Collective Activity Bursting in a Population of Excitable Units Adaptively Coupled to a Pool of Resources

We study the collective dynamics in a population of excitable units (neurons) adaptively interacting with a pool of resources. The resource pool is influenced by the average activity of the population, whereas the feedback from the resources to the population is comprised of components acting homogeneously or inhomogeneously on individual units of the population. Moreover, the resource pool dynamics is assumed to be slow and has an oscillatory degree of freedom. We show that the feedback loop between the population and the resources can give rise to collective activity bursting in the population. To explain the mechanisms behind this emergent phenomenon, we combine the Ott-Antonsen reduction for the collective dynamics of the population and singular perturbation theory to obtain a reduced system describing the interaction between the population mean field and the resources.Peer Reviewe

Understanding and optimising the packing density of perylene bisimide layers on CVD-grown graphene

The non-covalent functionalisation of graphene is an attractive strategy to alter the surface chemistry of graphene without damaging its superior electrical and mechanical properties. Using the facile method of aqueous-phase functionalisation on large-scale CVD-grown graphene, we investigated the formation of different packing densities in self-assembled monolayers (SAMs) of perylene bisimide derivatives and related this to the amount of substrate contamination. We were able to directly observe wet-chemically deposited SAMs in scanning tunnelling microscopy (STM) on transferred CVD graphene and revealed that the densely packed perylene ad-layers adsorb with the conjugated {\pi}-system of the core perpendicular to the graphene substrate. This elucidation of the non-covalent functionalisation of graphene has major implications on controlling its surface chemistry and opens new pathways for adaptable functionalisation in ambient conditions and on the large scale.Comment: 27 pages (including SI), 10 figure

Der internationale Weiterbildungsstudiengang „International Construction: Practice and Law“ an der Universität Stuttgart

Das Institut für Baubetriebslehre der Universität Stuttgart bietet seit dem Jahr 2015 einen Weiterbildungsstudiengang zum internationalen Bauen und Baurecht an. Das englischsprachige Bildungsangebot mit dem Ziel eines Master of Business Engineering zieht internationale Studierende aus der ganzen Welt an und ist ein interessantes Beispiel dafür, wie wissenschaftliche Weiterbildung mit internationalem Bezug funktionieren kann. Der Beitrag erläutert nach einführenden Worten zur verantwortlichen Bildungseinrichtung die Motivation zur Einrichtung des Studiengangs, die Historie und die Entwicklung sowie inhaltliche Fragestellungen. Vorgestellt wird auch das Distance Learning Angebot, das den Studierenden eine Teilnahme an den Veranstaltungen über das Internet ermöglicht. Zudem wird aufgezeigt, welcher Austausch und welche Lernmöglichkeiten auf wissenschaftlicher Ebene bereits stattfinden und künftig möglich sind

Automatisiertes Off-Line-Rüsten von Ummantelungsanlagen

Ummanteln ist eine Fertigungstechnologie, deren Bedeutung noch immer w~chst. Mit ihr werden Holzwerkstoffprofile und Kaschierungen mit Schmelzklebstoffen gefügt Zu deutlich geringeren Kosten werden Profjlelemente erzeugt, die heute ihren Vorbildern aus Massivholz oder Metallen in Optik und Haptik gleichkommen oder einen eigenständigen Charme aufweisen. Allerdings müssen beim Ummantelungsprozess eine Vielzahl an Andruckrollen und ggf. Heißluftdüsen entlang des durchlaufenden Profils angeordnet werden, um die meist nur eingeschränkt formbare, mit heißem Schmelzkleber beschichtete Kaschierung mit dem Profilkern zu fügen. Da die Maschinen im Stillstand manuell gerüstet werden, reduziert die dafür benötigte Rüstzeit deutlich die Produktivität der Ummantelungsanlagen. Daher muss das Rüsten off-line, parallel zu den Fertigungsaufträgen. an einem separaten ROststand erfolgen und sich somit die Belegungszeit der Anlage auf das Einwechseln der Rollensätze beschränken. Basierend auf einer umfangreichen Prozessbetrachtung wurde ein Prozessmodell entwickelt, welches mittels Geometriedaten, Rüstregeln sowie Informationen über Material, Werkzeug und Ummantelungsmaschine ein virtuelles Bild der Rollenpositionierung erzeugt Die daraus gewonnenen Positionen und Anstellwinkel der einzelnen Rollen werden dann Ober einen Postprozessor an einen roboterunterstutzten Rüstplatz weitergegeben, welcher die benötigten Rollenhalter automatisiert rüstet

