Factorization of leading chiral logarithms in the pion form factors

In the recently proposed framework of hard pion chiral perturbation theory, the leading chiral logarithms are predicted to factorize with respect to the energy dependence in the chiral limit. We have scrutinized this assumption in the case of vector and scalar pion form factors FV;S(s) by means of standard chiral perturbation theory and dispersion relations. We show that this factorization property is valid for the elastic contribution to the dispersion integrals for FV;S(s) but it is violated starting at three loops when the inelastic four-pion contributions arise.

From Broadstone to Zackenberg

Ecological networks are typically complex constructions of species and their interactions. During the last decade, the study of networks has moved from static to dynamic analyses, and has attained a deeper insight into their internal structure, heterogeneity, and temporal and spatial resolution. Here, we review, discuss and suggest research lines in the study of the spatio-temporal heterogeneity of networks and their hierarchical nature. We use case study data from two well-characterized model systems (the food web in Broadstone Stream in England and the pollination network at Zackenberg in Greenland), which are complemented with additional information from other studies. We focus upon eight topics: temporal dynamic space-for-time substitutions linkage constraints habitat borders network modularity individual-based networks invasions of networks and super networks that integrate different network types. Few studies have explicitly examined temporal change in networks, and we present examples that span from daily to decadal change: a common pattern that we see is a stable core surrounded by a group of dynamic, peripheral species, which, in pollinator networks enter the web via preferential linkage to the most generalist species. To some extent, temporal and spatial scales are interchangeable (i.e. networks exhibit ‘ergodicity’) and we explore how space-for-time substitutions can be used in the study of networks. Network structure is commonly constrained by phenological uncoupling (a temporal phenomenon), abundance, body size and population structure. Some potential links are never observed, that is they are ‘forbidden’ (fully constrained) or ‘missing’ (a sampling effect), and their absence can be just as ecologically significant as their presence. Spatial habitat borders can add heterogeneity to network structure, but their importance has rarely been studied: we explore how habitat generalization can be related to other resource dimensions. Many networks are hierarchically structured, with modules forming the basic building blocks, which can result in self-similarity. Scaling down from networks of species reveals another, finer-grained level of individual-based organization, the ecological consequences of which have yet to be fully explored. The few studies of individual-based ecological networks that are available suggest the potential for large intraspecific variance and, in the case of food webs, strong size-structuring. However, such data are still scarce and more studies are required to link individual-level and species-level networks. Invasions by alien species can be tracked by following the topological ‘career’ of the invader as it establishes itself within a network, with potentially important implications for conservation biology. Finally, by scaling up to a higher level of organization, it is possible to combine different network types (e.g. food webs and mutualistic networks) to form super networks, and this new approach has yet to be integrated into mainstream ecological research. We conclude by listing a set of research topics that we see as emerging candidates for ecological network studies in the near future.

Academic cooperation to foster research and advocacy competences in the occupied Palestinian territory (West Bank)

Palestinians living in the West Bank, a territory occupied by the State of Israel according to International Law, face deprived access to land and a limited ability to move freely which pertains to the presence of Israeli settlements and other infrastructure (closures, restricted or forbidden roads, etc.). This confinement has significant impacts on their economic and social livelihoods, and it is even worsening with the on-going construction of a 709 km long Barrier which mainly runs inside the West Bank. With regard to this situation, there is a clear need to strengthen the capacity of civil society and its representatives to apply sound research processes as a basis for improved advocacy for Palestinian human rights. Monitoring processes and tools are needed to assess the impacts of the Palestinians’ confinement, particularly in relation to the Barrier’s construction. Reliable data has also to be collected, managed, and above all, shared. These challenges have been addressed within the Academic Cooperation Palestine Project (ACPP) that brings together academic partners from the occupied Palestinian territory (oPt) West Bank (WB), and Switzerland as well as other international academic institutions and Palestinian governmental and non-governmental agencies. ACPP started in early 2011 and is designed as a large cooperation networking platform involving researchers, students, public servants and experts from the oPt WB. A large set of actions have already been developed during the first year of the project, including courses, training, and research actions. First relevant results and impacts of the different actions are presented in this paper. Taken as a whole, the project produces valuable results for all partners: useful advocacy material for the Palestinian partners, and a unique “real-scale laboratory” where investigations are jointly conducted to develop novel confinement and change indicators.

