Special Agents Can Promote Cooperation in the Population

Science.gov (United States)

Wang, Xin; Han, Jing; Han, Huawei

2011-01-01

Cooperation is ubiquitous in our real life but everyone would like to maximize her own profits. How does cooperation occur in the group of self-interested agents without centralized control? Furthermore, in a hostile scenario, for example, cooperation is unlikely to emerge. Is there any mechanism to promote cooperation if populations are given and play rules are not allowed to change? In this paper, numerical experiments show that complete population interaction is unfriendly to cooperation in the finite but end-unknown Repeated Prisoner's Dilemma (RPD). Then a mechanism called soft control is proposed to promote cooperation. According to the basic idea of soft control, a number of special agents are introduced to intervene in the evolution of cooperation. They comply with play rules in the original group so that they are always treated as normal agents. For our purpose, these special agents have their own strategies and share knowledge. The capability of the mechanism is studied under different settings. We find that soft control can promote cooperation and is robust to noise. Meanwhile simulation results demonstrate the applicability of the mechanism in other scenarios. Besides, the analytical proof also illustrates the effectiveness of soft control and validates simulation results. As a way of intervention in collective behaviors, soft control provides a possible direction for the study of reciprocal behaviors. PMID:22216202

Autonomous Agent-Based Systems and Their Applications in Fluid Dynamics, Particle Separation, and Co-evolving Networks

Science.gov (United States)

Graeser, Oliver

This thesis comprises three parts, reporting research results in Fluid Dynamics (Part I), Particle Separation (Part II) and Co-evolving Networks (Part III). Part I deals with the simulation of fluid dynamics using the lattice-Boltzmann method. Microfluidic devices often feature two-dimensional, repetitive arrays. Flows through such devices are pressure-driven and confined by solid walls. We have defined new adaptive generalised periodic boundary conditions to represent the effects of outer solid walls, and are thus able to exploit the periodicity of the array by simulating the flow through one unit cell in lieu of the entire device. The so-calculated fully developed flow describes the flow through the entire array accurately, but with computational requirements that are reduced according to the dimensions of the array. Part II discusses the problem of separating macromolecules like proteins or DNA coils. The reliable separation of such molecules is a crucial task in molecular biology. The use of Brownian ratchets as mechanisms for the separation of such particles has been proposed and discussed during the last decade. Pressure-driven flows have so far been dismissed as possible driving forces for Brownian ratchets, as they do not generate ratchet asymmetry. We propose a microfluidic design that uses pressure-driven flows to create asymmetry and hence allows particle separation. The dependence of the asymmetry on various factors of the microfluidic geometry is discussed. We further exemplify the feasibility of our approach using Brownian dynamics simulations of particles of different sizes in such a device. The results show that ratchet-based particle separation using flows as the driving force is possible. Simulation results and ratchet theory predictions are in excellent agreement. Part III deals with the co-evolution of networks and dynamic models. A group of agents occupies the nodes of a network, which defines the relationship between these agents. The

An Empirical Study of AI Population Dynamics with Million-agent Reinforcement Learning

OpenAIRE

Yang, Yaodong; Yu, Lantao; Bai, Yiwei; Wang, Jun; Zhang, Weinan; Wen, Ying; Yu, Yong

2017-01-01

In this paper, we conduct an empirical study on discovering the ordered collective dynamics obtained by a population of artificial intelligence (AI) agents. Our intention is to put AI agents into a simulated natural context, and then to understand their induced dynamics at the population level. In particular, we aim to verify if the principles developed in the real world could also be used in understanding an artificially-created intelligent population. To achieve this, we simulate a large-sc...

Selective Advantage of Recombination in Evolving Protein Populations:. a Lattice Model Study

Science.gov (United States)

Williams, Paul D.; Pollock, David D.; Goldstein, Richard A.

Recent research has attempted to clarify the contributions of several mutational processes, such as substitutions or homologous recombination. Simplistic, tractable protein models, which determine the compact native structure phenotype from the sequence genotype, are well-suited to such studies. In this paper, we use a lattice-protein model to examine the effects of point mutation and homologous recombination on evolving populations of proteins. We find that while the majority of mutation and recombination events are neutral or deleterious, recombination is far more likely to be beneficial. This results in a faster increase in fitness during evolution, although the final fitness level is not significantly changed. This transient advantage provides an evolutionary advantage to subpopulations that undergo recombination, allowing fixation of recombination to occur in the population.

An agent-based computational model for tuberculosis spreading on age-structured populations

Science.gov (United States)

Graciani Rodrigues, C. C.; Espíndola, Aquino L.; Penna, T. J. P.

2015-06-01

In this work we present an agent-based computational model to study the spreading of the tuberculosis (TB) disease on age-structured populations. The model proposed is a merge of two previous models: an agent-based computational model for the spreading of tuberculosis and a bit-string model for biological aging. The combination of TB with the population aging, reproduces the coexistence of health states, as seen in real populations. In addition, the universal exponential behavior of mortalities curves is still preserved. Finally, the population distribution as function of age shows the prevalence of TB mostly in elders, for high efficacy treatments.

Adaptive synonymous mutations in an experimentally evolved Pseudomonas fluorescens population

DEFF Research Database (Denmark)

Bailey, Susan; Hinz, Aaron; Kassen, Rees

2014-01-01

Conventional wisdom holds that synonymous mutations, nucleotide changes that do not alter the encoded amino acid, have no detectable effect on phenotype or fitness. However, a growing body of evidence from both comparative and experimental studies suggests otherwise. Synonymous mutations have been...... shown to impact gene expression, protein folding and fitness, however, direct evidence that they can be positively selected, and so contribute to adaptation, is lacking. Here we report the recovery of two beneficial synonymous single base pair changes that arose spontaneously and independently...... in an experimentally evolved population of Pseudomonas fluorescens. We show experimentally that these mutations increase fitness by an amount comparable to non-synonymous mutations and that the fitness increases stem from increased gene expression. These results provide unequivocal evidence that synonymous mutations...

Adaptation of Escherichia coli to glucose promotes evolvability in lactose.

Science.gov (United States)

Phillips, Kelly N; Castillo, Gerardo; Wünsche, Andrea; Cooper, Tim F

2016-02-01

The selective history of a population can influence its subsequent evolution, an effect known as historical contingency. We previously observed that five of six replicate populations that were evolved in a glucose-limited environment for 2000 generations, then switched to lactose for 1000 generations, had higher fitness increases in lactose than populations started directly from the ancestor. To test if selection in glucose systematically increased lactose evolvability, we started 12 replay populations--six from a population subsample and six from a single randomly selected clone--from each of the six glucose-evolved founder populations. These replay populations and 18 ancestral populations were evolved for 1000 generations in a lactose-limited environment. We found that replay populations were initially slightly less fit in lactose than the ancestor, but were more evolvable, in that they increased in fitness at a faster rate and to higher levels. This result indicates that evolution in the glucose environment resulted in genetic changes that increased the potential of genotypes to adapt to lactose. Genome sequencing identified four genes--iclR, nadR, spoT, and rbs--that were mutated in most glucose-evolved clones and are candidates for mediating increased evolvability. Our results demonstrate that short-term selective costs during selection in one environment can lead to changes in evolvability that confer longer term benefits. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Self-emergence of Lexicon Consensus in a Population of Autonomous Agents by Means of Evolutionary Strategies

Science.gov (United States)

Maravall, Darío; de Lope, Javier; Domínguez, Raúl

In Multi-agent systems, the study of language and communication is an active field of research. In this paper we present the application of evolutionary strategies to the self-emergence of a common lexicon in a population of agents. By modeling the vocabulary or lexicon of each agent as an association matrix or look-up table that maps the meanings (i.e. the objects encountered by the agents or the states of the environment itself) into symbols or signals we check whether it is possible for the population to converge in an autonomous, decentralized way to a common lexicon, so that the communication efficiency of the entire population is optimal. We have conducted several experiments, from the simplest case of a 2×2 association matrix (i.e. two meanings and two symbols) to a 3×3 lexicon case and in both cases we have attained convergence to the optimal communication system by means of evolutionary strategies. To analyze the convergence of the population of agents we have defined the population's consensus when all the agents (i.e. the 100% of the population) share the same association matrix or lexicon. As a general conclusion we have shown that evolutionary strategies are powerful enough optimizers to guarantee the convergence to lexicon consensus in a population of autonomous agents.

Simulating the Reproductive Behavior of a Region’s Population with an Agent-Based Model

Directory of Open Access Journals (Sweden)

Valeriy Leonidovich Makarov

2015-09-01

Full Text Available The research analyses the impact of the inequality of demographic transition on socio-demographic characteristics of the regional population and on the dynamics of these characteristics. The study was conducted with the help of computer-based experiments (simulations, which was run on the original agent-based model. The model is an artificial society, and personal characteristics of its members are set so that they could represent age-demographic structure of a simulate region. The agents are divided into two subgroups, which differ in their reproductive strategy. The first group has traditional strategy with high birth rate. The second group has considerably lower birth rate, observed in the modern developed societies. The model uses stochastic approaches to imitate the principle processes of population growth: mortality and morbidity. Mortality is set according to age-sex specific mortality coefficients, which do not differ across the population as a whole. New agents (child births appear as a choice of agents – women of reproductive age, and the choice depends on the subgroup. The overall age and social structure of the region is aggregated across individual agents. A number of experiments has been carried out with the model utilization. This allowed forecasting the size and structure of the population of a given region. The results of the experiments have revealed that despite its simplicity, the developed agent-based model well predicts the initial conditions in the region (e.g. age-demographic and social structure. The model shows good fit in terms of estimating the dynamics of major characteristics of the population.

Population-based resequencing of experimentally evolved populations reveals the genetic basis of body size variation in Drosophila melanogaster.

Directory of Open Access Journals (Sweden)

Thomas L Turner

2011-03-01

Full Text Available Body size is a classic quantitative trait with evolutionarily significant variation within many species. Locating the alleles responsible for this variation would help understand the maintenance of variation in body size in particular, as well as quantitative traits in general. However, successful genome-wide association of genotype and phenotype may require very large sample sizes if alleles have low population frequencies or modest effects. As a complementary approach, we propose that population-based resequencing of experimentally evolved populations allows for considerable power to map functional variation. Here, we use this technique to investigate the genetic basis of natural variation in body size in Drosophila melanogaster. Significant differentiation of hundreds of loci in replicate selection populations supports the hypothesis that the genetic basis of body size variation is very polygenic in D. melanogaster. Significantly differentiated variants are limited to single genes at some loci, allowing precise hypotheses to be formed regarding causal polymorphisms, while other significant regions are large and contain many genes. By using significantly associated polymorphisms as a priori candidates in follow-up studies, these data are expected to provide considerable power to determine the genetic basis of natural variation in body size.

Replaying Evolution to Test the Cause of Extinction of One Ecotype in an Experimentally Evolved Population.

Directory of Open Access Journals (Sweden)

Caroline B Turner

Full Text Available In a long-term evolution experiment with Escherichia coli, bacteria in one of twelve populations evolved the ability to consume citrate, a previously unexploited resource in a glucose-limited medium. This innovation led to the frequency-dependent coexistence of citrate-consuming (Cit+ and non-consuming (Cit- ecotypes, with Cit-bacteria persisting on the exogenously supplied glucose as well as other carbon molecules released by the Cit+ bacteria. After more than 10,000 generations of coexistence, however, the Cit-lineage went extinct; cells with the Cit-phenotype dropped to levels below detection, and the Cit-clade could not be detected by molecular assays based on its unique genotype. We hypothesized that this extinction was a deterministic outcome of evolutionary change within the population, specifically the appearance of a more-fit Cit+ ecotype that competitively excluded the Cit-ecotype. We tested this hypothesis by re-evolving the population from a frozen population sample taken within 500 generations of the extinction and from another sample taken several thousand generations earlier, in each case for 500 generations and with 20-fold replication. To our surprise, the Cit-type did not go extinct in any of these replays, and Cit-cells also persisted in a single replicate that was propagated for 2,500 generations. Even more unexpectedly, we showed that the Cit-ecotype could reinvade the Cit+ population after its extinction. Taken together, these results indicate that the extinction of the Cit-ecotype was not a deterministic outcome driven by competitive exclusion by the Cit+ ecotype. The extinction also cannot be explained by demographic stochasticity alone, as the population size of the Cit-ecotype should have been many thousands of cells even during the daily transfer events. Instead, we infer that the extinction must have been caused by a rare chance event in which some aspect of the experimental conditions was inadvertently perturbed.

Reduced swimming performance repeatedly evolves upon loss of migration in landlocked populations of Alewife

Science.gov (United States)

Velotta, Jonathan P.; McCormick, Stephen; Jones, Andrew W.; Schultz, Eric T.

2018-01-01

Whole-organism performance tasks are accomplished by the integration of morphological traits and physiological functions. Understanding how evolutionary change in morphology and physiology influences whole-organism performance will yield insight into the factors that shape its own evolution. We demonstrate that nonmigratory populations of alewife (Alosa pseudoharengus) have evolved reduced swimming performance in parallel, compared with their migratory ancestor. In contrast to theoretically and empirically based predictions, poor swimming among nonmigratory populations is unrelated to the evolution of osmoregulation and occurs despite the fact that nonmigratory alewives have a more fusiform (torpedo-like) body shape than their ancestor. Our results suggest that elimination of long-distance migration from the life cycle has shaped performance more than changes in body shape and physiological regulatory capacity.

Maintaining evolvability.

Science.gov (United States)

Crow, James F

2008-12-01

Although molecular methods, such as QTL mapping, have revealed a number of loci with large effects, it is still likely that the bulk of quantitative variability is due to multiple factors, each with small effect. Typically, these have a large additive component. Conventional wisdom argues that selection, natural or artificial, uses up additive variance and thus depletes its supply. Over time, the variance should be reduced, and at equilibrium be near zero. This is especially expected for fitness and traits highly correlated with it. Yet, populations typically have a great deal of additive variance, and do not seem to run out of genetic variability even after many generations of directional selection. Long-term selection experiments show that populations continue to retain seemingly undiminished additive variance despite large changes in the mean value. I propose that there are several reasons for this. (i) The environment is continually changing so that what was formerly most fit no longer is. (ii) There is an input of genetic variance from mutation, and sometimes from migration. (iii) As intermediate-frequency alleles increase in frequency towards one, producing less variance (as p --> 1, p(1 - p) --> 0), others that were originally near zero become more common and increase the variance. Thus, a roughly constant variance is maintained. (iv) There is always selection for fitness and for characters closely related to it. To the extent that the trait is heritable, later generations inherit a disproportionate number of genes acting additively on the trait, thus increasing genetic variance. For these reasons a selected population retains its ability to evolve. Of course, genes with large effect are also important. Conspicuous examples are the small number of loci that changed teosinte to maize, and major phylogenetic changes in the animal kingdom. The relative importance of these along with duplications, chromosome rearrangements, horizontal transmission and polyploidy

Continuum deformation of multi-agent systems

CERN Document Server

Rastgoftar, Hossein

2016-01-01

This monograph presents new algorithms for formation control of multi-agent systems (MAS) based on principles of continuum mechanics. Beginning with an overview of traditional methods, the author then introduces an innovative new approach whereby agents of an MAS are considered as particles in a continuum evolving in ℝn whose desired configuration is required to satisfy an admissible deformation function. The necessary theory and its validation on a mobile-agent-based swarm test bed are considered for two primary tasks: homogeneous transformation of the MAS and deployment of a random distribution of agents on a desired configuration. The framework for this model is based on homogeneous transformations for the evolution of an MAS under no inter-agent communication, local inter-agent communication, and intelligent perception by agents. Different communication protocols for MAS evolution, the robustness of tracking of a desired motion by an MAS evolving in ℝn, and the effect of communication delays in an MAS...

Mechanistic origin of dragon-kings in a population of competing agents

Science.gov (United States)

Johnson, N.; Tivnan, B.

2012-05-01

We analyze the mechanistic origins of the extreme behaviors that arise in an idealized model of a population of competing agents, such as traders in a market. These extreme behaviors exhibit the defining characteristics of `dragon-kings'. Our model comprises heterogeneous agents who repeatedly compete for some limited resource, making binary choices based on the strategies that they have in their possession. It generalizes the well-known Minority Game by allowing agents whose strategies have not made accurate recent predictions, to step out of the competition until their strategies improve. This generates a complex dynamical interplay between the number V of active agents (mimicking market volume) and the imbalance D between the decisions made (mimicking excess demand). The wide spectrum of extreme behaviors which emerge, helps to explain why no unique relationship has been identified between the price and volume during real market crashes and rallies.

Sex-specific effects of a parasite evolving in a female-biased host population.

Science.gov (United States)

Duneau, David; Luijckx, Pepijn; Ruder, Ludwig F; Ebert, Dieter

2012-12-18

Males and females differ in many ways and might present different opportunities and challenges to their parasites. In the same way that parasites adapt to the most common host type, they may adapt to the characteristics of the host sex they encounter most often. To explore this hypothesis, we characterized host sex-specific effects of the parasite Pasteuria ramosa, a bacterium evolving in naturally, strongly, female-biased populations of its host Daphnia magna. We show that the parasite proliferates more successfully in female hosts than in male hosts, even though males and females are genetically identical. In addition, when exposure occurred when hosts expressed a sexual dimorphism, females were more infected. In both host sexes, the parasite causes a similar reduction in longevity and leads to some level of castration. However, only in females does parasite-induced castration result in the gigantism that increases the carrying capacity for the proliferating parasite. We show that mature male and female Daphnia represent different environments and reveal one parasite-induced symptom (host castration), which leads to increased carrying capacity for parasite proliferation in female but not male hosts. We propose that parasite induced host castration is a property of parasites that evolved as an adaptation to specifically exploit female hosts.

Sex-specific effects of a parasite evolving in a female-biased host population

Directory of Open Access Journals (Sweden)

Duneau David

2012-12-01

Full Text Available Abstract Background Males and females differ in many ways and might present different opportunities and challenges to their parasites. In the same way that parasites adapt to the most common host type, they may adapt to the characteristics of the host sex they encounter most often. To explore this hypothesis, we characterized host sex-specific effects of the parasite Pasteuria ramosa, a bacterium evolving in naturally, strongly, female-biased populations of its host Daphnia magna. Results We show that the parasite proliferates more successfully in female hosts than in male hosts, even though males and females are genetically identical. In addition, when exposure occurred when hosts expressed a sexual dimorphism, females were more infected. In both host sexes, the parasite causes a similar reduction in longevity and leads to some level of castration. However, only in females does parasite-induced castration result in the gigantism that increases the carrying capacity for the proliferating parasite. Conclusions We show that mature male and female Daphnia represent different environments and reveal one parasite-induced symptom (host castration, which leads to increased carrying capacity for parasite proliferation in female but not male hosts. We propose that parasite induced host castration is a property of parasites that evolved as an adaptation to specifically exploit female hosts.

Sex-specific effects of a parasite evolving in a female-biased host population

Science.gov (United States)

2012-01-01

Background Males and females differ in many ways and might present different opportunities and challenges to their parasites. In the same way that parasites adapt to the most common host type, they may adapt to the characteristics of the host sex they encounter most often. To explore this hypothesis, we characterized host sex-specific effects of the parasite Pasteuria ramosa, a bacterium evolving in naturally, strongly, female-biased populations of its host Daphnia magna. Results We show that the parasite proliferates more successfully in female hosts than in male hosts, even though males and females are genetically identical. In addition, when exposure occurred when hosts expressed a sexual dimorphism, females were more infected. In both host sexes, the parasite causes a similar reduction in longevity and leads to some level of castration. However, only in females does parasite-induced castration result in the gigantism that increases the carrying capacity for the proliferating parasite. Conclusions We show that mature male and female Daphnia represent different environments and reveal one parasite-induced symptom (host castration), which leads to increased carrying capacity for parasite proliferation in female but not male hosts. We propose that parasite induced host castration is a property of parasites that evolved as an adaptation to specifically exploit female hosts. PMID:23249484

EvoCommander: A Novel Game Based on Evolving and Switching Between Artificial Brains

DEFF Research Database (Denmark)

Jallov, D.; Risi, S.; Togelius, J.

2016-01-01

Neuroevolution (i.e. evolving artificial neural networks (ANNs) through evolutionary algorithms) has shown promise in evolving agents and robot controllers, which display complex behaviours and can adapt to their environments. These properties are also relevant to video games, since they can...

Population pharmacokinetic (PK) analysis of laromustine, an emerging alkylating agent, in cancer patients.

Science.gov (United States)

Nassar, Ala F; Wisnewski, Adam V; King, Ivan

2017-05-01

1. Alkylating agents are capable of introducing an alkyl group into nucleophilic sites on DNA or RNA through covalent bond. Laromustine is an active member of a relatively new class of sulfonylhydrazine prodrugs under development as antineoplastic alkylating agents, and displays significant single-agent activity. 2. This is the first report of the population pharmacokinetic analysis of laromustine, 106 patients, 66 with hematologic malignancies and 40 with solid tumors, participated in five clinical trials worldwide. Of these, 104 patients were included in the final NONMEM analysis. 3. The population estimates for total clearance (CL) and volume of distribution of the central compartment (V 1 ) were 96.3 L/h and 45.9 L, associated with high inter-patient variability of 52.9% and 79.8% and inter-occasion variability of 26.7% and 49.3%, respectively. The population estimates for Q and V 2 were 73.2 L/h and 29.9 L, and inter-patient variability in V 2 was 63.1%, respectively. 4. The estimate of V ss (75.8 L) exceeds total body water, indicating that laromustine is distributed to tissues. The half-life is short, less than 1 h, reflecting rapid clearance. Population PK analysis showed laromustine pharmacokinetics to be independent of dose and organ function with no effect on subsequent dosing cycles.

Comparing methods of targeting obesity interventions in populations: An agent-based simulation.

Science.gov (United States)

Beheshti, Rahmatollah; Jalalpour, Mehdi; Glass, Thomas A

2017-12-01

Social networks as well as neighborhood environments have been shown to effect obesity-related behaviors including energy intake and physical activity. Accordingly, harnessing social networks to improve targeting of obesity interventions may be promising to the extent this leads to social multiplier effects and wider diffusion of intervention impact on populations. However, the literature evaluating network-based interventions has been inconsistent. Computational methods like agent-based models (ABM) provide researchers with tools to experiment in a simulated environment. We develop an ABM to compare conventional targeting methods (random selection, based on individual obesity risk, and vulnerable areas) with network-based targeting methods. We adapt a previously published and validated model of network diffusion of obesity-related behavior. We then build social networks among agents using a more realistic approach. We calibrate our model first against national-level data. Our results show that network-based targeting may lead to greater population impact. We also present a new targeting method that outperforms other methods in terms of intervention effectiveness at the population level.

Adaptive cyclically dominating game on co-evolving networks: numerical and analytic results

Science.gov (United States)

Choi, Chi Wun; Xu, Chen; Hui, Pak Ming

2017-10-01

A co-evolving and adaptive Rock (R)-Paper (P)-Scissors (S) game (ARPS) in which an agent uses one of three cyclically dominating strategies is proposed and studied numerically and analytically. An agent takes adaptive actions to achieve a neighborhood to his advantage by rewiring a dissatisfying link with a probability p or switching strategy with a probability 1 - p. Numerical results revealed two phases in the steady state. An active phase for p pc has three separate clusters of agents using only R, P, and S, respectively with terminated adaptive actions. A mean-field theory based on the link densities in co-evolving network is formulated and the trinomial closure scheme is applied to obtain analytical solutions. The analytic results agree with simulation results on ARPS well. In addition, the different probabilities of winning, losing, and drawing a game among the agents are identified as the origin of the small discrepancy between analytic and simulation results. As a result of the adaptive actions, agents of higher degrees are often those being taken advantage of. Agents with a smaller (larger) degree than the mean degree have a higher (smaller) probability of winning than losing. The results are informative for future attempts on formulating more accurate theories.

Evolvable Work-Practice Interfaces Between Humans and Agents, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — NASA science researchers and payload specialists will be supported in their tasks by increasingly complex computational components. Whether these are agents...

Proliferative kidney disease (PKD) agent Tetracapsuloides bryosalmonae in brown trout populations in Estonia.

Science.gov (United States)

Dash, Megha; Vasemägi, Anti

2014-05-13

Proliferative kidney disease (PKD) caused by the myxozoan parasite Tetracapsuloides bryosalmonae is a serious parasitic disease threatening both farmed and wild salmonid populations, but very little is currently known about the distribution of the parasite in the Baltic Sea region. In this study we (1) report the development of a novel multiplex PCR method for fast and reliable screening of T. bryosalmonae; (2) use this multiplex PCR method to show that the PKD agent T. bryosalmonae is widespread in natural brown trout Salmo trutta L. populations in Estonia; (3) evaluate monthly and yearly variation of T. bryosalmonae prevalence in juvenile trout; (4) assess T. bryosalmonae prevalence in different age-classes of fish (0+ vs. 1+ and older) and report the presence of the PKD agent in the kidneys of returning sea trout spawners; and (5) suggest the freshwater bryozoan Plumatella fungosa as a putative invertebrate host of T. bryosalmonae in Estonia. Our results demonstrate a highly heterogeneous distribution of T. bryosalmonae at the micro-geographic scale, indicating that PKD could have an important negative effect on recruitment in Estonian brown trout populations.

Bacterial agents and sensitivity pattern of neonatal conjuctivitis in ...

African Journals Online (AJOL)

Introduction: In Africa alone, between 1000 – 4000 children are blinded annually by conjunctivitis. In view of the changing aetiological agents documented in other parts of the world and evolving resistance of infective agents to therapeutic agents, the present study was designed to define the bacterial agents, their antibiotic ...

Swarm autonomic agents with self-destruct capability

Science.gov (United States)

Hinchey, Michael G. (Inventor); Sterritt, Roy (Inventor)

2011-01-01

Systems, methods and apparatus are provided through which in some embodiments an autonomic entity manages a system by generating one or more stay alive signals based on the functioning status and operating state of the system. In some embodiments, an evolvable synthetic neural system is operably coupled to one or more evolvable synthetic neural systems in a hierarchy. The evolvable neural interface receives and generates heartbeat monitor signals and pulse monitor signals that are used to generate a stay alive signal that is used to manage the operations of the synthetic neural system. In another embodiment an asynchronous Alice signal (Autonomic license) requiring valid credentials of an anonymous autonomous agent is initiated. An unsatisfactory Alice exchange may lead to self-destruction of the anonymous autonomous agent for self-protection.

Natural selection promotes antigenic evolvability.

Science.gov (United States)

Graves, Christopher J; Ros, Vera I D; Stevenson, Brian; Sniegowski, Paul D; Brisson, Dustin

2013-01-01

The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide an experimentally tractable system to test whether natural selection has favored mechanisms that increase evolvability. Many antigenic variation systems consist of paralogous unexpressed 'cassettes' that recombine into an expression site to rapidly alter the expressed protein. Importantly, the magnitude of antigenic change is a function of the genetic diversity among the unexpressed cassettes. Thus, evidence that selection favors among-cassette diversity is direct evidence that natural selection promotes antigenic evolvability. We used the Lyme disease bacterium, Borrelia burgdorferi, as a model to test the prediction that natural selection favors amino acid diversity among unexpressed vls cassettes and thereby promotes evolvability in a primary surface antigen, VlsE. The hypothesis that diversity among vls cassettes is favored by natural selection was supported in each B. burgdorferi strain analyzed using both classical (dN/dS ratios) and Bayesian population genetic analyses of genetic sequence data. This hypothesis was also supported by the conservation of highly mutable tandem-repeat structures across B. burgdorferi strains despite a near complete absence of sequence conservation. Diversification among vls cassettes due to natural selection and mutable repeat structures promotes long-term antigenic evolvability of VlsE. These findings provide a direct demonstration that molecular mechanisms that enhance evolvability of surface antigens are an evolutionary adaptation. The molecular evolutionary processes identified here can serve as a model for the evolution of antigenic evolvability in many pathogens which utilize similar strategies to establish chronic infections.

Natural selection promotes antigenic evolvability.

Directory of Open Access Journals (Sweden)

Christopher J Graves

Full Text Available The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide an experimentally tractable system to test whether natural selection has favored mechanisms that increase evolvability. Many antigenic variation systems consist of paralogous unexpressed 'cassettes' that recombine into an expression site to rapidly alter the expressed protein. Importantly, the magnitude of antigenic change is a function of the genetic diversity among the unexpressed cassettes. Thus, evidence that selection favors among-cassette diversity is direct evidence that natural selection promotes antigenic evolvability. We used the Lyme disease bacterium, Borrelia burgdorferi, as a model to test the prediction that natural selection favors amino acid diversity among unexpressed vls cassettes and thereby promotes evolvability in a primary surface antigen, VlsE. The hypothesis that diversity among vls cassettes is favored by natural selection was supported in each B. burgdorferi strain analyzed using both classical (dN/dS ratios and Bayesian population genetic analyses of genetic sequence data. This hypothesis was also supported by the conservation of highly mutable tandem-repeat structures across B. burgdorferi strains despite a near complete absence of sequence conservation. Diversification among vls cassettes due to natural selection and mutable repeat structures promotes long-term antigenic evolvability of VlsE. These findings provide a direct demonstration that molecular mechanisms that enhance evolvability of surface antigens are an evolutionary adaptation. The molecular evolutionary processes identified here can serve as a model for the evolution of antigenic evolvability in many pathogens which utilize similar strategies to establish

Revisiting Robustness and Evolvability: Evolution in Weighted Genotype Spaces

Science.gov (United States)

Partha, Raghavendran; Raman, Karthik

2014-01-01

Robustness and evolvability are highly intertwined properties of biological systems. The relationship between these properties determines how biological systems are able to withstand mutations and show variation in response to them. Computational studies have explored the relationship between these two properties using neutral networks of RNA sequences (genotype) and their secondary structures (phenotype) as a model system. However, these studies have assumed every mutation to a sequence to be equally likely; the differences in the likelihood of the occurrence of various mutations, and the consequence of probabilistic nature of the mutations in such a system have previously been ignored. Associating probabilities to mutations essentially results in the weighting of genotype space. We here perform a comparative analysis of weighted and unweighted neutral networks of RNA sequences, and subsequently explore the relationship between robustness and evolvability. We show that assuming an equal likelihood for all mutations (as in an unweighted network), underestimates robustness and overestimates evolvability of a system. In spite of discarding this assumption, we observe that a negative correlation between sequence (genotype) robustness and sequence evolvability persists, and also that structure (phenotype) robustness promotes structure evolvability, as observed in earlier studies using unweighted networks. We also study the effects of base composition bias on robustness and evolvability. Particularly, we explore the association between robustness and evolvability in a sequence space that is AU-rich – sequences with an AU content of 80% or higher, compared to a normal (unbiased) sequence space. We find that evolvability of both sequences and structures in an AU-rich space is lesser compared to the normal space, and robustness higher. We also observe that AU-rich populations evolving on neutral networks of phenotypes, can access less phenotypic variation compared to

Basal metabolic rate can evolve independently of morphological and behavioural traits.

Science.gov (United States)

Mathot, K J; Martin, K; Kempenaers, B; Forstmeier, W

2013-09-01

Quantitative genetic analyses of basal metabolic rate (BMR) can inform us about the evolvability of the trait by providing estimates of heritability, and also of genetic correlations with other traits that may constrain the ability of BMR to respond to selection. Here, we studied a captive population of zebra finches (Taeniopygia guttata) in which selection lines for male courtship rate have been established. We measure BMR in these lines to see whether selection on male sexual activity would change BMR as a potentially correlated trait. We find that the genetic correlation between courtship rate and BMR is practically zero, indicating that the two traits can evolve independently of each other. Interestingly, we find that the heritability of BMR in our population (h(2)=0.45) is markedly higher than was previously reported for a captive zebra finch population from Norway. A comparison of the two studies shows that additive genetic variance in BMR has been largely depleted in the Norwegian population, especially the genetic variance in BMR that is independent of body mass. In our population, the slope of BMR increase with body mass differs not only between the sexes but also between the six selection lines, which we tentatively attribute to genetic drift and/or founder effects being strong in small populations. Our study therefore highlights two things. First, the evolvability of BMR may be less constrained by genetic correlations and lack of independent genetic variation than previously described. Second, genetic drift in small populations can rapidly lead to different evolvabilities across populations.

Hyperthermia and chemotherapy agent

International Nuclear Information System (INIS)

Roizin-Towle, L.; Hall, E.J.

1981-01-01

The use of chemotherapeutic agents for the treatment of cancer dates back to the late 19th century, but the modern era of chemotherapy drugs was ushered in during the 1940's with the development of the polyfunctional alkylating agent. Since then, numerous classes of drugs have evolved and the combined use of antineoplastic agents with other treatment modalities such as radiation or heat, remains a large relatively unexplored area. This approach, combining local hyperthermia with chemotherapy agents affords a measure of targeting and selective toxicity not previously available for drugs. In this paper, the effects of adriamycin, bleomycin and cis-platinum are examined. The adjuvant use of heat may also reverse the resistance of hypoxic cells noted for some chemotherapy agents

The effect of trait type and strength of selection on heritability and evolvability in an island bird population.

Science.gov (United States)

Wheelwright, Nathaniel T; Keller, Lukas F; Postma, Erik

2014-11-01

The heritability (h(2) ) of fitness traits is often low. Although this has been attributed to directional selection having eroded genetic variation in direct proportion to the strength of selection, heritability does not necessarily reflect a trait's additive genetic variance and evolutionary potential ("evolvability"). Recent studies suggest that the low h(2) of fitness traits in wild populations is caused not by a paucity of additive genetic variance (VA ) but by greater environmental or nonadditive genetic variance (VR ). We examined the relationship between h(2) and variance-standardized selection intensities (i or βσ ), and between evolvability (IA :VA divided by squared phenotypic trait mean) and mean-standardized selection gradients (βμ ). Using 24 years of data from an island population of Savannah sparrows, we show that, across diverse traits, h(2) declines with the strength of selection, whereas IA and IR (VR divided by squared trait mean) are independent of the strength of selection. Within trait types (morphological, reproductive, life-history), h(2) , IA , and IR are all independent of the strength of selection. This indicates that certain traits have low heritability because of increased residual variance due to the age at which they are expressed or the multiple factors influencing their expression, rather than their association with fitness. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Gossip-based solutions for discrete rendezvous in populations of communicating agents.

Science.gov (United States)

Hollander, Christopher D; Wu, Annie S

2014-01-01

The objective of the rendezvous problem is to construct a method that enables a population of agents to agree on a spatial (and possibly temporal) meeting location. We introduce the buffered gossip algorithm as a general solution to the rendezvous problem in a discrete domain with direct communication between decentralized agents. We compare the performance of the buffered gossip algorithm against the well known uniform gossip algorithm. We believe that a buffered solution is preferable to an unbuffered solution, such as the uniform gossip algorithm, because the use of a buffer allows an agent to use multiple information sources when determining its desired rendezvous point, and that access to multiple information sources may improve agent decision making by reinforcing or contradicting an initial choice. To show that the buffered gossip algorithm is an actual solution for the rendezvous problem, we construct a theoretical proof of convergence and derive the conditions under which the buffered gossip algorithm is guaranteed to produce a consensus on rendezvous location. We use these results to verify that the uniform gossip algorithm also solves the rendezvous problem. We then use a multi-agent simulation to conduct a series of simulation experiments to compare the performance between the buffered and uniform gossip algorithms. Our results suggest that the buffered gossip algorithm can solve the rendezvous problem faster than the uniform gossip algorithm; however, the relative performance between these two solutions depends on the specific constraints of the problem and the parameters of the buffered gossip algorithm.

Gossip-based solutions for discrete rendezvous in populations of communicating agents.

Directory of Open Access Journals (Sweden)

Christopher D Hollander

Full Text Available The objective of the rendezvous problem is to construct a method that enables a population of agents to agree on a spatial (and possibly temporal meeting location. We introduce the buffered gossip algorithm as a general solution to the rendezvous problem in a discrete domain with direct communication between decentralized agents. We compare the performance of the buffered gossip algorithm against the well known uniform gossip algorithm. We believe that a buffered solution is preferable to an unbuffered solution, such as the uniform gossip algorithm, because the use of a buffer allows an agent to use multiple information sources when determining its desired rendezvous point, and that access to multiple information sources may improve agent decision making by reinforcing or contradicting an initial choice. To show that the buffered gossip algorithm is an actual solution for the rendezvous problem, we construct a theoretical proof of convergence and derive the conditions under which the buffered gossip algorithm is guaranteed to produce a consensus on rendezvous location. We use these results to verify that the uniform gossip algorithm also solves the rendezvous problem. We then use a multi-agent simulation to conduct a series of simulation experiments to compare the performance between the buffered and uniform gossip algorithms. Our results suggest that the buffered gossip algorithm can solve the rendezvous problem faster than the uniform gossip algorithm; however, the relative performance between these two solutions depends on the specific constraints of the problem and the parameters of the buffered gossip algorithm.

Higher rates of sex evolve in spatially heterogeneous environments.

Science.gov (United States)

Becks, Lutz; Agrawal, Aneil F

2010-11-04

The evolution and maintenance of sexual reproduction has puzzled biologists for decades. Although this field is rich in hypotheses, experimental evidence is scarce. Some important experiments have demonstrated differences in evolutionary rates between sexual and asexual populations; other experiments have documented evolutionary changes in phenomena related to genetic mixing, such as recombination and selfing. However, direct experiments of the evolution of sex within populations are extremely rare (but see ref. 12). Here we use the rotifer, Brachionus calyciflorus, which is capable of both sexual and asexual reproduction, to test recent theory predicting that there is more opportunity for sex to evolve in spatially heterogeneous environments. Replicated experimental populations of rotifers were maintained in homogeneous environments, composed of either high- or low-quality food habitats, or in heterogeneous environments that consisted of a mix of the two habitats. For populations maintained in either type of homogeneous environment, the rate of sex evolves rapidly towards zero. In contrast, higher rates of sex evolve in populations experiencing spatially heterogeneous environments. The data indicate that the higher level of sex observed under heterogeneity is not due to sex being less costly or selection against sex being less efficient; rather sex is sufficiently advantageous in heterogeneous environments to overwhelm its inherent costs. Counter to some alternative theories for the evolution of sex, there is no evidence that genetic drift plays any part in the evolution of sex in these populations.

Evolved pesticide tolerance in amphibians: Predicting mechanisms based on pesticide novelty and mode of action

International Nuclear Information System (INIS)

Hua, Jessica; Jones, Devin K.; Mattes, Brian M.; Cothran, Rickey D.; Relyea, Rick A.; Hoverman, Jason T.

2015-01-01

We examined 10 wood frog populations distributed along an agricultural gradient for their tolerance to six pesticides (carbaryl, malathion, cypermethrin, permethrin, imidacloprid, and thiamethoxam) that differed in date of first registration (pesticide novelty) and mode-of-action (MOA). Our goals were to assess whether: 1) tolerance was correlated with distance to agriculture for each pesticide, 2) pesticide novelty predicted the likelihood of evolved tolerance, and 3) populations display cross-tolerance between pesticides that share and differ in MOA. Wood frog populations located close to agriculture were more tolerant to carbaryl and malathion than populations far from agriculture. Moreover, the strength of the relationship between distance to agriculture and tolerance was stronger for older pesticides compared to newer pesticides. Finally, we found evidence for cross-tolerance between carbaryl and malathion (two pesticides that share MOA). This study provides one of the most comprehensive approaches for understanding patterns of evolved tolerance in non-pest species. - Highlights: • We explored patterns of tolerance to six insecticides across 10 wood frog populations. • We found evidence that wood frogs have evolved tolerance to carbaryl and malathion. • The likelihood of evolved tolerance was stronger for older compared to newer pesticides. • We found evidence for cross-tolerance between carbaryl and malathion. • This is one of the most comprehensive approaches studying evolved tolerance in a non-pest species. - Using 10 wood frog populations, we detected evidence for evolved tolerance, found that the evolved tolerance depends on insecticide novelty, and found evidence for cross-tolerance.

Environmental agents and erectile dysfunction: a study in a consulting population.

Science.gov (United States)

Oliva, Alejandro; Giami, Alain; Multigner, Luc

2002-01-01

We evaluated chemical and physical environmental agents as risk factors for erectile dysfunction among a consulting population. We studied 199 men who sought medical help for erectile disorders between 1996 and 1998 in 3 andrology units in the Litoral Sur region of Argentina. Patients were evaluated by monitoring nocturnal penile tumescence and rigidity, and were classified as having normal (n = 26), irregular (dissociation, short episode or low amplitude, n = 146), or flat erectile pattern (n = 26). Exposure to environmental agents was assessed by a detailed interview, and 4 groups were constituted: nonexposed, pesticide-exposed, solvent-exposed, and heat-exposed. A multivariate polytomous logistic regression model was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for association between quality of nocturnal erections and exposure groups adjusted for confounding factors. Exposure to environmental agents was a risk factor for a flat erectile pattern (OR 7.1, 95% CI 1.5-33.0 for pesticides; OR 12.2, 95% CI 1.2-124.8 for solvents; and OR 1.7, 95% CI 0.3-9.4 for heat). Associations were much weaker for an irregular erectile pattern (OR 1.8, 95% CI 0.5-6.7 for pesticides; OR 2.1, 95% CI 0.3-17.9 for solvents; and OR 1.2, 95% CI 0.4-4.0 for heat). Our results suggest that environmental agents constitute a risk factor for erectile dysfunction by interfering with erectile ability.

Multi-Agent Inference in Social Networks: A Finite Population Learning Approach.

Science.gov (United States)

Fan, Jianqing; Tong, Xin; Zeng, Yao

When people in a society want to make inference about some parameter, each person may want to use data collected by other people. Information (data) exchange in social networks is usually costly, so to make reliable statistical decisions, people need to trade off the benefits and costs of information acquisition. Conflicts of interests and coordination problems will arise in the process. Classical statistics does not consider people's incentives and interactions in the data collection process. To address this imperfection, this work explores multi-agent Bayesian inference problems with a game theoretic social network model. Motivated by our interest in aggregate inference at the societal level, we propose a new concept, finite population learning , to address whether with high probability, a large fraction of people in a given finite population network can make "good" inference. Serving as a foundation, this concept enables us to study the long run trend of aggregate inference quality as population grows.

On the Critical Role of Divergent Selection in Evolvability

Directory of Open Access Journals (Sweden)

Joel Lehman

2016-08-01

Full Text Available An ambitious goal in evolutionary robotics is to evolve increasingly complex robotic behaviors with minimal human design effort. Reaching this goal requires evolutionary algorithms that can unlock from genetic encodings their latent potential for evolvability. One issue clouding this goal is conceptual confusion about evolvability, which often obscures the aspects of evolvability that are important or desirable. The danger from such confusion is that it may establish unrealistic goals for evolvability that prove unproductive in practice. An important issue separate from conceptual confusion is the common misalignment between selection and evolvability in evolutionary robotics. While more expressive encodings can represent higher-level adaptations (e.g. sexual reproduction or developmental systems that increase long-term evolutionary potential (i.e. evolvability, realizing such potential requires gradients of fitness and evolvability to align. In other words, selection is often a critical factor limiting increasing evolvability. Thus, drawing from a series of recent papers, this article seeks to both (1 clarify and focus the ways in which the term evolvability is used within artificial evolution, and (2 argue for the importance of one type of selection, i.e. divergent selection, for enabling evolvability. The main argument is that there is a fundamental connection between divergent selection and evolvability (on both the individual and population level that does not hold for typical goal-oriented selection. The conclusion is that selection pressure plays a critical role in realizing the potential for evolvability, and that divergent selection in particular provides a principled mechanism for encouraging evolvability in artificial evolution.

Evolutionary snowdrift game incorporating costly punishment in structured populations

Science.gov (United States)

Chan, Nat W. H.; Xu, C.; Tey, Siew Kian; Yap, Yee Jiun; Hui, P. M.

2013-01-01

The role of punishment and the effects of a structured population in promoting cooperation are important issues. Within a recent model of snowdrift game (SG) incorporating a costly punishing strategy (P), we study the effects of a population connected through a square lattice. The punishers, who carry basically a cooperative (C) character, are willing to pay a cost α so as to punish a non-cooperative (D) opponent by β. Depending on α, β, the cost-to-benefit ratio r in SG, and the initial conditions, the system evolves into different phases that could be homogeneous or inhomogeneous. The spatial structure imposes geometrical constraint on how one agent is affected by neighboring agents. Results of extensive numerical simulations, both for the steady state and the dynamics, are presented. Possible phases are identified and discussed, and isolated phases in the r-β space are identified as special local structures of strategies that are stable due to the lattice structure. In contrast to a well-mixed population where punishers are suppressed due to the cost of punishment, the altruistic punishing strategy can flourish and prevail for appropriate values of the parameters, implying an enhancement in cooperation by imposing punishments in a structured population. The system could evolve to a phase corresponding to the coexistence of C, D, and P strategies at some particular payoff parameters, and such a phase is absent in a well-mixed population. The pair approximation, a commonly used analytic approach, is extended from a two-strategy system to a three-strategy system. We show that the pair approximation can, at best, capture the numerical results only qualitatively. Due to the improper way of including spatial correlation imposed by the lattice structure, the approximation does not give the frequencies of C, D, and P accurately and fails to give the homogeneous AllD and AllP phases.

Environmental Noise, Genetic Diversity and the Evolution of Evolvability and Robustness in Model Gene Networks

Science.gov (United States)

Steiner, Christopher F.

2012-01-01

The ability of organisms to adapt and persist in the face of environmental change is accepted as a fundamental feature of natural systems. More contentious is whether the capacity of organisms to adapt (or “evolvability”) can itself evolve and the mechanisms underlying such responses. Using model gene networks, I provide evidence that evolvability emerges more readily when populations experience positively autocorrelated environmental noise (red noise) compared to populations in stable or randomly varying (white noise) environments. Evolvability was correlated with increasing genetic robustness to effects on network viability and decreasing robustness to effects on phenotypic expression; populations whose networks displayed greater viability robustness and lower phenotypic robustness produced more additive genetic variation and adapted more rapidly in novel environments. Patterns of selection for robustness varied antagonistically with epistatic effects of mutations on viability and phenotypic expression, suggesting that trade-offs between these properties may constrain their evolutionary responses. Evolution of evolvability and robustness was stronger in sexual populations compared to asexual populations indicating that enhanced genetic variation under fluctuating selection combined with recombination load is a primary driver of the emergence of evolvability. These results provide insight into the mechanisms potentially underlying rapid adaptation as well as the environmental conditions that drive the evolution of genetic interactions. PMID:23284934

Effects of Orbital Lifetime Reduction on the Long-Term Earth Satellite Population as Modeled by EVOLVE 4.0

Science.gov (United States)

Krisko, Paula H.; Opiela, John N.; Liou, Jer-Chyi; Anz-Meador, Phillip D.; Theall, Jeffrey R.

1999-01-01

The latest update of the NASA orbital debris environment model, EVOLVE 4.0, has been used to study the effect of various proposed debris mitigation measures, including the NASA 25-year guideline. EVOLVE 4.0, which includes updates of the NASA breakup, solar activity, and the orbit propagator models, a GEO analysis option, and non-fragmentation debris source models, allows for the statistical modeling and predicted growth of the particle population >1 mm in characteristic length in LEO and GEO orbits. The initial implementation of this &odel has been to study the sensitivity of the overall LEO debris environment to mitigation measures designed to limit the lifetime of intact objects in LEO orbits. The mitigation measures test matrix for this study included several commonly accepted testing schemes, i.e., the variance of the maximum LEO lifetime from 10 to 50 years, the date of the initial implementation of this policy, the shut off of all explosions at some specified date, and the inclusion of disposal orbits. All are timely studies in that all scenarios have been suggested by researchers and satellite operators as options for the removal of debris from LEO orbits.

Water availability as an agent of selection in introduced populations of Arabidopsis thaliana: impacts on flowering time evolution.

Science.gov (United States)

Stock, Amanda J; McGoey, Brechann V; Stinchcombe, John R

2015-01-01

Flowering is one of the most influential events in the life history of a plant and one of the main determinants of reproductive investment and lifetime fitness. It is also a highly complex trait controlled by dozens of genes. Understanding the selective pressures influencing time to flowering, and being able to reliably predict how it will evolve in novel environments, are unsolved challenges for plant evolutionary geneticists. Using the model plant species, Arabidopsis thaliana, we examined the impact of simulated high and low winter precipitation levels on the flowering time of naturalized lines from across the eastern portion of the introduced North American range, and the fitness consequences of early versus late flowering. Flowering time order was significantly correlated across two environments-in a previous common garden experiment and in environmental chambers set to mimic mid-range photoperiod and temperature conditions. Plants in low water flowered earlier, had fewer basal branches and produced fewer fruits. Selection in both treatments favored earlier flowering and more basal branches. Our analyses revealed an interaction between flowering time and water treatment for fitness, where flowering later was more deleterious for fitness in the low water treatment. Our results are consistent with the hypothesis that differences in winter precipitation levels are one of the selective agents underlying a flowering time cline in introduced A. thaliana populations.

Water availability as an agent of selection in introduced populations of Arabidopsis thaliana: impacts on flowering time evolution

Directory of Open Access Journals (Sweden)

Amanda J. Stock

2015-04-01

Full Text Available Flowering is one of the most influential events in the life history of a plant and one of the main determinants of reproductive investment and lifetime fitness. It is also a highly complex trait controlled by dozens of genes. Understanding the selective pressures influencing time to flowering, and being able to reliably predict how it will evolve in novel environments, are unsolved challenges for plant evolutionary geneticists. Using the model plant species, Arabidopsis thaliana, we examined the impact of simulated high and low winter precipitation levels on the flowering time of naturalized lines from across the eastern portion of the introduced North American range, and the fitness consequences of early versus late flowering. Flowering time order was significantly correlated across two environments—in a previous common garden experiment and in environmental chambers set to mimic mid-range photoperiod and temperature conditions. Plants in low water flowered earlier, had fewer basal branches and produced fewer fruits. Selection in both treatments favored earlier flowering and more basal branches. Our analyses revealed an interaction between flowering time and water treatment for fitness, where flowering later was more deleterious for fitness in the low water treatment. Our results are consistent with the hypothesis that differences in winter precipitation levels are one of the selective agents underlying a flowering time cline in introduced A. thaliana populations.

Opinion dynamics of learning agents: does seeking consensus lead to disagreement?

International Nuclear Information System (INIS)

Vicente, Renato; Martins, André C R; Caticha, Nestor

2009-01-01

We study opinion dynamics in a population of interacting adaptive agents voting on a set of issues represented by vectors. We consider agents who can classify issues into one of two categories and can arrive at their opinions using an adaptive algorithm. Adaptation comes from learning and the information for the learning process comes from interacting with other neighboring agents and trying to change the internal state in order to concur with their opinions. The change in the internal state is driven by the information contained in the issue and in the opinion of the other agent. We present results in a simple yet rich context where each agent uses a Boolean perceptron to state their opinion. If the update occurs with information asynchronously exchanged among pairs of agents, then the typical case, if the number of issues is kept small, is the evolution into a society torn by the emergence of factions with extreme opposite beliefs. This occurs even when seeking consensus with agents with opposite opinions. If the number of issues is large, the dynamics becomes trapped, the society does not evolve into factions and a distribution of moderate opinions is observed. The synchronous case is technically simpler and is studied by formulating the problem in terms of differential equations that describe the evolution of order parameters that measure the consensus between pairs of agents. We show that for a large number of issues and unidirectional information flow, global consensus is a fixed point; however, the approach to this consensus is glassy for large societies

Opinion dynamics of learning agents: does seeking consensus lead to disagreement?

Science.gov (United States)

Vicente, Renato; Martins, André C. R.; Caticha, Nestor

2009-03-01

We study opinion dynamics in a population of interacting adaptive agents voting on a set of issues represented by vectors. We consider agents who can classify issues into one of two categories and can arrive at their opinions using an adaptive algorithm. Adaptation comes from learning and the information for the learning process comes from interacting with other neighboring agents and trying to change the internal state in order to concur with their opinions. The change in the internal state is driven by the information contained in the issue and in the opinion of the other agent. We present results in a simple yet rich context where each agent uses a Boolean perceptron to state their opinion. If the update occurs with information asynchronously exchanged among pairs of agents, then the typical case, if the number of issues is kept small, is the evolution into a society torn by the emergence of factions with extreme opposite beliefs. This occurs even when seeking consensus with agents with opposite opinions. If the number of issues is large, the dynamics becomes trapped, the society does not evolve into factions and a distribution of moderate opinions is observed. The synchronous case is technically simpler and is studied by formulating the problem in terms of differential equations that describe the evolution of order parameters that measure the consensus between pairs of agents. We show that for a large number of issues and unidirectional information flow, global consensus is a fixed point; however, the approach to this consensus is glassy for large societies.

Agent-Supported Mission Operations Teamwork

Science.gov (United States)

Malin, Jane T.

2003-01-01

This slide presentation reviews the development of software agents to support of mission operations teamwork. The goals of the work was to make automation by agents easy to use, supervise and direct, manage information and communication to decrease distraction, interruptions, workload and errors, reduce mission impact of off-nominal situations and increase morale and decrease turnover. The accomplishments or the project are: 1. Collaborative agents - mixed initiative and creation of instructions for mediating agent 2. Methods for prototyping, evaluating and evolving socio-technical systems 3. Technology infusion: teamwork tools in mISSIons 4. Demonstrations in simulation testbed An example of the use of agent is given, the use of an agent to monitor a N2 tank leak. An incomplete instruction to the agent is handled with mediating assistants, or Intelligent Briefing and Response Assistant (IBRA). The IBRA Engine also watches data stream for triggers and executes Act-Whenever actions. There is also a Briefing and Response Instruction (BRI) which is easy for a discipline specialist to create through a BRI editor.

Investigating Biological Control Agents for Controlling Invasive Populations of the Mealybug Pseudococcus comstocki in France.

Directory of Open Access Journals (Sweden)

Thibaut Malausa

Full Text Available Pseudococcus comstocki (Hemiptera: Pseudococcidae is a mealybug species native to Eastern Asia and present as an invasive pest in northern Italy and southern France since the start of the century. It infests apple and pear trees, grapevines and some ornamental trees. Biocontrol programmes against this pest proved successful in central Asia and North America in the second half of the 20th century. In this study, we investigated possible biocontrol agents against P. comstocki, with the aim of developing a biocontrol programme in France. We carried out systematic DNA-barcoding at each step in the search for a specialist parasitoid. First we characterised the French target populations of P. comstocki. We then identified the parasitoids attacking P. comstocki in France. Finally, we searched for foreign mealybug populations identified a priori as P. comstocki and surveyed their hymenopteran parasitoids. Three mealybug species (P. comstocki, P. viburni and P. cryptus were identified during the survey, together with at least 16 different parasitoid taxa. We selected candidate biological control agent populations for use against P. comstocki in France, from the species Allotropa burrelli (Hymenoptera: Platygastridae and Acerophagus malinus (Hymenoptera: Encyrtidae. The coupling of molecular and morphological characterisation for both pests and natural enemies facilitated the programme development and the rejection of unsuitable or generalist parasitoids.

Co-evolving prisoner's dilemma: Performance indicators and analytic approaches

Science.gov (United States)

Zhang, W.; Choi, C. W.; Li, Y. S.; Xu, C.; Hui, P. M.

2017-02-01

Understanding the intrinsic relation between the dynamical processes in a co-evolving network and the necessary ingredients in formulating a reliable theory is an important question and a challenging task. Using two slightly different definitions of performance indicator in the context of a co-evolving prisoner's dilemma game, it is shown that very different cooperative levels result and theories of different complexity are required to understand the key features. When the payoff per opponent is used as the indicator (Case A), non-cooperative strategy has an edge and dominates in a large part of the parameter space formed by the cutting-and-rewiring probability and the strategy imitation probability. When the payoff from all opponents is used (Case B), cooperative strategy has an edge and dominates the parameter space. Two distinct phases, one homogeneous and dynamical and another inhomogeneous and static, emerge and the phase boundary in the parameter space is studied in detail. A simple theory assuming an average competing environment for cooperative agents and another for non-cooperative agents is shown to perform well in Case A. The same theory, however, fails badly for Case B. It is necessary to include more spatial correlation into a theory for Case B. We show that the local configuration approximation, which takes into account of the different competing environments for agents with different strategies and degrees, is needed to give reliable results for Case B. The results illustrate that formulating a proper theory requires both a conceptual understanding of the effects of the adaptive processes in the problem and a delicate balance between simplicity and accuracy.

Biobanks in the United States: how to identify an undefined and rapidly evolving population.

Science.gov (United States)

Boyer, Gregory J; Whipple, Warren; Cadigan, R Jean; Henderson, Gail E

2012-12-01

As part of a larger organizational study, we sought to survey biobanks in the United States. However, we encountered two problems with this population. First, no common definition of biobanks exists. Second, no census is available of these facilities from which to sample in order to implement a survey. In light of these problems, we employed a multifaceted approach using electronic searches of PubMed, RePORTER, and Google. In addition, we systematically searched for biobanks housed within universities that have NIH-designated Clinical and Translational Science Awards (CTSA). We expanded this part of the search by looking for biobanks among all members of the American Association of Medical Colleges (AAMC). Finally, we added banks to our database found previously by other researchers and banks found via correspondence with our colleagues. Our search strategy produced a database of 624 biobanks for which we were able to confirm contact information in order to conduct our online survey. Another 140 biobanks were identified but did not respond to our requests to confirm their existence or contact information. In order to maximize both the uniqueness of banks found and the greatest return on effort for each search, we suggest targeting resources that are already organized. In our work, these included the CTSA, AAMC, and part of the Google searches. We contend that our search provides a model for analysis of new fields of research and/or rapidly evolving industries. Furthermore, our approach demonstrates that with the appropriate tools it is possible to develop a systematic and comprehensive database to investigate undefined populations.

