Precise mass-dependent QED contributions to leptonic g-2 at order alpha^2 and alpha^3

Improved values for the two- and three-loop mass-dependent QED contributions to the anomalous magnetic moments of the electron, muon, and tau lepton are presented. The Standard Model prediction for the electron (g-2) is compared with its most precise recent measurement, providing a value of the fine-structure constant in agreement with a recently published determination. For the tau lepton, differences with previously published results are found and discussed. An updated value of the fine-structure constant is presented in "Note added after publication."Comment: 6 pages, 1 figure. v2: New determination of alpha presented (based on the recent electron g-2 measurement). v3: New formulae added in Sec.IIB. v4: Updated value of alpha presente

Electron Transfer Rate Maxima at Large Donor−Acceptor Distances

Because of their low mass, electrons can transfer rapidly over long (>15 Å) distances, but usually reaction rates decrease with increasing donor–acceptor distance. We report here on electron transfer rate maxima at donor–acceptor separations of 30.6 Å, observed for thermal electron transfer between an anthraquinone radical anion and a triarylamine radical cation in three homologous series of rigid-rod-like donor–photosensitizer–acceptor triads with p-xylene bridges. Our experimental observations can be explained by a weak distance dependence of electronic donor–acceptor coupling combined with a strong increase of the (outer-sphere) reorganization energy with increasing distance, as predicted by electron transfer theory more than 30 years ago. The observed effect has important consequences for light-to-chemical energy conversion

Reaction Rate Maxima at Large Distances between Reactants

One commonly thinks that two reactants need to come very close to one another in order for a chemical reaction to occur. This is true for most reaction types, but electron transfer is an exception in this regard. It is a well-documented fact that electron transfers can occur over long distances (≥15 Å), but it is much less well-known that theory predicts a regime in which electron transfer rates in crease with increasing distance between reactants. This contribution explains the physical origin of this counter-intuitive behavior, and it identifies a set of conditions that might facilitate its experimental observation

Intraspecific plant-soil feedback and intraspecific overyielding in Arabidopsis thaliana

1\. Understanding the mechanisms of community coexistence and ecosystem functioning may help to counteract the current biodiversity loss and its potentially harmful consequences. In recent years, plant-soil feedback that can, for example, be caused by below-ground microorganisms, has been suggested to play a role in maintaining plant coexistence and to be a potential driver of the positive relationship between plant diversity and ecosystem functioning. Most of the studies addressing these topics have focused on the species level. However, in addition to interspecific interactions, intraspecific interactions might be important for the structure of natural communities. 2\. Here we examine intraspecific coexistence and intraspecific diversity effects using 10 natural accessions of the model species Arabidopsis thaliana (L.) Heynh. We assessed morphological intraspecific diversity by measuring several above- and below-ground traits. We performed a plant-soil feedback experiment that was based on these trait differences between the accessions in order to determine whether A. thaliana experiences feedback at intraspecific level as a result of trait differences. We also experimentally tested the diversity-productivity relationship at intraspecific level. 3\. We found strong differences in above- and below-ground traits between the A. thaliana accessions. Overall, plant-soil feedback occurred at intraspecific level. However, accessions differed in the direction and strength of this feedback: some accessions grew better on their own soils, some on soils from other accessions. Furthermore, we found positive diversity effects within A. thaliana: accession mixtures produced a higher total above-ground biomass than accession monocultures. 4\. Differences between accessions in their feedback response could not be explained by morphological traits. Therefore, we suggest that they might have been caused by accession-specific accumulated soil communities, root exudates or by accession-specific resource use based on genetic differences that are not expressed in morphological traits. 5\. Synthesis. Our results provide some of the first evidence for intraspecific plant-soil feedback and intraspecific overyielding. These findings may have wider implications for the maintenance of variation within species and the importance of this variation for ecosystem functioning. Our results highlight the need for an increased focus on intraspecific processes in plant diversity research to fully understand the mechanisms of coexistence and ecosystem functioning.Ecology and Evolution, 4 (12), 2533-254

