Analysis of behaviours in swarm systems

In nature animal species often exist in groups. We talk of insect swarms, flocks of birds, packs of lions, herds of wildebeest etc. These are characterised by individuals interacting by following their own rules, privy only to local information. Robotic swarms or simulations can be used explore such interactions. Mathematical formulations can be constructed that encode similar ideas and allow us to explore the emergent group behaviours. Some behaviours show characteristics reminiscent of the phenomena of criticality. A bird flock may show near instantaneous collective shifts in direction: velocity changes that appear to correlated over distances much larger individual separations. Here we examine swarm systems inspired by flocks of birds and the role played by criticality. The first system, Particle Swarm Optimisation (PSO), is shown to behave optimally when operating close to criticality. The presence of a critical point in the algorithm’s operation is shown to derive from the swarm’s properties as a random dynamical system. Empirical results demonstrate that the optimality lies on or near this point. A modified PSO algorithm is presented which uses measures of the swarm’s diversity as a feedback signal to adjust the behaviour of the swarm. This achieves a statistically balanced mixture of exploration and exploitation behaviours in the resultant swarm. The problems of stagnation and parameter tuning often encountered in PSO are automatically avoided. The second system, Swarm Chemistry, consists of heterogeneous particles combined with kinetic update rules. It is known that, depending upon the parametric configuration, numerous structures visually reminiscent of biological forms are found in this system. The parameter set discovered here results in a cell-division-like behaviour (in the sense of prokaryotic fission). Extensions to the swarm system produces a swarm that shows repeated cell division. As such, this model demonstrates a behaviour of interest to theories regarding the origin of life

The Shuffleboard Game: Effects of social drinking on mood and risky behaviour

Objective: Existing research examining how social forces and alcohol interact to impact risky behaviours has yielded contrasting findings, possibly due to the nature and variety of risk-taking tasks used and the failure to consider the role of emotion. Using a novel risk-task, akin to real world drinking games, this study examines the effect of intoxication and group contexts on risk-taking, considering mediating effects of mood. Method: 132 social drinkers (83 female) consumed an alcoholic (0.8g/kg) or placebo beverage before participating in the shuffleboard game (designed to mimic real drinking games) either individually (N = 66) or in the presence of two friends (N = 66). Mood was assessed before and after beverage consumption. Results: When controlling for group identity, intoxication (versus placebo) was associated with significantly higher risk-taking, although there was no impact of group context. No interaction between context and intoxication was observed, and mood did not mediate this relationship. Conclusions: Intoxication increases risk-taking behaviour regardless of whether an individual is in a group, or isolated, whereas groups do not appear to enhance risky behaviour. Previous evidence of an effect of groups on risk-taking may have been due to a failure to control for the effect of group identity. To reduce risky behaviours, interventions may benefit from targeting alcohol use while considering how pre-existing social norms within a friendship group may either mitigate or exacerbate risk. Results affirm the importance of considering both intoxication and group effects on affective states when investigating risk-taking behaviours

Assessing bed net use and non-use after long-lasting insecticidal net distribution: a simple framework to guide programmatic strategies

<p>Abstract</p> <p>Background</p> <p>Insecticide-treated nets (ITNs) are becoming increasingly available to vulnerable populations at risk for malaria. Their appropriate and consistent use is essential to preventing malaria, but ITN use often lags behind ITN ownership. In order to increase ITN use, it is necessary to devise strategies that accurately identify, differentiate, and target the reasons and types of non-use.</p> <p>Methods</p> <p>A simple method based on the end-user as the denominator was employed to classify each individual into one of four ITN use categories: 1) living in households not owning an ITN; 2) living in households owning, but not hanging an ITN; 3) living in households owning and hanging an ITN, but who are not sleeping under one; and 4) sleeping under an ITN. This framework was applied to survey data designed to evaluate long-lasting insecticidal nets (LLINs) distributions following integrated campaigns in five countries: Togo, Sierra Leone, Madagascar, Kenya and Niger.</p> <p>Results</p> <p>The percentage of children <5 years of age sleeping under an ITN ranged from 51.5% in Kenya to 81.1% in Madagascar. Among the three categories of non-use, children living in households without an ITN make up largest group (range: 9.4%-30.0%), despite the efforts of the integrated child health campaigns. The percentage of children who live in households that own but do not hang an ITN ranged from 5.1% to 16.1%. The percentage of children living in households where an ITN was suspended, but who were not sleeping under it ranged from 4.3% to 16.4%. Use by all household members in Sierra Leone (39.9%) and Madagascar (60.4%) indicate that integrated campaigns reach beyond their desired target populations.</p> <p>Conclusions</p> <p>The framework outlined in this paper provides a helpful tool to examine the deficiencies in ITN use. Monitoring and evaluation strategies designed to assess ITN ownership and use can easily incorporate this approach using existing data collection instruments that measure the standard indicators.</p