Programming adaptive control to evolve increased metabolite production.

Science.gov (United States)

Chou, Howard H; Keasling, Jay D

2013-01-01

The complexity inherent in biological systems challenges efforts to rationally engineer novel phenotypes, especially those not amenable to high-throughput screens and selections. In nature, increased mutation rates generate diversity in a population that can lead to the evolution of new phenotypes. Here we construct an adaptive control system that increases the mutation rate in order to generate diversity in the population, and decreases the mutation rate as the concentration of a target metabolite increases. This system is called feedback-regulated evolution of phenotype (FREP), and is implemented with a sensor to gauge the concentration of a metabolite and an actuator to alter the mutation rate. To evolve certain novel traits that have no known natural sensors, we develop a framework to assemble synthetic transcription factors using metabolic enzymes and construct four different sensors that recognize isopentenyl diphosphate in bacteria and yeast. We verify FREP by evolving increased tyrosine and isoprenoid production.

Evolving Neural Turing Machines for Reward-based Learning

DEFF Research Database (Denmark)

Greve, Rasmus Boll; Jacobsen, Emil Juul; Risi, Sebastian

2016-01-01

An unsolved problem in neuroevolution (NE) is to evolve artificial neural networks (ANN) that can store and use information to change their behavior online. While plastic neural networks have shown promise in this context, they have difficulties retaining information over longer periods of time...... version of the double T-Maze, a complex reinforcement-like learning problem. In the T-Maze learning task the agent uses the memory bank to display adaptive behavior that normally requires a plastic ANN, thereby suggesting a complementary and effective mechanism for adaptive behavior in NE....

SURVEYING THE AGENTS OF GALAXY EVOLUTION IN THE TIDALLY STRIPPED, LOW METALLICITY SMALL MAGELLANIC CLOUD (SAGE-SMC). II. COOL EVOLVED STARS

International Nuclear Information System (INIS)

Boyer, Martha L.; Meixner, Margaret; Gordon, Karl D.; Shiao, Bernie; Srinivasan, Sundar; Van Loon, Jacco Th.; McDonald, Iain; Kemper, F.; Zaritsky, Dennis; Block, Miwa; Engelbracht, Charles W.; Misselt, Karl; Babler, Brian; Bracker, Steve; Meade, Marilyn; Whitney, Barbara; Hora, Joe; Robitaille, Thomas; Indebetouw, Remy; Sewilo, Marta

2011-01-01

We investigate the infrared (IR) properties of cool, evolved stars in the Small Magellanic Cloud (SMC), including the red giant branch (RGB) stars and the dust-producing red supergiant (RSG) and asymptotic giant branch (AGB) stars using observations from the Spitzer Space Telescope Legacy program entitled 'Surveying the Agents of Galaxy Evolution in the Tidally Stripped, Low Metallicity SMC', or SAGE-SMC. The survey includes, for the first time, full spatial coverage of the SMC bar, wing, and tail regions at IR wavelengths (3.6-160 μm). We identify evolved stars using a combination of near-IR and mid-IR photometry and point out a new feature in the mid-IR color-magnitude diagram that may be due to particularly dusty O-rich AGB stars. We find that the RSG and AGB stars each contribute ∼20% of the global SMC flux (extended + point-source) at 3.6 μm, which emphasizes the importance of both stellar types to the integrated flux of distant metal-poor galaxies. The equivalent SAGE survey of the higher-metallicity Large Magellanic Cloud (SAGE-LMC) allows us to explore the influence of metallicity on dust production. We find that the SMC RSG stars are less likely to produce a large amount of dust (as indicated by the [3.6] - [8] color). There is a higher fraction of carbon-rich stars in the SMC, and these stars appear to reach colors as red as their LMC counterparts, indicating that C-rich dust forms efficiently in both galaxies. A preliminary estimate of the dust production in AGB and RSG stars reveals that the extreme C-rich AGB stars dominate the dust input in both galaxies, and that the O-rich stars may play a larger role in the LMC than in the SMC.

Evolvability Search: Directly Selecting for Evolvability in order to Study and Produce It

DEFF Research Database (Denmark)

Mengistu, Henok; Lehman, Joel Anthony; Clune, Jeff

2016-01-01

of evolvable digital phenotypes. Although some types of selection in evolutionary computation indirectly encourage evolvability, one unexplored possibility is to directly select for evolvability. To do so, we estimate an individual's future potential for diversity by calculating the behavioral diversity of its...... immediate offspring, and select organisms with increased offspring variation. While the technique is computationally expensive, we hypothesized that direct selection would better encourage evolvability than indirect methods. Experiments in two evolutionary robotics domains confirm this hypothesis: in both...... domains, such Evolvability Search produces solutions with higher evolvability than those produced with Novelty Search or traditional objective-based search algorithms. Further experiments demonstrate that the higher evolvability produced by Evolvability Search in a training environment also generalizes...

Hybrid weeds! Agent biotypes!: Montana's ever-evolving toadflax biological control soap opera

Science.gov (United States)

S. E. Sing; D. K. Weaver; S. M. Ward; J. Milan; C. L. Jorgensen; R. A. Progar; A. Gassmann; I. Tooevski

2013-01-01

An exotic toadflax stem mining weevil conventionally identified as Mecinus janthinus Germar has become widely established on Dalmatian toadflax [Linaria dalmatica (Linnaeus) Miller] in western North America, although agent density and control efficacy are highly variable across release sites (De Clerck-Floate & Miller, 2002; McClay & Hughes, 2007; Van Hezewijk...

Field-evolved resistance to imidacloprid and ethiprole in populations of brown planthopper Nilaparvata lugens collected from across South and East Asia.

Science.gov (United States)

Garrood, William T; Zimmer, Christoph T; Gorman, Kevin J; Nauen, Ralf; Bass, Chris; Davies, Thomas G E

2016-01-01

We report on the status of imidacloprid and ethiprole resistance in Nilaparvata lugens Stål collected from across South and East Asia over the period 2005-2012. A resistance survey found that field populations had developed up to 220-fold resistance to imidacloprid and 223-fold resistance to ethiprole, and that many of the strains collected showed high levels of resistance to both insecticides. We also found that the cytochrome P450 CYP6ER1 was significantly overexpressed in 12 imidacloprid-resistant populations tested when compared with a laboratory susceptible strain, with fold changes ranging from ten- to 90-fold. In contrast, another cytochrome P450 CYP6AY1, also implicated in imidacloprid resistance, was underexpressed in ten of the populations and only significantly overexpressed (3.5-fold) in a single population from India compared with the same susceptible strain. Further selection of two of the imidacloprid-resistant field strains correlated with an approximate threefold increase in expression of CYP6ER1. We conclude that overexpression of CYP6ER1 is associated with field-evolved resistance to imidacloprid in brown planthopper populations in five countries in South and East Asia. © 2015 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Partially satisfied to fully satisfied transitions in co-evolving inverse voter model and possible scaling behavior

International Nuclear Information System (INIS)

Choi, C.W.; Xu, C.; Hui, P.M.

2015-01-01

Understanding co-evolving networks characterized by the mutual influence of agents' actions and network structure remains a challenge. We study a co-evolving inverse voter model in which agents adapt to achieve a preferred environment with more opposite-opinion neighbors by rewiring their connections and switching opinion. Numerical studies reveal a transition from a dynamic partially satisfied phase to a frozen fully satisfied phase as the rewiring probability is varied. A simple mean field theory is shown to capture the behavior only qualitatively. An improved mean field theory carrying a longer spatial correlation gives better results. Motivated by numerical results in networks of different degrees and mean field results, we propose a scaling variable that combines the rewiring probability and mean degree in a special form. The scaling variable is shown to work well in analyzing data corresponding to different networks and different rewiring probabilities. An application is to predict the results for networks of different degrees based solely on results obtained from networks of one degree. Studying scaling behavior provides an alternative path for understanding co-evolving agent-based dynamical systems, especially in light of the trade-off between complexity of a theory and its accuracy. - Highlights: • Identified key features and phase transitions in coevolving inverse voter model. • Constructed a better theory incorporating longer spatial correlation. • Proposed scaling variable and illustrated possible scaling behavior. • Used scaling behavior to predict results of IVM in a different network.

Entrainment and Control of Bacterial Populations: An in Silico Study over a Spatially Extended Agent Based Model.

Science.gov (United States)

Mina, Petros; Tsaneva-Atanasova, Krasimira; Bernardo, Mario di

2016-07-15

We extend a spatially explicit agent based model (ABM) developed previously to investigate entrainment and control of the emergent behavior of a population of synchronized oscillating cells in a microfluidic chamber. Unlike most of the work in models of control of cellular systems which focus on temporal changes, we model individual cells with spatial dependencies which may contribute to certain behavioral responses. We use the model to investigate the response of both open loop and closed loop strategies, such as proportional control (P-control), proportional-integral control (PI-control) and proportional-integral-derivative control (PID-control), to heterogeinities and growth in the cell population, variations of the control parameters and spatial effects such as diffusion in the spatially explicit setting of a microfluidic chamber setup. We show that, as expected from the theory of phase locking in dynamical systems, open loop control can only entrain the cell population in a subset of forcing periods, with a wide variety of dynamical behaviors obtained outside these regions of entrainment. Closed-loop control is shown instead to guarantee entrainment in a much wider region of control parameter space although presenting limitations when the population size increases over a certain threshold. In silico tracking experiments are also performed to validate the ability of classical control approaches to achieve other reference behaviors such as a desired constant output or a linearly varying one. All simulations are carried out in BSim, an advanced agent-based simulator of microbial population which is here extended ad hoc to include the effects of control strategies acting onto the population.

Understanding the time dependence of atomic level populations in evolving plasmas

International Nuclear Information System (INIS)

Judge, Philip G.

2005-01-01

The time dependence of atomic level populations in evolving plasmas is studied using an eigenfunction expansion of the non-LTE rate equations. The work aims to develop understanding without the need for, and as an aid to, numerical solutions. The discussion is mostly limited to linear systems, especially those for optically thin plasmas, but the implicitly non-linear case of non-LTE radiative transfer is briefly discussed. Eigenvalue spectra for typical atomic systems are examined using results compiled by Hearon. Diagonal dominance and sign symmetry of rate matrices show that just one eigenvalue is zero (corresponding to the equilibrium state), that the remaining eigenvalues have negative real parts, and that oscillations, if any, are necessarily damped. Gershgorin's theorems are used to show that many eigenvalues are determined by the radiative lifetimes of certain levels, because of diagonal dominance. With other properties, this demonstrates the existence of both 'slow' and 'fast' time-scales, where the 'slow' evolution is controlled by properties of meta-stable levels. It is shown that, when collisions are present, Rydberg states contribute only 'fast' eigenvalues. This justifies use of the quasi-static approximation, in which atoms containing just meta-stable levels can suffice to determine the atomic evolution on time-scales long compared with typical radiative lifetimes. Analytic solutions for two- and three-level atoms are used to examine the basis of earlier intuitive ideas, such as the 'ionizing plasma' approximation. The power and limitations of Gershgorin's theorems are examined through examples taken from the solar atmosphere. The methods should help in the planning and interpretation of both experimental and numerical experiments in which atomic evolution is important. While the examples are astrophysical, the methods and results are applicable to plasmas in general

Minority games, evolving capitals and replicator dynamics

International Nuclear Information System (INIS)

Galla, Tobias; Zhang, Yi-Cheng

2009-01-01

We discuss a simple version of the minority game (MG) in which agents hold only one strategy each, but in which their capitals evolve dynamically according to their success and in which the total trading volume varies in time accordingly. This feature is known to be crucial for MGs to reproduce stylized facts of real market data. The stationary states and phase diagram of the model can be computed, and we show that the ergodicity breaking phase transition common for MGs, and marked by a divergence of the integrated response, is present also in this simplified model. An analogous majority game turns out to be relatively void of interesting features, and the total capital is found to diverge in time. Introducing a restraining force leads to a model akin to the replicator dynamics of evolutionary game theory, and we demonstrate that here a different type of phase transition is observed. Finally we briefly discuss the relation of this model with one strategy per player to more sophisticated minority games with dynamical capitals and several trading strategies per agent

Evolvable synthetic neural system

Science.gov (United States)

Curtis, Steven A. (Inventor)

2009-01-01

An evolvable synthetic neural system includes an evolvable neural interface operably coupled to at least one neural basis function. Each neural basis function includes an evolvable neural interface operably coupled to a heuristic neural system to perform high-level functions and an autonomic neural system to perform low-level functions. In some embodiments, the evolvable synthetic neural system is operably coupled to one or more evolvable synthetic neural systems in a hierarchy.

Impact of different policies on unhealthy dietary behaviors in an urban adult population: an agent-based simulation model.

Science.gov (United States)

Zhang, Donglan; Giabbanelli, Philippe J; Arah, Onyebuchi A; Zimmerman, Frederick J

2014-07-01

Unhealthy eating is a complex-system problem. We used agent-based modeling to examine the effects of different policies on unhealthy eating behaviors. We developed an agent-based simulation model to represent a synthetic population of adults in Pasadena, CA, and how they make dietary decisions. Data from the 2007 Food Attitudes and Behaviors Survey and other empirical studies were used to calibrate the parameters of the model. Simulations were performed to contrast the potential effects of various policies on the evolution of dietary decisions. Our model showed that a 20% increase in taxes on fast foods would lower the probability of fast-food consumption by 3 percentage points, whereas improving the visibility of positive social norms by 10%, either through community-based or mass-media campaigns, could improve the consumption of fruits and vegetables by 7 percentage points and lower fast-food consumption by 6 percentage points. Zoning policies had no significant impact. Interventions emphasizing healthy eating norms may be more effective than directly targeting food prices or regulating local food outlets. Agent-based modeling may be a useful tool for testing the population-level effects of various policies within complex systems.

Regulated open multi-agent systems (ROMAS) a multi-agent approach for designing normative open systems

CERN Document Server

Garcia, Emilia; Botti, Vicente

2015-01-01

Addressing the open problem of engineering normative open systems using the multi-agent paradigm, normative open systems are explained as systems in which heterogeneous and autonomous entities and institutions coexist in a complex social and legal framework that can evolve to address the different and often conflicting objectives of the many stakeholders involved. Presenting  a software engineering approach which covers both the analysis and design of these kinds of systems, and which deals with the open issues in the area, ROMAS (Regulated Open Multi-Agent Systems) defines a specific multi-agent architecture, meta-model, methodology and CASE tool. This CASE tool is based on Model-Driven technology and integrates the graphical design with the formal verification of some properties of these systems by means of model checking techniques. Utilizing tables to enhance reader insights into the most important requirements for designing normative open multi-agent systems, the book also provides a detailed and easy t...

Modeling misidentification errors in capture-recapture studies using photographic identification of evolving marks

Science.gov (United States)

Yoshizaki, J.; Pollock, K.H.; Brownie, C.; Webster, R.A.

2009-01-01

Misidentification of animals is potentially important when naturally existing features (natural tags) are used to identify individual animals in a capture-recapture study. Photographic identification (photoID) typically uses photographic images of animals' naturally existing features as tags (photographic tags) and is subject to two main causes of identification errors: those related to quality of photographs (non-evolving natural tags) and those related to changes in natural marks (evolving natural tags). The conventional methods for analysis of capture-recapture data do not account for identification errors, and to do so requires a detailed understanding of the misidentification mechanism. Focusing on the situation where errors are due to evolving natural tags, we propose a misidentification mechanism and outline a framework for modeling the effect of misidentification in closed population studies. We introduce methods for estimating population size based on this model. Using a simulation study, we show that conventional estimators can seriously overestimate population size when errors due to misidentification are ignored, and that, in comparison, our new estimators have better properties except in cases with low capture probabilities (<0.2) or low misidentification rates (<2.5%). ?? 2009 by the Ecological Society of America.

Technical specifications for monitoring Community trends in zoonotic agents in foodstuffs and animal populations on request from EFSA

DEFF Research Database (Denmark)

Borck Høg, Birgitte; Chriél, Mariann; Korsgaard, Helle

of criteria for the selection of the zoonotic agent/animal or food category combinations where trend analyses would be justified. Based on data available from 2004 to 2007, the following combinations are suggested for trend analyses: Salmonella in fresh broiler and pig meat, flocks of laying hens and broilers......Technical specifications are proposed for the monitoring of temporal trends in zoonotic agents in animal and food populations at Community or Member State group level in the framework of Directive 2003/99/EC. Two types of trend monitoring are identified: trend watching, which covers general...

Evidence of Field-Evolved Resistance to Bifenthrin in Western Corn Rootworm (Diabrotica virgifera virgifera LeConte) Populations in Western Nebraska and Kansas.

Science.gov (United States)

Pereira, Adriano E; Wang, Haichuan; Zukoff, Sarah N; Meinke, Lance J; French, B Wade; Siegfried, Blair D

2015-01-01

Pyrethroid insecticides have been used to control larvae or adults of the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, a key pest of field corn in the United States. In response to reports of reduced efficacy of pyrethroids in WCR management programs in southwestern areas of Nebraska and Kansas the present research was designed to establish a baseline of susceptibility to the pyrethroid insecticide, bifenthrin, using susceptible laboratory populations and to compare this baseline with susceptibility of field populations. Concentration-response bioassays were performed to estimate the baseline susceptibility. From the baseline data, a diagnostic concentration (LC99) was determined and used to test adults of both laboratory and field populations. Larval susceptibility was also tested using both laboratory and field populations. Significant differences were recorded in adult and larval susceptibility among WCR field and laboratory populations. The highest LC50 for WCR adults was observed in populations from Keith 2 and Chase Counties, NE, with LC50s of 2.2 and 1.38 μg/vial, respectively, and Finney County 1, KS, with 1.43 μg/vial, as compared to a laboratory non-diapause population (0.24 μg/vial). For larvae, significant differences between WCR field and laboratory populations were also recorded. Significant differences in mortalities at the diagnostic bifenthrin concentration (LC99) were observed among WCR adult populations with western Corn Belt populations exhibiting lower susceptibility to bifenthrin, especially in southwestern Nebraska and southwestern Kansas. This study provides evidence that resistance to bifenthrin is evolving in field populations that have been exposed for multiple years to pyrethroid insecticides. Implications to sustainable rootworm management are discussed.

Evidence of Field-Evolved Resistance to Bifenthrin in Western Corn Rootworm (Diabrotica virgifera virgifera LeConte Populations in Western Nebraska and Kansas.

Directory of Open Access Journals (Sweden)

Adriano E Pereira

Full Text Available Pyrethroid insecticides have been used to control larvae or adults of the western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte, a key pest of field corn in the United States. In response to reports of reduced efficacy of pyrethroids in WCR management programs in southwestern areas of Nebraska and Kansas the present research was designed to establish a baseline of susceptibility to the pyrethroid insecticide, bifenthrin, using susceptible laboratory populations and to compare this baseline with susceptibility of field populations. Concentration-response bioassays were performed to estimate the baseline susceptibility. From the baseline data, a diagnostic concentration (LC99 was determined and used to test adults of both laboratory and field populations. Larval susceptibility was also tested using both laboratory and field populations. Significant differences were recorded in adult and larval susceptibility among WCR field and laboratory populations. The highest LC50 for WCR adults was observed in populations from Keith 2 and Chase Counties, NE, with LC50s of 2.2 and 1.38 μg/vial, respectively, and Finney County 1, KS, with 1.43 μg/vial, as compared to a laboratory non-diapause population (0.24 μg/vial. For larvae, significant differences between WCR field and laboratory populations were also recorded. Significant differences in mortalities at the diagnostic bifenthrin concentration (LC99 were observed among WCR adult populations with western Corn Belt populations exhibiting lower susceptibility to bifenthrin, especially in southwestern Nebraska and southwestern Kansas. This study provides evidence that resistance to bifenthrin is evolving in field populations that have been exposed for multiple years to pyrethroid insecticides. Implications to sustainable rootworm management are discussed.

Hormonal evaluation of the infertile male: has it evolved?

Science.gov (United States)

Sussman, Ernest M; Chudnovsky, Aleksander; Niederberger, Craig S

2008-05-01

An endocrinologic evaluation of patients who have male-factor infertility has clearly evolved and leads to specific diagnoses and treatment strategies in a large population of infertile men. A well-considered endocrine evaluation is especially essential with the ever-growing popularity of assisted reproductive techniques and continued refinements with intracytoplasmic sperm injection.

Evolution favors protein mutational robustness in sufficiently large populations

Directory of Open Access Journals (Sweden)

Venturelli Ophelia S

2007-07-01

Full Text Available Abstract Background An important question is whether evolution favors properties such as mutational robustness or evolvability that do not directly benefit any individual, but can influence the course of future evolution. Functionally similar proteins can differ substantially in their robustness to mutations and capacity to evolve new functions, but it has remained unclear whether any of these differences might be due to evolutionary selection for these properties. Results Here we use laboratory experiments to demonstrate that evolution favors protein mutational robustness if the evolving population is sufficiently large. We neutrally evolve cytochrome P450 proteins under identical selection pressures and mutation rates in populations of different sizes, and show that proteins from the larger and thus more polymorphic population tend towards higher mutational robustness. Proteins from the larger population also evolve greater stability, a biophysical property that is known to enhance both mutational robustness and evolvability. The excess mutational robustness and stability is well described by mathematical theory, and can be quantitatively related to the way that the proteins occupy their neutral network. Conclusion Our work is the first experimental demonstration of the general tendency of evolution to favor mutational robustness and protein stability in highly polymorphic populations. We suggest that this phenomenon could contribute to the mutational robustness and evolvability of viruses and bacteria that exist in large populations.

The Primary Care Leadership Track at the Duke University School of Medicine: creating change agents to improve population health.

Science.gov (United States)

Sheline, Barbara; Tran, Anh N; Jackson, Joseph; Peyser, Bruce; Rogers, Susan; Engle, Deborah

2014-10-01

Physicians need training in community engagement, leadership, and population health to prepare them to work with partners within the community and to adapt medical care to address population health needs. With an overall goal of training primary care practitioners to be change agents for improving population health, the Duke University School of Medicine launched the Primary Care Leadership Track (PCLT) in 2011. The four-year PCLT curriculum requires students to contribute to existing community health initiatives, perform community-engaged research, and participate in leadership training. The clinical curriculum incorporates a longitudinal approach to allow students to follow patient outcomes. In addition, students regularly interact with faculty to explore population health issues, review patient cases, and adjust individual learning opportunities as needed. The first cohort of PCLT students will graduate in 2015. Prospective comparisons with traditional track students are planned on performance on standardized tests and career choices. The authors created the PCLT as a laboratory in which students can engage with the community and explore solutions to address the health of the public and the future delivery of health care. To meet the goal of training change agents, PCLT leaders need to expand opportunities for students to learn from providers and organizations that are successfully bridging the gap between medical care and public health.

Information Processing and Dynamics in Minimally Cognitive Agents

Science.gov (United States)

Beer, Randall D.; Williams, Paul L.

2015-01-01

There has been considerable debate in the literature about the relative merits of information processing versus dynamical approaches to understanding cognitive processes. In this article, we explore the relationship between these two styles of explanation using a model agent evolved to solve a relational categorization task. Specifically, we…

A model for ultrasound contrast agent in a phantom vessel

KAUST Repository

Qamar, Adnan; Samtaney, Ravi

2014-01-01

A theoretical framework to model the dynamics of Ultrasound Contrast Agent (UCA) inside a phantom vessel is presented. The model is derived from the reduced Navier-Stokes equation and is coupled with the evolving flow field solution inside

Agent-based models in economics a toolkit

CERN Document Server

Fagiolo, Giorgio; Gallegati, Mauro; Richiardi, Matteo; Russo, Alberto

2018-01-01

In contrast to mainstream economics, complexity theory conceives the economy as a complex system of heterogeneous interacting agents characterised by limited information and bounded rationality. Agent Based Models (ABMs) are the analytical and computational tools developed by the proponents of this emerging methodology. Aimed at students and scholars of contemporary economics, this book includes a comprehensive toolkit for agent-based computational economics, now quickly becoming the new way to study evolving economic systems. Leading scholars in the field explain how ABMs can be applied fruitfully to many real-world economic examples and represent a great advancement over mainstream approaches. The essays discuss the methodological bases of agent-based approaches and demonstrate step-by-step how to build, simulate and analyse ABMs and how to validate their outputs empirically using the data. They also present a wide set of applications of these models to key economic topics, including the business cycle, lab...

Characterization of field-evolved resistance to Bacillus thuringiensis-derived Cry1F δ-endotoxin in Spodoptera frugiperda populations from Argentina.

Science.gov (United States)

Chandrasena, Desmi I; Signorini, Ana M; Abratti, Gustavo; Storer, Nicholas P; Olaciregui, Magdalena L; Alves, Analiza P; Pilcher, Clinton D

2018-03-01

Transgenic maize (Zea mays L.) event TC1507 (Herculex ® I insect protection), expressing Cry1F δ-endotoxin derived from Bacillus thuringiensis var. aizawai, was commercialized in 2003 in the Americas. Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) susceptibility to Cry1F was monitored annually across several regions in Argentina using diagnostic concentration bioassays. Reduced performance of TC1507 maize against S. frugiperda was reported in 2013. A resistant population was established in the laboratory and the dominance of Cry1F resistance was characterized. During 2012-2015, high-survivorship of several populations was observed in the resistance monitoring program. Reciprocal crosses of a Cry1F-resistant population with a Cry1F-susceptible population were evaluated to calculate effective dominance (D ML ) based on mortality levels observed at 100 µg/ml Cry1F. Two additional dominance levels (D LC and D EC ) were calculated using lethal (LC 50 ) or effective concentration (EC 50 ) derived from concentration-response bioassays. Estimates indicated that Cry1F resistance in S. frugiperda in Argentina was either highly recessive (D ML = 0.005) or incompletely recessive (D LC frugiperda Cry1F field-evolved resistance in Argentina. The resistance to Cry1F in S. frugiperda populations collected in Argentina, is autosomal and incompletely recessive similar to the resistance reported in Brazil. © 2017 The Authors. Pest Management Science published by John Wiley © Sons Ltd on behalf of Society of Chemical Industry. © 2017 The Authors. Pest Management Science published by John Wiley © Sons Ltd on behalf of Society of Chemical Industry.

BSim: an agent-based tool for modeling bacterial populations in systems and synthetic biology.

Directory of Open Access Journals (Sweden)

Thomas E Gorochowski

Full Text Available Large-scale collective behaviors such as synchronization and coordination spontaneously arise in many bacterial populations. With systems biology attempting to understand these phenomena, and synthetic biology opening up the possibility of engineering them for our own benefit, there is growing interest in how bacterial populations are best modeled. Here we introduce BSim, a highly flexible agent-based computational tool for analyzing the relationships between single-cell dynamics and population level features. BSim includes reference implementations of many bacterial traits to enable the quick development of new models partially built from existing ones. Unlike existing modeling tools, BSim fully considers spatial aspects of a model allowing for the description of intricate micro-scale structures, enabling the modeling of bacterial behavior in more realistic three-dimensional, complex environments. The new opportunities that BSim opens are illustrated through several diverse examples covering: spatial multicellular computing, modeling complex environments, population dynamics of the lac operon, and the synchronization of genetic oscillators. BSim is open source software that is freely available from http://bsim-bccs.sf.net and distributed under the Open Source Initiative (OSI recognized MIT license. Developer documentation and a wide range of example simulations are also available from the website. BSim requires Java version 1.6 or higher.

Using stylized agent-based models for population-environment research: A case study from the Galápagos Islands.

Science.gov (United States)

Miller, Brian W; Breckheimer, Ian; McCleary, Amy L; Guzmán-Ramirez, Liza; Caplow, Susan C; Jones-Smith, Jessica C; Walsh, Stephen J

2010-05-01

Agent Based Models (ABMs) are powerful tools for population-environment research but are subject to trade-offs between model complexity and abstraction. This study strikes a compromise between abstract and highly specified ABMs by designing a spatially explicit, stylized ABM and using it to explore policy scenarios in a setting that is facing substantial conservation and development challenges. Specifically, we present an ABM that reflects key Land Use / Land Cover (LULC) dynamics and livelihood decisions on Isabela Island in the Galápagos Archipelago of Ecuador. We implement the model using the NetLogo software platform, a free program that requires relatively little programming experience. The landscape is composed of a satellite-derived distribution of a problematic invasive species (common guava) and a stylized representation of the Galápagos National Park, the community of Puerto Villamil, the agricultural zone, and the marine area. The agent module is based on publicly available data and household interviews, and represents the primary livelihoods of the population in the Galápagos Islands - tourism, fisheries, and agriculture. We use the model to enact hypothetical agricultural subsidy scenarios aimed at controlling invasive guava and assess the resulting population and land cover dynamics. Findings suggest that spatially explicit, stylized ABMs have considerable utility, particularly during preliminary stages of research, as platforms for (1) sharpening conceptualizations of population-environment systems, (2) testing alternative scenarios, and (3) uncovering critical data gaps.

Inheritance of evolved clethodim resistance in Lolium rigidum populations from Australia.

Science.gov (United States)

Saini, Rupinder Kaur; Malone, Jenna; Gill, Gurjeet; Preston, Christopher

2017-08-01

In Australia, the extensive use of clethodim for the control of Lolium rigidum has resulted in the evolution of many clethodim-resistant L. rigidum populations. Five clethodim-resistant populations of L. rigidum were analysed for the inheritance of clethodim resistance. Reciprocal crosses were made between resistant (R) and susceptible (S) populations. Within crosses, dose-responses of reciprocal F 1 families of all populations except A61 were similar to each other, indicating that clethodim resistance in these populations is encoded on the nuclear genome. The level of dominance observed in the dose-response experiments ranged from partial to complete within the herbicide rate used. In the A61 population, within each cross, the response of F 1 from the maternal and paternal parent was different, indicating that resistance is inherited through the female parent. All backcross populations segregated in a different manner. Only one population, FP, fitted a single-gene model (1:1). Two populations fitted two-gene models: a 3:1 inheritance model for F4 and a 1:3 inheritance model for A91. For population E2, no clear pattern of inheritance was determined, suggesting more complex inheritance. The results of this study indicate that different patterns of clethodim resistance in L. rigidum exist. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Genome scans on experimentally evolved populations reveal candidate regions for adaptation to plant resistance in the potato cyst nematode Globodera pallida.

Science.gov (United States)

Eoche-Bosy, D; Gautier, M; Esquibet, M; Legeai, F; Bretaudeau, A; Bouchez, O; Fournet, S; Grenier, E; Montarry, J

2017-09-01

Improving resistance durability involves to be able to predict the adaptation speed of pathogen populations. Identifying the genetic bases of pathogen adaptation to plant resistances is a useful step to better understand and anticipate this phenomenon. Globodera pallida is a major pest of potato crop for which a resistance QTL, GpaV vrn , has been identified in Solanum vernei. However, its durability is threatened as G. pallida populations are able to adapt to the resistance in few generations. The aim of this study was to investigate the genomic regions involved in the resistance breakdown by coupling experimental evolution and high-density genome scan. We performed a whole-genome resequencing of pools of individuals (Pool-Seq) belonging to G. pallida lineages derived from two independent populations having experimentally evolved on susceptible and resistant potato cultivars. About 1.6 million SNPs were used to perform the genome scan using a recent model testing for adaptive differentiation and association to population-specific covariables. We identified 275 outliers and 31 of them, which also showed a significant reduction in diversity in adapted lineages, were investigated for their genic environment. Some candidate genomic regions contained genes putatively encoding effectors and were enriched in SPRYSECs, known in cyst nematodes to be involved in pathogenicity and in (a)virulence. Validated candidate SNPs will provide a useful molecular tool to follow frequencies of virulence alleles in natural G. pallida populations and define efficient strategies of use of potato resistances maximizing their durability. © 2017 John Wiley & Sons Ltd.

An Agent-Based Model of Evolving Community Flood Risk.

Science.gov (United States)

Tonn, Gina L; Guikema, Seth D

2017-11-17

Although individual behavior plays a major role in community flood risk, traditional flood risk models generally do not capture information on how community policies and individual decisions impact the evolution of flood risk over time. The purpose of this study is to improve the understanding of the temporal aspects of flood risk through a combined analysis of the behavioral, engineering, and physical hazard aspects of flood risk. Additionally, the study aims to develop a new modeling approach for integrating behavior, policy, flood hazards, and engineering interventions. An agent-based model (ABM) is used to analyze the influence of flood protection measures, individual behavior, and the occurrence of floods and near-miss flood events on community flood risk. The ABM focuses on the following decisions and behaviors: dissemination of flood management information, installation of community flood protection, elevation of household mechanical equipment, and elevation of homes. The approach is place based, with a case study area in Fargo, North Dakota, but is focused on generalizable insights. Generally, community mitigation results in reduced future damage, and individual action, including mitigation and movement into and out of high-risk areas, can have a significant influence on community flood risk. The results of this study provide useful insights into the interplay between individual and community actions and how it affects the evolution of flood risk. This study lends insight into priorities for future work, including the development of more in-depth behavioral and decision rules at the individual and community level. © 2017 Society for Risk Analysis.

Robustness to Faults Promotes Evolvability: Insights from Evolving Digital Circuits.

Science.gov (United States)

Milano, Nicola; Nolfi, Stefano

2016-01-01

We demonstrate how the need to cope with operational faults enables evolving circuits to find more fit solutions. The analysis of the results obtained in different experimental conditions indicates that, in absence of faults, evolution tends to select circuits that are small and have low phenotypic variability and evolvability. The need to face operation faults, instead, drives evolution toward the selection of larger circuits that are truly robust with respect to genetic variations and that have a greater level of phenotypic variability and evolvability. Overall our results indicate that the need to cope with operation faults leads to the selection of circuits that have a greater probability to generate better circuits as a result of genetic variation with respect to a control condition in which circuits are not subjected to faults.

The dynamic influence of human resources on evidence-based intervention sustainability and population outcomes: an agent-based modeling approach.

Science.gov (United States)

McKay, Virginia R; Hoffer, Lee D; Combs, Todd B; Margaret Dolcini, M

2018-06-05

Sustaining evidence-based interventions (EBIs) is an ongoing challenge for dissemination and implementation science in public health and social services. Characterizing the relationship among human resource capacity within an agency and subsequent population outcomes is an important step to improving our understanding of how EBIs are sustained. Although human resource capacity and population outcomes are theoretically related, examining them over time within real-world experiments is difficult. Simulation approaches, especially agent-based models, offer advantages that complement existing methods. We used an agent-based model to examine the relationships among human resources, EBI delivery, and population outcomes by simulating provision of an EBI through a hypothetical agency and its staff. We used data from existing studies examining a widely implemented HIV prevention intervention to inform simulation design, calibration, and validity. Once we developed a baseline model, we used the model as a simulated laboratory by systematically varying three human resource variables: the number of staff positions, the staff turnover rate, and timing in training. We tracked the subsequent influence on EBI delivery and the level of population risk over time to describe the overall and dynamic relationships among these variables. Higher overall levels of human resource capacity at an agency (more positions) led to more extensive EBI delivery over time and lowered population risk earlier in time. In simulations representing the typical human resource investments, substantial influences on population risk were visible after approximately 2 years and peaked around 4 years. Human resources, especially staff positions, have an important impact on EBI sustainability and ultimately population health. A minimum level of human resources based on the context (e.g., size of the initial population and characteristics of the EBI) is likely needed for an EBI to have a meaningful impact on

Population crises and population cycles.

Science.gov (United States)

Russell, C; Russell, W M

2000-01-01

To prevent a population irretrievably depleting its resources, mammals have evolved a behavioural and physiological response to population crisis. When a mammalian population becomes dangerously dense, there is a reversal of behaviour. Co-operation and parental behaviour are replaced by competition, dominance and aggressive violence, leading to high mortality, especially of females and young, and a reduced population. The stress of overpopulation and the resulting violence impairs both the immune and the reproductive systems. Hence epidemics complete the crash of the population, and reproduction is slowed for three or four generations, giving the resources ample time to recover. In some mammal species, crisis and crisis response recur regularly, leading to cycles of population growth and relapse, oscillating about a fixed mean. Population crisis response and population cycles have been equally prominent in the history of human societies. But in man successive advances in food production have made possible growing populations, though with every such advance population soon outgrew resources again. Hence human cycles have been superimposed on a rising curve, producing a saw-tooth graph. Because advances in food production amounted to sudden disturbances in the relations between human populations and their environments, the crisis response in man has failed to avert famine and resource damage. In the large human societies evolved since the coming of settled agriculture and cities, the basic effects of violence, epidemics, famine and resource damage have been mediated by such specifically human disasters as inflation, unemployment, and political tyranny. An account of past crises, periods of relative relief from population pressure, and resulting cycles, is given for a number of regions: China, North Africa and Western Asia, the northern Mediterranean, and north-western Europe. The paper ends with an account of the present world-wide population crisis, and the solution

Preface: evolving rotifers, evolving science: Proceedings of the XIV International Rotifer Symposium

Czech Academy of Sciences Publication Activity Database

Devetter, Miloslav; Fontaneto, D.; Jersabek, Ch.D.; Welch, D.B.M.; May, L.; Walsh, E.J.

2017-01-01

Roč. 796, č. 1 (2017), s. 1-6 ISSN 0018-8158 Institutional support: RVO:60077344 Keywords : evolving rotifers * 14th International Rotifer Symposium * evolving science Subject RIV: EG - Zoology OBOR OECD: Zoology Impact factor: 2.056, year: 2016

Numeric, Agent-based or System dynamics model? Which modeling approach is the best for vast population simulation?

Science.gov (United States)

Cimler, Richard; Tomaskova, Hana; Kuhnova, Jitka; Dolezal, Ondrej; Pscheidl, Pavel; Kuca, Kamil

2018-02-01

Alzheimer's disease is one of the most common mental illnesses. It is posited that more than 25 % of the population is affected by some mental disease during their lifetime. Treatment of each patient draws resources from the economy concerned. Therefore, it is important to quantify the potential economic impact. Agent-based, system dynamics and numerical approaches to dynamic modeling of the population of the European Union and its patients with Alzheimer's disease are presented in this article. Simulations, their characteristics, and the results from different modeling tools are compared. The results of these approaches are compared with EU population growth predictions from the statistical office of the EU by Eurostat. The methodology of a creation of the models is described and all three modeling approaches are compared. The suitability of each modeling approach for the population modeling is discussed. In this case study, all three approaches gave us the results corresponding with the EU population prediction. Moreover, we were able to predict the number of patients with AD and, based on the modeling method, we were also able to monitor different characteristics of the population. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

The Multi-Agent Transport Simulation MATSim

OpenAIRE

Horni Andreas; Nagel Kai; Axhausen Kay W.

2016-01-01

"The MATSim (Multi-Agent Transport Simulation) software project was started around 2006 with the goal of generating traffic and congestion patterns by following individual synthetic travelers through their daily or weekly activity programme. It has since then evolved from a collection of stand-alone C++ programs to an integrated Java-based framework which is publicly hosted, open-source available, automatically regression tested. It is currently used by about 40 groups throughout the world. T...

Reduced inflammation in expanding populations of a neotropical bird species.

Science.gov (United States)

Bailly, Juliette; Garnier, Stéphane; Khimoun, Aurélie; Arnoux, Emilie; Eraud, Cyril; Goret, Jean-Yves; Luglia, Thomas; Gaucher, Philippe; Faivre, Bruno

2016-10-01

The loss of regulating agents such as parasites is among the most important changes in biotic interactions experienced by populations established in newly colonized areas. Under a relaxed parasite pressure, individuals investing less in costly immune mechanisms might experience a selective advantage and become successful colonizers as they re-allocate resources to other fitness-related traits. Accordingly, a refinement of the evolution of increased competitive ability (EICA) hypothesis proposed that immunity of invasive populations has evolved toward a reduced investment in innate immunity, the most costly component of immunity, and an increased humoral immunity that is less costly. Biogeographical approaches comparing populations between native and expansion ranges are particularly relevant in exploring this issue, but remain very scarce. We conducted a biogeographical comparison between populations of Spectacled Thrush ( Turdus nudigenis ) from the native area (South America) and from the expansion range (Caribbean islands). First, we compared haemosporidian prevalence and circulating haptoglobin (an acute-phase protein produced during inflammation). Second, we challenged captive birds from both ranges with Escherichia coli lipopolysaccharides ( LPS ) and measured postchallenge haptoglobin production and body mass change. Birds from the expansion range showed lower haemosporidian prevalence and lower levels of haptoglobin than birds from the native range. In addition, the inflammation elicited by LPS injection and its associated cost in terms of body mass loss were lower in birds from the expansion range than in birds from the native range. In accordance with the enemy release hypothesis, our results suggest that range expansion is associated with a reduced infection risk. Our study also supports the hypothesis that individuals from newly established populations have evolved mechanisms to dampen the inflammatory response and are in accordance with one prediction

Fiscal and monetary policies in complex evolving economies

NARCIS (Netherlands)

Dosi, G.; Fagiolo, G.; Napoletano, M.; Roventini, A.; Treibich, T.G.

2014-01-01

In this paper we explore the effects of alternative combinations of fiscal and monetary policies under different income distribution regimes. In particular, we aim at evaluating fiscal rules in economies subject to banking crises and deep recessions. We do so using an agent-based model populated by

Biological control agents elevate hantavirus by subsidizing deer mouse populations

Science.gov (United States)

Dean E. Pearson; Ragan M. Callaway

2006-01-01

Biological control of exotic invasive plants using exotic insects is practiced under the assumption that biological control agents are safe if they do not directly attack non-target species. We tested this assumption by evaluating the potential for two host-specific biological control agents (Urophora spp.), widely established in North America for spotted...

The next generation of interoperability agents in healthcare.

Science.gov (United States)

Cardoso, Luciana; Marins, Fernando; Portela, Filipe; Santos, Manuel; Abelha, António; Machado, José

2014-05-16

Interoperability in health information systems is increasingly a requirement rather than an option. Standards and technologies, such as multi-agent systems, have proven to be powerful tools in interoperability issues. In the last few years, the authors have worked on developing the Agency for Integration, Diffusion and Archive of Medical Information (AIDA), which is an intelligent, agent-based platform to ensure interoperability in healthcare units. It is increasingly important to ensure the high availability and reliability of systems. The functions provided by the systems that treat interoperability cannot fail. This paper shows the importance of monitoring and controlling intelligent agents as a tool to anticipate problems in health information systems. The interaction between humans and agents through an interface that allows the user to create new agents easily and to monitor their activities in real time is also an important feature, as health systems evolve by adopting more features and solving new problems. A module was installed in Centro Hospitalar do Porto, increasing the functionality and the overall usability of AIDA.

The Next Generation of Interoperability Agents in Healthcare

Directory of Open Access Journals (Sweden)

Luciana Cardoso

2014-05-01

Full Text Available Interoperability in health information systems is increasingly a requirement rather than an option. Standards and technologies, such as multi-agent systems, have proven to be powerful tools in interoperability issues. In the last few years, the authors have worked on developing the Agency for Integration, Diffusion and Archive of Medical Information (AIDA, which is an intelligent, agent-based platform to ensure interoperability in healthcare units. It is increasingly important to ensure the high availability and reliability of systems. The functions provided by the systems that treat interoperability cannot fail. This paper shows the importance of monitoring and controlling intelligent agents as a tool to anticipate problems in health information systems. The interaction between humans and agents through an interface that allows the user to create new agents easily and to monitor their activities in real time is also an important feature, as health systems evolve by adopting more features and solving new problems. A module was installed in Centro Hospitalar do Porto, increasing the functionality and the overall usability of AIDA.

THE MASS-LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD. VI. LUMINOSITIES AND MASS-LOSS RATES ON POPULATION SCALES

International Nuclear Information System (INIS)

Riebel, D.; Meixner, M.; Srinivasan, S.; Sargent, B.

2012-01-01

We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch ModelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80,843 radiative transfer models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to ∼30,000 asymptotic giant branch (AGB) and red supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published data set consists of thousands of evolved stars with individually determined evolutionary parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between oxygen- and carbon-rich chemistry. The global dust injection rate to the interstellar medium (ISM) of the LMC from RSGs and AGB stars is on the order of 2.1 × 10 –5 M ☉ yr –1 , equivalent to a total mass injection rate (including the gas) into the ISM of ∼6 × 10 –3 M ☉ yr –1 . Carbon stars inject two and a half times as much dust into the ISM as do O-rich AGB stars, but the same amount of mass. We determine a bolometric correction factor for C-rich AGB stars in the K s band as a function of J – K s color, BC K s = -0.40(J-K s ) 2 + 1.83(J-K s ) + 1.29. We determine several IR color proxies for the dust mass-loss rate (M-dot d ) from C-rich AGB stars, such as log M-dot d = (-18.90/((K s -[8.0])+3.37) - 5.93. We find that a larger fraction of AGB stars exhibiting the 'long-secondary period' phenomenon are more O-rich than stars dominated by radial pulsations, and AGB stars without detectable mass loss do not appear on either the first-overtone or fundamental-mode pulsation sequences.

Patterns of antimicrobial agent prescription in a sentinel population of canine and feline veterinary practices in the United Kingdom.

Science.gov (United States)

Singleton, D A; Sánchez-Vizcaíno, F; Dawson, S; Jones, P H; Noble, P J M; Pinchbeck, G L; Williams, N J; Radford, A D

2017-06-01

Antimicrobial resistance is an increasingly important global health threat and the use of antimicrobial agents is a key risk factor in its development. This study describes antimicrobial agent prescription (AAP) patterns over a 2year period using electronic health records (EHRs) from booked consultations in a network of 457 sentinel veterinary premises in the United Kingdom. A semi-automated classification methodology was used to map practitioner defined product codes in 918,333 EHRs from 413,870 dogs and 352,730 EHRs from 200,541 cats, including 289,789 AAPs. AAP as a proportion of total booked consultations was more frequent in dogs (18.8%, 95% confidence interval, CI, 18.2-19.4) than cats (17.5%, 95% CI 16.9-18.1). Prescription of topical antimicrobial agents was more frequent in dogs (7.4%, 95% CI 7.2-7.7) than cats (3.2%, 95% CI 3.1-3.3), whilst prescription of systemic antimicrobial agents was more frequent in cats (14.8%, 95% CI 14.2-15.4) than dogs (12.2%, 95% CI 11.7-12.7). A decreasing temporal pattern was identified for prescription of systemic antimicrobial agents in dogs and cats. Premises which prescribed antimicrobial agents frequently for dogs also prescribed frequently for cats. AAP was most frequent during pruritus consultations in dogs and trauma consultations in cats. Clavulanic acid potentiated amoxicillin was the most frequently prescribed antimicrobial agent in dogs (28.6% of prescriptions, 95% CI 27.4-29.8), whereas cefovecin, a third generation cephalosporin, was the most frequently prescribed antimicrobial agent in cats (36.2%, 95% CI 33.9-38.5). This study demonstrated patterns in AAP over time and for different conditions in a population of companion animals in the United Kingdom. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Laser assisted drug delivery: a review of an evolving technology.

Science.gov (United States)

Sklar, Lindsay R; Burnett, Christopher T; Waibel, Jill S; Moy, Ronald L; Ozog, David M

2014-04-01

Topically applied drugs have a relatively low cutaneous bioavailability. This article reviews the existing applications of laser assisted drug delivery, a means by which the permeation of topically applied agents can be enhanced into the skin. The existing literature suggests that lasers are a safe and effective means of enhancing the delivery of topically applied agents through the skin. The types of lasers most commonly studied in regards to drug delivery are the carbon dioxide (CO2 ) and erbium:yttrium-aluminum-garnet (Er:YAG) lasers. Both conventional ablative and fractional ablative modalities have been utilized and are summarized herein. The majority of the existing studies on laser assisted drug delivery have been performed on animal models and additional human studies are needed. Laser assisted drug delivery is an evolving technology with potentially broad clinical applications. Multiple studies demonstrate that laser pretreatment of the skin can increase the permeability and depth of penetration of topically applied drug molecules for both local cutaneous and systemic applications. © 2014 Wiley Periodicals, Inc.

Neural modularity helps organisms evolve to learn new skills without forgetting old skills.

Science.gov (United States)

Ellefsen, Kai Olav; Mouret, Jean-Baptiste; Clune, Jeff

2015-04-01

A long-standing goal in artificial intelligence is creating agents that can learn a variety of different skills for different problems. In the artificial intelligence subfield of neural networks, a barrier to that goal is that when agents learn a new skill they typically do so by losing previously acquired skills, a problem called catastrophic forgetting. That occurs because, to learn the new task, neural learning algorithms change connections that encode previously acquired skills. How networks are organized critically affects their learning dynamics. In this paper, we test whether catastrophic forgetting can be reduced by evolving modular neural networks. Modularity intuitively should reduce learning interference between tasks by separating functionality into physically distinct modules in which learning can be selectively turned on or off. Modularity can further improve learning by having a reinforcement learning module separate from sensory processing modules, allowing learning to happen only in response to a positive or negative reward. In this paper, learning takes place via neuromodulation, which allows agents to selectively change the rate of learning for each neural connection based on environmental stimuli (e.g. to alter learning in specific locations based on the task at hand). To produce modularity, we evolve neural networks with a cost for neural connections. We show that this connection cost technique causes modularity, confirming a previous result, and that such sparsely connected, modular networks have higher overall performance because they learn new skills faster while retaining old skills more and because they have a separate reinforcement learning module. Our results suggest (1) that encouraging modularity in neural networks may help us overcome the long-standing barrier of networks that cannot learn new skills without forgetting old ones, and (2) that one benefit of the modularity ubiquitous in the brains of natural animals might be to

Neural modularity helps organisms evolve to learn new skills without forgetting old skills.

Directory of Open Access Journals (Sweden)

Kai Olav Ellefsen

2015-04-01

Full Text Available A long-standing goal in artificial intelligence is creating agents that can learn a variety of different skills for different problems. In the artificial intelligence subfield of neural networks, a barrier to that goal is that when agents learn a new skill they typically do so by losing previously acquired skills, a problem called catastrophic forgetting. That occurs because, to learn the new task, neural learning algorithms change connections that encode previously acquired skills. How networks are organized critically affects their learning dynamics. In this paper, we test whether catastrophic forgetting can be reduced by evolving modular neural networks. Modularity intuitively should reduce learning interference between tasks by separating functionality into physically distinct modules in which learning can be selectively turned on or off. Modularity can further improve learning by having a reinforcement learning module separate from sensory processing modules, allowing learning to happen only in response to a positive or negative reward. In this paper, learning takes place via neuromodulation, which allows agents to selectively change the rate of learning for each neural connection based on environmental stimuli (e.g. to alter learning in specific locations based on the task at hand. To produce modularity, we evolve neural networks with a cost for neural connections. We show that this connection cost technique causes modularity, confirming a previous result, and that such sparsely connected, modular networks have higher overall performance because they learn new skills faster while retaining old skills more and because they have a separate reinforcement learning module. Our results suggest (1 that encouraging modularity in neural networks may help us overcome the long-standing barrier of networks that cannot learn new skills without forgetting old ones, and (2 that one benefit of the modularity ubiquitous in the brains of natural animals

Neural Modularity Helps Organisms Evolve to Learn New Skills without Forgetting Old Skills

Science.gov (United States)

Ellefsen, Kai Olav; Mouret, Jean-Baptiste; Clune, Jeff

2015-01-01

A long-standing goal in artificial intelligence is creating agents that can learn a variety of different skills for different problems. In the artificial intelligence subfield of neural networks, a barrier to that goal is that when agents learn a new skill they typically do so by losing previously acquired skills, a problem called catastrophic forgetting. That occurs because, to learn the new task, neural learning algorithms change connections that encode previously acquired skills. How networks are organized critically affects their learning dynamics. In this paper, we test whether catastrophic forgetting can be reduced by evolving modular neural networks. Modularity intuitively should reduce learning interference between tasks by separating functionality into physically distinct modules in which learning can be selectively turned on or off. Modularity can further improve learning by having a reinforcement learning module separate from sensory processing modules, allowing learning to happen only in response to a positive or negative reward. In this paper, learning takes place via neuromodulation, which allows agents to selectively change the rate of learning for each neural connection based on environmental stimuli (e.g. to alter learning in specific locations based on the task at hand). To produce modularity, we evolve neural networks with a cost for neural connections. We show that this connection cost technique causes modularity, confirming a previous result, and that such sparsely connected, modular networks have higher overall performance because they learn new skills faster while retaining old skills more and because they have a separate reinforcement learning module. Our results suggest (1) that encouraging modularity in neural networks may help us overcome the long-standing barrier of networks that cannot learn new skills without forgetting old ones, and (2) that one benefit of the modularity ubiquitous in the brains of natural animals might be to

Tumor biology and cancer therapy – an evolving relationship

Directory of Open Access Journals (Sweden)

Lother Ulrike

2009-08-01

Full Text Available Abstract The aim of palliative chemotherapy is to increase survival whilst maintaining maximum quality of life for the individual concerned. Although we are still continuing to explore the optimum use of traditional chemotherapy agents, the introduction of targeted therapies has significantly broadened the therapeutic options. Interestingly, the results from current trials put the underlying biological concept often into a new, less favorable perspective. Recent data suggested that altered pathways underlie cancer, and not just altered genes. Thus, an effective therapeutic agent will sometimes have to target downstream parts of a signaling pathway or physiological effects rather than individual genes. In addition, over the past few years increasing evidence has suggested that solid tumors represent a very heterogeneous group of cells with different susceptibility to cancer therapy. Thus, since therapeutic concepts and pathophysiological understanding are continuously evolving a combination of current concepts in tumor therapy and tumor biology is needed. This review aims to present current problems of cancer therapy by highlighting exemplary results from recent clinical trials with colorectal and pancreatic cancer patients and to discuss the current understanding of the underlying reasons.

Transhydrogenase promotes the robustness and evolvability of E. coli deficient in NADPH production.

Directory of Open Access Journals (Sweden)

Hsin-Hung Chou

Full Text Available Metabolic networks revolve around few metabolites recognized by diverse enzymes and involved in myriad reactions. Though hub metabolites are considered as stepping stones to facilitate the evolutionary expansion of biochemical pathways, changes in their production or consumption often impair cellular physiology through their system-wide connections. How does metabolism endure perturbations brought immediately by pathway modification and restore hub homeostasis in the long run? To address this question we studied laboratory evolution of pathway-engineered Escherichia coli that underproduces the redox cofactor NADPH on glucose. Literature suggests multiple possibilities to restore NADPH homeostasis. Surprisingly, genetic dissection of isolates from our twelve evolved populations revealed merely two solutions: (1 modulating the expression of membrane-bound transhydrogenase (mTH in every population; (2 simultaneously consuming glucose with acetate, an unfavored byproduct normally excreted during glucose catabolism, in two subpopulations. Notably, mTH displays broad phylogenetic distribution and has also played a predominant role in laboratory evolution of Methylobacterium extorquens deficient in NADPH production. Convergent evolution of two phylogenetically and metabolically distinct species suggests mTH as a conserved buffering mechanism that promotes the robustness and evolvability of metabolism. Moreover, adaptive diversification via evolving dual substrate consumption highlights the flexibility of physiological systems to exploit ecological opportunities.

Transhydrogenase Promotes the Robustness and Evolvability of E. coli Deficient in NADPH Production

Science.gov (United States)

Chou, Hsin-Hung; Marx, Christopher J.; Sauer, Uwe

2015-01-01

Metabolic networks revolve around few metabolites recognized by diverse enzymes and involved in myriad reactions. Though hub metabolites are considered as stepping stones to facilitate the evolutionary expansion of biochemical pathways, changes in their production or consumption often impair cellular physiology through their system-wide connections. How does metabolism endure perturbations brought immediately by pathway modification and restore hub homeostasis in the long run? To address this question we studied laboratory evolution of pathway-engineered Escherichia coli that underproduces the redox cofactor NADPH on glucose. Literature suggests multiple possibilities to restore NADPH homeostasis. Surprisingly, genetic dissection of isolates from our twelve evolved populations revealed merely two solutions: (1) modulating the expression of membrane-bound transhydrogenase (mTH) in every population; (2) simultaneously consuming glucose with acetate, an unfavored byproduct normally excreted during glucose catabolism, in two subpopulations. Notably, mTH displays broad phylogenetic distribution and has also played a predominant role in laboratory evolution of Methylobacterium extorquens deficient in NADPH production. Convergent evolution of two phylogenetically and metabolically distinct species suggests mTH as a conserved buffering mechanism that promotes the robustness and evolvability of metabolism. Moreover, adaptive diversification via evolving dual substrate consumption highlights the flexibility of physiological systems to exploit ecological opportunities. PMID:25715029

Revealing evolved massive stars with Spitzer

Science.gov (United States)

Gvaramadze, V. V.; Kniazev, A. Y.; Fabrika, S.