Exceptionally Long-Lived Photodriven Multi-Electron Storage without Sacrificial Reagents

Photoexcitation of a molecular pentad in the presence of Sc3+ in de-aerated CH3CN leads to a quinone dianion that is stable on the millisecond timescale. Light-driven electron accumulation on the quinone unit is sensitized by two Ru(bpy)32+ complexes in an intramolecular process, which relies on covalently attached triarylamine donors rather than on sacrificial reagents. Lewis acid–Lewis base interactions between Sc3+ and quinone dianion are responsible for the exceptionally long lifetime of this photoproduct. Our study of photoinduced multi-electron transfer is relevant in the greater context of solar energy conversion

Unusual Distance Dependences of Electron Transfer Rates

Usually the rates for electron transfer (kET) decrease with increasing donor–acceptor distance, but Marcus theory predicts a regime in which kET is expected to increase when the transfer distance gets longer. Until recently, experimental evidence for such counter-intuitive behavior had been very limited, and consequently this effect is much less well-known than the Gaussian free energy dependence of electron transfer rates leading to the so-called inverted driving-force effect. This article presents the theoretical concepts that lead to the prediction of electron transfer rate maxima at large donor–acceptor distances, and it discusses conditions that are expected to favor experimental observations of such behavior. It continues with a consideration of specific recent examples in which electron transfer rates were observed to increase with increasing donor–acceptor distance, and it closes with a discussion of the importance of this effect in the context of light-to-chemical energy conversion

Multitrophic biodiversity enhances ecosystem functions, services and ecological intensification in agriculture

One central challenge for humanity is to mitigate and adapt to an ongoing climate and biodiversity crisis while providing resources to a growing human population. Ecological intensification (EI) aims to maximize crop productivity while minimizing impacts on the environment, especially by using biodiversity to improve ecosystem functions and services. Many EI measures are based on trophic interactions between organisms (e.g. pollination, biocontrol). Here, we investigate how research on multitrophic effects of biodiversity on ecosystem functioning could advance the application of EI measures in agriculture and forestry. We review previous studies and use qualitative analyses of the literature to test how important variables such as land-use parameters or habitat complexity affect multitrophic diversity, ecosystem functions and multitrophic biodiversity–ecosystem functioning relationships. We found that positive effects of biodiversity on ecosystem functions are prevalent in production systems, largely across ecosystem function dimensions, trophic levels, study methodologies and different ecosystem functions, however, with certain context dependencies. We also found strong impacts of land use and management on multitrophic biodiversity and ecosystem functions. We detected knowledge gaps in terms of data from underrepresented geographical areas, production systems, organism groups and functional diversity measurements. Additionally, we identified several aspects that require more attention in the future, such as trade-offs between multiple functions, temporal dynamics, effects of climate change, the spatial scale of the measures and their implementation. This information will be vital to ensure that agricultural and forest landscapes produce resources for humanity sustainably within the environmental limits of the planet

Has the Covid-19 pandemic undermined public support for a diverse society? Evidence from a natural experiment in Germany

The Covid-19 pandemic has led to widespread worries that the health crisis is resulting in generalized hostility towards minorities and reduced support for a diverse society. Relying on a large survey of diversity attitudes in Germany fielded before and during the pandemic, we employ a quasi-experimental design to evaluate whether such a trend has occurred among the general public. Past work suggests two competing expectations – one anticipating a rise in hostility grounded in threat theories, and one anticipating stability grounded in public opinion research and theories of longer-term value change. Empirical results reveal generally high assent to socio-demographic diversity and minority accommodation, and remarkable stability during the pandemic period. Additionally, survey vignettes show strong and equally stable anti-discrimination norms that are inclusive of Asian-origin populations. Overall, results suggest that surges in racist incidents during the pandemic do not reflect analogous surges in hostility within the population at large