Dynamics of red blood cells in microporous membranes

We have performed microfluidic experiments with erythrocytes passing through a network of microchannels of 20–25 μm width and 5 μm of height. Red blood cells (RBCs) were flowing in countercurrent directions through microchannels connected by μm pores. Thereby, we have observed interesting flow dynamics. All pores were blocked by erythrocytes. Some erythrocytes have passed through pores, depending on the channel size and cell elasticity. Many RBCs split into two or more smaller parts. Two types of splits were observed. In one type, the lipid bilayer and spectrin network were cut at the same time. In the second type, the lipid bilayer reconnected, but the part of spectrin network stayed outside the cell forming a rope like structure, which could eventually break. The microporous membrane results in multiple breakups of the cells, which can have various clinical implications, e.g., glomerulus hematuria and anemia of patients undergoing dialysis. The cell breakup procedure is similar to the one observed in the droplet breakage of viscoelastic liquids in confinement.

Two-dimensional Lattice Gauge Theories with Superconducting Quantum Circuits

A quantum simulator of U(1) lattice gauge theories can be implemented with superconducting circuits. This allows the investigation of confined and deconfined phases in quantum link models, and of valence bond solid and spin liquid phases in quantum dimer models. Fractionalized confining strings and the real-time dynamics of quantum phase transitions are accessible as well. Here we show how state-of-the-art superconducting technology allows us to simulate these phenomena in relatively small circuit lattices. By exploiting the strong non-linear couplings between quantized excitations emerging when superconducting qubits are coupled, we show how to engineer gauge invariant Hamiltonians, including ring-exchange and four-body Ising interactions. We demonstrate that, despite decoherence and disorder effects, minimal circuit instances allow us to investigate properties such as the dynamics of electric flux strings, signaling confinement in gauge invariant field theories. The experimental realization of these models in larger superconducting circuits could address open questions beyond current computational capability.

Little evidence for release from herbivores as a driver of plant invasiveness from a multi-species herbivore-removal experiment

Enemy release is frequently posed as a main driver of invasiveness of alien species. However, an experimental multi-species test examining performance and herbivory of invasive alien, non-invasive alien and native plant species in the presence and absence of natural enemies is lacking. In a common garden experiment in Switzerland, we manipulated exposure of seven alien invasive, eight alien non-invasive and fourteen native species from six taxonomic groups to natural enemies (invertebrate herbivores), by applying a pesticide treatment under two different nutrient levels. We assessed biomass production, herbivore damage and the major herbivore taxa on plants. Across all species, plants gained significantly greater biomass under pesticide treatment. However, invasive, non-invasive and native species did not differ in their biomass response to pesticide treatment at either nutrient level. The proportion of leaves damaged on invasive species was significantly lower compared to native species, but not when compared to non-invasive species. However, the difference was lost when plant size was accounted for. There were no differences between invasive, non-invasive and native species in herbivore abundance. Our study offers little support for invertebrate herbivore release as a driver of plant invasiveness, but suggests that future enemy release studies should account for differences in plant size among species.

‘Idolatry’ and Religious Diversity: Thinking about the Other in Early Modern Europe

Idolatry is a key concept in the history of Western thinking about religion, as an all-encompassing category in which all religions more or less alien to the Christian tradition could be subsumed. From Late Antiquity to the Modern period, we can follow how the notion was put to work within Christian discourse to think about the religious “other. ” In fact, the word is almost ubiquitous in pre-modern debates on religion and the origins of religion. Theories on the nature and causes of “idolatry” framed much of the issue of “Religion” vs. the “religions,” and largely provided the conceptual space, in early modern Europe, in which religious anthropology would emerge. The present paper will investigate some aspects of the early modern discourse on idolatry, and its place in early modern discussions on the “diversity” of religions.

Herbaceous plant species invading natural areas tend to have stronger adaptive root foraging than other naturalized species

Although plastic root-foraging responses are thought to be adaptive, as they may optimize nutrient capture of plants, this has rarely been tested. We investigated whether nutrient-foraging responses are adaptive, and whether they pre-adapt alien species to become natural-area invaders. We grew 12 pairs of congeneric species (i.e., 24 species) native to Europe in heterogeneous and homogeneous nutrient environments, and compared their foraging responses and performance. One species in each pair is a USA natural-area invader, and the other one is not. Within species, individuals with strong foraging responses, measured as plasticity in root diameter and specific root length, had a higher biomass. Among species, the ones with strong foraging responses, measured as plasticity in root length and root biomass, had a higher biomass. Our results therefore suggest that root foraging is an adaptive trait. Invasive species showed significantly stronger root-foraging responses than non-invasive species when measured as root diameter. Biomass accumulation was decreased in the heterogeneous vs. the homogeneous environment. In aboveground, but not belowground and total biomass, this decrease was smaller in invasive than in non-invasive species. Our results show that strong plastic root-foraging responses are adaptive, and suggest that it might aid in pre-adapting species to becoming natural-area invaders.