2010-06-01

Massive evolved stars lose a large fraction of their mass via copious stellar wind or instant outbursts. During certain evolutionary phases, they can be identified by the presence of their circumstellar nebulae. In this paper, we present the results of a search for compact nebulae (reminiscent of circumstellar nebulae around evolved massive stars) using archival 24-μm data obtained with the Multiband Imaging Photometer for Spitzer. We have discovered 115 nebulae, most of which bear a striking resemblance to the circumstellar nebulae associated with luminous blue variables (LBVs) and late WN-type (WNL) Wolf-Rayet (WR) stars in the Milky Way and the Large Magellanic Cloud (LMC). We interpret this similarity as an indication that the central stars of detected nebulae are either LBVs or related evolved massive stars. Our interpretation is supported by follow-up spectroscopy of two dozen of these central stars, most of which turn out to be either candidate LBVs (cLBVs), blue supergiants or WNL stars. We expect that the forthcoming spectroscopy of the remaining objects from our list, accompanied by the spectrophotometric monitoring of the already discovered cLBVs, will further increase the known population of Galactic LBVs. This, in turn, will have profound consequences for better understanding the LBV phenomenon and its role in the transition between hydrogen-burning O stars and helium-burning WR stars. We also report on the detection of an arc-like structure attached to the cLBV HD 326823 and an arc associated with the LBV R99 (HD 269445) in the LMC. Partially based on observations collected at the German-Spanish Astronomical Centre, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC). E-mail: vgvaram@mx.iki.rssi.ru (VVG); akniazev@saao.ac.za (AYK); fabrika@sao.ru (SF)

Probing the Dusty Stellar Populations of the Local Volume Galaxies with JWST /MIRI

Energy Technology Data Exchange (ETDEWEB)

Jones, Olivia C.; Meixner, Margaret [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218 (United States); Justtanont, Kay [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala (Sweden); Glasse, Alistair [UK Astronomy Technology Centre, Royal Observatory, Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)

2017-05-20

The Mid-Infrared Instrument (MIRI) for the James Webb Space Telescope ( JWST ) will revolutionize our understanding of infrared stellar populations in the Local Volume. Using the rich Spitzer -IRS spectroscopic data set and spectral classifications from the Surveying the Agents of Galaxy Evolution (SAGE)–Spectroscopic survey of more than 1000 objects in the Magellanic Clouds, the Grid of Red Supergiant and Asymptotic Giant Branch Star Model (grams), and the grid of YSO models by Robitaille et al., we calculate the expected flux densities and colors in the MIRI broadband filters for prominent infrared stellar populations. We use these fluxes to explore the JWST /MIRI colors and magnitudes for composite stellar population studies of Local Volume galaxies. MIRI color classification schemes are presented; these diagrams provide a powerful means of identifying young stellar objects, evolved stars, and extragalactic background galaxies in Local Volume galaxies with a high degree of confidence. Finally, we examine which filter combinations are best for selecting populations of sources based on their JWST colors.

Optimizing agent-based transmission models for infectious diseases.

Science.gov (United States)

Willem, Lander; Stijven, Sean; Tijskens, Engelbert; Beutels, Philippe; Hens, Niel; Broeckhove, Jan

2015-06-02

Infectious disease modeling and computational power have evolved such that large-scale agent-based models (ABMs) have become feasible. However, the increasing hardware complexity requires adapted software designs to achieve the full potential of current high-performance workstations. We have found large performance differences with a discrete-time ABM for close-contact disease transmission due to data locality. Sorting the population according to the social contact clusters reduced simulation time by a factor of two. Data locality and model performance can also be improved by storing person attributes separately instead of using person objects. Next, decreasing the number of operations by sorting people by health status before processing disease transmission has also a large impact on model performance. Depending of the clinical attack rate, target population and computer hardware, the introduction of the sort phase decreased the run time from 26% up to more than 70%. We have investigated the application of parallel programming techniques and found that the speedup is significant but it drops quickly with the number of cores. We observed that the effect of scheduling and workload chunk size is model specific and can make a large difference. Investment in performance optimization of ABM simulator code can lead to significant run time reductions. The key steps are straightforward: the data structure for the population and sorting people on health status before effecting disease propagation. We believe these conclusions to be valid for a wide range of infectious disease ABMs. We recommend that future studies evaluate the impact of data management, algorithmic procedures and parallelization on model performance.

Training strategic community agents in health effects of ionizing radiation; Capacitacao de agentes comunitarios de saude em efeitos das radiacoes ionizantes

Energy Technology Data Exchange (ETDEWEB)

Leite, Teresa C.S.B.; Silva, IIson P.M. da; Jannuzzi, Denise M.S. [Fundacao Eletronuclear de Assistencia Medica (CIRA/FEAM), Angra dos Reis, RJ (Brazil). Centro de Informacoes em Radioepidemiologia; Maurmo, Alexandre M., E-mail: ammaurmo@gmail.com [Fundacao Eletronuclear de Assistencia Medica (CMRl/CTNV/FEAM), Angra dos Reis, RJ (Brazil). Centro de Treinamento Prof. Nelson Valverde. Centro de Medicina das Radiacoes Ionizantes

2013-11-01

The main motivation for the development of training was the need to train agents (opinion makers) with proximity and credibility among the population, to clarify the most frequently asked questions in relation to ionizing radiation, the operation of nuclear power plants, emergency plans and about the possibility of there effects of radiation on the health of inhabitants in regions close to the central Nuclear Almirante Alvaro Alberto - CNAAA. The project has a target audience of 420 agents, 60 of them have already been trained in a pilot project . The results indicate that the topics of training were adequate and the agents have expanded their knowledge. On the other hand, the information passed on to communities by agents, recognized by this population as ' the most reliable people', is of greater credibility and likelihood of success in communicating important issues for the population living in the vicinity of the CNAAA. (author)

The cultural evolution of human communication systems in different sized populations: usability trumps learnability.

Science.gov (United States)

Fay, Nicolas; Ellison, T Mark

2013-01-01

This study examines the intergenerational transfer of human communication systems. It tests if human communication systems evolve to be easy to learn or easy to use (or both), and how population size affects learnability and usability. Using an experimental-semiotic task, we find that human communication systems evolve to be easier to use (production efficiency and reproduction fidelity), but harder to learn (identification accuracy) for a second generation of naïve participants. Thus, usability trumps learnability. In addition, the communication systems that evolve in larger populations exhibit distinct advantages over those that evolve in smaller populations: the learnability loss (from the Initial signs) is more muted and the usability benefits are more pronounced. The usability benefits for human communication systems that evolve in a small and large population is explained through guided variation reducing sign complexity. The enhanced performance of the communication systems that evolve in larger populations is explained by the operation of a content bias acting on the larger pool of competing signs. The content bias selects for information-efficient iconic signs that aid learnability and enhance usability.

The Elementary Nature of Purposive Behavior: Evolving Minimal Neural Structures that Display Intrinsic Intentionality

Directory of Open Access Journals (Sweden)

John S. Watson

2005-01-01

Full Text Available A study of the evolution of agency in artificial life was designed to access the potential emergence of purposiveness and intentionality as these attributes of behavior have been defined in psychology and philosophy. The study involved Darwinian evolution of mobile neural nets (autonomous agents in terms of their adaptive weight patterning and structure (number of sensory, hidden, and memory units that controlled movement. An agent was embedded in a 10 × 10 toroidal matrix along with “containers” that held benefit or harm if entered. Sensory exposure to content of a container was only briefly available at a distance so that adaptive response to a nearby container required use of relevant memory. The best 20% of each generation of agents, based on net benefit consumed during limited lifetime, were selected to parent the following generation. Purposiveness emerged for all selected agents by 300 generations. By 4000 generations, 90% passed a test of purposive intentionality based on Piaget's criteria for Stage IV object permanence in human infants. An additional test of these agents confirmed that the behavior of 67% of them was consistent with the philosophical criterion of intention being “about” the container's contents. Given that the evolved neural structure of more than half of the successful agents had only 1 hidden and 1 memory node, it is argued that, contrary to common assumption, purposive and intentional aspects of adaptive behavior require an evolution of minimal complexity of supportive neural structure.

Trust in the CODA model: Opinion dynamics and the reliability of other agents

Energy Technology Data Exchange (ETDEWEB)

Martins, André C.R., E-mail: amartins@usp.br

2013-11-08

A model for the joint evolution of opinions and how much the agents trust each other is presented, using the framework of the Continuous Opinions and Discrete Actions (CODA) model. Instead of a fixed probability that the other agents will decide in the favor of the best choice, each agent considers that other agents might be one of two types: trustworthy or untrustworthy. Each agent its opinion and also the probability for each one of the other agents it interacts with being trustworthy. The dynamics of opinions and the evolution of the trust between the agents are studied. Clear evidences of the existence of two phases, one with strong polarization and the other tending to agreement, are observed. The transition shows signs of being a first-order transition. This happens despite the fact that the trust network evolves much slower than the opinion on the central issue.

Trust in the CODA model: Opinion dynamics and the reliability of other agents

International Nuclear Information System (INIS)

Martins, André C.R.

2013-01-01

A model for the joint evolution of opinions and how much the agents trust each other is presented, using the framework of the Continuous Opinions and Discrete Actions (CODA) model. Instead of a fixed probability that the other agents will decide in the favor of the best choice, each agent considers that other agents might be one of two types: trustworthy or untrustworthy. Each agent its opinion and also the probability for each one of the other agents it interacts with being trustworthy. The dynamics of opinions and the evolution of the trust between the agents are studied. Clear evidences of the existence of two phases, one with strong polarization and the other tending to agreement, are observed. The transition shows signs of being a first-order transition. This happens despite the fact that the trust network evolves much slower than the opinion on the central issue.

Evolving Policy Initiatives for Effective Vocational Technical Education in North Central Zone, Nigeria

Science.gov (United States)

Ombugus, Danjuma A.; Angbre, Francis Adams

2015-01-01

The study focused on evolving policy initiatives for effective Vocational Technical Education (VTE) on sustainable development. The study adopted a descriptive survey research design and was carried out in North Central Geopolitical Zone of Nigeria. The population for the study was 450 respondents (VTE teachers/lecturers, government officials,…

Pharmacokinetic studies of neuromuscular blocking agents: Good Clinical Research Practice (GCRP)

DEFF Research Database (Denmark)

Viby-Mogensen, J.; Østergaard, D.; Donati, F.

2000-01-01

Good Clinical Research Practice (GCRP), neuromuscular blocking agents, pharmacokinetics, pharmacokinetic/pharmacodynamic modeling, population pharmacokinetics, statistics, study design......Good Clinical Research Practice (GCRP), neuromuscular blocking agents, pharmacokinetics, pharmacokinetic/pharmacodynamic modeling, population pharmacokinetics, statistics, study design...

Phase Transitions in Sexual Populations Subject to Stabilizing Selection

Science.gov (United States)

Rogers, A.

2003-04-01

We show that a simple model of an evolving sexual population, which dates back to some of the earliest work in theoretical population genetics, exhibits an unexpected and previously unobserved phase transition between ordered and disordered states. This behavior is not present in populations evolving asexually without recombination and is thus important in any comparison of sexual and asexual populations. In order to calculate the details of the phase transition, we use techniques from statistical physics. We introduce the correlation of the population as the order parameter of the system and use maximum entropy inference to find the state of the population at any time.

The Dynamics of Population, Built-up Areas and their Evolving Associations in Gridded Population across Time and Space

Science.gov (United States)

Stevens, F. R.; Gaughan, A. E.; Tatem, A. J.; Linard, C.; Sorichetta, A.; Nieves, J. J.; Reed, P.

2017-12-01

Gridded population data is commonly used to understand the `now' of hazard risk and mitigation management, health and disease modelling, and global change-, economic-, environmental-, and sustainability-related research. But to understand how human population change at local to global scales influences and is influenced by environmental changes requires novel ways of treating data and statistically describing associations of measured population counts with associated covariates. One of the most critical components in such gridded estimates is the relationship between built-up areas and population located in these areas. This relationship is rarely static and accurately estimating changes in built-areas through time and the changing human population around them is critical when applying gridded population datasets in studies of other environmental change. The research presented here discusses these issues in the context of multitemporal, gridded population data, using new technologies and sources of remotely-sensed and modeled built-up areas. We discuss applications of these data in environmental analyses and intercomparisons with other such data across scales.

Adaptive response to DNA-damaging agents in natural Saccharomyces cerevisiae populations from "Evolution Canyon", Mt. Carmel, Israel.

Directory of Open Access Journals (Sweden)

Gabriel A Lidzbarsky

2009-06-01

Full Text Available Natural populations of most organisms, especially unicellular microorganisms, are constantly exposed to harsh environmental factors which affect their growth. UV radiation is one of the most important physical parameters which influences yeast growth in nature. Here we used 46 natural strains of Saccharomyces cerevisiae isolated from several natural populations at the "Evolution Canyon" microsite (Nahal Oren, Mt. Carmel, Israel. The opposing slopes of this canyon share the same geology, soil, and macroclimate, but they differ in microclimatic conditions. The interslope differences in solar radiation (200%-800% more on the "African" slope caused the development of two distinct biomes. The south-facing slope is sunnier and has xeric, savannoid "African" environment while the north-facing slope is represented by temperate, "European" forested environment. Here we studied the phenotypic response of the S. cerevisiae strains to UVA and UVC radiations and to methyl methanesulfonate (MMS in order to evaluate the interslope effect on the strains' ability to withstand DNA-damaging agents.We exposed our strains to the different DNA-damaging agents and measured survival by counting colony forming units. The strains from the "African" slope were more resilient to both UVA and MMS than the strains from the "European" slope. In contrast, we found that there was almost no difference between strains (with similar ploidy from the opposite slopes, in their sensitivity to UVC radiation. These results suggest that the "African" strains are more adapted to higher solar radiation than the "European" strains. We also found that the tetraploids strains were more tolerant to all DNA-damaging agents than their neighboring diploid strains, which suggest that high ploidy level might be a mechanism of adaptation to high solar radiation.Our results and the results of parallel studies with several other organisms, suggest that natural selection appears to select, at a

The cultural evolution of human communication systems in different sized populations: usability trumps learnability.

Directory of Open Access Journals (Sweden)

Nicolas Fay

Full Text Available This study examines the intergenerational transfer of human communication systems. It tests if human communication systems evolve to be easy to learn or easy to use (or both, and how population size affects learnability and usability. Using an experimental-semiotic task, we find that human communication systems evolve to be easier to use (production efficiency and reproduction fidelity, but harder to learn (identification accuracy for a second generation of naïve participants. Thus, usability trumps learnability. In addition, the communication systems that evolve in larger populations exhibit distinct advantages over those that evolve in smaller populations: the learnability loss (from the Initial signs is more muted and the usability benefits are more pronounced. The usability benefits for human communication systems that evolve in a small and large population is explained through guided variation reducing sign complexity. The enhanced performance of the communication systems that evolve in larger populations is explained by the operation of a content bias acting on the larger pool of competing signs. The content bias selects for information-efficient iconic signs that aid learnability and enhance usability.

Improving Disability Awareness among Extension Agents

Science.gov (United States)

Mahadevan, Lakshmi; Peterson, Rick L.; Grenwelge, Cheryl

2014-01-01

Increasing prevalence rates and legislative mandates imply that educators, parents, and Extension agents will need better tools and resources to meet the needs of special populations. The Texas A&M AgriLife Extension Service addresses this issue by using e-learning tools. Extension agents can take advantage of these courses to gain critical…

Evolvability Is an Evolved Ability: The Coding Concept as the Arch-Unit of Natural Selection.

Science.gov (United States)

Janković, Srdja; Ćirković, Milan M

2016-03-01

Physical processes that characterize living matter are qualitatively distinct in that they involve encoding and transfer of specific types of information. Such information plays an active part in the control of events that are ultimately linked to the capacity of the system to persist and multiply. This algorithmicity of life is a key prerequisite for its Darwinian evolution, driven by natural selection acting upon stochastically arising variations of the encoded information. The concept of evolvability attempts to define the total capacity of a system to evolve new encoded traits under appropriate conditions, i.e., the accessible section of total morphological space. Since this is dependent on previously evolved regulatory networks that govern information flow in the system, evolvability itself may be regarded as an evolved ability. The way information is physically written, read and modified in living cells (the "coding concept") has not changed substantially during the whole history of the Earth's biosphere. This biosphere, be it alone or one of many, is, accordingly, itself a product of natural selection, since the overall evolvability conferred by its coding concept (nucleic acids as information carriers with the "rulebook of meanings" provided by codons, as well as all the subsystems that regulate various conditional information-reading modes) certainly played a key role in enabling this biosphere to survive up to the present, through alterations of planetary conditions, including at least five catastrophic events linked to major mass extinctions. We submit that, whatever the actual prebiotic physical and chemical processes may have been on our home planet, or may, in principle, occur at some time and place in the Universe, a particular coding concept, with its respective potential to give rise to a biosphere, or class of biospheres, of a certain evolvability, may itself be regarded as a unit (indeed the arch-unit) of natural selection.

Natural selection promotes antigenic evolvability

NARCIS (Netherlands)

Graves, C.J.; Ros, V.I.D.; Stevenson, B.; Sniegowski, P.D.; Brisson, D.

2013-01-01

The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide

Disgust: Evolved function and structure

NARCIS (Netherlands)

Tybur, J.M.; Lieberman, D.; Kurzban, R.; DeScioli, P.

2013-01-01

Interest in and research on disgust has surged over the past few decades. The field, however, still lacks a coherent theoretical framework for understanding the evolved function or functions of disgust. Here we present such a framework, emphasizing 2 levels of analysis: that of evolved function and

Constraining the Population of Small Close-in Planets Around Evolved Intermediate Mass Stars

Science.gov (United States)

Medina, Amber; Johnson, John Asher

2018-01-01

Intermediate mass stars ( > 1.3 M_Sun) have high occurrence rates of Jupiter mass planets in predominately long period orbits (~1.0 AU). There is a prominent planet gap, known as the ‘Planet Desert’, for low mass planets (Super-Earth, Neptune) < 0.5 AU from subgiants, the evolved counterpart to intermediate mass stars. Thus far, using current radial velocity methods, we have not been able to detect short period planets around subgiants due to noise from p-mode oscillations perhaps mimicking radial velocity signals (~5 m/s) in this planetary regime. Here we present techniques and preliminary results with regards to finding low mass, short period planets around subgiants and its implications for the Planet Desert.

Epidemiology of postoperative endophthalmitis in an Asian population: 11-year incidence and effect of intracameral antibiotic agents.

Science.gov (United States)

Tan, Colin S H; Wong, Hon Kiat; Yang, Francine P

2012-03-01

To describe the incidence of postoperative endophthalmitis after cataract surgery in a multiethnic Asian population over an 11-year period, compare the endophthalmitis rates before and after the use of intracameral antibiotic agents, and identify potential risk factors for endophthalmitis. Department of Ophthalmology, Tan Tock Seng Hospital, Singapore. Cohort study. The incidence and risk factors for postoperative endophthalmitis in patients who had cataract surgery over 11 years were reviewed. Subconjunctival antibiotic agents only were administered over 7 years; in the subsequent 4 years, intracameral cefazolin (1.0 mg/0.1 mL) was used. The overall incidence of postoperative endophthalmitis in 50,177 was 0.042%. Over the 7 years without intracameral antibiotics, the endophthalmitis rate was 0.064% (19/29,539). With the use of intracameral cefazolin, the incidence decreased to 0.01% (2/20,638) (multivariate odds ratio [OR], 13.6; 95% confidence interval [CI], 3.15-58.58; P<.001). The independent risk factors for endophthalmitis were age (OR, 1.05; 95% CI, 1.01-1.09; P=.025) and male sex (0.06% versus 0.02%; OR, 2.96; 95% CI; 1.15-7.65; P=.025). There was a significant reduction in the rate of postoperative endophthalmitis in a multiethnic Asian population with the use of intracameral cefazolin. Men and older patients were at a higher risk for endophthalmitis. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

The impact of rapid evolution on population dynamics in the wild: experimental test of eco-evolutionary dynamics.

Science.gov (United States)

Turcotte, Martin M; Reznick, David N; Hare, J Daniel

2011-11-01

Rapid evolution challenges the assumption that evolution is too slow to impact short-term ecological dynamics. This insight motivates the study of 'Eco-Evolutionary Dynamics' or how evolution and ecological processes reciprocally interact on short time scales. We tested how rapid evolution impacts concurrent population dynamics using an aphid (Myzus persicae) and an undomesticated host (Hirschfeldia incana) in replicated wild populations. We manipulated evolvability by creating non-evolving (single clone) and potentially evolving (two-clone) aphid populations that contained genetic variation in intrinsic growth rate. We observed significant evolution in two-clone populations whether or not they were exposed to predators and competitors. Evolving populations grew up to 42% faster and attained up to 67% higher density, compared with non-evolving control populations but only in treatments exposed to competitors and predators. Increased density also correlates with relative fitness of competing clones suggesting a full eco-evolutionary dynamic cycle defined as reciprocal interactions between evolution and density. © 2011 Blackwell Publishing Ltd/CNRS.

Finding evolved stars in the inner Galactic disk with Gaia

Science.gov (United States)

Quiroga-Nuñez, L. H.; van Langevelde, H. J.; Pihlström, Y. M.; Sjouwerman, L. O.; Brown, A. G. A.

2018-04-01

The Bulge Asymmetries and Dynamical Evolution (BAaDE) survey will provide positions and line-of-sight velocities of ~20, 000 evolved, maser bearing stars in the Galactic plane. Although this Galactic region is affected by optical extinction, BAaDE targets may have Gaia cross-matches, eventually providing additional stellar information. In an initial attempt to cross-match BAaDE targets with Gaia, we have found more than 5,000 candidates. Of these, we may expect half to show SiO emission, which will allow us to obtain velocity information. The cross-match is being refined to avoid false positives using different criteria based on distance analysis, flux variability, and color assessment in the mid- and near-IR. Once the cross-matches can be confirmed, we will have a unique sample to characterize the stellar population of evolved stars in the Galactic bulge, which can be considered fossils of the Milky Way formation.

Measurably evolving populations

DEFF Research Database (Denmark)

Drummond, Alexei James; Pybus, Oliver George; Rambaut, Andrew

2003-01-01

The availability of nucleotide and amino acid sequences sampled at different points in time has fostered the development of new statistical methods that exploit this temporal dimension. Such sequences enable us to observe evolution in action and to estimate the rate and magnitude of evolutionary ...

Keeping current with the evolving makeup of the Pennsylvania population.

Science.gov (United States)

Waldman, H Barry

2010-01-01

The changing residential population of the Pennsylvania requires continued monitoring if health practitioners are to maintain an awareness of the individuals in their community. A review of federal agency reports provides a general overview of Pennsylvania and national demographic and health factor characteristics.

On Religion and Language Evolutions Seen Through Mathematical and Agent Based Models

Science.gov (United States)

Ausloos, M.

Religions and languages are social variables, like age, sex, wealth or political opinions, to be studied like any other organizational parameter. In fact, religiosity is one of the most important sociological aspects of populations. Languages are also obvious characteristics of the human species. Religions, languages appear though also disappear. All religions and languages evolve and survive when they adapt to the society developments. On the other hand, the number of adherents of a given religion, or the number of persons speaking a language is not fixed in time, - nor space. Several questions can be raised. E.g. from a oscopic point of view : How many religions/languages exist at a given time? What is their distribution? What is their life time? How do they evolve? From a "microscopic" view point: can one invent agent based models to describe oscopic aspects? Do simple evolution equations exist? How complicated must be a model? These aspects are considered in the present note. Basic evolution equations are outlined and critically, though briefly, discussed. Similarities and differences between religions and languages are summarized. Cases can be illustrated with historical facts and data. It is stressed that characteristic time scales are different. It is emphasized that "external fields" are historically very relevant in the case of religions, rending the study more " interesting" within a mechanistic approach based on parity and symmetry of clusters concepts. Yet the modern description of human societies through networks in reported simulations is still lacking some mandatory ingredients, i.e. the non scalar nature of the nodes, and the non binary aspects of nodes and links, though for the latter this is already often taken into account, including directions. From an analytical point of view one can consider a population independently of the others. It is intuitively accepted, but also found from the statistical analysis of the frequency distribution that an

Training strategic community agents in health effects of ionizing radiation

International Nuclear Information System (INIS)

Leite, Teresa C.S.B.; Silva, IIson P.M. da; Jannuzzi, Denise M.S.; Maurmo, Alexandre M.

2013-01-01

The main motivation for the development of training was the need to train agents (opinion makers) with proximity and credibility among the population, to clarify the most frequently asked questions in relation to ionizing radiation, the operation of nuclear power plants, emergency plans and about the possibility of there effects of radiation on the health of inhabitants in regions close to the central Nuclear Almirante Alvaro Alberto - CNAAA. The project has a target audience of 420 agents, 60 of them have already been trained in a pilot project . The results indicate that the topics of training were adequate and the agents have expanded their knowledge. On the other hand, the information passed on to communities by agents, recognized by this population as ' the most reliable people', is of greater credibility and likelihood of success in communicating important issues for the population living in the vicinity of the CNAAA. (author)

Evolving perspectives of the role of novel agents in androgen-independent prostate cancer

Directory of Open Access Journals (Sweden)

Sujith Kalmadi

2008-01-01

Full Text Available Metastatic androgen-independent prostate cancer presents an intriguing clinical challenge, with a subtle interaction between hormone-responsive and refractory tumor cell elements. The treatment of advanced prostate carcinoma, which had remained stagnant for several decades following the understanding of the link between androgenic stimulation and carcinogenesis, has now started to make steady headway with chemotherapy and targeted approaches. Metastatic prostate cancer is almost always treated with initial androgen deprivation, in various forms. However, despite such treatment androgen-independent prostate cancer cells eventually emerge and progress to threaten life. The therapeutic objectives for treatment of metastatic prostate cancer are to maintain the quality of life and prolong survival. The out-dated nihilistic dogma of deferring chemotherapy until the most advanced stages in advanced prostate cancer is now falling by the wayside with the development of newer effective, tolerable agents.

Population dynamics at high Reynolds number

NARCIS (Netherlands)

Perlekar, P.; Benzi, R.; Nelson, D.R.; Toschi, F.

2010-01-01

We study the statistical properties of population dynamics evolving in a realistic two-dimensional compressible turbulent velocity field. We show that the interplay between turbulent dynamics and population growth and saturation leads to quasi-localization and a remarkable reduction in the carrying

An Experiment on Behavior Generalization and the Emergence of Linguistic Compositionality in Evolving Robots

DEFF Research Database (Denmark)

Tuci, E.; Ferrauto, T.; Zeschel, A.

2011-01-01

Populations of simulated agents controlled by dynamical neural networks are trained by artificial evolution to access linguistic instructions and to execute them by indicating, touching, or moving specific target objects. During training the agent experiences only a subset of all object...... the target object and executing the required action). The comparison between two experimental conditions, in one of which the agents are required to ignore rather than to indicate objects, shows that the composition of the behavioral set significantly influences the development of compositional semantic...

Evolving trends in the epidemiology, resource utilization, and outcomes of pregnancy-associated severe sepsis: a population-based cohort study.

Science.gov (United States)

Oud, Lavi; Watkins, Phillip

2015-06-01

Infections are a well-known complication of pregnancy. However, pregnancy-associated severe sepsis (PASS) has not been as well-characterized, with limited population-level data reported to date. We performed a population-based study of the evolving patterns of the epidemiology, clinical characteristics, resource utilization, and outcomes of PASS in Texas over the past decade. The Texas Inpatient Public Use Data File was used to identify pregnancy-associated hospitalizations and PASS hospitalizations for the years 2001 - 2010. The Texas Center for Health Statistics reports of live births, abortions and fetal deaths, and a previously reported population-based, age-specific linkage study on miscarriage were used to derive the annual total estimated pregnancies (TEPs). The incidence, demographics, clinical characteristics, resource utilization and outcomes of PASS were examined. Logistic regression modeling was used to explore the predictors of PASS and its associated mortality. There were 4,060,201 pregnancy-associated hospitalizations and 1,007 PASS hospitalizations during study period. The incidence of PASS was increased by 236% over the past decade, rising from 11 to 26 hospitalizations per 100,000 TEPs. The key changes between 2001 - 2002 and 2009 - 2010 within PASS hospitalizations included: admission to ICU 78% vs. 90% (P = 0.002); development of ≥ 3 organ failures 9% vs. 35% (P < 0.0001); and inflation-adjusted median hospital charges (2,010 dollars) $64,034 vs. $89,895 (P = 0.0141). Hospital mortality (11%) remained unchanged during study period. Chronic liver disease (adjusted odds ratio (aOR) 41.4) and congestive heart failure (CHF) (aOR 20.5) were associated with the highest risk of PASS, in addition to black race, poverty, drug abuse, and lack of health insurance. The highest risk of death was among women with HIV infection (aOR 45.5), need for mechanical ventilation (aOR 4.5), drug abuse (aOR 3.0), and lacking health insurance (aOR 2.9). The incidence

Scaling of the propagation of epidemics in a system of mobile agents

OpenAIRE

Gonzalez, M. C.; Herrmann, H. J.

2004-01-01

For a two-dimensional system of agents modeled by molecular dynamics, we simulate epidemics spreading, which was recently studied on complex networks. Our resulting network model is time-evolving. We study the transitions to spreading as function of density, temperature and infection time. In addition, we analyze the epidemic threshold associated to a power-law distribution of infection times.

Information Security for Compliance with Select Agent Regulations

Science.gov (United States)

Lewis, Nick; Campbell, Mark J.

2015-01-01

The past decade has seen a significant rise in research on high-consequence human and animal pathogens, many now known as “select agents.” While physical security around these agents is tightly regulated, information security standards are still lagging. The understanding of the threats unique to the academic and research environment is still evolving, in part due to poor communication between the various stakeholders. Perhaps as a result, information security guidelines published by select agent regulators lack the critical details and directives needed to achieve even the lowest security level of the Federal Information Security Management Act (FISMA). While only government agencies are currently required to abide by the provisions of FISMA (unless specified as preconditions for obtaining government grants or contracts—still a relatively rare or narrowly scoped occurrence), the same strategies were recently recommended by executive order for others. We propose that information security guidelines for select agent research be updated to promulgate and detail FISMA standards and processes and that the latter be ultimately incorporated into select agent regulations. We also suggest that information security in academic and research institutions would greatly benefit from active efforts to improve communication among the biosecurity, security, and information technology communities, and from a secure venue for exchange of timely information on emerging threats and solutions in the research environment. PMID:26042864

Information security for compliance with select agent regulations.

Science.gov (United States)

Lewis, Nick; Campbell, Mark J; Baskin, Carole R

2015-01-01

The past decade has seen a significant rise in research on high-consequence human and animal pathogens, many now known as "select agents." While physical security around these agents is tightly regulated, information security standards are still lagging. The understanding of the threats unique to the academic and research environment is still evolving, in part due to poor communication between the various stakeholders. Perhaps as a result, information security guidelines published by select agent regulators lack the critical details and directives needed to achieve even the lowest security level of the Federal Information Security Management Act (FISMA). While only government agencies are currently required to abide by the provisions of FISMA (unless specified as preconditions for obtaining government grants or contracts--still a relatively rare or narrowly scoped occurrence), the same strategies were recently recommended by executive order for others. We propose that information security guidelines for select agent research be updated to promulgate and detail FISMA standards and processes and that the latter be ultimately incorporated into select agent regulations. We also suggest that information security in academic and research institutions would greatly benefit from active efforts to improve communication among the biosecurity, security, and information technology communities, and from a secure venue for exchange of timely information on emerging threats and solutions in the research environment.

Negative Drift in Populations

DEFF Research Database (Denmark)

Lehre, Per Kristian

2011-01-01

An important step in gaining a better understanding of the stochastic dynamics of evolving populations, is the development of appropriate analytical tools. We present a new drift theorem for populations that allows properties of their long-term behaviour, e.g. the runtime of evolutionary algorithms......, to be derived from simple conditions on the one-step behaviour of their variation operators and selection mechanisms....

A neighbourhood evolving network model

International Nuclear Information System (INIS)

Cao, Y.J.; Wang, G.Z.; Jiang, Q.Y.; Han, Z.X.

2006-01-01

Many social, technological, biological and economical systems are best described by evolved network models. In this short Letter, we propose and study a new evolving network model. The model is based on the new concept of neighbourhood connectivity, which exists in many physical complex networks. The statistical properties and dynamics of the proposed model is analytically studied and compared with those of Barabasi-Albert scale-free model. Numerical simulations indicate that this network model yields a transition between power-law and exponential scaling, while the Barabasi-Albert scale-free model is only one of its special (limiting) cases. Particularly, this model can be used to enhance the evolving mechanism of complex networks in the real world, such as some social networks development

What Does God Know? Supernatural Agents' Access to Socially Strategic and Non-Strategic Information

Science.gov (United States)

Purzycki, Benjamin G.; Finkel, Daniel N.; Shaver, John; Wales, Nathan; Cohen, Adam B.; Sosis, Richard

2012-01-01

Current evolutionary and cognitive theories of religion posit that supernatural agent concepts emerge from cognitive systems such as theory of mind and social cognition. Some argue that these concepts evolved to maintain social order by minimizing antisocial behavior. If these theories are correct, then people should process information about…

Evolved H II regions

International Nuclear Information System (INIS)

Churchwell, E.

1975-01-01

A probable evolutionary sequence of H II regions based on six distinct types of observed objects is suggested. Two examples which may deviate from this idealized sequence, are discussed. Even though a size-mean density relation of H II regions can be used as a rough indication of whether a nebula is very young or evolved, it is argued that such a relation is not likely to be useful for the quantitative assignment of ages to H II regions. Evolved H II regions appear to fit into one of four structural types: rings, core-halos, smooth structures, and irregular or filamentary structures. Examples of each type are given with their derived physical parameters. The energy balance in these nebulae is considered. The mass of ionized gas in evolved H II regions is in general too large to trace the nebula back to single compact H II regions. Finally, the morphological type of the Galaxy is considered from its H II region content. 2 tables, 2 figs., 29 refs

How the indirect reciprocity with co-evolving norm and strategy for 2 × 2 prisoner's dilemma game works for emerging cooperation

Science.gov (United States)

Tanimoto, Jun; Sagara, Hirokji

2015-11-01

We built a new indirect reciprocity model based on binary image scores, where an agent's strategy and norm co-evolve. The norm, meaning what behavior is evaluated as "good" or "bad," stipulates how image scores of two agents playing a game is altered, which has been presumed to be a fixed value in most previous studies. Also, unlike former studies, our model allows an agent to play with an agent who has a different norm. This point of relaxing the freedom of the model pulls down cooperation level vis-à-vis the case where an agent always plays with another one having same norm. However, it is observed that a rather larger dilemma shows robust cooperation establishing compared with a smaller dilemma, since a norm that punishes a so-called second-order free-rider is prompted. To encourage the evolution of norms to be able to punish second-order free-riders, a society needs a small number of defectors. This is elucidated by the fact that cases with action error are more cooperative than those without action error.

Is exposure to Agent Orange a risk factor for hepatocellular cancer?-A single-center retrospective study in the U.S. veteran population.

Science.gov (United States)

Krishnamurthy, Padmini; Hazratjee, Nyla; Opris, Dan; Agrawal, Sangeeta; Markert, Ronald

2016-06-01

factors for HCC development in this U.S. veteran population. There was no significant association between exposure to Agent Orange and HCC, although larger studies are needed in the U.S. military veteran population to evaluate further this toxic herbicide from the Vietnam War era.

Information processing and dynamics in minimally cognitive agents.

Science.gov (United States)

Beer, Randall D; Williams, Paul L

2015-01-01

There has been considerable debate in the literature about the relative merits of information processing versus dynamical approaches to understanding cognitive processes. In this article, we explore the relationship between these two styles of explanation using a model agent evolved to solve a relational categorization task. Specifically, we separately analyze the operation of this agent using the mathematical tools of information theory and dynamical systems theory. Information-theoretic analysis reveals how task-relevant information flows through the system to be combined into a categorization decision. Dynamical analysis reveals the key geometrical and temporal interrelationships underlying the categorization decision. Finally, we propose a framework for directly relating these two different styles of explanation and discuss the possible implications of our analysis for some of the ongoing debates in cognitive science. Copyright © 2014 Cognitive Science Society, Inc.

Impact of Different Policies on Unhealthy Dietary Behaviors in an Adult Population of Los Angeles County: An Agent-Based Simulation Model

OpenAIRE

Zhang, Donglan

2014-01-01

A typical American diet is comprised of too much high-calorie foods and insufficient fruits and vegetables. Many theories and models targeting unhealthy dietary behaviors focus exclusively on people as individuals, while behavior theories such as multi-level theory of population health emphasize the social component in human cognitive habits and behaviors, providing an alternative paradigm to understand dietary behaviors. This dissertation incorporates those behavioral theories into an agent-...

Rational Constraints and the Evolution of Fairness in the Ultimatum Game.

Science.gov (United States)

Tomlin, Damon

2015-01-01

Behavior in the Ultimatum Game has been well-studied experimentally, and provides a marked contrast between the theoretical model of a self-interested economic agent and that of an actual human concerned with social norms such as fairness. How did such norms evolve, when punishing unfair behavior can be costly to the punishing agent? The work described here simulated a series of Ultimatum Games, in which populations of agents earned resources based on their preferences for proposing and accepting (or rejecting) offers of various sizes. Two different systems governing the acceptance or rejection of offers were implemented. Under one system, the probability that an agent accepted an offer of a given size was independent of the probabilities of accepting the other possible offers. Under the other system, a simple, ordinal constraint was placed on the acceptance probabilities such that a given offer was at least as likely to be accepted as a smaller offer. For simulations under either system, agents' preferences and their corresponding behavior evolved over multiple generations. Populations without the ordinal constraint came to emulate maximizing economic agents, while populations with the constraint came to resemble the behavior of human players.

Evolving Technologies: A View to Tomorrow

Science.gov (United States)

Tamarkin, Molly; Rodrigo, Shelley

2011-01-01

Technology leaders must participate in strategy creation as well as operational delivery within higher education institutions. The future of higher education--the view to tomorrow--is irrevocably integrated and intertwined with evolving technologies. This article focuses on two specific evolving technologies: (1) alternative IT sourcing; and (2)…

Spacetimes containing slowly evolving horizons

International Nuclear Information System (INIS)

Kavanagh, William; Booth, Ivan

2006-01-01

Slowly evolving horizons are trapping horizons that are ''almost'' isolated horizons. This paper reviews their definition and discusses several spacetimes containing such structures. These include certain Vaidya and Tolman-Bondi solutions as well as (perturbatively) tidally distorted black holes. Taking into account the mass scales and orders of magnitude that arise in these calculations, we conjecture that slowly evolving horizons are the norm rather than the exception in astrophysical processes that involve stellar-scale black holes

Newer Clinical Strategies for Combining Interferon and Cytotoxic Agents Against Solid Tumours and Hematological Malignancies

Directory of Open Access Journals (Sweden)

Scott Wadler

1994-01-01

Full Text Available The role of interferons in the treatment of cancer continues to evolve. Despite limited single agent activity against solid tumours, interferons now appear to have an important role as modulators of the activity of a variety of cytotoxic drugs. Clinical benefits have been observed for combinations of interferons and alkylating agents against low grade lymphomas, interferons and dacarbazine against malignant melanoma, and interferons and 5-fluorouracil against gastrointestinal and genitourinary malignancies. Further progress will depend on a grealer understanding of the biology of the interaction.

Antihypertensive agents and risk of Parkinson's disease, essential tremor and dementia: a population-based prospective study (NEDICES).

Science.gov (United States)

Louis, Elan D; Benito-León, Julián; Bermejo-Pareja, Félix

2009-01-01

Recent interest in antihypertensive agents, especially calcium channel blockers, has been sparked by the notion that these medications may be neuroprotective. A modest literature, with mixed results, has examined whether these medications might lower the odds or risk of Parkinson's disease (PD) or dementia. There are no data for essential tremor (ET). To examine the association between antihypertensive use (defined broadly and by individual subclasses) and ET, PD and dementia. For each disorder, we used cross-sectional data (association with prevalent disease) and prospective data (association with incident disease). Prospective population-based study in Spain enrolling 5,278 participants at baseline. Use of antihypertensive medications (aside from beta-blockers) was similar in prevalent ET cases and controls. Baseline use of antihypertensive agents was not associated with reduced risk of incident ET. Antihypertensive medication use was not associated with prevalent or incident PD. Calcium channel blocker use was marginally reduced in prevalent dementia cases (OR(adjusted) = 0.63, p = 0.06) but was not associated with reduced risk of incident dementia (RR(adjusted) = 1.02, p = 0.95). We did not find evidence of a protective effect of antihypertensive medications in these three neurodegenerative disorders. Copyright 2009 S. Karger AG, Basel.

Evolvable Neural Software System

Science.gov (United States)

Curtis, Steven A.

2009-01-01

The Evolvable Neural Software System (ENSS) is composed of sets of Neural Basis Functions (NBFs), which can be totally autonomously created and removed according to the changing needs and requirements of the software system. The resulting structure is both hierarchical and self-similar in that a given set of NBFs may have a ruler NBF, which in turn communicates with other sets of NBFs. These sets of NBFs may function as nodes to a ruler node, which are also NBF constructs. In this manner, the synthetic neural system can exhibit the complexity, three-dimensional connectivity, and adaptability of biological neural systems. An added advantage of ENSS over a natural neural system is its ability to modify its core genetic code in response to environmental changes as reflected in needs and requirements. The neural system is fully adaptive and evolvable and is trainable before release. It continues to rewire itself while on the job. The NBF is a unique, bilevel intelligence neural system composed of a higher-level heuristic neural system (HNS) and a lower-level, autonomic neural system (ANS). Taken together, the HNS and the ANS give each NBF the complete capabilities of a biological neural system to match sensory inputs to actions. Another feature of the NBF is the Evolvable Neural Interface (ENI), which links the HNS and ANS. The ENI solves the interface problem between these two systems by actively adapting and evolving from a primitive initial state (a Neural Thread) to a complicated, operational ENI and successfully adapting to a training sequence of sensory input. This simulates the adaptation of a biological neural system in a developmental phase. Within the greater multi-NBF and multi-node ENSS, self-similar ENI s provide the basis for inter-NBF and inter-node connectivity.

[Biological agents].

Science.gov (United States)

Amano, Koichi

2009-03-01

There are two types of biological agents for the treatment of rheumatoid arthritis (RA); monoclonal antibodies and recombinant proteins. Among the latter, etanercept, a recombinant fusion protein of soluble TNF receptor and IgG was approved in 2005 in Japan. The post-marketing surveillance of 13,894 RA patients revealed the efficacy and safety profiles of etanercept in the Japanese population, as well as overseas studies. Abatacept, a recombinant fusion protein of CTLA4 and IgG, is another biological agent for RA. Two clinical trials disclosed the efficacy of abatacept for difficult-to-treat patients: the AIM for MTX-resistant cases and the ATTAIN for patients who are resistant to anti-TNF. The ATTEST trial suggested abatacept might have more acceptable safety profile than infliximab. These biologics are also promising for the treatment of RA for not only relieving clinical symptoms and signs but retarding structural damage.

The Psychological Self as Actor, Agent, and Author.

Science.gov (United States)

McAdams, Dan P

2013-05-01

The psychological self may be construed as a reflexive arrangement of the subjective "I" and the constructed "Me," evolving and expanding over the human life course. The psychological self begins life as a social actor, construed in terms of performance traits and social roles. By the end of childhood, the self has become a motivated agent, too, as personal goals, motives, values, and envisioned projects for the future become central features of how the I conceives of the Me. A third layer of selfhood begins to form in the adolescent and emerging adulthood years, when the self as autobiographical author aims to construct a story of the Me, to provide adult life with broad purpose and a dynamic sense of temporal continuity. An integrative theory that envisions the psychological self as a developing I-Me configuration of actor, agent, and author helps to synthesize a wide range of conceptions and findings on the self from social, personality, cognitive, cultural, and developmental psychology and from sociology and other social sciences. The actor-agent-author framework also sheds new light on studies of self-regulation, self-esteem, self-continuity, and the relationship between self and culture. © The Author(s) 2013.

Evolving phenotypic networks in silico.

Science.gov (United States)

François, Paul

2014-11-01

Evolved gene networks are constrained by natural selection. Their structures and functions are consequently far from being random, as exemplified by the multiple instances of parallel/convergent evolution. One can thus ask if features of actual gene networks can be recovered from evolutionary first principles. I review a method for in silico evolution of small models of gene networks aiming at performing predefined biological functions. I summarize the current implementation of the algorithm, insisting on the construction of a proper "fitness" function. I illustrate the approach on three examples: biochemical adaptation, ligand discrimination and vertebrate segmentation (somitogenesis). While the structure of the evolved networks is variable, dynamics of our evolved networks are usually constrained and present many similar features to actual gene networks, including properties that were not explicitly selected for. In silico evolution can thus be used to predict biological behaviours without a detailed knowledge of the mapping between genotype and phenotype. Copyright © 2014 The Author. Published by Elsevier Ltd.. All rights reserved.

Rapid divergence and convergence of life-history in experimentally evolved Drosophila melanogaster.

Science.gov (United States)

Burke, Molly K; Barter, Thomas T; Cabral, Larry G; Kezos, James N; Phillips, Mark A; Rutledge, Grant A; Phung, Kevin H; Chen, Richard H; Nguyen, Huy D; Mueller, Laurence D; Rose, Michael R

2016-09-01

Laboratory selection experiments are alluring in their simplicity, power, and ability to inform us about how evolution works. A longstanding challenge facing evolution experiments with metazoans is that significant generational turnover takes a long time. In this work, we present data from a unique system of experimentally evolved laboratory populations of Drosophila melanogaster that have experienced three distinct life-history selection regimes. The goal of our study was to determine how quickly populations of a certain selection regime diverge phenotypically from their ancestors, and how quickly they converge with independently derived populations that share a selection regime. Our results indicate that phenotypic divergence from an ancestral population occurs rapidly, within dozens of generations, regardless of that population's evolutionary history. Similarly, populations sharing a selection treatment converge on common phenotypes in this same time frame, regardless of selection pressures those populations may have experienced in the past. These patterns of convergence and divergence emerged much faster than expected, suggesting that intermediate evolutionary history has transient effects in this system. The results we draw from this system are applicable to other experimental evolution projects, and suggest that many relevant questions can be sufficiently tested on shorter timescales than previously thought. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Overall survival patterns in patients with multiple myeloma in the era of novel agents and the role of initial clinical presentation and comorbidities: A population-based study

NARCIS (Netherlands)

Oortgiesen, Berdien; Van Roon, Eric N.; Joosten, Peter; Kibbelaar, Robby; Storm, Huib; Hovenga, Sjoerd; Van Rees, Bas P.; Woolthuis, Gerhard; Veeger, Nic J. G. M.; Hoogendoorn, Mels

2014-01-01

Introduction Clinical trials have shown improved response rates, progression-free survival and overall survival (OS) in patients with multiple myeloma (MM) when using the novel agents thalidomide, lenalidomide and bortezomib. However, outcome data provided by population-based registries, reflecting

canEvolve: a web portal for integrative oncogenomics.

Directory of Open Access Journals (Sweden)

Mehmet Kemal Samur

Full Text Available BACKGROUND & OBJECTIVE: Genome-wide profiles of tumors obtained using functional genomics platforms are being deposited to the public repositories at an astronomical scale, as a result of focused efforts by individual laboratories and large projects such as the Cancer Genome Atlas (TCGA and the International Cancer Genome Consortium. Consequently, there is an urgent need for reliable tools that integrate and interpret these data in light of current knowledge and disseminate results to biomedical researchers in a user-friendly manner. We have built the canEvolve web portal to meet this need. RESULTS: canEvolve query functionalities are designed to fulfill most frequent analysis needs of cancer researchers with a view to generate novel hypotheses. canEvolve stores gene, microRNA (miRNA and protein expression profiles, copy number alterations for multiple cancer types, and protein-protein interaction information. canEvolve allows querying of results of primary analysis, integrative analysis and network analysis of oncogenomics data. The querying for primary analysis includes differential gene and miRNA expression as well as changes in gene copy number measured with SNP microarrays. canEvolve provides results of integrative analysis of gene expression profiles with copy number alterations and with miRNA profiles as well as generalized integrative analysis using gene set enrichment analysis. The network analysis capability includes storage and visualization of gene co-expression, inferred gene regulatory networks and protein-protein interaction information. Finally, canEvolve provides correlations between gene expression and clinical outcomes in terms of univariate survival analysis. CONCLUSION: At present canEvolve provides different types of information extracted from 90 cancer genomics studies comprising of more than 10,000 patients. The presence of multiple data types, novel integrative analysis for identifying regulators of oncogenesis, network

Whole-genome sequencing of a laboratory-evolved yeast strain

Directory of Open Access Journals (Sweden)

Dunham Maitreya J

2010-02-01

Full Text Available Abstract Background Experimental evolution of microbial populations provides a unique opportunity to study evolutionary adaptation in response to controlled selective pressures. However, until recently it has been difficult to identify the precise genetic changes underlying adaptation at a genome-wide scale. New DNA sequencing technologies now allow the genome of parental and evolved strains of microorganisms to be rapidly determined. Results We sequenced >93.5% of the genome of a laboratory-evolved strain of the yeast Saccharomyces cerevisiae and its ancestor at >28× depth. Both single nucleotide polymorphisms and copy number amplifications were found, with specific gains over array-based methodologies previously used to analyze these genomes. Applying a segmentation algorithm to quantify structural changes, we determined the approximate genomic boundaries of a 5× gene amplification. These boundaries guided the recovery of breakpoint sequences, which provide insights into the nature of a complex genomic rearrangement. Conclusions This study suggests that whole-genome sequencing can provide a rapid approach to uncover the genetic basis of evolutionary adaptations, with further applications in the study of laboratory selections and mutagenesis screens. In addition, we show how single-end, short read sequencing data can provide detailed information about structural rearrangements, and generate predictions about the genomic features and processes that underlie genome plasticity.

Design of an Agent-Based Model to Examine Population-Environment Interactions in Nang Rong District, Thailand.

Science.gov (United States)

Walsh, Stephen J; Malanson, George P; Entwisle, Barbara; Rindfuss, Ronald R; Mucha, Peter J; Heumann, Benjamin W; McDaniel, Philip M; Frizzelle, Brian G; Verdery, Ashton M; Williams, Nathalie; Xiaozheng, Yao; Ding, Deng

2013-05-01

The design of an Agent-Based Model (ABM) is described that integrates Social and Land Use Modules to examine population-environment interactions in a former agricultural frontier in Northeastern Thailand. The ABM is used to assess household income and wealth derived from agricultural production of lowland, rain-fed paddy rice and upland field crops in Nang Rong District as well as remittances returned to the household from family migrants who are engaged in off-farm employment in urban destinations. The ABM is supported by a longitudinal social survey of nearly 10,000 households, a deep satellite image time-series of land use change trajectories, multi-thematic social and ecological data organized within a GIS, and a suite of software modules that integrate data derived from an agricultural cropping system model (DSSAT - Decision Support for Agrotechnology Transfer) and a land suitability model (MAXENT - Maximum Entropy), in addition to multi-dimensional demographic survey data of individuals and households. The primary modules of the ABM are the Initialization Module, Migration Module, Assets Module, Land Suitability Module, Crop Yield Module, Fertilizer Module, and the Land Use Change Decision Module. The architecture of the ABM is described relative to module function and connectivity through uni-directional or bi-directional links. In general, the Social Modules simulate changes in human population and social networks, as well as changes in population migration and household assets, whereas the Land Use Modules simulate changes in land use types, land suitability, and crop yields. We emphasize the description of the Land Use Modules - the algorithms and interactions between the modules are described relative to the project goals of assessing household income and wealth relative to shifts in land use patterns, household demographics, population migration, social networks, and agricultural activities that collectively occur within a marginalized environment that

Antimicrobial activity of ceftaroline and other anti-infective agents against microbial pathogens recovered from the surgical intensive care patient population: a prevalence analysis.

Science.gov (United States)

Edmiston, Charles E; Krepel, Candace J; Leaper, David; Ledeboer, Nathan A; Mackey, Tami-Lea; Graham, Mary Beth; Lee, Cheong; Rossi, Peter J; Brown, Kellie R; Lewis, Brian D; Seabrook, Gary R

2014-12-01

Ceftaroline is a new parenteral cephalosporin agent with excellent activity against methicillin-sensitive (MSSA) and resistant strains of Staphylococcus aureus (MRSA). Critically ill surgical patients are susceptible to infection, often by multi-drug-resistant pathogens. The activity of ceftaroline against such pathogens has not been described. Three hundred thirty-five consecutive microbial isolates were collected from surgical wounds or abscesses, respiratory, urine, and blood cultures from patients in the surgical intensive care unit (SICU) of a major tertiary medical center. Using Clinical and Laboratory Standards Institute (CLSI) standard methodology and published breakpoints, all aerobic, facultative anaerobic isolates were tested against ceftaroline and selected comparative antimicrobial agents. All staphylococcal isolates were susceptible to ceftaroline at a breakpoint of ≤1.0 mcg/mL. In addition, ceftaroline exhibited excellent activity against all streptococcal clinical isolates and non-ESBL-producing strains of Enterobacteriaceae (93.5%) recovered from SICU patients. Ceftaroline was inactive against ESBL-producing Enterobacteriaceae, Pseudomonas aeruginosa, vancomycin-resistant enterococci, and selective gram-negative anaerobic bacteria. At present, ceftaroline is the only cephalosporin agent that is active against community and healthcare-associated MRSA. Further studies are needed to validate the benefit of this novel broad-spectrum anti-infective agent for the treatment of susceptible serious infections in the SICU patient population.

Language competition in a population of migrating agents

Science.gov (United States)

Lipowska, Dorota; Lipowski, Adam

2017-05-01

Influencing various aspects of human activity, migration is associated also with language formation. To examine the mutual interaction of these processes, we study a Naming Game with migrating agents. The dynamics of the model leads to formation of low-mobility clusters, which turns out to break the symmetry of the model: although the Naming Game remains symmetric, low-mobility languages are favored. High-mobility languages are gradually eliminated from the system, and the dynamics of language formation considerably slows down. Our model is too simple to explain in detail language competition of migrating human communities, but it certainly shows that languages of settlers are favored over nomadic ones.

Population level analysis of evolved mutations underlying improvements in plant hemicellulose and cellulose fermentation by Clostridium phytofermentans.

Directory of Open Access Journals (Sweden)

Supratim Mukherjee

Full Text Available The complexity of plant cell walls creates many challenges for microbial decomposition. Clostridium phytofermentans, an anaerobic bacterium isolated from forest soil, directly breaks down and utilizes many plant cell wall carbohydrates. The objective of this research is to understand constraints on rates of plant decomposition by Clostridium phytofermentans and identify molecular mechanisms that may overcome these limitations.Experimental evolution via repeated serial transfers during exponential growth was used to select for C. phytofermentans genotypes that grow more rapidly on cellobiose, cellulose and xylan. To identify the underlying mutations an average of 13,600,000 paired-end reads were generated per population resulting in ∼300 fold coverage of each site in the genome. Mutations with allele frequencies of 5% or greater could be identified with statistical confidence. Many mutations are in carbohydrate-related genes including the promoter regions of glycoside hydrolases and amino acid substitutions in ABC transport proteins involved in carbohydrate uptake, signal transduction sensors that detect specific carbohydrates, proteins that affect the export of extracellular enzymes, and regulators of unknown specificity. Structural modeling of the ABC transporter complex proteins suggests that mutations in these genes may alter the recognition of carbohydrates by substrate-binding proteins and communication between the intercellular face of the transmembrane and the ATPase binding proteins.Experimental evolution was effective in identifying molecular constraints on the rate of hemicellulose and cellulose fermentation and selected for putative gain of function mutations that do not typically appear in traditional molecular genetic screens. The results reveal new strategies for evolving and engineering microorganisms for faster growth on plant carbohydrates.

Time Evolving Fission Chain Theory and Fast Neutron and Gamma-Ray Counting Distributions

International Nuclear Information System (INIS)

Kim, K. S.; Nakae, L. F.; Prasad, M. K.; Snyderman, N. J.; Verbeke, J. M.

2015-01-01

Here, we solve a simple theoretical model of time evolving fission chains due to Feynman that generalizes and asymptotically approaches the point model theory. The point model theory has been used to analyze thermal neutron counting data. This extension of the theory underlies fast counting data for both neutrons and gamma rays from metal systems. Fast neutron and gamma-ray counting is now possible using liquid scintillator arrays with nanosecond time resolution. For individual fission chains, the differential equations describing three correlated probability distributions are solved: the time-dependent internal neutron population, accumulation of fissions in time, and accumulation of leaked neutrons in time. Explicit analytic formulas are given for correlated moments of the time evolving chain populations. The equations for random time gate fast neutron and gamma-ray counting distributions, due to randomly initiated chains, are presented. Correlated moment equations are given for both random time gate and triggered time gate counting. There are explicit formulas for all correlated moments are given up to triple order, for all combinations of correlated fast neutrons and gamma rays. The nonlinear differential equations for probabilities for time dependent fission chain populations have a remarkably simple Monte Carlo realization. A Monte Carlo code was developed for this theory and is shown to statistically realize the solutions to the fission chain theory probability distributions. Combined with random initiation of chains and detection of external quanta, the Monte Carlo code generates time tagged data for neutron and gamma-ray counting and from these data the counting distributions.

Criticality is an emergent property of genetic networks that exhibit evolvability.

Directory of Open Access Journals (Sweden)

Christian Torres-Sosa

Full Text Available Accumulating experimental evidence suggests that the gene regulatory networks of living organisms operate in the critical phase, namely, at the transition between ordered and chaotic dynamics. Such critical dynamics of the network permits the coexistence of robustness and flexibility which are necessary to ensure homeostatic stability (of a given phenotype while allowing for switching between multiple phenotypes (network states as occurs in development and in response to environmental change. However, the mechanisms through which genetic networks evolve such critical behavior have remained elusive. Here we present an evolutionary model in which criticality naturally emerges from the need to balance between the two essential components of evolvability: phenotype conservation and phenotype innovation under mutations. We simulated the Darwinian evolution of random Boolean networks that mutate gene regulatory interactions and grow by gene duplication. The mutating networks were subjected to selection for networks that both (i preserve all the already acquired phenotypes (dynamical attractor states and (ii generate new ones. Our results show that this interplay between extending the phenotypic landscape (innovation while conserving the existing phenotypes (conservation suffices to cause the evolution of all the networks in a population towards criticality. Furthermore, the networks produced by this evolutionary process exhibit structures with hubs (global regulators similar to the observed topology of real gene regulatory networks. Thus, dynamical criticality and certain elementary topological properties of gene regulatory networks can emerge as a byproduct of the evolvability of the phenotypic landscape.

