Re-establishing communication in teams of mobile robots

As communication is important for cooperation, teams of mobile robots need a way to re-establish a wireless connection if they get separated. We develop a method for mobile robots to maintain a belief of each other's positions using locally available information. They can use their belief to plan paths with high probabilities of reconnection. This approach also works for subteams cooperatively searching for a robot or group of robots that they would like to reconnect with. The problem is formulated as a constrained optimization problem which is solved using a branch-and-bound approach. We present simulation results showing the effectiveness of this strategy at reconnecting teams of up to five robots and compare the results to two other strategies

Rift-related paleogeography of the European margin in the Eastern Alps (Central Tauern Window)

Continent-derived tectonic units in the Tauern Window of the Alps exhibit stratigraphic and structural traces of extension of continental margins eventually leading to the opening of the Alpine Tethys. In this study, we reassess lithostratigraphic data from the central part of the Tauern Window to reconstruct the post-Variscan evolution of this area, particularly the rift-related geometry of the European continental margin. The lithostratigraphy of the Alpine nappes reflects systematic variations of the structure of the European margin. The lowest tectonic units (Venediger nappe system, Eclogite Zone and Trögereck Nappe) are characterized by a thick succession of arkose-rich Bündnerschiefer-type sediments of probably Early Cretaceous age that we interpret as syn-rift sequence and which stratigraphically overlies thinned continental basement and thin pre-rift sediments. In contrast, the highest tectonic unit derived from Europe (Rote Wand Nappe) preserves a thick pre-rift sedimentary sequence overlying thinned continental basement, as well as a thick syn- to post-rift succession characterized by turbiditic Bündnerschiefer-type sediments of probable Cretaceous age. These observations point towards a highly segmented structure of the European rifted margin. We propose that this involved the formation of an outer margin high, partly preserved in the Rote Wand Nappe, that was separated from the main part of the European margin by a rift basin overlying strongly-thinned continental crust. The along-strike discontinuity of the Rote Wand Nappe is proposed to reflect the lateral variation in thickness of the outer margin high that resulted from margin-parallel segmentation of the European continental crust during highly oblique rifting antecedent to the opening of Alpine Tethys

Sero-Prevalence and Factors Associated with Toxoplasma gondii Infection among Pregnant Women Attending Antenatal Care in Mwanza, Tanzania.

Serological screening of pregnant women for Toxoplasma gondii-specific antibodies is not practiced as an antenatal care in Tanzania; and there is a limited data about sero-prevalence of T. gondii infection in developing countries. We therefore conducted this study to determine the sero-prevalence and factors associated with T. gondii infection among pregnant women attending antenatal care clinics in Mwanza, Tanzania. Between 1st November 2012 and 31st May 2013 a total of 350 pregnant women attending antenatal care clinics in Mwanza were enrolled and screened for IgG and IgM antibodies against T. gondii using the ELISA technique. Of 350 pregnant women, 108 (30.9%) were sero-positive for T. gondii-specific antibodies. The risk of contracting T. gondii infection increases by 7% with each yearly increase in a woman's age (OR=1.07, 95% CI: 1.02 - 1.11, p=0.002). The sero-positivity rate of T. gondii-specific antibodies was higher among pregnant women from the urban than those from rural communities (41.5% versus 22.0%); [OR=2.2, 95% CI; 1.4 - 3.7, p=0.001]. Likewise employed/business women were more likely to get T. gondii infection than peasants (40.0% versus 25.9%) [OR=1.9, 95% CI: 1.2 - 3.0, p=0.006]. Sero-prevalence of T. gondii-specific antibodies is high among pregnant women in Mwanza with a significant proportion of women at risk of contracting primary T. gondii infections. Screening of T. gondii infections during antenatal care should be considered in Tanzania as the main strategy to minimize congenital toxoplasmosis

Evolution of a Fossil Subduction Zone: Insights from the Tauern Window, Eastern Alps

Subduction zones play a crucial role in the evolution of Earth's lithosphere. In many orogens, deeply subducted coherent high-pressure (HP) nappes were exhumed from deep to shallow parts of subduction channels. This process significantly affects the deformation pattern and internal structure of the orogen. Exhumation seems to occur preferentially during the transition from subduction to collision, when dense oceanic lithosphere has been consumed entirely and more buoyant continental lithosphere from a passive continental margin enters the subduction zone. Here, we present a detailed study on the structural, kinematic, and metamorphic evolution of a well-preserved paleo-subduction channel within the Tauern Window (Alps). First, we reevaluated the metamorphic history and regional tectono-stratigraphy of the tectonic units in the central Tauern Window. These units originate from the Alpine Tethys oceanic domain and the adjacent European passive continental margin. They experienced HP conditions during Alpine subduction, which was followed by exhumation to their current position in the Alpine nappe stack. By integrating new structural data and the well-preserved stratigraphy of the ocean-continent transition, we reconstructed the structure and kinematics of the nappes in great detail. Notably, we document a recumbent, tens-of-kilometers-scale sheath fold formed during pervasive top-to-the-foreland shear. This sheath fold comprises an isoclinally folded thrust that transported ophiolite relicts from the former Alpine Tethys onto a distal part of the European continental margin during early stages of subduction. It formed under HP conditions, immediately after the Europe-derived rocks in its core reached their maximum burial depth. The non-cylindrical shape of the sheath fold suggests its nucleation at a promontory of the former margin, inherited from Mesozoic rifting and subsequently amplified to a sheath geometry during top-to-the-foreland shear in the subduction zone. To gain insight into the temperature (T) structure of the sheath fold, we employed Raman spectroscopy on carbonaceous material (RSCM) thermometry on a large number of samples with high spatial resolution. The systematic spatial temperature trends reveal distinct domains related to the original subduction metamorphism and later T-dominated (Barrovian) metamorphic overprint. Integrating the peak-temperature pattern with the fold geometry unveils a two-stage process of nappe formation and sheath folding during exhumation. Our results highlight the existence of considerable along-strike heterogeneity within the deep portion of a fossil subduction zone, likely influenced by inherited rift structures and exhumation processes. Understanding such heterogeneities is crucial for interpreting seismic sections and numerical simulations of subduction zones, emphasizing the need to consider three-dimensional complexities beyond the idealized cylindrical models often used. By unraveling the structural and metamorphic evolution of exhumed HP nappes in the Tauern Window, this study contributes to a better understanding of the dynamic processes operating within subduction zones and their implications for mountain building

