Habitat suitability models based on expert knowledge – a comparison of fuzzy set approaches using the example of Western Mediterranean dwarf rush communities

This study examines the ability of two fuzzy logic approaches to adequately describe the realised niche of a specific target taxon in Western Mediterranean dwarf rush communities (I s o e t o - N a n o j u n c e t e a ). In a strongly fuzzified approach, which required a large set of rules, all independent and dependent variables are coded as linguistic variables. This approach is compared to a different approach which defines habitat suitability through a membership function per taxon and independent variable. Both approaches yield acceptable results. Advantages and disadvantages of both fuzzy logic approaches are discussed. It is shown that this method is well suited for the description of realised niches and that the approach should be chosen depending on the question of the study. Knowledge based model building is a crucial step for the integration of rare taxa in landscape models.Ausgehend von der Frage, ob es möglich ist, für selten auftretende Pflanzenarten oder Vegetationstypen auf der Grundlage vorhandenen Expertenwissens ein Modell zu erstellen, das die Realnische des Zieltaxons zutreffend beschreibt, werden hier zwei Fuzzy-Logik-Ansätze verglichen. Am Beispiel westmediterraner Zwergbinsenrasen (I s o e t o - N a n o j u n c e t e a ) wird untersucht, ob sich ein weitgehend fuzzifizierter Ansatz, der alle Eingangs- und Ergebnisvariablen als linguistische Variablen behandelt und einen umfangreichen Regelsatz benötigt, sich besser eignet als ein Ansatz, bei dem für jedes Zieltaxon die Habitateignung über eine Zugehörigkeitsfunktion pro Umweltvariable formuliert wird. Die Modellierung gelingt mit beiden Verfahren ähnlich gut. Die Vor- und Nachteile der beiden Fuzzy-Logik-Ansätze werden abgewogen. Insgesamt wird klar, dass sich dieser Weg für die Beschreibung der Realnische gut eignet und die Wahl der Variante in Abhängigkeit von der Fragestellung erfolgen sollte. Die Erarbeitung wissensbasierter Habitateignungsmodelle stellt einen sinnvollen Schritt dar, um seltenere Taxa in Landschaftsmodelle mit aufzunehmen

Composite Topological Excitations in Ferromagnet-Superconductor Heterostructures

We investigate the formation of a new type of composite topological excitation -- the skyrmion-vortex pair (SVP) -- in hybrid systems consisting of coupled ferromagnetic and superconducting layers. Spin-orbit interaction in the superconductor mediates a magnetoelectric coupling between the vortex and the skyrmion, with a sign (attractive or repulsive) that depends on the topological indices of the constituents. We determine the conditions under which a bound SVP is formed, and characterize the range and depth of the effective binding potential through analytical estimates and numerical simulations. Furthermore, we develop a semiclassical description of the coupled skyrmion-vortex dynamics and discuss how SVPs can be controlled by applied spin currents.Comment: Final version accepted by Physical Review Letters; 9 pages, 5 figure

A Precedent for Test Validation

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Anomalous edge states and the bulk-edge correspondence for periodically-driven two dimensional systems

Recently, several authors have investigated topological phenomena in periodically driven systems of noninteracting particles. These phenomena are identified through analogies between the Floquet spectra of driven systems and the band structures of static Hamiltonians. Intriguingly, these works have revealed phenomena that cannot be characterized by analogy to the topological classification framework for static systems. In particular, in driven systems in two dimensions (2D), robust chiral edge states can appear even though the Chern numbers of all the bulk Floquet bands are zero. Here, we elucidate the crucial distinctions between static and driven 2D systems, and construct a new topological invariant that yields the correct edge-state structure in the driven case. We provide formulations in both the time and frequency domains, which afford additional insight into the origins of the “anomalous” spectra that arise in driven systems. Possibilities for realizing these phenomena in solid-state and cold-atomic systems are discussed

Juncus maroccanus Kirschner, a new record to the european flora

Juncus maroccanus Kirschner, novedad para la Flora Europaea Palabras clave. Juncaceae, Península Ibérica, España, Estrecho de Gibraltar,  dunas. Keywords. Juncaceae, Iberian Peninsula, Spain, Straits of Gibraltar, dunes

Bacillus Subtilis SMC Complexes Juxtapose Chromosome Arms as They Travel from Origin to Terminus

Structural maintenance of chromosomes (SMC) complexes play critical roles in chromosome dynamics in virtually all organisms, but how they function remains poorly understood. In the bacterium Bacillus subtilis, SMC-condensin complexes are topologically loaded at centromeric sites adjacent to the replication origin. Here we provide evidence that these ring-shaped assemblies tether the left and right chromosome arms together while traveling from the origin to the terminus (>2 megabases) at rates >50 kilobases per minute. Condensin movement scales linearly with time, providing evidence for an active transport mechanism. These data support a model in which SMC complexes function by processively enlarging DNA loops. Loop formation followed by processive enlargement provides a mechanism by which condensin complexes compact and resolve sister chromatids in mitosis and by which cohesin generates topologically associating domains during interphase. Keywords: SMC; ParB; condensin; cohesion; loop extrusion; TADNational Institutes of Health (U.S.) (Grant GM082899

Spectrum of the Nuclear Environment for GaAs Spin Qubits

Using a singlet-triplet spin qubit as a sensitive spectrometer of the GaAs nuclear spin bath, we demonstrate that the spectrum of Overhauser noise agrees with a classical spin diffusion model over six orders of magnitude in frequency, from 1 mHz to 1 kHz, is flat below 10 mHz, and falls as $1/f^2$ for frequency $f \! \gtrsim \! 1$ Hz. Increasing the applied magnetic field from 0.1 T to 0.75 T suppresses electron-mediated spin diffusion, which decreases spectral content in the $1/f^2$ region and lowers the saturation frequency, each by an order of magnitude, consistent with a numerical model. Spectral content at megahertz frequencies is accessed using dynamical decoupling, which shows a crossover from the few-pulse regime ($\lesssim \! 16$ $\pi$-pulses), where transverse Overhauser fluctuations dominate dephasing, to the many-pulse regime ($\gtrsim \! 32$ $\pi$-pulses), where longitudinal Overhauser fluctuations with a $1/f$ spectrum dominate.Comment: 6 pages, 4 figures, 8 pages of supplementary material, 5 supplementary figure