Páramo is the world’s fastest evolving and coolest biodiversity hotspot

Directory of Open Access Journals (Sweden)

Santiago eMadriñán

2013-10-01

Full Text Available Understanding the processes that cause speciation is a key aim of evolutionary biology. Lineages or biomes that exhibit recent and rapid diversification are ideal model systems for determining these processes. Species rich biomes reported to be of relatively recent origin, i.e., since the beginning of the Miocene, include Mediterranean ecosystems such as the California Floristic Province, oceanic islands such as the Hawaiian archipelago and the Neotropical high elevation ecosystem of the Páramos. Páramos constitute grasslands above the forest tree-line (at elevations of c. 2800–4700 m with high species endemism. Organisms that occupy this ecosystem are a likely product of unique adaptations to an extreme environment that evolved during the last three to five million years when the Andes reached an altitude that was capable of sustaining this type of vegetation. We compared net diversification rates of lineages in fast evolving biomes using 73 dated molecular phylogenies. Based on our sample, we demonstrate that average net diversification rates of Páramo plant lineages are faster than those of other reportedly fast evolving hotspots and that the faster evolving lineages are more likely to be found in Páramos than the other hotspots. Páramos therefore represent the ideal model system for studying diversification processes. Most of the speciation events that we observed in the Páramos (144 out of 177 occurred during the Pleistocene possibly due to the effects of species range contraction and expansion that may have resulted from the well-documented climatic changes during that period. Understanding these effects will assist with efforts to determine how future climatic changes will impact plant populations.

Genetic structure and evolved malaria resistance in Hawaiian honeycreepers

Science.gov (United States)

Foster, J.T.; Woodworth, B.L.; Eggert, L.E.; Hart, P.J.; Palmer, D.; Duffy, D.C.; Fleischer, R.C.

2007-01-01

Infectious diseases now threaten wildlife populations worldwide but population recovery following local extinction has rarely been observed. In such a case, do resistant individuals recolonize from a central remnant population, or do they spread from small, perhaps overlooked, populations of resistant individuals? Introduced avian malaria (Plasmodium relictum) has devastated low-elevation populations of native birds in Hawaii, but at least one species (Hawaii amakihi, Hemignathus virens) that was greatly reduced at elevations below about 1000 m tolerates malaria and has initiated a remarkable and rapid recovery. We assessed mitochondrial and nuclear DNA markers from amakihi and two other Hawaiian honeycreepers, apapane (Himatione sanguinea) and iiwi (Vestiaria coccinea), at nine primary study sites from 2001 to 2003 to determine the source of re-establishing birds. In addition, we obtained sequences from tissue from amakihi museum study skins (1898 and 1948-49) to assess temporal changes in allele distributions. We found that amakihi in lowland areas are, and have historically been, differentiated from birds at high elevations and had unique alleles retained through time; that is, their genetic signature was not a subset of the genetic variation at higher elevations. We suggest that high disease pressure rapidly selected for resistance to malaria at low elevation, leaving small pockets of resistant birds, and this resistance spread outward from the scattered remnant populations. Low-elevation amakihi are currently isolated from higher elevations (> 1000 m) where disease emergence and transmission rates appear to vary seasonally and annually. In contrast to results from amakihi, no genetic differentiation between elevations was found in apapane and iiwi, indicating that slight variation in genetic or life-history attributes can determine disease resistance and population recovery. Determining the conditions that allow for the development of resistance to disease is

Language acquisition age effects and their role in the preservation and change of communication systems

NARCIS (Netherlands)

Verhoef, T.; de Boer, B.

2011-01-01

In this paper it is investigated what happens in a culturally evolving communication system if children learn faster than adults. An agent based computer model is investigated which contains a population of agents in which vowel systems emerge when individuals play imitation games. These vowel

On the Benefits of Divergent Search for Evolved Representations

DEFF Research Database (Denmark)

Lehman, Joel; Risi, Sebastian; Stanley, Kenneth O

2012-01-01

Evolved representations in evolutionary computation are often fragile, which can impede representation-dependent mechanisms such as self-adaptation. In contrast, evolved representations in nature are robust, evolvable, and creatively exploit available representational features. This paper provide...

Genome shuffling of Saccharomyces cerevisiae through recursive population mating to evolve tolerance to inhibitors of Spent Sulfite Liquor

Energy Technology Data Exchange (ETDEWEB)

Martin, V.J.J.; Pinel, D.J.; D' aoust, F. [Concordia Univ., Montreal, PQ (Canada). Dept. of Biological Sciences; Bajwa, P.K.; Trevors, J.T.; Lee, H. [Guelph Univ., ON (Canada). Dept. of Environmental Biology

2009-07-01

The biochemical steps in the conversion of cellulosics to biofuels include the pretreatment, hydrolysis and fermentation of substrates into a final product. Fermentation of lignocellulosic substrates derived from waste biomass requires metabolic engineering. A biochemical flow chart from the Tembec Biorefinery plant was presented in which Spent Sulfite Liquor (SSL) was used to add value to the pulp and paper industry. The sugars contained in this carbohydrate-rich effluent from sulfite pulping were used to produce ethanol. A robust, ethanologenic microorganism that can withstand the substrate toxicity was needed. Saccharomyces cerevisiae is currently used for the production of ethanol from SSL. This yeast will succumb to toxicity and inhibition, particularly in the most inhibitor rich forms of SSL such as hardwood SSL (HWSSL). A genome shuffling method was therefore developed to create a better SSL fermenting strain. This method was designed to improve polygenic traits by generating pools of mutants with improved phenotypes, followed by iterative recombination between their genomes. Through 5 rounds of recursive mating and screening, 3 strains that could survive and grow in undiluted HWSSL were obtained. The study demonstrated that the tolerance of these strains to SSL translates into an increased capacity to produce ethanol over time using this substrate, due to continued viability of the yeast population. Phenotypic analysis of the three strains revealed that the genome shuffling approach successfully co-evolved tolerance to acetic acid, NaCl (osmotic) and HMF. A systems biology analysis of strain R57 was initiated in order to establish the genetic basis for HWSSL tolerance. tabs., figs.

The genotype-phenotype map of an evolving digital organism

OpenAIRE

Fortuna, Miguel A.; Zaman, Luis; Ofria, Charles; Wagner, Andreas

2017-01-01

To understand how evolving systems bring forth novel and useful phenotypes, it is essential to understand the relationship between genotypic and phenotypic change. Artificial evolving systems can help us understand whether the genotype-phenotype maps of natural evolving systems are highly unusual, and it may help create evolvable artificial systems. Here we characterize the genotype-phenotype map of digital organisms in Avida, a platform for digital evolution. We consider digital organisms fr...

EVOLVE

CERN Document Server

Deutz, André; Schütze, Oliver; Legrand, Pierrick; Tantar, Emilia; Tantar, Alexandru-Adrian

2017-01-01

This book comprises nine selected works on numerical and computational methods for solving multiobjective optimization, game theory, and machine learning problems. It provides extended versions of selected papers from various fields of science such as computer science, mathematics and engineering that were presented at EVOLVE 2013 held in July 2013 at Leiden University in the Netherlands. The internationally peer-reviewed papers include original work on important topics in both theory and applications, such as the role of diversity in optimization, statistical approaches to combinatorial optimization, computational game theory, and cell mapping techniques for numerical landscape exploration. Applications focus on aspects including robustness, handling multiple objectives, and complex search spaces in engineering design and computational biology.

Topology of evolving, mutagenized viral populations: quasispecies expansion, compression, and operation of negative selection.

Science.gov (United States)

Ojosnegros, Samuel; Agudo, Rubén; Sierra, Macarena; Briones, Carlos; Sierra, Saleta; González-López, Claudia; Domingo, Esteban; Cristina, Juan

2008-07-17

The molecular events and evolutionary forces underlying lethal mutagenesis of virus (or virus extinction through an excess of mutations) are not well understood. Here we apply for the first time phylogenetic methods and Partition Analysis of Quasispecies (PAQ) to monitor genetic distances and intra-population structures of mutant spectra of foot-and-mouth disease virus (FMDV) quasispecies subjected to mutagenesis by base and nucleoside analogues. Phylogenetic and PAQ analyses have revealed a highly dynamic variation of intrapopulation diversity of FMDV quasispecies. The population diversity first suffers striking expansions in the presence of mutagens and then compressions either when the presence of the mutagenic analogue was discontinued or when a mutation that decreased sensitivity to a mutagen was selected. The pattern of mutations found in the populations was in agreement with the behavior of the corresponding nucleotide analogues with FMDV in vitro. Mutations accumulated at preferred genomic sites, and dn/ds ratios indicate the operation of negative (or purifying) selection in populations subjected to mutagenesis. No evidence of unusually elevated genetic distances has been obtained for FMDV populations approaching extinction. Phylogenetic and PAQ analysis provide adequate procedures to describe the evolution of viral sequences subjected to lethal mutagenesis. These methods define the changes of intra-population structure more precisely than mutation frequencies and Shannon entropies. PAQ is very sensitive to variations of intrapopulation genetic distances. Strong negative (or purifying) selection operates in FMDV populations subjected to enhanced mutagenesis. The quantifications provide evidence that extinction does not imply unusual increases of intrapopulation complexity, in support of the lethal defection model of virus extinction.

The evolving role of monoclonal antibodies in colorectal cancer: early presumptions and impact on clinical trial development.

Science.gov (United States)

Eng, Cathy

2010-01-01

Targeted biologic agents have an established role in treating metastatic colorectal cancer (mCRC). Bevacizumab, a recombinant monoclonal antibody against the vascular endothelial growth factor ligand is approved by the U.S. Food and Drug Administration (FDA) for bevacizumab-naïve patients. Cetuximab, a chimeric monoclonal antibody (mAb) against the epidermal growth factor receptor (EGFR) is FDA approved as a single agent, or in combination with irinotecan, in both irinotecan-naïve and refractory patients, and has additional efficacy in combination with oxaliplatin. Panitumumab, a fully human EGFR mAb, is FDA approved as a single agent in refractory patients but has additional efficacy in combination with chemotherapy. After reaching a temporary therapeutic plateau of FDA-approved agents for the treatment of mCRC, pivotal results have developed that critically affect the care for these patients. Correlative data from randomized trials of EGFR inhibitors across disease settings have demonstrated higher response rates, specifically for patients with wild-type K-RAS tumors. The interpretation of the B-RAF mutation and other molecular markers may further define the appropriateness of anti-EGFR therapy. Recent literature revealed that the first-line use of combined anti-EGFR therapy plus bevacizumab resulted in inferior outcomes and additional toxicities. Furthermore, the role of biologic agents for locally advanced colon cancer cannot be advocated at this time. With impending changes in the health care system, the economic impact of mAbs will continue to be scrutinized. Hence, as the significance of molecular markers continues to develop, their role as it pertains to the appropriate use of biologic agents in the treatment of mCRC will continue to evolve.

Movement disorders in elderly users of risperidone and first generation antipsychotic agents: a Canadian population-based study.

Directory of Open Access Journals (Sweden)

Irina Vasilyeva

Full Text Available Despite concerns over the potential for severe adverse events, antipsychotic medications remain the mainstay of treatment of behaviour disorders and psychosis in elderly patients. Second-generation antipsychotic agents (SGAs; e.g., risperidone, olanzapine, quetiapine have generally shown a better safety profile compared to the first-generation agents (FGAs; e.g., haloperidol and phenothiazines, particularly in terms of a lower potential for involuntary movement disorders. Risperidone, the only SGA with an official indication for the management of inappropriate behaviour in dementia, has emerged as the antipsychotic most commonly prescribed to older patients. Most clinical trials evaluating the risk of movement disorders in elderly patients receiving antipsychotic therapy have been of limited sample size and/or of relatively short duration. A few observational studies have produced inconsistent results.A population-based retrospective cohort study of all residents of the Canadian province of Manitoba aged 65 and over, who were dispensed antipsychotic medications for the first time during the time period from April 1, 2000 to March 31, 2007, was conducted using Manitoba's Department of Health's administrative databases. Cox proportional hazards models were used to determine the risk of extrapyramidal symptoms (EPS in new users of risperidone compared to new users of FGAs.After controlling for potential confounders (demographics, comorbidity and medication use, risperidone use was associated with a lower risk of EPS compared to FGAs at 30, 60, 90 and 180 days (adjusted hazard ratios [HR] 0.38, 95% CI: 0.22-0.67; 0.45, 95% CI: 0.28-0.73; 0.50, 95% CI: 0.33-0.77; 0.65, 95% CI: 0.45-0.94, respectively. At 360 days, the strength of the association weakened with an adjusted HR of 0.75, 95% CI: 0.54-1.05.In a large population of elderly patients the use of risperidone was associated with a lower risk of EPS compared to FGAs.

Topology of evolving, mutagenized viral populations: quasispecies expansion, compression, and operation of negative selection

Directory of Open Access Journals (Sweden)

Sierra Saleta

2008-07-01

Full Text Available Abstract Background The molecular events and evolutionary forces underlying lethal mutagenesis of virus (or virus extinction through an excess of mutations are not well understood. Here we apply for the first time phylogenetic methods and Partition Analysis of Quasispecies (PAQ to monitor genetic distances and intra-population structures of mutant spectra of foot-and-mouth disease virus (FMDV quasispecies subjected to mutagenesis by base and nucleoside analogues. Results Phylogenetic and PAQ analyses have revealed a highly dynamic variation of intrapopulation diversity of FMDV quasispecies. The population diversity first suffers striking expansions in the presence of mutagens and then compressions either when the presence of the mutagenic analogue was discontinued or when a mutation that decreased sensitivity to a mutagen was selected. The pattern of mutations found in the populations was in agreement with the behavior of the corresponding nucleotide analogues with FMDV in vitro. Mutations accumulated at preferred genomic sites, and dn/ds ratios indicate the operation of negative (or purifying selection in populations subjected to mutagenesis. No evidence of unusually elevated genetic distances has been obtained for FMDV populations approaching extinction. Conclusion Phylogenetic and PAQ analysis provide adequate procedures to describe the evolution of viral sequences subjected to lethal mutagenesis. These methods define the changes of intra-population structure more precisely than mutation frequencies and Shannon entropies. PAQ is very sensitive to variations of intrapopulation genetic distances. Strong negative (or purifying selection operates in FMDV populations subjected to enhanced mutagenesis. The quantifications provide evidence that extinction does not imply unusual increases of intrapopulation complexity, in support of the lethal defection model of virus extinction.

Toward Agent-Based Models of the Development And Evolution of Business Relations and Networks

Science.gov (United States)

Wilkinson, Ian F.; Marks, Robert E.; Young, Louise

Firms achieve competitive advantage in part through the development of cooperative relations with other firms and organisations. We describe a program of research designed to map and model the development of cooperative inter-firm relations, including the processes and paths by which firms may evolve from adversarial to more cooperative relations. Narrative-event-history methods will be used to develop stylised histories of the emergence of business relations in various contexts and to identify relevant causal mechanisms to be included in the agent-based models of relationship and network evolution. The relationship histories will provide the means of assuring the agent-based models developed.

Evolutionary autonomous agents and the nature of apraxia

Directory of Open Access Journals (Sweden)

Jin Frank

2005-01-01

Full Text Available Abstract Background Evolutionary autonomous agents are robots or robot simulations whose controller is a dynamical neural network and whose evolution occurs autonomously under the guidance of a fitness function without the detailed or explicit direction of an external programmer. They are embodied agents with a simple neural network controller and as such they provide the optimal forum by which sensorimotor interactions in a specified environment can be studied without the computational assumptions inherent in standard neuroscience. Methods Evolutionary autonomous agents were evolved that were able to perform identical movements under two different contexts, one which represented an automatic movement and one which had a symbolic context. In an attempt to model the automatic-voluntary dissociation frequently seen in ideomotor apraxia, lesions were introduced into the neural network controllers resulting in a behavioral dissociation with loss of the ability to perform the movement which had a symbolic context and preservation of the simpler, automatic movement. Results Analysis of the changes in the hierarchical organization of the networks in the apractic EAAs demonstrated consistent changes in the network dynamics across all agents with loss of longer duration time scales in the network dynamics. Conclusion The concepts of determinate motor programs and perceptual representations that are implicit in the present day understanding of ideomotor apraxia are assumptions inherent in the computational understanding of brain function. The strength of the present study using EAAs to model one aspect of ideomotor apraxia is the absence of these assumptions and a grounding of all sensorimotor interactions in an embodied, autonomous agent. The consistency of the hierarchical changes in the network dynamics across all apractic agents demonstrates that this technique is tenable and will be a valuable adjunct to a computational formalism in the understanding

Evolved changes in the intracellular distribution and physiology of muscle mitochondria in high-altitude native deer mice.

Science.gov (United States)

Mahalingam, Sajeni; McClelland, Grant B; Scott, Graham R

2017-07-15

Mitochondrial function changes over time at high altitudes, but the potential benefits of these changes for hypoxia resistance remains unclear. We used high-altitude-adapted populations of deer mice, which exhibit enhanced aerobic performance in hypoxia, to examine whether changes in mitochondrial physiology or intracellular distribution in the muscle contribute to hypoxia resistance. Permeabilized muscle fibres from the gastrocnemius muscle had higher respiratory capacities in high-altitude mice than in low-altitude mice. Highlanders also had higher mitochondrial volume densities, due entirely to an enriched abundance of subsarcolemmal mitochondria, such that more mitochondria were situated near the cell membrane and adjacent to capillaries. There were several effects of hypoxia acclimation on mitochondrial function, some of which were population specific, but they differed from the evolved changes in high-altitude natives, which probably provide a better indication of adaptive traits that improve performance and hypoxia resistance at high altitudes. High-altitude natives that have evolved to live in hypoxic environments provide a compelling system to understand how animals can overcome impairments in oxygen availability. We examined whether these include changes in mitochondrial physiology or intracellular distribution that contribute to hypoxia resistance in high-altitude deer mice (Peromyscus maniculatus). Mice from populations native to high and low altitudes were born and raised in captivity, and as adults were acclimated to normoxia or hypobaric hypoxia (equivalent to 4300 m elevation). We found that highlanders had higher respiratory capacities in the gastrocnemius (but not soleus) muscle than lowlanders (assessed using permeabilized fibres with single or multiple inputs to the electron transport system), due in large part to higher mitochondrial volume densities in the gastrocnemius. The latter was attributed to an increased abundance of subsarcolemmal

iCrowd: agent-based behavior modeling and crowd simulator

Science.gov (United States)

Kountouriotis, Vassilios I.; Paterakis, Manolis; Thomopoulos, Stelios C. A.

2016-05-01

Initially designed in the context of the TASS (Total Airport Security System) FP-7 project, the Crowd Simulation platform developed by the Integrated Systems Lab of the Institute of Informatics and Telecommunications at N.C.S.R. Demokritos, has evolved into a complete domain-independent agent-based behavior simulator with an emphasis on crowd behavior and building evacuation simulation. Under continuous development, it reflects an effort to implement a modern, multithreaded, data-oriented simulation engine employing latest state-of-the-art programming technologies and paradigms. It is based on an extensible architecture that separates core services from the individual layers of agent behavior, offering a concrete simulation kernel designed for high-performance and stability. Its primary goal is to deliver an abstract platform to facilitate implementation of several Agent-Based Simulation solutions with applicability in several domains of knowledge, such as: (i) Crowd behavior simulation during [in/out] door evacuation. (ii) Non-Player Character AI for Game-oriented applications and Gamification activities. (iii) Vessel traffic modeling and simulation for Maritime Security and Surveillance applications. (iv) Urban and Highway Traffic and Transportation Simulations. (v) Social Behavior Simulation and Modeling.

Evolving Ecological Social Dilemmas: A Spatial Individual-Based Model for the Evolution of Cooperation with a Minimal Number of Parameters

International Nuclear Information System (INIS)

Fort, H.

2007-01-01

Cooperation, both intraspecific and interspecific, is a well-documented phenomenon in nature that is not well understood. Evolutionary game theory is a powerful tool to approach this problem. However, it has important limitations. First, very often it is not obvious which game is more appropriate to use. Second, in general, identical payoff matrices are assumed for all players, a situation that is highly unlikely in nature. Third, slight changes in these payoff values can dramatically alter the outcomes. Here, I use an evolutionary spatial model in which players do not have a universal payoff matrix, so no payoff parameters are required. Instead, each is equipped with random values for the payoffs, fulfilling the constraints that define the game(s). These payoff matrices evolve by natural selection. Two versions of this model are studied. First is a simpler one, with just one evolving payoff. Second is the full version, with all the four payoffs evolving. The fraction of cooperator agents converges in both versions to nonzero values. In the case of the full version, the initial heterogeneity disappears and the selected game is the stag Hunt

Making Communication Strategy Choices in a Fast Evolving Crisis Situation—Results from a Table-Top Discussion on an Anthrax Scenario

Directory of Open Access Journals (Sweden)

Aino Ruggiero

2016-05-01

Full Text Available This paper aims at clarifying a timely topic of how communication strategy choices are made in evolving, complex crises, such as those caused by terrorism involving chemical, biological, radiological, or nuclear (CBRN agents. This is done by examining data gathered from a table-top discussion among crisis communication experts, focusing on a scenario of an anthrax attack and analysed qualitatively. The communication experts followed the evolving crisis situation by gathering inputs from various actors in the crisis management network, thereby creating situational understanding, and interpreted these inputs for decision-making on communication strategies. The underlying process of coping with complexity in evolving CBRN terrorism crises can be described as a continuous, dynamic process that can best be explained with a combination of traditional and more modern crisis communication approaches. Strategy-making in crisis situations by communication experts is still largely a black box. In this study, a novel approach of decomposing strategy-making by observing a table-top discussion is chosen to clarify the process. By identifying the core elements involved, a more detailed picture of communication strategy-making is created, thus promoting preparedness and professional resilience in the field.

Multi-disciplinary management of athletes with post-concussion syndrome: an evolving pathophysiological approach

Directory of Open Access Journals (Sweden)

Michael John Ellis

2016-08-01

Full Text Available Historically, patients with sports-related concussion (SRC have been managed in a uniform fashion consisting mostly of prescribed physical and cognitive rest with the expectation that all symptoms will spontaneously resolve with time. Although this approach will result in successful return to school and sports activities in the majority of athletes, an important proportion will develop persistent concussion symptoms characteristic of post-concussion syndrome (PCS. Recent advances in exercise science, neuroimaging, and clinical research suggest that the clinical manifestations of PCS are mediated by unique pathophysiological processes that can be identified by features of the clinical history and physical examination as well as the use of graded aerobic treadmill testing. Athletes who develop PCS represent a unique population whose care must be individualized and must incorporate a rehabilitative strategy that promotes enhanced recovery of concussion-related symptoms while preventing physical deconditioning. In this review we present our evolving evidence-based approach to evaluation and management of athletes with PCS that aims to identify the pathophysiological mechanisms mediating persistent concussion symptoms and guides the initiation of individually-tailored rehabilitation programs that target these processes. In addition, we outline the important qualified roles that multi-disciplinary healthcare professionals can play in the management of this patient population, and discuss where future research efforts must be focused to further validate this evolving pathophysiological approach.

Multi-Disciplinary Management of Athletes with Post-Concussion Syndrome: An Evolving Pathophysiological Approach.

Science.gov (United States)

Ellis, Michael J; Leddy, John; Willer, Barry

2016-01-01

Historically, patients with sports-related concussion (SRC) have been managed in a uniform fashion consisting mostly of prescribed physical and cognitive rest with the expectation that all symptoms will spontaneously resolve with time. Although this approach will result in successful return to school and sports activities in the majority of athletes, an important proportion will develop persistent concussion symptoms characteristic of post-concussion syndrome (PCS). Recent advances in exercise science, neuroimaging, and clinical research suggest that the clinical manifestations of PCS are mediated by unique pathophysiological processes that can be identified by features of the clinical history and physical examination as well as the use of graded aerobic treadmill testing. Athletes who develop PCS represent a unique population whose care must be individualized and must incorporate a rehabilitative strategy that promotes enhanced recovery of concussion-related symptoms while preventing physical deconditioning. In this review, we present our evolving evidence-based approach to evaluation and management of athletes with PCS that aims to identify the pathophysiological mechanisms mediating persistent concussion symptoms and guides the initiation of individually tailored rehabilitation programs that target these processes. In addition, we outline the important qualified roles that multi-disciplinary healthcare professionals can play in the management of this patient population, and discuss where future research efforts must be focused to further evaluate this evolving pathophysiological approach.

CATS-based Air Traffic Controller Agents

Science.gov (United States)

Callantine, Todd J.

2002-01-01

This report describes intelligent agents that function as air traffic controllers. Each agent controls traffic in a single sector in real time; agents controlling traffic in adjoining sectors can coordinate to manage an arrival flow across a given meter fix. The purpose of this research is threefold. First, it seeks to study the design of agents for controlling complex systems. In particular, it investigates agent planning and reactive control functionality in a dynamic environment in which a variety perceptual and decision making skills play a central role. It examines how heuristic rules can be applied to model planning and decision making skills, rather than attempting to apply optimization methods. Thus, the research attempts to develop intelligent agents that provide an approximation of human air traffic controller behavior that, while not based on an explicit cognitive model, does produce task performance consistent with the way human air traffic controllers operate. Second, this research sought to extend previous research on using the Crew Activity Tracking System (CATS) as the basis for intelligent agents. The agents use a high-level model of air traffic controller activities to structure the control task. To execute an activity in the CATS model, according to the current task context, the agents reference a 'skill library' and 'control rules' that in turn execute the pattern recognition, planning, and decision-making required to perform the activity. Applying the skills enables the agents to modify their representation of the current control situation (i.e., the 'flick' or 'picture'). The updated representation supports the next activity in a cycle of action that, taken as a whole, simulates air traffic controller behavior. A third, practical motivation for this research is to use intelligent agents to support evaluation of new air traffic control (ATC) methods to support new Air Traffic Management (ATM) concepts. Current approaches that use large, human

A model for the emergence of cooperation, interdependence, and structure in evolving networks

Science.gov (United States)

Jain, Sanjay; Krishna, Sandeep

2001-01-01

Evolution produces complex and structured networks of interacting components in chemical, biological, and social systems. We describe a simple mathematical model for the evolution of an idealized chemical system to study how a network of cooperative molecular species arises and evolves to become more complex and structured. The network is modeled by a directed weighted graph whose positive and negative links represent "catalytic" and "inhibitory" interactions among the molecular species, and which evolves as the least populated species (typically those that go extinct) are replaced by new ones. A small autocatalytic set, appearing by chance, provides the seed for the spontaneous growth of connectivity and cooperation in the graph. A highly structured chemical organization arises inevitably as the autocatalytic set enlarges and percolates through the network in a short analytically determined timescale. This self organization does not require the presence of self-replicating species. The network also exhibits catastrophes over long timescales triggered by the chance elimination of "keystone" species, followed by recoveries.

The Genetic Basis for Evolved Tolerance to Dioxin-Like Compounds in Wild Atlantic Killifish: More Than the Aryl Hydrocarbon Receptor

Science.gov (United States)

Populations of Atlantic killifish (Fundulus heteroclitus) resident to some US urban estuaries have independently evolved extreme and inherited tolerance to toxic dioxin-like compounds (DLCs). To further understand the genetic basis for this trait, we densely genotyped families o...

The genotype-phenotype map of an evolving digital organism.

Directory of Open Access Journals (Sweden)

Miguel A Fortuna

2017-02-01

Full Text Available To understand how evolving systems bring forth novel and useful phenotypes, it is essential to understand the relationship between genotypic and phenotypic change. Artificial evolving systems can help us understand whether the genotype-phenotype maps of natural evolving systems are highly unusual, and it may help create evolvable artificial systems. Here we characterize the genotype-phenotype map of digital organisms in Avida, a platform for digital evolution. We consider digital organisms from a vast space of 10141 genotypes (instruction sequences, which can form 512 different phenotypes. These phenotypes are distinguished by different Boolean logic functions they can compute, as well as by the complexity of these functions. We observe several properties with parallels in natural systems, such as connected genotype networks and asymmetric phenotypic transitions. The likely common cause is robustness to genotypic change. We describe an intriguing tension between phenotypic complexity and evolvability that may have implications for biological evolution. On the one hand, genotypic change is more likely to yield novel phenotypes in more complex organisms. On the other hand, the total number of novel phenotypes reachable through genotypic change is highest for organisms with simple phenotypes. Artificial evolving systems can help us study aspects of biological evolvability that are not accessible in vastly more complex natural systems. They can also help identify properties, such as robustness, that are required for both human-designed artificial systems and synthetic biological systems to be evolvable.

The genotype-phenotype map of an evolving digital organism.

Science.gov (United States)

Fortuna, Miguel A; Zaman, Luis; Ofria, Charles; Wagner, Andreas

2017-02-01

To understand how evolving systems bring forth novel and useful phenotypes, it is essential to understand the relationship between genotypic and phenotypic change. Artificial evolving systems can help us understand whether the genotype-phenotype maps of natural evolving systems are highly unusual, and it may help create evolvable artificial systems. Here we characterize the genotype-phenotype map of digital organisms in Avida, a platform for digital evolution. We consider digital organisms from a vast space of 10141 genotypes (instruction sequences), which can form 512 different phenotypes. These phenotypes are distinguished by different Boolean logic functions they can compute, as well as by the complexity of these functions. We observe several properties with parallels in natural systems, such as connected genotype networks and asymmetric phenotypic transitions. The likely common cause is robustness to genotypic change. We describe an intriguing tension between phenotypic complexity and evolvability that may have implications for biological evolution. On the one hand, genotypic change is more likely to yield novel phenotypes in more complex organisms. On the other hand, the total number of novel phenotypes reachable through genotypic change is highest for organisms with simple phenotypes. Artificial evolving systems can help us study aspects of biological evolvability that are not accessible in vastly more complex natural systems. They can also help identify properties, such as robustness, that are required for both human-designed artificial systems and synthetic biological systems to be evolvable.

High strength-of-ties and low mobility enable the evolution of third-party punishment

Science.gov (United States)

Roos, Patrick; Gelfand, Michele; Nau, Dana; Carr, Ryan

2014-01-01

As punishment can be essential to cooperation and norm maintenance but costly to the punisher, many evolutionary game-theoretic studies have explored how direct punishment can evolve in populations. Compared to direct punishment, in which an agent acts to punish another for an interaction in which both parties were involved, the evolution of third-party punishment (3PP) is even more puzzling, because the punishing agent itself was not involved in the original interaction. Despite significant empirical studies of 3PP, little is known about the conditions under which it can evolve. We find that punishment reputation is not, by itself, sufficient for the evolution of 3PP. Drawing on research streams in sociology and psychology, we implement a structured population model and show that high strength-of-ties and low mobility are critical for the evolution of responsible 3PP. Only in such settings of high social-structural constraint are punishers able to induce self-interested agents toward cooperation, making responsible 3PP ultimately beneficial to individuals as well as the collective. Our results illuminate the conditions under which 3PP is evolutionarily adaptive in populations. Responsible 3PP can evolve and induce cooperation in cases where other mechanisms alone fail to do so. PMID:24335985

Evolvability as a Quality Attribute of Software Architectures

NARCIS (Netherlands)

Ciraci, S.; van den Broek, P.M.; Duchien, Laurence; D'Hondt, Maja; Mens, Tom

We review the definition of evolvability as it appears on the literature. In particular, the concept of software evolvability is compared with other system quality attributes, such as adaptability, maintainability and modifiability.

A new evolutionary system for evolving artificial neural networks.

Science.gov (United States)

Yao, X; Liu, Y

1997-01-01

This paper presents a new evolutionary system, i.e., EPNet, for evolving artificial neural networks (ANNs). The evolutionary algorithm used in EPNet is based on Fogel's evolutionary programming (EP). Unlike most previous studies on evolving ANN's, this paper puts its emphasis on evolving ANN's behaviors. Five mutation operators proposed in EPNet reflect such an emphasis on evolving behaviors. Close behavioral links between parents and their offspring are maintained by various mutations, such as partial training and node splitting. EPNet evolves ANN's architectures and connection weights (including biases) simultaneously in order to reduce the noise in fitness evaluation. The parsimony of evolved ANN's is encouraged by preferring node/connection deletion to addition. EPNet has been tested on a number of benchmark problems in machine learning and ANNs, such as the parity problem, the medical diagnosis problems, the Australian credit card assessment problem, and the Mackey-Glass time series prediction problem. The experimental results show that EPNet can produce very compact ANNs with good generalization ability in comparison with other algorithms.

On the opinion formation of mobile agents with memory

Science.gov (United States)

Zhang, Yunhong; Liu, Qipeng; Wang, Zhenling; Zhang, Siying

2018-02-01

This paper studies the opinion formation problem in a group of mobile agents using a multi-agent modeling method. Suppose that all agents move in a two-dimensional space following a certain rule. The interaction range of each agent is determined by its physical location and its opinion similarity with other agents. Moreover, agents have memory of the opinions of their previous interactive neighbors. We investigate the influence of three factors on the formation of group opinion: moving probability, interactive radius, and population density. Using simulations, we find that an opinion consensus can be achieved easily under a small moving probability and a small interactive radius, which is a relatively counterintuitive phenomenon. We also find that a large interactive radius or the model with memory can facilitate the convergence of opinions in a group to either consensus or clusters.

DNA variation of the mammalian major histocompatibility complex reflects genomic diversity and population history

Energy Technology Data Exchange (ETDEWEB)

Yuhki, Naoya; O' Brien, S.J. (National Cancer Institute, Frederick, MD (USA))

1990-01-01

The major histocompatibility complex (MHC) is a multigene complex of tightly linked homologous genes that encode cell surface antigens that play a key role in immune regulation and response to foreign antigens. In most species, MHC gene products display extreme antigenic polymorphism, and their variability has been interpreted to reflect an adaptive strategy for accommodating rapidly evolving infectious agents that periodically afflict natural populations. Determination of the extent of MHC variation has been limited to populations in which skin grafting is feasible or for which serological reagents have been developed. The authors present here a quantitative analysis of restriction fragment length polymorphism of MHC class I genes in several mammalian species (cats, rodents, humans) known to have very different levels of genetic diversity based on functional MHC assays and on allozyme surveys. When homologous class I probes were employed, a notable concordance was observed between the extent of MHC restriction fragment variation and functional MHC variation detected by skin grafts or genome-wide diversity estimated by allozyme screens. These results confirm the genetically depauperate character of the African cheetah, Acinonyx jubatus, and the Asiatic lion, Panthera leo persica; further, they support the use of class I MHC molecular reagents in estimating the extent and character of genetic diversity in natural populations.

DNA variation of the mammalian major histocompatibility complex reflects genomic diversity and population history

International Nuclear Information System (INIS)

Yuhki, Naoya; O'Brien, S.J.

1990-01-01

The major histocompatibility complex (MHC) is a multigene complex of tightly linked homologous genes that encode cell surface antigens that play a key role in immune regulation and response to foreign antigens. In most species, MHC gene products display extreme antigenic polymorphism, and their variability has been interpreted to reflect an adaptive strategy for accommodating rapidly evolving infectious agents that periodically afflict natural populations. Determination of the extent of MHC variation has been limited to populations in which skin grafting is feasible or for which serological reagents have been developed. The authors present here a quantitative analysis of restriction fragment length polymorphism of MHC class I genes in several mammalian species (cats, rodents, humans) known to have very different levels of genetic diversity based on functional MHC assays and on allozyme surveys. When homologous class I probes were employed, a notable concordance was observed between the extent of MHC restriction fragment variation and functional MHC variation detected by skin grafts or genome-wide diversity estimated by allozyme screens. These results confirm the genetically depauperate character of the African cheetah, Acinonyx jubatus, and the Asiatic lion, Panthera leo persica; further, they support the use of class I MHC molecular reagents in estimating the extent and character of genetic diversity in natural populations

EVOLVE 2014 International Conference

CERN Document Server

Tantar, Emilia; Sun, Jian-Qiao; Zhang, Wei; Ding, Qian; Schütze, Oliver; Emmerich, Michael; Legrand, Pierrick; Moral, Pierre; Coello, Carlos

2014-01-01

This volume encloses research articles that were presented at the EVOLVE 2014 International Conference in Beijing, China, July 1–4, 2014.The book gathers contributions that emerged from the conference tracks, ranging from probability to set oriented numerics and evolutionary computation; all complemented by the bridging purpose of the conference, e.g. Complex Networks and Landscape Analysis, or by the more application oriented perspective. The novelty of the volume, when considering the EVOLVE series, comes from targeting also the practitioner’s view. This is supported by the Machine Learning Applied to Networks and Practical Aspects of Evolutionary Algorithms tracks, providing surveys on new application areas, as in the networking area and useful insights in the development of evolutionary techniques, from a practitioner’s perspective. Complementary to these directions, the conference tracks supporting the volume, follow on the individual advancements of the subareas constituting the scope of the confe...

Population structure of humpback whales in the western and central South Pacific Ocean as determined by vocal exchange among populations

OpenAIRE

Garland, E.C.; Goldizen, A.W.; Lilley, M.S.; Rekdahl, M.L.; Garrigue, Claire; Constantine, R.; Hauser, N.D.; Poole, M.M.; Robbins, J.; Noad, M.J.

2015-01-01

For cetaceans, population structure is traditionally determined by molecular genetics or photographically identified individuals. Acoustic data, however, has provided information on movement and population structure with less effort and cost than traditional methods in an array of taxa. Male humpback whales (Megaptera novaeangliae) produce a continually evolving vocal sexual display, or song, that is similar among all males in a population. The rapid cultural transmission (the transfer of inf...

Evolving self-assembly in autonomous homogeneous robots: experiments with two physical robots.

Science.gov (United States)

Ampatzis, Christos; Tuci, Elio; Trianni, Vito; Christensen, Anders Lyhne; Dorigo, Marco

2009-01-01

This research work illustrates an approach to the design of controllers for self-assembling robots in which the self-assembly is initiated and regulated by perceptual cues that are brought forth by the physical robots through their dynamical interactions. More specifically, we present a homogeneous control system that can achieve assembly between two modules (two fully autonomous robots) of a mobile self-reconfigurable system without a priori introduced behavioral or morphological heterogeneities. The controllers are dynamic neural networks evolved in simulation that directly control all the actuators of the two robots. The neurocontrollers cause the dynamic specialization of the robots by allocating roles between them based solely on their interaction. We show that the best evolved controller proves to be successful when tested on a real hardware platform, the swarm-bot. The performance achieved is similar to the one achieved by existing modular or behavior-based approaches, also due to the effect of an emergent recovery mechanism that was neither explicitly rewarded by the fitness function, nor observed during the evolutionary simulation. Our results suggest that direct access to the orientations or intentions of the other agents is not a necessary condition for robot coordination: Our robots coordinate without direct or explicit communication, contrary to what is assumed by most research works in collective robotics. This work also contributes to strengthening the evidence that evolutionary robotics is a design methodology that can tackle real-world tasks demanding fine sensory-motor coordination.

Prevalence of acid-reducing agents (ARA) in cancer populations and ARA drug-drug interaction potential for molecular targeted agents in clinical development.

Science.gov (United States)

Smelick, Gillian S; Heffron, Timothy P; Chu, Laura; Dean, Brian; West, David A; Duvall, Scott L; Lum, Bert L; Budha, Nageshwar; Holden, Scott N; Benet, Leslie Z; Frymoyer, Adam; Dresser, Mark J; Ware, Joseph A

2013-11-04

Acid-reducing agents (ARAs) are the most commonly prescribed medications in North America and Western Europe. There are currently no data describing the prevalence of their use among cancer patients. However, this is a paramount question due to the potential for significant drug-drug interactions (DDIs) between ARAs, most commonly proton pump inhibitors (PPIs), and orally administered cancer therapeutics that display pH-dependent solubility, which may lead to decreased drug absorption and decreased therapeutic benefit. Of recently approved orally administered cancer therapeutics, >50% are characterized as having pH-dependent solubility, but there are currently no data describing the potential for this ARA-DDI liability among targeted agents currently in clinical development. The objectives of this study were to (1) determine the prevalence of ARA use among different cancer populations and (2) investigate the prevalence of orally administered cancer therapeutics currently in development that may be liable for an ARA-DDI. To address the question of ARA use among cancer patients, a retrospective cross-sectional analysis was performed using two large healthcare databases: Thomson Reuters MarketScan (N = 1,776,443) and the U.S. Department of Veterans Affairs (VA, N = 1,171,833). Among all cancer patients, the total prevalence proportion of ARA use (no. of cancer patients receiving an ARA/total no. of cancer patients) was 20% and 33% for the MarketScan and VA databases, respectively. PPIs were the most commonly prescribed agent, comprising 79% and 65% of all cancer patients receiving a prescription for an ARA (no. of cancer patients receiving a PPI /no. of cancer patients receiving an ARA) for the MarketScan and VA databases, respectively. To estimate the ARA-DDI liability of orally administered molecular targeted cancer therapeutics currently in development, two publicly available databases, (1) Kinase SARfari and (2) canSAR, were examined. For those orally administered

Mentoring: An Evolving Relationship.

Science.gov (United States)

Block, Michelle; Florczak, Kristine L

2017-04-01

The column concerns itself with mentoring as an evolving relationship between mentor and mentee. The collegiate mentoring model, the transformational transcendence model, and the humanbecoming mentoring model are considered in light of a dialogue with mentors at a Midwest university and conclusions are drawn.

Mobile agents affect worm spreading in wireless ad hoc networks

International Nuclear Information System (INIS)

Huang, Zi-Gang; Sun, Jin-Tu; Wang, Ying-Hai; Wang, Sheng-Jun; Xu, Xin-Jian

2009-01-01

Considering the dynamic nature of portable computing devices with wireless communication capability, an extended model is introduced for worm spreading in the wireless ad hoc network, with a population of mobile agents in a planar distribution, starting from an initial infected seed. The effect of agents' mobility on worm spreading is investigated via extensive Monte Carlo simulations. The threshold behavior and the dynamics of worm epidemics in the wireless networks are greatly affected by both agents' mobility and spatial and temporal correlations. The medium access control mechanism for the wireless communication promotes the sensitivity of the spreading dynamics to agents' mobility

Nonsynonymous substitution rate (Ka is a relatively consistent parameter for defining fast-evolving and slow-evolving protein-coding genes

Directory of Open Access Journals (Sweden)

Wang Lei

2011-02-01

Full Text Available Abstract Background Mammalian genome sequence data are being acquired in large quantities and at enormous speeds. We now have a tremendous opportunity to better understand which genes are the most variable or conserved, and what their particular functions and evolutionary dynamics are, through comparative genomics. Results We chose human and eleven other high-coverage mammalian genome data–as well as an avian genome as an outgroup–to analyze orthologous protein-coding genes using nonsynonymous (Ka and synonymous (Ks substitution rates. After evaluating eight commonly-used methods of Ka and Ks calculation, we observed that these methods yielded a nearly uniform result when estimating Ka, but not Ks (or Ka/Ks. When sorting genes based on Ka, we noticed that fast-evolving and slow-evolving genes often belonged to different functional classes, with respect to species-specificity and lineage-specificity. In particular, we identified two functional classes of genes in the acquired immune system. Fast-evolving genes coded for signal-transducing proteins, such as receptors, ligands, cytokines, and CDs (cluster of differentiation, mostly surface proteins, whereas the slow-evolving genes were for function-modulating proteins, such as kinases and adaptor proteins. In addition, among slow-evolving genes that had functions related to the central nervous system, neurodegenerative disease-related pathways were enriched significantly in most mammalian species. We also confirmed that gene expression was negatively correlated with evolution rate, i.e. slow-evolving genes were expressed at higher levels than fast-evolving genes. Our results indicated that the functional specializations of the three major mammalian clades were: sensory perception and oncogenesis in primates, reproduction and hormone regulation in large mammals, and immunity and angiotensin in rodents. Conclusion Our study suggests that Ka calculation, which is less biased compared to Ks and Ka

Playing With Population Protocols

Directory of Open Access Journals (Sweden)

Xavier Koegler

2009-06-01

Full Text Available Population protocols have been introduced as a model of sensor networks consisting of very limited mobile agents with no control over their own movement: A collection of anonymous agents, modeled by finite automata, interact in pairs according to some rules. Predicates on the initial configurations that can be computed by such protocols have been characterized under several hypotheses. We discuss here whether and when the rules of interactions between agents can be seen as a game from game theory. We do so by discussing several basic protocols.

Holograms as Teaching Agents

Science.gov (United States)

Walker, Robin A.

2013-02-01

Hungarian physicist Dennis Gabor won the Pulitzer Prize for his 1947 introduction of basic holographic principles, but it was not until the invention of the laser in 1960 that research scientists, physicians, technologists and the general public began to seriously consider the interdisciplinary potentiality of holography. Questions around whether and when Three-Dimensional (3-D) images and systems would impact American entertainment and the arts would be answered before educators, instructional designers and students would discover how much Three-Dimensional Hologram Technology (3DHT) would affect teaching practices and learning environments. In the following International Symposium on Display Holograms (ISDH) poster presentation, the author features a traditional board game as well as a reflection hologram to illustrate conventional and evolving Three-Dimensional representations and technology for education. Using elements from the American children's toy Operation® (Hasbro, 2005) as well as a reflection hologram of a human brain (Ko, 1998), this poster design highlights the pedagogical effects of 3-D images, games and systems on learning science. As teaching agents, holograms can be considered substitutes for real objects, (human beings, organs, and animated characters) as well as agents (pedagogical, avatars, reflective) in various learning environments using many systems (direct, emergent, augmented reality) and electronic tools (cellphones, computers, tablets, television). In order to understand the particular importance of utilizing holography in school, clinical and public settings, the author identifies advantages and benefits of using 3-D images and technology as instructional tools.

Interactively Evolving Compositional Sound Synthesis Networks

DEFF Research Database (Denmark)

Jónsson, Björn Þór; Hoover, Amy K.; Risi, Sebastian

2015-01-01

the space of potential sounds that can be generated through such compositional sound synthesis networks (CSSNs). To study the effect of evolution on subjective appreciation, participants in a listener study ranked evolved timbres by personal preference, resulting in preferences skewed toward the first......While the success of electronic music often relies on the uniqueness and quality of selected timbres, many musicians struggle with complicated and expensive equipment and techniques to create their desired sounds. Instead, this paper presents a technique for producing novel timbres that are evolved...

Evolving effective incremental SAT solvers with GP

OpenAIRE

Bader, Mohamed; Poli, R.

2008-01-01

Hyper-Heuristics could simply be defined as heuristics to choose other heuristics, and it is a way of combining existing heuristics to generate new ones. In a Hyper-Heuristic framework, the framework is used for evolving effective incremental (Inc*) solvers for SAT. We test the evolved heuristics (IncHH) against other known local search heuristics on a variety of benchmark SAT problems.

History of chemical and biological warfare agents

International Nuclear Information System (INIS)

Szinicz, L.

2005-01-01

Chemical and biological warfare agents constitute a low-probability, but high-impact risk both to the military and to the civilian population. The use of hazardous materials of chemical or biological origin as weapons and for homicide has been documented since ancient times. The first use of chemicals in terms of weapons of mass destruction goes back to World War I, when on April 22, 1915 large amounts of chlorine were released by German military forces at Ypres, Belgium. Until around the 1970s of the 20th century, the awareness of the threat by chemical and biological agents had been mainly confined to the military sector. In the following time, the development of increasing range delivery systems by chemical and biological agents possessors sensitised public attention to the threat emanating from these agents. Their proliferation to the terrorists field during the 1990s with the expanding scale and globalisation of terrorist attacks suggested that these agents are becoming an increasing threat to the whole world community. The following article gives a condensed overview on the history of use and development of the more prominent chemical and biological warfare agents

History of chemical and biological warfare agents.

Science.gov (United States)

Szinicz, L

2005-10-30

Chemical and biological warfare agents constitute a low-probability, but high-impact risk both to the military and to the civilian population. The use of hazardous materials of chemical or biological origin as weapons and for homicide has been documented since ancient times. The first use of chemicals in terms of weapons of mass destruction goes back to World War I, when on April 22, 1915 large amounts of chlorine were released by German military forces at Ypres, Belgium. Until around the 1970s of the 20th century, the awareness of the threat by chemical and biological agents had been mainly confined to the military sector. In the following time, the development of increasing range delivery systems by chemical and biological agents possessors sensitised public attention to the threat emanating from these agents. Their proliferation to the terrorists field during the 1990s with the expanding scale and globalisation of terrorist attacks suggested that these agents are becoming an increasing threat to the whole world community. The following article gives a condensed overview on the history of use and development of the more prominent chemical and biological warfare agents.

Multi-dimensional information diffusion and balancing market supply: an agent-based approach

NARCIS (Netherlands)

Osinga, S.A.; Kramer, M.R.; Hofstede, G.J.; Beulens, A.J.M.

2013-01-01

This agent-based information management model is designed to explore how multi-dimensional information, spreading through a population of agents (for example farmers) affects market supply. Farmers make quality decisions that must be aligned with available markets. Markets distinguish themselves by

Evolving Intelligent Systems Methodology and Applications

CERN Document Server

Angelov, Plamen; Kasabov, Nik

2010-01-01

From theory to techniques, the first all-in-one resource for EIS. There is a clear demand in advanced process industries, defense, and Internet and communication (VoIP) applications for intelligent yet adaptive/evolving systems. Evolving Intelligent Systems is the first self- contained volume that covers this newly established concept in its entirety, from a systematic methodology to case studies to industrial applications. Featuring chapters written by leading world experts, it addresses the progress, trends, and major achievements in this emerging research field, with a strong emphasis on th

Evolving paradigm of illnesses presented to medical Intensive Care Unit in body builders: Cases from tertiary care center.

Science.gov (United States)

Garg, Sunil Kumar

2015-04-01

Bodybuilding is the use of progressive resistance exercise to control and develop one's musculature. With the rise in number of persons adopting this activity, there is evolving paradigm of illnesses presented to intensive care in this population subset. Strict adherence to details of bodybuilding and avoidance of unsupervised medications are essential to prevent untoward effects.

Methods Evolved by Observation

Science.gov (United States)

Montessori, Maria

2016-01-01

Montessori's idea of the child's nature and the teacher's perceptiveness begins with amazing simplicity, and when she speaks of "methods evolved," she is unveiling a methodological system for observation. She begins with the early childhood explosion into writing, which is a familiar child phenomenon that Montessori has written about…

Population genomics reveals that an anthropophilic population of Aedes aegypti mosquitoes in West Africa recently gave rise to American and Asian populations of this major disease vector

KAUST Repository

Crawford, Jacob E.

2017-02-20

BackgroundThe mosquito Aedes aegypti is the main vector of dengue, Zika, chikungunya and yellow fever viruses. This major disease vector is thought to have arisen when the African subspecies Ae. aegypti formosus evolved from being zoophilic and living in forest habitats into a form that specialises on humans and resides near human population centres. The resulting domestic subspecies, Ae. aegypti aegypti, is found throughout the tropics and largely blood-feeds on humans.ResultsTo understand this transition, we have sequenced the exomes of mosquitoes collected from five populations from around the world. We found that Ae. aegypti specimens from an urban population in Senegal in West Africa were more closely related to populations in Mexico and Sri Lanka than they were to a nearby forest population. We estimate that the populations in Senegal and Mexico split just a few hundred years ago, and we found no evidence of Ae. aegypti aegypti mosquitoes migrating back to Africa from elsewhere in the tropics. The out-of-Africa migration was accompanied by a dramatic reduction in effective population size, resulting in a loss of genetic diversity and rare genetic variants.ConclusionsWe conclude that a domestic population of Ae. aegypti in Senegal and domestic populations on other continents are more closely related to each other than to other African populations. This suggests that an ancestral population of Ae. aegypti evolved to become a human specialist in Africa, giving rise to the subspecies Ae. aegypti aegypti. The descendants of this population are still found in West Africa today, and the rest of the world was colonised when mosquitoes from this population migrated out of Africa. This is the first report of an African population of Ae. aegypti aegypti mosquitoes that is closely related to Asian and American populations. As the two subspecies differ in their ability to vector disease, their existence side by side in West Africa may have important implications for

Population genomics reveals that an anthropophilic population of Aedes aegypti mosquitoes in West Africa recently gave rise to American and Asian populations of this major disease vector.

Science.gov (United States)

Crawford, Jacob E; Alves, Joel M; Palmer, William J; Day, Jonathan P; Sylla, Massamba; Ramasamy, Ranjan; Surendran, Sinnathamby N; Black, William C; Pain, Arnab; Jiggins, Francis M

2017-02-28

The mosquito Aedes aegypti is the main vector of dengue, Zika, chikungunya and yellow fever viruses. This major disease vector is thought to have arisen when the African subspecies Ae. aegypti formosus evolved from being zoophilic and living in forest habitats into a form that specialises on humans and resides near human population centres. The resulting domestic subspecies, Ae. aegypti aegypti, is found throughout the tropics and largely blood-feeds on humans. To understand this transition, we have sequenced the exomes of mosquitoes collected from five populations from around the world. We found that Ae. aegypti specimens from an urban population in Senegal in West Africa were more closely related to populations in Mexico and Sri Lanka than they were to a nearby forest population. We estimate that the populations in Senegal and Mexico split just a few hundred years ago, and we found no evidence of Ae. aegypti aegypti mosquitoes migrating back to Africa from elsewhere in the tropics. The out-of-Africa migration was accompanied by a dramatic reduction in effective population size, resulting in a loss of genetic diversity and rare genetic variants. We conclude that a domestic population of Ae. aegypti in Senegal and domestic populations on other continents are more closely related to each other than to other African populations. This suggests that an ancestral population of Ae. aegypti evolved to become a human specialist in Africa, giving rise to the subspecies Ae. aegypti aegypti. The descendants of this population are still found in West Africa today, and the rest of the world was colonised when mosquitoes from this population migrated out of Africa. This is the first report of an African population of Ae. aegypti aegypti mosquitoes that is closely related to Asian and American populations. As the two subspecies differ in their ability to vector disease, their existence side by side in West Africa may have important implications for disease transmission.

Evolving artificial metalloenzymes via random mutagenesis

Science.gov (United States)

Yang, Hao; Swartz, Alan M.; Park, Hyun June; Srivastava, Poonam; Ellis-Guardiola, Ken; Upp, David M.; Lee, Gihoon; Belsare, Ketaki; Gu, Yifan; Zhang, Chen; Moellering, Raymond E.; Lewis, Jared C.

2018-03-01

Random mutagenesis has the potential to optimize the efficiency and selectivity of protein catalysts without requiring detailed knowledge of protein structure; however, introducing synthetic metal cofactors complicates the expression and screening of enzyme libraries, and activity arising from free cofactor must be eliminated. Here we report an efficient platform to create and screen libraries of artificial metalloenzymes (ArMs) via random mutagenesis, which we use to evolve highly selective dirhodium cyclopropanases. Error-prone PCR and combinatorial codon mutagenesis enabled multiplexed analysis of random mutations, including at sites distal to the putative ArM active site that are difficult to identify using targeted mutagenesis approaches. Variants that exhibited significantly improved selectivity for each of the cyclopropane product enantiomers were identified, and higher activity than previously reported ArM cyclopropanases obtained via targeted mutagenesis was also observed. This improved selectivity carried over to other dirhodium-catalysed transformations, including N-H, S-H and Si-H insertion, demonstrating that ArMs evolved for one reaction can serve as starting points to evolve catalysts for others.

Innovative agents in cancer prevention.

Science.gov (United States)

Manson, Margaret M; Farmer, Peter B; Gescher, Andreas; Steward, William P

2005-01-01

There are many facets to cancer prevention: a good diet, weight control and physical activity, a healthy environment, avoidance of carcinogens such as those in tobacco smoke, and screening of populations at risk to allow early detection. But there is also the possibility of using drugs or naturally occurring compounds to prevent initiation of, or to suppress, tumour growth. Only a few such agents have been used to date in the clinic with any success, and these include non-steroidal anti-inflammatory drugs for colon, finasteride for prostate and tamoxifen or raloxifene for breast tumours. An ideal chemopreventive agent would restore normal growth control to a preneoplastic or cancerous cell population by modifying aberrant signalling pathways or inducing apoptosis (or both) in cells beyond repair. Characteristics for such an agent include selectivity for damaged or transformed cells, good bioavailability and more than one mechanism of action to foil redundancy or crosstalk in signalling pathways. As more research effort is being targeted towards this area, the distinction between chemotherapeutic and chemopreventive agents is blurring. Chemotherapeutic drugs are now being designed to target over- or under-active signalling molecules within cancer cells, a philosophy which is just as relevant in chemoprevention. Development of dietary agents is particularly attractive because of our long-standing exposure to them, their relative lack of toxicity, and encouraging indications from epidemiology. The carcinogenic process relies on the cell's ability to proliferate abnormally, evade apoptosis, induce angiogenesis and metastasise to distant sites. In vitro studies with a number of different diet-derived compounds suggest that there are molecules capable of modulating each of these aspects of tumour growth. However, on the negative side many of them have rather poor bioavailability. The challenge is to uncover their multiple mechanisms of action in order to predict their

Agent-Based Models and Optimal Control in Biology: A Discrete Approach

Science.gov (United States)

2012-01-01

alive. Thus, the rules are reminiscent of a population whose survival is affected by under- and overpopulation . If we now initialize this “Game” by...helpful in models consisting of many agents of the same type, or many agents that follow the same set of rules. In modeling seasonal animal migration

The evolution of resource adaptation: how generalist and specialist consumers evolve.