Resolving diffusion in clay minerals at different time scales: Combination of experimental and modeling approaches

Since no single experimental or modeling technique provides data that allow a description of transport processes in clays and clay minerals at all relevant scales, several complementary approaches have to be combined to understand and explain the interplay between transport relevant phenomena. In this paper molecular dynamics simulations (MD) were used to investigate the mobility of water in the interlayer of montmorillonite (Mt), and to estimate the influence of mineral surfaces and interlayer ions on the water diffusion. Random Walk (RW) simulations based on a simplified representation of pore space in Mt were used to estimate and understand the effect of the arrangement of Mt particles on the meso- to macroscopic diffusivity of water. These theoretical calculations were complemented with quasielastic neutron scattering (QENS) measurements of aqueous diffusion in Mt with two pseudo-layers of water performed at four significantly different energy resolutions (i.e. observation times). The size of the interlayer and the size of Mt particles are two characteristic dimensions which determine the time dependent behavior of water diffusion in Mt. MD simulations show that at very short time scales water dynamics has the characteristic features of an oscillatory motion in the cage formed by neighbors in the first coordination shell. At longer time scales, the interaction of water with the surface determines the water dynamics, and the effect of confinement on the overall water mobility within the interlayer becomes evident. At time scales corresponding to an average water displacement equivalent to the average size of Mt particles, the effects of tortuosity are observed in the meso- to macroscopic pore scale simulations. Consistent with the picture obtained in the simulations, the QENS data can be described using a (local) 3D diffusion at short observation times, whereas at sufficiently long observation times a 2D diffusive motion is clearly observed. The effects of tortuosity measured in macroscopic tracer diffusion experiments are in qualitative agreement with RW simulations. By using experimental data to calibrate molecular and mesoscopic theoretical models, a consistent description of water mobility in clay minerals from the molecular to the macroscopic scale can be achieved. In turn, simulations help in choosing optimal conditions for the experimental measurements and the data interpretation. (C) 2014 Elsevier B.V. All rights reserved.

Compactified N = 1 supersymmetric Yang-Mills theory on the lattice: continuity and the disappearance of the deconfinement transition

Fermion boundary conditions play a relevant role in revealing the confinement mechanism of N=1 supersymmetric Yang-Mills theory with one compactified space-time dimension. A deconfinement phase transition occurs for a sufficiently small compactification radius, equivalent to a high temperature in the thermal theory where antiperiodic fermion boundary conditions are applied. Periodic fermion boundary conditions, on the other hand, are related to the Witten index and confinement is expected to persist independently of the length of the compactified dimension. We study this aspect with lattice Monte Carlo simulations for different values of the fermion mass parameter that breaks supersymmetry softly. We find a deconfined region that shrinks when the fermion mass is lowered. Deconfinement takes place between two confined regions at large and small compactification radii, that would correspond to low and high temperatures in the thermal theory. At the smallest fermion masses we find no indication of a deconfinement transition. These results are a first signal for the predicted continuity in the compactification of supersymmetric Yang-Mills theory.

Pressure from the vacuum of confined spinor matter

Charged spinor matter field is quantized in a spatial region bounded by two parallel neutral plates. The most general set of boundary conditions ensuring the confinement of matter within the plates is considered. We study a response of the vacuum of the confined matter to the background uniform magnetic field which is directed orthogonally to the plates. It is proven that, in the case of a sufficiently strong magnetic field, the vacuum pressure onto the plates is positive and independent of the boundary condition, as well as of the distance between the plates.

Rapid divergence in physiological and life-history traits between northern and southern populations of the British introduced neo-species, Senecio squalidus

Alien plants provide a unique opportunity to study evolution in novel environments, but relatively little is known about the extent to which they become locally adapted to different environments across their new range. Here, we compare northern and southern populations of the introduced species Senecio squalidus in Britain; S. squalidus has been in southern Britain for approximately 200 years and reached Scotland only about 50 years ago. We conducted common garden experiments at sites in the north and south of the species’ range in Britain. We also conducted glasshouse and growth chamber experiments to test the hypothesis that southern genotypes flower later, are more drought-tolerant, germinate and establish better at warmer temperatures, and are less sensitive to cold stress than their more northern counterparts. Results from the common garden experiments are largely consistent with the hypothesis of rapid adaptive divergence of populations of the species within the introduced range, with genotypes typically showing a home-site advantage. Results from the glasshouse and growth chamber experiments demonstrate adaptive divergence in ability to tolerate drought stress and high temperatures, as well as in phenology. In particular, southern genotypes were more tolerant of dry conditions and high temperatures and they flowered later than northern genotypes. Our results show that rapid local adaptation can occur in alien species, and they have implications for our understanding of the ecological genetics of range expansion of introduced weeds.