Algorithmic bisimulation for communicating piecewise deterministic Markov processes

In this paper we present an algorithm for finding a bisimulation relation for stochastic hybrid systems from the class of CPDPs (Communicating Piecewise Deterministic Markov Processes). We prove that the fixed point of the algorithm forms a bisimulation on the state space of the CPDP. We give sufficient conditions on the continuous dynamics and the transition structure of a CPDP, for the computation of the algorithm to be decidable

Invasion success of a global avian invader is explained by within-taxon niche structure and association with humans in the native range

Aim To mitigate the threat invasive species pose to ecosystem functioning, reli- able risk assessment is paramount. Spatially explicit predictions of invasion risk obtained through bioclimatic envelope models calibrated with native species distribution data can play a critical role in invasive species management. Fore- casts of invasion risk to novel environments, however, remain controversial. Here, we assess how species’ association with human-modified habitats in the native range and within-taxon niche structure shape the distribution of invasive populations at biogeographical scales and influence the reliability of predictions of invasion risk. Location Africa, Asia and Europe. Methods We use ~1200 native and invasive ring-necked parakeet (Psittacula krameri) occurrences and associated data on establishment success in combi- nation with mtDNA-based phylogeographic structure to assess niche dynam- ics during biological invasion and to generate predictions of invasion risk. Niche dynamics were quantified in a gridded environmental space while bioclimatic models were created using the biomod2 ensemble modelling framework. Results Ring-necked parakeets show considerable niche expansion into climates colder than their native range. Only when incorporating a measure of human modification of habitats within the native range do bioclimatic envelope mod- els yield credible predictions of invasion risk for parakeets across Europe. Inva- sion risk derived from models that account for differing niche requirements of phylogeographic lineages and those that do not achieve similar statistical accu- racy, but there are pronounced differences in areas predicted to be susceptible for invasion. Main conclusions Information on within-taxon niche structure and especially association with humans in the native range can substantially improve predic- tive models of invasion risk. To provide policymakers with robust predictions of invasion risk, including these factors into bioclimatic envelope models is recommended

Axial electrokinetic trapping of single particles at kHz feedback rates

Anti-Brownian Electrokinetic (ABEL) trapping has proven to be a valuable novel tool for analysis at the single-nanoparticle level. In previous work, we explored axial (in the z-direction only) ABEL trapping with planar ITO electrodes based on video image analysis. In this work, we improved the method by using total-internal-reflection (TIR) in combination with a single-photon-counting module. This allows us to axially trap single nanoparticles with a homogeneous field at feedback rates of several kHz such that screening of the electric field becomes negligible