Science.gov (United States)

Ma, Junling; Levin, Simon A

2006-07-01

Why and how specialist and generalist strategies evolve are important questions in evolutionary ecology. In this paper, with the method of adaptive dynamics and evolutionary branching, we identify conditions that select for specialist and generalist strategies. Generally, generalist strategies evolve if there is a switching benefit; specialists evolve if there is a switching cost. If the switching cost is large, specialists always evolve. If the switching cost is small, even though the consumer will first evolve toward a generalist strategy, it will eventually branch into two specialists.

Ranking in evolving complex networks

Science.gov (United States)

Liao, Hao; Mariani, Manuel Sebastian; Medo, Matúš; Zhang, Yi-Cheng; Zhou, Ming-Yang

2017-05-01

Complex networks have emerged as a simple yet powerful framework to represent and analyze a wide range of complex systems. The problem of ranking the nodes and the edges in complex networks is critical for a broad range of real-world problems because it affects how we access online information and products, how success and talent are evaluated in human activities, and how scarce resources are allocated by companies and policymakers, among others. This calls for a deep understanding of how existing ranking algorithms perform, and which are their possible biases that may impair their effectiveness. Many popular ranking algorithms (such as Google's PageRank) are static in nature and, as a consequence, they exhibit important shortcomings when applied to real networks that rapidly evolve in time. At the same time, recent advances in the understanding and modeling of evolving networks have enabled the development of a wide and diverse range of ranking algorithms that take the temporal dimension into account. The aim of this review is to survey the existing ranking algorithms, both static and time-aware, and their applications to evolving networks. We emphasize both the impact of network evolution on well-established static algorithms and the benefits from including the temporal dimension for tasks such as prediction of network traffic, prediction of future links, and identification of significant nodes.

Interactive macroeconomics stochastic aggregate dynamics with heterogeneous and interacting agents

CERN Document Server

Di Guilmi, Corrado

2017-01-01

One of the major problems of macroeconomic theory is the way in which the people exchange goods in decentralized market economies. There are major disagreements among macroeconomists regarding tools to influence required outcomes. Since the mainstream efficient market theory fails to provide an internal coherent framework, there is a need for an alternative theory. The book provides an innovative approach for the analysis of agent based models, populated by the heterogeneous and interacting agents in the field of financial fragility. The text is divided in two parts; the first presents analytical developments of stochastic aggregation and macro-dynamics inference methods. The second part introduces macroeconomic models of financial fragility for complex systems populated by heterogeneous and interacting agents. The concepts of financial fragility and macroeconomic dynamics are explained in detail in separate chapters. The statistical physics approach is applied to explain theories of macroeconomic modelling a...

Military chemical warfare agent human subjects testing: part 2--long-term health effects among participants of U.S. military chemical warfare agent testing.

Science.gov (United States)

Brown, Mark

2009-10-01

Military chemical warfare agent testing from World War I to 1975 produced thousands of veterans with concerns about how their participation affected their health. A companion article describes the history of these experiments, and how the lack of clinical data hampers evaluation of long-term health consequences. Conversely, much information is available about specific agents tested and their long-term health effects in other populations, which may be invaluable for helping clinicians respond effectively to the health care and other needs of affected veterans. The following review describes tested agents and their known long-term health consequences. Although hundreds of chemicals were tested, they fall into only about a half-dozen pharmaceutical classes, including common pharmaceuticals; anticholinesterase agents including military nerve agents and pesticides; anticholinergic glycolic acid esters such as atropine; acetylcholine reactivators such as 2-PAM; psychoactive compounds including cannabinoids, phencyclidine, and LSD; and irritants including tear gas and riot control agents.

O Programa de Controle do Dengue em São José do Rio Preto, São Paulo, Brasil: dificuldades para a atuação dos agentes e adesão da população Dengue Control Program in São José do Rio Preto, São Paulo State, Brazil: problems with health agents' work and population adherence

Directory of Open Access Journals (Sweden)

Francisco Chiaravalloti Neto

2007-07-01

Full Text Available O objetivo do trabalho foi identificar aspectos que interferem na atuação dos agentes de controle de vetores e comunitários de saúde no Programa de Controle do Dengue e na adesão da população. Utilizou-se metodologia de grupos focais, nos quais foi discutida a relação agente-serviço-população. O controle e prevenção do dengue foram considerados atividades de menor importância, e o agente ideal seria aquele capaz de encaminhar todas as demandas e não só aquelas relacionadas ao dengue. Os agentes de controle de vetores apontaram para problemas como recusa e falta de adesão, identificação como coletores de lixo, diferenciação de status em relação aos agentes comunitários de saúde. Entre as mulheres, identificaram-se a relação de culpabilização entre vizinhos, a associação do problema do dengue à falta de higiene e a relação entre casa limpa e ausência de criadouros. Os aspectos destacados interferem negativamente na atuação dos agentes e são condicionados pela característica vertical do programa. Encaminhamentos possíveis: incorporação dos agentes de controle às Unidades de Saúde, investimento na integração intersetorial e criação de condições para que os agentes atuem sobre o meio ambiente.This study aimed to identify the aspects that interfere with the performance of vector control agents and community health workers and population adherence to dengue control programs. The focal group methodology was applied to discuss the relations between the program, health agents, and population. According to the results, dengue control and prevention were considered relatively unimportant activities, i.e., ideal community health workers would be capable of solving other (supposedly more important problems. Vector control agents emphasized the population's lack of adherence and the fact that they (the control agents were confused with garbage collectors (considered less important than community health workers

DrawCompileEvolve: Sparking interactive evolutionary art with human creations

DEFF Research Database (Denmark)

Zhang, Jinhong; Taarnby, Rasmus; Liapis, Antonios

2015-01-01

This paper presents DrawCompileEvolve, a web-based drawing tool which allows users to draw simple primitive shapes, group them together or define patterns in their groupings (e.g. symmetry, repetition). The user’s vector drawing is then compiled into an indirectly encoded genetic representation......, which can be evolved interactively, allowing the user to change the image’s colors, patterns and ultimately transform it. The human artist has direct control while drawing the initial seed of an evolutionary run and indirect control while interactively evolving it, thus making DrawCompileEvolve a mixed...

Evolutionary Dynamics and Diversity in Microbial Populations

Science.gov (United States)

Thompson, Joel; Fisher, Daniel

2013-03-01

Diseases such as flu and cancer adapt at an astonishing rate. In large part, viruses and cancers are so difficult to prevent because they are continually evolving. Controlling such ``evolutionary diseases'' requires a better understanding of the underlying evolutionary dynamics. It is conventionally assumed that adaptive mutations are rare and therefore will occur and sweep through the population in succession. Recent experiments using modern sequencing technologies have illuminated the many ways in which real population sequence data does not conform to the predictions of conventional theory. We consider a very simple model of asexual evolution and perform simulations in a range of parameters thought to be relevant for microbes and cancer. Simulation results reveal complex evolutionary dynamics typified by competition between lineages with different sets of adaptive mutations. This dynamical process leads to a distribution of mutant gene frequencies different than expected under the conventional assumption that adaptive mutations are rare. Simulated gene frequencies share several conspicuous features with data collected from laboratory-evolved yeast and the worldwide population of influenza.

Spodoptera frugiperda (J.E. Smith) with field-evolved resistance to Bt maize are susceptible to Bt pesticides.

Science.gov (United States)

Jakka, S R K; Knight, V R; Jurat-Fuentes, J L

2014-10-01

Field-evolved resistance to maize event TC1507 expressing the Cry1Fa toxin from Bacillus thuringiensis (Bt) was detected in populations of Spodoptera frugiperda from Puerto Rico. We tested for cross-resistance to purified Cry1A toxins and commercial Bt pesticides in susceptible (Benzon) and TC1507-resistant (456) strains of S. frugiperda. Larvae from the 456 strain exhibited cross-resistance to Cry1Ab and Cry1Ac toxins, while no differences in susceptibility to XenTari WG and DiPel ES pesticides were detected. These data support cross-resistance to toxins that share binding sites with Cry1Fa and no cross-resistance to Bt pesticides in S. frugiperda with field-evolved resistance to Bt maize. Copyright © 2014 Elsevier Inc. All rights reserved.

Navigating the evolving paradigms in the diagnosis and treatment of myeloproliferative disorders.

Science.gov (United States)

Mesa, Ruben A

2007-01-01

The diagnosis and management of the BCR-ABL-negative myeloproliferative disorders (MPDs) of polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) are at an explosive crossroads of scientific investigation and evolving paradigms since the discovery of the tyrosine kinase-activating JAK2V617F mutation in 2005. Additional discovery of relevant molecular lesions (JAK2 exon 12 mutations and c-MplW515L/K) have only further enriched our understanding of MPD pathogenesis. The improved diagnostic certainty these molecular markers provide have resulted in the modification, and simplification, of the World Health Organization (WHO) diagnostic algorithms for MPDs. Despite these scientific advances, however, the initial management of MPDs continues to rely upon a risk-based strategy to minimize the risk of vascular events with control of erythrocytosis, targeted antiplatelet therapy, and risk-based myelosuppressive therapy. No current medical therapy has altered the natural trend of the MPDs to lead to overt severe myelofibrosis or acute leukemia. Investigations into targeted therapies for MPDs are proceeding at a brisk pace with agents aimed at immunomodulation, decreasing marrow stromal reaction to the aberrant clone, DNA hypomethylation, or the inhibition of tyrosine kinases. Specific inhibition of JAK2 itself appears promising by in vitro investigations, and clinical trials with multiple agents are planned to commence enrollment in 2007. The potential impact of JAK2 inhibitors on the manifestations of the MPDs is unclear, but is awaited with great interest.

Evolved Phenological Asynchrony as a Baseline for Climate-change Impacts. (Invited)

Science.gov (United States)

Singer, M. C.; Parmesan, C.

2010-12-01

Changing climate can disrupt existing phenological relations between interacting species. We might expect the historical baseline for these effects to be precise synchrony between the season at which a consumer most requires food and the time when its resources are most available. When this is the case, change in any direction would be detrimental to the consumer. But is baseline synchrony the appropriate assumption? Here, we develop the theme that the starting point for climate change impacts may often have been asynchrony or mismatch between consumer and resource. To the extent that this has been true, assumptions of baseline synchrony risk mis-detection, mis-estimation, and mis-attribution of climate change impacts. Natural selection can result in asynchrony between exploiter and victim when victims successfully evolve to occupy enemy-free time. Asynchrony can also result from life-history tradedoffs. We illustrate asynchrony arising from tradeoffs for two species: Edith’s checkerspot butterfly and the winter moth. Initial observations of phenological mismatch in both systems were made prior to the onset of major impacts of anthropogenically-driven climate change. Neither species can detect the phenological stage of its host plants with precision. In both species, evolution of life history has involved compromise between maximizing fecundity and minimizing mortality, with the outcome being superficially maladaptive strategies in which many or even most individuals die of starvation through poor synchrony with their host plants. Both species have evolved high-risk life history strategies. While winter moth eggs gamble with their own lives by hatching early, bay checkerspots gamble with the lives of their offspring by growing large and eclosing late as adults. In both cases the result is the evolution of populations in which large numbers of individuals die because, as individuals, they fail to fit their life cycles into the available timespan. Because such a

Evolving Procurement Organizations

DEFF Research Database (Denmark)

Bals, Lydia; Laine, Jari; Mugurusi, Godfrey

Procurement has to find further levers and advance its contribution to corporate goals continuously. This places pressure on its organization in order to facilitate its performance. Therefore, procurement organizations constantly have to evolve in order to match these demands. A conceptual model...... and external contingency factors and having a more detailed look at the structural dimensions chosen, beyond the well-known characteristics of centralization, formalization, participation, specialization, standardization and size. From a theoretical perspective, it opens up insights that can be leveraged...

Prostate cancer in East Asia: evolving trend over the last decade

Directory of Open Access Journals (Sweden)

Yao Zhu

2015-02-01

Full Text Available Prostate cancer is now becoming an emerging health priority in East Asia. Most of our current knowledge on Prostate cancer has been generated from studies conducted in Western population; however, there is considerable heterogeneity of Prostate cancer between East and West. In this article, we reviewed epidemiologic trends, risk factors, disease characteristics and management of Prostate cancer in East Asian population over the last decade. Growing evidence from East Asia suggests an important role of genetic and environmental risk factors interactions in the carcinogenesis of Prostate cancer. Exposure to westernized diet and life style and improvement in health care in combination contribute substantially to the increasing epidemic in this region. Diagnostic and treatment guidelines in East Asia are largely based on Western knowledge. Although there is a remarkable improvement in the outcome over the last decade, ample evidence suggests an inneglectable difference in diagnostic accuracy, treatment efficacy and adverse events between different populations. The knowledge from western countries should be calibrated in the Asian setting to provide a better race-based treatment approach. In this review, we intend to reveal the evolving trend of Prostate cancer in the last decade, in order to gain evidence to improve Prostate cancer prevention and control in East Asia.

Laplacian Estrada and normalized Laplacian Estrada indices of evolving graphs.

Science.gov (United States)

Shang, Yilun

2015-01-01

Large-scale time-evolving networks have been generated by many natural and technological applications, posing challenges for computation and modeling. Thus, it is of theoretical and practical significance to probe mathematical tools tailored for evolving networks. In this paper, on top of the dynamic Estrada index, we study the dynamic Laplacian Estrada index and the dynamic normalized Laplacian Estrada index of evolving graphs. Using linear algebra techniques, we established general upper and lower bounds for these graph-spectrum-based invariants through a couple of intuitive graph-theoretic measures, including the number of vertices or edges. Synthetic random evolving small-world networks are employed to show the relevance of the proposed dynamic Estrada indices. It is found that neither the static snapshot graphs nor the aggregated graph can approximate the evolving graph itself, indicating the fundamental difference between the static and dynamic Estrada indices.

Advance directives: the clinical nurse specialist as a change agent.

Science.gov (United States)

Meehan, Karen Anne

2009-01-01

The purpose of this article is to describe the impact the clinical nurse specialist (CNS) has on the advance directive process within the cardiac surgery patient population. As a change agent, the CNS needs to be able to increase the number of advance directives obtained and increase the provision of dignified, self-directed, quality patient care. With requirements from The Joint Commission and the Patient Self-determination Act, the change in process must take place to ensure that healthcare professionals are doing all they can do to carry out a patient's wishes. The 6-Source Influencer Model is applied to a case study to illustrate the role of the CNS as a change agent. Following this model, the CNS can facilitate lasting institutional change in the advance directive process. Based on the example, it is possible that a CNS can act as a change agent for other patient populations within the healthcare setting.

Evolution of increased adult longevity in Drosophila melanogaster populations selected for adaptation to larval crowding.

Science.gov (United States)

Shenoi, V N; Ali, S Z; Prasad, N G

2016-02-01

In holometabolous animals such as Drosophila melanogaster, larval crowding can affect a wide range of larval and adult traits. Adults emerging from high larval density cultures have smaller body size and increased mean life span compared to flies emerging from low larval density cultures. Therefore, adaptation to larval crowding could potentially affect adult longevity as a correlated response. We addressed this issue by studying a set of large, outbred populations of D. melanogaster, experimentally evolved for adaptation to larval crowding for 83 generations. We assayed longevity of adult flies from both selected (MCUs) and control populations (MBs) after growing them at different larval densities. We found that MCUs have evolved increased mean longevity compared to MBs at all larval densities. The interaction between selection regime and larval density was not significant, indicating that the density dependence of mean longevity had not evolved in the MCU populations. The increase in longevity in MCUs can be partially attributed to their lower rates of ageing. It is also noteworthy that reaction norm of dry body weight, a trait probably under direct selection in our populations, has indeed evolved in MCU populations. To the best of our knowledge, this is the first report of the evolution of adult longevity as a correlated response of adaptation to larval crowding. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Capsules with evolving brittleness to resist the preparation of self-healing concrete

Directory of Open Access Journals (Sweden)

Gruyaert, E.

2016-09-01

Full Text Available Capsules for self-healing concrete have to possess multifunctional properties and it would be an enormous advantage in the valorization process when they could also be mixed in. Therefore, we aimed to develop capsules with evolving brittleness. Capsules with high initial flexibility were prepared by adding a plasticizer to an ethyl cellulose matrix. During hardening of the concrete, the plasticizing agent should leach out to the moist environment yielding more brittle capsules which break upon crack appearance. The tested capsules could easily be mixed in during concrete production. However, incompatibility issues between the capsule wall and the inner polymeric healing agent appeared. Moreover, the capsules became insufficiently brittle and the bond strength to the cementitious matrix was too weak. Consequently, multilayer capsules were tested. These capsules had a high impact resistance to endure concrete mixing and were able to break upon crack formation.Las cápsulas para la auto-reparación del hormigón tienen que poseer propiedades multifuncionales. Una enorme ventaja en el proceso para su valorización se obtendría si aquellas pudieran resistir con éxito el mezclado. Por lo tanto, nos propusimos desarrollar cápsulas cuya fragilidad evoluciona. Cápsulas con una alta flexibilidad inicial se prepararon mediante la adición de un plastificante a una matriz de etil celulosa. Durante el endurecimiento del hormigón, el agente plastificante debe filtrarse hacia el medio ambiente húmedo produciendo cápsulas más frágiles que se rompen con el surgimiento de fisuras. Las cápsulas pudieron ser fácilmente mezcladas durante la producción de hormigón. Sin embargo, aparecieron problemas de incompatibilidad entre la pared de la cápsula y el agente de curación polimérico interior. Por otra parte, las cápsulas se comportaron insuficientemente frágiles y con una baja adherencia hacia la matriz cementicia. En consecuencia, se probaron las c

A three-state kinetic agent-based model to analyze tax evasion dynamics

Science.gov (United States)

Crokidakis, Nuno

2014-11-01

In this work we study the problem of tax evasion on a fully-connected population. For this purpose, we consider that the agents may be in three different states, namely honest tax payers, tax evaders and undecided, that are individuals in an intermediate class among honests and evaders. Every individual can change his/her state following a kinetic exchange opinion dynamics, where the agents interact by pairs with competitive negative (with probability q) and positive (with probability 1-q) couplings, representing agreement/disagreement between pairs of agents. In addition, we consider the punishment rules of the Zaklan econophysics model, for which there is a probability pa of an audit each agent is subject to in every period and a length of time k detected tax evaders remain honest. Our results suggest that below the critical point qc=1/4 of the opinion dynamics the compliance is high, and the punishment rules have a small effect in the population. On the other hand, for q>qc the tax evasion can be considerably reduced by the enforcement mechanism. We also discuss the impact of the presence of the undecided agents in the evolution of the system.

Laplacian Estrada and normalized Laplacian Estrada indices of evolving graphs.

Directory of Open Access Journals (Sweden)

Yilun Shang

Full Text Available Large-scale time-evolving networks have been generated by many natural and technological applications, posing challenges for computation and modeling. Thus, it is of theoretical and practical significance to probe mathematical tools tailored for evolving networks. In this paper, on top of the dynamic Estrada index, we study the dynamic Laplacian Estrada index and the dynamic normalized Laplacian Estrada index of evolving graphs. Using linear algebra techniques, we established general upper and lower bounds for these graph-spectrum-based invariants through a couple of intuitive graph-theoretic measures, including the number of vertices or edges. Synthetic random evolving small-world networks are employed to show the relevance of the proposed dynamic Estrada indices. It is found that neither the static snapshot graphs nor the aggregated graph can approximate the evolving graph itself, indicating the fundamental difference between the static and dynamic Estrada indices.

Evolutionary Agent-Based Simulation of the Introduction of New Technologies in Air Traffic Management

Science.gov (United States)

Yliniemi, Logan; Agogino, Adrian K.; Tumer, Kagan

2014-01-01

Accurate simulation of the effects of integrating new technologies into a complex system is critical to the modernization of our antiquated air traffic system, where there exist many layers of interacting procedures, controls, and automation all designed to cooperate with human operators. Additions of even simple new technologies may result in unexpected emergent behavior due to complex human/ machine interactions. One approach is to create high-fidelity human models coming from the field of human factors that can simulate a rich set of behaviors. However, such models are difficult to produce, especially to show unexpected emergent behavior coming from many human operators interacting simultaneously within a complex system. Instead of engineering complex human models, we directly model the emergent behavior by evolving goal directed agents, representing human users. Using evolution we can predict how the agent representing the human user reacts given his/her goals. In this paradigm, each autonomous agent in a system pursues individual goals, and the behavior of the system emerges from the interactions, foreseen or unforeseen, between the agents/actors. We show that this method reflects the integration of new technologies in a historical case, and apply the same methodology for a possible future technology.

Combined effects of biocontrol agents and soil amendments on soil microbial populations, plant growth and incidence of charcoal rot of cowpea and wilt of cumin

Directory of Open Access Journals (Sweden)

Vijeta SINGH

2012-09-01

Full Text Available Field experiments were conducted for 2 years to determine the effectiveness of combined use of two biocontrol agents, Bacillus firmus and Aspergillus versicolor for control of Macrophomina phaseolina induced charcoal rot of cowpea and Fusarium oxysporum f. sp. cumini induced wilt of cumin. The lowest level of plant mortality (3‒4% due to charcoal rot of cowpea was recorded when bacterium coated seeds were sown in radish compost amended soil compared to the non-amended soil (13.8‒20.5%, but this was not significantly better than some other treatments. Cowpea roots from B. firmus coated seeds had better nodulation than any of the individual A. versicolor treatments. Although B. firmus coated seeds + A. versicolor + farmyard manure resulted in maximum nodulation this was not significantly different to B. firmus seed coating. Root colonization by the combined biocontrol agent treatments was better than the individual biocontrol agent treatments. Combining A. versicolor with farmyard manure supported the maximum populations of total fungi and actinomycetes. In both winter seasons, the lowest incidence of wilt (1.0‒5.2% on cumin was recorded when A. versicolor was amended with neem compost compared to the non-amended soil (5.7‒10.5%. Maximum colonization of A. versicolor on roots was observed in B. firmus + A. versicolor + farmyard manure amended plots. During both years, the treatment combination of A. versicolor in neem compost amended plots resulted in maximum populations of fungi, bacteria and A. versicolor in the soil, which was greater than in the non-amended soil. Significant increases in disease control were not recorded after single or repeated delivery of A. versicolor. These results suggest that combining B. firmus as seed coatings with A. versicolor as soil applications gives improved control of M. phaseolina and Fusarium induced diseases on legume and seed spice crops in arid soils.

Face-to-Face With your Assistant. Realization Issues of Animated User Interface Agents for Home Appliances

OpenAIRE

Alexa, M.; Müller, W.; Spierling, U.; Rieger, T.

2000-01-01

With the introduction of software agents and assistants, the concept of so-called social user interfaces evolved, incorporating natural language interaction, context awareness and anthropomorphic representations of visuals, scales, and degrees of freedom for interactions. Today s challenge is to build a suitable visualization architecture for anthropomorphic conversational user interfaces, and to design for the believable and appropriate inclusion of human attributes (such as emotions) in a f...

Biological control agents (Arthropoda - Insecta associated with cultivation of the sugar apple (Annona squamosa L. = Agentes de controle biológico (Arthropoda - Insecta associados ao cultivo da pinha (Annona squamosa L.

Directory of Open Access Journals (Sweden)

Laise Malaspina Rossi

2017-03-01

Full Text Available Knowledge of biological control agents occurring naturally in agricultural areas is of great importance in adopting methods of integrated pest management. The aim of this work therefore, was to undertake a population survey of biological control agents (Insecta associated with cultivation of Annona squamosa. The research was carried out during the 2015/2016 harvest in a conventional orchard of A. squamosa, located in the town of Tabatinga in the State of São Paulo, Brazil. The biological control agents were captured using yellow sticky traps. The following faunistic indices were calculated: dominance, abundance, frequency and constancy. Population fluctuations in the natural enemies sampled were analysed by histogram. The coccinellid predators, Scymnus sp. (Coleoptera: Coccinellidae and Cycloneda sanguinea (Coleoptera: Coccinellidae were the principal biological control agents sampled during the study, and considered superdominant, superabundant, superfrequent and constant. As for population fluctuation of predominant natural enemies, high population density was seen in Scymnus sp. between September and January 2015, whereas there were three population peaks for C. sanguinea during the study, in September 2015 and January and July 2016. The coccinellids, Scymnus sp. and C. sanguinea, were the predominant biological control agents in the cultivation of A. squamosa, with a higher population density for the genus Scymnus seen in the spring and summer seasons, and no distribution pattern for C. sanguinea observed. = O conhecimento acerca dos agentes de controle biológico presentes naturalmente em áreas agrícolas apresenta grande importância na adoção de metodologias voltadas ao manejo integrado de pragas. Assim, objetivou-se com este trabalho realizar o levantamento da ocorrência populacional de agentes de controle biológico (Insecta associado ao cultivo de Annona squamosa. A pesquisa foi realizada na safra agrícola 2015/2016 em pomar

The evolving cobweb of relations among partially rational investors

Science.gov (United States)

DiMeglio, Anna; Garofalo, Franco; Lo Iudice, Francesco

2017-01-01

To overcome the limitations of neoclassical economics, researchers have leveraged tools of statistical physics to build novel theories. The idea was to elucidate the macroscopic features of financial markets from the interaction of its microscopic constituents, the investors. In this framework, the model of the financial agents has been kept separate from that of their interaction. Here, instead, we explore the possibility of letting the interaction topology emerge from the model of the agents’ behavior. Then, we investigate how the emerging cobweb of relationship affects the overall market dynamics. To this aim, we leverage tools from complex systems analysis and nonlinear dynamics, and model the network of mutual influence as the output of a dynamical system describing the edge evolution. In this work, the driver of the link evolution is the relative reputation between possibly coupled agents. The reputation is built differently depending on the extent of rationality of the investors. The continuous edge activation or deactivation induces the emergence of leaders and of peculiar network structures, typical of real influence networks. The subsequent impact on the market dynamics is investigated through extensive numerical simulations in selected scenarios populated by partially rational investors. PMID:28196144

Quantitative morphometrical analysis of a North African population ...

Indian Academy of Sciences (India)

2008-12-23

Dec 23, 2008 ... the genetic architecture of a natural population. In several cases, and .... transferred to ordinary food vials, at a lesser temperature. (18–20 ..... 2007). Both W/T and body pigmentation may be considered as fast evolving.

Evolution of antibiotic resistance in biofilm and planktonic P. aeruginosa populations exposed to sub-inhibitory levels of ciprofloxacin

DEFF Research Database (Denmark)

Ahmed, Marwa N.; Porse, Andreas; Sommer, Morten Otto Alexander

2018-01-01

in planktonic cultures and are less studied in biofilms. We experimentally evolved P. aeruginosa PAO1 colony-biofilms and stationary-phase planktonic cultures for seven passages in the presence of sub-inhibitory levels (0.1 mg/L) of ciprofloxacin (CIP) and performed a genotypic (whole bacterial population......The opportunistic Gram-negative pathogen Pseudomonas aeruginosa, known for its intrinsic and acquired antibiotic resistance, has a notorious ability to form biofilms, which often facilitate chronic infections. The evolutionary paths to antibiotic resistance have mainly been investigated......-dependent adaptations. A general trend towards a reduction in type IV-pili dependent motility (twitching) in CIP-evolved populations, and towards loss of virulence associated traits in the populations evolved in the absence of antibiotic, was observed. In conclusion, our data indicate that biofilms facilitate...

How Academic Health Systems Can Achieve Population Health in Vulnerable Populations Through Value-Based Care: The Critical Importance of Establishing Trusted Agency.

Science.gov (United States)

Wesson, Donald E; Kitzman, Heather E

2018-01-16

Improving population health may require health systems to proactively engage patient populations as partners in the implementation of healthy behaviors as a shared value using strategies that incentivize healthy outcomes for the population as a whole. The current reactive health care model, which focuses on restoring the health of individuals after it has been lost, will not achieve the goal of improved population health. To achieve this goal, health systems must proactively engage in partnerships with the populations they serve. Health systems will need the help of community entities and individuals who have the trust of the population being served to act on behalf of the health system if they are to achieve this effective working partnership. The need for these trusted agents is particularly pertinent for vulnerable and historically underserved segments of the population. In this Invited Commentary, the authors discuss ways by which health systems might identify, engage, and leverage trusted agents to improve the health of the population through value-based care.

Biological agents with potential for misuse: a historical perspective and defensive measures

International Nuclear Information System (INIS)

Bhalla, Deepak K.; Warheit, David B.

2004-01-01

Biological and chemical agents capable of producing serious illness or mortality have been used in biowarfare from ancient times. Use of these agents has progressed from crude forms in early and middle ages, when snakes and infected cadavers were used as weapons in battles, to sophisticated preparations for use during and after the second World War. Cults and terrorist organizations have attempted the use of biological agents with an aim to immobilize populations or cause serious harm. The reasons for interest in these agents by individuals and organizations include relative ease of acquisition, potential for causing mass casualty or panic, modest financing requirement, availability of technology, and relative ease of delivery. The Centers for Disease Control and Prevention has classified Critical Biological Agents into three major categories. This classification was based on several criteria, which include severity of impact on human health, potential for delivery in a weapon, capacity to cause panic and special needs for development, and stockpiling of medication. Agents that could cause the greatest harm following deliberate use were placed in category A. Category B included agents capable of producing serious harm and significant mortality but of lower magnitude than category A agents. Category C included emerging pathogens that could be developed for mass dispersion in future and their potential as a major health threat. A brief description of the category A bioagents is included and the pathophysiology of two particularly prominent agents, namely anthrax and smallpox, is discussed in detail. The potential danger from biological agents and their ever increasing threat to human populations have created a need for developing technologies for their early detection, for developing treatment strategies, and for refinement of procedures to ensure survival of affected individuals so as to attain the ultimate goal of eliminating the threat from intentional use of

Biological agents with potential for misuse: a historical perspective and defensive measures.

Science.gov (United States)

Bhalla, Deepak K; Warheit, David B

2004-08-15

Biological and chemical agents capable of producing serious illness or mortality have been used in biowarfare from ancient times. Use of these agents has progressed from crude forms in early and middle ages, when snakes and infected cadavers were used as weapons in battles, to sophisticated preparations for use during and after the second World War. Cults and terrorist organizations have attempted the use of biological agents with an aim to immobilize populations or cause serious harm. The reasons for interest in these agents by individuals and organizations include relative ease of acquisition, potential for causing mass casualty or panic, modest financing requirement, availability of technology, and relative ease of delivery. The Centers for Disease Control and Prevention has classified Critical Biological Agents into three major categories. This classification was based on several criteria, which include severity of impact on human health, potential for delivery in a weapon, capacity to cause panic and special needs for development, and stockpiling of medication. Agents that could cause the greatest harm following deliberate use were placed in category A. Category B included agents capable of producing serious harm and significant mortality but of lower magnitude than category A agents. Category C included emerging pathogens that could be developed for mass dispersion in future and their potential as a major health threat. A brief description of the category A bioagents is included and the pathophysiology of two particularly prominent agents, namely anthrax and smallpox, is discussed in detail. The potential danger from biological agents and their ever increasing threat to human populations have created a need for developing technologies for their early detection, for developing treatment strategies, and for refinement of procedures to ensure survival of affected individuals so as to attain the ultimate goal of eliminating the threat from intentional use of

Interntional Migration with Heterogeneous Agents: Theory and Evidence

DEFF Research Database (Denmark)

Schröder, Philipp J.H.; Brücker, Herbert

Two puzzling facts of international migration are that only a small share of a sending country's population emigrates and that net migration rates tend to cease over time. This paper addresses these issues in a migration model with heterogeneous agents that features temporary migration...

Novel R tools for analysis of genome-wide population genetic data with emphasis on clonality

Science.gov (United States)

To gain a detailed understanding of how plant microbes evolve and adapt to hosts, pesticides, and other factors, knowledge of the population dynamics and evolutionary history of populations is crucial. Plant pathogen populations are often clonal or partially clonal which requires different analytica...

PCBA demand forecasting using an evolving Takagi-Sugeno system

NARCIS (Netherlands)

van Rooijen, M.; Almeida, R.J.; Kaymak, U.

2016-01-01

This paper investigates the use of using an evolving fuzzy system for printed circuit board (PCBA) demand forecasting. The algorithm is based on the evolving Takagi-Sugeno (eTS) fuzzy system, which has the ability to incorporate new patterns by changing its internal structure in an on-line fashion.

Pythium species and isolate diversity influence inhibition by the biological control agent Streptomyces lydicus

Science.gov (United States)

Disease control of soilborne pathogens by biological control agents has often been inconsistent under field conditions. One factor that may contribute to this inconsistency is the variability in response among pathogen populations and/or communities to the selected biological control agent. One hund...

Complex agent networks explaining the HIV epidemic among homosexual men in Amsterdam

NARCIS (Netherlands)

Mei, S.; Sloot, P.M.A.; Quax, R.; Zhu, Y.; Wang, W.

2010-01-01

Simulating the spreading of the human immunodeficiency virus (HIV) epidemic requires a detailed description of the population network, especially for small populations in which individuals can be represented in detail and accuracy. In this paper, we introduce the concept of a complex agent network

China's Population Policy at the Crossroads: Social Impacts and Prospects

OpenAIRE

Jiang, Quanbao; Li, Shuzhuo; Feldman, Marcus W.

2013-01-01

China's total fertility rate fell below replacement level in the 1990s. From the 1970s the fertility rate declined dramatically, mainly as a consequence of the national population policy whose aim has been to limit birth numbers, control population growth and boost economic growth. Having achieved such a low fertility rate, how will China's population policy evolve in the future? This paper first reviews the history of China's population policy since 1970 in terms of three stages: 1970-1979; ...

CMIP6 Data Citation of Evolving Data

Directory of Open Access Journals (Sweden)

Martina Stockhause

2017-06-01

Full Text Available Data citations have become widely accepted. Technical infrastructures as well as principles and recommendations for data citation are in place but best practices or guidelines for their implementation are not yet available. On the other hand, the scientific climate community requests early citations on evolving data for credit, e.g. for CMIP6 (Coupled Model Intercomparison Project Phase 6. The data citation concept for CMIP6 is presented. The main challenges lie in limited resources, a strict project timeline and the dependency on changes of the data dissemination infrastructure ESGF (Earth System Grid Federation to meet the data citation requirements. Therefore a pragmatic, flexible and extendible approach for the CMIP6 data citation service was developed, consisting of a citation for the full evolving data superset and a data cart approach for citing the concrete used data subset. This two citation approach can be implemented according to the RDA recommendations for evolving data. Because of resource constraints and missing project policies, the implementation of the second part of the citation concept is postponed to CMIP7.

Estimated general population control limits for unitary agents in drinking water, milk, soil, and unprocessed food items

Energy Technology Data Exchange (ETDEWEB)

Watson, A.P.; Adams, J.D.; Cerar, R.J.; Hess, T.L.; Kistner, S.L.; Leffingwell, S.S.; MacIntosh, R.G.; Ward, J.R.

1992-01-01

In the event of an unplanned release of chemical agent during any stage of the Chemical Stockpile Disposal Program (CSDP), the potential exists for contamination of drinking water, forage crops, grains, garden produce, and livestock. Persistent agents such as VX or sulfur mustard pose the greatest human health concern for reentry. This White Paper has been prepared to provide technical bases for these decisions by developing working estimates of agent control limits in selected environmental media considered principal sources of potential human exposure. To date, control limits for public exposure to unitary agents have been established for atmospheric concentrations only. The current analysis builds on previous work to calculate working estimates of control limits for ingestion and dermal exposure to potentially contaminated drinking water, milk, soil, and unprocessed food items such as garden produce. Information characterizing agent desorption from, and detection on or in, contaminated porous media are presently too developed to permit reasonable estimation of dermal exposure from this source. Thus, dermal contact with potentially contaminated porous surfaces is not considered in this document.

Marshal: Maintaining Evolving Models, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — SIFT proposes to design and develop the Marshal system, a mixed-initiative tool for maintaining task models over the course of evolving missions. Marshal-enabled...

Learning Natural Selection in 4th Grade with Multi-Agent-Based Computational Models

Science.gov (United States)

Dickes, Amanda Catherine; Sengupta, Pratim

2013-01-01

In this paper, we investigate how elementary school students develop multi-level explanations of population dynamics in a simple predator-prey ecosystem, through scaffolded interactions with a multi-agent-based computational model (MABM). The term "agent" in an MABM indicates individual computational objects or actors (e.g., cars), and these…

Systematic review of miscellaneous agents for the management of oral mucositis in cancer patients

DEFF Research Database (Denmark)

Jensen, Siri Beier; Jarvis, Virginia; Zadik, Yehuda

2013-01-01

/or conflicting evidence. CONCLUSIONS: None of the agents reviewed was determined to be effective for the prevention or treatment of OM. Two agents, pilocarpine and pentoxifylline, were determined to be ineffective, in the populations listed above. Additional well-designed research is needed on other...

Agent-Based Crowd Simulation Considering Emotion Contagion for Emergency Evacuation Problem

Science.gov (United States)

Faroqi, H.; Mesgari, M.-S.

2015-12-01

During emergencies, emotions greatly affect human behaviour. For more realistic multi-agent systems in simulations of emergency evacuations, it is important to incorporate emotions and their effects on the agents. In few words, emotional contagion is a process in which a person or group influences the emotions or behavior of another person or group through the conscious or unconscious induction of emotion states and behavioral attitudes. In this study, we simulate an emergency situation in an open square area with three exits considering Adults and Children agents with different behavior. Also, Security agents are considered in order to guide Adults and Children for finding the exits and be calm. Six levels of emotion levels are considered for each agent in different scenarios and situations. The agent-based simulated model initialize with the random scattering of agent populations and then when an alarm occurs, each agent react to the situation based on its and neighbors current circumstances. The main goal of each agent is firstly to find the exit, and then help other agents to find their ways. Numbers of exited agents along with their emotion levels and damaged agents are compared in different scenarios with different initialization in order to evaluate the achieved results of the simulated model. NetLogo 5.2 is used as the multi-agent simulation framework with R language as the developing language.

AGENT-BASED CROWD SIMULATION CONSIDERING EMOTION CONTAGION FOR EMERGENCY EVACUATION PROBLEM

Directory of Open Access Journals (Sweden)

H. Faroqi

2015-12-01

Full Text Available During emergencies, emotions greatly affect human behaviour. For more realistic multi-agent systems in simulations of emergency evacuations, it is important to incorporate emotions and their effects on the agents. In few words, emotional contagion is a process in which a person or group influences the emotions or behavior of another person or group through the conscious or unconscious induction of emotion states and behavioral attitudes. In this study, we simulate an emergency situation in an open square area with three exits considering Adults and Children agents with different behavior. Also, Security agents are considered in order to guide Adults and Children for finding the exits and be calm. Six levels of emotion levels are considered for each agent in different scenarios and situations. The agent-based simulated model initialize with the random scattering of agent populations and then when an alarm occurs, each agent react to the situation based on its and neighbors current circumstances. The main goal of each agent is firstly to find the exit, and then help other agents to find their ways. Numbers of exited agents along with their emotion levels and damaged agents are compared in different scenarios with different initialization in order to evaluate the achieved results of the simulated model. NetLogo 5.2 is used as the multi-agent simulation framework with R language as the developing language.

Response to bronchodilators in very preterm infants with evolving bronchopulmonary dysplasia

Directory of Open Access Journals (Sweden)

Morrow DK

2015-12-01

Full Text Available Daniel K Morrow, Diane Schilling, Cindy T McEvoy Department of Pediatrics, Oregon Health and Science University, Portland, OR, USA Background: There are few effective and safe medications to treat very low birth weight (VLBW infants with evolving bronchopulmonary dysplasia. Bronchodilators are often given to patients who have clinical signs of reactive airway disease, but there is not enough information regarding their effectiveness within this population. Objective: To quantify the pulmonary function response to bronchodilator therapy in a population of VLBW infants with evolving bronchopulmonary dysplasia. Materials and methods: This is a retrospective analysis of an ongoing large database of pulmonary function tests (PFTs in premature infants. We reviewed the pre- and post-bronchodilator PFTs ordered by a physician due to concern for reactive airway disease. Inclusion criteria: Birth weight (BW <1,500 g; >14 days of age; admission diagnosis of respiratory distress syndrome; requiring ongoing oxygen, continuous positive airway pressure, or ventilator support at the time of PFT. PFTs were done prior to albuterol therapy and repeated 30 minutes after the therapy was given. PFTs included the measurement of passive respiratory mechanics with the single breath occlusion technique, including passive respiratory system compliance, resistance, and tidal volume. Results: Forty VLBW infants (mean gestation of 27.4 weeks; mean BW of 848 g were identified as having PFTs. Twenty-nine of these patients had a BW of ≤1,000 g. The patients were studied at a mean corrected gestational age of 34.9 weeks. Twenty-nine of 40 patients were extubated at the time of the PFT. Of these patients, 21 (52.5% had a decrease in respiratory system resistance of ≥10%. From the other 19 patients, five (12.5% had a decrease of 0% to <10% in respiratory system resistance, and 14(35% showed no response to therapy. There was no significant difference in respiratory system

Computational Genetic Regulatory Networks Evolvable, Self-organizing Systems

CERN Document Server

Knabe, Johannes F

2013-01-01

Genetic Regulatory Networks (GRNs) in biological organisms are primary engines for cells to enact their engagements with environments, via incessant, continually active coupling. In differentiated multicellular organisms, tremendous complexity has arisen in the course of evolution of life on earth. Engineering and science have so far achieved no working system that can compare with this complexity, depth and scope of organization. Abstracting the dynamics of genetic regulatory control to a computational framework in which artificial GRNs in artificial simulated cells differentiate while connected in a changing topology, it is possible to apply Darwinian evolution in silico to study the capacity of such developmental/differentiated GRNs to evolve. In this volume an evolutionary GRN paradigm is investigated for its evolvability and robustness in models of biological clocks, in simple differentiated multicellularity, and in evolving artificial developing 'organisms' which grow and express an ontogeny starting fr...

Adaptive inferential sensors based on evolving fuzzy models.

Science.gov (United States)

Angelov, Plamen; Kordon, Arthur

2010-04-01

A new technique to the design and use of inferential sensors in the process industry is proposed in this paper, which is based on the recently introduced concept of evolving fuzzy models (EFMs). They address the challenge that the modern process industry faces today, namely, to develop such adaptive and self-calibrating online inferential sensors that reduce the maintenance costs while keeping the high precision and interpretability/transparency. The proposed new methodology makes possible inferential sensors to recalibrate automatically, which reduces significantly the life-cycle efforts for their maintenance. This is achieved by the adaptive and flexible open-structure EFM used. The novelty of this paper lies in the following: (1) the overall concept of inferential sensors with evolving and self-developing structure from the data streams; (2) the new methodology for online automatic selection of input variables that are most relevant for the prediction; (3) the technique to detect automatically a shift in the data pattern using the age of the clusters (and fuzzy rules); (4) the online standardization technique used by the learning procedure of the evolving model; and (5) the application of this innovative approach to several real-life industrial processes from the chemical industry (evolving inferential sensors, namely, eSensors, were used for predicting the chemical properties of different products in The Dow Chemical Company, Freeport, TX). It should be noted, however, that the methodology and conclusions of this paper are valid for the broader area of chemical and process industries in general. The results demonstrate that well-interpretable and with-simple-structure inferential sensors can automatically be designed from the data stream in real time, which predict various process variables of interest. The proposed approach can be used as a basis for the development of a new generation of adaptive and evolving inferential sensors that can address the

An Evolving Asymmetric Game for Modeling Interdictor-Smuggler Problems

Science.gov (United States)

2016-06-01

ASYMMETRIC GAME FOR MODELING INTERDICTOR-SMUGGLER PROBLEMS by Richard J. Allain June 2016 Thesis Advisor: David L. Alderson Second Reader: W...DATES COVERED Master’s thesis 4. TITLE AND SUBTITLE AN EVOLVING ASYMMETRIC GAME FOR MODELING INTERDICTOR- SMUGGLER PROBLEMS 5. FUNDING NUMBERS 6...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited AN EVOLVING

Nanoparticle Contrast Agents for Computed Tomography: A Focus on Micelles

Science.gov (United States)

Cormode, David P.; Naha, Pratap C.; Fayad, Zahi A.

2014-01-01

Computed tomography (CT) is an X-ray based whole body imaging technique that is widely used in medicine. Clinically approved contrast agents for CT are iodinated small molecules or barium suspensions. Over the past seven years there has been a great increase in the development of nanoparticles as CT contrast agents. Nanoparticles have several advantages over small molecule CT contrast agents, such as long blood-pool residence times, and the potential for cell tracking and targeted imaging applications. Furthermore, there is a need for novel CT contrast agents, due to the growing population of renally impaired patients and patients hypersensitive to iodinated contrast. Micelles and lipoproteins, a micelle-related class of nanoparticle, have notably been adapted as CT contrast agents. In this review we discuss the principles of CT image formation and the generation of CT contrast. We discuss the progress in developing non-targeted, targeted and cell tracking nanoparticle CT contrast agents. We feature agents based on micelles and used in conjunction with spectral CT. The large contrast agent doses needed will necessitate careful toxicology studies prior to clinical translation. However, the field has seen tremendous advances in the past decade and we expect many more advances to come in the next decade. PMID:24470293

Agent Programming Languages and Logics in Agent-Based Simulation

DEFF Research Database (Denmark)

Larsen, John

2018-01-01

and social behavior, and work on verification. Agent-based simulation is an approach for simulation that also uses the notion of agents. Although agent programming languages and logics are much less used in agent-based simulation, there are successful examples with agents designed according to the BDI...

Oral Antidiabetic Agents and Cardiovascular Outcomes

DEFF Research Database (Denmark)

Pareek, Manan; Bhatt, Deepak L

2018-01-01

Cardiovascular disease is the leading cause of morbidity and mortality among patients with type 2 diabetes; however, a direct protective effect of tight glycemic control remains unproven. In fact, until 2008, when concerns related to rosiglitazone prompted regulatory agencies to mandate assessment...... of cardiovascular safety of new antidiabetic agents, little was known about how these medications affected cardiovascular outcomes. Since then, there has been a considerable increase in the number of cardiovascular trials, which employ a noninferiority design and focus on high-risk populations to establish safety...... in the shortest time possible. In this article, we summarize the 4 major cardiovascular outcome trials of oral antidiabetic agents, completed so far. These include 3 dipeptidyl peptidase-4 inhibitors (saxagliptin, alogliptin, and sitagliptin) and 1 sodium-glucose cotransporter-2 inhibitor (empagliflozin). We...

Climate Change and the Representative Agent

Energy Technology Data Exchange (ETDEWEB)

Howarth, R.B. [Environmental Studies Program, Dartmouth College, Hanover, New Hampshire 03755 (United States)

2000-02-01

The artifice of an infinitely-lived representative agent is commonly invoked to balance the present costs and future benefits of climate stabilization policies. Since actual economies are populated by overlapping generations of finite-lived persons, this approach begs important questions of welfare aggregation. This paper compares the results of representative agent and overlapping generations models that are numerically calibrated based on standard assumptions regarding climate economy interactions. Under two social choice rules - Pareto efficiency and classical utilitarianism - the models generate closely similar simulation results. In the absence of policies to redistribute income between present and future generations, efficient rates of carbon dioxide emissions abatement rise from 15 to 20% between the years 2000 and 2105. Under classical utilitarianism, in contrast, optimal control rates rise from 48 to 79% this same period. 23 refs.

Symbiotic Composition and Evolvability

OpenAIRE

Watson, Richard A.; Pollack, Jordan B.

2001-01-01

Several of the Major Transitions in natural evolution, such as the symbiogenic origin of eukaryotes from prokaryotes, share the feature that existing entities became the components of composite entities at a higher level of organisation. This composition of pre-adapted extant entities into a new whole is a fundamentally different source of variation from the gradual accumulation of small random variations, and it has some interesting consequences for issues of evolvability. In this paper we p...

Population thinking and natural selection in dual-inheritance theory

NARCIS (Netherlands)

Houkes, W.N.

2012-01-01

A deflationary perspective on theories of cultural evolution, in particular dual-inheritance theory, has recently been proposed by Lewens. On this ‘pop-culture’ analysis, dual-inheritance theorists apply population thinking to cultural phenomena, without claiming that cultural items evolve by

Impacts of memory on a regular lattice for different population sizes with asynchronous update in spatial snowdrift game

Science.gov (United States)

Shu, Feng; Liu, Xingwen; Li, Min

2018-05-01

Memory is an important factor on the evolution of cooperation in spatial structure. For evolutionary biologists, the problem is often how cooperation acts can emerge in an evolving system. In the case of snowdrift game, it is found that memory can boost cooperation level for large cost-to-benefit ratio r, while inhibit cooperation for small r. Thus, how to enlarge the range of r for the purpose of enhancing cooperation becomes a hot issue recently. This paper addresses a new memory-based approach and its core lies in: Each agent applies the given rule to compare its own historical payoffs in a certain memory size, and take the obtained maximal one as virtual payoff. In order to get the optimal strategy, each agent randomly selects one of its neighbours to compare their virtual payoffs, which can lead to the optimal strategy. Both constant-size memory and size-varying memory are investigated by means of a scenario of asynchronous updating algorithm on regular lattices with different sizes. Simulation results show that this approach effectively enhances cooperation level in spatial structure and makes the high cooperation level simultaneously emerge for both small and large r. Moreover, it is discovered that population sizes have a significant influence on the effects of cooperation.

Agents unleashed a public domain look at agent technology

CERN Document Server

Wayner, Peter

1995-01-01

Agents Unleashed: A Public Domain Look at Agent Technology covers details of building a secure agent realm. The book discusses the technology for creating seamlessly integrated networks that allow programs to move from machine to machine without leaving a trail of havoc; as well as the technical details of how an agent will move through the network, prove its identity, and execute its code without endangering the host. The text also describes the organization of the host's work processing an agent; error messages, bad agent expulsion, and errors in XLISP-agents; and the simulators of errors, f

Chandra Detection of an Evolved Population of Young Stars in Serpens South

Science.gov (United States)

Winston, E.; Wolk, S. J.; Gutermuth, R.; Bourke, T. L.

2018-06-01

We present a Chandra study of the deeply embedded Serpens South star-forming region, examining cluster structure and disk properties at the earliest stages. In total, 152 X-ray sources are detected. Combined with Spitzer and 2MASS photometry, 66 X-ray sources are reliably matched to an IR counterpart. We identify 21 class I, 6 flat spectrum, 16 class II, and 18 class III young stars; 5 were unclassified. Eighteen sources were variable in X-rays, 8 exhibiting flare-like emission and one source being periodic. The cluster’s X-ray luminosity distance was estimated: the best match was to the nearer distance of 260 pc for the front of the Aquila Rift complex. The ratio of N H to A K is found to be ∼0.68 × 1022, similar to that measured in other young low-mass regions, but lower than that measured in the interstellar medium and high-mass clusters (∼(1.6–2) × 1022). We find that the spatial distribution closely follows that of the dense filament from which the stars have formed, with the class II population still strongly associated with the filament. There are four subclusters in the field, with three forming knots in the filament, and a fourth to the west, which may not be associated but may be contributing to the distributed class III population. A high percentage of diskless class IIIs (upper limit 30% of classified X-ray sources) in such a young cluster could indicate that processing of disks is influenced by the cluster environment and is not solely dependent on timescale.

Cognitive Agents in Virtual Worlds : a Middleware Design Approach

NARCIS (Netherlands)

van Oijen, Joost

2014-01-01

In the past decade, significant advances have been made in the technologies for creating virtual worlds. These advances are accompanied with the need for intelligent, human-like characters to populate these virtual worlds. Such characters are also known as intelligent virtual agents (IVAs). IVAs are

Improving Agent Based Models and Validation through Data Fusion.

Science.gov (United States)

Laskowski, Marek; Demianyk, Bryan C P; Friesen, Marcia R; McLeod, Robert D; Mukhi, Shamir N

2011-01-01

This work is contextualized in research in modeling and simulation of infection spread within a community or population, with the objective to provide a public health and policy tool in assessing the dynamics of infection spread and the qualitative impacts of public health interventions. This work uses the integration of real data sources into an Agent Based Model (ABM) to simulate respiratory infection spread within a small municipality. Novelty is derived in that the data sources are not necessarily obvious within ABM infection spread models. The ABM is a spatial-temporal model inclusive of behavioral and interaction patterns between individual agents on a real topography. The agent behaviours (movements and interactions) are fed by census / demographic data, integrated with real data from a telecommunication service provider (cellular records) and person-person contact data obtained via a custom 3G Smartphone application that logs Bluetooth connectivity between devices. Each source provides data of varying type and granularity, thereby enhancing the robustness of the model. The work demonstrates opportunities in data mining and fusion that can be used by policy and decision makers. The data become real-world inputs into individual SIR disease spread models and variants, thereby building credible and non-intrusive models to qualitatively simulate and assess public health interventions at the population level.

Effective but costly, evolved mechanisms of defense against a virulent opportunistic pathogen in Drosophila melanogaster.

Directory of Open Access Journals (Sweden)

Yixin H Ye

2009-04-01

Full Text Available Drosophila harbor substantial genetic variation for antibacterial defense, and investment in immunity is thought to involve a costly trade-off with life history traits, including development, life span, and reproduction. To understand the way in which insects invest in fighting bacterial infection, we selected for survival following systemic infection with the opportunistic pathogen Pseudomonas aeruginosa in wild-caught Drosophila melanogaster over 10 generations. We then examined genome-wide changes in expression in the selected flies relative to unselected controls, both of which had been infected with the pathogen. This powerful combination of techniques allowed us to specifically identify the genetic basis of the evolved immune response. In response to selection, population-level survivorship to infection increased from 15% to 70%. The evolved capacity for defense was costly, however, as evidenced by reduced longevity and larval viability and a rapid loss of the trait once selection pressure was removed. Counter to expectation, we observed more rapid developmental rates in the selected flies. Selection-associated changes in expression of genes with dual involvement in developmental and immune pathways suggest pleiotropy as a possible mechanism for the positive correlation. We also found that both the Toll and the Imd pathways work synergistically to limit infectivity and that cellular immunity plays a more critical role in overcoming P. aeruginosa infection than previously reported. This work reveals novel pathways by which Drosophila can survive infection with a virulent pathogen that may be rare in wild populations, however, due to their cost.

Variable mutation rates as an adaptive strategy in replicator populations.

Directory of Open Access Journals (Sweden)

Michael Stich

2010-06-01

Full Text Available For evolving populations of replicators, there is much evidence that the effect of mutations on fitness depends on the degree of adaptation to the selective pressures at play. In optimized populations, most mutations have deleterious effects, such that low mutation rates are favoured. In contrast to this, in populations thriving in changing environments a larger fraction of mutations have beneficial effects, providing the diversity necessary to adapt to new conditions. What is more, non-adapted populations occasionally benefit from an increase in the mutation rate. Therefore, there is no optimal universal value of the mutation rate and species attempt to adjust it to their momentary adaptive needs. In this work we have used stationary populations of RNA molecules evolving in silico to investigate the relationship between the degree of adaptation of an optimized population and the value of the mutation rate promoting maximal adaptation in a short time to a new selective pressure. Our results show that this value can significantly differ from the optimal value at mutation-selection equilibrium, being strongly influenced by the structure of the population when the adaptive process begins. In the short-term, highly optimized populations containing little variability respond better to environmental changes upon an increase of the mutation rate, whereas populations with a lower degree of optimization but higher variability benefit from reducing the mutation rate to adapt rapidly. These findings show a good agreement with the behaviour exhibited by actual organisms that replicate their genomes under broadly different mutation rates.

Estimating mutation parameters, population history and genealogy simultaneously from temporally spaced sequence data.

Science.gov (United States)

Drummond, Alexei J; Nicholls, Geoff K; Rodrigo, Allen G; Solomon, Wiremu

2002-07-01

Molecular sequences obtained at different sampling times from populations of rapidly evolving pathogens and from ancient subfossil and fossil sources are increasingly available with modern sequencing technology. Here, we present a Bayesian statistical inference approach to the joint estimation of mutation rate and population size that incorporates the uncertainty in the genealogy of such temporally spaced sequences by using Markov chain Monte Carlo (MCMC) integration. The Kingman coalescent model is used to describe the time structure of the ancestral tree. We recover information about the unknown true ancestral coalescent tree, population size, and the overall mutation rate from temporally spaced data, that is, from nucleotide sequences gathered at different times, from different individuals, in an evolving haploid population. We briefly discuss the methodological implications and show what can be inferred, in various practically relevant states of prior knowledge. We develop extensions for exponentially growing population size and joint estimation of substitution model parameters. We illustrate some of the important features of this approach on a genealogy of HIV-1 envelope (env) partial sequences.

Population inversion of two atoms under the phase decoherence in the multiphoton process

International Nuclear Information System (INIS)

Zhang Dongxia; Sa Chuerfu; Mu Qier

2011-01-01

By means of the quantum theory, the population inversion of two atoms in the system of two two-level atoms coupled to a light field in the Binomial Optical Field are investigated in the presence of phase decoherence in the multiphoton Tavis-Cumming Model. The influences of the phase decoherence coefficient, the parameters η of the binomial optical field, the maximum number of photons and the number of the transitional photons on the properties of the population inversion of two atoms have been discussed. The results show that the phase decoherence reduced the oscillation amplitude of the population inversion of two atoms and destroyed the atomic quantum characteristic. Changing the number of the transitional photons, evolved cycle and evolved intensity the population inversion of two atoms can be changed. The phenomena of collapse and revival disappear as photon number increase. When the binomial optical state changes from a coherent state to a Fock state, the oscillation frequency of the atomic population reduces gradually, the phenomena of collapse and revival vanishes gradually. (authors)

Consentaneous agent-based and stochastic model of the financial markets.

