Lower bumblebee colony reproductive success in agricultural compared with urban environments

Urbanization represents a rapidly growing driver of land-use change. While it is clear that urbanization impacts species abundance and diversity, direct effects of urban land use on animal reproductive success are rarely documented. Here, we show that urban land use is linked to long-term colony reproductive output in a key pollinator. We reared colonies from wild-caught bumblebee (Bombus terrestris) queens, placed them at sites characterized by varying degrees of urbanization from inner city to rural farmland and monitored the production of sexual offspring across the entire colony cycle. Our land-use cluster analysis identified three site categories, and this categorization was a strong predictor of colony performance. Crucially, colonies in the two clusters characterized by urban development produced more sexual offspring than those in the cluster dominated by agricultural land. These colonies also reached higher peak size, had more food stores, encountered fewer parasite invasions and survived for longer. Our results show a link between urbanization and bumblebee colony reproductive success, supporting the theory that urban areas provide a refuge for pollinator populations in an otherwise barren agricultural landscape

GiViP: A Visual Profiler for Distributed Graph Processing Systems

Analyzing large-scale graphs provides valuable insights in different application scenarios. While many graph processing systems working on top of distributed infrastructures have been proposed to deal with big graphs, the tasks of profiling and debugging their massive computations remain time consuming and error-prone. This paper presents GiViP, a visual profiler for distributed graph processing systems based on a Pregel-like computation model. GiViP captures the huge amount of messages exchanged throughout a computation and provides an interactive user interface for the visual analysis of the collected data. We show how to take advantage of GiViP to detect anomalies related to the computation and to the infrastructure, such as slow computing units and anomalous message patterns.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

Integrating Abstraction Techniques for Formal Verification of Analog Designs

The verification of analog designs is a challenging and exhaustive task that requires deep understanding of physical behaviours. In this paper, we propose a qualitative based predicate abstraction method for the verification of a class of non-linear analog circuits. In the proposed method, system equations are automatically extracted from a circuit diagram by means of a bond graph. Verification is applied based on combining techniques from constraint solving and computer algebra along with symbolic model checking. Our methodology has the advantage of avoiding exhaustive simulation normally encountered in the verification of analog designs. To this end, we have used Dymola, Hsolver, SMV and Mathematica to implement the verification flow. We illustrate the methodology on several analog examples including Colpitts and tunnel diode oscillators

Networked buffering: a basic mechanism for distributed robustness in complex adaptive systems

A generic mechanism - networked buffering - is proposed for the generation of robust traits in complex systems. It requires two basic conditions to be satisfied: 1) agents are versatile enough to perform more than one single functional role within a system and 2) agents are degenerate, i.e. there exists partial overlap in the functional capabilities of agents. Given these prerequisites, degenerate systems can readily produce a distributed systemic response to local perturbations. Reciprocally, excess resources related to a single function can indirectly support multiple unrelated functions within a degenerate system. In models of genome:proteome mappings for which localized decision-making and modularity of genetic functions are assumed, we verify that such distributed compensatory effects cause enhanced robustness of system traits. The conditions needed for networked buffering to occur are neither demanding nor rare, supporting the conjecture that degeneracy may fundamentally underpin distributed robustness within several biotic and abiotic systems. For instance, networked buffering offers new insights into systems engineering and planning activities that occur under high uncertainty. It may also help explain recent developments in understanding the origins of resilience within complex ecosystems. \ud \u