of 2.9 eV between the two O $1s$ components. These two components can not be motivated from a crystallographic point of view as the oxygen sites are all equivalent in the unit cell. We interpret this double peak structure as a characteristic feature of AgO and discuss it in terms of mixed valences.

Applicability of electrical resistivity tomography monitoring to coarse blocky and ice-rich permafrost landforms

Abstract: The inversion and interpretation of electrical resistivity tomography (ERT) data from coarse blocky and ice-rich permafrost sites are challenging due to strong resistivity contrasts and high contact resistances. To assess temporal changes during ERT monitoring (ERTM), corresponding inversion artefacts have to be separated from true subsurface changes. Appraisal techniques serve to analyse an ERTM data set from a rockglacier, including synthetic modelling, the depth of investigation index technique and the so-called resolution matrix approach. The application of these methods led step by step to the identification of unreliable model regions and thus to the improvement in interpretation of temporal resistivity changes. An important result is that resistivity values of model regions with strong resistivity contrasts and highly resistive features are generally of critical reliability, and resistivity changes within or below the ice core of a rockglacier should therefore not be interpreted as a permafrost signal. Conversely, long-term degradation phenomena in terms of warming of massive ground ice at the permafrost table are detectable by ERTM.

Rarefied Basis Sets for the Calculation of Optical Tensors. 1. The Importance of Gradients on Hydrogen Atoms for the Raman Scattering Tensor

Abstract: A systematic investigation has been undertaken on the basis set requirements for the calculation of optical tensors. In this first of a series of two papers we present a comparison of the performance of various basis sets for the calculation of the Raman and Raman optical activity (ROA) scattering tensor. We show that it is possible to obtain results in excellent qualitative and in reasonable quantitative agreement with those from complex sets by highly rarefied sets provided the vibrational problem is solved in a separate calculation. It is shown that, for hydrogen-containing molecules, a basic requirement for the effectiveness of rarefied basis sets is the proper description of gradients of electronic tensors on these atoms and that this can only be achieved by the inclusion of moderately diffuse p-type functions on these atoms. In addition, the correct rendering of the Raman and ROA tensor for main atom−hydrogen and main atom−deuterium stretching vibrations requires a layer of diffuse functions with va...