Science.gov (United States)

Gontis, Vygintas; Kononovicius, Aleksejus

2014-01-01

We are looking for the agent-based treatment of the financial markets considering necessity to build bridges between microscopic, agent based, and macroscopic, phenomenological modeling. The acknowledgment that agent-based modeling framework, which may provide qualitative and quantitative understanding of the financial markets, is very ambiguous emphasizes the exceptional value of well defined analytically tractable agent systems. Herding as one of the behavior peculiarities considered in the behavioral finance is the main property of the agent interactions we deal with in this contribution. Looking for the consentaneous agent-based and macroscopic approach we combine two origins of the noise: exogenous one, related to the information flow, and endogenous one, arising form the complex stochastic dynamics of agents. As a result we propose a three state agent-based herding model of the financial markets. From this agent-based model we derive a set of stochastic differential equations, which describes underlying macroscopic dynamics of agent population and log price in the financial markets. The obtained solution is then subjected to the exogenous noise, which shapes instantaneous return fluctuations. We test both Gaussian and q-Gaussian noise as a source of the short term fluctuations. The resulting model of the return in the financial markets with the same set of parameters reproduces empirical probability and spectral densities of absolute return observed in New York, Warsaw and NASDAQ OMX Vilnius Stock Exchanges. Our result confirms the prevalent idea in behavioral finance that herding interactions may be dominant over agent rationality and contribute towards bubble formation.

Mobile Agent Data Integrity Using Multi-Agent Architecture

National Research Council Canada - National Science Library

McDonald, Jeffrey

2004-01-01

.... Security issues for mobile agents continue to produce research interest, particularly in developing mechanisms that guarantee protection of agent data and agent computations in the presence of malicious hosts...

A review of research on common biological agents and their impact on environment

International Nuclear Information System (INIS)

Mashiatullah, A.; Qureshi, R.M.

2009-01-01

Biological agents are unique class of microorganisms which can be used to produce the disease in large populations of humans, animals and plants. If used for hostile purposes, any disease-causing microorganism could be considered a weapon. The use of biological agents is not a new concept and history is replete with examples of biological weapon use. Before the twenty century, biological warfare took on three main forms by deliberate poisoning of food and water with infectious material, use of microorganisms or toxins in some form of weapon system, and use of biologically inoculated fabrics. Four kinds of biological warfare agents are bacteria, viruses, rickettsiae, fungi. These are distinguished by being living organisms, that reproduce within their host victims, who then become contagious with a deadly multiplier effect, bacteria, viruses, or fungi or toxin found in nature can be used to kill or injure people. Biological agents may be used for an isolated assassination, as well as to cause incapacitation or death to thousands. These biological agents represent a dangerous military threat because they are alive, and are therefore unpredictable and uncontrollable once released. The act of bioterrorism can range from a simple hoax to the actual use of biological weapons. Biological agents have the potential to make an environment more dangerous over time. If the environment is contaminated, a long-term threat to the population could be created. This paper discusses common biological agents, their mode of action in living organisms and possible impact on the environment. (author)

Evolving Systems: Adaptive Key Component Control and Inheritance of Passivity and Dissipativity

Science.gov (United States)

Frost, S. A.; Balas, M. J.

2010-01-01

We propose a new framework called Evolving Systems to describe the self-assembly, or autonomous assembly, of actively controlled dynamical subsystems into an Evolved System with a higher purpose. Autonomous assembly of large, complex flexible structures in space is a target application for Evolving Systems. A critical requirement for autonomous assembling structures is that they remain stable during and after assembly. The fundamental topic of inheritance of stability, dissipativity, and passivity in Evolving Systems is the primary focus of this research. In this paper, we develop an adaptive key component controller to restore stability in Nonlinear Evolving Systems that would otherwise fail to inherit the stability traits of their components. We provide sufficient conditions for the use of this novel control method and demonstrate its use on an illustrative example.

Is the whole the sum of its parts? Agent-based modelling of wastewater treatment systems.

Science.gov (United States)

Schuler, A J; Majed, N; Bucci, V; Hellweger, F L; Tu, Y; Gu, A Z

2011-01-01

Agent-based models (ABMS) simulate individual units within a system, such as the bacteria in a biological wastewater treatment system. This paper outlines past, current and potential future applications of ABMs to wastewater treatment. ABMs track heterogeneities within microbial populations, and this has been demonstrated to yield different predictions of bulk behaviors than the conventional, "lumped" approaches for enhanced biological phosphorus removal (EBPR) completely mixed reactors systems. Current work included the application of the ABM approach to bacterial adaptation/evolution, using the model system of individual EBPR bacteria that are allowed to evolve a kinetic parameter (maximum glycogen storage) in a competitive environment. The ABM approach was successfully implemented to a simple anaerobic-aerobic system and it was found the differing initial states converged to the same optimal solution under uncertain hydraulic residence times associated with completely mixed hydraulics. In another study, an ABM was developed and applied to simulate the heterogeneity in intracellular polymer storage compounds, including polyphosphate (PP), in functional microbial populations in enhanced biological phosphorus removal (EBPR) process. The simulation results were compared to the experimental measurements of single-cell abundance of PP in polyphosphate accumulating organisms (PAOs), performed using Raman microscopy. The model-predicted heterogeneity was generally consistent with observations, and it was used to investigate the relative contribution of external (different life histories) and internal (biological) mechanisms leading to heterogeneity. In the future, ABMs could be combined with computational fluid dynamics (CFD) models to understand incomplete mixing, more intracellular states and mechanisms can be incorporated, and additional experimental verification is needed.

Qualitative Functional Decomposition Analysis of Evolved Neuromorphic Flight Controllers

Directory of Open Access Journals (Sweden)

Sanjay K. Boddhu

2012-01-01

Full Text Available In the previous work, it was demonstrated that one can effectively employ CTRNN-EH (a neuromorphic variant of EH method methodology to evolve neuromorphic flight controllers for a flapping wing robot. This paper describes a novel frequency grouping-based analysis technique, developed to qualitatively decompose the evolved controllers into explainable functional control blocks. A summary of the previous work related to evolving flight controllers for two categories of the controller types, called autonomous and nonautonomous controllers, is provided, and the applicability of the newly developed decomposition analysis for both controller categories is demonstrated. Further, the paper concludes with appropriate discussion of ongoing work and implications for possible future work related to employing the CTRNN-EH methodology and the decomposition analysis techniques presented in this paper.

Effects of biological control agents and exotic plant invasion on deer mouse populations

Science.gov (United States)

Yvette K. Ortega; Dean E. Pearson; Kevin S. McKelvey

2004-01-01

Exotic insects are commonly introduced as biological control agents to reduce densities of invasive exotic plants. Although current biocontrol programs for weeds take precautions to minimize ecological risks, little attention is paid to the potential nontarget effects of introduced food subsidies on native consumers. Previous research demonstrated that two gall flies (...

Agent-Based Modeling in Systems Pharmacology.

Science.gov (United States)

Cosgrove, J; Butler, J; Alden, K; Read, M; Kumar, V; Cucurull-Sanchez, L; Timmis, J; Coles, M

2015-11-01

Modeling and simulation (M&S) techniques provide a platform for knowledge integration and hypothesis testing to gain insights into biological systems that would not be possible a priori. Agent-based modeling (ABM) is an M&S technique that focuses on describing individual components rather than homogenous populations. This tutorial introduces ABM to systems pharmacologists, using relevant case studies to highlight how ABM-specific strengths have yielded success in the area of preclinical mechanistic modeling.

Fortune Favours the Bold: An Agent-Based Model Reveals Adaptive Advantages of Overconfidence in War

Science.gov (United States)

Johnson, Dominic D. P.; Weidmann, Nils B.; Cederman, Lars-Erik

2011-01-01

Overconfidence has long been considered a cause of war. Like other decision-making biases, overconfidence seems detrimental because it increases the frequency and costs of fighting. However, evolutionary biologists have proposed that overconfidence may also confer adaptive advantages: increasing ambition, resolve, persistence, bluffing opponents, and winning net payoffs from risky opportunities despite occasional failures. We report the results of an agent-based model of inter-state conflict, which allows us to evaluate the performance of different strategies in competition with each other. Counter-intuitively, we find that overconfident states predominate in the population at the expense of unbiased or underconfident states. Overconfident states win because: (1) they are more likely to accumulate resources from frequent attempts at conquest; (2) they are more likely to gang up on weak states, forcing victims to split their defences; and (3) when the decision threshold for attacking requires an overwhelming asymmetry of power, unbiased and underconfident states shirk many conflicts they are actually likely to win. These “adaptive advantages” of overconfidence may, via selection effects, learning, or evolved psychology, have spread and become entrenched among modern states, organizations and decision-makers. This would help to explain the frequent association of overconfidence and war, even if it no longer brings benefits today. PMID:21731627

Genetic programming for evolving due-date assignment models in job shop environments.

Science.gov (United States)

Nguyen, Su; Zhang, Mengjie; Johnston, Mark; Tan, Kay Chen

2014-01-01

Due-date assignment plays an important role in scheduling systems and strongly influences the delivery performance of job shops. Because of the stochastic and dynamic nature of job shops, the development of general due-date assignment models (DDAMs) is complicated. In this study, two genetic programming (GP) methods are proposed to evolve DDAMs for job shop environments. The experimental results show that the evolved DDAMs can make more accurate estimates than other existing dynamic DDAMs with promising reusability. In addition, the evolved operation-based DDAMs show better performance than the evolved DDAMs employing aggregate information of jobs and machines.

Directional selection effects on patterns of phenotypic (co)variation in wild populations.

Science.gov (United States)

Assis, A P A; Patton, J L; Hubbe, A; Marroig, G

2016-11-30

Phenotypic (co)variation is a prerequisite for evolutionary change, and understanding how (co)variation evolves is of crucial importance to the biological sciences. Theoretical models predict that under directional selection, phenotypic (co)variation should evolve in step with the underlying adaptive landscape, increasing the degree of correlation among co-selected traits as well as the amount of genetic variance in the direction of selection. Whether either of these outcomes occurs in natural populations is an open question and thus an important gap in evolutionary theory. Here, we documented changes in the phenotypic (co)variation structure in two separate natural populations in each of two chipmunk species (Tamias alpinus and T. speciosus) undergoing directional selection. In populations where selection was strongest (those of T. alpinus), we observed changes, at least for one population, in phenotypic (co)variation that matched theoretical expectations, namely an increase of both phenotypic integration and (co)variance in the direction of selection and a re-alignment of the major axis of variation with the selection gradient. © 2016 The Author(s).

No evidence of conpopulation sperm precedence between allopatric populations of house mice.

Directory of Open Access Journals (Sweden)

Renée C Firman

Full Text Available Investigations into the evolution of reproductive barriers have traditionally focused on closely related species, and the prevalence of conspecific sperm precedence. The effectiveness of conspecific sperm precedence at limiting gene exchange between species suggests that gametic isolation is an important component of reproductive isolation. However, there is a paucity of tests for evidence of sperm precedence during the earlier stages of divergence, for example among isolated populations. Here, we sourced individuals from two allopatric populations of house mice (Mus domesticus and performed competitive in vitro fertilisation assays to test for conpopulation sperm precedence specifically at the gametic level. We found that ova population origin did not influence the outcome of the sperm competitions, and thus provide no evidence of conpopulation or heteropopulation sperm precedence. Instead, we found that males from a population that had evolved under a high level of postcopulatory sexual selection consistently outcompeted males from a population that had evolved under a relatively lower level of postcopulatory sexual selection. We standardised the number of motile sperm of each competitor across the replicate assays. Our data therefore show that competitive fertilizing success was directly attributable to differences in sperm fertilizing competence.

No evidence of conpopulation sperm precedence between allopatric populations of house mice.

Science.gov (United States)

Firman, Renée C; Simmons, Leigh W

2014-01-01

Investigations into the evolution of reproductive barriers have traditionally focused on closely related species, and the prevalence of conspecific sperm precedence. The effectiveness of conspecific sperm precedence at limiting gene exchange between species suggests that gametic isolation is an important component of reproductive isolation. However, there is a paucity of tests for evidence of sperm precedence during the earlier stages of divergence, for example among isolated populations. Here, we sourced individuals from two allopatric populations of house mice (Mus domesticus) and performed competitive in vitro fertilisation assays to test for conpopulation sperm precedence specifically at the gametic level. We found that ova population origin did not influence the outcome of the sperm competitions, and thus provide no evidence of conpopulation or heteropopulation sperm precedence. Instead, we found that males from a population that had evolved under a high level of postcopulatory sexual selection consistently outcompeted males from a population that had evolved under a relatively lower level of postcopulatory sexual selection. We standardised the number of motile sperm of each competitor across the replicate assays. Our data therefore show that competitive fertilizing success was directly attributable to differences in sperm fertilizing competence.

[Alkylating agents].

Science.gov (United States)

Pourquier, Philippe

2011-11-01

With the approval of mechlorethamine by the FDA in 1949 for the treatment of hematologic malignancies, alkylating agents are the oldest class of anticancer agents. Even though their clinical use is far beyond the use of new targeted therapies, they still occupy a major place in specific indications and sometimes represent the unique option for the treatment of refractory diseases. Here, we are reviewing the major classes of alkylating agents and their mechanism of action, with a particular emphasis for the new generations of alkylating agents. As for most of the chemotherapeutic agents used in the clinic, these compounds are derived from natural sources. With a complex but original mechanism of action, they represent new interesting alternatives for the clinicians, especially for tumors that are resistant to conventional DNA damaging agents. We also briefly describe the different strategies that have been or are currently developed to potentiate the use of classical alkylating agents, especially the inhibition of pathways that are involved in the repair of DNA lesions induced by these agents. In this line, the development of PARP inhibitors is a striking example of the recent regain of interest towards the "old" alkylating agents.

Views on Evolvability of Embedded Systems

NARCIS (Netherlands)

Laar, P. van de; Punter, T.

2011-01-01

Evolvability, the ability to respond effectively to change, represents a major challenge to today's high-end embedded systems, such as those developed in the medical domain by Philips Healthcare. These systems are typically developed by multi-disciplinary teams, located around the world, and are in

Views on evolvability of embedded systems

NARCIS (Netherlands)

Laar, van de P.J.L.J.; Punter, H.T.

2011-01-01

Evolvability, the ability to respond effectively to change, represents a major challenge to today's high-end embedded systems, such as those developed in the medical domain by Philips Healthcare. These systems are typically developed by multi-disciplinary teams, located around the world, and are in

Contrast agent choice for intravenous coronary angiography

International Nuclear Information System (INIS)

Zeman, H.D.; Siddons, D.P.

1989-01-01

The screening of the general population for coronary artery disease would be practical if a method existed for visualizing the extent of occlusion after an intravenous injection of contrast agent. Measurements performed with monochromatic synchrotron radiation x-rays and an iodine containing contrast agent at the Stanford Synchrotron Radiation Laboratory have shown that such an intravenous angiography procedure would be possible with an adequately intense monochromatic x-ray source. Because of the size and cost of synchrotron radiation facilities it would be desirable to make the most efficient use of the intensity available, while reducing as much as possible the radiation dose experienced by the patient. By choosing contrast agents containing elements with a higher atomic number than iodine, it is possible to both improve the image quality and reduce the patient radiation dose, while using the same synchrotron source. By using Si monochromator crystals with a small mosaic spread, it is possible to increase the x-ray flux available for imaging by over an order of magnitude, without any changes in the storage ring or wiggler magnet. The most critical imaging task for intravenous coronary angiography utilizing synchrotron radiation x-rays is visualizing a coronary artery through the left ventricle or aorta which also contains a contrast agent. Calculations have been made of the signal to noise ratio expected for this imaging task for various contrast agents with atomic numbers between that of iodine and bismuth

Fitness costs associated with field-evolved resistance to Bt maize in Spodoptera frugiperda (Lepidoptera: Noctuidae).

Science.gov (United States)

Jakka, S R K; Knight, V R; Jurat-Fuentes, J L

2014-02-01

Increasing adoption of transgenic crops expressing cry toxin genes from Bacillus thuringiensis (Bt crops) represents an augmented risk for development of insect resistance. While fitness costs can greatly influence the rate of resistance evolution, most available data related to Bt resistance have been obtained from laboratory-selected insect strains. In this article, we test the existence of fitness costs associated with high levels of field-evolved resistance to Bt maize event TC1507 in a strain of Spodoptera frugiperda (JE Smith) originated from maize fields in Puerto Rico. Fitness costs in resistant S. frugiperda were evaluated by comparing biological performance to susceptible insects when reared on meridic diet, maize or soybean leaf tissue, or cotton reproductive tissues. Parameters monitored included larval survival, larval and pupal weights, developmental time (larval and pupal), adult longevity, reproductive traits (fecundity and fertility), and sex ratio. We found that all monitored parameters were influenced to a similar extent by the host, independently of susceptibility to Bt maize. The only parameter that significantly differed between strains for all hosts was a longer larval developmental period in resistant S. frugiperda, which resulted in emergence asynchrony between susceptible and resistant adults. To test the relevance of fitness costs in resistant S. frugiperda, we performed a selection experiment to monitor the stability of resistance in a heterogeneous strain through 12 generations of rearing on meridic diet. Our data demonstrate lack of fitness costs relevant to stability of field-evolved resistance to Bt maize and help explain reported stability of field-evolved resistance in Puerto Rican populations of S. frugiperda.

Modeling and clustering users with evolving profiles in usage streams

KAUST Repository

Zhang, Chongsheng; Masseglia, Florent; Zhang, Xiangliang

2012-01-01

Today, there is an increasing need of data stream mining technology to discover important patterns on the fly. Existing data stream models and algorithms commonly assume that users' records or profiles in data streams will not be updated or revised once they arrive. Nevertheless, in various applications such asWeb usage, the records/profiles of the users can evolve along time. This kind of streaming data evolves in two forms, the streaming of tuples or transactions as in the case of traditional data streams, and more importantly, the evolving of user records/profiles inside the streams. Such data streams bring difficulties on modeling and clustering for exploring users' behaviors. In this paper, we propose three models to summarize this kind of data streams, which are the batch model, the Evolving Objects (EO) model and the Dynamic Data Stream (DDS) model. Through creating, updating and deleting user profiles, these models summarize the behaviors of each user as a profile object. Based upon these models, clustering algorithms are employed to discover interesting user groups from the profile objects. We have evaluated all the proposed models on a large real-world data set, showing that the DDS model summarizes the data streams with evolving tuples more efficiently and effectively, and provides better basis for clustering users than the other two models. © 2012 IEEE.

Modeling and clustering users with evolving profiles in usage streams

KAUST Repository

Zhang, Chongsheng

2012-09-01

Today, there is an increasing need of data stream mining technology to discover important patterns on the fly. Existing data stream models and algorithms commonly assume that users\\' records or profiles in data streams will not be updated or revised once they arrive. Nevertheless, in various applications such asWeb usage, the records/profiles of the users can evolve along time. This kind of streaming data evolves in two forms, the streaming of tuples or transactions as in the case of traditional data streams, and more importantly, the evolving of user records/profiles inside the streams. Such data streams bring difficulties on modeling and clustering for exploring users\\' behaviors. In this paper, we propose three models to summarize this kind of data streams, which are the batch model, the Evolving Objects (EO) model and the Dynamic Data Stream (DDS) model. Through creating, updating and deleting user profiles, these models summarize the behaviors of each user as a profile object. Based upon these models, clustering algorithms are employed to discover interesting user groups from the profile objects. We have evaluated all the proposed models on a large real-world data set, showing that the DDS model summarizes the data streams with evolving tuples more efficiently and effectively, and provides better basis for clustering users than the other two models. © 2012 IEEE.

Small molecules as therapy for uveitis: a selected perspective of new and developing agents.

Science.gov (United States)

Pleyer, Uwe; Algharably, Engi Abdel-Hady; Feist, Eugen; Kreutz, Reinhold

2017-09-01

Intraocular inflammation (uveitis) remains a significant burden of legal blindness. Because of its immune mediated and chronic recurrent nature, common therapy includes corticosteroids, disease-modifying anti-rheumatic drugs and more recently biologics as immune modulatory agents. The purpose of this article is to identify the role of new treatment approaches focusing on small molecules as therapeutic option in uveitis. Areas covered: A MEDLINE database search was conducted through February 2017 using the terms 'uveitis' and 'small molecule'. To provide ongoing and future perspectives in treatment options, also clinical trials as registered at ClinicalTrials.gov were included. Both, results from experimental as well as clinical research in this field were included. Since this field is rapidly evolving, a selection of promising agents had to be made. Expert opinion: Small molecules may interfere at different steps of the inflammatory cascade and appear as an interesting option in the treatment algorithm of uveitis. Because of their highly targeted molecular effects and their favorable bioavailability with the potential of topical application small molecules hold great promise. Nevertheless, a careful evaluation of these agents has to be made, since current experience is almost exclusively based on experimental uveitis models and few registered trials.

STFTP: Secure TFTP Protocol for Embedded Multi-Agent Systems Communication

Directory of Open Access Journals (Sweden)

ZAGAR, D.

2013-05-01

Full Text Available Today's embedded systems have evolved into multipurpose devices moving towards an embedded multi-agent system (MAS infrastructure. With the involvement of MAS in embedded systems, one remaining issues is establishing communication between agents in low computational power and low memory embedded systems without present Embedded Operating System (EOS. One solution is the extension of an outdated Trivial File Transfer Protocol (TFTP. The main advantage of using TFTP in embedded systems is the easy implementation. However, the problem at hand is the overall lack of security mechanisms in TFTP. This paper proposes an extension to the existing TFTP in a form of added security mechanisms: STFTP. The authentication is proposed using Digest Access Authentication process whereas the data encryption can be performed by various cryptographic algorithms. The proposal is experimentally tested using two embedded systems based on micro-controller architecture. Communication is analyzed for authentication, data rate and transfer time versus various data encryption ciphers and files sizes. STFTP results in an expected drop in performance, which is in the range of similar encryption algorithms. The system could be improved by using embedded systems of higher computational power or by the use of hardware encryption modules.

On-lattice agent-based simulation of populations of cells within the open-source Chaste framework.

Science.gov (United States)

Figueredo, Grazziela P; Joshi, Tanvi V; Osborne, James M; Byrne, Helen M; Owen, Markus R

2013-04-06

Over the years, agent-based models have been developed that combine cell division and reinforced random walks of cells on a regular lattice, reaction-diffusion equations for nutrients and growth factors; and ordinary differential equations for the subcellular networks regulating the cell cycle. When linked to a vascular layer, this multiple scale model framework has been applied to tumour growth and therapy. Here, we report on the creation of an agent-based multi-scale environment amalgamating the characteristics of these models within a Virtual Physiological Human (VPH) Exemplar Project. This project enables reuse, integration, expansion and sharing of the model and relevant data. The agent-based and reaction-diffusion parts of the multi-scale model have been implemented and are available for download as part of the latest public release of Chaste (Cancer, Heart and Soft Tissue Environment; http://www.cs.ox.ac.uk/chaste/), part of the VPH Toolkit (http://toolkit.vph-noe.eu/). The environment functionalities are verified against the original models, in addition to extra validation of all aspects of the code. In this work, we present the details of the implementation of the agent-based environment, including the system description, the conceptual model, the development of the simulation model and the processes of verification and validation of the simulation results. We explore the potential use of the environment by presenting exemplar applications of the 'what if' scenarios that can easily be studied in the environment. These examples relate to tumour growth, cellular competition for resources and tumour responses to hypoxia (low oxygen levels). We conclude our work by summarizing the future steps for the expansion of the current system.

On-lattice agent-based simulation of populations of cells within the open-source Chaste framework

KAUST Repository

Figueredo, G. P.

2013-02-21

Over the years, agent-based models have been developed that combine cell division and reinforced random walks of cells on a regular lattice, reaction-diffusion equations for nutrients and growth factors; and ordinary differential equations for the subcellular networks regulating the cell cycle. When linked to a vascular layer, this multiple scale model framework has been applied to tumour growth and therapy. Here, we report on the creation of an agent-based multi-scale environment amalgamating the characteristics of these models within a Virtual Physiological Human (VPH) Exemplar Project. This project enables reuse, integration, expansion and sharing of the model and relevant data. The agent-based and reaction-diffusion parts of the multi-scale model have been implemented and are available for download as part of the latest public release of Chaste (Cancer, Heart and Soft Tissue Environment; http://www.cs.ox.ac.uk/chaste/), part of the VPH Toolkit (http://toolkit.vph-noe.eu/). The environment functionalities are verified against the original models, in addition to extra validation of all aspects of the code. In this work, we present the details of the implementation of the agent-based environment, including the system description, the conceptual model, the development of the simulation model and the processes of verification and validation of the simulation results. We explore the potential use of the environment by presenting exemplar applications of the \\'what if\\' scenarios that can easily be studied in the environment. These examples relate to tumour growth, cellular competition for resources and tumour responses to hypoxia (low oxygen levels). We conclude our work by summarizing the future steps for the expansion of the current system.

Risk factors which cause senile cataract evolvement: outline

Directory of Open Access Journals (Sweden)

E.V. Bragin

2018-03-01

Full Text Available Examination of natural ageing processes including those caused by multiple external factors has been attracting re-searchers' attention over the last years. Senile cataract is a multi-factor disease. Expenditure on cataract surgery remain one of the greatest expenses items in public health care. Age is a basic factor which causes senile cataract. Morbidity with cataract doubles each 10 years of life. This outline considers some literature sources which describe research results on influence exerted on cataract evolvement by such risk factors as age, sex, race, smoking, alcohol intake, pancreatic diabetes, intake of certain medications, a number of environmental factors including ultraviolet and ionizing radiation. mane of these factors are shown to increase or reduce senile cataract risk; there are conflicting data on certain factors. The outline also contains quantitative characteristics of cataract risks which are given via odds relation and evolve due to age parameters impacts, alcohol intake, ionizing radiation, etc. The authors also state that still there is no answer to the question whether dose-effect relationship for cataract evolvement is a threshold or non-threshold.

Evolving insights on metabolism, autophagy and epigenetics in liver myofibroblasts

Directory of Open Access Journals (Sweden)

Zeribe Chike Nwosu

2016-06-01

Full Text Available Liver myofibroblasts (MFB are crucial mediators of extracellular matrix (ECM deposition in liver fibrosis. They arise mainly from hepatic stellate cells (HSCs upon a process termed activation. To a lesser extent, and depending on the cause of liver damage, portal fibroblasts, mesothelial cells and fibrocytes may also contribute to the MFB population. Targeting MFB to reduce liver fibrosis is currently an area of intense research. Unfortunately, a clog in the wheel of antifibrotic therapies is the fact that although MFB are known to mediate scar formation, and participate in liver inflammatory response, many of their molecular portraits are currently unknown. In this review, we discuss recent understanding of MFB in health and diseases, focusing specifically on three evolving research fields: metabolism, autophagy and epigenetics. We have emphasized on therapeutic prospects where applicable and mentioned techniques for use in MFB studies. Subsequently, we highlighted uncharted territories in MFB research to help direct future efforts aimed at bridging gaps in current knowledge.

Evolutionary dynamics of division of labor games with selfish agents

Science.gov (United States)

Zhang, Jianlei; Li, Qiaoyu; Zhang, Chunyan

2017-11-01

The division of labor is one of the most basic and widely studied aspects of collective behavior in natural systems. Studies of division of labor are concerned with the integration of the individual worker behavior into a colony level task organization and with the question of how the regulation of the division of labor may contribute to the colony efficiency. This paper investigates the evolution of the division of labor with three strategies by employing the evolutionary game theory. Thus, these available strategies are, respectively, strategy A (performing task A), strategy B (performing task B), and strategy D (not performing any task but only free riding others' contributions). And, two typical networks (i.e., BA scale-free network and lattice network) are employed here for describing the interaction structure among agents. The theoretical analysis together with simulation results reveal that the division of labor can evolve and leads to players that differ in their tendency to take on a given task. The conditions under which the division of labor evolves depend on the costs for performing the task, the benefits led by performing the task, and the interaction structures among the players who are involved with division of labor games.

Estimation of the age-specific per-contact probability of Ebola virus transmission in Liberia using agent-based simulations

Science.gov (United States)

Siettos, Constantinos I.; Anastassopoulou, Cleo; Russo, Lucia; Grigoras, Christos; Mylonakis, Eleftherios

2016-06-01

Based on multiscale agent-based computations we estimated the per-contact probability of transmission by age of the Ebola virus disease (EVD) that swept through Liberia from May 2014 to March 2015. For the approximation of the epidemic dynamics we have developed a detailed agent-based model with small-world interactions between individuals categorized by age. For the estimation of the structure of the evolving contact network as well as the per-contact transmission probabilities by age group we exploited the so called Equation-Free framework. Model parameters were fitted to official case counts reported by the World Health Organization (WHO) as well as to recently published data of key epidemiological variables, such as the mean time to death, recovery and the case fatality rate.

Peripapillary Choroidal Neovascularization Associated with Optic Nerve Head Drusen Treated with Anti-VEGF Agents

Directory of Open Access Journals (Sweden)

Norman A. Saffra

2015-02-01

Full Text Available Optic nerve head drusen can be associated with peripapillary choroidal neovascularization, in both the pediatric and adult population. These membranes can involve the macula, causing significant visual loss. Herein, we present a case that required treatment with an anti-VEGF agent. The patient failed to respond to the initial agent, but subsequently responded to a change of agent. Adult patients with macular degeneration involving peripapillary choroidal neovascularization associated with optic nerve head drusen may require individualized treatment plans.

Occurrence and characterisation of the hydrogen-evolving enzyme in Frankia sp.

Energy Technology Data Exchange (ETDEWEB)

Mohapatra, A.; Leul, M.; Sellstedt, A. [Umeaa Plant Science Centre, Department of Plant Physiology, Umeaa University, S-901 87 Umeaa (Sweden); Sandstroem, G. [Karolinska Institutet, Department of Laboratory Medicine, Division of Clinical Bacteriology, Karelinska University Hospital, Huddinge, S-141 86 Stockholm (Sweden)

2006-09-15

An increase in hydrogen evolution from the hydrogen-evolving enzyme in the actinomycete Frankia was recorded in the presence of nickel. Immunogold localisation analysis of the intracellular distribution of hydrogenase proteins indicated that they were evenly distributed in the membranes and cytosol of both hyphae and vesicles. In addition, molecular characterisation of the hydrogen-evolving enzyme at the proteomic level, using two-dimensional gel electrophoresis combined with mass spectrometry, confirmed that the Frankia hydrogen-evolving enzyme is similar to the cyanobacterial bidirectional hydrogenase of Anabena siamensis. (author)

Modeling the 2014 Ebola Virus Epidemic - Agent-Based Simulations, Temporal Analysis and Future Predictions for Liberia and Sierra Leone.

Science.gov (United States)

Siettos, Constantinos; Anastassopoulou, Cleo; Russo, Lucia; Grigoras, Christos; Mylonakis, Eleftherios

2015-03-09

We developed an agent-based model to investigate the epidemic dynamics of Ebola virus disease (EVD) in Liberia and Sierra Leone from May 27 to December 21, 2014. The dynamics of the agent-based simulator evolve on small-world transmission networks of sizes equal to the population of each country, with adjustable densities to account for the effects of public health intervention policies and individual behavioral responses to the evolving epidemic. Based on time series of the official case counts from the World Health Organization (WHO), we provide estimates for key epidemiological variables by employing the so-called Equation-Free approach. The underlying transmission networks were characterized by rather random structures in the two countries with densities decreasing by ~19% from the early (May 27-early August) to the last period (mid October-December 21). Our estimates for the values of key epidemiological variables, such as the mean time to death, recovery and the case fatality rate, are very close to the ones reported by the WHO Ebola response team during the early period of the epidemic (until September 14) that were calculated based on clinical data. Specifically, regarding the effective reproductive number Re, our analysis suggests that until mid October, Re was above 2.3 in both countries; from mid October to December 21, Re dropped well below unity in Liberia, indicating a saturation of the epidemic, while in Sierra Leone it was around 1.9, indicating an ongoing epidemic. Accordingly, a ten-week projection from December 21 estimated that the epidemic will fade out in Liberia in early March; in contrast, our results flashed a note of caution for Sierra Leone since the cumulative number of cases could reach as high as 18,000, and the number of deaths might exceed 5,000, by early March 2015. However, by processing the reported data of the very last period (December 21, 2014-January 18, 2015), we obtained more optimistic estimates indicative of a remission of

Evolution of networks for body plan patterning; interplay of modularity, robustness and evolvability.

Directory of Open Access Journals (Sweden)

Kirsten H Ten Tusscher

2011-10-01

Full Text Available A major goal of evolutionary developmental biology (evo-devo is to understand how multicellular body plans of increasing complexity have evolved, and how the corresponding developmental programs are genetically encoded. It has been repeatedly argued that key to the evolution of increased body plan complexity is the modularity of the underlying developmental gene regulatory networks (GRNs. This modularity is considered essential for network robustness and evolvability. In our opinion, these ideas, appealing as they may sound, have not been sufficiently tested. Here we use computer simulations to study the evolution of GRNs' underlying body plan patterning. We select for body plan segmentation and differentiation, as these are considered to be major innovations in metazoan evolution. To allow modular networks to evolve, we independently select for segmentation and differentiation. We study both the occurrence and relation of robustness, evolvability and modularity of evolved networks. Interestingly, we observed two distinct evolutionary strategies to evolve a segmented, differentiated body plan. In the first strategy, first segments and then differentiation domains evolve (SF strategy. In the second scenario segments and domains evolve simultaneously (SS strategy. We demonstrate that under indirect selection for robustness the SF strategy becomes dominant. In addition, as a byproduct of this larger robustness, the SF strategy is also more evolvable. Finally, using a combined functional and architectural approach, we determine network modularity. We find that while SS networks generate segments and domains in an integrated manner, SF networks use largely independent modules to produce segments and domains. Surprisingly, we find that widely used, purely architectural methods for determining network modularity completely fail to establish this higher modularity of SF networks. Finally, we observe that, as a free side effect of evolving segmentation

EVOLVING AN EMPIRICAL METHODOLOGY DOR DETERMINING ...

African Journals Online (AJOL)

The uniqueness of this approach, is that it can be applied to any forest or dynamic feature on the earth, and can enjoy universal application as well. KEY WORDS: Evolving empirical methodology, innovative mathematical model, appropriate interval, remote sensing, forest environment planning and management. Global Jnl ...

EVOLVE : a Bridge between Probability, Set Oriented Numerics, and Evolutionary Computation II

CERN Document Server

Coello, Carlos; Tantar, Alexandru-Adrian; Tantar, Emilia; Bouvry, Pascal; Moral, Pierre; Legrand, Pierrick; EVOLVE 2012

2013-01-01

This book comprises a selection of papers from the EVOLVE 2012 held in Mexico City, Mexico. The aim of the EVOLVE is to build a bridge between probability, set oriented numerics and evolutionary computing, as to identify new common and challenging research aspects. The conference is also intended to foster a growing interest for robust and efficient methods with a sound theoretical background. EVOLVE is intended to unify theory-inspired methods and cutting-edge techniques ensuring performance guarantee factors. By gathering researchers with different backgrounds, a unified view and vocabulary can emerge where the theoretical advancements may echo in different domains. Summarizing, the EVOLVE focuses on challenging aspects arising at the passage from theory to new paradigms and aims to provide a unified view while raising questions related to reliability,  performance guarantees and modeling. The papers of the EVOLVE 2012 make a contribution to this goal. 

Intractable hiccups due to herpetic esophagitis in an immunocompromised patient

Directory of Open Access Journals (Sweden)

John Harris

2016-01-01

This case illustrates an exceptionally rare presentation of herpetic esophagitis in an immunocompromised host. As novel immunotherapeutic/suppressive agents continue to emerge, the evolving role of herpes virus prophylaxis and diagnosis of atypical presentations in new host populations is a topic of growing importance.

Evolving Systems: An Outcome of Fondest Hopes and Wildest Dreams

Science.gov (United States)

Frost, Susan A.; Balas, Mark J.

2012-01-01

New theory is presented for evolving systems, which are autonomously controlled subsystems that self-assemble into a new evolved system with a higher purpose. Evolving systems of aerospace structures often require additional control when assembling to maintain stability during the entire evolution process. This is the concept of Adaptive Key Component Control that operates through one specific component to maintain stability during the evolution. In addition, this control must often overcome persistent disturbances that occur while the evolution is in progress. Theoretical results will be presented for Adaptive Key Component control for persistent disturbance rejection. An illustrative example will demonstrate the Adaptive Key Component controller on a system composed of rigid body and flexible body modes.

Experimental evolution reveals differences between phenotypic and evolutionary responses to population density.

Science.gov (United States)

McNamara, K B; Simmons, L W

2017-09-01

Group living can select for increased immunity, given the heightened risk of parasite transmission. Yet, it also may select for increased male reproductive investment, given the elevated risk of female multiple mating. Trade-offs between immunity and reproduction are well documented. Phenotypically, population density mediates both reproductive investment and immune function in the Indian meal moth, Plodia interpunctella. However, the evolutionary response of populations to these traits is unknown. We created two replicated populations of P. interpunctella, reared and mated for 14 generations under high or low population densities. These population densities cause plastic responses in immunity and reproduction: at higher numbers, both sexes invest more in one index of immunity [phenoloxidase (PO) activity] and males invest more in sperm. Interestingly, our data revealed divergence in PO and reproduction in a different direction to previously reported phenotypic responses. Males evolving at low population densities transferred more sperm, and both males and females displayed higher PO than individuals at high population densities. These positively correlated responses to selection suggest no apparent evolutionary trade-off between immunity and reproduction. We speculate that the reduced PO activity and sperm investment when evolving under high population density may be due to the reduced population fitness predicted under increased sexual conflict and/or to trade-offs between pre- and post-copulatory traits. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

The Itch-Producing Agents Histamine and Cowhage Activate Separate Populations of Primate Spinothalamic Tract Neurons

Science.gov (United States)

Davidson, Steve; Zhang, Xijing; Yoon, Chul H.; Khasabov, Sergey G.; Simone, Donald A.; Giesler, Glenn J.

2010-01-01

Itch is an everyday sensation, but when associated with disease or infection it can be chronic and debilitating. Several forms of itch can be blocked using antihistamines, but others cannot and these constitute an important clinical problem. Little information is available on the mechanisms underlying itch that is produced by nonhistaminergic mechanisms. We examined the responses of spinothalamic tract neurons to histaminergic and, for the first time, nonhistaminergic forms of itch stimuli. Fifty-seven primate spinothalamic tract (STT) neurons were identified using antidromic activation techniques and examined for their responses to histamine and cowhage, the nonhistaminergic itch-producing spicules covering the pod of the legume Mucuna pruriens. Each examined neuron had a receptive field on the hairy skin of the hindlimb and responded to noxious mechanical stimulation. STT neurons were tested with both pruritogens applied in a random order and we found 12 that responded to histamine and seven to cowhage. Each pruritogen-responsive STT neuron was activated by the chemical algogen capsaicin and two-thirds responded to noxious heat stimuli, demonstrating that these neurons convey chemical, thermal, and mechanical nociceptive information as well. Histamine or cowhage responsive STT neurons were found in both the marginal zone and the deep dorsal horn and were classified as high threshold and wide dynamic range. Unexpectedly, histamine and cowhage never activated the same cell. Our results demonstrate that the spinothalamic tract contains mutually exclusive populations of neurons responsive to histamine or the nonhistaminergic itch-producing agent cowhage. PMID:17855615

Incorporating BDI Agents into Human-Agent Decision Making Research

Science.gov (United States)

Kamphorst, Bart; van Wissen, Arlette; Dignum, Virginia

Artificial agents, people, institutes and societies all have the ability to make decisions. Decision making as a research area therefore involves a broad spectrum of sciences, ranging from Artificial Intelligence to economics to psychology. The Colored Trails (CT) framework is designed to aid researchers in all fields in examining decision making processes. It is developed both to study interaction between multiple actors (humans or software agents) in a dynamic environment, and to study and model the decision making of these actors. However, agents in the current implementation of CT lack the explanatory power to help understand the reasoning processes involved in decision making. The BDI paradigm that has been proposed in the agent research area to describe rational agents, enables the specification of agents that reason in abstract concepts such as beliefs, goals, plans and events. In this paper, we present CTAPL: an extension to CT that allows BDI software agents that are written in the practical agent programming language 2APL to reason about and interact with a CT environment.

Whole genome duplication affects evolvability of flowering time in an autotetraploid plant.

Directory of Open Access Journals (Sweden)

Sara L Martin

Full Text Available Whole genome duplications have occurred recurrently throughout the evolutionary history of eukaryotes. The resulting genetic and phenotypic changes can influence physiological and ecological responses to the environment; however, the impact of genome copy number on evolvability has rarely been examined experimentally. Here, we evaluate the effect of genome duplication on the ability to respond to selection for early flowering time in lines drawn from naturally occurring diploid and autotetraploid populations of the plant Chamerion angustifolium (fireweed. We contrast this with the result of four generations of selection on synthesized neoautotetraploids, whose genic variability is similar to diploids but genome copy number is similar to autotetraploids. In addition, we examine correlated responses to selection in all three groups. Diploid and both extant tetraploid and neoautotetraploid lines responded to selection with significant reductions in time to flowering. Evolvability, measured as realized heritability, was significantly lower in extant tetraploids (^b(T =  0.31 than diploids (^b(T =  0.40. Neotetraploids exhibited the highest evolutionary response (^b(T  =  0.55. The rapid shift in flowering time in neotetraploids was associated with an increase in phenotypic variability across generations, but not with change in genome size or phenotypic correlations among traits. Our results suggest that whole genome duplications, without hybridization, may initially alter evolutionary rate, and that the dynamic nature of neoautopolyploids may contribute to the prevalence of polyploidy throughout eukaryotes.

Chemical warfare agents.

Science.gov (United States)

Kuca, Kamil; Pohanka, Miroslav

2010-01-01

Chemical warfare agents are compounds of different chemical structures. Simple molecules such as chlorine as well as complex structures such as ricin belong to this group. Nerve agents, vesicants, incapacitating agents, blood agents, lung-damaging agents, riot-control agents and several toxins are among chemical warfare agents. Although the use of these compounds is strictly prohibited, the possible misuse by terrorist groups is a reality nowadays. Owing to this fact, knowledge of the basic properties of these substances is of a high importance. This chapter briefly introduces the separate groups of chemical warfare agents together with their members and the potential therapy that should be applied in case someone is intoxicated by these agents.

Mutually catalyzed birth of population and assets in exchange-driven growth

Science.gov (United States)

Lin, Zhenquan; Ke, Jianhong; Ye, Gaoxiang

2006-10-01

We propose an exchange-driven aggregation growth model of population and assets with mutually catalyzed birth to study the interaction between the population and assets in their exchange-driven processes. In this model, monomer (or equivalently, individual) exchange occurs between any pair of aggregates of the same species (population or assets). The rate kernels of the exchanges of population and assets are K(k,l)=Kkl and L(k,l)=Lkl , respectively, at which one monomer migrates from an aggregate of size k to another of size l . Meanwhile, an aggregate of one species can yield a new monomer by the catalysis of an arbitrary aggregate of the other species. The rate kernel of asset-catalyzed population birth is I(k,l)=Iklμ [and that of population-catalyzed asset birth is J(k,l)=Jklν ], at which an aggregate of size k gains a monomer birth when it meets a catalyst aggregate of size l . The kinetic behaviors of the population and asset aggregates are solved based on the rate equations. The evolution of the aggregate size distributions of population and assets is found to fall into one of three categories for different parameters μ and ν : (i) population (asset) aggregates evolve according to the conventional scaling form in the case of μ⩽0 (ν⩽0) , (ii) population (asset) aggregates evolve according to a modified scaling form in the case of ν=0 and μ>0 ( μ=0 and ν>0 ), and (iii) both population and asset aggregates undergo gelation transitions at a finite time in the case of μ=ν>0 .

Evolving Procurement Organizations

DEFF Research Database (Denmark)

Bals, Lydia; Laiho, Aki; Laine, Jari

Procurement has to find further levers and advance its contribution to corporate goals continuously. This places pressure on its organization in order to facilitate its performance. Therefore, Procurement organizations constantly have to evolve in order to match these demands. A conceptual model...... is presented and results of a first case study discussed. The findings highlight the importance of taking a contingency perspective on Procurement organization, understanding the internal and internal contingency factors. From a theoretical perspective, it opens up insights that can be furthermore leveraged...... in future studies in the fields of hybrid procurement organizations, global sourcing organizations as well as international procurement offices (IPOs). From a practical standpoint, an assessment of external and internal contingencies provides the opportunity to consciously match organization to its...

Logics for Intelligent Agents and Multi-Agent Systems

NARCIS (Netherlands)

Meyer, John-Jules Charles

2014-01-01

This chapter presents the history of the application of logic in a quite popular paradigm in contemporary computer science and artificial intelligence, viz. the area of intelligent agents and multi-agent systems. In particular we discuss the logics that have been used to specify single agents, the

Genome-wide analysis of allele frequency change in sunflower crop-wild hybrid populations evolving under natural conditions

Science.gov (United States)

Hybridization is known to occur between cultivated and wild populations of numerous plant species. This represents a major mechanism by which a wild population’s genetic structure and evolutionary dynamics could be altered. Studying crop-derived alleles in wild populations is also relevant to assess...

Is cascade reinforcement likely when sympatric and allopatric populations exchange migrants?

Science.gov (United States)

Yukilevich, Roman; Aoki, Fumio

2016-04-01

When partially reproductively isolated species come back into secondary contact, these taxa may diverge in mating preferences and sexual cues to avoid maladaptive hybridization, a process known as reinforcement. This phenomenon often leads to reproductive character displacement (RCD) between sympatric and allopatric populations of reinforcing species that differ in their exposure to hybridization. Recent discussions have reinvigorated the idea that RCD may give rise to additional speciation between conspecific sympatric and allopatric populations, dubbing the concept "cascade reinforcement." Despite some empirical studies supporting cascade reinforcement, we still know very little about the conditions for its evolution. In the present article, we address this question by developing an individual-based population genetic model that explicitly simulates cascade reinforcement when one of the hybridizing species is split into sympatric and allopatric populations. Our results show that when sympatric and allopatric populations reside in the same environment and only differ in their exposure to maladaptive hybridization, migration between them generally inhibits the evolution of cascade by spreading the reinforcement alleles from sympatry into allopatry and erasing RCD. Under these conditions, cascade reinforcement only evolved when migration rate between sympatric and allopatric populations was very low. This indicates that stabilizing sexual selection in allopatry is generally ineffective in preventing the spread of reinforcement alleles. Only when sympatric and allopatric populations experienced divergent ecological selection did cascade reinforcement evolve in the presence of substantial migration. These predictions clarify the conditions for cascade reinforcement and facilitate our understanding of existing cases in nature.

Biological Agents

Science.gov (United States)

... E-Tools Safety and Health Topics / Biological Agents Biological Agents This page requires that javascript be enabled ... 202) 693-2300 if additional assistance is required. Biological Agents Menu Overview In Focus: Ebola Frederick A. ...

Accelerated Distributed Dual Averaging Over Evolving Networks of Growing Connectivity

Science.gov (United States)

Liu, Sijia; Chen, Pin-Yu; Hero, Alfred O.

2018-04-01

We consider the problem of accelerating distributed optimization in multi-agent networks by sequentially adding edges. Specifically, we extend the distributed dual averaging (DDA) subgradient algorithm to evolving networks of growing connectivity and analyze the corresponding improvement in convergence rate. It is known that the convergence rate of DDA is influenced by the algebraic connectivity of the underlying network, where better connectivity leads to faster convergence. However, the impact of network topology design on the convergence rate of DDA has not been fully understood. In this paper, we begin by designing network topologies via edge selection and scheduling. For edge selection, we determine the best set of candidate edges that achieves the optimal tradeoff between the growth of network connectivity and the usage of network resources. The dynamics of network evolution is then incurred by edge scheduling. Further, we provide a tractable approach to analyze the improvement in the convergence rate of DDA induced by the growth of network connectivity. Our analysis reveals the connection between network topology design and the convergence rate of DDA, and provides quantitative evaluation of DDA acceleration for distributed optimization that is absent in the existing analysis. Lastly, numerical experiments show that DDA can be significantly accelerated using a sequence of well-designed networks, and our theoretical predictions are well matched to its empirical convergence behavior.

Profiling the Buzz Agent: Product Referral and the Study of Social Community and Brand Attachment

Directory of Open Access Journals (Sweden)

Danny Pimentel Claro

2015-04-01

Full Text Available The buzz agent is any consumer perceived by others as a source of product referral. Previous literature in word of mouth (WOM has looked into characteristics of individuals who successfully persuade others to choose a brand. While there have been studies in this field, the literature is still scattered and little has been done to profile the consumer playing the buzz-agent role. We aim to deepen our understanding about the consumer who must be recruited as a buzz agent by a firm in a WOM marketing (WOMM initiative. The proposed profile is comprised of three key characteristics: the consumer’s position in the social community, nature of ties in the community and brand attachment. We tested our hypotheses with a survey of 542 consumers from a controlled population. Rather than relying on self-reported questions about referral behavior, we asked respondents in the population to name the individuals to whom the respondents go to obtain information to help pick a brand. This accurately pinpoints which individuals fit the profile of a buzz agent. Results show that buzz agents are popular in their social community (friends and tech experts, carry dissimilar brands as target consumers and are product experts. Our study identifies a profile of consumers that helps firms select buzz agents for WOMM initiatives.

Quantum condensation from a tailored exciton population in a microcavity

International Nuclear Information System (INIS)

Eastham, P. R.; Phillips, R. T.

2009-01-01

An experiment is proposed on the coherent quantum dynamics of a semiconductor microcavity containing quantum dots. Modeling the experiment using a generalized Dicke model, we show that a tailored excitation pulse can create an energy-dependent population of excitons, which subsequently evolves to a quantum condensate of excitons and photons. The population is created by a generalization of adiabatic rapid passage and then condenses due to a dynamical analog of the BCS instability.

Cosmic Biology How Life Could Evolve on Other Worlds

CERN Document Server

Irwin, Louis Neil

2011-01-01

It is very unlikely that little green humanoids are living on Mars. But what are the possible life forms that might exist in our Solar System and how might they have evolved? This uniquely authoritative and imaginative book on the possibilties for alien life addresses the intrinsic interest that we have about life on other worlds - reinforcing some of our assumptions and reshaping others. It introduces new possibilties that will enlarge our understanding of the issue overall, in particular the enormous range of environments and planetary conditions within which life might evolve. Cosmic Biology -discusses a broad range of possible environments where alien life might have evolved; -explains why carbon-based, water-borne life is more likely that its alternatives, but is not the only possiblity; -applies the principles of planetary science and modern biology to evolutionary scenarios on other worlds; -looks at the future fates of living systems, including those on Earth.

Efficacy of antidotes (midazolam, atropine and HI-6) on nerve agent induced molecular and neuropathological changes

OpenAIRE

RamaRao, Golime; Afley, Prachiti; Acharya, Jyothiranjan; Bhattacharya, Bijoy Krishna

2014-01-01

Background Recent alleged attacks with nerve agent sarin on civilians in Syria indicate their potential threat to both civilian and military population. Acute nerve agent exposure can cause rapid death or leads to multiple and long term neurological effects. The biochemical changes that occur following nerve agent exposure needs to be elucidated to understand the mechanisms behind their long term neurological effects and to design better therapeutic drugs to block their multiple neurotoxic ef...

Treatment with different fining agents of white musts from spoiled wine grapes

Directory of Open Access Journals (Sweden)

Eric Meistermann

2018-03-01

Full Text Available Fining agents have evolved significantly over the last twenty years. The need for winemakers to have objective references about the new products has prompted this study. The experiment consists in comparing the new fining products (charcoal, pea proteins, derivatives of chitin and composite products generally mixing PVPP + various proteins + bentonite with reference products such as casein and PVPP and with non-treated controls. Fining agents were applied during clarification of 15 different musts obtained from wine grapes affected by different degrees and types of rot: fresh and dry Botrytis cinerea rot, powdery mildew and Botrytis contaminated with other fungi (Aspergillus, Penicillium, Basidiomycetes, giving the bunches offflavours that were earthy and resembled fresh mushrooms. This study highlights the importance of good clarification of musts. The quality of control wines, without any treatment, increases with the clarity of the must. In most experiments, clarification of the must around 50 Nephelometric Turbidity Units (NTU can eliminate or reduce any organoleptic defects in wine without fining. Use of pectolytic enzymes may be necessary in order to reach this level of clarity. The new allergen-free fining agents have the same effectiveness as reference products such as casein and polyvinylpolypyrolidone (PVPP. Composite products are more efficient than pea protein alone and less than products including charcoal. However, the improvement of aromatic quality goes hand in hand with loss of body and persistence.

Contrast agent choice for intravenous coronary angiography

International Nuclear Information System (INIS)

Zeman, H.D.; Siddons, D.P.

1990-01-01

The screening of the general population for coronary artery disease would be practical if a method existed for visualizing the extent of occlusion after an intravenous injection of contrast agent. Measurements performed with monochromatic synchrotron radiation X-rays and an iodine-containing contrast agent at the Stanford Synchrotron Radiation Laboratory have shown that such an intravenous angiography procedure would be possible with an adequately intense monochromatic X-ray source. Because of the size and cost of synchrotron radiation facilities it would be desirable to make the most efficient use of the intensity available, while reducing as much as possible the radiation dose experienced by the patient. By choosing contrast agents containing elements with a higher atomic number than iodine, it is possible to both improve the image quality and reduce the patient radiation dose, while using the same synchrotron radiation source. By using Si monochromator crystals with a small mosaic spread, it is possible to increase the X-ray flux available for imaging by over an order of magnitude, without any changes in the storage ring or wiggler magnet. The most critical imaging task for intravenous coronary angiography utilizing synchrotron radiation X-rays is visualizing a coronary artery through the left ventricle or aorta which also contain contrast agent. Calculations have been made of the signal to noise ratio expected for this imaging task for various contrast agents with atomic numbers between that of iodine and bismuth. The X-ray energy spectrum of the X-17 superconduction wiggler beam line at the National Synchrotron Light Source at Brookhaven National Laboratory has been used for these calculations. Both perfect Si crystals and Si crystals with a small mosaic spread are considered as monochromators. Contrast agents containing Gd or Yb seem to have about the optimal calculated signal to noise ratio. (orig./HSI)

The influence of persuasion in opinion formation and polarization

Science.gov (United States)

La Rocca, C. E.; Braunstein, L. A.; Vazquez, F.

2014-05-01

We present a model that explores the influence of persuasion in a population of agents with positive and negative opinion orientations. The opinion of each agent is represented by an integer number k that expresses its level of agreement on a given issue, from totally against k=-M to totally in favor k = M. Same-orientation agents persuade each other with probability p, becoming more extreme, while opposite-orientation agents become more moderate as they reach a compromise with probability q. The population initially evolves to (a) a polarized state for r=p/q\\gt 1 , where opinions' distribution is peaked at the extreme values k=+/- M , or (b) a centralized state for r < 1, with most opinions around k=+/- 1 . When r \\gg 1 , polarization lasts for a time that diverges as r^M \\ln N , where N is the population's size. Finally, an extremist consensus (k = M or -M ) is reached in a time that scales as r^{-1} for r \\ll 1 .

WSC-07: Evolving the Web Services Challenge

NARCIS (Netherlands)

Blake, M. Brian; Cheung, William K.W.; Jaeger, Michael C.; Wombacher, Andreas

Service-oriented architecture (SOA) is an evolving architectural paradigm where businesses can expose their capabilities as modular, network-accessible software services. By decomposing capabilities into modular services, organizations can share their offerings at multiple levels of granularity

Parameter Estimates in Differential Equation Models for Population Growth

Science.gov (United States)

Winkel, Brian J.

2011-01-01

We estimate the parameters present in several differential equation models of population growth, specifically logistic growth models and two-species competition models. We discuss student-evolved strategies and offer "Mathematica" code for a gradient search approach. We use historical (1930s) data from microbial studies of the Russian biologist,…

Quantitation of MRI sensitivity to quasi-monodisperse microbubble contrast agents for spatially resolved manometry.

Science.gov (United States)

Bencsik, Martin; Al-Rwaili, Amgad; Morris, Robert; Fairhurst, David J; Mundell, Victoria; Cave, Gareth; McKendry, Jonathan; Evans, Stephen

2013-11-01

The direct in-vivo measurement of fluid pressure cannot be achieved with MRI unless it is done with the contribution of a contrast agent. No such contrast agents are currently available commercially, whilst those demonstrated previously only produced qualitative results due to their broad size distribution. Our aim is to quantitate then model the MR sensitivity to the presence of quasi-monodisperse microbubble populations. Lipid stabilised microbubble populations with mean radius 1.2 ± 0.8 μm have been produced by mechanical agitation. Contrast agents with increasing volume fraction of bubbles up to 4% were formed and the contribution the bubbles bring to the relaxation rate was quantitated. A periodic pressure change was also continuously applied to the same contrast agent, until MR signal changes were only due to bubble radius change and not due to a change in bubble density. The MR data compared favourably with the prediction of an improved numerical simulation. An excellent MR sensitivity of 23 % bar(-1) has been demonstrated. This work opens up the possibility of generating microbubble preparations tailored to specific applications with optimised MR sensitivity, in particular MRI based in-vivo manometry. Copyright © 2012 Wiley Periodicals, Inc.