Changes in strain patterns after implantation of a short stem with metaphyseal anchorage compared to a standard stem: an experimental study in synthetic bone

Short stem hip arthroplasties with predominantly metaphyseal fixation, such as the METHA® stem (Aesculap, Tuttlingen, Germany), are recommended because they are presumed to allow a more physiologic load transfer and thus a reduction of stress-shielding. However, the hypothesized metaphyseal anchorage associated with the aforementioned benefits still needs to be verified. Therefore, the METHA short stem and the Bicontact® standard stem (Aesculap, Tuttlingen, Germany) were tested biomechanically in synthetic femora while strain gauges monitored their corresponding strain patterns. For the METHA stem, the strains in all tested locations including the region of the calcar (87% of the non-implanted femur) were similar to conditions of synthetic bone without implanted stem. The Bicontact stem showed approximately the level of strain of the non-implanted femur on the lateral and medial aspect in the proximal diaphysis of the femur. On the anterior and posterior aspect of the proximal metaphysis the strains reached averages of 78% and 87% of the non-implanted femur, respectively. This study revealed primary metaphyseal anchorage of the METHA short stem, as opposed to a metaphyseal-diaphyseal anchorage of the Bicontact stem

Stochastic Dispersal Rather Than Deterministic Selection Explains the Spatio-Temporal Distribution of Soil Bacteria in a Temperate Grassland

Spatial and temporal processes shaping microbial communities are inseparably linked but rarely studied together. By Illumina 16S rRNA sequencing, we monitored soil bacteria in 360 stations on a 100 square meter plot distributed across six intra-annual samplings in a rarely managed, temperate grassland. Using a multi-tiered approach, we tested the extent to which stochastic or deterministic processes influenced the composition of local communities. A combination of phylogenetic turnover analysis and null modeling demonstrated that either homogenization by unlimited stochastic dispersal or scenarios, in which neither stochastic processes nor deterministic forces dominated, explained local assembly processes. Thus, the majority of all sampled communities (82%) was rather homogeneous with no significant changes in abundance-weighted composition. However, we detected strong and uniform taxonomic shifts within just nine samples in early summer. Thus, community snapshots sampled from single points in time or space do not necessarily reflect a representative community state. The potential for change despite the overall homogeneity was further demonstrated when the focus shifted to the rare biosphere. Rare OTU turnover, rather than nestedness, characterized abundance-independent β-diversity. Accordingly, boosted generalized additive models encompassing spatial, temporal and environmental variables revealed strong and highly diverse effects of space on OTU abundance, even within the same genus. This pure spatial effect increased with decreasing OTU abundance and frequency, whereas soil moisture – the most important environmental variable – had an opposite effect by impacting abundant OTUs more than the rare ones. These results indicate that – despite considerable oscillation in space and time – the abundant and resident OTUs provide a community backbone that supports much higher β-diversity of a dynamic rare biosphere. Our findings reveal complex interactions among space, time, and environmental filters within bacterial communities in a long-established temperate grassland

Perspectives on adaptive dynamical systems

Adaptivity is a dynamical feature that is omnipresent in nature, socio-economics, and technology. For example, adaptive couplings appear in various real-world systems, such as the power grid, social, and neural networks, and they form the backbone of closed-loop control strategies and machine learning algorithms. In this article, we provide an interdisciplinary perspective on adaptive systems. We reflect on the notion and terminology of adaptivity in different disciplines and discuss which role adaptivity plays for various fields. We highlight common open challenges and give perspectives on future research directions, looking to inspire interdisciplinary approaches

Perspectives on adaptive dynamical systems

Adaptivity is a dynamical feature that is omnipresent in nature, socio-economics, and technology. For example, adaptive couplings appear in various real-world systems like the power grid, social, and neural networks, and they form the backbone of closed-loop control strategies and machine learning algorithms. In this article, we provide an interdisciplinary perspective on adaptive systems. We reflect on the notion and terminology of adaptivity in different disciplines and discuss which role adaptivity plays for various fields. We highlight common open challenges, and give perspectives on future research directions, looking to inspire interdisciplinary approaches.Comment: 46 pages, 9 figure