Groups of Agents with a Leader

We describe simulations of groups of agents that have to reach a target in a two dimensional environment, the performance criterion being the time taken by the last agent to reach the target. If the target is within a given distance from the agent, the agent moves towards the target; otherwise it moves randomly. The simulations contrast groups with and without a leader, where a leader is a member of the group which other members of the group follow as it moves through the environment. We investigate three factors that affect group performance: (1) group size; (2) the presence or absence of an individual agent with the ability to detect targets at a greater distance than those \'visible\' to its companions; (3) the existence of a communication network among group members. The results show that, in groups without communication, leaders have a beneficial effect on group performance, especially in large groups and if the individual with better than average sensory capabilities is the leader of the group. However, in situations where group members can communicate, these results are reversed, with leaders being detrimental, rather than beneficial, to group performanceAgent Based Models, Leaders, Social Simulation, Social Structure, Communication Topologies

The Theoretical Probability Distribution of Peak Outflows of Small Detention Dams

The functional relationship between detention dam inflows and outflows was derived in a closed form in a recent work, which led to a theoretically derived probability distribution (TDD) of the peak outflows from in-line detention dams. This TDD is tested using the generalized extreme value (GEV) as a reference distribution for floods

Monitoring Water Turbidity Using Remote Sensing Techniques

In the present work, the use of optical cameras for turbidity measurements is tested on the Bode River in Germany, which is one of the best-instrumented catchments in Central Germany with a long-term time series on water quantity and quality. Four trap cameras have been installed on monitored cross-sections with the aim to explore the potential of RGB indices for the description of water turbidity. A description of the experimental setup and some preliminary results are introduced

Delineation of flood‐prone areas in cliffed coastal regions through a procedure based on the geomorphic flood index

The geomorphic flood index (GFI) method provides a good representation of flood-prone areas. However, the method does not account for floodwater transfers in undefined interbasins (UIBs), which represent intercluded small basins along the coastline likely to be flooded by adjacent major rivers. The present work addresses this shortcoming by complementing the GFI approach with an iterative procedure that considers UIBs and water transfers between basins. The methodology was tested on a coastal basin in southern Italy and the outcome was compared with a flood map obtained by a two-dimensional hydraulic simulation. GFI performance as a morphological descriptor improved from 74% (standard method) to 94% with the addition of the iterative procedure. The proposed methodology, with the same parameterization, was applied on a second adjacent coastal basin obtaining improvements both in terms of true positive (from 56 to 79%) and false negative rates (from 44 to 21%). Finally, a sensitivity analysis to the flood return periods highlighted a strong influence on model parameterization for return periods below 20 years. This achievement represents a new development in the application of the GFI method, which can help stakeholders in a more time- and cost-effective flood risk management in hazard-prone areas

Response of high-risk MDS to azacitidine and lenalidomide is impacted by baseline and acquired mutations in a cluster of three inositide-specific genes

Specific myeloid-related and inositide-specific gene mutations can be linked to myelodysplastic syndromes (MDS) pathogenesis and therapy. Here, 44 higher-risk MDS patients were treated with azacitidine and lenalidomide and mutations analyses were performed at baseline and during the therapy. Results were then correlated to clinical outcome, overall survival (OS), leukemia-free-survival (LFS) and response to therapy. Collectively, 34/44 patients were considered evaluable for response, with an overall response rate of 76.25% (26/34 cases): 17 patients showed a durable response, 9 patients early lost response and 8 patients never responded. The most frequently mutated genes were ASXL1, TET2, RUNX1, and SRSF2. All patients early losing response, as well as cases never responding, acquired the same 3 point mutations during therapy, affecting respectively PIK3CD (D133E), AKT3 (D280G), and PLCG2 (Q548R) genes, that regulate cell proliferation and differentiation. Moreover, Kaplan–Meier analyses revealed that this mutated cluster was significantly associated with a shorter OS, LFS, and duration of response. All in all, a common mutated cluster affecting 3 inositide-specific genes is significantly associated with loss of response to azacitidine and lenalidomide therapy in higher risk MDS. Further studies are warranted to confirm these data and to further analyze the functional role of this 3-gene cluster

Rats, nets, maps, and the emergence of place cells

We study through computer simulations the motion in space of small networks consisting of a few sensory, intermediate, and motor units linked by feedforward connections of initially random strengths. Evolutionary pressure, exerted through random differentiation and selective reproduction, can force such objects to adapt to perform elementary navigation tasks similar to those used in investigating hippocampal function in rats. The connection strengths resulting from the adaptation process are shown to provide intermediate units with response characteristics similar to those of place cells found in the rat hippocampus. These results illustrate the ease with which \u201cplace\u201d units emerge in any minimal circuitry geared to solve simple navigation tasks, and highlight the importance of considering the complexity of the memory performance required, rather than the relatively trivial spatial \u201ccomputations\u201d involved, while using those tasks to explore hippocampal structure and function. \ua9 1992, Psychonomic Society, Inc.. All rights reserved

Discontinuity in Evolution: How Different Levels of Organization Imply Pre-Adaptation

this paper allowing the genotype to determine the development of the nervous system during all individual lifetime and making the developmental process sensitive to the external environment. We believe that this is a very promising direction that simulative models should pursue. A direction that for example may shed some light on fundamental questions like: how and in which conditions phenotypic plasticity has evolved? Biological systems can be described at various hierarchical levels. For example, an organism can be described at the genetic level, at the neural level, at the behavioral level, and at the fitness level. Each level determines the structure of the organism at the successive level but not all changes that occur at a certain level cause corresponding changes at higher levels. Since only part of the structure at each level (the functional part) is responsible for determining the structure at successive levels, only changes that affect these functional parts can cause changes at successive levels. If we examine the lineage of the best individual of the last generation in an evolutionary simulation with growing neural networks and we compare the two Os in each parent/offspring pair we see that different levels change at different rate. While at the genetic level almost all offspring differ from their parents, the probability that the two members of a pair differ at higher levels gradually decreases as one ascends levels. This implies that most of the mutations do not affect the fitness level and as a consequence should be considered nonadaptive or neutral. However, these mutations may produce changes at other levels and this can have long term consequences for the evolutionary process

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