(N+1)-dimensional Lorentzian evolving wormholes supported by polytropic matter

Energy Technology Data Exchange (ETDEWEB)

Cataldo, Mauricio [Universidad del Bio-Bio, Departamento de Fisica, Facultad de Ciencias, Concepcion (Chile); Arostica, Fernanda; Bahamonde, Sebastian [Universidad de Concepcion, Departamento de Fisica, Concepcion (Chile)

2013-08-15

In this paper we study (N+1)-dimensional evolving wormholes supported by energy satisfying a polytropic equation of state. The considered evolving wormhole models are described by a constant redshift function and generalizes the standard flat Friedmann-Robertson-Walker spacetime. The polytropic equation of state allows us to consider in (3+1)-dimensions generalizations of the phantom energy and the generalized Chaplygin gas sources. (orig.)

A standard protocol for describing individual-based and agent-based models

Science.gov (United States)

Grimm, Volker; Berger, Uta; Bastiansen, Finn; Eliassen, Sigrunn; Ginot, Vincent; Giske, Jarl; Goss-Custard, John; Grand, Tamara; Heinz, Simone K.; Huse, Geir; Huth, Andreas; Jepsen, Jane U.; Jorgensen, Christian; Mooij, Wolf M.; Muller, Birgit; Pe'er, Guy; Piou, Cyril; Railsback, Steven F.; Robbins, Andrew M.; Robbins, Martha M.; Rossmanith, Eva; Ruger, Nadja; Strand, Espen; Souissi, Sami; Stillman, Richard A.; Vabo, Rune; Visser, Ute; DeAngelis, Donald L.

2006-01-01

Simulation models that describe autonomous individual organisms (individual based models, IBM) or agents (agent-based models, ABM) have become a widely used tool, not only in ecology, but also in many other disciplines dealing with complex systems made up of autonomous entities. However, there is no standard protocol for describing such simulation models, which can make them difficult to understand and to duplicate. This paper presents a proposed standard protocol, ODD, for describing IBMs and ABMs, developed and tested by 28 modellers who cover a wide range of fields within ecology. This protocol consists of three blocks (Overview, Design concepts, and Details), which are subdivided into seven elements: Purpose, State variables and scales, Process overview and scheduling, Design concepts, Initialization, Input, and Submodels. We explain which aspects of a model should be described in each element, and we present an example to illustrate the protocol in use. In addition, 19 examples are available in an Online Appendix. We consider ODD as a first step for establishing a more detailed common format of the description of IBMs and ABMs. Once initiated, the protocol will hopefully evolve as it becomes used by a sufficiently large proportion of modellers.

Evolving NASA's Earth Science Data Systems

Science.gov (United States)

Walter, J.; Behnke, J.; Murphy, K. J.; Lowe, D. R.

2013-12-01

NASA's Earth Science Data and Information System Project (ESDIS) is charged with managing, maintaining, and evolving NASA's Earth Observing System Data and Information System (EOSDIS) and is responsible for processing, archiving, and distributing NASA Earth science data. The system supports a multitude of missions and serves diverse science research and other user communities. Keeping up with ever-changing information technology and figuring out how to leverage those changes across such a large system in order to continuously improve and meet the needs of a diverse user community is a significant challenge. Maintaining and evolving the system architecture and infrastructure is a continuous and multi-layered effort. It requires a balance between a "top down" management paradigm that provides a coherent system view and maintaining the managerial, technological, and functional independence of the individual system elements. This presentation will describe some of the key elements of the current system architecture, some of the strategies and processes we employ to meet these challenges, current and future challenges, and some ideas for meeting those challenges.

How Large Asexual Populations Adapt

Science.gov (United States)

Desai, Michael

2007-03-01

We often think of beneficial mutations as being rare, and of adaptation as a sequence of selected substitutions: a beneficial mutation occurs, spreads through a population in a selective sweep, then later another beneficial mutation occurs, and so on. This simple picture is the basis for much of our intuition about adaptive evolution, and underlies a number of practical techniques for analyzing sequence data. Yet many large and mostly asexual populations -- including a wide variety of unicellular organisms and viruses -- live in a very different world. In these populations, beneficial mutations are common, and frequently interfere or cooperate with one another as they all attempt to sweep simultaneously. This radically changes the way these populations adapt: rather than an orderly sequence of selective sweeps, evolution is a constant swarm of competing and interfering mutations. I will describe some aspects of these dynamics, including why large asexual populations cannot evolve very quickly and the character of the diversity they maintain. I will explain how this changes our expectations of sequence data, how sex can help a population adapt, and the potential role of ``mutator'' phenotypes with abnormally high mutation rates. Finally, I will discuss comparisons of these predictions with evolution experiments in laboratory yeast populations.

Field-Evolved Resistance to Bt Maize by Western Corn Rootworm

Science.gov (United States)

Gassmann, Aaron J.; Petzold-Maxwell, Jennifer L.; Keweshan, Ryan S.; Dunbar, Mike W.

2011-01-01

Background Crops engineered to produce insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) are planted on millions of hectares annually, reducing the use of conventional insecticides and suppressing pests. However, the evolution of resistance could cut short these benefits. A primary pest targeted by Bt maize in the United States is the western corn rootworm Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae). Methodology/Principal Findings We report that fields identified by farmers as having severe rootworm feeding injury to Bt maize contained populations of western corn rootworm that displayed significantly higher survival on Cry3Bb1 maize in laboratory bioassays than did western corn rootworm from fields not associated with such feeding injury. In all cases, fields experiencing severe rootworm feeding contained Cry3Bb1 maize. Interviews with farmers indicated that Cry3Bb1 maize had been grown in those fields for at least three consecutive years. There was a significant positive correlation between the number of years Cry3Bb1 maize had been grown in a field and the survival of rootworm populations on Cry3Bb1 maize in bioassays. However, there was no significant correlation among populations for survival on Cry34/35Ab1 maize and Cry3Bb1 maize, suggesting a lack of cross resistance between these Bt toxins. Conclusions/Significance This is the first report of field-evolved resistance to a Bt toxin by the western corn rootworm and by any species of Coleoptera. Insufficient planting of refuges and non-recessive inheritance of resistance may have contributed to resistance. These results suggest that improvements in resistance management and a more integrated approach to the use of Bt crops may be necessary. PMID:21829470

Sex determination: ways to evolve a hermaphrodite.

OpenAIRE

Braendle , Christian; Félix , Marie-Anne

2006-01-01

Most species of the nematode genus Caenorhabditis reproduce through males and females; C. elegans and C. briggsae, however, produce self-fertile hermaphrodites instead of females. These transitions to hermaphroditism evolved convergently through distinct modifications of germline sex determination mechanisms.

A model for ultrasound contrast agent in a phantom vessel

KAUST Repository

Qamar, Adnan

2014-02-01

A theoretical framework to model the dynamics of Ultrasound Contrast Agent (UCA) inside a phantom vessel is presented. The model is derived from the reduced Navier-Stokes equation and is coupled with the evolving flow field solution inside the vessel by a similarity transformation approach. The results are computed, and compared with experiments available in literature, for the initial UCA radius of Ro=1.5 μm and 2 μm for the vessel diameter of D=12 μm and 200 μm with the acoustic parameters as utilized in the experiments. When compared to other models, better agreement on smaller vessel diameter is obtained with the proposed coupled model. The model also predicts, quite accurately, bubble fragmentation in terms of acoustic and geometric parameters. © 2014 IEEE.

Sperm should evolve to make female meiosis fair.

Science.gov (United States)

Brandvain, Yaniv; Coop, Graham

2015-04-01

Genomic conflicts arise when an allele gains an evolutionary advantage at a cost to organismal fitness. Oögenesis is inherently susceptible to such conflicts because alleles compete for inclusion into the egg. Alleles that distort meiosis in their favor (i.e., meiotic drivers) often decrease organismal fitness, and therefore indirectly favor the evolution of mechanisms to suppress meiotic drive. In this light, many facets of oögenesis and gametogenesis have been interpreted as mechanisms of protection against genomic outlaws. That females of many animal species do not complete meiosis until after fertilization, appears to run counter to this interpretation, because this delay provides an opportunity for sperm-acting alleles to meddle with the outcome of female meiosis and help like alleles drive in heterozygous females. Contrary to this perceived danger, the population genetic theory presented herein suggests that, in fact, sperm nearly always evolve to increase the fairness of female meiosis in the face of genomic conflicts. These results are consistent with the apparent sperm dependence of the best characterized female meiotic driversin animals. Rather than providing an opportunity for sperm collaboration in female meiotic drive, the "fertilization requirement" indirectly protects females from meiotic drivers by providing sperm an opportunity to suppress drive. © 2015 The Author(s).

Sperm should evolve to make female meiosis fair

Science.gov (United States)

Brandvain, Yaniv; Coop, Graham

2017-01-01

Genomic conflicts arise when an allele gains an evolutionary advantage at a cost to organismal fitness. Oögenesis is inherently susceptible to such conflicts because alleles compete for inclusion into the egg. Alleles that distort meiosis in their favor (i.e. meiotic drivers) often decrease organismal fitness, and therefore indirectly favor the evolution of mechanisms to suppress meiotic drive. In this light, many facets of oögenesis and gametogenesis have been interpreted as mechanisms of protection against genomic outlaws. That females of many animal species do not complete meiosis until after fertilization, appears to run counter to this interpretation, because this delay provides an opportunity for sperm-acting alleles to meddle with the outcome of female meiosis and help like alleles drive in heterozygous females. Contrary to this perceived danger, the population genetic theory presented herein suggests that, in fact, sperm nearly always evolve to increase the fairness of female meiosis in the face of genomic conflicts. These results are consistent with the apparent sperm dependence of the best characterized female meiotic drivers in animals. Rather than providing an opportunity for sperm collaboration in female meiotic drive, the ‘fertilization requirement’ indirectly protects females from meiotic drivers by providing sperm an opportunity to suppress drive. PMID:25662355

Biodiversity and ecosystem functioning in evolving food webs.

Science.gov (United States)

Allhoff, K T; Drossel, B

2016-05-19

We use computer simulations in order to study the interplay between biodiversity and ecosystem functioning (BEF) during both the formation and the ongoing evolution of large food webs. A species in our model is characterized by its own body mass, its preferred prey body mass and the width of its potential prey body mass spectrum. On an ecological time scale, population dynamics determines which species are viable and which ones go extinct. On an evolutionary time scale, new species emerge as modifications of existing ones. The network structure thus emerges and evolves in a self-organized manner. We analyse the relation between functional diversity and five community level measures of ecosystem functioning. These are the metabolic loss of the predator community, the total biomasses of the basal and the predator community, and the consumption rates on the basal community and within the predator community. Clear BEF relations are observed during the initial build-up of the networks, or when parameters are varied, causing bottom-up or top-down effects. However, ecosystem functioning measures fluctuate only very little during long-term evolution under constant environmental conditions, despite changes in functional diversity. This result supports the hypothesis that trophic cascades are weaker in more complex food webs. © 2016 The Author(s).

Probability distributions in conservative energy exchange models of multiple interacting agents

International Nuclear Information System (INIS)

Scafetta, Nicola; West, Bruce J

2007-01-01

Herein we study energy exchange models of multiple interacting agents that conserve energy in each interaction. The models differ regarding the rules that regulate the energy exchange and boundary effects. We find a variety of stochastic behaviours that manifest energy equilibrium probability distributions of different types and interaction rules that yield not only the exponential distributions such as the familiar Maxwell-Boltzmann-Gibbs distribution of an elastically colliding ideal particle gas, but also uniform distributions, truncated exponential distributions, Gaussian distributions, Gamma distributions, inverse power law distributions, mixed exponential and inverse power law distributions, and evolving distributions. This wide variety of distributions should be of value in determining the underlying mechanisms generating the statistical properties of complex phenomena including those to be found in complex chemical reactions

Contrast agents for cardiac angiography: effects of a nonionic agent vs. a standard ionic agent

International Nuclear Information System (INIS)

Bettmann, M.A.; Bourdillon, P.D.; Barry, W.H.; Brush, K.A.; Levin, D.C.

1984-01-01

The effects on cardiac hemodynamics and of a standard contrast agent, sodium methylglucamine diatrizoate [Renografin 76] were compared with the effects of a new nonionic agent (iohexol) in a double-blind study in 51 patietns undergoing coronary angiography and left ventriculography. No significant alteration in measured blood parameters occurred with either contrast agent. Hemodynamic changes occurred with both, but were significantly greater with the standard renografin than with the low-osmolality, nonionic iohexol. After left ventriculography, heart rate increased and peripheral arterial pressure fell with both agents, but less with iohexol. It is concluded that iohexol causes less alteration in cardiac function than does the agent currently most widely used. Nonionic contrast material is likely to improve the safety of coronary angiography, particularly in those patients at greatest risk

Satcom access in the Evolved Packet Core

NARCIS (Netherlands)

Cano Soveri, M.D.; Norp, A.H.J.; Popova, M.P.

2011-01-01

Satellite communications (Satcom) networks are increasingly integrating with terrestrial communications networks, namely Next Generation Networks (NGN). In the area of NGN the Evolved Packet Core (EPC) is a new network architecture that can support multiple access technologies. When Satcom is

Satcom access in the evolved packet core

NARCIS (Netherlands)

Cano, M.D.; Norp, A.H.J.; Popova, M.P.

2012-01-01

Satellite communications (Satcom) networks are increasingly integrating with terrestrial communications networks, namely Next Generation Networks (NGN). In the area of NGN the Evolved Packet Core (EPC) is a new network architecture that can support multiple access technologies. When Satcom is

A population study of killer viruses reveals different evolutionary histories of two closely related Saccharomyces sensu stricto yeasts.

Science.gov (United States)

Chang, Shang-Lin; Leu, Jun-Yi; Chang, Tien-Hsien

2015-08-01

Microbes have evolved ways of interference competition to gain advantage over their ecological competitors. The use of secreted killer toxins by yeast cells through acquiring double-stranded RNA viruses is one such prominent example. Although the killer behaviour has been well studied in laboratory yeast strains, our knowledge regarding how killer viruses are spread and maintained in nature and how yeast cells co-evolve with viruses remains limited. We investigated these issues using a panel of 81 yeast populations belonging to three Saccharomyces sensu stricto species isolated from diverse ecological niches and geographic locations. We found that killer strains are rare among all three species. In contrast, killer toxin resistance is widespread in Saccharomyces paradoxus populations, but not in Saccharomyces cerevisiae or Saccharomyces eubayanus populations. Genetic analyses revealed that toxin resistance in S. paradoxus is often caused by dominant alleles that have independently evolved in different populations. Molecular typing identified one M28 and two types of M1 killer viruses in those killer strains. We further showed that killer viruses of the same type could lead to distinct killer phenotypes under different host backgrounds, suggesting co-evolution between the viruses and hosts in different populations. Taken together, our data suggest that killer viruses vary in their evolutionary histories even within closely related yeast species. © 2015 John Wiley & Sons Ltd.

Sales of veterinary antibacterial agents in nine European countries during 2005-09: trends and patterns.

Science.gov (United States)

Grave, Kari; Greko, Christina; Kvaale, Mari K; Torren-Edo, Jordi; Mackay, David; Muller, Arno; Moulin, Gerard

2012-12-01

To identify trends and patterns of sales of veterinary antimicrobial agents in nine European countries during 2005-09 in order to document the situation. Existing sales data, in tonnes of active ingredients, of veterinary antimicrobial agents by class were collected from nine European countries in a standardized manner for the years 2005-09 (one country for 2006-09). A population correction unit (PCU) is introduced as a proxy for the animal population potentially treated with antimicrobial agents. The sales data are expressed as mg of active substance/PCU. Data coverage was reported to be 98%-100% for the nine countries. Overall, sales of veterinary antimicrobials agents, in mg/PCU, declined during the reporting period in the nine countries. Substantial differences in the sales patterns and in the magnitude of sales of veterinary antimicrobial agents, expressed as mg/PCU, between the nine countries are observed. The major classes sold were penicillins, sulphonamides and tetracyclines. The sales accounted for by the various veterinary antimicrobial agents have changed substantially for most countries. An increase in the sales of third- and fourth-generation cephalosporins and fluoroquinolones were observed for the majority of the countries. Through re-analysis of existing data by application of a harmonized approach, an overall picture of the trends in the sales of veterinary antimicrobial agents in the nine countries was obtained. Notable differences in trends in sales between the countries were observed. Further studies, preferably including data by animal species, are needed to understand the factors that explain these observations.

Shared Bacterial and Viral Respiratory Agents in Bighorn Sheep (Ovis canadensis, Domestic Sheep (Ovis aries, and Goats (Capra hircus in Montana

Directory of Open Access Journals (Sweden)

David S. Miller

2011-01-01

Full Text Available Transmission of infectious agents from livestock reservoirs has been hypothesized to cause respiratory disease outbreaks in bighorn sheep (Ovis canadensis, and land management policies intended to limit this transmission have proven controversial. This cross-sectional study compares the infectious agents present in multiple populations of bighorn sheep near to and distant from their interface with domestic sheep (O. aries and domestic goat (Capra hircus and provides critical baseline information needed for interpretations of cross-species transmission risks. Bighorn sheep and livestock shared exposure to Pasteurellaceae, viral, and endoparasite agents. In contrast, although the impact is uncertain, Mycoplasma sp. was isolated from livestock but not bighorn sheep. These results may be the result of historic cross-species transmission of agents that has resulted in a mosaic of endemic and exotic agents. Future work using longitudinal and multiple population comparisons is needed to rigorously establish the risk of outbreaks from cross-species transmission of infectious agents.

Shared bacterial and viral respiratory agents in bighorn sheep (Ovis canadensis), domestic sheep (Ovis aries), and goats (Capra hircus) in Montana

Science.gov (United States)

Miller, David S.; Weiser, Glen C.; Aune, Keith; Roeder, Brent; Atkinson, Mark; Anderson, Neil; Roffe, Thomas J.; Keating, Kim A.; Chapman, Phillip L.; Kimberling, Cleon; Rhyan, Jack C.; Clarke, P. Ryan

2011-01-01

Transmission of infectious agents from livestock reservoirs has been hypothesized to cause respiratory disease outbreaks in bighorn sheep (Ovis canadensis), and land management policies intended to limit this transmission have proven controversial. This cross-sectional study compares the infectious agents present in multiple populations of bighorn sheep near to and distant from their interface with domestic sheep (O. aries) and domestic goat (Capra hircus) and provides critical baseline information needed for interpretations of cross-species transmission risks. Bighorn sheep and livestock shared exposure to Pasteurellaceae, viral, and endoparasite agents. In contrast, although the impact is uncertain, Mycoplasma sp. was isolated from livestock but not bighorn sheep. These results may be the result of historic cross-species transmission of agents that has resulted in a mosaic of endemic and exotic agents. Future work using longitudinal and multiple population comparisons is needed to rigorously establish the risk of outbreaks from cross-species transmission of infectious agents.

Real-time evolvable pulse shaper for radiation measurements

Energy Technology Data Exchange (ETDEWEB)

Lanchares, Juan, E-mail: julandan@dacya.ucm.es [Facultad de Informática, Universidad Complutense de Madrid (UCM), C/Prof. José García Santesmases s/n, 28040 Madrid (Spain); Garnica, Oscar, E-mail: ogarnica@dacya.ucm.es [Facultad de Informática, Universidad Complutense de Madrid (UCM), C/Prof. José García Santesmases s/n, 28040 Madrid (Spain); Risco-Martín, José L., E-mail: jlrisco@dacya.ucm.es [Facultad de Informática, Universidad Complutense de Madrid (UCM), C/Prof. José García Santesmases s/n, 28040 Madrid (Spain); Ignacio Hidalgo, J., E-mail: hidalgo@dacya.ucm.es [Facultad de Informática, Universidad Complutense de Madrid (UCM), C/Prof. José García Santesmases s/n, 28040 Madrid (Spain); Regadío, Alberto, E-mail: alberto.regadio@insa.es [Área de Tecnologías Electrónicas, Instituto Nacional de Técnica Aeroespacial (INTA), 28850 Torrejón de Ardoz, Madrid (Spain)

2013-11-01

In the last two decades, recursive algorithms for real-time digital pulse shaping in pulse height measurements have been developed and published in number of articles and textbooks. All these algorithms try to synthesize in real time optimum or near optimum shapes in the presence of noise. Even though some of these shapers can be considered effective designs, some side effects like aging cannot be ignored. We may observe that after sensors degradation, the signal obtained is not valid. In this regard, we present in this paper a novel technique that, based on evolvable hardware concepts, is able to evolve the degenerated shaper into a new design with better performance than the original one under the new sensor features.

Additive genetic variance in polyandry enables its evolution, but polyandry is unlikely to evolve through sexy or good sperm processes.

Science.gov (United States)

Travers, L M; Simmons, L W; Garcia-Gonzalez, F

2016-05-01

Polyandry is widespread despite its costs. The sexually selected sperm hypotheses ('sexy' and 'good' sperm) posit that sperm competition plays a role in the evolution of polyandry. Two poorly studied assumptions of these hypotheses are the presence of additive genetic variance in polyandry and sperm competitiveness. Using a quantitative genetic breeding design in a natural population of Drosophila melanogaster, we first established the potential for polyandry to respond to selection. We then investigated whether polyandry can evolve through sexually selected sperm processes. We measured lifetime polyandry and offensive sperm competitiveness (P2 ) while controlling for sampling variance due to male × male × female interactions. We also measured additive genetic variance in egg-to-adult viability and controlled for its effect on P2 estimates. Female lifetime polyandry showed significant and substantial additive genetic variance and evolvability. In contrast, we found little genetic variance or evolvability in P2 or egg-to-adult viability. Additive genetic variance in polyandry highlights its potential to respond to selection. However, the low levels of genetic variance in sperm competitiveness suggest that the evolution of polyandry may not be driven by sexy sperm or good sperm processes. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Genetic variability, local selection and demographic history: genomic evidence of evolving towards allopatric speciation in Asian seabass.

Science.gov (United States)

Wang, Le; Wan, Zi Yi; Lim, Huan Sein; Yue, Gen Hua

2016-08-01

Genomewide analysis of genetic divergence is critically important in understanding the genetic processes of allopatric speciation. We sequenced RAD tags of 131 Asian seabass individuals of six populations from South-East Asia and Australia/Papua New Guinea. Using 32 433 SNPs, we examined the genetic diversity and patterns of population differentiation across all the populations. We found significant evidence of genetic heterogeneity between South-East Asian and Australian/Papua New Guinean populations. The Australian/Papua New Guinean populations showed a rather lower level of genetic diversity. FST and principal components analysis revealed striking divergence between South-East Asian and Australian/Papua New Guinean populations. Interestingly, no evidence of contemporary gene flow was observed. The demographic history was further tested based on the folded joint site frequency spectrum. The scenario of ancient migration with historical population size changes was suggested to be the best fit model to explain the genetic divergence of Asian seabass between South-East Asia and Australia/Papua New Guinea. This scenario also revealed that Australian/Papua New Guinean populations were founded by ancestors from South-East Asia during mid-Pleistocene and were completely isolated from the ancestral population after the last glacial retreat. We also detected footprints of local selection, which might be related to differential ecological adaptation. The ancient gene flow was examined and deemed likely insufficient to counteract the genetic differentiation caused by genetic drift. The observed genomic pattern of divergence conflicted with the 'genomic islands' scenario. Altogether, Asian seabass have likely been evolving towards allopatric speciation since the split from the ancestral population during mid-Pleistocene. © 2016 John Wiley & Sons Ltd.

Climate change, transgenic corn adoption and field-evolved resistance in corn earworm.

Science.gov (United States)

Venugopal, P Dilip; Dively, Galen P

2017-06-01

Increased temperature anomaly during the twenty-first century coincides with the proliferation of transgenic crops containing the bacterium Bacillus thuringiensis (Berliner) (Bt) to express insecticidal Cry proteins. Increasing temperatures profoundly affect insect life histories and agricultural pest management. However, the implications of climate change on Bt crop-pest interactions and insect resistance to Bt crops remains unexamined. We analysed the relationship of temperature anomaly and Bt adoption with field-evolved resistance to Cry1Ab Bt sweet corn in a major pest, Helicoverpa zea (Boddie). Increased Bt adoption during 1996-2016 suppressed H. zea populations, but increased temperature anomaly buffers population reduction. Temperature anomaly and its interaction with elevated selection pressure from high Bt acreage probably accelerated the Bt-resistance development. Helicoverpa zea damage to corn ears, kernel area consumed, mean instars and proportion of late instars in Bt varieties increased with Bt adoption and temperature anomaly, through additive or interactive effects. Risk of Bt-resistant H. zea spreading is high given extensive Bt adoption, and the expected increase in overwintering and migration. Our study highlights the challenges posed by climate change for Bt biotechnology-based agricultural pest management, and the need to incorporate evolutionary processes affected by climate change into Bt-resistance management programmes.

Screening of Anti-Obesity Agent from Herbal Mixtures

Directory of Open Access Journals (Sweden)

Sung-Kee Jo

2012-03-01

Full Text Available Globally, one in three of the World’s adults are overweight and one in 10 is obese. By 2015, World Health Organization (WHO estimates the number of chubby adults will balloon to 2.3 billion—Equal to the combined populations of China, Europe and the United States. The discovery of bioactive compounds from herbs is one possible way to control obesity and to prevent or reduce the risks of developing various obesity-related diseases. In this study, we screened anti-obesity agents such as methyl gallate from the herbal composition known as HemoHIM that actively inhibits lipid formation as evidenced by Oil Red O staining and triglyceride (TG contents in 3T3-L1 adipocytes, suggesting their use as an anti-obesity agent. Furthermore, the amount of glycerol released from cells into the medium had increased by treatment of methyl gallate in a concentration-dependent manner. The present study suggests that a promising anti-obesity agent like methyl gallate might be of therapeutic interest for the treatment of obesity.

Screening of anti-obesity agent from herbal mixtures.

Science.gov (United States)

Roh, Changhyun; Jung, Uhee; Jo, Sung-Kee

2012-03-23

Globally, one in three of the World's adults are overweight and one in 10 is obese. By 2015, World Health Organization (WHO) estimates the number of chubby adults will balloon to 2.3 billion--Equal to the combined populations of China, Europe and the United States. The discovery of bioactive compounds from herbs is one possible way to control obesity and to prevent or reduce the risks of developing various obesity-related diseases. In this study, we screened anti-obesity agents such as methyl gallate from the herbal composition known as HemoHIM that actively inhibits lipid formation as evidenced by Oil Red O staining and triglyceride (TG) contents in 3T3-L1 adipocytes, suggesting their use as an anti-obesity agent. Furthermore, the amount of glycerol released from cells into the medium had increased by treatment of methyl gallate in a concentration-dependent manner. The present study suggests that a promising anti-obesity agent like methyl gallate might be of therapeutic interest for the treatment of obesity.

Genome sequence of Yersinia pestis, the causative agent of plague.

Science.gov (United States)

Parkhill, J; Wren, B W; Thomson, N R; Titball, R W; Holden, M T; Prentice, M B; Sebaihia, M; James, K D; Churcher, C; Mungall, K L; Baker, S; Basham, D; Bentley, S D; Brooks, K; Cerdeño-Tárraga, A M; Chillingworth, T; Cronin, A; Davies, R M; Davis, P; Dougan, G; Feltwell, T; Hamlin, N; Holroyd, S; Jagels, K; Karlyshev, A V; Leather, S; Moule, S; Oyston, P C; Quail, M; Rutherford, K; Simmonds, M; Skelton, J; Stevens, K; Whitehead, S; Barrell, B G

2001-10-04

The Gram-negative bacterium Yersinia pestis is the causative agent of the systemic invasive infectious disease classically referred to as plague, and has been responsible for three human pandemics: the Justinian plague (sixth to eighth centuries), the Black Death (fourteenth to nineteenth centuries) and modern plague (nineteenth century to the present day). The recent identification of strains resistant to multiple drugs and the potential use of Y. pestis as an agent of biological warfare mean that plague still poses a threat to human health. Here we report the complete genome sequence of Y. pestis strain CO92, consisting of a 4.65-megabase (Mb) chromosome and three plasmids of 96.2 kilobases (kb), 70.3 kb and 9.6 kb. The genome is unusually rich in insertion sequences and displays anomalies in GC base-composition bias, indicating frequent intragenomic recombination. Many genes seem to have been acquired from other bacteria and viruses (including adhesins, secretion systems and insecticidal toxins). The genome contains around 150 pseudogenes, many of which are remnants of a redundant enteropathogenic lifestyle. The evidence of ongoing genome fluidity, expansion and decay suggests Y. pestis is a pathogen that has undergone large-scale genetic flux and provides a unique insight into the ways in which new and highly virulent pathogens evolve.

Limit cycles and the benefits of a short memory in rock-paper-scissors games

Science.gov (United States)

Burridge, James

2015-10-01

When playing games in groups, it is an advantage for individuals to have accurate statistical information on the strategies of their opponents. Such information may be obtained by remembering previous interactions. We consider a rock-paper-scissors game in which agents are able to recall their last m interactions, used to estimate the behavior of their opponents. At critical memory length, a Hopf bifurcation leads to the formation of stable limit cycles. In a mixed population, agents with longer memories have an advantage, provided the system has a stable fixed point, and there is some asymmetry in the payoffs of the pure strategies. However, at a critical concentration of long memory agents, the appearance of limit cycles destroys their advantage. By introducing population dynamics that favors successful agents, we show that the system evolves toward the bifurcation point.

Limit cycles and the benefits of a short memory in rock-paper-scissors games.

Science.gov (United States)

Burridge, James

2015-10-01

When playing games in groups, it is an advantage for individuals to have accurate statistical information on the strategies of their opponents. Such information may be obtained by remembering previous interactions. We consider a rock-paper-scissors game in which agents are able to recall their last m interactions, used to estimate the behavior of their opponents. At critical memory length, a Hopf bifurcation leads to the formation of stable limit cycles. In a mixed population, agents with longer memories have an advantage, provided the system has a stable fixed point, and there is some asymmetry in the payoffs of the pure strategies. However, at a critical concentration of long memory agents, the appearance of limit cycles destroys their advantage. By introducing population dynamics that favors successful agents, we show that the system evolves toward the bifurcation point.

Sextant: Visualizing time-evolving linked geospatial data

NARCIS (Netherlands)

C. Nikolaou (Charalampos); K. Dogani (Kallirroi); K. Bereta (Konstantina); G. Garbis (George); M. Karpathiotakis (Manos); K. Kyzirakos (Konstantinos); M. Koubarakis (Manolis)

2015-01-01

textabstractThe linked open data cloud is constantly evolving as datasets get continuously updated with newer versions. As a result, representing, querying, and visualizing the temporal dimension of linked data is crucial. This is especially important for geospatial datasets that form the backbone

A Composite Agent Architecture for Multi-Agent Simulations

OpenAIRE

VanPutte, Michael; Osborn, Brian; Hiles, John

2002-01-01

CGF Computer Generated Forces and Behavioral Representation The MOVES Institute’s Computer-Generated Autonomy Group has focused on a research goal of modeling complex and adaptive behavior while at the same time making the behavior easier to create and control. This research has led to several techniques for agent construction, that includes a social and organization relationship management engine, a composite agent architecture, an agent goal apparatus, a structure for capturi...

TACtic- A Multi Behavioral Agent for Trading Agent Competition

Science.gov (United States)

Khosravi, Hassan; Shiri, Mohammad E.; Khosravi, Hamid; Iranmanesh, Ehsan; Davoodi, Alireza

Software agents are increasingly being used to represent humans in online auctions. Such agents have the advantages of being able to systematically monitor a wide variety of auctions and then make rapid decisions about what bids to place in what auctions. They can do this continuously and repetitively without losing concentration. To provide a means of evaluating and comparing (benchmarking) research methods in this area the trading agent competition (TAC) was established. This paper describes the design, of TACtic. Our agent uses multi behavioral techniques at the heart of its decision making to make bidding decisions in the face of uncertainty, to make predictions about the likely outcomes of auctions, and to alter the agent's bidding strategy in response to the prevailing market conditions.

Repeated evolution of fungal cultivar specificity in independently evolved ant-plant-fungus symbioses.

Science.gov (United States)

Blatrix, Rumsaïs; Debaud, Sarah; Salas-Lopez, Alex; Born, Céline; Benoit, Laure; McKey, Doyle B; Attéké, Christiane; Djiéto-Lordon, Champlain

2013-01-01

Some tropical plant species possess hollow structures (domatia) occupied by ants that protect the plant and in some cases also provide it with nutrients. Most plant-ants tend patches of chaetothyrialean fungi within domatia. In a few systems it has been shown that the ants manure the fungal patches and use them as a food source, indicating agricultural practices. However, the identity of these fungi has been investigated only in a few samples. To examine the specificity and constancy of ant-plant-fungus interactions we characterised the content of fungal patches in an extensive sampling of three ant-plant symbioses (Petalomyrmex phylax/Leonardoxa africana subsp. africana, Aphomomyrmex afer/Leonardoxa africana subsp. letouzeyi and Tetraponera aethiops/Barteria fistulosa) by sequencing the Internal Transcribed Spacers of ribosomal DNA. For each system the content of fungal patches was constant over individuals and populations. Each symbiosis was associated with a specific, dominant, primary fungal taxon, and to a lesser extent, with one or two specific secondary taxa, all of the order Chaetothyriales. A single fungal patch sometimes contained both a primary and a secondary taxon. In one system, two founding queens were found with the primary fungal taxon only, one that was shown in a previous study to be consumed preferentially. Because the different ant-plant symbioses studied have evolved independently, the high specificity and constancy we observed in the composition of the fungal patches have evolved repeatedly. Specificity and constancy also characterize other cases of agriculture by insects.

The Role of Implicit Motives in Strategic Decision-Making: Computational Models of Motivated Learning and the Evolution of Motivated Agents

Directory of Open Access Journals (Sweden)

Kathryn Merrick

2015-11-01

Full Text Available Individual behavioral differences in humans have been linked to measurable differences in their mental activities, including differences in their implicit motives. In humans, individual differences in the strength of motives such as power, achievement and affiliation have been shown to have a significant impact on behavior in social dilemma games and during other kinds of strategic interactions. This paper presents agent-based computational models of power-, achievement- and affiliation-motivated individuals engaged in game-play. The first model captures learning by motivated agents during strategic interactions. The second model captures the evolution of a society of motivated agents. It is demonstrated that misperception, when it is a result of motivation, causes agents with different motives to play a given game differently. When motivated agents who misperceive a game are present in a population, higher explicit payoff can result for the population as a whole. The implications of these results are discussed, both for modeling human behavior and for designing artificial agents with certain salient behavioral characteristics.

Nonlinear Dynamics in Gene Regulation Promote Robustness and Evolvability of Gene Expression Levels.

Science.gov (United States)

Steinacher, Arno; Bates, Declan G; Akman, Ozgur E; Soyer, Orkun S

2016-01-01

Cellular phenotypes underpinned by regulatory networks need to respond to evolutionary pressures to allow adaptation, but at the same time be robust to perturbations. This creates a conflict in which mutations affecting regulatory networks must both generate variance but also be tolerated at the phenotype level. Here, we perform mathematical analyses and simulations of regulatory networks to better understand the potential trade-off between robustness and evolvability. Examining the phenotypic effects of mutations, we find an inverse correlation between robustness and evolvability that breaks only with nonlinearity in the network dynamics, through the creation of regions presenting sudden changes in phenotype with small changes in genotype. For genotypes embedding low levels of nonlinearity, robustness and evolvability correlate negatively and almost perfectly. By contrast, genotypes embedding nonlinear dynamics allow expression levels to be robust to small perturbations, while generating high diversity (evolvability) under larger perturbations. Thus, nonlinearity breaks the robustness-evolvability trade-off in gene expression levels by allowing disparate responses to different mutations. Using analytical derivations of robustness and system sensitivity, we show that these findings extend to a large class of gene regulatory network architectures and also hold for experimentally observed parameter regimes. Further, the effect of nonlinearity on the robustness-evolvability trade-off is ensured as long as key parameters of the system display specific relations irrespective of their absolute values. We find that within this parameter regime genotypes display low and noisy expression levels. Examining the phenotypic effects of mutations, we find an inverse correlation between robustness and evolvability that breaks only with nonlinearity in the network dynamics. Our results provide a possible solution to the robustness-evolvability trade-off, suggest an explanation for

Nonlinear Dynamics in Gene Regulation Promote Robustness and Evolvability of Gene Expression Levels.

Directory of Open Access Journals (Sweden)

Arno Steinacher

Full Text Available Cellular phenotypes underpinned by regulatory networks need to respond to evolutionary pressures to allow adaptation, but at the same time be robust to perturbations. This creates a conflict in which mutations affecting regulatory networks must both generate variance but also be tolerated at the phenotype level. Here, we perform mathematical analyses and simulations of regulatory networks to better understand the potential trade-off between robustness and evolvability. Examining the phenotypic effects of mutations, we find an inverse correlation between robustness and evolvability that breaks only with nonlinearity in the network dynamics, through the creation of regions presenting sudden changes in phenotype with small changes in genotype. For genotypes embedding low levels of nonlinearity, robustness and evolvability correlate negatively and almost perfectly. By contrast, genotypes embedding nonlinear dynamics allow expression levels to be robust to small perturbations, while generating high diversity (evolvability under larger perturbations. Thus, nonlinearity breaks the robustness-evolvability trade-off in gene expression levels by allowing disparate responses to different mutations. Using analytical derivations of robustness and system sensitivity, we show that these findings extend to a large class of gene regulatory network architectures and also hold for experimentally observed parameter regimes. Further, the effect of nonlinearity on the robustness-evolvability trade-off is ensured as long as key parameters of the system display specific relations irrespective of their absolute values. We find that within this parameter regime genotypes display low and noisy expression levels. Examining the phenotypic effects of mutations, we find an inverse correlation between robustness and evolvability that breaks only with nonlinearity in the network dynamics. Our results provide a possible solution to the robustness-evolvability trade-off, suggest

Evolving perspectives on caribou population dynamics, have we got it right yet?

Directory of Open Access Journals (Sweden)

A.T. Bergerud

1996-01-01

Full Text Available The roles of food, weather and predation are compared between sedentary and migratory caribou herds. Sedentary herds disperse (space out at calving time while the cows of migratory herds move in masse (space away to calving grounds to reduce predation risk. The sedentary ecotype calves on ranges near open water if tree cover is present or in rugged topography in the absence of tree cover. The migratory ecotype aggregates on calving grounds located on alpine mountain plateaus or on the tundra north of the Arctic tree line. The two herds with the greatest densities in North America, the sedentary Slate Islands Herd and the migratory George River Herd both had changes in abundance that followed summer food problems. The hypothesis that winter lichen supplies determine abundance and set the carrying capacity is rejected. Lichens are not a necessary food for caribou. A review of the mortality of young calves documented in the past 30 years provides no support for the hypothesis that hypothermia is a common mortality problem. Young calves documented can be born inviable at birth if their dams are severely malnourished. The migratory caribou in North America reached peak numbers in the 1980s after wolf populations were heavily harvested in the 1970s. The sedentary ecotype is frequently regulated by wolf predation that affects both recruitment (R and the mortality of adults (M. The balance between R/M schedules commonly occurs when R (calves represents, about 15% of the herd and when numbers (prorated to the area of the dispersed annual range approximate 0.06 caribou/km2. Population limitation of migratory herds by predation has occurred in the NWT and in several herds in Alaska but only when wolf densities were > 6.5/1000 km2. Wolf predation halted the growth of the George River Herd in 1980 but then wolves contracted rabies and the herd again increased and degraded spring/summer ranges. The reduced summer phytomass resulted in lower birth rates and

Deducing the multi-trader population driving a financial market

Science.gov (United States)

Gupta, Nachi; Hauser, Raphael; Johnson, Neil

2005-12-01

We have previously laid out a basic framework for predicting financial movements and pockets of predictability by tracking the distribution of a multi-trader population playing on an artificial financial market model. This work explores extensions to this basic framework. We allow for more intelligent agents with a richer strategy set, and we no longer constrain the distribution over these agents to a probability space. We then introduce a fusion scheme which accounts for multiple runs of randomly chosen sets of possible agent types. We also discuss a mechanism for bias removal on the estimates.

Diversity Generation in Evolving Microbial Populations

DEFF Research Database (Denmark)

Markussen, Trine

Pseudomonas aeruginosa infections in the airways of patients with cystic fibrosis (CF) offer opportunities to study bacterial evolution and adaptation in natural environments. Significantly phenotypic and genomic changes of P. aeruginosa have been observed during chronic infection. While P. aeruginosa...... bacterial genome sequencing, phenotypic profiling and unique sampling materials which included clonal bacterial isolates sampled for more than 4 decades from chronically infected CF patients, we were able to investigate the diversity generation of the clinical important and highly successful P. aeruginosa...... DK1 clone type during chronic airway infection in CF patients. We show here that diversification of P. aeruginosa DK1 occurs through the emergence of coexisting subpopulations with distinct phenotypic and genomic features and demonstrate that this diversification was a result of niche specialization...

Mechanism of action of direct-acting antiviral agents in treatment of chronic hepatitis C

Directory of Open Access Journals (Sweden)

WEN Xiaoyu

2016-09-01

Full Text Available With the development and launch of direct-acting antiviral agents (DAAs in the world in recent years, therapeutic regimens for chronic hepatitis C are constantly evolving. DAAs will also be launched in China in the near future. DAAs mainly target at the non-structural proteins of HCV and can inhibit HCV RNA replication. This article introduces the targets, mechanism of action, and resistance characteristics of different DAAs, as well as their current research and development in China and the results of phase Ⅲ clinical studies, in order to provide a reference for combined therapeutic strategies with DAAs in the treatment for chronic hepatitis C.

Learning in a game context: strategy choice by some keeps learning from evolving in others.

Science.gov (United States)

Dubois, Frédérique; Morand-Ferron, Julie; Giraldeau, Luc-Alain

2010-12-07

Behavioural decisions in a social context commonly have frequency-dependent outcomes and so require analysis using evolutionary game theory. Learning provides a mechanism for tracking changing conditions and it has frequently been predicted to supplant fixed behaviour in shifting environments; yet few studies have examined the evolution of learning specifically in a game-theoretic context. We present a model that examines the evolution of learning in a frequency-dependent context created by a producer-scrounger game, where producers search for their own resources and scroungers usurp the discoveries of producers. We ask whether a learning mutant that can optimize its use of producer and scrounger to local conditions can invade a population of non-learning individuals that play producer and scrounger with fixed probabilities. We find that learning provides an initial advantage but never evolves to fixation. Once a stable equilibrium is attained, the population is always made up of a majority of fixed players and a minority of learning individuals. This result is robust to variation in the initial proportion of fixed individuals, the rate of within- and between-generation environmental change, and population size. Such learning polymorphisms will manifest themselves in a wide range of contexts, providing an important element leading to behavioural syndromes.

Continual Learning through Evolvable Neural Turing Machines

DEFF Research Database (Denmark)

Lüders, Benno; Schläger, Mikkel; Risi, Sebastian

2016-01-01

Continual learning, i.e. the ability to sequentially learn tasks without catastrophic forgetting of previously learned ones, is an important open challenge in machine learning. In this paper we take a step in this direction by showing that the recently proposed Evolving Neural Turing Machine (ENTM...

Dentists' approach to patients on anti-platelet agents and warfarin: a survey of practice.

LENUS (Irish Health Repository)

Murphy, James

2010-04-23

In everyday practice, dentists are confronted with the dilemma of patients on anti-platelet agents and warfarin who require invasive dental procedures and, more pertinently, dental extractions. There may be a divergence of opinion among dentists regarding how they manage these patients. AIMS: To assess general dental practitioners\\' approach to the management of patients taking anti-platelet agents and\\/or warfarin who are undergoing invasive dental procedures. METHODS AND DATA: A semi-structured questionnaire was designed to survey general dental practitioners in a large Irish urban area. RESULTS: A response rate of 89% was achieved in a study population of 54 general dental practitioners. A total of 25% of respondents who carry out extractions on warfarinised patients do not check the INR prior to invasive dental procedures. Some 90% of respondents stop anti-platelet agents prior to extractions. CONCLUSIONS: A significant proportion of respondents fail to check warfarinised patients\\' INR prior to invasive dental procedures. Furthermore, a trend of stopping anti-platelet agents was noted, which is in contrast with current recommendations in the dental literature. Certain practices in this small study population proved alarming and highlight the need for improved awareness of current guidelines. A further large-scale study may be justified, as variation in practice may have clinical and medico-legal repercussions.

The combination of novel targeted molecular agents and radiation in the treatment of pediatric gliomas

Directory of Open Access Journals (Sweden)

Tina eDasgupta

2013-05-01

Full Text Available Brain tumors are the most common solid pediatric malignancy. For high-grade, recurrent or refractory pediatric brain tumors, radiation therapy (XRT is an integral treatment modality. In the era of personalized cancer therapy, molecularly targeted agents have been designed to inhibit pathways critical to tumorigenesis. Our evolving knowledge of genetic aberrations in low-grade gliomas is being exploited with targeted inhibitors. These agents are also being combined with XRT to increase their efficacy. In this review, we discuss novel agents targeting three different pathways in low-grade gliomas, and their potential combination with XRT. B-Raf is a kinase in the Ras/Raf/MAPK kinase pathway, which is integral to cellular division, survival and metabolism. In low-grade pediatric gliomas, point mutations in BRAF (BRAF V600E or a BRAF fusion mutation (KIAA1549:BRAF causes overactivation of the MEK/MAPK pathway. Pre-clinical data shows cooperation between XRT and tagrgeted inhibitors of BRAF V600E, and MEK and mTOR inhibitors in the gliomas with the BRAF fusion. A second important signaling cascade in pediatric glioma pathogenesis is the PI3 kinase (PI3K/mTOR pathway. Dual PI3K/mTOR inhibitors are poised to enter studies of pediatric tumors. Finally, many brain tumors express potent stimulators of angiogenesis. Several inhibitors of immunomodulators are currently being evaluated in in clinical trials for the treatment of recurrent or refractory pediatric central nervous system (CNS tumors. In summary, combinations of these targeted inhibitors with radiation are currently under investigation in both translational bench research and early clinical trials. We summarize the molecular rationale for, and the pre-clinical data supporting the combinations of these targeted agents with other anti-cancer agents and XRT in pediatric gliomas. Parallels are drawn to adult gliomas, and the molecular mechanisms underlying the efficacy of these agents is discussed

Multi-Agent Pathfinding with n Agents on Graphs with n Vertices

DEFF Research Database (Denmark)

Förster, Klaus-Tycho; Groner, Linus; Hoefler, Torsten

2017-01-01

We investigate the multi-agent pathfinding (MAPF) problem with $n$ agents on graphs with $n$ vertices: Each agent has a unique start and goal vertex, with the objective of moving all agents in parallel movements to their goal s.t.~each vertex and each edge may only be used by one agent at a time....... We give a combinatorial classification of all graphs where this problem is solvable in general, including cases where the solvability depends on the initial agent placement. Furthermore, we present an algorithm solving the MAPF problem in our setting, requiring O(n²) rounds, or O(n³) moves...... of individual agents. Complementing these results, we show that there are graphs where Omega(n²) rounds and Omega(n³) moves are required for any algorithm....

Designing Garments to Evolve Over Time

DEFF Research Database (Denmark)

Riisberg, Vibeke; Grose, Lynda

2017-01-01

This paper proposes a REDO of the current fashion paradigm by investigating how garments might be designed to evolve over time. The purpose is to discuss ways of expanding the traditional role of the designer to include temporal dimensions of creating, producing and using clothes and to suggest...... to a REDO of design education, to further research and the future fashion and textile industry....

The utility of dermoscopy in the diagnosis of evolving lesions of vitiligo

Directory of Open Access Journals (Sweden)

Sarvesh S Thatte

2014-01-01

Full Text Available Background: Early lesions of vitiligo can be confused with various other causes of hypopigmentation and depigmentation. Few workers have utilized dermoscopy for the diagnosis of evolving lesions of vitiligo. Aim: To analyze the dermoscopic findings of evolving lesions in diagnosed cases of vitiligo and to correlate them histopathologically. Methods: Dermoscopy of evolving lesions in 30 diagnosed cases of vitiligo was performed using both polarized light and ultraviolet light. Result: On polarized light examination, the pigmentary network was found to be reduced in 12 (40% of 30 patients, absent in 9 (30%, and reversed in 6 (20% patients; 2 patients (6.7% showed perifollicular hyperpigmentation and 1 (3.3% had perilesional hyperpigmentation. A diffuse white glow was demonstrable in 27 (90% of 30 patients on ultraviolet light examination. Melanocytes were either reduced in number or absent in 12 (40% of 30 patients on histopathology. Conclusion: Pigmentary network changes, and perifollicular and perilesional hyperpigmentation on polarized light examination, and a diffuse white glow on ultraviolet light examination were noted in evolving vitiligo lesions. Histopathological examination was comparatively less reliable. Dermoscopy appears to be better than routine histopathology in the diagnosis of evolving lesions of vitiligo and can obviate the need for a skin biopsy.

9th KES Conference on Agent and Multi-Agent Systems : Technologies and Applications

CERN Document Server

Howlett, Robert; Jain, Lakhmi

2015-01-01

Agents and multi-agent systems are related to a modern software paradigm which has long been recognized as a promising technology for constructing autonomous, complex and intelligent systems. The topics covered in this volume include agent-oriented software engineering, agent co-operation, co-ordination, negotiation, organization and communication, distributed problem solving, specification of agent communication languages, agent privacy, safety and security, formalization of ontologies and conversational agents. The volume highlights new trends and challenges in agent and multi-agent research and includes 38 papers classified in the following specific topics: learning paradigms, agent-based modeling and simulation, business model innovation and disruptive technologies, anthropic-oriented computing, serious games and business intelligence, design and implementation of intelligent agents and multi-agent systems, digital economy, and advances in networked virtual enterprises. Published p...

10th International Conference on Practical Applications of Agents and Multi-Agent Systems

CERN Document Server

Pérez, Javier; Golinska, Paulina; Giroux, Sylvain; Corchuelo, Rafael; Trends in Practical Applications of Agents and Multiagent Systems

2012-01-01

PAAMS, the International Conference on Practical Applications of Agents and Multi-Agent Systems is an evolution of the International Workshop on Practical Applications of Agents and Multi-Agent Systems. PAAMS is an international yearly tribune to present, to discuss, and to disseminate the latest developments and the most important outcomes related to real-world applications. It provides a unique opportunity to bring multi-disciplinary experts, academics and practitioners together to exchange their experience in the development of Agents and Multi-Agent Systems.   This volume presents the papers that have been accepted for the 2012 in the workshops: Workshop on Agents for Ambient Assisted Living, Workshop on Agent-Based Solutions for Manufacturing and Supply Chain and Workshop on Agents and Multi-agent systems for Enterprise Integration.

Riot Control Agents

Science.gov (United States)

... Submit What's this? Submit Button Facts About Riot Control Agents Interim document Recommend on Facebook Tweet Share Compartir What riot control agents are Riot control agents (sometimes referred to ...

Population ecology, nonlinear dynamics, and social evolution. I. Associations among nonrelatives.

Science.gov (United States)

Avilés, Leticia; Abbot, Patrick; Cutter, Asher D

2002-02-01

Using an individual-based and genetically explicit simulation model, we explore the evolution of sociality within a population-ecology and nonlinear-dynamics framework. Assuming that individual fitness is a unimodal function of group size and that cooperation may carry a relative fitness cost, we consider the evolution of one-generation breeding associations among nonrelatives. We explore how parameters such as the intrinsic rate of growth and group and global carrying capacities may influence social evolution and how social evolution may, in turn, influence and be influenced by emerging group-level and population-wide dynamics. We find that group living and cooperation evolve under a wide range of parameter values, even when cooperation is costly and the interactions can be defined as altruistic. Greater levels of cooperation, however, did evolve when cooperation carried a low or no relative fitness cost. Larger group carrying capacities allowed the evolution of larger groups but also resulted in lower cooperative tendencies. When the intrinsic rate of growth was not too small and control of the global population size was density dependent, the evolution of large cooperative tendencies resulted in dynamically unstable groups and populations. These results are consistent with the existence and typical group sizes of organisms ranging from the pleometrotic ants to the colonial birds and the global population outbreaks and crashes characteristic of organisms such as the migratory locusts and the tree-killing bark beetles.

FY1995 evolvable hardware chip; 1995 nendo shinkasuru hardware chip

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-03-01

This project aims at the development of 'Evolvable Hardware' (EHW) which can adapt its hardware structure to the environment to attain better hardware performance, under the control of genetic algorithms. EHW is a key technology to explore the new application area requiring real-time performance and on-line adaptation. 1. Development of EHW-LSI for function level hardware evolution, which includes 15 DSPs in one chip. 2. Application of the EHW to the practical industrial applications such as data compression, ATM control, digital mobile communication. 3. Two patents : (1) the architecture and the processing method for programmable EHW-LSI. (2) The method of data compression for loss-less data, using EHW. 4. The first international conference for evolvable hardware was held by authors: Intl. Conf. on Evolvable Systems (ICES96). It was determined at ICES96 that ICES will be held every two years between Japan and Europe. So the new society has been established by us. (NEDO)

FY1995 evolvable hardware chip; 1995 nendo shinkasuru hardware chip

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-03-01

This project aims at the development of 'Evolvable Hardware' (EHW) which can adapt its hardware structure to the environment to attain better hardware performance, under the control of genetic algorithms. EHW is a key technology to explore the new application area requiring real-time performance and on-line adaptation. 1. Development of EHW-LSI for function level hardware evolution, which includes 15 DSPs in one chip. 2. Application of the EHW to the practical industrial applications such as data compression, ATM control, digital mobile communication. 3. Two patents : (1) the architecture and the processing method for programmable EHW-LSI. (2) The method of data compression for loss-less data, using EHW. 4. The first international conference for evolvable hardware was held by authors: Intl. Conf. on Evolvable Systems (ICES96). It was determined at ICES96 that ICES will be held every two years between Japan and Europe. So the new society has been established by us. (NEDO)

Evolvability of thermophilic proteins from archaea and bacteria.

Science.gov (United States)

Takano, Kazufumi; Aoi, Atsushi; Koga, Yuichi; Kanaya, Shigenori

2013-07-16

Proteins from thermophiles possess high thermostability. The stabilization mechanisms differ between archaeal and bacterial proteins, whereby archaeal proteins are mainly stabilized via hydrophobic interactions and bacterial proteins by ion pairs. High stability is an important factor in promoting protein evolution, but the precise means by which different stabilization mechanisms affect the evolution process remain unclear. In this study, we investigated a random mutational drift of esterases from thermophilic archaea and bacteria at high temperatures. Our results indicate that mutations in archaeal proteins lead to improved function with no loss of stability, while mutant bacterial proteins are largely destabilized with decreased activity at high temperatures. On the basis of these findings, we suggest that archaeal proteins possess higher "evolvability" than bacterial proteins under temperature selection and are additionally able to evolve into eukaryotic proteins.

The 'E' factor -- evolving endodontics.

Science.gov (United States)

Hunter, M J

2013-03-01

Endodontics is a constantly developing field, with new instruments, preparation techniques and sealants competing with trusted and traditional approaches to tooth restoration. Thus general dental practitioners must question and understand the significance of these developments before adopting new practices. In view of this, the aim of this article, and the associated presentation at the 2013 British Dental Conference & Exhibition, is to provide an overview of endodontic methods and constantly evolving best practice. The presentation will review current preparation techniques, comparing rotary versus reciprocation, and question current trends in restoration of the endodontically treated tooth.

Narrative incoherence in schizophrenia: the absent agent-protagonist and the collapse of internal dialogue.

Science.gov (United States)

Lysaker, Paul H; Wickett, Amanda M; Wilke, Neil; Lysaker, John

2003-01-01

It is widely known that people with schizophrenia have difficulty telling a coherent story of their lives and that this is linked to impoverished function. But what specifically has gone wrong in the narratives in schizophrenia? Is it the case that some elements of narrative remain intact in schizophrenia while others are uniquely affected? To address these questions, we qualitatively analyze the personal narratives of three persons with schizophrenia, which have emerged in psychotherapy. Based on this analysis we suggest that narratives in schizophrenia uniquely fail to situate agency within the narrator resulting in a story that is missing an agent-protagonist. While the narratives we present contain coherent accounts of how others are connected to one another, they fail to evolve into a story about the self as an agent that others could associate with the narrator. We speculate that this may reflect neuro-cognitively based difficulties maintaining the internal dialogue that propels agency as well as fears that any emergent subjectivity may be appropriated or objectified by others. Implications for psychotherapy are discussed.