Subsumption architecture for enabling strategic coordination of robot swarms in a gaming scenario

The field of swarm robotics breaks away from traditional research by maximizing the performance of a group - swarm - of limited robots instead of optimizing the intelligence of a single robot. Similar to current-generation strategy video games, the player controls groups of units - squads - instead of the individual participants. These individuals are rather unintelligent robots, capable of little more than navigating and using their weapons. However, clever control of the squads of autonomous robots by the game players can make for intense, strategic matches. The gaming framework presented in this article provides players with strategic coordination of robot squads. The developed swarm intelligence techniques break up complex squad commands into several commands for each robot using robot formations and path finding while avoiding obstacles. These algorithms are validated through a 'Capture the Flag' gaming scenario where a complex squad command is split up into several robot commands in a matter of milliseconds

Reactive Interactions between the Ionic Liquid BMP‐TFSI and a Na Surface

In order to obtain atomistic insights into the initial stages of the formation of the solid electrolyte interphase (SEI) in Na ion or Na metal batteries, we employ surface chemistry experiments and DFT calculations to study the interactions and reactions between a Na surface and the ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-TFSI), a candidate to be used as electrolyte in batteries. Oxygen-free Na thin films, which were grown on Ru(0001) and characterized by X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS), can be understood as model of a Na-rich electrode. After deposition of submonolayer to multilayer BMP-TFSI films on the Na thin films at room temperature, XPS measurements revealed partial decomposition and the formation of a ‘contact layer’ at the Na surface, consisting of mainly TFSI-based decomposition products

Presenting the Compendium Isotoporum Medii Aevi, a multi-isotope database for Medieval Europe

Here we present the Compendium Isotoporum Medii Aevi (CIMA), an open-access database gathering more than 50,000 isotopic measurements for bioarchaeological samples located within Europe and its margins, and dating between 500 and 1500 CE. This multi-isotope (δ13C, δ15N, δ34S, δ18O, and 87Sr/86Sr) archive of measurements on human, animal, and plant archaeological remains also includes a variety of supporting information that offer, for instance, a taxonomic characterization of the samples, their location, and chronology, in addition to data on social, religious, and political contexts. Such a dataset can be used to identify data gaps for future research and to address multiple research questions, including those related with studies on medieval human lifeways (i.e. human subsistence, spatial mobility), characterization of paleo-environmental and -climatic conditions, and on plant and animal agricultural management practices. Brief examples of such applications are given here and we also discuss how the integration of large volumes of isotopic data with other types of archaeological and historical data can improve our knowledge of medieval Europe.Background & Summary Methods Data Records Technical Validation Usage Note

Relocation in Carsharing Systems using Flows in Time-Expanded Networks

A manuscript on this topic can be found at: http://hal.archives-ouvertes.fr/hal-00908242International audienceIn a carsharing system, a fleet of cars is distributed at stations in an urban area, customers can take and return cars at any time and station, provided that there is a car available at the start station and a free place at the final station. To ensure the latter, customers have to book their demands in advance; hereby, customer requests can be accepted or rejected by the operator. The stations have to keep a good ratio between available cars and free places in each station, in order to serve already accepted customer requests and to refuse as few new customer requests as possible. This leads to the problem of relocating cars between stations, which can be modeled as Pickup and Delivery Problem in a metric space induced by the urban area or, alternatively, by means of flows of cars in convoys in a time-expanded network.Note that we consider an innovative carsharing system with partly autonomous cars which allows to build convoys of cars, each moved by only one driver. This leads to a similar situation as in bikesharing systems, where trucks can simultaneously move several bikes, but no requests are booked in advance. Hereby, two flows are coupled in the sense that the flow of cars is dependent from the flow of drivers (since cars can only be moved in convoys); the flow coupling constraints reflect the complexity of the studied problem.We present integer programming formulations for two variants of the relocation problem: a min-cost flow problem to serve a given set of customer requests at minimal costs (quality of service aspect), and a max-profit flow problem to additionally solve the decision problem of accepting or rejecting customer requests (economic aspect). Both models take advantage of users booking their demands in advance and can be applied to the offline as well as the online version of the relocation problem in order to fully capture the dynamic evolution of the system over time.</p

Recent developments in self-assembling multi-robot systems

Purpose of Review This review studies recent developments towards the physical design and control of self-assembling multi-robot systems. Recent Findings A wide range of novel robotic systems have been developed lately, for potential applications in terrestrial, aquatic, and aerospace environments. They increasingly make use of connectors which enable modules to join with each other at arbitrary points instead of discrete locations. Although the majority of contemporary algorithms are shape-driven, an increased focus on task-driven algorithms is observed. Summary Self-assembling multi-robot systems allow the same set of robots to adopt specific morphologies for different tasks. The requirements for robots to be able to connect to each other, locomote, and communicate have led to a wide range of physical designs realising different trade-offs. While algorithms are validated extensively in simulation, only a small portion are yet tested on real robotic platforms. Future research should investigate the real-world application of these systems, possibly aided by the introduction of standardised and open hardware