Asynchronous quantum key distribution on a relay network

We show how quantum key distribution on a multi-user, multi-path, network can be used to establish a key between any two end-users in an asynchronous fashion using the technique of bit-transport. By a suitable adaptation of our previous secret-sharing scheme we show that an attacker has to compromise all of the intermediate relays on the network in order to obtain the key. Thus, two end-users can establish a secret key provided they trust at least one of the network relays

Engineering design in a different way: cognitive perspective on the contact and channel model approach

Engineering design often involves the integration of new design ideas into existing products, requiring designers to think simultaneously about abstract properties and functions as well as concrete solution constraints. Often designers struggle to reason with functional descriptions, while not fixating on existing solutions. This paper introduces the Contact & Channel Model (C&CM) approach, which combines abstract functional models of technical systems with the concrete geometric descriptions that many designers are familiar with. By locating functions at working surface pairs, they receive a concrete location in mental models. The C&CM approach can be applied to analyze existing product descriptions and synthesize creative new solutions for parts of the system or for entire new systems. At the moment the approach is being developed into an complete modeling and problem solving approach. C&CM has been used for several years in undergraduate engineering teaching at the University of Karlsruhe (TH) and is increasingly being introduced into industry by its use in research and development projects, by its students and its alumni

Beyond ‘Interaction’: How to Understand Social Effects on Social Cognition

In recent years, a number of philosophers and cognitive scientists have advocated for an ‘interactive turn’ in the methodology of social-cognition research: to become more ecologically valid, we must design experiments that are interactive, rather than merely observational. While the practical aim of improving ecological validity in the study of social cognition is laudable, we think that the notion of ‘interaction’ is not suitable for this task: as it is currently deployed in the social cognition literature, this notion leads to serious conceptual and methodological confusion. In this paper, we tackle this confusion on three fronts: 1) we revise the ‘interactionist’ definition of interaction; 2) we demonstrate a number of potential methodological confounds that arise in interactive experimental designs; and 3) we show that ersatz interactivity works just as well as the real thing. We conclude that the notion of ‘interaction’, as it is currently being deployed in this literature, obscures an accurate understanding of human social cognition

The onset of grasses in the Amazon drainage basin, evidence from the fossil record

Poaceae (the grass family) originated in the Cretaceous, but first dominate the palynological records of the Amazon drainage basin (ADB) in the Neogene (23 to 2.5 million years ago (Ma)). However, the ecological role of grasses in the landscape during this time remains to be resolved. In this paper, we summarise the global significance of grasses and the relevance of the fossil record, and evaluate the history of the grasses in the ADB. We present a 3-stage model of the changing role of grasses, which we based on a revision of Neogene depositional environments, the palynological record, and modern grass distribution in the Neotropics. Our model comprises the following hypotheses: (H1) assumes that from c. 23 to 9 Ma western Amazonia was dominated by a megawetland (the ‘Pebas system’) that harboured large amounts of (aquatic?) grasses. In (H2) we propose that from c. 9 Ma Andean uplift prompted megafans (extremely large alluvial fans) that extended from the Andes into the lowlands. Meanwhile, the ‘Pebas’ megawetland gradually transformed into a fluvial system. In this scenario, grasses would have had a competitive advantage and were able to colonise the newly formed megafan and fluvial landscapes. Finally, in (H3) we suggest that landscape dynamics and climatic change intensified from c. 3.5 Ma, allowing for a renewed expansion of the grasses. In addition, both the fossil and molecular records suggest that from c. 5 Ma grasses were firmly established in the tropical alpine vegetation (páramo), the tropical lowland floodplains (várzeas), and savannas (cerrado). Although further study will have to confirm the precise nature of the ADB grass history, we anticipate that abiotic processes during the Neogene and Quaternary left a strong imprint in the grass phytogeography of northern South America