Dissemination of Cultural Norms and Values: Agent-Based Modeling

Directory of Open Access Journals (Sweden)

Denis Andreevich Degterev

2016-12-01

Full Text Available This article shows how agent-based modeling allows us to explore the mechanisms of the dissemination of cultural norms and values both within one country and in the whole world. In recent years, this type of simulation is particularly prevalent in the analysis of international relations, becoming more popular than the system dynamics and discrete event simulation. The use of agent-based modeling in the analysis of international relations is connected with the agent-structure problem in international relations. Structure and agents act as interdependent and dynamically changing in the process of interaction between entities. Agent-structure interaction could be modeled by means of the theory of complex adaptive systems with the use of agent-based modeling techniques. One of the first examples of the use of agent-based modeling in political science is a model of racial segregation T. Shellinga. On the basis of this model, the author shows how the change in behavioral patterns at micro-level impacts on the macro-level. Patterns are changing due to the dynamics of cultural norms and values, formed by mass-media and other social institutes. The author shows the main areas of modern application of agent-based modeling in international studies including the analysis of ethnic conflicts, the formation of international coalitions. Particular attention is paid to Robert Axelrod approach based on the use of genetic algorithms to the spread of cultural norms and values. Agent-based modeling shows how to how to create such conditions that the norms that originally are not shared by a significant part of the population, eventually spread everywhere. Practical application of these algorithms is shown by the author of the article on the example of the situation in Ukraine in 2015-2016. The article also reveals the mechanisms of international spread of cultural norms and values. The main think-tanks using agent-based modeling in international studies are

Effect of Different Mediated Agents on Morphology and Crystallinity of Synthesized Silver Nanowires Prepared by Polyol Process

Directory of Open Access Journals (Sweden)

Mohammad Taghi Satoungar

2016-01-01

Full Text Available Synthesis and characterization of multiple crystalline silver nanowires (NWs with uniform diameters were carried out by using 1,2-propandiol and ethylene glycol (EG as comediated solvents and FeCl3 as mediated agent in the presence of poly(vinyl pyrrolidone (PVP. Experimental data and structural characterizations revealed that AgNWs have evolved from the multiple crystalline seeds initially generated by reduction of AgNO3 with EG and 1,2-propandiol followed by reducing Fe(III to Fe(II which in turn reacts with and removes adsorbed atomic oxygen from the surfaces of silver seeds. In addition, uniform silver nanowires were obtained by using FeCl2 and AlCl3 as mediated agents in EG solution. Field emission scanning electron microscopy (FESEM and transmission electron microscopy (TEM showed uniform nanowires in both diameter and length. UV-Vis spectra showed adsorption peaks confirming the formation of nanowires. X-ray diffraction (XRD patterns displayed the final product with high crystallinity and purity. In this study, a growth mechanism for forming AgNWs was proposed and a comparison between different mediated agents was carried out.

Constructing Secure Mobile Agent Systems Using the Agent Operating System

NARCIS (Netherlands)

van t Noordende, G.J.; Overeinder, B.J.; Timmer, R.J.; Brazier, F.M.; Tanenbaum, A.S.

2009-01-01

Designing a secure and reliable mobile agent system is a difficult task. The agent operating system (AOS) is a building block that simplifies this task. AOS provides common primitives required by most mobile agent middleware systems, such as primitives for secure communication, secure and

Nondestructive Intervention to Multi-Agent Systems through an Intelligent Agent

Science.gov (United States)

Han, Jing; Wang, Lin

2013-01-01

For a given multi-agent system where the local interaction rule of the existing agents can not be re-designed, one way to intervene the collective behavior of the system is to add one or a few special agents into the group which are still treated as normal agents by the existing ones. We study how to lead a Vicsek-like flocking model to reach synchronization by adding special agents. A popular method is to add some simple leaders (fixed-headings agents). However, we add one intelligent agent, called ‘shill’, which uses online feedback information of the group to decide the shill's moving direction at each step. A novel strategy for the shill to coordinate the group is proposed. It is strictly proved that a shill with this strategy and a limited speed can synchronize every agent in the group. The computer simulations show the effectiveness of this strategy in different scenarios, including different group sizes, shill speed, and with or without noise. Compared to the method of adding some fixed-heading leaders, our method can guarantee synchronization for any initial configuration in the deterministic scenario and improve the synchronization level significantly in low density groups, or model with noise. This suggests the advantage and power of feedback information in intervention of collective behavior. PMID:23658695

Nondestructive intervention to multi-agent systems through an intelligent agent.

Directory of Open Access Journals (Sweden)

Jing Han

Full Text Available For a given multi-agent system where the local interaction rule of the existing agents can not be re-designed, one way to intervene the collective behavior of the system is to add one or a few special agents into the group which are still treated as normal agents by the existing ones. We study how to lead a Vicsek-like flocking model to reach synchronization by adding special agents. A popular method is to add some simple leaders (fixed-headings agents. However, we add one intelligent agent, called 'shill', which uses online feedback information of the group to decide the shill's moving direction at each step. A novel strategy for the shill to coordinate the group is proposed. It is strictly proved that a shill with this strategy and a limited speed can synchronize every agent in the group. The computer simulations show the effectiveness of this strategy in different scenarios, including different group sizes, shill speed, and with or without noise. Compared to the method of adding some fixed-heading leaders, our method can guarantee synchronization for any initial configuration in the deterministic scenario and improve the synchronization level significantly in low density groups, or model with noise. This suggests the advantage and power of feedback information in intervention of collective behavior.

Dynamics of bloggers’ communities: Bipartite networks from empirical data and agent-based modeling

Science.gov (United States)

Mitrović, Marija; Tadić, Bosiljka

2012-11-01

We present an analysis of the empirical data and the agent-based modeling of the emotional behavior of users on the Web portals where the user interaction is mediated by posted comments, like Blogs and Diggs. We consider the dataset of discussion-driven popular Diggs, in which all comments are screened by machine-learning emotion detection in the text, to determine positive and negative valence (attractiveness and aversiveness) of each comment. By mapping the data onto a suitable bipartite network, we perform an analysis of the network topology and the related time-series of the emotional comments. The agent-based model is then introduced to simulate the dynamics and to capture the emergence of the emotional behaviors and communities. The agents are linked to posts on a bipartite network, whose structure evolves through their actions on the posts. The emotional states (arousal and valence) of each agent fluctuate in time, subject to the current contents of the posts to which the agent is exposed. By an agent’s action on a post its current emotions are transferred to the post. The model rules and the key parameters are inferred from the considered empirical data to ensure their realistic values and mutual consistency. The model assumes that the emotional arousal over posts drives the agent’s action. The simulations are preformed for the case of constant flux of agents and the results are analyzed in full analogy with the empirical data. The main conclusions are that the emotion-driven dynamics leads to long-range temporal correlations and emergent networks with community structure, that are comparable with the ones in the empirical system of popular posts. In view of pure emotion-driven agents actions, this type of comparisons provide a quantitative measure for the role of emotions in the dynamics on real blogs. Furthermore, the model reveals the underlying mechanisms which relate the post popularity with the emotion dynamics and the prevalence of negative

Quantum games on evolving random networks

OpenAIRE

Pawela, Łukasz

2015-01-01

We study the advantages of quantum strategies in evolutionary social dilemmas on evolving random networks. We focus our study on the two-player games: prisoner's dilemma, snowdrift and stag-hunt games. The obtained result show the benefits of quantum strategies for the prisoner's dilemma game. For the other two games, we obtain regions of parameters where the quantum strategies dominate, as well as regions where the classical strategies coexist.

Differntiation genetique des populations geographiques de ...

African Journals Online (AJOL)

Differntiation genetique des populations geographiques de Colletotrichum kahawae, agent pathogene responsable de l\\'anthracnose des baies du cafeier Arabica. B Manga, J V Fabre, D Bieysse, J A Mouen Bedimo, C Herail, D Berry. Abstract. No Abstract. Cameroon Journal of Agricultural Science Vol. 1 (2) 2005 pp.

Organizations as Socially Constructed Agents in the Agent Oriented Paradigm

NARCIS (Netherlands)

G. Boella (Guido); L.W.N. van der Torre (Leon)

2005-01-01

htmlabstractIn this paper we propose a new role for the agent metaphor in the definition of the organizational structure of multiagent systems. The agent metaphor is extended to consider as agents also social entities like organizations, groups and normative systems, so that mental attitudes can

Further Screening of Entomopathogenic Fungi and Nematodes as Control Agents for Drosophila suzukii

Directory of Open Access Journals (Sweden)

Andrew G. S. Cuthbertson

2016-06-01

Full Text Available Drosophila suzukii populations remain low in the UK. To date, there have been no reports of widespread damage. Previous research demonstrated that various species of entomopathogenic fungi and nematodes could potentially suppress D. suzukii population development under laboratory trials. However, none of the given species was concluded to be specifically efficient in suppressing D. suzukii. Therefore, there is a need to screen further species to determine their efficacy. The following entomopathogenic agents were evaluated for their potential to act as control agents for D. suzukii: Metarhizium anisopliae; Isaria fumosorosea; a non-commercial coded fungal product (Coded B; Steinernema feltiae, S. carpocapsae, S. kraussei and Heterorhabditis bacteriophora. The fungi were screened for efficacy against the fly on fruit while the nematodes were evaluated for the potential to be applied as soil drenches targeting larvae and pupal life-stages. All three fungi species screened reduced D. suzukii populations developing from infested berries. Isaria fumosorosea significantly (p < 0.001 reduced population development of D. suzukii from infested berries. All nematodes significantly reduced adult emergence from pupal cases compared to the water control. Larvae proved more susceptible to nematode infection. Heterorhabditis bacteriophora proved the best from the four nematodes investigated; readily emerging from punctured larvae and causing 95% mortality. The potential of the entomopathogens to suppress D. suzukii populations is discussed.

Economic feasibility of a wood biomass energy system under evolving demand

Directory of Open Access Journals (Sweden)

Giorgio Guariso

2016-01-01

Full Text Available In some European regions, particularly in mountainous areas, the demand for energy is evolving due to the decrease of resident population and the adoption of energy efficiency measures. Such changes are rapid enough to significantly impact on the planning process of wood-to-energy chains that are supposed to work for the following 20–25 years. The paper summarizes a study in an Italian pre-alpine district where some municipality shows a declining resident population together with increasing summer tourism. The planning of conversion plants to exploit the local availability of wood is formulated as a mathematical programming problem that maximizes the economic return of the investment, under time-varying parameters that account for the demand evolution. Such a demand is estimated from current trends, while biomass availability and transport is computed from the local cartography, through standard GIS operations. Altogether, the mixed integer optimization problem has 11 possible plant locations of different sizes and technologies taking their feedstock from about 200 parcels. The problem is solved with a commercial software package and shows that the optimal plan changes if one considers the foreseen evolution of the energy demand. As it always happen in this type of biomass-based plants, while the problem formulation is general and may be applied to other cases, the solution obtained is strongly dependent on local values and thus cannot be extrapolated to different contexts.

Circulating type 1 vaccine-derived poliovirus may evolve under the pressure of adenosine deaminases acting on RNA.

Science.gov (United States)

Liu, Yanhan; Ma, Tengfei; Liu, Jianzhu; Zhao, Xiaona; Cheng, Ziqiang; Guo, Huijun; Xu, Ruixue; Wang, Shujing

2015-01-01

Poliovirus, the causative agent of poliomyelitis, is a human enterovirus and member of the Picornaviridae family. An effective live-attenuated poliovirus vaccine strain (Sabin 1) has been developed and has protected humans from polio. However, a few cases of vaccine virulence reversion have been documented in several countries. For instance, circulating type 1 vaccine-derived poliovirus is a highly pathogenic poliovirus that evolved from an avirulent strain, but the mechanism by which vaccine strains undergo reversion remains unclear. In this study, vaccine strains exhibited A to G/U to C and G to A/C to U hypermutations in the reversed evolution of Sabin 1. Furthermore, the mutation ratios of U to C and C to U were higher than those of other mutation types. Dinucleotide editing context was then analyzed. Results showed that A to G and U to C mutations exhibited preferences similar to adenosine deaminases acting on RNA (ADAR). Hence, ADARs may participate in poliovirus vaccine evolution.

Neuroprotective "agents" in surgery. Secret "agent" man, or common "agent" machine?

Science.gov (United States)

Andrews, R. J.

1999-01-01

The search for clinically-effective neuroprotective agents has received enormous support in recent years--an estimated $200 million by pharmaceutical companies on clinical trials for traumatic brain injury alone. At the same time, the pathophysiology of brain injury has proved increasingly complex, rendering the likelihood of a single agent "magic bullet" even more remote. On the other hand, great progress continues with technology that makes surgery less invasive and less risky. One example is the application of endovascular techniques to treat coronary artery stenosis, where both the invasiveness of sternotomy and the significant neurological complication rate (due to microemboli showering the cerebral vasculature) can be eliminated. In this paper we review aspects of intraoperative neuroprotection both present and future. Explanations for the slow progress on pharmacologic neuroprotection during surgery are presented. Examples of technical advances that have had great impact on neuroprotection during surgery are given both from coronary artery stenosis surgery and from surgery for Parkinson's disease. To date, the progress in neuroprotection resulting from such technical advances is an order of magnitude greater than that resulting from pharmacologic agents used during surgery. The progress over the last 20 years in guidance during surgery (CT and MRI image-guidance) and in surgical access (endoscopic and endovascular techniques) will soon be complemented by advances in our ability to evaluate biological tissue intraoperatively in real-time. As an example of such technology, the NASA Smart Probe project is considered. In the long run (i.e., in 10 years or more), pharmacologic "agents" aimed at the complex pathophysiology of nervous system injury in man will be the key to true intraoperative neuroprotection. In the near term, however, it is more likely that mundane "agents" based on computers, microsensors, and microeffectors will be the major impetus to improved

Using the Agent-Based Modeling in Economic Field

Directory of Open Access Journals (Sweden)

Nora Mihail

2006-12-01

Full Text Available The last ten years of the XX century has been the witnesses of the apparition of a new scientific field, which is usually defined as the study of “Complex adaptive systems”. This field, generic named Complexity Sciences, shares its subject, the general proprieties of complex systems across traditional disciplinary boundaries, with cybernetics and general systems theory. But the development of Complexity Sciences approaches is determined by the extensive use of Agent-Based-Models (ABM as a research tool and an emphasis on systems, such as markets, populations or ecologies, which are less integrated or “organized” than the ones, such as companies and economies, intensively studied by the traditional disciplines. For ABM, a complex system is a system of individual agents who have the freedom to act in ways that are not always totally predictable, and whose actions are interconnected such that one agent’s actions changes the context (environment for other agents. These are many examples of such complex systems: the stock market, the human body immune system, a business organization, an institution, a work-team, a family etc.

Project Seahorse evolves into major marine protector | IDRC ...

International Development Research Centre (IDRC) Digital Library (Canada)

2012-10-29

Oct 29, 2012 ... Project Seahorse evolves into major marine protector ... local people, have greatly improved the prospects of survival for threatened species. ... “We tackle issues on any political level or geographical scale, according to what ...

Percolation and cooperation with mobile agents: geometric and strategy clusters.

Science.gov (United States)

Vainstein, Mendeli H; Brito, Carolina; Arenzon, Jeferson J

2014-08-01

We study the conditions for persistent cooperation in an off-lattice model of mobile agents playing the Prisoner's Dilemma game with pure, unconditional strategies. Each agent has an exclusion radius r(P), which accounts for the population viscosity, and an interaction radius r(int), which defines the instantaneous contact network for the game dynamics. We show that, differently from the r(P)=0 case, the model with finite-sized agents presents a coexistence phase with both cooperators and defectors, besides the two absorbing phases, in which either cooperators or defectors dominate. We provide, in addition, a geometric interpretation of the transitions between phases. In analogy with lattice models, the geometric percolation of the contact network (i.e., irrespective of the strategy) enhances cooperation. More importantly, we show that the percolation of defectors is an essential condition for their survival. Differently from compact clusters of cooperators, isolated groups of defectors will eventually become extinct if not percolating, independently of their size.

The effect of increasing water temperatures on Schistosoma mansoni transmission and Biomphalaria pfeifferi population dynamics: an agent-based modelling study.

Directory of Open Access Journals (Sweden)

Nicky McCreesh

Full Text Available There is increasing interest in the control and elimination of schistosomiasis. Little is known, however, about the likely effects of increasing water-body temperatures on transmission.We have developed an agent-based model of the temperature-sensitive stages of the Schistosoma and intermediate host snail life-cycles, parameterised using data from S. mansoni and Biomphalaria pfeifferi laboratory and field-based observations. Infection risk is calculated as the number of cercariae in the model, adjusted for their probability of causing infection.The number of snails in the model is approximately constant between 15-31°C. Outside this range, snail numbers drop sharply, and the snail population cannot survive outside the range 14-32°C. Mean snail generation time decreases with increasing temperature from 176 days at 14°C to 46 days at 26°C. Human infection risk is highest between 16-18°C and 1pm and 6-10pm in calm water, and 20-25°C and 12-4pm in flowing water. Infection risk increases sharply when temperatures increase above the minimum necessary for sustained transmission.The model suggests that, in areas where S. mansoni is already endemic, warming of the water at transmission sites will have differential effects on both snails and parasites depending on abiotic properties of the water-body. Snail generation times will decrease in most areas, meaning that snail populations will recover faster from natural population reductions and from snail-control efforts. We suggest a link between the ecological properties of transmission sites and infection risk which could significantly affect the outcomes of interventions designed to alter water contact behaviour--proposing that such interventions are more likely to reduce infection levels at river locations than lakes, where infection risk remains high for longer. In cooler areas where snails are currently found, increasing temperatures may significantly increase infection risk, potentially leading

The Comet Cometh: Evolving Developmental Systems.

Science.gov (United States)

Jaeger, Johannes; Laubichler, Manfred; Callebaut, Werner

In a recent opinion piece, Denis Duboule has claimed that the increasing shift towards systems biology is driving evolutionary and developmental biology apart, and that a true reunification of these two disciplines within the framework of evolutionary developmental biology (EvoDevo) may easily take another 100 years. He identifies methodological, epistemological, and social differences as causes for this supposed separation. Our article provides a contrasting view. We argue that Duboule's prediction is based on a one-sided understanding of systems biology as a science that is only interested in functional, not evolutionary, aspects of biological processes. Instead, we propose a research program for an evolutionary systems biology, which is based on local exploration of the configuration space in evolving developmental systems. We call this approach-which is based on reverse engineering, simulation, and mathematical analysis-the natural history of configuration space. We discuss a number of illustrative examples that demonstrate the past success of local exploration, as opposed to global mapping, in different biological contexts. We argue that this pragmatic mode of inquiry can be extended and applied to the mathematical analysis of the developmental repertoire and evolutionary potential of evolving developmental mechanisms and that evolutionary systems biology so conceived provides a pragmatic epistemological framework for the EvoDevo synthesis.

Leukemia after therapy with alkylating agents for childhood cancer

International Nuclear Information System (INIS)

Tucker, M.A.; Meadows, A.T.; Boice, J.D. Jr.

1987-01-01

The risk of leukemia was evaluated in 9,170 2-or-more-year survivors of childhood cancer in the 13 institutions of the Late Effects Study Group. Secondary leukemia occurred in 22 nonreferred individuals compared to 1.52 expected, based on general population rates [relative risk (RR) = 14; 95% confidence interval (CI), 9-22]. The influence of therapy for the first cancer on subsequent leukemia risk was determined by a case-control study conducted on 25 cases and 90 matched controls. Treatment with alkylating agents was associated with a significantly elevated risk of leukemia (RR = 4.8; 95% CI, 1.2-18.9). A strong dose-response relationship was also observed between leukemia risk and total dose of alkylating agents, estimated by an alkylator score. The RR of leukemia reached 23 in the highest dose category. Radiation therapy, however, did not increase risk. Although doxorubicin was also identified as a possible risk factor, the excess risk of leukemia following treatment for childhood cancer appears almost entirely due to alkylating agents

Repeated evolution of fungal cultivar specificity in independently evolved ant-plant-fungus symbioses.

Directory of Open Access Journals (Sweden)

Rumsaïs Blatrix

Full Text Available Some tropical plant species possess hollow structures (domatia occupied by ants that protect the plant and in some cases also provide it with nutrients. Most plant-ants tend patches of chaetothyrialean fungi within domatia. In a few systems it has been shown that the ants manure the fungal patches and use them as a food source, indicating agricultural practices. However, the identity of these fungi has been investigated only in a few samples. To examine the specificity and constancy of ant-plant-fungus interactions we characterised the content of fungal patches in an extensive sampling of three ant-plant symbioses (Petalomyrmex phylax/Leonardoxa africana subsp. africana, Aphomomyrmex afer/Leonardoxa africana subsp. letouzeyi and Tetraponera aethiops/Barteria fistulosa by sequencing the Internal Transcribed Spacers of ribosomal DNA. For each system the content of fungal patches was constant over individuals and populations. Each symbiosis was associated with a specific, dominant, primary fungal taxon, and to a lesser extent, with one or two specific secondary taxa, all of the order Chaetothyriales. A single fungal patch sometimes contained both a primary and a secondary taxon. In one system, two founding queens were found with the primary fungal taxon only, one that was shown in a previous study to be consumed preferentially. Because the different ant-plant symbioses studied have evolved independently, the high specificity and constancy we observed in the composition of the fungal patches have evolved repeatedly. Specificity and constancy also characterize other cases of agriculture by insects.

Social networks: Evolving graphs with memory dependent edges

Science.gov (United States)

Grindrod, Peter; Parsons, Mark

2011-10-01

The plethora of digital communication technologies, and their mass take up, has resulted in a wealth of interest in social network data collection and analysis in recent years. Within many such networks the interactions are transient: thus those networks evolve over time. In this paper we introduce a class of models for such networks using evolving graphs with memory dependent edges, which may appear and disappear according to their recent history. We consider time discrete and time continuous variants of the model. We consider the long term asymptotic behaviour as a function of parameters controlling the memory dependence. In particular we show that such networks may continue evolving forever, or else may quench and become static (containing immortal and/or extinct edges). This depends on the existence or otherwise of certain infinite products and series involving age dependent model parameters. We show how to differentiate between the alternatives based on a finite set of observations. To test these ideas we show how model parameters may be calibrated based on limited samples of time dependent data, and we apply these concepts to three real networks: summary data on mobile phone use from a developing region; online social-business network data from China; and disaggregated mobile phone communications data from a reality mining experiment in the US. In each case we show that there is evidence for memory dependent dynamics, such as that embodied within the class of models proposed here.

Advances on Practical Applications of Agents and Multi-Agent Systems 10th International Conference on Practical Applications of Agents and Multi-Agent Systems

CERN Document Server

Müller, Jörg; Rodríguez, Juan; Pérez, Javier

2012-01-01

Research on Agents and Multi-Agent Systems has matured during the last decade and many effective applications of this technology are now deployed. PAAMS provides an international forum to present and discuss the latest scientific developments and their effective applications, to assess the impact of the approach, and to facilitate technology transfer. PAAMS started as a local initiative, but has since grown to become THE international yearly platform to present, to discuss, and to disseminate the latest developments and the most important outcomes related to real-world applications. It provides a unique opportunity to bring multi-disciplinary experts, academics and practitioners together to exchange their experience in the development and deployment of Agents and Multi-Agent Systems. PAAMS intends to bring together researchers and developers from industry and the academic world to report on the latest scientific and technical advances on the application of multi-agent systems, to discuss and debate the major ...

Highlights on Practical Applications of Agents and Multi-Agent Systems 10th International Conference on Practical Applications of Agents and Multi-Agent Systems

CERN Document Server

Sánchez, Miguel; Mathieu, Philippe; Rodríguez, Juan; Adam, Emmanuel; Ortega, Alfonso; Moreno, María; Navarro, Elena; Hirsch, Benjamin; Lopes-Cardoso, Henrique; Julián, Vicente

2012-01-01

Research on Agents and Multi-Agent Systems has matured during the last decade and many effective applications of this technology are now deployed. PAAMS provides an international forum to present and discuss the latest scientific developments and their effective applications, to assess the impact of the approach, and to facilitate technology transfer. PAAMS started as a local initiative, but has since grown to become THE international yearly platform to present, to discuss, and to disseminate the latest developments and the most important outcomes related to real-world applications. It provides a unique opportunity to bring multi-disciplinary experts, academics and practitioners together to exchange their experience in the development and deployment of Agents and Multi-Agent Systems. PAAMS intends to bring together researchers and developers from industry and the academic world to report on the latest scientific and technical advances on the application of multi-agent systems, to discuss and debate the major ...

Diffusion between evolving interfaces

International Nuclear Information System (INIS)

Juntunen, Janne; Merikoski, Juha

2010-01-01

Diffusion in an evolving environment is studied by continuous-time Monte Carlo simulations. Diffusion is modeled by continuous-time random walkers on a lattice, in a dynamic environment provided by bubbles between two one-dimensional interfaces driven symmetrically towards each other. For one-dimensional random walkers constrained by the interfaces, the bubble size distribution dominates diffusion. For two-dimensional random walkers, it is also controlled by the topography and dynamics of the interfaces. The results of the one-dimensional case are recovered in the limit where the interfaces are strongly driven. Even with simple hard-core repulsion between the interfaces and the particles, diffusion is found to depend strongly on the details of the dynamical rules of particles close to the interfaces.

Anomalous dependence of population growth on the birth rate in the plant-herbivore system

International Nuclear Information System (INIS)

Cui, Xue M.; Han, Seung K.; Chung, Jean S.

2010-01-01

We performed a simulation of the two-species plant-herbivore system by using the agent-based NetLogo program and constructed a dynamic model of populations consistent with the simulation results. The dynamic model is a three-dimensional system including the mean energy of the herbivore in addition to two variables denoting the populations of plants and herbivores. A steady-state analysis of the dynamic model shows that the dependence of the herbivore population on the birth and the death rates observed from the agent model is consistent with the prediction of the dynamic model. Especially, the anomalous dependence of the herbivore population on the birth rate, where the population decreases with the birth rate for small death rate, is consistently explained by a phase plane analysis of the dynamic model.

Heart rate variability in healthy population

International Nuclear Information System (INIS)

Alamgir, M.; Hussain, M.M.

2010-01-01

Background: Heart rate variability has been considered as an indicator of autonomic status. Little work has been done on heart rate variability in normal healthy volunteers. We aimed at evolving the reference values of heart rate variability in our healthy population. Methods: Twenty-four hour holter monitoring of 37 healthy individuals was done using Holter ECG recorder 'Life card CF' from 'Reynolds Medical'. Heart rate variability in both time and frequency domains was analysed with 'Reynolds Medical Pathfinder Digital/700'. Results: The heart rate variability in normal healthy volunteers of our population was found in time domain using standard deviation of R-R intervals (SDNN), standard deviation of average NN intervals (SDANN), and Square root of the mean squared differences of successive NN intervals (RMSSD). Variation in heart rate variability indices was observed between local and foreign volunteers and RMSSD was found significantly increased (p<0.05) in local population. Conclusions: The values of heart rate variability (RMSSD) in healthy Pakistani volunteers were found increased compared to the foreign data reflecting parasympathetic dominance in our population. (author)

Environmental carcinogenic agents and cancer prevention. Risk assessment and management

International Nuclear Information System (INIS)

Tsugane, Shoichiro

2013-01-01

Many agents in our environment have been established as being carcinogenic, and in most cases, the carcinogenic properties of these agents were identified because of high-dose occupational or accidental exposure. Risk characterization, taking into account the dose-response relationship, and exposure assessment are essential for risk assessment and subsequent cancer prevention. Based on scientific risk assessment, risk management should be conducted practically by considering the economic, social, political, and other technical issues and by balancing the risks and benefits. Asbestos and environmental tobacco smoke are typical examples of established carcinogenic agents in the general environment, contributing to low-dose exposure. Further epidemiological studies are required to investigate the carcinogenicity of low-dose exposure to known carcinogenic agents such as arsenic and cadmium through dietary intake, radiation via medical and natural exposure, and air pollution due to diesel exhaust. In contrast, occupational chemical exposure to 1,2-dichloropropane and/or dichloromethane, whose carcinogenicity had not been established, was suggested to cause cholangiocarcinoma among workers involved in offset color proof-printing only after a rare situation of high-dose exposure was unveiled. Continuous monitoring of unusual cancer occurrences in target populations such as workers in occupational and regional settings as well as exposure reduction to suspected carcinogenic agents to levels as low as reasonably achievable is essential for reducing the risk of cancer due to environmental carcinogens. (author)

Radiographic scanning agent

International Nuclear Information System (INIS)

Bevan, J.A.

1983-01-01

This invention relates to radiodiagnostic agents and more particularly to a composition and method for preparing a highly effective technetium-99m-based bone scanning agent. One deficiency of x-ray examination is the inability of that technique to detect skeletal metastases in their incipient stages. It has been discovered that the methanehydroxydiphosphonate bone mineral-seeking agent is unique in that it provides the dual benefits of sharp radiographic imaging and excellent lesion detection when used with technetium-99m. This agent can also be used with technetium-99m for detecting soft tissue calcification in the manner of the inorganic phosphate radiodiagnostic agents

Further Screening of Entomopathogenic Fungi and Nematodes as Control Agents for Drosophila suzukii.

Science.gov (United States)

Cuthbertson, Andrew G S; Audsley, Neil

2016-06-09

Drosophila suzukii populations remain low in the UK. To date, there have been no reports of widespread damage. Previous research demonstrated that various species of entomopathogenic fungi and nematodes could potentially suppress D. suzukii population development under laboratory trials. However, none of the given species was concluded to be specifically efficient in suppressing D. suzukii. Therefore, there is a need to screen further species to determine their efficacy. The following entomopathogenic agents were evaluated for their potential to act as control agents for D. suzukii: Metarhizium anisopliae; Isaria fumosorosea; a non-commercial coded fungal product (Coded B); Steinernema feltiae, S. carpocapsae, S. kraussei and Heterorhabditis bacteriophora. The fungi were screened for efficacy against the fly on fruit while the nematodes were evaluated for the potential to be applied as soil drenches targeting larvae and pupal life-stages. All three fungi species screened reduced D. suzukii populations developing from infested berries. Isaria fumosorosea significantly (p nematodes significantly reduced adult emergence from pupal cases compared to the water control. Larvae proved more susceptible to nematode infection. Heterorhabditis bacteriophora proved the best from the four nematodes investigated; readily emerging from punctured larvae and causing 95% mortality. The potential of the entomopathogens to suppress D. suzukii populations is discussed.

Incremental Frequent Subgraph Mining on Large Evolving Graphs

KAUST Repository

Abdelhamid, Ehab; Canim, Mustafa; Sadoghi, Mohammad; Bhatta, Bishwaranjan; Chang, Yuan-Chi; Kalnis, Panos

2017-01-01

, such as social networks, utilize large evolving graphs. Mining these graphs using existing techniques is infeasible, due to the high computational cost. In this paper, we propose IncGM+, a fast incremental approach for continuous frequent subgraph mining problem

When Darwin meets Lorenz: Evolving new chaotic attractors through genetic programming

International Nuclear Information System (INIS)

Pan, Indranil; Das, Saptarshi

2015-01-01

Highlights: •New 3D continuous time chaotic systems with analytical expressions are obtained. •The multi-gene genetic programming (MGGP) paradigm is employed to achieve this. •Extends earlier works for evolving generalised family of Lorenz attractors. •Over one hundred of new chaotic attractors along with their parameters are reported. •The MGGP method have the potential for finding other similar chaotic attractors. -- Abstract: In this paper, we propose a novel methodology for automatically finding new chaotic attractors through a computational intelligence technique known as multi-gene genetic programming (MGGP). We apply this technique to the case of the Lorenz attractor and evolve several new chaotic attractors based on the basic Lorenz template. The MGGP algorithm automatically finds new nonlinear expressions for the different state variables starting from the original Lorenz system. The Lyapunov exponents of each of the attractors are calculated numerically based on the time series of the state variables using time delay embedding techniques. The MGGP algorithm tries to search the functional space of the attractors by aiming to maximise the largest Lyapunov exponent (LLE) of the evolved attractors. To demonstrate the potential of the proposed methodology, we report over one hundred new chaotic attractor structures along with their parameters, which are evolved from just the Lorenz system alone

AUTOMOTIVE APPLICATIONS OF EVOLVING TAKAGI-SUGENO-KANG FUZZY MODELS

Directory of Open Access Journals (Sweden)

Radu-Emil Precup

2017-08-01

Full Text Available This paper presents theoretical and application results concerning the development of evolving Takagi-Sugeno-Kang fuzzy models for two dynamic systems, which will be viewed as controlled processes, in the field of automotive applications. The two dynamic systems models are nonlinear dynamics of the longitudinal slip in the Anti-lock Braking Systems (ABS and the vehicle speed in vehicles with the Continuously Variable Transmission (CVT systems. The evolving Takagi-Sugeno-Kang fuzzy models are obtained as discrete-time fuzzy models by incremental online identification algorithms. The fuzzy models are validated against experimental results in the case of the ABS and the first principles simulation results in the case of the vehicle with the CVT.

A Preclinical Evaluation of Antimycin A as a Potential Antilung Cancer Stem Cell Agent

Directory of Open Access Journals (Sweden)

Chi-Tai Yeh

2013-01-01

Full Text Available Drug resistance and tumor recurrence are major obstacles in treating lung cancer patients. Accumulating evidence considers lung cancer stem cells (CSCs as the major contributor to these clinical challenges. Agents that can target lung CSCs could potentially provide a more effective treatment than traditional chemotherapy. Here, we utilized the side-population (SP method to isolate lung CSCs from A549 and PC-9 cell lines. Subsequently, a high throughput platform, connectivity maps (CMAPs, was used to identify potential anti-CSC agents. An antibiotic, antimycin A (AMA, was identified as a top candidate. SP A549 cells exhibited an elevated stemness profile, including Nanog, β-catenin, Sox2, and CD133, and increased self-renewal ability. AMA treatment was found to suppress β-catenin signaling components and tumor sphere formation. Furthermore, AMA treatment decreased the proliferation of gefitinib-resistant PC-9/GR cells and percentage of SP population. AMA demonstrated synergistic suppression of PC-9/GR cell viability when combined with gefitinib. Finally, AMA treatment suppressed tumorigenesis in mice inoculated with A549 SP cells. Collectively, we have identified AMA using CMAP as a novel antilung CSC agent, which acts to downregulate β-catenin signaling. The combination of AMA and targeted therapeutic agents could be considered for overcoming drug resistance and relapse in lung cancer patients.

Identification and genotyping of the etiological agent of tuberculous lymphadenitis in Ethiopia

NARCIS (Netherlands)

Beyene, Demissew; Bergval, Indra; Hailu, Elena; Ashenafi, Senait; Yamuah, Lawrence; Aseffa, Abraham; Wiker, Harald G.; Engers, Howard; Klatser, Paul; Sviland, Lisbet

2009-01-01

In Ethiopia, little has been done to assess how Mycobacterium bovis has contributed to human tuberculosis, though the population routinely consumes unpasteurized milk and raw meat. The aim of this study was to determine the proportion of M. tuberculosis and M. bovis as etiological agents of

Evaluation and testing methodology for evolving entertainment systems

NARCIS (Netherlands)

Jurgelionis, A.; Bellotti, F.; IJsselsteijn, W.A.; Kort, de Y.A.W.; Bernhaupt, R.; Tscheligi, M.

2007-01-01

This paper presents a testing and evaluation methodology for evolving pervasive gaming and multimedia systems. We introduce the Games@Large system, a complex gaming and multimedia architecture comprised of a multitude of elements: heterogeneous end user devices, wireless and wired network

Biofabrication : reappraising the definition of an evolving field

NARCIS (Netherlands)

Groll, Jürgen; Boland, Thomas; Blunk, Torsten; Burdick, Jason A; Cho, Dong-Woo; Dalton, Paul D; Derby, Brian; Forgacs, Gabor; Li, Qing; Mironov, Vladimir A; Moroni, Lorenzo; Nakamura, Makoto; Shu, Wenmiao; Takeuchi, Shoji; Vozzi, Giovanni; Woodfield, Tim B F; Xu, Tao; Yoo, James J; Malda, Jos|info:eu-repo/dai/nl/412461099

2016-01-01

Biofabrication is an evolving research field that has recently received significant attention. In particular, the adoption of Biofabrication concepts within the field of Tissue Engineering and Regenerative Medicine has grown tremendously, and has been accompanied by a growing inconsistency in

Biofabrication : Reappraising the definition of an evolving field

NARCIS (Netherlands)

Groll, Jürgen; Boland, Thomas; Blunk, Torsten; Burdick, Jason A.; Cho, Dong Woo; Dalton, Paul D.; Derby, Brian; Forgacs, Gabor; Li, Qing; Mironov, Vladimir A.; Moroni, Lorenzo; Nakamura, Makoto; Shu, Wenmiao; Takeuchi, Shoji; Vozzi, Giovanni; Woodfield, Tim B.F.; Xu, Tao; Yoo, James J.; Malda, Jos

2016-01-01

Biofabrication is an evolving research field that has recently received significant attention. In particular, the adoption of Biofabrication concepts within the field of Tissue Engineering and Regenerative Medicine has grown tremendously, and has been accompanied by a growing inconsistency in

No association between personality and candidate gene polymorphisms in a wild bird population

NARCIS (Netherlands)

Edwards, Hannah A.; Hajduck, GK; Durieux, G; Burke, T; Dugdale, Hannah

2015-01-01

Consistency of between-individual differences in behaviour or personality is a phenomenon in populations that can have ecological consequences and evolutionary potential. One way that behaviour can evolve is to have a genetic basis. Identifying the molecular genetic basis of personality could

The pharmacology and toxicology of three new biologic agents used in pulmonary medicine.

Science.gov (United States)

Albertson, T E; Walby, W F; Allen, R P; Tharratt, R S

1995-01-01

Biological agents have played an important role in the evolution of modern medical therapeutics. Recent advances in biologicals have in part been stimulated by the biotechnology revolution seen over the last several years. Toxicologists need to be aware of the proposed mechanisms and approved and experimental uses of these new biologic agents. Further, controversies about their use, efficacy, cost issues and potential toxicities should be known. Often these drugs are designed for small patient populations thus limiting the availability of human toxicological data bases. This paper reviews the pharmacology and toxicology of three new biologics (recombinant human DNase I, alpha 1-protease inhibitor, and nitric oxide). These agents appear to have important roles in treating specific diseases or disease states seen in pulmonary medicine.

Smart Agents and Sentiment in the Heterogeneous Agent Model

Czech Academy of Sciences Publication Activity Database

Vácha, Lukáš; Baruník, Jozef; Vošvrda, Miloslav

2009-01-01

Roč. 18, č. 3 (2009), s. 209-219 ISSN 1210-0455 R&D Projects: GA MŠk(CZ) LC06075; GA ČR GP402/08/P207; GA ČR(CZ) GA402/09/0965 Institutional research plan: CEZ:AV0Z10750506 Keywords : heterogeneous agent model * market structure * smart traders * Hurst exponent Subject RIV: AH - Economics http://library.utia.cas.cz/separaty/2009/E/vacha- smart agent s and sentiment in the heterogeneous agent model.pdf

Evolution of learned strategy choice in a frequency-dependent game.

Science.gov (United States)

Katsnelson, Edith; Motro, Uzi; Feldman, Marcus W; Lotem, Arnon

2012-03-22

In frequency-dependent games, strategy choice may be innate or learned. While experimental evidence in the producer-scrounger game suggests that learned strategy choice may be common, a recent theoretical analysis demonstrated that learning by only some individuals prevents learning from evolving in others. Here, however, we model learning explicitly, and demonstrate that learning can easily evolve in the whole population. We used an agent-based evolutionary simulation of the producer-scrounger game to test the success of two general learning rules for strategy choice. We found that learning was eventually acquired by all individuals under a sufficient degree of environmental fluctuation, and when players were phenotypically asymmetric. In the absence of sufficient environmental change or phenotypic asymmetries, the correct target for learning seems to be confounded by game dynamics, and innate strategy choice is likely to be fixed in the population. The results demonstrate that under biologically plausible conditions, learning can easily evolve in the whole population and that phenotypic asymmetry is important for the evolution of learned strategy choice, especially in a stable or mildly changing environment.

Did Language Evolve Like the Vertebrate Eye?

Science.gov (United States)

Botha, Rudolf P.

2002-01-01

Offers a critical appraisal of the way in which the idea that human language or some of its features evolved like the vertebrate eye by natural selection is articulated in Pinker and Bloom's (1990) selectionist account of language evolution. Argues that this account is less than insightful because it fails to draw some of the conceptual…

Implementation of Capacity Planning Agent of Demand Responsive Planning Framework : Master’s Thesis in Production Engineering of The Royal Institute of Technology

OpenAIRE

Juhong, Nirut

2013-01-01

This master’s thesis is conducted as a conclusion of Master degree of Science in Production Engineering and Management at The Royal Institute of Technology. The focus of this thesis work is to implement a Capacity planning agent. Nowadays, companies need to adapt themselves to be as responsive to customers’ demand as possible. However, the responsiveness is usually limited by the fixed capacity of the production. Evolvable Production System (EPS), motivated by the limitation mentioned above, ...

Mean-field games with logistic population dynamics

KAUST Repository

Gomes, Diogo A.; De Lima Ribeiro, Ricardo

2013-01-01

In its standard form, a mean-field game can be defined by coupled system of equations, a Hamilton-Jacobi equation for the value function of agents and a Fokker-Planck equation for the density of agents. Traditionally, the latter equation is adjoint to the linearization of the former. Since the Fokker-Planck equation models a population dynamic, we introduce natural features such as seeding and birth, and nonlinear death rates. In this paper we analyze a stationary meanfield game in one dimension, illustrating various techniques to obtain regularity of solutions in this class of systems. In particular we consider a logistic-type model for birth and death of the agents which is natural in problems where crowding affects the death rate of the agents. The introduction of these new terms requires a number of new ideas to obtain wellposedness. In a forthcoming publication we will address higher dimensional models. ©2013 IEEE.

Mean-field games with logistic population dynamics

KAUST Repository

Gomes, Diogo A.

2013-12-01

In its standard form, a mean-field game can be defined by coupled system of equations, a Hamilton-Jacobi equation for the value function of agents and a Fokker-Planck equation for the density of agents. Traditionally, the latter equation is adjoint to the linearization of the former. Since the Fokker-Planck equation models a population dynamic, we introduce natural features such as seeding and birth, and nonlinear death rates. In this paper we analyze a stationary meanfield game in one dimension, illustrating various techniques to obtain regularity of solutions in this class of systems. In particular we consider a logistic-type model for birth and death of the agents which is natural in problems where crowding affects the death rate of the agents. The introduction of these new terms requires a number of new ideas to obtain wellposedness. In a forthcoming publication we will address higher dimensional models. ©2013 IEEE.

Genetic Algorithms Evolve Optimized Transforms for Signal Processing Applications

National Research Council Canada - National Science Library

Moore, Frank; Babb, Brendan; Becke, Steven; Koyuk, Heather; Lamson, Earl, III; Wedge, Christopher

2005-01-01

.... The primary goal of the research described in this final report was to establish a methodology for using genetic algorithms to evolve coefficient sets describing inverse transforms and matched...

The effects of stabilizing and directional selection on phenotypic and genotypic variation in a population of RNA enzymes.

Science.gov (United States)

Hayden, Eric J; Bratulic, Sinisa; Koenig, Iwo; Ferrada, Evandro; Wagner, Andreas

2014-02-01

The distribution of variation in a quantitative trait and its underlying distribution of genotypic diversity can both be shaped by stabilizing and directional selection. Understanding either distribution is important, because it determines a population's response to natural selection. Unfortunately, existing theory makes conflicting predictions about how selection shapes these distributions, and very little pertinent experimental evidence exists. Here we study a simple genetic system, an evolving RNA enzyme (ribozyme) in which a combination of high throughput genotyping and measurement of a biochemical phenotype allow us to address this question. We show that directional selection, compared to stabilizing selection, increases the genotypic diversity of an evolving ribozyme population. In contrast, it leaves the variance in the phenotypic trait unchanged.

Self-regulating and self-evolving particle swarm optimizer

Science.gov (United States)

Wang, Hui-Min; Qiao, Zhao-Wei; Xia, Chang-Liang; Li, Liang-Yu

2015-01-01

In this article, a novel self-regulating and self-evolving particle swarm optimizer (SSPSO) is proposed. Learning from the idea of direction reversal, self-regulating behaviour is a modified position update rule for particles, according to which the algorithm improves the best position to accelerate convergence in situations where the traditional update rule does not work. Borrowing the idea of mutation from evolutionary computation, self-evolving behaviour acts on the current best particle in the swarm to prevent the algorithm from prematurely converging. The performance of SSPSO and four other improved particle swarm optimizers is numerically evaluated by unimodal, multimodal and rotated multimodal benchmark functions. The effectiveness of SSPSO in solving real-world problems is shown by the magnetic optimization of a Halbach-based permanent magnet machine. The results show that SSPSO has good convergence performance and high reliability, and is well matched to actual problems.

Asymptotically Optimal Agents

OpenAIRE

Lattimore, Tor; Hutter, Marcus

2011-01-01

Artificial general intelligence aims to create agents capable of learning to solve arbitrary interesting problems. We define two versions of asymptotic optimality and prove that no agent can satisfy the strong version while in some cases, depending on discounting, there does exist a non-computable weak asymptotically optimal agent.

Characterization of colloidal manganese hydroxylapatite: A potential magnetic resonance contrast agent

Science.gov (United States)

Dorshow, Richard B.; Kofi Adzamli, I.; Nosco, Dennis L.; Joslin, Frederick L.

1996-03-01

Particulate contrast agents for blood pool imaging need to be constructed with the appropriate particle size distribution (PSD), and need to be resistant to opsonization. Hence, the PSD of an aqueous colloidal suspension of polyethylene glycol (PEG)-stabilized manganese hydroxylapatite (potentially useful as a magnetic resonance contrast agent for blood pool imaging) has been investigated as a function of PEG concentration and molecular weight. At low PEG concentrations, dynamic light scattering (DLS) and sedimentation field flow fractionation measurements yield a broad PSD, with the largest particle diameters near 100nm. Flow field flow fractionation (FlFFF) measurements, however, yield a distinct population near 10nm, which is not readily detectable by the other two techniques. As the PEG concentration is increased, the PSD shifts toward the lower size population. At the highest PEG concentration employed, only particles of diameter 10nm remain, verified by both FlFFF and DLS. Thus, the search for an optimum PSD for blood pool imaging is facilitated by choice of PEG molecular weight and concentration, and by employing complementary use of light scattering and field flow fractionation techniques.

An Adaptive Agent-Based Model of Homing Pigeons: A Genetic Algorithm Approach

Directory of Open Access Journals (Sweden)

Francis Oloo

2017-01-01

Full Text Available Conventionally, agent-based modelling approaches start from a conceptual model capturing the theoretical understanding of the systems of interest. Simulation outcomes are then used “at the end” to validate the conceptual understanding. In today’s data rich era, there are suggestions that models should be data-driven. Data-driven workflows are common in mathematical models. However, their application to agent-based models is still in its infancy. Integration of real-time sensor data into modelling workflows opens up the possibility of comparing simulations against real data during the model run. Calibration and validation procedures thus become automated processes that are iteratively executed during the simulation. We hypothesize that incorporation of real-time sensor data into agent-based models improves the predictive ability of such models. In particular, that such integration results in increasingly well calibrated model parameters and rule sets. In this contribution, we explore this question by implementing a flocking model that evolves in real-time. Specifically, we use genetic algorithms approach to simulate representative parameters to describe flight routes of homing pigeons. The navigation parameters of pigeons are simulated and dynamically evaluated against emulated GPS sensor data streams and optimised based on the fitness of candidate parameters. As a result, the model was able to accurately simulate the relative-turn angles and step-distance of homing pigeons. Further, the optimised parameters could replicate loops, which are common patterns in flight tracks of homing pigeons. Finally, the use of genetic algorithms in this study allowed for a simultaneous data-driven optimization and sensitivity analysis.

Traitement de l'hétérogénéité sémantique dans les interactions humain-agent et agent-agent

OpenAIRE

Mazuel , Laurent

2008-01-01

The main purpose of this thesis is the management of semantic heterogeneity in human-agent and agent-agent interaction. We especially focus on the situation where a software agent, supplied with a knowledge representation model, has to understand requests coming from different interlocutors; either it is a human user or another software agent.Most work in this domain either focus on human-agent interaction or agent-agent interaction. On the contrary, we suggest that it is possible to use a co...

Role of chemotherapy in the treatment of lung cancer: evolving strategies for non-small cell histologies

International Nuclear Information System (INIS)

Muggia, F.M.; Blum, R.H.; Foreman, J.D.

1984-01-01

Lung cancer treatment has been considered to have made little progress except for advances in small cell carcinoma. For other histologies an attitude of nihilism has prevailed principally because of lack of effective systemic therapy and of no persuasive evidence that results could be improved by combined modality treatment. On the other hand, favorable results from surgery are confined to a small percent of all patients with this disease. This review emphasizes possibilities for progress in evolving new therapeutic strategies. Although improvement over other systemic therapies is modest, cisplatin-containing regimens yield more consistent response rates and apparent survival advantage relative to single agents. Immediate progression occurs in the minority of patients. In addition, regimens combining cisplatin with vinca alkaloids have no substantial deleterious effects on the lung, marrow or esophagus to aggravate radiation-induced complications. These features encourage the evolution of strategies which begin with chemotherapy and then use consolidation with radiation therapy. Clinical trials using these and newer strategies must be instituted if progress is to occur in the treatment of non-small cell histologies at all stages

Role of chemotherapy in the treatment of lung cancer: evolving strategies for non-small cell histologies

Energy Technology Data Exchange (ETDEWEB)

Muggia, F.M. (NYU Medical Center, New York); Blum, R.H.; Foreman, J.D.

1984-01-01

Lung cancer treatment has been considered to have made little progress except for advances in small cell carcinoma. For other histologies an attitude of nihilism has prevailed principally because of lack of effective systemic therapy and of no persuasive evidence that results could be improved by combined modality treatment. On the other hand, favorable results from surgery are confined to a small percent of all patients with this disease. This review emphasizes possibilities for progress in evolving new therapeutic strategies. Although improvement over other systemic therapies is modest, cisplatin-containing regimens yield more consistent response rates and apparent survival advantage relative to single agents. Immediate progression occurs in the minority of patients. In addition, regimens combining cisplatin with vinca alkaloids have no substantial deleterious effects on the lung, marrow or esophagus to aggravate radiation-induced complications. These features encourage the evolution of strategies which begin with chemotherapy and then use consolidation with radiation therapy. Clinical trials using these and newer strategies must be instituted if progress is to occur in the treatment of non-small cell histologies at all stages.

Radiolabeled enzyme inhibitors and binding agents targeting PSMA: Effective theranostic tools for imaging and therapy of prostate cancer

International Nuclear Information System (INIS)

Pillai, Maroor Raghavan Ambikalmajan; Nanabala, Raviteja; Joy, Ajith; Sasikumar, Arun; Knapp, Furn F.

2016-01-01

Because of the broad incidence, morbidity and mortality associated with prostate-derived cancer, the development of more effective new technologies continues to be an important goal for the accurate detection and treatment of localized prostate cancer, lymphatic involvement and metastases. Prostate-specific membrane antigen (PSMA; Glycoprotein II) is expressed in high levels on prostate-derived cells and is an important target for visualization and treatment of prostate cancer. Radiolabeled peptide targeting technologies have rapidly evolved over the last decade and have focused on the successful development of radiolabeled small molecules that act as inhibitors to the binding of the N-acetyl-L-aspartyl-L-glutamate (NAAG) substrate to the PSMA molecule. A number of radiolabeled PSMA inhibitors have been described in the literature and labeled with SPECT, PET and therapeutic radionuclides. Clinical studies with these agents have demonstrated the improved potential of PSMA-targeted PET imaging agents to detect metastatic prostate cancer in comparison with conventional imaging technologies. Although many of these agents have been evaluated in humans, by far the most extensive clinical literature has described use of the 68 Ga and 177 Lu agents. This review describes the design and development of these agents, with a focus on the broad clinical introduction of PSMA targeting motifs labeled with 68 Ga for PET-CT imaging and 177 Lu for therapy. In particular, because of availability from the long-lived 68 Ge (T 1/2 = 270 days)/ 68 Ga (T 1/2 = 68 min) generator system and increasing availability of PET-CT, the 68 Ga-labeled PSMA targeted agent is receiving widespread interest and is one of the fastest growing radiopharmaceuticals for PET-CT imaging.

Relay tracking control for second-order multi-agent systems with damaged agents.

Science.gov (United States)

Dong, Lijing; Li, Jing; Liu, Qin

2017-11-01

This paper investigates a situation where smart agents capable of sensory and mobility are deployed to monitor a designated area. A preset number of agents start tracking when a target intrudes this area. Some of the tracking agents are possible to be out of order over the tracking course. Thus, we propose a cooperative relay tracking strategy to ensure the successful tracking with existence of damaged agents. Relay means that, when a tracking agent quits tracking due to malfunction, one of the near deployed agents replaces it to continue the tracking task. This results in jump of tracking errors and dynamic switching of topology of the multi-agent system. Switched system technique is employed to solve this specific problem. Finally, the effectiveness of proposed tracking strategy and validity of the theoretical results are verified by conducting a numerical simulation. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

The evolving role of alemtuzumab (Campath-1H in renal transplantation

Directory of Open Access Journals (Sweden)

Phuong-Thu T Pham

2008-12-01

provide rapid and profound depletion of lymphocytes from the peripheral blood has sparked interest in the use of this agent as induction therapy in steroid and/or CNI minimization or avoidance protocols. This article provides an overview of the literarure on the evolving role of alemtuzumab in renal transplantation.Keywords: alemtuzumab, Campath-1H, induction, renal transplantation, calcineurin inhibitor minimization, steroid avoidance

On the Spatially Resolved Star Formation History in M51. II. X-Ray Binary Population Evolution

Science.gov (United States)

Lehmer, B. D.; Eufrasio, R. T.; Markwardt, L.; Zezas, A.; Basu-Zych, A.; Fragos, T.; Hornschemeier, A. E.; Ptak, A.; Tzanavaris, P.; Yukita, M.

2017-12-01

We present a new technique for empirically calibrating how the X-ray luminosity function (XLF) of X-ray binary (XRB) populations evolves following a star formation event. We first utilize detailed stellar population synthesis modeling of far-UV-to-far-IR photometry of the nearby face-on spiral galaxy M51 to construct maps of the star formation histories (SFHs) on subgalactic (≈400 pc) scales. Next, we use the ≈850 ks cumulative Chandra exposure of M51 to identify and isolate 2-7 keV detected point sources within the galaxy, and we use our SFH maps to recover the local properties of the stellar populations in which each X-ray source is located. We then divide the galaxy into various subregions based on their SFH properties (e.g., star formation rate (SFR) per stellar mass ({M}\\star ) and mass-weighted stellar age) and group the X-ray point sources according to the characteristics of the regions in which they are found. Finally, we construct and fit a parameterized XLF model that quantifies how the XLF shape and normalization evolves as a function of the XRB population age Our best-fit model indicates that the XRB XLF per unit stellar mass declines in normalization, by ˜3-3.5 dex, and steepens in slope from ≈10 Myr to ≈10 Gyr. We find that our technique recovers results from past studies of how XRB XLFs and XRB luminosity scaling relations vary with age and provides a self-consistent picture for how XRB XLFs evolve with age.

Agentes Comunitários de Saúde e os sentidos de "ser agente" Community Health Agents and the meanings of "being an agent"

Directory of Open Access Journals (Sweden)

Viviane Milan Pupin

2008-08-01

Full Text Available O Programa Saúde da Família constitui-se enquanto estratégia de mudança do modelo assistencial. O artigo apresenta os resultados de uma pesquisa qualitativa sobre os sentidos de "ser agente" produzidos, por meio de entrevistas abertas, com Agentes Comunitários de Saúde que trabalham nos cinco Núcleos de Saúde da Família da cidade de Ribeirão Preto - São Paulo, vinculados à Faculdade de Medicina de Ribeirão Preto - USP. As entrevistas foram gravadas e transcritas na íntegra e analisadas segundo princípios da análise de conteúdo. A análise permitiu a descrição de sentidos acerca de ser agente subdivididos em: Sentidos produzidos na relação com a comunidade e Sentidos produzidos na relação com a equipe. A análise dos sentidos de ser agente possibilitou construir um diálogo sobre as tensões relacionadas a um fazer em saúde ora permeado por concepções atreladas ao modelo biomédico, ora atrelado aos novos paradigmas em saúde.The Family Health Program consists of a strategy to change the health care model. This article presents the results from a qualitative study about the meanings of "being an agent" obtained through open interviews with Community Health Agents who work in five Family Health Centers of the Ribeirão Preto School of Medicine (University of São Paulo, located in Ribeirão Preto, São Paulo. Interviews were tape recorded, fully transcribed, and then content analyzed. The analysis allowed for descriptions of meanings toward "being an agent", subdivided into: Meanings produced by relationships with the community, and Meanings produced by relationships with the team. Analyzing the meanings of being an agent provided the establishment of a dialogue about the tensions related to a health practice that is at times influenced by conceptions associated with the biomedical method, and at other times with the new health paradigm.

Trading Control Intelligence for Physical Intelligence: Muscle Drives in Evolved Virtual Creatures

DEFF Research Database (Denmark)

Lessin, Dan; Fussell, Don; Miikkulainen, Risto

2014-01-01

Traditional evolved virtual creatures [12] are actuated using unevolved, uniform, invisible drives at joints between rigid segments. In contrast, this paper shows how such conven- tional actuators can be replaced by evolvable muscle drives that are a part of the creature’s physical structure....... This design is important for two reasons: First, the con- trol intelligence is made visible in the purposeful develop- ment of muscle density, orientation, attachment points, and size. Second, the complexity that needs to be evolved for the brain to control the actuators is reduced, and in some cases can...... be essentially eliminated, thus freeing brain power for higher-level functions. Such designs may thus make it pos- sible to create more complex behavior than would otherwise be achievable....

Evolving approaches to the ethical management of genomic data.

Science.gov (United States)

McEwen, Jean E; Boyer, Joy T; Sun, Kathie Y

2013-06-01

The ethical landscape in the field of genomics is rapidly shifting. Plummeting sequencing costs, along with ongoing advances in bioinformatics, now make it possible to generate an enormous volume of genomic data about vast numbers of people. The informational richness, complexity, and frequently uncertain meaning of these data, coupled with evolving norms surrounding the sharing of data and samples and persistent privacy concerns, have generated a range of approaches to the ethical management of genomic information. As calls increase for the expanded use of broad or even open consent, and as controversy grows about how best to handle incidental genomic findings, these approaches, informed by normative analysis and empirical data, will continue to evolve alongside the science. Published by Elsevier Ltd.

Skin Stem Cell Hypotheses and Long Term Clone Survival - Explored Using Agent-based Modelling