The shuffleboard game: investigating group drinking, mood, and risky behavior

Objective: Existing research examining how social forces and alcohol interact to impact risky behaviors has yielded contrasting findings, possibly due to the nature and variety of risk-taking tasks used and the failure to consider the role of emotion. Using a novel risk task, akin to real-world drinking games, this study examines the effect of intoxication and group contexts on risk-taking, considering mediating effects of mood. Method: One hundred thirty-two social drinkers (83 females) consumed an alcoholic (0.8 g/kg) or placebo beverage before participating in the shuffleboard game (designed to mimic real drinking games) either individually (N = 66) or in the presence of two friends (N = 66). Mood was assessed before and after beverage consumption. Results: When controlling for group identity, intoxication (vs. placebo) was associated with significantly higher risk-taking, although there was no impact of group context. No interaction between context and intoxication was observed, and mood did not mediate this relationship. Conclusions: Intoxication increases risk-taking behavior regardless of whether an individual is in a group, or isolated, whereas groups do not appear to enhance risky behavior. Previous evidence of an effect of groups on risk-taking may have been due to a failure to control for the effect of group identity. To reduce risky behaviors, interventions may benefit from targeting alcohol use while considering how preexisting social norms within a friendship group may either mitigate or exacerbate risk. Results affirm the importance of considering both intoxication and group effects on affective states when investigating risk-taking behaviors

TTN genotype is associated with fascicle length and marathon running performance.

Titin provides a molecular blueprint for muscle sarcomere assembly and sarcomere length can vary according to titin isoform expression. If variations in sarcomere length influence muscle fascicle length, this may provide an advantage for running performance. Thus the aim of this study was to investigate if the titin (TTN) rs10497520 polymorphism was associated with muscle fascicle length in recreationally active men (RA; n = 137) and marathon personal best time in male marathon runners (MR; n = 141). Fascicle length of the vastus lateralis was assessed in vivo using B-mode ultrasonography at 50% of muscle length in RA. All participants provided either a whole blood, saliva or buccal cell sample, from which DNA was isolated and genotyped using real-time polymerase chain reaction. Vastus lateralis fascicle length was 10.4% longer in CC homozygotes, those carrying two copies of the C-allele, than CT heterozygotes (p = 0.003) in RA. In the absence of any TT homozygotes, reflective of the low T-allele frequency within Caucasian populations, it is unclear if fascicle length for this group would have been smaller still. No differences in genotype frequency between the RA and MR groups were observed (p = 0.500), although within the MR group the T-allele carriers demonstrated marathon personal best times 2 min 25 s faster than CC homozygotes (p = 0.020). These results suggest that the T-allele at rs10497520 in the TTN gene is associated with shorter skeletal muscle fascicle length and conveys an advantage for marathon running performance in habitually trained men. This article is protected by copyright. All rights reserved

Concussion-Associated Gene Variant COMT rs4680 Is Associated With Elite Rugby Athlete Status

Objective: Concussions are common match injuries in elite rugby, and reports exist of reduced cognitive function and long-term health consequences that can interrupt or end a playing career and produce continued ill health. The aim of this study was to investigate the association between elite rugby status and 8 concussion-associated risk polymorphisms. We hypothesized that concussion-associated risk genotypes and alleles would be underrepresented in elite rugby athletes compared with nonathletes. Design: A case-control genetic association study.Setting:  Institutional (university). Participants: Elite White male rugby athletes [n = 668, mean (SD) height 1.85 (0.07) m, mass 102 (12) kg, and age 29 (7) years] and 1015 nonathlete White men and women (48% men). Interventions: Genotype was the independent variable, obtained by PCR of genomic DNA using TaqMan probes.Main Outcome Measure:  Elite athlete status with groups compared using χ2 and odds ratio (OR). Results: The COMT rs4680 Met/Met (AA) genotype, Met allele possession, and Met allele frequency were lower in rugby athletes (24.8%, 74.6%, and 49.7%, respectively) than nonathletes (30.2%, 77.6%, and 54.0%; P &lt; 0.05). The Val/Val (GG) genotype was more common in elite rugby athletes than nonathletes (OR 1.39, 95% confidence interval 1.04-1.86). No other polymorphism was associated with elite athlete status. Conclusions: Elite rugby athlete status is associated with COMT rs4680 genotype that, acting pleiotropically, could affect stress resilience and behavioral traits during competition, concussion risk, and/or recovery from concussion. Consequently, assessing COMT rs4680 genotype might aid future individualized management of concussion risk among athletes.