Self-Assembling of Networks in an Agent-Based Model

We propose a model to show the self-assembling of network-like structures between a set of nodes without using preexisting positional information or long-range attraction of the nodes. The model is based on Brownian agents that are capable of producing different local (chemical) information and respond to it in a non-linear manner. They solve two tasks in parallel: (i) the detection of the appropriate nodes, and (ii) the establishment of stable links between them. We present results of computer simulations that demonstrate the emergence of robust network structures and investigate the connectivity of the network by means of both analytical estimations and computer simulations. PACS: 05.65.+b, 89.75.Kd, 84.30.Bv, 87.18.SnComment: 10 pages, 8 figures. A video of the computer simulations can be found at http://www.ais.fhg.de/~frank/network.html. After publication, this paper was also included in: Virtual Journal of Biological Physics Research 4/5 (September 1, 2002) and Virtual Journal of Nanoscale Science & Technology 6/10 (September 2, 2002). For related work, see also http://www.ais.fhg.de/~frank/active.htm

Uphill Motion of Active Brownian Particles in Piecewise Linear Potentials

We consider Brownian particles with the ability to take up energy from the environment, to store it in an internal depot, and to convert internal energy into kinetic energy of motion. Provided a supercritical supply of energy, these particles are able to move in a ``high velocity'' or active mode, which allows them to move also against the gradient of an external potential. We investigate the critical energetic conditions of this self-driven motion for the case of a linear potential and a ratchet potential. In the latter case, we are able to find two different critical conversion rates for the internal energy, which describe the onset of a directed net current into the two different directions. The results of computer simulations are confirmed by analytical expressions for the critical parameters and the average velocity of the net current. Further, we investigate the influence of the asymmetry of the ratchet potential on the net current and estimate a critical value for the asymmetry in order to obtain a positive or negative net current.Comment: accepted for publication in European Journal of Physics B (1999), for related work see http://summa.physik.hu-berlin.de/~frank/active.htm

Genetics of Restless Legs Syndrome

The genetically complex restless legs syndrome (RLS) was tested for associations with genes using rare variant ExomeChip genotypes of 9,192 cases/controls. Candidate genes were sequenced together with candidate genes from a meta-GWAS using MIPseq in 1,456 cases/controls. A list of potential RLS genes was obtained. Furthermore, 843 individuals from 79 RLS families were genotyped/imputed for RLS risk SNPs. They were associated with RLS in 15 families and explained 17% to 100% of the phenotypic variance. « Übersetzte Kurzfassung: Das komplex-genetische Restless Legs Syndrom (RLS) wurde unter der Verwendung seltener Varianten aus dem ExomeChip von 9.192 Fällen/Kontrollen auf Assoziationen mit Genen getestet. Die resultierenden Kandidatengene und weitere Kandidatengene aus einer Meta-GWAS wurden mittels MIPseq in 1.456 Fällen/Kontrollen sequenziert. Eine Liste potentieller RLS Gene wurde erhalten. Auch wurden bekannte RLS-Risiko-SNPs in 843 Personen aus 79 RLS-Familien typisiert. Die SNPs waren mit RLS in 15 Familien assoziiert und erklärten 17 % bis 100 % der phänotypischen Varianz

A power law for the duration of high-flow states and its interpretation from a heterogeneous traffic flow perspective

We study the duration of "high-flow states” in freeway traffic, defined as the time periods for which traffic flows exceed a given flow threshold. Our empirical data are surprisingly well represented by a power law. Moreover, the power law exponent for a two-lane freeway seems to be independent of the chosen flow threshold. In order to interpret this discovery, we investigate a simple theoretical model of heterogeneous traffic with overtaking maneuvers, which is able to reproduce both, the empirical power law and its exponen

Analysis of the runoff response of an Alpine catchment at different scales

International audienceTo understand how hydrological processes are related across different spatial scales, 201 rainfall runoff events were examined in three nested catchments of the upper river Saalach in the Austrian Alps. The Saalach basin is a nested catchment covering different spatial scales, from the micro-scale (Limberg, 0.07 km2), to the small-catchment scale (Rammern, 15.5 km2), and the meso-scale (Viehhofen, 150 km2). At these three scales two different event types could clearly be identified, depending on rainfall characteristics and initial baseflow level: (1) a unimodal event type with a quick rising and falling hydrograph, responding to short duration rainfall, and (2) a bimodal event type with a double peak hydrograph at the micro-scale and substantially increased flow values at the larger basins Rammern and Viehhofen, responding to long duration rainfall events. In all cases where a bimodal event was identified at the microscale, the hydrographs at the larger scales exhibited significantly attenuated recession behavior, quantified by recession constants. At all scales, the bimodal events are associated with considerably higher runoff volumes than the unimodal events. From the investigations at the headwater Limberg we came to the conclusion that the higher amount of runoff of bimodal events is due to the mobilization of subsurface flow processes. The analysis shows that the occurrence of the two event types is consistent over three orders of magnitude in area. This link between the scales means that the runoff behavior of the headwater may be used as an indicator of the runoff behavior of much larger areas

Analysis of the runoff response of an alpine catchment at different scales

International audienceTo understand how hydrological processes are related across different spatial scales, 201 rainfall runoff events were examined in three nested catchments of the upper river Saalach in the Austrian Alps. The Saalach basin is a nested catchment covering different spatial scales, from the micro-scale (Limberg, 0.07 km²), to the small-catchment scale (Rammern, 15.5 km²), and the meso-scale (Viehhofen, 150 km²). At these three scales two different event types could clearly be identified, depending on rainfall characteristics and initial baseflow level: (1) a unimodal event type with a quick rising and falling hydrograph, responding to short duration rainfall, and (2) a bimodal event type with a double peak hydrograph at the micro-scale and substantially increased flow values at the larger basins Rammern and Viehhofen, responding to long duration rainfall events. In all cases where a bimodal event was identified at the microscale, the hydrographs at the larger scales exhibited significantly attenuated recession behavior, quantified by recession constants. At all scales, the bimodal events are associated with considerably higher runoff volumes than the unimodal events. From the investigations at the headwater Limberg we came to the conclusion that the higher amount of runoff of bimodal events is due to the mobilization of subsurface flow processes. The analysis shows that the occurrence of the two event types is consistent over three orders of magnitude in area. This link between the scales means that the runoff behavior of the headwater may be used as an indicator of the runoff behavior of much larger areas

A Spatiotemporal Study and Location-Specific Trip Pattern Categorization of Shared E-Scooter Usage

This study analyzes the temporally resolved location and trip data of shared e-scooters over nine months in Berlin from one of Europe’s most widespread operators. We apply time, distance, and energy consumption filters on approximately 1.25 million trips for outlier detection and trip categorization. Using temporally and spatially resolved trip pattern analyses, we investigate how the built environment and land use affect e-scooter trips. Further, we apply a density-based clustering algorithm to examine point of interest-specific patterns in trip generation. Our results suggest that e-scooter usage has point of interest related characteristics. Temporal peaks in e-scooter usage differ by point of interest category and indicate work-related trips at public transport stations. We prove these characteristic patterns with the statistical metric of cosine similarity. Considering average cluster velocities, we observe limited time-saving potential of e-scooter trips in congested areas near the city center