Temperature-dependent change of the fractal dimension of Cu dendrites on Cu(111)

We investigate the shape of monatomic high Cu islands on a Cu(111) surface by variable-temperature scanning tunneling microscopy between 110 K and 240 K. Low temperature dendrites evolve towards more compact shapes at increasing temperature; finally reaching the equilibrium shape of a hexagon with rounded corners. Time-lapsed imaging at increasing temperature reveals the onset of shape change to be at ≈170 K, corresponding to the onset of edge and corner diffusion of atoms along the island's borders. Despite a substantial variation for individual islands at each temperature, the mean fractal dimension increases monotonously between 170 K up to 240 K, from the smallest to the largest values feasible for islands grown on surfaces. © 2020 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft

Zusammenhang zwischen Kommunikation und Suboptimalität für verteilte Regelungssysteme

Distributed systems are present in every day's life: For example, distributed systems occur in the form of the internet, system architectures utilising edge computing, robotic scenarios in manufacturing processes, or the upcoming spreading of autonomous, connected vehicles. Distributed systems require a coordination or communication mechanism and an appropriate choice of control methods. Here, the Distributed Model Predictive Control scheme was applied in various application fields such as process control, robotic scenarios and traffic scenarios. As these robotic or traffic scenarios as examples for distributed systems encounter a high changing dynamic, the chosen coordination and communication mechanism should be efficient due to necessary synchronisation between the subsystems. A non-cooperative setting is examined, where each subsystem follows an individual target and has to exchange information steadily to ensure first and foremost collision avoidance. With utilisation of wireless communication resources and their finite bandwidth, this work present methods to attenuate the communication effort between the subsystems. Based on a quantisation implemented on the communication exchange between the subsystems, it is shown that each subsystems achieves their assigned target, i.e. the overall system still converge. The improvements for the communication load is presented and for a robotic scenario convergence is shown utilising a weaker assumption than terminal constraints. Additionally, to improve convergence, dynamic priority rules are introduced, which calculate an dynamic optimisation order for the subsystems, where different schemes are utilised: While the first is based on a simple sort based on a priority criterion in every time instant, the latter prevents deadlocks and examine additionally concurrent execution of the subsystems. We close with an overview of possible applications and transformation to other scenarios and give an outlook on further developments

Assisted suicide – an alternative for Germany?

Until last year assisted suicide was not regulated in Germany. It was, within certain limits, not prohibited although this fact was widely unknown. Over the last years organisations and individuals offered suicide assistance and became more and more popular. Therefore the government planned to change the law in order to regulate the uncontrolled development of organized assisted suicide. The legislative process was proceeded by an intense and emotional debate in media, public and politics. Data from The Netherlands, Belgium, Switzerland and Oregon can help to evaluate the consequences of legalising euthanasia and/or assisted suicide. They demonstrate a steady increase in numbers and indications. They also show that safeguards that were implemented to prevent malpractice or abuse of vulnerable people fail on a large scale. There is no reason to believe that these safeguards work better in Germany than in other countries. Bioethical concepts provide arguments for proponents as well as for opponents of legalisation of euthanasia and/or assisted suicide. If assisted suicide does not seem to be an alternative for Germany then another options have to be offered. Only one day before the vote for the law on assisted suicide a law was passed that ensures support and financing of palliative medicine and hospice care. These are better alternatives for end-of-life care than assisted suicide

Altering the stability of nanoislands through core–shell supports

We follow the decay of two-dimensional Ag nanoclusters, called islands, on Cu–Ag core–shell supports by variable low temperature scanning tunneling microscopy in the temperature range between 160 and 260 K.</p